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Permit No. G-200

Safety Study

Risk Factors Associated with Weather-Related 

General Aviation Accidents

NTSB/SS-05/01

PB2005-917004 National Transportation Safety Board

Notation 7565A 490 LíEnfant Plaza, S.W.

Adopted September 7, 2005 Washington, D.C. 20594
National Transportation Safety Board. 2005. Risk Factors Associated with Weather-Related General

Aviation Accidents. Safety Study NTSB/SS-05/01. Washington, DC.

Abstract: The goal of this National Transportation Safety Board study was to better understand the risk

factors associated with accidents that occur in weather conditions characterized by IMC or poor visibility

(ìweather-related accidentsî). Safety Board air safety investigators collected data from 72 general aviation

accidents that occurred between August 2003 and April 2004. When accidents occurred, study managers

also contacted pilots of flights that were operating in the vicinity at the time of those accidents for

information about their flight activity. A total of 135 nonaccident flights were included in the study. All

nonaccident pilots voluntarily consented to interviews and provided information about their flights, their

aircraft, and details about their training, experience, and demographics. Additionally, the Federal Aviation

Administration provided information about pilotsí practical and written test results and their previous

accident/incident involvement. Statistical analyses were used to determine the relationships between study

variables and accident/nonaccident status and to identify variables that could be linked to an increased risk

of weather-related general aviation accident involvement. The analysis revealed several pilot- and flightrelated factors associated with increased risk of accident involvement. The safety issues discussed in this

report include: 1) pilot age and training-related differences, 2) pilot testing, accident, and incident history,

and 3) pilot weather briefing sources and methods. Safety recommendations concerning these issues were

made to the Federal Aviation Administration.

The National Transportation Safety Board is an independent Federal agency dedicated to promoting aviation, railroad, highway, marine,

pipeline, and hazardous materials safety. Established in 1967, the agency is mandated by Congress through the Independent Safety Board

Act of 1974 to investigate transportation accidents, determine the probable causes of the accidents, issue safety recommendations, study

transportation safety issues, and evaluate the safety effectiveness of government agencies involved in transportation. The Safety Board

makes public its actions and decisions through accident reports, safety studies, special investigation reports, safety recommendations, and

statistical reviews.

Recent publications are available in their entirety on the Web at <http://www.ntsb.gov>. Other information about available publications also

may be obtained from the Web site or by contacting:

National Transportation Safety Board

Records Management Division

490 LíEnfant Plaza, S.W.

Washington, D.C. 20594

(800) 877-6799 or (202) 314-6551

Safety Board publications may be purchased, by individual copy or by subscription, from the National Technical Information Service. To

purchase this publication, order report number PB2005-917004 from:

National Technical Information Service

5285 Port Royal Road

Springfield, Virginia 22161

(800) 553-6847 or (703) 605-6000

The Independent Safety Board Act, as codified at 49 U.S.C. Section 1154(b), precludes the admission into evidence or use of Board reports

related to an incident or accident in a civil action for damages resulting from a matter mentioned in the report. 
iii Safety Study

Contents

Acronyms and Abbreviations ......................................................................................... v

Executive Summary ....................................................................................................... vii

Chapter 1: Background ....................................................................................................1

Historical Trends in IMC Accidents .........................................................................................1

Previous Safety Board Studies of Weather-Related GA Accidents ..........................................1

Previous Safety Board Recommendations Pertaining to Weather ............................................3

Other Research on Flight in IMC ..............................................................................................4

Chapter 2: Federal Aviation Regulations Pertaining to Instrument Flight ................ 7

Visual Flight Rules (VFR) Minimums ......................................................................................7

Training Requirements ..............................................................................................................7

Recency Requirements ..............................................................................................................8

Chapter 3: Aviation Weather .........................................................................................10

Preflight Requirements ............................................................................................................11

Preflight Weather Information .................................................................................................11

In-Flight Weather Information .................................................................................................13

Chapter 4: Study Design and Methodology ..................................................................14

Case Control Methodology ......................................................................................................14

Study Procedures .....................................................................................................................15

Study Inclusion Criteria ...................................................................................................15

Matching Accident and Nonaccident Flights ...................................................................16

Identifying Pilots of Matching Nonaccident Flights.........................................................16

Interviewing Nonaccident Pilots ......................................................................................17

Accident Data ..........................................................................................................................17

Additional Data Sources ..........................................................................................................18

Weather Data .....................................................................................................................18

Pilot History ......................................................................................................................18

Statistical Analyses ..................................................................................................................18

Chi-Square Analysis ..........................................................................................................19

Binary Logistic Regression Analysis ................................................................................20

Chapter 5: Results ..........................................................................................................21

Description of Study Accidents ...............................................................................................21

Pilot Information ......................................................................................................................21

Accident Pilots ...................................................................................................................21

Nonaccident Pilots .............................................................................................................24

Pilot Flight Hours ..............................................................................................................26

Pilot Testing History .........................................................................................................27
Contents iv Safety Study

Accident, Incident, and Violation History ........................................................................28

Flight Information ....................................................................................................................28

Planned Length of Flights .................................................................................................28

Purpose of Flight ...............................................................................................................30

Aircraft Information ................................................................................................................30

Aircraft Ownership ............................................................................................................30

Aircraft Equipment ............................................................................................................31

Summary of Chi-Square Analysis ...........................................................................................31

Binary Logistic Regression Model...........................................................................................31

Flight Leg Length ..............................................................................................................32

Age at Private Certificate ..................................................................................................34

Prior Accident/Incident Involvement ................................................................................34

Instrument Rating ..............................................................................................................34

Chapter 6: Discussion .....................................................................................................35

Age-Related Differences .........................................................................................................35

Flight Training Differences ...............................................................................................37

Testing, Accident, and Incident History ..................................................................................39

Airman Knowledge and Practical Test Requirements ......................................................39

Test Performance and Accident Risk ................................................................................40

Accidents and Incidents ....................................................................................................41

Pilot History of Accidents and Incidents ..........................................................................42

Tracking a Pilotís Testing and Accident/Incident History ................................................42

Pilot Weather Briefing Sources and Methods ..........................................................................43

Summary ...........................................................................................................................46

Findings ............................................................................................................................47

Recommendations ...........................................................................................................48

Appendixes

A: Previous National Transportation Safety Board Safety Recommendations .......................49

B: Basic VFR Weather Minimums ..........................................................................................59

C: Evaluation of Matching Procedure .....................................................................................60

D: Guided Interview ................................................................................................................62

E: Supplemental Accident Form .............................................................................................65

F: A Comparison of Forecast and Actual Visibility Conditions for Study Accidents ............67

G: Study Accidents .................................................................................................................69
v Safety Study

Acronyms and Abbreviations

ADMS Accident Data Management System

AFSS automated flight service station

AIRMET airmenís meteorological information

ASI air safety investigator

ASOS automated surface observing system

ATC air traffic control

ATIS automated terminal information system

AWOS automated weather observation system

BFR biennial flight review

CFR Code of Federal Regulations

DUATS direct user access terminal system

FA area forecast

FAA Federal Aviation Administration

FBO fixed base operator

Flight Watch en route flight advisory service

FSS flight service station

GA general aviation

HIWAS hazardous inflight weather advisory service

IFR instrument flight rules

IMC instrument meteorological conditions

METAR aviation routine weather report/meteorological aerodrome 

report

NEXRAD next generation weather radar

nm nautical miles

NOAA National Oceanic and Atmospheric Administration

NWS National Weather Service

PATWAS pilotsí automatic telephone weather answering system
Acronyms and Abbreviations vi Safety Study

PIREP pilot report

PRIA Pilot Records Improvement Act of 1996

QICP Qualified Internet Communication Provider

SIGMET significant meteorological information

TAF terminal aerodrome forecast

TIBS telephone information briefing system

TWEB transcribed weather en route broadcast

VFR visual flight rules

VMC visual meteorological conditions

VOR very high frequency omnidirectional range

WINGS FAA Pilot Proficiency Award Program
vii Safety Study

Executive Summary

Historically, about two-thirds of all general aviation (GA) accidents that occur in

instrument meteorological conditions (IMC) are fatalóa rate much higher than the overall

fatality rate for GA accidents. The goal of this National Transportation Safety Board

study was to better understand the risk factors associated with accidents that occur in

weather conditions characterized by IMC or poor visibility (ìweather-related accidentsî). 

The study accomplished this goal using the case control methodology, which

compared a group of accident flights to a matching group of nonaccident flights to identify

patterns of variables that distinguished the two groups from each other. This methodology

expands on previous Safety Board efforts that have typically concentrated on summaries

of accident cases. The advantage of the case control methodology is that, instead of

focusing on the factors that accidents have in common, and possibly being misled by

characteristics common to most pilots/flights, it identifies characteristics that set accidents

apart and contribute to their occurrence. 

For this study, Safety Board air safety investigators (ASI) collected data from 72

GA accidents that occurred between August 2003 and April 2004. When accidents

occurred, study managers also contacted pilots of flights that were operating in the vicinity

at the time of those accidents for information about their flight activity. A total of 135

nonaccident flights were included in the study. All nonaccident pilots voluntarily

consented to interviews and provided information about their flights, their aircraft, and

details about their training, experience, and demographics. That information was

compared with data that regional ASIs collected about the accident flights as part of their

normal investigations. Additionally, the Federal Aviation Administration provided

information about pilotsí practical and written test results and their previous accident/

incident involvement.

Statistical analyses were used to determine the relationships between study variables and accident/nonaccident status and to identify variables that could be linked to an

increased risk of weather-related GA accident involvement. The analysis revealed several

pilot- and flight-related factors associated with increased risk of accident involvement,

and the recommended approaches to mitigating those risk factors are discussed in the context of three issue areas:

1. Ensuring a minimum level of proficiency for all pilots to recognize and safely

respond to hazardous weather situations.

2. Identifying and providing additional support for pilots whose performance

history indicates an increased risk of weather-related accidents.

3. Providing GA pilots with additional guidance regarding sources of preflight

weather information.
viii Safety Study

The Safety Board emphasizes that the conclusions reached in this study are not

based on a summary of accident cases, although the merits of such Board studies have

proven valuable in the past. Rather, the results are based on a statistical comparison of

accident and nonaccident flights that allows for the generalization of findings from this

study to the wider population of GA pilots and flights that may be at risk for a weatherrelated accident.

The Safety Board wishes to acknowledge the significant contribution to this study

by the GA pilot community. All of the pilots contacted voluntarily provided needed

information concerning their flight and aviation experience, providing the control group

necessary for this study.

As a result of this study, six recommendations were issued to the Federal Aviation

Administration.

Executive Summary
1 Safety Study

Chapter 1

Background

Historical Trends in IMC Accidents

The total number of general aviation (GA) accidents per year has declined over the

past two decades. However, as shown in figure 1, the relative proportion of GA accidents

that occur during instrument meteorological conditions (IMC) has remained fairly stable,

ranging from 5 to 9 percent of annual GA accident totals. The National Transportation

Safety Board has long been

concerned about GA accidents that

occur in poor weather or in IMC

(referred to in this study as

ìweather-related accidentsî), especially because they are far more

likely to be fatal than accidents that

take place in visual meteorological

conditions (VMC). Over the past

20 years, about two-thirds of all

IMC accidents have resulted in at

least one fatality, a rate that is three

times higher than the fatality rate

of all GA accidents. In 2004, 103

accidents, or 6 percent of all GA

accidents, occurred in IMC. Of

these accidents, 70 percent were

fatal, and the 147 fatalities that

resulted from these accidents

accounted for more than 25

percent all deaths from GA accidents in 2004.

Previous Safety Board Studies of Weather-Related GA Accidents

The Safety Board published reports on weather- or visibility-related GA accidents

in 1968,1

 1974,2 1976,3 and 1989.4 The 1968 study considered in detail all GA accidents

1 National Transportation Safety Board, An Analysis of U.S. General Aviation Accidents Involving

Weather as a Cause/Related Factor 1966, Notation 155 (Washington, DC: 1968).

2 National Transportation Safety Board, Special Study of Fatal, Weather-Involved General Aviation

Accidents, NTSB-AAS-74-2 (Washington, DC: 1974).

3 National Transportation Safety Board, Nonfatal, Weather-Involved General Aviation Accidents,

NTSB AAS-76-3 (Washington, DC: 1976).

4 National Transportation Safety Board, General Aviation Accidents Involving VFR Flight Into IMC,

NTSB/SR-89-01 (Washington, DC: 1989).

On November 2, 2003, at 1847 central standard time, a

Commander Aircraft 114TC, N6107Z, piloted by a private

pilot, was destroyed during an in-flight collision with terrain at

the Hutchinson Municipal Airport, Hutchinson, Kansas. The

pilot was fatally injured. Night instrument meteorological

conditions prevailed at the time of the accident

(CHI04FA025).
Chapter 1 2 Safety Study

that occurred in 1966 and included an analysis of the weather- and pilot-related causes and

factors cited in the Boardís accident findings. The 1974, 1976, and 1989 studies each

examined a large number of accidents sampled over several years based on common

causal or contributing factors: 

ï The 1974 study focused on fatal GA accidents involving weather.

ï The 1976 follow-up study focused on nonfatal weather-related GA accidents.

ï The 1989 study considered accidents in which ìVFR-into-IMCî was cited as a

probable cause or contributing factor. 

In each of these studies, descriptive statistics were used to characterize the

accident group in terms of factors relating to the pilot, aircraft, environment, and accident

circumstances. Additionally, the 1989 study included some comparisons between the

VFR-into-IMC group and two other groupsóone representing pilots in all GA accidents

and one representing all active GA pilots.

In all of the studies, the selected group of accidents typically occurred during

flights for which no flight plan had been filed. They usually involved relatively

inexperienced5

 pilots with private pilot certificates and no instrument ratings. Pilots in

fatal weather-related accidents were generally older than those in nonfatal accidents, and

pilots involved in VFR-into-IMC accidents were older than the comparison group of all

active pilots. The most common weather phenomena for fatal accidents were low cloud

Figure 1

5 For example, in the 1974 study, 53 percent of pilots had less than 600 total flight hours. In the 1976 study,

84 percent of pilots had less than 100 total flight hours, and in the 1989 study, 52 percent of pilots involved in

VFR-into-IMC accidents had less than 500 total flight hours compared to 41 percent of pilots in all GA accidents.

The Proportion of GA Accidents that Occurred

During IMC Between 1983 and 2004

0%

20%

40%

60%

80%

100%

1983198419851986198719881989199019911992199319941995199619971998199920002001200220032004
Chapter 1 3 Safety Study

ceilings, fog, rain, and snow; nonfatal accidents, on the other hand, were dominated by

accidents attributed to unfavorable wind. 

Recommendations from the 1968, 1974, and 1976 studies were directed to the Federal

Aviation Administration (FAA), the Environmental Science Services Administration,6 and the

National Oceanic and Atmospheric Administration (NOAA). Recommendations from the

1968 and 1974 studies focused on increasing pilotsí knowledge and awareness of weather

through training and through expansion of weather forecasting and reporting products tailored

to pilots. Conversely, recommendations associated with the 1976 study emphasized hazards

associated with winds during the landing phase of flight and did not pertain to conditions of

reduced visibility. The 1989 report did not generate any new recommendations. 

Previous Safety Board Recommendations Pertaining to Weather

In addition to the recommendations associated with safety studies, numerous

recommendations concerning weather and visibility issues have resulted from accident

investigations. The Safety Boardís Recommendations Database shows that the Board has

issued 82 recommendations relating to GA flight in IMC or visibility-related weather

conditions since 1968.7 These recommendations have addressed a variety of topics, which

may be grouped into three broad areas: the collection and dissemination of weather

Figure 2

6 The Environmental Science Services Administration was the predecessor agency to the National

Oceanic and Atmospheric Administration.

7 Recommendations were selected for this group if they affected GA flight in weather conditions, even

if they were issued in the context of an accident that did not involve GA operations.

The Proportion of all GA Accidents and GA Accidents in

IMC that Resulted in a Fatality Between 1983 and 2004 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

2004

0%

20%

40%

60%

80%

100%

IMC All GA
Chapter 1 4 Safety Study

information, pilot training and operations, and air traffic control (ATC). Most of these

recommendations were addressed to FAA, NOAA, or the National Weather Service

(NWS),8 which is part of NOAA. Appendix A summarizes these recommendations and

lists each recommendation and its status.

Other Research on Flight in IMC

Weather-related accidents in general, and VFR-into-IMC accidents in particular,

have generated considerable interest from other governmental agencies and the aviation

research community.9

 Studies have focused on pilotsí evaluations and assessments of

deteriorating visibility10 or on their flight-related decisions in the presence of weather.11

Additionally, some researchers have suggested that a lack of good weather information

during flight contributes to the incidence of weather-related accidents.12

Studies of accidents involving continued VFR flight into IMC often focus on pilot

judgment and the factors influencing aeronautical decision-making. For instance, Jensen

and Benel13 concluded that approximately 50 percent of aviation fatalities were related to

poor pilot judgment. Examples of so-called poor judgment accidents in IMC included

pilots continuing VFR flight into IMC or pilots descending below a published minimum

altitude while attempting an instrument approach. In some cases, these actions were

intentional violations of rules or safety procedures; in other cases, they were unintentional

or resulted from a misinterpretation of available information. 

Other researchers have attempted to characterize the types of decision-making

errors that lead pilots to make unsafe decisions. One class of decision-making error

attributed to pilots in weather accidents is known as a plan continuation error. A plan

continuation error is defined as ìfailure to revise a flight plan despite emerging evidence

that suggests it is no longer safe.î14 For example, rather than revising the intended route

8 NWS responsibilities include providing weather forecasts in support of aviation and the mission of

the FAA.

9 For a recent example, see General Aviation Pilot Behaviours in the Face of Adverse Weather

(Australian Transport Safety Board: June 2005).

10 D.A. Wiegmann, J. Goh, and D. OíHare, Pilotsí Decisions to Continue Visual Flight Rules (VFR)

Flight into Adverse Weather: Effects of Distance Traveled and Flight Experience, FAA Technical Report,

ARL-01-11/FAA-01-3 (2001). 

11 B. Burian, J. Orasanu, and J. Hitt, ìWeather-Related Decision Errors: Differences Across Flight

Types,î Proceedings of the 14th Triennial Congress of the International Ergonomics Association/44th Annual

Meeting of the Human Factors and Ergonomics Society (San Diego, CA: 2000), 1, 22-25.

12 K. Latorella, S. Lane, and D. Garland, General Aviation Pilotsí Perceived Usage and Valuation of

Aviation Weather Sources, NASA Technical Memorandum 211443 (2002).

13 R.S. Jensen and R.A. Benel, Judgment Evaluation and Instruction in Civil Pilot Training, Final

Report FAA-RD-78-24 (Springfield, VA: National Technical Information Service, 1977).

14 J. Orasanu, L. Martin and J. Davison, ìCognitive and Contextual Factors in Aviation Accidents,î in

E. Salas and G.A. Klein (Eds.), Linking Expertise and Naturalistic Decision Making (Mahwah, NJ:

Lawrence Erlbaum Associates: 2001), pp. 209-225.
Chapter 1 5 Safety Study

of flight by changing course or altitude, deviating to an alternate airport, or returning to

the departure airport, pilots may opt to press on into deteriorating weather. Another type

of decision-making error can occur when pilots continue visual flight into instrument

conditions because they incorrectly assess the risks of the situation.15 In these cases, pilots

who appear to be intentionally engaging in risky behavior may actually be making choices

that they mistakenly believe to be safe. Such diagnostic errors have been found to result in

more serious accidents than have errors in aircraft control.16 Even if pilots are able to

correctly assess current weather conditions, they may still underestimate the risk

associated with continued flight under those conditions, or they may overestimate their

ability to handle that risk.17

Errors in decision-making, such as plan continuation errors or incorrect

assessments of weather-related risk, may be made by pilots who are unfamiliar with the

climate of the local area, who lack total and/or recent experience identifying marginal

weather conditions, or who lack experience accessing or reading weather reports. For

example, operational experience with weather has been found to affect weather-related

decision-making and information acquisition. Targeted weather-related training programs

have demonstrated some success in teaching pilots to recognize and respond to

deteriorating weather conditions.18

It is also possible that decision-making errors and/or accident involvement are

associated with more general pilot-related factors, such as total flight experience,

certification-level, or risk-taking behavior. However, comparisons of pilotsí experience,

self-assessment of ability, and actual accident involvement have yielded conflicting

results.19 For example, low-time pilots may lack the experience they need for making

decisions, whereas high-time pilots may misjudge the risk associated with weather

conditions because they have successfully operated in similar weather conditions in the

past. A comparison of pilot survey data with past and future accident involvement found

that individual differences in attitude toward risk-taking behaviors made certain

individuals more likely to be involved in an accident, regardless of experience.20 The

15 D. Wiegmann and J. Goh, Visual Flight Rules (VFR) Flight Into Adverse Weather: An Empirical

Investigation of Factors Affecting Pilot Decision Making, FAA Technical Report ARL-00-15/FAA-00-8

(Washington, DC: FAA, 2000).

16 D. Wiegmann and S.A. Shappell, ìHuman Factors Analysis of Postaccident Data: Applying Theoretical

Taxonomies of Human Error,î The International Journal of Aviation Psychology, 7 (1997): 67-81.

17 D. OíHare, ìPilotsí Perception of Risks and Hazards in General Aviation,î Aviation, Space, and

Environmental Medicine, 61 (1990): 599-603.

18 (a) M. Wiggins and D. OíHare, ìExpertise in Aeronautical Weather-Related Decision Making: A CrossSectional Analysis of General Aviation Pilots,î Journal of Experimental Psychology: Applied, 1(4) (1995):

305-320; (b) M. Wiggins and D. OíHare, ìWeatherwise: Evaluation of a Cue-Based Training Approach for the

Recognition of Deteriorating Weather Conditions During Flight,î Human Factors 45(2) (2003): 337-345.

19 (a) D.R. Hunter, Airman Research Questionnaire: Methodology and Overall Results, Report No.

DOT/FAA/AM-95/27 (Washington, DC: FAA, 1995); (b) D.R. Hunter, ìRetrospective and Prospective

Validity of Aircraft Accident Risk Indicators,î Human Factors, 43(4) (2001): 509-518; (c) M. Lubner, ìA

Risk Profile for Aviation Accidents, Incidents, and Violations Among U.S. Pilots,î Proceedings of the 9th

International Symposium on Aviation Psychology (Columbus, OH: 1997).

20 Hunter, 2001.
Chapter 1 6 Safety Study

same study found that previous accident involvement was associated with future accident

risk. Some authors have also suggested that pilotsí willingness to accept weather-related

risks depends upon their tendency to focus on either the gains or losses associated with

each option.21 In addition to differences in individual decision-making style, the

cost/benefit determination may be further influenced by the amount of time, money, and

effort a pilot has already invested in a particular flight. 

A substantial amount of existing research has used questionnaires or flight

simulators in laboratory settings. Laboratory studies allow for scientific control but fail to

replicate the complex demands placed on pilots conducting real-world flight operations.

For example, flight simulator studies have provided a better understanding of the types of

evaluation and decision-making errors that can lead to weather-related accidents. Far

fewer studies have linked specific pilot, aircraft, or flight-related factors to the occurrence

of actual weather-related accidents. Because of its role as the primary investigator of U.S.

civil aviation accidents, the Safety Board is uniquely suited to gather information related

to weather-related accidents and to identify the factors that distinguish them from

successful flights.

21 D. OíHare and T. Smitheram, ì ëPressing Oní into Deteriorating Conditions: An Application of

Behavioral Decision Theory to Pilot Decision Making,î The International Journal of Aviation Psychology,

5(4) (1995): 351-370.
7 Safety Study

Chapter 2

Federal Aviation Regulations Pertaining to Instrument 

Flight

Visual Flight Rules (VFR) Minimums

According to the FAA Pilot/Controller Glossary, instrument meteorological conditions, or IMC, are defined as ìmeteorological conditions expressed in terms of visibility,

distance from clouds, and ceiling less than the minimums specified for visual meteorological conditions (VMC).î22 This legal definition is used to prescribe the minimum weather

conditions in which a pilot may operate an aircraft without meeting additional requirements of pilot qualification,

aircraft equipment, and communication. These minimums account

for altitude in relation to terrain

and obstructions, time of day, and

location in relation to areas of high

air traffic density, such as airports.

An example of criteria defining

VMC are 3 statute miles flight visibility and a clearance of 1,000

feet above, 500 feet below, and

2,000 feet horizontal distance

from clouds. Meteorological conditions are also commonly

referred to as either VFR (visual

flight rules) or IFR (instrument

flight rules) in reference to the

regulations that apply to pilots

who are operating under those

conditions.

Training Requirements

Because of the unique demands related to safely managing weather, the FAA has

established knowledge and training requirements for pilots to help them recognize and

respond to weather hazards. All pilot applicantsóregardless of certificate levelómust

receive training in how to avoid potential weather hazards when possible, and how to

safely respond to weather hazards if they are encountered. These training requirements

include the recognition and avoidance of hazardous weather, preflight actions related to

22 Basic VFR weather minimums as defined in 14 Code of Federal Regulations (CFR) 91.155 are

presented in appendix B.

On March 21, 2004, about 2050 eastern standard time, a

Piper PA-32R-301, N8173U, was destroyed when it

impacted mountainous terrain while in cruise flight near

Harlan, Kentucky. The cerficated private pilot and five

passengers were fatally injured. Instrument meteorological

conditions prevailed near the accident site (NTC04FA092).
Chapter 2 8 Safety Study

the procurement and use of aeronautical weather reports and forecasts, and aeronautical

decision-making and risk management. For instrument-rated pilots, this training is meant

to provide the additional knowledge and skills needed for safe flight in IMC. Conversely,

the goal of instrument flight training for VFR-only pilots is to enable them to maintain

control of an aircraft while making a course reversal or diversion if they inadvertently

enter clouds. Specifically, private pilot applicants who are not instrument rated must have

logged a minimum of 3 hours of flight training on the control and maneuvering of an

airplane solely by reference to instruments, including straight and level flight, constant

airspeed climbs and descents, turns to a heading, recovery from unusual flight attitudes,

radio communications, and the use of navigation systems/facilities and radar services

appropriate to instrument flight. Commercial pilot applicants who are not instrument rated

must have logged a minimum of 10 hours of similar instrument training.23

Because aircraft used in recreational and sport operations are typically not

equipped for instrument flight, requirements for the recreational and sport pilot certificates

do not include flight training or proficiency standards for flight by reference to aircraft

instruments. Consequently, pilots holding recreational pilot or sport pilot certificates are

prohibited from operating aircraft unless they maintain at least 3 statute miles visibility

and visual contact with the surface.24 Additionally, recreational pilot certificate holders

may not operate an aircraft at night with less than 5 statute miles visibility, and sport pilot

certificate holders may not operate an aircraft at night.

In order to pilot an aircraft on an IFR flight plan in IMC, private pilot and

commercial pilot certificate holders must add an instrument rating to their pilot certificates

by completing additional training and passing both knowledge and practical tests.

Instrument rating applicants are required by 14 Code of Federal Regulations (CFR) 61.65

to also receive additional ground training in how to obtain and use aviation weather

reports and forecasts, the forecasting of weather trends based on that information and on

their personal observation of weather conditions, the safe and efficient operation of

aircraft under instrument flight conditions, the recognition and avoidance of critical

weather situations, and aeronautical decision-making and judgment. The flight

requirements of the instrument rating include 40 hours of actual or simulated instrument

flight, including at least 15 hours of instrument flight training.25

Recency Requirements

Like any complex skill, flying an aircraft solely by reference to aircraft flight

instruments requires periodic practice to maintain proficiency. Pilots with an instrument

23 Title 14 CFR 141, Appendix D, requires that commercial pilot training conducted by a certificated

flight school include 5 hours of training in the same category and class of aircraft. Commercial pilot

applicants trained under this part must either hold an instrument rating or be concurrently enrolled in an

instrument pilot course.

24 Title 14 CFR 61.101 and Title 14 CFR 61.315, respectively. 

25 Title 14 CFR 141, Appendix C.4, requires pilots trained at a certificated pilot school to have a

minimum of 35 hours of instrument training if the course is for an initial instrument rating or 15 hours of

instrument training if the course is for an additional instrument rating.
Chapter 2 9 Safety Study

rating on their private pilot or commercial pilot certificates must therefore meet

instrument flight recency requirements in order to operate aircraft in instrument

conditions. Title 14 CFR 61.57 states that no person may act as pilot-in-command under

IFR or in weather conditions less than the minimums prescribed for VFR unless, within

the preceding 6 calendar months, that person has conducted at least 6 instrument

approaches, holding procedures, and intercepting and tracking courses through the use of

navigation systems in actual or simulated instrument conditions. Pilots who do not meet

this requirement have an additional 6 months after the prescribed time to meet the

requirement, but may not act as pilot-in-command under IFR. Pilots who do not meet the

requirement after that must pass an instrument proficiency check given by an authorized

instructor, examiner, or check pilot.

Even though they are subject to an initial certification requirement, noninstrument-rated pilots are not currently required to receive recurrent instrument flight

training, nor are they required to periodically demonstrate proficiency in flight by

reference to instruments. All pilots are subject to 14 CFR 61.56, which specifies that, to

act as pilot-in-command of an aircraft, they must have satisfactorily completed a flight

review during the previous 24 months.26 That reviewócommonly referred to as a

biennial flight review or BFRómust include a minimum 1 hour each of ground and flight

instruction covering general knowledge, operating rules, and procedures. The instructor

giving the flight review is free to determine the content; therefore, the BFR may or may

not include a demonstration of the weather knowledge and instrument flight skills

required for initial certification.

26 Title 14 CFR 61.56 specifies several additional ways for pilots to satisfy the flight review

requirement, such as a practical test for an additional certificate or rating, a pilot proficiency check, or

recurrent training, such as the FAA voluntary Pilot Proficiency Award Program (WINGS).
10 Safety Study

Chapter 3

Aviation Weather

Over the years, the measuring and reporting of aviation weather conditions has

shifted from human observations to the use of automated systems. For example, upper-air

weather data collection that once relied on sounding balloons and pilot reports (PIREP)

has been supplemented by information gathered from wind profilers and aircraft equipped

with instruments that automatically downlink weather observations. In addition, manual

surface observations have now been augmented or replaced by the automated surface

observing system (ASOS) and the automated weather observing system (AWOS).

Established in the 1990s, ASOS and AWOS systems are now installed at more than 1,500

airports in the United States. 

Radar and satellites have

also become major sources of

weather information. In the 1980s

and 1990s, using Doppler technology, the NWS developed nextgeneration radar (NEXRAD),

which provides advanced and

detailed information about precipitation and winds. Weather

satellites provide additional information in the form of visible,

infrared, and other images that are

made available on a near-real-time

basis to NWS and FAA facilities. 

Pilotsí use of weather

information for flight-planning and

decision-making has also changed

greatly over the years. Up until the

late 1960s, most pilots planned

their flights with the aid of face-toface weather briefings from trained

FAA personnel working at flight service stations (FSS). In the 1970s, telephone briefings

from FSS and prerecorded weather information like the telephone information briefing

service (TIBS) and the pilotsí automatic telephone weather answering system (PATWAS)

became commonplace. In the cockpit, pilots gained access to radio broadcasts of airport

information, including current weather conditions, using the automatic terminal information

service (ATIS). The 1970s also saw the advent of in-flight weather information like the en

route flight advisory service (ìFlight Watchî), transcribed weather broadcasts (TWEB), and

the hazardous in-flight weather advisory service (HIWAS).

On February 11, 2004, about 2110 eastern standard time, a

Piper PA-28-180, N6473J, collided with trees and the ground

during approach to Bacon County Airport, Alma, Georgia.

Instrument meteorological conditions prevailed. The private

pilot, the pilot-rated passenger, and the rear-seated

passenger received fatal injuries, and the airplane sustained

substantial damage (ATL04FA075).
Chapter 3 11 Safety Study

Today, many pilots receive preflight weather briefings via computer using the FAA

direct user access terminal system (DUATS). Additionally, Internet websites and computer

terminals displaying live radar and graphical weather data are available at airports and

fixed base operators (FBOs) to support flight planning with supplemental weather

information. For local and en route applications, real-time weather information from

ASOS has joined many of the existing in-flight weather information sources. 

Most preflight and in-flight weather briefing services employ text-based or audiobased products like aviation routine weather reports (METAR), area forecasts (FA), terminal

aerodrome forecasts (TAF), airmenís meteorological information reports (AIRMETs), and

significant meteorological information reports (SIGMETs). Additionally, numerous graphical

products are now available to pilots. For example, surface analysis and weather depiction

charts portray recent atmospheric pressure patterns and surface weather observations from

across the United States. Radar summary charts provide information about the location and

intensity of thunderstorms and other forms of precipitation, and low-level prognostic charts

provide forecast information pertaining to IMC, turbulence, and icing for 12- and 24-hour

periods. Graphic products like these, as well as radar and satellite images, are available to

pilots on the ground, and new services are making them available in the cockpit with the aid of

datalink or satellite communications and advanced multifunctional displays.

Preflight Requirements

Title 14 CFR 91.103 requires that all pilots, ìbefore beginning a flight, become

familiar with all available information concerning that flight.î Specific examples of such

information are airport elevation and runway lengths, aircraft takeoff and landing

distances, and aircraft gross weight. Pilots of IFR flights and non-local flights must also be

familiar with weather reports and forecasts, fuel requirements, and alternatives available if

the planned flight cannot be completed. When considered with 14 CFR 91.3, which

stipulates that pilots-in-command are ìdirectly responsible for, and the final authority as

to, the operation ofî their aircraft, pilots are solely responsible for knowing everything

there is to know about the weather along their planned route of flight.

Preflight Weather Information

Preflight weather information enables pilots to prepare for conditions they may

encounter during flight, or to decide that they are not qualified to fly in the reported

conditions. Unlike regulations governing Parts 121 and 135, which limit operators to the

use of ìapprovedî weather sources,27 Part 91 regulations do not specify a particular source

27 According to the FAA Air Transport Operations Inspectors Handbook (8400.10), ìfor all operations

conducted under Parts 121 and 135, weather reports either must be prepared by the National Weather

Service (NWS) or by sources approved by the NWS or Federal Aviation Administration (FAA).î These

sources include NWS offices, FAA Flight Service Stations, Automated Surface Observations, and certain

Qualified Internet Communication Providers (QICP).
Chapter 3 12 Safety Study

of weather information for GA pilots. The FAA and NWS provide numerous sources of

weather information to pilots, including FSS telephone briefings, DUATS, and Internet

website services such as <http://www.aviationweather.gov>. Commercial providers also

offer data and services, such as satellite weather or flight planning software packages that

include weather information.

In its Instrument Flying Handbook (FAA-H-8083-15), the FAA suggests that, in

preparing for an IFR flight, pilots should call an automated flight service station (AFSS) to

obtain a weather briefing. A ìstandardî preflight briefing is meant to provide pilots with

sufficient weather information to prepare for their flights, and is defined by FAA Advisory

Circular AC00-45E as comprising the following components:

1. Adverse conditions. Meteorological or aeronautical conditions reported or

forecast that may influence a pilot to alter the proposed flight.

2. VFR flight not recommended. VFR flight proposed and sky conditions or

visibilities present or forecast, surface or aloft, that, in the judgment of the

AFSS/FSS briefer, would make flight under VFR doubtful.

3. Synopsis. A brief statement describing the type, location, and movement of

weather systems and/or air masses that might affect the proposed flight.

4. Current conditions. A summary from all available sources reporting weather

conditions applicable to the flight.

5. En route forecast. A summary from appropriate data forecast conditions

applicable to the proposed flight.

6. Destination forecast. Destination forecast that includes significant changes

expected within 1 hour before and after the expected time of arrival.

7. Winds aloft. Forecast winds aloft for the proposed route; temperature

information on request.

8. Notices to airmen. A notice containing information concerning the

establishment, condition, or change in any component of, or hazard in, the

National Airspace System.

9. ATC delays. Any known ATC delays and/or flow control advisories that may

affect the proposed flight.

10. Request for PIREP. A request made if a report of actual in-flight conditions

would be beneficial or when conditions meet the criteria for solicitation of

PIREPs.

11. Flight Watch. The availability of in-flight weather information (for example,

Flight Watch) for weather updates.

12. Any other information the pilot requests (for example, military training activity

along the route of flight). 
Chapter 3 13 Safety Study

In-Flight Weather Information

Each time they fly, pilots must continuously evaluate in-flight weather to identify

conditions that could potentially affect the safety of their flights. In so doing, pilots must

integrate what they see outside the cockpit with data presented by aircraft instruments and

any additional information they receive from ATC, weather reporting facilities, and other

pilots. Pilots must then compare that information against their expectations based on the

forecast weather.

Pilots without a current instrument rating, or those flying aircraft certified for VFR

flight only, must base their decisions on the need to maintain minimum VFR cloud

clearances at all times. A pilot may be able to change altitude or deviate from the planned

route of flight in order to maintain VFR requirements. If not, the pilot must either turn

back or find a suitable alternate route or destination. 

Because they are permitted to operate in degraded weather conditions, instrumentrated pilots operating on IFR flight plans are more concerned with avoiding hazards like

icing, turbulence, and embedded thunderstorms that they may encounter when flying in

the clouds. Detection and avoidance of in-flight weather hazards require pilots either to

use weather avionics like radar or lightning detection equipment or to communicate with

ATC or Flight Watch to obtain this information. Pilots can communicate directly with

most local FSSs through Flight Watch or HIWAS, or if controller workload allows, request

weather information through ATC. Recently, aircraft-based equipment and radio

communications have begun to merge with avionics capable of displaying weather data,

such as METARs, TAFs, FAs, AIRMETS, SIGMETS, and PIREPs transmitted through

either a ground-based array or a satellite network.28

28 For an example of a system that combines datalinked traffic, weather, and terrain information with

advanced aircraft displays, see the FAAís Alaska Capstone project, <http://www.alaska.faa.gov/capstone/>.
14 Safety Study

Chapter 4

Study Design and Methodology

The goal of this study was to identify factors that are predictive of accident risk for

GA pilots flying in weather-related conditions characterized by poor visibility, like IMC

or marginal VMC.29 This goal

was accomplished by comparing

a set of weather-related GA accidents to a corresponding set of

nonaccident flights that took

place under similar weather conditions. This approach, referred

to as the case control methodology, allows for a determination of

the odds of involvement in accidents based on identified risk

factors. The advantage of this

approach is that, instead of focusing on what accidents have in

common, and possibly being misled by characteristics common to

most pilots/flights, it identifies

characteristics that set accidents

apart and contribute to their

occurrence. 

Case Control Methodology

The case control methodology is commonly used in epidemiological research to

compare a group of interest, such as people with a certain disease (that is, ìcasesî) with a

group of individuals from the same population who do not exhibit the disease (that is,

ìcontrolsî). Control groups may be randomly selected from within the population of

interest or may be selected to ìmatchî cases on certain variables, such as age, sex, or

exposure to potential risk factors.

In the aviation domain, the case control methodology has been used in only a handful

of studies. For example, one study compared characteristics of accident pilots to a larger pilot

sample and found that accident pilots were more likely to have medical problems than the

29 Marginal VMC is used to refer to conditions in which visibility is between 3 and 5 miles or when

ceiling height is between 1,000 and 3,000 feet.

On January 10, 2004, about 1840 central standard time, a

Cessna 182P, N5787J, was destroyed during an in-flight

collision with trees and terrain 7 1/2 miles southwest of the

Baudette International Airport, Baudette, Minnesota. Night

instrument meteorological conditions prevailed at the time

of the accident. The non-instrument-rated pilot and

passenger sustained fatal injuries (CHI04FA055).
Chapter 4 15 Safety Study

overall pilot population.30 A similar approach was used to a lesser extent in the Safety

Boardís 1989 safety study, which found that pilots involved in VFR-into-IMC accidents were

older and less likely to have an instrument rating than a sample of all active GA pilots.31

Other case control studies have gathered preexisting survey or accident data from

groups of pilots and then categorized the data by a variable of interest, like the pilotís

involvement in an accident or an accidentís fatal or nonfatal outcome. For example, one

study, which compared fatal-to-the-pilot GA crashes to those in which the pilot survived,

found that aircraft fires, off-airport locations, nighttime flight, and IMC were linked to

pilot fatality.32 Another study examining predictors of pilot fatality among weatherrelated GA accidents resulted in similar findings.33

One challenge associated with using historical accident records or surveys is that

the data they contain may be incomplete or inadequate to address the research goals. The

present study addressed that challenge by identifying variables of interest a priori, which

facilitated more consistent and complete data collection from cases and controls. 

Study Procedures

Study managers from the Safety Boardís Office of Research and Engineering

worked closely with air safety investigators (ASI), air traffic specialists, and Safety Board

meteorologists from the Office of Aviation Safety. When GA accidents occurred during

the study time frame (August 2003 through April 2004), ASIs used preliminary

information to determine if the accident met the study inclusion criteria and notified the

study managers accordingly. Study managers also monitored FAA incident/accident daily

reports to identify additional qualifying accidents.

Study Inclusion Criteria

Before data collection began, study managers established a set of criteria to guide

the selection of accident cases. Study inclusion criteria were based on initial observations

of the weather at the time of the accident and characteristics of the accident flight.

Accidents were selected if they involved a GA operation and happened in either IMC or

marginal VMC. Also included were accidents that appeared to have involved spatial

disorientation, loss of control, or collision with terrain or object due to a lack of visual

references or encounter with weather. 

30 C.R. Harper, ìPhysical Defects of Civilian Pilots Related to Aircraft Accidents,î Aerospace

Medicine, 35 (1964): 462-464.

31 NTSB/SR-89-01.

32 G. Li and S.P. Baker, ìCorrelates of Pilot Fatality in General Aviation Crashes,î Aviation, Space, and

Environmental Medicine, 70 (1999): 305-309.

33 J. M. Price and L.S. Groff, ìRisk Factors for Fatal General Aviation Accidents in Degraded Visual

Conditions,î Proceedings of the 13th International Symposium on Aviation Psychology (Oklahoma City, OK,

2005), 469-474.
Chapter 4 16 Safety Study

Matching Accident and Nonaccident Flights

Once a candidate accident was identified, staff began to identify and locate

matching nonaccident flights based on the factors listed below. 

ï Weather conditions

ï Location (within 30 miles of accident)

ï Time (within 30 minutes of accident)

ï Rules of flight 

ï Number of engines

ï Engine type

For example, if an accident flight was operating under VFR, corresponding

nonaccident flights were selected from other VFR flights operating in similar conditions

and in similar aircraft near the accident site. A subsequent review of data from accident

and nonaccident flights, presented in appendix C, confirmed the success of the matching

procedure.

Identifying Pilots of Matching Nonaccident Flights

If the accident flight was operating on an IFR flight plan, nonaccident aircraft were

identified with the use of commercially available flight tracking software.34 Information

presented by the software is based on composite radar data used by the FAA for systemwide traffic monitoring and flow control. As shown in figure 3, the software provided

graphical displays of aircraft radar data, as well as such weather products as NEXRAD

radar. After an accident occurred, Safety Board staff used the software to review flight

traffic and weather information around the accident site at the time of the accident and to

obtain registration numbers of matching nonaccident flights.

Because the software depicted only flights receiving ATC radar services, an

alternative procedure was used for accident flights that were operating under VFR. For

those flights, study managers telephoned airports and FBOs within a 30-mile radius of the

accident and along the accident route of flight to identify matching aircraft. Airport and

FBO employees were informed about the study and its purpose and were asked if they

were aware of any aircraft that had arrived, departed, or passed through the area around

the time of the accident. An effort was also made to identify pilots who intended to fly but

chose not to because of the weather. For VFR accidents, multiple inquiries were typically

necessary to identify appropriate nonaccident pilots. In addition to telephone inquires,

primary radar was used when necessary to determine whether any other aircraft had

passed through the area.

34 Flight Explorer Professional (Version 4.6) [Computer software]. Alexandria, VA: Flight Explorer,

Inc.
Chapter 4 17 Safety Study

Interviewing Nonaccident Pilots

Once candidate nonaccident aircraft matches were identified, a study manager

contacted the registered owners via telephone. Aircraft owners were informed about the

purpose of the study and allowed either to accept or decline participation. If the owner was

not piloting the aircraft during the flight of interest, or if the aircraft was being operated

for rent, the flying pilot was identified and contacted. In most cases, study managers were

able to identify and interview pilots within 72 hours of the accident flight.

Of the aircraft pilots who were contacted, 100 percent volunteered to participate in

a structured interview designed to elicit details of their flights, available equipment in the

aircraft they were flying, and their previous flight experience. A copy of the interview

form is included in appendix D. Much of the information collected from nonaccident

pilots corresponded to information typically collected as part of Safety Board accident

investigations. No personally identifiable information pertaining to nonaccident pilots was

retained after the collection of study-related data.

Accident Data

Every effort was made to assemble matching data concerning both the accident

and nonaccident flights. Safety Board accident investigators routinely collect a core set of

factual data for aviation accident investigations and for populating a census of all U.S.

civil aviation accidents. This census, known as the Aviation Accident/Incident Database,

includes details about accident events (for example, time, location, and weather

Figure 3. Screenshot of flight tracking software depicting weather, 

an accident aircraft, and potential nonaccident matches.

accident 

aircraft

potential

nonaccident 

matches
Chapter 4 18 Safety Study

conditions), aircraft (for example, model type, inspection records, and engine

specifications), and pilots (for example, certificates, ratings, and flight hours flown).

Most of the data needed for this study were available using the Aviation

Accident/Incident Database. For data not typically collected during accident

investigations, the investigator completed a supplemental form and sent it to the study

managers. The supplemental form, shown in appendix E, requested such information as

the number of instrument instruction hours received and whether the aircraft had various

equipment used to display navigation and weather information.

Additional Data Sources

Weather Data

To determine the forecast weather conditions for each accident, Safety Board

meteorologists requested weather products that were released immediately before the

accident airplaneís departure time for the region surrounding the accident location. The

actual conditions at the time and location of the accident were determined from the Safety

Board factual report associated with the accident. (As part of all factual reports,

investigators identify the ìbasic weatherî conditions as either IMC or VMC.) A

subsequent analysis, described in appendix F, found that in many cases, the weather at the

time of the accident was similar to forecast conditions.

Pilot History

FAA records were used to obtain a variety of historical data for both accident and

nonaccident pilots, including previous accidents, incidents, and violations, as well as the

results of all knowledge and practical tests. Testing records included the type (for example,

private, instrument, or commercial), date, and outcome (pass or fail) of each practical and

knowledge test taken by a pilot. Practical test records included each test attempted, the

outcome of each test, and the flight hours reported by the applicant at the time of the test.

Knowledge test reports were copies of the results presented to test applicants, which typically

include the number of tests attempted and the percentage score for the most recent attempt. 

Additional pilot data, such as certificates, ratings, and total flight hours reported

when pilots renew their medical certificate, were also obtained from the FAA Airmanís

Registry. This information was used to substitute for missing data (for example, when log

books were destroyed in an accident.) 

Statistical Analyses

Study analyses involved initial comparisons of the accident and nonaccident

groups with regard to individual variables of interest, followed by development of a

multivariate prediction model. Using statistical methods typical of case control studies,
Chapter 4 19 Safety Study

initial comparisons were conducted using chi-square analyses, and the multivariate

prediction model was developed using binary logistic regression. All statistical analyses

were conducted using the SPSS statistical package.35

Chi-Square Analysis

Data obtained from accident flights (cases) and from matching nonaccident flights

(controls) were used to compare accident risk based on factors specific to the pilot, flight,

and aircraft.36 Chi-square tests were used to determine the extent to which accidents and

nonaccidents differed on individual variables. Chi-square is a statistical test that can be

used to determine whether two or more samples differ significantly with respect to the

proportional distribution of a given characteristic or quality. Tests of statistical

significance provide a measure of the probability that a particular finding was due to

ìchance.î If that probability is found to be very low (for example, 5 percent or less), the

finding is considered statistically significant and thereby unlikely due to random

differences. Statistical significance tests are sensitive to the number of observations

included in the study sample, as well as to the size of any observed difference(s).

In the context of this study, chi-square statistics were used to determine whether

the study accident and nonaccident groups were different enough with regard to variables

of interest to suggest that study results represent GA weather accidents in general.

The following variables were selected for the chi-square analysis:

Pilot Information

ï Pilot age at the time of the accident 

ï Pilot age at the time of initial private certification

ï Years as pilot

ï Pilot highest certification level and instrument rating

ï Pilot flight hours

ï FAA knowledge test performance

ï FAA practical test performance

ï Accident/incident history

ï Violation history

Flight Information

ï Planned length of flight

ï Purpose of flight

35 SPSS for Windows, Rel. 13.0. 2004. Chicago: SPSS Inc.

36 A table containing data used in this study is available in the NTSB Docket Management System. 
Chapter 4 20 Safety Study

Aircraft Information

ï Aircraft ownership

ï Aircraft equipment

Binary Logistic Regression Analysis

Binary logistic regression was used to identify the variables that were most

predictive of accident involvement and to develop an overall accident prediction model.

Binary logistic regression evaluates the combined effect of a set of predictor variables on a

dichotomous outcome variable (for example, accident or nonaccident status). One

strength of binary logistic regression is that the results not only indicate which variables

are associated with accident involvement, but also provide an estimate of the relative risk

associated with different levels of a given predictor variableófor example, the accident

risk associated with flights of various lengths.37 For this study, predictor variables were

selected for inclusion in the regression model based on the initial findings from the chisquare tests, as well as on hypothesized relationships between specific variables and

weather-related accidents. 

37 For a more detailed discussion of binary logistic regression, refer to the following: (a) D. Hosmer and

S. Lemeshow, Applied Logistic Regression, 2nd ed. (New York: Wiley and Sons, 2000) or (b) B.G.

Tabachnick and L.S. Fidell, Using Multivariate Statistics, 3rd ed. (New York: Harper Collins, 1996).
21 Safety Study

Chapter 5

Results

Description of Study Accidents

Study data were collected for GA accidents that occurred between August 1, 2003,

and April 30, 2004,38 that appeared, at the time of initial notification, to involve hazardous

weather or visibility-related factors. A total of 72 accidents met the predefined selection

criteria and were selected for the

study.39 Of these, 78 percent

were fatal accidents that resulted

in a total of 108 fatalities.

Figure 4 shows the

distribution of study accidents by

month and figure 5 by time of

day. About 41 percent of

accidents occurred at night and

59 percent during daylight.

Additionally, about 56 percent

were operating on an instrument

flight plan and 44 percent

operated under VFR. A review

of the narrative data available for

the 72 study accidents showed

that 7 occurred during takeoff or

climb, 23 during cruise flight, 17

during descent or maneuvering

flight, and 25 during approach,

landing, or go-around (figure 6). 

Pilot Information

Accident Pilots 

Accident pilots ranged in age from 23 to 81, with a mean age of 53, and all pilots

but one were male. Accident pilot training records showed that the mean number of years

38 Between August 1, 2003, and April 30, 2004, the Safety Board investigated a total 1,129 GA

accidents involving 1,144 aircraft. Of these, 226 were fatal accidents that resulted in a total of 381 deaths.

39 Refer to appendix G for a list of the accidents included in this study.

On December 7, 2003, about 1708 Pacific standard time, a

Piper PA-28R-200, N16264, collided with hilly terrain about 6

miles southwest of Chino Hills, California. The private pilot

and passenger were fatally injured and the airplane was

destroyed. Instrument meteorological conditions prevailed in

the accident area, and no flight plan had been filed

(LAX04FA061).
Chapter 5 22 Safety Study

as pilot at the time of the accident was approximately 18 years and the mean age at which

accident pilots received their first pilot certificate was 35 years. Of the 72 accident pilots,

4 percent held airline transport pilot certificates, 32 percent commercial pilot certificates,

61 percent private pilot certificates, and 3 percent student pilot certificates. As shown in

figure 7, the distribution of study accident pilots by highest certificate was similar to the

Figure 4

Figure 5

Distribution of Study Accidents by Month

0

5

10

15

20

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

Distribution of Study Accidents

by the Time of Occurrence

0

2

4

6

8

10

12

0001-01000101-02000201-03000301-04000401-05000501-06000601-07000701-08000801-09000901-10001001-11001101-12001201-13001301-14001401-15001501-16001601-17001701-18001801-19001901-20002001-21002101-22002201-23002301-0000
Chapter 5 23 Safety Study

distribution of pilots involved in weather-related accidents from 1983 through 2001.40 In

comparison, 2003 FAA airman registry data41 indicated that 23 percent of active pilots at

that time held airline transport pilot certificates, 20 percent commercial pilot certificates,

39 percent private pilot certificates, and 14 percent student pilot certificates.42

Approximately 68 percent of accident pilots were rated for instrument flight, compared to

the 51 percent of the active pilot population who held an instrument rating. 

Figure 6

40 Price and Groff (2005). 

41 U.S. Department of Transportation, Federal Aviation Administration, U.S. Civil Airmen Statistics, 2003,

available online at<http://www.faa.gov/data_statistics/aviation_data_statistics/civil_airmen_statistics/>.

42 The remainder includes recreational pilot, rotorcraft (only), and glider (only) certificates.

Figure 7

Distribution of Study Accidents by Phase of Flight

Takeoff/Climb Cruise Descent/Manuever Approach/Landing/Go-around

7 23 17 25

Comparison of Study Pilots to Population Totals

and Previous Accident Research

0%

20%

40%

60%

80%

100%

Student Private Commercial Airline Transport

2003 Active

Pilots

(FAA Registry)

Current Study

Nonacc Pilots

Weather Acc

Pilots

1983-2001

(Price & Groff, 2005)

Current Study

Acc Pilots
Chapter 5 24 Safety Study

Nonaccident Pilots

Interviews were conducted with 135 pilots of matching nonaccident flights.

Nonaccident study participants included 131 male and 4 female pilots, ranging in age from

19 to 74 years, with a mean age of 46 years. The mean number of years as a pilot was

approximately 18 years for the nonaccident group, and the mean age at which nonaccident

pilots received their first pilot certificate was 28 years. 

Data pertaining to pilot age at the time of the flight, years as pilot, and age at first

certificate were categorized in four groups43 for analysis (figures 8, 9, and 10). The chisquare test indicated a significant difference between the accident and nonaccident groups

with regard to age at the time of accident, χ2 (3, N = 207) = 12.33, p < .01.44 Specifically,

the nonaccident group included a higher percentage of pilots in the youngest (≤40) group,

while the accident group included a higher percentage of pilots in the oldest (>60) group.

However, there was no corresponding difference in the years of piloting experience

between the accident and nonaccident groups, χ2 (3, N = 207) = 1.52, p = .679. The

accident and nonaccident pilots did differ significantly by the age at which they first

obtained their pilot certificates, χ2 (3, N = 207) = 22.62, p < .001. Figure 10 illustrates that

a higher percentage of nonaccident pilots received their first pilot certificates before age 25,

while the percentages represented in all other age groups were higher for accident pilots. . 

43 Continuous variables were divided into discrete variables for analysis to simplify interpretation of

results. Discrete variable categories were determined by dividing continuous values into quartiles. The

resulting category cut-points were adjusted as necessary to create meaningful groups.

44 In this study, results were considered statistically significant if the probability of the result being due

to chance was less than 5 percent (p < .05).

Figure 8

Distribution of Study Pilots by Age at Accident

0%

20%

40%

60%

80%

100%

≤40 40.1-50 50.1-60 >60

Accident Nonaccident
Chapter 5 25 Safety Study

As shown in figure 7, 27 percent of the nonaccident pilots held airline transport

pilot certificates, 37 percent commercial pilot certificates, 35 percent private pilot

certificates, and 1 percent student pilot certificates. The chi-square analysis compared

pilots with student or private pilot certificates to those with commercial or transport pilot

Figure 9

Figure 10

≤5 5.1-15 15.1-25 >25

Distribution of Study Pilots by

Years of Pilot Experience

0%

20%

40%

60%

80%

100%

Accident Nonaccident

Distribution of Study Pilots

by Age at First Certificate

0%

20%

40%

60%

80%

100%

Accident Nonaccident

≤25 25.1-35 35.1-45 >45
Chapter 5 26 Safety Study

certificates and found a significant difference between the accident and nonaccident

groups, χ2 (1, N = 207) = 15.21, p < .001, with a higher proportion of student and private

pilots in the accident group. Additionally, about 90 percent of pilots in the nonaccident

group held an instrument rating, compared to 68 percent of pilots in the accident group.

The proportion of pilots with instrument ratings differed significantly for the accident and

nonaccident groups, χ2 (1, N = 207) = 16.28, p < .001.

Pilot Flight Hours

For most flight hour variables (for example, total time in aircraft make and model,

actual instrument time, and time in the last 90 days), statistical comparisons could not be

calculated because flight hour data for a large number of accident pilots were unavailable

due to incomplete or missing pilot logs. The most commonly available information was

that for total flight hours in all aircraft, partly because pilots are asked to report this

information when renewing a medical certificate. Using this information, study managers

were able to estimate total flight hours for accident pilots whose logbooks could not be

recovered. The median total number of flight hours for the accident group (1,300 hours)

was lower than the median total flight hours for the nonaccident group (2,270 hours).

However, when pilots were divided into groups for analysis by total flight hours (shown in

figure 11), the distributions were not found to be significantly different for the accident

and nonaccident pilot groups, χ2(3, N = 207) = 3.89, p = .274.

Figure 11

Total Flight Hours of Study Pilots

0%

20%

40%

60%

80%

100%

≤500hrs 500.1-1500hrs 1500.1-3000hrs >3000hrs

Accident Nonaccident
Chapter 5 27 Safety Study

Pilot Testing History

Using test information for all accident and nonaccident pilots involved in the

study, study managers calculated separate knowledge and practical test pass rates for each

pilot using the results of his or her private, commercial, and instrument test(s). To allow

them to compare the testing history of all study pilots regardless of the number of tests

taken, study managers determined a ìcumulative pass rateî by dividing the total number

of written or practical tests passed by the total number of tests a pilot had taken.

Knowledge and practical test records indicated that accident pilots had a mean cumulative

pass rate of 86 percent for knowledge tests (max = 100 percent, min = 30 percent) and, for

practical tests, a mean cumulative pass rate of 84 percent (max = 100 percent, min = 43

percent). Pilots in the nonaccident control group had a mean cumulative pass rate of 95

percent (max = 100 percent, min = 59 percent) for knowledge tests and, for practical tests,

a mean cumulative pass rate of 95 percent (max = 100 percent, min = 50 percent). 

Pilots were divided into two groups for the statistical analysis: a ìhigh pass rateî

group for all pilots with a cumulative pass rate of 70 percent or higher and a ìlow pass

rateî group for those with a cumulative pass rate of less than 70 percent. As shown in

figures 12 and 13, larger percentages of accident pilots were in the low pass rate group for

both knowledge and practical tests. For the practical test, this difference between accident

and nonaccident pilots was statistically significant, χ2

 (1, N = 207) = 4.42, p = .036, with

28 percent of accident pilots and 16 percent of nonaccident pilots falling into the low pass

rate group. The difference in knowledge test pass rates between the groups was

marginally significant, χ2 (1, N = 207) = 3.75, p = .053. 

Figure 12

Practical Test Pass Rate of Study Pilots

(private, instrument, and commercial pilot tests)

0%

20%

40%

60%

80%

100%

Accident Nonaccident

≥70% <70%
Chapter 5 28 Safety Study

Accident, Incident, and Violation History

A review of the accident and incident history of study pilots indicated that 19

percent of accident pilots had an accident or incident before the study accident. In four of

these cases, the event included in the study was the pilotís third recorded mishap. In

contrast, figure 14 shows that a smaller proportion of pilots in the nonaccident control

group were ever involved in an accident or incident. The differences in accident and

incident history between groups was statistically significant, χ2 (1, N = 207) = 3.99, p =

.046, with a larger percentage of accident pilots having been involved in a prior

occurrence.

In addition to accidents and incidents, FAA records indicated that 6 of the 72 study

accident pilots had civil aviation violations on their records, in contrast to only 3 of the

135 nonaccident pilots. The descriptive comparison suggests that a higher percentage of

accident pilots had violation records, but because of the small numbers of all study pilots

with violations, statistical analyses were not conducted for these values.

Flight Information

Planned Length of Flights

The mean planned length of accident flights was 232 nautical miles, compared to a

mean of 162 nautical miles for nonaccident flights. Study flights were separated into four

groups according to the length of the planned flight (figure 15). Results of the chi-square

analysis indicated a significant difference between the accident and nonaccident flights

Figure 13

Knowledge Test Pass Rate of Study Pilots

(private, instrument, and commercial pilot tests)

0%

20%

40%

60%

80%

100%

Accident Nonaccident

≥70% <70%
Chapter 5 29 Safety Study

with regard to the intended length of flights, χ2 (3, N = 207) = 8.25, p = .041. As figure 15

shows, the accident group included a higher percentage of planned flights in the longest

group (>300nm), and the nonaccident group included a higher percentage of flights in the

shortest planned length group (≤50nm).

Figure 14

Figure 15

Accident/Incident History of Study Pilots

0%

20%

40%

60%

80%

100%

Accident Nonaccident

No Prior Acc/Inc Prior Acc/Inc

Distribution of Study Flights by Planned Length

0%

20%

40%

60%

80%

100%

Accident Nonaccident

≤50nm 50.01-150nm 150.01-300nm >300nm
Chapter 5 30 Safety Study

Purpose of Flight

As for the purpose of flight, the available information indicated that 17 percent of

accident flights were being operated for pay, and the remaining 83 percent were unpaid

operations. In contrast, 33 percent of the matching nonaccident flights were conducted for

pay, and the remaining 67 percent were unpaid. Analysis results indicated a significant

difference between the groups, χ2 (1, N = 207) = 6.54, p = .011. The differences in

proportion of paid flights are illustrated in figure 16.

Aircraft Information

Aircraft Ownership

As shown in figure 17, 76 percent of the aircraft involved in study accidents were

owned by the pilot either directly, through a limited liability corporation, or through

shared ownership. About 10 percent of accident aircraft were rented, and the remaining 14

percent were owned by the pilotís employer or another entity. In comparison, 56 percent

of the nonaccident aircraft were owned by the pilot, 13 percent were rented, and

approximately 30 percent were owned by the pilotís employer or another entity.45

Differences in aircraft ownership between the accident and nonaccident groups were

statistically significant, χ2

 (2, N = 207) = 8.68, p = .013.

Figure 16

45 Values do not sum to 100 percent due to rounding.

Distribution of Study Flights by Purpose of Flight

0%

20%

40%

60%

80%

100%

Accident Nonaccident

Non-paid Paid
Chapter 5 31 Safety Study

Aircraft Equipment 

Pilot interviews, aircraft records, and examinations of accident aircraft wreckage

were used in combination to collect information about the equipment on board accident

and nonaccident aircraft. The equipment information available for accident aircraft was

markedly less than for nonaccident aircraft. Fifteen of the accident aircraft in this study, or

about 21 percent, sustained impact and/or post-crash fire damage so extensive that little or

no information was available about aircraft avionics. For many of the accident aircraft,

only partial equipment information was available from aircraft maintenance logs and

repair and alteration records.46 The extent of missing data for accident cases, and the lack

of information about equipment use at the time of the accident, prevented study managers

from making meaningful comparisons of accident and nonaccident aircraft equipment. 

Summary of Chi-Square Analysis

Overall, the chi-square analysis identified several variables indicating significant

differences between the accident and nonaccident groups: 1) age at accident, 2) age at first

certificate, 3) highest certification, 4) instrument rating, 5) practical test cumulative pass

rate, 6) accident/incident history, 7) planned length of flight, 8) purpose of flight, and 9)

aircraft ownership. 

Binary Logistic Regression Model

Following the individual comparisons, a binary logistic regression model was

developed based on the results of the chi-square analyses and relationships hypothesized by

Figure 17

46 As reported on FAA form 337, Major Repair and Alteration.

Distribution of Study Aircraft by Ownership

0%

20%

40%

60%

80%

100%

Accident Nonaccident

Other Own Rent
Chapter 5 32 Safety Study

other researchers. The decision to include an individual variable in the logistic regression

model was ultimately made based on the resulting effect on the ability of the model to

predict accident/nonaccident status. In some cases, variables were included (for example,

total flight time) because, although not statistically significant on their own, they added to

the overall predictive capability of the regression model. In other cases, the strongest

predictor was selected from two or more related variables (for example, age at private

certificate instead of age at accident). Table 1 lists each of the variables included in the final

binary logistic regression model, along with the results of the logistic regression analysis.

An overall test of the logistic regression model significance was calculated using a

chi-square test of the model coefficients. The results of that test indicated that the model

was statistically significant, χ2

 (16, N = 207) = 57.45, p < .001. The results of the logistic

regression were also evaluated with regard to how accurately the model classifies accident

and nonaccident flights. In this case, the logistic regression model resulted in an overall

classification success rate of 77 percent (accurately identifying 121 of 135 nonaccidents

and 38 of 72 accidents) compared to 65 percent without the model. 

The significance of individual variables within the model was assessed using the

Wald chi-square statistic, which tests the unique contribution of each variable. The Wald

statistic is interpreted like the chi-square comparisons presented earlier. Of the variables

entered into the model, planned length of flight, pilot age at first certificate,

accident/incident history, and instrument rating were identified as unique and statistically

significant predictors of accident involvement. Table 1 includes the Wald statistic and

significance for all variables, and levels of variable, in the logistic regression.

For each predictor variable, the binary logistic regression analysis also produced

odds ratios that reflected the relative accident risk associated with different levels of the

variable. An odds ratio is interpreted as a comparison of the risk associated with each level

of a variable with the selected reference. For example, if a variable has two levels (for

example, yes and no), and the comparison of one level of the variable (for example, yes) to

the level chosen as the reference (for example, no) results in an odds ratio of 2.0, the risk

of involvement in a weather-related GA accident for a flight with that characteristic is

twice as high as a flight that does not share that trait. The rightmost column of table 1

indicates the odds ratios associated with each level of variable.

Flight Leg Length

In comparison to a flight of 50 nautical miles (nm) or less, pilots on flights of

50.01 to 150 nm were 2.9 times more likely to be involved in a weather-related GA

accident, and those on flights of more than 300 nm were 4.7 times more likely to be

involved in a weather-related accident.
Chapter 5 33 Safety Study

Table 1
Chapter 5 34 Safety Study

Age at Private Certificate

Pilots with the lowest risk of accident involvement were those who received their

private certificates at or before age 25. Pilots who received their private certificates between

age 25 and 35 were found to be at 4.5 times greater risk than those in the youngest group of

being involved in a weather-related accident, and those who received their certificates between

35 and 45 were at 4.8 times greater risk. Pilots who received their licenses after age 45 were 3.4

times more likely than the youngest group to be involved in a weather-related accident.

Prior Accident/Incident Involvement

Pilots with a history of any type of accident or incident were found to be 3.1 times

more likely to be represented in the accident group than pilots with no such history.

Instrument Rating

Not having an instrument rating was associated with significantly higher accident

risk. Specifically, pilots who did not hold an instrument rating were found to be 4.8 times

more likely than instrument-rated pilots to be involved in a weather-related accident. 
Chapter 6 35 Safety Study

Chapter 6

Discussion

This study compared GA

accident flights that occurred in

reduced visibility conditions

(ìweather-related accidentsî)

with a corresponding set of nonaccident GA flights and

identified several pilot- and

flight-related factors that are

associated with increased risk of

accident involvement. This section focuses on several factors

that distinguished accident from

nonaccident pilots including their

age, flight training, and performance history. It also discusses

the sources of weather information used by all GA pilots in this

study. The recommendations

issued as a result of the study

findings focus on three specific

issue areas:

1. Ensuring a minimum level of proficiency for all pilots to recognize and safely

respond to hazardous weather situations.

2. Identifying and providing additional support for pilots whose performance

history indicates an increased risk of weather-related accidents.

3. Providing GA pilots with additional guidance regarding sources of preflight

weather information.

Age-Related Differences

The relationship between pilot age and accident risk has been the subject of

research and debate, especially as it relates to the mandatory retirement age for Part 121

flight operations. Studies of age-related risk are subject to methodological choices and 

On January 19, 2004, about 0106 eastern standard time, a

Piper PA-28-181, N298PA, impacted trees, a power line, and

the ground while on an instrument landing system approach to

the Saint Lucie County Airport, Fort Pierce, Florida. The

certificated flight instructor and the private pilot-rated student

were fatally injured, and a private-pilot rated passenger

received serious injuries. Instrument meteorological

conditions prevailed at the time and an instrument flight rules

flight plan was filed for the 14 CFR Part 91 instructional flight

(MIA04FA045).
36 Safety Study

analytical issues that can substantially affect the resulting conclusions.47 As a result, prior

studies of age-related aviation risk have produced remarkably different findings, including

a linear increase in risk with age,48 a decreasing risk with age,49 or no relationship between

age and accident risk.50

The analysis in this study identified significant differences between accident pilots

and nonaccident control group pilots with respect to age, but the groups were not found to

be significantly different in experience as measured in years as a pilot or total flight hours.

The combination of these results indicated that pilots in the nonaccident group started

flying earlier in life, on average, than accident pilots. This finding was supported by the

chi-square analysis finding that showed a significant difference between the accident and

control groups with respect to age at certification, and the logistic regression analysis that

identified pilot age at private certificate as a significant predictor of accident risk. Based

on the results of these analyses, the Safety Board concludes that pilots who start flying

earlier in life are at lower risk of being involved in a weather-related GA accident than

those who start flying when they are older, and age at first certificate is a better predictor

of future accident involvement than age at time of flight.

The changes in cognitive and physical functioning that occur with aging are well

documented.51 Conditions typically associated with age-related performance decrements,

such as visual impairment or decreased mobility, are generally considered to begin about

age 60, and an age-related increase in driving risk has been identified after age 75.52

However, this study identified a significantly lower risk for pilots who began flying at age

25 or younger. Therefore, the Safety Board concludes that the observed connection

between age and accident risk in this study is not likely due to physical aging issues, but to

other factors associated with the age at which a person starts flight training.

47 For a discussion of the specific methodological issues facing studies of age-related aviation risk, see

the following: (a) D. Broach, Methodological Issues in the Study of Airplane Accident Rates by Pilot Age:

Effects of Accident and Pilot Inclusion Criteria and Analytic Strategy, DOT/FAA/AM-04/8 (Washington,

DC: FAA Office of Aerospace Medicine, 2004); and (b) G. Li, ìPilot-Related Factors in Aircraft Crashes: A

Review of Epidemiologic Studies,î Aviation, Space, and Environmental Medicine, 65 (1994): 979-85.

48 D. Broach, Methodological Issues in the Study of Airplane Accident Rates by Pilot Age: Effects of

Accident and Pilot Inclusion Criteria and Analytic Strategy, DOT/FAA/AM-04/8 (Washington, DC. FAA

Office of Aerospace Medicine, 2004).

49 E.J. Kay, D.J. Hillman, D.T. Hyland, R.S. Voros, R.M. Harris, and J.D. Deimler, Age 60 Rule

Research, Part III: Consolidated Data Base Experiments Final Report, DOT/FAA/AM-94/22 (Washington,

DC: FAA Office of Aerospace Medicine, 1994).

50 G. Li, S.P. Baker, J.G. Grabowski, Y. Qiang, M.L. McCarthy, and G.W. Rebok, ìAge, Flight

Experience, and Risk of Crash Involvement in a Cohort of Professional Pilots,î American Journal of

Epidemiology, 157 (2003): 874-880.

51 For reviews of aging literature, see the following: (a) A.D. Fisk and W.A. Rogers (eds.), Handbook

of Human Factors and the Older Adult (San Diego, CA: Academic Press: 1997); (b) D.J. Hardy and R.

Parasuraman, ìCognition and Flight Performance in Older Pilots,î Journal of Experimental Psychology:

Applied 3(4) (1997): 313-348; or (c) T.A. Salthouse, Adult Cognition: An Experimental Psychology of

Human Aging (New York: Springer-Verlag, 1982).

52 G.H. Li, E.R. Braver, and L.H. Chen, ìFragility Versus Excessive Crash Involvement as

Determinants of High Death Rates per Vehicle-Mile of Travel Among Older Drivers,î Accident Analysis

and Prevention, 35(2) (2003): 227-235.
Chapter 6 37 Safety Study

Although there may be several reasons for this finding, one of the likely differences

between pilots who begin flying at different ages is their motivation for learning to fly and

what they plan to do with their flying privileges. These factors can affect initial choices

about the type of flight training pilots pursue and also have implications for the type of

flying environment and oversight they will encounter over the long-term. 

Many pilots who invest the time and money to learn to fly during their late teens or

early twenties may do so with the intention of pursuing a career in aviation. In contrast,

pilots who start flying in their thirties or later may be more likely to pursue flying for

pleasure or personal transportation rather than as a potential career path. Support for this

suggestion comes from this studyís findings that nonaccident pilots had higher levels of

certification, were more likely to be conducting paid flight operations, and were more

likely to be flying an airplane belonging to someone else rather than their own airplane.

The differences between pilots pursuing a career in aviation and those who fly for

recreation or personal travel extend beyond flight hours and the equipment they operate,

and those differences may explain the study findings.

Flight Training Differences 

Many persons who start flight training with the intent of becoming paid

professional pilots engage in full-time flight training that typically results in a regular

schedule for practicing and testing knowledge and skills, regular oversight, and an

immersion in the aviation environment. A typical professional pilot curriculum culminates

with a commercial pilot certificate, multiengine rating, and either flight instructor or

instrument flight instructor certificate. For these pilots, milestones like the private

certificate or instrument rating are steps leading to the higher levels of experience and

certification necessary for employment. Pilots who go on to find employment in aviation

are subject to additional scrutiny and requirements from third parties such as their

employers, the aircraft owners, their customers, and passengers.

Conversely, persons not training for a career in aviation may be more likely to train

part-time with instructors at local airport FBOs or flight schools, and to have longer

intervals between training sessions. Persons who pursue flying for recreation or personal

travel may view the private pilot certificate or instrument rating as a finalónot a firstó

step in flight training. Pilots who do not pursue higher levels of certification are expected

to maintain and improve their skills and knowledge on their own through regular flight

activity. Unlike the direct and indirect oversight of most paid flight operations, pilots

engaging in personal or business flight operations are required to fly with instructors again

only to satisfy the flight review requirement of 14 CFR 61.56.53 Consequently, the safety

of personal flight operations may be more dependent on the skill, ability, and judgment of

individual pilots.

53 Although nonregulatory, many aviation insurance companies stipulate additional recurrent training in

order to maintain policies and/or favorable rates.
Chapter 6 38 Safety Study

Periodic training is an important part of maintaining and increasing knowledge and

skills, and this seems to be particularly true for weather-related information and flight

operations. For example, a survey study of the general weather knowledge of GA pilots54

found no differences related to total hours of experience or experience during the previous

6 months after correcting for the highest level of pilot training/certification. These findings prompted the study author to conclude the following:

It appears that pilots generally require formal training to obtain weather

knowledge and cannot be expected to acquire it on their own as they simply gain

more flight experience.

To obtain any pilot certificate, applicants are required to demonstrate aeronautical

knowledge and skills related to identifying hazardous weather, obtaining and interpreting

weather information, and performing associated decision-making tasks. After initial

certification, the only specific weather-related requirement applies to instrument-rated

pilots, who must maintain a minimum level of flight activity in order to exercise the

privileges of that rating. The results from this study and previous research suggest that

flight activity alone may not be sufficient to enable pilots to maintain or improve their

ability to avoid hazardous weather conditions. The Safety Board concludes that periodic

training and evaluation may be necessary to ensure that pilots maintain weather-related

knowledge and skills.

The Safety Board therefore recommends that the FAA add a specific requirement

for all pilots who do not receive weather-related recurrent training, that the biennial flight

review include the following: recognition of critical weather situations from the ground

and in flight, procurement and use of aeronautical weather reports and forecasts,

determination of fuel requirements, and planning for alternatives if the intended flight

cannot be completed or delays are encountered.

In addition, pilots who were required to demonstrate a minimum level of

proficiency in flight by reference to aircraft instruments for certification should maintain

that minimum proficiency. Therefore, the Safety Board also recommends that the FAA

should, for pilots holding a private, commercial, or airline transport pilot certificate in the

airplane category who do not receive recurrent instrument training, add a specific

requirement that the biennial flight review include a demonstration of control and

maneuvering of an airplane solely by reference to instruments, including straight and level

flight, constant airspeed climbs and descents, turns to a heading, and recovery from

unusual flight attitudes. 

54 B. Burian, General Aviation Pilot Weather Knowledge and Training, final report of the FAA, grant

#00-G-020 (2002).
Chapter 6 39 Safety Study

Testing, Accident, and Incident History

A history of mishaps and/or violations has been shown to be an indicator of an

individualís future accident risk in both driving55 and aviation,56 and is a key component for

the actuarial calculations used to set vehicle insurance rates and demerit-based law

enforcement programs. Less is known about the relationship between airman test

performance and aviation accident risk; however, a 2004 Safety Board accident investigation

report suggested that multiple test failures are an indicator of poor pilot proficiency.57

Airman Knowledge and Practical Test Requirements

To obtain pilot certifications and ratings, airmen must pass knowledge and

practical tests. Knowledge tests are designed to assess an applicantís understanding of the

information that is necessary to exercise the privileges of a particular certificate or rating.

Using a computerized testing system, the FAA administers over 100,000 knowledge tests

each year at hundreds of testing centers. Three knowledge testsóthe private pilot

airplane, commercial airplane, and airplane instrument ratingóaccount for almost half of

all knowledge tests administered. Once airmen have passed a written test, received

appropriate flight training, and obtained an instructorís endorsement, they are eligible to

take the corresponding practical test. Practical tests, typically administered by FAAdesignated pilot examiners, are designed to evaluate pilotsí ability to apply their

knowledge and skills in the actual flying environment.

As an example of FAA airman certification requirements, pilots who wish to add an

instrument rating to their private or commercial certificates must pass both the instrument

rating airplane knowledge test and the practical test. In 2004, the FAA administered 13,794

knowledge tests for the instrument airplane rating, and 93 percent of these tests received a

passing score.58 The test has 60 multiple-choice questions59 representing multiple

ìknowledge areas,î such as general aeronautical information, navigation using instruments,

and aviation weather. The applicant must receive a score of 70 percent or higher to pass.

55 L.S. Robertson and S.P. Baker, ìPrior Violation Records of 1,447 Drivers Involved in Fatal Crashes,

Accident Analysis and Prevention, 7 (1975), 121-128.

56 (a) D.R. Hunter, ìRetrospective and Prospective Validity of Aircraft Accident Risk Indicators,î

Human Factors, 43(4) (2001): 509-518; (b) G. Li and S.P. Baker, ìCrash and Violation Experience of Pilots

Involved in Prior Commuter and Air Taxi Crashes: A Historical Cohort Study,î Aviation, Space, and

Environmental Medicine, 66, 1131-35; and (c) G. Li and S.P. Baker, ìPrior Crash and Violation Records of

Pilots in Commuter and Air Taxi Crashes: A Case-Control Study,î Aviation, Space, and Environmental

Medicine, 65 (1994), 979-85.

57 National Transportation Safety Board, In-Flight Engine Failure and Subsequent Ditching, Air

Sunshine, Inc., Flight 527, Cessna 402C, N314AB, About 7.35 Nautical Miles West-Northwest of Treasure

Cay Airport, Treasure Cay, Great Abaco Island, Bahamas, July 13, 2003, Aircraft Accident Report

NTSB/AAR-04/03 (Washington, DC: NTSB, 2004).

58 See <http://av-info.faa.gov/data/teststat/04volume.htm>. Pass rate data were not available for the

private pilot instrument practical test.

59 The 60 questions are selected from a test bank of over 700 questions.
Chapter 6 40 Safety Study

FAA practical test standards for obtaining an airplane instrument rating require that

pilot applicants be assessed on eight ìareas of operationî that include topics such as

preflight procedures, flight by reference to instruments, and emergency operations. Within

those areas of operation, pilots must demonstrate proficiency by performing specific tasks,

including an instrument cockpit check, basic instrument flight maneuvers, several

instrument approach procedures, and emergency operations. In addition to demonstrating

competency in each required task, applicants must successfully respond to an oral test,

show overall proficiency, and exhibit good use of aeronautical decision-making.

Applicants who fail the knowledge or practical test receive a notice of disapproval

that specifies the knowledge areas with incorrect answers or areas of operation in which

tasks were not performed satisfactorily. According to 14 CFR 61.49, before re-taking a

failed knowledge or practical test, applicants must receive additional training and

endorsement from an authorized instructor stating that they are proficient to pass the test.

Test Performance and Accident Risk

In this study, pilots were grouped into high- and low-pass-rate groups depending

on their past performance on knowledge and practical tests. Overall, higher percentages of

accident pilots were represented in the low-pass-rate group for both the knowledge and the

practical test. Results of the chi-square analyses indicated a significant difference

between the accident and nonaccident groups, suggesting a relationship between test

performance and subsequent accident involvement. Therefore, the Safety Board

concludes that knowledge and practical test failures are both associated with a higher risk

of a pilot being involved in a weather-related GA accident.

The Safety Board also notes that, unlike the practical test standards in which failure

of one ìarea of operationî is grounds for failure of the entire test, no minimum number of

questions must be answered correctly within a given ìknowledge areaî on the knowledge

test. For example, an average of 12 out of 60 questions on the private pilot certification

knowledge test are weather-related.60 A pilot could answer all 12 questions incorrectly and

still receive a score as high as 80 percent, which is well above the minimum passing score of

70 percent. The Safety Board concludes that a pilot can incorrectly answer all questions

relating to weather on an airman knowledge test and still receive a passing score on the test. 

The Safety Board believes that a basic understanding of aviation weather is an

important prerequisite to obtaining any pilot certificate or rating. Therefore, the Safety

Board recommends that the FAA establish a minimum number of weather-related

questions that must be answered correctly in order to pass FAA airman knowledge tests.

The establishment of such requirements will further ensure that pilots who pass a

knowledge test will have demonstrated a basic understanding of aviation weather.

For pilots who repeatedly fail knowledge or practical tests, failure limits may be

appropriate. The Safety Board suggested the potential need for such a limit during the

60 According to the FAA Airman Testing Standards Branch, there are 10 versions of the private pilot

airplane knowledge test, and the number of questions pertaining to weather range from 11 to 13.
Chapter 6 41 Safety Study

investigation of a fatal accident on July 13, 2003, involving a Cessna 402C operated as an

Air Sunshine commuter flight that ditched in the Atlantic Ocean following an in-flight

engine failure.61

A review of FAA records revealed that over a 15-year period, the pilot involved in

that accident had failed nine practical tests. Specifically, the pilot had failed two practical

tests for his private pilot certificate, one practical test for his instrument pilot rating, one

practical test for his airline transport pilot certificate, two practical tests for his flight

instructor certificate, and three practical tests for his instrument instructor certificate.62

The Safety Board concluded that ìthe pilot had a history of below-average proficiency

before the accident flight, including numerous failed FAA flight tests, which contributed

to his inability to maintain maximum flight performance and reach land after the right

engine failed.î

As a result of the Air Sunshine accident, the Safety Board recommended that the

FAA:

Conduct a study to determine whether the number of flight checks a pilot can fail

should be limited and whether the existing system of providing additional training

after a notice of disapproval is adequate for pilots who have failed multiple flight

checks. On the basis of the findings of the study, establish a flight check failure

limit and modify the recheck training requirements, if necessary. (A-05-02)63

The Air Sunshine accident is an example in which the pilotís poor test

performance may have indicated an underlying skill or knowledge deficit. If failure limits

or other measures had been in place when the Air Sunshine pilot undertook the

certification process, he might have been identified for remedial training or prevented

from flying.

Accidents and Incidents

During the same timeframe that data were being collected for the 72 accidents

included in this study, the Safety Board investigated a total of 1,129 GA accidents,

involving 1,144 pilots. In the 10 years from 1993 through 2002, an average of about 1 in

every 330 active pilots in the United States was involved in a GA accident annually. A far

greater number of pilots are involved in incidents each year that have less severe outcomes

but represent similar lapses in safety. Typically, pilots involved in accidents and incidents

are not seriously injured, and most continue to fly after being involved in these events. 

61 NTSB/AAR-04/03.

62 Cumulative pass rate, 36 percent.

63 Recommendation A-05-02 was issued on January 27, 2005, and its status is ìOpenóAwait

Response.î
Chapter 6 42 Safety Study

Pilot History of Accidents and Incidents

This study used FAA records to determine whether pilots with a history of

accidents or incidents are at an increased risk of future weather-related accidents. Analysis

of the accident and incident records for all study pilots showed significant differences

between the accident and incident histories for the accident and nonaccident pilots. Not

only were accident pilots significantly more likely to have had prior accidents and

incidents, several accident pilots had been involved in more than one accident or incident

before the study. Results of the logistic regression indicated that pilots involved in prior

accidents or incidents were about 3 times more likely to be involved in a weather-related

accident than pilots with no record of accidents or incidents. This finding is particularly

interesting because the increased risk was not limited to prior accidents and incidents

involving weather. Therefore, the Safety Board concludes that a history of accident or

incident involvement is associated with a higher risk of being involved in a future

weather-related GA accident. 

Tracking a Pilotís Testing and Accident/Incident History

The results of this study demonstrate that both poor test performance and prior

accident/incident involvement are linked to future accident involvement among GA pilots.

Prior accident and incident involvement may indicate a pattern of risk and operating

performance, whereas knowledge and practical testing performance may reflect an

airmanís overall training, knowledge, skills, and proficiency. These findings suggest a

possibility for reducing accidents by identifying pilots at increased risk for weather-related

accident involvement.

Currently, no formal requirements exist for tracking and reviewing GA pilot

performance histories. However, a 1996 law established such a system for air carrier pilots

after a series of Safety Board recommendations,64 and ultimately the action of United

States Congress, led to the Pilot Records Improvement Act (PRIA).

65 The intent of the

PRIA was to make operators aware of the performance history of potential employees so

that they could make appropriate hiring decisions about applicants who have exhibited a

pattern of performance problems or regulatory violations. Pilots with a history of testing

failures or violations are not restricted from engaging in flight operations by the PRIA, but

they may be subject to more scrutiny by potential air carrier employers than applicants

with better performance histories.

Once pilots are hired, the PRIA precludes employers from using pilotsí

preemployment records. However, as a means to identify pilots who may be at risk of

accident involvement, certain companies have established oversight programs that allow

them to identify and track pilots who have demonstrated performance deficiencies or

failures in the training environment. The Safety Board highlighted the importance of such

programs during its investigation of the December 18, 2003, accident involving Federal

64 A-88-141 (Superseded), A-88-145 (ClosedóAcceptable), A-89-004 (ClosedóAcceptable),

A-90-141 (ClosedóUunacceptable), A-90-144 (ClosedóAcceptable), A-93-014 (ClosedóUnacceptable).

65 Section 502 of Public Law 104-26.
Chapter 6 43 Safety Study

Express Flight 647, 66 and recommended that the FAA require all Part 121 air carrier

operators to establish similar programs. 67

Although there are currently no formal efforts to identify and track pilots with

patterns of performance that indicate they are at increased risk of weather-related GA

accidents, the results of this study suggest that it would be possible to use existing records

to develop such a program. Because of the associations between testing performance, past

accident and incident involvement, and future accidents, the Safety Board recommends

that the FAA develop a means to identify pilots whose overall performance history

indicates that they are at future risk of accident involvement, and develop a program to

reduce risk for those pilots.

Pilot Weather Briefing Sources and Methods

In addition to the statistical analyses conducted as part of this study, the numerous

nonaccident pilot interviews provided an opportunity to identify other weather-related

safety issues. One of those issues was the use of preflight weather information. A common

assumption is that pilots involved in weather-related accidents did not obtain adequate

preflight weather forecast information for their route of flight and were therefore unaware

of the weather conditions they encountered. In addition to attempting to determine if the

pilot had obtained weather forecast information before the flight, study managers also

tried to discover what sources the pilots used to obtain this information and the number of

sources they consulted before their flights. The intent of collecting this information was to

determine if the weather briefing activities of accident and nonaccident pilots varied

systematically and if certain activities were more predictive of accident involvement.

Information about accident pilotsí use of preflight weather was obtained by ASIs

as part of their normal investigations. When pilots were fatally injured, investigators

relied on documented briefings to determine if the pilots had obtained weather

information before their flights. Although the FAA maintains records of FSS transactions,

pilotsí use of other weather information provided via television, Internet, or satellite

sources is not typically documented. In 66 percent of the 72 study accidents, ASIs

reported that the pilot had received preflight weather information. However, it is likely

that some of the remaining 34 percent of accident pilots sought weather information that

could not be identified after their accidents.

Weather briefing information for nonaccident pilots was gathered during their

post-flight interviews, usually within 72 hours of a given flight, increasing the likelihood

that the pilotsí memories of their preflight activities were accurate. According to their

reports, 94 percent of nonaccident pilots had checked at least one source for weather

66 National Transportation Safety Board, Hard Landing, Gear Collapse, Federal Express Flight 647,

Boeing MD-10-10F, N364FA, Memphis, Tennessee, December 18, 2003, NTSB/AAR-05/01 (Washington,

DC: NTSB, 2005).

67 Recommendation A-05-014 was issued on May 31, 2005, and its status is ìOpenóAwait Response.î
Chapter 6 44 Safety Study

information before their flights, and 57 percent reported checking two or more sources.

FSS was the most widely reported source of weather information, used by 58 percent of

nonaccident pilots. Other sources, by order of use, were commercial satellite services

such as WSI or Meteorologix68 (28 percent), DUATS (25 percent), various Internet

websites (21 percent), automated services like ATIS, ASOS, or AWOS (14 percent), and

television (11 percent).

These data are consistent with survey research suggesting that pilots use a variety

of sources and products to gather information about weather before a flight.69 On the

surface, the nonaccident pilots may appear to be more likely to gather preflight weather

information. However, for the nonaccident pilots interviewed, 42 percent used only those

sources that may not have left any record in the case of an accident. This proportion is

even higher than the 34 percent of accident pilots for whom no weather briefing

information was found. Knowing this, study managers concluded that current methods do

not provide a means for determining if accident pilots are more or less likely than

nonaccident pilots to seek weather information before a flight. Furthermore, because of

the adverse weather conditions that were common to all flights in this study, both accident

and nonaccident pilots may have been more motivated to check weather and to check

multiple sources. 

A majority of accident and nonaccident pilots in this study had contacted FSS

before their flights, but most nonaccident pilots also reported checking other sources of

weather information to supplement their FSS briefings. For example, many nonaccident

pilots reported that they routinely use Internet and satellite services to obtain graphical

depictions of current and forecast conditions. This information was consistent with

previous surveys of GA pilots, which indicated that the pilots rely on a variety of weather

sources including sources that are not part of a standard FSS briefing. 

Pilots may choose to supplement the standard FSS briefing with weather

information from alternative sources for a number of reasons. With the proliferation of

websites and electronic sources that provide weather information, pilots can now easily

access detailed weather images that can be printed for use in the cockpit; they can also

access interactive tools that provide a more detailed representation of in-flight weather

conditions than would be available through oral or textual briefings. The Safety Board

concludes that GA pilots routinely consult alternative sources of aviation weather to

obtain information that is not currently available from a standard weather briefing. 

Part 91 regulations do not specifically require the use of any particular sources of

weather information for GA pilots, but do require that all pilots familiarize themselves

with weather and weather forecast information before beginning a flight. The instructions

given to pilots about how to obtain a good preflight weather briefing in FAA Advisory

68 WSI and Meteorologix are examples of commercial providers of weather products. Many airport

FBOs provide GA pilots with data connections to such services. 

69 D. B. Beringer and R. Schvaneveldt, ìPriorities of Weather Information in Various Phases of Flight,î

Proceedings of the Human Factors and Ergonomics Society 46th Annual Meeting (2002).
Chapter 6 45 Safety Study

Circular AC00-45E, ìAviation Weather Service,î are limited to FSS briefings and DUATS

and do not provide guidance on how to evaluate or select other sources of weather

information, and the FAA Aeronautical Information Manual identifies FSS and DUATS as

primary weather sources. Because FSS and DUATS are currently the only sources of

weather information endorsed by the FAA for use by GA pilots, it is important to ensure

that the information and services provided by those sources meet the needs of the GA pilot

community.

In February 2005, the FAA announced that it had selected a contractor to operate

the agencyís FSS system, which comprises 58 stations throughout the United States. At

the time of this report, the contractor is expected to take over the FSS operations in late

2005. The Safety Board believes that the transition to new management for the FSS

system is an opportune time for the FAA and its contractor to evaluate FSS methods for

providing weather information. For example, the FAA should seek to understand why

some pilots choose other sources over FSS briefings and to consider whether the FSS

system would benefit from an updating and/or broadening of the services and products it

provides. A better understanding of pilotsí weather needs would allow the FAA and its

contractor to improve the weather services and products they provide to pilots. The Safety

Board therefore recommends that the FAA determine optimal information presentation

methods and delivery systems for FSS weather information briefings, including the

possibility of supplementing or replacing some portions of the current standard weather

briefing with graphical data.

The results of study interviews suggest that many pilots use other sources to obtain

weather data not included in a standard briefing and then contact FSS or DUATS to fulfill

a perceived regulatory obligation. This creates the potential for pilot misinterpretation or

confusion if weather information gathered from various sources appears to be more

detailed than the FSS information. In some cases, the FAA and NWS contribute to this

potential confusion by providing detailed graphical weather products with disclaimers

indicating that the products are not suitable to meet the briefing requirement.70

Without specific guidance, some pilots may hesitate to consult electronic data

sources or may use sources that are not adequate to meet the intent of 14 CFR Part 91.103.

Therefore, the Safety Board recommends that the FAA revise guidance materials

associated with pilot weather briefings to include guidance for pilots in the use of Internet,

satellite, and other data sources for obtaining weather information suitable for meeting the

intent of 14 CFR Part 91.103 and subsequently inform the aviation community about this

change.

70 For example, the ìstandard briefingî section of NWS/FAA site www.aviationweather.gov contains

all of the information cited in AC00-45E as constituting a standard briefing, as well as additional graphical

weather products, yet it includes a disclaimer stating that it should be ìused for advisory purposes only.î
46 Safety Study

Summary

This study used the case control methodology to determine factors associated with

an increased risk of being involved in a weather-related GA accident. Within the context

of this study, the identified factors resulted in a statistically significant model of weatherrelated accident risk. Although study analysesóand the recommendations that resulted

from those analysesówere limited to the domain of weather-related GA accidents, it is

possible that study findings would generalize to the larger population of GA operations. 

Historic accident data suggest that reduced-visibility weather represents a

particularly high risk to GA operations. However, rather than being unique, weather may

simply test the limits of pilot knowledge, training, and skill to the point that underlying

issues are identified. Additional research is necessary to determine whether the identified

safety issues extend beyond weather, but it is likely that implementation of study

recommendations will improve the safety of GA in general.
47 Safety Study

Findings 

1. Pilots who start flying earlier in life are at lower risk of being involved in a weatherrelated general aviation accident than those who start flying when they are older, and

age at first certificate is a better predictor of future accident involvement than age at

time of flight.

2. The observed connection between age and accident risk in this study is not likely due

to physical aging issues, but to other factors associated with the age at which a person

starts flight training.

3. Periodic training and evaluation may be necessary to ensure that pilots maintain

weather-related knowledge and skills.

4. Knowledge and practical test failures are both associated with a higher risk of a pilot

being involved in a weather-related general aviation accident. 

5. A pilot can incorrectly answer all questions relating to weather on an airman

knowledge test and still receive a passing score on the test. 

6. A history of accident or incident involvement is associated with a higher risk of being

involved in a future weather-related general aviation accident. 

7. General aviation pilots routinely consult alternative sources of aviation weather to

obtain information that is not currently available from a standard weather briefing.
48 Safety Study

Recommendations

As a result of this safety study, the National Transportation Safety Board makes the

following recommendations to the Federal Aviation Administration: 

Add a specific requirement for all pilots who do not receive weatherrelated recurrent training, that the biennial flight review include the

following: recognition of critical weather situations from the ground and in

flight, procurement and use of aeronautical weather reports and forecasts,

determination of fuel requirements, and planning for alternatives if the

intended flight cannot be completed or delays are encountered. (A-05-024) 

For pilots holding a private, commercial, or airline transport pilot

certificate in the airplane category who do not receive recurrent instrument

training, add a specific requirement that the biennial flight review include a

demonstration of control and maneuvering of an airplane solely by

reference to instruments, including straight and level flight, constant

airspeed climbs and descents, turns to a heading, and recovery from

unusual flight attitudes. (A-05-025)

Establish a minimum number of weather-related questions that must be

answered correctly in order to pass Federal Aviation Administration airman

knowledge tests. (A-05-026)

Develop a means to identify pilots whose overall performance history

indicates that they are at future risk of accident involvement, and develop a

program to reduce risk for those pilots. (A-05-027)

Determine optimal information presentation methods and delivery systems

for flight service station weather information briefings, including the

possibility of supplementing or replacing some portions of the current

standard weather briefing with graphical data. (A-05-028)

Revise guidance materials associated with pilot weather briefings to

include guidance for pilots in the use of Internet, satellite, and other data

sources for obtaining weather information suitable for meeting the intent of

14 Code of Federal Regulations Part 91.103 and subsequently inform the

aviation community about this change. (A-05-029)
49 Safety Study

Appendix A

Previous National Transportation Safety Board Safety 

Recommendations

A search of the Safety Boardís Recommendations Database revealed that 82

recommendations on the safety of flight in IMC or visibility-related weather conditions

have been issued since 1968. Recommendations have addressed a variety of topics, which

may be grouped into three broad areas: 1) the collection and dissemination of weather

information, 2) pilot training and operations, and 3) air traffic control issues. 

Collection and Dissemination of Weather Information

A focus on the collection, measurement, presentation, and communication of weather

information is apparent in the 82 recommendations the National Transportation Safety Board has

made since 1968. Early recommendations called on the Federal Aviation Administration (FAA)

to increase the number of weather observation sites and to develop or improve measurements of

cloud heights, runway visual range (RVR), and slant visibility range. Other recommendations

called for audio-recorded preflight weather information, a system for providing en route flight

advisories, and data-linked information on precipitation and turbulence.

Although not all of the recommendations related to weather information were

implemented at the time they were issued, most of the concerns raised in these

recommendations have been addressed over the years by system-wide improvements in

the way that weather information is gathered, presented, and disseminated. Pilots are now

able to access an array of up-to-date meteorological information from the telephone, the

Internet, and avionics that provide graphical weather information. 

Pilot Training and Operations

Recommendations concerning the safety of flight in adverse weather have targeted

both pilot training and flight operations. Initial training-related recommendations called

for increased emphasis on aviation meteorology in pilot training. In the mid-1970s, the

Safety Board recommended that the FAAó 

1. increase the emphasis of meteorology and its applications in pilot training, 

2. specify a minimum number of instructional hours dedicated to meteorological

instruction, 

3. require written examinations to assess a pilotís meteorological knowledge, and

4. require pilot license applicants to demonstrate their ability to procure and

utilize weather information. 
50 Safety Study

In response to these early recommendations, FAA increased its emphasis on the

use of weather products and took action to encourage commercial pilots to obtain

instrument ratings. However, the FAA did not set a minimum number of instructional

hours dedicated to meteorological instruction, nor did it require any assessment of a pilotís

knowledge or use of meteorological products. Since that time, the FAA has modified the

curriculum for the private pilot certificate to include information on gathering and using

weather information. The examination for the private pilot certificate also includes

questions on these topics; however, due to the way the exam is scored, pilots who answer

all of these questions incorrectly still may achieve a passing score. 

The curriculum for the private pilot certificate also includes material on basic

control of an aircraft by reference to instruments, and in 1997, the FAA began requiring a

minimum 3 hours of instrument flight training as part of the experience requirements for a

private pilot certificate. This instruction is intended to train pilots to recognize, avoid,

andóif necessaryóescape instrument meteorological conditions (IMC) if encountered.

Additional instrument flight training is required for the commercial pilot license and for

the instrument rating that allows pilots to fly in IMC.

Air Traffic Control

Recommendations directed to air traffic control (ATC) personnel have focused on

informing pilots about changes in weather and providing assistance to pilots when

visibility is limited. In response to Safety Board recommendations, FAA improved ATC

distribution of center weather advisories (CWA) and hazardous inflight weather advisory

service (HIWAS) information to pilots. The FAA also instituted procedures for tower

supervisors to communicate deteriorating weather conditions to pilots via approach

controllers. FAA has also developed training for controllers to assist VFR pilots who are

caught in IMC. Finally, FAA has emphasized that controllers should adjust traffic flow to

accommodate low altitude en route traffic when visibility is poor.

Table of Safety Recommendations

Please note that in table A1, the following abbreviations are used to denote the

current status of the safety recommendations.

CAA: ClosedóAcceptable Action

CAAA: ClosedóAcceptable Alternate Action

CNLA: ClosedóNo Longer Applicable

CR: ClosedóReconsidered

CUA: ClosedóUnacceptable Action

OAA: OpenóAcceptable Response

OUA: OpenóUnacceptable Response

Appendix A
Table A1. Previous NTSB Recommendations on the Safety of Flight in IMC or Visibility-Related Weather Condition

Rec. 

Number Addressee Year Status Status Date Summary of Recommendation

A-02-8 FAA 2002 OAA Revise any restrictions and prohibitions that currently reference or address "night" or "n

operations in mountainous terrain so that those restrictions and prohibitions account foinsufficient ambient light conditions, and ensure that it is clear to flight crews when sucprohibitions apply.

A-01-35 FAA 2001 CR 07/16/2002 Amend FAA order 7110.65, "air traffic control," paragraph 10-2-5, "emergency situation

emergencies (1) inadvertent entry into instrument meteorological conditions (IMC) by a 

aircraft and (2) in-flight failure of attitude instruments needed to operate safely in IMC icannot remain in visual meteorological conditions for the remainder of its flight.

A-01-36 FAA 2001 OAA Develop and ensure that air traffic controllers receive academic and simulator training 

controllers to quickly recognize and aggressively respond to potential distress and emewhich pilots may require air traffic control (ATC) assistance, including but not limited to 

situations in which visual flight rules aircraft may be encountering instrument meteorolo

an understanding of common aircraft system failures that may require ATC assistance and (3) the application of specific techniques for assisting pilots that encounter such weaircraft system failures. Further, this training should be based on actual accidents or incomprehensive review of successful flight assists and the techniques used, and be revensure that the training materials remain current and effective.

A-01-58 FAA 2001 OAA In cooperation with the National Weather Service, ensure that Center Weather Service 

staffed at all times when any significant weather is forecast.

A-01-71 NWS 2001 CAA 01/27/2003 In cooperation with the Federal Aviation Administration, ensure that Center Weather S

adequately staffed at all times when any significant weather is forecast.

A-01-59 FAA 2001 OAA Modify automated weather systems to accept runway visual range (RVR) data directly A-01-56 FAA 2001 OUA Incorporate, at all air traffic control facilities, a near-real-time color weather radar display 

precipitation intensities. This display could be incorporated by configuring existing and 

Doppler Weather Radar or Weather Systems Processor systems with this capability or b

year, a commercial computer weather program currently available through the Internet alone computer hardware that displays the closest single-site Weather Surveillance Radata or regional mosaic images.

A-01-72 NWS 2001 OAA Eliminate the Automated Surface Observing System lockout feature as soon as possibA-97-27 FAA 1997 CAAA 01/14/1999 Require, under the Standard Terminal Automation Replacement System (STARS) Prog

safe altitude warning (MSAW) alerts on instrument flight rules (IFR) aircraft be duplicateoperational quarters designated for supervisory personnel and that the supervisor dete

the alert and whether appropriate corrective action has been initiated or is required.

A-96-049 FAA 1996 CUA 07/08/1998 Require that hazardous in-flight weather advisory service (HIWAS) broadcasts consiste

pertinent info contained in weather reports & forecasts, including in-flight weather advismeteorological info (AIRMETs), significant meteorological info (SIGMETs), & center we(CWAs).
A-96-050 FAA 1996 CAA 08/20/1997 Encourage principal operations inspectors (POIs) & operators to reemphasize to pilots 

flight weather advisory service (HIWAS) is a source of timely weather info & should be are operating in or near areas of potentially hazardous weather conditions.

A-95-41 FAA 1995 CAA 06/09/1997 Amend FAA order 7110.65, Air Traffic Control, Chapter 2, General Control, section 6, w

paragraph 2-115, reporting weather conditions, to require the tower supervisor to notify approach control facility personnel, in addition to the National Weather Service observeof prevailing visibility to less than 3 miles. Additional, require the controllers to issue the 

pilots until the info is broadcast on the ATIS & the pilots have acknowledged receipt of 

A-89-112 FAA 1989 CAA 05/04/1992 Provide radar control trainees in the en route option at the radar training facility an eme

which a VFR pilot is asking for assistance, is caught in weather, but is below the minim

A-89-113 FAA 1989 CAA 05/04/1992 Provide radar control trainees in the terminal option at the radar training facility an eme

which a VFR pilot is asking for assistance, is caught in weather, but is below the minim

A-88-20 FAA 1988 CUA 01/10/1989 Amend chapter 2, section 6, paragraph 2-101, of the air traffic control handbook, 7110.

traffic controllers to frequently broadcast the significant hazardous weather reports tha

A-88-21 FAA 1988 CAA 06/21/1989 Amend chapter 4, section 7, paragraph 343, subparagraph (1)(h) of the airmanís inform

include airborne weather radar as an item of equipment whose complete or partial loss be reported to air traffic control.

A-88-22 FAA 1988 CAA 06/21/1989 Amend chapter 2, paragraph 2-7 of the air traffic control handbook, 7110.65e, to includ

radar equipment as an in-flight equipment loss or malfunction covered by this paragrap

A-88-23 FAA 1988 CAAA 08/16/1991 Expedite the implementation of the hazardous in-flight weather advisory service progra

traffic control centers within the conterminous united states, before the summer convecof 1988.

A-86-68 FAA 1986 CUA 10/07/1987 Include a message on the automatic terminal information service broadcast whenever 

conducive to thunderstorm or microburst development exist in the terminal area or wheconditions have been observed or reported.

A-86-69 FAA 1986 CAA 07/28/1987 Amend Federal Aviation Handbook 7210.3g, Facility Operation and Administration, to 

observation of lightning or existence of cumulonimbus and towering cumulus clouds as on Automatic Terminal Information Service broadcast when that information has been remarks section of official weather reports.

A-86-71 FAA 1986 CUA 10/27/1988 Develop a position in major terminal facilities, to be staffed with national weather servic

Federal Aviation Administration personnel trained for meteorological observations, to bweather information coordination during periods of convective weather activity that advand air traffic control system operations.

A-86-74 FAA 1986 CAA 12/16/1986 Issue a general notice to all en route and terminal facilities emphasizing the phraseolog

describing weather areas as stated in Federal Aviation Administration Handbook 7110

A-86-76 FAA/NWS 1986 CUA/

CAAA

10/13/1987, 2/22/1994

Develop procedures to require that center weather service units are attended constantly that information concerning hazardous weather conditions, such as thunderstorms, winturbulence, either occurring or expected to occur, receives prompt, appropriate dissem
A-86-77 FAA/NWS 1986 CUA 10/13/1987, 

07/22/1988

Develop procedures to require the center weather service unit meteorologist to dissemrapidly developing hazardous weather conditions, such as thunderstorms and low-altituFederal Aviation Administration terminal radar approach control and/or tower facilities detection of the conditions.

A-86-78 FAA/NWS 1986 CAA 07/04/1991, 

07/22/1988

Expedite the implementation of equipment to upgrade all center weather service units technology in data acquisition and display capability.

A-86-80 NOAA 1986 CAA 07/22/1988 Require that all offices that have a weather radar display or displays and an aviation w

responsibility to airports have those airports clearly located on a usable map on each w

A-86-81 NOAA 1986 CUA 04/15/1998 Develop definitive aviation weather warning criteria based on radar weather echo inten

proximities of radar weather echos to airport approach and departure corridors, and imcommunicate this information immediately to Federal Aviation Administration terminal control and tower facilities.

A-84-111 FAA 1984 CAA 01/17/1986 Postpone nationwide implementation of the hazardous inflight weather advisory service 

control centers until the broadcasting procedures are improved and program informatiowidely.

A-84-112 FAA 1984 CUA 01/17/1986 Designate communication frequencies within the 118-135 mhz band for each air route 

to broadcast hazardous inflight weather advisory service information.

A-84-113 FAA 1984 CUA 01/17/1986 Develop procedures similar to those currently used in terminal areas for automatic term

service, for flight crews to monitor an individual facilityís hazardous inflight weather advfrequency and to inform the controller/facility on initial contact that the flight has the cuinformation.

A-84-114 FAA 1984 CAA 01/17/1986 During a transition period following the further implementation of hazardous inflight we

service, require air traffic controllers to advise flight crews when critical safety informatavailable through HIWAS. For example, ARTCC controllers should be required to adviscontact "significant weather information available on HIWAS."

A-83-17 FAA 1983 CAA 04/02/1985 Require that automatic terminal information service advisories be amended promptly to 

shear information and other information pertinent to hazardous meteorological conditioarea as provided by center weather service unit meteorologists, and that all aircraft ope

area be advised by blind broadcast when a new automatic terminal information service issued.

A-83-18 FAA 1983 CAAA 01/23/1996 Evaluate methods and procedures for the use of current weather information from sou

low level wind shear alert systems, and pilot reports as criteria for delaying approach aoperations which would expose the flight to low altitude penetration of severe convectiv

A-82-045 NWS 1982 CAA 10/05/1982 Establish a policy of transmitting all nonscheduled airport terminal forecasts and amend

Aviation Administration weather message switching center in Kansas City, Missouri, foservice a circuits.

A-82-17 FAA 1982 CAA 07/15/1982 Issue an emergency airworthiness directive specifying the installation of the dual vacuu

kit in all Cessna model 210n aircraft equipped with deicer boots as a requirement for flinstrument meteorological conditions.
A-82-30 FAA 1982 CUA 01/07/1983 Take action to amend 14 CFR 91.116 to provide that takeoffs cannot be initiated or an 

past the final approach fix or into the final approach segment of an instrument approacthe latest weather report for that airport issued by the U.S. National Weather Service, a that service, or a source approved by the administrator, reports the visibility to be equavisibility minimums prescribed for that procedure.

A-81-162 FAA 1981 CAA 01/28/1985 Require all holders of an instrument rating and a multiengine rating to demonstrate the

multiengine aircraft under normal and emergency conditions by reference to flight instr

prerequisite to exercising the privileges of an instrument rating in multiengine aircraft.

A-81-23 FAA 1981 CAA 05/24/1984 Publish procedures in air traffic control handbook 7110.65b covering the control handli

advisories.

A-81-8 FAA 1981 CAA 01/06/1984 Develop and implement a priority message-handling procedure to assure the immediat

weather messages to all weather circuits that originate from the weather message switKansas City, Missouri.

A-81-94 FAA 1981 CAA 12/10/1981 Audio-record all weather briefings provided by FSS personnel and retain such records 

period of time.

A-81-95 FAA 1981 CAA 12/10/1981 Take steps to ensure that all FSS personnel who provide weather briefings comply with 

procedures published in flight services handbook 7110.10.

A-80-115 FAA 1980 CAA 06/19/1985 Expedite the delivery of NWS weather radar color remote displays to all air route traffic 

center weather service units.

A-80-117 FAA 1980 CAA 10/15/1984 Expedite the development of appropriate graphic mapping techniques for correlation o

radar color remote display and the air traffic controllerís radar display presentation.

A-80-118 FAA 1980 CAA 07/02/1993 Expedite the development of an integrated weather radar/air traffic control radar single 

capable of providing multiple weather echo intensity discrimination without derogation radar intelligence.

A-80-119 FAA 1980 CAA 06/19/1985 Require air route traffic control centers to make maximum use of the existing national w

sites as inputs to the color remote displays at their facilities.

A-80-135 FAA 1980 CAA 05/24/1982 Require that flow controllers and supervisory personnel assess the potential effects of 

on low-altitude en route traffic and use the evaluation to adjust air traffic flow as necess

A-80-136 FAA 1980 CAA 06/08/1982 Require that the effect of precipitation-induced attenuation on x-band airborne weather 

incorporated into airline training programs and that airborne weather radar manufacturattenuation data in radar operators handbooks.

A-80-109 FAA 1980 CUA 07/23/1986 Require that the effect of precipitation-induced attenuation on x-band airborne weather 

incorporated into airline training programs and that airborne weather radar manufacturattenuation data in radar operators handbooks.
A-79-055 FAA 1979 CAA 10/29/1979 Revise air traffic control handbook 7110.65a so that a VFR aircraft issued an altitude a

instruction is provided terrain protection comparable to that received by an IFR aircraftlatitude should be provided in the handbook so that the controller may approve a requewishes to exercise the provisions of the exceptions to 14 CFR 91.79.

A-78-34 FAA 1978 CUA 10/26/1988 Install an alerting feature on all existing and new equipment for disseminating essential 

in all air traffic control facilities, at positions that require timely information and at positio

to issue current weather information as a part of their air traffic control functions.

A-77-63 FAA 1977 CAA 06/18/1990 Expedite the development and implementation of an aviation weather subsystem for bo

terminal area environments, which is capable of providing a real-time display of either turbulence, or both and which includes a multiple-intensity classification scheme. Transto pilots either via the controller as a safety advisory or via an electronic data link.

A-77-65 FAA 1977 CAAA 08/15/1978 Transmit SIGMETs more frequently on NAVAIDs so that pilots can receive more timely 

hazardous weather.

A-77-66 FAA 1977 CAA 08/15/1978 Code, according to geographic applicability, severe thunderstorm watch bulletins and t

bulletins issued by the national severe storms forecast center so that they may be transair traffic control facilities by the FAA weather message switching center; thus, air traffic 

relay the earliest warning of severe weather to flight crews.

A-76-123 FAA 1976 CR 05/22/1980 Institute procedures which require air traffic controllers to release an aircraft from all air

least 3 to 4 miles outside of the outer marker on all ILS approaches when the reported basic VFR minimums.

A-76-29 FAA 1976 CAAA 04/07/1977 Amend that portion of 14 CFR 91.33 applicable to instrument flight rules to require a sou

rate-of-turn indicator separate from that used to power the bank and pitch indicator.

A-75-70 FAA 1975 CAA 12/22/1978 Change the wording of the restriction on the national ocean survey instrument approac

where night approaches are not authorized so that the restriction is clearly understood

A-75-71 FAA 1975 CAAA 01/27/1977 Advise pilots arriving in a terminal area on an IFR flight plan whenever the published in

procedure is not authorized for night operations. Instead of an approach clearance, isscruise at the appropriate minimum en route altitude/minimum obstruction clearance altitnight.

A-74-19 FAA 1974 CAA 09/14/1978 Issue an advisory circular which describes the RVR equipment and emphasizes that th

sampling of a small segment of the atmosphere, usually near the touchdown point. it semphasized that RVR value does not necessarily represent actual runway visibility con

touchdown point and includes a significant time delay before reaching the crew. This inf

be placed in the airmanís information manual.

A-74-127 FAA 1974 CR 10/01/1975 Amend 14 CFR 91.105 to require the same weather minimums outside controlled airsp

within controlled airspace.

A-74-14 FAA 1974 CAA 05/24/1984 Implement, in cooperation with the national weather service, a system to relay severe t

tornado warning bulletins expeditiously to inbound and outbound flights when such bulterminal area.
A-74-30 FAA 1974 CUA 01/11/1979 Install conventional transmissometers or other visibility measuring devices in the appro

instrument runways.

A-74-32 FAA 1974 CUA 01/11/1979 Combine the approach zone transmissometer or visibility readings with the ceilometer 

estimates of "threshold contact height."

A-74-33 FAA 1974 CUA 01/11/1979 Employ runway observers to take cloud height and visibility observations in the approac

prevailing visibility becomes 1 mile or less at those locations having minimums of less observers should be used until the instruments described in 1. Above are installed in th

A-74-67 FAA 1974 CAA 12/03/1975 Amend 14 CFR 141 to increase the required minimum of 35 hours of classroom instruc

pilot trainees, and specify the number of hours of meteorological instruction required.

A-74-68 FAA 1974 CUA 12/03/1975 Require that written meteorology examinations be designed to measure an applicantís 

practical application in addition to technical aspects of meteorology.

A-74-69 FAA 1974 CAAA 03/10/1977 Amend 14 CFR 61.57(b) to require a demonstration of the applicantís competence to p

weather information which will enable him to exercise safely the privileges of his pilotís 

A-74-70 FAA 1974 CR 10/01/1975 Amend 14 CFR 61.125 aeronautical knowledge (a) airplanes, to require an applicant fo

certificate to present evidence of meteorological knowledge in addition to the other areknowledge now specified, similar to the requirements of 14 CFR 61.125 (b)(2), (c)(3), (

A-74-71 FAA 1974 CAA 06/04/1975 Increase the emphasis on aviation meteorology and weather limitations of pilots throug

accident prevention program.

A-74-72 FAA 1974 CAA 06/04/1975 Take priority action in order to adhere to the proposed 4-year implementation plan for t

advisory service (Flightwatch) program.

A-74-73 FAA 1974 CAA 12/03/1975 Implement, at least on an experimental basis at selected high general aviation activity 

recording of preflight weather briefings.

A-74-74 NOAA 1974 CAA 12/03/1975 Accelerate efforts to update, publish, advertise, and disseminate the document entitled 

Pilots and Operations Personnel.

A-74-75 NOAA 1974 CAA 02/20/1975 Accelerate the expansion of the evaluation staff to its proposed complement of one eva

meteorologist per state and include in his responsibilities the implementation of a qualit

aviation weather observations.

A-74-76 NOAA 1974 CNLA 02/20/1975 Accelerate efforts to improve the presentation of aviation weather products.A-72-105 FAA 1972 CAA 01/01/1975 Visibility and separation from cloud distances should be assessed conservatively in VF

that VFR flight should be continued only when visibility is unquestionable.

A-72-139 FAA 1972 CUA 12/03/1975 Combined efforts and resources of government and industry be applied toward the exp

and use of technological advances in the field of all weather flight navigation and approa

Although it cannot be stated unequivocally that this accident would not have occurred landing system or more advanced landing system had been in use, it is the boardís beliof the occurrence of such an accident would have been greatly reduced.
A-72-198 FAA 1972 CAA 11/30/1973 The FAA ensure widespread dissemination of information to pilots in all segments of av

potential hazards associated with weather conditions characterized by a partial obscurcaused by a shallow layer of dense fog.

A-72-43 FAA 1972 CUA 06/08/1972 Issue an advisory circular incorporating excerpts of this report, including the findings, s

instrument and airline transport pilots the need for continuous surveillance of flight instoperating in instrument meteorological conditions.

A-70-63 10 airlines 

and private flying organizations

1970 CNLA 03/22/1971 The Boardís review of these and other approach and landing accidents show that they 

regularity and that they are not confined to a single segment of aviation. It was emphasa number of factors which must be considered in preventing this type of accident, namground equipment, procedures and piloting techniques and judgment. Safety should be improving the quality and increasing the quantity of landing aids and weather reporting services. it was further emphasized that all pilots should be thoroughly instructed in the with shallow fog penetration and be prepared to make the missed approach decision adelay whenever the alternative course is required. Illusions tending to disorientate the phases of the approach and the limitations of various systems are but two of the areas decision which must be recognized.

A-69-1 FAA 1969 CAA 02/17/1969 1. Amend sections 91.117 and 121.649 of the federal aviation regulations "to prohibit a

200 feet above field level unless the pilot has the runway threshold in sight and require have same in sight during the remainder of the approach." 2. "Bring to the attention of the hazards associated with shallow fog penetration." 3. Include as mandatory items in 

programs and FAA-approved instrument flight school curriculums "information on shallthe effect upon the guidance segment, and the potential illusions that can be created." expeditiously as possible" its research into instrumentation which would provide slant vinformation. 5. set standards and specifications and encourage the development of "reapproach flight simulators. 6. program improved approach zone lighting covering "at leaof the approach" for "installation on a priority basis," when and if "financial conditions p

prone to frequent heavy fog.

A-69-32 FAA 1969 CUA 11/12/1973 (1) That section 91.116 of the FAR be changed to agree with the provisions of section 

similar requirements of parts 123 and 135 in order that the approach be restricted as wThat section 91.117 be amended to the effect that in no event shall descent below 200 unless landing minimums are present. (3) that while section 91.116(b) clearly states th

be made unless the visibility is at or above the landing minimum required, neverthelesssafety and in order to insure proper interpretation, all conditions requiring a missed appcontained in section 91.117 (b). Accordingly, an additional condition should be added to the effect that if landing minimums cannot be maintained, a missed approach must be 
A-68-06 FAA and 

ESSA

1968 CAA/

CNLA

01/01/1975 1. Increase the number of aviation weather observing sites. 2. Vigorous program of qu

aviation weather observations should be developed. 3. Cloud-height measuring equipprovided at all aviation weather observing stations. 4. Additional efforts should be madlocation of weather instruments at airports. 5. Methods should be developed for measulow level wind shear in the terminal area. 6. In order to insure more accurate visibility oadequate visibility reference markers (particularly nighttime markers) should be provideobservers. 7. Continued efforts should be made to expand the upper-air observing netwthe number of rawinsonde ascents to four per day. 8. The weather radar network shouparticularly west of approximately 100 degree west longitude, and weak, obsolete, warshould be replaced with up-to-date, long-range weather radar sets. 9. It is recognized timpractical to base a staffing plan on the "bad weather" situation. It appears, however, or expansions are required, so that a continuous weather watch could be maintained abriefing services provided at those locations manned by one person during certain houexpansion of the runway visual range (RVR) program including the multiple installationtransmissometers. 11. A means of measuring slant visibility or slant visual range which experience on an approach to landing would certainly enhance air safety. 12. In view osupport by the users of the pilot-to-forecaster experimental programs at Kansas City asuggested that serious consideration be given to establishing an operational program o13. The transcribed weather broadcasts (TWEB) network should be expanded to provi

coverage. 14. The pilots automatic telephone weather answering service (PATWAS) shexpanded to provide its service to many additional areas, particularly those areas wherbriefing may not now be available. 15. There is a need for more pilot weather briefing fSubstantial improvements in weather briefings could be realized by the provision of fac

all weather briefing facilities. This would also assist in the desired standardization of piprocedures. 17. Additional efforts should be made to improve and standardize weather Provision should be made for additional telephone lines to weather briefing facilities. 1the safety board in accident investigations and for ESSA/FAA quality control purposes, pilot weather briefings is advocated. 20. Aviation stands to benefit from information dersatellites. Accordingly, it is considered that special efforts should be made to devise ref

procedures for providing aviation-oriented weather satellite information on a national bcontinues to be a need for improved delineation of aviation forecast area boundaries. present system of delineation should be considered in order to define more precisely thperhaps a reassignment of areas of forecast responsibility to make the boundaries conboundaries. 23. We adhere to the belief that a centralized Clear Air Turbulence (CAT) should be established, similar to the Severe Local Storms (SELS) unit. Certainly safet

economy would be enhanced by such an establishment. 24. Continued efforts should the procedures for obtaining and disseminating in-flight weather information. 25. We ainstructions to forecasters regarding the modifiers to be used for In-flight Advisories (SClear Air Turbulence (CAT) forecasts. Forecasters are directed to use the phrase ìmoCAT forecasts and may only use ìsevereî or ìextremeî in CAT reports. These instructio

of the Weather Bureau Operations Manual) appear to be contrary to preceding instructwhich call for SIGMETS to be issued when (among other things) ìsevereî or ìextremeî expected. Unfortunately, ìmoderate or more turbulenceî includes all intensities except it seems unfair and certainly not very helpful to the pilot not to be apprised of the forecaintent in regard to the category of turbulence to be anticipated. 26. There has always bemore accurate aviation weather forecasts, particularly for the terminal area, and researforecasting methods should continue to be pursued. Research should also be conduc

objective methods for measuring or forecasting the intensity of icing and turbulence.

A-68-24 FAA 1968 CAA 09/04/1969 It is recommended that the installation of adverse weather warning devices (light) be e

airports where official weather observations are taken.
59 Safety Study

Appendix B

Basic VFR Weather Minimums

Airspace Flight Visibility Distance from Clouds

Class B 3 statute miles Clear of Clouds 

Class C 3 statute miles 500 feet below

1,000 feet above

2,000 feet horizontal 

Class D 3 statute miles 500 feet below

1,000 feet above

2,000 feet horizontal 

Class E

Less than 10,000 feet MSL 

3 statute miles 500 feet below

1,000 feet above

2,000 feet horizontal 

At or above 10,000 feet MSL 5 statute miles 1,000 feet below

1,000 feet above

1 statute mile horizontal 

Class G

1,200 feet or less above the surface (regardless of 

MSL altitude) 

Day, except as provided in section 91.155(b) 1 statute mile Clear of clouds 

Night, except as provided in section 91.155(b) 3 statute miles 500 feet below

1,000 feet above

2,000 feet horizontal 

Class G

More than 1,200 feet above the surface but less than 

10,000 feet MSL 

Day 1 statute mile 500 feet below

1,000 feet above

2,000 feet horizontal 

Night 3 statute miles 500 feet below

1,000 feet above

2,000 feet horizontal 

Class G

More than 1,200 feet above the surface and at or 

above 10,000 feet MSL 

5 statute miles 1,000 feet below

1,000 feet above

1 statute mile horizontal 
60 Safety Study

Appendix C

Evaluation of Matching Procedure 

Interviews were conducted with 135 pilots of matching nonaccident flights. The

mean number of matches identified per accident was 2.2 for accidents involving IFR

flights, and 1.5 per accident for those involving VFR flights. There were no statistically

significant differences between the accident and nonaccident groups on the variables used

for matching, and the absence of any differences confirmed the soundness of the

procedures used to match accident and nonaccident flights.

Aircraft Types

Of the study accidents, 74 percent involved single-engine aircraft and 26 percent

involved multiengine aircraft. The nonaccident aircraft group included 72 percent singleengine and 28 percent multiengine airplanes. In comparison, estimates from the 2002

General Aviation and Air Taxi Activity (GAATA) Survey1

 indicated that single-engine

airplanes accounted for 69 percent of aircraft involved in GA operations, and multiengine

airplanes accounted for 13 percent. Additionally, 93 percent of study accidents involved

piston-powered airplanes, 6 percent involved turboprops, and 1 percent involved jet

aircraft. The nonaccident group included 90 percent piston-powered aircraft, 7 percent

turboprop aircraft, and 2 percent jet aircraft.2 GAATA Survey estimates indicated that

piston-powered airplanes accounted for 77 percent of the GA fleet, while turboprops

accounted for 3 percent, and jets for 4 percent. See figures C1 and C2.

1 U.S. Department of Transportation, Federal Aviation Administration, General Aviation and Air Taxi

Activity Survey, Calendar Year 2002 (Washington, DC: FAA, 2004), available at <http://api.hq.faa.gov/pubs.asp>.

2 Values do not sum to 100 percent due to rounding.
61 Safety Study

Figure C1

Figure C2

Distribution of Study Aircraft

by Number of Engines

Multi Single

0%

20%

40%

60%

80%

100%

Accident Nonaccident

Distribution of Study Aircraft

by Type of Engine

Piston Turbo-jet Turbo-prop 0%

20%

40%

60%

80%

100%

Accident Nonaccident

Appendix C
62 Safety Study

Appendix D

Guided Interview 

Departure Point Time 

Destination Time 

En route Altitude 

N-number Aircraft Manufacturer Aircraft Model 

Do you rent or own other: ?

Notes: 

Purpose of flight 

Personal Travel Proficiency Flight to or from work, or work-related 

Pleasure Paid to fly (Instructor, observation, delivery) 

Regulation

Part 91 Part 135 Part 121 

Leg of Trip 

Inbound Outbound Intermediate Local

Were you familiar with the airplane? Yes No

Were you familiar with the area? Yes No

Flew in the region in the last 6 months? Yes No

What flight rules were you operating under? VFR VFR with flight following 

 VFR to IFR (filed en route) IFR

if VFR, did you file a flight plan or use flight following? Yes No

Was there more than 1 pilot aboard the aircraft? Yes No

Notes: 
63 Safety Study

Weather Briefing 

Did you get a briefing prior to departure? Yes No

If yes, what source? DUATS Flight Service Television

ATIS/METAR Internet Other: 

Did you get more than one briefing? Yes No

Approximate time of last briefing: 

Did you request weather en route? Yes No

How would you describe the weather you encountered on that flight? 

Basic Weather: IFR MVFR Convective 

 VFR – degraded visual reference 

Was it better or worse than the forecast? Better Worse Same 

Did you have to deviate from your planned route or altitude? Yes No

What type of approach did you do at your destination? 

Visual ILS Localizer VOR NDB GPS

Basic aircraft equipment VFR only IFR certified 

Navigation Avionics VOR DME RNAV/LORAN 

 ADF GPS (VFR-only) GPS (IFR en route) 

 GPS (IFR approach) Moving Map Glideslope 

 Marker Beacon Other: 

Comments: 

Weather equipment Weather Radar Storm scope/Strike finder 

 Structural Anti-ice/De-ice Other: 

Is your aircraft certified for known icing? Yes No

Comments: 

Aircraft Control Equipment Wing-leveler Autopilot (2 axis)

 Autopilot (2 axis, coupled) Altitude Hold Yaw Damper 

 Other: 

Comments: 

Additional Avionics Altitude alert Radar altimeter 

 Multifunction Display(s) GPWS TCAS

 Other: 

Comments: 

Appendix D
64 Safety Study

Pilot Details 

 

Sex Male Female 

Certificates: None Student Private Commercial 

ATP DATE(S): 

Ratings: SEL MEL SES MES Other: 

Instrument Ratings: Airplane Other: DATE(S): 

Instructor Rating(s)? None Airplane Multi-engine Airplane 

Instrument Airplane Other: 

Date of most recent flight review 

Date of most recent flight instruction 

Date of most recent instrument competency check (if applicable) 

Date of most recent instrument flight instruction 

Date of last medical exam 

Medical Certificate First Class Second Class Third Class 

 Waivers/Limitations No Yes If yes, what? 

Certificate number (this will be de-identified) 

Pilot Date of Birth 

Flight Activity 

The rest of my questions have to do with the number of flight hours you have, and you 

may not have all of the information immediately available. If not, is there a time that I 

can call you back? 

 All A/C In Type 

A/C

Night Actual 

Instrument 

Simulated 

Instrument 

Total Time 

PIC 

Instruction Received 

Last 90 Days 

Appendix D
65 Safety Study

Appendix E

Supplemental Accident Form

NTSB General Aviation Weather Supplemental Form 

1. Accident/Incident Information 

Date City State 

Aircraft N-number NTSB# 

Basic Weather IFR MVFR VFR – with reduced visual reference Convective 

2. Purpose of Flight (Check one) 

 Personal Travel Proficiency Paid to fly (e.g. Instructor, observation, delivery) 

 Pleasure Flight to or from work, or work-related Other: 

Comments: 

Pilot’s connection to the accident aircraft: Own (full or part) Rent Other: 

3. Leg of Trip 

 Outbound leg Intermediate leg Inbound leg Local Flight 

Comments: 

4. Weather Briefing 

4.1 Pilot received a weather briefing prior to departure Yes No Record 

4.2 Pilot received more than one weather briefing Yes No Record 

4.3 Time of last weather briefing (UTC) 

4.3 Pilot requested updated weather while en route Yes No Record 

4.4 Comments: 

5. Pilot Experience 

5.1 Date of most recent flight review Could not be determined 

5.2 Date of most recent instrument competency check (if applicable) Could not be determined 

5.3 Pilot was familiar with the area Yes No Could not be determined 

5.4 Pilot was familiar with the accident aircraft Yes No Could not be determined 

5.5 Comments: 

6. Pilot Instrument Training

6.1 Total hours of simulated instrument instruction received Could not be determined 

6.2 Total hours of actual instrument instruction received Could not be determined 

6.3 Date of most recent flight instruction Could not be determined 

6.4 Date of most recent instrument flight instruction Could not be determined 

6.5 Comments: 

7. Basic Aircraft Instruments (Check one) 

VFR-only IFR certified Unknown / Destroyed 

Comments: 

8. Navigation Avionics (Check all that apply) 

VOR DME RNAV/LORAN ADF 

 GPS (VFR-only) GPS (IFR en route) GPS (IFR approach) Moving Map 

 Glideslope Marker Beacon Unknown / Destroyed Other: 

Comments: 

9. Weather Equipment (Check all that apply) 

Weather Radar Storm scope/Strike finder Anti-ice/De-ice Equipment 

 Unknown / Destroyed Other: 

Was the accident aircraft certified for known icing? Yes No Unknown 

Comments: 

10. Aircraft Control Equipment

Wing-leveler Autopilot (2 axis) Unknown / Destroyed 

 Autopilot (2 axis, coupled) Altitude Hold Yaw Damper 

 Other: 

Comments: 
66 Safety Study

11. Additional Avionics 

 Altitude alert Radar altimeter Multifunction Display(s) 

 GPWS TCAS Unknown / Destroyed 

 Other: 

Comments: 

12. Did the pilot declare an emergency, communicate a problem, or request help?

 Yes No 

 if Yes, briefly explain 

13. Additional Information (Use this space to add any additional information that did not fit in the above spaces) 

 

14. Administrative information 

Investigator Date 

Please complete and return within 30 days of the accident. 

Appendix E
67 Safety Study

Appendix F

A Comparison of Forecast and Actual Visibility Conditions for 

Study Accidents

Accidents were included in this study if they took place in IMC or marginal VMC

or if they were preceded by a loss of visual reference or encounter with weather. One step

in the analysis was to determine if pilots could have anticipated the weather conditions

they experienced based on the weather forecasts that were available before their departure. 

Aviation weather forecasts provide several types of information, including

horizontal visibility, ceiling heights, cloud coverage, precipitation types, wind, and

convective activity. The decision that a forecast is consistent with actual conditions is

somewhat subjective, and a difference that is acceptable to one person may not be

acceptable to another. For this study, the FAAís legal definition of VFR minimums was

used to classify the forecast conditions into categories of VFR or IFR. VFR minimums

dictate the minimum ceiling and visibility conditions for a pilot to fly without an IFR

flight plan. While the threshold between VFR and IFR varies somewhat depending on the

type of airspace and time of day, VFR conditions are generally present when the cloud

ceiling1 is 1,000 feet or greater and the horizontal visibility is 3 miles or greater. IFR

conditions exist when either horizontal visibility or cloud ceilings are less than these

minimums. 

To determine the forecast conditions for each accident, Safety Board

meteorologists obtained Sierra AIRMETs that were released immediately before the

accident airplaneís departure time for the region surrounding the accident location. (The

Sierra AIRMET describes IFR conditions and mountain obscurations.) Staff then plotted

the Sierra AIRMETS and determined whether the accident site was located within its

boundaries. When an accident site was within the boundaries of the IFR AIRMET, the

forecast was classified as IFR; otherwise it was classified as VFR.

The actual conditions at the time and location of the accident were determined

from the Safety Boardís factual report. As part of the factual report, the investigator

assigns basic weather conditions as either IMC or VMC. 

Table F1 provides an overview of the forecast and actual conditions for the 72

accidents in the study. In terms of forecast quality, actual conditions matched forecast

conditions in 61 percent of cases. Within the 39 percent of cases in which the forecast did

not match the actual conditions, the visibility conditions were ìbetterî than forecast (that

is, forecast IFR, actual VFR) in 39 percent, and were ìworseî than forecast (that is,

forecast VFR, actual IFR) in 61 percent of cases.

1 Ceiling in this case is defined as the lowest cloud layer of broken (BKN) or greater coverage.
68 Safety Study

Table F1

Using FAA definitions as criteria for evaluating the accuracy of the forecasts

suggests that in approximately 25 percent of all accident cases, the actual conditions were

worse than predicted. A few of the many possible explanations include the following:

1. Forecasts of IMC or VMC are issued from the perspective of someone on the

ground. In-flight conditions also depend on the operating altitude. 

2. The weather conditions may have been isolated to an area so small that an

AIRMET was not warranted. A Sierra AIRMET is issued for ceilings less than

1,000 feet and/or for visibility less than 3 miles affecting over 50 percent of an

area at one time, or for extensive mountain obscuration for an area of at least

3,000 square miles.

3. Using this verification methodology, a fairly small deviation between the

forecast and actual conditions could result in a change in classification. For

example, if the ceiling was forecast to be 1,000 feet, and the actual ceiling was

900 feet, it would be classified as a change from VFR to IFR conditions. 

The term marginal VFR or MVFR is sometimes used to refer to conditions that are

near the VFR minimums. MVFR refers to conditions in which visibility is between 3 and

5 miles or when ceiling height is between 1,000 and 3,000 feet. At present, the FAAís use

of the term marginal VFR is limited to the section of an area forecast corresponding to the

period of time more than 6 hours after the time of forecast issuance.

A closer look at the forecast and actual data reveals that in 4 of the 23 cases where

VMC was forecast, and in 6 of the 49 cases where IMC was forecast, the actual conditions

fell into the definition of MVFR. In these cases, actual conditions were closer to the

forecast than the dichotomous categorization of IFR and VFR would suggest. 

Actual

VFR IFR Total

VFR 6

(8.3%)

17 

(23.6%)

23

(31.9%)

IFR 11

(15.3%)

38

(52.8%)

49

(68.1%)

Forecast

Total 17

(23.6%)

55

(76.4%)

72

 Forecast and Actual Conditions

for the Study Accidents

Appendix F
69 Safety Study

Appendix G

Study Accidents

NTSB Accident 

Number Date Location

Aircraft

Registration Make Model

Accident

Severity

1 IAD03FA069 Aug 02, 2003 Galion, OH N577SK Piper PA-34-200T Fatal

2 CHI03FA246 Aug 05, 2003 &ODUN¿HOG01 N4577T Piper PA-28-180 Fatal

3 NYC03FA176 Aug 06, 2003 Pleasantville, PA N28788 Grumman AA-5B Fatal

4 IAD03FA070 Aug 08, 2003 Factoryville, PA N6373C Piper PA-32-300 Fatal

5 CHI03LA267 Aug 19, 2003 +DPPRQG01 N1812S Beech BE-76 Non-fatal

6 0,$)$ Aug 21, 2003 Clearwater, FL N93DC Piper PA-31 Fatal

7 CHI03FA296 Aug 28, 2003 *UDQG0DUDLV01 N285V Beech 58P Fatal

8 CHI03FA291 Sep 01, 2003 8QLRQGDOH,1 N8018J Beech B36TC Fatal

9 CHI03LA315 Sep 22, 2003 Chanute, KS N122CC Piper PA-24-250 Non-fatal

10 NYC03FA205 Sep 27, 2003 &RQFRUG0$ N963LP Cessna 182T Fatal

11 SEA04LA001 Oct 02, 2003 %ODNHO\,VODQG:$ N2695S Cessna 340 Non-fatal

12 SEA04FA009 Oct 20, 2003 6HDVLGH25 N136SB Beech A36 Fatal

13 ATL04FA027 Oct 26, 2003 Spartanburg, SC N7799Y Piper PA-30 Fatal

14 CHI04FA025 Nov 02, 2003 Hutchinson, KS N6107Z &RPPDQGHU 114TC Fatal

15 )7:)$ Nov 16, 2003 Tolar, TX N777SG Cessna 0 Fatal

16 LAX04GA051 Nov 21, 2003 Big Bear City, CA 1: Piper PA-28-180 Fatal

17 SEA04FA022 Nov 25, 2003 :DUUHQ25 N10BX Beech S35 Fatal

18 0,$)$ Nov 27, 2003 Jacksonville, FL N698X Swearingen SA-26-AT Fatal

19 )7:)$ Dec 04, 2003 +DUULVRQ$5 N350JL Beech S35 Fatal

20 LAX04LA058 Dec 04, 2003 San Diego, CA N15C Cessna 525 Non-fatal

21 ATL04FA045 Dec 04, 2003 0RUODQ*$ N85BK Beech B200 Fatal

22 LAX04FA061 Dec 07, 2003 Chino Hills, CA N16264 Piper 3$5 Fatal

23 ATL04FA049 Dec 10, 2003 Vestavia Hills, AL 1: Cessna 441 Fatal

24 ATL04FA051 Dec 11, 2003 Greeneville, TN N1592T Cessna 414 Fatal

25 SEA04LA026 Dec 11, 2003 0F0LQQYLOOH25 N29CV Upright 59$ Fatal

26 LAX04FA066 Dec 14, 2003 Claremont, CA N6887L Cessna 421C Fatal

27 ANC04FA015 Dec 14, 2003 Tonopah, NV N4674A Cessna P210N Fatal

28 LAX04FA081 Dec 15, 2003 Corona, CA N61303 Cessna 150J Fatal

29 )7:)$ Dec 15, 2003 0HQD$5 N7929D Beech H-35 Fatal

30 CHI04FA044 Dec 17, 2003 Brooklyn, IA 1: Piper PA-32-260 Fatal

31 CHI04FA043 Dec 17, 2003 Daytona Beach, FL 1%0 Piper PA46-500TP Fatal

32 ATL04FA056 Dec 17, 2003 6DQIRUG1& N9562L Cessna 206H Fatal

33 LAX04LA074 Dec 20, 2003 Angwin, CA N20480 Beech B55 Non-fatal

34 SEA04LA029 Dec 22, 2003 0LVVRXOD07 1$0 Beech 58P Non-fatal

35 LAX04FA077 Dec 24, 2003 Avalon, CA N3747U Piper PA-34-200T Fatal

36 SEA04LA030 Dec 25, 2003 Elk City, ID N1363U Cessna 0 Non-fatal
70 Safety Study

176%$FFLGHQW

Number Date Location

Aircraft

5HJLVWUDWLRQ 0DNH 0RGHO

$FFLGHQW

Severity

37 SEA04FA032 Jan 01, 2004 *ODVJRZ07 N3171S Cessna 182G Fatal

38 )7:)$ Jan 01, 2004 Dallas, TX N4104B Bellanca 17-30A Fatal

39 SEA04FA031 Jan 01, 2004 &DYH-XQFWLRQ25 N53505 Piper PA-44-180 Fatal

40 )7:)$ Jan 02, 2004 Beaumont, TX N396HP Piper 3$5 Fatal

41 CHI04LA052 Jan 02, 2004 Fishers, IN N21992 Piper 3$57 Non-fatal

42 DEN04FA035 Jan 03, 2004 Cortez, CO 165 5RFNZHOO 690A Fatal

43 CHI04FA055 Jan 10, 2004 %DXGHWWH01 N5787J Cessna 182P Fatal

44 LAX04LA092 Jan 11, 2004 Vacaville, CA N77S Cessna 140 Non-fatal

45 0,$&$ Jan 14, 2004 )RUW0HDGH)/ 10& Cessna 210L Non-fatal

46 )7:)$ Jan 15, 2004 :LOORZ3DUN7; N7252X Beech B36TC Fatal

47 LAX04FA096 Jan 19, 2004 Grass Valley, CA 1/5 Cessna 172K Fatal

48 0,$)$ Jan 19, 2004 Fort Pierce, FL N298PA Piper PA-28-181 Fatal

49 SEA04LA038 Jan 28, 2004 5LJE\,' N734CB Cessna 172N Non-fatal

50 0,$)$ Jan 31, 2004 +RPHVWHDG)/ N75GC Beech C90 Fatal

51 LAX04FA113 Jan 31, 2004 Laupahoehoe, HI N5637C Cessna 414A Fatal

52 DEN04FA043 Feb 06, 2004 :DOFRWW:< N51192 Cessna T206H Fatal

53 CHI04LA064 Feb 07, 2004 /RQH5RFN:, N5039S Piper 3$5 Non-fatal

54 ATL04FA075 Feb 11, 2004 Alma, GA N6473J Piper PA-28-180 Fatal

55 ANC04LA022 Feb 14, 2004 Crescent City , FL 1:% Thorp T-18 Fatal

56 CHI04FA071 Feb 16, 2004 5R]HO.6 15' Cessna 182Q Fatal

57 CHI04FA069 Feb 17, 2004 5LFK+LOO02 1: Piper PA-28-180 Fatal

58 )7:)$ Feb 22, 2004 Valley Spring, TX N6175Y Cessna 210N Fatal

59 ATL04FA077 Feb 23, 2004 Arlington, AL N9103Z Piper PA-46-310P Fatal

60 LAX04FA139 Feb 27, 2004 3LQH0WQ&OXE&$ N7687J Piper 3$5 Fatal

61 CHI04LA085 0DU Dubuque, IA N105FS Cessna 5 Non-fatal

62 0,$)$ 0DU Spring Hill, FL N8148G Cessna 182P Fatal

63 LAX04FA162 0DU Los Angeles, CA N1148V 0RRQH\ 0. Fatal

64 NYC04FA092 0DU Harlan, KY N8173U Piper 3$5 Fatal

65 ATL04LA087 0DU %D\0LQHWWH$/ 1$0 Alarus CH2T Non-fatal

66 NYC04FA100 Apr 02, 2004 Harrietstown, NY N4686J Piper 3$5 Fatal

67 LAX04FA177 Apr 04, 2004 Ukiah, CA N4130D Piper 3$57 Fatal

68 DEN04FA057 Apr 06, 2004 Burlington, CO N3524Y Cessna 182F Fatal

69 0,$/$ Apr 10, 2004 1/DXGHUGDOH)/ N916LJ Cirrus 65 Non-fatal

70 ATL04FA093 Apr 12, 2004 North Augusta, SC 10( Cessna 182S Fatal

71 SEA04LA071 Apr 17, 2004 Gibbonsville, ID N5XK Keller Prospector FK1 Non-fatal

72 ATL04LA097 Apr 23, 2004 2DNODQG71 1:' Durr Lancair Legacy Fatal

Appendix G