aviation

Crash During Approach to Landing

Circuit City Stores, Inc.

Cessna Citation 560, N500AT

Pueblo, Colorado

February 16, 2005

ACCIDENT REPORT

NTSB/AAR-07/02

PB2007-910403

Aircraft Accident Report

Crash During Approach to Landing

Circuit City Stores, Inc.

Cessna Citation 560, N500AT

Pueblo, Colorado

February 16, 2005

NTSB/AAR-07/02

PB2007-910403 National Transportation Safety Board

Notation 7713C 490 L’Enfant Plaza, S.W.

Adopted January 23, 2007 Washington, D.C. 20594

E PLUR IBUS UNUM

NATIONAL TRA S PORTATION

B OAR D

SAFE T Y

N
National Transportation Safety Board. 2007. Crash During Approach to Landing, Circuit City Stores,

Inc., Cessna Citation 560, N500AT, Pueblo, Colorado, February 16, 2005, Aircraft Accident Report

NTSB/AAR-07/02. Washington, DC.

Abstract: This report explains the accident involving a Cessna Citation 560, N500AT, operated by

Martinair, Inc., for Circuit City Stores, Inc., which crashed about 4 nautical miles east of Pueblo Memorial

Airport, Pueblo, Colorado, while on an instrument landing system approach to runway 26R. The safety

issues discussed in this report include inadequate training on operations in icing conditions, inadequate

deice boot system operational guidance, the need for automatic deice boot systems, inadequate

certification requirements for flight into icing conditions, and inadequate stall warning margins in icing

conditions.

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

Public Inquiries Section, RE-51

490 L’Enfant 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 PB2007-910403 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 Aircraft Accident Report

Contents

Abbreviations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

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

1. Factual Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 History of Flight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 The Sister Ship History of Flight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Injuries to Persons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.3 Damage to Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.4 Other Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.5 Personnel Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.5.1 The Captain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.5.2 The First Officer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.6 Aircraft Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.6.1 General Aircraft Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.6.2 Stall Warning System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.6.3 Anti-Ice and Deice Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.7 Meteorological Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.7.1 National Weather Service Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.7.2 Airport Weather Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.7.3 Additional Icing Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.8 Aids to Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.9 Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.10 Airport Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.10.1 Air Traffic Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.10.2 Air Traffic Control Guidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.11 Flight Recorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.11.1 Cockpit Voice Recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.11.1.1 Cockpit Voice Recorder Sound Spectrum Study . . . . . . . . . . . . . . . . . . . . . . . . 13

1.11.2 Flight Data Recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.12 Wreckage and Impact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.13 Medical and Pathological Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.14 Fire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.15 Survival Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.16 Tests and Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.16.1 Enhanced Ground Proximity Warning System Data Study . . . . . . . . . . . . . . . . . . 14

1.16.2 Airplane Performance Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1.17 Organizational and Management Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1.17.1 Operational Guidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.17.1.1 Normal Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.17.1.2 Operations in Icing Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.17.1.3 Anti-Ice and Deice Systems Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
iv Aircraft Accident Report

1.17.2 Flight Crew Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

1.17.2.1 Operations in Icing Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

1.17.2.2 Stall Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

1.18 Additional Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

1.18.1 Cessna 550 and 560 Airplanes Icing-Related 

Flight Testing and Subsequent Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

1.18.2 Previous Icing-Related Safety Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . 20

1.18.2.1 Deice Boot System Activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

1.18.2.2 Certification Requirements for Flight into 

Icing Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

1.18.2.3 Stall Warning Margins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

1.18.3 Residual and Intercycle Ice and Automatic 

Deice Boot System Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

2. Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

2.2 Accident Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

2.2.1 Descent Into Icing Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

2.2.2 Approach to Landing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.2.3 Final Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.2.4 Flight Crew Monitoring and Workload Management . . . . . . . . . . . . . . . . . . . . . . . 30

2.3 Deice Boot Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

2.4 Certification Requirements for Flight Into Icing Conditions . . . . . . . . . . . . . . . . . . . . . 34

2.5 Inadequate Stall Warning Margins in Icing Conditions . . . . . . . . . . . . . . . . . . . . . . . . 36

3. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.1 Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.2 Probable Cause . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

4. Safety Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

4.1 New Safety Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

4.2 Previously Issued Safety Recommendations Reiterated in This Report . . . . . . . . . . . . 41

5. Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

A: Investigation and Public Hearing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

B: Cockpit Voice Recorder Transcript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Contents
v Aircraft Accident Report

Abbreviations

agl above ground level

AC advisory circular

AD airworthiness directive

AFM airplane flight manual

AIRMET airmen’s meteorological information

AOA angle-of-attack

ARAC aviation rulemaking advisory committee

ARTCC air route traffic control center

ASOS automated surface observing system

ASR-7 airport surveillance radar-7

ATC air traffic control

ATIS automatic terminal information service 

ATP airline transport pilot

BFU German Federal Bureau of Accidents Investigation

C Celsius

CAM cockpit area microphone 

CFR Code of Federal Regulations

CG center of gravity

COU Columbia Regional Airport

CVR cockpit voice recorder

EGPWS enhanced ground proximity warning system

FAA Federal Aviation Administration

fpm feet per minute

FSS flight service station

Hg mercury

ILS instrument landing system 
Abbreviations vi Aircraft Accident Report

IMC instrument meteorological conditions

IPHWG Ice Protection Harmonization Working Group

METAR meteorological aerodrome report

mm millimeter

msl mean sea level

NASA National Aeronautics and Space Administration

NCAR National Center for Atmospheric Research

nm nautical mile

NPRM notice of proposed rulemaking

NWS National Weather Service

PIREP pilot report

PUB Pueblo Memorial Airport

PWC Pratt & Whitney Canada

SB service bulletin

SLD supercooled large droplet

sm statute mile

TCAS traffic alert and collision avoidance system 

UTC universal coordinated time
vii Aircraft Accident Report

Executive Summary

On February 16, 2005, about 0913 mountain standard time, a Cessna Citation 560,

N500AT, operated by Martinair, Inc., for Circuit City Stores, Inc., crashed about 4 nautical

miles east of Pueblo Memorial Airport, Pueblo, Colorado, while on an instrument landing

system approach to runway 26R. The two pilots and six passengers on board were killed,

and the airplane was destroyed by impact forces and postcrash fire. The flight was

operating under the provisions of 14 Code of Federal Regulations Part 91 on an

instrument flight rules flight plan. Instrument meteorological conditions prevailed at the

time of the accident.

The National Transportation Safety Board determines that the probable cause of

this accident was the flight crew’s failure to effectively monitor and maintain airspeed and

comply with procedures for deice boot activation on the approach, which caused an

aerodynamic stall from which they did not recover. Contributing to the accident was the

Federal Aviation Administration’s failure to establish adequate certification requirements

for flight into icing conditions, which led to the inadequate stall warning margin provided

by the airplane’s stall warning system.

The safety issues discussed in this report include inadequate training on operations

in icing conditions, inadequate deice boot system operational guidance, the need for

automatic deice boot systems, inadequate certification requirements for flight into icing

conditions, and inadequate stall warning margins in icing conditions. Safety

recommendations concerning these issues are addressed to the Federal Aviation

Administration.

1 Aircraft Accident Report

1. Factual Information

1.1 History of Flight

On February 16, 2005, about 0913 mountain standard time,1 a Cessna

Citation 560, N500AT, operated by Martinair, Inc., for Circuit City Stores, Inc.,2 crashed

about 4 nautical miles (nm) east of Pueblo Memorial Airport (PUB), Pueblo, Colorado,

while on an instrument landing system (ILS) approach to runway 26R. The two pilots and

six passengers on board were killed, and the airplane was destroyed by impact forces and

postcrash fire. The flight was operating under the provisions of 14 Code of Federal

Regulations (CFR) Part 91 on an instrument flight rules flight plan. Instrument

meteorological conditions (IMC) prevailed at the time of the accident.

The accident flight and another Circuit City Stores Cessna 560 (N500FK, referred

to in this report as the “sister ship”) were scheduled to transport Circuit City Stores

employees from Richmond International Airport, Richmond, Virginia, to John Wayne

Airport, Santa Ana, California, with scheduled fuel stops at Columbia Regional Airport

(COU), Columbia, Missouri, and PUB. The accident flight departed Richmond about

0600 eastern standard time. The flight arrived at COU about 0736 central standard time

and departed for PUB about 30 minutes later. 

At 0847:48, while descending through about flight level 370,3

 the cockpit voice

recorder (CVR)4 recorded the Denver Air Route Traffic Control Center (ARTCC)

instructing the flight crew to descend to and maintain 13,000 feet. About 0851, the CVR

recorded the flight crew start discussing the icing conditions. Specifically, at 0850:40, the

captain stated, “I’m gonna heat ‘em up.”5 About 4 minutes later, the captain stated that he

turned the windshield heat on, and he then asked the first officer to let him know if he saw

any ice on the wing. The first officer replied that he saw ice “building a little bit right on

1 Unless otherwise indicated, all times in this report are mountain standard time based on a 24-hour

clock.

2 Circuit City Stores owned the airplane. Martinair, an aircraft management and charter company,

operated and managed the accident airplane for Circuit City Stores. See section 1.17 for more information.

3 Flight level 370 is an altitude of 37,000 feet mean sea level (msl) based on an altimeter setting of

29.92 inches of mercury (Hg). Unless otherwise indicated, all altitudes referenced in this report are reported

as height above msl.

4 Correlation of the CVR recording to mountain standard time was established using times from the air

traffic control (ATC) transcript prepared by the Federal Aviation Administration and PUB airport

surveillance radar-7 radar. The time alignment of the CVR recording and radar revealed that the CVR clock

was about 10 seconds ahead of the radar clock. As a result, the CVR times are presented with a 10-second

offset to provide a consistent time base between the CVR and ATC sources. The airplane was not equipped

with a flight data recorder.

5 The captain’s comment most likely refers to the activation of the engine anti-ice system, which heats

the engine inlets and the inboard wing leading edges. For more information about the airplane’s anti-ice and

deice systems and guidance on the usage of these systems, see sections 1.6.3 and 1.17.1.3, respectively.
Factual Information 2 Aircraft Accident Report

the [wing] leading edge...it’s not the real white ice like we had yesterday. It’s more of a

grayish.” The first officer then stated, “there’s a real thin line back there.” About 2 minutes

later, the captain stated that it did not look like the airplane had accumulated any more ice. 

At 0858:20, as the airplane was descending through about 18,000 feet, the first

officer suggested that the captain cycle the deice boots. After cycling the deice boots, the

captain stated, “might’ve gotten rid of a little but not much.” At 0859:29, the first officer

stated that the Vref was 96 knots.

6

 About 3 1/2 minutes later, the captain told the first officer

to “leave the heats on,” and the first officer replied, “okay. Got everything nice and

warmed up.”

At 0905:50, the first officer contacted PUB approach control and stated, “Pueblo

approach...thirteen thousand with [automatic terminal information service] Juliet.”7 The

PUB local controller instructed the flight crew to fly heading 240° for the ILS runway 26R

final approach course and to descend to and maintain 7,000 feet. The first officer asked,

“did you say two six right now?” The controller confirmed that runway 26R was in use.

The controller also reported that a regional jet was in a holding pattern over PUB at

9,000 feet and asked the pilots to report when they had the airplane in sight.8

 The first

officer then told the captain that the controller had changed the landing runway from 8L to

26R.

At 0907:36, the PUB local controller asked the pilots if they had the airplane in

sight, and the first officer stated that he did not. The controller replied, “give me a best rate

of descent through niner thousand or maintain one zero thousand. I’ll just turn you.” The

first officer stated that they would descend to 7,000 feet. At 0908:25, the first officer

reported to the controller that the flight was in IMC at an altitude of about 9,400 feet. The

controller then instructed the flight to turn left to a heading of 170°. At 0908:55, the

controller instructed the flight crew to turn right to a heading of 290° to intercept the

localizer inbound. He then instructed the flight crew to maintain 7,000 feet and cleared the

flight for the approach. 

6 Vref is the landing reference airspeed with full flaps and landing gear down. In accordance with

company guidance, if any amount of residual ice (that is, ice that remains on the deice surface after the deice

boots have been cycled) is present, the Vref should be increased by 8 knots, which would have resulted in a

Vref of 104 knots instead of the 96 knots reported by the first officer. For more information about guidance on

operations in icing conditions, see section 1.17.1.2.

7 Automatic terminal information service (ATIS) information “Juliet,” which broadcast the

0753 weather, reported the following: wind 060° at 6 knots, visibility 10 statute miles, measured ceiling

1,400 feet overcast, temperature -3° Celsius (C), dew point -5° C, altimeter 30.16 inches of Hg. ATIS

information “Juliet” also indicated that the landing runway in use was 8L. Altitudes referenced in this report

from surface weather observations and terminal aerodrome forecasts are reported as height above ground

level (agl). See section 1.7 for more meteorological information.

8 During postaccident interviews, the captain of the holding airplane stated that he had initially

requested and received a holding pattern altitude of 8,000 feet. He stated that, although he was informed by

ATC that icing conditions existed at that altitude, he decided to descend to 8,000 feet. As the airplane

descended toward 8,000 feet into IMC, it began accumulating ice. He stated that he turned on the airplane’s

wing anti-ice and immediately requested a climb to 9,000 feet to exit the icing conditions. He stated that, at

9,000 feet, the airplane was above the cloud layer and mostly in the clear. He characterized the icing as rime

ice but did not know its accumulation rate or severity.
Factual Information 3 Aircraft Accident Report

At 0909:19, the first officer stated, “you got a little different ice on there now. It’s

clear.” The captain replied, “yeah,” and he then instructed the first officer to “open up

those valves all the way.”9 The first officer replied, “all right, will do.” At 0909:41, the

PUB local controller provided the flight crew with the current weather, which indicated

the following: cloud ceilings broken at 900 feet and overcast at 1,400 feet, visibility

6 statute miles (sm) in mist, temperature -3° Celsius (C), dew point -4° C, wind 070° at

7 knots, and altimeter 30.16 inches of mercury (Hg). 

At 0910:22, the first officer stated, “ignition is on with the anti-ice, now it’s on for

sure. Glideslope is alive.” At 0911:10, the captain stated, “[landing] gear’s down.” The

PUB local controller cleared the flight to land on runway 26R and instructed the flight

crew to maintain its present heading and altitude until established on the ILS localizer. At

0911:45, the CVR recorded the captain stating, “speed brakes coming back out.” The first

officer replied, “okay...there’s your glideslope intercept.” The captain then called for full

flaps. The first officer responded, “full flaps, here we go...full selected and indicated.” At

0912:00, the first officer briefed the missed approach. Four seconds later, he stated, “you

are plus twenty five,”10 and the captain replied, “slowing.” At 0912:37, the first officer

stated, “I don’t know if you want to run your ice a little bit. You got the Vref there.” 

Airplane performance calculations show that, about 0912:40, immediately after

passing through about 6,100 feet,11 the airplane experienced an upset and the onset of a

large roll to the left concurrent with a rapid decrease in pitch. The CVR recorded a short

tone concurrent with the beginning of the upset. The frequency and the duration of the

tone were consistent with the autopilot disconnect horn.12 At 0912:46, the CVR recorded

the enhanced ground proximity warning system (EGPWS) “bank angle” aural warning

alert.13 The last radar return was received at 0912:54 while the airplane was at an altitude

of about 4,922 feet. One second later, the CVR stopped recording. According to the

Federal Aviation Administration (FAA) air traffic control (ATC) transcript, at 0912:57,

the PUB local controller issued an altitude alert to the accident flight, stating, “zero alpha

tango altitude alert altitude indicates four thousand niner hundred over.”

1.1.1 The Sister Ship History of Flight

During postaccident interviews, the sister ship captain indicated that, according to

the airplane’s traffic alert and collision avoidance system (TCAS), the accident airplane

was about 19 nm ahead of the sister ship en route to PUB. The flight crewmembers

reported that, during the descent to PUB, the airplane was accreting rime ice;14 however,

9 The captain was most likely referring to the windshield anti-ice bleed air valves, which control the

volume of engine bleed air to the windshield. The three-position (LOW, OFF, and HIGH) windshield bleed

air switch controls the temperature of the air to the windshield.

10 The first officer’s comment “plus twenty five” refers to the Vref plus 25 knots.

11 The airplane was at an altitude of about 1,500 feet above ground level at the time of the upset. 

12 The autopilot can be manually disconnected by the pilot or it can be automatically disconnected if

certain conditions occur, such as a roll angle of more than 40° or a roll rate of more than 20° per second. 

13 Analysis of the EGPWS data indicated that the bank angle at the time of the alert was about 50°.
Factual Information 4 Aircraft Accident Report

they stated that no visible precipitation was present. The first officer estimated that the ice

was less than 1/2-inch thick and stated that the deice boots effectively shed the ice. He

stated that there was no ice on the heated inboard wing leading edge or on the top of the

wing. The first officer stated that a little ice had formed on the windshield and that he

selected the HIGH heat setting to deice and defog the windshield. The captain stated that

they kept the airspeed up on the approach because of the icing conditions.15 The captain

stated that they broke out of the clouds about 1,200 to 1,400 feet and that the visibility was

about 6 nm with no precipitation.

The captain stated that he heard the PUB controller clear the accident airplane to

land and the flight crew acknowledge the clearance. He stated that, shortly afterward, he

heard the controller issue a low-altitude warning of about 4,900 feet. He stated that the

controller called for the accident flight three or four times but that the flight crew did not

acknowledge. He stated that he then looked at the TCAS and saw that the accident

airplane was no longer displayed. The sister ship landed on runway 8L about 0926 without

incident. The flight crew and passengers reported that they observed some ice on the

airplane after landing. 

A review of the sister ship’s CVR revealed that the pilots conducted several

procedures to minimize any icing problems, including cycling the wing deice boots five

times, turning the windshield heat to the HIGH position, using only approach flaps until

close to the ground, and keeping the engine power and speed as high as possible until clear

of the clouds and landing was assured.

1.2 Injuries to Persons

Table 1. Injury chart.

14 Rime ice is an opaque, granular, and rough deposit of ice that usually forms on the airplane’s

surfaces, including, in part, the wing leading edges, the horizontal stabilizers, and the engine inlets. 

15 Airplane performance calculations revealed that the sister ship’s airspeed was more than 160 knots as

the airplane descended through about 6,200 feet and that the airplane maintained an airspeed of about

120 knots until it was about 200 feet above airport elevation. Calculations revealed that the accident

airplane’s airspeed was about 98 knots as it descended through about 6,200 feet. 

Injuries Flight Crew Cabin Crew Passengers Other Total

Fatal 2 0 60 8

Serious 0 0 00 0

Minor 0 0 00 0

None 0 0 00 0

Total 2 0 6 0 8
Factual Information 5 Aircraft Accident Report

1.3 Damage to Aircraft

The airplane was destroyed by impact forces and a postcrash fire.

1.4 Other Damage

No other damage resulted from this accident.

1.5 Personnel Information

1.5.1 The Captain

The captain, age 53, was hired by Martinair on February 1, 2002. He held a

multiengine airline transport pilot (ATP) certificate, issued October 11, 1996, with type

ratings in Beechcraft 300 and 1900, Cessna 500, and Dassault Falcon DA-10 series

airplanes. The captain held a first-class FAA airman medical certificate, dated February 7,

2005, with the limitations that he “must wear lenses for distance” and “possess glasses for

near vision.”

According to the captain’s employment application for Martinair, from July 1989

to January 2001, he worked as a pilot in Cessna 560 airplanes at Southern States. From

January 2001 to February 2002, he worked as a pilot in Cessna Citation Ultra airplanes at

Chesapeake Corporation. Martinair records indicated that the captain had accumulated

8,577 total flight hours, including 2,735 hours in Cessna Citation airplanes, 1,500 hours of

which were as pilot-in-command. He had flown about 113, 39, 12, and 3 hours in the 90,

30, and 7 days and 24 hours, respectively, before the accident. The captain’s last

Cessna 500 series proficiency check occurred on November 1, 2004; his last recurrent

ground training occurred on November 30, 2004; and his last line check occurred on

January 4, 2005. A search of FAA records revealed no accident or incident history,

enforcement action, or pilot certificate or rating failure or retest history. A search of the

National Driver Register found no record of driver’s license suspension or revocation. 

According to the captain’s wife, he slept his normal sleep schedule16 at home in

Richmond for several nights before February 15, 2005. On February 14, he flew a

roundtrip to South Bend, Indiana, during the day (with the accident first officer). She

stated that, on February 15, he left home by early afternoon, returned about 1500, and was

awake in bed when she returned about 2030 to 2100. She stated that, on the morning of the

accident, he awoke early; however, she did not know what time he departed for the airport. 

16 According to the captain’s wife, he normally went to sleep about 2200 to 2300 and awoke by 0700

when he did not have to work. She stated that the captain sometimes had difficulty sleeping. 
Factual Information 6 Aircraft Accident Report

1.5.2 The First Officer

The first officer, age 42, was hired by Martinair in November 2004. He held a

multiengine ATP certificate, issued March 3, 2004, with a type rating in Cessna 500 series

airplanes. The first officer held a first-class FAA airman medical certificate, dated

August 2, 2004, with no limitations. 

According to the first officer’s employment application for Martinair, from

April 2002 to November 2004, he worked as a pilot in Cessna Citation airplanes for

Commonwealth Aviation Services, Inc. Martinair records indicated that the first officer

had accumulated 2,614 total flight hours, including 1,397 hours in Cessna Citation series

airplanes, 322 hours of which were as pilot-in-command. He had flown about 127, 37, 11,

and 3 hours in the 90, 30, and 7 days and 24 hours, respectively, before the accident. The

first officer’s last Cessna Citation 500 series proficiency check and line check occurred on

February 10, 2005, and his last recurrent ground training occurred on December 30, 2004.

A search of FAA records revealed no accident or incident history, enforcement action, or

pilot certificate or rating failure or retest history. A search of the National Driver Register

found no record of driver’s license suspension or revocation.

According to the first officer’s wife, he slept his normal sleep schedule17 at home

in Richmond for several nights before February 15, 2005. She stated that, on February 14,

he was still in bed when she left the house about 0730; he flew a roundtrip to South Bend

that afternoon; and he went to bed about 2200 to 2300. On February 15, he flew another

roundtrip to South Bend, and he went to bed about 2100 to 2130. On the morning of the

accident, he awoke about 0300 and left the house about 0345 to 0400.

1.6 Aircraft Information

1.6.1 General Aircraft Information

The accident airplane, serial number 0146, was manufactured by Cessna Aircraft

Company on October 22, 1991, and was certified to 14 CFR Part 25 standards. At the time

of the accident, the airplane had accumulated about 3,658 total flight hours. The airplane

was equipped with two Pratt & Whitney Canada (PWC) JT15D-5A turbofan engines. The

time since new for both engines was about 3,585 hours, and the time since overhaul for

both engines was about 114 hours.

Martinair provided National Transportation Safety Board investigators with

estimated weight and balance information for the accident flight.18 According to these

estimates, the accident airplane’s landing weight was about 13,040 pounds, including

17 According to the first officer’s wife, he normally went to sleep about 2200 and awoke by 0800 when

he did not have to work.

18 The actual weight and balance information for the accident airplane was not found. Title 14 CFR

Part 91 regulations do not require pilots to leave a manifest at the departure airport.
Factual Information 7 Aircraft Accident Report

2,000 pounds of fuel, 1,100 pounds of passenger weight, and 180 pounds of baggage,

which was within the landing weight limit of 15,200 pounds. The estimates showed that

the airplane’s landing center of gravity (CG) was 16.8 percent mean aerodynamic chord,

which was within the landing CG limits of 16 to 28 percent.

The airplane was equipped with speedbrakes, which are small panels that extend

from the upper and lower surfaces of each wing to increase descent rates.19 After the

accident, the left speedbrakes remained attached to the wing and were in the fully

extended position. The right speedbrakes remained attached to the wing but were in an

intermediate position. However, the speedbrake panels and hydraulic actuators on both

wings were able to move freely.

1.6.2 Stall Warning System

The accident airplane was equipped with a stall warning and angle-of-attack

(AOA) system, which consisted of an AOA vane, indicator, indexer, and computer, and a

stickshaker mounted on the forward side of the pilot’s control column. The AOA vane,

which is located on the forward right side of the fuselage, streamlines with the relative

airflow and transmits the sensed angle to the AOA system. Inputs from the AOA system

are transmitted to the stickshaker, which has an electric motor with rotating weights that

induce vibration to the control columns, providing a tactile warning to pilots of an

impending stall. The stickshaker is designed to alert pilots of an impending stall about

7 percent above the actual stall speed when the airplane’s surfaces are not contaminated

by ice.20

According to the Cessna Model 560 Citation V Operating Manual, the airplane

was equipped with an upgraded, dual-mode AOA computer, which incorporated normal

and ice modes. The ice mode is activated when either engine anti-ice switch is selected

ON. In normal mode, stickshaker activation is referenced to standard airplane stall speeds,

and, in ice mode, stickshaker activation is referenced to standard airplane stall speeds plus

5 knots to account for the increase in stall speed caused by airframe ice accumulation.21

According to the Cessna Model 560 Citation V Airplane Flight Manual (AFM),

the accident airplane’s stall speed, with no ice on the wings and assuming an airplane

weight of about 13,300 pounds and full flaps selected, should have been about 76 knots.

The AFM states that, with ice on the wings, the stall speed increases by 5 knots; therefore,

19 The speedbrakes are electrically controlled and hydraulically actuated by a switch located on the

throttle quadrant in the cockpit and may be selected to the fully extended or fully retracted (stowed) position.

The speedbrakes are held in the stowed position by mechanical catches. A light illuminates in the cockpit

when the speedbrakes are in transition and when they are fully extended.

20 According to Advisory Circular 25-7, “Flight Test Guide for Certification for Transport Category

Airplanes,” “the stall warning should normally begin at a speed not less than 7 percent above the stall

speed.”

21 During flight tests of Cessna 560 series airplanes, which were conducted by the FAA in 1996, it was

determined that the stall speed increased from 3 to 5 knots in icing conditions. In early 1999, Cessna began

installing stall warning systems that incorporated the ice mode. For more information about these tests and

subsequent FAA and Cessna actions, see section 1.18.1.
Factual Information 8 Aircraft Accident Report

the stall speed for the accident airplane should have been about 81 knots. As noted, the

stickshaker is designed to alert pilots of an impending stall about 7 percent above the

actual stall speed; therefore, the stickshaker should have activated at about 86 knots.

The Cessna Model 560 Citation V AFM states that the stall warning system must

be operable and a preflight check must be performed before takeoff. The sister ship

captain, who flew the accident airplane the day before the accident, reported no pre- or

in-flight stall warning system problems. Further, no discrepancies were noted during the

last scheduled maintenance inspection of the stall warning system, which was completed

on December 1, 2003.

Postaccident examinations of the stall warning system components revealed that

the AOA computer and vane electrical heating element exhibited heat and fire damage,

which precluded functional checks. The AOA vane was able to move freely. The stall

warning stickshaker and the vane heating elements were found to be functional during

postaccident tests.

1.6.3 Anti-Ice and Deice Systems

The Cessna 560 is certified to operate in known icing conditions and is equipped

with anti-ice and deice systems to prevent ice accumulation on various exterior areas of

the airplane.22 The engine anti-ice system uses engine bleed air to heat the engine inlets

and the inboard wing leading edges, and the windshield anti-ice system uses engine bleed

air to heat the windshield. The pitot static anti-ice system uses electrical heating elements

to prevent ice buildup on the pitot tubes, static ports, and AOA vane. The anti-ice systems

are activated by switches in the cockpit. Activation of the engine and windshield anti-ice

systems and failures of the engine and pitot static anti-ice systems are annunciated by

lights in the cockpit. 

The surface deice system consists of pneumatic boots on the outboard wing

leading edges and the horizontal stabilizer. The deice system is typically activated by

selecting the surface deice switch to the AUTO position. During the 18-second automatic

deice boot cycle,23 pneumatic pressure from engine bleed air inflates the lower boots on

the wing leading edges and the boot on the left horizontal stabilizer, then these boots

completely deflate. The upper boots on the wing leading edges and the boot on the right

horizontal stabilizer then inflate and deflate. After deflation of the upper deice boots, the

cycle is terminated. Deice boot system activation is annunciated by lights in the cockpit. 

The deice boot system can also be operated manually by holding the deice surface

control switch in the MANUAL position. As long as the control switch is held in the

MANUAL position, all of the deice boots will inflate simultaneously and deflate when the

22 According to the Cessna Model 560 Citation V AFM, the airplane’s anti-ice and deice systems were

not designed to protect against freezing rain or severe conditions of mixed or clear ice.

23 The AUTO mode automatically cycles the deice boots through one 18-second deice boot cycle.

However, to activate another 18-second cycle, the pilot would have to move the surface deice switch to the

AUTO position again. 
Factual Information 9 Aircraft Accident Report

switch is released. If the switch is placed and held in the MANUAL position during

automatic cycle operation, the MANUAL will override the AUTO function, all of the

deice boots will simultaneously inflate, and the automatic cycle will time out. 

CVR information indicated that the captain activated the deice boots and that the

boots had removed some of the ice. Further, no discrepancies were noted during the last

scheduled maintenance inspections of the anti-ice and deice systems, which were

completed on December 1, 2003.

After the accident, the engine anti-ice switches were found fractured, and their

positions could not be determined. The windshield bleed air switches were missing. The

left and right windshield bleed air valve positions could not be determined because the

cables had been pulled out of both control mechanisms. The pitot static heat switch was

found in the ON position. The surface deice switch was found spring-loaded to the neutral

position. The deice control valves were found separated from the wreckage and damaged.

On-scene disassembly revealed that the deice control valves were free of obstruction, and

a functional test showed that the valves functioned properly.

The left- and right-wing leading edge deice boots were severely damaged by

impact and postcrash fire. The left and right horizontal stabilizer deice boots were

damaged. The deice boot air supply lines from the tail section to the wings were damaged

and/or consumed by fire. 

1.7 Meteorological Information 

1.7.1 National Weather Service Information

A terminal aerodrome forecast prepared for PUB by the National Weather Service

(NWS), which was issued at 0442 and was valid at the time of the accident, stated, in part,

the following: 

winds 080° at 8 knots, visibility greater than 6 miles, skies scattered at 2,000 feet

and overcast at 2,500 feet. Temporary condition between 1200Z[24] to 1600Z,

visibility 3 miles in light freezing drizzle, mist, skies overcast at 1,000 feet. From

1600Z, winds 070° at 8 knots, visibility greater than 6 miles, skies scattered at

1,000 feet and overcast at 2,500 feet.

 The NWS also issued several winter weather advisories on the morning of the

accident.25 The advisories issued at 0750 and 0934 warned that freezing drizzle existed

along the accident flightpath through the midmorning hours. 

24 Weather forecasts are transmitted in coordinated universal time (UTC). The “Z” designation that

follows the time in the weather observation stands for Zulu, which indicates UTC time. Mountain standard

time is 7 hours behind UTC time.

25 Although winter weather advisories are not aviation-related products, they provide additional

information about atmospheric conditions.
Factual Information 10 Aircraft Accident Report

About 0745, the NWS issued AIRMET [airmen’s meteorological information]

Zulu, which covered the Pueblo area and was valid at the time of the accident. AIRMET

Zulu warned of “occasional moderate rime or mixed icing in clouds and precipitation

between freezing level and 22,000 feet, with the freezing level between the surface and

8,000 feet.” About 0830, the NWS issued AIRMET Sierra, which also covered the Pueblo

area and was valid at the time of the accident. AIRMET Sierra warned of “occasional

[cloud] ceilings below 1,000 feet and/or visibilities below 3 statute miles.” AIRMET

Sierra also warned of obscured mountains caused by precipitation, clouds, mist, and/or

fog.

Base reflectivity image data were derived from the Weather Surveillance

Radar-1988 Doppler system, which is located 15 nm northeast of the accident site. Data

from the system’s 0911 atmospheric profile showed weak reflectivity values near the

accident site, consistent with the presence of freezing drizzle atmospheric conditions.

Geostationary Operational Environmental Satellite 10 data from the National Oceanic and

Atmospheric Administration satellite indicated cloud top temperatures from -19° to -11° C

and the presence of cloud layers in the area surrounding the airplane’s flightpath. 

The 0500 upper air sounding (that is, a vertical profile of atmospheric conditions)

from Denver, Colorado (about 92 nm northeast of the site), showed temperatures below

freezing from the surface to 30,000 feet. The sounding showed no layers in the

atmosphere with temperatures above freezing.

1.7.2 Airport Weather Information

Weather observations at PUB are made by an automated surface observing system

(ASOS) located about 3 nm west of the accident site. The ASOS records continuous

information on wind speed and direction, cloud cover, temperature, precipitation, and

visibility and transmits an official meteorological aerodrome report (known as a METAR)

each hour. The 0853 METAR indicated the following: 

wind 060° at 8 knots; visibility 8 miles; skies broken at 900 feet and overcast at

1,400 feet; temperature minus 3° C; dew point temperature minus 5° C...Remarks

[cloud] ceiling varying between 700 to 1,100 feet. 

The 0944 METAR indicated the following: 

wind 070° at 7 knots; visibility 6 miles; skies overcast at 600 feet; temperature

minus 3° C; dew point temperature minus 4° C...Remarks [cloud] ceiling varying

between 400 and 900 feet.

The PUB ASOS provides unofficial weather observations that are recorded every

5 minutes. At 0910, the PUB ASOS indicated the following: winds 070° at 7 knots and

6 sm in mist. At 0915, the PUB ASOS indicated the following: winds 060° and visibility

8 sm. Both reports reported the following: clouds broken at 900 feet and overcast at

1,400 feet, temperature -3° C, and dew point -4° C. 
Factual Information 11 Aircraft Accident Report

1.7.3 Additional Icing Information

Scientists from the National Center for Atmospheric Research (NCAR), Boulder,

Colorado, conducted studies for the National Transportation Safety Board to determine

whether the accident airplane encountered supercooled26 large droplet (SLD) conditions,

which are more conducive to the accumulation of thin, rough ice on or aft of the protected

surfaces, and to estimate the amount of airframe ice accumulation. NCAR reported that,

on the basis of surface, radar, upper air, and satellite data, the airplane likely encountered

SLD conditions from about 9,400 to 6,100 feet (the calculated altitude at which the upset

occurred). NCAR indicated that, during the time that the airplane was in this cloud layer

(about 4 1/2 minutes), from 1 to 4 millimeters (mm) (0.039 to 0.157 inch) of ice likely

accumulated along the wing leading edges.27 Severe icing conditions are those in which

5 mm (0.195 inch) of ice accumulates in 5 minutes.

Several pilot reports (PIREP) were provided around the time of the accident in the

area over PUB. A PIREP received about 0646 from a pilot flying a Swearingen Merlin IV

reported moderate mixed icing on final approach to runway 8. A PIREP received about

0809 from the pilot flying a Hawker jet who had landed on runway 8 about 1 minute

earlier reported light to moderate and/or mixed icing and a “little” ice accumulation on the

wing leading edges. A PIREP received about 1020 from a pilot flying a Learjet 31

reported light to moderate rime icing on final approach to runway 8. An urgent PIREP28

received about 1023 from a pilot flying a Beechcraft King Air 90 at an altitude of about

6,000 feet reported moderate mixed icing and ice accumulation from 1/4 to 1/2 inch on

final approach to runway 8. 

1.8 Aids to Navigation

No problems with any navigational aids were reported. 

1.9 Communications

No communications problems between the pilots and any of the air traffic

controllers who handled the accident flight were reported. 

26 Supercooled is the liquid state of a substance that is below the normal freezing temperature for that

substance.

27 The ice accumulation estimates do not account for all of the effects of SLD conditions, including the

effect of the droplets’ running aft of the protected surfaces before freezing. 

28 FAA Order 7210.3, “Facility Operation and Administration,” states that weather phenomena reported

by a pilot that represents a hazard or a potential hazard to flight operations, including severe icing, should be

disseminated as “urgent PIREPs.”
Factual Information 12 Aircraft Accident Report

1.10 Airport Information

PUB is located about 5 nm southeast of Pueblo at an elevation of 4,726 feet. PUB

has one set of parallel runways, 8L/26R and 8R/26L, and runway 17/35.

1.10.1 Air Traffic Control

PUB has a combined tower and radar approach control facility. The tower is

located on the south side of the airport, left of and about midway down runway 26R. PUB

tower controllers use DBRITE (digital bright radar indicator tower equipment), which

provides a visual display of the airport surveillance radar (ASR)-7 data and radar and

beacon signals received from the PUB automated radar terminal system IIE radar

processing system.

1.10.2 Air Traffic Control Guidance

FAA Order 7110.65, “Air Traffic Control,” paragraph 2-6-3, “PIREP

Information,” states that, when an air traffic controller receives a PIREP that involves

icing, the controller should record the icing type and intensity and the air temperature in

which the icing is occurring. The order states that controllers are required to “relay

pertinent PIREP information to concerned aircraft in a timely manner” and the flight

service station (FSS) “serving the area in which the report was obtained.” 

As noted previously, about 0809 (about 1 hour before the accident), the pilot of a

Hawker jet, who had flown inbound to PUB from the southeast and had just landed,

reported to the PUB local controller that a little bit of ice had accumulated on the

airplane’s wing leading edges. The controller asked the pilot if the icing conditions were

“moderate mixed,” and the pilot replied that the icing conditions were “light to moderate

but it looks like it’s mixed.” The controller did not provide the PIREP to the accident flight

crew or to the Denver FSS. In postaccident interviews, the controller stated that he had

interpreted the pilot’s statement as “a trace or less” of ice and, therefore, not a reportable

amount. 

FAA Order 7110.65, Section 9, “Automatic Terminal Information Service

Procedures,” paragraph 2-9-1, “Application,” states that controllers should “use the ATIS

information, where available, to provide advance non-control airport/terminal area and

meteorological information to aircraft.” ATIS information includes the landing runway in

use; however, air traffic controllers are allowed to amend the ATIS information at any time

as situations change. ATIS information “Juliet,” which was effective at 0753, broadcast

that the landing runway in use at PUB was 8L; however, at 0905:56, the PUB local

controller instructed the flight crew to expect to land on runway 26R. During postaccident

interviews, the controller stated that he was often asked by corporate pilots to use the

runway opposite that being advertised on ATIS and that, as a service, he would provide the

closest runway as a matter of course as long as the winds allowed it.
Factual Information 13 Aircraft Accident Report

1.11 Flight Recorders

1.11.1 Cockpit Voice Recorder

The accident airplane was equipped with a B&D Instruments and Avionics CVR,

serial number A01148. The exterior of the CVR exhibited slight structural damage. The

CVR was sent to the Safety Board’s laboratory in Washington, D.C., for readout and

evaluation. The tape was played back normally and without difficulty. The recording

consisted of three separate channels of good quality audio information:29 the captain and

first officer audio panels and the cockpit area microphone (CAM). A transcript was

prepared of the entire 31-minute, 36-second recording (see appendix B). 

1.11.1.1 Cockpit Voice Recorder Sound Spectrum Study

The accident CVR recording was examined using computer signal and spectrum

analyzers30 at the Safety Board’s laboratory to determine whether the stall warning system

generated any aural alerts during the last 60 seconds of the flight. Specifically, the CAM

channel was examined to determine whether any sounds could be identified that

corresponded to the rotation rate of the stickshaker motor or weights. The study showed

that the stall warning appears to have activated at 0912:44.5 (about 1 second after the loss

of control) and continued to 0912:50.5. The stall warning appears to have reactivated at

0912:53.4 and continued to 0912:54.5 (the end of the recording). 

1.11.2 Flight Data Recorder

The airplane was not equipped with a flight data recorder nor was it required to be

so equipped.31

1.12 Wreckage and Impact Information

The airplane wreckage was located about 4 nm east of runway 26R at an elevation

of about 4,600 feet. The debris field was about 550 feet long and extended along a 230°

magnetic heading. All of the airplane’s major structures, including the cockpit, wings,

29 The Safety Board rates the quality of CVR recordings according to a five-category scale: excellent,

good, fair, poor, and unusable. See appendix B for a description of these ratings.

30 The computer signal analyzer provides detailed analysis of the analog waveform and provides the

specific frequency content of the signals and detailed timing information. The spectrum analyzer provides a

visual presentation of the frequency content of the recorded signals.

31 On December 22, 2003, the Safety Board issued Safety Recommendation A-03-65, which

recommended that the FAA require that all turbine-powered aircraft manufactured before January 1, 2007,

being used for commercial or corporate purposes under Part 91 be retrofitted with a crash-protected image

recording system by January 1, 2010. The Board reiterated Safety Recommendation A-03-65 on January 24,

2006. For additional information, see National Transportation Safety Board, Collision with Trees and Crash

Short of Runway, Corporate Airlines Flight 5966, British Aerospace BAE-J3201, N875JX, Kirksville,

Missouri, October 19, 2004, Aircraft Accident Report NTSB/AAR-06/01 (Washington, DC: NTSB, 2006). 
Factual Information 14 Aircraft Accident Report

fuselage, and empennage were found at the accident site. The main wreckage consisted of

a section of the airframe from the aft pressure bulkhead to the cockpit. The cockpit was

consumed by fire, and the instrument panel was crushed. The throttle quadrant was

melted, and only stubs of the control handles were present. The left and right wings were

found separated from the fuselage. The position of the landing gear actuators was

consistent with the landing gear being in the down-and-locked position at impact. 

Evidence of a postcrash fire was found along the debris field, beginning about

55 feet after the initial impact marks. Both engines were found separated from the

airplane. The engines showed no indications of uncontainment, case rupture, or in-flight

fire. Both engines were disassembled at PWC’s facility in Bridgeport, West Virginia,

under Safety Board supervision. Disassembly of the engines revealed no preexisting

defects or malfunctions. 

1.13 Medical and Pathological Information

Fluid and tissue specimens obtained from the captain and a fluid specimen

obtained from the first officer were transported to the FAA’s Civil Aerospace Medical

Institute for toxicological analysis. The specimens tested negative for alcohol and a wide

range of drugs, including drugs of abuse.32

1.14 Fire

No evidence of an in-flight fire was found. 

1.15 Survival Aspects

According to the Pueblo County Coroner’s Office autopsy report, the cause of

death for the captain, first officer, and six passengers was “multiple traumatic injuries.”

1.16 Tests and Research

1.16.1 Enhanced Ground Proximity Warning System Data Study

The EGPWS computer, which contained two flash memory chips, was recovered

on site. One of the memory chips exhibited several visible cracks to the package, and the

other chip was found undamaged. The two memory chips were sent to Honeywell’s

facility in Redmond, Washington, for examination and data recovery. 

32 The drugs tested in the postaccident analysis include (but are not limited to) marijuana, cocaine,

opiates, phencyclidine, amphetamines, benzodiazapines, barbiturates, antidepressants, antihistamines,

meprobamate, and methaqualone.
Factual Information 15 Aircraft Accident Report

Honeywell could only recover EGPWS data from the undamaged memory chip.

EGPWS data from 12 flight parameters, including altitude, ground speed, descent rate,

pitch, roll, and ground track, were available on the undamaged chip for about the last

30 seconds of the flight. A flight simulation conducted using the EGPWS data indicated

that two EGPWS alerts had been recorded; however, the identification of the alert types

was contained on the damaged chip and, therefore, the alert types could not be identified.

Further, the EGPWS data were compared with the radar-data-based calculations and

showed a good correlation with the calculations up to about 2 to 3 seconds into the loss of

control, after which time the data were considered unreliable because of the large dynamic

movements of the airplane.

1.16.2 Airplane Performance Study

The Safety Board conducted an airplane performance study using EGPWS data,

PUB ASR-7 radar data, manufacturer-provided aerodynamic data, and meteorological

information to establish a time history of the airplane’s motions and to estimate the

airplane’s performance parameters (including ground speed, airspeed, descent rate, and

aircraft pitch and roll angles) for the final portion of the flight. Nominal error or

uncertainty in the radar and wind data led to variables in the airplane performance

parameters; therefore, the performance parameters should be considered approximations.

According to the airplane performance study, the airplane started its final descent

from 7,000 feet at an airspeed of about 155 knots about 0911:26. Over about the next

30 seconds, the descent rate was about 800 feet per minute (fpm). By about 0912:30, as

the airplane was passing through about 6,200 feet, the descent rate had decreased to about

490 fpm, and the airspeed had decreased to about 98 knots. Over the next 10 seconds, the

airspeed continued to decrease to about 90 knots. Immediately after passing through about

6,100 feet, the airplane experienced the onset of a large roll to the left concurrent with a

sudden decrease in the pitch angle, consistent with the motion of an airplane that has

experienced an aerodynamic stall. 

1.17 Organizational and Management Information

At the time of the accident, Circuit City Stores, Inc., which is headquartered in

Richmond, Virginia, owned and maintained operational control of the accident airplane,

another Cessna 560 airplane (the sister ship), and a Cessna Citation 650 airplane.

Martinair, Inc., is a Part 135 aircraft charter and management company that began

operations in July 1986. Martinair has provided pilots and maintenance support for Circuit

City Stores airplanes through a management services agreement since 1993. At the time of

the accident, Martinair managed 15 aircraft, operated 11 aircraft, and had 33 full- and

part-time pilots and 8 aircraft mechanics. Martinair’s chief pilot stated that, although

Circuit City Stores flights fell under 14 CFR Part 91 operating rules, company pilots

generally adhered to Part 135 operating rules for these flights and used the same checklists

and standard operating procedures used for Part 135 flights. 
Factual Information 16 Aircraft Accident Report

1.17.1 Operational Guidance

1.17.1.1 Normal Operations 

According to the SimuFlite Cessna Citation V Technical Manual,33 a typical ILS

approach should be flown, in part, as follows:

When established on the localizer inbound to the FAF [final approach fix], ensure

that flaps are set to T.O. [takeoff] and APPR [approach].

Maintain airspeed at Vref+20+wind factor and initiate the Before Landing

checklist...

At glideslope intercept, start timing, begin descent, and extend full flaps.

Complete Before Landing checklist to the autopilot/yaw damper.

Maintain airspeed at Vref+10+wind factor...

Reduce power slightly to ensure crossing the runway threshold at Vref+wind factor. 

Martinair’s Operations Manual stated that, under normal circumstances, the

airspeed on final must be held at Vref+10 ±5 knots and that the airspeed must be bled off to

Vref at the runway threshold. 

1.17.1.2 Operations in Icing Conditions

The SimuFlite Cessna Citation V Technical Manual contains the following

warning: “with any residual ice present do not attempt to fly uncorrected Vref/Vapp

[34]

speeds. Stall speeds increase and stall warning margins decrease.” The technical manual

also contains the following caution:

In icing conditions, a small amount of residual ice forms on unprotected areas.

This is normal, but can cause an increase in stall speeds. When any amount of

residual ice is visible, the stall speeds increase by 8 knots; the Vref/Vapp speeds and

landing distances and the maximum landing weight permitted by brake energy

must be corrected.

Assuming some residual icing was present on the airplane’s surfaces during the

accident flight, the corrected Vref would have been 104 knots. At 0859:29, the CVR

recorded the first officer stating that the Vref was 96 knots. 

33 The guidance for operating in icing conditions in the Simuflite Cessna Model 560 Citation V

Technical Manual, which was used as the training manual for Martinair pilots, is in accordance with the

guidance contained in the Cessna Model 560 Citation V AFM.

34 Vapp is the landing approach airspeed with approach flaps and landing gear up.
Factual Information 17 Aircraft Accident Report

1.17.1.3 Anti-Ice and Deice Systems Usage 

According to the SimuFlite Cessna Citation V Technical Manual, when operating

in visible moisture and when the outside air temperature is between -30° and +10° C, the

pitot static heat and engine anti-ice systems should be turned to ON. The manual also

states that, if the temperature is above -18° C, the windshield bleed air switch should be

turned to LOW, and, if the temperature is below -18° C, the windshield bleed air switch

should be turned to HIGH. 

According to SimuFlite’s technical manual (and the Cessna AFM), the surface

deice boots should be used when ice buildup is estimated to be between 1/4- to 1/2-inch

thick. The manual further states, “Early activation of the boots may result in ice

bridging[35] on the wing, rendering the boots ineffective. Late activation (if accumulation

is more than 1/2-inch thick) may not clear the ice.” The manual also states the following:

When reconfiguring for approach and landing...with any ice accretion visible on

the wing leading edge, regardless of thickness, activate the surface deice system.

Continue to monitor the wing leading edge for any reaccumulation.

1.17.2 Flight Crew Training 

Martinair provides initial in-house ground school training to company pilots. After

the in-house training, pilots attend flight simulator training at CAE SimuFlite. 

1.17.2.1 Operations in Icing Conditions

During postaccident interviews, several SimuFlite instructors stated that guidance

on operations in icing conditions is taught in initial and recurrent ground school. The

training includes a review of the anti-ice and deice systems and their usage and anti-ice

failure scenarios. The instructors also stated that icing operations in the simulator involved

introducing ice on the wings. Pilots are taught to activate the deice boots after about 1/4 to

1/2 inch of ice has accumulated on the wings and to use the anti-ice systems when flying

in visible moisture36 and when the outside air temperature is between -30° and +10° C. 

According to the SimuFlite instructors, the specific items to be covered during

simulator training on operations in icing conditions are left to the discretion of the

individual instructors. A review of SimuFlite’s training syllabus also revealed that no

specific instruction exists to evaluate a pilot’s performance of the AFM procedures to

increase the airspeed and operate the deice boots during approaches when ice is present on

the wings. Further, one of the SimuFlite Cessna 560 instructors was unaware of these

AFM procedures. Investigators also interviewed a Cessna 560 instructor from another

35 Ice bridging is a phenomenon in which ice in the shape of an inflated deice boot forms after the boot

is cycled. Ice bridging had been known to occur on older deice boot designs that used larger tubes and lower

pressures, resulting in slower inflation and deflation rates.

36 The manual indicates that visible moisture includes, but is not limited to, the following conditions:

fog with visibility less than 1 mile, wet snow, and rain.
Factual Information 18 Aircraft Accident Report

major flight training center, and he stated that, although he believed that each instructor

emphasized the icing approach procedures during simulator training, the center’s syllabus

contained no instruction to ensure that the instructors are evaluating the procedures.

1.17.2.2 Stall Recovery 

A SimuFlite instructor indicated that stalls in the clean, takeoff, and landing

configurations are covered during training and checkrides. He stated that stall recovery in

the Cessna 560 should be initiated at stickshaker activation and that recovery from an

impending stall consisted of adding maximum power while conserving the altitude as

much as possible.

1.18 Additional Information

1.18.1 Cessna 550 and 560 Airplanes Icing-Related Flight Testing 

and Subsequent Actions

In early 1996, the FAA conducted preliminary evaluations of the Cessna 560 stall

speeds and characteristics when operating in icing conditions. The evaluations were

conducted partially as the result of the following icing-related Cessna 55037 and 560

accidents:38

• On December 30, 1995, a Cessna 560 crashed while circling to land in icing

conditions in Eagle River, Wisconsin.39 The investigation revealed that about

1/8 inch of rime ice had accumulated on the left wing and horizontal stabilizer

leading edges. 

• On January 2, 1996, a Cessna 560 crashed while on final approach in icing

conditions in Augsburg, Germany.40 The pilots reported that the airplane

started to buffet, entered a stall, and rolled right. No stall warnings were

activated during the flight. The investigation by the German Federal Bureau of

Accidents Investigation (BFU) revealed that about 2 mm (0.078 inch) of ice

had accumulated along the wing leading edges.

37 The airfoil used on model 560 series airplanes is a modified version of the airfoil used on

model 550 series airplanes. The main spar height is the same; however, the leading edge and the upper

surface curvature have been changed to improve high airspeed performance. 

38 The FAA also noted that several test pilots from its training academy had reported concerns about the

Cessna 560’s stall handling characteristics.

39 The description of this accident, CHI96FA067, can be found on the Safety Board’s Web site at

<http://www.ntsb.gov>.

40 For more information, see German Federal Bureau of Accidents Investigation, Report on the

Accident to the Aircraft Cessna 560 on January 2, 1996, at Augsburg, File No. CX 001-0/96 (Braunschweig

City, Germany: BFU, 1996).
Factual Information 19 Aircraft Accident Report

• On February 19, 1996, a Cessna 550 crashed while on final approach in

Salzburg, Austria.41 On the basis of radar recordings and witness testimony, the

BFU determined that the airplane entered a stall, banked left, and became

uncontrollable. The BFU stated that heavy icing at low altitudes prevailed

during the approach and that the accident “happened because the minimum

control airspeed was undershot during the final approach.” 

As a result of flight tests conducted in early 1996 with the Cessna 560, the FAA

issued Priority Letter Airworthiness Directive (AD) 96-24-06, which was applicable to the

Cessna 560, in November 1996. AD 96-24-06 required revising the Cessna Model 560

Citation V AFM to provide flight crews with airspeed limitations, deice system

operational procedures, and landing performance information to be used during approach

and landing when residual ice was present or expected to prevent the uncommanded roll

of the airplane in such conditions. 

In late 1996, with Cessna participation, the FAA conducted additional flight tests

with Cessna 550 and 560 series airplanes to assess the airplanes’ stall speeds, warnings,

and characteristics. The FAA conducted the flight tests using airplanes with and without

1/2-inch-thick ice shapes installed on the protected (that is, those surfaces with deice

boots) and unprotected surfaces of the wing.42 The flight tests of the Cessna 550 revealed

that the airplane had an acceptable stall warning margin with and without the ice shapes

installed. The flight tests of the Cessna 560 revealed that the stall warning margin was

insufficient with and without ice shapes installed.43

Specifically, the flight tests of the Cessna 560 revealed that, even without ice

shapes installed, the stall warning system activated only about 1 to 2 knots before a

significant lateral roll tendency and subsequent stall occurred. The tests also showed that,

with ice shapes installed, the stall warning system activated shortly after or concurrent

with a stall and a subsequent significant lateral roll. The tests indicated that the stall speed

increased from 3 to 5 knots with the ice shapes installed and that the stall warning system

did not compensate for the increased stall speed. 

In early 1999, Cessna began incorporating modified stall warning systems on the

Cessna 560 airplane (including the accident airplane) to provide a sufficient stall warning

margin for operations in icing conditions. The modifications resulted in a stall warning

margin increase of about 5 knots and were outlined in Cessna Service Bulletins (SB)

SB560-34-69 and SB560-34-70. On April 3, 2000, the FAA issued AD 2000-03-09,

41 An English translation of the full accident report was not available; however, an English summary of

the findings and the probable cause was provided to investigators by the BFU.

42 At the time of the Cessna 560 certification flight tests, artificial ice shapes were not required to be

installed on the protected surfaces of the airplane. According to the original Cessna 560 flight testing

certification, the flight tests were conducted in natural icing conditions and with artificial ice shapes

installed on the unprotected surfaces of the airplane. According to the FAA, 1/2-inch ice shapes were used

for the 1996 tests because these shapes represented the type of ice accumulated during the most likely

encountered icing conditions and because the Cessna Model 560 Citation V AFM instructed pilots to

activate the deice boots when ice accumulation was estimated to be from 1/4- to 1/2-inch thick. 

43 Title 14 CFR 25.207 requires that the stall warning begin at a speed exceeding the stall speed by a

margin of not less than 5 knots. 
Factual Information 20 Aircraft Accident Report

which superseded AD 96-24-06. AD 2000-03-69 retained the requirements contained in

AD 96-24-06 and added a requirement to mandate the modifications outlined in Cessna

SBs SB560-34-69 and SB560-34-70. The FAA indicated that the modified stall warning

systems would also protect against the undesirable stall characteristics exhibited during

the previous icing-related Cessna accidents and the 1996 ice shape tests. 

1.18.2 Previous Icing-Related Safety Recommendations 

The Safety Board has previously issued numerous icing-related safety

recommendations, several of which are on the Safety Board’s List of Most Wanted

Transportation Safety Improvements. Five previously issued icing-related safety

recommendations are relevant to the Pueblo accident and are detailed in this section. One

of these recommendations was issued as a result of the investigation of the October 31,

1994, accident involving American Eagle flight 4184, which crashed during a rapid

descent after an uncommanded roll excursion during icing conditions.44 The other four

relevant recommendations were issued as a result of the investigation of the January 9,

1997, accident involving Comair Airlines, Inc., flight 3272, which experienced a loss of

control while maneuvering with ice accumulation on the wings.45

1.18.2.1 Deice Boot System Activation

During the Comair flight 3272 accident investigation, the Safety Board learned

that the AFMs for many aircraft, including the Cessna 560, instructed pilots to delay initial

deice boot activation until they observed 1/4- to 1/2-inch-thick ice accumulation on the

wing surface. Further, the Cessna Model 560 Citation V AFM states, “early activation of

the boots may result in ice bridging on the wing.” Additionally, Advisory Circular

(AC) 25.1419-1A, “Certification of Transport Category Airplanes for Flight in Icing

Conditions,” dated May 7, 2004, states, “many AFMs specify ice accumulation thickness

prior to activation of the deicer boot system. The practice originates from a belief that a

bridge of ice could form if boots are operated prematurely.” However, the AC further

states the following:

Although ice may not shed completely by one cycle of the boots, this residual ice

will usually be removed during subsequent boot cycles and does not act as a

foundation for a bridge to form. The AFM procedure for boot operations should

be to operate the boots at the first sign of ice and not wait for a specific amount of

ice to accumulate. 

44 For additional information, see National Transportation Safety Board, In-flight Icing Encounter and

Loss of Control, Simmons Airlines, d.b.a. American Eagle Flight 4184, Avions de Transport Regional (ATR)

Model 72-212, N401AM, Roselawn, Indiana, October 31, 1994; Volume I Safety Board Report, Aircraft

Accident Report NTSB/AAR-96/02 (Washington, DC: NTSB, 1996).

45 For additional information, see National Transportation Safety Board, In-Flight Icing Encounter and

Uncontrolled Collision With Terrain, Comair Airlines, Inc., Flight 3272, Embraer EMB-120RT, N265CA,

Monroe, Michigan, January 9, 1997, Aircraft Accident Report NTSB/AAR-98/04 (Washington, DC: NTSB,

1998).
Factual Information 21 Aircraft Accident Report

Additionally, information gathered at a 1997 Airplane Deice Boot Bridging

Workshop, which included participants from the FAA and the National Aeronautics and

Space Administration (NASA); subsequent icing tunnel studies; and flight tests conducted

as part of the Comair investigation revealed no evidence that modern turbine-powered

airplanes (that is, airplanes equipped with high-pressure, segmented pneumatic deice

boots that quickly inflate and deflate) were at risk for ice bridging. Further, a search of the

Safety Board’s accident database revealed no accidents related to ice bridging.

The icing tunnel tests, wind tunnel data, and existing icing research data revealed

that thin (1/4 inch or less), rough ice accumulations on the wing leading edge deice boot

surfaces could be, depending on distribution, as aerodynamically detrimental to an

airplane’s performance as larger ice accumulations and that such ice could be difficult for

pilots to perceive. As a result of these findings, the Safety Board issued Safety

Recommendation A-98-91, which asked the FAA to do the following:

Require manufacturers and operators of modern turbopropeller-driven airplanes in

which ice bridging is not a concern to review and revise the guidance contained in

their manuals and training programs to emphasize that leading edge deicing boots

should be activated as soon as the airplane enters icing conditions.

On July 16, 1999, the FAA issued Notice for Proposed Rulemaking

(NPRM) 99-NM-136-AD, which was applicable to Cessna model 500, 501, 550, 551, and

560 series airplanes and proposed revising the applicable AFMs to include a requirement

to activate the deice boots at the first sign of ice accumulation and to cycle the boots

automatically, if the automatic mode was available, or to cycle the boots manually to

minimize ice accumulation on the airframe. From July 1999 to March 2000, the FAA

issued 18 similar NPRMs applicable to 14 CFR Part 23 airplanes and 21 NPRMs

applicable to Part 23 and 25 airplanes equipped with pneumatic deice boots.46

In an August 12, 1999, letter to the FAA, Cessna requested that NPRM

99-NM-136-AD be withdrawn, contending that the affected airplanes’ service history in

icing conditions, the modifications made to the airplanes’ stall warning systems, and the

minimum airspeed in icing conditions guidance contained in its AFM validated that the

airplanes could operate safely in icing conditions and that, therefore, the NPRM was not

warranted. In a September 25, 2000, response letter to Safety Recommendation A-98-91,

the FAA stated that it withdrew NPRM 99-NM-136-AD in November 1999 because

manufacturer’s data indicated that the affected aircraft could operate safely with ice

accretion on the protected surfaces. The FAA also withdrew six of the other NPRMs it

issued from July 1999 to March 2000 for similar reasons. 

On May 19, 2003, the FAA informed the Safety Board about recommendations an

Aviation Rulemaking Advisory Committee (ARAC) Ice Protection Harmonization

Working Group (IPHWG) had made to revise Parts 25 and 121. The proposed revisions

46 In a March 12, 2000, response letter, the Safety Board expressed concern that the proposed ADs

would require that the deice boot system be activated at the first sign of ice accumulation, not as soon as the

airplane enters icing conditions.
Factual Information 22 Aircraft Accident Report

would add a requirement that operators’ guidance state that the deice system be activated

as soon as the airplane enters icing conditions.47 However, in the intervening 3 years, the

FAA has taken no further action; therefore, on May 10, 2006, the Board classified

Safety Recommendation A-98-91 “Open—Unacceptable Response,” pending issuance of

a final rule adopting the regulatory changes proposed by the ARAC IPHWG. 

1.18.2.2 Certification Requirements for Flight into Icing Conditions

The Safety Board determined during the American Eagle flight 4184 accident

investigation that SLD conditions can cause ice accretions that are more aerodynamically

detrimental than those that were considered during the initial certification of many

existing airplanes for flight in icing conditions (that is, those conditions that fell within the

Part 25, Appendix C envelope).48 As a result, the Board issued Safety Recommendation

A-96-54 (superseding Safety Recommendation A-81-116), which asked the FAA to do the

following: 

Revise the icing criteria published in 14...CFR Parts 23 and 25, in light of both

recent research into aircraft ice accretion under varying conditions of liquid water

content, drop size distribution, and temperature, and recent developments in both

the design and use of aircraft. Also, expand the Appendix C icing certification

envelope to include freezing drizzle/freezing rain and mixed water/ice crystal

conditions, as necessary. 

Safety Recommendation A-96-54 was reiterated in the Comair flight 3272

accident report and is currently on the Safety Board’s List of Most Wanted Transportation

Safety Improvements. In a March 6, 2006, letter, the FAA stated that the ARAC IPHWG

is continuing to develop a revision to Part 25 to require a demonstration that an airplane

can safely operate in SLD conditions for an unrestricted time or can detect SLD and safely

exit icing conditions. 

The Safety Board noted in its May 10, 2006, letter that, although the work of the

IPHWG is responsive to this recommendation, the actions are proceeding at an

unacceptably slow pace and that the FAA has not yet received the recommendations from

the IPHWG, prepared regulatory analyses, issued an NPRM, analyzed comments, or

completed the many other tasks involved in issuing new regulations. Pending

development and issuance of regulatory requirements for both Part 23 and 25 airplanes to

demonstrate that they can safely operate in SLD conditions for an unrestricted time or can

detect the SLD and safely exit icing conditions, the Board classified Safety

Recommendation A-96-54 “Open—Unacceptable Response.”

The Safety Board also determined during the Comair flight 3272 accident

investigation that the ice accretions and conditions considered during certification for

47 The ARAC IPHWG also stated that an operator’s guidance could only state that the deice system

should be activated at the first sign of ice accumulation if the operator had demonstrated through additional

flight tests that the airplane could operate safely with some ice accumulation.

48 Part 25, Appendix C specifies the kind of icing conditions in which an airplane’s ice protection

system must be able to operate. 
Factual Information 23 Aircraft Accident Report

flight into icing conditions were not representative of all types of ice that could be

encountered while operating in icing conditions, including rough ice accretions of less

than 1/4 inch, which can severely degrade an airplane’s performance. Further, the effects

of delayed anti-ice and deice system activation, intercycle ice accretions,49 or residual ice

accretions were not addressed in the icing certification rules. Therefore, the Board issued

Safety Recommendations A-98-92 and -100, both of which are currently on the Board’s

List of Most Wanted Transportation Safety Improvements. Safety Recommendation

A-98-92 asked the FAA to do the following:

Conduct additional research to identify realistic ice accumulations, to include

intercycle and residual ice accumulations and ice accumulations on unprotected

surfaces aft of the deicing boots, and to determine the effects and criticality of

such ice accumulations; further, the information developed through such research

should be incorporated into aircraft certification requirements and pilot training

programs at all levels. 

In a September 21, 2001, response letter, the FAA indicated that sufficient

information and methods were not available at that time to provide additional guidance

concerning the determination of critical ice shapes in aircraft certification and that,

therefore, it would sponsor additional needed research. In an October 26, 2005, response

letter, the FAA indicated that it had completed and would shortly issue a draft revision to

AC 20-73, “Aircraft Ice Protection,” which included the certification guidance on

determining critical ice shapes, descriptions of intercycle and residual ice accretions, and

the aerodynamic penalties associated with these ice shapes. Although the FAA issued

AC 20-73A on August 16, 2006, Safety Recommendation A-98-92 remains classified

“Open—Unacceptable Response,” pending the receipt of information regarding any new

research conducted in response to this recommendation. 

The Safety Board also issued a safety recommendation concerning the

determination of critical ice shapes, A-98-100, to the FAA, which stated the following:

When the revised icing certification standards [recommended in Safety

Recommendation A-98-92] and criteria are complete, review the icing

certification of all turbopropeller-driven airplanes that are currently certificated

for operation in icing conditions and perform additional testing and take action as

required to ensure that these airplanes fulfill the requirements of the revised icing

certification standards.

On November 4, 2005, in response to Safety Recommendation A-98-100, the FAA

issued an NPRM titled, “Airplane Handling Characteristics in Icing Conditions,” which

proposed to revise 14 CFR 25.143, “Proof of Compliance,” by adding a new paragraph,

(i)(1), that specifies the certification requirements for airplane performance or handling

qualities for flight in icing conditions and the type of ice accretions (including the size,

shape, and location) that must be used to demonstrate compliance in each phase of flight.

Specifically, the NPRM stated that thin, rough ice accretions must be considered to show

49 Intercycle ice is ice that has accreted on the deice surface between boot activation cycles.
Factual Information 24 Aircraft Accident Report

compliance with proposed paragraph 25.143(i)(1). In its January 2006 comments on the

NPRM, the Safety Board stated that it agreed with the intent of the NPRM and added that

the ice used to demonstrate compliance with proposed paragraph 25.143(i)(1) should

accurately represent thin, rough ice accretions, which can cause severe aerodynamic

penalties. 

On November 4, 2005, the FAA also proposed AC 25-1X, “Performance and

Handling Characteristics in the Icing Conditions Specified in Part 25, Appendix C,” which

was intended to provide guidance for implementing the regulations proposed in the

NPRM. In its January 2006 comments on the proposed AC, the Safety Board noted that

the results of the research conducted as a part of the Comair flight 3272 accident

investigation are currently included in Appendix R of draft AC 20-73, “Aircraft Ice

Protection.” Appendix R, which is also referenced in Appendixes 1 and 2 of proposed

AC 25.21-1X, includes guidance on determining critical ice shapes and their associated

roughness, descriptions of intercycle and residual ice accretions, and the aerodynamic

penalties associated with these ice shapes.50

Although the Safety Board agreed with the FAA’s proposed regulatory changes, in

its May 10, 2006, response letter, the Board noted that the FAA has not applied the new

information to all in-service turbopropeller-driven airplanes. Although the FAA indicated

that no airplanes have an unsafe condition, the Board stated that it was concerned that the

FAA reached this conclusion based on its belief that no accidents or serious incidents had

occurred related to this issue. However, the Board stated that, during the 1990s, a number

of accidents had occurred involving airplanes that had passed the certification standards

and for which the FAA believed there was no unsafe condition requiring action and that

these accidents generated new information that the FAA could now use. The Board stated

that, to meet the intent of Safety Recommendation A-98-100, the FAA would need to

formally evaluate (perhaps by conducting flight tests) all in-service turbopropeller-driven

aircraft to ensure that these aircraft comply with all current icing certification criteria for

new aircraft. The Board asked the FAA to provide a list of the aircraft that it had formally

evaluated and a summary of the findings and resultant actions. Pending receipt of this

information, Safety Recommendation A-98-100 was classified “Open—Unacceptable

Response.” 51

1.18.2.3 Stall Warning Margins

The Safety Board also determined during the Comair flight 3272 investigation that

the stall warning did not activate until after the stall, as in this accident, because ice

accumulation on the airplane had increased the stall speed and that the stall warning

system was not designed to account for the increase caused by the type of ice that had

50 For more information about the testing conducted to determine the effects of residual and intercycle

ice accretions, see section 1.18.3.

51 Safety Recommendation A-98-100 is on the Safety Board’s List of Most Wanted Transportation

Safety Improvements. Accordingly, Safety Recommendation A-07-16, which supersedes Safety

Recommendation A-98-100, will automatically be placed on the Most Wanted List.
Factual Information 25 Aircraft Accident Report

accreted on the airplane. As a result, the Board issued Safety Recommendation A-98-96,

which asked the FAA to do the following:

Require manufacturers and operators of all airplanes that are certificated to

operate in icing conditions to install stall warning/protection systems that provide

a cockpit warning (aural warning and/or stick shaker) before the onset of stall

when the airplane is operating in icing conditions.

In a September 21, 2001, response letter, the FAA stated that it was pursuing

regulatory development projects that would require both new and in-service airplanes to

have stall warning systems installed that provide a cockpit warning before the onset of a

stall when operating in icing conditions. However, in an October 26, 2005, response letter,

the FAA stated that, after further review, it had determined that such a requirement for all

in-service airplanes would impose a cost burden not commensurate with the potential

safety benefits and that, therefore, it would take appropriate action on in-service airplane

designs only if an unsafe condition were identified. 

The November 2005 NPRM proposed changes to 14 CFR 25.207 to require that

newly type-certificated airplanes be equipped with stall warning systems that provide a

stall warning before the onset of a stall when the airplane is operating in icing conditions.

In its comments on the NPRM, the Safety Board stated that the proposed changes appear

to address the intent of Safety Recommendation A-98-96 for newly type-certificated

airplanes; however, the proposed changes do not address in-service airplanes. Further, in

its May 2006 response letter, the Board stated that it was not acceptable for the FAA to

wait until an accident or serious incident occurred to reveal that an unsafe condition

existed on an in-service airplane. As a result, the Board classified Safety Recommendation

A-98-96 “Open—Unacceptable Response,” pending issuance of a final rule associated

with the November 2005 NPRM that includes a requirement that both newly

type-certificated and in-service airplanes be equipped with stall warning systems that

provide a cockpit warning before the onset of a stall in icing conditions. 

1.18.3 Residual and Intercycle Ice and Automatic Deice Boot 

System Information 

In May 2002, as a result of additional testing conducted during the Comair

flight 3272 investigation, the FAA published a report titled, Effect of Residual and

Intercycle Ice Accretions on Airfoil Performance,

52 which presented the results of testing

designed to characterize and evaluate the aerodynamic performance effects of residual and

intercycle ice accretions resulting from the cyclic operation of a typical aircraft deice boot

system.53 The tests were conducted using a scaled version of the EMB-120 airfoil

outboard wing section, which is similar to the Cessna Citation airfoil, and liquid water

52 Federal Aviation Administration, Office of Aviation Research, Effect of Residual and Intercycle Ice

Accretions on Airfoil Performance, DOT/FAA/AR-02/68 (Washington, DC: 2002).

53 Some pneumatic deice boot systems can be turned on and activated automatically at either slow/low

(3-minute) or fast/high (1-minute) cycle intervals. Cessna Citation series airplanes are not equipped with

automatic deice boot recycling systems.
Factual Information 26 Aircraft Accident Report

contents and mean volumetric diameters that fell within the current envelopes for known

icing certification. During the tests, the deice boots were cycled at both 1- and 3-minute

intervals. 

Results from the icing tests showed that the intercycle ice accretions were much

larger in size and surface extent than residual ice accretions and that the intercycle ice

shapes caused significant performance degradation. The testing showed that the deice

boots generally removed the ice from the wing leading edge and left little residual ice. A

single continuous maximum case was run with 1-minute boot cycles, which was found to

be very effective in minimizing the size of the intercycle ice accretion. The tests also

revealed that the deice boot system was equally effective at shedding ice when activated at

the first sign of ice as when activated once a 1/4 inch of ice had accumulated. The FAA’s

test report recommended the “early and often” approach to deicing (that is, activating the

deice boots as soon as ice is detected and cycling the boots at 1-minute intervals) to limit

the size of residual and intercycle ice accretions.

On May 7, 2004, the FAA issued AC 25.1419-1A, which stated the following.

The recommended AFM procedure for boot operation should be to operate the

boots at the first sign of ice. ... The boots should be operated until icing

conditions are exited and ice no longer adheres to the airframe. 

On July 21, 2004, the FAA issued revised AC 23.1419-2C, “Certification of

Part 23 Airplanes for Flight in Icing Conditions,” which reiterated the FAA’s technical

report findings and added the following:

For deicing systems that do not have a timer to cycle the system automatically

once activated, the additional task of manually cycling deicing systems on pilot

workload should be evaluated. A recent Part 23 applicant found that definition of

airframe deicing boot intercycle and residual ice steered them toward one-minute

boot cycles and the workload evaluation dictated an automatic timer for the boots.
27 Aircraft Accident Report

2. Analysis

2.1 General

The captain and first officer were properly certificated and qualified under Federal

regulations. No evidence indicated any preexisting medical or physical condition that

might have adversely affected the flight crew’s performance during the accident flight. A

review of the pilots’ 72-hour histories revealed that the pilots slept well in the days leading

up to the accident flight and went to bed early in preparation for an early departure. No

evidence was found that fatigue degraded the performance of either pilot on the day of the

accident.

The weight and balance of the airplane were within landing limits.

The recovered components showed no evidence of any preexisting powerplant,

structural, or system failures.

The PUB local controller did not provide the accident flight crew or the Denver

FSS with the PIREP reporting light to moderate icing; however, this was not a factor in the

accident because CVR information indicated that the flight crew was aware of the icing

conditions.

During the approach, the flight crew of the sister ship, which was following the

accident flight, cycled the deice boots numerous times and maintained a high airspeed

and, subsequently, landed safely, indicating the importance of taking these actions to

counteract the hazardous effects of icing.

This analysis discusses the accident sequence, including the flight crew’s

performance. This analysis also discusses inadequate training on operations in icing

conditions, inadequate deice boot system operational guidance, the need for automatic

deice boot systems, inadequate icing flight test certification requirements, and inadequate

stall warning margins in icing conditions.

2.2 Accident Sequence

2.2.1 Descent Into Icing Conditions

Surface observations and radar data indicated that freezing drizzle conditions

existed in the PUB area around the time of the accident and that temperatures were below

freezing from the surface to 30,000 feet. Several PIREPs and NWS products transmitted

around the time of the accident, including winter weather advisories that warned of

freezing drizzle, confirmed the presence of icing conditions in the PUB area. CVR
Analysis 28 Aircraft Accident Report

evidence indicates that, starting about 0851, the flight crew began taking actions to

minimize the icing’s hazardous effects, such as activating the airplane’s engine and

windshield anti-ice systems. About 4 minutes later, the first officer stated that he saw a

little bit of “grayish ice,” which is indicative of ice that has a rough surface, building up on

the wing leading edges. He then stated that there was “a real thin line back there.” 

An analysis of the CVR and meteorological information indicated that mixed icing

conditions existed from about 21,000 to 14,000 feet. Radar data and CVR information

indicated that the airplane was in this icing layer for about 5 1/2 minutes. At 0858:20, as

the airplane was descending through about 18,000 feet, the first officer suggested to the

captain that he might want to cycle the deice boots.54 After cycling the deice boots, the

captain indicated that the deice boots might have shed a little of the ice but that some ice

remained on the wing, indicating the presence of residual ice. 

2.2.2 Approach to Landing 

In accordance with the SimuFlite Cessna Citation V Technical Manual and the

Cessna Model 560 Citation V AFM, pilots were trained that, when any residual ice is

present or can be expected during approach and landing, Vref must be increased by 8 knots.

The manuals also contained both a caution and a warning indicating that stall speeds

increased during operations in icing conditions, and that, therefore, Vref must be increased. 

At 0859:29, the CVR recorded the first officer state that the Vref was 96 knots. In

the case of this flight, the Vref should have been increased from 96 to 104 knots because of

the icing conditions. The CVR did not record either pilot mention increasing the airspeed

at any point during the approach. Therefore, the Safety Board concludes that the flight

crew did not increase the Vref while operating in icing conditions, contrary to company

procedures and manufacturer guidance. 

2.2.3 Final Approach

At 0908:25, while at an altitude of about 9,400 feet, the first officer reported that

the flight was in IMC, and, about 1 minute later, while at an altitude of about 7,400 feet, he

reported that clear ice had accumulated on the airplane’s wing. CVR and meteorological

information indicated that the airplane likely encountered SLD conditions from 9,400 to

6,100 feet (the calculated altitude at the time of the upset) and that the airplane was likely

in these conditions for about 4 1/2 minutes. During this time, about 1 to 4 mm (0.039 to

0.156 inch) of additional ice could have accumulated on the wing leading edges. The

Safety Board concludes that the airplane encountered SLD conditions, which are most

conducive to the formation of thin, rough ice on or aft of the protected surfaces, during

about the last 4 1/2 minutes of the flight. The Safety Board further concludes that the

airplane had residual ice on the wings after the deice boots were activated earlier in the

54 As noted, the pilots had been trained to wait until 1/4- to 1/2-inch-thick ice accumulation was visible

on the wing leading edges before activating the deice boots.
Analysis 29 Aircraft Accident Report

flight and that this ice would have affected the overall thickness, roughness, and

distribution of the SLD ice accumulation. 

According to the airplane performance study, about 0910, the airplane started its

final descent from 7,000 feet at an airspeed of about 155 knots. By about 0911:35, the

airspeed had started to decrease. CVR evidence indicated that the landing gear was

extended at 0911:10, followed by extension of the speedbrakes and selection of full flaps.

At 0912:04, the first officer stated, “and you are plus twenty five,” to which the captain

replied, “slowing.” On the basis of a Vref of 96 knots, the airspeed would have been about

121 knots at the time of the first officer’s statement. At 0912:37, when the airplane was at

an altitude of about 6,100 feet, the first officer told the captain that he might want to run

the deice boots and that they had the Vref. 

Company procedures for approach and landing in icing conditions stated that,

when reconfiguring for approach and landing (extending landing gear and selecting full

flaps), pilots should activate the deice boot system when any ice accumulation, regardless

of thickness, is visible on the wing leading edges and continue to monitor the leading

edges for any reaccumulation. Although the CVR recorded the first officer mention to the

captain that they might want to activate the deice boots at 0912:37, there is no evidence

that the deice system was activated during the approach. Therefore, the Safety Board

concludes that the flight crew did not activate the deice boots when configuring for the

approach and landing, which was contrary to company procedures and manufacturer

guidance.

The airplane performance calculations showed that, immediately after passing

through about 6,100 feet, the airplane entered a large roll to the left concurrent with a

sudden decrease in pitch, indicating the start of the loss of control and aerodynamic stall.

No evidence exists indicating that the stall warning activated before or concurrent with the

upset. In accordance with the Cessna Model 560 Citation V AFM and the design of the

stall warning system, the accident airplane’s stall warning should have activated about

86 knots. 

Although it could not be determined at precisely what airspeed the loss of control

occurred, airplane performance calculations indicated that the stall occurred at an airspeed

of about 90 knots, which was well above the expected stall speed in icing conditions of

81 knots. According to company and manufacturer guidance on approach airspeeds in

icing conditions, the airplane’s airspeed at the time of the upset should have been about

114 knots.55 The performance calculations and EGPWS ground speed data showed that

the airspeed continued to decrease until the loss of control. The Safety Board concludes

that the flight crew failed to maintain adequate airspeed during the final approach in icing

conditions, which led to an aerodynamic stall from which they did not recover. 

55 According to the guidance, the approach airspeed should be Vref+10 knots, in this case, 106 knots.

Because the guidance requires that 8 knots be added to the approach airspeed in icing conditions, the

approach airspeed should have been 114 knots. 
Analysis 30 Aircraft Accident Report

As noted, the flight crew did not increase the approach airspeed or activate the

deice boots during the approach, which is required for the Cessna 560 when ice is present

on the wing. Although it could not be determined precisely why the flight crew did not

maintain adequate airspeed or activate the deice boots during the approach, the Safety

Board discovered during the investigation that there may be insufficient training on

operational procedures in icing conditions. For example, postaccident interviews with

simulator flight instructors revealed that these procedures might not be getting

emphasized during simulator training because the details of the training are left up to the

individual instructors. Further, a review of two flight training centers’ syllabuses revealed

that they do not state that instructors should emphasize these procedures. The Board is

concerned that these operational procedures are not being consistently evaluated during

simulator training.

The Safety Board concludes that pilots could benefit from the reinforcement

during training of the Cessna 560 AFM requirements to increase the airspeed and operate

the deice boots during approaches when ice is present on the wings. Therefore, the Safety

Board believes that the FAA should require that operational training in the Cessna 560

airplane emphasize the AFM requirements that pilots increase the airspeed and operate the

deice boots during approaches when ice is present on the wings. 

2.2.4 Flight Crew Monitoring and Workload Management

The Safety Board examined the flight crew’s actions during the approach to

determine the role of the timing of the approach briefing in the accident sequence.

Although the flight crew had expected to land on runway 8L, based on the current ATIS

information, at 0905:56, approach control issued vectors for the ILS to runway 26R.

According to the CVR, the flight crew noted the change in the runway assignment and

immediately tuned the radios and set the inbound course. However, subsequent discussion

about the details of the runway 26R approach was not initiated until almost 5 minutes

later, at 0910:47. During the remaining 2 minutes before the stall, the flight crew needed

to intercept the localizer and glideslope and configure and slow the airplane for the

approach. However, CVR evidence showed that, although these airplane-handling tasks

were being performed, the flight crew was concurrently briefing the ILS 26R approach.

Specifically, from 0912:17 to 0912:31, as the airspeed was decreasing, the flight crew

briefed the missed approach procedure for runway 26R. It was only at the end of this

discussion that the first officer recognized and called for the need to run the deice boots

and indicated that the airplane had slowed to Vref.

The Safety Board recognizes that a runway change can disrupt a flight crew’s

planning and may affect the pilots’ ability to conduct an approach briefing during a

relatively low workload phase of flight, such as the top of the descent. When the runway

change occurs late in the approach, it is important for flight crews to determine how and

when to conduct the briefing to ensure that the objectives of the briefing are achieved

without compromising safety of flight.56 For the accident flight crew, the runway change

occurred early enough for the briefing to have been completed before the pilots began to

configure and slow the airplane for final approach. Literature on monitoring emphasizes
Analysis 31 Aircraft Accident Report

that cockpit workload should be distributed to minimize conflicting task demands during

critical phases of flight. In this case, the flight crew’s delayed approach briefing served to

divert the pilots’ attention from handling the airplane, managing the deice boot system,

and monitoring the tasks that had to be performed during that period. The Safety Board

concludes that the briefing conducted late in the approach was a distraction that impeded

the flight crew’s ability to monitor and maintain airspeed and manage the deice system. 

The Safety Board has long recognized the importance of flight crew monitoring

skills in accident prevention. For example, the Board’s 1994 safety study of 37 major

flight crew-involved accidents found that, for 31 of these accidents, inadequate

monitoring and/or cross-checking had occurred.57 The study found that flight

crewmembers frequently failed to recognize and effectively draw attention to critical cues

that led to the accident sequence. As a result of this safety study, the Board issued Safety

Recommendations A-94-3 and -4 to the FAA concerning the need for enhanced training of

pilot monitoring skills. The recommendations stated, in part, that the FAA should require

airlines operating under 14 CFR Part 121 to provide line operational simulation training

that “allows flightcrews to practice, under realistic conditions, non-flying pilot functions,

including monitoring and challenging errors made by other crewmembers” and that

airlines’ initial operating experience programs should include training and experience for

check airmen and pilots “in enhancing the monitoring and challenging functions.”58

In response to these recommendations, the FAA upgraded its written guidance to

industry to enhance pilot training on monitoring. Specifically, on September 8, 1995, the

FAA revised AC 120-51, “Crew Resource Management Training,” to emphasize

monitoring issues. The guidance in AC 120-51 stated that “effective monitoring and

cross-checking can be the last line of defense that prevents an accident” and that “the

56 Industry guidance states that crews should ask ATC for assistance, such as requesting to receive

delayed vectors or enter a holding pattern, when they become rushed or otherwise behind on their duties as a

result of unanticipated routings.

57 For additional information, see National Transportation Safety Board, A Review of

Flightcrew-Involved, Major Accidents of U.S. Carriers, 1978 through 1990, Safety Study NTSB/SS-94/01

(Washington, DC: NTSB, 1994). 

58 The complete text of Safety Recommendation A-94-3 to the FAA was as follows: “Require U.S. air

carriers operating under 14 CFR Part 121 to provide, for flight crews not covered by the Advanced

Qualification Program, line operational simulation training during each initial or upgrade qualification into

the flight engineer, first officer, and captain position that (1) allows flight crews to practice, under realistic

conditions, non-flying pilot functions, including monitoring and challenging errors made by other

crewmembers; (2) attunes flight crews to the hazards of tactical decision errors that are errors of omission,

especially when those errors are not challenged; and (3) includes practice in monitoring and challenging

errors during taxi operations, specifically with respect to minimizing procedural errors involving

inadequately performed checklists.” The complete text of Safety Recommendation A-94-4 to the FAA was

as follows: “Require that U.S. air carriers operating under 14 CFR Part 121 structure their initial operating

experience programs to include: (a) training for check airmen in enhancing the monitoring and challenging

functions of captains and first officers; (b) sufficient experience for new first officers in performing the

non-flying pilot role to establish a positive attitude toward monitoring and challenging errors made by the

flying pilot; and (c) experience (during initial operating experience and annual line checks) for captains in

giving and receiving challenges or errors.” On January 19, 1996, the Safety Board classified these

recommendations “Closed—Acceptable Alternate Action” in response to the FAA’s upgrades of its training

guidance.
Analysis 32 Aircraft Accident Report

monitoring function is always essential, particularly during approach and landing.” Since

that action, other FAA guidance on workload management and monitoring skills has been

developed. For example, on February 27, 2003, the FAA expanded its guidance in this

area in a revision of AC 120-71, “Standard Operating Procedures for Flight Deck

Crewmembers,” to emphasize the importance of procedures, such as distributing cockpit

workload to avoid interfering with pilot monitoring and assigning cockpit responsibilities

so that one pilot can monitor continuously during high workload periods. With respect to

conducting approach briefings and their impact on monitoring, the AC states that pilots

should “when able, brief the anticipated approach prior to top-of-descent” to allow

“greater attention to be devoted to properly monitoring ... because the crew is not having

to divide attention between reviewing the approach and monitoring the descent.” The

guidance contained in both ACs is available to operators to support pilot training

programs but is not mandatory.

The Safety Board is aware of recent accidents in which inadequate pilot

monitoring was a causal or contributing factor to the accident and in which pilots on

approach to landing failed to observe critical and salient cues.59 These accidents

demonstrate the importance of monitoring skills and effective workload management in

ensuring safety of flight. Existing FAA guidance to operators addresses these skills but

providing specific pilot training on effective monitoring and cockpit workload

management would be a way for the aviation industry to effectively deliver and reinforce

the importance of these skills to pilots. The Safety Board concludes that all operators

would benefit from an increased focus on providing monitoring skills in their training

programs, including those operating under 14 CFR Parts 121 and 135, as would pilots

completing FAA-approved training programs for Part 91 operations.60 Therefore, the

Safety Board believes that the FAA should require pilot training programs be modified to

contain modules that teach and emphasize monitoring skills and workload management

and include opportunities to practice and demonstrate proficiency in these areas.

2.3 Deice Boot Systems 

Company and manufacturer guidance states that the surface deice boots should be

used when ice buildup is estimated to be between 1/4- to 1/2-inch thick and that “early

activation of the boots may result in ice bridging on the wing.” During the Comair

59 For additional information, see National Transportation Safety Board, Collision With Trees on Final

Approach, Federal Express Flight 1478, Boeing 727-232, N497FE, Tallahassee, Florida, July 26, 2002,

Aviation Accident Report NTSB/AAR-04/02 (Washington, DC: NTSB, 2004); National Transportation

Safety Board, Crash During Approach to Landing, Air Tahoma, Inc., Flight 185, Convair 580, N586P,

Covington, Kentucky, August 13, 2004, Aviation Accident Report NTSB/AAR-06/03 (Washington, DC:

NTSB, 2006); and National Transportation Safety Board, Crash During Approach to Landing, Business Jet

Services Ltd., Gulfstream G-1159A (G-III), N85VT, Houston, Texas, November 22, 2004, Aviation Accident

Brief NTSB/AAB-06/06 (Washington, DC: NTSB, 2006).

60 The Safety Board recognizes that many pilots engaged primarily in noncommercial flying under

14 CFR Part 91 do not complete formal training programs but believes that these pilots can benefit from the

increased industry emphasis and specific training principles on monitoring.
Analysis 33 Aircraft Accident Report

flight 3272 investigation, the Safety Board learned that many manufacturers and operators

had similar deice boot operational guidance and concerns about ice bridging. 

However, AC 25.1419-1A states that, although ice may not be completely shed by

one cycle of the boots, the residual ice will usually be removed by subsequent cycles and

does not act as a foundation for a bridge of ice to form. Further, information gathered at a

1997 Airplane Deice Boot Bridging Workshop, subsequent icing tunnel tests, and flight

tests conducted as part of the Comair investigation revealed that ice bridging did not occur

on modern airplanes, which are equipped with deice boots that quickly inflate and deflate.

The icing tunnel tests also revealed that thin (1/4 inch or less), rough ice accumulations on

the wing leading edge deice boot surfaces could be, depending on distribution, as

aerodynamically detrimental to an airplane’s performance as larger ice accumulations. 

A search of the Safety Board accident database revealed no accidents related to ice

bridging. Conversely, the Board has investigated many icing accidents in which the

airplane stalled prematurely and the stall warning system did not activate before the stall

because of ice accumulation on the wing leading edges. This accident, previous accident

investigations, Safety Board accident data, and existing icing information clearly show

that delaying the activation of the deice boots can create unsafe operations. The Safety

Board concludes that ice bridging does not occur on modern airplanes; therefore, it is not a

reason for pilots to delay activation of the deice boots.

As a result of its findings during the Comair flight 3272 investigation, the Safety

Board issued Safety Recommendation A-98-91, which recommended that the FAA do the

following:

Require manufacturers and operators of modern turbopropeller-driven airplanes in

which ice bridging is not a concern to review and revise the guidance contained in

their manuals and training programs to emphasize that leading edge deicing boots

should be activated as soon as the airplane enters icing conditions.

In May 2002, the FAA issued an icing test report that recommended an “early and

often” approach to deice boot usage to limit the size of residual and intercycle ice

accretions. Further, in January 2003, an ARAC IPHWG recommended revisions to

Parts 25 and 121 to require that deice systems be activated as soon as an airplane enters

icing conditions. However, since that time, the FAA has taken no action to issue a final

rule adopting the regulatory changes proposed by the ARAC IPHWG. 

Although the accident airplane most likely accumulated less than 1/4-inch-thick

ice while operating in the lower cloud layer, the pilots’ failure to activate the deice boots

during the approach led to the continued accumulation of thin, rough ice on the protected

surfaces, which can severely degrade an airplane’s performance. The circumstances of this

accident, information gathered during the Comair flight 3272 accident, and reports issued

by the FAA and the ARAC IPHWG clearly demonstrate that existing guidance instructing

pilots to delay activation of the deice boots until they observe 1/4- to 1/2-inch-thick ice

accumulation is not adequate because it does not protect against the detrimental effects

caused by thin, rough ice accumulation on or aft of the protected surfaces. If pilots
Analysis 34 Aircraft Accident Report

continue to adhere to guidance about delaying deice boot activation, similar accidents

could still occur. 

The Safety Board concludes that activating the deice boots as soon as an airplane

enters icing conditions provides the greatest safety measure. On the basis of this accident

and the Board’s continued concerns in this area, the Board believes that the FAA should

require manufacturers and operators of pneumatic deice boot-equipped airplanes to revise

the guidance contained in their manuals and training programs to emphasize that leading

edge deice boots should be activated as soon as the airplane enters icing conditions. The

new recommendation will supersede Safety Recommendation A-98-91 and will be

classified “Open—Unacceptable Response.”

The Safety Board is concerned that workload increases significantly when pilots of

airplanes equipped with deice boots that do not cycle automatically operate in icing

conditions because they must continuously monitor the ice accumulation on the airplane’s

surfaces and determine when to reactivate the deice boots. This consideration is consistent

with FAA concerns in AC 23.1419-2C.61 Having to operate the deice boot system

manually is even more critical during the approach and landing phases of flight when pilot

workload and monitoring demands are greatest. 

The Safety Board concludes that manual operation of the deice boot system

increases pilot workload, which can result in distraction during critical phases of flight,

such as approach and landing. Therefore, the Safety Board believes that the FAA should

require that all pneumatic deice boot-equipped airplanes certified to fly in known icing

conditions have a mode incorporated in the deice boot system that will automatically

continue to cycle the deice boots once the system has been activated.

2.4 Certification Requirements for Flight Into Icing 

Conditions

The Safety Board has previously identified concerns about inadequate flight test

certification requirements. For example, the American Eagle flight 4184 accident

investigation revealed that SLD conditions can cause ice accretions that are more

aerodynamically detrimental than those accretions that fall within the Part 25, Appendix C

envelope. As a result, the Safety Board issued Safety Recommendation A-96-54, which

asked the FAA to do the following: 

Revise the icing criteria published in 14...CFR Parts 23 and 25, in light of both

recent research into aircraft ice accretion under varying conditions of liquid water

content, drop size distribution, and temperature, and recent developments in both

the design and use of aircraft. Also, expand the Appendix C icing certification

envelope to include freezing drizzle/freezing rain and mixed water/ice crystal

conditions, as necessary. 

61 AC 23.1419-2C stated that the effect on pilot workload of continuously cycling the deice boots

should be evaluated.
Analysis 35 Aircraft Accident Report

Further, icing tunnel tests conducted as part of the Comair flight 3272 accident

investigation indicated that the effects of ice accretion on airplane performance could vary

widely depending on the size, distribution, and type of ice accumulated on the airplane’s

surfaces. However, the Board learned that manufacturers are not required to demonstrate

an airplane’s flight handling characteristics or stall margins using thin, rough ice that can

accrete on protected surfaces before the activation of the deice boot system or between

activation cycles. As a result of its findings, the Board issued Safety Recommendation

A-98-92, which asked the FAA (in cooperation with NASA and other interested aviation

organizations) to do the following:

[C]onduct additional research to identify realistic ice accumulations and ...

determine the effects and criticality of such ice accumulations ... the information

developed ... should be incorporated into aircraft certification requirements. 

The Safety Board also issued Safety Recommendation A-98-100, which asked the

FAA to review the icing certification of all turbopropeller-driven airplanes currently

certificated for operation in icing conditions, perform additional testing, and take action as

required to ensure that these airplanes fulfill the requirements of the revised icing

certification standards asked for in Safety Recommendation A-98-92.

The FAA indicated in a March 6, 2006, response to Safety

Recommendation A-96-54 that the ARAC IPHWG is continuing to develop a revision to

Part 25 to require a demonstration that an airplane can safely operate in SLD conditions

for an unrestricted time or can detect SLD and safely exit icing conditions. However, the

FAA has still not received the recommendations from the IPHWG, prepared regulatory

analyses, issued the NPRM, analyzed comments, or completed the many other tasks

involved in issuing new regulations. 

The FAA indicated in an October 26, 2005, response to Safety

Recommendation A-98-92 that it had completed and would shortly issue a draft revision

to AC 20-73, which included the certification guidance on determining critical ice shapes,

descriptions of intercycle and residual ice accretions, and the aerodynamic penalties

associated with these ice shapes. Although the FAA issued AC 20-73A on August 16,

2006, it has still not provided the Safety Board with information regarding any new

research conducted in response to this recommendation. 

Regarding Safety Recommendation A-98-100, the FAA issued an NPRM in

November 2005, which proposed to expand 14 CFR Part 25 to include specific

certification requirements for airplane performance or handling qualities for flight in icing

conditions and to specify the ice accumulations that must be considered for each phase of

flight. Further, the FAA proposed changes to AC 25-1X, which intended to provide

guidance for implementing the regulations proposed in the NPRM.

In May 2006, the Safety Board expressed concern that, although it agreed with the

proposed regulatory changes, the FAA had not applied the new standards to all in-service

turbopropeller-driven aircraft. The FAA further indicated that no airplanes have an unsafe

condition in icing environments despite a number of accidents in the 1990s that involved
Analysis 36 Aircraft Accident Report

airplanes that had passed the certification standards. The Board stated that, to meet the

intent of Safety Recommendation A-98-100, the FAA would need to formally evaluate

(perhaps by conducting flight tests) all in-service turbopropeller-driven aircraft to ensure

that these aircraft comply with all current icing certification criteria for new aircraft.

The Board asked the FAA to provide a list of the aircraft that it had formally evaluated and

a summary of the findings and resultant actions. To date, this information has not been

received.

The circumstances of the Comair flight 3272, American Eagle 4184, and Pueblo

accidents and the icing tunnel test data show that the ice shapes used during initial

certification flight tests were not adequate because the tests did not account for thin, rough

ice on the wing. The 1996 ice shapes tests on the Cessna 560 were also inadequate

because, although tests were conducted with ice shapes on the protected surfaces, tests

were not conducted using thin, rough ice. Therefore, additional ice sizes, distribution

patterns, and types need to be considered during flight testing to more adequately gauge an

airplane’s performance in icing conditions. 

The Safety Board concludes that existing flight test certification requirements for

flight into icing conditions do not test the effects of thin, rough ice on or aft of an

airplane’s protected surfaces, which can cause severe aerodynamic penalties. The

circumstances of this accident clearly show that the actions requested in Safety

Recommendations A-96-54 and A-98-92 are needed to improve the safety of all airplanes

operating in icing conditions. Therefore, the Safety Board reiterates Safety

Recommendations A-96-54 and A-98-92. As noted, Safety Recommendation A-98-100

only addressed turbopropeller-driven airplanes. 

The circumstances of this accident clearly demonstrate that deice boot-equipped

turbojet airplanes also require additional testing in an expanded Appendix C icing

certification envelope, which would include thin, rough ice accumulations and intercycle

and residual ice. Therefore, the Safety Board believes that the FAA should, when the

revised icing certification standards and criteria are complete, review the icing

certification of all pneumatic deice boot-equipped airplanes that are currently certificated

for operation in icing conditions and perform additional testing and take action as required

to ensure that these airplanes fulfill the requirements of the revised icing certification

standards. The new recommendation (A-07-16) will supersede Safety Recommendation

A-98-100 and will be classified “Open—Unacceptable Response.” 62

2.5 Inadequate Stall Warning Margins in Icing 

Conditions

Stall warning systems are intended to provide flight crews with adequate warning

of an impending stall to give them enough time to take necessary action to prevent a stall.

62 Safety Recommendation A-98-100 is on the Safety Board’s List of Most Wanted Transportation

Safety Improvements. Accordingly, Safety Recommendation A-07-16 will automatically be placed on the

Most Wanted List.
Analysis 37 Aircraft Accident Report

The CVR sound spectrum study indicated that the accident airplane’s stall warning did not

activate until after the stall. The Pueblo accident is not the first accident in which a stall

has occurred before the stall warning activated. For example, the Safety Board determined

during the Comair flight 3272 accident investigation that the airplane departed controlled

flight before the stall warning activated and that stall warning systems “often do not

provide adequate warning when the airplane is operating in icing conditions.” 

As a result of the Comair investigation, the Safety Board issued Safety

Recommendation A-98-96, which recommended that the FAA require manufacturers and

operators of all airplanes certificated to operate in icing conditions to install stall warning

systems that provide a cockpit warning before the onset of a stall when the airplane is

operating in icing conditions. The FAA stated in an October 26, 2005, response letter that

it was pursuing rule changes to require only that newly certificated airplanes have stall

warning systems installed that provide a cockpit warning before the onset of a stall when

operating in icing conditions and that it would take appropriate action on in-service

airplanes only if an unsafe condition were identified. 

The November 2005 NPRM proposed changes to 14 CFR 25.207 to require that

only newly type-certificated airplanes be equipped with stall warning systems that provide

a stall warning before the onset of a stall when the airplane is operating in icing

conditions. In its comments on the proposed NPRM and in its May 2006 response letter to

the FAA, the Safety Board stated that it was not acceptable for the FAA to wait until an

accident or serious incident occurred to reveal that an unsafe condition existed on an

in-service airplane and that, because the proposed changes did not address in-service

airplanes, Safety Recommendation A-98-96 was classified “Open—Unacceptable

Response.” The Board continues to believe that not requiring in-service airplanes to be

equipped with improved stall warning systems until an unsafe condition is identified is

unacceptable and encourages the FAA to expedite issuance of a final rule that contains

such a requirement.

Regarding the Cessna 560’s stall warning system, in 1996, the FAA conducted ice

testing using 1/2-inch ice shapes installed on the protected surfaces. As a result of these

tests, in early 1999, Cessna began incorporating a modified stall warning system on

Cessna 560 airplanes (including the accident airplane) to provide a 5-knot increase in the

stall warning margin for operations in icing conditions. However, as this accident has

shown, these modifications were not adequate because they did not take into account the

effects of thin, rough ice on the protected surfaces; therefore, additional modifications to

the airplane’s stall warning system are necessary. 

The Safety Board concludes that the Cessna 560 airplane’s stall warning system

did not provide a stall warning before the upset. The Safety Board further concludes that

the Cessna 560 airplane’s stall warning system does not provide a warning in all icing

conditions, including those conditions in which thin, rough ice can accumulate on the

protected surfaces. Therefore, the Safety Board believes that the FAA should require

modification of the Cessna 560 airplane’s stall warning system to provide a stall warning

margin that takes into account the size, type, and distribution of ice, including thin, rough

ice on or aft of the protected surfaces.
38 Aircraft Accident Report

3. Conclusions

3.1 Findings

1. The captain and first officer were properly certificated and qualified under Federal

regulations. No evidence indicated any preexisting medical or physical condition that

might have adversely affected the flight crew’s performance during the accident

flight. A review of the pilots’ 72-hour histories revealed that they slept well in the

days leading up to the accident flight and went to bed early in preparation for an early

departure. No evidence was found that fatigue degraded the performance of either

pilot on the day of the accident.

2. The weight and balance of the airplane were within landing limits.

3. The recovered components showed no evidence of preexisting powerplant, structural,

or system failures.

4. The Pueblo Memorial Airport local controller did not provide the accident flight crew

or the Denver Flight Service Station with the pilot report reporting light to moderate

icing; however, this was not a factor in the accident because cockpit voice recorder

information indicated that the flight crew was aware of the icing conditions.

5. During the approach, the flight crew of the sister ship, which was following the

accident flight, cycled the deice boots numerous times and maintained a high airspeed

and, subsequently, landed safely, indicating the importance of taking these actions to

counteract the hazardous effects of icing.

6. The flight crew did not increase the landing reference airspeed while operating in

icing conditions, contrary to company procedures and manufacturer guidance.

7. The airplane encountered supercooled large droplet (SLD) conditions, which are most

conducive to the formation of thin, rough ice on or aft of the protected surfaces,

during about the last 4 1/2 minutes of the flight. Further, the airplane had residual ice

on the wings after the deice boots were activated earlier in the flight, and this ice

would have affected the overall thickness, roughness, and distribution of the SLD ice

accumulation.

8. The flight crew did not activate the deice boots when configuring for the approach

and landing, which was contrary to company procedures and manufacturer guidance. 

9. The flight crew failed to maintain adequate airspeed during the final approach in icing

conditions, which led to an aerodynamic stall from which they did not recover.
Conclusions 39 Aircraft Accident Report

10. Pilots could benefit from the reinforcement during training of the Cessna Model 560

Citation V Airplane Flight Manual requirements to increase the airspeed and operate

the deice boots during approaches when ice is present on the wings.

11. The briefing conducted late in the approach was a distraction that impeded the flight

crew’s ability to monitor and maintain airspeed and manage the deice system.

12. All operators would benefit from an increased focus on providing monitoring skills in

their training programs, including those operating under 14 Code of Federal

Regulations Parts 121 and 135, as would pilots completing Federal Aviation

Administration-approved training programs for Part 91 operations.

13. Ice bridging does not occur on modern airplanes; therefore, it is not a reason for pilots

to delay activation of the deice boots.

14. Activating the deice boots as soon as an airplane enters icing conditions provides the

greatest safety measure. 

15. Manual operation of the deice boot system increases pilot workload, which can result

in distraction during critical phases of flight, such as approach and landing.

16. Existing flight test certification requirements for flight into icing conditions do not

test the effects of thin, rough ice on or aft of an airplane’s protected surfaces, which

can cause severe aerodynamic penalties.

17. The Cessna 560 airplane’s stall warning system did not provide a stall warning before

the upset. 

18. The Cessna 560 airplane’s stall warning system does not provide a warning in all

icing conditions, including those conditions in which thin, rough ice can accumulate

on the protected surfaces.

3.2 Probable Cause

The National Transportation Safety Board determines that the probable cause of

this accident was the flight crew’s failure to effectively monitor and maintain airspeed and

comply with procedures for deice boot activation on the approach, which caused an

aerodynamic stall from which they did not recover. Contributing to the accident was the

Federal Aviation Administration’s failure to establish adequate certification requirements

for flight into icing conditions, which led to the inadequate stall warning margin provided

by the airplane’s stall warning system.
40 Aircraft Accident Report

4. Safety Recommendations

4.1 New Safety Recommendations

As a result of its investigation of the February 16, 2005, accident involving a

Cessna Citation 560, the National Transportation Safety Board makes the following

recommendations to the Federal Aviation Administration:

Require that operational training in the Cessna 560 airplane emphasize the

airplane flight manual requirements that pilots increase the airspeed and

operate the deice boots during approaches when ice is present on the wings.

(A-07-12)

Require that all pilot training programs be modified to contain modules

that teach and emphasize monitoring skills and workload management and

include opportunities to practice and demonstrate proficiency in these

areas. (A-07-13)

Require manufacturers and operators of pneumatic deice boot-equipped

airplanes to revise the guidance contained in their manuals and training

programs to emphasize that leading edge deice boots should be activated as

soon as the airplane enters icing conditions. (A-07-14) (This safety

recommendation supersedes Safety Recommendation A-98-9163 and is

classified “Open—Unacceptable Response.”)

Require that all pneumatic deice boot-equipped airplanes certified to fly in

known icing conditions have a mode incorporated in the deice boot system

that will automatically continue to cycle the deice boots once the system

has been activated. (A-07-15)

When the revised icing certification standards (recommended in Safety

Recommendations A-96-54 and A-98-92) and criteria are complete, review

the icing certification of pneumatic deice boot-equipped airplanes that are

currently certificated for operation in icing conditions and perform

additional testing and take action as required to ensure that these airplanes

fulfill the requirements of the revised icing certification standards.

(A-07-16) (This safety recommendation supersedes Safety

Recommendation A-98-10064 and is classified “Open—Unacceptable

Response.”)

63 For more information about this recommendation, see sections 1.18.2.1 and 2.3.

64 For more information about this recommendation, see sections 1.18.2.2 and 2.4.
Safety Recommendations 41 Aircraft Accident Report

Require modification of the Cessna 560 airplane’s stall warning system to

provide a stall warning margin that takes into account the size, type, and

distribution of ice, including thin, rough ice on or aft of the protected

surfaces. (A-07-17)

4.2 Previously Issued Safety Recommendations 

Reiterated in This Report

The Safety Board reiterates the following safety recommendations to the Federal

Aviation Administration: 

Revise the icing criteria published in 14 Code of Federal Regulations Parts 23

and 25, in light of both recent research into aircraft ice accretion under

varying conditions of liquid water content, drop size distribution, and

temperature, and recent developments in both the design and use of

aircraft. Also, expand the Appendix C icing certification envelope to

include freezing drizzle/freezing rain and mixed water/ice crystal

conditions, as necessary. (A-96-54)65

With the National Aeronautics and Space Administration and other

interested avation organizations, conduct additional research to identify

realistic ice accumulations, to include intercycle and residual ice

accumulations and ice accumulations on unprotected surfaces aft of the

deicing boots, and to determine the effects and criticality of such ice

accumulations; further, the information developed through such research

should be incorporated into aircraft certification requirements and pilot

training programs at all levels. (A-98-92)

For more information about these recommendations, see sections 1.18.2.2 and 2.4.

65 Safety Recommendation A-96-54 superseded Safety Recommendation A-81-116, which was issued

in 1981.

BY THE NATIONAL TRANSPORTATION SAFETY BOARD

MARK V. ROSENKER

Chairman

ROBERT L. SUMWALT

Vice Chairman

DEBORAH A. P. HERSMAN

Member

KATHRYN O. HIGGINS

Member

STEVEN R. CHEALANDER

Member

Adopted: January 23, 2007
42 Aircraft Accident Report

Board Member Statements

Member Deborah A.P. Hersman’s Statement, Concurring in part and

Dissenting in part:

 While I agree with the general outcome of this report, I believe the probable cause 

ultimately approved by the Board is not entirely consistent with the rest of the report. As 

I asserted at the Board meeting on January 23, 2007, the inadequate guidance provided to 

aircraft operators regarding the operation of deice boots should have been cited as a 

contributing factor. Furthermore, the FAA’s inadequate certification requirements for 

flight into icing conditions should have been cited as one of the two primary causes of the 

accident, rather than as a contributing cause. 

 The final probable cause would lead one to believe that this was not an icing 

accident but simply an accident of pilot failures—failure to effectively monitor and 

maintain airspeed and failure to properly activate the deice boots. However, the rest of 

the report lays a foundation for finding that this accident was very much about ice and a 

lack of understanding among operators about whether an aircraft can safely operate in 

any type of ice and how to appropriately manage ice accumulation. 

FAA’s failure to establish proper certification requirements for aircraft flying in 

icing conditions should be cited as one of the primary causes of this accident. The Board 

has long been concerned about aircraft icing and inadequate certification standards.

Following the Safety Board’s 1981 study on aircraft icing, numerous recommendations 

were issued to the FAA to revise certification standards regarding ice accretion under 

varying conditions. In over 25 years, the FAA has done little to address this issue and we 

have reiterated the original recommendations over and over and they remain on our Most 

Wanted List of Safety Improvements in an unacceptable status. 

According to the Cessna Model 560 Citation V AFM, the airplane’s anti-ice and 

de-ice systems were not designed to protect against freezing rain or severe conditions of 

mixed or clear ice. However, during the investigation of this accident, the National 

Center for Atmospheric Research determined that, on the basis of surface, radar, upper 

air, and satellite data, the airplane likely encountered Supercooled Large Droplet 

conditions, which are more conducive to the accumulation of thin, rough ice, between 

9,400 to 6,100 feet (the altitude at which the upset occurred). The pilots were unaware 

that they were flying in conditions that the plane was not certificated for because there 

are no reliable methods for flight crews to differentiate, in flight, between water drop 

sizes that are outside the certification envelope. Furthermore, the Cessna 560 airplane’s 

stall warning system does not provide warning in this type of icing condition.

In a recommendation in 1996, the Board recommended that FAA revise its icing 

criteria. That recommendation is being reiterated in this report. Another 

recommendation issued to FAA in 1996 is being revised and re-issued in this report, 

recommending that FAA revise icing certification requirements for airplanes equipped 

with pneumatic deice boots. Perhaps, if FAA had taken such measures 10 years ago, 

much more would have been understood by the pilots about flying in this type of icing 
Board Member Statements 43 Aircraft Accident Report

condition. For that reason, FAA has a place in the probable cause equal to that of the 

pilots who executed the errors in the conduct of this flight. 

 The narrative of the accident is clear that the pilots of this aircraft did not fail to 

monitor the icing conditions. The cockpit voice recorder revealed that they were aware 

of the icing conditions and they activated the de-ice boots at least once. The First Officer 

talked about the color of the ice, the rate of accumulation, and compared it to the ice 

accumulated on the previous day, and the Captain discussed the ice remaining on the 

wings after the initial activation of the deice boots. The probable cause faults the crew, 

not because they did not effectively monitor the icing conditions, but because they failed 

to activate the deice boots at the correct time. 

The report states that the manufacturer’s guidance and language in the AFM 

recommends that the deice boots be used when the ice buildup is between 1⁄4 to 1⁄2 inches 

thick and that early activation of the boots could result in ice bridging. Despite 

information revealed during previous NTSB accident investigations (Comair Flight 3272, 

Monroe, Michigan, January 9, 1997), NASA published research on the topic, public 

information events such as the November 1997 Airplane Deicing Boot Ice Bridging 

Workshop, and various FAA publications, the ice bridging concept is still real to some 

pilots and operators. This concern about ice bridging was reinforced to this Board 

Member during a conversation earlier this month, with a well-respected pilot of a modern 

Cessna aircraft equipped with pneumatic boots, who repeatedly spoke of ice bridging and 

the guidance from the manual requiring a 1⁄4 to 1⁄2 inch of ice accumulation before 

activating the boots. Regrettably, it appears that little has changed in the 10 years since 

the Board investigated the Monroe accident, the following language was contained in our 

November 30, 1998, recommendation letter to Administrator Garvey on 

recommendations A-98-88 through –106: 

“This illustrates how thoroughly ingrained the ice bridging 

concept was in pilots and operators and the importance of an ice bridging 

pilot education program. Therefore, a thin, yet performance-decreasing 

type of ice (similar to that likely accumulated by Comair flight 3272) can 

present a more hazardous situation that a 3-inch ram’s horn ice 

accumulation because it would not necessarily prompt the activation of 

the boots. Based on this information, the Safety Board concludes that the 

current operating procedures recommending that pilots wait until ice 

accumulates to an observable thickness before activating leading edge 

deicing boots results in unnecessary exposure to a significant risk... Based 

primarily on concerns about ice bridging, pilots continue to use 

procedures and practices that increase the likelihood of (potentially 

hazardous) degraded airplane performance resulting from small amounts 

of rough ice accumulated on the leading edges.”

Yet in another part of the AFM, the direction to the crew is contradictory, “When 

configuring for approach and landing... with any ice accretion visible on the wing 

leading edge, regardless of thickness, activate the surface deice system. Continue to 
Board Member Statements 44 Aircraft Accident Report

monitor the wing leading edge for any accumulation.” Unfortunately, our investigators 

found that the SimuFlite training syllabus had no specific instruction to evaluate crew 

performance of the AFM procedures to increase the airspeed and operate the deice boots 

during approaches when ice is present on the wings. In addition, one of the instructors 

was unaware of these AFM procedures. Furthermore, this guidance about activating the 

deice boots on approach with any ice accretion seems to nullify the earlier guidance about 

waiting for a measurable ice build up prior to boot activation and de-bunking the myth of 

ice-bridging. Which leads me to question why Cessna requested, and the FAA agreed to 

withdraw NPRM 99-NM-136-AD, which was applicable to Cessna model 500, 501, 550, 

551, and 560 series airplanes and proposed revising the applicable AFMs to include a 

requirement to activate the deice boots at the first sign of ice accumulation and to cycle 

the boots to minimize ice accumulation. When the NPRM was withdrawn, Cessna 

continued to publish the 1⁄4 to 1⁄2 inch accumulation language. If it is safer to eliminate 

any visible ice from the wings during the approach phase of flight, then the same logic 

ought to apply to all phases of flight.

FAA Advisory Circular AC 25.1419-1A states that residual ice does not act as a 

foundation for bridging ice. Furthermore, our report states, additional tests have shown 

that ice bridging does not occur on modern airplanes and deice boots should be activated 

as soon as an aircraft enters icing conditions. This contradiction between recent studies, 

the FAA Advisory Circular, and manufacturer guidance led the Board to include in this 

report a recommendation that FAA require manufacturers and operators of airplanes with 

deice boots to revise the guidance in their manuals to emphasize that deice boots should 

be activated as soon as the airplane enters icing conditions. Furthermore, the Board 

reiterated an older recommendation that FAA conduct additional research on the effects 

of residual ice accumulations behind the deicing boots and incorporate those new 

findings into the certification requirements and pilot training programs. 

I believe that in failing to cite the inadequate guidance as a contributing factor in 

the probable cause, and in relegating FAA’s failures to only a contributing cause, the 

Board is leaving a part of this investigation report undone. In our quest to make flying 

ever safer, we may never reach a time when pilots don’t sometimes make inexplicable 

errors. But in a case such as this one where we can piece the evidence together and spot 

plausible reasons why the pilots made the mistakes they made, we should do so 

emphatically. In almost 40 years of accident investigations, we have improved aviation 

safety and improved our process of accident investigations, but I believe we can and 

should reach further in our efforts. Simply citing the flight crew’s failure to monitor and 

maintain airspeed and de-ice the wings as required by the AFM is not going far enough. 

Until the AFMs fly the airplanes, we need to address the actions of the human beings 

who do fly the airplanes. In this accident, the reason the pilots failed in their critical tasks 

is because they did not have the benefit of proper guidance from the FAA and from the 

manufacturer about flying in the conditions they found themselves. While the Board 

articulated this issue very clearly in our conclusions and our recommendations, I believe 

the Board should have included this aspect in the probable cause as the best means of 

helping to prevent other pilots from making the same error in the future. 
Board Member Statements 45 Aircraft Accident Report

Member Higgins joined Member Hersman in this statement. 

[Original signed] 

 Deborah A. P. Hersman 

 January 30, 2007 

47 Aircraft Accident Report

5. Appendixes

Appendix A

Investigation and Public Hearing

Investigation

The National Transportation Safety Board was initially notified about this accident

on the afternoon of February 16, 2005. A full go-team was assembled in Washington,

D.C., and traveled to the accident scene. The go-team was accompanied by former

Chairman Engleman Conners.

The following investigative groups were formed: Operations, Meteorology, Air

Traffic Control, Airworthiness, Maintenance Records, Powerplants, Aircraft Performance,

Survival Factors, and Cockpit Voice Recorder.

Parties to the investigation were the Federal Aviation Administration; Martinair,

Inc.; and Cessna Aircraft Company. An accredited representative from the Transportation

Safety Board of Canada and a technical advisor from Pratt and Whitney Canada also

assisted in the investigation.

Public Hearing

No public hearing was held for this accident.
48 Aircraft Accident Report

Appendix B

Cockpit Voice Recorder Transcript

The following is the transcript of the B&D Instruments and Avionics cockpit voice

recorder, serial number A01148, installed on a Cessna 560 that crashed while on approach

to Pueblo Memorial Airport, Pueblo, Colorado, on February 16, 2005.

LEGEND

HOT Crewmember hot microphone voice or sound source

RDO Radio transmission from accident aircraft

CTR1 Radio transmission from 1st Denver Center controller

CTR2 Radio transmission from 2nd Denver Center controller

APR Radio transmission from Pueblo approach control

FBO Radio transmission from Pueblo fixed base operator

TWR Radio transmission from Pueblo tower

TWR Radio transmission from aircraft N500FK

SW6431 Radio transmission from Skywest flight six four three one

-1 Voice identified as Pilot-in-Command (PIC)

-2 Voice identified as Co-Pilot (SIC)

-3 Voice identified as aircraft mechanical voice

-? Voice unidentified

* Unintelligible word

@ Non-pertinent word

# Expletive

- - - Break in continuity

( ) Questionable insertion

[ ] Editorial insertion

... Pause

Note 1: Times are expressed in mountain standard time (MST).

Note 2: For ATC transmissions, generally only radio transmissions to and from the accident aircraft were transcribed.
1 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0841:19 START of RECORDING START of TRANSCRIPT 0842:27 HOT-2 the secondary held in there pretty good on that little bit of de- scent. 0842:30 HOT-1 yeah. 0842:32 HOT-2 called standby I guess they call it. 0842:35 HOT-1 twenty feet. 0843:50 HOT-2 one thing I was thinking about, I'm surprised that Jepps didn't show that, as good as Jepps is. 0843:59 HOT-1 yeah, I would have thought it would have been on there. 0844:01 HOT-2 I mean that's not your every day departure procedure if you're an east coast flier. 0844:03 HOT-1 yeah.
2 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0844:21 CTR1 Citation five hundred Alpha Tango, descend and main

level two seven zero. 0844:25 RDO-2 five hundred Alpha Tango, three six oh for two seven o

0844:31 HOT-1 twenty seven. 0844:32 HOT-2 twenty seven. 0844:50 HOT-2 uh, no arrivals or nothing. they do have a uh, a radar, ASR if we had to have it. that's old as #. I reckon it's still in use. 0845:00 HOT-1 yeah. 0845:43 500FK Denver, good morning, Citation five zero zero Fox Kilo

out of thirty five and a half down to three four zero. 0845:49 CTR1 Citation five zero zero Foxtrot Kilo Denver center, roge

0846:06 HOT-2 did you got number, well number one for me. 0846:07 HOT-1 I got one.
3 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0846:13 RDO-2 Flower Aviation, Pueblo, Citation five hundred Alpha T

0846:20 FBO good morning five hundred Alpha Tango, this is Flowe

in Pueblo, go ahead. 0846:25 RDO-2 yes ma'am, how you doing this morning? we'll be landabout twenty minutes and we have uh, six passengerspit stop and a quick turn. and, gonna give you a fuel (oin just a second. 0846:43 FBO I understand that you're twenty minutes out. you have sengers for a pit stop and a quick turn and you'll give min just a minute. 0846:51 HOT-2 you still want, you still want two hundred? 0846:54 HOT-1 uuh, yeah uh, have you already talked to 'em? 0846:58 HOT-2 no, I've got her on the radio. 0847:00 HOT-1 let's make it two ten a side. 0847:01 HOT-2 okay. that sounds good.
4 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0847:06 RDO-2 and uh, young lady there at Flower Aviation for five hu

pha Tango. we'll take two hundred and ten gallons a sPrist. 0847:16 FBO I understand that you're gonna want two one zero, two and ten gallons a side and our Jet A is pre-mixed. 0847:23 RDO-2 okeydoke, and we'll, and we'll see you in just a little bit quick turn. and we have uh, just to let you know, we gpany traffic behind us uh, about ten minutes too. 0847:24 CTR1 Citation five hundred Alpha Tango contact Denver centhree three point four. 0847:28 RDO-1 thirty three four uh, Alpha Tango, so long. 0847:31 FBO okay, we'll see you in twenty minutes on the west end terminal and we'll see your company in thirty minutes oend of the main terminal. 0847:39 RDO-2 okeydoke, thank you. 0847:40 RDO-1 and Denver center, Citation five hundred Alpha Tangochecking in three two zero for two seven zero.
5 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0847:48 CTR2 Citation five hundred Alpha Tango Denver center, cros

change that to just descend and maintain one three, ththousand. the Pueblo altimeter's three zero one six. 0847:57 RDO-1 thirty sixteen and one three thousand uh, Alpha Tango

0848:02 HOT-2 all right, I'm back with you. 0848:04 HOT-1 all right. 0848:06 HOT-2 uh, down to thirteen thousand. 0848:07 HOT-1 I see that. 0848:08 HOT-2 uh.... what'd he say? three zero one six? 0848:14 HOT-1 think that's what he said. 0848:16 HOT-2 yeah, that's what I got. she says she'll be waiting at the main ramp.
6 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0848:23 HOT-1 okay. I wonder what that means, she'll be waiting at the main ramp? 0848:37 HOT-2 the, the fueler will. 0848:38 HOT-1 uh, okay. 0848:41 HOT-2 I, I, I think, I think it's just one ramp there. 0848:42 HOT-1 okay. 0848:48 HOT-2 it appears, I think, I didn't quite understand kinda staticy, but she said they'd be waiting. 0850:47 HOT-1 okay. 0851:30 HOT-1 * interesting, I wonder how we got on heading? 0850:40 HOT-1 *, I'm gonna heat 'em up. 0850:48 HOT-2 all righty, sounds good.... you get these kind of descents out here too. just come right on down.... 0850:48 HOT-1 yeah.
7 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0851:17 HOT-2 ... don't worry about all this leveling off stuff. 0851:23 HOT-2 I don't know how far out? seventeen miles seems like a long ways. uh, usually they do about ten, don't they? 0851:25 HOT-1 yeah. 0851:33 HOT-2 I don't know if there's a reason for that, but uh.... or it shows a procedure turn. they may bring you in right to the uh.... 0851:36 HOT-1 well, they've got approach control there don't they? 0851:38 HOT-2 yeah, we got Pueblo approach. 0851:39 HOT-1 yeah, they'll probably give us just radar vectors. 0852:18 HOT-2 now if you were on one engine, and you wanted to.... 0852:21 500FK Denver, five hundred Fox Kilo's uh, with you descendin

seven zero. 0852:24 HOT-2 ...heat that thing up. heat both edges. you would put your engine anti-ice switch down....
8 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0852:26 CTR2 five hundred Foxtrot Kilo, Denver Center roger and uh

descend and *** descend and maintain one three, one thousand. the uh, Pueblo altimeter is three zero one s

0852:29 HOT-1 yeah transfer yeah.... 0852:29 HOT-2 on the engine that's running and that..... 0852:31 HOT-1 ...would then heat the opposite side. 0852:32 HOT-2 that would bleed both of 'em. 0852:33 HOT-1 yeah. 0852:39 500FK thirty sixteen. down to one three thousand. Foxtrot Ki0852:39 HOT-1 I guess I'm trying to remember is the two that way. 0852:40 HOT-2 no. 0852:41 HOT-1 no? 0852:42 HOT-2 no. it does not have cr... 'cause it's electric.
9 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0852:45 HOT-1 that's right, that's right. 0852:46 HOT-2 the, the front of the wing is electric. 0852:57 HOT-2 and why would you need the heat on a dead engine, just to keep the ice from flying back into it? 0853:02 HOT-1 yeah. yeah, just keeps everything clean. 0853:10 HOT-2 oh, not so much engine protection, just the wing.... 0853:11 HOT-1 it's the wing yeah. 0853:13 HOT-2 ...itself. 0853:14 HOT-1 aah. 0853:17 HOT-2 you want me to ask them if we can slow down a little bit? 0853:19 HOT-1 yeah. 0853:57 HOT-2 they got the white knuckle guy on the other airplane, right?
10 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0854:00 HOT-1 yeah. oh, ** I don't know if any of these are or not but I know that @ is on theirs. 0854:16 HOT-1 all right, windshield heat's comin' on. 0854:18 HOT-2 okay. 0854:19 HOT-1 you got 'em cracked. 0854:24 HOT-2 yeah. 0854:35 HOT-1 I really can't see lookin' into the sun. you'll have to let me know if you see anything. 0854:39 HOT-2 okay, it's building a little bit right on the leading edge. 0854:43 HOT-1 all right. 0855:07 HOT-2 it's not the real white ice like we had yesterday. it's more of a grayish. 0855:10 HOT-1 all right. 0856:18 HOT-2 there's a real thin line back there.
11 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0856:19 HOT-1 okay, I can see now yeah. couldn't see b', when on top of those clouds, so bright. 0856:39 HOT-2 and, just a little positional awareness, that's direct to Pueblo there too. 0856:44 HOT-1 all right. 0856:46 HOT-2 anything west of it, the terrain starts rising. 0857:13 HOT-1 uh, too bad it's not a clear day, it'd be right pretty. 0857:16 HOT-2 yeah, I imagine it would. 0858:00 HOT-2 uh, one eight oh, three zero one six. 0858:03 HOT-1 sixteen is set twice. recogs are coming on. 0858:05 HOT-2 all right. transition check complete. 0858:15 HOT-1 uh, doesn't look like we picked up any more. 0858:17 HOT-2 nope.
12 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0858:20 HOT-2 I don't know if you want to cycle it one time. it ain't gonna, at mi- nus three it ain't gonna melt much on the ground. 0858:25 HOT-1 naw, it isn't.... might've gotten rid of a little but not much. 0858:45 HOT-2 little sticky ice today. 0858:46 HOT-1 yeah. 0858:58 HOT-2 okay belts and harness, good on my side. 0859:00 HOT-1 good on the left. 0859:02 HOT-2 passenger seats. everybody still looks okay. exits are clear. avionics, flight instruments. I've got Pueblo on hold. localizer, one oh nine five and we set the inbound oh seven seven. 0859:15 HOT-1 set up. 0859:17 HOT-2 crossfeed? 0859:17 HOT-1 is normal. 0859:18 HOT-2 passenger lights are on. anti-skids?
13 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0859:20 HOT-1 is on. 0859:23 HOT-2 ground idle? 0859:24 HOT-1 is normal. 0859:25 HOT-2 I'll hold there on the sync. 0859:28 HOT-1 all righty. 0859:29 HOT-2 ninety six on your ref. 0859:32 HOT-1 that's set. 0859:32 HOT-2 and crew brief we've talked about. I'll hold right there. 0859:53 HOT-2 the descent accumulation comes a little bit different than the climb accumulation. 0859:57 HOT-1 yeah. a whole lot faster in the descent than in the climb. 0900:30 RDO [sound Morse code identification similar to pilot identify

gation station]
14 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0901:09 HOT-2 yeah I bet this would be really pretty if it was clear. 0901:11 HOT-1 oh yeah. 0901:23 HOT-2 so Pueblo's just a little south of Denver still on the east side of the front range. 0901:27 HOT-1 yeah, yeah and it's south also of uh, of Colorado Springs.... 0901:32 HOT-2 uh huh. 0901:32 CAM [sound similar to altitude alerter] 0901:33 HOT-1 ...Colorado Springs sits in the middle, one to go. 0901:38 HOT-2 one to go. got clear air for a little bit. 0902:14 HOT-2 this is kinda equivalent of being down to eight thousand to hand off to Potomac. 0902:20 HOT-1 yeah. 0902:52 HOT-1 just leave the heats on.
15 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0902:55 HOT-2 okay. got everything nice and warmed up. 0903:01 HOT-1 yeah. 0903:08 HOT-1 yeah, there's uh.... 0903:09 HOT-2 am I seeing clouds or am I possibly seeing Pikes Peak? 0903:12 HOT-1 eeeh, that's probably Pikes Peak. 0903:14 HOT-2 all that range. 0903:15 HOT-1 yeah, well they're clouds I think behind it, but uh, I think what you're seeing on this side of it, the dark ridges, that's, that's the mountains. it looks like it could be clouds on the uh, west side of that, though. 0903:36 HOT-2 very deceiving illusional up here with the clouds an.... 0903:37 HOT-1 yeah. 0903:38 HOT-2 ...when they slope and everything. 0903:50 HOT-2 I got one little static wick back there on the aileron just....
16 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0903:54 HOT-1 vibrating. 0903:55 HOT-2 ...flapping like devil. the three right beside it are dead still. 0904:02 HOT-1 the one that's vibrating, is it out on the tip? 0904:04 HOT-2 nope. in, inboard of the aileron. 0904:07 HOT-1 okay. 0905:24 HOT-2 seems like they should be handing us down to the approach, huh? 0905:26 HOT-1 yeah, you might want to check with 'em. 0905:30 HOT-2 only thing is we got to go past * a little. 0905:32 CTR2 Citation zero Alpha Tango, contact Pueblo approach o

zero point one. we'll see you. 0905:39 RDO-2 okay, one twenty dot one and we'll see you in just a litt
17 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0905:43 CTR2 all right. 0905:50 RDO-2 and Pueblo approach, Citation five hundred Alpha Tan

thousand with Juliet. 0905:56 APR Citation five hundred Alpha Tango, Pueblo approach. two four zero vectors ILS runway two six right final appcourse. descend and maintain seven thousand. 0906:05 RDO-2 'kay, two four zero on the heading and down to seven and did you say two six right now? 0906:13 APR Citation zero Alpha Tango, affirmative, runway two six the ILS. traffic holding over the airport is a regional jet thousand. report if you get him in sight. 0906:23 RDO-2 okay, I'll be looking and uh, looking for the ILS two six 

0906:27 HOT-2 changed up on us. 0906:28 HOT-1 yeah. 0906:29 HOT-2 he did a change on us here. 0906:30 HOT-1 yeah, yeah.
18 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0906:40 HOT-2 'kay, one oh eight point three.... inbound's gonna be a little bit different this time. 0906:51 HOT-1 right. 0906:52 HOT-2 it's gonna be inbound two five seven. 0906:54 HOT-1 all right. two five seven. you still holding Pueblo? 0906:58 HOT-2 I'm still holding Pueblo. 0906:59 HOT-1 all right. 0907:00 HOT-2 two five seven. the regional is holding. 0907:02 HOT-1 all right. 0907:03 HOT-2 do you want me to ask him if he is holding for, or is he climbing out or is.... 0907:05 HOT-1 I, I.... 0907:07 HOT-2 ...holding for the missed?
19 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0907:07 HOT-1 I suspect, oh no, it couldn't be for a miss. I'm sure he, he's either climbing out or.... I mean you can ask him but uh, he didn't say anything about us to expect any holding. 0907:30 RDO-2 and Pueblo, just a little heads up for Alpha Tango. is a 

expected or is that fellow climbing out in a holding patt

0907:36 APR Citation zero Alpha Tango, that aircraft is holding in the 

uh, pattern. he needs to burn off some fuel. do you hasight, twelve o'clock and uh, one zero miles? 0907:46 HOT-1 naw. 0907:47 RDO-2 uh, no sir. what's his altitude? 0907:51 APR roger, he's holding at niner thousand. why don't you gand uh, give me a best rate of descent through niner thmaintain one zero thousand. I'll just turn you. 0908:01 RDO-2 okay, we'll head on down to seven thousand and throu

0908:05 HOT-2 so we don't have.... 0908:06 APR Citation zero Alpha Tango roger, that traffic eleven mo

o'clock and niner miles turning northbound at niner tho
20 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0908:14 RDO-2 okay, we're out of ten now hurrying on down to seven. 

be IMC. 0908:20 APR negative, he's just on top. 0908:24 HOT-1 aah, we're well.... 0908:25 RDO-2 okay but we're IMC now at ninety four hundred ah, Alp

0908:29 APR Citation zero Alpha Tango roger. turn left heading of o

zero. 0908:35 RDO-2 left turn one seven zero, Alpha Tango. 0908:40 APR Skywest sixty four thirty one, are you IMC? 0908:43 SW6431 yeah, we're just at the top here. it's pretty darn hazy thtin' a little ice here and there. and uh, we have them o** passing behind us now. 0908:49 APR regional jet or correction Skywest sixty four thirty one, 

0908:55 HOT-2 all right, comin' up on, one to go.
21 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0908:55 APR Citation zero Alpha Tango, turn right heading of two ni

tercept the localizer inbound. traffic five miles.... 0909:02 CAM [sound similar to altitude alert signal] 0909:03 APR ...west your position level at niner thousand. maintain thousand until established, you're cleared approach. 0909:07 RDO-2 okay, that's a right turn to two niner zero to intercept afor the approach uh, five hundred Alpha Tango at sevesand. 0909:16 APR Citation zero Alpha Tango, affirmative. 0909:19 HOT-2 you got a little different ice on there now. it's clear. 0909:22 HOT-1 yeah. 0909:26 HOT-1 and open up those valves all the way. 0909:28 HOT-2 all right, will do.... okay, you're cleared for the approach. do you want the uh.... 0909:38 HOT-1 yeah, I want to keep that out 'til we slow down and we can get some flaps out.
22 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0909:41 APR Citation zero Alpha Tango, measured ceiling niner hun

ken, one thousand four hundred overcast. visibility sixtemperature minus three, dew point minus four. wind zero seven zero at seven. and altimeter's three zero o

0909:59 RDO-2 okay, copy that on the weather for Alpha Tango. 0910:03 HOT-1 we're cleared, we're cleared for the approach? 0910:05 HOT-2 yeah, we have been. 0910:08 RDO-2 Alpha Tango, just want to verify. we are cleared for th

proach. 0910:11 APR Citation zero Alpha Tango, affirmative you are cleared 

0910:22 HOT-2 'kay, ignition is on with the anti-ice, now it's on for sure. glideslope is alive. 0910:30 500FK five hundred Fox Kilo's uh, with you, one three thousan
23 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0910:35 APR Citation five hundred Foxtrot Kilo, Pueblo approach. d

and maintain eight thousand. expect ILS runway two snal approach course. reduce your speed to two one zand then descend and maintain uh, seven thousand oeight thousand. 0910:47 HOT-2 it's two hundred decision height and three quarters of a mile. 0910:47 500FK back to two ten, down to eight thousand and uh, are yJuliet's advertising the eight left ILS? 0910:51 HOT-1 all right. 0910:55 APR affirmative, just kinda trying to save you a little bit of fliyou'd like runway eight left, I can certainly provide that

0911:01 500FK no that's fine. we were just double checking you knew 

going on here and we're down to uh, eight thousand nohundred and ten knots for Alpha Tango. 0911:06 HOT-2 localizer's got it. 0911:09 CAM [sound of tone]
24 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0911:09 APR Citation zero Foxtrot uh.... 0911:10 HOT-1 all right, gear's coming down. 0911:12 HOT-2 there's your gear. 0911:13 APR ...or correction uh, Cita, correction Citation zero Alpha 

you're cleared approach. just remain with me runway right. cleared to land. 0911:19 RDO-2 okay, five hundred Alpha Tango, cleared to land with yseven thousand. intercepting the glide slope. 0911:26 APR Citation zero Foxtrot Kilo, intercept the localizer inbounpresent heading. maintain seven thousand 'til establiscleared ILS runway two six right approach. 0911:27 HOT-1 all right, this, this time it'll be what a, left turn off, or right turn off. uuuuuh. left turn off. 0911:34 HOT-2 two six'll be a left turn off Hotel or Fox. 0911:37 HOT-1 all right, all right.
25 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0911:37 500FK 'kay uh, we are cleared for the approach now for five h

Foxtrot Kilo. 0911:44 CAM [sound similar to altitude alerter] 0911:45 HOT-1 and speed brakes coming back out again. 0911:46 HOT-2 okay. and standing, there's your glide slope intercept. 0911:48 HOT-1 full flaps. 0911:49 HOT-2 full flaps, here we go. 0911:53 APR Citation zero Foxtrot Kilo, you picking up the localizer o

0911:57 500FK uh, yes sir. we're coming left to intercept it a little bit a

right on it here in a second. 0912:00 HOT-2 full, full selected and indicated. 0912:01 HOT-1 all right. 0912:04 HOT-2 and you are plus twenty five.
26 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0912:07 HOT-1 slowing. 0912:08 HOT-2 slowing, sinking seven. captured the localizer and the glideslope. I've got some ground but stay on them gauges. 0912:16 HOT-1 all right. 0912:17 HOT-2 just a brief on the missed if we have to. it's climb to seven thou- sand, direct to the Pueblo localizer. 0912:23 HOT-1 all right. 0912:24 HOT-2 uh, Pueblo outer marker. 0912:28 HOT-1 right turn or left turn? 0912:29 HOT-2 it doesn't say. it says direct to it uh.... 0912:30 HOT-1 all right. 0912:31 HOT-2 ...straight ahead on the other side.
27 of 27 INTRA-COCKPIT COMMUNICATION AIR-GROUND COMMUNICATION TIME (MST) TIME (MST) & SOURCE CONTENT & SOURCE CONTENT 0912:37 HOT-2 I don't know if you want to run your ice a little bit. you got the, Vref there. 0912:40 APR Citation Foxtrot Kilo uh, traffic.... 0912:42 CAM [sound of high pitch tone for one second] 0912:44 HOT-1 #. 0912:46 CAM-3 bank angle, bank angle... bank angle. 0912:49 HOT-1 oh #. 0912:50 HOT-1 [groaning sound to end of recording] 0912:55 END of RECORDING END of TRANSCRIPT