National Transportation Safety Board / 

Washington D.C. 20594 

Safety Recommendation 

Date: August 15, 1996 

In reply refer to: A-96-48 through 

-69 

Honorable David R. Hinson 

Administrator 

Federal Aviation Adminisbation 

Washington, D.C. 20591 

On October 31, 1994, at 1559 Central Standard Time, an Avions de 

Transport Regional, model 72-212 (ATR 72), registration number N401AM, 

leased to and operated by Simmons Airlines, Incorporated, and doing 

-business-as-(d,b~a~)-~encan-Eaglefligh184~crash~d-d~g a rapiddescent after an uncommanded roll excursion. The airplane was in a holding 

pattern and was descending to a newly assigned altitude of 8,000 feet when 

the initial roll excursion occurred. The airplane was destroyed by impact 

forces; and the captain, ftrst officer, 2 flight attendants and 64 passengers 

received fatal injuries. Flight 4184 was a regularly scheduled passenger flight 

being conducted under 14 Code of Federal Regulations (CFR) Part 121; and 

an insment flight rules flight plan had been filed.' 

'For more detailed information, read Aircraft Accident Report--"In-flight Icing 

Encounter and Loss of Control, Simmons Airlines, d.b.a. American Eagle Right 4184, 

Avions de Transport Regional (ATR), Model 72-212, N401AM, Roselawn, Indiana, 

October 31, 1994" (NTSB/AAR-96/01) 

6486C 
2 

I The National Transportation Safety Board has determined that the 

probable causes of this accident were the loss of control, attributed to a 

sudden and unexpected aileron hinge moment reversal that occurred after a 

ridge of ice accreted beyond the deice boots because: 1) ATR failed to 

completely disclose to operators, and incorporate in the ATR 72 airplane 

flight manual, flightcrew operating manual and flightcrew training programs, 

adequate information concerning previously known effects of freezing 

precipitation on the stability and control characteristics, autopilot and related 

operational procedures when the ATR 72 was operated in such conditions; 2) 

the French Directorate General for Civil Aviation's (DGAC's) inadequate 

oversight of the ATR 42 and 72, and its failure to take the necessary 

corrective action to ensure continued airworthiness in icing conditions; and 3) 

the DGAC's failure to provide the Federal Aviation Administration (FAA) 

with timely airworthiness information developed from previous ATR 

incidents and accidents in icing conditions, as specified under the Bilateral 

Airworthiness Agreement and Annex 8 of the International Civil Aviation 

Organization. 

Contributing to the accident were: 1) the FAA's failure to ensure that 

aircraft icing certification requirements, operational requhments for flight 

hito icing conditions, and FAA published aircraft icing information, 

adequately accounted for the hazards that can result from flight in freezing 

rain and other icing conditions not specified in 14 CFR Part 25, Appendix C; 

and 2) the FAA's inadequate oversight of the ATR 42 and 72 to ensure 

continued airworthiness in icing conditions. 

As a result of the investigation of this accident, the Safety Board has 

concluded that the weather forecasts produced by the National Weather 

Service (NWS) were correct based on the available information, and that the 

actions of the forecasters at the National Aviation Weather Advisory Unit, 

Kansas City, and the Center Weather Service Unit meteorologists at the 

Chicago air route traffic control center were in accordance with NWS 

guidelines and procedures. 

Nonetheless, the Safety Board has some concerns about the lack of 

weather information disseminated to the crew of flight 4184. Specifically, the 

information contained in AIRh4E'Ts [airman's meteorological information] 

"Zulu," "Sierra" and "Tango," and Update 2, was available well in advance of 
3 

flight 4184‘s departure, and was pertinent to the airplane‘s route of flight. 

This information was not, and typically would not be, included in the weather 

portion of the flight release provided by Simmons Airlies/AMR Eagle. 

Further, it could not be determined if the flightcrew had obtained the updated 

weather information via the hazardous in-flight weather advisory service 

(HIWAS) while en route or prior to the recorded conversations on the cockpit 

voice recorder (CVR). 

14 CFR Part 121.601 (b) and (c) state, in part, respectively, “before 

beginning-a flight the-aircraft-dispatcher-shall-provide-thc pilot-in-commandwith all available weather reports and forecasts of weather phenomena that 

may affect the safety of flight” and that during a flight the dispatcher shall 

provide “any additional available information of meteorological conditions 

including adverse weather phenomena.“ FAA Order 8400.10, paragraph 

1423, (Operational Requirements - Flightcrews) requires that AIRMET 

information be considered in the preflight planning process; however, Center 

Weather Advisories (CWAs) are not required to be included or considered. 

Simmons Airlines dispatchers review the AIRMETs, but they do not typically 

include them in the flight release package. CWAs are not included in the 

release packages because they are not required. The Safety Board is 

concerned that because Simmons Airlines dispatchers do not include 

AIRMETs (which include information regarding moderate icing) and CWA 

information, flightcrews may not be provided “all available weather reports 

and forecasts of weatheiphenornenahecssaqtomake informed decisions. 

Although the Safety Board concludes that the actions of the flightcrew 

would not have been significantly different if they had received the 

AIRMETs, the Safety Board believes that Simmons AirlinedAMR Eagle 

should require its dispatchers to include in the flight release AIRMETs and 

CWAs that are pertinent to the route of flight so that this information can be 

available for preflight and in-flight decisionmaking. Therefore, the Safety 

Board believes that the FAA should direct its principal operations inspectors 

(POIs) to ensure that all air carriers require their dispatchers to provide 

pertinent information, including AIRMETs and CWAs, to flightcrews for 

preflight and in-flight planning purposes. Further, the FAA should Revise 

FAA Order 8400.10, Chapter 7, Section 2, paragraph 1423 to specify that 

CWAs be included and considered in the flightcrew’s preflight planning 

process. 
4 

With regard to the availability of in-flight weather information, the 

Safety Board notes that the HIWAS broadcast generated by the Kankakee 

(AFSS) included all of the icing information contained in AIRMET "Zulu," 

Update 3. Although the HIWAS broadcast generated by the Terre Haute 

AFSS indicated that icing was forecast above the freezing level, it did not 

indicate the icing levels, the intensity and type of icing, or the existence of 

icing conditions in clouds and precipitation included in AKRMET "Zulu," 

Update 3. The Safety Board understands that the HIWAS broadcasts are 

intended to provide hazardous weather information in a short format that will 

facilitate the pilot's understanding of the potentially hazardous conditions. 

However, the Safety Board concludes that safety would be enhanced if the 

information were presented more consistently among HIWAS stations and if 

those broadcasts included all of the information pertinent to the safety of 

flight, such as the altitudes of the icing conditions, the intensity and type of 

icing, and the location of the actual or expected icing conditions (i.e. in clouds 

and precipitation). Therefore, the Safety Board believes that the FAA should 

require that HIWAS broadcasts consistently include all pertinent information 

contained in weather reports and forecasts, including in-flight weather 

advisories (AIRMETs, SIGME'I's, and CWAs). The Safety Board also 

believes that the FAA and air carriers should reemphasize to pilots that 

HIWAS is a source of timely weather information and that it should be used 

whenever aircraft are operating in or near areas of potentially hazardous 

weather conditions. 

Air traffic controllers are required by FAA Order 7110.65 to solicit a 

pilot report (PREP) when certain weather conditions that are specified in the 

order are either forecast or reported for the area of jurisdiction. "Lighter or 

greater ..." icing conditions, which include freezing rain, are one of the five 

conditions specified by the order for which a controller will solicit a PREP. 

When the BOONE sector controller assumed control of the position and 

received a briefing by the departing controller, he was told, "...no one was 

complaining about the weather." This included flight 4184 which had been 

on the radio frequency for approximately 3 minutes when the BOONE 

controller assumed control. Because there were no PREPS provided to the 

previous controller, and the crew of flight 4184 did not provide a PIREP of 

icing conditions at the LUCI" intersection, it was reasonable for the 

controller to assume that there were no significant weather events in that area, 

and that the crew of flight 4184 was not experiencing any problems that 
5 

would have required the controller to take alternative actions. Nonetheless, 

the Safety Board believes that the FAA should revise FAA Order 7110.65, 

“Air Traffic Control,” Chapter 2, “General Control,” Section 6, “Weather 

Information,” paragraph 2-6-3, “PIREP” Information, to include freezing 

drizzle and freezing rain. These conditions should also be clearly defined in 

the PiloVController Glossary. 

The investigation revealed that although the icing definitions in the 

Aeronautical Information Manual (AIM) provide some basis for assessing ice 

accumulation%-PIREPs; they-are-subjectiv-daf lifEt~Wt~il~6T 

different aircraft types. For example, using these definitions, “light” icing for 

a B-727 could be “severe” icing for an ATR 72 or a Piper Malibu. The icing 

report provided by the captain of the A-320 Airbus that was holding at the 

HALE intersection near Roselawn indicated that he observed about 1 inch of 

ice accumulate rapidly on his aircraft‘s icing probe. The captain provided a 

PIREP to air traffic control (ATC) and reported the icing as “light rime.” 

After the accident, he stated that the anti-ice equipment on the airplane 

“handled the icing adequately,” and that he believed the icing intensity to have 

been “light to moderate.” 

The Safety Board concludes that icing reports based on the current 

icing severity definitions may often be misleading to pilots, especially to 

pilots of aircraft that may be more vulnerable to the effects of icing conditions 

-than-others7-Therefore~the-Safe~Board-believes~t-~e-F~-s~o~ld 

develop new aircraft icing intensity reporting criteria that are not subjective 

and are related to specific types of aircraft. 

In addition, the investigation revealed a problem with the aviation 

carnmunity’s general understanding of the phrase “icing in precipitation,” 

which is used by the NWS but is not defined in any aeronautical publications, 

including advisory circulars, Part 1 of the Federal Aviation Regulations or the 

AIM. This phrase is often contained in in-flight weather advisories; however, 

it does not typically specify types of precipitation. According to the NWS, 

this phrase is intended to include freezing drizzle and freezing rain. Therefore, 

the Safety Board concludes that defining “icing in precipitation” in these 

publications would make pilots and dispatchers more aware of the types of 

precipitation and icing conditions that are implied by this phrase. 

Accordingly, the Safety Board believes that the FAA should provide a 
6 

definition of the phrase "icing in pmcipitation" in the appropriate aeronautical I 

publications. Fwther, the Safety Board believes the FAA should require all 

POIs of 14 CFR Part 121 and 135 operators to ensure that training programs 

include information about all icing conditions, including flight into freezing 

drizzle/freezing rain. 

Based on the evidence uncovered in this accident, the Safety Board 

believes that the cmnt methods of forecasting icing conditions are of limited 

value because they typically cover very large geographic areas, do not 

provide specific information about liquid water content (LWC) or water drop 

sizes, and use only relative humidity and temperature. According to 

testimony from a scientist from the National Center for Atmospheric 

Research (NCAR), it is not possible to infer the severity of icing using only 

temperature and humidity. Rather, the severity of the icing also depends on 

the LWC and the size of the water droplets, information which is not 

currently identified and forecasted. 

The Safety Board is concerned that there are no reliable methods for 

flightcrews to differentiate, in flight, between water drop sizes that are 

outside the 14 CFR Part 25, Appendix C, icing envelope and those within the 

envelope. Further, although side window icing was recognized as an 

indicator of ice accretions from freezing drizzle during fight tests of an ATR 

72 after the accident, the crew of fight 4184 could not have been expected to 

know this visual cue because its significance was unknown to the ATR pilot 

community at the time. Moreover, in-service A?'R incidents and pilot reports 

have shown that side window icing does not always accompany ice 

accretions aft of the deice boots, which ATR has stated only occurs in 

freezing drizzle and/or freezing rain. 

The Safety Board acknowledges the efforts of atmospheric research in 

the meteorological cornmunity and hopes that its importarit findings will 

eventually provide the aviation industry with a better understanding of the 

freezing drizzlehain phenomenon. "he Safety Board concludes that the 

continued development of atmospheric measuring and monitoring equipment, 

such as atmospheric profilers, use of the WSR-88D [weather surveillance 

radar] and teiminal Doppler weather radars, multispectral satellite data, 

aircraft-transmitted atmospheric reports, and sophisticated mesoscale models, 

and the development of computer algorithms, such as those contained in the I 
7 

FAA's Advanced Weather Products Generator program to provide 

comprehensive aviation weather warnings, could permit forecasters to refine 

the data sufficiently to produce more accurate icing forecasts and real-time 

wamings. Therefore, the Safety Board believes that the FAA should continue 

to sponsor the development of methods to produce weather forecasts that 

define very specific locations of potentially hazardous atmospheric icing 

conditions (including freezing drizzle and freezing rain) and to produce shortrange forecasts ("nowcasts") that identify icing conditions for a specific 

geographic area with a valid time of 2 hours or less. 

__.-_l______-._-.l..--------.--.--.-. - 

Although the Safety Board has found no evidence that the ATR 42 and 

72 were not properly certificated for flight into icing conditions, the 

investigation has raised a number of concerns relating to the process for 

certlfying an airplane for flight into icing conditions. Among these concerns 

are the acceptance by regulatory authorities of a limited number of icing test 

data points, most of which are not near the boundaries of the envelope; the 

limited range of conditions (LWC and MVD [median volumetric diameter] 

size) provided by the Appendix C icing certification envelope; the lack of 

standardized methods for processing LWC and MVD data; the implied 

authorization of flight into conditions beyond the envelope; and the 

certification of stall protection systems that are intended to prevent exposure 

to undesirable (even dangerous) characteristics of the airplane without a 

requirement for the manufacturer to advise the FAA, operators, and pilots of 

.- -such-sharasteristics. 

This investigation has revealed that the ATR 42 and 72 were not 

required to be tested throughout a significant portion of the icing conditions 

that are specified in the Appendix C icing envelope. The limited number of 

test points accepted by the FAA as sufficiently comprehensive were well 

within the boundaries of the envelope and did not include the warmer, near 

freezing conditions at the upper boundary of the Appendix C envelope in 

which run-back icing and asymmetric slidingkhedding are likely to occur. 

Thus, by allowing liited data well within the envelope to suffice for 

certification purposes, the FAA effectively precluded any chance of 

identlfying the phenomena that led to flight 4184's ice ridge buildup, 

uncommanded aileron deflection and loss of control. 
8 

The Safety Board's concern about the adequacy of Appendix C criteria ( 

was heightened by the results of one December 1994 ATR icing tanker test in 

which ice accumulated behind the active portion of the ATR 72's deice boots 

during exposure to water droplet sizes of only 57 microns MVD, which is 

only slightly outside the Appendix C envelope. Further, data developed by 

NACA, the NASA predecessor, indicated in the 1950s that MVDs of 70 

microns or more could be encountered in layer clouds. Flight in layer clouds 

is not an unusual event in this country, but flight into layer clouds can result in 

encounters with icing conditions beyond those set forth in 14 CFR Part 25, 

Appendix C. Several ATR 42 icing incidents with ice aft of the boots 

occurred in layer clouds, which supports the conclusion that icing encounters 

in high altitude layer clouds can exceed the capabilities of aircraft certified to 

the Appendix C envelope. 

Thus, because the Appendix C envelope is limited and does not include 

larger water drop conditions, such as freezing drizzle or freezing rain 

(conditions that can be routinely encountered in winter operations throughout 

much of the northern United States, and were most liely encountered by 

flight 4184), the Safety Board concludes that the current process by which 

aircraft are certified using the Appendix C icing envelope is inadequate and 

does not require manufacturers to sufficiently demonstrate the airplane's 

capabilities under a sufficiently realistic range of icing conditions. 

In addition, the lack of standardized methods for processing icing data 

to determine MVDs raises concern that certification icing tests may be 

conducted at actual MVDs below the calculated values. For example, during 

the series of icing tanker tests at Edwards Air Force Base, it was determined 

that two generally accepted methods of calculating MVD and LWC provided 

sigrdcantly different results. Therefore, it is possible that airplanes 

certificated in accordance with Appendix C criteria may not actually have 

been tested in the icing conditions described in the certification 

documentation. Thus, the Safety Board believes that the FAA should revise 

the icing certification requirements and advisory material to speclfy the 

numerical methods to be used in determining MVD and LWC during 

certification tests. 

I 

A sigdicant Safety Board finding in this investigation is that no 

airplane should be authorized or certified for flight into icing conditions more 
9 

severe than those to which the airplane was subjected in certification testing, 

unless the manufachwr can otherwise demonstrate the safety of flight in such 

conditions. Although no aircraft are certified for flight into freezing drizzle or 

freezing rain, the ATR 72 flight manual did not spec@ the operational limits 

and capabilities of the airplane in conditions such as freezing drizzle and 

freezing rain. 

Currently, FAA ground deice and anti-ice programs permit operators to 

dispatch aircraft into freezing drizzle and light freezing rain2 provided they 

use-TypeX anti=ice-fluid-and-respect-the-speGified-holdover-timetables~-- - --- 

Specifically, Flight Standards Information Bulletin (FSIB) for Air Transport 

@SAT), 95-29, dated October 25, 1995, states that Type TI deicing fluid will 

be used when "operating during light freezing rain and freezing drizzle 

weather conditions" and that the "use of special procedures (Le. visual 

inspections, remote deice capability) is required." The Safety Board 

recognizes that the FAA's intent of this FSAT is to provide operators with the 

means to dispatch airplanes that will quickly depart and climb through the 

freezing drizzle or light freezing rain conditions and that the FAA's 

permission of limited operations in fitezing drizzle and light freezing rain is 

apparently based on the assumption that the airplane will depart within the 

prescribed "holdover" time of the anti-ice fluid, and transit through the 

freezing drizzle/light freezing rain conditions with minimal exposure. 

However, FSAT 95-29 does not specifically state that continued flight in such 

condi t ionsis-prohbited.The-Safe~-Board-is-concemed-that-in-some 

situations it may be necessary to operate in such conditions for an extended 

period of time. One such situation is the failure of an engine shortly after 

takeoff, a situation that could require maneuvering for an indeterminate period 

of time while returning to the departure airport where freezing drizzle or light 

freezing rain conditions are known to exist. 

FtuTher, although it is known by many in the aviation community that 

flight into freezing drizzle or freezing rain is not safe, the Safety Board is 

unaware of an explicit provision in the Federal Aviation Regulations that 

The NCAR definition for light freezing rain is: "measured intensity up to 0.10 

inh (2.5 mm or 25 g/drn*/hr); Maximum 0.01 inch in 6 minutes from scattered drops 

that, regardless of duration, do not completely wet an exposed surface up to a condition 

where individual drops are easily seen." 
10 

prohibits flight into freezing drizzle and freezing rain. Additionally, as was 

noted in the Safety Boards 1981 study on aircraft icing, airplanes certificated 

for flight into known icing are authorized to fly into weather conditions that 

produce "severe" icing under 14 CFR Parts 91, 135 and 121. However, by 

definition, severe icing conditions result in a rate of ice accumulation that 

exceeds the capabilities of the airplane deice/anti-icing system or that require 

immediate diversion from the planned route of flight. 

The Safety Board is concerned that these unclear and inconsistent 

messages to pilots about the operation of aircraft that are certified for flight in 

icing conditions may create the misconception that flight in freezing drizzle 

and/or freezing rain is acceptable when it is not. Such confusing and 

apparently contradictory information could have contributed to the belief by 

Simmons AirlinedAMR Eagle management that it was permissible for ATR 

42 and 72 airplanes to be dispatched and flown into conditions of freezing 

drizzle and light freezing rain when it disseminated a memorandum to its 

pilots in 1991 setting forth the conditions for such flights. 

The Safety Board concludes that no airplane should be authorized or 

certified for flight into icing conditions more severe than those to which the 

airplane was subjected in certification testing unless the manufacturer can 

otherwise demonstrate the safety of flight in such conditions. Thus, the 

Safety Board believes that the FAA should revise its certification regulations 

to ensure that airplanes are properly tested for all conditions in which they are 

authorized to operate, or are otherwise shown to be capable of safe flight into 

such conditions. If safe operation cannot be demonstrated by the 

manufacturer, operational limitations should be imposed to prohibit flight in 

such conditions, and flightcrews should be provided with the means to 

positively determine when they are in icing conditions that exceed the limits 

for aircraft certification. 

The Safety Board understands that as a result of this accident, the FAA 

is currently planning a review of its icing certification and operational 

regulations, including the icing severity definitions issue. The Safety Board 

supports and encourages this action but believes that the FAA should revise 

14 CFR Parts 91.527 and 135.227 in a tirrKly manner to ensure that the 

regulations are compatible with the published definition of severe icing, and 
11 

to eliminate the implied authorization of flight into severe icing conditions for 

aircraft certified for flight in such conditions. 

The Safety Board recognizes that the risk of another ATR 42 or 72 

accident resulting from an uncommanded aileron excursion in freezing 

drizzlelfreezing rain has been reduced by the addition of extended deice 

boots, improved operational procedures, extensive crew training, and 

heightened awareness by pilots. Because wind tunnel and in-flight tanker 

tests have been performed for only a limited range of icing and flight 

- _--conditions,-the- Safety- Board-remains concemed-whetheri-even-with- the 

improvements, the airplane can be controlled under all naturally occurring 

combinations of conditions of liquid drop size and content, temperature, 

airplane configuration, load factors, speeds, and time of exposure. Moreover, 

the Safety Board found that ATR’s post-Roselawn brochure entitled, “ATR 

Icing Conditions Procedures,” still does not adequately address or clearly 

represent the exact nature of the ATR ice-induced aileron hinge moment 

reversal. 

The Safety Board notes that Special Condition B6, developed by the 

MjAC in the 1980’s and initially applied during the ATR 72 certification, 

includes a ”zero G” flight test maneuver (pushover) designed to identlfy iceinduced elevator hinge moment reversals. The Safety Board understands that 

at least some manufacturers in the world aviation community (including the 

UntehStates)-are-cancemed-that-Special-~ondition-B6-is-too-de~ding~ 

particularly the tailplane icing pushover test. However, the Safety Board 

concludes that the addition of a test procedure to determine the susceptibility 

to aileron hinge moment reversals in both the clean and iced-wing conditions 

could help to prevent accidents such as that involving flight 4184. Thus, the 

Safety Board believes that the FAA should develop a test procedure similar to 

the tailplane icing pushover test to determine the susceptibility of airplanes to 

aileron hinge moment reversals in the clean and iced-wing conditions. 

As part of the investigation, the Safety Board reviewed historical 

accident and incident data of similar turbopropeller aircraft. The data did not 

show other airplane models to have a similar incidenvaccident history 

involving uncommanded aileron excursions in the presence of freezing 

drizzle/freezing rain. One possible reason for this is that other model aircraft 

use hydraulically powered ailerons, smaller mechanical ailerons with larger 
12 

hydraulically powered spoilers, or different balancehinge moment control j 

devices to provide adequate roll control with less propensity for aileron hinge 

moment reversals. The Safety Board understands that ATR is considering 

design changes to the lateral control system for current and future ATR 

airplanes that are expected to reduce the susceptibility to flow separationinduced aileron hinge moment reversals and/or uncommanded aileron 

deflections. The Safety Board concludes that such design changes, if 

effective, would reduce the need to rely on the changes to flight operations 

and pilot training that have alxeady been mandated to ensure the safety of 

flight. Thus, the Safety Board believes that the FAA should encourage ATR 

to test lateral control system design changes and, if they correct the aileron 

hinge moment reversal/uncommanded aileron deflection problem, require 

these design changes on all existing and new ATR airplanes. 

In a related area, the Safety Board is concerned that the FAA and other 

airworthiness authorities still permit airplane manufacturers to use stall 

protection systems (SPS) to prevent flightcrews from experiencing known 

undesirable flight characteristics unique to their particular aircraft design 

without requiring the manufacturers to reveal these characteristics to the 

airworthiness authorities, operators, and pilots. According to ATR, its use of 

an SPS to prevent, among other things, aileron hinge moment reversals in the 

clean and iced configurations was not explained to the ainvorthiriess 

authorities or the operators because ATR was not required to do so. The 

Safety Board concludes that the failure of the DGAC and the FAA to require 

that they be provided with documentation of known undesirable post-SPS 

flight characteristics contributed to their failure to identlfy and correct, or 

otherwise properly address, the abnormal aileron behavior early in the history 

of the ATR icing incidents. Therefore, the Safety Board believes that the 

FAA should require aircraft manufacturers to provide, as part of the 

certification criteria, information to the FAA and operators about any known 

undesirable flight characteristics beyond the SPS and related shaker/pushier 

flight regime. 

Evidence from the investigation revealed that the FAA's Aircraft 

Evaluation Group (AEG) does not maintain a data base of incidenvaccident 

information. Moreover, a communications deficiency resulted in the failure 

of the AEG to receive pertinent documentation regarding ATR icing incidents 

that could have been used to monitor the continued airworthiness of the I 
13 

airplane. This is not the first time that the Safety Board has identifed 

problems with the timeliness and effectiveness of the FAA's continuing 

airworthiness oversight of foreign-built aircraft. The Safety Board noted in its 

1987 report on the crash of a CASA C-212-CC that the FAA's monitoring of 

airworthiness issues relating to that aircraft was inadequate. Specifically, that 

investigation revealed that the FAA delayed for more than 3 years taking 

actions to correct known issues of noncompliance with 14 CFR Part 25, and 

that there "was an apparent lack of standardization and coordination" among 

various offices within the FAA.3 

_II-. _____-l_lll~.__._I-...___ 

Accordingly, the Safety Board concludes that the lack of defined lines 

of communication and adequate means to retrieve pertinent airworthiness 

information prevented the AEG from effectively monitoring the continuing 

airworthiness of aircraft. Therefore, the Safety Board believes that the FAA 

should develop an organizational structure and communications system that 

will enable the AEG to obtain and record all domestic and foreign aircraft and 

partshystems manufacturers' reports and analyses canceming incidents and 

accidents involving aircraft types operated in the LJnited States, and ensure 

that the information is collected in a timely manner for the effective AEG 

monitoring of the continued airworthiness of aircraft. 

The investigation has revealed the FAA's limited involvement during 

the initial certification of the ATR 42 and 72. For example, there were 

s-exeralmee tingsin_wbch-only-one-pemon-from-thcEAA-~viewed-vas t 

amounts of certification documentation and had to resolve prablems from 

many technical disciplines. Further, because FAA personnel were either 

unavailable, or budget constraints restricted travel, issues involving 

noncompliance or other concerns were resolved through "issue papers." An 

issue paper, of which there were more than 90 for the ATR 42 and 17 for the 

ATR 72, describes the FAA's position on a certification issue and the 

method@) necessary to achieve compliance. For the ATR, the FAA 

delegated the compliance oversight for the issue papers to the DGAC. 

- - 

3NTSB Accident Report AAR-88-08, Fischer Bros. Aviation, Inc., dba Northwest 

Airlink, Flight 2268, Construcciones Aeronauticas, S. A, (CASA) C-212-CC. Detroit 

Metropolitan Wayne County Airport, Romulus, Michigan, March 4, 1987, p.44. 
14 

Included in the certification process is the FAA review of test data, 

including data acquired from flight tests. According to testimony provided by 

the FAA's ATR certification team leader, the FAA does not flight test the 

aircrak rather, it conducts "evaluation" flights for the purpose of "familiarity 

with airplane ... and [to] determine suitability for use in airline service ...." The 

FAA conducted about 10 hours of evaluation flights on the ATR; however, 

none of these flights duplicated any tests required for certification, and none 

were conducted in icing conditions. 

The Safety Board concludes that the FAA's limited involvement in the 

AIR 42 certification does not appear to have resulted in an improperly 

certificated airplane (ATR 42/72). However, such excessive reliance on a 

foreign airworthiness authority could result in improper certification of an 

aircraft. Therefore, the Safety Board believes that the FAA should review 

and revise, as necessary, the manner in which it monitors a foreign 

airworthiness authority's compliance with U.S. type certification requirements 

under the Bilateral Airworthiness Agreement (BAA). 

The Safety Board is also concerned about the process by which the 

FAA ensures the continuing airworthiness of airplanes certificated under the 

BAA. For example, the FAA did not receive pertinent information about the 

airworthiness of the ATR 42 and 72 series airplanes, including AIR'S 

analyses of the icinginduced aileron hinge moment reversal incidents in 

1991, and those in 1993 and 1994. The FAA could have been more 

aggressive in requesting data from the DGAC following these incidents. 

However, the DGAC should have, on its own accord, taken actions to de 

sure that the FAA was provided with all information about the ATR incidents 

to ensure FAA involvement in the continuing airworthiness of the airplane. 

The Safety Board concludes that the FAA's ability to monitor the 

continued airworthiness of the ATR airplanes has been hampered by an 

insufficient flow of critical airworthiness information. The DGAC's apparent 

belief that such information was not required to be provided under the terms 

of the BAA raises concerns about the scope and effectiveness of the BAA. 

Thus, the Safety Board believes that the FAA should establish policies and 

procedures to ensure that all pertinent information is received, including the 

manufacturer's analysis of incidents, accidents or other airworthiness issues, 
15 

from the exporting country’s airworthiness authority so that it can monitor and 

ensure the continued airworthiness of airplanes certified under the BAA. 

In this accident, the flightcrew did not indicate that it was concerned 

about holding in icing conditions, but the Safety Board notes that there were 

some potentially distracting events durlng the hold. The cockpit voice 

recorder (CVR) recorded about 15 minutes of personal conversation between 

a flight attendant and the captain from 1528:Qo to 1542:38. The CVR also 

recorded music playing for about 18 minutes, as well as the sounds of the 

___ ____I---- captain’s departure-from-the cockpit-for-aboutSminutes-to use-the-rest room;- 

According to 14 CFR Part 121.542 (the “sterile cockpit” mle) and 

FAA staff testimony at the Safety Boards public hearing on this accident, 

holding at 10,000 feet or above is not considered to be a “critical” phase of 

flight. Thus, the presence of the flight attendant in the cockpit and the 

ensuing conversation were not in violation of AMR Eagle policy or Federal 

regulations. 

Although the presence of the flight attendant and the music could have 

been a distraction to the flightcrew, both pilots appeared attentive to flightrelated duties immediately before, as well as during the roll upset. Thus, the 

Safety Board concludes that neither the flight attendant’s presence in the 

cockpit nor the flightcrew’s conversations with her contributed to the 

_accident .Be-Safety-Board-no ted,-ho wever,tha t-the-AMR-Eagle-A-TR-7-2 

flight manual gives the captain the authority to declare “any other phase of a 

particular flight“ a critical phase depending on the circumstances and thus to 

invoke the sterile cockpit rule. Therefore, the Safety Board concludes that a 

sterile cockpit environment would have reduced flightcrew distractions and 

could have heightened the flightcrew’s awareness to the potentially hazardous 

environmental conditions in which the airplane was being operated. 

However, the sterile cockpit environment would not have increased the 

flightcrew’s understanding of the events that eventually transpired. 

Nonetheless, the Safety Board believes that the FAA should evaluate the need 

to require a sterile cockpit environment for all air carriers holding in certain 

weather conditions, such as icing and convective activity. 

In this accident, the Safety Board attempted to determine why the crew 

of flight 4184 was unable to successfully recover the airplane and prevent the 
16 

accident when the flightcrews of the airplanes involved in the prior incidents i 

were able to do so. At the time of the accident, the AMR Eagle pilot training 

program did not include an "unusual attitude" or "advanced maneuvers" 

segment (nor was such training required). During simulator training, AMR 

Eagle pilots were not exposed to aircraft attitudes that were typically beyond 

those used for normal operations or considered unusual, and they only 

experienced an abnormal pitch attitude when they practiced emergency 

descents. 

In four separate safety recomnendations over the past 27 years, the 

Safety Board has addressed the issue of unusual attitude training. The FAA's 

unfavorable responses and failure to require such training have resulted in the 

Safety Board classifying the FAA's past actions as "Unacceptable" in three of 

the four cases. In the fourth case, Safety Reconmendation A-93-72, the 

FAA's actions to promulgate rules to bring most 14 CFR Part 135 scheduled 

passenger operators under 14 CFR 121 training requirements (which include 

the use of simulaton) was classified "Closed-Acceptable Action" on August 

29, 1995. However, the Safety Board remains concerned that this does not 

necessitate a requirement to provide unusual event/attitude training. 

Based on the circumstances of this accident, the historical data of 

similar accidents, and safety recommendations previously issued by the 

Safety Board, the FAA, in August 1995, in joint cooperation with the aviation 

industry, issued an FAA Inspector Handbook Bulletin detailing a program 

that encourages air carriers to implement advanced maneuver/unusual attitude 

training in their pilot training program. AMR Eagle implemented an unusual 

attitude training curriculum into its pilot training syllabus, action that the 

Safety Board supports. Additionally, the Safety Board is encouraged by the 

FAA's latest position regarding unusual attitude/events training; however, 

there remains a concern that the kick of a required program might result in 

some carriers not providing unusual attitude training, and that their respective 

training programs might be insufficient to demonstrate the cause for and the 

recovery from aircraft attitudes that are not considered to be "~iormal." 

Therefore, the Safety Board believes that the FAA should amend the Federal 

Aviation Regulations to require air carriers to provide standardized training 

that adequately addresses the recovery from unusual events and attitudes, 

including extreme flight attitudes, in large, transport categoy airplanes. 
17 

Therefore, as a result of its investigation of this accident, the National 

Transportation Safety Board recommends that the Federal Aviation 

Administration: 

Direct principal operations inspectors (Pols) to ensure that all 

14 Code of Federal Regulations (CR) Part 121 air carriers 

require their dispatchers to provide all pertinent information, 

including airman’s meteorological infomation (AIRMETs) and 

Center Weather Advisories (CWAs), to flightcrews for preflight 

and in-flight planning .. purgoses. .. (Class --.--?-.-- II Priority Action) {A:- 

96-48) ~~.-I 

Require that Hazardous In-flight Weather Advisory Service 

(HIWAS) broadcasts consistently include all pertinent 

information contained in weather reports and forecasts, including 

in-flight weather advisories, airman’s meteorological information 

(AIRMETs), significant meteorological information (SIGMETs), 

and Center Weather Advisories (CWA’s). (Class II, Priority 

Action) (A-96-49) 

Encourage principal operations inspectors (Pols) and operators 

to reemphasize to pilots that Hazardous In-flight Weather 

Advisory Service (IIIWAS) is a source of timely weather 

information and should be used whenever they are operating in 

or near areas of potentially hazardous weather conditions. 

(Class TI, Priority Action) (A-96-SO) 

Revise the existing aircraft icing intensity reporting criteria (as 

defined in the Aeronautical Information Manual (AIM) and other 

Federal Aviation Administration (FAA) literature) by including 

nomenclature that is related to specific types of aircraft, and that 

is in logical agreement with existing Federal Aviation 

Regulations (FARs). (Class 11, Priority Action) (A-96-5 1) 

Publish the definition of the phrase “icing in precipitation” in the 

appropriate aeronautical publications, emphasizing that the 

condition may exist both near the ground and at altitude. (Class 

11, Priority Action) (A-96-52) 
18 

Continue to sponsor the development of methods to produce 

weather forecasts that both define specific locations of 

atmospheric icing conditions (including freezing drizzle and 

freezing rain) and produce short-range forecasts (“nowcasts”) 

that identlfy icing conditions for a specific geographic area with 

a valid time of 2 hours or less. (Class I[, Priority Action) (A-96- 

53) 

Revise the icing criteria published in 14 Code of Federal 

Regulations (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. (Class II, P~iority Action) ) (A-96-54) 

(Supersedes A-81-116 and -118) 

Revise the Federal Aviation Regulations (FARs) icing 

certification requirements and advisory material to spec@ the 

numerical methods to be used in determining median volunietric 

diameter (MVD) and liquid water content (LWC) during 

certification tests. (Class 11, Priority Action) (A-96-55) 

Revise the icing certification testing regulation to emure that 

airplanes are properly tested for all conditions in which they are 

authorized to operate, or are otherwise shown to be capable of 

safe flight into such conditions. If safe operations carmot be 

demonstrated by the manufacturer, operational limitations should 

be irnposed to prohibit flight in such conditions and flightcrews 

should be provided with the meam to positively determine when 

they are in icing conditions that exceed the liits for aircraft 

certification. (Class II, Priority Action) (A-96-56) 

Require all aircraft manufacturers to provide, as part of the 

certification criteria, information to the FAA and operators about 

any known undesirable characteristics of flight beyond the 
19 

protected (stall system and related shaker/pusher) flight regime. 

(Class z[, Priority Action) (A-96-57) 

Develop an icing certification test procedure similar to the 

tailplane icing pushover test to determine the susceptibility of 

airplanes to aileron hinge moment reversals in the clean and 

iced-wing conditions. Revise 14 CFR Parts 23 and 25 icing 

certification requirements to include such a test. (Class 11, 

Priority Action) (A-96-58) 

Encourage ATR to test the newly developed lateral control 

system design changes and upon verification of the improved or 

corrected hinge moment reversal/uncommanded aileron 

deflection problem, require these design changes on all new and 

existing ATR airplanes. (Class-11, Priority Action) (A-96-59) 

-.I..-.__-____ ___-- _.____l.l_l____l_l_.---.l-l----.---..--- 

Revise 14 CFR Parts 91.527 and 135.227 to ensure that the 

regulations are compatible with the published definition of 

severe icing, and to eliminate the implied authorization of flight 

into severe icing conditions for aircraft certified for flight in such 

conditions. (Class II, Priority Action) (A-96-60) 

Require all principal operations inspectors (POIS) of 14CFR 

-Part-l-2l1-and-l-3-5-operators-to-ensm-that-tra~g-programs 

include information about all icing conditions, including flight 

into freezing drizzle/freezing rain conditions. (Class 11, Priority 

Action) (A-96-61) 

Develop an organizational structure and a communications 

system that will enable the Aircraft Evaluation Group (AEG) to 

obtain and record all domestic and foreign aircraft and 

parts/systems manufacturers’ reports and analyses concerning 

incidents and accidents involving aircraft types operated in the 

United States, and ensm that the information is collected in a 

timely manner for effective AEG monitoring of the continued 

airworthiness of aircraft. (Class TI, Priority Action) (A-96-62) 
20 

Review and revise, as necessary, the manner in which the FAA 

monitors a foreign airworthiness authority’s compliance with 

U.S. type certification requirements under the Bilateral 

Airworthiness Agreement (BAA). (Class II, Priority Action) (A96-63) 

Establish policies and procedures to ensure that all pertinent 

information is received, including the manufacturer’s analysis of 

incidents, accidents or other airworthiness issues, from the 

exporting country’s airworthiness authority so that the FAA can 

monitor and ensure the continued airworthiness of airplanes 

certified under the Bilateral Airworthiness Agreement (BAA). 

(Class 11, Priority Action) (A-96-64) 

Evaluate the need to require a sterile cockpit environment for 

airplanes holding in such weather conditions as icing and 

convective activity, regardless of altitude. (Class 11, Priority 

Action) (A-96-65) 

Amend the Federal Aviation Regulations to require operators to 

provide standardized training that adequately addresses the 

recovery from unusual events, including extreme flight attitudes 

in large, transport category airplanes. (Class II, Priority Action) 

(A-96-66) 

Revise FAA Order 8400.10, Chapter 7, Section 2, paragraph 

1423 (Operational Requirements - Flightcrews) to specify that 

Center Weather Advisories (CWAs) be included and considered 

in the flightcrew’s preflight planning process. (Class II, Priority 

Action) (A-96-67) 

Revise FAA Order 7110.65, “Air Traffic Control,” Chapter 2, 

“General Control,” Section 6, “Weather Information,” paragraph 

2-6-3, “PIREP” Information, to include freezing drizzle and 

freezing rain. Additionally, these conditions should be clearly 

defined in the PilotlController Glossary. (Class II, Priority 

Action) (A-96-68) 
21 

Conduct or sponsor research and development of on-board 

aircraft ice protection and detection systems that will detect and 

alert flightcrews when the airplane is encountering freezing 

drizzle and freezing rain and accreting resultant ice. (Class II, 

Priority Action) (A-96-69) 

Also, the Safety Board issued Safety Recommendations A-96-70 to the 

National Oceanic and Atmospheric Admhstration and A-96-71 through -73 

to AbfR Eagle. ________________.---.-I 

Chairman HAL,L, and Members HAMMERSCHMIDT, GOGLIA, and 

BLACK concurred in these recommendations. Vice Chairman FRANCIS did 

not participate. 

[, Ch& 

L.. . . --'