Skip Ribbon Commands
Skip to main content
Safety Recommendation Details

Safety Recommendation A-06-016
Details
Synopsis: On December 8, 2005, about 1914 Central Standard Time, Southwest Airlines flight 1248, a Boeing 737-7H4, N471WN, landed on runway 31C at Chicago Midway Airport (MDW), Chicago, Illinois. The runway was contaminated with snow. The airplane departed the end of the runway and rolled through a blast fence and a perimeter fence and then into traffic on an off-airport street. The airplane came to a stop after impacting two cars, which resulted in the death of a child passenger in one of the vehicles. Of the 2 flight crewmembers, 3 flight attendants, and 98 passengers aboard the airplane, 5 reported minor injuries, and the airplane was substantially damaged. The flight was operating under the provisions of 14 Code of Federal Regulations Part 121 as a commercial passenger flight from Baltimore/Washington International Thurgood Marshall Airport, Baltimore, Maryland. Instrument meteorological conditions prevailed for the flight. The National Transportation Safety Board believes that the urgent recommendation contained in this letter requires immediate attention to restore landing safety margins on contaminated runways.
Recommendation: TO THE FEDERAL AVIATION ADMINISTRATION: Immediately prohibit all 14 Code of Federal Regulations Part 121 operators from using the reverse thrust credit in landing performance calculations. (Urgent) (Superseded by A-07-57)
Original recommendation transmittal letter: PDF
Overall Status: Closed - Unacceptable Action/Superseded
Mode: Aviation
Location: Chicago, IL, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA06MA009
Accident Reports: Runway Overrun and Collision Southwest Airlines Flight 1248 Boeing 737-74H, N471WN
Report #: AAR-07-06
Accident Date: 12/8/2005
Issue Date: 1/27/2006
Date Closed: 10/4/2007
Addressee(s) and Addressee Status: FAA (Closed - Unacceptable Action/Superseded)
Keyword(s): Pre-Flight, Procedures, Procedures: Pre-Flight

Safety Recommendation History
From: NTSB
To: FAA
Date: 10/4/2007
Response: As a result of the SWA flight 1248 accident, the Safety Board issued urgent Safety Recommendation A-06-16, which asked the FAA to immediately prohibit all 14 CFR Part 121 operators from using reverse thrust credit in landing performance calculations. The stated intent of this recommendation was to ensure adequate landing safety margins on contaminated runways. In response, in June 2006, the FAA issued an advance notice of its intent to issue mandatory Operations Specification (OpSpec) N 8400.C082, which would have required 14 CFR Part 121, 135, and 91 subpart K operators to conduct landing performance assessments (not necessarily a specific calculation) before every arrival based, in part, on planned touchdown point, procedures and data at least as conservative as the manufacturer’s, updated wind and runway conditions, and an additional 15 percent safety margin. However, the FAA subsequently decided not to issue the mandatory OpSpec at that time and, in August 2006, published Safety Alert For Operators (SAFO) 06012 as an interim guidance measure. SAFO 06012 addressed similar issues to the mandatory OpSpec, but operator compliance with the SAFO is, by definition, voluntary. Although the FAA published SAFO 06012 with the intent of pursuing rulemaking in the area of landing distance assessments, in the interim, operators are still not required to comply with its recommendations and, currently, many operators do not. For example, on February 18, 2007, a Shuttle America Embraer ERJ-170 ran off the end of snow-contaminated runway 28 at Cleveland Hopkins International Airport, Cleveland, Ohio.6 The investigation to date has revealed that Shuttle America did not require its pilots to perform (and therefore did not incorporate landing distance safety margins into) arrival landing distance assessments. About 2 months later, a Pinnacle Airlines Bombardier Regional Jet CL600-2B19 ran off the end of snow-covered runway 28 at Cherry Capital Airport in Traverse City, Michigan.7 By contrast, the investigation into this accident showed that Pinnacle’s OpSpecs required its pilots to perform arrival landing distance assessments (including a minimum 15 percent safety margin) per SAFO 06012;8 however, the pilots did not perform the required assessment before the accident landing. If an arrival landing distance assessment had been performed, given the existing conditions, Pinnacle’s OpSpecs would have dictated that a diversion was required. The Safety Board is concerned that, because of operational and conditional variations, it is possible for an airplane to use more of the landing runway than preflight (dispatch) calculations predicted and for pilots to continue to run off the end of contaminated runways. The circumstances of the flight 1248 accident (among others) demonstrate that conditions9 can change between dispatch and arrival and that there is a safety benefit to landing distance assessments at both times. The Safety Board notes that the FAA concluded in SAFO 06012 that operator compliance with preflight landing distance planning requirements alone does not ensure that the airplane can safely land within the distance available on the runway in the conditions that exist at the time of arrival, particularly if the runway, runway surface condition, meteorological conditions, airplane configuration, airplane weight, or use of airplane ground deceleration devices is different than that used in the preflight calculation. In addition, the FAA stated that a landing distance assessment should be made under the conditions existing at the time of arrival in order to support a determination of whether conditions exist that may affect the safety of the flight and whether operations should be restricted or suspended. Existing FAA regulations do not specify either the type of arrival landing distance assessment that should be performed or specify a safety margin that should be applied. The FAA-advocated minimum safety margin of 15 percent for arrival landing distance assessments published in SAFO 06012 is based on historic links to the FAA-mandated additional 15 percent factor for wet/slippery preflight planning requirements and the 15 percent factor embedded in the European Aviation Safety Agency and Joint Aviation Authorities operational requirements for contaminated runway landing performance. Although during public hearing testimony10 the FAA stated that the 15 percent landing safety margin has not been substantiated by a specific data collection and evaluation effort, the Safety Board is convinced that a defined landing safety margin is necessary for air carrier operations on contaminated runways. The Board was encouraged when the FAA proposed OpSpec N 8400.C082, which would have required operators of transport-category airplanes to incorporate a 15 percent safety margin in arrival landing distance calculations. The proposed 15 percent safety margin identified in FAA OpSpec N 8400.C082 would have satisfied the intent of the Board’s Safety Recommendation A-06-16. However, the FAA subsequently sought voluntary operator implementation of such actions through SAFO 06012; although SAFO 06012 contains similar information to OpSpec N 8400.C082, compliance with the SAFO is not required by the FAA.11 Because the FAA has had adequate time to require landing distance assessments and implement a landing distance safety margin but has not, Safety Recommendation A-06-16 was classified Open Unacceptable Response on May 8, 2007. Because the FAA has not required actions to address urgent Safety Recommendation A-06-16, flight crews of transport-category airplanes may still be permitted to land in wet, slippery, or contaminated runway conditions, without performing arrival landing distance assessments that incorporate adequate safety margins. As another winter season approaches, the urgent need for such margins becomes more critical. The Safety Board concludes that because landing conditions may change during a flight, preflight landing assessments alone may not be sufficient to ensure safe stopping margins at the time of arrival; arrival landing distance assessments would provide pilots with more accurate information regarding the safety of landings under arrival conditions. Further, the Safety Board concludes that although landing distance assessments incorporating a landing distance safety margin are not required by regulation, they are critical to safe operation of transport-category airplanes on contaminated runways. The Board recognizes that development of a standardized methodology for arrival landing distance assessments will take time. Therefore, the Safety Board believes that, until a standardized methodology can be developed, the FAA should immediately require all 14 CFR Part 121, 135, and 91 subpart K operators to conduct arrival landing distance assessments before every landing based on existing performance data, actual conditions, and incorporating a minimum safety margin of 15 percent. Because the objectives of this recommendation and Safety Recommendation A-06-16 are identical, the Safety Board classifies A-06-16 Closed Unacceptable Action/Superceded and the superceding safety recommendation (A-07-57) will maintain the status of Open Unacceptable Response.

From: NTSB
To: FAA
Date: 5/8/2007
Response: On June 7, 2006, the FAA published "Announcement of Policy for Landing Performance Assessments After Departure for All Turbojet Operators." This announcement stated that the FAA considered a 15-percent margin between the expected actual airplane landing distance and the landing distance available at the time of arrival as the minimum acceptable safety margin for normal operations. As a result, the FAA planned to issue Operations Specification/Management Specification (OpSpec/MSpec) C082, implementing a requirement to add a 15-percent safety margin to the actual landing distance calculated. OpSpec/Mspec C082 was to have been in force by the beginning of the 2006-2007 winter season. In its June 13, 2006, letter, the FAA stated that it believed that the approach described in the June 7, 2006, notice would yield a greater safety benefit than a blanket prohibition against taking credit for thrust reverse. The FAA’s plan for a mandatory OpSpec/MSpec C082 was discussed at length during the Safety Board’s June 20-21, 2006, public hearing concerning the Southwest Airlines flight 1248 accident. The OpSpec/MSpec would have required operators to make a landing distance assessment prior to every arrival based in part on (1) an air distance specific to their normal operations; (2) the most adverse reliable braking action report; (3) procedures and data that yield results at least as conservative as the manufacturer’s approved or advisory information for the associated conditions; (4) a landing distance assessment as close to the time of arrival as practicable; (5) at least a 15-percent safety margin applied to the actual performance data; and (6) flight crew and dispatcher training programs that provide knowledge in all aspects and assumptions used in determinations of landing distance performance. OpSpec/Mspec C082 would not necessarily have required a landing distance calculation prior to every airplane landing. The Safety Board believed that use of the procedures in OpSpec/Mspec C082 was roughly equivalent to prohibiting credit for thrust reversers and that issuance of the OpSpec/MSpec was an acceptable alternative response to address this recommendation. However, the FAA encountered considerable public comments and opposition to the proposal published on June 7, 2006, and at the end of August, decided to pursue formal rulemaking and to not issue OpSpec/MSpec C082. Because such rulemaking is likely to take several years to complete, the FAA issued Safety Alert for Operators (SAFO) 06012, "Landing Performance Assessments at Time of Arrival (Turbojets)." The SAFO contained very similar guidance and procedures to those proposed in OpSpec/MSpec C082; however, while the procedures in the OpSpec/Mspec would have been mandatory, the SAFO is advisory only and does not require compliance. On September 15, 2006, staff from the Safety Board and the FAA met to discuss the FAA’s response to this urgent recommendation, and the FAA’s decision not to issue the OpSpec/MSpec. During this meeting, Safety Board staff indicated that if the FAA could determine how many Part 121 operators had implemented the procedures in SAFO 06012, this might be an acceptable alternative response to the recommendation. The FAA agreed to survey Part 121 operators for this purpose. Although the Safety Board has requested updates on the results of the survey, the FAA has not yet informed the Board how many operators have voluntarily adopted in full or in part the procedures in SAFO 06012. The Board notes with disappointment that the 2006-2007 winter season, when landing distance calculations on slippery runways may become a significant operational issue, has already started. A year after this urgent recommendation was issued, the FAA has not yet taken any effective action in response to it. At the start of the winter season, the FAA issued guidance on landing distance assessments, including use of a 15-percent safety factor, but the FAA is unable to tell the Safety Board how many Part 121 operators have adopted this procedure. Accordingly, pending the FAA’s taking the recommended action or an acceptable alternative, Safety Recommendation A-06-16 is classified "Open--Unacceptable Response."

From: NTSB
To: FAA
Date: 7/28/2006
Response: Notation 7753D: The National Transportation Safety Board has reviewed the Federal Aviation Administration’s (FAA) advance notice of policy statement titled “Announcement of Policy for Landing Performance Assessments After Departure for All Turbojet Operators,” which was published in 71 Federal Register, 32877-32882 on June 7, 2006, and modified in 71 Federal Register 34856-34857 on June 16, 2006. This policy would provide clarification and guidance for all operators of turbojet aircraft for establishing methods of ensuring that sufficient landing distance exists to safely make a full-stop landing with an acceptable safety margin. On December 8, 2005, a Southwest Airlines Boeing 737 overran the runway while landing during a snowstorm at Midway Airport, Chicago, Illinois. After exiting the runway, the airplane went through the airport perimeter fence and impacted a car, fatally injuring one occupant. Several airplane passengers were injured, and the airplane received substantial damage. As a result of this ongoing investigation, on January 27, 2006, the Safety Board issued urgent Safety Recommendation A-06-16 to the FAA. This recommendation, which was intended to improve the margin of safety for landings on contaminated runways, asked the FAA to immediately prohibit all 14 Code of Federal Regulations Part 121 operators from using the reverse thrust credit in landing performance calculation. In a June 13, 2006, letter to the Board, the Administrator stated that the FAA agrees with the Board’s concern for an adequate landing distance safety margin and stated that the proposed policy on landing performance will yield a greater safety benefit than a blanket prohibition against taking credit for thrust reverse. The Safety Board has studied the policy statement and the testimony provided by the FAA at the Board’s June 20-21, 2006, Public Hearing and agrees that the policy statement will provide additional safety margin. Therefore, the Safety Board supports the “Announcement of Policy for Landing Performance Assessments After Departure for All Turbojet Operators.” The requirement that flight crews compute landing rollout distances using the actual conditions at the time of the computation then add a 15 percent safety factor will enhance the safety of winter operations for all U.S. air carriers. The Board appreciates the opportunity to comment on this proposed policy.

From: FAA
To: NTSB
Date: 6/13/2006
Response: Letter Mail Controlled 6/20/2006 2:17:07 PM MC# 2060295: The Federal Aviation Administration agrees with the Board's concern for an adequate landing distance safety margin. Although the regulations have not been specific on the criteria for the computation of actual landing distance at the time of arrival, this basic safety tenant is imbedded throughout the operation rules. Likewise, the safety margin requirements for actual landing distance, at time of arrival, have not been specifically addressed in the regulations. The amount of safety margin required for a particular landing varies widely based on the make/model/series of aircraft, runway length and composition, runway condition (types and depth of contaminants), metrological conditions, and the aircraft ground deceleration devices used. These variables make it difficult to specify definitively a safety margin for landing distance calculations at the time of arrival. For this reason, a very generous safety margin of 40 percent for a dry runway and an additional 15 percent for a wet runway is required on preflight landing distance calculations for the destination and alternate airports. These calculations do not include the added safety margin that would be available through the use of thrust reversers, auto brakes, and auto ground spoilers. With these large safety margins built into the preflight landing distance calculations and the many variables affecting the actual landing distance requirement calculations at the time of arrival, the FAA has not mandated a specific actual landing distance calculation safety margin requirement. This determination is the responsibility of the air carrier in coordination with the pilot in command considering the actual conditions present at the time of arrival. Based on information received from a survey coliducted after the Chicago Midway accident, it is now evident that some operators are not completing actual landing distance calculations at the time of arrival. Of those operators accomplishing these actual landing distance calculations, some might not be allowing for an adequate safety margin between the runway required and the runway available under the actual conditions present. In response to this recominendation and the results of the FAA survey of 14 CFR Part 121 turbojet operators, the FAA is issuing a new mandatory Operation Specification and associated guidance material. The Operation Specification will require all turbojet operators to develop procedures for and implement the following practices: All turbojet operations must perform an actual landing distance calculation as close as practicable to arrival at the destination and/or alternate airport. This calculation must account for the runway to be used, runway condition (type and depth of contamination and effects on aircraft stopping capability), current metrological conditions, and the aircraft ground deceleration devices available and planned to be used. These actual landing distance calculations must be based on landing data that is at least as conservative as the manufacturer's approved or advisory data for determining landing distances under the conditions and aircraft configuration present at the time of arrival. The available runway must allow for at least a 15 percent safety margin to be added to the required landing distance calculation determined in the above step. NOTE: The FAA believes that there are conditions where the flightcrew does, in fact, need to know the absolute perforniance capability of the airplane. These situations include emergencies or abnormal and irregular configurations of the airplane, such as engine failure or flight control malfunctions. In these circumstances the pilot must choose between the safety of continued flight or immediate landing and must be able to calculate his actual landing performance without an added safety margin. Flight crewmembers and dispatchers must be trained on the landing performance calculations required by this paragraph. This training must include instruction on the aircraft ground deceleration devices used in computation of landing distance requirementsunder various conditions and the correct operation of the aircraft systems to obtain optimum aircraft stopping performance. Some operators currently have procedures in place that closely parallel the specific requirements of the new Operation Specification and will be able to implement these requirements in a relatively short period. As stated above, our survey has indicated that other operators do not currently conduct actual landing distance calculations and, therefore, these operators will require a longer period to develop the proper procedures and adequately train the operations personnel. Our target is for all operators to be in compliance with the applicable regulatory requirements and the specifics of this Operation Specification by September 1, 2006. We believe that this approach will yield a greater safety benefit than a blanket prohibition against taking credit for thrust reverse. Our concerns about a blanket prohibition include: Operators who currently compute actual landing distance requirements accounting for the use of thrust reversers may discontinue providing this actual landing distance information to the flightcrew. This would remove a valuable piece of safety information that pilots use to make better-informed decisions as to the adequacy of a runway for the proposed operation. A prohibition against credit for thrust reverse would not provide an additional safety margin for aircraft that are not equipped with thrust reversers, whereas our approach will. Under runway conditions with low friction values, these are the operations most in need of added safety margins. This recommendation would be problematic for operations that base landing distances calculations on the use of auto brake systems. These systems typically meter brake application to obtain a deceleration rate. On runways with low friction values, these deceleration rates may not be obtainable with wheel braking alone and require the use of reverse thrust. So, in effect, the use of reverse thrust is imbedded in the actual landing distance calculation with auto brakes when the runway friction values are low. There is no way to discount the thrust reverser component in this manufacturer data. Note that the landing distance calculations required at dispatch remain unchanged, and are based on data which allows no credit for thrust reverse. I will keep the Board informed of the FAA's progress on this safety recommendation.