Rejected Take-off/Runway Overrun - Canadian Airlines International - Vancouver International Airport, British Columbia
19 October 1995
Safety Action Taken
(as presented in the TSB Report)
Since the occurrence, CAI has taken steps to enhance the timeliness of its processing of engine trend monitoring data. In March 1996, CAI completed a program, begun before the occurrence, of equipping all of its DC-10 aircraft with an Aircraft Communications and Reporting System (ACARS), which can relay the flight data to ground stations. An interface program will be installed to acquire the airborne data and to feed this data through a ground-based personal-computer ADEPT program at CAI. The new procedures will require flight crews, using ACARS, to transmit engine readings to the ground station at the time that they are recorded. This new system will provide a near real-time acquisition, processing, and evaluation of the engine trend monitoring data.
Following the accident, the TSB forwarded a Safety Advisory to Transport Canada (TC) suggesting that other users of engine trend monitoring systems be advised of the safety benefits associated with timely analysis of engine data. TC subsequently published an article regarding jet engine fault monitoring in its Maintainer newsletter and is planning a similar article for the Feedback newsletter.
Evacuation Slide/Raft Cover Hinge Springs
Following the discovery of the problem with the hinge springs, CAI conducted a special inspection of the slide/raft covers on all its DC-10 aircraft, and found similar problems. As a result, CAI has begun retrofitting its DC-10 aircraft with larger hinge springs as recommended in McDonnell Douglas MD-11 Service Bulletin 25-148.
TC has sent a letter to the Federal Aviation Administration (FAA), requesting that the FAA urge McDonnell Douglas to address the problem of the DC-10 chute/raft cover hinge springs through action similar to that recommended in Service Bulletin 25-148 for the MD-11.
The FAA and McDonnell Douglas agreed with this course of action, and Service Bulletin DC10-25-367, applicable to DC-10 chute/raft cover hinge springs, has been issued by McDonnell Douglas.
Take-off Performance System Changes
American Airlines Corporation (AMR) has stated that software changes are being developed to correct the Take-off Performance System (TPS) program errors in calculating engine thrust when pressure altitudes are below sea level. AMR is also amending the TPS program to make it possible for crews to obtain performance data for power settings other than the TPS selected settings.
The TSB is investigating occurrences in which errors in ground-based aviation related software adversely affected safety. The adequacy of current quality assurance methods for such software is being examined.
The Vancouver International Airport Authority reports that, in response to the delays in recovering the passengers of Flight 17 from the accident site, the Airport Duty Manager Incident Call Out/Checklist has been revised. The checklist for the Airport Duty Manager in the Emergency Operations Centre now reflects the need to call the Vancouver International Airport Authority Ground Transportation Department to acquire immediate bus transportation. Buses will be requested from the Airport Authority's fleet of shuttle buses normally used for transportation to and from public and employee parking lots. Using the Airport Authority shuttle buses is meant to complement the efforts of the individual air carriers, who remain responsible for transporting the passengers from the accident site to the terminal building.
Spoiler Extension During Rejected Take-offs
As a result of CAI's assessment of the potential delay resulting from relying on the selection of thrust reversers to deploy the spoilers to activate the auto-brake system, CAI has redrafted its DC-10 Flight Crew Operating Manual (FCOM) rejected take-off checklist to indicate that the second officer "deploys the spoilers without command." CAI's DC-10 Standard Operating Procedures on rejected take-offs have also been amended to direct the second officer "as soon as the throttles are closed to pull the spoiler handle full aft and up without command."
As a result of CAI's assessment of the potential adverse effect of a disabled thrust reverser on a high-weight rejected take-off, CAI redrafted its DC-10 MEL Item 78-01 Thrust Reverser/Fan Reverser. TC has approved CAI's MEL amendment which specifies that the dispatch of DC-10-30 aircraft within 20,000 pounds of its runway-limit weight or above 572,000 pounds with a thrust reverser disabled will require the concurrence of the captain and chief pilot and their favourable assessment of the take-off conditions and environment.
CAI amended its DC-10 FCOM and crew training program to include information about the unavailability of audio panel 2 when the aircraft emergency power switch is ON.
The TSB sent a Safety Advisory to TC suggesting that they liaise with McDonnell Douglas and the FAA concerning dissemination of information regarding the communication limitations associated with the use of emergency power on the DC-10.
Definition of V1 in DC-10 FCOM
The wording in the CAI DC-10 FCOM may be ambiguous in that it implies that some time beyond V1 is available before the pilot needs to initiate the rejected take-off. Given the potential for pilots to misconstrue the definition of V1 in the FCOM, and given the potential for adverse consequences as a result of rejecting a take-off after V1 (in a field-length-limited context), the TSB forwarded a Safety Advisory to CAI. The Advisory suggested that CAI might wish to amend the definition of V1 in the DC-10 FCOM and review the V1 definition in other pilot reference materials, including those for other CAI aircraft.
Safety Action Required
(as presented in the TSB Report)
Engine Malfunction Recognition
The captain did not recognize the loud bang as a symptom of a high bypass ratio engine compressor stall and thought that the noise might have been caused by a bomb. Consequently, he decided to reject the take-off even though the speed was above V1. Although the flight crew members were all very experienced pilots and had taken simulator and ground training throughout their careers, they had not been trained to recognize a loud bang as a symptom of a high bypass ratio engine compressor stall, and none of the crew members noticed the cockpit indications of power loss.
Rejecting a take-off at a speed above V1 during a field-length-limited take-off places an aircraft at more risk than continuing the take-off, and should not be attempted unless the pilot has reason to conclude that the airplane is unsafe or unable to fly. The FAA's Takeoff Safety Training Aid states that "in order to eliminate unnecessary RTOs, the crew must differentiate between situations that are detrimental to a safe take-off, and those that are not." Also, a Boeing report entitled Engine Plus Crew Error Events indicates that positive recognition and correct identification of engine malfunctions appear to be significant contributors to the outcome of engine-plus-crew-error events. If pilots do not consider a loud bang as a symptom of a possible compressor stall, they may assume that the noise was caused by a bomb (a much less likely event) and unnecessarily reject the take-off.
Crew errors are often associated with engine failures that create loud noises. The Boeing report indicates that the majority of engine-plus-crew-error events involved engine malfunctions that generated loud noise. The report further indicated that the number of such events involving high bypass powered aircraft had steadily increased over the last five years covered by the study. Few resources are available to flight crews to aid in the quick identification of engine failure conditions. Neither engine manufacturers nor aircraft manufacturers have specific information available on the characteristics of high bypass ratio engine compressor stalls. The Boeing report observes that there is currently no flight crew training for positive recognition and correct identification of engine failure conditions; the noises, vibration, and other "cues" of real engine failures are not simulated in the vast majority of flight crew training simulators. In light of the risks associated with unnecessary rejected take-offs, the Board recommends that:
The Department of Transport ensure that flight crews operating high bypass ratio engines can correctly identify and respond to compressor stalls or surges. (A96-13)
Transport Canada's Response:
Flight crew training encompassing recognition and response to engine malfunctions is a part of initial and recurrent training. All flight crews that operate high bypass ratio engines accomplish this training in approved simulators. Although there are varying levels of simulator sophistication, most generate representative sounds that are as real as empirical data permits. Until such time that engine and airframe manufacturers develop parameters for all the different types of compressor stalls, Transport Canada considers this training to be both reasonable and adequate.
Transport Canada is currently following the work of the Aerospace Industries Association (AIA) propulsion committee which has been formed to address issues related to "Propulsion System Malfunctions Plus Inappropriate Crew Responses" and Transport Canada has been invited to help form the focus of the group. Based on the results of these initiatives, Transport Canada will ensure improvements are made to better enable flight crews to properly identify and respond to compressor stalls or surges.
Additionally, Transport Canada will feature this occurrence in its "Aviation Safety Letter" which is distributed to all licensed pilots. The recognition of high bypass ratio engine compressor stalls will be among the items discussed.
Wet Runway Considerations
Despite the various recommendations, studies, and working groups pertaining to wet runway take-offs over the last 10 years, there is still no requirement for manufacturers to provide approved performance data for aircraft taking off on wet runways, other than for newly certified aircraft. Furthermore, there is no requirement for operators to take into account such data when calculating aircraft take-off performance. Although TC is pursuing these issues, corrective action does not appear to be imminent.
In light of previous recommendations on this subject and in recognition of TC's current related activities, the TSB does not plan to make new safety recommendations on this deficiency at this time. Nevertheless, the Board remains concerned that fare-paying passengers continue to be placed at risk when field-length-limited take-offs are conducted without taking into account reduced braking effectiveness on wet runways
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