Show #48: Fourth Update of the AAIB
Investigation of the Crash of a British Airways 777
Title: Crash of British Airways 777 at Heathrow on 17 January 2008 - Update 4
Date: 20 May 2008; Length: 5:00
This is the fourth update from AirSafe.com on the ongoing investigation into the accident at London's Heathrow Airport involving a British Airways 777. This update is based on information released by the AAIB on 11 May 2008, and focuses on analyses of the fuel system, the engines, and their associated control systems. You can listen to or watch the podcast at the following links:
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Welcome to the Conversation at AirSafe.com, with your host Dr. Todd Curtis.
This is show #48 - Crash of British Airways 777 at Heathrow on 17 January 2008 - Update 4.
This show was first broadcast on May 20, 2008.
In this show, I'll review the most recent update from the Air Accidents Investigation Branch concerning the status of the investigation. I'll briefly review the details of the accident, and will discuss in greater detail the information provided by the AAIB report released on the 11th of May 2008.
The accident aircraft was a scheduled international flight from Beijing, China to London, England, and the flight was routine until about two miles from touchdown.
The engines would not respond to commands to increase thrust, and as a result the aircraft touched down about 1000 feet short of the runway.
There was a significant fuel leak, but no post-crash fire. All 136 passengers and 16 crew members were able to successfully evacuate the aircraft, and the most serious injury was a broken leg suffered by one passenger.
The three previous AAIB updates in January and February 2008 provided detailed information about the flight, including the state of the fuel and fuel systems, and the condition of the engines and their associated control systems. You'll find details about the previous updates, as well as links to previous podcasts describing the accident sequence, at 777.airsafe.org.
For the last several months, the AAIB has focused on the fuel and fuel systems of the aircraft. Extensive examination of the aircraft and detailed analysis of information from the flight data recorder and other onboard recording systems have revealed no evidence of an aircraft or engine control system malfunction.
The fuel was extensively tested, and showed no evidence of contamination or excessive water content. Although the aircraft had experienced very cold temperatures, the fuel temperature remained well above freezing. Detailed examination of the fuel system revealed a loose connection in one of the fuel lines as well as the presence of small pieces of debris, but these conditions led to no unusual deterioration or physical blockages.
The ongoing investigation has also found no evidence that a wake vortex encounter, bird strike, engine icing, or electromagnetic interference played a role in the accident. The focus of the investigation continues to be the fuel system and the engines, with the goal of understanding why neither engine responded to demands for increased power even though all of the engine control functions operated normally.
Under the direction of the AAIB, the engine manufacturer Rolls-Royce and the aircraft manufacturer Boeing are conducting further tests on the engines and fuel system with the goal of replicating the fuel system performance seen in the accident flight. Additional work is being conducted to gain a more complete understanding of the dynamics of the fuel as it flows from the tank to the engine.
No individual parameter associated with the accident flight was outside of previous operating experience. However, the AAIB is using a data analysis team to review data from a large sample of flights on similar aircraft to see if there was a combination of parameters that was outside of previous experience.
Unlike the last interim report in February, this report did not contain any recommended operational changes for the 777.
I'd like to take a moment to share my opinion about the progress of this investigation. This crash investigation has not yet come up with an explanation for what happened. This is in spite of having a largely intact aircraft, a large volume of data from the accident aircraft and comparison data from similar flights, and the combined resources the engine manufacturer, the aircraft manufacturer, and the British government. This probably means that if the AAIB does come up with an explanation for why the accident happened, the explanation will include a combination of circumstances that had not been previously anticipated by aircraft designers or aircraft operators.
The suggestions made in previous AirSafe.com podcasts about how to evaluate what's being published about this investigation are still valid .
If you're interested in following the investigation online or in the news media, keep in mind that prior to the completion of the investigation by the AAIB, anyone outside of the investigation, including aviation safety experts and the largest news media organizations, will have access only to a fraction of the relevant information.
The AAIB will likely provide several more updates prior to publishing a final report, and these updates represent the most authoritative sources of information about the ongoing investigation.
Finally, take the time to read between the lines and figure out what's fact and what's speculation. For additional information and other resources related to this investigation, please visit 777.airsafe.org. That's seven seven seven dot airsafe dot o-r-g.
There you'll find a synopsis of the findings of the accident investigation, links to previous podcasts about this accident, and links to other resources related to airline safety and security. You'll also find links to contact information for AirSafe.com.
Thanks for listening, and I'll see you next time.
http://www.airsafe.com/podcasts/show48.htm -- Revised: 20 May 2008