Carburettors on a B777? I don't think so!!!

After reading the interview with the F/O I don't think there is any doubt if both engine failed, or just failed to respond etc...Coward told Sky News:

------------------------------------------------------------A qantus 747 had a power outage recently on descent into BKK------------------------------------------------------------Interestingly I was just reading about that in Flight International. This incident was caused by water contamination. Water entered an avionics bay that was not properly sealed against moisture.

All the preliminary AAIB report says is:"At approximately 600 ft and 2 miles from touch down, the Autothrottle demanded an increase in thrust from the two engines but the engines did not respond. Following further demands for increased thrust from the Autothrottle, and subsequently the flight crew moving the throttle levers, the engines similarly failed to respond. "Let's not speculate further. On post here suggested carburettor icing might have been the cause!

>Let's not speculate further. On post here suggested>carburettor icing might have been the cause!I think and hope he was kidding about that. :)Marco

Air Canada flight 143 July 23, 1983Engine shutdown during cruise due to fuel exaustion.Procedures allowed operation without the normal redundancy in fuel level detection systems provided fuel level was measured manually before flight.Unfortunately during that particular incident the operational fuel level system would only operate properly if the malfunctioning system was disabled by opening the breaker supplying power to the malfunctioning system. During efforts to repair the malfunctioning system that circuit breaker was left closed (despite being tagged as open). Aircraft departed without ANY properly operating fuel level system.This problem was compounded by errors converting between measuring units comparing between fuel depth measured in the tanks, calculations for the upcoming flight's fuel requirements and the indicators on the departing airport's fuel dispensing equipment. The participants used the conversion factor for pounds, while the manuals specified quantities and consumption rates in Kilograms. Checking the calculations with the same erroneous conversion factor did not detect the error.The flight departed without adequate fuel for the planned route.No injuries due to the unpowered landing itself, although there were some minor injuries attributed to steep rear evacuation slides (nose gear collapsed)http://en.wikipedia.org/wiki/Gimli_Glider

>After reading the interview with the F/O I don't think there>is any doubt if both engine failed, or just failed to respond>etc...>>Regards>>Bernt >>Capt 767With all this speculation going on, any guesses about the role the twizzler played?http://www.newsoftheworld.co.uk/2001_hero_pilot_romp.shtml

Maybe they have them on the 707. He did mention that he had many hours on the sim in the forces. I just can't remember where the lever is on the 707 panel.Joe

The thing I find intriguing is the reports of extremely cold air at alt on the polar route from Beiging to LHR, with talk of icing conditions near LHR. Most commentators have been emphatic that they don't think it would be so cold that the fuel (supposedly equiv to Jet A-1) would have waxing effect (apparently the flight had some hold time prior to approach, and the assumption is that the fuel would have warmed, at any rate there should have been an EICAS alert if the fuel was cold.My thought is to consider the sensors that are used by the engine EEC (FADEC) and the possibility of multifailure, possibly due to icing conditions? Obviously a very low probability (I assume multiple sensors per engine and of course two entirely independent engines, the only thing in common is the physical environment they were operating in.It appears that in the RR/Trent EEC in "normal" mode the input from the thrust angle resolver is interpreted as an EPR demand, while in "alternate" mode is interpreted as N1 demand. I'm curious as to what logic is used in the EPR demand function which the FOM refers to as "thrust protection". I take it that the EEC is competing "max rated" thrust, based on sensor inputs, so that "full forward" thrust lever position equates to some thrust level probably less than "redline" thrust.scott s..

More info http://www.flightglobal.com/articles/2008/...h-evidence.html

Any word yet on what the flight recorders showed regarding fuel quantities? This should be known by now.

The latest AAIB report states:"As previously reported, whilst the aircraft was stabilised on an ILS approach with the autopilot engaged, the autothrust system commanded an increase in thrust from both engines. The engines both initially responded but after about 3 seconds the thrust of the right engine reduced. Some eight seconds later the thrust reduced on the left engine to a similar level. The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.Recorded data indicates that an adequate fuel quantity was on board the aircraft and that the autothrottle and engine control commands were performing as expected prior to, and after, the reduction in thrust."

Thanks, somewhat like the last update, wording leads to some tantalizing questions (what exactly are they trying to say). "engine control commands were performing as expected" -- exactly what are they referring to?scott s..

>Thanks, somewhat like the last update, wording leads to some>tantalizing questions (what exactly are they trying to say). >"engine control commands were performing as expected" -->exactly what are they referring to?>>scott s.>.>That means that the software of the EECs was working properly. The EECs were commanding a high power setting, but the engines were not responding to the commands. So the investigators now are focusing on possibilities in the fuel metering systems or contaminated fuel.http://seattletimes.nwsource.com/html/busi...syndication=rss

>>Thanks, somewhat like the last update, wording leads to>some>>tantalizing questions (what exactly are they trying to say).>>>"engine control commands were performing as expected" -->>exactly what are they referring to?>>>>scott s.>>.>>>>That means that the software of the EECs was working properly.> The EECs were commanding a high power setting, but the>engines were not responding to the commands. So the>investigators now are focusing on possibilities in the fuel>metering systems or contaminated fuel.>>http://seattletimes.nwsource.com/html/busi...syndication=rss>>Thanks, somewhat like the last update, wording leads to>some>>tantalizing questions (what exactly are they trying to say).>>>"engine control commands were performing as expected" -->>exactly what are they referring to?>>>>scott s.>>.>>>>That means that the software of the EECs was working properly.> The EECs were commanding a high power setting, but the>engines were not responding to the commands. So the>investigators now are focusing on possibilities in the fuel>metering systems or contaminated fuel.>If I could make a slight trim correction on that last statement, the investigators will focus on the "complete fuel flow path from the aircraft tanks to the engine fuel nozzles," but not to the exclusion of also examining "All possible scenarios that could explain the thrust reduction and continued lack of response of the engines to throttle lever inputs." Preceding quoted from the official investigation.I just add that because, in a fly-by-wire and digital engine control system, there are many, many scenarios that could explain thrust reduction and subsequent lack of engine response. I was joking about the carburetor heat, by the way. It was a way of saying "things used to be much simpler."Barry