Posted on 01/24/2008 8:45:55 AM PST by Moonman62
nvestigators have determined that the British Airways Boeing 777-200ER which crashed on approach to London Heathrow last week had adequate fuel on board and that both engines continued to generate thrust, albeit much-reduced, during the event.
Preliminary findings from the Air Accidents Investigation Branch had indicated that the aircraft’s Rolls-Royce Trent 800 engines had failed to respond to an auto-throttle command for increased thrust during the final stage of the approach.
In a newly-issued update, however, the AAIB says both engines did initially respond to the auto-throttle command, but that the starboard engine’s thrust reduced after about 3s and the port engine’s thrust also reduced to a similar level 8s later.
“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,” it adds.
(Excerpt) Read more at flightglobal.com ...
Here’s the official AAIB update:
Accident to a Boeing 777-236, G-YMMM, on 17 January 2008 - Initial Report Update
Accident to a Boeing 777-236, G-YMMM, on 17 January 2008 at 1243 hrs
Initial Report Update 23 January 2008
Since the issue of the Air Accidents Investigation Branch (AAIB) 1st Preliminary Report on Friday 18 January 2008 at 1700 hrs, work has continued on all fronts to identify why neither engine responded to throttle lever inputs during the final approach. The 150 tonne aircraft was moved from the threshold of Runway 27L to an airport apron on Sunday evening, allowing the airport to return to normal operations.
The AAIB, sensitive to the needs of the industry including Boeing, Rolls Royce, British Airways and other Boeing 777 operators and crews, is issuing this update to provide such further factual information as is now available.
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.
All possible scenarios that could explain the thrust reduction and continued lack of response of the engines to throttle lever inputs are being examined, in close cooperation with Boeing, Rolls Royce and British Airways. This work includes a detailed analysis and examination of the complete fuel flow path from the aircraft tanks to the engine fuel nozzles.
Further factual information will be released as and when available.
Curiouser and curiouser...
It’s good they didn’t shut down completely...plane would’ve dropped like a rock.
OK, now that’s scary.
The decision of the pilot to drop the nose to build up speed then pull up sharply before touchdown instead of just pulling up was what saved them. That guy deserves every bit of praise heaped on him, he really did save lives that day.
Worst case IMHO, is it was a commanded throttled back, deliberately caused by hacked autopilot or engine interface software.
With only a little more tinfoil I can imagine that this craft was affected early because the internal calendar was off by, say, a month, and this was scheduled to happen to every aircraft in the air next month...
(how'd I do???)
So an initial response to the increased thrust request. At first glance then it sounds like *something* (whatever it was) caused the starboard engine to wind down a bit and, shortly after that, apparently there was automatic compensation on the port engine to prevent yaw? And after this happened, no further increase in power was processed?
Did I read that correctly?
Keep reading...
Oh yes, the guy was on the ball. Reminds me of the heroism of the pilot who landed that DC-10 in Iowa back 1989 after losing complete hydraulics. Half of the passengers lives were spared thanks to his piloting abilities despite having very little control of the plane.
Airplanes without power do not drop like rocks. They continue to fly like airplanes. See e.g. Final flight for famous 'Gimli Glider' posted earlier today.
ML/NJ
You bet! Kudos to the flight crew.
Keep reading...
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Hacked software obviously caused by the Captain or co-pilot downloading illegal mp3's to the flight software computers that were infected by a trojan???? Do ya think they have WiFi cards hooked up to those computers??? Now I know why they are so slow at offering in-flight internet connections.
Excellent! Now we can blame RIAA!
Thank you for playing!
It sounds like the autopilot is a Vista application.
In a world without walls, who needs Windoze?
The event was blamed on the ice.
At the same time the final report noted that engine speed didn't increase in response to the throtle.
A device on top of the fusilage called (as I recall a "fuel feed regulator") was protected by little more than a fiberglas housing.
This fact alone prohibited the plane from being flown higher than 35,000 feet (for fear of cosmic rays knocking out the device). Here, the "fuel feed regulator" seems to have not worked. The NTSB quietly recommended using aluminum cowlings to house those devices.
Ice had nothing to do with the failure of the device on top of the fusilage, nor the failure of the engines to increase speed and power. "Software" wasn't even a question at that time, but still, the engines failed to perform, the plane flipped after touchdown on 14th street bridge (immediately behind the car I was in), and all but a few people on that plane were killed. One of the fellows was a USPS lawyer whose desk was just one floor up.
I remember that accident quite well and have followed it intently.
So, why might the engines not rev if fully supplied with fuel?
Hopefully, this includes a thorough examination of the fuel for quality and contaminants.
This flight originated in china. Having lost a wonderful Dog to chinese contamination of food ingredients, I suspect chinese contamination of fuel before anything else.
Yes. So the auto engine-control worked to keep it from yawing.
They also say that the auto-throttle and engine-control commands worked properly before and after the low throttle condition.
SO the autopilot, the auto-throttle, and engine-control commands all worked fine. I assume they can see the signals in the data recorders.
I went from fuel to pilot error to flight software flaw and now I’m back to fuel preventing the starboard engine from spooling up to the engine mgmt command. They had fuel. I wonder if they can tell flow rates from the data recorder. Read a while back about some problems with non OEM fuel filters. Hard to imagine. Could happen.
Yow! That was one Hell of a crash. Air Florida, IIRC.
Made in? Bangladesh???
Stalled ones do.
You’re talking about (IIRC) Air Florida flight 90, where the plane was not properly de-iced, and, if memory serves, because of noise regulations, all departures off that runway had to bank immediately and follow the river.
Wow, lucky that you made it, being so close.
The plane was de-iced a time or two, but sat longer on the runway after the last de-icing than it was supposed to. The pilots then hoped to pull up behind a 727 or similar and get close enough to have the engines of the plane in front of them give them a final wash with exhaust heat (or at least they joked about it). A 727 with the three engines so close together would not have washed the wings very well (and it was against regulations, maybe only company regulations).
Now what I recall was the frozen component would not give accurate thrust readings and so they lifted off with too little thrust. The plane immediately indicated they were in a stall and as you say, settled on the bridge, killing many in their cars, too. It’s amazing anyone lived.
I don’t recall the engines not giving thrust, but due to the icing of the wings and a possibly frozen sensor, liftoff was achieved into a stall that was unrecoverable.
I’m typing this all from memory so please forgive. It was 1980 or 1981 I think when that occurred.
Correct. I tried to explain this (unsuccessfully) to a friend a number of years ago. When lift is gone, down you go, perhaps never even achieving glide.
Pretty good, nully, you could just about wrap a book or a movie around that idea.
Maybe the Chicoms filled the 777 with leaded JP8?
Vista sp2? Media player 11
The lag between the engines cutting back explains the turn that was reported by witnesses.
I would think they would be VERY anxious to solve this since while they’re working at finding the cause approaches of the 777’s continue hourly around the world. Not a comforting thought for those who fly them!
Nyuk, nyuk, nyuk
Actually, the instant I read that the flight originated from china, I suspected a fuel contamination/quality issue. The notion that there could have been some leaded fuel adulterants (maybe a little 100LL?) is certainly not out of the question.
A thorough chemical analysis will reveal whether or not my suspicion has merit.
Water in the gas tank.
One would think that on a 2 engine plane, that the pilot would have some input as to whether engine #2 throttles back to reduce yaw because engine #1 failed. I see a little logic error with this programming.
Not really, they were on final approach, descending and the throttles would be pulled way back at that point by the autopilot. Once they are established on the localizer and descending the throttles aren’t used until the last minute or two, if then. Engine power is needed to keep the plane in the air. When it’s time to land they just cut engine power and let the airplane glide down toward the ground. In smaller airplanes they can often go all the way to touchdown without needing to advance the throttles again. Students learn to cut the power when they are on the downwind leg of the approach and even with the point on the runway where they intend to touch down. Good pilots learn to glide right over the numbers on the runway and touchdown without ever having to advance the throttle again. In fact, in the old flying clubs at little airports all over the country they used to have ‘spot landing’ contests once a month and the winner would be the one who could cut the engine then glide to a landing closest to a mark on the runway.
Had they had any indication they were experiencing difficulties they could easily have gone all the way to the runway without additional power. Every shuttle does exactly that, from miles and miles above the earth. No throttles there.
Would it be correct to say that the plane would have glided like a rock then?
Just one trip at, for example, 37,000 feet would have increased the probability of the inadequately protected device being damaged by cosmic rays.
It was hardly "frozen" ~ but it didn't work just the same.
Something else was afoot that day. At the time there was a very powerful Department of Navy microwave communication system located on a line from a microwave tower at White Flint (in DC) and Quantico, VA.
Ordinarily the beam was no big thing, but during inclement weather it was designed to automatically increase beam strength so that this vital national defense system communication link wasn't impaired.
That day we had an absolutely incredible snowstorm taking place ~ it alternated between snow, frozen rain, sleet, heavy frozen mist, and so on. They canceled work and sent us home (which was why I was on 14th street bridge at that time).
Other incidents along the path of the microwave included failure of all GM automotive products with electronic ignitions; failure of all traffic signal light systems using a new microchip control system that replaced older switches; the failure of a controller in a room in USPS Headquarters in L'Enfant Plaza (said controller serving to take signals from an old fashioned card reader and route them to a data processing device.
Then, the ultimate failure ~ right at the corner of the L'Enfant Plaza postal complex there's an airshaft down to the Metro system.
Right at the bottom a switch control device failed ~ again, it had modern chip technology (just then the rage) housed in a fiberglass box (also just then the rage).
When that switch failed a subway train jumped the track, two cars jacknifed. My secretary was sitting in a seat right next to two men who were crushed to death by this accident.
You'd best believe I really, really, really got interested in this one once I found out all the stuff that happened under the line of travel of that microwave.
You don't need to burn out a control on an airplane with cosmic rays when you have a conveniently located microwave system of sufficient power toking up next to you.
Oh, yeah, story is not over ~ that beam was just parallel to our floor in the USPS headquarters, and if there were any serious leakage folks in my office would have been injured by it. In the 3 years following we had 4 individuals die of brain tumors of the sort that can be induced by high levels of microwave frequency radiation. 8 others died of sceleric inflammation and other cardiovascular problems frequently associated with microwave exposure.
My coworkers (and I) have had a serious rash of early cataracts.
Since this system was under the control of the Department of Defense no one regulated it. There was no recourse. They don't care.
So, did this latest plane get cooked somewhere?
re: So, why might the engines not rev if fully supplied with fuel?
Everything on that plane is controlled by computer. Advancing the throttle signals the computer and the computer then signals the engine. All sorts of things could prevent the signal from getting from the throttle quadrant to the computer, or from the computer to the engines. The fact that they responded initially would seem to me to rule out the link between the throttles and the computer.
Disclaimer: I know little of which I speak. Hopefully someone who has actually sat in the left or right seat, and maybe even FLOWN, one of these magnificent machines will hop in and give us the straight shinny!
Probably some uninitialized variable in a method call.
The plane was blanketed with ice numerous times ~ not even sure the de-icing process worked.
When we were on the bridge, the center of the worst of the storm moved in over us and we were covered with over 6 inches of snow in seconds. It was the worst snowstorm I'd ever seen.
I remember those MW stations. There is a huge one in central NC, cost millions of bucks to build. Never heard what its mission was. Could not see it from the ground, but at 2000 ft, it looked odd to see a 50 car parking lot next to a small block building 5 miles from the nearest paved road.
They are very anxious. Just like they were when the grounded an entire fleet to inspect the wiring when defective wiring caused a center fuel tank explosion...
I wonder what the computer would do if yaw was sensed when the first engine spooled down? What would it take to get it off autopilot at that point? If the autopilot was still engaged and the one engine couldn’t spool up would it try to prevent the other one from responding even if it’s was commanded to do so, to avoid the good engine pushing the aircraft around the slow engine? Could be some failsafe mechanism intended to keep one engine from running away just thought it was doing its job.
Also, how would the autopilot handle an engine failure at that stage of the final?
Say what they want, no machine can do as good a job as the pilot when something untoward starts to unfold!
Whatever it turns out to be it’s going to be interesting!
In addition to the ice on the wings, AF 90 had the engine pressure ratio probes at the front of the engines ice over and give incorrect readings. EPR was used on 737-200s to set takeoff power. So the pilot pushed the throttles forward to what the gauges said was, say, 2.00 EPR, but the engines were actually running closer to 1.70, considerably down on power. For reasons unknown, the crew elected not to use engine anti-ice on takeoff, which would’ve (IIRC) de-iced the probes and restored proper engine power readings. So not only was the airframe contaminated with ice and snow, the plane was basically taking off at two-thirds throttle. Had they been at normal takeoff power, they may well have had enough thrust to limp over the bridges, even with the iced-over wings.
}:-)4
Yep. My dad used to win those all the time.
Actually, they had full thrust available, but because the EPR probes were partially frozen over, the pilot in the left seat only advanced the power to a fraction of take off power. The indicator in the cockpit receiving inputs from the EPR probe told him he had takeoff power in, but he didn't.
Hence, they didn't have sufficient airspeed and crashed on takeoff.
There are several sub routines in the auto-throttle software (obviously). One would be “auto-sysc” (between engines), and that one appears to have been working. The auto-throttle to glideslope tracking in the auto-pilot looks to have been a bit sketchy.
That plane, was (again IIRC) a 737-100 or 200. I always hated getting on one with the smaller engines like those. I’ll have to go back and check. I always felt better on a -300 or -400. But then when I was a passenger (a lot) during 1994-1995 that -400 had the crash near Detroit(?).
I also was a passenger a lot in 1981-1982, and I remember the DC-10 that rolled off Logan. Just weeks prior, while landing (L-1011) I remarked to my father that Logan looked too short (just joking) and that somebody would drive off the end. 2-3 weeks later that DC-10 did. One trip home, our L-1011 sat down at O’Hare on the longest rollout I’ve ever been on a plane. Had to have been a 12,000 or 15,000 foot runway because we simply kept going and all the time snow blowing over the wings (I liked to sit next to the wing back then so I could see the Rolls-Royce engines deploy the radial thrust-reversers).
There seemed to be a lot of winter crashes in America those 3 years. Might have just been perception.
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