Boeing 777 accident: Engineers giveth and Programmers taketh away

Friends have been asking me to guess what happened to the Boeing 777 that crashed while landing at London Heathrow the other day. The preliminary report is that the pilots pushed the throttles forward for more power and the engines did not respond. How is it possible for a $50 million airplane connected to $10 million engines to fail in this manner? The connection is through a collection of software known as a full authority digital engine control (FADEC). There is no mechanical linkage from the cockpit of a Boeing 777 to the engines. If the software fails, the engines cannot be controlled.

Could that ever happen? It happened in 2006, according to
http://findarticles.com/p/articles/mi_m0UBT/is_39_20/ai_n16766814 . One engine was essentially killed by the software while the plane was trying to take off. The failure was traced to “a flawed software algorithm”. If the software flaked out on one engine and the same code runs on both engines, what is to stop the software from failing on both engines at the same time?

http://www.aaib.gov.uk/latest_news/accident__heathrow_17_january_2008___initial_report.cfm is the preliminary report and the best guess answer at this point might be “nothing stops the software from failing on both engines simultaneously”.

[September 2008 Update:  Look as though we won’t be able to blame Windows Vista for this one…  http://news.bbc.co.uk/1/hi/england/london/7598267.stm talks about the latest report from investigators and has a video.  It looks like the problem was simply ice in the fuel system.  Why the ice formed when it shouldn’t have and how the engines were both stopped almost simultaneously remain mysteries.  Details:  official interim report]

77 Comments

  1. jerry loeb

    February 24, 2008 @ 1:37 am

    1

    Howdy,

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Good Greetings to All

    Heads Up! This not the first problem from China fuel contractors. For those aircraft operations requiring refueling in China, it might be prudent to be very selective and closely (personally) attend to the refueling operations. Dip sticks won’t cut it.

    Subject: British Airways — London — Boeing777 Complete Power Loss (Approach to Landing — Heathrow Int’l. Airport, London)

    This snippet of early findings came from several sources such as Boeing 777 powerplant engineers, Boeing777 pilots and feed back from our British cousins.

    The magic word again is China. The subject of the dead Boeing777 is showing early signs of fuel contamination as to primarily fuel/water ingestion. The flight originated in China. The suspected water mix probably migrated to the bottom of the tank. It was an extremely long flight so cruise occurred with a high fuel/water ratio for most of the flight. During the landing approach phase, as the fuel supply reduced to normal approach quantity, the ratio changed more toward water. Due to the many hours of cruise -50 C temp the water in the bottom of the tank was either frozen or of a high viscosity sludge. As power was reduced at some late stage on final approach, the engine fuel pumps provide less suction pump power and as the throttles were advanced — the fuel filters were now probably clogged.

    There is also evidence that the RAT (Ram Air Turbine) had deployed automatically by sensing lack of hydraulic pressure indicating that both engines had now failed. The RAT probably saved the day in that the world’s largest glider still had enough hydraulics to provide flight controls allowing control to the clear way at the end of the runway.

    The Boeing777 then slid through the overrun and onto the runway that provided a surface that was at least survivable. All aboard survived. Obviously the fuel and the fueling operation originated in China which has repeatedly demonstrated a lack of quality control or concern in many areas.

    None of this has yet been officially confirmed. Typically engines do not share much in the way of common components except fuel and in the new age possibly computer software, which is also a player. Based on the complete isolation of the engines the Feds have long ago signed off on the concept that all engines would not fail simultaneously.

    Now we know differently at this point of the accident investigation Phase One. The NTSB, FAA and the British National Safety Bureau will eventually determine the dual-engine failure as to the primary and secondary causes and factors.

    The copilot (First Officer) made the the approach and “landing” which addresses the left seat’s (Captain’s) cool measure of confidence in the lad.

    Note: The RAT (Ram Air Turbine) senses a lack of hydraulic pressure and automatically or manually deploys into the airstream.

    Stay safe, stay well and stay positive.

    Best regards to all,

    Jerry K. Loeb

  2. Duncan Stewart

    February 25, 2008 @ 6:35 pm

    2

    Alternative suggestion from the British magazine “Private Eye” regarding the 777 crash this week. They state that the software development was compromised such that what should have been developed by three separate teams working separately to produce completely different control systems thereby creating redundancy in the systems was in fact produced by one company with three internal teams. Despite “Chinese walls” production controls in fact, say Private Eye, there was, via Boeing, a high degree of interworking such that in effect, there is only one software set operating the electronics. This for hundreds of thousands of lines of computer code. Reliable?

    Not sure.

    Duncan Stewart, Chartered Member Chartered Institute of Logistics & Transport, Associate Member British Computer Society

  3. dc spurlock

    February 25, 2008 @ 11:57 pm

    3

    Better than 30 days since BA38 made the runway at close to stalling due to insufficient power response from both engines. Not one word of advice to operators of this “Queen of the Skies”, aka, “Titanic”….. What would you think of a clever electronic jamming of FADEC signals to the engines.. eg. “minimum power only”. Most distant seating to the FADEC’S from center aircraft, 15-20 mtrs?
    I’ve been flying professionally (military,corporate, airlines) since 1973 and trained by USN Post Grad School, as an Aircraft Mishap Investigator. Never in my entire aviation career have I ever seen such a “Blackout” from the professionals regarding an aircraft problem with such potential for a “poor outcome” if repeated. Really folks….. we have a plane, the crew, and the best brains of the industry. I fly this machine, and, the “blackout” really bothers me!
    So, maybe they (the pro’s) know so much about the cause of this mishap that they view it as highly improbable to ever be repeated…. and that is their justification to keep everything cool. But, it did happen…. and, they (the pro’s) have convinced everyone that it could never happen.
    My uncle is 81yr old and huge aviation fan, although a retired minister,and, a B-17 gunner of hundreds of missions in theatre, and several patents of electronics…… his first question to me post mishap BA38…. How do those engines get their fuel signals? Are the motors highly shielded from electronic interference? Think about it!

  4. Bill Rendell

    February 26, 2008 @ 8:21 am

    4

    China fuel? That should have been established by now, after bowser checks.

    Fuel freezing? Still more than a possibility of high water level in sumps, proportionate to ‘end of sector’ fuel contents.

    Solid contaminants and debris at LP pump inlets? Still more than a possibility; resulting in (damage to vanes at LP and HP pumps and damage to matrix of the oil heated fuel heaters)

    Ecc software? A possibility, if recent updates or modifications were applied to both engine systems at the same time. In my day it was considered prudent to modify only one ‘critical’ system until results of the alteration were proven in service.//

    Being an engineer, not a pilot. I believe we should turn every stone in our own areas and disciplines, before even a mention of ‘pilot error’ They accept our signed certificates that all is in order. They are at the coal face if anything goes wrong. In this case it did, (and seriously)//

    Crew reaction and expertise, resulted in a hard landing, loss of an aircraft, but only one serious injury. Well executed by all crew aboard.

  5. Bill Rendell

    March 4, 2008 @ 9:34 pm

    5

    A further consideration in the area of fuel pump cavitation.

    The possibility of partial or complete blockage in the fuel cell ‘venting’ system has ocurred to me.

    If the vent system were defective or blocked, ambient pressure above the fuel head would not increase as normal during descent; therefore, differential pressure between LP pump inlet and outlet would be adversely affected . This flow ‘reduction’ would be passed on to HP pump and engine injectors.

    Apart from the structural effect upon wings, fuel flow to the Engine burners could have been severely reduced, such that a ‘increase in thrust’ demand would not have been met. (however hard fadec or other electronic devices worked on it).

    Let’s face it// Trust devices need fossil fuel energy to produce power// These motors did not get enough of it at a critical stage; however much it was required.

    We can either guess and blame software, or dwell on more simple and basic causes.
    My own guess is that forces of nature had the winning hand in this incident// Fuel starvation resulting from adversely low temperatures over a long flight time period.

  6. David

    March 7, 2008 @ 12:55 am

    6

    Wow. This is a great comment thread.
    I want to hone in on something Paul said “In the end it may be some type of obscure defect, brought to light by a screw up.” This reminded me of Noam Chomsky debunking 9/11 conspiracy theories (video on youtube) and explaining that even in highly controlled scientific experiments, unexplained coincidences and events happen. I see landing a huge aircraft as a usually well controlled and incredibly routine experiment in physics — but increasingly, electronics and embedded systems programming too. As much as you can test, validate, verify, run disaster simulations, have redundant backups, etc. you are still depending on increasingly complex systems to perform the same task that a a few pulleys and cables performed for decades. So to me it seems possible that as Paul speculates, there might combination of factors, which one could “put…in some kind of pattern…which may be completely meaningless” as Chomsky puts it about the WTC collapse.

    Having read the thread though, I think the fuel argument is a compelling one. But to related it to the point I was trying to make about complex systems and strange coincidences, allow me to totally, wildly speculate with a little science fiction. What if on a first-generation passenger jet aircraft (747), the fuel pump works like that an older car. It just pumps with a primitive feedback mechanism. This is probably not true but let’s say it was. On a jet with ice sludged fuel, the throttle – however that works on a jet engine – will open, and be partly block by the slush, but enough gets through that the engine spools up, just a little slowly. On a computer controlled aircraft, we can precisely modulate the fuel pump to match the demand from the engine. Computer signals throttle to open. Engine doesn’t response as quickly as computer predicts it should. Who knows why. It just sucked in a bird or the ice has already been blocking the flow. Computer freaks out, adjusts PWM of fuel pumps to put them in super pumping mode. Because maybe the throttle is jammed and the jammed-thottle detector is sending ambiguous signals and the only thing it can think to do is the rev up the fuel pumps to push more fuel in. Oops! The incredible suction now magnifies the problem, sucks in much more slurpee slush, and lifting it from the tank bottom, than the former pump that puttered along at the same rate would have done. And maybe, just maybe, most pilots like to slowly edge that throttle up, linearly, as they approach. For whatever reason this pilot decides to use more of an log shaped throttling, uniquely (given the bad fuel and mis-programmed fuel doohickey) triggering this unfortunate outcome.

    Of course I KNOW this is all absolutely incorrect. I’m sure people who actually know _anything_ about jet engines or flying them – and I don’t -might well be laughing. Fine. It’s just a hypothetical example of how well-meaning automation could compound the problems of “unintended consequences” in a complex system event like an aircraft landing with bad fuel. I’m sure it can’t be something so simple because Boeing has a huge collective of millions of experience-hours designing jets…but even the huge collective could have missed something really obscure.

    BTW I only happen to know about fuel pumps (not being much of a gear head myself), and to have thought of them in this case, because once or twice a summer or so my Accord refuses to start. (never had this happen in 12 years of driving 3 different Camrys) First time it happened I asked a guy at work who’s a Honda gear-head what to do. Instantly, he said, “Leave the key in the on position for 5 seconds. Turn it to the off position but then immediately start it.” Works every time. Systems have quirks.

  7. Bill Rendell

    March 8, 2008 @ 8:53 am

    7

    David has produced some interesting points, using basic physics and creditably, not confusing them ‘with high tech jargon’

    Another, ‘AAL’ B777 aircraft powered with RR TRENT engines was involved in a similar incident on approach to Los Angeles from Miami. On this occasion it occurred at around 2000ft and probably, away from interference from any ground electronic devices ‘such as PM’s mobile’. The a/c was on autothrottle.
    A demand for more thrust was answered by the right engine but the left engine hung at approach idle for a ‘trembling’ period of 10 to 15 seconds and then spooled up to the demanded power. This indicates to me, that the electronic controller was functioning correctly, but fuel supply was not sufficient.

    I submit: what else but a fuel system defect, ice or other contamination, would prevent this mighty thrust provider from getting it’s food. (kerosene) Probably, the AAL flight was using the standard fuel specification on that sector. ie. not containing low temperature anti icing chemicals.

    Kerosene contains water in suspension:
    Aviation fuel supplied to a/c operating at high altitudes, at very low temperatures over long time periods, should contain an anti icing additive to minimise freezing effects. Also, engines incorporate a heat exchanger device to cool the engine oil and heat the fuel at the inlet to the high pressure pump (engine driven).

    One point to be considered: On descent, when motors are running at low power, engine oil temperatures are obviously lower; therefore the “hot oil” effect upon fuel heating is possibly less than required. Could it be, that at this stage a significant reduction in safety margins takes place???
    Could it be that on initial descent the heat exchanger cooling the engine oil or heating the fuel supply inlet to HP pump is not able to pass sufficient BTU’s to prevent ice contamination?? Is this not ‘food for thought’ ??

    Another point for consideration: Fuels containing the anti icing additive are usually more expensive than standard specs. Could it be that certain suppliers are capable of uplifting standard specs but charging for ‘more expensive’ low temp specs ??

    This is not intended as an accusation; simply more food for thought ??

    Please comment.

  8. Peter Field

    March 9, 2008 @ 12:43 pm

    8

    One can submit what else but a fuel system defect (kerosene) could prevent such a ,mighty thrust provider from gett ing its food……. and one can answer that. The kerosene needs oxygen to burn well and the mighty inlet fan needs a steady supply of cold dense air. Compromise either of these by warm, vitiated, potentially vortex-ridden exhaust streams from the convoy of planes and their giant engines exactly in line in front……and you could really flummox the fadecs. These risks are slight; but if they occur millions of times per year, one day they could cause exactly the symptoms seen at the 777 crash landing. I for one will be very glad when Heathrow operates both runways in mixed mode to space out take offs and landings more.

  9. Bill Rendell

    March 9, 2008 @ 2:36 pm

    9

    So true Peter// kerosene and oxygen are certainly the two most important food supplements for thirsty giant jet engines.

    Airplanes approaching the worlds busiest airport are now probably less than 90 seconds apart at peak times. However. Hot air rises, according to physical laws; your theory should surely affect other traffic in the same approach path.

    This aircraft was well below the glide slope at 2 miles out. Surely there would be an abundance of oxygen at that level.

    I have been in the line waiting to take off at Heathrow// If the oxygen theory is plausible then it would surely affect ‘heavily laden’ aircraft taking off behind others at high power settings, much more than approaching traffic at low powers. Good thinking but I don’t think so. Regards//

  10. Bill Rendell

    March 10, 2008 @ 8:48 am

    10

    Regarding my posting on March 8th: AAL 777 aproach to Los Angeles from Miami. I have learned that the speed brake lever is positioned to the left of the port engine thrust lever// Therefore, if Captain was handling, then P2 would need to pass his hand over and above thrust levers in order to operate speed brakes. An auto throttle demand for thrust increase moves levers fwd of course; but apparently, only approx 1.5 lb restriction is sufficient to halt movement.

    Could Left engine lever have been restricted by P2’s arm, thereby causing the ‘hang up of the engine power response to auto throttle demands??

    That incident may not be allied to BA 777 since P2 was the handling pilot in that case. However, I submit, it is more ‘food for thought’ in relation to revising operating procedures. If restriction or friction to thrust lever movement is able to prevent a power increase demand from taking effect!! then perhaps the Jan 28th posting by ‘Speculation is Fun’ holds water//// ‘a cup of coffee spilled in just the wrong place’ Let’s think on it//

  11. Mark 777 loyalist

    March 13, 2008 @ 4:29 pm

    11

    Awesome thread everyone! Have you noticed the miraculous presence of the longer clearway before the runway and then NO approach lights?!?!? Imagine the destruction and explosion of that aircraft decelerating thru approach lights. How does one of the busiest international airports in the world not have approach lights?! And if this is primarily a takeoff runway, then thank Goodness they landed here. Remember the AA crash in LIT June 1999….approach lights were the killer. Thanx all for your deeply insightful posts.

  12. Bill Rendell

    March 14, 2008 @ 8:01 am

    12

    Mark 777 loyalist. Please take another look//

    Runway 27L does have approach lights. They go all the way up to A30. opposite the fence. This flight could easily have contacted them at 60 feet lower. (and the vehicles passing under it’s path). Regards//

  13. Weng

    March 21, 2008 @ 9:51 am

    13

    I’m a frequent flyer, after noticed the BA 777 accident, I remembered that, before I had the strange experience on Beoing 777s, on both Japan Air Lines (JAL) and Air China (CA) 777s, during the final approaching stage, I don’t know the altitude, maybe 3,000~5,000 ft, engines generated normal sound and some slight “vibration” that made you feel the engines were running, but suddently, there were about at least 30 seconds of ” very slient and quiet ” period, it’s so strange to me, that you could not feel any sign that the 2 giant engines were running, that made people nervous about the possibility of engine stall in the mid air during the final approaching stage. maybe FADEC works well, but personally, I would prefer the mechanical linkage as the back-up.

  14. peter field

    March 25, 2008 @ 6:17 am

    14

    Weng, I notice the same feelings. It’s either adjustment of flaps, lowering of undercarriage, or the more likely movement of wax in the ears as cabin pressure changes giving moments of silence and then normal hearing.
    Or was it something else…..the deadly, silent, invisible menace at the approach to busy airports……streams of vortices from the planes in front (can cause slight aircraft movements to the aircraft behind), or hot low density vitiated exhaust gases that cause far less power and noise from the giant inlet fans….and sudden loss of thrust! Yes I know hot air rises…..but it rises up into the descending flight path of the plane behind. Older long thin turbo-jets would be unaffected by poor inlet conditions.

  15. Bill Rendell

    March 29, 2008 @ 8:56 pm

    15

    peter field. Referring to your last comment. Final sentence.

    Why would older long thin turbo jets be unaffected by poor inlet conditions??
    It has been my experience that a starvation of oxygen or a reduction in mass air flow through the engines of ‘older’ jets due to compressor inefficiency, resulted in a serious rise in JPT or EGT causing immediate concern to flight deck crews. (Bird strikes etc. sometimes caused compressor damage) They would then have taken action to (manually) throttle the affected engine to prevent further damage, after observing the sudden rise in turbine temperature.
    This of course, was way before the introduction of FADEC that apparently takes the option out of their hands. We await the official final report, but I will hold to the fuel starvation ‘due to ice formation’ probability. It would be interesting to learn how you arrived at the conclusion in the last sentence of your post.
    The Engineer Officer was responsible for monitoring parameters on the older jets// now he is redundent. We now have machines and software doing his job. More food for thought??

  16. peter field

    April 5, 2008 @ 7:51 am

    16

    Bill, you were right to challenge my over simplistic last sentence that older thin turbo-jets would be unaffected by unsatisfactory inlet conditions. I meant that in days past, bad inlet conditions would be less likely to compromise thrust so severely. There are several reasons.
    Older “heavies” tended to have 4 engines, thus reducing risk of all exactly in line to scoop up bad conditions; the long sleek engines had a far smaller inlet cross sectional area so less lileky to scoop up vast volumes of bad air; the sleek engines had a far smaller radius of gyration so could spool up quicker to compensate for compromised conditions; the older engines got the same “oomph” (mass of air times velocity rise) by more velocity and less mass flow, so less affected by compromised mass flow; the giant 110″ fans of the 777 do most of the thrust and are very affected by vortices/temperature. My gut feeling is larger numbers of smaller diameter compressors are less prone to trouble. Compromised conditions on older engines could temporarily give poor performance but didn’t have the extra complication of fadecs scratching their heads working out best adjustments which can take valuable seconds; older planes may not have all followed such an accurate flight path where all planes add thrust (and dump extra exhaust gases)at exactly the same place; large fan jets need extra fuel (and exhaust gases) to accelerate the 110″ fans first before extra thrust is obtained.
    But you are right; most likely cause is a fuel problem per se or a mixture of fuel problem and fadec confusion.
    Its just that when one sees (from the M25 at night) convoys of jets one after the other,coming in to land, millions of times globally in a year, one wonders that a chance in ten million of gathering hot vitiated gases lingering, could just cause a mysterious mishap such as this.

  17. egl

    April 8, 2008 @ 3:14 pm

    17

    April 7 WSJ article on engine icing:

    “The odds of both of a plane’s engines shutting down at once were supposed to be about one in a billion. Since 2002, however, internal ice has been blamed for at least 14 instances of dual-engine shutdowns, called “flameouts,” and several times that many single-engine outages. Investigators now believe that since the mid-1990s, so-called crystalline icing has prompted dramatic power drops or midair engine stoppages in more than 100 jets. So far, the flameouts haven’t been blamed for any crashes, because the engines on big commercial jets have always managed to restart.”

  18. Bill Rendell

    April 10, 2008 @ 8:03 am

    18

    Peter, Thanks for your plausible and detailed explanation of my query about older slimmer power plants// I found it interesting and could identify with your line of reasoning.
    PAPIS or ‘line ahead’ approaches may easily cause the ‘big boys’ to dump thrust or eject exhaust gass, in precisely the same area. Combined with 50% reduction of power against 25% on thinner 4 motor jets; as well as the added penalty of increased spool up times, could well reduce the margins we have been used to. (add to this the fuel icing probability in this case)
    Living in a quieter area close to Heathrow, I have also observed the apparent reduction in the ‘line ahead’ distance between approaches. The ‘supply and demand’ effect upon traffic density can surely only reduce the expected safety margines// unless modern technology is capable of (at least) keeping abreast. But at what cost??

    I am sure an alternating !curved! approach path would help to reduce the compressor contamination theory, but of course in turn, would cause concern for residents living below the 3 flight paths’, as well as commercial considerations of costs (and who will pay ???)

    After very many years in aviation, I know, that maintaining ‘even minimal’ safety and quality standards do not come cheap. However, Jo Public will most likely try to fly with an ailine charging less than the pioneers. (Band Wagons??)

    There is yet another lesson to be learned from this accident. Let us hope it will be learned and that “All” will take note//

  19. Bill Rendell

    May 29, 2008 @ 6:09 am

    19

    http://www.aaib.gov.uk/cms_resources/S3-2008%20G-YMMM.pdf

    For those who have not yet seen it. Above, is the reference for the latest aaib report.

    Perhaps (if it is not aready underway) it would be prudent to investigate possible restriction of the tank vent system and its effect upon’a less than ambient’ pressure head above the fuel, on descent.

  20. Toss

    July 20, 2008 @ 1:10 am

    20

    Its taking a very long time for a complete report to come out.

  21. Flt.Eng.(retired)

    July 25, 2008 @ 6:04 am

    21

    Where can fuel turn to slush, not freeze, and reduce the flow to the engine after a long cold soak at altitude ?
    Filters?
    Fuel cooled oil coolers ?

  22. David

    July 29, 2008 @ 6:34 am

    22

    I do not want to even take a chance on guessing as to when the B-777 investigation will be complete. Now, with the stakes being so high .That is, the Boeing Vs Air Bus competition for sales being what they are at the moment. However, had the BA B-777 accident occured in France instead, the JAA investigation would by now be history.
    The British have this unwritten attitude and behaviour towards the Americans. Go anywhere and we will blindly follow you. Yeah, be it to Iraq , Iran or Timbuktu. Worry not how you blunder , we’re there to muffle the thunder.
    The truth will however come out in the open. It always does.

  23. J Gittins

    September 6, 2008 @ 6:44 am

    23

    Sirs, the report on the 777 accident is now published, to quote a lady in a letter to a newspaper eloquently commenting on a 2 year study by a university in Belgium ” After 2 years hard study they have come out with the bleeding obvious”
    As time went by after the occurrence we heard many theories given by both manufacturers and pundits, strangely enough the airline was staying very quiet, this led to people ‘experienced aviation people being very suspicious’
    HP pump cavitation, both at the same time, hardly!
    Some sort of fuel contamination? FM procedure is for straight feed on approach each engine dependent on its own tank.
    Fuel shortage? with FMS you would have to work at running out of fuel ‘Fuel on Board, Distance to Go, Fuel remaining at Destination, all on permanent display two separate CDU’s.
    There was only one common denominator “ICE” the general need for Engine ant-ice ‘ below +5c with visible moisture, “those conditions did’nt prevail”
    Cold soak! in a later report the CAA stated that the A/C had encountered an area of very cold air -74 deg C over Siberia/Scandinavia the aircraft I believe was using fuel with a freeze point of -47 deg C.
    An extract from the fuel management section of the B747 FM states that fuel tank temp should not be allowed to decrease to within 5 deg’s of min fuel freeze point. If total outside air temp approaches -65 deg’s then tank temp should be monitered as indicated temp is TOAT minus 25, action to be taken is to shake the wings and if this is not successful descend to a lower altitude.
    Flying many times between Alaska and London we would get a TOAT of approaching -65c and the fuel temp would be hovering around -35, but then the F Eng had a gauge that could be monitored (two things missing on the triple 7) I find it hard to believe that with a prolonged temp of -74 the tank fuel did not fall below -34. Also as the vol/mass of fuel in the tank decreases conduction of hot to cold increases and in descent with idle power there is little fuel movement. As for the FADEC I think in 2000/1 there was a special check initiated on the American engine this entailed checking the joints of the pipes supplying air data to the FADEC to eliminate moisture that had frozen and caused nil response to thrust demand.
    Well the report is published but I fear it is a compromise as ever between the aviation authorities, manufacturers and airlines. The push towards full automation, need to know training, min cost, min crew, min fuel, min engines and min diversion distances.

  24. peter field

    September 8, 2008 @ 12:07 pm

    24

    Having seen the new, very detailed AAIB report, ice may well be a contributory cause. But now having seen the layout of the kerosene fuel system, a thousand times more risky is the spill return from the fuel metering valves passing back into the inlet of the h.p pumps AND the fuel preheater just upstream. Any problems with the control of the preheater, receiving very hot lub oil from the engine, and the kerosene could easily get up to gassing temperature… a situation exascerbated by the spill back control. The very constant fuel flows of 5000 and 6000 lb/hr in the last 40 seconds, could be caused by the pumps handing an amalgam of gases and kerosene. This is the elephant in the room. The Report cleverly does not mention fuel temperature AFTER the preheater, how the preheater is controlled; or how the flow meters work. The actual liquid kerosene flows could have been a lot lower than the above figures.

  25. Bill Rendell

    October 31, 2008 @ 6:44 am

    25

    The AAIB report is very detailed as expected. However, it does include more than a few estimations and presumptions. I would have expected such a report would be confined to established facts. However it is interesting reading that provokes thought by all interested parties.

    I dont believe much attention was paid to the probability of a reduction in engine oil temperatures after a lengthy ‘staight in’ descent. Thus reducing fuel heating efficiency. In turn, adversely affecting dispersion of ice into EDP’s.

    Should that be a possibility, then certainly, oil/fuel heat exchangers ‘do’ require modification to include an alternative means of maintaining efficiency under those conditions.

    To Peter Field// The lube oil may not be that hot; using supercooled fuel to remove heat from it, after a legthy period at flight idle.

    Let’s trust it will be sorted soon.. A similar accident surely would not meet the same fortunate conclusion///

  26. Alex

    February 5, 2010 @ 11:10 am

    26

    The 777 fuel system is one of the most advanced fuel system of any commercial aircraft. It is not a old capacitance system it is Ultrasonic. Water detection, fuel density are just a part of the triangular calculation to determine fuel weight.
    The idea of the FADEC code being the same for both engines is highly unlikely as the dual redundant system addresses are totally different. What I am wondering is if BA had equipped their 77s with a different engine other than RR would this incident have even occurred.

  27. Bill Rendell

    March 27, 2010 @ 9:22 am

    27

    Bill RendellMarch 27, 2010 @ 8:59 am
    77
    Alex

    Good to see you are keeping Phil’s Web Thread going into 2010. My opinion is, it has produced an interesting compilation of ideas and comments from many individuals. ‘Almost’ all, posessing an avid interest in aviation and safety.
    It could be considered as a ‘Think Tank’ where all ideas are consulted; (however likely or unlikely). No idea or opinion is ridiculed and basics are treated equally with specialist technical opinions. Congratulations to all contributers.

    Of course safety is paramount, but comes at a high cost to designers, manufacturers and the Airline (end users). They are constantly monitoring events ‘on a budget’ and applying corrections (enforced or otherwise)

    On the other hand, ‘Jo Public’ is looking on line to find the cheapest fare to his holiday destination. He does not know the cost of operating and maintaining a modern aircraft.

    To say “That is the real world” may be an understatement. Could cost cutting in fares lead to short cutting in maintenance? (“Get it out// it has to make the xxxx alloted service slot to Geneva”)

    None of this is intended to reflect upon the 777 accident, only to provoke thoughts on dollas and pounds. But for the exemplary action by Handling pilot and Captain, This could have been a catastrophy involving thousands of deaths under the flight path.

    Keep the thread going///

Log in