Boeing 777 crashed at Heathrow

Hans-Georg's picture
Sat, 2008-01-19 11:24 by Hans-Georg

Both engines of the big airliner, manned with 136 passengers and 16 crew, failed 40 seconds before landing. Fuel contamination with water is one suspected cause. There were also rumors about a total electric failure. Read BBC News

Read Daily Mail article

I'm a pilot. I don't fly airliners, but I still understand some of the issues in a situation like this.

The articles didn't contain the really interesting information.

To fill in some of the blanks, I will now speculate. Please keep in mind that the following is mere speculation out of insufficient and possibly wrong information. Everything I write may be wrong. But it could have happened that way.

Technical information:

NTSB Identification: DCA08RA028
Scheduled 14 CFR Non-U.S., Commercial operation of British Airways
Accident occurred Thursday, January 17, 2008 in London, United Kingdom
Aircraft: Boeing 777-236ER, registration: G-YMMM
Injuries: 2 Minor, 191 Uninjured.
On January 17, 2008, at 12:42 UTC, a British Airways Boeing 777-236ER, registration G-YMMM, s/n 30314, landed short of runway 27 left at Heathrow International Airport, London, England. The 136 passengers deplaned by using the emergency slides and there are 2 minor injuries reported. ... Read the initial report

A few points that struck me are these:

I find it remarkable that the pilot let the copilot steer the aeroplane. I think this is actually a good sign. I'm sure that any of the two could have done the landing. There isn't that much to the actual steering. You can't do much, but steer the plane into the best place possible. Any well-trained pilot can do that.

The more important point is to think of all possible factors that can still be influenced, and this can be done by any of the crew and communicated to the pilot at the controls. This includes considerations like glide path optimization and flap settings.

My first thought was that the pilot wanted to, or was happy to have his head free to be able to think about possible supporting actions. Or he wasn't in the best position to take the controls for some other reason. It is also possible that the copilot was in command anyway, and the pilot didn't want to change command in such a sudden problem situation. And it is possible that the pilot knew the copilot well and knew that he was up to the task.

We cannot know what really happened. Who knows, but perhaps the copilot said, "That's just what I did last week in the simulator. You can let me do it." And there was no good reason to refuse.

As to the flaps, they are fully extended during this phase of a landing anyway. If there is enough time left until landing, one could think about retracting them to improve the glide factor, but in this case a full retraction is out of the question, because without the flaps you need a higher speed. In other words, you would have trade some height for speed first, and they didn't have any extra height to trade. The time was far too short, the altitude already much too low. The normal glide path angle for an airliner is 3°, which is everything but steep. The missing energy can only come from the momentum of the big, heavy airliner, because the glide angle alone is insufficient.

What they may have done is to retract the trailing flaps partially to reduce the braking effect without giving up too much lift. The last part of the full extension yields more braking effect than lift. One of the eyewitnesses mentioned that the pilot had to use the wing flaps. In my speculation I will assume that that eyewitness knew what he was talking about, but I must admit that I find it a bit difficult to believe that they actually retracted the flaps partly, because that could upset the plane's attitude angle and flight path and make things more difficult. Perhaps the eyewitnesses saw no more than that the flaps were extended and didn't know that that is the only normal way to land such a plane.

I also hear that at least the pilots in England and America, possibly in most industrialized countries, are very well trained. This happens in regular simulator sessions where they are confronted with all kinds of failures and problems.

So my guess of what happened is this.

  1. They realized that they had lost most or all power from both engines.
  2. The copilot had control and kept it. The pilot was happy with this, because he had his head free to think of other possible assisting action.
  3. The copilot switched off the autopilot immediately and began to steer the plane by hand. This is standard procedure and hardly requires thought.
  4. Somebody, most likely the pilot, looked at the engine instruments to check whether there is any chance to get more power from the engines. No way was found, and there was not enough time for any detailed analysis. There may even be a rule that at this low altitude during a landing you should not try to restart an engine, because it is much more important to do a good controlled crash than to waste your attention and time on something that is likely to fail.
  5. They discussed hastily, in the few seconds they had, what they could do, mainly whether they could make it to the field, where else they could possibly land, and what they could do to increase their gliding range.
  6. If this isn't standard procedure in such a situation anyway, at least one of them proposed to partially retract the flaps to maximize the gliding distance at the low speed they had, initially about 250 km/h, steadily reducing. They did that. (I'm not at all sure about this, of course. It's just my guess, supported by one eyewitness report mentioning flap use. Being low and slow and about to land are all good reasons not to fiddle with the flaps.)
  7. They probably discussed the wind, because the wind at 500 ft altitude is stronger than at the ground. They need a little extra speed when they come down, because their airspeed reduces as they come down, for this reason. Since their airspeed reduces additionally because they had no engines, estimating the combined effect is tricky.
  8. They cannot have been entirely sure whether they would make it to the field, so their only choice was to glide as far as possible and then crash, hopefully already on flat ground without trees, houses, or other nasty obstacles.
  9. Once they were sure to reach flat ground, perhaps they extended the flaps again fully to squeeze the last bit of lift out of the wings. Not sure about that. It may be counterproductive or so minimal that it's not worth doing.
  10. Shortly before touching down they tried to hold the plane in the air for as long as possible, until the diminishing speed led to the wing stall. They may have been able to make use of the ground effect, a hovercraft-like pillow of slightly compressed air that occurs between wings and ground during very low flight. The ground effect improves wing performance, particularly in low-wing aeroplanes like most airliners.
  11. The stall is usually irregular. One wing stalls before the other. The plane may bank and hit the ground in a somewhat uncontrolled attitude and direction. On the other hand, this big plane wouldn't turn much in such a short time.
  12. Most of the wheels didn't make it and broke off, but the plane came to a halt without major damage.

That was mostly luck. The crew did all the right things and should be commended for this, but the real cause for reaching the airfield was that the engines died when and where they died. 10 seconds earlier, and they would not have made it. 10 seconds later, and the whole thing might have ended relatively uneventfully, perhaps even without damage to the plane.

If anybody reads this and has more information or knowledge, please add a comment. (You have to register first, but it is free, quick, and automatic on the server side.)

[Additional keywords: engine power failed failure 600 feet ft contaminated crash London airport Captain Peter Burkill Senior First Officer John Coward]