Here are my questions - I know it's too early to speculate and I know that the pilots of 777 Heathrow crash are called heroes but I think they are very lucky.

If the plane had lost power on both engines at 600 feet and after trying to increase thrust manually and failing to get a response, then surely their prime concern at that moment must have been that plane would stall and fall short of runway...correct?

In that case why did they not retract landing gear to reduce drag and therefore give the plane few hundred meters more distance to make belly landing?

Which is safer, gears down or gears up? I mean, they were lucky that the landing gears came off when it got stuck in the mud. If it had got stuck firmly and then turned over, there would have been greater chance for the plane to break up and catch fire, right?

Just out of curiosity - how long does it take to retract and deploy the landing gear on the Boeing 777?

Kind Regards,

Nisheel

Hi Nisheel,

I do agree with you that the pilots of the Boeing 777 were very lucky to have walked away safely from the crash. I am not sure whether both the engines of the plane had in fact lost power at 600 feet.

Here is part of the text from an initial report released by the Air Accidents Investigation Branch (AAIB) on the crash-landing at Heathrow:

"Initial indications from the interviews and Flight Recorder analysis show the flight and approach to have progressed normally until the aircraft was established on late finals for Runway 27L.

At approximately 600 ft and two 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.

The aircraft speed reduced and the aircraft descended onto the grass short of the paved runway surface"

As promised in my earlier posting, your queries give me an opportunity to update my readers about the first crash of the Boeing 777.

It would be premature to speculate but the result of the investigation would take some time to be released. Meanwhile, lots of theories on the possible causes of the crash are floating around...

Well, the most likely cause appears to be a catastrophic electrical failure that struck the auto thrust system without warning just 20 seconds before it was due to touch down. When the Cockpit Voice Recorder (CVR) and the Flight Data Recorder (FDR) are analyzed, the exact cause of the accident would definitely be revealed.

When I first read the news in the London Daily Mail (through the Internet), I was rather surprised to see a statement attributed to the captain that he had to select flaps in order to get the necessary lift to clear the 15-foot perimeter fence. Normally, all landings on the Boeing 777 are made with full flaps (30 degrees) and there are no more flaps available to select at that low level - like what he seems to have done unless he was deliberately attempting a 20-degrees flap landing. If so, selecting flaps 30 would create more drag than lift - my opinion is that, the plane would likely sink further!

So, it was unwise to manipulate the flaps at such a low altitude unless it was in response to a single engine failure. (There is a procedure whereby flaps may be reduced from 30 to 20 degrees, but the airplane speed must be increased by 15 knots. Caution: Changing the airplane configuration at low speed or altitude may cause the plane to sink!)

Later, it was revealed that it was the copilot who actually landed the plane. So, in fact, it was the captain who was the PNF (pilot non flying), meaning that, even though he was the commander of the flight, he was doing the supporting role. The copilot was the PF (pilot flying), that is, he was physically flying the plane. Yes, this is normal as the crew alternates their roles to allow the junior pilot a chance to fly the plane, but overall, the ultimate responsibility rests with the captain.

In this case, if flaps selection was commanded by the PF (copilot), the PNF (captain) would physically move it.

In a normal situation without gusty wind conditions, the Boeing 777 would have been fully stabilized by 600 feet with fairly constant power.

According to one report (flightglobal.com) the general wind speed in the area at the time of the incident was 16 knot (30km/h) "with a warning that the wind might vary temporarily to 240° at 20 knot (37km/h), gusting to 32 knot (60 km/h)."

So the condition could be a little gusty, giving rise to the possibility of a minor wind shear (that may not trigger the B777's Predictive Wind Shear Warning System) and pushing the plane down. In such a situation, the speed would drop, causing the auto throttle to demand for more power. Since no power was forthcoming, it may have caused the plane to crash land as fast as it did.

(Disclaimer: This is only my opinion of a possible scenario but it may not be what had actually happened)

Why didn't the captain retract the gears prior to the crash landing?

That would be unwise because the recommended procedure for any crash landing is to leave the landing gears extended. If it were a ditching onto the water, then you are right.

What is the rationale for leaving the gears down? You saw the result... the landing gears were ripped off from the main frame and it absorbed the impact, probably saving the lives of the 152 people on board the plane!

On the other hand, if the gears were to be left extended for water crash landing (ditching), the plane would likely cartwheel and disintegrate - it would probably be worse than the actual B767 ditching scenario seen here.

How long does it take to retract and extend the landing gears on the Boeing 777?

I cannot be exact but it is in the region of between 10 to 15 seconds. According to the report, the auto throttle system failed at 600 feet and about 40 seconds from touchdown. So, that left very little time for the pilots to analyze the problem except to control the sink to the best of what they have been trained to do. They didn't even have time to alert the control tower or talk to the passengers at all!