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Home > Flying the Plane > What happens when the landing gears cannot extend?
What happens when the landing gears cannot extend?
Flying - Flying the Plane
Wednesday, 12 December 2007 22:17

Hi Captain Lim

Firstly, thank you for a great site. It is very informative and I like the fact that you are taking the time to answer some layman type questions from the everyday flyer. I fly on the Boeing 777's all the time from Phoenix to London as I am an Englishman living in Arizona and they are my favorite aircraft.

I have a question regarding the landing gear. I have often seen old WW2 movies where pilots have to climb down to the wheel bay and manually wind down the landing gear during a failure. I wonder, what contingency is there in place on the Boeing 777? What happens if the front gear won't come down? Do you have a manual override switch?

Many thanks

Chris Spalding

Hi Chris,

Thanks for your compliments. I am pleased that my service is appreciated by you and the other air travelers.

The Boeing 777 is among the most advanced airplane at the moment and obviously the technology today is more superior than those of the WW2 vintage, yet it can be very simple when it comes to lowering the landing gears during an emergency. No more cranking because the main landing gears are so massive and heavy that it virtually drop down by its own weight! When the gears fail to extend in the normal position, emergency lowering is achieved by the use of an alternate extension system which electrically releases all the gear lock devices. This enables the landing gears to free fall to the down position due to gravity.

It is the retraction process that requires a lot of hydraulic power to pull in the landing gears. Once the gears are securely retracted, they are electrically locked in the up position.

If the front gear won't come down, it would be a very rare event! Nevertheless, if it ever happen, the pilot will declare an emergency and it is possible to land the aircraft after the runway is sprayed with foam by the fire trucks. This calls for some special flying technique whereby, after the main wheels are in contact with the runway, the pilot will hold the nose up as long as possible. The foam will prevent sparks cause by the friction with the runway to develop into a fire and the aircraft will usually come to a stop quite quickly.

The manual override switch you refer to is not to lower the front gear but to retract the gears in an emergency. For example, you can't intentionally retract the landing gears when the aircraft is on the ground because of some fail-safe ground switches. But this manual override switch, or what we call the lever override switch permits the lever to be unlocked manually. When do we use it? We use it when the normal system fail after airborne and pilots don't like to have the gears hanging down after airborne because they cause a lot of drag on the aircraft, more so when one of the engine fails!

Think and fly safely,

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