Hey everybody! I have a question. At 1:35 video time you can see the gear stopped moving before being locked in the fuselage. When I say stop I mean stopped as will power. What is the name of this system?
I’m not sure about the 777, but Boeing typically uses a device attached to the Brake metering valve module called the De-spin Actuator. Essentially, after gear up, some hydraulic fluid is sent and it actuates the brakes automatically. That’s all I know, but I’m sure @Yuan_Tugo or @Heavydriver will know more.
This is correct, there is a de-spin actuator which activates to stop the wheels from spinning. If it goes tech, the plane has to keep in the air for 2 min with the gear down to allow the wheels to slowly stop spinning. Wheels spinning can cause more noise in the cabin as well as more vibrations throughout the airframe.
This document is for the 744 as it is more detailed, but another one exists below that confirms the existence of the de-spin actuator for the 777.
This assembly is installed in the main landing gear wheel well and is con- trolled by the pilot through a mechanical system of linkages, quadrants and cables. The purpose of the unit is to control the hydraulic actuation pressures to the brakes as a function of input force. Included in the assembly are two force command metering valves for modulating brake pressure and a de-spin actuator to stop the wheels from spinning upon landing gear retraction. Input to the metering valves is by means of a splined common shaft. Input to the de-spin actuator is hydraulic pressure from the aircraft’s hydraulic system. The same valve is used on the 757 and 767.
Brake Metering Valve
Eaton’s brake metering valve
controls hydraulic pressure to
the aircraft brakes. Using spool
and sleeve technology, the brake
valve has two separate normallyclosed
metering valves, a despin
actuator, and a common
input shaft for both metering
valves. The metering valve for
the left hydraulic system is
opened by rotation of the input
shaft or for the right system by
actuation of the de-spin actuator.
As stated above the braking system ‘dabs’ the brakes prior to them being tucked up in the wheel wells. The last thing you want is big dunlops spinning around in the wheel wells with all the hydraulic gubbins in there!!! Not only do moving parts have a lot of kinetic energy (big tyres, Vrotate speed of 170kts (195mph) = lots of energy!) but also any debris that might be stuck to the tyres could cause damage.
The nose wheel doesn’t have brakes so there are ‘snubbers’ in the wheel well that the tyres bump against when the nose gear is retracted. It’s a bit noisy in the cockpit but we are obviously made of sterner stuff than the passengers! ;)
I’ll try and get a picture of the nose bay next time I’m at work.
Closed at OP’s request.