AW139 Parking Brake
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Join Date: Jul 2008
Location: Flying
Age: 45
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AW139 Parking Brake
Hello there,
Ladies and Gentlemen;
Is it possible for pilot to lock the Parking Brake on AW139 without operating the Parking Brake Handle on both Powered Parking brake or Manual Parking Brake?
What I mean is ; when you push hard on the Toe Brake on top of the pedals, does that lock your wheels or once you release it, it unlocks?
I hope the question is clear!
CIAO
Ladies and Gentlemen;
Is it possible for pilot to lock the Parking Brake on AW139 without operating the Parking Brake Handle on both Powered Parking brake or Manual Parking Brake?
What I mean is ; when you push hard on the Toe Brake on top of the pedals, does that lock your wheels or once you release it, it unlocks?
I hope the question is clear!
CIAO
Hmmm, that answer didn't seem to be too clear to me, so I'll give it a go 
If the handle is left in the unlocked position, the brake pedals work just like a car. Push the pedal to operate the brake, the harder you push, the more braking you get. Take your foot off the pedal and the brakes are off.
With the park brake handle out and turned 90 degrees to lock it, pushing on the brake pedals applys pressure to the wheel brakes, and this is trapped in the system, so when you take your feet off the brake pedals, the brakes remain on. Pumping the brake pedals increases the pressure held in the system.
To release the parking brake, twist the park brake handle 90 degrees, and tap on the left hand brake pedal, from either seat. The park brake handle should retract on its own when you do this.
I can't comment on the powered brake, as I haven't seen it.
If the handle is left in the unlocked position, the brake pedals work just like a car. Push the pedal to operate the brake, the harder you push, the more braking you get. Take your foot off the pedal and the brakes are off.
With the park brake handle out and turned 90 degrees to lock it, pushing on the brake pedals applys pressure to the wheel brakes, and this is trapped in the system, so when you take your feet off the brake pedals, the brakes remain on. Pumping the brake pedals increases the pressure held in the system.
To release the parking brake, twist the park brake handle 90 degrees, and tap on the left hand brake pedal, from either seat. The park brake handle should retract on its own when you do this.
I can't comment on the powered brake, as I haven't seen it.
Straight from the Ground School Manual, minus the drawings
The static braking is achieved through a parking brake handle located in the Landing Gear Control Panel which is used to trap pressure provided by the brake pedals by operating, through a push-pull cable, a parking brake valve such to keep the brake assembly engaged.
Pressure is trapped by operating a shuttle valve provided with two check valves. A spring loaded pin locks the push-pull cable in the engaged position every time the handle is pulled. To remove the locking action is required to push left brake pedal such that the hydraulic pressure overcome the spring load of the locking pin which retracts and allows cable movement.
A hydraulic accumulator in the parking brake valve is provided for each hydraulic pipeline to compensate for fluid leaks and/or pressure changes due to temperature effect.
The parking brake valve can keep the helicopter parked for at least 8 hours on a ground with a 12% slope with a change of temperature of 45°C (to be confirmed). A pressure switch in installed on each hydraulic pipeline
supplying the brake assembly. A position microswitch is installed in the parking brake valve.
h
Pressure is trapped by operating a shuttle valve provided with two check valves. A spring loaded pin locks the push-pull cable in the engaged position every time the handle is pulled. To remove the locking action is required to push left brake pedal such that the hydraulic pressure overcome the spring load of the locking pin which retracts and allows cable movement.
A hydraulic accumulator in the parking brake valve is provided for each hydraulic pipeline to compensate for fluid leaks and/or pressure changes due to temperature effect.
The parking brake valve can keep the helicopter parked for at least 8 hours on a ground with a 12% slope with a change of temperature of 45°C (to be confirmed). A pressure switch in installed on each hydraulic pipeline
supplying the brake assembly. A position microswitch is installed in the parking brake valve.
h
I'd settle for 2 hours and a 6 degree slope if it meant I didn't need two men and a donkey trying to bend the pedals for enough pressure to get a green park brake light. Serious design flaw in the 139 - they should pay for the electric brake themselves. Wait a minute, I haven't seen it yet either - maybe just as bad a cock-up as the manual one.
It really does not need more than three or four pumping presses on the brake pedals, it's less an exertion than climbing on top for a preflight inspection.
If you are in flight the Monitoring Pilot can guard and the FP can pump.
Or your company can buy the Powered Brake Kit.
If you are in flight the Monitoring Pilot can guard and the FP can pump.
Or your company can buy the Powered Brake Kit.
