Parking Brake?
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Parking Brake?
The simplest internal aircraft parking brake that I am aware of is a “parking valve” in a hydraulic system which is closed to maintain applied brake pressure in the system, thus preventing wheel rotation. There is no accumulator, etc. in the system. You are relying to some extent on the elasticity of the brake lines to maintain this pressure, assuming no obvious leaks.
‘Question: How long should you expect such a brake to hold? I’ve never trusted them and would usually rely on chocks for long term parking.
‘Question: How long should you expect such a brake to hold? I’ve never trusted them and would usually rely on chocks for long term parking.
I’ve never trusted them and would usually rely on chocks for long term parking.
Join Date: Jan 2008
Location: turn L @ Taupo, just past the Niagra Falls...
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You essentially describe how the C208 Caravan and BN2 Islander parking brake systems work, in broad strokes. I certainly don’t trust mine any longer than absolutely unavoidable. Preflight cockpit set-up every day includes releasing and properly resetting the parking brake, with pressure on the toe-brakes before I get out to do the externals. In the past, I’ve been caught by engineers that have had reason to move my aircraft “setting” the parking brake Only by moving the lever to the parked position, without toe-brake pressure. In that circumstance, the brake won’t hold initially, but will roll forward a few metres before the brakes bind. Disconcerting at best, potentially dangerous.
on turn-arounds and subsequent engine starts, I always check again the brake is set and hold light pressure on the toe-brakes until I’m ready to taxi. The park brake levers are relatively easy to bump off unintentionally. Overnight leak-down of system pressure is just something I assume has happened, so the brakes get reset.
I always do a “golden walk-around” too... I’m the last one in the aircraft, after I’ve done a complete lap of her, checking all hatches/fuselage penetrations are closed and secure, nothing foreign has been inserted in my control/flap tracks, tyre condition and critically, my brake lines are secure and no leaks. I’ve seen more than a few aircraft return to Base w pod hatches open, tailstands bouncing along runways and cargo/pax hatches open in-flight. It’s worth doing the walk around.
In 8yrs now on the Van, usually in & out of very remote airstrips, I’ve had brake-line failures on 3 seperate occasions. Every one of them remote, every one of them I caught before it became a major issue. Critically on the Van too, every one of them was the Right brake-line that popped off. Propeller torque in the Van pulls you Left w power application, so the right brake can get a bit of a workout on some strips, until you have sufficient speed for aerodynamic rudder authority.
on turn-arounds and subsequent engine starts, I always check again the brake is set and hold light pressure on the toe-brakes until I’m ready to taxi. The park brake levers are relatively easy to bump off unintentionally. Overnight leak-down of system pressure is just something I assume has happened, so the brakes get reset.
I always do a “golden walk-around” too... I’m the last one in the aircraft, after I’ve done a complete lap of her, checking all hatches/fuselage penetrations are closed and secure, nothing foreign has been inserted in my control/flap tracks, tyre condition and critically, my brake lines are secure and no leaks. I’ve seen more than a few aircraft return to Base w pod hatches open, tailstands bouncing along runways and cargo/pax hatches open in-flight. It’s worth doing the walk around.
In 8yrs now on the Van, usually in & out of very remote airstrips, I’ve had brake-line failures on 3 seperate occasions. Every one of them remote, every one of them I caught before it became a major issue. Critically on the Van too, every one of them was the Right brake-line that popped off. Propeller torque in the Van pulls you Left w power application, so the right brake can get a bit of a workout on some strips, until you have sufficient speed for aerodynamic rudder authority.
RadioSaigon:
A very wise young employee taught me that no matter how late you are now, your failure to walk once around the aircraft checking those critical things (fuel caps, chocks, pitot covers, bungs...) can only make you more late.
Sunfish
Park brakes are for holding a parked aircraft long enough for you to get out and place the chocks. They can then be released. Your words above largely align with mine.
Cheers
A very wise young employee taught me that no matter how late you are now, your failure to walk once around the aircraft checking those critical things (fuel caps, chocks, pitot covers, bungs...) can only make you more late.
Sunfish
Park brakes are for holding a parked aircraft long enough for you to get out and place the chocks. They can then be released. Your words above largely align with mine.
Cheers
Industry SOP (well, mostly) is to fit wheel chocks asap after shutdown then release park brake.This is regardless of whether it is a simple closed system or a more complex one which will have thermal relief lines and accumulator etc. Reasons:
1. hot brakes will cool more rapidly
2. thermal relief in brake lines, thus prolonging seal life
3. should some bright spark decide to tow the aircraft without following procedure, reduces potential for damage
The only exception I have seen to this advice is when the aircraft must be left out in strong winds, when leaving the park brake set adds a layer of security.
1. hot brakes will cool more rapidly
2. thermal relief in brake lines, thus prolonging seal life
3. should some bright spark decide to tow the aircraft without following procedure, reduces potential for damage
The only exception I have seen to this advice is when the aircraft must be left out in strong winds, when leaving the park brake set adds a layer of security.
Yep on an A320 the park brake is left on in normal circumstances even with the wheels chocked. In fact with the park brake off the CVR test can't be done. On an A320 it could have something to do with brake fans being fitted whereas the 737 doesn't have anything fancy like brake fans or brake temperature indications.
