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Messing with the parking brake involves surprisingly large...'human factors'. While proper hydraulic parking brakes are rather reliable (they route brake accumulator pressure directly into the brake system), knowing whether they are applied or not, or when to release or not to release them allows for rather many whoops moments in particular when communication is restricted and everyone's busy. It has been demonstrated that when started rolling even at very low pace, an airliner cannot be easily brought into stop again by throwing chocks, it simply rolls over them. The results are typically rather expensive, and fairly embarrassing as well.

The parking brake system in many GA airplanes is not a proper parking brake. I mean, if you know how to use it, it may be good enough for you to chock your own airplane (and vice versa), but that's about it.

-Esa

Indeed, hydraulic parking brakes are pretty effective too:-

https://www.youtube.com/watch?v=md3KXhJGhck

HighBypass wrote:Indeed, hydraulic parking brakes are pretty effective too:-

https://www.youtube.com/watch?v=md3KXhJGhck

Speaking of those "human factors"..

-Esa

I went for a quick flight this afternoon with my wife. We just had some time to kill and the weather was nice for a flight. I stopped in 47N to tank up on some cheap fuel before returning to CDW.

When I got to the fuel pump and went to attach the ground strap to the exhaust the clamp tore away from the cable. I played good Samaritan by taking it apart, shaving off some insulation and reassembling it.

The pilot of the aircraft behind me came over to talk as I fixed the ground strap clamp. I was in the middle of fuelling my aircraft and standing on a ladder when he yelped and scrambled to get to his plane which was rolling forward into the tail of my aircraft. He caught it with about 5 feet to spare. He then pulled the chocks out of his plane to secure it on the ramp.

He said that the parking brake was set. This is now the fourth time I've witnessed planes rolling around with their "parking brakes" set. Those parking brakes aren't worth a dime!

Be careful out there!

Then obviously, "Yes of course did I set the parking brake, it just started rolling!"

-Esa

What was interesting is that there is a decent incline at that spot on the ramp, and the plane did stay put for at least 5 minutes before rolling forward.

It has me thinking that the brakes actually permit a very small amount of movement that is initially imperceptible. I doubt the brakes suddenly "let go". It just takes a little time for the rate of movement to pick up to the point that it becomes obvious.

Almost want to conduct an experiment, but in the end. It isn't going to change my opinion of these next to useless features of our light aircraft.

They should call them "hold the aircraft still until you can properly chock it" brakes.