"flyncatfish" wrote

That's a good question. I think it's more like a truck brake.

Snippage

The Yak 52 has no parking brake, other than a latch on the stick handle
for keeping the brake handle compressed.

So if I understand correctly, you say if there is no air pressure there are no
brakes?

If that is the case, it is not like truck brakes.

Truck brakes have a very heavy spring that keeps the brakes applied on full
force, if there is no air. You can see why, so that if an air line or tank
ruptures going down the road, you just stop. Right now! I did it once from a
slow speed to see how good they grab. Very good is the answer! g You would
have major flat spots if you did it from any great speed!

How they work is by applying air to the back side of the air cylinder that
operates the brake. That pulls the shoes away from the drum, against the
"applying" action of the spring. When you want to stop, air is let into the
side of the cylinder on the opposite side of the piston as the first supply I
mentioned, and it pushes the shoe towards the drum, and at the same time, pushes
some of that first air back into the air tank. Really, what you are doing is
letting the spring apply the brake, by reducing the pressure differential from
one side of the piston to the other.

It sounds like you are worried if the air pressure drops too low from starting,
and that would not be a problem with truck brakes. Also, holding the brake
lever down for parking makes it sound like there is no applying spring, and air
on one side of the piston, only.
--
Jim in NC