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red07ss

unusual brake issues

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Okay I'll start by setting up the aircraft:

-Power on

-Both emergency and normal brakes powered to 3000 psi (all is good)

-9-port handle is in the down position (powering all systems with aux pump)

Snag

-Turn off aux pump and normal pressure begins to deplete to 2700ish psi while emergency stays at 3000

-Select emergency brakes and start pumping to release hydraulic pressure

-Emergency pressure depletes, but so does the Normal at almost the same rate (this isn’t good lol)

-If you power up both systems again, kill aux pump, select Normal Brakes, and start pumping the pedals. Normal brakes deplete as they should and emergency stays solid at 3000 (works as advertised)

We have changed both Normal and Emergency Brake Selector Valves but snag persists. I’m starting to lean towards a faulty Normal Brake pressure return check valve OR the dual brake control valves.

Hope someone has a bit of input here, could really use the help lol. Thank a lot guys! :)

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Okay I'll start by setting up the aircraft:

-Power on

-Both emergency and normal brakes powered to 3000 psi (all is good)

-9-port handle is in the down position (powering all systems with aux pump)

Snag

-Turn off aux pump and normal pressure begins to deplete to 2700ish psi while emergency stays at 3000

-Select emergency brakes and start pumping to release hydraulic pressure

-Emergency pressure depletes, but so does the Normal at almost the same rate (this isn’t good lol)

-If you power up both systems again, kill aux pump, select Normal Brakes, and start pumping the pedals. Normal brakes deplete as they should and emergency stays solid at 3000 (works as advertised)

We have changed both Normal and Emergency Brake Selector Valves but snag persists. I’m starting to lean towards a faulty Normal Brake pressure return check valve OR the dual brake control valves.

Hope someone has a bit of input here, could really use the help lol. Thank a lot guys! :)

I would check the brake shuttle valves before replacing any other parts. There is one shuttle valve on each brake. This is another place the emerg. and normal brake systems tie together.

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Sounds like your normal brake control valve isn't working. When switching from normal to emergency, do you hear a loud clunking sound from the spool in the normal brake c/v slamming closed? When you switch from one system to another, in this case, normal to emergency, the normal brake c/v energizes and closes preventing fluid from going to your metering valve and out to your brakes.

But since you have changed it, have you shot power? As far as it bleeding down to 2700psi, that could be normal ops, there is a valve seating period, i want to say you wait 10 minutes after killing pressure, and then see how far it drops in the next 10 minutes. I'd have to check the book on that one.

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Make sure you have 28VDC at the normal brake selector valve cannon plug with the brake selector switch in Emergency. The valve is energized closed (no pressure) if you have no power the valve will be open supplying pressure.

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Sounds like your normal brake control valve isn't working. When switching from normal to emergency, do you hear a loud clunking sound from the spool in the normal brake c/v slamming closed? When you switch from one system to another, in this case, normal to emergency, the normal brake c/v energizes and closes preventing fluid from going to your metering valve and out to your brakes.

But since you have changed it, have you shot power? As far as it bleeding down to 2700psi, that could be normal ops, there is a valve seating period, i want to say you wait 10 minutes after killing pressure, and then see how far it drops in the next 10 minutes. I'd have to check the book on that one.

You were right, was the normal control valve. We did replace it once already for this snag, but the replacement valve was faulty.

Thanks for the replies guys

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