Forum: F-16 Procedures

Hi Everyone, I had this question about the F16 wheel brakes system. During a troubleshooting process, I came across this dragging check.

Can anyone advised me on why the FI call for to "dump" the JFS accumulator pressure while rotating the wheels simultaneously. If the wheel stop, we have to change the brakes asembly. By dumping, are we trying to simulate that the pressure is being used but without aircraft power and pedal input, the wheels should not lock?

What puzzled me is that why should we change the brakes assembly? Is there something within the brakes or what is preventing the JFS pressure from "actuating" the brakes? And when the wheel locks means that particular thing has failed thus we have to change the brakes assembly?

Thanks in advance. Pardon my little knowledge.

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Dumping the bottles removes any possible pressure from the system. Without any pressure the brake stacks should release and rotate freely. If the brake stacks aren't releasing when there's no pressure then there's something wrong with them and they need to be replaced.

Possiably a problem with maybe 1 or 2 pucks. It is possiable to have pucks sticking and others operating normally.

But the thing is, we need to jack up the wheels to rotate. Why is there a need to dump JFS and rotate when I can just rotate to check the brakes? Without any pedal input, I supposed the pressure will not be present at the brakes.

I’m shooting from the hip here because I don’t have an FI in front of me to look at the schematic but,

Most likely check/shuttle valve is installed within brake assy … when you dump the bottless you are porting fluid back into B system return. If a valve is bypassing return fluid under pressure will actuate the brake.

VarkVet wrote:

I’m shooting from the hip here because I don’t have an FI in front of me to look at the schematic but,

Most likely check/shuttle valve is installed within brake assy … when you dump the bottless you are porting fluid back into B system return. If a valve is bypassing return fluid under pressure will actuate the brake.

I thought the check/shuttle valves are located within the brakes control valve? Can anyone advise me?

simonlwa wrote:

I thought the check/shuttle valves are located within the brakes control valve?

They are … I looked at the schematic.
The only thing I can think of as why to replace the brake assy is if anything is warped or distorted in the stack then the minute return pressure that is present in the brake assembly will actuate the pucks enough for the wheel to drag!

Forum: F-16 Procedures

Brakes Dragging Check