ATA 78-30, Thrust Reverser

A300-600, Right-Hand T/R inop. Both sides deploy, but only the left stows.



The indication for deploy is correct with the green reverse light on. With the T/R throttle handle down...... you're left with



There are some simple troubleshooting steps that can be used to isolate the problem. First off...... with this particular situation, electrons can be ruled out. The commands are right. The indications are right. We're down to air inputs or problems with the CDU (center drive unit).

Both halves are controlled by the "same" air supply. This air comes from the Directional Pilot Valve.



There is a "T fitting" just to the right of the valve in this image. This control air goes to both L/H and R/H CDU's.



Left Hand CDU



Right Hand CDU (problem unit)


One simple check is to disconnect the DPV control air input "B Nut" on the CDU. It is located on the bottom of the R/H CDU and on the top for the left.



The air pressure needed for the internal CDU directional control valve is about 5 PSI. With the throttle handle in the reverse position, air pressure is present at the line. With the throttle handle down, no air.

You can put your finger right on the end and feel the pressure. You can actually control the opposite sleeve (T/R handle up) by either blocking or releasing that control air. Plug it, the sleeve opens. Pull your thumb off (pressure releases on both sides) the sleeve closes.

In our case with this aircraft, the control air was correct. When we went to manually close the sleeve a "pop" was heard at the beginning of forward travel (something jammed). When air was reapplied, the sleeve closed. A rig will need to be completed. If that doesn't do it..... a CDU change.

ONE WARNING..... NEVER PLACE YOUR HAND AT THE SLEEVE CLOSE POINT AT ANY TIME, AIR ON OR OFF. IF YOU'RE TROUBLESHOOTING AND THE SLEEVE CLOSES ON YOUR HAND, YOUR HAND WILL LOSE "EVERY TIME"!!!!

A300-600 AMM 78-31-00
ASM 78-31-00
FIM 78-31-30

Part number of the CDU (subject to change) is 3269086-14.

No luck with the beating.

Handy information, thanks Mark!! On our GEs, find high pressure and PRV valves bad. See T/Rs stuck in reverse, and we find bad flex cables a bunch.