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NEWS | June 25, 2020

TMSS: Pinning Down a Problem

Dear Editor, 
I’m hoping PS can help with a problem we’re seeing in the field. It’s with the Trailer Mounted Support System (TMSS–Medium) Power Plant, Utility, PU-822A/T, NSN 6115-01-547-6738.

The trailer has a lockout pin on the brake actuator assembly. TM 11-6115-742-13&P (May 12) doesn’t address its use in the normal towing procedures section. It’s only addressed in the off-road travel section of the TM.
Actuator pin locationP
Actuator pin location
(Photos by Scott Campisi)

The braking system uses the weight of the trailer on the tow pintle to engage the brake. When the lockout pin is inserted, it prevents the trailer’s brakes from engaging when the tow vehicle brakes.

When the tow vehicle is moving at convoy speed, if the driver brakes and turns at the same time, the trailer can jackknife and strike the back of the tow vehicle. This often results in a trailer rollover or damage to the frame. There have been Financial Liability Investigations of Property Loss (FLIPLs) due to trailers rolling over because the lockout pin was inserted when it shouldn’t have been.

During a recent visit to a unit, I observed damage on one of their TMSS. Both sides of the frame were bent and the tow pintle was twisted. The unit had their lockout pin in, and I asked them about its use. That’s when I found out they didn’t know they weren’t supposed to have the lockout pin in during normal travel.
Bent frame curbside
Bent frame curbside

Twisted tow pintle
Twisted tow pintle

A new trailer has a placard that says to only have the lockout pin in for off-road use, but most of those placards are gone or they’re unreadable on older TMSS.
Lockout pin warning placardW
Warning placard is often obscured
Can you help spread the word so we can hopefully prevent more incidents?

Scott Campisi
Editor’s Note: You’ve got it, Scott. Soldiers, let’s pin down this pricey problem. Remember, during normal on-road travel, do not have the lockout pin inserted.

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