NEWS | Feb. 25, 2020

MEDEVAC: Are Setscrews Set?



Mechanics,

The external rescue hoist, NSN 1680-01-505-3913, has a roller housing attached to the bottom of the cable guide assembly.

Inside the housing is an assembly with four rollers allowing for fleet angle operations up to 30 degrees. The roller housing is attached by three small setscrews.

That’s where the potential problem comes in. In some instances, the setscrews have backed out enough that the roller housing can disengage from the cable guide assembly. In the event the roller housing guide setscrews fail to hold the roller housing, it will slide down the cable like a heavy weight and can land on your hand and break some bones. While not a load-bearing part of the hoist, the separation can cause quite a scare, if not injury.
 
Roller housing set screws
Roller housing set screws set? Good

Roller housing bad
Roller housing set screws not set? Not Good
 
It’s not clear exactly what causes the setscrews to back out. When installed, the setscrews are first given a dab of sealing compound, NSN 8030-01-054-3968 (PN 222-MS), to prevent such issues. And TM 1-1520-237-23P (Jan 19) and TM 1-1520-280-23&P (Feb 19) don’t require removal of the roller housing.

The setscrews aren’t currently part of the aircraft TM’s preflight inspection, so it’s a good idea to act as if they are and eyeball them during your normal preflight inspection. A quick glance at the top of the roller housing just below the cable cutter anvil on the cable guide assembly is enough to ensure the setscrews are in place. It’ll also keep you from worrying about an unexpected hoist separation on your watch.