CH-53/MH-53 helicopter washer corrosion problem

Referenced as the parallel Sikorsky engineering group that had already discovered the T6 stress corrosion problem and ordered fleet-wide washer replacement before the Black Hawk accident.

Aluminum, and different colors for different services, but it's got an oxide hard-coating. Here's the shaft that slides in here, which does have a little bit of wear where it engages with the rest of the thing. The question was why we had the failed washer. I don't have the failed washer — these are just the exemplars. It was stress corrosion cracking. You look at the microstructure and the fracture, and it's clearly stress corrosion cracking. But there shouldn't have been enough stress on this thing for it to crack. This is, remember, 7075 aluminum alloy in the T6 condition. I told you there's a problem with the T6 condition — it has the maximum strength properties, the peak. Sikorsky divides their helicopter fleet into different models, and so all the Black Hawks have an engineering group over here, the MH-53 has another group over there. They have a whole bunch of different models of helicopters, and each one has its own engineering group.

Sikorsky's earlier encounter with the same washer corrosion problem on a different helicopter line, which they fixed by switching from T6 to T7 over-aged heat treatment. Tom uses this to set up the indictment: Sikorsky knew the fix and failed to apply it to the Blackhawk part.

The Navy noticed this and told Sikorsky. Of course Sikorsky keeps their Blackhawk program separate from their CH-53 or MH-53 program, which is a different helicopter, and different again from some other helicopter. They said, "Oh, we saw the same corrosion problem in one of our other helicopters on the same washer. So instead of the T6 heat treatment, we went to the T7 heat treatment, which is over-aged."