dual manifold pressure problems - HELP

Hi everyone,

Weird thing happening while I am going through my Initial 337 Transition course. I bought N937DY up in Canada and when the Canadian Instructor and I flew down to KHND, we cruised nonstop at 17k with no issues whatsoever. Heat and pressurization were wonderful.

The plane sat on HND’s flight line for about two months while I wrangled with the Insurance cartels and finding a Initial/Transition school.

When the Initial school instructor and I flew to KDVT, we noted manifold pressures sub nominal for a turbo/pressurized aircraft. We flew it again the next day in a meticulous test profile and (here’s the weird part) both MPs are low to the point of seeming like a normally aspirated plane. Take off pressures are normal but as we get up to and past 10k, the MPs don’t keep up with the climbs and the cabin pressures don’t seem to keep up either. CHTs, TITs and etc are good; engines are leaned properly and everything else is conducted in accordance with the current POH.

Does anyone out there know of a great 337 A&P in the Phoenix area. We have elected to slow down or suspend the Initial/Transition training until we can get the A&P to check things out.

Please help - I want to fly my airplane solo!!!!!!!!

It's pretty unlikely that you are having two turbos on separate engines failing in the same manner simultaneously, so I'd take a look at the cabin pressure outlet valve. If it's hung open, the turbos may be using all their boost to try to pressurize the cabin. Even easier, check for any place the cabin may be leaking pressure, door seals in particular or a wiring or control bulkhead seal.

-Cub Builder