EAA493 Mailing List: Typical P&W R-985 operating problems

[Don Treadwell (donald]

Here is an old post from a mechanic talking about the overhaul on the R-985:

For every R-985-AN-14B (rated at 450 hp continuous) I've changed at
1500 hrs, I've had to yank one somewhere around 1,200. I've also seen a
couple spit off cylinders, and one had some sort of massive rod failure
(I couldn't tell exactly what went wrong, the cylinder skirts were
peened over and wouldn't come out of the case).

Direct operating costs can be tough to figure, but they are going to be

similar to a boxer engine. To get one to TBO, you can plan on going
through around 650 gallons of oil and around 45,000 gallons of gas. You
need to set the valves at least every 400 hours, and it's a good idea
to re-torque the cylinder base nuts every 500 hours. You'll go through
around 75-80 massive electrode spark plugs, or maybe 35 fine-wire's
(depending how many you drop).

Figure in 2 magneto overhauls, plus probably 3 cracked jugs. If you
only use the 450 ponies when you have to, you might get by with 2-if
you like to make it roar, plan on 4-5. If you can find low-cycle jugs
(good luck) you might get off with 1 (or none). If you keep the valves
adjusted and the rockers in good shape, plan on yanking 2 to get the
valves/seats ground. Exchange jugs used to be relatively cheap and
plentiful, but it's been 10 years since I had to shop for any.

Back when I was working on them there wasn't a good aftermarket
external oil filter kit, now there are several. I would think that an
oil filter (instead of a screen) would make a big difference in making
it to TBO.

Bearing in mind that you're talking about an integrally supercharged
engine, the fuel burn-to-hp really isn't as bad as what you might think.

Oh, if you keep your bird in an un-heated hangar in a moderate climate,
plan on having to dry out the ignition harness at least a couple of
times in the spring and in the fall. You either have to loosen all the
nuts and heat the crap out of it, or flush out the water with a
dielectric.

These numbers are based on maintenance I've performed in the course of
about 25,000 flight hours on relatively well-maintained "working" Super
18's. That includes 3 catastrophic in-flights (all over 1,000 hrs SMOH,
and all with uneventful on-airport landings-no engine fires).