"Kevin O'Brien" kevin@org-header-is-my-domain-name wrote in message
news:2005081317121511272%kevin@orgheaderismydomain name...
On 2005-07-22 10:12:05 -0400, said:

Question: Why did my A&P send the engine out? I understand it might
have been a workload problem, but arn't A&Ps allowed to inspect an
engine after a propstrike?

As (until recently) one of the owners of an FAR 145 Repair Station, I
can tell you that while you may be certified to work on engines it
isn't always a good idea. Just to tear down and reassemble an engine
properly requires both tools and perishable skills that not every A&P
may have on hand.

An engine shop can probably dismantle, inspect, and reassemble that
engine, faster and with more confidence than your own mechanic, even if
your guy has the tools and the confidence. It may actually cost you
less for your mechanic to send it out, which doesn't seem to be an
option you've considered.

One of my many lessons learned is that customers who are trying to
maintain their aircraft on a shoestring need to be kept far away from
your shop.

cheers

-=K-POOH=-

Rule #1: Don't hit anything big.


I watch people rebuild their certified engines and shake my head when the
crank and bearings make metal or something goes bad in the bottom or top.

I don't know how many times I have seen a hamfisted rebuilder trash a ring
while trying to squeeze the rings and ram the jug onto the piston. It's a
job demanding finesse, cleanliness, the right tools, plenty lubricating oil
all over the moving surfaces, and meticulous attention to a hundred details.
The manual is not good enough; you need the SB's too, plus all the lore not
in the SB's.

However. I couldn't fly if I didn't do my own work. Under the watchful
eyes of an IA, of course. (Who, btw, has signed me off to take the A&P
exam.) I just did a top on an A-65 that was sticking a valve and blowing
blue smoke. So far so good: the pistons were cleaned and new rings
installed in honed cylinders. So far, after the overhaul and carefully
tracking the prop with the trial-and-error use of several half-moons of
mylar, the little A-65 now runs as smooth as silk, flies like an angel,
doesn't make blue smoke, has great compression and produces textbook power
on static runup; but there were a few problems with the previous rebuild
done by an A&P/IA. The sticking exhaust valve had zero lash, so we had to
take .035 of the top of the valve stem to get that .030 to .110 dry
clearance in the valve train and make the hydraulic lifter happy. Another
valve was too tight, but we went through about 20 pushrods until we found
one just the right length.

Fingers crossed.

It's not a major repair to rebuild an engine. That said, though, the
rebuilder had better do it with due care. It's a religious ritual. Or
maybe end up in the trees.

The certified engine shops have an advantage over the field rebuilder.
They have all the right tools, plus a big plan and a track record, plus the
equipment and test cell and club prop to break the engine in and keep it
cool while the rings seat. Fresh cylinders, pistons, and rings are very
unhappy when the newly rebuilt engine cranks. And they stay unhappy for a
while. Take a look at the manual where it suggests you monitor the CHT of
your hottest cylinder. When the temperature comes down, your rings are
seated. Theoretically. That is NOT a suggestion; that's an order.

From my tool and die maker friend I borrow a garden sprayer rigged to
pre-pressurize the oil in the engine so the needle on the oil pressure gauge
moves up to twenty pounds or so -- before ever cranking the rebuilt engine.
There's one at 0A7 you pump 30 pounds of pressure into with compressed air.
That one will send oil into every nook and cranny.

I regularly fly a 172 from the fifties. Just a wonder of an airplane, with
barndoor flaps and the legendary coveted Johnson bar. The engine was
rebuilt by our tool and die maker who understands what makes the Continental
tick. So it makes great power and goes. And is dependable. But we got
it quickly into the air without a lot of taxiing and runups and kept the
engine cool while the rings were seating. And there we stayed over the
airport for a good 45 minutes for the first run. If the engine had taken
the abuse I have seen heaped on a fresh engine roaring on the ground,
overheating and glazing the cylinders, it would never have performed the way
it has --- and the way it keeps its oil on the bottom end and doesn't pump
it up into the combustion chambers or blow crap out the vent hose onto the
belly because of blowby.

With the A-65 I got the oil pressure up, pushed the aircraft from the ramp
to the runway, cranked it, and rushed off into the cool air in a shallow
climb as soon as the engine showed it made book power. Pure heaven.

For you who have not enjoyed the priceless inexpressible thrill of winging
through the air @4 gallons an hour and 100 mph in an A-65-powered
Taylorcraft with that wonderful zippy airfoil and responsive controls and
the eternal risk of groundlooping when you put down, well, I pity you.

BTW, if you don't want to stick a valve, and you will probably do it sooner
or later with a Lycoming or Continental, put a little Avblend or that other
stuff in your crankcase. That's advice from a good ol' A&P who used to
maintain a fleet of 180 and 185 seaplanes. He said the other seaplane
bases on the big lake always wanted to know his secret, they stuck so many
valves, so that's it.