Professionally built?

"Orval Fairbairn" wrote in message
news
The "professionally built" term really doesn't amount to a hill of
beans. A friend here bought a Harmon Rocket that an A&P built. The metal
work was good, but the engine installation was very poor. I coined the
term "flyable but not airworthy" to describe the plane as purchased.

He could not maintain cruise power in vevel flight without overtemping
the oil. Our "Spruce Creek Skunk Works" took on the job of sorting it
out.

What we found (and corrected):

1. The oil cooler had insufficient airflow (both in and out). Remember
-- any cooling MUST provide an exit path for the air, as well as an
entry path. This installaltion had neither.

2. There was no blockage of cooling air in the nose bowl behind the
spinner, allowing air to exit behind the spinner. We installed the
appropriate baffles and seals there.

3. The air entering the cowling inlets passed over a sharp lip behind
the inlets. We added some internal fairing to the inlets.

4. Baffle seals were poorly thought out, allowing air to leak out the
top of the baffles, rather than passing over the cylinder fins.

5. Exhaust pipes were cantilevered, creating the opportunity for fatigue
failure. We added some support to reduce stress there.

6. The owner had the pipes ceramic coated, both inside and out, to
reduce heat transfer into the engine compartment. IMHO, it is more
important to coat the INSIDE of an exhaust pipe than the outside -- to
reduce heat transfer into the metal.

Result: The plane runs cool and FAST!

Very good example Orval. The phrase might mean a lot or it could mean
nothing. Based on the rules for constructing amateur built aircraft, it
"certifies" absolutely nothing.