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Posted for Greg Nelson <gregsays@swbell.net>:
Tom Giddings:
Don't jump into an A/C just yet. Instead, do this quick test. Conduct a
normal flight of at least one half hour then land, stop (do not taxi), turn
off and dismount your airplane. Walk to the front of the airplane and grab
hold of your nose gear main retract cylinder.
If you have to let go quite fast because it is hot then you have the same
problem that I had and substantially solved in my half-finished 360 test
flying. The problem in my airplane was not (primarily) one of extra heat
load caused by a large canopy as I believe I have heard some suggest in
this forum. Instead, the problem is caused by engine conducted heat
through the nose gear oleo structure AND airflow directly into the wheel
well around the oleo. A flimsy and poorly-designed gear door simply permits
engine heat to flow into the wheel well to such extent that everything
including the walls of the wheel well become hot.
The flimsy door in this instance was designed by me because I observed that
Lancair's was inadequate in stopping air flow. Predictably (because I am
not an engineer and do only trial and error experimentation where
necessary), my first gear door design was a total flop but my second has
shown to be quite successful.
Inside cockpit temperatures with my previous door were 35 to 45 degrees
hotter than outside but I have reduced this to just 10 degrees difference
and improved safety with the following:
1. Stop the airflow into the wheel well. THIS IS A SAFETY CRITICAL
MATTER. If air can flow past the firewall, so can fire. The Lancair
design does not stop air or fire but rather only slows it.
2. Insulate the firewall and nose wheel well interiors with a fire-safe
material.
3. To help prevent fire, keep your engine, firewall and exterior wheel
well free of oil and combustibles.
4. Unfortunately, the heat which is conducted through the metal mass of
the oleo cannot be attenuated inexpensively or by someone of my engineering
skills (or lack thereof).
5. Be sure to insulate the wheel boot on the wheel well side per the
Lancair Builder's Manual.
Greg Nelson
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LML homepage: http://www.olsusa.com/Users/Mkaye/maillist.html
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