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<< Lancair Builders' Mail List >>
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Lance is correct in that per the FARs the Nylaflow tubing is OK to use based
on the surge pressure verses the rated pressure of the tubing. For all the
**anticipated** loads and operating conditions, the design is sound. Just
like the Tacoma Narrows Bridge. It is the un-anticipated conditions that
worry me. Age, heat, chemical degreasers, kinks, parking brakes, nicks, ham
fisted A&Ps, second owners, FOD ejected from the wheel (al la Concord),
panic stops and abrasions can singularly or in combination cause that little
piece of unarmored plastic to surrender to the stresses imposed.
Brakes are critical to flight safety. We practice dead stick landings. We
practice emergency gear extensions. We don't practice "no brake" landings.
Why? It may be because that if your brakes fail on the landing roll, you are
going for a ride and there is little or nothing you can do to prevent it.
My concern for this comes from the desire for preventing the FIRST brake
failure. If the Nylaflow was a little weaker and there were a few failures,
we wouldn't be having this discussion.
Just after I bought my kit I visited the factory to take pictures of the
then under construction pressurized prototype. To my dismay I saw that the
hydraulic system was using spool type hydraulic valves to actuate the gear
and flaps. In recent personal experience I became acutely aware that these
valves were VERY sensitive to contamination. A metal chip the size of a sand
grain could jam the valve. Not to mention that the valves required that the
electrical system was also functional to operate. I marched up to Lance's
office, introduced myself and went on to say that it was not a question of
"if" there would be a gear up landing with those valves but "how many".
Since I try not to complain without offering a solution, on my return home I
purchased a sample of a robust and compact manual valve, sketched up a
hydraulic schematic and shipped them to Lance. I was very relieved to learn
that the solenoid valves were deleted from the design. The current design is
lighter, cheaper and more far reliable than the original. The only one who
wasn't pleased with the change was Ross who had to tear out hours and hours
of fine craftsmanship in order to make the change. Sorry Ross;)
Regarding the main gear pivot pin that must be removed and reinstalled to
change the brake line, if you are unable to press a pin out of a bore an
then reinstall it successfully, you have no business building an airplane.
Even if you do damage the pivot pin you can still buy a new one.
One last question for Lance and then I'll shut up. Will the FAA let you use
Nylaflow on the brakes of the retractable gear Columbia?
D H Instruments 800 414 9990
www.dhinstruments.com
Regards.
Brent Regan
PS. Brent alert! With three Brents on the list I would recommend also using
last names to avoid confusion;)
BR
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LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
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