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Posted for "terrence o'neill" <troneill@charter.net>:
Fellow Pilots (our Lancair isn't flying yet),
It's a good time to add some comments to Mike's valid ones.
I'm going to comment on the Lancair's pitch controls, so consideer the
source when you evaluate my opinions.
Learned to fly at 17, in Porterfields and Cubs till the money ran out in
1947. Out of college and into NavCad program in 1953; trained in SNJs
including carquals, then to multi-engine in P2Vs in VP-4 for 3-plus years.
Back to civilian life.
Started designing homebuilts in 1959, but bought the last Waco (AristoCraft)
in 1961 complete with extra engine, all the engineering and drafting files,
with tail-prop and retract gear, variable pitch prop; restored and showed it
at Rockford 1964 after learning a lot about drive shafts and landing gears,
both of whcih I had to redesign and re-build. Test flying this plane I
realized I needed to know the AOA, so I made an indicator and mounted it on
the left wing in my field of vision. That was when the confident Navy pilot
learned a lot more about how airpalnes fly. I could slow-fly down to about a
degree above stall AOA, make steep turns and never stall, just keeping the
AOA vane under the stall AOA mark. AOAs on all my planes ever since.
In 1967 started a company to type certify a simplified version of the
Waco... basically keeping only the wing structure. I designed, built and
flight tested the Model W,a nd the FAA awarded a Provisional TC (A19CE) after
all the reports and tests were done. That occurred the year the GA market
'stalled' and we then exhausted our capital. But when testing, part of the
testing was establishing the CG range, aft end of which strongly affects
stability and stall recovery. My AOA was very helpful, but I found out a
number of other things: trim authority with a stabilizer-elevator was weak, so
I changed to a Piper-type stabilator with anti-servo tab and designed the
mechanism for it. I could then trim down to a degree from stall AOA, and vary
the stick/G load with the tab-stabilator ratios.
I also SAW (tuft testing) that the prototype's horizontal tail stalled a
few degrees after the wing stalled, and that weakened pitch authority a lot...
slowed the effect of wheel-forward stall recovery. So I made slots for the
horizontal tail, which extended the unstalled range of of the stabilizer --and
later,the stabilator -- by about ten more degrees, and maintained powerful
force to push the wing's AOA quickly down to its unstalled-zone for quick
stall recovery. I'm probably going to putthese two-position 'spats' on our
Lancair, because they increase the pitch power about 50 percent and increase
the useful tail unstalled range more than 10 degrees, either plus or minus.
I'll probably make a 2-position slot becasue of what I'm hearing about
limited pitch authority at the ends of the CG range and with full flaps. It
works both for stall recovery and for balancing full-flap moment. Also used
them on my Magnum Pickup prototype.
I am NOT suggesting anyone do this, at least until I work it out. There
are pitfalls... like, if you don't have enough anti-servo tab deflection
versus elevator, the elevator will (from experience) flutter.
The spouse-partner and I this summer bought a L235 with an O-320 in it,
needing wiring, panel and instruments, completion of the fuel injection
system, rudder cables, a tow bar, etc.; and so I've been evaluating the
design, reading CAFE tests and the LML correspondence. The rudder cables are
in, the hydr.pump is moved to the front of the aft baggage bulkhead; the
fuel-injection stuff is bought and flow-divider in, the panel is in place, and
we're deciding what 'glass' to populate the panel with now.
So here are my thoughts and personal opinions on LNC2 control-related
features of this beautiful airplane, for what they're worth.
The stick pitch forces-per-G are too light. This can be fixed by
changing the elevator trim to an anti-servo tabbed elevator, driven by a
simple MAC unit. This can be tuned to pilot-preference, because a higher
anti-tab deflection per elevator deflection will require more stick force per
G. I did this on the Model W, the Magnum Pickup, and on the last plane we
owned, a Dragonfly w/ 80-hp Cont..
The LNC2's horizontal tail volume is marginal for above-stall AOAs, and
I'd like to see some wind tunnel or FEA info for AOAs of around 40 degrees...
as I suspect that at aft CGs the unstalling pitching moment may be very weak,
or possibly negative, which is why I'm thinking about adding slots to the
horizontal stabilizer. Possibly this is the same reason the Aussies (?)
required a larger tail.
Has anyone recovered A LNC2 from a developed spin, at the aft CG? That's
a spin of more than two full turns. Until about 1946 the (then) CAA used to
require GA standard category aircraft be recoverable from a six-turn spin at
aft CG (plus), to be Type Certified. If not, I certainly would not try it
without a 'chute and a jettisonable canopy.
In 1946, bowing to pressure from war-bloated airplane builders, our
safety-minded brothers changed the rules to provide 'safety' by sticking on
the familiar "Intentional Spins Prohibited'. Last I heard (1970) they just
require demonstrating recovery from an 'incipient spin'... that's the first
two turns, when most planes unstall themselves twice.
That's it. The rest looks very good.
We're putting on DeBongers, of course, and are excited about getting our
Lancair into the air.
Please feel free to comment or criticize my remarks and opinions, as I am
of the anti-secrecy political persuasion. : )
T.
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