In a message dated 8/14/2004 1:59:16 PM Central Standard Time,
WarbirdAeroPress@cox.net writes:
1. I got what I thought was a good checkout by the previous
owner, and didn't really see a problem with flying the airplane. I am using
half flaps for landing to limit the aft stick pressure I need to maintain a
good approach. There is not enough nose up trim from the elec mac servo to
compensate for this. Thoughts, ideas and background? I do know about the Mk II
tail, but that is probably not an option. Is there some sort of bob-weight I
can install to lower the pitch
sensitivity?
Scotty,
First, everything Mark said is absolutely correct.
Second, every wee Lancair 235/320/360 (hereafter 360) is somebody's custom
airplane. You may need to adjust some things to your liking and pilot
style.
1. Most 360's have stayed with the mechanical friction/spring
elevator trim system. There may be some limits if your servo operated
system is moving a trim tab that is not effective enough (not large
enough?) to meet the requirements of elevator forces at low speeds and
certain CG limits. However, a larger trim tab may exceed the ability of
the servo (I have seen stripped gears in MAC servos) and alter the balance
of the control surface. Your elevator linkage should have been built with
a bob-weight (just behind the baggage bulkhead) to add proper feed back
during G-loaded maneuvering - make sure it is rigged exactly as Lancair calls
out in the construction manual. Small tail 360s are renowned for pitch
sensitivity - stay alert.
Here is some further discussion of pitch trim:
Many, if not most, 360 builders shortened the elevator bellcrank hole
location from a 4" arm to a 3" arm. This was first proposed by a
girth-challenged builder and results in a 25% reduction in stick movement for
the same elevator movement. Another benefit is the that the force
necessary to move the elevator is increased by 25% , thus reducing the
"lightness." Of course, pitch control is a system - all the consequences
must be considered. This change required stronger springs be used for the
trim and that required the friction holding the manual trim control be increased
so that it became quite an effort to make trim adjustments. Dick Reichel
then invented the gear driven spring loaded trim system (with a walnut wheel, no
less) that works very well with the increased trim spring forces.
I have such modifications and trim system and it is adjusted so that
I also run out of nose down trim when fully loaded at race speeds,
that is up until about half the fuel is burned off. I have never run out
of nose up trim at full flaps even though I have biased my airplane to a more
forward CG. My W&B notes that the minimum solo pilot weight is 150
pounds since the CG will be too far forward if the only fuel remaining is in the
header tank and the baggage compartment is empty.
As you may have noticed, flap deployment has a great effect on the pitch of
the airplane. Ergo, half-flaps leaves you with relevant nose up
"trim." That is, you are not pitched nose down as much as you would be at
full flaps. In the example you gave, the flaps are participating in the
trim of your airplane. That is OK if you realize the limits (and
options) imposed by their use. Maybe you could examine the range your
trim tab moves thru and see if it would be useful to change the range to give
more nose up trim?
The "big" tail is good but moves the CG aft - not good in airplanes
already built with an aft CG bias.
The long engine mount moves the engine forward 3" and the CG forward about
1.5". This option is frequently chosen for those with rear CG problems and/or
the big tail. It is not so good in an airplane with nose-up trim
problems.
<<<
2. What should I look for with the stock (Non-Outback) gear?
The plane pulls left a bit during taxi, and the rudder is a bit biased to the
left. Is this a landing gear issue or a rudder spring tension issue? The
nosegear seems pretty fragile and shimmies if I don't keep the nose light with
elevator. (It does appear to be serviced properly.)
>>>
2. The 360 left-turning tendency is well known - P-factor, small tail lack
of control below 40 Kts, weather vaning, even from the prop circulation,
etc. Right brake tapping is useful when taxiing and sometimes, even at the
start of the take-off roll - especially with a left cross wind. Slow
application of throttle during take-off runs and go-arounds is very
important. Do some 720 degree steep turns and notice the
difference in the force required to hold altitude in left and right
turns.
The nose gear shimmy should be fixed before the next flight! I have
seen cracked and broken engine mounts from operation with shimmy. Contact
Lancair since they can re-build the strut or, if it is trash, re-place it.
In aviation, nothing that's broken ever fixes itself. Consider the
self-centering option if you don't already have it.
<<<
3. Blew out both nylo seal brake lines today... got the plane
stopped Fred Flintsone style before I ran into anything. The lines in the
cockpit are still pliable and flexible, but the portion of the lines in the gear
wells are brittle and broke easy when we tore it apart. There appeared to be
some heat damage/discoloring there, even though it was within the black plastic
cover. Thoughts? Parts already on order from AC Spruce.
>>>
3. There are some options. Some people have replaced a
foot or so of line at the brake with something more substantial than nyla-flow
because of the heat/pressure problem. Some have replaced the lines
completely. Others have had the wheel-well brittleness problem - others
have not? Some must use their brakes (short runways), others avoid use as
much as possible.
I was concerned with the fragile look of Nyla-flow, so mine run thru
clear Tygon tubing all the way to the brake fitting. The brake line
is supported by an adele clamp fastened to the rear of the casting and is tie
wrapped to the gear leg in several places so it doesn't flap in the wind.
There is a gentle curve from the front of the gear leg to the rear of the wheel
well to avoid stress on the line when the gear comes up. I avoid all heavy
braking. These are the original circa 1989 lines with 700 landings
(701 takeoffs, don't ask).
Scott Krueger
AKA Grayhawk
Sky2high@aol.com
II-P N92EX IO320 Aurora, IL
(KARR)
Opinions and results may
vary!