Dom,
My hackles are in shackles.
I am not a test pilot (Hmmmmm, not trained anyway), but I stayed in a
Holiday Inn once. While the OZ analysis is true, there are ways to
ameliorate the unfriendly small tail characteristics. Here are some
thoughts gained over 850 hours behind the stick of a 320 and generally within a
100 feet of a purposely hand held altitude in reasonably smooth air.
1. Neutral to negative longitudinal stability confirmed.
Recognize it, understand it, deal with it (one way is with a larger tail, there
are others).
2. Every Lancair 200/300 series is uniquely customized and details of
handling may differ while general characteristics could and should be
understood.
3. Instrument approaches in smooth air are a moderate challenge and whilst
in turbulent air, they are more interesting. (I believe that is a
quote from the Marquis de Sade shortly after he went flying in his 360.)
OK, here is a limited description of my components, customization
and their consequences.
a. Slow built 320, 1200 # empty weight and empty CG a hair forward of
specs.
b. Properly installed bob-weight with the elevator bell crank arm
reduced to 3" (stick throw reduced by 25%, forces increased from none to some).
60 degree banked (2G) full circle steep turns to the left with cruise trim
untouched require far more than 7 lbs of pull to hold altitude (no opposite
rudder) and the need for the pull is quite delayed after first entering the
turn. Right turns require less force and and the need to
apply the full holding force is delayed further than those steep
turns to the left. Holding the altitude within 50 feet throughout the
360 turn is a real challenge. 720 degree turns are easier because by
then you've got it - until you hit your self induced burble.
Drat.
c. I have the Reichel geared trim wheel with stronger springs to
compensate for the shorter arm. In cruise, spring controlled trim
characteristics add to the sensitivity in pitch because of the broad dead
band of little spring force exerted at the trimmed position, thus the
non-holding spring is relaxed and, if the plane is "balanced," even the
hold spring is not pushing very hard. In slow flight with flaps at some
extension, the holding spring is under greater tension and the sensitivity is
somewhat reduced. I cannot compare my flight
characteristics to Lancairs equipped with tabbed-elevator trim
systems.
d. My horizontal tail surfaces are thinner than the plans call
for. Don't ask. I don't know if there is a flight effect from that,
but it is different than the design. I also have gap seals with unknown
effect on elevator/pitch controlability.
e. More forward CG results in a more stabilized pitch control. The
rear quarter of the CG range results in much less stability than
the front half. Be aware of this when loading the plane. Lancair
moved the CG forward 1.5 inches without a detrimental effect (3" longer engine
mount to compensate for added weight from the larger tail that
moved the CG aftward). So, keep the CG more forward for better
flights.
Observed behavior and/or techniques to compensate:
i. Some have experienced an extreme nose bobbing when slipping at slow air
speeds. Try as I might, I could only induce gentle sinusoidal
bobbing, different from left or right (I don't remember which was
more). Since I fly differently than others (Don't we all?), I have little
use for slip attitudes until just above the runway. If not on an
instrument approach, slow down early, fly a higher pattern, fly a steeper
final descent angle, carefully control the speed (AOA has helped).
ii. With respect to slow flight when nearing the airfield - in my
airplane, throttle back and slow to 160 KIAS early, tick the flaps out of reflex
(resulting in rapid loss of airspeed and lowering the nose) and re-trim. A
stabilized slow speed approach(110 to 120 KIAS) at low power with flaps at
the takeoff position and everything trimmed is the most
stabilized, comfortable and with the least workload. Final at
85-90 Kts.
iii. The lack of longitudinal stability is a bummer during an
approach: Change of speed <=> change of attitude <=> change of
descent rate. Note the double pointed arrows. Instrument approach
workload is increased when trying to manage these. Turbulence does
not assist the pilot.
iv. Gap seals have provided a benefit such
that the rudder came alive at a lower airspeed (maybe 5 to 10
Kts). I cannot say I noticed a difference with respect to the
elevator. Gap seals are high maintenance items unless they are
built-in during construction.
v. I cannot get my Lancair to enter a turn by applying strong rudder inputs
(Hmmmm, maybe I only tested this at cruise speeds). In other words, I do
not feel much, if any, roll tendencies from applying the rudder in level
flight at cruise speeds. I don't remember if I had to compensate
for roll in the bobbing tests. The feel is different from left to
right rudder.
The conclusion for me: Yes, in certain flight regimes where stability
is desirable, it would be nice to have that stability available by design.
Understanding your steed's characteristics can be useful if you
remember to take those into account when flying. There are many
experimental and aerobatic planes extant that are twitchy - deal with them
for they are not as forgiving as those designed to be fool-proof.
Possible conclusions for others: Man, this ain't no spam can.
Experiences will vary. Learn it. Love it. Stay on your toes.
Use O2 as needed. Pay attention to Mother Nature. Occasionally
look out the window. Don't do noth'n stoopid!
Scott Krueger
AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)
Pilot
not TSO'd, Certificated score only > 70%.
PS: Is it possible the CG range was originally computed from the
un-reflexed wing characteristics? That is, computed from the "normal"
wing shape and thus set too far aft?
In a message dated 1/13/2008 7:31:02 A.M. Central Standard Time,
domcrain@tpg.com.au writes:
The recent comments regarding
the Small v. Big tail draw my attention to the fact that on a recent visit to
the wide brown land up over, LML lister Angier was privileged to see two
examples of large tail Lancair's. One belonging to me (didn’t build it), and the other
being the example quoted in the attached letter to Rob Wolf’s post “A look at
Lancair 360 Handling Qualities”. Now owned by another lister
here.
The only Lancair’s I have handled in the air
were all large tail versions, with one exception, that being N5ZQ in the
States. Bill will undoubtedly recall that I was – let’s say “ropey” – to say
the least. While I am prepared to accept that is my lack of skill, and I
reflect long and hard on this after each flight I have made over forty odd
years, I do come to the conclusion that there is a distinct improvement in
stability and handling of the Lancair with the large tail.
Over the past few months
–almost a year actually, there has been a slow but steady approach to the
improvement of training of, and understanding by, Lancair pilots here up over, brought
on by the historical global accident rate, and highlighted by two fatals
within six days in Australia, 20 months ago.
A Lancair Pilot Group has been
established, and having been asked to be involved, I have sought advice from
various sources regarding their views on the matter of Lancair training and opinions on
handling.
In this process I have had
email discussions with the test pilot who undertook some of the test flying on
the Lancair which resulted in the recommendation to enlarge the
tail.
I quote from the email I
received from one him on 20 September 2007:
“…….When the
first example (a 320 I think?) was evaluated, it was found to have 2 major
design problems/defects. First the aft CG condition was unrealistic (in
excess of 30% MAC), and the horizontal stabiliser was too small.
Combined these resulted in neutral or negative stick free longitudinal
stability. Also manoeuvre stability (stick force per G) was at best
measured in ounces per G. Standard comment from then owners was"I like
it like that because it has fighter like feel." These pilots had
obviously never flown a fighter, at least not one built since about 1920,
which all have positive long stab, and minimum stick forces of about 7
lb/G.
CASA insisted
(under the good/bad old 101.28 rule) that stability be improved. I think
the aft CG limit was moved forward (not sure how much) and bigger tails were
required. The bigger tails (2 local REG 35 solutions by Graham Swannel
and Dave Simons) produced adequate solutions, but the practicalities of
keeping CG forward remained. The Lancair 235/230/360
models also have negative lateral sideslip stability; with a low wing and
no dihedral the predominant rolling force in a sideslip is due to the
rudder. This characteristic is rarely seen, and is disturbing when
deliberately sideslipping during cross wind approaches. For IFR
approval, CASA insisted this be fixed and a rudder/aileron interconnect was
developed (I think by Dave Simons) which produced apparent lateral sideslip
stability and hence predictable handling qualities in
sideslip.
The kit
manufacturer was not amused by these criticisms of his creation and refused to
have anything to do with them. However, shortly after CASA came the
heavy, Aviation Consumer magazine in the US conducted some flight tests on the
Lancair, and another
fast plastic of similar size and shape, and concluded their findings with some
not very flattering remarks along the lines of ......... how dare you foist on
the unsuspecting public expensive machines with such bad design
features........ - I was very pleased to hear this as it vindicated the
position taken by CASA and other professional Test Pilots who had flown the
machines.
Very quickly
the manufacturer of kit X came out with a bigger tail (about 50% bigger!), and
some advice on how to fix the CG problem. Lancair eventually
did the same……”
CASA is the current name for
the old CAA here up over. Under a Labour Government, the name changes every
few weeks to create jobs. Although the quote uses the current term CASA, at
the time of testing the authority was called CAA.
Hopefully this will help, if
not cause the usual broad-ranging hackles raising.
Cheers,
Dom Crain
VH-CZJ
Melbourne
Not Florida