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1. 07:26 AM - FW: Old Lancair IV elevator trim tab incident (Bernard Melendez, Jr.)
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| Subject: | FW: Old Lancair IV elevator trim tab incident |
This was forwarded to me by a friend in Australia. Thoughts and comments?
Bernardo Melendez, Kit #110
--- On Sun, 3/20/11, Norm Edmunds <idgara.aviation@bigpond.com> wrote:
From: Norm Edmunds <idgara.aviation@bigpond.com>
Subject: FW: FW: [LML] Old Lancair IV elevator trim tab incident
Just info, for your Lightning. =C2-From: John Livsey [m
ailto:jlivsey@bigpond.com]
Sent: Sunday, 20 March 2011 8:32 PM
Subject: Fwd: FW: [LML] Old Lancair IV elevator trim tab incident =C2-
=C2-
Regards,=C2-=C2-John Livsey
-------- Original Message -------- Subject: FW: [LML] Old Lancair IV elevat
or trim tab incidentDate: Sat, 19 Mar 2011 16:01:31 +1100From: Dominic V. C
rain <domcrain@tpg.com.au>To: <jlivsey@bigpond.com>
=C2-=C2-From: Lancair Mailing List [mailto:lml@lancaironline.net] On Be
half Of Frederick Moreno
Sent: Monday, 14 March 2011 8:40 AM
Subject: [LML] Old Lancair IV elevator trim tab incident=C2-Here is a hea
d's up for owners of older Lancair IVs. =C2-My original kit is circa 1992
and came with the=C2-now-obsolete MAC 6A servo for the elevator trim tab
.=C2- Returning from a big=C2-military-civil air show in Melbourne, Aus
tralia, we experienced an interesting incident that taught several lessons.
=C2- The guy in the right seat was flying the airplane while we descended
below an overcast, manuvering between rain showers toward our destination
airport in the late morning.=C2- We were indicating about 180 KIAS with a
few bumps when we got severely hammered with a violent down draft.=C2-
=C2-=C2-Reconstructing the event it appears the following occurred:1) T
he co-pilot's arm was raised off the arm rest. He hung onto the stick, but
his hand slid up far enough to knock off the round pad at the top containin
g all the trim tab buttons. 2) Immediately following was a savage up push,
probably arising when=C2- we exited
the down draft.=C2- The co-pilot's arm was pulled down, but was moved of
f the arm rest and so continued downward while he was still holding he stic
k.=C2- Result: a big pull up.3) Instinctive response when the nose went w
ay up: he pushed down hard and we went negative G and everything hit the ro
of. 4) He handed the airplane=C2-over to me and I locked the stick in pos
ition to re-establish more or less horizontal flight and stop what was beco
ming a pilot induced oscillation. 5) Event over.=C2- Elapsed time about t
wo to three seconds after which the guy in the back seat complained about s
omething behind his back.=C2- Meanwhile=C2-holding horizontal flight re
quired a large stick force nose down.=C2- The elevator trim tab was non-r
esponsive.=C2- I slowed the airplane way down, put out gear and flaps, an
d landed in about 10 minutes holding the stick forward the entire time. =C2
-The trim tab is somewhat larger than stock for the earlier models becaus
e of reports of insufficient
trim in the pattern.=C2- The larger trim tab imposes a larger load on th
e servo.=C2-Result: 1) The hammer used to drive in the tie-downs and a fi
re extinguisher in the=C2-baggage compartment=C2- ended up in front of
the rear seat back and behind the back of the guy sitting there.=C2- They
had to migrate up and past several luggage bags to arrive at that location
. 2) We found the trim tab could be moved up and down a bit when=C2-wiggl
ed by hand.=C2- Clearly something in the servo was wrong. 3) We pulled th
e servo and=C2-found that the force on the trim tab=C2-during the upset
had been=C2-enough to apply a compression load that broke the back side
(thrust bearing side) of the trim servo out by breaking its containment gro
oves out as shown in the attached photo.=C2- This allowed the=C2- final
driven gear on the push shaft to disengage from the gear train making it i
noperative.=C2-We were still four hours from home, and so jury rigged a f
ix with cable ties and wire that worked for a
while but=C2-ultimately slipped allowing the servo to fail again during
the next descent (when further trimmed nose down).=C2- We finally locked
the trim tab in place with some carved wood behind the servo and a lot of t
ape on the trim tab itself, made a couple of=C2-flights until we got it a
bout right, and flew it home with a gentle tug on the stick while we trucke
d along staying below 170-180 KIAS. =C2-I wrote to Gary Menzimer at Ray A
llen Company and found I was not the first to experience a servo failure in
an older LIV during a severe upset.=C2- Another pilot had the same thing
happen when a side window blew out the door on a P model, and probably pul
led the pilot's arm out (and back on the stick) during the decompression.
=C2-The fix: There is a direct replacement=C2- Ray Allen 7A servo that
has been substantially modified to increase strength.=C2- Additionally, a
sister company, Bristol S. G. Inc. offers a newer, much stronger and upgra
ded servo that is a near
drop-in for the 6A-7A models dubbed the=C2- B6 series.=C2-=C2- See w
ww.bristolsg.com=C2-=C2- One can also=C2- purchase new clevis rod end
s which are also significantly stronger than the earlier units.=C2- The j
ack screw exits the back of the box which may necessitate drilling a small
hole in the elevator spar web, but otherwise it is a near drop - in install
ation. =C2-The Lessons:=C2-1) The forecast included thunderstorms formi
ng in the afternoon.=C2- We descended below the overcast after seeing som
e building cumulus but no thunderstorms during the late morning.=C2- We t
hought we had beat the strong convective activity.=C2- Wrong.=C2- Alway
s be suspicious even when it is relatively smooth.=C2-=C2- An isolated
down burst can=C2-ruin your whole day with no warning. 2) Keep your arm s
olidly on the arm rest to avoid unintentional stick movements. 3) Keep the
baggage net spread over the baggage (non-P models).=C2- We got complacent
during the long=C2-trip (seven hours going, seven and a half
returning) and did not bother to pull it over everything.=C2- Result: so
me potentially dangerous stuff migrated forward of the rear seat back makin
g for some uncomfortable seating back there.=C2- 4) If you have an old MA
C servo in your elevator, consider an upgrade.=C2- The servos have moved
forward two generations since the early 1990's and are much stronger which
is appropriate for these fast airplanes.=C2-Fred=C2-=C2-=C2-=C2-
=C2-
=C2-
--
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