Jay,
I have a Lancair 360 with an IO-360 engine. I recently had the
same sound - like a slamming gear door against the bottom of the fuselage - only
it was on full power take-off. It turned out to be an intermittent ignition
timing sensor on the front of the engine. I have the Electroair dual
electronic ignition system on my 360.
If you have electronic ignition, you might check this out.
Randy Hartman
319 360-9775
N360DE
From: Jay M. Sabot
[mailto:jsabot@oxforditconsult.com]
Sent: Tuesday, November 17, 2009 9:44 AM
To: lml
Subject: What could be causing this in-flight noise on my Legacy?
Yesterday afternoon while flying Legacy N26XY (with about 17 hours
to date), power and speed were reduced to explore the lower speed range of the
airplane. Was at 4,500 MSL, smooth air.
As the airplane decelerated thru 89 knots TAS, once or twice a
sound was heard that can best be described as a door closing shut firmly. It
sounded like a landing gear door being slapped against the fuselage/cowling by
the slip stream. However, the gear was retracted.
Opening the throttle and increasing speed eliminated the noise.
The slapping sound, like a door closing firmly, did not reoccur. The noise
occurred only once or twice per event. I proceeded to repeat the flight
conditions, and the same thing happened: As the airplane decelerated to below
90 knots with the gear retracted and no flaps extended, just like the first
time, the noise was heard again two or three times over about 6 or 7 seconds.
The throttle was advanced and the noise did not repeat itself.
I reduced the throttle and lowered the landing gear and allowed
the airplane to decelerate again. Same thing happened with the gear extended,
(no flaps). A sound much like I imagine would be made if a gear door was
swinging loose in the slipstream and occasionally hitting the wing skin or
cowling. Advancing the throttle and retracting the gear was normal and the
noise did not reoccur.
Returned for a normal landing.
In the hangar, the gear and doors were examined only to find them all attached
firmly as they have been from the beginning. Nothing is loose, no sign of
anything striking the cowl or lower wing skins.
Anyone had any similar experience? Would appreciate any commentary on the
situation and their findings in this regard.
Thanks
all.
Jay M.
Sabot