Service Bulletin #3
Vne-Velocity never exceed
two Kitfox™ builders have related to us similar experiences that
resulted in damage to their airplanes, which in either case could have
led to even more serious consequences. Coincidentally these incidents
occurred within one week. One builder had logged about 140 hours on
his Kitfox™ while the other had flown only about 2 hours. Both
pilots reported that they were flying very near, or perhaps in excess
of 100 mph, when the flaperons fluttered.
the first case an overseas builder was flight testing the airplane
with less that two hours flight time, and with two persons on board,
initiated a high speed shallow dive. The airspeed was probably in
excess of 100 mph when the flaperons fluttered with enough force to
break the mixer bell crank in the center.
the second case, a U. S. builder had his Kitfox™ in a shallow diving
left urn near 100 mph. He over flew a bluff and encountered turbulence
which may have triggered the flaperons to flutter with such force that
they both separated from the trailing edge.
both cases, to the credit of the Kitfox™ design and the flyer’s
good fortune, these pilots were able to control the airplane with
elevator and rudder alone and land safely.
of these incidents, we are issuing a mandatory change in
the Vne to 90 mph.
have received isolated reports from builders who have experienced
flaperon flutter at lower airspeeds, but they reported no structural
damage. in every case these problems at lower airspeeds were the
result of slack in the control system. From the very first page of the
construction manual (F-i) and here again we emphasize the importance
of “tight” controls with absolutely minimal free play. It is much
better to have some friction resistance to control movement than for
the controls to move too freely or with “ball bearing” feel.
Also we want to emphasize the significance of the Vne and of a careful well-planned flight test program. The Vne means velocity, never exceed. This limitation in any airplane is the
have designed and are testing a mass balance counterweight that should
eliminate any flutter problem at or below Vne. It is designed to
retrofit any Kitfox™ flaperon and will be available very shortly.
soon as we have completed testing the counterweight we will notify all
builders of its availability by a separate letter.
you need assistance in any way, please call customer service. Before
returning any items to Denney Aerocraft Co. please
obtain a Return Goods Authorization (RMA) number from customer service.