Lift strut, Kitfox lift strut modification advisory.

KITFOX SERVICE LETTER # 8

SUBJECT:   LIFT STRUT MODIFICATION

TO:   KITFOX OWNERS WITH SERIAL NUMBERS 02 THROUGH 116

FROM:  DENNEY AEROCRAFT COMPANY

LIFT STRUT MODIFICATION. We have designed a new stronger spar for the KITFOX that enables us to raise the gross weight to 950 pounds. In doing this, we had an outside engineering firm additionally analyze the lift strut and lift strut attach point. The attach point on the fuselage is well above necessary strength values. The lift strut lower clevis may not be sufficient for 6 g’s at 850 lbs gross, however. If the material is at minimum specs and the edge distance of the hole in the lower tang is marginal, the strut could fail at 4 1/2 g’s.

We have designed a modification that can be made to your lift strut which will ensure 6 g’s plus at 850 lbs gross. It is a piece of .090” 4130 steel plate that is welded on to the lower tang of the lift strut. We recommend that you install this to your aircraft. Otherwise, you should placard the aircraft for not more than 4.5 g’s positive. It will also require an AN5-lO bolt instead of the AN5-7 that was included in the kit.

This modification can be installed after the speed fairings and fabric are on. Hold a wet cloth around the fabric next to the weld area to prevent it from melting back. The part can be welded on with oxy-acetylene, TIG, or MIG welding process. The welded area should be annealed afterwards.