The following service
bulletin is one the manufacturer issued several years ago. It is being repeated here because of the manufacturer's concern that they were not widely publicized at the time and that many Hawk owners, especially those who have re-purchased used craft may not be aware of these problems that need to be addressed.
Issued by MANUFACTURER
Service bulletin 4-20-89A
dated: April 20,1989
MODELS AFFECTED: All CGS Hawk Aircraft
SUBJECT: Main Boom At Rear Bulkhead
SUMMARY: A CGS Hawk single seat with approximately 400 hours flight time experienced a tail boom failure in flight resulting in a fatal accident. The aircraft was reported to be flying straight and level when the main boom failed at the rear bulkhead area.
Black sooty residue was found around the area of failure which indicates loose rivets around the bulkhead collar and the bulkhead and boom
rubbing against each other. This action eroded away at the boom tube under the bulkhead flange.
REQUIRED ACTION: Inspect the area of the rear bulkhead for loose rivets or black sooty residue. If either is present, remove the rear bulkhead sheet by drilling out the rivets and sliding the bulkhead sheet towards the tail. Inspect the main boom in the area that was under the bulkhead. If erosion is present, contact CGS Aviation immediately for a fix. If none is found, clean the area with acetone and apply PC-7 epoxy putty around the tube and reinstall the bulkhead. Insert the rivets while the epoxy is still wet. Wipe off any left over epoxy with acetone. Do the front sheet of the rear bulkhead too. Do not add doublers or sleeves without contacting CGS first. A wrong size doubler can cause more trouble later on.
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