Troubleshooting the Buccaneer XA - Airframe
The Buccaneer airframe has proven to be one of the strongest and most durable in the industry. Part of this can be attributed to the fact that the hull and landing gear prevent shock loads from being passed through to the airframe.
One of area that was updated was the main upper boom running from just behind the pilot to the tail section. With the installation of the heavier 377/447 engines, coupled with rough field operation it was found that this tube would bend directly below the engine mount, and/or where the leading edge of the vertical fin attaches to the main tube.
This was almost impossible to detect. The main boom is covered with Dacron sailcloth and the bending takes place under two plastic saddles. The problem was discovered when pilots started to complain about a difference in pitch control, over a period of time. What was happening was that with the tube bending it would change the angle of incidence between the wing and tail.
To correct the problem, a sleeve was added in the area that the main tube bent, and a set of support wires were added running from the front upper bulkhead cross member to the lower aft bulkhead. These cables then in effect help support the tube.
To correct the problem, a sleeve was added in the area that the main tube bent, and a set of support wires were added running from the front upper bulkhead cross member to the lower aft bulkhead. These cables then in effect help support the tube. A set of flying wires running from the trailing edge of the wing to the horizontal stabilizer/vertical fin was also added.
To correct the bending under the vertical fin, the main tube was sleeved, and a bulkhead was added that joins all three main tubes together in the area of bending. These solution cured the problem.
Another reported problem was in the aft vertical stabilizer tube. This tube was reported to crack or break at the point where it joins into the lower tail section assembly. The factory updated this tube by installing an inner sleeve.
Pilots have also reported that the leading edges of their horizontal stabilizers have bent, in the centre. This causes loose fitting fabric on the stabilizer. To my knowledge this problem was not addressed by the factory. Our solution was to inner sleeve the leading edge tube.
Probably the most potentially dangerous problem of the airframe was with the main bulkhead. During preflight several pilots have reported this bulkhead to have cracked directly above a welded support gusset.
The main bulkhead supports the flying wires and landing gear. The factory solution was to extend the support gusset farther up the bulkhead. This problem was discovered on some models as late as 1989.
Another reported airframe problem occurred in very early production aircraft using the 277 Rotax engine with the Eipper style exhaust mounted to the kingpost. The problem, cracks developing in the kingpost where the retention bolt was drilled through the tube.
The factory updated by first changing to a bracket that did not require the king post to be drilled. Second by changing to a side mount exhaust and completely changing the exhaust mount.