Prevent Exhaust Leak Damage

Engine beams and canted bulkheads are victims of the corrosive action of exhaust. The damage is severe. Usually, it could have been prevented. So often the concern for the immediate consequences of an exhaust leak center around fuel and oil lines, but the long range concern is structural damage to the engine support structure. Aircraft owners and mechanics are aware of the corrosive nature of hot exhaust on the bottom of the wings and in the flap area. The same thing happens to an engine beam when subjected to exhaust leaks.

When performing exhaust leak checks, be sure to examine the adjacent air frame structures. Using solvents, thoroughly clean the structures. Look for damage in the form of distortion, buckling, pitting or flaking of the aluminum. Check for missing rivet heads. Inspect the inboard and outboard engine beam assemblies as well as the canted bulkhead.

Check the aft web, the structure on which the turbo mount is attached. Also, inspect the cap assembly and web for heat damage. These areas are subject to high temperatures. Even if not yet exposed to exhaust leaks, they may be damaged due to their proximity to extreme temperature. The corrosive effect of a future exhaust leak will thus lead to greater damage and the potential for structural failure. For further information on exhaust hazards and leak checks, consult FAA Airworthiness Directives AD 71-09-07R1 and AD 2000-01-16.