Prop Strike Inspection: Better safe then sorry

Prop Strike Inspections Better safe than sorry By Greg Napert September 1999 The following was overheard recently at a maintenance facility after a very irritable looking pilot walked in with a look of embarrassment on his face. As he...


Textron Lycoming must take the position that in the case of a sudden stoppage, propeller/rotor strike or loss of propeller/ rotor blade or tip, the safest procedure is to remove and disassemble the engine and completely inspect the reciprocating and rotating parts including crankshaft gear and dowel parts. Any decision to operate an engine which was involved in a sudden stoppage, propeller/rotor strike or loss of propeller/rotor blade or tip without such an inspection must be the responsibility of the agency returning the aircraft to service.

Even tip damage is considered cause for teardown
Lycoming's Service Bulletin 475B requires that in the event that the engine has experienced a propeller strike, inspection and possible rework of the accessory gear train as well as the rear of the engine's crankshaft is required. Compliance with this service bulletin is mandatory per AD 91-14-22. The AD specifies the inspection at each engine overhaul, after a propeller strike, sudden stoppage, or whenever gear train repair is required. Lycoming's new SB seems to generalize the term propeller strike and sudden stoppage to be quite inclusive.

Russell says, it should be noted that to comply with A.D. note 91-14-22, the engine does not need to be completely disassembled and that access to the accessory gear train can be accomplished, in most cases, with the engine still installed in the aircraft.

Type of operator/engine makes a difference
In the case of any accidental damage to a propeller installed on a aircraft operating under Part 91 of the FARs, it is ultimately up to the inspecting technician to determine if the engine should continue in service without total disassembly and inspection. A Textron Lycoming engine, that is being operated on a Part 91 aircraft, that had a sudden engine stoppage, not a propeller strike, must comply with AD 91-14-22 and Service Bulletin 475B at a minimum.

Teledyne Continental Motors has a slightly different approach, but not much different in practice.

Russell explains, "Aircraft operating under Part 135 of the FARs must comply with all manufacturer's service bulletins, and would have to comply with Service Bulletin 96-11 requiring total disassembly and inspection after any incident that required removal of the propeller for repairs or if the engine physically lost rpms during the incident. Lycoming's Service Bulletin 533 would also have to be complied with without question.

Putting the puzzle together
Although many in the industry still like to interpret rules to their advantage, the mechanic is being faced with fewer and fewer "outs" for the aircraft owner. The pressure from an owner to ignore the engine and fix the prop may be great, but it is certainly in the best interest of the mechanic's career to persuade the owner that any amount of damage to the propeller constitutes the need for a thorough inspection. So carefully consider all factors related to propeller strikes. Start with all relative ADs, collect all service bulletins and service letters offered by the particular engine manufacturer, and sit with the insurance adjuster. Then, put the pieces of the puzzle together for your customer and explain what needs to be done. A bit of homework will go a long way towards helping you persuade your customer to do the right thing.

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