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Post-Maintenance Preflight - Take a Closer Look

Posted 7 years 196 days ago ago by Admin


Prior to the flight portion of an FAA exam, the applicant will be tested on their knowledge and ability to conduct a preflight on the aircraft being tested. It is imperative that a pilot understand the systems of the aircraft they plan to operate. The ability to determine airworthiness can only be accomplished when the pilot has adequate knowledge of their aircraft and knows what to look for (normal vs. abnormal) during the preflight process.

A few weeks ago, I was picking up an aircraft that had just completed a heavy maintenance inspection. Many of the aircraft’s flight components had been removed, overhauled, and reinstalled. Before I conduct an operational check flight (OCF), I like to establish a personal relationship with the maintenance staff working on the aircraft. Having conducted many post-maintenance OCFs, I’ve grown accustomed to the nuances of maintenance technicians and appreciate that each maintenance facility’s processes and procedures may differ. In the case of the aircraft in question, I did not know all of the mechanics. The main gearbox and rotorhead was completed by a mechanic new to the facility. Since this situation occurs often within our industry, it gave me no great concern; I had faith and trust in the quality assurance process of the system.

The aircraft was rolled outside and prepped for its required CFR 14 91.407 return-to-service operational check flight. Having verified the maintenance tool and parts inventory (All tools and parts utilized during aircraft maintenance were accounted for.), I checked all the aircraft logs for the appropriate endorsements and proceeded to preflight the aircraft.

The preflight went well, with only a few discrepancies that were quickly remedied. After a few flight manual updates that were due, I was ready to go. Before I get into any aircraft, I walk around verifying cowlings to be closed and just make sure I didn’t miss something obvious.

As I stepped up on the flight step, I happened to look up at the swash plate. Immediately, I noticed something I had missed on the preflight. Each bolt on the rotating portion of the swash plate was put in backwards. On this portion of the swash plate, the head of the bolt is to be in the direction of rotation. It is a safety design and procedure so that the bolt will be driven into the hole during rotation, not thrown out of it due to centrifugal force.

I pointed out this discrepancy to the maintenance manager. The aircraft was immediately returned to the hangar, where all of the rotating bolts were removed and reinstalled in the correct direction. Still, I needed to know: How did this happen?

The answer was that the new mechanic had previously only worked on helicopters with rotor systems that turned in the opposite direction. When queried on what had happened, he admitted that he just put the bolts in “from left to right out of habit.” It was a simple human error ... that completely eliminated a safety design to prevent catastrophic failures.

Either after maintenance or when just going out on your next flight, make no assumptions when conducting a preflight on an aircraft. It’s definitely worth the few moments it takes to have a closer look.

Your life may depend on it.