Our pride and joy has just come out of its annual inspection. It has had a good going over and a few new parts. The log book says it is airworthy. What can go wrong?
A PA 140 Cherokee pilot had a rough running engine shortly after take-off. The pilot immediately returned for landing. During the final stage of the 100 hour inspection, his mechanic had installed the last spark plug lead nut on the plug and was reaching for his wrench to tighten it when he was called away to assist another mechanic. When he returned to the aircraft, he installed the engine cowl and towed the aircraft out of the hangar.
An instructor and student started a spin in a Cessna 150. They were unable to recover with full rudder. They crashed and somehow survived with severe injuries. During the last inspection, the rudder had been removed for repair. The rudder bolts can only be installed in one direction as on only one side is there enough room for the nut and cotter pin to be installed. One of the bolts had been installed backwards and it restricted rudder travel in one direction.
During the start-up checks the pilot of a PA 31 Navajo, noticed a small screw driver sticking up through the throttle quadrant in front of the RPM levers. Fortunately, the screw driver had not fallen out of sight where it could have jammed one of the levers.
An avionics technician was working on one of the radios had been told that the aircraft was scheduled to depart in an hour. A delay of the flight was not possible. If it did not depart on time, the flight would have to be cancelled. While working on the radio, the technician could see the pilot pacing near the aircraft. Minutes before departure, the technician finished up his work, collected his equipment and left the aircraft – minus a small screw driver.
The crew of a PA 31 Navajo did not get all 3 green lights when they extended the landing gear. The left main gear would not come down. It would not go up either. It had jammed about half way. The crew burned off fuel and landed on an out of wind runway so as not to close down a major airport.
The aircraft had just come out of maintenance where work was done on the landing gear. The maintenance facility had only one torque wrench which was out for calibration. One of the AMEs attempted to borrow one from a neighbouring shop, but they were using theirs. Rather than wait for the torque wrench to become available and then take the time again to go request it, the AME tightened a landing gear arm bolt by feel. He over-torqued the bolt, the arm broke and the landing gear jammed in-transit when it was selected down.
Aviation mechanics, avionics technicians and parts people are human. Industry estimates vary, but between six per cent and 25 per cent of aircraft accidents are the direct result of maintenance errors.
Maintenance personnel are subject to the same human factors we are; fatigue, distractions, pressure, stress, complacency, communications errors, norms, lack of knowledge, lack of resources, lack of teamwork, lack of awareness and lack of assertiveness.
The mechanic working on the Cherokee was distracted. Distraction is the number one cause of forgetting things. Add in even a little fatigue, pressure or stress and it doesn’t take much to become distracted.
The mechanic working on the C-150 lacked knowledge, knowledge he could easily have found in the work sheets, or the aircraft maintenance manual. If he still wasn’t certain, he could have asked a more experienced mechanic.
The avionics tech was under pressure and forgot a tool in his hurry to complete the job. We often don’t realize we are putting pressure on maintenance personnel. Making demands to get a job completed in a certain time frame, constantly looking at a watch where we can be seen by the mechanic or tech, pacing, or looking over a person’s shoulder loads on the pressure. We blame the maintenance person, when we carry some of the blame.
Fatigue can occur for any number of reasons and it seriously affects one’s judgement, which can result in a maintenance error.
Stress affects all of us at one time or another and it can have an effect on our judgement with the same results.
We are all susceptible to complacency. Inspections are routine. Doing the same inspection over and over leaves a mechanic wide open to complacency. The more experienced the mechanic, the more possible he or she may become complacent. It makes it very easy to over look something that could become a problem.
We are not all good communicators and if communications break down between mechanics or between us and the mechanics, things can be missed.
Norms are unwritten policies or procedures that can develop within a company, even a very small one. Often they develop when someone finds that a corner can be cut that may save time or money. This may happen without anyone being aware of the long term consequences of this action – lack of awareness.
Lack of teamwork may occur if there are problems among the personnel in a maintenance shop, they may not be working as a team. This may result in poor communications and stress.
Many of us lack assertiveness. We don’t know when to say no. Mechanics often take on more work than they can handle or they agree to complete a task in an unreasonable time period to satisfy a customer. This results in pressure or stress, or fatigue if they work long hours to get the work done.
Maintenance people make mistakes. They may sign the aircraft off as airworthy, but it is up to us to make sure the aircraft is airworthy before we go flying. A little extra of our time spent on a pre-flight inspection may be appropriate after our bird has been in the shop.
Dale Nielsen is an ex-Armed Forces pilot and aerial photography pilot. He lives in Abbotsford, B.C., and currently flies medevacs from Victoria in a Lear 25. Nielsen is also the author of seven flight training manuals published by Canuck West Holdings.
Got an aviation safety story to tell? Dale Nielsen would like to hear from pilots who have educational aviation experiences to relate. Excerpts from these stories will be used in upcoming safety articles. Dale can be contacted via e-mail: firstname.lastname@example.org.