December 8, 2016

Do you know what your mechanic is doing?


Do you know what your mechanic is doing?


Several years ago I decided to go on a pleasure flight in my family’s C-172 Skyhawk on a nice summer day. Departure was from a Class-C radar controlled airport. Shortly after takeoff the tower controller handed me off to departure (radar controller), and that’s when the trouble started.

I checked in as usual, “Champaign departure, NXXXXR (number changed to protect current owner of aircraft) climbing through 2,000 for 3,000.” Departure replied with, “NXXXXR, recycle transponder, squawk 0214.” I was already squawking that code and the unit was on, so I turned it off and back on.

A couple of minutes later, departure said they still had no reply from my transponder. Given previous experience with this particular transponder, I told ATC to hang-on for a minute and I’d see what I could do to fix the problem. My solution was to smack the front of the transponder really hard (some pilots call that percussive maintenance!).

“Are you getting anything now?” Departure responded with an affirmative. Unfortunately, even though they were now painting me on their scope, the altitude readout showed something just short of the stratosphere. Not a problem for a Douglas A-4 Skyhawk. A definite problem for a Cessna Skyhawk! ATC suggested I get that fixed.

This wasn’t the first time I’d had problems with that transponder, so I decided it best to finally take the airplane to a local avionics shop for repairs. I dropped the airplane off and went to lunch. Upon return to the shop I enquired with the manager about the airplane.

He said it was “all fixed, sort off. You should talk with Bob (name changed to protect the shop) before you leave.”

Bob was one of those guys who has been around since the Wright Brothers first flight and so he’s worked on a plane or two. I found Bob and introduced myself as belonging to the airplane in question. Bob had a concerned look on his face. He explained that my airplane was a tangled up mess of wiring that only a rodent could appreciate, and that it could spontaneously combust at any moment, taking the nearest three aircraft with it!

I responded with, ” Bob, don’t mix your words, tell me what you really think!” Just kidding. I was actually quite shocked at the news that I was flying in a potential deathtrap.

Bob went on to say that he had repaired some grounding issues he found, but that there were about five old radios worth of wiring and power-packs still in the aircraft and none of it was still listed as being in the weight & balance.

At this point I was wondering what all those previous mechanics and/or aviation technicians had been doing and why this machine was getting through its annual inspections in this state.

This is where the title of this month’s article takes life. Do you know what your mechanics and avionics technicians are doing when they work on your airplane? Do you know what they should be doing? Do you put your trust in them, that they will follow all the rules for installation and/or removal of old equipment? If you don’t keep track of what they’re doing, you should!

The responsibility for maintaining the aircraft in an airworthy state falls to the owner or operator and the final determination for airworthiness prior to flight falls to the pilot. Obviously no one expects us to know exactly what is supposed to be done when a mechanic works on our airplane, but we should inquire ahead of time to determine what is going to be done, and then follow-up to see if it has been done.

In many cases, the work performed is not evident to the pilot, nor can he or she visually determine that something has been done. However, in the case of radio work, the equipment list for the aircraft will change as a result of the removal of old equipment and installation of the new.

In the case of my airplane, anyone, including me, could have looked at the radio shelf behind the cargo compartment to verify exactly what equipment was supposed to be there (i.e. it would be on the equipment list with a weight and associated arm!). I never thought to do that. Have you?

Luckily, the weight and balance issues for my aircraft were not dangerous due to the location of the weight both forward and aft. Of course the airplane was approximately 50 lbs heavier than the paperwork showed so that might have led to problems if flying near the advertised max weight for the airplane.

Over the years after this situation occurred, I’ve had the opportunity to talk with several mechanics and avionics people and found that it’s not uncommon to find abandoned radio components, wiring, etc. in older G.A. aircraft. Some less-than-reputable radio shops or mechanics simply cut the old wires, leaving them in place, and run the new wires. This presents a potentially serious hazard, as loose wires can rub on other wires or even interfere with control column movement.

They also agree that it’s the owner’s responsibility to have that junk removed if a mechanic notices and informs them about the problem. The mechanic is happy to do that, but it’s going to take extra time and cost extra money. Maybe that’s why my airplane had so much junk left in it. Shame on those previous owners!

I suppose one way to avoid inherited problems when you buy a used aircraft is to have both a mechanical and avionics pre-purchase inspection completed by trustworthy approved technicians. Large shops are generally trustworthy, but regardless of size I would still try to get some testimonials prior to going to a shop or individual I’d never been to before. With that said, I’ve found the majority of mechanics to be trustworthy and highly skilled!

I’ve had a few old-timers (relative term since I’ve now been flying 25 years myself) tell me not to worry so much about radios, since the airplane doesn’t fall out of the air just because a radio fails. Radio problems during flight are more than just a nuisance however. Any type of radio issue becomes a potential distraction to the pilot, and we all know the dangers of being distracted from our primary job of flying the plane. For this very reason, it is well worth it to get a radio checkup from time to time.

Before you make your next visit to the avionics shop, do some research to find out exactly what your technician is likely to do to fix your radio problem. One way to do that is to call several shops and have them explain what they intend to do. Consensus between these explanations should give you some confidence that you will actually know what should be done.

Remember this, although the leftovers from old equipment may not be hazardous in many cases, it is most likely not in compliance with requirements for removal, and if the weight and balance information reflects complete removal, there are definitely airworthiness issues from a legal standpoint.

This month’s Pilot Primer is written by Donald Anders Talleur, an Assistant Chief Flight Instructor at the University of Illinois, Institute of Aviation. He holds a joint appointment with the Professional Pilot Division and Human Factors Division. He has been flying since 1984 and in addition to flight instructing since 1990, has worked on numerous research contracts for the FAA, Air Force, Navy, NASA, and Army. He has authored or co-authored over 180 aviation related papers and articles and has an M.S. degree in Engineering Psychology, specializing in Aviation Human Factors.