Most of my public presentations are given to pilot/owners about maintenance related topics. As a result, pilot/owners tend to open up and voice opinions during these events that they might not do in other settings. Often they share stories about experiences with their mechanics during maintenance events. It’s an interesting position to be in and elicits unexpected thoughts on my part.

A typical comment from an owner would be about loose screws noted on an access panel after maintenance. The concern is then extended to all the other maintenance performed on the plane. Somewhere in the conversation there is often a comment expressing concern for the mechanic’s abilities. My first response is to point out errors the pilot likely made during his or her last flight. I’ll ask the pilot/owner whether he/she maintained altitude within 20 feet at all times, held heading within a couple of degrees, flew a perfect approach, never missed a radio call, made a perfect landing and the list goes on. I rarely get past the second or third question before they get the point that everyone dealing with the plane has a responsibility toward safety and we all fall short, not just the mechanic.

I would pat myself on the back for adjusting the pilot’s attitude and enlightening his outlook. However, the problem is that I had missed the real concern, which is catching these human errors before the plane takes flight. Most pilots attend lots of safety seminars and perform recurrent training to help maintain skill levels and attention to details. There is absolutely no requirement for any sort of recurrent training on the part of FAA certificated mechanics. Mechanics are often not aviation enthusiasts in the way pilots are and rarely attend safety seminars or volunteer for training. To compound the concern is that there is no required double inspection for any work performed on FAA part 91 aircraft during or after maintenance events.

Scope and Detail

The function of the person performing an inspection of work performed is to ensure the entire job is successful. It does not include any maintenance functions at all, so the only tools needed are a flashlight, mirror, borescope, a thorough understanding of the aircraft’s system, and a very inquisitive mind. A complete inspection also means no part of the work performed is off limits.

Some of the items in the scope and detail of these inspections may seem ridiculously obvious at first reading. Whenever I think anything is too obvious or too simple to be
included, I remind myself of the stories about the patient that had the wrong part amputated. It can happen anywhere to anyone even when all involved have the best of intentions.

An inspector begins by determining what maintenance discrepancy was requested and verifies the corrective action performed is appropriate. The inspector would then proceed to verify the following:

● That left or right in discrepancy is the same as the left or right in the repair.
● The manufacturer’s procedures were found, used, and documented
● Proper tools were used and within calibration
● Torque wrench settings checked prior to use.

● Safety wire is in the correct direction, attached to proper points, and of proper diameter
● Proper parts and hardware are used
○ What was removed may not be the correct part to install. The parts catalog should be consulted, especially for hardware.
● In progress inspections (when appropriate) to check items prior to being covered up.
● Quality of work meets the required standards
● No tools left behind
● Paperwork is completed and fully describes all work performed
● Full function of the system repaired as well as any related items or systems.

The above list isn’t exhaustive, but is a good starting point. Specific repairs may require additional items to be considered, which is where the experience of the inspector is valued.

Resident Pathogens

For many general aviation maintenance shops, the idea of performing in progress and final inspections of work performed is a foreign topic. Each mechanic is expected to
be professional in every aspect of performing his work. In a perfect world this would be sufficient. As humans we all have inherent flaws or inabilities that require mitigation. The following are some examples of these resident pathogens:

● Inability to proof one’s own work
● Unwillingness to allow others to proof
one’s work. This may be due to
○ Arrogance, ignorance, protectionism, fear of exposure

○ A general culture of isolationism among GA mechanics
● Unwillingness of one mechanic to “throw the other guy under the bus” by condemning the work. This logic is wrong minded because it throws the pilot and passengers under the bus in the case of a failure which eventually gets back to the mechanic when the bus backs up in the form of action by the FAA or plaintiff attorneys.

● Working as a lone mechanic exaggerates errors in judgement and workmanship.
● Distractions during work are a prime problem area

○ Phone calls may be the lifeblood of a small business but are just as significant a distraction. Not only does it interrupt the maintenance process, it distracts the                             thought process for a fair amount of time after the call.

○ Lunch may be planned, but it still breaks the focus in concentration.

○ a visitor in the shop is one of the most distracting elements available.

○ A mechanic’s favorite distraction may be the tool truck.

● A very false perception that inspecting all work cost too much time and money.


We’ve experimented with several iterations of the inspection of work performed process and don’t feel we’ve fully arrived at the Holy Grail just yet. Like most shops/mechanics, we used to rely on the integrity and ability of each mechanic to examine his/her final product. We found it interesting how difficult it is for a technician to identify a problem he created.

A second mechanic in the same shop seems like a good solution. However, we discovered a problem in the inspector mechanic having too much familiarity with the job mechanic’s work. There’s also a ready willingness on the part of the inspecting mechanic to accept the word of the job mechanic instead of actually performing a detailed inspection.

Eventually, we arrived at the same place the large commercial operators and the military figured out decades ago. That is, an independent inspection department. We can do this because we have a large enough shop to afford to dedicate one person as the primary inspector. This inspector does pull double duty as the records inspector and inventory controller which helps with the economics. The relatively small amount of dedicated inspection labor cost pales in comparison to the savings in safety and warranty expense.

My experience with the FAA Part 121 world and a few decades operating my own shop has yielded some helpful antidotes for the earlier mentioned pathogens:

● The inspector should not be part of the maintenance operation to allow more independent and objective review.
● The inspector must have full authority to inspect everything and even require reopening of areas for full inspection.

● Those having their work inspected must understand that having oversight of their work is in everyone’s best interest. Everyone’s everything’s are at stake.

○ inspect now by local peers or later by someone you don’t know with actions you don’t control think lawyers and the FAA.

● The mechanic should be a willing participant explaining the entire maintenance process helps the inspector determine the extent of the needed inspection.

● Most vulnerable are one man shops that don’t have the luxury of easy independent inspections. Since there is no FAA minimum requirement or certification for an inspector of this sort, the aircraft owner, the mechanic’s spouse or any interested party would be helpful as a second pair of eyes.

None of this is news. For many, it is a new application for a small segment of the industry not often open to outside influences. The added security of a second pair of eyes is an absolute necessity in our little general aviation world for all the same reasons it’s a standard policy requirement in the realm of the big commercial operators. Acceptance of this knowledge may be painful for some, as it requires admission of a lack of knowledge to start. If you’re reading this as a mechanic, take it as advice from one that’s worked through the process to get to a place of relative safety. If you’re the owner/ pilot, also take it from one with experience finding a problem while airborne that would
have been far less exciting had it been found on the ground.