How do you mitigate the risks of mechanic error?

Sudburian

Sudburian

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Sudburian
I am about to become an airplane owner. So to keep myself humble and at a healthy state of nervousness, I look up NTSB reports now and then on the plane type I am interested in, and found one in California where an A&P mechanic conducted an annual on a Cessna 182, didn't install the throttle correctly on a new engine, and the pilot was killed a couple months later due to the unexpected power loss caused by the throttle problem. Here's the NTSB finding:

Postaccident examination of the wreckage revealed that the engine's throttle control rod was separated from the throttle body control arm. None of the attachment hardware, which comprised of a bolt, washer, castellated nut, and cotter pin, was found. Additionally, no evidence of impact damage was noted in the throttle lever linkage control rod end or the control arm where it attached. The airplane's most recent annual inspection was 78 flight hours and about 2 months before the accident. During the inspection, a new engine was installed. Based on the available information, it is likely that the throttle control connecting hardware was improperly installed or secured during the most recent maintenance, which resulted in its disconnection and a loss of engine power and throttle control while on final approach.
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Docket here. Question: How do we mitigate the risk of this happening any time we take a plane in for work by these good folks who we rely so heavily on? If you yourself are a mechanics pro, great, but let's say that you are not?
 
Find a mechanic you trust,you can ask him to fly with you after major maintenance done to the airplane.
 
Yeah, we'd like to think that a certified guy brings knowledge and diligence. Unfortunately, my experience is the knowledge frequently is present but the diligence less so.

What can you do? Find a mechanic you trust. This may be easier said than done.

What else can you do? Do much of your own maintenance. This is easier for the EAB crowd. Also, always look over work hired out. You might be surprised at what you find.
 
Understand the mechanicals of your aircraft. Be participatory, as much as possible. The ideal is to find a mechanic that will allow owner assist annuals. Anyone can pull off inspection panels.
Don't be the guy that drops off and then fly away after writing the check.
 
Be there if possible while the work is being done and pay attention to what is being done.
Inspect the plane very closely after work has been done with the cowl off. You learn how to put the cowl on and off and get very familiar with what’s under it.

When your mechanic discovers how interested you are they will hopefully pay a little closer attention to your plane.
 
Owners should have a copy of the Maintenance Manual, Parts Manual, The Instructions for Continued Airworthiness (ICA) for each modification and the AC 43.13-1B.

There's absolutely no rule that prevents you from studying the maintenance publications and participating in maintenance conversation. The regulations are very clear that no one may work on any aircraft without the Maintenance Publications. Also acquire all the Service Bulletins, Letters, Alerts and every other Service Document. Once you collect all these publications organize and keep them handy for research.
 
How do you know that they guy at Discount Tire properly tightened the lug nuts when they installed new tires?

Most systems tend to be remarkably robust in the face of less than perfect maintenance - the throttle cable example being one of the exceptions - or perhaps, a fatal accident as a result of the throttle cable failure being one of the exceptions. You can look over the work to see what you might spot, but in the end, if you are comfortable with someone working on your car, then why not your airplane? If the wheel falls off on your airplane, there is likely not much around to hit when you go off the runway. When the wheel falls off your car, then you go across the centerline right into an oncoming semi truck.
 
Sudburian said:
So to keep myself humble and at a healthy state of nervousness, I look up NTSB reports now and then
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When I've been asked this question in past by up coming owners, I try to put it into contaxt. For example, in your post how many of those NTSB reports listed pilot error? Once you have that context in place, the next step is to address each specific part of the mx process that gives you pause or you question. Sometimes its simply educating yourself on the maintenance side that keeps your "nervousness" in check.

And you can start today. I'm a big proponent of picking your mechanic before picking your aircraft. So perhaps start there and see who gives you the best response to your inquiries.

There's also a number of free maintenance references out there which can build up your knowledge on your responsibilities and your mechanics responsibilities for the maintenace in addition details on the mx itself.

And lastly, start posting questions of the specific issues that continue to bother you. Good luck.
 
I’ll also say that even if you’re not mechanically inclined, it’s worth your time and money to have the mechanic visually show you the repair made and explain it in terms you understand. That’s part of being the owner/operator since you are the ultimate decision maker on airworthiness.

You learned basic airframe and systems during PPL ground school and just like the PPL is a license to learn, so is ownership. Our planes are not that complex and, unlike your car, they are extremely unforgiving to an uninvolved owner.
 
Your mechanic can be the best.
And miss stuff.
You can be great as your own A&P.
And miss stuff.

If a second person looks over the airplane after it’s been worked on, I think less is going to be missed.
 
If you are mechanically inclined, maybe you could open and close the panels for your annuals and other maintenance. That would give you the chance to put a second set of eyes on everything before it is closed up.
 
I installed a new engine on my plane last year. Well, I mean I had one installed by a mechanic. He improperly installed my throttle cable (geometry wouldn’t allow idle below 1100 rpm), and actually reused the mixture cable (with end broke off just past the pinch bolt). They are out there.
 
Canada has a regulation that requires a second inspection, and a signature, for any control that has been "disturbed" during maintenance. It looks like this:

1694384657537.png

This minimizes the chances of something being incorrectly installed or connected or locked. The rule arose out of a deHavilland Beaver accident where the aileron controls had been reversed during reassembly.
 
Start by downloading and getting familiar with AC 43.13 B.
 
Knowledge is a double edged sward. But be informed. I always liked owners who took an interest in their plane. A second pair of eyes is sometimes required for a good reason. But its worth being respectful as well. My Dr has a sign that says........"your 15 minutes on the internet isn't that same as my years of college and med school." very true, but its my (body) and life. So some respect goes a long way, as well as genuine interest in your plane. Time is money, so compensate your A&P for his/her time and knowledge may be appropriate. It always takes a lot more time to do a job when the owner is there asking questions. AND a big one to consider. When you interrupt, you destroy a train of thought. Things are easily missed when interruptions are dealt with. I really don't mind telling anyone, " they will have to wait until I Finnish for an answer" There is a really good reason for the 10,000 ft rule! No unnecessary conversation below 10,000 ft. It's supposed to be all business in that environment. I always used 17,000 ft for my personal rule. Most of the people I preferred to work with, knew more about their personal airplane, than I did. I liked that.
 
Try to be there before the cowling goes back on. Ask him to point to relevant things as he explains what was done.

But don’t sweat this too much. If you can’t be there, you can’t be there. Things like the example you cite are rare. They’re part of the risk you accept when you strap on an airplane, whether an Ercoupe or an Airbus.
 
As said ; get familiar with the process.

DO NOT go tightening up things when the Tech is done!

Some items must be loose. Suggest a cell vid or discuss the situation.

Missing cotter pins? Should there even be one in that location?

Not a quick Yes- No on this.

Few things I find pilots are not familiar with:

Static RPM Limits

“Cushion” or “Springback” as relates to engine controls.

When are ADs due!

Work on these for starters.

Dan‘s comment somewhat reminds me USAF “ Red X “ status.

Only certain folks were authorized to clear them.

Preferably not the person that did the task.
 
What I picture happening:

Mechanic had every intention of attaching the cable correctly. Some yahoo walks into the shop with a question about his plane or a part. Mechanic gets sidetracked, cable forgotten and yada yada. Not saying it happened here but it happens.

Moral: Don’t bug mechanics especially when they AREN’T working on YOUR airplane
 
Whatever happened to flying the approach high enough to make the runway when (not if) the engine quits?
 
Stewartb said:
Whatever happened to flying the approach high enough to make the runway when (not if) the engine quits?
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That seems to have disappeared from the training syllabus sometime in the 1980s. I was taught that in the early '70s, and when I earned my CPL in the early '90s, the power-on, flatter approach was the standard, as if we were all going to be airline pilots. Later on, as an instructor, I found it in the PPL stuff too.

And it IS dumb. The majority of light GA airplanes use carburetors, and carb ice is a real threat on a low-power approach, depending on temp and dewpoint and engine type and installation. Put a pilot in it that never did understand the physics of carb icing, and we have a problem: an engine that quits short of the runway.
 
Timbeck2 said:
Don’t bug mechanics especially when they AREN’T working on YOUR airplane
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That's a great rule that should be followed. Another one I have is to not fly with folks that do their preflight while on their cell phone ... :dunno:
 
I’ve seen Tim‘s situation many times.

Too many ro describe.

Often it is the Owner that creates the issue.

Waiting until the current task completed is a lot safer.
 
Daleandee said:
That's a great rule that should be followed. Another one I have is to not fly with folks that do their preflight while on their cell phone ... :dunno:
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I don't know about the US, but in Canada mechanics have to take training on Human Performance in Aircraft Maintenance (formerly known as Human Factors). There are 12 of the factors that can lead to maintenance mistakes, and we call them The Dirty Dozen:

1694453332021.png

I outlined the one being discussed in the thread.
 
Sudburian said:
...How do we mitigate the risk of this happening any time we take a plane in for work by these good folks who we rely so heavily on? If you yourself are a mechanics pro, great, but let's say that you are not?
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In the Navy, I spent quite a few days on the flight schedule as a "functional check flight" aircrewman. This involved reviewing the maintenance log books, long, detailed pre-flight inspections, and both ground and in-flight testing appropriate to the maintenance performed.

For example, if an engine was changed we would have to complete an "FCF card" that encluded a 5 minute groun run and shut down for leak checks, recording engine parameters at idle, any flight-idle adjustments, and a vibration analysis test and correction before takeoff. Then a hover-check with all engine parameters recorded again. Then an inflight check with all engine parameters recorded and a subjective statement of engine operation and smoothness.

I take that same approach on my own aircraft. Before I leave gliding distance of the airfield, I've completed a thorough functional check of the aircraft, then shut down and a 2nd thorough preflight.
 
Dan:

You implied Mandatory.

Is the HF training one time or recurrent?

This topic is often at IA Renewal Meetings.
 
Dan Thomas said:
I don't know about the US, but in Canada mechanics have to take training on Human Performance in Aircraft Maintenance (formerly known as Human Factors). There are 12 of the factors that can lead to maintenance mistakes, and we call them The Dirty Dozen:

View attachment 120526

I outlined the one being discussed in the thread.
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Maybe the Aviation community as a whole need to brush up on their Federal Aviation Regulations (FARs). The FAA has dedicated a whole Part to "Human Factors":

Title 14 / Chapter 1/ Subchapter A / PART 5—SAFETY MANAGEMENT SYSTEMS (SMS)

Just because the government does not require or force Part 91 operators to implement an SMS Program does not mean we can't. There's no regulation preventing implementation of an SMS Program. In fact, insurance companies reward any operator who uses an SMS Program. As an individual I have drawn up my own SMS and it has worked well so far. The likelihood of being distracted if following your own SMS program as a Pilot or Mechanic becomes nil.

"Safety Management System (SMS) means the formal, top-down, organization-wide approach to managing safety risk and assuring the effectiveness of safety risk controls. It includes systematic procedures, practices, and policies for the management of safety risk."

Next time you take your aircraft to a mechanic ask them how they deal with FAA FAR Part 5 ? ... If they laugh at you, well..., Good Luck, you'll need it. ;)
 
Dan Thomas said:
Canada has a regulation that requires a second inspection,
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Is that for all maintenance operations or only Air Taxi like our Part 135? We have similar rules in Part 135 for those type "required inspections" along with a requirement to list each task and only certain people could perform them. However, there are no regulatory requirements below Part 135.
Dan Thomas said:
I don't know about the US, but in Canada mechanics have to take training on Human Performance in Aircraft Maintenance
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Down here the "human factors" mx training has been around for quite some time especially at the shop level. The Dirty Dozen posters are usually standard wall fare and been around for ages. One-man, small ops not so much. But there has been an on-going push by the FAA to reach all mx ops with human factors guidance such as AC 120-72. Plus its been part of the Part 147 school curriculum for a while. The new FAA maintenance training standards have elevated its importance even higher:

1694459797171.png
https://www.faa.gov/sites/faa.gov/files/Aviation_Mechanic_Certification_Standards.pdf
 
Magman said:
Dan:

You implied Mandatory.

Is the HF training one time or recurrent?

This topic is often at IA Renewal Meetings.
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Commercially-registered aircraft must be maintained by an AMO (Approved Maintenance Organization), similar to the FAA Repair Station certification. Aircraft Maintenance Engineers (AMEs) must be trained in Human Factors if they are to work in the AMO. Recurrency is this:

1694466460805.png

So unless the AMO's QA program is robust enough to extend the updating interval, the three years applies.
 
Bell206 said:
Is that for all maintenance operations or only Air Taxi like our Part 135? We have similar rules in Part 135 for those type "required inspections" along with a requirement to list each task and only certain people could perform them. However, there are no regulatory requirements below Part 135.
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All aircraft, private and commercial. The work done on any aircraft must be recorded in the technical logs, and that provision for an independent inspection of engine or flight controls applies. There are no exemptions.
 
I’ll guess a very small percentage of the time Tech 2 finds an issue?
 
When ever possible checking throttle linkages is one of my pre-flight items, especially in a new to me aircraft or after maintenance.
I have been around at least 3 incidents involving disconnected throttles.

The tow plane that was towing me had the throttle fail about 15 seconds after I released. He made a great dead stick, off airport landing, good enough that they fixed the throttle and flew it back to the airport before I landing my glider 2 hours later not knowing anything unusual had happened. (cotter pin not installed or failed on throttle linkage)

A Champ I was regularly instructing in, landing at a back-country air-strip and while taxing had the throttle linkage come undone, they had to wait for someone else to show up to bring them a replacement nut and cotter pin for the throttle linkage.

A 182 the company I worked for had a new engine installed and the owner was doing the 1st start of the engine in the airplane. The throttle was not connected and started at full power, the plane went about 150 feet into a hanger with 3 other aircraft in it, totaling 4 aircraft. Of course there was no insurance because he wasn't planning on flying the airplane, ended up bankrupting the company.

Brian
 

Airworthiness Notices - C010, Edition 2 - 10 October 2001

tc.canada.ca tc.canada.ca

This is how control system errors are mitigated here in Canada. Does it fix everything? Nope, there are still errors made, but I am sure it is better than nothing.

When I was training, flight and engine controls were at the top of my list of things to check during preflight.
 
FORANE said:
What else can you do? Do much of your own maintenance.
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If I went that route, I'd be dead for sure.
I vote for finding a mechanic you can trust.
And buy a Bonanza.
 
It appears the 182 owner was not familiar with Throttle Cushion (Springback).
 
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