Guy Prevost
Well Known Member
Pierre’s post about his fuel line (here: http://www.vansairforce.com/community/showthread.php?t=71747) made me think about inspection and how difficult it really is.
In my day job I work with a small team to design and build unmanned rockets. Although I was already an experienced engineer when I came into this job I still served an apprenticeship under the watchful eye of someone who had been in the rocket business much longer. One of the biggest and most difficult things I had to learn was how to inspect. A missed problem in my job can cost megabucks and lost lives. We take it very seriously.
If one sits and looks at a large bundle of plumbing and wiring without a methodical approach, any problems found are mostly due to being lucky. The mind and eye both need a systematic approach. Here are some pointers that may help:
1. Have a written list of systems you are going to inspect. A mental list doesn’t cut it.
2. Inspect each system one at a time. Group systems by location when feasible. Do not mix systems.
3. Pick one cable, hose, or tube at a time and follow its entire length. Touch is a huge help. Trace the item of interest with your finger. It takes discipline to not get distracted and start looking at something else. Use mirrors, lights, etc to facilitate.
4. While inspecting an item look not only for existing problems, but for problems that may arise if something moves, etc.
5. Don’t do it all at once. You will become weary and less attentive fairly soon. Take a short break, do something else for a bit and resume your inspection.
6. Try and have some time between the time you work on a system and when you inspect it. If you have just replaced a fuel hose it takes extreme discipline to inspect that hose and its connections adequately. Since you just installed it and it is now perfect in your mind it is really hard to get a fresh look. Time between the operations helps.
7. More sets of eyes are better. Get other folks to take a look too. Everybody sees things differently. With my team, my technicians inspect, followed by the conduct of operations lead, followed by myself. I inspect last so that I am the accountable party.
As an example, I will pick a component inside a vehicle. I start with the first cable, and check each cable on that component one at a time. With each cable I check the fasteners on the connector and inspect for torque seal or other indicator that it is finialized. I then check for strain relief from the backshell. I then follow the cable checking all along for both problems with the cable and possible problems that may arise when it or something else moves. I’m always looking for sharp edges. At the other end of the cable I inspect strain relief and connector fasteners again. This cable will get inspected again in the other direction when I get to the component that the second end was attached to.
For tying wires, the standard we use is bundles tied together every 4” with actual support every 12”. This seems to work very well in my plane.
I insist that every connector, B-nut, fitting, etc has some indicator that it has been finalized. This is usually torque seal, but can be RTV (doesn’t create FOD and is easy to remove), safety wire, or something else as appropriate for the item at hand. I also avoid leaving anything in a test fit state. It’s good to test fit, but either remove or finalize the item before walking away. At the very least flag anything that looks like it is finalized but is not really.
This all seems like basic stuff, but the difference in what a person using a methodical approach finds vs. what a person that just looks at everything finds is huge.
In my day job I work with a small team to design and build unmanned rockets. Although I was already an experienced engineer when I came into this job I still served an apprenticeship under the watchful eye of someone who had been in the rocket business much longer. One of the biggest and most difficult things I had to learn was how to inspect. A missed problem in my job can cost megabucks and lost lives. We take it very seriously.
If one sits and looks at a large bundle of plumbing and wiring without a methodical approach, any problems found are mostly due to being lucky. The mind and eye both need a systematic approach. Here are some pointers that may help:
1. Have a written list of systems you are going to inspect. A mental list doesn’t cut it.
2. Inspect each system one at a time. Group systems by location when feasible. Do not mix systems.
3. Pick one cable, hose, or tube at a time and follow its entire length. Touch is a huge help. Trace the item of interest with your finger. It takes discipline to not get distracted and start looking at something else. Use mirrors, lights, etc to facilitate.
4. While inspecting an item look not only for existing problems, but for problems that may arise if something moves, etc.
5. Don’t do it all at once. You will become weary and less attentive fairly soon. Take a short break, do something else for a bit and resume your inspection.
6. Try and have some time between the time you work on a system and when you inspect it. If you have just replaced a fuel hose it takes extreme discipline to inspect that hose and its connections adequately. Since you just installed it and it is now perfect in your mind it is really hard to get a fresh look. Time between the operations helps.
7. More sets of eyes are better. Get other folks to take a look too. Everybody sees things differently. With my team, my technicians inspect, followed by the conduct of operations lead, followed by myself. I inspect last so that I am the accountable party.
As an example, I will pick a component inside a vehicle. I start with the first cable, and check each cable on that component one at a time. With each cable I check the fasteners on the connector and inspect for torque seal or other indicator that it is finialized. I then check for strain relief from the backshell. I then follow the cable checking all along for both problems with the cable and possible problems that may arise when it or something else moves. I’m always looking for sharp edges. At the other end of the cable I inspect strain relief and connector fasteners again. This cable will get inspected again in the other direction when I get to the component that the second end was attached to.
For tying wires, the standard we use is bundles tied together every 4” with actual support every 12”. This seems to work very well in my plane.
I insist that every connector, B-nut, fitting, etc has some indicator that it has been finalized. This is usually torque seal, but can be RTV (doesn’t create FOD and is easy to remove), safety wire, or something else as appropriate for the item at hand. I also avoid leaving anything in a test fit state. It’s good to test fit, but either remove or finalize the item before walking away. At the very least flag anything that looks like it is finalized but is not really.
This all seems like basic stuff, but the difference in what a person using a methodical approach finds vs. what a person that just looks at everything finds is huge.
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