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Engineers & Technicians In this day and age of increased CRM and safety awareness, a forum for the guys and girls who keep our a/c serviceable.

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Old 3rd Oct 2017, 08:38   #1 (permalink)


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Human Factors in aircraft maintenance

Dear PPRuNe aircraft engineer,

Soon I will be teaching young-adults about human factors in aircraft maintenance. In order to make boring lectures out of these, I'm looking for real-world examples that have been encountered while on the job. Of course I do have some stories of my own, but the more, the better.

This is all about showing the seriousness of the dirty dozen and what they involve. In my opinion, teaching is best done with real-life examples and visual support (e.g. videos, etc.).

I would like to bundle the stories and discuss them in-class. Would you like to share your story/stories when it comes to human factors while at work? The book that's used offers some examples. I have examples of my own but even if you've heard or know of great examples, please do share.

Greatly appreciated! Keywords will do if time is limited.

Kind regards,

Bas - NL
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Old 3rd Oct 2017, 11:08   #2 (permalink)
 
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Around 30 years ago, before the two words 'Human Factors' were linked, I'd worked all day and then most of the following night to fit and rig the ailerons on a large piston-engined aircraft. I finished the task and locked everything up. The mechanic I was working with noticed that I'd missed putting the locking wire through one of the turnbarrel holes, even though I'd made a perfect figure-of-eight.
I'd worked more or less twenty hours since clocking in and was obviously tired. The frightening thing is that I would have signed for one half of the duplicate inspections. A lesson learned...
It wasn't uncommon back then to work those sort of hours to keep aircraft serviceable as there were hefty penalty clauses if the operator couldn't keep to schedule.
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Old 3rd Oct 2017, 21:24   #3 (permalink)
 
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Lots of stories, from real life on line maintenance.

#1 fatigue/stress?
Guys towed aircraft from hangar to apron/passenger bridge end of the 12hrs nightshift.If my memory serves right, it wasnīt first night on row. Both guys well experienced and "good" guys overall. Longish, booring towing job during early morning hours end to collision with bridge as guy behind tug steering wheel almost fell to sleep and another guy on brakes was too slow to react due to fatigue. Big damages to a/c engines, and bridge damaged as well. No damages to personnel.

Fatigue is big issue as lots of work is carried out during nights, and long shift patterns. Seems to be quite regular see 7 x 12hrs shifts on row.
I did 12hrs shifts, three on row earlier and later with different company seven on row but they were usually shorter nights. Even i am evening person, canīt say it is easy or light work.

Lots of unnecessary damages or faults due to people are not concentrate on their task. Sometimes it is because distraction, sometimes people are just thinking something else than actual task.
Saw too many times "council work", one individual doing relatively simple task but his/her colleagues buzzing around and creates distraction etc etc...

#2 Maybe lack of knowledge?
Aircraft was flying very first legs after C-check. Aircraft grounded away from home base due to heavy fuel leak from wing, during refuelling.
Found out slat track punctured its "canister" on wing leading edge, causing fuel to leak out.
Cause was wrongly installed/missing bushing/roller which supports slat track.

Same kind of problem found on weekly check, by non type rated mechanic. Part of landing gear retraction mechanism linkages were installed wrong way, actually only one bolt was wrong way. Bolt head chafed nearby linkage badly, fortunately linkage material was softer and bolt head eats its way thru material. Not creating any actual jamming etc etc.

#3 Complacency?
Flap interconnect cables extremely badly damaged, almost broken. Area easily visible on weekly/daily check. Damage noted when cable almost cut, and according to broken strands condition not happened just on last landing. These cables are 3/16 size on that particular a/c.
Reason for cable damage was loose up stop block on flap, this creates big stress for cables as one side flap moves few cm more in than other. This was found after someone thinks "why relatively thick cable almost snapped w/o obvious reason.

#4 Lack of team work, pressure...?
During night shift, fuel control unit was replaced and work was ready for final check and eng run. By oncoming day shift.
Quick double checks were performed and wet run was performed before actual eng start, which ended heavy fuel leak. Fuel inlet fitting was only hand tight and when engine motored, mechanical fuel pump pumps enough pressure to cause big spraying fuel leak.
Nightshift missed loose fitting, as did next shift as well even shift hand over was done. + visual check for installation.
Aircraft needed to service, so pressure to get eng run done was great. Installation was corrected, eng run performed w/o problems and a/c released to service. This was good sign for importance of checks and tests, if a/c released for service w/o leak run... fuel leak all over cowling and engine... real risk for eng fire.

These may be classified differently, think there is not only one answer.

Saw lots of different damages, incidents, problems during my +30 years with general aviation and airline life. Done mistakes by myself as well, but tried to learn from every lessons. Fortunately, never had any serious mistakes, yet, and hopefully i can retire some day without any. Canīt relay self-satisfaction too much, always check, and check again. Ask someone else to check. Ask if you donīt know.

Last edited by Corrosion; 3rd Oct 2017 at 21:48.
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Old 4th Oct 2017, 13:28   #4 (permalink)
 
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Human Factors items

Many years ago on a Boeing we had a C-Check. We were supposed to check the engine fire extinguishing squib triggering circuit with a low power meter. What we found out was that bottle one switch position triggered bottle two and vice versa. Boeing had modified the connector keying, so one could not install them to the wrong position.

Also many hydraulic lines to hydraulic power units have now different sizes in their connecting unions, so you cannot install the lines the wrong way.

Cheers
easaman
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Old 4th Oct 2017, 15:14   #5 (permalink)
 
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The BA A319 engine cowl incident offers a wealth of human-factors and human-performance issues - maintenance topics with a bonus of organisational problems, team resource management and lessons not learned, and so on.

Investigation report at https://www.gov.uk/aaib-reports/airc...oe-24-may-2013.

To bring it closer to home, IIRC, there was a similar, although less spectacular, incident with a KLM aircraft.
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Old 4th Oct 2017, 17:20   #6 (permalink)
 
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"easaman" brightens my memory, we had few fire extinguisher related mishaps during years.
One a/c type have very similar studs for squib and bottle used indicator, SB calls to install extension to one of those studs, which is also slightly different diameter to avoid wrong connections. One aircraft found without these extensions, and off course at least one bottle was connected wrong way.
This remains us to perform requested system tests without any shortcuts, this a/c type requires time consuming and relatively complex test for whole eng fire ext system time to time, with multimeter. Its purpose serves to find hidden problems or system faults. Four engine, two bottle/engine.

Another a/c type found with completely empty fire extinguisher bottle, noted after removal for weight check. It wasnīt fired, just empty with unused cartridge.

Saw numerous accidentally fired cargo fire extinguisher on one a/c type, problem is bad design for shot switches on cockpit roof panel. System to be tested daily by pilots, shot and test buttons are both on roof panel... and shot buttons have only flimsy plastic cover. It is very tempting button when your list says "press to test". PSUHHHH!!!
Not nice if you have loaders in, or if this happens during maintenance when there is people working in cargo bay.

One test for pilots oxygen masks found hidden problem with mask. This remains me for importance of routine tests, even smallest one.
Test calls to visually inspect, and test mask by actually don it to make sure oxygen is flowing and regulator is working.
This mask was broken, first it didnīt pressurize rubber bands to allow don mask easily (remember this should be done easily in possible emergency). After small fiddling with triggers, mask was pressurized but now it didnīt left oxygen out from bubbers bands... so mask wouldnīt stay on head. Mask was clearly u/s,but tried one more time just to make sure positive fault.
Suddenly mask deflates, and at the same time oxygen regulator locks somehow and prevent flow in or out.
In that case, you have mask which sits tightly on your face and you cannot breath...
I would say this is not nice if you have cockpit filled with smoke, or pressurization is gone.

Been quite serious with tests or inspections for emergency equipment, those should work w/o any problems when needed. There is no time to start troubleshooting or start finding missing smoke goggles etc etc...
Those things, in good case, never see real action but they must be there. In perfect working condition.

Last edited by Corrosion; 6th Oct 2017 at 21:45.
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Old 7th Oct 2017, 14:03   #7 (permalink)
 
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HF for engineers

CASA (Australian NAA) produces a very good toolkit for training HF for engineers including a video case study which runs through the carious modules . The whole thing can be downloaded here:
https://www.casa.gov.au/safety-manag...s-resource-kit
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Old 8th Oct 2017, 04:01   #8 (permalink)
 
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I have spent over 25 years as a mechanical systems design engineer working on military and commercial aircraft programs, and both manned and unmanned space vehicle projects. I've heard dozens of stories from older engineers about manufacturing/maintenance/repair situations involving "human factors".

Over the last few years, human factors in manufacturing/maintenance/repair have become less of a problem, due to implementation of standard QA procedures (like AS9100) for every function performed by companies involved in the aircraft industry. Every work task must be performed according to a controlled and validated procedure.

Newer aircraft systems are designed to minimize maintenance required, using concepts like Condition Based Maintenance. And while it has long been standard practice to design the attachment interfaces of aircraft components so that they cannot be installed incorrectly, a detailed FMEA analysis is now required during the design phase to verify this condition exists everywhere.

Here's a human factors maintenance failure I personally witnessed while working as a mechanical systems engineer on the Space Shuttle program. A small locknut was not installed by a technician according to procedure, came loose, and caused the outer airlock hatch mechanism to jam during an EVA. The loss of that EVA cost tens of millions of dollars.
https://www.nasa.gov/pdf/740020main_...13%20Basic.pdf
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Old 8th Oct 2017, 08:11   #9 (permalink)
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This may help, several good examples with report references at the bottom:

https://www.faa.gov/about/initiative...ting12_8.0.pdf
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Old 9th Oct 2017, 18:51   #10 (permalink)


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A big thank you!

Dear posters,

Thank you for all your information! A wealth of it! Great files for teaching and wonderful materials for in-class use. Thank you, also for taking the time to reply!

Kind regards,

Bas
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Old 12th Oct 2017, 09:32   #11 (permalink)
 
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In case you are still monitoring this thread, a fairly recent incident involved many Human Factors, and demonstrated that a poor corporate culture can exist in even the world's favourite organisations.....you may find some of the report hard to believe. The report does not name the airline/MRO involved, but the clues are fairly obvious. This report also brings out a wealth of human-factors and human-performance issues - maintenance topics with a bonus of organisational problems, team resource management and lessons not learned, and so on.
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Old 15th Oct 2017, 14:10   #12 (permalink)


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I definitely am. Thank you for sharing. Perfect example of what, amongst other factors, the engineer did which led to the incident. Appreciated!
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Old 17th Oct 2017, 08:56   #13 (permalink)
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If you are entering the training world, it's not a bad idea to offer your students the opportunity to do some personal research into other sectors where "Human Factors" have played a prominent role in accidents / incidents.

Get them to present their findings and then move on to correlating the overlapping areas that induced the errors. This way, they get a much broader understanding of the significance of "Human Factors" rather than concentrating on purely aviation related issues.

A key point here however is to stress to your students, that, the intent of getting them to do the research themselves is not to abrogate your responsibility as a trainer, it's to enable them to become personally involved in the learning process with no detriment to themselves.

Have a look, if you don't already practice these, at Evidence Based Training, Virtual Learning and Facilitation techniques in respect of student development.

The only reason a lecture becomes boring is when the trainer makes it boring, usually with minimal class interaction and involvement plus the use of "Death by Powerpoint" as the sole means (PP has a use as part of integrated learning I hasten to add ) of presenting the subject.

Feel free to PM me if you would be interested in learning more about my suggestions.

Last edited by Krystal n chips; 17th Oct 2017 at 09:32.
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Old 17th Oct 2017, 15:12   #14 (permalink)
 
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Quote:
a lecture becomes boring is when the trainer makes it boring
The point of Human Factors training is that it is not a lecture and it is not carried out by a trainer. OK, substitute "should not be" for "is not" in that sentence.

A really good Human Factors training session is a facilitated and guided discussion among those present, who should come from all parts of the organisation, which aims to introduce the topics in the syllabus, and to draw out attendees' own experience and knowledge, leading to conclusions about what they AND THE ORGANISATION can and should do to reduce maintenance errors, with particular reference to the "dirty dozen" known causes of errors.

The facilitator must be an experienced aircraft maintenance engineer who can apply his/her knowledge and experience to lead the discussion.

Standing up with a Powerpoint presentation to "teach" Human Factors is a waste of everyone's time, unless some or all present can catch up on their sleep, as they probably will.

I do realise that I'm talking about an ideal world, but there's no harm in having an almost unattainable target to aim at.
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Old 17th Oct 2017, 17:25   #15 (permalink)
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Quote:
Originally Posted by Capot View Post
The point of Human Factors training is that it is not a lecture and it is not carried out by a trainer. OK, substitute "should not be" for "is not" in that sentence.

A really good Human Factors training session is a facilitated and guided discussion among those present.

The facilitator must be an experienced aircraft maintenance engineer who can apply his/her knowledge and experience to lead the discussion.

Standing up with a Powerpoint presentation to "teach" Human Factors is a waste of everyone's time, unless some or all present can catch up on their sleep, as they probably will.

I do realise that I'm talking about an ideal world, but there's no harm in having an almost unattainable target to aim at.
Capot,

Couldn't agree more with you, in the main. That said, and I've no wish to appear to be hijacking or diverting this thread from the perfectly reasonable request of the OP, what you suggest forms part of the delivery forms I've already mentioned.

Plus, facilitation also requires some training on the part of the trainer as a facilitator. No matter how experienced an engineer may be, it's not that easy to actually stand before a group and then deliver / facilitate the topic.

As I've been doing this successfully for about 6 years, prior to retirement, I think I may have some experience here...

A trained trainer is essential therefore.

PP does have a use, as an integral of blended learning, but, that's as far as it goes when you start to involve EBT / VLE ( and they work, trust me ) and get students actively involved.

Hence another reason for them doing some personal research on HF on other sectors to add to the diversity of the topic delivery and for them to gain a deeper understanding as to how prominent HF is in the working environment.
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Old 18th Oct 2017, 17:55   #16 (permalink)
 
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Another one hot of the press;


AvroRJ departs, experiences stick shaker right at lift off. A few hundred feet up the stick pusher. The AoA vane had been replaced during the night. Poor layout of the AMM combined with pressure from other departments to get the plane ready had the engineer perform the wrong functionality test. The AoA assembly that was installed came faulty from the manufacturer.
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