Thursday, April 19, 2012

Are You Doing PM Right: 5 Things to Keep You in Flight


So earlier this week I had the opportunity to fly the helicopter shown to the right in for its 100 hour Preventive Maintenance Inspection, which led to many of the thoughts in this post. Private or General  Aviation as it is known is really at about the same place as many of us on the reliability maturity scale. You might say they are "not quite best practice". Now for those of you that travel commercially don’t fret, that world tends to operate on a different level with a different mindset. While talking with the mechanic who was servicing the helicopter these points came to light. 
1. They could really remove a lot of non-value added step in the PM. Many of these have no discernible link to actual failure modes. Some of them looked more like an exercise by the vendor in selling parts and satisfying lawyers. As an aside someone should explain the basic tenets of RCM and the failure curves to lawyers so that they understand new does not equal reliable. Statistically, the most dangerous plane a private pilot can fly is one that just went through an overhaul and it is full of new bits.
2. If a skilled pilot or a skilled operator can perform the check then teach them and let them do these as part of a pre-flight or walk down inspection. This will lower maintenance cost and increase the organizations understanding and ability to identify failures early allowing for planning and scheduling of the repair work.
On the helicopter the rear drive pulley was worn and the damage was visible without tools or removal of guards but on the preflight checklist all it says is “check the pulley” and most pilots don’t know what the failure modes of the pulley are so they only check the most obvious and catastrophic. If a pilot noted the defect on the pulley during their inspection then the parts could have been ordered in advance and the ship would have been out of operation much less time and could have been  generating additional revenue and making the business more profitable.
3. Simply put, use Predictive Maintenance (PdM) technologies where you can to replace invasive Preventive Maintenance (PM) task that require downtime and can induce failures.
If you can check the equipment while it is running then you have less downtime and many times less maintenance cost not to mention you catch the failure much earlier allowing for the proper parts to be ordered and shipped in for your downtime windows.
4. PMs and check list should be quantifiable and repeatable. Each step should give tolerances or operating ranges that allow each operator or mechanic to do it the same way each time. One step in the Helicopter PM job plan ask the technician to use a screwdriver to pry against a valve and check for movement. This is quite ubiquitous. The mechanic and I both were left with questions like:
How big of a screwdriver? How much force should we apply? How much movement is acceptable?
In the end the mechanic shared with me that he does not follow the PM for that step because he has no idea what is “good”. He has opted for a different method that he was taught by others.
5. Lastly, If you see the phrase “As needed” or” As necessary” then you know you have a problem. Most of us do not know what these phrases mean therefor we need additional detail to be successful.
In the end, whether you are hanging on for dear life under a set of spinning blades or running a packaging line in a manufacturing facility you need to do great PMs to get great results and hopefully these suggestions might help you look at things in a new way.

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