Mooney_Driver wrote:
were done with i.e. the control surfaces in place
On many homebuilts it’s of main importance to keep the control surfaces as light as possible. Any painting must be done before balancing. On faster aircraft the ailerons and/or elevator (typically) must be balanced to prevent flutter. This of course means that any re-painting requires re-balancing. I don’t think the average car painter knows about this, yet alone how to do proper balancing. On an airliner with hydraulic actuators and much heavier construction, I’m not sure if this is even an issue.
Flutter is something which occurs on the control surface itself – it is a very local resonance. Having minimal play in the control linkage and in the control surface bearings suppresses the onset of flutter but it will still “try it”. So having lots of power in the hydraulics may not help.
However this is not related to the Q of paintwork needing a design approval (which AIUI is a Part 21 job and very expensive).
I think this is potential bad news because revenue generation within the Part M business will latch onto anything. All the time I see people grounded for months because they are waiting for some part, while an obviously perfectly serviceable part is readily available but without the right (or any) paperwork. On an N-reg that would simply not happen (unless the N-reg is maintained by a Part M company and “their” A&P is also clueless or is ar*se-covering).
Peter wrote:
Flutter is something which occurs on the control surface itself – it is a very local resonance
It’s a resonance/lock-in phenomenon due to aerodynamic forces combined with weight, CG and the elasticity of the control linkages. Making the linkage stiff enough will prevent it. But this is close to impossible with long cables or push rods. Play will for sure trig flutter, if it’s large enough. It’s not the power of the hydraulic that prevents flutter, it’s the removal of long (and elastic) control linkage.
Peter wrote:
or is ar*se-covering
That’s one of the main problems with all of EASA regs and the way they are supposed to be implemented. It’s a truly perverted system built around the idea that as long as you cannot be blamed, all is OK. Somewhat understandable, but it looses sight of the fact that in the end, reality is always right and reality is what counts. It also causes a “interesting” culture.
Peter wrote:
particularly if foreign registered airplanes are concerned.They should be outside the local CAA’s jurisdiction, no?
Well, no, it is not. If a plane registered in EASA country A has some work done in a shop supervised by EASA country B, then it is very much the jurisdiction of B’s CAA that the shop makes the work in accordance with regulations! That’s only logical, among all CAA, it is B’s CAA is in the best position to inspect the shop, rather than A’s CAA which would have to travel out. And imagine the poor shop having to undergo inspections from 31 CAAs! That would completely destroy the EU+EFTA-wide “free trade” of maintenance!
There must be more to it.
My maintenance shop recently had a visit from the Croatian CAA to check on the naintenance procedures and all – because there is a Robin registered in Croatia which is based and maintained there.
Was apparently constructive and fair, thus much better than the LBA audits :-) , but nonetheless…
I find myself agreeing with Pilot_DAR, the document is badly written and some on here are putting the most restrictive interpretation on a poor document and the resulting conclusions are unworkable.
Over the years I have seen a lot of re-finished aircraft the usual shortcomings being the lack of mandatory placards and control surfaces that have clearly not been balanced.
The average metal aircraft paint job is not too bad and some ( like Mick Allen ) would produce superb work . However the real problems start when composite aircraft are involved, removing the old paint is troublesome as chemical strippers are likely to damage the structure and re-balancing of the flying controls is so critical that only small changes to the weight of the control surfaces may put them out of balance limits.
The biggest paint fail I have seen was a two seat training glider that emerged from the paint shop looking superb with an almost glass like finish however when they put it on the load cells for the weight & balance it was found that so much paint ( weight ) had been added to the glider it could only fly with one pilot.
Certainly balancing flight controls is important, and and assuring that balance after new paint equally important. Generally a metal airplane strip and paint has a pretty good chance of not fussing it up, but it still needs to be checked – that is a maintenance activity, as there is no provision to declare the airplane airworthy with flight controls which do not conform to the manufacturer’s required balance limits. It’s a design change if you seek, and receive approval for different balancing limits. I have issued two such approvals over the years, both in cases where the original service manual was so poorly worded/thought out, that conforming balancing after appropriate painting was not possible. In one of those cases (a very early meal Cessna), balance was required, and the maximum mass of balance weight prescribed. The problem was, as the paint shop showed me, that the flight control wound not even balance with the maximum balance mass with no paint! Further research revealed that Cessna built that (and other) flight controls with differing skin thicknesses (so weights), but did not account for this possible difference in appropriate balancing instructions.
If your airplane is being painted, your maintenance shop must be involved. As they are, they should know what the correct practices will be – without making the event a design change!
