I had been concerned to find out why the limit switches on Mark's aircraft
had not been in the correct position to prevent the engine over-speeding on
takeoff when the connection to the electric pitch-adjustment motor failed
after he'd left it at fully fine for starting. Mark has responded as
follows to my points (marked >) and I have accepted his invitation to
publish his reply verbatim on the list to complete the picture. Once again,
I'm grateful to Mark for "baring his chest" on this incident.
Mike
Europa Club Safety Officer
safety@europaclub.org.uk
Hello Mike,
> I'm not sure what you have to reproach yourself with, unless there was
some requirement (e.g. at Annual) for you to check the fine pitch stop
subsequent to the original installation flight test and sign off for the
permit that you failed to carry out.
All I can do is explain how it all happened. You as a safety officer will
recognise that as it is often the case, it took a sequence events to cause
the end result.
Back in 2001, I fitted my first PV50. I carried out all the adjustments and
flight tests required by the PFA. It is worth noting that to obtain an
acceptable fine pitch limit position I had to round the corner on the small
piece of brass that secures the fine limit microswitch so that it could
travel another 1/2 mm or so in its adjustment slot. Without that tiny mod,
the range of adjustment was too small.
Everything was fine for a couple of years until I foolishly ground looped
G-NEAT and comprehensively destroyed the PV50. So a new PV50 was obtained
and hung on the front. By then, I had forgotten about having to mod the
limit switch securing block and so I simply put the switches in
approximately the right positions and started ground testing. As you know,
the final positions can only be determined by flight testing.
Once flight testing started, I discovered that my brand new PV50 had a
problem in that the pitch change motor had an intermittent fault and so the
motor was swapped. After that, the normal PFA flight test was carried out
but not the VP prop test that we have been discussing. I can't say why I
didn't do the VP prop test at that time, it probably got forgotten due to
the hassle of the broken pitch motor. I certainly didn't deliberately avoid
doing it. I suppose my inspector could have checked whether I had done it or
not but, really, he had done his part
in insuring that the aircraft was airworthy following the repairs needed
after the ground loop and left it to me to carry out the flight testing.
I claim full responsibility for the limit being incorrect.
Incidentally, my CS controller has a "soft fine pitch limit" that stops the
pitch reducing below a preset point. This means that unless, I deliberately
reduced the pitch by using the manual control, it would not normally be
actually at the hard limit during take off. The other day, because it is
winter and I have always had problems starting my engine in winter, I
manually reduced the pitch to the hard limit. If I had remembered to coarsen
the pitch again before take off as I often do, the flight would have been
much less scary.
> When I spoke to Pete yesterday he was surprised that there was not enough
adjustment on your fine pitch stop to achieve the ideal setting ~ he
expected there to be more than enough to meet the requirement.
On the 2 PV50s that I have have had experience with, neither have provided
sufficient adjustment. In fact, they were dispatched from the factory with
the limit switches set to completely unrealistic positions. But hell, they
are French, so perhaps that is to be expected.
> What is of concern to me (and would no doubt exercise Francis) is why
there was any significant change in the setting from your original setup,
assuming no disturbance/ damage. Is there a case for calling up a periodic
check for this particular propeller, or indeed for all VP props?
No, the setting didn't change over time so I don't believe that it is an
issue. Having said that, when I carry out my annual, I always check that the
switches have not moved as a matter of course.
> From Francis's reply to my message of yesterday afternoon (copied to Mark)
I would not expect him to be in "punishment" mode in respect of your
incident.
Well that's nice to know. I shall, of course, be shortly providing FD with
the explanation given above along with a new VP prop flight test report.
> Thanks again for your full and frank disclosure ~ I've already had
somebody e-mail me direct with a query about his Arplast propeller.
Overall, I do not believe that the Arplast is a bad product. Its weakest
point is the pitch motor which has a poor track record (they tend to burn
out rather too easily (that's another story)). Also, their wiring could be
better. To compensate, the hub is OK and the blades are very good indeed. I
would still choose an Arplast instead of an Airmaster any day.
Finally, I have no problem at all with anyone discussing these issues either
privately or publicly but it would be more polite if they could at least
take the time to learn the facts before making pronouncements about what I
or my inspector may or may not have done.
Feel free to send verbatim copies of this email to anyone you wish
(including the Europa list if you feel that is appropriate).
Regards,
Mark
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