Dear Graham
Thanks for your input on this one -- I know the subject is dear to your
heart!
There are of course many factors that decide the question "to tip or not to
tip" in any set of circumstances. Three that I considered, but did not
include because I thought I had probably reached the limit of the average
Member's wish (not yours, of course) to be bombarded with technical details
were:
a. Although the fuel tank is only just behind the cg, the fuel's
centre of mass is higher the more there is of it.
b. A half full tank is likely to be the worst case for sloshing,
especially important while turning with or without braking. This is likely
to be the fuel state on most landings, but I could not readily estimate the
effect. The momentum of any loose baggage rolling from one side to the other
might also be significant.
c. The the tailwheel modification (and, as mentioned by one
respondent, the main wheel tyre profile) affects the deck angle. This in
turn governs how far the aircraft has to tip before the propeller has no
tips.
I checked my facts with Andy Draper and Francis Donaldson before I sent my
Safety Note. Andy confirmed that the allowable cg range is from 58-62.5
inches aft of datum. He suggests that if the empty cg is forward of 59.5,
then it is worth thinking about repositioning equipment to move it further
aft.
Francis pointed out that the outrigger is aft of the cg. Andy said it was at
station 87 aft, but the wheel may be deflected further aft by weight and
drag. It may therefore be some 30 inches to the rear of the cg, which is why
the Monowheel is more susceptible to tipping forward when braking in a turn
than when braking straight ahead. The small wheel on the outrigger is much
more likely to catch in a rut than the main wheel, which could effectively
add unintended braking.
One of my original concerns was to recommend that full power run-ups should
not be done as a matter of routine pre-flight, but Francis pointed out the
importance of being sure there were no vapour locks when using Mogas. I
accepted that, but people must be very careful.
I don't think any of the above does more than flesh out the reasons behind
the lessons I spelt out, except perhaps to add:
"If your empty cg is forward of 59.5 inches aft of datum, consider moving
equipment such as the battery to an aft location."
"Ensure that baggage is secured so that it cannot move sideways."
When I have collected any further additional points, I shall ask Dave Watts
to publish the full set of advice in the next Europa Flyer.
Best wishes
Mike
-----Original Message-----
From: Grahamclk@aol.com
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