> hear more about actual flight figures. I hear some of the aircraft
> flying do not live up to the prototype in cruise speeds etc. Has anyone
> come up with an average, mode and standard deviation for the various
> aircraft flying.
As a happy Europa owner with some 140 hours of experience in my standard 912,
I would like to make the following contribution.
The problem is that it is very difficult to define 'cruise', and easy to
make mistakes/omit certain facts when assessing it.
Here IMHO, are some factors it is essential to consider when assessing cruise
performance so that we all operate from a 'level playing field'.
1/ Ensure prop. blades set to an exact value (17 degrees, +- 0.25 deg)
2/ Ensure RPM gauge accurate (+- 20 rpm). Difficult with mechanical ones
3/ Ensure 'runs' are DIRECTLY into/away from wind. (+- 10 deg or so)
(NB. wind generally 'veers' as you rise)
Track across ground should correspond to course. Can use fixed
ground reference points at start and end of run to check.
4/ Ensure altitude held constant for duration of test. (+-50 ft)
5/ Make notes of both, average GPS values obtained for later analysis.
6/ Repeat test several times to ensure consistancy.
7/ Anything else I've forgotton !
It takes real concentration to hold a course/rpm/altitude setting for the
duration of the test. It is also tricky to then do an exact 180 and follow the
same track backwards.
Having done all this, after early elation about over-optimistic results (I had
forgotton the contribution that sidewind component can make if flights are not
directly into/away from wind direction), I have now found a surprising
consistancy in the results I am getting. These results are similar to those
obtained by several other individuals who have conducted similar rigorous
assesments.
Reviewing the results obtained by G-YURO/G-ELSA published on the web, I can
now see that these results too, are roughly consistant, if one makes allowances
for RPM setting/prop setting as detailed above.
YURO http://www.europa-aviation.co.uk/testyuro.htm, Section 5.8
In view of the static/takeoff RPM of 4800/4600, I considered that prop=145o
must equate to a figure of around 19 degrees)
ELSA http://www.europa-aviation.co.uk/testelsa.htm, Report 12
My findings, briefly:
I would not describe my Europa as an aeroplane capable of cruising at 120-130
knots. (I might if I was trying to sell it !)
I would describe it as capable of a realistic TAS of 110-120 knots, with
fast cross country's returning a nil wind of about 105-110 knots, burning
about 15l/hr.
I would be surprised if most owners obtained results which were greatly at
variance with this (unmodified monowheel 912's with fixed pitch WD prop at
17 deg).
Contrary to what has been said, I find the aircraft to be surprisingly
insensitive in cruise to issues like weight and balance, wing and prop
cleanliness. I was amazed to find that removing my spinner completely did
not significantly affect cruise.
I would not feel happy about take-off from a short field (<400 yds), in summer,
at AUW, with a prop value set much greater that 17 degrees.
Hope this helps builders, as to what to expect from their aircraft.
alan (with apologies for spelling, double letters was never my strong point!)
PS. For 17 deg prop, I get static 5150rpm, climb 5000rpm, max S&L 5850rpm,
measured digitally on Flydat.
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