Air blowing over a hole with a cavity, like a flutist blowing over the
hole in the flute, can set up vibrations. You may remember driving the
car with one window open, and sensing a low frequency vibration.
Vibrations, if they are allowed to resonate, can have amplitudes with
very large peaks, and can be structurally dangerous. I suspect that
when Dave held the edge of the door frame he dampened the vibrations.
Lord mounts on engine frames dampen potentially damaging resonant
frequencies coming from the engine.
Its possible that removing both doors might have eliminated the
vibration, just as, by analogy, opening several car windows eliminates
air flutter in the car. The doors per se do not lend much structural
strength to the airplane. They do prevent air from resonating with the
fuselage cavity, however.
Donald Ingram
A-204 monowheel XS
----- Original Message -----
From: nigel charles
To: europa-list@matronics.com
Sent: Friday, June 23, 2006 7:29 PM
Subject: RE: Europa-List: Doors ( - not "The Doors"...)
In the case of the Europa the door apertures represent quite a large
surface area of that part of the fuselage. Although several pilots have
shown that the aircraft can be flown satisfactorily with one of the
doors removed, it bothers me that it without doubt reduces the
structural strength of the fuselage. As we know when building the
aircraft the rigidity of the fuselage greatly increases when the windows
are installed. Whilst flights have been carried out without incident I
would question the loads the fuselage could take with one or both of the
doors removed. Certainly with both doors removed there will be an
increased load on the narrow overhead panel between the doors. I had to
significantly reinforce the overhead panel when I cut a small overhead
vent because the overhead panel is considered a strength critical part
of the airframe. I would not be happy flying the Europa with one or both
of the doors removed without the necessary stress calculations proving
it not to be a problem. If the calculations have been done and prove
this not to be a problem please ignore all the above.
Nigel Charles
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of David Watts
Sent: 23 June 2006 21:37
To: europa-list@matronics.com
Subject: Re: Europa-List: Doors ( - not "The Doors"...)
Well I have done it and I have to say it was awful. Admitted it was an
appaling day with the weather, but the vibration through the airframe
was unreal. Sarah, my daughter was actually flying the aircraft whilst I
was doing the photos (a photo shoot of Pete Kember's kit 1000 for the
PFA magazine).
Stangely, when we came round for the second attempt at landing
(because all the sensations seemed completely wrong the first time), for
some unknown reason I put my hand up and held the edge of the door
frame, at about forehead level, and suddenly most of the vibrations went
away. That probably means that it was some sort of swirling set up
through the single open door. Maybe both doors off would be a better
proposition.
But still, we got the photos in the can, and we know what we will not
be doing again.
Dave Watts
G-BXDY - Monowheel Classic - 912S/Airmaster - 1200 hours
Question: Have anyone tried to fly the Europa without one door?
Problem: we need a platform for some air/air photos of span-cans,
and my AC should be able to fly slow enough...... :-)))
Answer: dismount the right door, but who knows what will happen..?
Regards Gert
#151
OY-GDS
Mono with 914
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