Hi All
I was greatly saddend to hear about Cliff Shaw's accident. His happened
near the ground on approach; as most of you know I have some experience
of Europa stall/spin, mine happened just after take off. In both cases
spin recovery is impossible this close to the ground, indeed partial
recovery may make things worse. You hit the ground harder.
Pete Clarke tested the spins of the original Classic prototype, G-YURO
extensively. One notable feature he found was that even after a twelve
turn spin he could let go of the controls and the aeroplane would
recover in less than two turns.
There are many GA types that are designed to be almost spin proof, this
is a mixed blessing because if it's hard to spin it will be just as hard
to stop the spin when it occurs. The Yankee was notorious and there were
several fatal accidents until intentional spinning during training was
forbidden. Remember also that very few certified or homebuilt GA types
had anything like the testing the Europa had. I remember Richard Trikle
asking Pete Clarke if he'd test the Kiss. No American pilot was prepared
to do it.
There are quite a few Classics that have a nasty wing drop flaps down.
G-KWIP was one. We had removed the stall strips because we felt we
needed the extra take off performance for farm strip flying. Ours was
around 450 meters at the time. The trouble with the Classic wing is that
it is not easy to finish the leading edge without degrading the very
subtle leading edge shape, which has a slight bump underneath and a
fairly sharp nose radius. Eventually, after much arm twisting, I got
hold of the coordinates of the airfoil and made some templates for the
leading edge. These were used on several Classics, Charlie Laverty's,
Tony Higgins' and Colin Smallwood's, I haven't heard from Tony re flying
qualities but the other two have excellent stall characteristics and so
does Trevor Jackson's, (kit no. 4!)
This illustrates the variability that Mike Parkin mentions.
Ivan did a lot of tuft testing trying to master the stalling
characterisitics and found that as long as the stall starts at the
leading edge it will be relatively progressive. However, sometimes the
stall starts at the trailing edge and then the whole upper surface
"unzips" and will cause a sharp wing drop. The stall strips help to make
the stall start at the front and at the wing root. The sharp LE radius
has a similar effect and I'm sure this is why some Classics are
unpredictable ( too large LE radius) whereas most XSs, which have a jig
moulded LE are relatively benign. (Not that I've flown many btw, so get
a second opinion!) The XS also has more washout which helps keep the
stall away from the tips.
Mike will have a much more valid opinion than me but I believe the
sensible way to monitor airspeed is by angle of attack, the instrument
tells that that your airspeed is going to change, you can correct the
changed AoA instantly and speed won't change The ASI tells you at least
20 seconds after it's changed which means you then have to regain
momentum which will take another 20 seconds or more. Another advantage
that correct AoA is not dependant on weight, so the figure for stall,
cruise max range etc all remain constant.
my 2 cents
Graham
>From: "Mike Parkin" <mikenjulie.parkin@btopenworld.com>
>Subject: Europa-List: Re Wing Drop in the Stall
>
>
> Jos,
>
>I think that the original foam built wings are likely to vary slightly
>more
>in performance than the factory made wings purely because of the nature
>of
>construction. Profiling the wing is a laborious process and the end
>result
>is very much an 'eyeball dependent' operation. I think it would be fair
>to
>say that the jig made factory wings are likely to produce a more
>consistent
>result.
> The very nature of the
>wing
>seems to provide a useable amount of lift until the stall, at which
>point
>the loss of lift from the wing seems to be almost total. Now if one
>wing
>stalls before the other it is conceivable that the aircraft might roll
>on
>its back.
>
>
|