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VK5QX > INFO 23.07.02 12:29l 103 Lines 3957 Bytes #999 (0) @ WW
BID : FA0287VK5QX
Read: DB0FHN GUEST
Subj: RE - BALLOONS
Path: DB0FHN<DB0ZWI<DB0CHZ<OK0PKL<OK0PPL<RZ6HXA<SP7MGD<WB0TAX<VK3AVE<VK5BRC<
VK5SPG<VK5LZ
Sent: 020722/0536Z @:VK5LZ.#ADL.#SA.AUS.OC #:39804 [Elizabeth] $:FA0287VK5QX
From: VK5QX@VK5LZ.#ADL.#SA.AUS.OC
To : INFO@WW
SOME CLARIFICATION (? ?)
Ray VK4LU said :-
_______________
" Just a few points I think are wrong. First on the plane wing. I seem
to remember that about two thirds of the lift is provided by the
differential pressure. The rest of the lift is provided by the wind
straiking (sic) the underside of the wing.
_______________
I have never seen anything which suggests that lift is obtained by wind
striking the underside of the wing.
My understanding is that forward motion causes a flow of air to pass over
both the top and bottom surfaces of the wing.
The SHAPE of the wing, (known as an aerofoil) is such that the distance
travelled by air over the upper surface is different to that afforded by
the lower surface, and thus a pressure differential is created.
Over the upper surface the resultant air pressure is lower whilst below
the wing a greater pressure is developed. It is this condition that
provides "lift".
(It could be considered as being similar to having created a "partial"
vacuum above the wing.)
The "SHAPE" of the wing can be altered by means of such things as extended
"FLAPS". The increased amount of lift can become very obvious,
particularly when one is in a light aircraft, when the flaps are deployed.
You can note a marked change when such an action is taken, as is commonly
done during an approach for landing. The aircraft seems to almost hang in
the air with very little forward motion.
I have had some experience of this when flying in relatively small
aircraft in the desert areas in the north of the state of South Australia.
It is an unusual experience to be seated in an aircraft where the pilot
gains quite a speed down the strip at take-off, at the same time
endeavouring to keep the aircraft still on the ground.
At a suitable time he then selects a condition to actuate the flaps and
quickly pumps them into a definite "flaps down" position. (Yes, in this
aircraft the flaps were pumped manually.)
The sudden extra lift that is produced causes the aircraft to almost leap
into the sky. One might almost believe that you have suddenly transferred
to a helicopter or VTOL aircraft.
Another interesting experience is to be in an aircraft of the nature
described, in this instance a high wing monoplane called the "De-Havilland
Otter" (single engined), where the pilot throttles back the engine revs,
making careful and continuous adjustments, at the same time adjusting the
flaps so as to slow the aircraft to a great degree. This was done when
travelling into a strong head wind.
Later, when asked what that particular manouver was about, the pilot
simply explained that he was trying to make the aircraft fly BACKWARDS or
remain almost in the same position over the ground.
I had not noticed that particular effect as I had been too interested in
watching his various adjustments rather than keep observation on our
surroundings.
I might add that I was sitting in the cockpit beside the pilot and was the
only passenger on that particular flight. (The aircraft was capable of
carrying about 13 people.) The manouver was executed at a height of around
5,000 feet.
I make little comment regarding balloons, and resultant lift as utilised
in this area of operations, apart from saying that I find the explanations
provided as part of this discussion sometimes interesting and at other
times quite confusing.
Regards,
Ian
P.S. I still believe that you only have to look at a helicopter on the
ground to determine that such a device obviously could not fly. (Although,
I have been up to 10,000 feet in such a machine.)
My understanding is that they probably use a similar method of operation
to that of a boomerang, namely, something known as gyroscopic precession.
(Or alternatively, that may be the phenomena that (supposedly) makes a
boomerang return.)
__________
73 de Ian, VK5QX
@ VK5LZ.#ADL.#SA.AUS.OC
22 July 2002
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