G'day,
The place for Fergus to look for airbrake inspiration is the gliding
movement. All but one make of glider have airbrakes with the
Schempp-Hirth type being the most common. This type has perpendicular
plates extending from the upper surface, and sometimes both upper and
lower surfaces of the wing just behind the spar. They create drag,
which reduces speed, but also spoil the wing profile in that region and
hence reduce lift. Their main advantage compared with trailing edge
brakes is that when they are retracted the lift is restored and, of
course, the drag is reduced.
A variation on this theme consists of flat plates which lie flat in the
upper surface of the wing and are hinged at the leading edge. They work
well and are not as heavy to operate as may be expected.
Trailing edge brakes, linked to the flaps, work well, but have the
disadvantage that when retracted the drag is reduced, but so is the lift
generated by the wing. This can dump the aircraft on the runway fence.
I agree that expert knowledge is required to design brakes which are
strong enough, produce enough drag and do not spoil too much of the
wing's lifting surface.
Happy landings,
John Anselmi
Fergus Kyle wrote:
>Cheers, Please excuse the previous message with dive brakes in the title, as
>after I typed the subject, some fool hit the Send button.
>
> The subject may seem flippant, but I have always had the advantage
>of being able to vary the descent rate during an emergency (or practice for
>same) by changing the lift/drag component, courtesy of a number of
>forward-looking designers. from the Vampire wing brakes, thru F86 fuselage
>panels to the TriStar magnificent floating liftdump panels, there has always
>been an opportunity to control excessive speed/height in an emergency.
>Knowing this, the mental processes are immensely easier to
>control and execute. This is the culmination of just under 35 minutes of
>unplanned glider time (spread over 40 years and several events). None of
>this makes me an expert, but I am a consumer......
> Having planned in Graham Clarke's landing radar, and Frantz's
>immaculate AoA iundicator, there is one more device which would set my mind
>at ease. It is a "dive brake" (spoiler, liftdump, speed brake) system.
>While it may be very simple in operation, it is most sensitive in control
>and security aspects. It occurred to me that I am not qualified to
>experiment with the design - although I would be happy to air-test the
>prototype at my own risk.
> Naturally a number of variations come to mind - the Sabre panels
>would require heavy buttressing, the Vampire trailing edge plates excessive
>wing mods, the Hunter belly barrel much the same, and the advertised
>vertical wing plates expensive revision. However, there are simple
>forward-hinged belly panels which might be activated by Nigel Charles'
>cooling panel rollers against a spring and there is the very sensitive
>throat of the flaps. There may be other alternatives, but these two require
>the lesser mechanism and may easily be incorporated retroactively.
> The trick is to design a system which avoids jamming,
>inadvertent extension and rapid, secure retraction. It must be faultless for
>obvious reasons. It must also not interfere with the proper functioning of
>flaps, lift surfaces or flight controls (blanking the tail is an example).
> All of that is outside my bailliewick by several hundred metres,
>so that Slap! is the sound of a gauntlet hitting the Drafting Table - a
>challenge to contribute what I think is a very useful device to an already
>amazing machine.
> Will anyone pick up my glove?
>Happy (and successful) landings,
>Ferg Kyle
>A064
>
>
--
John Anselmi,
20 Jones St.,
Stawell,
Victoria 3380,
Australia
Ph. 03 5358 2713
Fax 03 5358 2713
e-mail janselmi@netconnect.com.au
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