Spoilers vs Airbrakes
Richard Larsen
wbe...@trentu.ca
>What is the difference between spoilers and air brakes?
The way I understand it, spoilers serve primarily to ruin flow over the wing,
hastening one's sink rate, with no guarantees about reductions or limits on
airspeed. Airbrakes serve to spoil lift in a similar fashion, but will also
limit airspeed to a safe maximum. I remember reading in an introductory article
in SOARING that the pilot of a Mini Nimbus, if sufficiently looney, could
overfly his or her touchdown point at 1000 meters in the direction of landing,
push over past vertical with the trailing edge spoiler-flap combo fully open
and pull out in time to land on the original target, all without exceding safe
rough air limits. I wouldn't try that in the single surface spoiler equipped
1-26 we have at our club!
Wayne Bezner Kerr
Christopher Carlyle O'Callaghan
variety of ships were all a little exagerated. The
HP, PIK, 20. Mosquito and other ships with powerful
drag devices can do some mighty interesting aproaches.
But overflying the aim point, then diving vertically for
a perfect landing on that self-same spot is a little too
interesting. What these ships can do is nonetheless im-
pressive. In the 20A with its 55 degree flaps and spoilers,
you can fly a high final until your aimpoint just disappears
under the nose (pilot's point of view). Put everything out and
fly at 50 knots and you'll still get the ship down just
beyond the aim point.
I once watched an HP 18 clear the goalposts, land, and stop at
the opposing 10 yard line. It was a very low energy approach,
with a roundout, but no flair. Klunk!
r...@uihepa.hep.uiuc.edu
as "speed limiting airbrakes". After reading a few years ago (in either
Seibel's of Wolters book) about the speed limiting airbrakes on the Ka-6, and
how they were appreciated during a game they played, I thought I'd give it a try
in a 1-26E (which extend on the top and bottom of the wing). I knew the 1-26
airbrakes were not "speed limiting", but I had no plan to push the nose over
for the "game", as I didn't think it was needed.
The game consisted of throwing a roll of toilet paper out of the glider
at altitude, which would unroll to a long vertical streamer. Then, using the
glider, you "swoop" through the streamer to see how many pieces you could cut
it into.
I learned several things during that flight. The first is to make sure
your hat is secured, or you will lose it when cracking open the canopy. The
second is that without speed limiting dive brakes, you will not catch the
streamer unless it is in the middle of a thermal. I had full spoilers and a
slip, and the streamer drifted below me with my hat descending alongside it. I
never found the hat, although I spent several hours looking (the corn was tall
that time of year).
I also learned that I would rather stay high than to waste the
altitude, although it was interesting to try once, for the "visual effect".
Raymond L. Swartz Jr. (r...@uihepa.hep.uiuc.edu)
================================================================================
"Those who cannot remember history have a lot easier time thinking up solutions
to problems." -- Eric Zorn
================================================================================
I Johnston
: In article <1994Mar4.2...@blaze.trentu.ca>, <wbe...@TrentU.CA> wrote:
: >In article <CM5Dt...@nrtpa22.bnr.ca>, rla...@b4pph134.bnr.ca (Richard Larsen) writes:
: >>What is the difference between spoilers and air brakes?
: >
: >The way I understand it, spoilers serve primarily to ruin flow over the wing,
: >hastening one's sink rate, with no guarantees about reductions or limits on
: >airspeed. Airbrakes serve to spoil lift in a similar fashion, but will also
: What you're talking about here is a subset of airbrakes commonly
: called "speed limiting airbrakes." A spoiler extends only from the
: top of the wing. Airbrakes extend from the top and bottom.
That's not strictly true, I fear. For example...
K13's have top and bottom surface airbrakes but
Astir's have top surface only airbrakes
In both cases the brake surfaces move out of the wing. In contrast
Slingsby T21's have top surface only spoilers whereas
Fauvel AV36's (early ones) have bottom surface only spoilers (which also
work as flaps on takeoff) and
L-Spatz's (or at least one!) have top and bottom spoilers
defining "spoilers" as swinging from a flush to erect position. Not to
mention
Club Libelles which have trailing edge airbrakes.
In short, in the brief time I've been gliding I have seen done to wings
just about anything that could be done to increase the glide angle.
There was a time when airbrakes (= speed limiting airbrakes = dive
brakes) had, under JAR, to restrict vertical dive speed to less than VNE
but that requirement has been dropped. Another argument for exploring
clouds in wood!
Ian Johnston
PS Anyone out there remember which Vintage Glider(s) had a split rudder
as an airbrake: press right and yaw right (to a first approximation,
Mike), press left and yaw left, press both and the rudder opens up and
down you go