Spoilers or Airbrakes - Whats in a name?

I spotted the following statement in Wikipedia.

http://en.wikipedia.org/wiki/Spoiler_%28aeronautics%29
http://en.wikipedia.org/wiki/Air_brake_%28aircraft%29

"Spoilers differ from airbrakes in that airbrakes are designed to
increase drag while making little change to lift, while spoilers
greatly reduce lift while making only a moderate increase in drag."

I had always used the terms spoilers and airbrakes interchangeable.
This statement makes it seem like they are not. So what does the
typical sailplane have? Spoilers or airbrakes?

- John "67" DeRosa

On May 16, 9:31 am, ContestID67 wrote:
I spotted the following statement in Wikipedia.

http://en.wikipedia.org/wiki/Spoiler...%28aircraft%29

"Spoilers differ from airbrakes in that airbrakes are designed to
increase drag while making little change to lift, while spoilers
greatly reduce lift while making only a moderate increase in drag."

I had always used the terms spoilers and airbrakes interchangeable.
This statement makes it seem like they are not. So what does the
typical sailplane have? Spoilers or airbrakes?

- John "67" DeRosa

Oh boy!

According the the original Glasser-Dirks owner's manual for a DG100G,
the sailplane has "spoilers".

On May 16, 8:56*am, Mike wrote:
On May 16, 9:31 am, ContestID67 wrote:

I spotted the following statement in Wikipedia.

http://en.wikipedia.org/wiki/Spoiler...ttp://en.wikip...

"Spoilers differ from airbrakes in that airbrakes are designed to
increase drag while making little change to lift, while spoilers
greatly reduce lift while making only a moderate increase in drag."

I had always used the terms spoilers and airbrakes interchangeable.
This statement makes it seem like they are not. *So what does the
typical sailplane have? *Spoilers or airbrakes?

- John "67" DeRosa

Oh boy!

According the the original Glasser-Dirks owner's manual for a DG100G,
the sailplane has "spoilers".

Don't forget "Dive Brakes"!

Launch Robert Mudd post on glidepath control nomenclature on my mark:
three... two... one...

Bob K.

On May 16, 8:31*am, ContestID67 wrote:
I am not an aerodynamicist and therefore I could be wrong (and
probably am), but I have always thought of airbrakes being terminal
devices. That is, they will limit speed, such as in a dive or on
glidepath. My old BG-12 had terminal flaps and with them all the way
out, you could not go more than about 60 kts no matter where the nose
was pointed. It has been 25 years since I flew one, but if I recall
correctly, doesn't the 1-34 also has terminal dive brakes.

By extrapolation therefore, spoilers are speed devices which spoil
lift and slow the aircraft down but do not limit dive speed.
Airbrakes will limit speed, and that is why you have to be so careful
not to open them when you are too fast.

If I am wrong, so what? I am an idiot anyway.

I spotted the following statement in Wikipedia.

http://en.wikipedia.org/wiki/Spoiler...%28aircraft%29

"Spoilers differ from airbrakes in that airbrakes are designed to
increase drag while making little change to lift, while spoilers
greatly reduce lift while making only a moderate increase in drag."

I had always used the terms spoilers and airbrakes interchangeable.
This statement makes it seem like they are not. *So what does the
typical sailplane have? *Spoilers or airbrakes?

- John "67" DeRosa

"ContestID67" wrote in message
...
I spotted the following statement in Wikipedia.

http://en.wikipedia.org/wiki/Spoiler_%28aeronautics%29
http://en.wikipedia.org/wiki/Air_brake_%28aircraft%29

"Spoilers differ from airbrakes in that airbrakes are designed to
increase drag while making little change to lift, while spoilers
greatly reduce lift while making only a moderate increase in drag."

I had always used the terms spoilers and airbrakes interchangeable.
This statement makes it seem like they are not. So what does the
typical sailplane have? Spoilers or airbrakes?

- John "67" DeRosa

Both common sense and aerodynamics say that if the G-meter says 1.0 then
lift = weight. Applying 'spoilers' doesn't change that. Spoilers do not
'reduce lift' if the G-meter continues to say 1.0 - they increase drag.
The general formula is lift = weight x G

The steady state effect of spoilers, airbrakes, dive brakes, and even flaps
all do the same thing - they increase drag. I carefully included the term
'steady state' to exclude brief transient effects that may occur as these
devices are deployed.

If they all do the same thing, why the different terms? I think it goes to
the intent of the pilot. If a pilot wishes to limit airspeed in a steep
dive, whatever device the aircraft is equipped with is used as a 'dive
brake'. If the pilot desires to reduce airspeed without raising the nose
and zooming, the term becomes 'airbrakes'. If the intent is to steepen a
glide without increasing airspeed, 'spoilers' is an appropriate term.

The different terms may also have arisen due to pilots making erroneous snap
judgements about the effect of drag control devices based on the transient
effects. Flaps applied suddenly make the aircraft surge upward so they
'increase lift'. Spoilers make the aircraft drop so they 'decrease lift'.
These transients are very brief and have little effect on the aircraft
trajectory. Thinking "increase drag" is more accurate and will result in
better flying skills. All these terms describe that.

Bill Daniels

snip

The steady state effect of spoilers, airbrakes, dive brakes, and even flaps
all do the same thing - they increase drag. * I carefully included the term
'steady state' to exclude brief transient effects that may occur as these
devices are deployed.

snip

You are correct in steady state the all pretty much do the same thing.
The difference in terms comes in the non steady state effects and how
they produce drag.

Take a glider at approach speed about 5 feet off the runway in steady
state (at least for a glider) level flight with all drag devices
retracted..

If you deploy the spoilers and do not change attitude the glider will
drop onto runway, speed will change very little.

if you deploy airbrakes the glider will slow and settle to the runway.

If you deploy flaps the glider will balloon up.


Brian CFIIG/ASEL

"Spoilers differ from airbrakes in that airbrakes are designed to increase
drag while making little change to lift, while spoilers
greatly reduce lift while making only a moderate increase in drag."
what does the typical sailplane have? Spoilers or airbrakes?
- John "67" DeRosa

A spoiler would be a flap on the top of the wing front hinged forward of the
COP (centre-of-pressure)
such that the when it opens at the free end the airflow across the wing is
spoiled (and hence the lifting action decreased) but not
directly blocked (or braked).

A brake would be a paddle that operates at a right angle to the airflow and
directly blocks the airflow - effectively slowing the movement
of the wing relative to the airflow.

Sort of visualise the difference between a wing (spoiler) on a racing car
creating downpressure and throwing a dirty great parachute out the back to
assist braking?

Jim.

On May 16, 8:56*am, Mike wrote:
According the the original Glasser-Dirks owner's manual for a DG100G,
the sailplane has "spoilers".

I suspect that the original owner's manual is written in German and
that the word "spoilers" is not mentioned. I don't have my
Schleicher manual here but I think they call them Klappen. Not being
picky for the sake of it, but pointing out that "spoiler" was probably
the word chosen by the translator not necessarily by the manufacturer.

Andy

On May 16, 12:59*pm, "jonathan"
PLEASE.REMOVE.THIS.PREFIX.jonathan.go...@ntlworld .com wrote:

Sort of visualise the difference between a wing (spoiler) on a racing car
creating downpressure and throwing a dirty great parachute out the back to
assist braking?

Jim.

Oh, boy - where to begin?

First: In the automobile world, the difference between a "spoiler"
and a "wing" is very important. A wing is a device that allows air to
flow over both top and bottom surfaces, and is typically used to
create down-force (just like the horizontal tail on your glider). A
spoiler actually has the leading edge fixed to the auto in such a way
that air flows over the top surface only. It, too, creates down-
force, but it also creates a lot more drag than a wing.

Second: Technically "spoilers" are supposed to be there to change the
airflow over the _wing_. By "spoiling" the airflow such that it
cannot follow the curves of the airfoil, it changes the glide-path and/
or drag of the aircraft. "Airbrakes" are technically a device
_anywhere_ on the aircraft that increases drag.

Now here's where most people fall down: They want to categorize every
device as one or the other type. But the plain truth is that most
devices on sailplanes do BOTH.

Have fun debating spoilers and airbrakes! I don't think this one will
ever be fully settled...

--Noel