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"!

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

Hi All, just to be pedantic... If you only partially deploy any device,
it has a different aerodynamic characteristic.....

The first stage of Flaps gives an increase in Lift.
Second Stage of Flaps gives Lift And Drag.
Final Stage of Flaps gives Huge amounts of Drag, without any more Lift.

A quick look at your 'Barn Doors' will give you a reasonable idea of
what is likely to happen... I cannot imagine that vertical airbrakes
would ever give an increase in lift, even if only just cracked open a
millimeter or so.

Pilot Pete


At 20:14 16 May 2008, Andy wrote:
On May 16, 8:56=A0am, 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

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

Bob K.

On May 16, 10:43 am, Bob Kuykendall wrote:
Launch Robert Mudd post on glidepath control nomenclature on my mark:
three... two... one...

Bob K.

LOL!

I set Robert up once calling the DG's divebrakes spoilers, after
seeing the term in my DG's manual. The response was as expected. I
then had the pleasure to show him the term in the manual. He told me
he would have to have a talk with Herr Dirks about this the next time
he saw him.

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