Typical glide angles with airbrakes deployed

Can anyone help with references for glide ratios for basic training gliders, Blanik, K13, Puchatek etc, with full brake or half brake deployed?

The internet is not very helpful for finding this information. A reference of 29 to 1 for a K6 -no brake and 7.1 full brake is about all I can find.

Given a Blanik at, say 28 to 1 no brake deployed, would around 8 to 1 full brake and say around 15 to one half brake sound about right?

Thanks in advance.

On 2/14/2011 1:15 PM, Ronald Locke wrote:
Can anyone help with references for glide ratios for basic training
gliders, Blanik, K13, Puchatek etc, with full brake or half brake
deployed?

The internet is not very helpful for finding this information. A
reference of 29 to 1 for a K6 -no brake and 7.1 full brake is about all
I can find.

Given a Blanik at, say 28 to 1 no brake deployed, would around 8 to 1
full brake and say around 15 to one half brake sound about right?

I have say, it makes curious: for what purpose do you want the data?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On Feb 14, 1:15*pm, Ronald Locke Ronald.Locke.
wrote:

Given a Blanik at, say 28 to 1 no brake deployed, would around 8 to 1
full brake and say around 15 to one half brake sound about right?

Thanks in advance.

Ronald Locke

If they're terminal velocity brakes then 0:1 (straight down) is
possible without exceeding Vne. Form drag is highly speed-dependent so
speed affects the answer a lot. The size of the brakes also matters so
it is unlikely you will get a consistent number across multiple types.
You'd also need to define "half brake" - halfway out, half the
additional drag, half the difference in glide angle, one brake in and
one out?

Given all the variables I suspect it's possible to fly a Blanik to
achieve the glide angles you describe. The tricky calculation would be
to estimate the best L with dive brakes deployed. I'm trying to
figure out the circumstances under which someone would try to achieve
best L with the brakes out rather than just retracting the brakes.

9B

Originally Posted by Andy[_10_]

On Feb 14, 1:15*pm, Ronald Locke Ronald.Locke.
wrote:

Given a Blanik at, say 28 to 1 no brake deployed, would around 8 to 1
full brake and say around 15 to one half brake sound about right?

Thanks in advance.

Ronald Locke

If they're terminal velocity brakes then 0:1 (straight down) is
possible without exceeding Vne. Form drag is highly speed-dependent so
speed affects the answer a lot. The size of the brakes also matters so
it is unlikely you will get a consistent number across multiple types.
You'd also need to define "half brake" - halfway out, half the
additional drag, half the difference in glide angle, one brake in and
one out?

Given all the variables I suspect it's possible to fly a Blanik to
achieve the glide angles you describe. The tricky calculation would be
to estimate the best L with dive brakes deployed. I'm trying to
figure out the circumstances under which someone would try to achieve
best L with the brakes out rather than just retracting the brakes.

9B

My query is simply related to the different approach angles on final glide to the aiming point during final approach for landing. Obviously different gliders will have different glide ratios for full brake and half brake approaches. Hope this explanation clears up any misunderstanding.

On Feb 15, 12:27*am, Andy wrote:

I'm trying to
figure out the circumstances under which someone would try to achieve
best L with the brakes out rather than just retracting the brakes.

Well I know of one case for an L13. The pilot didn't realize the
brakes were open so closing them was never on the list of things to
try. (No it wasn't me).

Agree that the OP needs to better define what data is needed, but it
still may not be available. Somewhere in my logs I have data for max
achieved sink rates for the ASW-19 and ASW-28. I did tests with full
brakes and with full brakes and full rudder slips. It's amazing how
quick you can get a glider to come down if you really want to. I found
the feeling of hanging on the brakes at 80kts to be quite
uncomfortable though and never tried speeds much higher than that.

What is more useful to know is how to get the max descent angle while
still maintaining minimum safe approach speed. For the 19 and 28,
full brakes and full rudder slip is very effective. Try it at
altitude first to get used to controlling speed with only pitch
attitude as the indicated airspeed may be zero.

Andy

On Feb 15, 10:15*am, Ronald Locke Ronald.Locke.
wrote:
Can anyone help with references for glide ratios for basic training
gliders, Blanik, K13, Puchatek etc, with full brake or half brake
deployed?

The internet is not very helpful for finding this information. A
reference of 29 to 1 for a K6 -no brake and 7.1 full brake is about all
I can find.

Given a Blanik at, say 28 to 1 no brake deployed, would around 8 to 1
full brake and say around 15 to one half brake sound about right?

I believe there is a legal requirement to be no flatter than 7:1 with
full brake at typical approach speed.

At one time there was a requirement to be able to do a 45º descent
without exceeding Vne (or was it rough air?)

The Blanik is much older than the requirement, but would easily meet
it. I recall when I was a beginning pilot one instructor had me do a
near vertical descent in the Blanik from around 8000 ft. If I recall
correctly, it topped out at about 115 knots (well below Vne). That's a
0:1 glide angle.

There's also the question of flaps. We practiced landing approaches
with full brake and full flap at maximum flap speed (60 knots IIRC).
They were really quite steep, perhaps around 2:1 (30º) or even more.
When you leveled out the speed washed off quickly so it was actually
quite practical.

At 09:41 15 February 2011, Ronald Locke wrote:

'Andy[_10_ Wrote:
;762804']On Feb 14, 1:15*pm, Ronald Locke Ronald.Locke.
wrote:
-
Given a Blanik at, say 28 to 1 no brake deployed, would around 8 to 1
full brake and say around 15 to one half brake sound about right?

Thanks in advance.

Ronald Locke-

If they're terminal velocity brakes then 0:1 (straight down) is
possible without exceeding Vne. Form drag is highly speed-dependent so
speed affects the answer a lot. The size of the brakes also matters so
it is unlikely you will get a consistent number across multiple types.
You'd also need to define "half brake" - halfway out, half the
additional drag, half the difference in glide angle, one brake in and
one out?

Given all the variables I suspect it's possible to fly a Blanik to
achieve the glide angles you describe. The tricky calculation would be
to estimate the best L with dive brakes deployed. I'm trying to
figure out the circumstances under which someone would try to achieve
best L with the brakes out rather than just retracting the brakes.

9B

My query is simply related to the different approach angles on final
glide to the aiming point during final approach for landing. Obviously
different gliders will have different glide ratios for full brake and
half brake approaches. Hope this explanation clears up any
misunderstanding.




--
Ronald Locke


So do you want to teach gliding by numbers?? Using airbrakes on finals
involves a feedback loop - Aiming point going up the view? Close the
brakes a bit. Aiming point disappearing under the nose? open the brakes
some more. It isn't rocket science, nor can you define how open or
closed the brakes need to be at a specific point.

Form drag is highly speed-dependent so
speed affects the answer a lot.

The Pegasus flight manual claims a glide angle of 5 with the airbrakes
fully extended and an indicated speed of 49 knots.

Given the history of the Pegasus design the ASW19 is probably fairly
similar.

[90 km/h = 49 knots is the minimum approach speed - personally I add a
few!]

James Thomson wrote:
Form drag is highly speed-dependent so
speed affects the answer a lot.

The Pegasus flight manual claims a glide angle of 5 with the airbrakes
fully extended and an indicated speed of 49 knots.

Given the history of the Pegasus design the ASW19 is probably fairly
similar.


The Pegasus flight behavior could not be more different (and far
better) than the ASW19.

[90 km/h = 49 knots is the minimum approach speed - personally I add a
few!]


--

Michel TALON