S-turns on final

On Thursday, February 16, 2017 at 5:17:58 PM UTC-8, Steve Leonard wrote:
On Thursday, February 16, 2017 at 4:17:08 PM UTC-6, Charlie M. (UH & 002 owner/pilot) wrote:
While a slip is considered aerodynamically coordinated, not sure ...

Crabbing is coordinated. Slipping is not. By any book, stretch of the imagination, or even alternate fact. It may be aerodynaimcally "balanced", as there is no steady state pitch, roll, or yaw RATE. But, not coordinated..

Thanks, Steve. I was getting twitchy on this one (but not pitchy). But hey,
Charlie M. wasn't the only one to say a slip was 'coordinated' in this thread.
Youch.

A fair range of opinions, and fewer with some slipping experience at altitude that then allows application at lower altitudes with familiarity and confidence.
I find it pretty common that pilots will lower their nose "a bunch" when slipping and then getting down to the chosen angle and unslipping to find they have ~ten more knots than they wanted.

Pretty soon it will be the "Silly Season". This sounds like a good topic for spring brush ups with a CFI - doing slips in 32:1. Balanced slips ( on a track), turning slips, and doing either with no speed change on entry and recovery. Can you tell your CFI what descent rate you can manufacture with your slip in your ship in calm air? It's a helpful data point, rather than conjecture.

My alternative aerodynamics fact is to be happy with pilots who slip, crab, S-turn, buttonhook, angle in or out, min sink loiter, full-spoiler parasitic drag plummet or even make a perfectly coordinated circle to address spacing and slope to satisfy the situation in a pattern. If it is done well, there are lots of ways to 'approach'. Adaptability is a good thing.

Best,
Cindy B

Dammit, Steve and Cindy! You should never interject knowledge,
experience, and logic into a discussion on RAS!

On 2/16/2017 8:17 PM, CindyB wrote:
On Thursday, February 16, 2017 at 5:17:58 PM UTC-8, Steve Leonard wrote:
On Thursday, February 16, 2017 at 4:17:08 PM UTC-6, Charlie M. (UH & 002 owner/pilot) wrote:
While a slip is considered aerodynamically coordinated, not sure ...
Crabbing is coordinated. Slipping is not. By any book, stretch of the imagination, or even alternate fact. It may be aerodynaimcally "balanced", as there is no steady state pitch, roll, or yaw RATE. But, not coordinated.
Thanks, Steve. I was getting twitchy on this one (but not pitchy). But hey,
Charlie M. wasn't the only one to say a slip was 'coordinated' in this thread.
Youch.

A fair range of opinions, and fewer with some slipping experience at altitude that then allows application at lower altitudes with familiarity and confidence.
I find it pretty common that pilots will lower their nose "a bunch" when slipping and then getting down to the chosen angle and unslipping to find they have ~ten more knots than they wanted.

Pretty soon it will be the "Silly Season". This sounds like a good topic for spring brush ups with a CFI - doing slips in 32:1. Balanced slips ( on a track), turning slips, and doing either with no speed change on entry and recovery. Can you tell your CFI what descent rate you can manufacture with your slip in your ship in calm air? It's a helpful data point, rather than conjecture.

My alternative aerodynamics fact is to be happy with pilots who slip, crab, S-turn, buttonhook, angle in or out, min sink loiter, full-spoiler parasitic drag plummet or even make a perfectly coordinated circle to address spacing and slope to satisfy the situation in a pattern. If it is done well, there are lots of ways to 'approach'. Adaptability is a good thing.

Best,
Cindy B

--
Dan, 5J

Time was when we used to teach S turns, both for final approach and
launch failures, and this was fine in slow, wooden open cockpit gliders.
We also taught slipping. Pitching nose down 10 or even 20 degrees in
a T21 when side slipping was not a problem, doing the same in a
modern glass glider certainly is, especially when you stop the slip, the
glider will accelerate rapidly, unlike the T21 which did not understand
acceleration.
The difference is between what we teach, which has very little do do
with what is possible to do. Modern teaching tends towards getting the
circuit right so that the "emergency" procedures are not needed.
Modern airbrakes tend to be so good that even if you get it wrong they
are all that is needed.
S turns and sideslips are perfectly valid solutions, just not something
you want to teach a low hours pilot, concentrating on getting the
circuit right and effective use of airbrake is much safer.
I still fly a T21 and sideslip a lot. I sideslip very little in glass ships
as
proper use of airbrake, at the correct speed, is much more effective.

I think the main point against S turns is that they will not actually lose that much altitude -- unless you turn 90 degrees or more. If you are so high that full flap spoiler and slip are not going to work, then try to do S turns, but get nervous about it and don't head the nose more than 45 degrees away from the runway, you're just not going to get down that fast, and the runway will still slide along below you.

Then there is always the Marty Eiler special: Full spoiler, point the nose at the ground, go VNE to 5 feet off the deck. Even accounting for the float in ground effect, it uses up gobs of altitude.

John Cochrane.

Then there is always the Marty Eiler special: Full spoiler, point the nose at the ground, go VNE to 5 feet off the deck. Even accounting for the float in ground effect, it uses up gobs of altitude.

John Cochrane.

Any video links to this technique? Heard of it before, don't doubt it works, just like to see it. No, I'm not going to teach it to myself.

At 19:16 17 February 2017, wrote:
Then there is always the Marty Eiler special: Full spoiler, point
the nose
at the ground, go VNE to 5 feet off the deck. Even accounting
for the float
in ground effect, it uses up gobs of altitude.

The Vne approach is an interesting idea that I won't be trying
without 6000 feet of runway available! How do you get rid of
all that speed 5 feet off the ground? It must produce an
incredibly long float?

Here in France "S" bends on approach are the standard
method taught for microlights, but they all tend to be a lot
dragger than even the poorest glider. Seems to me to be a
valid idea (like the side slip) assuming it's done correctly; any
method that doesn't involve flying through the far hedge/wall
must be good.

On Friday, February 17, 2017 at 3:45:08 PM UTC-6, Dave Walsh wrote:
At 19:16 17 February 2017, wrote:
Then there is always the Marty Eiler special: Full spoiler, point
the nose
at the ground, go VNE to 5 feet off the deck. Even accounting
for the float
in ground effect, it uses up gobs of altitude.

The Vne approach is an interesting idea that I won't be trying
without 6000 feet of runway available! How do you get rid of
all that speed 5 feet off the ground? It must produce an
incredibly long float?

When I took the glider acro course at Estrella back in the early 90s, one of the "party tricks" was to dive at Vne to the deck on entry to downwind, then fly the whole pattern in ground effect - you had to climb to turn base and final - aiming to be near the approach end of the runway, 10 ft over the desert, at about 60 knots. Then you just cracked the spoilers and landed.. Interesting, to say the least!

It did teach you that once in ground effect, a little speed would take you a LONG WAY.

Helps to have an airport out in the middle of nowhere (then); at my local field there would be too much dodging of houses, water tower, trucks on the interstate, etc..! (although I have tried it in Condor and it still works).

Kirk
66

wrote on 2/17/2017 11:16 AM:
Then there is always the Marty Eiler special: Full spoiler, point the nose at the ground, go VNE to 5 feet off the deck. Even accounting for the float in ground effect, it uses up gobs of altitude.

John Cochrane.

Any video links to this technique? Heard of it before, don't doubt it works, just like to see it. No, I'm not going to teach it to myself.

The technique is simple and easy to learn. Just don't start out with the
extreme version John related! Basically, you are just increasing the
rate of energy/altitude loss by 2 or 3 times normal by using full
spoiler at high speeds. Try this for starters:

-enter the pattern at least 1000' AGL
-fly the pattern all the way until after you've turned final...NO
spoilers or sideslip
-continue down final without spoilers or side slip until it seems you
are almost too high to get down to your aim point with full spoilers
-open the spoilers fully, point the nose down until you are going 80-90
knots (but NO MORE than the max allowed speed for your landing
configuration - flap setting is the usual thing limiting the allowed speed)
-When the angle to your aim point looks about right for a half-spoiler
approach, pull the nose up gradually to maintain that angle
-when your speed drops to the desired speed on final, retract the
spoilers to one-half
-proceed with a normal landing

Use the technique a few times, and it won't seem very extreme at all.
The altitude loss is very rapid with full spoiler, gear down, and high
speeds, and it's very effective at dumping excess altitude.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "A Guide to Self-Launching Sailplane Operation"

https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf

On Sunday, 19 February 2017 06:35:49 UTC+2, Eric Greenwell wrote:
The technique is simple and easy to learn. Just don't start out with the
extreme version John related! Basically, you are just increasing the
rate of energy/altitude loss by 2 or 3 times normal by using full
spoiler at high speeds. Try this for starters:

-enter the pattern at least 1000' AGL
-fly the pattern all the way until after you've turned final...NO
spoilers or sideslip
-continue down final without spoilers or side slip until it seems you
are almost too high to get down to your aim point with full spoilers
-open the spoilers fully, point the nose down until you are going 80-90
knots (but NO MORE than the max allowed speed for your landing
configuration - flap setting is the usual thing limiting the allowed speed)
-When the angle to your aim point looks about right for a half-spoiler
approach, pull the nose up gradually to maintain that angle
-when your speed drops to the desired speed on final, retract the
spoilers to one-half
-proceed with a normal landing

Use the technique a few times, and it won't seem very extreme at all.
The altitude loss is very rapid with full spoiler, gear down, and high
speeds, and it's very effective at dumping excess altitude.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "A Guide to Self-Launching Sailplane Operation"

https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf


The irony of reading this, and then discovering link to something called "soaringsafety" below.

On Saturday, February 18, 2017 at 8:35:49 PM UTC-8, Eric Greenwell wrote:
wrote on 2/17/2017 11:16 AM:
Then there is always the Marty Eiler special: Full spoiler, point the nose at the ground, go VNE to 5 feet off the deck. Even accounting for the float in ground effect, it uses up gobs of altitude.

John Cochrane.

Any video links to this technique? Heard of it before, don't doubt it works, just like to see it. No, I'm not going to teach it to myself.

The technique is simple and easy to learn. Just don't start out with the
extreme version John related! Basically, you are just increasing the
rate of energy/altitude loss by 2 or 3 times normal by using full
spoiler at high speeds. Try this for starters:

-enter the pattern at least 1000' AGL
-fly the pattern all the way until after you've turned final...NO
spoilers or sideslip
-continue down final without spoilers or side slip until it seems you
are almost too high to get down to your aim point with full spoilers
-open the spoilers fully, point the nose down until you are going 80-90
knots (but NO MORE than the max allowed speed for your landing
configuration - flap setting is the usual thing limiting the allowed speed)
-When the angle to your aim point looks about right for a half-spoiler
approach, pull the nose up gradually to maintain that angle
-when your speed drops to the desired speed on final, retract the
spoilers to one-half
-proceed with a normal landing

Use the technique a few times, and it won't seem very extreme at all.
The altitude loss is very rapid with full spoiler, gear down, and high
speeds, and it's very effective at dumping excess altitude.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "A Guide to Self-Launching Sailplane Operation"

https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf

The "fast and dirty" approach works better, the dirtier you can get. On a flapped glider, full landing flaps and spoilers, point the nose down and you pick up some speed, but you lose energy much faster.

There are landing sites where this makes a lot of sense (including the one at which I fly). One reason is you are flying through the gradient and boundary layer turbulence at well over stall speed and can withstand a 40 knot gradient without stalling.

On my ASH26, this works really well. On the Duo Discus I owned and flew at the same site, not so well - wasn't dirty enough in landing configuration to lose the energy.