S-turns on final

On Wednesday, February 15, 2017 at 7:10:55 PM UTC-8, Bruce Hoult wrote:

It's good to have as many techniques in your arsenal as possible.

Even NASA does (did) S-turns in the circuit.


Gosh, I would hesitate to call the roll reversals "S-turns"

Read below article, very interesting.

https://www.nasa.gov/centers/johnson...pgs226-241.pdf

Le jeudi 16 février 2017 08:38:18 UTC+1, Jonathan St. Cloud a écritÂ*:
On Wednesday, February 15, 2017 at 7:10:55 PM UTC-8, Bruce Hoult wrote:

It's good to have as many techniques in your arsenal as possible.

Even NASA does (did) S-turns in the circuit.


Gosh, I would hesitate to call the roll reversals "S-turns"

Read below article, very interesting.

https://www.nasa.gov/centers/johnson...gs226-241..pdf

Great article.

On Wed, 15 Feb 2017 23:38:17 -0800, Jonathan St. Cloud wrote:

On Wednesday, February 15, 2017 at 7:10:55 PM UTC-8, Bruce Hoult wrote:

It's good to have as many techniques in your arsenal as possible.

Even NASA does (did) S-turns in the circuit.


Gosh, I would hesitate to call the roll reversals "S-turns"

Read below article, very interesting.

https://www.nasa.gov/centers/johnson...in_Wings-ch4d-
pgs226-241.pdf

Thanks for posting that. However, whether you consider those S-turns or
not, they were certainly not in the circuit (the shuttle flew straight-in
patterns IIRC), rather they were en route to destination.

BTW, somewhere I have an ancient shuttle landing simulator (for Win 95)
that was interesting to experiment with. Does anybody know if a Linux
version is available? There should be a port - NASA's original version
ran on a Unix-based laptop that got sat on the Shuttle glare shield
during command pilot training. The PC sim started you at 350kts and
55,000ft and no matter what you did with it, you were on the ground after
2.5 - 3 minutes.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

With the very high degree of spoiler effectiveness on most gliders, if "said pilot" is regularly "forced" to slip or S-turn in order to make their intended touch down point, there is probably something else wrong "upstream" in said pilots landing pattern decision making process. Also, the majority of sailplane landing patterns appear to me to be rather high (again, IMO).

I commented here only to state (I'll say it again now) that slipping a high performance glider is almost useless (IMO). It requires such an aggressive slip angle (in order to result in any measurable increase in descent rate) that it is uncomfortable (and unnecessary) for me, personally (IMO). I'm surprised to hear otherwise, but that certainly doesn't change my opinion or practices. Perhaps their fuselages are the "slab sided" ASG29 version ;-). Perhaps I am a poor pilot. Perhaps this is a skill I need to work on. Oh well, for now, I don't slip unless absolutely necessary. I prefer docile S turns, but can only really recall one time I have done this. I have never needed a slip in my ASG29 or (ex) Lak17a (in the execution of many, many land-outs)

That said, slips are an important skill in glider pilot training. To need to use them on a regular basis (or even rare basis) is perhaps indicative of some other concerns or areas of potential landing pattern/planning skill improvement. The need to slip or S-turn means that to that point in the approach, the pilot has misjudged the approach extremely high in terms of altitude and/or total energy, requiring a last resort maneuver (slip or S-turn) in order to bleed it off. Desperate. Poor planning. Poor energy management. This is how people get hurt.

For those who have not yet flown higher performance glider, when you do, I would strongly suggest practicing slips at high altitude before trying (or being forced to exectute) a true, aggressive (full rudder) slip, with full spoilers (and perhaps 25-30% water remaining, simulating real world stress, for example) and at low (minimum possible) final approach speed while at very low altitude into a short land-out field (perhaps with tall trees on both ends and in some wind).

I strongly prefer striving to execute consistent, well managed, stable approaches without big transitions from slip to non slip (close to the ground, at the last moment), especially when flying in a high performance glider (in which I feel slips are ineffective). Gliders have outstanding glideslope control with spoilers (and perhaps flaps). My goal is to fly the entire approach (from midfield downwind to near touchdown) with a set pitch, set flap setting, set speed and set spoiler setting (33%, I have a mark I use). The exact same approach every time. This takes significant practice. I prefer focusing on precisely controlling my energy (not too fast, not too high, good base turn decision) as early as possible in every approach. That is the critical moment in the approach for me, not the final leg. Everything flows from this mindset of setting the approach up with great precision and getting stable early.. If necessary, I prefer managing my glideslope with spoilers (only) and in a very smooth, controlable manner. If I must use them, I try and minimize adjustments rather than making constant adjustments (unstable). If I ultimately need to S turn, or slip, it means I have really (enormously) misjudged the approach and/or the landing area (perhaps the height of the trees on the approach end, wires I didn't see, or the usable length of the field (perhaps identifying a rock or a post on final)). If I started experiencing gross errors in general landing pattern decisions regularly (landouts or normal landings at an airport), requiring slips or S-turns to make the touchdown point (and stress), I would schedule some meaningful time with a respected flight instructor and sort myself out.

Perhaps I'll be having a talk with one about slips in my 29 in fact. So, thanks for this discussion.

Sean
7T

Sorry Sean,

if you think that slips are not effective in high performance ships, you should get some training.

Not that I think that they are much needed, but you should know how to comfortably perform them down to 30 ft off the ground.


In the lasr 35 years of flying all types of gliders, it never came to my mind to use S-turns. But I had to use slips some time.

Bert

Ventus cM
which slips nicely...

On Thursday, February 16, 2017 at 8:26:51 AM UTC-8, Sean Fidler wrote:
With the very high degree of spoiler effectiveness on most gliders, if "said pilot" is regularly "forced" to slip or S-turn in order to make their intended touch down point, there is probably something else wrong "upstream" in said pilots landing pattern decision making process. Also, the majority of sailplane landing patterns appear to me to be rather high (again, IMO)..

I commented here only to state (I'll say it again now) that slipping a high performance glider is almost useless (IMO). It requires such an aggressive slip angle (in order to result in any measurable increase in descent rate) that it is uncomfortable (and unnecessary) for me, personally (IMO). I'm surprised to hear otherwise, but that certainly doesn't change my opinion or practices. Perhaps their fuselages are the "slab sided" ASG29 version ;-). Perhaps I am a poor pilot. Perhaps this is a skill I need to work on. Oh well, for now, I don't slip unless absolutely necessary. I prefer docile S turns, but can only really recall one time I have done this. I have never needed a slip in my ASG29 or (ex) Lak17a (in the execution of many, many land-outs)

That said, slips are an important skill in glider pilot training. To need to use them on a regular basis (or even rare basis) is perhaps indicative of some other concerns or areas of potential landing pattern/planning skill improvement. The need to slip or S-turn means that to that point in the approach, the pilot has misjudged the approach extremely high in terms of altitude and/or total energy, requiring a last resort maneuver (slip or S-turn) in order to bleed it off. Desperate. Poor planning. Poor energy management. This is how people get hurt.

For those who have not yet flown higher performance glider, when you do, I would strongly suggest practicing slips at high altitude before trying (or being forced to exectute) a true, aggressive (full rudder) slip, with full spoilers (and perhaps 25-30% water remaining, simulating real world stress, for example) and at low (minimum possible) final approach speed while at very low altitude into a short land-out field (perhaps with tall trees on both ends and in some wind).

I strongly prefer striving to execute consistent, well managed, stable approaches without big transitions from slip to non slip (close to the ground, at the last moment), especially when flying in a high performance glider (in which I feel slips are ineffective). Gliders have outstanding glideslope control with spoilers (and perhaps flaps). My goal is to fly the entire approach (from midfield downwind to near touchdown) with a set pitch, set flap setting, set speed and set spoiler setting (33%, I have a mark I use).. The exact same approach every time. This takes significant practice. I prefer focusing on precisely controlling my energy (not too fast, not too high, good base turn decision) as early as possible in every approach. That is the critical moment in the approach for me, not the final leg. Everything flows from this mindset of setting the approach up with great precision and getting stable early.. If necessary, I prefer managing my glideslope with spoilers (only) and in a very smooth, controlable manner. If I must use them, I try and minimize adjustments rather than making constant adjustments (unstable). If I ultimately need to S turn, or slip, it means I have really (enormously) misjudged the approach and/or the landing area (perhaps the height of the trees on the approach end, wires I didn't see, or the usable length of the field (perhaps identifying a rock or a post on final)). If I started experiencing gross errors in general landing pattern decisions regularly (landouts or normal landings at an airport), requiring slips or S-turns to make the touchdown point (and stress), I would schedule some meaningful time with a respected flight instructor and sort myself out.

Perhaps I'll be having a talk with one about slips in my 29 in fact. So, thanks for this discussion.

Sean
7T

How do people feel about aggressive slips with partial water? I had an experience where exiting the slip and leveling off on approach was more difficult than expected due to water shifting to the downhill portion of both wings.

Matt

Eh, I get twitchy getting uncoordinated anywhere low with partial water. While a slip is considered aerodynamically coordinated, not sure water in the wings would agree.

On Thursday, February 16, 2017 at 4:17:08 PM UTC-6, Charlie M. (UH & 002 owner/pilot) wrote:
Eh, I get twitchy getting uncoordinated anywhere low with partial water. While a slip is considered aerodynamically coordinated, not sure water in the wings would agree.

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.

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

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:
Eh, I get twitchy getting uncoordinated anywhere low with partial water. While a slip is considered aerodynamically coordinated, not sure water in the wings would agree.

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.

Well spoken buy the guy who owns an ASW-12!