Are 'Single 180 Turn From Downwind to Final' and 'Stall-spin on Turnfrom Base to Final' mutually exclusive?

On Saturday, July 30, 2016 at 8:50:08 AM UTC-4, Tango Eight wrote:
On Saturday, July 30, 2016 at 12:51:25 AM UTC-4, son_of_flubber wrote:
My default procedure is to set spoilers to 50% open, then adjust pattern shape to make my aim point.

I'd like to hear some well experienced CFIGs weigh in on that statement.

What I left unsaid, because I thought it was understood, is that the pilot will first adjust the spoilers moderately, and then if necessary, change the heading of the base leg.

You want a CFIG to weigh in?

To quote Tom Knauff from 'Preventing Launching and Landing Accidents' page 27

"After the turn onto the base leg, the pilot has two plans of action in case the apparent final approach glide angle appears too steep or too shallow. If the slope appears too steep, the pilot uses a plan of action to open the dive brakes and angle away to extend the glide path to lose some altitude.. If the glide angle appears too shallow, the pilot will immediately close the dive brakes and turn towards the landing area." Copyright 2004 Knauff and Grove

A schematic figure that shows a non-rectangular pattern follows immediately in the text.

On page 26 "The dive brakes of a typical modern glider will allow the glider to descend anywhere from 5:1 to a very conservative 20:1. The pilot should never be very close to either of these extremes." Copyright 2004 Knauff and Grove

Based on this and other things written by Tom, I conclude that aiming to keep the spoilers near 50% effectiveness gives the pilot the most flexibility (either way) to compensate for things that don't go according to plan. That's my default (goal) as previously noted.

So changing the heading on base leg (non-square pattern) is a Knauff-recommended means to recover from an incorrectly timed turn to base. That said, almost all of my patterns are square, my turns are steep, and my spoilers stay open to about 50% until I touch down.

If my pattern speed needs to be higher to deal with wind and turbulence, I'll delay opening the spoilers, and if conditions are intimidating, I might turn to base a bit early, so that I have more reserve to deal with the possibility of extraordinary sink, and if it turns out to be just ordinary sink, I'll add a little more spoiler on final to get down.

In the last 30 days, I've flown glider on 13 days, and because I think safe and optimal landing is utterly important and merits practice, I've landed 21 times, (and as often as possible in utter crap conditions in order to stay proficient). So if you think I'm a mad anarchist pilot trying to tear down the status quo, then I've communicated poorly and/or you're projecting something that isn't there.

On Saturday, July 30, 2016 at 11:33:26 PM UTC-4, son_of_flubber wrote:
On Saturday, July 30, 2016 at 8:50:08 AM UTC-4, Tango Eight wrote:
On Saturday, July 30, 2016 at 12:51:25 AM UTC-4, son_of_flubber wrote:
My default procedure is to set spoilers to 50% open, then adjust pattern shape to make my aim point.

I'd like to hear some well experienced CFIGs weigh in on that statement..

What I left unsaid, because I thought it was understood, is that the pilot will first adjust the spoilers moderately, and then if necessary, change the heading of the base leg.

You want a CFIG to weigh in?

To quote Tom Knauff from 'Preventing Launching and Landing Accidents' page 27

"After the turn onto the base leg, the pilot has two plans of action in case the apparent final approach glide angle appears too steep or too shallow. If the slope appears too steep, the pilot uses a plan of action to open the dive brakes and angle away to extend the glide path to lose some altitude. If the glide angle appears too shallow, the pilot will immediately close the dive brakes and turn towards the landing area." Copyright 2004 Knauff and Grove

A schematic figure that shows a non-rectangular pattern follows immediately in the text.

On page 26 "The dive brakes of a typical modern glider will allow the glider to descend anywhere from 5:1 to a very conservative 20:1. The pilot should never be very close to either of these extremes." Copyright 2004 Knauff and Grove

Based on this and other things written by Tom, I conclude that aiming to keep the spoilers near 50% effectiveness gives the pilot the most flexibility (either way) to compensate for things that don't go according to plan. That's my default (goal) as previously noted.

So changing the heading on base leg (non-square pattern) is a Knauff-recommended means to recover from an incorrectly timed turn to base. That said, almost all of my patterns are square, my turns are steep, and my spoilers stay open to about 50% until I touch down.

If my pattern speed needs to be higher to deal with wind and turbulence, I'll delay opening the spoilers, and if conditions are intimidating, I might turn to base a bit early, so that I have more reserve to deal with the possibility of extraordinary sink, and if it turns out to be just ordinary sink, I'll add a little more spoiler on final to get down.

In the last 30 days, I've flown glider on 13 days, and because I think safe and optimal landing is utterly important and merits practice, I've landed 21 times, (and as often as possible in utter crap conditions in order to stay proficient). So if you think I'm a mad anarchist pilot trying to tear down the status quo, then I've communicated poorly and/or you're projecting something that isn't there.

No, I'm not projecting anything. I just wanted to see if the very experienced guys had a different take on your story than I did.

FWIW, putting the *priority* on maintaining spoilers half open, and adjusting the pattern to keep it that way struck me as profoundly odd. In fact I'd rate it right up there with the advice in Joy of Soaring about how to fly the final approach**: it's precisely backwards. Sure, you can make it work. That doesn't make it a best practice.

The normal procedure for correcting glide slope is to use more or less spoiler to capture the desired glide slope for the pattern being flown. Adjustments to the pattern are sometimes necessary or desirable, and the ability to make these adjustments when needed is essential skill for any glider pilot. The passages you've quoted from Tom's books are fine as far as they go, I simply think you've misunderstood the application. Generally, one can make corrections for all but the grossest of errors with spoilers alone. In the case of a really big error (or rotor, or big wind shear or whatever), then you add the pattern variations as Tom describes.

**The Joy of Soaring approach to final approach was this: aim with the nose (in pitch), control airspeed with spoilers.

best,
Evan

Evan,
Flying a pattern with the intention of 50% spoilers is to provide the safety buffer in both directions (high and low), rather than needing to adjust your ground track and preserve the sacred rectangular pattern. While you are completely correct that most spoilers can cure your excessive altitude problems in the pattern, if you fly a pattern that is sized to not need any spoilers/airbrakes and you are too low, you must now change your pattern rather than closing the airbrakes a bit. It is mostly about making the size of your pattern halfway between what would be required for a no-spoilers pattern and a full spoilers pattern.

Chris

On Sunday, July 31, 2016 at 8:08:51 AM UTC-4, Giaco wrote:
Evan,
Flying a pattern with the intention of 50% spoilers is to provide the safety buffer in both directions (high and low), rather than needing to adjust your ground track and preserve the sacred rectangular pattern. While you are completely correct that most spoilers can cure your excessive altitude problems in the pattern, if you fly a pattern that is sized to not need any spoilers/airbrakes and you are too low, you must now change your pattern rather than closing the airbrakes a bit. It is mostly about making the size of your pattern halfway between what would be required for a no-spoilers pattern and a full spoilers pattern.

Chris

Hi Chris,

In a word -- baloney! Read it again:

On Saturday, July 30, 2016 at 12:51:25 AM UTC-4, son_of_flubber wrote:
My default procedure is to set spoilers to 50% open, then adjust pattern shape to make my aim point.

That is a very different SOP / not something I ever do / not something I plan to teach / something I would likely intercept and work on correcting if a pilot brought it to my club.

I like Tom's emphasis on best practices.

See ya,

Evan

Maybe I misunderstood, but Flub’s description of his approach technique seems very mechanical and/or contrived. To me it seems very similar to how I was taught in a 2-33 using Joy of Soaring, except instead of “being at 500 feet over the red barn� he keeps 50% spoiler and moves his ground track toward and away from the airport.

Tom Knauff transitioned me into my ASW-19 at Ridge Soaring, and of course he taught me to use TLAR. What I took away from him was to “always look and judge how the approach is going�, and to do what you had to do with the controls to put the glider into the proper position. Those of you who’ve flown at Ridge Soaring know that the approach to 25 is never amenable to recipe flying...

Tom’s TLAR has served me well during both routine and very tricky approaches. Honestly I couldn’t tell you where my spoilers are, unless I hit either the forward or aft limit while reacting to extreme sink or lift. But I can always tell you if I’m too high or too low! And during every approach I always hear my instructor Jack chanting “airspeed, yaw string�, over and over.

-John, Q3

One consideration I don't think was mentioned; A straight base leg gives the pilot a chance to really look hard for head-on traffic in the opposite pattern. A situation that killed a friend of mine.

Matt

I may have mentioned this before, but the series of my articles and tests currently being printed in Soaring magazine will continue for a few more months. As a result of this discussion, I am submitting a rather lengthy article about landing procedures / technique. My guess is it will not be published until early next year.

If I send in two pages of my popular Glider Flight Training Manual each month, it will take 15 years to publish all the information it contains.

You might consider upgrading to this new version rather than waiting.

Tom Knauff

On Sunday, July 31, 2016 at 11:46:23 AM UTC-7, wrote:
I may have mentioned this before, but the series of my articles and tests currently being printed in Soaring magazine will continue for a few more months. As a result of this discussion, I am submitting a rather lengthy article about landing procedures / technique. My guess is it will not be published until early next year.

If I send in two pages of my popular Glider Flight Training Manual each month, it will take 15 years to publish all the information it contains.

You might consider upgrading to this new version rather than waiting.

Tom Knauff

I thought of four situations when this "military",or button hook, landing pattern MIGHT be appropriate:

1. Terrain/buildings forced a tight base leg, such as an airstrip in a canyon.
2. Remaining altitude is at an absolute minimum for landing.
3. Unusual local weather conditions, like microbursts, are occurring.
4. The pilot wanted to impress his/her girl/boyfriend (just JOKING!).

In all other situations a square pattern (or a modified square pattern) is far safer. Flying a button hook pattern puts the runway out of sight to the pilot, so it is hard to judge how far you have flown, making it much more likely that an overshoot or undershoot landing will occur.

An important aspect of the square pattern, in addition to the visibility part, is to assess the winds aloft by the amount of crab required. I have been flying lately in conditions of high cross winds (10-20 kt) and even higher gusts (20-30 kt). Having a stabilized base leg is essential to judge this (the AWOS is just to old to be relied upon). If I were to fly a button hook pattern I would have a ground speed of 110-130 kt, given the high density altitudes we are flying and an 80 kt IAS (100 kt TAS + 10-30 kt tail wind)! This translates to up to 220 ft/sec (a 180 deg turn takes 10-20 sec and complicates the design point on when to start the turn). If you hit unexpected sinking air during this turn you could be in a real pickle! You may not experience these conditions where you fly, but a lot of accidents occur when flatlanders venture into high density altitude airports.

I also like to have A LOT of altitude when entering the pattern (2,000 ft). It is easy to burn off that altitude in modern gliders and it gives me options if something unexpected happens (like a plane pulling out onto the runway unannounced). Altitude lost is like runway behind you - it doesn't do you any good.

Tom

Hi Chris,

In a word -- baloney! Read it again:

On Saturday, July 30, 2016 at 12:51:25 AM UTC-4, son_of_flubber wrote:
My default procedure is to set spoilers to 50% open, then adjust pattern shape to make my aim point.

That is a very different SOP / not something I ever do / not something I plan to teach / something I would likely intercept and work on correcting if a pilot brought it to my club.

I like Tom's emphasis on best practices.

See ya,

Evan

Sorry, i totally misread that... That pattern makes no sense to me then if you are just setting an arbitrary airbrake setting and building a pattern around it.

In all other situations a square pattern (or a modified square pattern) is far safer. Flying a button hook pattern puts the runway out of sight to the pilot, so it is hard to judge how far you have flown, making it much more likely that an overshoot or undershoot landing will occur.
What??? I always fly a descending 180 to short final and I /_never_/
lose sight of the runway. What are you doing that puts you in that
position? It's trivial to keep the landing point in view over your
shoulder until you begin the turn, unless you're flying way too far out
before beginning your final.

An important aspect of the square pattern, in addition to the visibility part, is to assess the winds aloft by the amount of crab required.
It's easy to assess winds on downwind and continuously through the final
turn without losing sight of the touchdown point. Drift is recognized
with peripheral vision and quick glances down at the ground. Final and
opposite patterns are monitored from downwind throughout the final
turn. Angle of descent is easily controlled by keeping the angle to the
touchdown point constant.

I have been flying lately in conditions of high cross winds (10-20 kt) and even higher gusts (20-30 kt). Having a stabilized base leg is essential to judge this
As said above, it's easy to judge during the downwind and throughout the
turn.
(the AWOS is just to old to be relied upon).
Very true!
If I were to fly a button hook pattern I would have a ground speed of 110-130 kt, given the high density altitudes we are flying and an 80 kt IAS (100 kt TAS + 10-30 kt tail wind)!
Why would you have a higher ground speed in turning flight than in
straight flight?
This translates to up to 220 ft/sec (a 180 deg turn takes 10-20 sec and complicates the design point on when to start the turn). If you hit unexpected sinking air during this turn you could be in a real pickle!
No, you're close enough that reducing dive brake will compensate for any
sink. If you're in a location with known high sink on final, e.g.,
Salida, CO, you should make your turn at the proper height and distance
from the runway.
You may not experience these conditions where you fly, but a lot of accidents occur when flatlanders venture into high density altitude airports.

I also like to have A LOT of altitude when entering the pattern (2,000 ft).
There goes flying where other pilots expect to see you!
It is easy to burn off that altitude in modern gliders and it gives me options if something unexpected happens (like a plane pulling out onto the runway unannounced). Altitude lost is like runway behind you - it doesn't do you any good.

Tom
Fly what works for you and don't disparage techniques that are out of
your sphere of experience.
--
Dan, 5J