Fatal crash Arizona

On Wednesday, May 7, 2014 7:20:33 AM UTC-6, Vaughn wrote:
On 5/7/2014 2:55 AM, Bruce Hoult wrote:

On Wednesday, May 7, 2014 1:20:44 PM UTC+12, Bill D wrote:

I can assure you that the higher a glider's performance, the safer

it is. It's the old, low L/D gliders that can run out of altitude

before getting lined up with the runway.

I agree with you. I'm shaking my head every time I read this thread.



In a modern glass glider (such as the DG1000's I instruct in) with a

40 knot stall speed and being towed at 70 knots you should be able to

execute a safe 180� turn with*zero* loss of height.



The comparison isn't quite as simple as just looking at L/D. Turn

radius also has a lot to do with your chances of making it back to the

field, and turn radius is proportional to the SQUARE of airspeed.



Compare your example (40 knot stall) with a (horrors) 2-33. The highest

stall listed for a 2-33 is around 30 knots. If you do the math, you

will find that your DG1000 has nearly double the turn radius of the

slower glider.



Vaughn

You're exaggerating the stall speed differences. Regardless of what the 2-33 "manual" says, no 2-33 ever got as slow as 30 knots. 35 knots is a practical minimum speed. The flight test stall speed for a DG 1000 is 37 knots..

However, no one should consider a turn back at stall speed. Virtually all gliders will be at 50 - 55 knots so the turn radius will be essentially the same.

8 knots sink? That's a straw man argument. While extreme air movement is always possible, most PT3 incidents are in relatively benign conditions. In extreme conditions a turn back is probably moot anyway.

The point is when conditions allow, a pilot should know how to turn back safely.

On Wednesday, May 7, 2014 10:34:48 AM UTC-5, Bill D wrote:

The point is when conditions allow, a pilot should know how to turn back safely.

Precisely. It's called airmanship - knowing how to handle your plane in any conceivable situation.

If you aren't practicing something new and unusual (or at least thinking about it) on every flight, you are limiting your growth as a pilot.

My one real PTT happened at Turf Soaring (Pleasant Valley Airport) many years ago, giving a ride in old 66W - a beat up old 2-32. Tow rope was hooked up incorrectly (muddy) and released just past the end of the runway (taking off to the East) at what i guess was around 150 - 200 ft, no more. No good options other than turning back or landing in the desert; so I turned back...and had enough energy to roll back up to the surprised line boy who had just launched me. Turned the glider around, hooked up again, and the customer got his full ride the second time.

BUT--conditions were calm with light winds and no lift; and the tow was fast - and it was pretty easy to whip that big old beast around in a steep turn and bring it back to land, as I had a lot of time in 2-32s at the time. Never felt that I was too low during the turn, but didn't even try getting real slow (if you have time in 2-32s you will appreciate why!).

Yes, it can be done. But you have to know your plane WELL, and have the right conditions, and fully understand the consequences of pooching it!

Get out there and practice!

Kirk
66

At 17:01 07 May 2014, kirk.stant wrote:
On Wednesday, May 7, 2014 10:34:48 AM UTC-5, Bill D wrote:
=20
The point is when conditions allow, a pilot should know how to turn
back
=
safely.

Precisely. It's called airmanship - knowing how to handle your plane in
an=
y conceivable situation.

If you aren't practicing something new and unusual (or at least thinking
ab=
out it) on every flight, you are limiting your growth as a pilot.

My one real PTT happened at Turf Soaring (Pleasant Valley Airport) many
yea=
rs ago, giving a ride in old 66W - a beat up old 2-32. Tow rope was
hooked=
up incorrectly (muddy) and released just past the end of the runway
(takin=
g off to the East) at what i guess was around 150 - 200 ft, no more. No
go=
od options other than turning back or landing in the desert; so I turned
ba=
ck...and had enough energy to roll back up to the surprised line boy who
ha=
d just launched me. Turned the glider around, hooked up again, and the
cus=
tomer got his full ride the second time.

BUT--conditions were calm with light winds and no lift; and the tow was
fas=
t - and it was pretty easy to whip that big old beast around in a steep
tur=
n and bring it back to land, as I had a lot of time in 2-32s at the time.
N=
ever felt that I was too low during the turn, but didn't even try getting
r=
eal slow (if you have time in 2-32s you will appreciate why!).

Yes, it can be done. But you have to know your plane WELL, and have the
ri=
ght conditions, and fully understand the consequences of pooching it!

Get out there and practice!

Kirk
66

and that dear reader illustrates the problem nicely. Emergency procedures
do not have to be formulated for experienced thinking pilots. I would like
to think that I could get away with doing what Kirk has done. Emergency
procedures have to be formulated for the lowest common denominator, would a
low launches pilot be able to achieve success? Would a relatively
experience pilot who is flying minimum launches per year cope with it? That
is what formulating procedures is all about, having something that everyone
can achieve, not just the top 10%.

On Wednesday, May 7, 2014 12:40:09 PM UTC-6, Don Johnstone wrote:
At 17:01 07 May 2014, kirk.stant wrote:

On Wednesday, May 7, 2014 10:34:48 AM UTC-5, Bill D wrote:

=20

The point is when conditions allow, a pilot should know how to turn

back

=

safely.



Precisely. It's called airmanship - knowing how to handle your plane in

an=

y conceivable situation.



If you aren't practicing something new and unusual (or at least thinking

ab=

out it) on every flight, you are limiting your growth as a pilot.



My one real PTT happened at Turf Soaring (Pleasant Valley Airport) many

yea=

rs ago, giving a ride in old 66W - a beat up old 2-32. Tow rope was

hooked=

up incorrectly (muddy) and released just past the end of the runway

(takin=

g off to the East) at what i guess was around 150 - 200 ft, no more. No

go=

od options other than turning back or landing in the desert; so I turned

ba=

ck...and had enough energy to roll back up to the surprised line boy who

ha=

d just launched me. Turned the glider around, hooked up again, and the

cus=

tomer got his full ride the second time.



BUT--conditions were calm with light winds and no lift; and the tow was

fas=

t - and it was pretty easy to whip that big old beast around in a steep

tur=

n and bring it back to land, as I had a lot of time in 2-32s at the time..

N=

ever felt that I was too low during the turn, but didn't even try getting

r=

eal slow (if you have time in 2-32s you will appreciate why!).



Yes, it can be done. But you have to know your plane WELL, and have the

ri=

ght conditions, and fully understand the consequences of pooching it!



Get out there and practice!



Kirk

66



and that dear reader illustrates the problem nicely. Emergency procedures

do not have to be formulated for experienced thinking pilots. I would like

to think that I could get away with doing what Kirk has done. Emergency

procedures have to be formulated for the lowest common denominator, would a

low launches pilot be able to achieve success? Would a relatively

experience pilot who is flying minimum launches per year cope with it? That

is what formulating procedures is all about, having something that everyone

can achieve, not just the top 10%.

So, if the dumbest, least competent guy on the airfield might not be able to pull it off the UK solution is to eliminate the requirement for everybody? Talk about dumbing down.

I'm absolutely sure I can pull off at turn back and I'm certain my students can as well. I'll probably have to when I take a check ride in a couple of weeks in a 2-32. If so, the examiner will give me no warning whatsoever when he pulls the release at 200' AGL on departure. No sweat - even though there's no off field options.

I've had it happen for real many times including a couple of "What's this gizmo do?" on ride flights. I've watched post solo students pull it off when a rope broke. If we had not trained for this skill, we wouldn't be here. It's a lifesaver.

On Wednesday, May 7, 2014 2:40:09 PM UTC-4, Don Johnstone wrote:
Emergency procedures do not have to be formulated for experienced thinking pilots.

Why do so many experienced thinking pilots enter spins from low altitude turns?

I want to know because I'm becoming more experienced and thoughtful with every flight.

Why do so many experienced thinking pilots enter spins from low altitude turns?

I want to know because I'm becoming more experienced and thoughtful with every flight.

My sincere sympathies to the friends and family of this pilot. John did a great job explaining the the answer to this question: Why do experienced pilots spin in low. Here is a link to his thoughts:

https://groups.google.com/forum/?fromgroups#!searchin/rec.aviation.soaring/john$20cochrane|sort:date/rec.aviation.soaring/ibhUAkQ6Z1s/8WoOYyZIlqEJ

Stay safe,
Bruno - B4

On Thursday, May 8, 2014 3:37:26 PM UTC+12, wrote:
Why do so many experienced thinking pilots enter spins from low altitude turns?

I want to know because I'm becoming more experienced and thoughtful with every flight.

My sincere sympathies to the friends and family of this pilot. John did a great job explaining the the answer to this question: Why do experienced pilots spin in low. Here is a link to his thoughts:

https://groups.google.com/forum/?fromgroups#!searchin/rec.aviation.soaring/john$20cochrane|sort:date/rec.aviation.soaring/ibhUAkQ6Z1s/8WoOYyZIlqEJ

Hi Bruno, and thanks for all the great videos.

I agree with what John says there. The primary one is that around steep hills adverse horizontal gusts are a much bigger danger than many people realise, and a bigger danger than sink.

I vary my speed a lot. When I'm pointing at the rocks, or low over them, I want to see 65-70 knots on the clock on a normal day. A sudden 20 knot gust up the tail isn't going to stall me. If it's windy then I'll use 80.

As soon as I'm pointing away from the ridge and suddenly have hundreds of feet under the nose I'm happy to drop it back to 50 or 55, and accelerate again as I turn back towards the hill.

You can see an example here, in a video a passenger shot back in 2009 on their iPhone 3GS (the new ones are MUCH better).

https://www.youtube.com/watch?v=IU8IDDBgwg0

Remember: it's not actually the gust from behind and loss of airspeed that makes you stall and spin -- it's only if/when YOU pull the stick back to try to stop the nose from dropping (or to tighten the turn). If you keep the stick in the same place it was before the gust then YOU CAN NOT STALL/SPIN. The nose will drop. You'll eventually speed up again. Nothing worse than that will happen provided there is nothing solid in front of you, even if the ASI is reading well below your 1 G stall speed.

The bigger mystery is why competent people stall and spin over flat land, on the notorious turn from base to final.

If it's windy then the gradient can explain it. The lower wingtip gets less windspeed, less lift. The upper wingtip gets more speed, more lift. You could get rolled a lot, rather than a spin as such. Still not healthy. Turning higher can keep you out of the gradient. Flying faster will keep everything flying and give you more control authority.

That's on turns into wind (for landing). With turns away from the wind (turning back after a PTT), the gradient helps you into the turn at the start, but helps right you as you complete it.

Not that I want to be landing downwind on a day with enough wind to have that kind of gradient!! Fortunately, on those days you should have plenty of height over the fence to do a proper circuit.

On Wednesday, May 7, 2014 9:51:43 PM UTC-4, son_of_flubber wrote:

Why do so many experienced thinking pilots enter spins from low altitude turns?

The explanations offered for ridge flyers make sense. I wonder if risk taken in normal ridge flying (and the low-altitude experience gained) reduce pattern spin risk?

On Thursday, May 8, 2014 1:00:20 AM UTC-4, Bruce Hoult wrote:

The bigger mystery is why competent people stall and spin over flat land, on the notorious turn from base to final.

Just after posting my question, I found something in Dr. Dan's latest Soaring RX column "How to Spin Unintentionally":

Dr. Dan wrote in Soaring Magazine May 2014:
"We may get into trouble because we spend too much of our time soaring and not enough doing pattern tows. Our brains then build patterns that don't include the sensations of low-level flight. A reason to go to the airfield and do pattern work on poor soaring days is to rebuild those low-level gestalts, so that our brains easily shift from the high-altitude to the low-altitude vection sensations as both being normal and expected."

This is a compelling idea. As the average duration of my flights gets longer, I get relatively more experience flying at high-altitude than at low-altitude. I spent a much higher percentage of my time doing pattern tows as a student pilot. As a student, I was much more current at low-altitude flight. Dr. Dan recommends pattern tows to keep my low-altitude proficiency current and in balance with my ever stronger high-altitude proficiency.

Dr. Dan also notes (as have others) that soaring pilots can refresh their proficiency in low-altitude flight by practicing ground reference maneuvers in a power plane (with a CFI that is current in low-level flight).

So the next time that the lift does not materialize at the airport, I will 'waste money' on some pattern tows. I also plan to 'waste money' flying ground-reference maneuvers in a power plane with a current CFI.

On Thursday, May 8, 2014 3:34:48 AM UTC+12, Bill D wrote:
You're exaggerating the stall speed differences. Regardless of what the 2-33 "manual" says, no 2-33 ever got as slow as 30 knots. 35 knots is a practical minimum speed. The flight test stall speed for a DG 1000 is 37 knots.

I knew 40 knots was conservative with the DG1000 stall speed, but that difference is less than I'd have expected. I've never flown a 2-33, but I've had Blaniks under 35 knots :-)


However, no one should consider a turn back at stall speed. Virtually all gliders will be at 50 - 55 knots so the turn radius will be essentially the same.

I've put together a spreadsheet for the calculations and In fact it turns out that for minimum loss of height in a 180º turn -- and also much smaller turn radius -- you should fly a bit faster and bank a bit steeper.

https://docs.google.com/spreadsheets...FXBnfP8tauGK1k

No matter what your stall speed or L/D, it turns out the optimum to minimise loss of height in a turn is to bank at 54.7 degrees.

This is the bank angle at which the total G loading is 1.732 (sqrt(3)) and the G available to turn you is 1.414 (sqrt(2)).

In that glass ship with 120 fpm min sink at 45 knots you're looking at 67m turn radius at 59 knots, with 24 feet loss of height in a 180º turn.

In a Blanik with 160 fpm at 42 knots you'll get a 58m turn radius at 55 knots, with 30 feet loss of height.

In a 2-33 with 168 fpm at 35 knots you'll get a 40.5m turn radius at 46 knots, with 26 feet loss of height.

Feel free to play.

On Wednesday, May 7, 2014 6:24:23 PM UTC-7, Bruce Hoult wrote:

No matter what your stall speed or L/D, it turns out the optimum to minimise loss of height in a turn is to bank at 54.7 degrees.

Feel free to play.

Thanks Bruce - I did play with this a bit. Always helpful to do the math.

Several observations pop out from the numbers:

1) The 25-30' height loss for a 180 is small compared to the 200' I always use as the minimum safe altitude to make this maneuver. Not that I'm recommending a smaller margin - there are considerations of sink and wind and clearance for the bottom wingtip in the bank.

2) Speaking of the bottom wingtip in the bank, if you subtract that height difference for each different bank angle you get a height loss for a 180 measured at the bottom wingtip that is actually minimal at a lower bank angle than 54.7 degrees. Obviously this would be most likely to apply at the end of the maneuver, not the beginning, unless there is unusual terrain.

3) Whether you include the wingtip clearance in the calculation or not, the total height loss doesn't vary all that much between 30 and 60 degrees of bank - about 6 feet of difference for the center of the aircraft and only a foot or two of difference at the lower wingtip.

The conclusion this draws me to is that the most important consideration in PTT is to make a smooth, coordinated, deliberate turn that you can manage easily - and to make sure not to dig the bottom wing into the ground. Within a pretty broad range, there isn't much percentage in optimizing the bank angle.

9B