Fatal crash Arizona

"Why is anyone aero towing with a tow hook that will back release?"

Some of us don't have much of a choice. For example the two ASW-19's and two ASW-15's at my field all have both a C of G hook AND a forward mounted aerotow hook. The forward hooks have a back release function as well. Short of engineering, building, installing and getting an STC from Transport Canada for a completely redesigned forward hook mechanism there's not much we can do about this.

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.

Well, we have plenty of opinions about what to do after the rope suddenly releases, lets take a quick check on how to keep the rope firmly attached until we decide to release it. When you hooked up the rope, did the 'pull' feel normal? If it didn't take much of a pull, one of the springs in the over-center mechanism may have failed. Did the cable return all the way back into its tube? If not, broken cable strands may be flaring out and preventing the tow hook from returning all the way back to its fully closes and locked position. I have seen low altitude releases caused by both of these malfunctions.
Condolences to the family,
JJ

At 04:02 08 May 2014, wrote:
"Why is anyone aero towing with a tow hook that will back release?"

Some of us don't have much of a choice. For example the two ASW-19's and
tw=
o ASW-15's at my field all have both a C of G hook AND a forward mounted
ae=
rotow hook. The forward hooks have a back release function as well. Short
o=
f engineering, building, installing and getting an STC from Transport
Canad=
a for a completely redesigned forward hook mechanism there's not much we
ca=
n do about this.=20

I had for a time an ASW17 which has the same release arrangement as the
ASW15,19,and 20. There was a wooden block attached to the rear of the
aerotow release aperture which prevented operation of the back release. It
never crossed my mind that this was not how it was built. It was
effective.
In the days of yore it was common practice to use bodge tape to prevent the
operation of the back release when aerotowing.

At 23:50 07 May 2014, Bruce Hoult wrote:
However your height estimates are systematically biased 20% too large.
Well, about 8% for a pull-up, and 17% for a dive - at the high-speed end of
the scale.
(Better and worse, respectively, at the low-speed end.) Whereas your rule
is about 10%
low throughout.

By me: 28^2 - 12^2 = ~800 - ~150 = 650 ft (784-144 = 640 if you do it
exact)
By you: 130+120+110+100+90+80+70+60 = 760 ft
By you with my -20% correction: 760 - 152 = 608
And the truth (from v^2 = u^2 + 2gh ... whence we both started, I'm sure)
is 708.66 ft. (I
knew you'd like the ".66" ;o) )

Spreadsheet he http://tinyurl.com/mzokpyk for those amused by such
things.

But of course these are both rules of thumb, intended more to give better
understanding
than for exact calculation. I have more often referred to mine in
discussing recovery of
lost speed low on finals (or after a low winch-launch failure) than for the
120kt beat-up
case!

On Thursday, May 8, 2014 7:00:00 AM UTC-6, JJ Sinclair wrote:
Well, we have plenty of opinions about what to do after the rope suddenly releases, lets take a quick check on how to keep the rope firmly attached until we decide to release it.

It is interesting how this discussion has become a data geek's exchange about the physics of a turn back. If the rope had stayed attached he would likely not have tried to turn back, if indeed that is what he tried to do. Apparently no one saw it.

I was always told a Superior pilot uses his superior judgment to keep himself out of situations where his superior piloting skill are needed. The superior judgment in this case would be to not use a back releasing tow hook for aero tow.

When you hooked up the rope, did the 'pull' feel normal? If it didn't take much of a pull, one of the springs in the over-center mechanism may have failed.

JJ, the "Zuni towhook" does not use an over center system. This one of the problems with it. Unlike the Tost hook the force to actuate it is proportional to the tow rope tension.

I am very interested in knowing if there is an obvious malfunction of any part of the tow release system, that was not caused by the actual crash.

Robert Mudd

On Friday, May 9, 2014 4:44:38 AM UTC+12, James Metcalfe wrote:
At 23:50 07 May 2014, Bruce Hoult wrote:
(Better and worse, respectively, at the low-speed end.) Whereas your rule
is about 10% low throughout.

Yes, it's deliberately biased a little to the low side from the true (as you note) /4.7516 to make it more of a "guaranteed to pull up that far". Also useful for "I'd like to be down on that ridge line, but I don't want to overspeed". Of course in that case the height difference is going to be pure guess anyway.

I've contemplated using /4 for dives where you want to make sure you have some minimum speed, but I think that overdoes it. /4.5 would be better but not easy to calculate in your head.

On Tuesday, May 6, 2014 6:20:44 PM UTC-7, Bill D wrote:
On Tuesday, May 6, 2014 5:56:44 PM UTC-6, Don Johnstone wrote:

At 22:22 06 May 2014, Bill D wrote:



On Tuesday, May 6, 2014 2:41:23 PM UTC-6, Don Johnstone wrote:







Frankly I would be horrified to be required to conduct a turn back at



=20



200ft, I would suggest that this is one of those occasions where the



dang=



er



=20



of practice is to great to justify.







If you should check out in the USA, you'll be required to demonstrate



compe=



tence in this maneuver. Every pre-solo student is required to do so and



mo=



re than a half century of safety records do not suggest a problem. In



fact=



, even with low performance gliders, there's quite a large safety margin.



T=



he most likely outcome is a pilot will find the glider uncomfortably high



f=



or a downwind landing requiring full spoilers and a slip.







The logic is simple - it's better to have pilots trained for the option.



N=



o one says a pilot is required to turn back or that 200' is always



adequate=



to do so. What is illogical is to suggest a pilot be required to crash



in=



unlandable terrain when a safe option exists to land on the departure



runw=



ay.







What are you trying to save? The pilot or the aircraft? The priority should



be survival of the soft bit, that is you and me.



As an instructor with nearly 50 years experience I know that when I



initiate an emergency procedure I do so allowing a margin to ensure my



survival if it does not work out, I have been bold but never certifiable.



Most living instructors have the same survival instinct. That is why I have



lived long enough to do 10,000 launches, and of course landings. It has



already been hinted that the practice you describe involves modifying what



you normally do, in my view that probably makes it pretty useless and not



real preparation for the event. If you did carry out the training in



exactly the same way as the possible real event you might find that the



results were very different, not to mention painful. I will stick with my



300ft thank you, I know it works. Low turns, below that height may have



been acceptable in old wooden gliders, the minimum height in T31 and T21



gliders was 150ft, but for modern glass gliders it is just far too low, you



only have to look at the accident statistics to see that low final turns



figure to a large degree in accidents so why plan for it?



I repeat a controlled descent with wings level is far more likely to have a



better result than hitting the ground in a turn or even worse spinning in



trying to avoid it.







PS Despite all that there have been times when I have initiated a practice



emergency and very quickly wished I had not, no plan survives first



contact.



So, you're saying the pilot will be safer if they don't learn to perform the return to runway maneuver when it's safe to do so?



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.

The discussion seems to focus exclusively on the decision height for a turn around. I think that is only one factor in making this decision. As reported by Bob T there was heavy sinking air on the departure end of the runway. Returning to the airport would have required transiting thru this air a 2nd time, which strikes me as inadvisable without much more altitude than Knauff had.

The other issue is that a tow rope break requires immediate lowering of the nose. This is done routinely at altitude, but at low altitude this means pointing the glider's nose uncomfortably down at the ground while executing a steep banked turn. If the ground is rising, as it is at Sampley, the picture seen by the pilot is even more disturbing. All that it takes is a momentary hesitation in this reflex and the outcome can be fatal.

As an aside, I once did a wind mill start in my DG400 below 1000' (over a runway). This maneuver requires achieving in excess of 90 kt airspeed. Because the engine & prop act like dive brakes, you feel like you are standing on your rudder pedals when you do this close to the ground. I got to this airspeed and the prop still didn't rotate. This meant that I had to steepen the descent even more. All of my instincts said no, but my brain said yes, which is what I did. The engine started, but I decided that this maneuver really needs to be started at a higher altitude.

On Thursday, May 8, 2014 6:39:06 PM UTC-6, 2G wrote:

The other issue is that a tow rope break requires immediate lowering of the nose.

Why would anyone lower the nose? The glider is presumably at aero tow speed - 65 - 70 knots which is way above the pattern speed. A better plan is to use the excess airspeed to maintain height while turning until airspeed drops to pattern speed.


This is done routinely at altitude, but at low altitude this means pointing the glider's nose uncomfortably down at the ground while executing a steep banked turn. If the ground is rising, as it is at Sampley, the picture seen by the pilot is even more disturbing. All that it takes is a momentary hesitation in this reflex and the outcome can be fatal.

The nose is not "uncomfortably down". The turn back is a normal turn.



As an aside, I once did a wind mill start in my DG400 below 1000' (over a runway). This maneuver requires achieving in excess of 90 kt airspeed. Because the engine & prop act like dive brakes, you feel like you are standing on your rudder pedals when you do this close to the ground. I got to this airspeed and the prop still didn't rotate. This meant that I had to steepen the descent even more. All of my instincts said no, but my brain said yes, which is what I did. The engine started, but I decided that this maneuver really needs to be started at a higher altitude.

Aha! You're really a motor glider pilot, not an aero tow pilot which explains your misconceptions.