The aerodynamics of a towplane in a kiting glider situation

Just because one system is superior and safer to another has nothing to do with whether it is approved for installation by the FAA. The documentation for installing a tow release on a particular aircraft is clearly spelled out. If it permits a Schweizer hook, then that's what has to be installed to pass inspection. Changing to a Tost is not in compliance with the documentation, so it would not pass inspection.

Getting a Tost approved for retrofit to an aircraft for which it is not specifically approved can be an arduous and time consuming process. ANYTHING having to do with the regulatory environment at the FAA is a long and painful experience. Bob Carlton and I spent NINE YEARS getting the FAA to agree to a method to extend the life limit on the Pegasus. And that was an instance where the FAA had obviously made a mistake, violated their own procedures and the Administrative Procedures Act and still "circled the wagons' to defend the one guy who pushed the life limit AD through.

I am certainly not arguing that getting a Tost approved for all aircraft would be a desirable thing. It is just that EACH aircraft type would have to be individually approved. There are very few if any "blanket" approvals across aircraft types for mechanical devices. Avionics are another story, but we aren't talking about that type of equipment.

As far as releasing liability, the big question is whether the tow pilot or his employer (club or commercial) is providing an aviation service for compensation. If the glider pilot is paying for the tow, then it is fairly obvious. However, as you say, four lawyers can easily deliver six opinions.

On Wednesday, May 20, 2020 at 6:47:15 AM UTC-7, wrote:
Just because one system is superior and safer to another has nothing to do with whether it is approved for installation by the FAA. The documentation for installing a tow release on a particular aircraft is clearly spelled out. If it permits a Schweizer hook, then that's what has to be installed to pass inspection. Changing to a Tost is not in compliance with the documentation, so it would not pass inspection.

Getting a Tost approved for retrofit to an aircraft for which it is not specifically approved can be an arduous and time consuming process. ANYTHING having to do with the regulatory environment at the FAA is a long and painful experience. Bob Carlton and I spent NINE YEARS getting the FAA to agree to a method to extend the life limit on the Pegasus. And that was an instance where the FAA had obviously made a mistake, violated their own procedures and the Administrative Procedures Act and still "circled the wagons' to defend the one guy who pushed the life limit AD through.

I am certainly not arguing that getting a Tost approved for all aircraft would be a desirable thing. It is just that EACH aircraft type would have to be individually approved. There are very few if any "blanket" approvals across aircraft types for mechanical devices. Avionics are another story, but we aren't talking about that type of equipment.

As far as releasing liability, the big question is whether the tow pilot or his employer (club or commercial) is providing an aviation service for compensation. If the glider pilot is paying for the tow, then it is fairly obvious. However, as you say, four lawyers can easily deliver six opinions.

STCs have been issued for many different aircraft for many different alterations - it is not an impossible task. Your Pegasus issue is not a valid comparison to an STC. Yes, a different STC would have to be developed for each aircraft type using a KGARS, but so what - you take the same paperwork and change the make and model, and resubmit it. If you have the data to support the superior performance of a KGARS - and you definitely need that data - I think the FAA would be very receptive to approving it.

Tom

On Wednesday, May 20, 2020 at 9:47:15 AM UTC-4, wrote:
Just because one system is superior and safer to another has nothing to do with whether it is approved for installation by the FAA. The documentation for installing a tow release on a particular aircraft is clearly spelled out. If it permits a Schweizer hook, then that's what has to be installed to pass inspection. Changing to a Tost is not in compliance with the documentation, so it would not pass inspection.

Getting a Tost approved for retrofit to an aircraft for which it is not specifically approved can be an arduous and time consuming process. ANYTHING having to do with the regulatory environment at the FAA is a long and painful experience. Bob Carlton and I spent NINE YEARS getting the FAA to agree to a method to extend the life limit on the Pegasus. And that was an instance where the FAA had obviously made a mistake, violated their own procedures and the Administrative Procedures Act and still "circled the wagons' to defend the one guy who pushed the life limit AD through.

I am certainly not arguing that getting a Tost approved for all aircraft would be a desirable thing. It is just that EACH aircraft type would have to be individually approved. There are very few if any "blanket" approvals across aircraft types for mechanical devices. Avionics are another story, but we aren't talking about that type of equipment.

As far as releasing liability, the big question is whether the tow pilot or his employer (club or commercial) is providing an aviation service for compensation. If the glider pilot is paying for the tow, then it is fairly obvious. However, as you say, four lawyers can easily deliver six opinions.

MARK, I think you missed my point but that's okay. I understand everything you said, still the FAA is now knowingly insisting on utilization of a device on some airplanes which has been proven to fail to do what it is supposed to do when the feces makes physical contact with the whirling blades of an electrically driven air moving device. Change can be accomplished, someone needs to make the first move. I understand government bureaucracy, I had to deal with OSHA in the Nuclear Power Plant world but I do have to say the OSHA guys were quite reasonable, UNLESS there was a glaring violation and then they insisted on compliance.

Flying with the Schweizer hook is kinda like driving drunk. Happens countless times each day as does towing with the Schweizer hook but nothing happens. Then someone get caught just like a tow pilot gets kited but no one gets killed but lesson learned. The drunk driver gets away with maybe a big fine, license suspended for a period as the tow pilot gets away with his life. Then the s--t hits the fan. The drunk kills someone and perhaps himself, the tow pilot crashes, loses his life. The drunk driver knew he was driving drunk, his family and friends knew he did it but no intervention. The Tug pilot knows he is pulling with a questionable device...

It's easier to look the other way and decide to do nothing than to take action and correct a known deficit. Easier until someone dies. Granted the Byron example might not have been avoided by any current release system, the pilot didn't have time to release and recover but another tow pilot will die in the future due to a system which is known to fail when it is needed the most. And what is the value of a life?

Walt Connelly
Former Tow Pilot
Now Happy Helicopter Pilot.

I invite anyone who thinks getting an STC approval is a simple process to just download this handy 96 page guide from the FAA.

https://www.faa.gov/documentLibrary/.../AC_21-40A.pdf

And, no, you can't just change the make/model on the paperwork and resubmit it. The process is the same for a different aircraft. (Pawnee vs. Cessna 185 etc.) You CAN apply for an STC within certain parameters for aircraft of a similar "family," like Cessna 180, 182, 185, but there are still differences that must be defined for each model unless the equipment, processes, installation and materials are IDENTICAL.

On Sunday, May 17, 2020 at 4:48:22 PM UTC-6, Tom BravoMike wrote:
I know there is a thread going on about and around the latest tragic accident from 5-9-2020 and I preferred to start a new thread as I felt uncomfortable going into a dry technical discussion in the context. So the issue is:

I would like to know more about the aerodynamics of the towplane in all those accident situations (and I mean above certain altitude minimum): Statistically, do they crash being stalled or in a deep dive? What is the usual reaction to the tail being pulled up - does the towpilot try to overrule the pulling glider and he gets into a stall? He cannot dive until the rope breaks. Recovering from a stall he has to get out of a dive anyway. So it seems that pushing down into a dive instead of trying to pull up would result in a smaller loss of altitude (and cause the rope to break earlier), rather than in the sequence: struggle to overrule the pulling glider - stalling (loss of height) - pulling out of a dive (loss of height).

Just thinking loud, curious if any research has been done and if so, to what conclusions? Does anybody know?

Dont forget people Towing is not that dangerous and there are plenty of Happy towpilots out there and not just happy helicopter pilots

Folks
If anyone thinks getting an STC is easy or even moderately difficult you are badly mistaken. Having gone thru the attempt on two separate occasions, I can tell you unless an STC has been approved year’s previously addressing a similar application, your chances of getting an approval are next to nil! The dirty little secret is, the FAA is not interested in helping the process. In fact, they do not want to involve themselves at all. Maybe if you have a very friendly fsdo, you could possibly get a one time field approval but those are even very difficult to obtain nowadays.
Is the schweizer hook an issue? Possibly but Karl Streideck addressed the modifications suggested in a very succinct post earlier. Or switch to a tost hook and move on. We’ve been towing for decades now and once again it comes down to proper airmanship. Get the idiots be they experienced or not OUT of the cockpit or beat some sense into them. As a tow pilot, insist on a release that is easy and immediately at hand, be ready to pop it the very MOMENT someone starts a kiting action. Absolute diligence is required from both glider guy and tow pilot the first 1,000 ft of a tow.
Dan

On Thursday, May 21, 2020 at 7:27:39 AM UTC-7, Hightime wrote:
On Sunday, May 17, 2020 at 4:48:22 PM UTC-6, Tom BravoMike wrote:
I know there is a thread going on about and around the latest tragic accident from 5-9-2020 and I preferred to start a new thread as I felt uncomfortable going into a dry technical discussion in the context. So the issue is:

I would like to know more about the aerodynamics of the towplane in all those accident situations (and I mean above certain altitude minimum): Statistically, do they crash being stalled or in a deep dive? What is the usual reaction to the tail being pulled up - does the towpilot try to overrule the pulling glider and he gets into a stall? He cannot dive until the rope breaks. Recovering from a stall he has to get out of a dive anyway. So it seems that pushing down into a dive instead of trying to pull up would result in a smaller loss of altitude (and cause the rope to break earlier), rather than in the sequence: struggle to overrule the pulling glider - stalling (loss of height) - pulling out of a dive (loss of height).

Just thinking loud, curious if any research has been done and if so, to what conclusions? Does anybody know?

Dont forget people Towing is not that dangerous and there are plenty of Happy towpilots out there and not just happy helicopter pilots



The loss in airspeed during a kiting incident must be significant. Chris Rollings notes that a 'marked deceleration' was observed by the towpilot in his report from kiting tests in 1978 and 1982, but focusses on the pitch down. I've had two kiting incidents as an aerotow pilot, both above 2000agl, when the glider didn't release as desired. In both cases it felt like a mild aerobatic maneuver, not alarming to me due to the safe altitude, and my attention was so focussed on the pitch-down that I didn't notice any airspeed decrease, although it probably occurred. In those experiences, the kiting did not seem at all dangerous to me, at altitude, and might even be a good thing for all aerotow pilots to experience, at altitude and intentionally, as part of training. It would be best if the towpilot was comfortable with mild aerobatics before trying it however. Chris Rollings did not mention any danger in his kiting tests. Such intentional kiting might build up a better body of knowledge, and would increase the awareness of tow and glider pilots to the danger.

Reducing the towrope breaking tension seems desirable. I don't know the reason for the FAA 80% rule, maybe that should be reduced. Most glider manufacturers only specify a maximum breaking tension.

Another interesting consideration is the time taken for rope tension to rise to breaking tension. The tension in the rope will probably rise gradually during kiting, probably over a few seconds. The rise in tension is probably non-linear, and at some angle, but its easier to do a calculation if the rope tension is assumed to rise linearly and to act directly backwards. If the rope tension builds up linearly to 1800lbs (a typical rope break strength) and then breaks, a Pawnee with full tanks (say weighing 1800lbs) will decelerate linearly, reaching a maximum deceleration of 32ft/sec2 ie about 20kts per second, at the instant the rope breaks. The longer it takes for the rope tension to build up to breaking, the greater the total Pawnee airspeed loss will be, since the rope forces on the Pawnee will be the same but last for a longer time. Calculation shows the Pawnee total airspeed loss varies as t^2, where t is the time taken for the rope tension to rise to the breaking point. If the rope breaks in 1 sec, the Pawnee in this example would slow by about 10kts by the time the rope breaks. If the rope takes 2 secs to break, the Pawnee airspeed loss would be about 40kts. In a non-kiting rope-break, eg due to a slack line suddenly snatching tight, the time t would be very short, maybe 0.1sec, and the airspeed loss probably unnoticable.

The full analysis should consider both pitchdown and airspeed loss, and perhaps negative g effect on the pilot, and then the height needed to recover. This might be too complicated, and be too dependent on particular towplane types. Maybe intentional practice at altitude might give practical data more quickly.

On Thursday, May 21, 2020 at 9:47:42 AM UTC-5, wrote:
Folks
If anyone thinks getting an STC is easy or even moderately difficult you are badly mistaken. Having gone thru the attempt on two separate occasions, I can tell you unless an STC has been approved year’s previously addressing a similar application, your chances of getting an approval are next to nil! The dirty little secret is, the FAA is not interested in helping the process. In fact, they do not want to involve themselves at all. Maybe if you have a very friendly fsdo, you could possibly get a one time field approval but those are even very difficult to obtain nowadays.
Is the schweizer hook an issue? Possibly but Karl Streideck addressed the modifications suggested in a very succinct post earlier. Or switch to a tost hook and move on. We’ve been towing for decades now and once again it comes down to proper airmanship. Get the idiots be they experienced or not OUT of the cockpit or beat some sense into them. As a tow pilot, insist on a release that is easy and immediately at hand, be ready to pop it the very MOMENT someone starts a kiting action. Absolute diligence is required from both glider guy and tow pilot the first 1,000 ft of a tow.
Dan

It almost sounds like we are orphans here in the US, no SSA, no AOPA, no EAA - of which many of us are members and pay the dues. Is there any support and lobbying on part of those organizations when dealing with the FAA? Don't the other countries' national gliding organizations take care of talking to their aviation administrations in similar cases? BGA, DAeC, FFVP ...

On Thursday, May 21, 2020 at 10:01:09 AM UTC-4, wrote:
I invite anyone who thinks getting an STC approval is a simple process to just download this handy 96 page guide from the FAA.

https://www.faa.gov/documentLibrary/.../AC_21-40A.pdf

And, no, you can't just change the make/model on the paperwork and resubmit it. The process is the same for a different aircraft. (Pawnee vs. Cessna 185 etc.) You CAN apply for an STC within certain parameters for aircraft of a similar "family," like Cessna 180, 182, 185, but there are still differences that must be defined for each model unless the equipment, processes, installation and materials are IDENTICAL.

Yes, it is not easy, no one has said it is easy, obviously it is hard and unnecessarily so...BUT many things in life are hard and still worth doing. Kennedy said "we choose to go to the moon in this decade and do the other things, NOT because hey are easy but because they are hard." As a kid I saw a man save a life, what he did was hard and dangerous but he saved a life, what can we do better than that? Some choose to discuss why it can't be done, I choose to see things from another perspective. I am not in a position to take the necessary steps, I don't own or fly a tow plane, I'm not an employee or an operation or club but I can see my hand in front of my face. If these comments and rantings move ONE more club or commercial operator to take the obvious necessary steps and replace a proven failed system for a proven better one then it's worth it.

Walt Connelly
Former Tow Pilot
Now Happy Helicopter Pilot

Dont forget people Towing is not that dangerous and there are plenty of Happy towpilots out there and not just happy helicopter pilots

Hightime, you're kidding right? Towing is not that dangerous? Please tell that to the poor chap who died recently in California. Or to the tow pilot at Front Royal Virginia or any of the tow pilots who have perished due to a mistake on the part of the glider pilot in tow only to then be amplified by the failure of a device meant to save their life. Towing is not "that" dangerous until it become THAT dangerous.

It's not THAT dangerous until someone in back of the tow plane makes a big, stupid mistake. It's not THAT dangerous until a poorly trained student (in my case) or an inattentive, distracted instructor or one of the many squirrels who abound in the soaring community SCREW UP. Then it becomes THAT dangerous and for the record, how do you define "that?"

Plenty of Happy tow pilots? I'm sure there are and they will be happy until the s--t hits the fan and they find themselves a second or two from the end of their life, happy will go out the window. The fact of the matter is we don't know what we don't know and what we don't know can kill us. Every tow has the potential to end in disaster. Towing

Towing is not that dangerous, what a dumb f--king statement to make. Flying helicopters is dangerous too but not THAT dangerous? The difference is that I am responsible for my mistakes.

Walt Connelly
Former Tow Pilot
Now Happy Helicopter Pilot