Are Weak Links really Necessary for Aero Tow?

KM wrote:

I dont see how
I could pull 6Gs while on tow.

Fair enough -- I don't either, but I'm not going to argue about it.
Unless I find some reliable info that states otherwise, Doug might be
right. Got some?


Also, in reference to Dougs post, If a tow pilot was losing pitch
authority, why wouldnt he just pull the release?

Would, if he could -- if he didn't wait too long.


...some tow pilots I know keep their free
hand on the release till they are through pattern altitude.

Pretty smart. So, whatever the g-load of which a sailplane might be
capable while on tow, it's more than enough to upset the tow plane.


...lets get back to this experience thing. I notice from your nickname that
you fly a Baron.

Yet another unfounded assumption on your part. I fly a 1-26.


...we can get into the cockpit of my 737-800 and talk more
about this experience thing.

Oh, excellent! A "mine is bigger than yours" retort. We rarely get those
on r.a.s. -- unlike most of the rest of USENET. When we do it's usually
just some lurking wannabee.

There are probably some folks here whose aviation careers could put both
mine and yours to shame, if we wanted to talk about experience -- so
let's not embarrass ourselves. If "my 737-800" means you own it,
congratulations are in order! But if Delta just pays you to fly it, I
ain't that impressed.


Or better yet, lets just get back to the post that started this
thread.

First smart thing you said. What was that post all about? Oh yeah, here
it is:

wrote: "A lot of the clubs here tow with
thickish
(5/8 inch and some 1/2inch) poly and nylon ropes, without weak
links, and pilots with years of experience say that no load exerted
by the glider can damage the tug - and in the worst of cases even a
5/8 rope will break before damaging the Tug (Most often a supercub)

Comments from knowlegable people please ---

Thanks and kind regards

JS


So civil, not contentious at all -- what a guy that JS is.

So, what do you think KMU -- now that you have reviewed the original post?



Jack

baron58y wrote:
KM wrote:

I dont see how
I could pull 6Gs while on tow.

Fair enough -- I don't either, but I'm not going to argue about it.

Dude!We agree on something!But I do think you want to argue about it or
you wouldnt keep posting marginally coherent responses.

Unless I find some reliable info that states otherwise, Doug might be
right. Got some?

Well consider this.If you take a look at the report (Elswhere on this
thread) about Shchweitzer tow hooks, it states that there were 3
accidents in this 12 year period that were caused by loss of pitch
control.During this same time frame there were at least 4 accidents
where tow planes came apart during aerobatics after the release of the
sailplane.So you have to ask yourself, What causes more damage to
towplanes? I hope you are reading this Doug.
I was flying in So Cal back in the 90s, and right at release the tow
pilot applied (What appeared from my vantage point) full left rudder
and snap rolled the tow plane upside down.He then split S'ed out the
bottom (With a Pawnee).Now I know alot of people on this list are gonna
counter that this wont hurt a towplane if you are slow enough, but I
beg to differ.I used to fly for an aerobatics flight school, and the
types of cracks Doug is descibing showed up on planes that were NEVER
used for towing.I have no idea why Doug had to make a silly remark
about tailslides.You have to also consider that most of our tugs are
tired old ships to begin with.


Also, in reference to Dougs post, If a tow pilot was losing pitch
authority, why wouldnt he just pull the release?

Would, if he could -- if he didn't wait too long.

Jack this is an excellent point, and I would ad that if this happened
low to the ground, a weak link would not matter.

Yet another unfounded assumption on your part. I fly a 1-26.

Now Jack you silly goose!You cant sign yourself "Baron 58Y" and not
have people assume you fly a Baron.

Oh, excellent! A "mine is bigger than yours" retort. We rarely get those
on r.a.s. -- unlike most of the rest of USENET.
There are probably some folks here whose aviation careers could put both
mine and yours to shame, if we wanted to talk about experience -- so
let's not embarrass ourselves. If "my 737-800" means you own it,
congratulations are in order! But if Delta just pays you to fly it, I
ain't that impressed.

Jack, you would be even less impressed if you saw my paycheck
lately.But more to the point, I threw this in because you had to make
a "unfounded assumption" about my experience level.Now once again I
will be the first to acknowlege that 9/10s of this list has more time
in tow planes and sailplanes than I do.


Or better yet, lets just get back to the post that started this
thread.

First smart thing you said. What was that post all about? Oh yeah, here
it is:
Jack, was that a compliment? Iam touched!

So civil, not contentious at all -- what a guy that JS is.

So, what do you think KMU -- now that you have reviewed the original post?

???? Once again for you and Doug.Keep a week ling in your plane.And if
your tow pilot is pulling any shenanigans, kindly ask him or her to
knock it off.

Jack

Your Pal,
KMU

This topic is worthy of discussion, so it would be nice to avoid having
it degenerate into the typical RAS morass. I've flown at commercial
operations that use large diameter "tugboat" rope. The explanation
for this is usually something like, "Oh well, we put a knot at the
end that cuts the breaking strength in half", or "We can't afford
to keep changing those little skinny ropes...".

Let's start at the top of the list: Number one - In the US, FAR
Part 91.309(3) seems crystal clear in terms of requirements - A
towline (or weaklink) is required to be not less than 80% of max glider
weight and not more than twice the max operating weight. I am not
aware of any options in the regulations to do something different. In
fact, if you are doing something different I suspect the FAA, your
insurance company, or maybe some plaintiff's attorney might be very
interested should an accident occur.

Doug and Papa3 are right in their assessment and experience that a
glider can damage a towplane. I've seen an overstress failure of a
tow hitch which broke and bent parts in the attachment assembly.
Notwithstanding excess structural loads on the empennage, the very real
danger is the tow plane running out of pitch control in the event of a
kiting incident.

I witnessed a kiting accident caused by a glider elevator misconnect.
The glider climb resembled a winch launch with the tow plane at 50-100
feet off the ground. The tow rope broke at about the same time the
towpilot had the stick on the back stop and was pitching down. This
happened so fast, had the rope not broken as it was designed to it is
very doubtful the towplane could have either released or recovered.
There would have most likely been two fatalities that day if the tow
rope had not been the correct breaking strength.

It would take a foolhardy towpilot to believe: 1) An over-strength rope
would be legal 2) An over-strength rope could not cause structural
damage to the towplane 3) The tow pilot could react quickly enough to
release in a low level kiting incident.

The tow "system" works with multiple layers of protection if the
rope is the proper specification.

Bob

Bob's post below is clear and correct.

I would like to add, however, that at least my reading of accident reports
suggest that a fatal glider accident is more likely when the towline fails
prematurely. For that reason, I like to stay near the stronger end of the
FAR 80% - 200% range.

Actually, reading the POH for several German gliders, I note the weak link
for aerotow is specified as as exact figure. For example, the weak link for
both aero tow and winch for my Nimbus 2C is specified as 600 Kg (1323 Lbs)
or a blue Tost weak link. The tolerance is + or -10%. The US Airworthiness
Certificate specifies that the Nimbus 2C is to be flown as specified in the
Pilots Handbook (POH). Considering the possible flying weights, this ranges
between 95% - 160% which is a narrower range than specified in the FAR's.

Make me wonder if we should be using Tost weak links instead of old bits of
rope.

Bill Daniels

"RL" wrote in message
ups.com...
This topic is worthy of discussion, so it would be nice to avoid having
it degenerate into the typical RAS morass. I've flown at commercial
operations that use large diameter "tugboat" rope. The explanation
for this is usually something like, "Oh well, we put a knot at the
end that cuts the breaking strength in half", or "We can't afford
to keep changing those little skinny ropes...".

Let's start at the top of the list: Number one - In the US, FAR
Part 91.309(3) seems crystal clear in terms of requirements - A
towline (or weaklink) is required to be not less than 80% of max glider
weight and not more than twice the max operating weight. I am not
aware of any options in the regulations to do something different. In
fact, if you are doing something different I suspect the FAA, your
insurance company, or maybe some plaintiff's attorney might be very
interested should an accident occur.

Doug and Papa3 are right in their assessment and experience that a
glider can damage a towplane. I've seen an overstress failure of a
tow hitch which broke and bent parts in the attachment assembly.
Notwithstanding excess structural loads on the empennage, the very real
danger is the tow plane running out of pitch control in the event of a
kiting incident.

I witnessed a kiting accident caused by a glider elevator misconnect.
The glider climb resembled a winch launch with the tow plane at 50-100
feet off the ground. The tow rope broke at about the same time the
towpilot had the stick on the back stop and was pitching down. This
happened so fast, had the rope not broken as it was designed to it is
very doubtful the towplane could have either released or recovered.
There would have most likely been two fatalities that day if the tow
rope had not been the correct breaking strength.

It would take a foolhardy towpilot to believe: 1) An over-strength rope
would be legal 2) An over-strength rope could not cause structural
damage to the towplane 3) The tow pilot could react quickly enough to
release in a low level kiting incident.

The tow "system" works with multiple layers of protection if the
rope is the proper specification.

Bob

Bill, thank you for the addendum - You are right in pointing out that
within the FAA 80%-200% limitation there may be a more restrictive
specification in a glider's POH. That's why, in many cases, private
glider owners carry their own weaklink to be sure the rope doesn't
exceed the manufacturer's requirement.

I also agree that a PT3 caused by a towline failure has a history of
bad endings.... better to be toward the higher side within the limits.

Bob

RL wrote:
Bill, thank you for the addendum - You are right in pointing out that
within the FAA 80%-200% limitation there may be a more restrictive
specification in a glider's POH. That's why, in many cases, private
glider owners carry their own weaklink to be sure the rope doesn't
exceed the manufacturer's requirement.

I also agree that a PT3 caused by a towline failure has a history of
bad endings.... better to be toward the higher side within the limits.

Bob

Unfortunately, here's a recent PT3.

http://tinyurl.com/gsp6s

Frank

"RL" wrote in message
oups.com...

Bill, thank you for the addendum - You are right in pointing out that
within the FAA 80%-200% limitation there may be a more restrictive
specification in a glider's POH. That's why, in many cases, private
glider owners carry their own weaklink to be sure the rope doesn't
exceed the manufacturer's requirement.

I also agree that a PT3 caused by a towline failure has a history of
bad endings.... better to be toward the higher side within the limits.

Bob


Bob, as a tow operator, maybe you can answer this.

In consideration of the rule that the tug end weak link must be 25% stronger
than the glider end weak link and that the glider being towed may be
anything from a Sparrowhawk to a fully ballasted ASH 25, how do you insure
that the rope and/or tug end weak link is within the rules?

A partial answer to my own question is that towing at a FAI class contest
the glider weights may be within a narrow range but what about sports class
or just a commercial tow operation?

Bill Daniels

"RL" wrote in message
oups.com...

Bill, thank you for the addendum - You are right in pointing out that
within the FAA 80%-200% limitation there may be a more restrictive
specification in a glider's POH. That's why, in many cases, private
glider owners carry their own weaklink to be sure the rope doesn't
exceed the manufacturer's requirement.

I also agree that a PT3 caused by a towline failure has a history of
bad endings.... better to be toward the higher side within the limits.

Bob

Uh, "PT3" ?

I know what a PT6 is.

Al G

Premature Termination of The Tow.

Tom Knauff has many examples of causes and preventive measures he
http://www.eglider.org/newsarticles/...mergencies.htm

Some
"Al" wrote in message
...



I know what a PT6 is.

Al G