Aerotow Regulations and Rope Specifications

On Jan 5, 10:58*am, Markus Graeber wrote:
Thanks all, especially the BGA Aerotowing Guidance Notes linked to by
John is very good stuff (by the same author as the mentioned book), I
hadn't seen those yet even though we use quite a few BGA publications
as a reference here. Just to clarify the situation, I am not going to
write any legally binding regulations for the civil aviation
authorities here (Aerocivil). The idea is a common sense set of rules
for the federation level and a very specific set of rules for the
club's operation based on the equipment and operating environment we
have. Since we control these rules ourselves (much like the BGA does
in the UK as well as the AU GFA and NZ GN as largely selfgoverning
gliding organisations) it will be easy for us to change them quickly
if needed.

In addition, gliders here in Colombia are in practical terms treated
like experimentals in the US so we can pretty much do as we please as
long as we can reasonably assure it's safe to fly. If for example I
want to install a nose hook I don't have to worry about STCs from the
FAA/EASA, if I can dig up install instructions based on solid
engineering I can just go ahead and install it. One example is the 2
LAK 12s we have in the club. They are known for lacking a bit of
rudder so the owners got together and developed a slight extension to
improve rudder effectiveness. Both LAKs also came without CG hooks so
in order to get them ready for our winch launch operation I just
organized the factory drawings for the CG hook install with the
necessary specifications for the belly reinforcement. The actual
install with the factory information is not that big of a deal if you
have a good A&P around that has experience with fibreglass, no
artificial legal barriers to worry about.

Here, like all over the world, but sadly sometime more so, people have
a habit of just improvising and out of convenience ingnore what should
be common sense. Hence the need to be very specific, at least at the
club level, based on a general set of reference rules. In addition,
the club has a professional pilot school that is now starting to
implement glider training into the general power pilot curriculum so
we have to make every effort to develop a sound set of rules we can
point to that can safe our ass and the school's certification when
that accident that shouldn't happen eventually does.

Hence my desire to make the best out of the situation and, free from
any governmental tight jacket, develop a set of rules based on best
practices and the latest research/developments. So for starters I
would for example have no problem mandating that the school needs to
replace the Schweizer aerotow hook on our PA-18 with a Tost for use
for aerotow training while resticting the use of the Schweizer hook on
our private C-180 to glider pilots with a certain aerotow experience
level until it is replaced by a Tost. Taking into account the UK tests
and fatal accidents that have happened due to the inability to trigger
the release of a Schweizer hook under high loads I find it a bit mind
boggling that these hooks are still legal in many countries and not
being phased out on a mandatory basis. All the club's gliders have
dedicated aerotow hooks so the only thing that needs to be done for
now is mandating their use for aerotow to limit the risk of kiting. If
someone eventually brings in a glider with a CG hook only (e.g. an ASW
20) we could then deal with it on a case by case basis on the
federation or club level.

As far as the aerotow ropes are concerned I am considering requiring a
minimum rope strength (e.g. 1000 daN) and and weak links on both ends
that comply with the max limits in the respective airplane's manual, I
don't really see any valid excuse for not making that relatively small
investment into proper safety equipment. On top of that would then be
the recommendation to use a 400 or 500 daN weak link on the tow plane
side not exceeding any limits imposed by the manufacturer while
recommending 300 daN for most gliders or 400 daN for Open Class
gliders with a take off weight of more than 600 kg (having in mind
recent research and DG's weak link recommendation of half the glider's
take-off weight).

Keep it coming,

Markus Graeber

Markus,

About the Schweizer tow hooks on towplanes: While the Tost is without
a doubt a better solution, and safer, we have been using the Schweizer
in the US for a long time with few problems. Unless you fly a fleet
of early trainers, the pitch up problem is probably more theoretical
than real (for that matter, it would still be a problem with the Tost
at low altitude, since you still have to release and recover!). That
being said, one relatively simple fix is to invert the Schweizer
release on the towplane, so the arm releases from the bottom (like on
the glider). That way, upwards tension on the towrope caused by
kiting is taken by the fixed arm and pivot, avoiding the problem of
the towrope tension jamming the release arm. There is a 337 for this
mod on Pawnees - Turf Soaring in Arizona developed it and they could
help if interested.

Regardless of the type of tow hook, a good briefing for both the tow
pilot and glider pilot on the causes and consequences of this type of
upset is essential!

Cheers,

Kirk

Thanks Kirk, good point, I had heard about inverting the Schweizer tow
hook many years ago while still flying in ABQ but somehow forgot about
it. We have to worry within the club about a PA-18 and a C-180, will
check with the shop what it would take to invert them and if/what the
legal ramifications in Colombia would be.

Markus

On Jan 5, 11:45*am, "kirk.stant" wrote:
On Jan 5, 10:58*am, Markus Graeber wrote:









Thanks all, especially the BGA Aerotowing Guidance Notes linked to by
John is very good stuff (by the same author as the mentioned book), I
hadn't seen those yet even though we use quite a few BGA publications
as a reference here. Just to clarify the situation, I am not going to
write any legally binding regulations for the civil aviation
authorities here (Aerocivil). The idea is a common sense set of rules
for the federation level and a very specific set of rules for the
club's operation based on the equipment and operating environment we
have. Since we control these rules ourselves (much like the BGA does
in the UK as well as the AU GFA and NZ GN as largely selfgoverning
gliding organisations) it will be easy for us to change them quickly
if needed.

In addition, gliders here in Colombia are in practical terms treated
like experimentals in the US so we can pretty much do as we please as
long as we can reasonably assure it's safe to fly. If for example I
want to install a nose hook I don't have to worry about STCs from the
FAA/EASA, if I can dig up install instructions based on solid
engineering I can just go ahead and install it. One example is the 2
LAK 12s we have in the club. They are known for lacking a bit of
rudder so the owners got together and developed a slight extension to
improve rudder effectiveness. Both LAKs also came without CG hooks so
in order to get them ready for our winch launch operation I just
organized the factory drawings for the CG hook install with the
necessary specifications for the belly reinforcement. The actual
install with the factory information is not that big of a deal if you
have a good A&P around that has experience with fibreglass, no
artificial legal barriers to worry about.

Here, like all over the world, but sadly sometime more so, people have
a habit of just improvising and out of convenience ingnore what should
be common sense. Hence the need to be very specific, at least at the
club level, based on a general set of reference rules. In addition,
the club has a professional pilot school that is now starting to
implement glider training into the general power pilot curriculum so
we have to make every effort to develop a sound set of rules we can
point to that can safe our ass and the school's certification when
that accident that shouldn't happen eventually does.

Hence my desire to make the best out of the situation and, free from
any governmental tight jacket, develop a set of rules based on best
practices and the latest research/developments. So for starters I
would for example have no problem mandating that the school needs to
replace the Schweizer aerotow hook on our PA-18 with a Tost for use
for aerotow training while resticting the use of the Schweizer hook on
our private C-180 to glider pilots with a certain aerotow experience
level until it is replaced by a Tost. Taking into account the UK tests
and fatal accidents that have happened due to the inability to trigger
the release of a Schweizer hook under high loads I find it a bit mind
boggling that these hooks are still legal in many countries and not
being phased out on a mandatory basis. All the club's gliders have
dedicated aerotow hooks so the only thing that needs to be done for
now is mandating their use for aerotow to limit the risk of kiting. If
someone eventually brings in a glider with a CG hook only (e.g. an ASW
20) we could then deal with it on a case by case basis on the
federation or club level.

As far as the aerotow ropes are concerned I am considering requiring a
minimum rope strength (e.g. 1000 daN) and and weak links on both ends
that comply with the max limits in the respective airplane's manual, I
don't really see any valid excuse for not making that relatively small
investment into proper safety equipment. On top of that would then be
the recommendation to use a 400 or 500 daN weak link on the tow plane
side not exceeding any limits imposed by the manufacturer while
recommending 300 daN for most gliders or 400 daN for Open Class
gliders with a take off weight of more than 600 kg (having in mind
recent research and DG's weak link recommendation of half the glider's
take-off weight).

Keep it coming,

Markus Graeber

Markus,

About the Schweizer tow hooks on towplanes: *While the Tost is without
a doubt a better solution, and safer, we have been using the Schweizer
in the US for a long time with few problems. *Unless you fly a fleet
of early trainers, the pitch up problem is probably more theoretical
than real (for that matter, it would still be a problem with the Tost
at low altitude, since you still have to release and recover!). *That
being said, one relatively simple fix is to invert the Schweizer
release on the towplane, so the arm releases from the bottom (like on
the glider). *That way, upwards tension on the towrope caused by
kiting is taken by the fixed arm and pivot, avoiding the problem of
the towrope tension jamming the release arm. *There is a 337 for this
mod on Pawnees - Turf Soaring in Arizona developed it and they could
help if interested.

Regardless of the type of tow hook, a good briefing for both the tow
pilot and glider pilot on the causes and consequences of this type of
upset is essential!

Cheers,

Kirk

You might also want to revisit the pros and cons of high versus low
tow. Low tow seems likely to be safer for the tow pilot as kiting
upsets are less likely.

Mike

Low tow very tricky in a glider with only a CoG hook.

John

You might also want to revisit the pros and cons of high versus
low
tow. Low tow seems likely to be safer for the tow pilot as kiting
upsets are less likely.

Mike

The other question is who is responsible for compliance with the tow regs?

The glider pilot (who probably never sees the rope)?

The glider pilot (who only gets to see one end if the ground crew happens to show it to him)?

The ground crewmember (who has no regulatory responsibility)?

Separately, in ASI's operation procedures manual, section 4.1 says: "Tow ropes are typically set up with a combination of Schweizer and Tost rings. If weak links are desired they must be provided by the glider owner."

well shucks. corrected:

On Wednesday, May 20, 2015 at 11:58:12 AM UTC-4, Bob Pasker wrote:
The other question is who is responsible for compliance with the tow regs?

The TOW pilot (who probably never sees the rope)?

The glider pilot (who only gets to see one end if the ground crew happens to show it to him)?

The ground crewmember (who has no regulatory responsibility)?

Separately, in ASI's operation procedures manual, section 4.1 says: "Tow ropes are typically set up with a combination of Schweizer and Tost rings. If weak links are desired they must be provided by the glider owner."

On Wednesday, May 20, 2015 at 10:59:04 AM UTC-5, Bob Pasker wrote:

The TOW pilot (who probably never sees the rope)?

Bob, whatever makes you think the tow pilot never sees the rope? Aside from the fact that most tow pilots are also glider pilots, it's usually the tow pilot who preflights and attaches the towrope to his towplane at the start of operations, who checks it out during breaks in tows (usually by "snaking" it out behind his towplane), and who winds it up (or coils it) at the end of the day prior to storing it.

Some big operations (and races) may drop ropes and reattach a new one prior to each tow - but those are probably exceptions.

When I'm towing I often end up inspecting the tow rope several times a day - and often find knots and other problems before they become an issue - I consider it part of my job as a tow pilot.

I get the feeling that your experiences with tow pilots has not left you with a very high opinion of the breed... ;^)

Kirk
Pawnee.__________________.LS6

thanks for the correction! i'm sure there's a broad range of tow rope inspections going on, but i've honestly never seen the tow *pilot* handle and inspect the rope, only the ground crew

on the hookup side of things, I've had all sorts of different experiences:

everything from the ground crew just grabbing the end rope and giving me hand signals to open/close the release knob

to handing me the glider end of the rope for my inspection, attaching the ring, and giving a glider-moving tug on the rope



On Wednesday, May 20, 2015 at 12:42:04 PM UTC-4, kirk.stant wrote:
On Wednesday, May 20, 2015 at 10:59:04 AM UTC-5, Bob Pasker wrote:

The TOW pilot (who probably never sees the rope)?

Bob, whatever makes you think the tow pilot never sees the rope? Aside from the fact that most tow pilots are also glider pilots, it's usually the tow pilot who preflights and attaches the towrope to his towplane at the start of operations, who checks it out during breaks in tows (usually by "snaking" it out behind his towplane), and who winds it up (or coils it) at the end of the day prior to storing it.

Some big operations (and races) may drop ropes and reattach a new one prior to each tow - but those are probably exceptions.

When I'm towing I often end up inspecting the tow rope several times a day - and often find knots and other problems before they become an issue - I consider it part of my job as a tow pilot.

I get the feeling that your experiences with tow pilots has not left you with a very high opinion of the breed... ;^)

Kirk
Pawnee.__________________.LS6

On 5/20/2015 9:59 AM, Bob Pasker wrote:
well shucks. corrected:

On Wednesday, May 20, 2015 at 11:58:12 AM UTC-4, Bob Pasker wrote:
The other question is who is responsible for compliance with the tow
regs?

The TOW pilot (who probably never sees the rope)?
In my club, a daily responsibility of the tow pilot prior to the day's first
tow is visually inspecting the entire length of the towrope. Decision to use
as-is, shorten, or discard (meaning: cut into "obviously too-short-for-towing"
lengths) is entirely the towpilot's responsibility.

The glider pilot (who only gets to see one end if the ground crew happens
to show it to him)?
Every tow, SOP is for the wing runner to show (and hand-to, if requested by
the glider pilot) the glider-end of the towrope to the glider pilot for his or
her inspection, after which the glider type can choose to launch, replace the
weak link or (very rarely) request the line be shortened or replaced prior to
the tow.

The ground crewmember (who has no regulatory responsibility)?
See above...

A host of obvious questions likely springs to each reader's mind, all centered
on the "burning question": How can anyone KNOW any of this does any good/meets
regulatory compliance/etc.?

FWIW, strictly my own personal conclusions as a self-interested glider
sort/engineer, and based on having done my own digging over time into these
sorts of questions, here's my take on things:

a) "Actual line safety," "legally-binding regulatory safety," and "known
regulatory compliance" are pretty much different things, with VERY fuzzy,
arguably smallish-to-largish overlapping subsets. Some of the fuzziness is due
to unavoidable, practical, realities...e.g. testing/methodology,
continuing-use vs. degradation testing, correlating visual degradation to
measurable strength, etc. Some is due to the inherent difficulties in trying
to define/describe/place hard/legal bounds on engineering problems. Some is, I
would bet, almost certainly due to bureaucratic hand-washing/disinterest/etc.

b) At least one (engineer) member of my club built a pull-to-failure test rig
(resides in the towplane hangar for any curious club member to "play with")
and (more than once) performed extensive parametric testing over the years, of
new and used tow ropes and weak link methodologies (e.g. separate links of
smaller-than-towrope diameters, knots in the rope, etc.). In large part the
club's daily procedures described above are derived from this testing, said
testing coupling at some level with regulatory guidelines.

c) A former (late) on-field glider FBO (CFIG, FAA designated examiner, A&P [w.
IA?], "engineer-head") had done his own independent pull-to-failure testing
along the lines of B) above...and interestingly came to essentially the same
conclusions as my (operationally independent) club, regarding "the best
method" to safely "meet the intent of regulations."

Strictly from personal engineering curiosity, I picked the brains of both men
once learning of their test efforts. My interest was in doing what I could to
reassure myself the club's towrope guidelines conveyed to every member,
weren't simply picked out of the air or otherwise "of dubious provenance." I
had zero interest in bringing "Philadelphia lawyer-ism" to the regulatory
question of "What's safe?"

Bottom line is in over 30 years of operations from the field - over which time
I've seen towrope/weaklink methods evolve and "reinvent a wheel" once or twice
- zero "entirely unforeseeable" towrope/weaklink issues come to mind, while I
*can* remember some unknown quantity of self-inflicted rope/link failures (aka
footshots from slack line training or PIC inattention). My conclusion?
Regardless of the fun-to-discuss, of-legal-implication issues surrounding how
"to best define & regulate" towrope/weaklink strengths, is that "for all
practical purposes" our gliderpilot derived, local towrope procedures, pretty
much "work acceptably" and have the benefit of simplicity.

In my mind, "If it ain't broke, don't fix it," applies on this front, though I
realize "Better is the enemy of good enough," might also be brought to the
discussion. Meanwhile, I'll bet Real Money that anyone "needing absolute
assurance" of towline/weaklink breaking strength on every given tow, is doomed
to the same unquantifiable disappointment as those arguing how many angels can
fit on the head of a pin. And, yes, I'm aware of Tost's metallic weaklinks,
and readily acknowledge their superiority for winch launching, while being
prepared to debate their "necessity" for aerotow.

YMMV,
Bob W.

On Wednesday, May 20, 2015 at 4:22:37 PM UTC-4, BobW wrote:
500 words of tantalizing buildup and then no mention of the actual 'club procedures'