91.309 a (3) ii

*Does your glider operation use a weak link at the tow plane end of the
rope, as required by 91.309 a (3) ii?


Jack

---*

§ 91.309 Towing: Gliders and unpowered ultralight vehicles.

http://tinyurl.com/fllgz

_ (a) No person may operate a civil aircraft towing a glider or
unpowered ultralight vehicle unless---_

(1) The pilot in command of the towing aircraft is qualified under
§61.69 of this chapter;

(2) The towing aircraft is equipped with a tow-hitch of a kind, and
installed in a manner, that is approved by the Administrator;

_ (3) The towline used has breaking strength not less than 80 percent of
the maximum certificated operating weight of the glider or unpowered
ultralight vehicle and not more than twice this operating weight.
However, the towline used may have a breaking strength more than twice
the maximum certificated operating weight of the glider or unpowered
ultralight vehicle if---_

_ (i) A safety link is installed at the point of attachment of the
towline to the glider or unpowered ultralight vehicle with a breaking
strength not less than 80 percent of the maximum certificated operating
weight of the glider or unpowered ultralight vehicle and not greater
than twice this operating weight;_

_ (ii) A safety link is installed at the point of attachment of the
towline to the towing aircraft with a breaking strength greater, but not
more than 25 percent greater, than that of the safety link at the towed
glider or unpowered ultralight vehicle end of the towline and not
greater than twice the maximum certificated operating weight of the
glider or unpowered ultralight vehicle;_

(4) Before conducting any towing operation within the lateral boundaries
of the surface areas of Class B, Class C, Class D, or Class E airspace
designated for an airport, or before making each towing flight within
such controlled airspace if required by ATC, the pilot in command
notifies the control tower. If a control tower does not exist or is not
in operation, the pilot in command must notify the FAA flight service
station serving that controlled airspace before conducting any towing
operations in that airspace; and

(5) The pilots of the towing aircraft and the glider or unpowered
ultralight vehicle have agreed upon a general course of action,
including takeoff and release signals, airspeeds, and emergency
procedures for each pilot.

(b) No pilot of a civil aircraft may intentionally release a towline,
after release of a glider or unpowered ultralight vehicle, in a manner
that endangers the life or property of another.

At 17:54 10 September 2006, 588 wrote:
*Does your glider operation use a weak link at the
tow plane end of the
rope, as required by 91.309 a (3) ii?


Jack

---*

Nope....1,000lb rope used for Standards, 15 and 18
meter ships, ergo no weaklink required on either end.

Just out of curiousity...the breaking strength of the
rope is for brand new, unused rope. I wonder what
the actual strength of most rope being used is?

Stewart Kissel wrote:
At 17:54 10 September 2006, 588 wrote:
*Does your glider operation use a weak link at the
tow plane end of the
rope, as required by 91.309 a (3) ii?


Jack

---*

Nope....1,000lb rope used for Standards, 15 and 18
meter ships, ergo no weaklink required on either end.

Just out of curiousity...the breaking strength of the
rope is for brand new, unused rope. I wonder what
the actual strength of most rope being used is?

The information I received from my rope distributor is that the initial
breaking strength is reduced by 25% with use. We incorporated this in
the operating procedures at our club (LISA). We use 250' (230' when
doubled at the ends) of 5/16" hollow braided polypropeleyne rope with a
nominal breaking strength of 1500 lb.

When the rope is new, we intall a new 1/4" poly rope weak link with
nominal breaking strength of 1200 lb at the glider end. This allows us
to tow gliders between 600 and 1488 lb, so it covers a 1-26E through a
2-32. Since the main rope strength is not more than 25% greater than
the weak link, no separate weak link is required at the
towplane--because there is a weak point at the towplane end where the
rope is doubled (and another at the glider end).

Once the ropes have been used for about a day, we discard the 1/4" weak
link and just use the 5/16" rope, under the assumption that it's
breaking strength has been reduced by approx 25%. This allows us to
contunue to tow the entire fleet with the same rope. We have to discard
the weak link, because it is assumed to also be reduced in breaking
strength, but it only uses about $1 worth of rope.

Now, of course there is a lot of variation in inital and used breaking
strength of actual ropes, so this is not an exact process. But it does
represent a good faith effort to comply with the regs, and is a
workable operating procedure.

Note that the maximum weak link strength is 1200 lbs for Schweizer
hooks on the tow plane, so this is the upper limit for breaking
strength for most tow planes. Some gliders have lower maximum breaking
strength, depending on the tow hook type and mounting structure. So if
you have one of these gliders, you may need to bring your own weak
links.

Another important note--do not splice a broken aero-tow rope! The point
where the rope is doubled will wear out faster from abrasion. At the
tow plane end, this is not an issue, because it is held off the ground,
and can be checked at the beginning of each day. At the glider end, it
can be checked at each hook-up. But if it is in the middle of the rope,
it will not get checked, and will wear until it breaks in flight.
Besides, if the rope broke once already, it's time to replace it. Use
the broken half to replace that ratty rope on the tow car that's too
short anyway.

Stewart Kissel wrote:

At 17:54 10 September 2006, 588 wrote:
*Does your glider operation use a weak link at the
tow plane end of the
rope, as required by 91.309 a (3) ii?

Nope....1,000lb rope used for Standards, 15 and 18
meter ships, ergo no weak link required on either end.

Poorly presented question on my part -- sorry.

What I should have said was: _when_ FAR 91.309.a.(3) requires the weak
link, do you use two or just one at the glider end?

The question is really about interpretation of (3) i and ii. Some
(many?) glider operations use only one weak link. I read the reg as
requiring two weak links, one at each end. To me, ii references the weak
link required by i in such a way that I can't see it as an either/or
situation -- both are required. I wondered whether anyone has a cite for
a ruling or other definitive interpretation beyond what is set forth in
the reg. quoted below.

---

§ 91.309 Towing: Gliders and unpowered ultralight vehicles.

http://tinyurl.com/fllgz

(a) No person may operate a civil aircraft towing a glider or unpowered
ultralight vehicle unless—

[....]

(3) The towline used has breaking strength not less than 80 percent of
the maximum certificated operating weight of the glider or unpowered
ultralight vehicle and not more than twice this operating weight.
However, the towline used may have a breaking strength more than twice
the maximum certificated operating weight of the glider or unpowered
ultralight vehicle if—

(i) A safety link is installed at the point of attachment of the towline
to the glider or unpowered ultralight vehicle with a breaking strength
not less than 80 percent of the maximum certificated operating weight of
the glider or unpowered ultralight vehicle and not greater than twice
this operating weight;

(ii) A safety link is installed at the point of attachment of the
towline to the towing aircraft with a breaking strength greater, but not
more than 25 percent greater, than that of the safety link at the towed
glider or unpowered ultralight vehicle end of the towline and not
greater than twice the maximum certificated operating weight of the
glider or unpowered ultralight vehicle;

[....]

---

Just out of curiousity...the breaking strength of the
rope is for brand new, unused rope. I wonder what
the actual strength of most rope being used is?

Less. But that's OK since the FAR's are not concerned with weakening of
the rope as long as its breaking strength remains no less than 80% of
the max weight of the glider -- which we can all assess just be looking
at it.


Jack

I should have caught up on intervening posts before responding to the
previous one. Thanks very much, Doug for a clear and useful explanation.


Jack

---

Doug Haluza wrote:

The information I received from my rope distributor is that the initial
breaking strength is reduced by 25% with use. We incorporated this in
the operating procedures at our club (LISA). We use 250' (230' when
doubled at the ends) of 5/16" hollow braided polypropeleyne rope with a
nominal breaking strength of 1500 lb.

When the rope is new, we intall a new 1/4" poly rope weak link with
nominal breaking strength of 1200 lb at the glider end. This allows us
to tow gliders between 600 and 1488 lb, so it covers a 1-26E through a
2-32. Since the main rope strength is not more than 25% greater than
the weak link, no separate weak link is required at the
towplane--because there is a weak point at the towplane end where the
rope is doubled (and another at the glider end).

Once the ropes have been used for about a day, we discard the 1/4" weak
link and just use the 5/16" rope, under the assumption that it's
breaking strength has been reduced by approx 25%. This allows us to
contunue to tow the entire fleet with the same rope. We have to discard
the weak link, because it is assumed to also be reduced in breaking
strength, but it only uses about $1 worth of rope.

Now, of course there is a lot of variation in inital and used breaking
strength of actual ropes, so this is not an exact process. But it does
represent a good faith effort to comply with the regs, and is a
workable operating procedure.

Note that the maximum weak link strength is 1200 lbs for Schweizer
hooks on the tow plane, so this is the upper limit for breaking
strength for most tow planes. Some gliders have lower maximum breaking
strength, depending on the tow hook type and mounting structure. So if
you have one of these gliders, you may need to bring your own weak
links.

Another important note--do not splice a broken aero-tow rope! The point
where the rope is doubled will wear out faster from abrasion. At the
tow plane end, this is not an issue, because it is held off the ground,
and can be checked at the beginning of each day. At the glider end, it
can be checked at each hook-up. But if it is in the middle of the rope,
it will not get checked, and will wear until it breaks in flight.
Besides, if the rope broke once already, it's time to replace it. Use
the broken half to replace that ratty rope on the tow car that's too
short anyway.

The information I received from my rope distributor is that the initial
breaking strength is reduced by 25% with use. We incorporated this in
the operating procedures at our club (LISA). We use 250' (230' when
doubled at the ends) of 5/16" hollow braided polypropeleyne rope (HBPR) with a
nominal breaking strength of 1500 lb.


This is interesting information and coincides with some of my
experience.

A few years ago I did a bunch of winch launches with an operation that
was using a length of 5/16" HBPR as a weak link. We would pretty
consistly break the weak link after about 15 to 20 launches. I had
pretty much assumed the rope was loosing its strength as it was used. I
just had never heard a number as to how much.

Brian
CFIIG/ASEL

yes...
we use a 7/16" 3 ply poly (200ft) for durability over time in our desert climate, so weak links are required
we use the 1/4" 3 ply poly for weak links, and very quickly the new weak link on the tug end is stronger than the glider end, the tug end never touches the ground

we use the weak link to change between schweizer and tost rings

BT
"588" wrote in message ...
Does your glider operation use a weak link at the tow plane end of the rope, as required by 91.309 a (3) ii?


Jack

---

§ 91.309 Towing: Gliders and unpowered ultralight vehicles.

http://tinyurl.com/fllgz


(a) No person may operate a civil aircraft towing a glider or unpowered ultralight vehicle unless-

(1) The pilot in command of the towing aircraft is qualified under §61.69 of this chapter;

(2) The towing aircraft is equipped with a tow-hitch of a kind, and installed in a manner, that is approved by the Administrator;

(3) The towline used has breaking strength not less than 80 percent of the maximum certificated operating weight of the glider or unpowered ultralight vehicle and not more than twice this operating weight. However, the towline used may have a breaking strength more than twice the maximum certificated operating weight of the glider or unpowered ultralight vehicle if-

(i) A safety link is installed at the point of attachment of the towline to the glider or unpowered ultralight vehicle with a breaking strength not less than 80 percent of the maximum certificated operating weight of the glider or unpowered ultralight vehicle and not greater than twice this operating weight;

(ii) A safety link is installed at the point of attachment of the towline to the towing aircraft with a breaking strength greater, but not more than 25 percent greater, than that of the safety link at the towed glider or unpowered ultralight vehicle end of the towline and not greater than twice the maximum certificated operating weight of the glider or unpowered ultralight vehicle;

(4) Before conducting any towing operation within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for an airport, or before making each towing flight within such controlled airspace if required by ATC, the pilot in command notifies the control tower. If a control tower does not exist or is not in operation, the pilot in command must notify the FAA flight service station serving that controlled airspace before conducting any towing operations in that airspace; and

(5) The pilots of the towing aircraft and the glider or unpowered ultralight vehicle have agreed upon a general course of action, including takeoff and release signals, airspeeds, and emergency procedures for each pilot.

(b) No pilot of a civil aircraft may intentionally release a towline, after release of a glider or unpowered ultralight vehicle, in a manner that endangers the life or property of another.