Double Release Failure

On Sep 7, 11:21*pm, wrote:
**Is anyone teaching this

anymore?

Barry

Sure. *It's a good exercise for proficiency and confidence building.
Touch and goes, taxiing and even turning at runway intersection to
take off on a different runway. *Good communication, experienced tow
pilots, proper conditions, *FUN!


Why all CFIG's (in the USA) must discuss and teach this maneuver: It
appears in your FAA Practical Test Standards (PTS) for Glider
"checkrides" under the Area of Operation "Launches and Landings"/
"Abnormal Occurrences" / "Glider and towplane release
failure" (meaning both releases fail.) This is one of five listed
abnormal situations in your FAA PTS. FAA allows the Examiner to ask
you to perform this maneuver, as the Examiner may ask you to perform
any or all of the tasks under "Abnormal Occurrences." Most Examiners
just ask for the "towline break" demonstration and the "glider (only)
release failure" signal on tow, but "double release" is part of the
PTS, so be prepared to at least discuss the procedure on your
checkride.

Note to CFIG's: Just because a double release failure is rare does
not mean you can skip over it in the PTS. The FAA discusses double
release failure in the FAA Glider Flying Handbook, Chapter 7. Not
much of a discussion however, but there it is. Towpilots need to be
thoroughly briefed by a towpilot who has flown this maneuver. The
descent is very gradual at a proper approach airspeed. If the
approach doesn't look or feel right, the towpilot has the option to go
around and climb with glider still in tow.

Note to Readers: My discussion posted here is abbreviated and not
complete and not to be substituted or used for any aspect of your
ground and flight instruction. This post is discussion, not
instruction.

Regarding the glider in "low tow" position: Because the towplane is
gradually descending the wake is relatively higher, so the glider does
not need to be too low in relation to the towplane. The sight picture
is usually not as low as when you box the wake -- just enough to be
just under the wake, and with a full view of the towrope. Keep the
airbrakes unlocked and deployed as needed to keep a tight towrope at
all times. Overrunning the towplane is the dangerous part both in the
air and on the ground roll out. Be ready to release.

Important Timing Aspect: The glider (in low tow) must not touch down
much before the towplane -- this can be a hazardous aspect -- touching
down well before the towplane and stalling it. The glider wings are
still carrying the weight of the glider while it is flying. Once the
glider touches the wings stop lifting and the glider creates more
weight drag on the towplane, which if still well above the runway will
be slowed and may stall. If you try this maneuver, keep the glider
flying until the towplane is about one meter above the runway. Make
sure the towpilot keeps the towplane moving forward (no brakes) with
some power to help keep the rope tight. Glider pilot deploys nearly
full airbrake (spoiler) to keep from lifting off again and some wheel
brake, AFTER the towplane is on the ground. Just roll out and not be
in a hurry to stop. Both pilots should release if slack rope
develops. If lots of runway ahead a touch and go is possible. Long
runways and a good headwind make landing on tow a bit less
challenging. A long towrope may be a good idea.

For the most comprehensive discussion and training on landing on tow,
along with purposely breaking the towrope, contact Cindy & Marty at
Caracole Soaring in California. They have developed this procedure to
be relatively safe, and fun.

Remember, I am not your personal Flight Instructor here. My
discussion posted here is abbreviated and not complete and not to be
used as part of your ground and flight instruction. For more
instruction in "abnormal occurrences" on tow consult with your local
Certificated Flight Instructor, one who is proficient in landing on
tow. You, your Flight Instructor, Towpilot, and FAA Examiner must
determine the level of acceptable risk when performing this or any
maneuver. You decide if you want to fly a "landing on tow", and don't
blame me if you screw it up.

I've heard some pilots say they would prefer to do an intentional rope
break than to try to land with the tow plane.

Tom

On Sep 7, 7:05*pm, ZZ wrote:
It is likely that the probability of an ACTUAL double release failure on
tow is what ever positive number is closest to zero. Of course that
doesn't mean that Mr.Murphy can't serve one of these up.

I would be interested in hearing any accounts of actual, non-instructor
induced double release failures which required either a landing on tow
or purposely breaking he rope to end the problem.

I would also be interested in any opinions regarding practicing landing
on tow to prepare oneself for this unlikely event. (I know that this is
or was a required maneuver in some European countries...but is it worth
the risk?)

Paul
ZZ

It's probably worth mentioning that 'release failure' can also be an
uncommanded release. I've had a couple of those when the wing runner
didn't fully insert the Tost ring set into the hook but it somehow
partially engaged only to release on it's own later. Examination
showed nothing wrong with the hook.

I recall the story of a woman in a 1-26 who had the red ball come off
in her hand due to the steel cable breaking off inside the ball. She
looked at it for a moment, then reached under the panel and pulled on
the remaining cable activating the release. Cool head.

I've flown several training gliders which required an unusual amount
of pulling motion to effect a release - the usual 2" tug wouldn't do
it. Many pilots checking out in the glider would report a 'release
failure' and I'd have to say "pull further". The take home is that
you need to make sure you've fully actuated the release.

Final note: The FAA and NTSB seem to be taking a serious look at
release mechanisms, ring sets and weak links. If there's an accident
investigation, it probably isn't wise to be found to be using a chain
link in instead of a Tost ring set or a weak link at variance from
that specified in the POH.

I've been informed that the weak link, Tost hook and ring set are part
of a gliders airworthiness certificate documentation and substitutions
are judged to be an unauthorized modification from a regulatory and
enforcement perspective. Most JAR 22 gliders specify a weak link
strength + or - 10% (read your POH) for both aero tow and winch which
effectively requires a metal link made by Tost or equivalent. Rope
weak links can't meet that strength tolerance.

On Sep 8, 8:13*am, tstock wrote:
I've heard some pilots say they would prefer to do an intentional rope
break than to try to land with the tow plane.

Tom

That would be my preference - especially with a high performance
glider. Landing a 50:1 glider with marginal air/wheel brakes on tow
doesn't sound workable to me.

The breaking strength of the weak link only has to be exceeded for a
millisecond to break it. It's easy to do that using full spoilers
applied with slack in the rope while raising the nose. Neither the
glider pilot nor tuggee will feel more than a slight tug as the link
breaks - if you're using the correct weak link.

Student pilots break links/ropes all the time so it shouldn't be hard
to do it on purpose. Obviously, this works better with a heavy glider.

On Sep 8, 7:13*am, FBCompton wrote:
On Sep 7, 11:21*pm, wrote:

**Is anyone teaching this

anymore?

Barry

Sure. *It's a good exercise for proficiency and confidence building.
Touch and goes, taxiing and even turning at runway intersection to
take off on a different runway. *Good communication, experienced tow
pilots, proper conditions, *FUN!

Why all CFIG's (in the USA) must discuss and teach this maneuver: *It
appears in your FAA Practical Test Standards (PTS) for Glider
"checkrides" under the Area of Operation "Launches and Landings"/
"Abnormal Occurrences" / "Glider and towplane release
failure" (meaning both releases fail.) *This is one of five listed
abnormal situations in your FAA PTS. *FAA allows the Examiner to ask
you to perform this maneuver, as the Examiner may ask you to perform
any or all of the tasks under "Abnormal Occurrences." *Most Examiners
just ask for the "towline break" demonstration and the "glider (only)
release failure" signal on tow, but "double release" is part of the
PTS, so be prepared to at least discuss the procedure on your
checkride.

Note to CFIG's: *Just because a double release failure is rare does
not mean you can skip over it in the PTS. * The FAA discusses double
release failure in the FAA Glider Flying Handbook, Chapter 7. *Not
much of a discussion however, but there it is. * Towpilots need to be
thoroughly briefed by a towpilot who has flown this maneuver. *The
descent is very gradual at a proper approach airspeed. *If the
approach doesn't look or feel right, the towpilot has the option to go
around and climb with glider still in tow.

Note to Readers: *My discussion posted here is abbreviated and not
complete and not to be substituted or used for any aspect of your
ground and flight instruction. *This post is discussion, not
instruction.

Regarding the glider in "low tow" position: *Because the towplane is
gradually descending the wake is relatively higher, so the glider does
not need to be too low in relation to the towplane. *The sight picture
is usually not as low as when you box the wake -- just enough to be
just under the wake, and with a full view of the towrope. *Keep the
airbrakes unlocked and deployed as needed to keep a tight towrope at
all times. Overrunning the towplane is the dangerous part both in the
air and on the ground roll out. *Be ready to release.

Important Timing Aspect: *The glider (in low tow) must not touch down
much before the towplane -- this can be a hazardous aspect -- touching
down well before the towplane and stalling it. *The glider wings are
still carrying the weight of the glider while it is flying. *Once the
glider touches the wings stop lifting and the glider creates more
weight drag on the towplane, which if still well above the runway will
be slowed and may stall. *If you try this maneuver, keep the glider
flying until the towplane is about one meter above the runway. *Make
sure the towpilot keeps the towplane moving forward (no brakes) with
some power to help keep the rope tight. *Glider pilot deploys nearly
full airbrake (spoiler) to keep from lifting off again and some wheel
brake, AFTER the towplane is on the ground. *Just roll out and not be
in a hurry to stop. *Both pilots should release if slack rope
develops. *If lots of runway ahead a touch and go is possible. *Long
runways and a good headwind make landing on tow a bit less
challenging. *A long towrope may be a good idea.

For the most comprehensive discussion and training on landing on tow,
along with purposely breaking the towrope, contact Cindy & Marty at
Caracole Soaring in California. *They have developed this procedure to
be relatively safe, and fun.

Remember, I am not your personal Flight Instructor here. *My
discussion posted here is abbreviated and not complete and not to be
used as part of your ground and flight instruction. * For more
instruction in "abnormal occurrences" on tow consult with your local
Certificated Flight Instructor, one who is proficient in landing on
tow. *You, your Flight Instructor, Towpilot, and FAA Examiner must
determine the level of acceptable risk when performing this or any
maneuver. *You decide if you want to fly a "landing on tow", and don't
blame me if you screw it up.

How much runway do you normally consume before both towplane and
glider come to a safe stop? I realize field elevation, density
altitude, wind,
obstructions, type of towplane and glider, are all variables. We have
a 3000ft dirt strip at 780ft MSL
field elevation, but have barbed wire fences to clear at both ends and
a ditch on one end. Is that enough to do it comfortably?

That would be my preference - especially with a high performance
glider. *Landing a 50:1 glider with marginal air/wheel brakes on tow
doesn't sound workable to me.


Unless you're flying an ASW-12, most high performance sailplanes in
the 50:1 class have very effective airbrakes.

On Sep 8, 8:13*am, tstock wrote:

I've heard some pilots say they would prefer to do an intentional rope
break than to try to land with the tow plane.

* * * * *
And what happens if the rope does NOT break? How is this rather benign
"emergency" magnified?
How many tow ropes /weak links (much) stronger than legal?

I am aware of one documented double release failure in the USA.


Tom Knauff

On Sep 8, 11:21*am, Tom wrote:
On Sep 8, 8:13*am, tstock wrote:

I've heard some pilots say they would prefer to do an intentional rope
break than to try to land with the tow plane.

* ** ** ** **
And what happens if the rope does NOT break? How is this rather
benign "emergency" magnified?

It isn't 'magnified'.

A the correct way to attempt a deliberate rope break is gentle and
safe - far more so than a landing on tow. It's just the regular rope
slack maneuver taught to private pilots without the effort to take the
slack out smoothly plus opening the spoilers. You're aiming for about
10' of slack while in the normal center high-tow position. Once you
have that, open the spoilers and raise the nose as needed to maintain
normal tow position.

If it doesn't work, you still have the landing option. Why not try a
gentle, controlled, rope break first? You might find you have a rope
that breaks easily. If you try the landing option first and it goes
wrong you may never get the chance to break the rope.

How many tow ropes /weak links (much) stronger than legal?

Probably less than the number of understrength ropes/weak links. But
that's a different issue being addressed by regulatory authorities.


I am aware of one documented double release failure in the USA.

That 's one more than I was aware of.

Probably less than the number of understrength ropes/weak links. *But
that's a different issue being addressed by regulatory authorities.


Bill,

Which regulatory authorities and where are they doing the addressing?

On Sep 8, 1:16*pm, FBCompton wrote:
Probably less than the number of understrength ropes/weak links. *But
that's a different issue being addressed by regulatory authorities.

Bill,

Which regulatory authorities and where are they doing the addressing?

The FAA & NTSB based on a conversation during a recent accident
investigation. The NTSB showed up at an accident site that would not
normally be on their radar - i.e. a minor accident with no in-flight
breakup, fire or fatality.

Their main interest was the weak link, ring set and release hook
maintenance/replacement records. They were obviously educating
themselves while building a data set for a report leading to further
action.

Another point which arose in that discussion is that if your POH says
you need a 650 KG weak link with a + or - 10% tolerance for both winch
and aero tow, the old 80 - 200% rule doesn't satisfy that
requirement. In most cases, the POH value falls within the 80-200%
range. but if it doesn't, the POH weak link value trumps the 80-200%
rule.