Compare/Contrast: CG hook on aerotow vs. CG hook on winch

On May 25, 7:20*pm, Markus Graeber wrote:
On Friday, May 25, 2012 9:36:16 AM UTC-5, Bill D wrote:
On May 24, 11:05*pm, b4soaring wrote:
On Friday, 25 May 2012 03:54:00 UTC+1, son_of_flubber *wrote:

Also, CG hooks can back release if you get a lot of slack in the rope.. The manual may suggest a method for blocking the back release - make sure you remove it before winching.

If the CG hook is functioning properly (i.e. no weak springs), it
would take a LOT of slack to get a back release. *So much so that
you'd be in front of the tug and probably want to release anyway.
Don't mess with the hook or you might make it malfunction completely.

Uncommanded releases are not a problem.

Actually they very well can be. I was piloting an IS-28B2 Twin Lark a couple of years ago behind a Super Cub during a 175 km transfer aerotow to another airport. We had to go over a pass and coming over the pass flew straight into serious rotor off a sharp mountain ridge bordering the valley we were entering.

Keeping the glider in position behind the super cub was a handful (a Twin Lark flies a bit like tank depending on what you are used to), I did end up getting some serious slack at one point while perfectly pointed at the cub. The cable bow reached back (the bow being to the left and almost level with the glider) to about where I was sitting in the front seat of the glider when I heard the "clonk" of the back release, the very moment I was starting to get worried it might just do that while remembering that the back release was not blocked...

The Twin Lark has a non-structural nose cone and the aerotow hook mounted just in front of the front rudder pedals. It is the same Tost hook as the CG hook installed and hence back releases unless you do something about it....

I could have grabbed the released cable if it hadn't been for the canopy, it was right next to me before I banked away to avoid potential damage. The bow was never a danger to the glider and never went anywhere near the wing tip or something else it could have caught onto, so the back release was completely unwarranted in this scenario.

An uneventful outlanding in unfamiliar terrain followed since we had plenty of altitude and I had a variety of fields to choose from but it was an all-nighter to get the trailer and crew there, load up the glider in the dark and get it to the destination airport through some serious mountain roads..

I made sure with a metal angle blocking any backwards movement of the hook rim that this would not happen again...

Markus Graeber

I used to own a Twin Lark equipped for serious wave and flew it in
some pretty darn turbulent Rocky mountain rotor. I never once got a
back release. I suspect you have weak springs in the hook or some
seriously draggy rope.

In the spirit of embarrasing admissions here.

I transitioned to aerotow at around 300 flights. Only ever winch
launched for the first part of my career.

By then I was a happy and reasonably competent Std Cirrus driver. (no
nose hook) I found aerotow difficult to get right because of over
controlling the Grob Twin Astir - I was not used to the momentum in
those heavy wings, and we were towing on CG hook so that I would be used
to it when I transited to the Cirrus - and we wallowed all over the
place behind the tug. To the despair of my instructors who no doubt
started wondering how I had flown solo...
Trying to simultaneously transition to aerotow, on CG hook, with a
completely new class of glider to me - put me back at ab-initio
competence for a while.

To shorten a long and frustrating experience - the winch experience on
the CG hook was little help. In fact the winch training can impede
progress. If you can fly aerotow competently the CG hook makes it only a
little more difficult. The aircraft will not self correct nearly as much
as on nose hook, so sloppy flying will be rewarded with diverging
excursions.

Then the good news - to get back to your questions - as soon as the CFI
let me go fly my own nimble little Cirrus it all went a lot better.
There is no substitute for experience - on type, and yes training will
help. The control harmony of what you are flying will influence the
outcome and what really counts is experience with aerotow in general,
and experience with what you are flying. Specifically the ability to fly
very precisely, and experience on the type you plan to fly on the CG hook.

CG hook specific misadventures:
If you get too high - especially with some designs, there is danger of
kiteing.
On the ground run, crosswinds are much more of an issue. No correcting
force on the nose so the grass at the side of the runway exerts an
inexorable attraction. You have to be on top of lateral control all the
time and be prepared to release the moment if goes sideways. Lateral
diversions on the ground run that are recoverable on nose hook tow will
result in a ground loop on the CG hook.
If your mount has airbrakes behind the CG you can help with directional
stability at any point by cracking them open.
Nose up pitch - the CG hook is below the centreline, so jerks on the tow
rope will tend to rotate the nose up. Especially on a light high drag
single seater like a Ka8. (this is one way to go kiteing)

(PS: The Grob STILL flies like a pig on CG hook - just my biased
personal view.)



On 2012/05/25 4:54 AM, son_of_flubber wrote:
I've been told (and witnessed) that aerotow on CG hook is initially difficult for someone who has trained for aerotow with a "nose hook" (aka hook-forward-of-CG). Suppose this CG-hook-newbie were to take winch tow training (with CG hook). Would the winch training reduce the initial difficulty of a CG hook aerotow?

Do the difficulties/danger of aerotow with CG hook go away completely with training and experience?

What sorts of misadventures are reasonably attributed to aerotow on CG hook?

I understand why CG hook is superior for winch tow. No need to rehash that explanation.

--
Bruce Greeff
T59D #1771

CG hook specific misadventures:

On the ground run, crosswinds are much more of an issue. No correcting
force on the nose so the grass at the side of the runway exerts an
inexorable attraction. You have to be on top of lateral control all the
time and be prepared to release the moment if goes sideways. Lateral
diversions on the ground run that are recoverable on nose hook tow will
result in a ground loop on the CG hook.


Yes, to all of the above.

Plus, the glider type seems to make a difference. The Pegasus 101A that
I used to own a piece of always wanted to head for the weeds in any kind
of cross wind (and I've seen two others get damaged like that). OTOH,
the LS6-b that I now fly simply tracks straight under the same
conditions - no fuss.

Be sure that the glider is perfectly aligned before the take off roll on
a normal launch.

On an unassisted launch (read 'land out'), I put the down wingtip
slightly ahead, expecting the tip drag to straighten me out by the time
the wings level. How much of a lead depends on the surface type.

A nose hook is clearly superior for aero tow.

Tony "6N"

On May 24, 7:54*pm, son_of_flubber wrote:

Do the difficulties/danger of aerotow with CG hook go away completely with training and experience?

What sorts of misadventures are reasonably attributed to aerotow on CG hook?

It all depends on the glider. There is no generic answer.

To put my reply in context I have 456 aero tow launches with CG hook
in ASW19b and 243 aero tow launches with CG hook in ASW 28.

Neither glider has any issue at all with pitch stability or
directional control while in flight. The ASW 28 has no issues at all
with directional control on the the ground. However, the ASW 19b with
its small tail wheel could be tricky in moderate to strong cross winds
at the start of the takeoff roll. I have no way of knowing how much
better it would have been with a nose hook. With proper positioning
of the glider and with proper pilot technique I was able to make
takeoffs in any wind condition other gliders or pilots could handle.

Unless you are planning to fly a vintage glider that is prone to
kiting, and if you are competent at aerotow with a nose hook, the only
issues you are likely to experience with a CG hook a

1. Risk of rope over-run and back release if the tug takes up slack
quickly. That's easily avoided by using the wheel brake.

2. Inadequate directional control at start of takeoff roll with cross
winds. This can be reduced by positioning the glider to compensate or
by using a wing runner who understands the problem and helps to keep
you straight.

The other side of the coin is that, as a tow pilot, I have been
subjected to moderate to severe abuse by pilots learning to fly the
Std Cirrus. As I said it depends on glider type and pilot skill
level.

A final data point - My ASW 28 has both a forward belly hook and a CG
hook. I choose to always use the CG hook for aerotow.

Andy (GY)

To put my reply in context I have 456 aero tow launches with CG
hook
in ASW19b and 243 aero tow launches with CG hook in ASW 28.

Well, if you can manage ASW19b in aerotow using CG hook, you
should not have any problems with anyting else. I think that in
ASW19b the hook position is a typical compromise - works well
neither in winch or aerotow.

On May 24, 7:54*pm, son_of_flubber wrote:
I've been told (and witnessed) that aerotow on CG hook is initially difficult for someone who has trained for aerotow with a "nose hook" (aka hook-forward-of-CG). *Suppose this CG-hook-newbie were to take winch tow training (with CG hook). *Would the winch training reduce the initial difficulty of a CG hook aerotow?

Do the difficulties/danger of aerotow with CG hook go away completely with training and experience?

What sorts of misadventures are reasonably attributed to aerotow on CG hook?

I understand why CG hook is superior for winch tow. *No need to rehash that explanation.

Our primary trainer is an SGS 2-33A, with the low forward tow hook, it
likes to climb (kite) on tow and students learn to keep the nose down.
After solo they transition to the SGS 1-26D. After they are rated,
they transition to our Grob 103 on the nose hook. When they are ready
for single seat glass, we'll do a few tows in the Grob on the CG hook.

Big issue, on a CG hook the glider goes where it is pointed. No
assistance from rope tension on the nose to help keep you pointed on
the tow. We teach slack line recoveries to get the nose pointed at tow
before the line comes taught. That training transitions to tow with
the CG hook. Law of Primacy.

If on the ground, a wing goes down and you are pulled to the low wing
and can't correct, RELEASE!
If you are in the air and get wide in a turn on tow, get your nose
pointed back at tow. The glider will accelerate and faster means it
wants to climb. If you've ever been on water skis you'll understand.

T

I agree it's very type-specific. My first CG aerotow was an LS4 with a
tailskid on a gravel runway. 10 yds of furious pedal work and then it
all came together. On tow I could feel no difference from a nose hook
as the LS4 has perfect manners. My tailwheel Open Cirrus is even
easier, including launching (from short grass) with no wing runner and
the wing down.

I once aerotowed a K13 on the CG hook by accident - chatting to my
pupil and didn't notice the wrong hook was selected. No problem on the
ground run, but the offset CG hook meant that I had to fly the entire
tow with some rudder.

Other types may be harder to handle. An earlier poster said that only
a stupid pilot would allow kiting, but the BGA experiments some years
back demonstrated that stupidity would not be necessary. Take
something like a K8, which pitches up aggressively when there is a
strong pull on the rope. Add in strong thermals and a pilot who reacts
a second or two late (say low hours or out of currency) and kiting
goes out of control rapidly, leading to a tug upset.

Most UK clubs won't allow a light, high-wing glider to be aerotowed
off a CG hook (though experienced pilots might, or might not, be an
acceptable risk).

But a decent-handling glass glider should be perfectly manageable.
Directional instability on the ground run? Fix it with the rudder and,
if you can't, pull the bung. Perfectly safe enough. If you might hit
another glider or run off the field, even if you pull the release,
then you're launching from the wrong place.

At 15:34 25 May 2012, T wrote:

If on the ground, a wing goes down and you are pulled to the low wing
and can't correct, RELEASE!

The above statement is probably the best advice you will ever receive, if I
was picky I would make it even shorter, "If on the ground, a wing goes
down, RELEASE!"
Several years ago the BGA in the UK recommended that the hand was on the
release at all times once the cable is attached (winch and aerotow). This
means that the pilot cannot give hand signals for the take up slack/all out
so the attachment of the cable is the indication that the pilot is ready
for launch. If the pilot wants to stop the launch he releases. In flapped
gliders I used a length of para cord attached to the release and looped
over my wrist.
I had reservations about this system but on balance it is the safest of the
alternatives, early release prevents a bad situation becoming a disaster.

To add to the chorus:

Any of the more-modern ships I've flown (70's glass/metal and newer)
seem to fly just fine on Aerotow with a CG hook. There are three
points to consider during the launch, in this order:

1) Wing position and cross-wind corrections. This has been covered by
others in the thread well-enough; but I'd like to emphasize that
starting with full downwind rudder helps a lot, at least in my
experience. And, as others have said: The best thing to do is watch
your first 50 feet of ground-roll. If it is going from bad to worse
yank the release and come to a controlled stop. In my experience with
auto-racing and flying, the worst situations always seem to happen
when something starts to go wrong and a person tries to "save it" (by
leaving their foot on the gas, or over-correcting, or whatever).
Don't try that - just call it off and try again.

2) On liftoff - as you get rolling try to use forward-stick and stick-
trim to get the tailwheel off the ground as soon as your rudder is
effective. That'll give you better steering control on the remainder
of takeoff *and* put the wing at a lower angle of attack (so you won't
jump/kite as quickly). Be prepared to add forward stick as you come
off the ground, and don't be shy about changing your trim multiple
times on the takeoff and aerotow. I'm not yet a CFIG but I've been
flying with a lot of new-to-XC pilots recently and I've noticed that a
LOT of them don't trim on aerotow, during thermalling, or in many
other phases of flight. Trim is your friend - the less you're pulling
or pushing on the stick, the better control-inputs you can provide for
roll & pitch excursions and the more relaxed you'll fly (making you
better able to feel and focus on other things).

3) Throughout the launch and aerotow - USE YOUR FEET! Aerotowing with
a CG hook means that you can pretty-much point the nose in any
direction you want. I actually view it as a nice "bonus" and prefer
towing with a CG hook for this reason (excepting the crosswind
difficulties during the beginning of the ground-roll). But I again
have found many newbies recently that don't think to use their feet on
aerotow. Its far easier to make small corrections with a bit of
rudder and slipping, than with big bank-angles on tow. Keep your feet
active and don't be shy about using some rudder (within reason) to
keep the glider behind the towplane and pointed in the direction you
want.

Just my $0.02,

--Noel
P.S. The back-release of the rope is a tricky thing on the ground in
my DG-300; like others I find a bit of wheelbrake while taking up
slack and just at the beginning of the roll is an effective "cure".

Originally Posted by noel.wade

To add to the chorus:

Just my $0.02,

--Noel
P.S. The back-release of the rope is a tricky thing on the ground in
my DG-300; like others I find a bit of wheelbrake while taking up
slack and just at the beginning of the roll is an effective "cure".

Not that I can claim to be an expert or know much, but in my Pilatus manual it mentions removing part of the Tost Release to allow for Winch launches --i.e. to allow a back release (I know my Pilatus is set for Aerotow and doesn;t back release with big slack...). If the part is not removed, there is no back release. Perhaps the different experiences in the same planes is tied to how their planes and the release mechanism were set up...

Just a WAG,
Squeak