This relates to the accident on 26th April, 2002 reported by NTSB as
DEN02GA039:
synopsis
http://www.ntsb.gov/NTSB/brief.asp?e...10X00654&key=1 ,
full report
http://www.ntsb.gov/NTSB/brief2.asp?...GA039& akey=1 .

I am not surprised that the widow wishes to sue; there are some features of
this accident which seem hard to excuse, but she is after the wrong people.

A./ THE AREAS WHICH SHOULD BE LOOKED AT INCLUDE THE FOLLOWING:

!./ Why did the tug only release the tow rope after it had broken?

Was this because the friction on an unmodified Schweitzer prevented release
under heavy load?

2./ Why did the glider only release the tow rope after it had broken?

Was this also because the hook fitted to the glider would not release under
heavy load?

3./ There is no mention in the NTSB report of the tug Schweitzer towing
hook being modified.

The difficulty of releasing under load from an unmodified hook is by now
well known, and suitable modifications are also now common knowledge.

4./ Why did the glider get too high behind the tug?

Did the glider with the towing hook in use have positive longitudinal
stability when on aerotow? If not, was this a factor?

If it was not stable, could another hook have been fitted and used which
would have given positive stability on tow?

5./ Was the experience, currency and training of the instructor adequate?

This is a question to be answered by those who trained, supervised and
authorised the instructor, not by the actual instructor.

The question applies both to the training given to the instructor as a solo
pilot; and how the instructor was coached, in particular as to how to teach
aerotowing.

B./ OBSERVATIONS.

a./ COMMENTS ON THE ACCIDENT.

Comments on the accident by Chris Rollings (who was recently for one year
Chief Flying Instructor at Mile High Gliding, Boulder Colorado) may be found
at:
http://www.glidingmagazine.com/ListF...Dtl.asp?id=327 .

Note particularly what he says about the Schweitzer hook.

Note also the difference between a K13 on the nose hook, a K13 on the winch
hook and a K8 on the winch hook.

The accident at the USAF Academy sounds like the case described by Rollings
of the K13 on a nose hook, but with a tug hook which would not release under
load.

b./ STABILITY AND RISK.

On the question of stability on tow, and on the question of risk generally,
Chris Rollings posted to R.A.S. (on 07 January 2004 07:57 to the thread
CG hook on aero tows??), I copy his posting below:

"Under JAR 22 (Glider Certification Rules), a glider is required to have
positive (or at least neutral) longitudinal stability. Put simply, if you
move the nose up (or down) a bit and then leave it alone, it should tend to
move back towards where it started from, or at least stay where it is, not
continue to pitch further up (or down).

"It is quite possible (easy in most cases) to learn to handle a glider that
does not have this stability, but it requires CONSTANT vigilance on the part
of the pilot. A failure in concentration of only one or two seconds can
result in a massive divergence of the flight path with catastrophic
consequences.

"Following the flight tests referred to earlier in this thread, conducted by
Verdun Luck, Brian Spreckley and myself in 1978 and 1982, it became obvious
to me that many gliders did not meet this requirement for positive pitch
stability when being aerotowed on a C of G release.

"My suggestion, at the time, was to change JAR 22 so as to make it explicit
that the requirement for positive pitch stability applied when the glider
was being aerotowed as well as in free flight (the only practical way I
could see to achieve this in most cases was with a release well forward of
the C of G, but I felt that other ways of achieving the desired result
should be acceptable if they could be found).

"The change over to requiring nose hooks is happening very gradually because
of the gliding movement's resistance to change, particularly any change that
costs money. The result of this is that changes in airworthiness
requirements are often not made retroactive. Pre-existing aircraft with
what are now seen to be unacceptable characteristics are 'Grandfathered in',
rather than face the hassle of making them comply.

"An argument, which has appeared often through this thread, is that an
individual or a club has done so many aerotows, or operated for so many
years, towing on C of G hooks without accident, so there is clearly no
problem.

"Let's look at the numbers. I will use the UK as an example, since I have
a fairly accurate knowledge of the statistics there, but the principals are
the same for any of the World's gliding nations. UK gliding fatalities
average about four per year, if it goes down to one or two everyone involved
in safety promotion starts to feel pleased, if it goes up to six or seven
there is concern that there is a problem growing and 'something needs to be
done'. The more sensible people, of course, look at a five or ten year
moving average rather than being overly influenced by one year's results.
There are around (OK probably just under) one hundred gliding operations in
the UK; if each one 'only' had a fatal aerotowing accident once every
twenty-five years, that would produce four such fatalities a year Nationally
and make EVERY year a problem year, with the average number of fatalities
double the present level. Central Government would doubtless step in with
some very heavy handed legislation.

"My point? That the fact that you, or your club, may have been operating
in a certain way for 25 years without a fatal accident, does not mean that
the practices are at an acceptable level of risk viewed nationally, simply
that they are not actually suicidal.

"Aerotowing on a C of G hook is something you can 'get away with', given a
high level of concentration, reasonable skill and the absence of bad luck.
However it carries a significantly higher risk of a nasty accident (often
fatal for the blameless tow-pilot), with the only real gain being the saving
of the (relatively) small cost of fitting a forward release. In my opinion
it should be something that is only done rarely, in case of real need, not
something that anyone accepts as the 'normal' way to launch to save the cost
of fitting the proper equipment.

"I am a staunch defender of anyone's right to risk his or her own life in
pursuit of any goal they hold dear (including saving money). In launching
on a C of G hook you are risking the tow-pilots life more than your own, and
this I will not defend."

c./ INSTRUCTOR TRAINING AND EXPERIENCE.

From the NTSB report,
"The instructor aboard N7538, a cadet third class, said she had made about
100 glider flights, each flight averaging about 15 minutes."

If this means what it says, the instructor had a total gliding flight
experience of about 100 flights and about 25 hours. This presumably
includes dual instruction as pupil, solo flying, coaching to become an
instructor, and experience as an instructor.

I do not know what is normal in the U.S.A., either in the U.S.A.F. or in
civilian life, for an instructor teaching aerotow launching; but this is
vastly less than enough by U.K. standards.

The minimum requirements for U.K. civilian gliding instructors are set out
in "Laws and Rules for Glider Pilots" first revision to 14th edition, July
2004 published by the British Gliding association at
http://www.gliding.co.uk/bgainfo/doc...tion14rev1.pdf .
Instructor Ratings and Endorsements are covered on pages 41 to 45,
Instruction and Passenger Carrying is covered on pages 19 and 20.

The requirements for a BGA Basic Instructor Rating include "Silver badge"
and "Minimum of 50 hours P1 on gliders". Basic instructors are only
allowed to teach the first upper air lessons, collision avoidance, effects
of controls etc.; they are not allowed (or trained) to teach launching or
landing.

The BGA Assistant Instructor Rating requirements include "Silver badge" and
"Minimum of 75 hours P1 on gliders, including 100 launches". Before
training to be an Assistant instructor, it is first necessary to become a
Basic instructor (see 15.8, p.44).

These are minimums, many clubs require much more experience.

d./ PUPIL TRAINING AND EXPERIENCE.

From the NTSB report,
"The student pilot aboard N7538 said that this was his second glider
flight."

So, on his second glider flight ever the pupil was unable to maintain
station behind the tug. No surprise there then!

There is nothing in the NTSB report to suggest that the accident was the
fault of the pupil in anyway whatever.

It is the instructor who is supposed to prevent things going disastrously
wrong, that is what an instructor (and the coaching of instructors) is for.

e./ AEROTOW LAUNCH TRAINING.

From the NTSB report,
"She decided to hold their position and raised the nose about 1-3 degrees to
reduce airspeed and make it easier for the tow plane to get back in
position."

This is extraordinary.

Aerotowing is (among other things) an exercise in formation flying. It is
for the glider to formate on the tug, not the other way around!

Where did the instructor get this idea, was she trained to think like this?
If not, why was this not picked up in her training, either as a pilot or as
an instructor?

The UK methods of instruction are covered in the BGA Instructors' Manual
(Second edition) available by mail and internet order from the BGA (but not
available to read online) http://www.gliding.co.uk click on "B.G.A. Shop"
then on "Manuals, Logbooks & handbooks" then on "Instructors' Handbook",
anyone may buy it.

Aerotowing is covered in section 4, chapter 17. I now give some quotes.

From the introduction (in full):

"Many aerotow trained pilots look back on their training and remember how
difficult it was to learn to aerotow. Some will admit to having been so
discouraged that they almost gave up. This is usually the result of
introducing aero-towing too early.

"If a trainee cannot fly the glider in a reasonably straight and coordinated
line in free flight, they won't be able to handle an aerotow. Ability to
fly in a decent straight line suggests that the trainee can detect and
correct for small changes in the bank angle - this is a must. Attempting
aero-towing too early (say after a set number of flights) will reduce a
trainee's confidence and probably prolong the training to solo. This is
certainly not 'giving value for money'. Post-solo pilots with wire launch
experience only, generally find learning to aerotow much easier, and
progress more rapidly. However, if tug upset accidents are to be avoided
(see page 17-8), you need to be thorough with these pilots as well.

"The trainee should not attempt the take-off and early part of the launch
until he can maintain position successfully during the later part of the
tow. Even experienced solo pilots converting to aerotow should follow this
sequence, though they might be given the complete aerotow briefing in one
session.

"The demonstrations and the trainee's early attempts shouldn't begin until
the tow reaches a height and position from which landing back on the
airfield poses no problem. Good airmanship requires the trainee and the
instructor to be aware of the circuit and landing options available during
every moment of the tow. Then, if there is a launch failure, or you have
to release unexpectedly, there will be less thinking to do. In the tow's
early stages this reduction in workload can be critical.

"The briefing and flying exercises are divided into three sections:

* positioning behind the tug, slack in the rope and releasing
* ground operations, ground run, take-off and initial climb
* launch failures, tug upsets and emergency signals."

From "Tug Upset Accidents" p. 17-6 (extracts):

"These are serious, and have caused the deaths of a number of tug pilots.
If the glider is allowed to climb rapidly behind the tug, it can very
quickly become impossible to prevent it accelerating upwards in a slingshot
action (rather like a winch launch), and tipping the tug over into a
vertical dive. Once this has happened only height can save the tug pilot
from disaster. Downward displacement of the glider to a position below the
slipstream is quite acceptable, but upward displacements are much more
critical.

"The glider pilot must release immediately if:

* the glider is going high and the tendency cannot be controlled, or
* the pilot loses sight of the tug.

"Factors which can combine to create a tug-upset accident a

* a light pilot flying close to the minimum cockpit weight
* an inexperienced pilot - particularly wire launch pilots with little
recent aerotow experience
* glider with a belly or CG hook
* short rope
* turbulent conditions."

From "Advice to Instructors" p. 17.9 (extracts):

"Aerotowing should not be taught before the trainee is capable of reasonably
well coordinated straight and turning flight. Because most early trainees
find the workload in this exercise very high, it is best to allow them to
fly only the last 500' to 1,000' of the tow. Progressively increase the
workload by lowering the height at which they take over control. Don't
allow them to attempt the take-off and first 500' until they can keep
station without assistance or frequent prompting on the upper part of the
tow. As a rule, if trainees get out of position below about 400', take
over rather than try to prompt them back."

From "Common Difficulties" p. 17-10 (extracts);

"Tends to rise above tug soon after take-off. Explain that (at least)
until the tug climbs away, the combination is still accelerating, so the
glider will rise unless it is prevented from doing so. The strength of
this tendency will depend, to a large extent, on the trim setting at the
time."

C./ CONCLUSIONS.

This post is already too long, I plan to complete this in another post.

W.J. (Bill) Dean (U.K.).
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