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