Grob Twin Astir

On 9/29/2016 6:55 AM, Don Johnstone wrote:
At 02:02 29 September 2016, Michael Opitz wrote:
At 09:59 28 September 2016, Don Johnstone wrote:
Snip...
Very true, the original Grob 103 Twin Astir had no nosewheel so a super
efficient brake is not a good idea, unless of course you want to
grind off the gel coat, or even worse the underlying structure under
the nose. The Grob103 Acro did have a nosewheel and therefore the
more efficient disc brake was not a problem. I always wonder if people
actually think through the implications of
making something "better". Perhaps there was a reason why the original
design did not have a super efficient brake. Duct tape can't fix
stupid, it can muffle the noise.

Snip...
I view the extra stopping power of the disc brake as another tool in my
toolbox of flight controls. I don't use all of its capabilities under
normal conditions, but if a situation occurs where I need that power,
want to be able to access it NOW. For example, if I have a low altitude
rope break and am forced into a situation where there is not much room to
stop, I (personally) would rather get on the brake hard (even if it means
scraping the nose) in order to avoid being forced to make an intentional
ground loop (and breaking the tail boom +) to avoid a looming obstacle.

I flew professionally for 42 years, and it always grated on me when
someone took a useful tool out of my toolbox "for my own good".

Whether one is a pilot, cabinet maker, electrician or whatever, one has
tools to ply one's trade. Some of those tools will have the capability
to kill or maim. It is the responsibility of the OPERATOR to use those
provided tools with skill, accuracy and judgement. Don't blame the tool,
when the problem is in reality an inept operator....

RO

I would agree with you IF gliders, especially 2 seat gliders were always
flown by pilots experience as you and I. Truth is they are not, they are
frequently flown by very inexperienced and sometimes inept pilots, that is
the nature of gliding. The wheel brake on a glider is not a mission
critical item, unlike a powered aircraft the brakes are not tested before
taxiing, in most cases we only find they do not work on landing which is
why I never rely on them. I accept a good brake may be best in the
situation you describe but that occurs rarely. The risk of damage by a
nose over is much greater and more common. One of those cases where the
cure is worse than the disease. I do accept that the Twin Astir is very
tail heavy and almost impossible to nose down with the OEM brake, not so
with a more efficient disc brake.


Hmmm...Izziss (i.e. inexperience/incompetency/inattention/etc.) why anti-skid
brake technology on motor vehicles has become so popular? Would it not be
simpler/cheaper/better to have weaker brakes on motor vehicles? Ah, for the
good ol' days of drum brakes all around and no power assist. Thanks for
helping me belatedly realize weak, fading brakes on my first tow vehicle were
actually a safety *asset!*

In this particular "religious argument" I cast my vote for "overly powerful,"
easily modulatable, glider wheel brakes. My 2nd high-performance single seater
(purchased w. me having a whopping 200 hours stick time) actually had this
combination...and some 39 years later I still have difficulty imagining
anything better.

Bob W.

I learned the hard way that automobile antiskid brakes do not shorten braking distance. They only improve handling during heavy braking.

Paul A.
Jupiter, FL
Treasure Coast Soaring

.... And 4-wheel-drive simply gets you in deeper before you get stuck.

I think I'll slink off to my safe place now and hide so I don't feel
uncomfortable any more.

On 9/29/2016 11:33 AM, Paul Agnew wrote:
I learned the hard way that automobile antiskid brakes do not shorten braking distance. They only improve handling during heavy braking.

Paul A.
Jupiter, FL
Treasure Coast Soaring

--
Dan, 5J

The Twin Astir Trainer (fixed gear version) came with a standard
hydraulic disc brake from the factory. The ones which people
are
retrofitting are the more numerous retractable gear versions.
There
was a problem with that disc being too thin and deforming, but
TOST put out a retrofit kit to fix that issue last year.

I view the extra stopping power of the disc brake as another tool
in
my toolbox of flight controls. I don't use all of its capabilities
unde

normal conditions, but if a situation occurs where I need that
power,
want to be able to access it NOW. For example, if I have a
low altitude rope break and am forced into a situation where
there is
not much room to stop, I (personally) would rather get on the
brake
hard (even if it means scraping the nose) in order to avoid being
forced to make an intentional ground loop (and breaking the tail
boom +) to avoid a looming obstacle.

I flew professionally for 42 years, and it always grated on me
when
someone took a useful tool out of my toolbox "for my own good".

Whether one is a pilot, cabinet maker, electrician or whatever,
one
has tools to ply one's trade. Some of those tools will have the
capability to kill or maim. It is the responsibility of the
OPERATOR to
use those provided tools with skill, accuracy and judgement.
Don't
blame the tool, when the problem is in reality an inept
operator....

RO

I would agree with you IF gliders, especially 2 seat gliders were
alway
flown by pilots experience as you and I. Truth is they are not, they
ar
frequently flown by very inexperienced and sometimes inept
pilots, that i
the nature of gliding. The wheel brake on a glider is not a missio
critical item, unlike a powered aircraft the brakes are not tested
befor
taxiing, in most cases we only find they do not work on landing
which i
why I never rely on them. I accept a good brake may be best in th
situation you describe but that occurs rarely. The risk of damage
by a nos
over is much greater and more common. One of those cases
where the cure i
worse than the disease. I do accept that the Twin Astir is very tail
heav
and almost impossible to nose down with the OEM brake, not so
with a mor
efficient disc brake.

The Twin Astir was the Duo Discus of its day. Training was done in
K-7's and K-13's, and the inept pilots were not allowed to fly the
"sacred cow" higher performance Twin Astirs. The Twins were
used for the more experienced pilots enjoyment, and to teach XC.
This is evident in how the two Twin Astirs which our club operates
were kept in absolute pristine condition for 30+ years.

The Twin II was designed for training, but had a low max gross
weight, and a lower payload than the Twin Astir. Fast forward a few
decades, and most of the Twin II's have been crashed and repaired
to the point that the seat load is no longer very usable
(except in England where you have a higher gross weight
agreement with Grob). So now, due to prices and seat loads being
what they are, people are starting to try and use the Twin Astir for
primary training. There are trade-offs because this glider wasn't
designed with this purpose in mind. Ground handling is one trade-
off, and the wheel brake is another.

To your point of a low altitude rope break being rare, well we had a
towplane engine failure at about 50' three years ago. The glider
wound up in the bushes off the end of the runway with significant
damage. These scenarios do happen. The more likely scenario in
the Northeast USA is that the inept pilot gets low too far away from
home, and then has to land off airport in one of our small hilly
fields. In that case, I would still want the inept pilot to have a
strong wheel brake to stand the glider on its nose if he/she has to.
The philosophy here is that even though the field may look good,
one stops the glider right away for fear of ripping the gear off due
to falling into an unseen gopher hole, etc. Most fields here are short
enough that there is usually no question about the need to get it
stopped immediately anyway. If they are going to be allowed to fly
a Twin Astir, the inept people need to be taught not to yank on the
dive brake handle (during a normal landing) as though they have a
death wish...

Obviously, you people can operate your gliders as you see fit. I had
thought of using the automotive technology argument, but someone
else already brought that up. We have chosen to upgrade our
equipment to the newer technology, (that most new gliders come
equipped with) and are happily operating our Twins with it. If you
want to take a useful tool out of your pilot's toolbox, that is your
decision. I will keep that useful tool in mine though...

RO

On Wednesday, September 28, 2016 at 7:37:29 AM UTC-7, John wrote:
It's ironic that the I received an email from the Utah Soaring Association indicating yesterday telling about one of our Grob Astir's had a hard landing a few weeks ago that ripped off the disk brake caliper. The damage inspection found this is not the first time this has happened as the caliper hangs down at the 6 o'clock position. The Utah board is looking at taking it back to the original drum brake design for better hard landing durability.


I guess someone didn't read my post from January -- recommending the ten ply tire... and smooooooth landings. Sorry for their troubles. Pilot training issues, usually. More training. I side with Mike O -- leave me all the tools. Then I can choose which to use, or what parts to sacrifice.

Cindy B

On Thursday, 29 September 2016 15:00:07 UTC+2, Don Johnstone wrote:
I would agree with you IF gliders, especially 2 seat gliders were always
flown by pilots experience as you and I. Truth is they are not, they are
frequently flown by very inexperienced and sometimes inept pilots, that is
the nature of gliding. The wheel brake on a glider is not a mission
critical item, unlike a powered aircraft the brakes are not tested before
taxiing, in most cases we only find they do not work on landing which is
why I never rely on them.

If a student is inept then he/she should not be sent solo.
I had less than 10 flights to my name and I could already feel when I was over braking and skidding on a grass runway in the clubs G103 without an instructor needing to correct me.

Do you propose that we send students into the air with only half the tools in the bag and then plead ignorance when they decapitate themselves going through a fence during an off field landing because they couldn't stop in time and messed up an attempted ground loop?

I consider brakes mission critical and test them on every pre-flight.
No brakes or inefficient brakes means the glider is grounded.

Sheesh ... just now someone is going to propose that a half functioning elevator is safer for students because it will help reduce PIO's.

....Actually, the Grob already has the half functioning elevator, but that is to prevent spins not stop PIO!
I'm sorry!😉 I agree with your post but had to take the bait.

On Fri, 30 Sep 2016 02:30:40 -0700, dtarmichael wrote:

...Actually, the Grob already has the half functioning elevator, but
that is to prevent spins not stop PIO!

IME the elevator is reasonably functional on a G103 Twin 2 Acro but it
could certainly use a better rudder.

However it will spin: I did my annual spin checks one year in our one.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

IME the elevator is reasonably functional on a G103 Twin 2 Acro but it
could certainly use a better rudder.

Does it have the Z tape installed in front of the control surfaces as per
the Grob/Lindner optional service letter SL-12? If not, you might find
the effectiveness will be enhanced if you do install it. It works
wonders for the Twin Astir rudder... It is certainly easy and cheap
enough to try, and it is factory approved as well.....

RO

On Fri, 30 Sep 2016 13:26:10 +0000, Michael Opitz wrote:

IME the elevator is reasonably functional on a G103 Twin 2 Acro but it
could certainly use a better rudder.

Does it have the Z tape installed in front of the control surfaces as
per the Grob/Lindner optional service letter SL-12? If not, you might
find the effectiveness will be enhanced if you do install it. It works
wonders for the Twin Astir rudder... It is certainly easy and cheap
enough to try, and it is factory approved as well.....

I don't recall seeing any zigzag strip in front of the rudder hinge. I'll
look next time I'm at the club and mention this where it may do some good
if it is not turbulated.

Thanks for the tip.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |