Grob Twin Astir

At 23:25 30 September 2016, Martin Gregorie wrote:
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 |


Martin,

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if
the efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the Acro
are close, I suspect that you will notice a favorable improvement.

Good luck...

RO

At 05:40 30 September 2016, Surge wrote:
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
i=
s
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
o=
ver braking and skidding on a grass runway in the clubs G103
without an
ins=
tructor 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
t=
hrough a fence during an off field landing because they couldn't
stop in
ti=
me 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
ele=
vator is safer for students because it will help reduce PIO's.

I have just spent a week flying in the backseat of nothing but a
Twin Astir, with a cable and drum brake. I found that the well
maintained drum brake is more than efficient enough to stop the
glider and is well able to rub the nose on the ground if over used.
So I repeat my question, why would anyone want to "improve" the
brake by including a hydraulic system when proper maintenance
will provide a perfectly effective brake and one which is far less
likely to cause problems?

"According to this FADEC dump, you ran the engines up to 106% on this takeoff out of Jackson Hole. Care to explain why you went to 106%?"

"Because they wouldn't go to 110%."

On Monday, October 10, 2016 at 12:11:16 PM UTC-5, Bob Kuykendall wrote:
"According to this FADEC dump, you ran the engines up to 106% on this takeoff out of Jackson Hole. Care to explain why you went to 106%?"

"Because they wouldn't go to 110%."

No, Bob. If it is a FADEC, you are not in control of the limits. :-)

On Sat, 01 Oct 2016 00:40:43 +0000, Michael Opitz wrote:

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if the
efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the
Acro are close, I suspect that you will notice a favorable improvement.

I finally checked our Acro II last Sunday: as I thought there's no fin
turbulation on it, so I've passed your reference to the Lindner TN to the
relevent club committee member.

It turns out that our Acro now has a fairly low cockpit weight capacity.
On Sunday we were using it for trial flights but we had to temporarily
take one of our ASK-21s off scheduled training duties to fly a reasonably
heavy trial flighter. Some of our members would like to use it for mutual
XC flying since its a better XC glider than an ASK-21 and has a decent
SDI flight computer fitted. That said, our ASK-21s do routinely go XC on
good days with students who are close to soloing - an 80km o/r to HusBos
is favourite with our paid instructors.


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

On Friday, October 7, 2016 at 5:00:07 PM UTC-7, Don Johnstone wrote:
So I repeat my question, why would anyone want to "improve" the
brake by including a hydraulic system when proper maintenance
will provide a perfectly effective brake and one which is far less
likely to cause problems?

Perhaps because some people have a different idea of maintenance?
Jim

At 22:46 10 October 2016, Martin Gregorie wrote:
On Sat, 01 Oct 2016 00:40:43 +0000, Michael Opitz wrote:

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if the
efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the
Acro are close, I suspect that you will notice a favorable
improvement.

I finally checked our Acro II last Sunday: as I thought there's no
fin
turbulation on it, so I've passed your reference to the Lindner TN
to the
relevent club committee member.

It turns out that our Acro now has a fairly low cockpit weight
capacity.
On Sunday we were using it for trial flights but we had to
temporarily
take one of our ASK-21s off scheduled training duties to fly a
reasonably
heavy trial flighter. Some of our members would like to use it for
mutual
XC flying since its a better XC glider than an ASK-21 and has a
decent
SDI flight computer fitted. That said, our ASK-21s do routinely go
XC on
good days with students who are close to soloing - an 80km o/r to
HusBos
is favourite with our paid instructors.


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


Martin,

Low seat load was the reason we sold our Acro several years ago.
If you have a lot of 2 seaters, you can schedule around it, but the
issue becomes a pain if you only have one or two 2-seaters to work
with.

If you can put up with the ground handling issues of a tail dragger,
and a little bit stiffer flight controls, you may find (as we have) that
the original Twin Astir gives a lot for the money invested. A lot of
them had been used as advanced XC trainers, and not for basic
training, so therefore minimal damage history.. This equates to a
retention of the already very high factory seat load of 242 Lbs/seat
plus another 22 Lbs in the baggage compartment. Some even have
water ballast. For XC training, the Twin 1 has a markedly slower
stall speed (with very effective trim) than the Twin II for better
thermalling performance. Best L/D is also ~4 points better than the
Twin II, so it is also noticeably better on the glides as well. For XC
training, I would take the Twin Astir over an Acro any day....IMHO

You can crash a Twin Astir, then add 40 Lbs of repair material and
still have a higher seat load than a NDH (No Damage History)
Twin II (let alone an Acro which will be 30-40 Lbs less than a
regular Twin II). Of course, these numbers are for the rest of the
world which doesn't have the RAF and BGA Twin II increased gross
weight agreements with Grob.....

RO

On Monday, October 10, 2016 at 9:00:20 PM UTC-6, Michael Opitz wrote:
At 22:46 10 October 2016, Martin Gregorie wrote:
On Sat, 01 Oct 2016 00:40:43 +0000, Michael Opitz wrote:

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if the
efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the
Acro are close, I suspect that you will notice a favorable
improvement.

I finally checked our Acro II last Sunday: as I thought there's no
fin
turbulation on it, so I've passed your reference to the Lindner TN
to the
relevent club committee member.

It turns out that our Acro now has a fairly low cockpit weight
capacity.
On Sunday we were using it for trial flights but we had to
temporarily
take one of our ASK-21s off scheduled training duties to fly a
reasonably
heavy trial flighter. Some of our members would like to use it for
mutual
XC flying since its a better XC glider than an ASK-21 and has a
decent
SDI flight computer fitted. That said, our ASK-21s do routinely go
XC on
good days with students who are close to soloing - an 80km o/r to
HusBos
is favourite with our paid instructors.


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


Martin,

Low seat load was the reason we sold our Acro several years ago.
If you have a lot of 2 seaters, you can schedule around it, but the
issue becomes a pain if you only have one or two 2-seaters to work
with.

If you can put up with the ground handling issues of a tail dragger,
and a little bit stiffer flight controls, you may find (as we have) that
the original Twin Astir gives a lot for the money invested. A lot of
them had been used as advanced XC trainers, and not for basic
training, so therefore minimal damage history.. This equates to a
retention of the already very high factory seat load of 242 Lbs/seat
plus another 22 Lbs in the baggage compartment. Some even have
water ballast. For XC training, the Twin 1 has a markedly slower
stall speed (with very effective trim) than the Twin II for better
thermalling performance. Best L/D is also ~4 points better than the
Twin II, so it is also noticeably better on the glides as well. For XC
training, I would take the Twin Astir over an Acro any day....IMHO

You can crash a Twin Astir, then add 40 Lbs of repair material and
still have a higher seat load than a NDH (No Damage History)
Twin II (let alone an Acro which will be 30-40 Lbs less than a
regular Twin II). Of course, these numbers are for the rest of the
world which doesn't have the RAF and BGA Twin II increased gross
weight agreements with Grob.....

RO

Competent repairs add little weight. A former BGA senior inspector who had a repair station flew a DG-300 through some wires and smashed it to pieces.. When rebuilt, it weighed within 10oz of new. That same inspector removed 37 lbs of filler from my previously repaired Kestrel 19 while re-contouring the fuselage between the wheel and tail boom. Takes a craftsman I guess..

The Twin Astir and T version winch launch very nicely and are quite cross country capable. If someone designed a nice filet for the wing root, it would probably go 10% better.

I'd heard there might be an effort to increase the Twin II payload, but nothing recently.

Frank Whiteley

At 06:00 11 October 2016, Frank Whiteley wrote:
On Monday, October 10, 2016 at 9:00:20 PM UTC-6, Michael Opitz wrote:
At 22:46 10 October 2016, Martin Gregorie wrote:
On Sat, 01 Oct 2016 00:40:43 +0000, Michael Opitz wrote:

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if the
efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the
Acro are close, I suspect that you will notice a favorable=20
improvement.

I finally checked our Acro II last Sunday: as I thought there's no=20
fin=20
turbulation on it, so I've passed your reference to the Lindner TN=20
to the=20
relevent club committee member.=20

It turns out that our Acro now has a fairly low cockpit weight=20
capacity.=20
On Sunday we were using it for trial flights but we had to=20
temporarily=20
take one of our ASK-21s off scheduled training duties to fly a=20
reasonably=20
heavy trial flighter. Some of our members would like to use it for=20
mutual=20
XC flying since its a better XC glider than an ASK-21 and has a=20
decent=20
SDI flight computer fitted. That said, our ASK-21s do routinely go=20
XC on=20
good days with students who are close to soloing - an 80km o/r to=20
HusBos=20
is favourite with our paid instructors.


--=20
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
=20
=20
Martin,
=20
Low seat load was the reason we sold our Acro several years ago.
If you have a lot of 2 seaters, you can schedule around it, but the=20
issue becomes a pain if you only have one or two 2-seaters to work=20
with.
=20
If you can put up with the ground handling issues of a tail dragger,
and a little bit stiffer flight controls, you may find (as we have)
that=
=20
the original Twin Astir gives a lot for the money invested. A lot
of=20
them had been used as advanced XC trainers, and not for basic=20
training, so therefore minimal damage history.. This equates to a=20
retention of the already very high factory seat load of 242 Lbs/seat
plus another 22 Lbs in the baggage compartment. Some even have=20
water ballast. For XC training, the Twin 1 has a markedly slower=20
stall speed (with very effective trim) than the Twin II for better=20
thermalling performance. Best L/D is also ~4 points better than the=20
Twin II, so it is also noticeably better on the glides as well. For
XC=20
training, I would take the Twin Astir over an Acro any day....IMHO
=20
You can crash a Twin Astir, then add 40 Lbs of repair material and=20
still have a higher seat load than a NDH (No Damage History)
Twin II (let alone an Acro which will be 30-40 Lbs less than a=20
regular Twin II). Of course, these numbers are for the rest of the=20
world which doesn't have the RAF and BGA Twin II increased gross=20
weight agreements with Grob.....
=20
RO

Competent repairs add little weight. A former BGA senior inspector who
had=
a repair station flew a DG-300 through some wires and smashed it to
pieces=
.. When rebuilt, it weighed within 10oz of new. That same inspector
remove=
d 37 lbs of filler from my previously repaired Kestrel 19 while
re-contouri=
ng the fuselage between the wheel and tail boom. Takes a craftsman I
guess=
..

The Twin Astir and T version winch launch very nicely and are quite cross
c=
ountry capable. If someone designed a nice filet for the wing root, it
wou=
ld probably go 10% better.

I'd heard there might be an effort to increase the Twin II payload, but
not=
hing recently.

Frank Whiteley

20 years ago we had an Acro with a strange history. Apparently it had spun
in and the whole front end replaced with one from another that had caught
fire in the factory. I don't remember any weiight problems. It was a lovely
glider to fly, except, with the slightest rain on the wings it reverted to
the performance of a brick. Never managed to spin it, and a 1g stall
attempt would just result in mushing flight. I have ridge soared it with
the stick on the back stop. It was a very well engineered and made glider,
and we too used it for cross country training, and I well remember once
taking a visiting king for a flight in it.
It came with a small pair of canards, to enable it to enter a spin more
easily, but because it had a new nose, the fixing holes were not there, and
we didn't need it to spin anyway as we had Puchaczs. Not the easiest to
rig, but it lived in the hangar, so not a problem. A glider I remember
with a great deal of affection.
Re the Kestrel 19, when mine was being rigged, you could hear the loose
bits left in thhe wings, rattling around.
Dave

On Tuesday, October 11, 2016 at 4:00:20 PM UTC+13, Michael Opitz wrote:
At 22:46 10 October 2016, Martin Gregorie wrote:
On Sat, 01 Oct 2016 00:40:43 +0000, Michael Opitz wrote:

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if the
efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the
Acro are close, I suspect that you will notice a favorable
improvement.

I finally checked our Acro II last Sunday: as I thought there's no
fin
turbulation on it, so I've passed your reference to the Lindner TN
to the
relevent club committee member.

It turns out that our Acro now has a fairly low cockpit weight
capacity.
On Sunday we were using it for trial flights but we had to
temporarily
take one of our ASK-21s off scheduled training duties to fly a
reasonably
heavy trial flighter. Some of our members would like to use it for
mutual
XC flying since its a better XC glider than an ASK-21 and has a
decent
SDI flight computer fitted. That said, our ASK-21s do routinely go
XC on
good days with students who are close to soloing - an 80km o/r to
HusBos
is favourite with our paid instructors.


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


Martin,

Low seat load was the reason we sold our Acro several years ago.
If you have a lot of 2 seaters, you can schedule around it, but the
issue becomes a pain if you only have one or two 2-seaters to work
with.

If you can put up with the ground handling issues of a tail dragger,
and a little bit stiffer flight controls, you may find (as we have) that
the original Twin Astir gives a lot for the money invested. A lot of
them had been used as advanced XC trainers, and not for basic
training, so therefore minimal damage history.. This equates to a
retention of the already very high factory seat load of 242 Lbs/seat
plus another 22 Lbs in the baggage compartment. Some even have
water ballast. For XC training, the Twin 1 has a markedly slower
stall speed (with very effective trim) than the Twin II for better
thermalling performance. Best L/D is also ~4 points better than the
Twin II, so it is also noticeably better on the glides as well. For XC
training, I would take the Twin Astir over an Acro any day....IMHO

All you say is correct.

The only problem is the diabolical rear seat shape cause by making room for the wheel to retract.

My club flew a pair of original 1978 Twin Astirs as the basic trainers for about a dozen years (mid 90s to late 00s). They were great in almost every way and a huge step up from the Blanik's we had before them. But the DG1000 18s we've replaced the Grobs result in sooo much less money going to the instructors' chiropractors.