motorgliders as towplanes

At 20:28 11 March 2009, Mike the Strike wrote:
You're right - it was the Samba, the Lambada's cousin. I witnessed
several launches there, including some ballasted ships and none of
them looked scary, although ground run was long.

I'm a great believer in towplane mass and power - my all time favorite
is the 600 HP AgCat.

Mike


Long ? About 3km available on the northerly run and 1.4 south!
The Samba didn't need anything like that. It is still being used for
towing at Gariep and other places.
Its launch rate was only a little less than the other tugs used (C182's
mostly). It might have been entertaining if he had been towing the Nimbus
3 with brakes open instead of a C182 (which was only just climbing!).

Bruce wrote:
wrote:
On Mar 8, 1:03 pm, Brad wrote:
Can a MG tug pull a loaded 2 place Blanik on a standard day at SL,
from a 1800' grass strip? Or perhaps such a tug could be used to tow
the members single place ships, and the heavier/ 2-place ships stow
behind the clubs remaining pawnee?
Brad

http://www.youtube.com/watch?v=5UYPyNgf4Q4

Lambada motorglider towing
UFM 13 Rotax 912 100hp

Personally I would far rather be behind the 100hp Samba or Lambada with
my Std Cirrus - hot and high off grass the accelleration is slower, but
the propwash is limited and climb is better than the asthmatic 180hp
(must be really little ponies over there) super cub.

The wingloading on the Lambada is very similar and the tow combination
is nicely balanced. Behind a 235hp Rallye it is, by comparison
wonderful. Same time to altitude without all the - extreme speed just
off the deck waiting for the tug to leap skyward, then get to be like a
good martini and get all shaken up by the wake turbulence - then scream
around on the outside of all the thermals.

Give me a motorglider any time...

Bruce
In case anyone thought that the MG/UL has too little grunt.
Follow the link below.

The story behind it is - experienced pilot in getting current again on
Janus forgot the thing has a drogue chute.
On a check flight the Janus is towed up from an airfield (Orient) at
5100" MSL at around 20 centigrade.
As you can see the Samba accelerates slowly - then the drogue chute
deploys. (one bump too many )
Tuggie happens to be enormously experienced CFI - uses his head and
abuses the Rotax a little. Combination manages to make a circuit and the
Janus gets dropped over the threshold.
Samba engine did not over heat or suffer any apparent damage, although
it was kept in the time limited maximum power range for the entire circuit.
For information , low down there are very few options straight out on 36
that would not include reducing the Janus to kit form if he had been
dropped before getting back to the runway.

http://www.youtube.com/watch?v=4_w3n...eature=related

With a light single seater it beats the climb performance of the super cub.

On Mar 12, 1:09*pm, Bruce wrote:
Bruce wrote:
wrote:
On Mar 8, 1:03 pm, Brad wrote:
Can a MG tug pull a loaded 2 place Blanik on a standard day at SL,
from a 1800' grass strip? Or perhaps such a tug could be used to tow
the members single place ships, and the heavier/ 2-place ships stow
behind the clubs remaining pawnee?
Brad

http://www.youtube.com/watch?v=5UYPyNgf4Q4

Lambada motorglider towing
UFM 13 Rotax 912 100hp

Personally I would far rather be behind the 100hp Samba or Lambada with
my Std Cirrus - hot and high off grass the accelleration is slower, but
the propwash is limited and climb is better than the asthmatic 180hp
(must be really little ponies over there) super cub.

The wingloading on the Lambada is very similar and the tow combination
is nicely balanced. Behind a 235hp Rallye it is, by comparison
wonderful. Same time to altitude without all the - extreme speed just
off the deck waiting for the tug to leap skyward, then get to be like a
good martini and get all shaken up by the wake turbulence - then scream
around on the outside of all the thermals.

Give me a motorglider any time...

Bruce

In case anyone thought that the MG/UL has too little grunt.
Follow the link below.

The story behind it is - experienced pilot in getting current again on
Janus forgot the thing has a drogue chute.
On a check flight the Janus is towed up from an airfield (Orient) at
5100" MSL at around 20 centigrade.
As you can see the Samba accelerates slowly - then the drogue chute
deploys. (one bump too many )
Tuggie happens to be enormously experienced CFI - uses his head and
abuses the Rotax a little. Combination manages to make a circuit and the
Janus gets dropped over the threshold.
Samba engine did not over heat or suffer any apparent damage, although
it was kept in the time limited maximum power range for the entire circuit.

Mike I don't think the effect has anything to do with standard vs
flapped gliders. I've owned three flapped ships and this phenomenon
has perplexed me on each.

I had a tow in my ballasted ASG-29 yesterday and I'd told the tow
pilot to maintain minimum 80 mph. Several times he got down to 70 mph
(60 knots IAS) and I was fighting to maintain control of the glider,
at a speed that would be just a couple knots below best L/D were I in
free glide.

I've learned to ask for a speed that will keep the glider happy at
neutral flap setting (think standard class) and then lower the flaps
when the tug is flying to slow, and I have to do this at some point on
darn near every tow.

2NO

On Mar 13, 9:09*am, Bruce wrote:
The story behind it is - experienced pilot in getting current again on
Janus forgot the thing has a drogue chute.
On a check flight the Janus is towed up from an airfield (Orient) at
5100" MSL at around 20 centigrade.
As you can see the Samba accelerates slowly - then the drogue chute
deploys. (one bump too many )
Tuggie happens to be enormously experienced CFI - uses his head and
abuses the Rotax a little. Combination manages to make a circuit and the
Janus gets dropped over the threshold.

Nice.

We disable the parachute on our Janus. I'm not even sure why it has
one. The spoilers are about the same as a Duo, PLUS it has a landing
flap setting that is effective enough that you need a fairly steep
approach if you want to use half spoilers as well, PLUS it has one
heck of an effective slip which (unlike the parachute) can be
modulated or used multiple times as desired.

Running out of elevator authority is very different then stalling. A glider
stalls when the angle of attack increases past a critical point. Reducing
the angle of attack, increases your stall margin.

Mike Schumann

"Mike the Strike" wrote in message
...
On Mar 11, 6:33 pm, "Mike Schumann" mike-nos...@traditions-
nospam.com wrote:
I can't imagine why the stall speed would change on tow. The controls may
feel different because the tow rope is pulling on the nose, so any attempt
to turn or change the angle of attack will face an increased counter
force,
but that's different than a change in the stall speed of the glider.

Read my earlier post!

The tow rope in some gliders (especially those standard class racing
gliders with a shallow angle of incidence) acts to pull the nose down,
reducing the angle of attack of the wing and tailplane. The stall
speed depends not only on speed, but angle of attack - if you reduce
it by pulling down on the nose, lift will be reduced. As I mentioned
earlier, the Discus 2 runs out of elevator authority somewhere below
60 knots and descends into low tow, even though its free-flight stall
speed is less than 40 knots. It's not just a difference of feel - the
glider wallows and almost becomes uncontrollable.

Mike

On Mar 12, 4:02*pm, Tuno wrote:
Mike I don't think the effect has anything to do with standard vs
flapped gliders. I've owned three flapped ships and this phenomenon
has perplexed me on each.

Region 12 contest at Cal City maybe 20 years ago, I was flying my
ASW-20B. Fully ballasted, behind a Maule the takeoff and first 4-500'
were OK, then inexplicably the tow pilot decides to slow down. I
start asking, then screaming for more speed, but to no avail - the
IDIOT decided to fly with the radio off for some reason.

I forget what the indicated airspeed was, but it was a little above
stall, perhaps 50-55 knots. With the stick at the aft stop, the
glider still settled slowly into low tow and that's where I stayed up
to release altitude. The ailerons had almost no authority - the stick
felt as sloppy as it would on the ground with no air loads on the
ailerons.

My left hand was holding the release as I waited for indications of a
spin entry. Had I been lower when this started to happen, the only
safe option would have been to release and land in the desert scrub.
But I was comfortable enough with the ship's stall / spin
characteristics (exciting to say the least, but manageable) that I
felt it was safer to just hang on to 2K or a thermal - again I don't
recall that detail. But I do remember that it took a good 15 - 20
minutes of thermalling away from the other contestants before I
stopped shaking from both fear and anger.

-Tom

At moderate climb angles, and as long as you are not totally dangling on
the end a bit or rope (as in a helicopter lift), the glider is essentially
still in free flight during an aerotow. To produce enough lift to climb,
the glider's wing must be at a higher angle of attack for a given
airspeed than it would be in normal gliding flight. Therefore the airspeed
at which the wing stalls must be higher.

Or looking at it another way, the wing has to support the normal weight of
the glider and its occupants, plus the component of the weight acting
backwards and downwards, so an effective increase in wing loading.

Quite a few pilots who have aerotowed behind motorgliders and other slow,
low powered, tugs have commented on how the glider feels uncomfortably
close to the stall, even when the airspeed is a least 10 knots above the
normal stalling speed, so I am reasonably sure that this is a real effect.


Derek Copeland


At 18:19 13 March 2009, Mike Schumann wrote:
Running out of elevator authority is very different then stalling. A
glider
stalls when the angle of attack increases past a critical point.
Reducing

the angle of attack, increases your stall margin.

Mike Schumann

"Mike the Strike" wrote in message
...
On Mar 11, 6:33 pm, "Mike Schumann" wrote:
I can't imagine why the stall speed would change on tow. The controls
may
feel different because the tow rope is pulling on the nose, so any
attempt
to turn or change the angle of attack will face an increased counter
force,
but that's different than a change in the stall speed of the glider.

Read my earlier post!

The tow rope in some gliders (especially those standard class racing
gliders with a shallow angle of incidence) acts to pull the nose down,
reducing the angle of attack of the wing and tailplane. The stall
speed depends not only on speed, but angle of attack - if you reduce
it by pulling down on the nose, lift will be reduced. As I mentioned
earlier, the Discus 2 runs out of elevator authority somewhere below
60 knots and descends into low tow, even though its free-flight stall
speed is less than 40 knots. It's not just a difference of feel - the
glider wallows and almost becomes uncontrollable.

Mike

On 13 Mar, 20:15, Derek Copeland wrote:
At moderate climb angles, and as long as you are not totally dangling on
the end a bit or rope (as in a helicopter lift), the glider is essentially
still in free flight during an aerotow. To produce enough lift to climb,
the glider's wing must be at a higher angle of attack for a given
airspeed than it would be in normal gliding flight.

How much extra lift do you think is required to climb?

Or looking at it another way, the wing has to support the normal weight of
the glider and its occupants, plus the component of the weight acting
backwards and downwards, so an effective increase in wing loading.

I'm sorry, but that just doesn't make sense. Lift has to balance all
the other forces acting at right angles to the direction of flight.
You can't count the weight twice.

Ian

On 12 Mar, 22:29, Bruce Hoult wrote:

We disable the parachute on our Janus. *I'm not even sure why it has
one.

I believe the answer is "as a fudge to meet the old JAR speed-limiting-
in-a-45-degree-dive requirement.Most drag chutes were never seriously
intended to be used for approach, or indeed to be used at all.

Do your insurers know, by the way, that you have disabled a flight
control?

Ian