Accelerated spin questions

Did my first accelerated spins yesterday (in a Grob). Woohoo.
Unfortunately my stomach wasn't wild about them, so I only
did a couple. But I did get to thinking about the aerodynamics
of them (maybe as a way to forget my nausea!), and I had a
couple of questions which I wondered if anyone here can answer.

We recovered by un-accelerating the spin (stick slowly back) then
a normal recovery. Even so it was pretty eye-popping and stomach
churning.

What would happen if you put in full anti-spin rudder while in a
stable accelerated spin? There seem to be four possibilities:

-- rudder stall
-- rudder/vertical stab falls off (shades of AA587)
-- the yaw is enough to break the spin (unstall the downgoing wing).
But the yaw will rotate the airplane in the vertical plane, so now the
nose will be pointing horizontally (or at least not nose down) with
some random bank angle (-180 - +180) when suddenly both wings
start flying again. This would really be the unusual attitude recovery
from Hell since you could really be absolutely anywhere and massively
disorientated with it.
-- the yaw isn't enough to break the spin (gentle rudder application).
This seems the most intriguing of all. Since you have airspeed, the rudder
will cause continuing yaw - I guess flattening the spin somewhat. But now
you have full anti-spin rudder which means that recovery options are
limited! Presumably recovery would be: full pro-spin rudder, stick back
to flatten the spin, then normal recovery - if you have any altitude
left.

Anyway I'd appreciate any comments from people who've tried any of
this - of course I'll be asking my instructor next time I see him too.

Thanks,

John
of all

"John Harper" wrote in message news:1060020100.727307@sj-nntpcache-5...
Did my first accelerated spins yesterday (in a Grob). Woohoo.
Unfortunately my stomach wasn't wild about them, so I only
did a couple. But I did get to thinking about the aerodynamics
of them (maybe as a way to forget my nausea!), and I had a
couple of questions which I wondered if anyone here can answer.............


Two modes of spinning that inhibit (if not totally block) your ability
to recover are Accelerated, and Flat. It is always best to take the
spin out of these modes and back to a normal un-accelerated, not flat
spin before recovering.

Accelerated spins, as you have seen, rotate much faster than
un-accelerated spins. Available rudder on a given aircraft may not be
sufficient to cancel yaw in this situation. Once the spin is
converted to a normal (un-accelerated) spin (stick back in the case of
an upright, positive spin), normal recovery methods can be used.

Upright positive flat spins are technically "unrecoverable" (without
first converting them to normal spins) in many aircraft. A standard
tail configuration with the horizontal stab and elevator located below
the rudder, does not allow sufficient airflow to get to the rudder for
normal operation in these spins. This means that the rudder will
loose much of its effectiveness in a flat spin. Since the flat spin
also rotates faster and has a larger yaw component, the rudder will
probably be nearly useless while the spin is flat. The correct
proceedure requires power be set to idle, hold the stick back so there
will not be acceleration, and roll aileron into the direction of spin
to return to a normal spin condition. Once this has been accomplished
the spin can be stopped normally. The faster rotation rate (inertia)
will still slow the recovery somewhat.


Dave Swartz
Fort Lauderdale, Florida
http://www.FlightFantastic.US

You have to be really careful with that. The worst thing that can happen in such
a recovery attempt is that you cross over from a positive spin into an inverted
spin. You will then think you are using recovery rudder but will have in-spin
rudder and will not recover from the spin. A good friend of mine died in just
such a situation, so be very careful with that.

Guenther
---------------------------------------------------
Dr. Guenther Eichhorn |
ADS Project Scientist | Phone: 617-495-7260
http://ads.harvard.edu | Fax: 617-496-7577
Smithsonian Astrophysical Observatory
60 Garden Street, MS-83, Cambridge, MA 02138, USA


In article 1060020100.727307@sj-nntpcache-5,
"John Harper" writes:
Did my first accelerated spins yesterday (in a Grob). Woohoo.
Unfortunately my stomach wasn't wild about them, so I only
did a couple. But I did get to thinking about the aerodynamics
of them (maybe as a way to forget my nausea!), and I had a
couple of questions which I wondered if anyone here can answer.

We recovered by un-accelerating the spin (stick slowly back) then
a normal recovery. Even so it was pretty eye-popping and stomach
churning.

What would happen if you put in full anti-spin rudder while in a
stable accelerated spin? There seem to be four possibilities:

-- rudder stall
-- rudder/vertical stab falls off (shades of AA587)
-- the yaw is enough to break the spin (unstall the downgoing wing).
But the yaw will rotate the airplane in the vertical plane, so now the
nose will be pointing horizontally (or at least not nose down) with
some random bank angle (-180 - +180) when suddenly both wings
start flying again. This would really be the unusual attitude recovery
from Hell since you could really be absolutely anywhere and massively
disorientated with it.
-- the yaw isn't enough to break the spin (gentle rudder application).
This seems the most intriguing of all. Since you have airspeed, the rudder
will cause continuing yaw - I guess flattening the spin somewhat. But now
you have full anti-spin rudder which means that recovery options are
limited! Presumably recovery would be: full pro-spin rudder, stick back
to flatten the spin, then normal recovery - if you have any altitude
left.

Anyway I'd appreciate any comments from people who've tried any of
this - of course I'll be asking my instructor next time I see him too.

Thanks,

John
of all

Spinning a Grob, right-side up, has been a subject of some concern.
Supposedly, most of the time they behave "normally" but "1 time out of
a 100" they will spin flat and be very difficult to impossible to
recover. The story, as I heard it from my aerobatic instructor, is
that Les Horvath was giving spin instruction for the umteenth time in
a Grob and was not wearing a parachute. Normal spin entry that
transitioned flatter and became refractive to all attempts at
recovery. He is quoted as saying he would have exited the glider (a
tandem seat configuration) if he had a chute on but instead they
unbuckled their straps and climbed onto the glareshields over the
panels in order to shift the CG farther forward. Although this
maneuver is not advocated in the owners manual, it apparently was
successful in aiding the spin recovery.
One of the explanations that has been given to me for caution in
spinning a Grob is the offset rudder hinge. It has more rudder travel
in one direction than the other. So (I don't remember which) it is
easier to enter a spin from one direction but less opposite rudder
travel available for recovery. Likewise, it is more difficult to
enter a spin from the other direction but easier to recover. For
reasons I don't understand this does not seem to be a concern during
inverted spins... I avoid spinning a Grob. Gene (SZD-59)

Interesting. I'm actually flying the Grob 115 which is a two-seat powered
trainer, drawing heavily on their glider experience but not a powered
glider. My instructor has no worries about doing anything in it...
we tried flat(-ish) spins and it unflattened and recovered just as it
should. (But we do wear chutes, although exiting the airplane in
an accelerated spin isn't something I'd like to try).

John

"snaproll59" wrote in message
m...
Spinning a Grob, right-side up, has been a subject of some concern.
Supposedly, most of the time they behave "normally" but "1 time out of
a 100" they will spin flat and be very difficult to impossible to
recover. The story, as I heard it from my aerobatic instructor, is
that Les Horvath was giving spin instruction for the umteenth time in
a Grob and was not wearing a parachute. Normal spin entry that
transitioned flatter and became refractive to all attempts at
recovery. He is quoted as saying he would have exited the glider (a
tandem seat configuration) if he had a chute on but instead they
unbuckled their straps and climbed onto the glareshields over the
panels in order to shift the CG farther forward. Although this
maneuver is not advocated in the owners manual, it apparently was
successful in aiding the spin recovery.
One of the explanations that has been given to me for caution in
spinning a Grob is the offset rudder hinge. It has more rudder travel
in one direction than the other. So (I don't remember which) it is
easier to enter a spin from one direction but less opposite rudder
travel available for recovery. Likewise, it is more difficult to
enter a spin from the other direction but easier to recover. For
reasons I don't understand this does not seem to be a concern during
inverted spins... I avoid spinning a Grob. Gene (SZD-59)

Oops. Sorry to confuse Grobs. My point of reference is the Grob 103
Acro, a 2-place tandem glider. For a different look at acro try this
home video (not by me) but very well done. Takes a few minutes to
load but you might like it. This is an ASK 21. Similar to the Grob
103. It is used by the Air Force Academy cadets in glider acro:

http://www2.dfk.no/Arkiv/Videoarkiv/...00/SEILFLY.mov

Gene


If everything's under control, you're going too slow.
-- Mario Andretti

"John Harper" wrote in message news:1060020100.727307@sj-nntpcache-5...
Did my first accelerated spins yesterday (in a Grob). Woohoo.
Unfortunately my stomach wasn't wild about them, so I only
did a couple. But I did get to thinking about the aerodynamics
of them (maybe as a way to forget my nausea!), and I had a
couple of questions which I wondered if anyone here can answer.

We recovered by un-accelerating the spin (stick slowly back) then
a normal recovery. Even so it was pretty eye-popping and stomach
churning.

What would happen if you put in full anti-spin rudder while in a
stable accelerated spin? There seem to be four possibilities:

-- rudder stall
-- rudder/vertical stab falls off (shades of AA587)
-- the yaw is enough to break the spin (unstall the downgoing wing).
But the yaw will rotate the airplane in the vertical plane, so now the
nose will be pointing horizontally (or at least not nose down) with
some random bank angle (-180 - +180) when suddenly both wings
start flying again. This would really be the unusual attitude recovery
from Hell since you could really be absolutely anywhere and massively
disorientated with it.
-- the yaw isn't enough to break the spin (gentle rudder application).
This seems the most intriguing of all. Since you have airspeed, the rudder
will cause continuing yaw - I guess flattening the spin somewhat. But now
you have full anti-spin rudder which means that recovery options are
limited! Presumably recovery would be: full pro-spin rudder, stick back
to flatten the spin, then normal recovery - if you have any altitude
left.

Anyway I'd appreciate any comments from people who've tried any of
this - of course I'll be asking my instructor next time I see him too.

Thanks,

John
of all

Hey John, You wouldn't happen to be doing your training at Attitude
Aviation in Livermore would you?

The reason I ask is there aren't too many places that use the Grob
115C. If so, who is your instructor? I did some aerobatic training
there last year in the Grob, very cool plane. Only thing I don't like
about doing acro in the Grob is the fuel smell that gets in the
cockpit during manuevers. I flew with Rich Perkins and an older
instructor who name has slipped my mine at the moment.

Indeed - training in 115FN & 216AR with Rich at Attitude. I like
the Grob a lot except for the constant stink of avgas. I really like Rich
as an instructor. And Attitude have an extremely cool collection
of aircraft to think about for later...

John

"Donovan" wrote in message
om...
"John Harper" wrote in message
news:1060020100.727307@sj-nntpcache-5...
Did my first accelerated spins yesterday (in a Grob). Woohoo.
Unfortunately my stomach wasn't wild about them, so I only
did a couple. But I did get to thinking about the aerodynamics
of them (maybe as a way to forget my nausea!), and I had a
couple of questions which I wondered if anyone here can answer.

We recovered by un-accelerating the spin (stick slowly back) then
a normal recovery. Even so it was pretty eye-popping and stomach
churning.

What would happen if you put in full anti-spin rudder while in a
stable accelerated spin? There seem to be four possibilities:

-- rudder stall
-- rudder/vertical stab falls off (shades of AA587)
-- the yaw is enough to break the spin (unstall the downgoing wing).
But the yaw will rotate the airplane in the vertical plane, so now the
nose will be pointing horizontally (or at least not nose down) with
some random bank angle (-180 - +180) when suddenly both wings
start flying again. This would really be the unusual attitude recovery
from Hell since you could really be absolutely anywhere and massively
disorientated with it.
-- the yaw isn't enough to break the spin (gentle rudder application).
This seems the most intriguing of all. Since you have airspeed, the
rudder
will cause continuing yaw - I guess flattening the spin somewhat. But
now
you have full anti-spin rudder which means that recovery options are
limited! Presumably recovery would be: full pro-spin rudder, stick back
to flatten the spin, then normal recovery - if you have any altitude
left.

Anyway I'd appreciate any comments from people who've tried any of
this - of course I'll be asking my instructor next time I see him too.

Thanks,

John
of all

Hey John, You wouldn't happen to be doing your training at Attitude
Aviation in Livermore would you?

The reason I ask is there aren't too many places that use the Grob
115C. If so, who is your instructor? I did some aerobatic training
there last year in the Grob, very cool plane. Only thing I don't like
about doing acro in the Grob is the fuel smell that gets in the
cockpit during manuevers. I flew with Rich Perkins and an older
instructor who name has slipped my mine at the moment.