Spin recovery vs tail design

I would like to solicit comments on the question: Compared to a standard
tail configuration such as a 2-33 or Blanik L-13, does the initiation and
recovery from a spin vary substantially in T-tail (ASK-21 type),
all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
to reading and learning.

On 11 May 2009 16:00:06 GMT, Ron Ogden wrote:

I would like to solicit comments on the question: Compared to a standard
tail configuration such as a 2-33 or Blanik L-13, does the initiation and
recovery from a spin vary substantially in T-tail (ASK-21 type),
all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
to reading and learning.

No significant differences - stick neutral, rudder against direction
of the pin.

Some V-tail gliders require the stick to be pushed fully forward (to
achieve sufficient deflection of the V-tail).

Bye
Andreas

"Andreas Maurer" wrote in message ...
On 11 May 2009 16:00:06 GMT, Ron Ogden wrote:

I would like to solicit comments on the question: Compared to a standard
tail configuration such as a 2-33 or Blanik L-13, does the initiation and
recovery from a spin vary substantially in T-tail (ASK-21 type),
all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
to reading and learning.

No significant differences - stick neutral, rudder against direction
of the pin.

Some V-tail gliders require the stick to be pushed fully forward (to
achieve sufficient deflection of the V-tail).


Ron,

Like Andreas, I find no significant dirrerences. My "V" tail HP-14 doesn't require any special technique.

Wayne
HP-14 "6F"
http://www.soaridaho.com/Schreder

On May 11, 10:24*am, "Wayne Paul" wrote:
"Andreas Maurer" wrote in messagenews:3jjg05hpl4e6hth12gegpo24l4718kv571@4ax .com...
On 11 May 2009 16:00:06 GMT, Ron Ogden wrote:

I would like to solicit comments on the question: Compared to a standard
tail configuration such as a 2-33 or Blanik L-13, does the initiation and
recovery from a spin vary substantially in *T-tail (ASK-21 type),
all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
to reading and learning.

No significant differences - stick neutral, rudder against direction
of the pin.

Some V-tail gliders require the stick to be pushed fully forward (to
achieve sufficient deflection of the V-tail).

Ron,

Like Andreas, I find no significant dirrerences. *My "V" tail HP-14 doesn't require any special technique.

Wayne
HP-14 "6F"http://www.soaridaho.com/Schreder

Read the manual for the glider; the spin characteristics were worked out by
a professional test pilo, and the best advice you can get will be in the
operating handbook.

tAt 16:13 11 May 2009, Andreas Maurer wrote:
On 11 May 2009 16:00:06 GMT, Ron Ogden wrote:

I would like to solicit comments on the question: Compared to a
standard
tail configuration such as a 2-33 or Blanik L-13, does the initiation
and
recovery from a spin vary substantially in T-tail (ASK-21 type),
all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look
forward
to reading and learning.

No significant differences - stick neutral, rudder against direction
of the pin.

Some V-tail gliders require the stick to be pushed fully forward (to
achieve sufficient deflection of the V-tail).

Bye
Andreas

On May 11, 10:24*am, "Wayne Paul" wrote:
"Andreas Maurer" wrote in messagenews:3jjg05hpl4e6hth12gegpo24l4718kv571@4ax .com...
On 11 May 2009 16:00:06 GMT, Ron Ogden wrote:

I would like to solicit comments on the question: Compared to a standard
tail configuration such as a 2-33 or Blanik L-13, does the initiation and
recovery from a spin vary substantially in *T-tail (ASK-21 type),
all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
to reading and learning.

No significant differences - stick neutral, rudder against direction
of the pin.

Some V-tail gliders require the stick to be pushed fully forward (to
achieve sufficient deflection of the V-tail).

Ron,

Like Andreas, I find no significant dirrerences. *My "V" tail HP-14 doesn't require any special technique.

Wayne
HP-14 "6F"http://www.soaridaho.com/Schreder

I would disagree.

Studies done on exactly this in the early 1960's by NASA at Edwards
AFB did show an effect. To understand the finding, consider how the
airflow moves over the tail at a very high angle of attack as in a
well developed spin.

The flow tends to parallel the swept rudder hinge line on a 2-32 or
2-33. The low mounted tail disrupts or blanks some of the air flowing
toward the rudder. The result is a measurable reduction in rudder
effectiveness which manifests itself in a delayed spin recovery.

Swept tails are undesirable at any airspeed below transonic and are
used merely for styling.

A "T" tail with a vertical rudder hinge is a good solution since the
rudder sees clean airflow and the horizontal acts as an end plate on
the fin and rudder. The one caveat is that the "T" tail shouldn't be
in the wings turbulent wake at any achievable angle of attack - else
you risk a "deep stall" phenomenon.

The second best configuration is a low stab/elevator mounted ahead of
the fin as seen in a BG-12 or K-13 so the free flow has unobstructed
access to the rudder at high angles of attack.

Finally, a separate stabilizer and elevator produces more nose down
moment than an all moving "slab" tail which can stall in it's full-
down position. A stab/elevator can also stall but will nonetheless
produce enough nose down moment to break the stall/spin.

This led to the NACA standard spin recovery technique which called for
anti-spin rudder while holding full up elevator until the auto-
rotation slowed and only then applying down elevator. The reasoning
was that full up elevator exposed more of the rudder to high energy
flow.

Read the manual for the glider; the spin characteristics were worked out by
a professional test pilot, and the best advice you can get will be in the
operating handbook.

Great advice, although with my Sisu 1a no such manual exists... that
said, it had a very well designed V tail that required no special
considerations for initiating or recovering from spins, and there were
no other indications in flight that would indicate it's unconventional
configuration. Spin recovery was quicker with the flaps retracted
though, so that too was a consideration, although probably not one
specific to V tails.

I personally enjoy spinning ships, and like to do what I call 'spot
spinning', meaning coming out on predetermined headings after a
predetermined number of revolutions... WEEE great fun!! Haven't got
into inverted spins yet though...

-Paul

Ron Ogden wrote:
I would like to solicit comments on the question: Compared to a standard
tail configuration such as a 2-33 or Blanik L-13, does the initiation and
recovery from a spin vary substantially in T-tail (ASK-21 type),
all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
to reading and learning.


The main difference, to the extent that there is any generic difference,
might be that T-tails tend to end up rather more nose down after you've
stopped the spin. However, this may not be true for a particular model
of glider. Also, your timing of the spin recovery will alter this, and
other matters.

Of those I've spun:

K13 (low tail) - quite gentle, recovers into a dive but not a
particularly steep one.

K6cr (low tail) - ditto, though it all happen quicker than a K13.

Puchacz (mid tail) - recovery may be into a dive beyond the vertical and
substantial height loss per turn, but it does exactly what the manuals
say if you perform the recovery properly.

Astir CS (Grob 103, T-tail) - quite gentle, recovers into a steeper dive
than the K13

IS28 (T-tail) - like the Astir, but a bit slower all round.

Open Cirrus (mid tail) - fairly gentle, dive after recovery about as
steep as the Astir. However, you do need FULL rudder to stop the spin
(and the last inch requires a hard push; it feels like you're on the
stop but you're not).

I've read that some V-tails need full forward stick before they recover,
but haven't had the pleasure of flying any.

Of my list I'd say the most "extreme" attitudes on recovery are from the
Puchacz, so from my limited experience the difference in tail
configuration is not the most important factor.

Primary answer: Use the spin recovery technique which is described in
the AFM.

Secondary answer: All certificated modern gliders will recover with the
"standad procedure", it's a requirement for certification.

That said: Eric Müller was a, no, probably *the* spin expert. He
described the ins and outs of spins in detail in his book "flight
unlimited". According to him, most "conventional" tail designs recover
best when you keep holding the stick back until the rotation stops,
because pushing it forward will blank the rudder. With T-tails it's
exactly the other way: Pushing the stick generates more airflow on the
rudder to stop the rotation. V-Tails are a story by themselves. There
has been at least one fatal accident with a salto which spun into the
ground. Eric was the accident investigator for this case and examined
the spin behaviour of another salto. He found that the salto would only
recover with the stick pushed *fully* forward.

But again, this is the theory, in practice, do whatever the AFM recommends.

On May 11, 5:00*pm, Ron Ogden wrote:
I would like to solicit comments on the question: Compared to a standard
tail configuration such as a 2-33 or Blanik L-13, does the initiation and
recovery from a spin vary substantially in *T-tail (ASK-21 type),
all-flying (Phoebus) or V-tail (HP series) sailplanes? Really look forward
to reading and learning.

If your glider is JAR 22 certified then it will respond to the
standard spin recovery - reverse rudder, stick centrally forwards
(e.g. ailerons neutral) until the spin stop, centralise the rudder and
pull out of the dive. Exactly how it responds depends on the type of
glider and probably the spin itself.

There are also several ways of getting a glider to spin, but AFAIK the
recover is the same for all. For check flights I slowly ease back on
the stick until the nose drops (or it mushes) and kick in with the
rudder. The wing drops, and I have to hold it in to start the spin
proper. I have heard of one club where three ways of getting a glider
(K13) to spin have to be demonstrated.

But, as someone else said, read the manual and talk to instructors.
And if you can get an ASK-21 to spin I suggest you check the cockpit
weights - I don't know anyone who has without the use of tail ballast.