Aerobatics in semi acrobatic certified sailplanes

[jams]

Hi all,

I have recently become interested in gliding and have been exploring the
aspects associated with the sport.

I'm going to use the term 'standard glider' to represent any non-acro
15m glider, (ASW 19/20, Speed Astir, LS range, DG range, PIK20D etc) not
standard class.

I recently started looking at aerobatics and sailplanes certified for
this. Started looking at datasheets for aircraft and most 'standard
gliders' are semi aerobatic only, in addition to this some give g
ratings. The most common I have found is +5.3 / -2.65. Seems to be
almost a standard.

When I started looking at what maneuvers 'semi acrobatic' gliders could
perform, the standard list seems to be loops, spins, chandelle, spiral
dive.

I then came across some more advanced maneuvers like cuban 8, barrel
rolls, inverted flight etc. I thought that these type of maneuvers would
exceed the -g rating of -2.65, so wouldn't be feasible. Then I came
across this you tube footage of a PIK20D doing some, what I think to be,
serious aerobatics.

http://www.youtube.com/watch?v=tSB-JAFqrhU

Pretty sure there is some significant -g going on in some of these
moves, however the PIK20D (according to the BGA datasheet) is only rated
to -2.5g.

So what I'm asking is:

Is this still basic stuff, (just looks impressive too me!)?

What sort of -g would be experienced in these maneuvers, would it exceed
-2.65?

Would other 'standard gliders' be able to do stuff like this (assuming
they had the same g rating as the PIK)?

I did think for a minute that this was a brave chap wondering what it
would take to snap the wings off, but on translating the German it says
its part of his bronze acro training. So it must be signed off by some
CFI somewhere?!

What do you think?

One interesting thing I came across was the g ratings for the
LAK-12...+6 -4...thats quite high up the g rating ladder, and pretty
impressive for an 20.5m Open class machine!

Cheers

James




--
jams

[Squeaky]

Pilatus B4 PC11, PC11A, PC11AF

Pilatus B4-PC11- Semi aerobatic,(+6.4, - 4.3). Cleared for outside
loops, split S, Immelman, wing overs, chandelle, Lazy 8, Steep Spiral,
Spins, Inverted -1G.

Pilatus B4-PC11-A - Fully aerobatic (+ 7.00, -4.79 g). Cleared for
inverted flying, rolling manoeuvres inside and outside loops.
Structurally as B4-PC11 but with toe straps, 5-point harness and
increase down elevator travel.

Pilatus B4-PC11-AF - Fully aerobatic. Cleared as “A” model
and for flick manoeuvres. As B4-PC11-A model but with rear fuselage
strengthening to cater for flick manoeuvres. Strengthening may be
factory fitted internally or external, fitted as a modification.

Span 15 meters, L/D 30-33ish

Example available (W&W):

Pilatus B4 PC-11
04-29-12 updated 07-18-12

s/n 237. Mfg 1976, TT 1650 hrs. Retractable gear.The glider was
completely refinished in 2006: the finish is impeccable. BALL and
Cambridge varios, iCOM radio, Winter ASI. Oxygen system.Easy to rig.
Working, closed all-metal trailer. Always hangared - owned since 1986
by Pittsburgh Soaring Club. Last annual and maintenance/repairs
performed by Gehrlein. Located at Bandel (22D) near Pittsburgh, PA.
http://tinyurl.com/9krqpyp

$17,300.00




--
Squeaky

[Peter Thomas]

This says the PIK 20 D is fully aerobatic if you fit toe straps and
a g meter

http://easa.europa.eu/certification/docs/sas/A.024/EASA%20SA
S%20PIK-20D%2020110428.pdf

although the video shows rolls and inverted flight. the pushovers
are probably fairly low speed (watch the asi)

[kirk.stant]

On Wednesday, October 3, 2012 9:17:51 AM UTC-5, jams wrote:
> Hi all, I have recently become interested in gliding and have been exploring the aspects associated with the sport. I'm going to use the term 'standard glider' to represent any non-acro 15m glider, (ASW 19/20, Speed Astir, LS range, DG range, PIK20D etc) not standard class. I recently started looking at aerobatics and sailplanes certified for this. Started looking at datasheets for aircraft and most 'standard gliders' are semi aerobatic only, in addition to this some give g ratings. The most common I have found is +5.3 / -2.65. Seems to be almost a standard. When I started looking at what maneuvers 'semi acrobatic' gliders could perform, the standard list seems to be loops, spins, chandelle, spiral dive. I then came across some more advanced maneuvers like cuban 8, barrel rolls, inverted flight etc. I thought that these type of maneuvers would exceed the -g rating of -2.65, so wouldn't be feasible. Then I came across this you tube footage of a PIK20D doing some, what I think to be, serious aerobatics. http://www.youtube.com/watch?v=tSB-JAFqrhU Pretty sure there is some significant -g going on in some of these moves, however the PIK20D (according to the BGA datasheet) is only rated to -2.5g. So what I'm asking is: Is this still basic stuff, (just looks impressive too me!)? What sort of -g would be experienced in these maneuvers, would it exceed -2.65? Would other 'standard gliders' be able to do stuff like this (assuming they had the same g rating as the PIK)? I did think for a minute that this was a brave chap wondering what it would take to snap the wings off, but on translating the German it says its part of his bronze acro training. So it must be signed off by some CFI somewhere?! What do you think? One interesting thing I came across was the g ratings for the LAK-12...+6 -4...thats quite high up the g rating ladder, and pretty impressive for an 20.5m Open class machine! Cheers James -- jams

You obviously have never tried to push out to -2.5Gs! Seriously, unless you are into competition aerobatics, -1.0Gs would be a lot. All the basic maneuvers can be done without exceeding +3gs or so and without any negative Gs at all - it's not until you get into slow rolls that you get into any negative G, and unless you are doing outside loops, not much.

Glider acro (unless in a Swift/Fox, etc) is a relaxed, gentle form of the art. It's not about pulling a lot of G, it's about energy management, and not exceeding VNE.

But - DO NOT TRY ACRO IN A GLIDER (OR ANY AIRCRAFT) WITHOUT PROPER TRAINING, AN APPROVED GLIDER, PARACHUTES, AND AIRSPACE!

Seriously, gliders are so slick that something as simple as a barrel roll will end up exceeding VNE if not done correctly. And exceeding VNE is not good...

Kirk
66
Occasional glider acro pilot (ASK-21, G-103Acro, Swift S-1, Blanik L-13AC, Pilatus B4, LS4, LS6)

[Andrzej Kobus]

On Oct 3, 5:29 pm, "kirk.stant" <kirk.st...@gmail.com> wrote:
> On Wednesday, October 3, 2012 9:17:51 AM UTC-5, jams wrote:

> > Hi all, I have recently become interested in gliding and have been exploring the aspects associated with the sport. I'm going to use the term 'standard glider' to represent any non-acro 15m glider, (ASW 19/20, Speed Astir, LS range, DG range, PIK20D etc) not standard class. I recently started looking at aerobatics and sailplanes certified for this. Started looking at datasheets for aircraft and most 'standard gliders' are semi aerobatic only, in addition to this some give g ratings. The most common I have found is +5.3 / -2.65. Seems to be almost a standard. When I started looking at what maneuvers 'semi acrobatic' gliders could perform, the standard list seems to be loops, spins, chandelle, spiral dive. I then came across some more advanced maneuvers like cuban 8, barrel rolls, inverted flight etc. I thought that these type of maneuvers would exceed the -g rating of -2.65, so wouldn't be feasible. Then I came across this you tube footage of a PIK20D doing some, what I think to be, serious aerobatics.http://www.youtube.com/watch?v=tSB-JAFqrhUPretty sure there is some significant -g going on in some of these moves, however the PIK20D (according to the BGA datasheet) is only rated to -2.5g. So what I'm asking is: Is this still basic stuff, (just looks impressive too me!)? What sort of -g would be experienced in these maneuvers, would it exceed -2.65? Would other 'standard gliders' be able to do stuff like this (assuming they had the same g rating as the PIK)? I did think for a minute that this was a brave chap wondering what it would take to snap the wings off, but on translating the German it says its part of his bronze acro training. So it must be signed off by some CFI somewhere?! What do you think? One interesting thing I came across was the g ratings for the LAK-12...+6 -4...thats quite high up the g rating ladder, and pretty impressive for an 20.5m Open class machine! Cheers James -- jams

>
> You obviously have never tried to push out to -2.5Gs!  Seriously, unless you are into competition aerobatics, -1.0Gs would be a lot.  All the basic maneuvers can be done without exceeding +3gs or so and without any negative Gs at all - it's not until you get into slow rolls that you get into any negative G, and unless you are doing outside loops, not much.
>
> Glider acro (unless in a Swift/Fox, etc) is a relaxed, gentle form of the art.  It's not about pulling a lot of G, it's about energy management, and not exceeding VNE.
>
> But - DO NOT TRY ACRO IN A GLIDER (OR ANY AIRCRAFT) WITHOUT PROPER TRAINING, AN APPROVED GLIDER, PARACHUTES, AND AIRSPACE!
>
> Seriously, gliders are so slick that something as simple as a barrel roll will end up exceeding VNE if not done correctly. And exceeding VNE is not good...
>
> Kirk
> 66
> Occasional glider acro pilot (ASK-21, G-103Acro, Swift S-1, Blanik L-13AC, Pilatus B4, LS4, LS6)

Look at SZD-59 (+7/-5) more than you need when you screw up.

http://szd.com.pl/en/products/szd-59-acro

[jams]

Thanks for all the input.

I have found out a fair bit more info on aerobatics since I posted this
question. I think a better way of asking the question would have been:
What aerobatic manoeuvres can a 'semi-aerobatic' sailplane perform!?

I have amassed quite a bit of info on the subject now, some interesting
technical stuff that suggests that you cannot overstress a well designed
sailplane at Va no matter what you do. I will have a read up on it all
and post something here with my findings.

Kirk,

Your sentence: 'Glider acro (unless in a Swift/Fox, etc) is a relaxed,

gentle form of the art. It's not about pulling a lot of G, it's about

energy management, and not exceeding VNE.' Sums up exactly what I'm
interested in. I dont want a pure acro aircraft, because I dont want to
do anything to mad but would like to be able to explore more than just
loops and chandelle during flights.

Also having found what G forces are generated in the figures i'm
interested in (in the PIK aerobatics supplement), and your comment about
not much neg G occurring, suggests that most sailplanes could handle
what the PIK was doing in the video anyway.

Regards

James




--
jams

[Papa3]

On Thursday, October 4, 2012 8:02:37 AM UTC-4, jams wrote:
> Thanks for all the input.
>
>
>
>

> Kirk,
>
>
>
> Your sentence: 'Glider acro (unless in a Swift/Fox, etc) is a relaxed,
>
> gentle form of the art. It's not about pulling a lot of G, it's about
>
> energy management, and not exceeding VNE.' Sums up exactly what I'm
>
> interested in. I dont want a pure acro aircraft, because I dont want to
>
> do anything to mad but would like to be able to explore more than just
>
> loops and chandelle during flights.
>
>
>
> Also having found what G forces are generated in the figures i'm
>
> interested in (in the PIK aerobatics supplement), and your comment about
>
> not much neg G occurring, suggests that most sailplanes could handle
>
> what the PIK was doing in the video anyway.
>
>
> Regards
>
>
> James

Successfully executed positive G maneuvers are not a problem for many standard category gliders. But, there's a good reason why most of them are not approved or not recommended for acro. Failed maneuvers can quickly go badly wrong and put you into a situation where you can rapidly exceed the speed and load limitations. Rolling over the top in an overly aggressive stall turn or dishing out on an aileron roll would be two examples. When I was routinely doing a lot of acro in an L-13AC, it was the "oopsies" that really tested the limits, and this was in a glider that is much less slick than the high-performance ships in your examples.

[Cedric Sponge]

No it doesn't.

[Cedric Sponge]

No it doesn't.

At 20:04 03 October 2012, Peter Thomas wrote:

[Roel Baardman]

As the owner of a Pilatus B4AF, and with some experience on B4/21/Fox, I feel I can at least give some hints.

I started with some figures on Utility class gliders. These often have max G ratings of +5.3 and -2.65 in my experience, although this is at Va speed. At Vne they often are limited to +4 and -2,
which is to take flying through strong thermals into account as far as I know.

The G-limits on gliders and allowed figures are two different things. Especially the high-performance gliders pick up speed fast.

I found that a truely Aerobatic-class glider (which often have +7 and -5 rating) is also suitable to learn figures on. In other words: if you screw up badly you will still not easily damage the
glider.
Think about kicking the rudder too late in a stall-turn and then ending up in an unintended tail-slide.

Also, the high-performance gliders often have a very laid-back body position for the pilot. In the DG-303 Acro handbook the pilot is warned about this, since G-awareness is lower in a reclined
position. And thus the risk of accidentally overstressing the aircraft.

In my B4 I fly rolls, inverted flight, spins, rolling turns (rolling and turning combined), tailslides, stall-turns and cubans (both forward and reverse).
I often have roughly +5 and -2 on the G-meter after a practice run. The +5 is during stall-turn pulls (to get a nice line) and the -2 is achieved during the pushing in rolling turns.
I would say for the first inverted flight and rolling (see the German Prufungsprogramm) you wouldn't go beyond +5 and -1.5 (achieved when pushing out your speed in a Split-S maneuver).

Long story short: I would recommend you learn to fly aerobatics on a Aerobatic-class two-seater. Then, if you become addicted, get yourself a B4/SZD-59/ASK-21.

[Jim Crawford]

>>>>>"I have amassed quite a bit of info on the subject now, some
interesting technical stuff that suggests that you cannot overstress a well
designed sailplane at Va no matter what you do."

Then you still have some reading to do!!!!

http://www.flyingmag.com/myth-maneuvering-speed

http://uras.gliderpilot.net/?op=s2&id=39082&vt=

[Glenn Fisher]

On Thursday, October 4, 2012 8:02:37 AM UTC-4, jams wrote:

> I have amassed quite a bit of info on the subject now, some interesting
>
> technical stuff that suggests that you cannot overstress a well designed
>
> sailplane at Va no matter what you do.

This is a common misconception, and was cited as contributing to the American Airlines flight 587 crash of an A300. I know there will be differences between the transport category vs. glider and US vs. European standards. However, be aware that Va may only give you protection for one full deflection of a control surface on one axis. If you make alternating applications on one axis or apply large deflections on more than one axis simultaneously, you can defeat the structure even at a speed below Va. Here is the FAA summary written after AAL587.

SUMMARY: The Federal Aviation Administration amends the airworthiness standards applicable to transport category airplanes to clarify that flying at or below the design maneuvering speed does not allow a pilot to make multiple large control inputs in one airplane axis or single full control inputs in more than one airplane axis at a time without endangering the airplane's structure. The FAA is issuing this final rule to prevent pilots from misunderstanding the meaning of an airplane's maneuvering speed, which could cause or contribute to a future accident.

http://en.wikipedia.org/wiki/American_Airlines_Flight_587

http://www.ntsb.gov/doclib/reports/2004/AAR0404.pdf

http://en.wikipedia.org/wiki/Maneuvering_speed


Glenn Fisher

[son_of_flubber]

What are the G forces in unintentional aerobatic maneuvers... say flying through extreme rotor?

Have there been cases of gliders losing their wings in rotor on their way to mountain wave?

[kirk.stant]

On Saturday, October 6, 2012 12:59:58 PM UTC-5, son_of_flubber wrote:
> What are the G forces in unintentional aerobatic maneuvers... say flying through extreme rotor?
>
>
>
> Have there been cases of gliders losing their wings in rotor on their way to mountain wave?

Not sure about gliders, but a B-52 lost it's vertical tail in CAT (may have been rotor?).

http://www.usread.com/flight587/Prev_Tail_Sep.html

Interesting read on how the crew, with the help of Boeing engineers on ground, reconfigured their crippled bomber inflight and got it home safely.

As Winston Churchill said: "Never, never, never give up!"


Kirk
66

[Martin Gregorie]

A Nimbus 4 broke up in severe turbulence during practice for the 1995
World Champs at Omarama, NZ:
http://aviation-safety.net/wikibase/wiki.php?id=29823


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

[guy]

I have been flying acro in gliders for many years. I own and fly an
LS-8/SZD-59/Fox and have flown acro in other gliders and powered
aircraft. It is true that most modern sailplanes are built to a
JAR-22 standard and have +/- G limits that are well within the forces
expected in WELL EXECUTED acro maneuvers. The problems develop in
learning maneuvers and how to recover from BLOWN maneuvers. In a
modern sailplane with a T-tail the speeds build very quickly in blown
maneuvers and the chances for overstressing really increase rapidly.
THe other thing to remember is that most truely aerobatic gliders do
not have T-tails...they have standard configurations with a low
horizontal stabilizer. Why?????? Because a T-tail can't take much
twisting forces.

I think loops are good in virtually any sailplane. But, once you add
rotations about the longitudinal axis you are in danger of
overstressing the tail. Remember, the G limits are for purely non-
rotational loads. Tailslides are another complete subject. Most acro
gliders have control surface limits built into the control surfaces at
the interface between the control surface and the wing structure.
Most regular gliders have the control surface limits built into the
control linkage system, usually at the connections to the stick. In
a tail slide you run the risk of bending/breaking the control linkage
system in a regular sailplane.

Anyway, after years of tickling the dragon's tail in many different
aircraft with many different pilots...don't learn acro in a regular
sailplane. Learn acro in a rated aircraft with a competent pilot and
then make your own decisions. I think you will find that the more you
learn about acro maneuvers...especially failed maneuvers...the less
likely you are to be adventurous in your PIK-20 or Discus.

Guy "DDS"

[Bob Whelan]

Happened a long time ago, but to a superbly maintained, "reasonably new"
Pratt-Read descending through rotor in the Jet Stream Project...estimated 20G
rotor-induced gust encountered (as I recall without verifying) "well below"
maneuvering speed...arguable whether the wings or wing carry-through structure
failed first.

Details can be found in old "Soaring" mags (article by the project-pilot/pilot
Larry Edgar), or the book "Exploring the Monster".

Regards,
Bob W.

[philp...@gmail.com]

On Sunday, 7 October 2012 07:38:04 UTC+13, Martin Gregorie wrote:
> On Sat, 06 Oct 2012 10:59:58 -0700, son_of_flubber wrote:
>
> > What are the G forces in unintentional aerobatic maneuvers... say flying
> > through extreme rotor?
>
> > Have there been cases of gliders losing their wings in rotor on their
> > way to mountain wave?
>
> A Nimbus 4 broke up in severe turbulence during practice for the 1995
> World Champs at Omarama, NZ:
>
> http://aviation-safety.net/wikibase/wiki.php?id=29823

That glider was overspeed and in cloud, so not really a case of G induced failure.

I fly in the wave a lot, and used to fly a DG1000 with a G meter. The most I saw in rotor was around 4G positive and maybe 1.5G negative.

I do remember a ridge crossing that was particularly rough that got 5G positive and 2.5G negative once. That was very unpleasant.

--
Phil Plane

[Martin Gregorie]

On Sat, 06 Oct 2012 13:31:44 -0700, philplane36 wrote:

> On Sunday, 7 October 2012 07:38:04 UTC+13, Martin Gregorie wrote:
>> On Sat, 06 Oct 2012 10:59:58 -0700, son_of_flubber wrote:
>>
>> > What are the G forces in unintentional aerobatic maneuvers... say
>> > flying through extreme rotor?
>>
>> > Have there been cases of gliders losing their wings in rotor on their
>> > way to mountain wave?
>>
>> A Nimbus 4 broke up in severe turbulence during practice for the 1995
>> World Champs at Omarama, NZ:
>>
>> http://aviation-safety.net/wikibase/wiki.php?id=29823
>
> That glider was overspeed and in cloud, so not really a case of G
> induced failure.
>
> I fly in the wave a lot, and used to fly a DG1000 with a G meter. The
> most I saw in rotor was around 4G positive and maybe 1.5G negative.
>

I was responding to the 'loosing wings in rotor' comment, not the
'aerobatic G' one. I thought I'd heard it was an overspeed in rotor
situation but the report I dug up didn't mention that so neither did I,
in order to avoid speculating.

> I do remember a ridge crossing that was particularly rough that got 5G
> positive and 2.5G negative once. That was very unpleasant.
>

Sounds nasty.