Accelerated spin in unexpected direction at low altitude

At 06:36 04 July 2018, CindyB wrote:

Don't spin a Puch without chutes and a hard deck(1000m agl). Ever.

Best wishes,

Cindy B

Setting a hard deck of 1000ft agl is not really of much use. It is very
unlikely that you would be able to make a successful abandonment if in
a spin at 1000ft. You should really double that if you are serious about
having a hard deck which leaves you with another option if the spin
cannot be stopped. I rejected an abandonment with a control restriction
in level flight at 1000ft as I was not sure that I had the time. My
parachute was reputed to open and decelerate in time at 750ft when it
was new.

The reasons why Puchs have spun in is speculative in most cases. In
most cases the only witnesses worth anything at all, who could tell you
what happened, couldn't. It is very easy to blame pilots who are unable
to speak for themselves. As far as I can make out in most cases the
cause should have been recorded as undetermined. Probably is just not
good enough.

On Thursday, July 5, 2018 at 3:00:06 PM UTC-7, Don Johnstone wrote:
At 06:36 04 July 2018, CindyB wrote:

Don't spin a Puch without chutes and a hard deck(1000m agl). Ever.

Best wishes,

Cindy B

Setting a hard deck of 1000ft agl is not really of much use. It is very
unlikely that you would be able to make a successful abandonment if in
a spin at 1000ft. You should really double that if you are serious about
having a hard deck which leaves you with another option if the spin
cannot be stopped. I rejected an abandonment with a control restriction
in level flight at 1000ft as I was not sure that I had the time. My
parachute was reputed to open and decelerate in time at 750ft when it
was new.

The reasons why Puchs have spun in is speculative in most cases. In
most cases the only witnesses worth anything at all, who could tell you
what happened, couldn't. It is very easy to blame pilots who are unable
to speak for themselves. As far as I can make out in most cases the
cause should have been recorded as undetermined. Probably is just not
good enough.


Don: Cindy said meters not feet.

At 22:35 05 July 2018, Steve Koerner wrote:
On Thursday, July 5, 2018 at 3:00:06 PM UTC-7, Don Johnstone
wrote:
At 06:36 04 July 2018, CindyB wrote:

Don't spin a Puch without chutes and a hard deck(1000m
agl). Ever.

Best wishes,

Cindy B

Setting a hard deck of 1000ft agl is not really of much use. It is
very
unlikely that you would be able to make a successful
abandonment if in
a spin at 1000ft. You should really double that if you are serious
about
having a hard deck which leaves you with another option if the
spin
cannot be stopped. I rejected an abandonment with a control
restriction
in level flight at 1000ft as I was not sure that I had the time. My
parachute was reputed to open and decelerate in time at 750ft
when it
was new.

The reasons why Puchs have spun in is speculative in most
cases. In
most cases the only witnesses worth anything at all, who could
tell you
what happened, couldn't. It is very easy to blame pilots who are
unable
to speak for themselves. As far as I can make out in most cases
the
cause should have been recorded as undetermined. Probably is
just not
good enough.


Don: Cindy said meters not feet.

Sorry I missed that, 1000 metres is a sensible number.

I have also been instructing & regularly spinning the Puchacz in many different configurations for 17 years now. In Australia our "hard deck" has always been 1000ft agl.

At 03:03 25 June 2018, wrote:
I witnessed Jantar Std3 doing 180 from downwind to short final in 60
degree of bank at an altitude about 150 feet. In the middle of RIGHT 180
turn the glider flipped LEFT and made ONE full turn of accelerated spin in
about 2-3 seconds before hitting ground.

Does anyone know the date and location of this accident. I haven't heard
back from the original poster in this regard.

Normally you think of a spin associated with turning flight where there is an inside wing that is going slower than the outside wing and thus already at a higher AOA than the outside wing. The discussion about flipping into a spin to the outside seems very weird until you start thinking about a turn at very high bank angle.

Consider a turn at 90 deg bank angle. In that case there no longer is an inside wing going slower than the other. Both wings are on equal footing with respect to their vulnerability to stall. In a very steep turn, it's easy to see that the top wing could well stall first if there was a bit of yawing action introduced or if the air had the right sort of irregularity to it. Near the ground, horizontal wind shear is the commonplace and could easily provide the irregularity that would be the impetus for a "backwards" spin. Clearly, depending on the degree of shear that's going on, the bank angle could be well less than 90 degrees and still get the backwards spin induced.

n Friday, July 6, 2018 at 3:14:51 PM UTC-4, Steve Koerner wrote:
It is confusing when the top wing is coming down instead of the bottom wing, for sure, but the airplane is spinning to the direction of the rudder. To recover, opposite rudder and forward stick is needed, just like the "normal" spin.
Dan
Normally you think of a spin associated with turning flight where there is an inside wing that is going slower than the outside wing and thus already at a higher AOA than the outside wing. The discussion about flipping into a spin to the outside seems very weird until you start thinking about a turn at very high bank angle.

Consider a turn at 90 deg bank angle. In that case there no longer is an inside wing going slower than the other. Both wings are on equal footing with respect to their vulnerability to stall. In a very steep turn, it's easy to see that the top wing could well stall first if there was a bit of yawing action introduced or if the air had the right sort of irregularity to it. Near the ground, horizontal wind shear is the commonplace and could easily provide the irregularity that would be the impetus for a "backwards" spin. Clearly, depending on the degree of shear that's going on, the bank angle could be well less than 90 degrees and still get the backwards spin induced.

OK, any decent comments in this thread.

My feeling, many things happen at low altitude.

Wind shear
Wind gradient
Wind shift due to ground based stuff (trees, hills, buildings, etc.)
Thermal wind shift
Changed pilot perspective
Major change in pitch attitude vs. horizon (trees or hills have a big impact here)
Unintentional control inputs (rudder the turn is common and may be missed)

Below 800' agl or so, things are different.

Add in different quality of control seals, maybe different wing twist (either as built or later repairs) plus things I listed above, close to the ground has a bad habit of accentuating ANYTHING done wrong or incorrect.

The only time I have been "caught unaware" for a spin was when I was behind the aft limit in a ASW-20 (medium story, not worth repeating unless asked).
This was at altitude, took it in stride, remembered when in the pattern.

My early training was, "does it look good, does it sound good, does it feel good?". If not, fix it.......! Now......

Not saying departed pilots did something wrong, nor that there are killer ships out there.
Just saying things are/seem different when low and the escape margin is either thin or nonexistent.

Carry on the discussion.

Years ago I read an article in a R/C model magazine which included the advice

"Stay 3 mistakes high"

Not bad advice for piloted vehicles as well...