Accident in Namibia, SH Ventus 2cxm

Don,

the answer is simple. Don't fly a Nimbus 4 if you do not feel competent to
do so.

There is a sh1t load of opinions in this thread and some frankly outlandish
comments from people (most of whom) have not flown the aircraft.

"I wonder how many other people have to die or parachute to safety
before someone asks the question, should this glider be flying at all"

A knee jerk response to a factually correct but ill-informed statement
which lacked all of the information.

So far as I can see, there are two people on this thread who has
constructively contributed. JMC and Francois.

I would happily fly a Nimbus 4DM with either of these people.




At 11:05 03 February 2016, Don Johnstone wrote:
As glider pilots there are many things we do which are familiar to
us, we deal with these events very quickly, the so called muscle
memory. If we are prudent we practise, on a regular basis so
emergency situations, such as launch failures and every one we
practise increases the chance of recognition and proper recovery
action.

As regards spinning we may practise in a glider cleared for
intentional spinning but we seldom if ever practise a spiral dive
which is uncontrolled, we have no experience of such an event. We
may have been told that it can happen, briefed on the symptoms
and warned of the consequences but never actually seen it and
recovered unless we are one of the very few test pilots.

The difference between a spiral dive and a spin may be bleedin
obvious to a few but for most of us it is a situation which requires
the processing of information which is completely unfamiliar.

Some gliders are prohibited from deliberate spinning so we never
have the opportunity to practice, it is likely therefore that the first
time we see an event be it spinning or spiral dive is when it occurs
unintentionally. One of the symptoms which distinguishes a spiral
dive from a spin is the already high and increasing airspeed. To
recognise the difference you have to see it. The problem is that the
increase in airspeed, the acceleration, is very high, maybe
approaching 18kts per second per second (32fps/ps). If we take
just 3 seconds to see that the speed is in fact increasing we will
have added 57kts and we still have to decide how to correct that
and take the appropriate action. If we take a further 3 seconds to
decide on and start to carry out the appropriate recovery we are
already through VA, approaching or exceeding VNE and headed for
the scene of the accident. It has been said that recovery will result
in uncommanded airbrake deployment which transfers and
increased load to the outer wing panels, which are likely to fail.

When a test pilot carries out his tests he deliberately does so, he
knows what to expect and has already decided on his recovery
action, his recovery is likely to be close to optimum. He is likely to
guard the airbrake control. I would suggest that anyone, including
our test pilot might have difficulty if the event was completely
unexpected.

Even if the acceleration is only 90% of the maximun in a Nimbus
4DM, the speed will increase by 100kts in the 6 seconds. Assuming
we started with 50kts the recovery will go through VNE (177kts).
Max manouvering speed (VA) for a Nimbus 4 is 100kts, so full
control deflection is not available after 3 seconds. It seems to me
that if it happens unexpectedly it is not going to end well however
lighting fast our reactions might be.

Le mercredi 3 février 2016 13:15:10 UTC+1, Justin Craig a écrit*:
Don,

the answer is simple. Don't fly a Nimbus 4 if you do not feel competent to
do so.

Justin,

"feeling competent to" is probably he cause of death #1 amongst glider pilots.

I absolutely agree with you that if one doesn't feel competent to fly an open glass glider, then he shouldn't. But "feeling compentent" might be a different thing than "being competent".
I'm not addressing that to any person in specific. However, having spin experience in a ASK21 or a Discus does not mean that you will survive a fully developed spin in an open glass ship. The momentum of the wing is about 3-5 times larger than that of a 15m glider, and when you do the right inputs to stop the spin, the large momentum means that until the actual rotation is stopped, you are accelerating nose down by 70-80 deg with negative flaps for almost a full turn. So if you wait for the rotation to have stopped before you pull up, there is almost no way that the wings would stay with you. If you don't wait long enough, you might re-stall the wing. The margin for a successful exit is very slim, while on a 15 m ship it is absolutely easy.

Been there, done that long ago on a 26 m ship, happy to be still alive. After that event, any incipent stall on a ASH25 got my immediate attention.

Hallo Bert "TW"
Through a convoluted series of links, I stumbled into and read a very good article on "How To Survive Gliding" which at the end credits you.
Wielen danke.
Jim

http://www.tango-whisky.com/How%20to...%20Gliding.pdf


On Wednesday, February 3, 2016 at 5:51:16 AM UTC-8, Tango Whisky wrote:
Le mercredi 3 février 2016 13:15:10 UTC+1, Justin Craig a écrit*:
Don,

the answer is simple. Don't fly a Nimbus 4 if you do not feel competent to
do so.

Justin,

"feeling competent to" is probably he cause of death #1 amongst glider pilots.

I absolutely agree with you that if one doesn't feel competent to fly an open glass glider, then he shouldn't. But "feeling compentent" might be a different thing than "being competent".
I'm not addressing that to any person in specific. However, having spin experience in a ASK21 or a Discus does not mean that you will survive a fully developed spin in an open glass ship. The momentum of the wing is about 3-5 times larger than that of a 15m glider, and when you do the right inputs to stop the spin, the large momentum means that until the actual rotation is stopped, you are accelerating nose down by 70-80 deg with negative flaps for almost a full turn. So if you wait for the rotation to have stopped before you pull up, there is almost no way that the wings would stay with you.. If you don't wait long enough, you might re-stall the wing. The margin for a successful exit is very slim, while on a 15 m ship it is absolutely easy.

Been there, done that long ago on a 26 m ship, happy to be still alive. After that event, any incipent stall on a ASH25 got my immediate attention.

On 2/6/2016 6:50 PM, JS wrote:
Hallo Bert "TW" Through a convoluted series of links, I stumbled into and
read a very good article on "How To Survive Gliding" which at the end
credits you. Wielen danke. Jim

http://www.tango-whisky.com/How%20to...%20Gliding.pdf

Excellent, thoughtful, thought-provoking link!!! I thought what it touches
upon worthy of its own thread...

As to the article's ending point, here's a public, recent, "There I Wuz..."
soaring-centric article to see if it's possible on RAS to help jump-start such
a discussion.

http://www.flyingmag.com/i-learned-a...t-at-kitt-peak

The experienced glider pilot in me cringed upon reading the Flying magazine
article...but long exposure and participation in recreational soaring had also
long ago led to my concluding the "mental mindset errors" displayed by the
pilot in the Flying magazine article are (excuse the pun) dirt common. *Why*
they are has also long been a real puzzler for me: Lack of exposure? Denial?
("e.g. Only a ignorant idiot would do that - not me!" mindset.) Risk-raising
mental compartmentalization? ???

What do others think?

Bob W.