The article was very interesting. The idea of aileron
stiffness at high bending was thought-provoking.

'Abandoning ailerons for a more effective way of starting
and stopping roll...' Perhaps a reference to
full span spoilers for roll?

'the smoking gun was the aircraft's incredibly high
performance.' This is consistent with, but not a proof
of, the things I've written before about USA fatalities
and L/D.
Of course, this was however NOT a ridge flying accident.

The article didn't mention the possibility that the
other
pilot may have popped the airbrakes/two pilots on the
controls working at odds with each other. Of course
there
is absolutely no way to confirm or deny this.

Lastly, I liked the article's end, and the idea of
big bold red letters in the AFM. It also occered to
me that some of the
'seconds to accelerate from stall speed to ...' and
a lot
of the ideas we have, and how we practice spins and
spirals, is in STILL AIR. I generally don't go up
in huge
thermals/turbulence to practice spins, specifically
so I don't exceed Va and gust loads and 1/3 deflection,
etc.

Does a spin turn into a spiral on it's own sometimes
in turbulent air? Can AOAs be changed by turbulence
alone,
with no movement of controls? Oh, yes.

Start throwing in severe turbulence (which we love,
when it
suits us) and I think we are closer to the 'naked edge
of safety'
than is obvious.

The 2-32 accident in Hawaii was anectdotally in 'the
toilet bowl' there in turbulent air, too. Shear 10/20/30
knots in a few
seconds and 1/4 mile vertically or horizontally, and
our
still air analysis can't be done with a pristine slide-rule...
At 17:12 30 June 2005, Don Johnstone wrote:
If Stans analysis is right, and I can see no obvious
flaw, once the spiral dive/spin situation is met then
the chances of a sucessful recovery are slim. The 4DT
would not be unique in this. Perhaps a tail parachute
is an essential item of equipment.

Food for thought


At 15:18 30 June 2005, Bill wrote:

Stan Hall presented his analysis of the Nimbus-4DB
accident in Minden,
NV, 1999. Stan's analysis is scary, to say the least.

The article, Probing for the Smoking Gun, was reprinted
in the Soaring
Association of Canada's free flight, 2/04. Go to the
link below. Click
on free flight on the side bar. Go to free flight back
issues - 2004 -
issue 2. Down load the PDF file.

http://www.sac.ca/

Bill Feldbaumer 09






Mark J. Boyd