On Jan 6, 1:10 pm, "
wrote:
Hi Gang
I received a large number of responses to my posting both on RAS
(25) and privately and would like to respond to some of the issues.
Firstly I would like to reiterate that the reason for my posting was
to make pilots aware of not paying attention to critical
considerations, situations can quickly get out of hand. We seem to
have here in Minden at least one destruction of an aircraft (Carat and
ASW26) every 2 years and almost the same number of deaths in
situations where if the pilots had flown reasonably in wave these
accidents could have been avoided. I came close and it was a wake up
call. Enough!
I would like to discuss communications with ATC especially around
Reno which is an International Airport. My rule of thumb is never to
burden them with chit chat but to communicate when necessary. When
flying in wave I monitor Reno Approach ( 2 frequencies - one from the
south and one from the north) and if close to 18k I do not
communicate. If flying anywhere close to approaches or flyways I speak
to them and give them my intentions. This works well and if there are
several gliders flying doing the same this doesbad not over burden
them. When I got into my situation I was monitoring Reno Approach and
there were no other aircraft in my vicinity. I knew I would have to
fly higher for a very short time so should I have called them and
declared an emergency? I think not! What would I have said: "This is
an ultalight vehicle (FAA definition of my flying machine), 8 miles
NV of Reno declaring an emergency, squawking 0440, request operation
to 19k from present altitude." What would ATC have said in
response: :You are what? Repeat request and say N number." Would this
have started a useful interchange of ideas. I think not. No I had to
as safely as possible fix my mess and get down to below 18k.
Lets talk reporting altitudes to ATC. Below is a private response to
a question concerning altitudes:

"Thanks for your reply. The actual difference in indicated altitudes
between the transponder and the pressure altitude altimeter that day
was very small because barometric air pressure was close to the
standard value. You are correct that up to Class A air space altitudes
are given based on surface pressures. Above 18k all altitudes must be
given using the standard pressure. So there can be a dilemma. There is
a region of uncertainty around 18k. If the transponder says 18.2k (my
Becker transponder displays its altitude) and the pressure altitude
reading says 17.8k and ATC asks what altitude you are what do you say?
OK. So what happens in practice? When I am close to Reno monitoring
ATC and ATC informs another aircraft of my presence they always use my
transponder altitude using an expression like this: "Glider at your 3
o'clock indicating one five thousand one hundred feet" ATC never
corrects my transponder altitude below 18k to actual altitude. So in
extreme conditions there can be errors of several hundred feet between
what is reported and reality. The solution? GPS, GPS, and GPS! "

And finally VNE at altitude. IAS has to be adjusted for altitude to
give TAS. It is generally accepted that rule of thumb reckoning for
every 1000 feet above sea level TAS has to be increased by 1.5%
although at high altitudes 30k it is closer to 2% (Check site given
below. It has an excellent article). So how do sailplane manufacturers
rate their machines? In general fairly close to the above. Eric
Greenwell in a previous posting gives the IAS for the ASW26 and I have
checked the same for my Stemme S10-VT and in private correspondence I
find other sailplanes are similarly placarded. This does not answer my
original question about the sensitivity of flutter to altitude and
true air speed. No one, including me, to date has been able to
identify any meaningful articles on the subject.
Dave

http://tvnz.co.nz/view/video_popup_windows_skin/1519472

Dave,

Couple of articles from the Ostiv Congress.

Technical Soaring, Vol 18, nr 3, July 1994
Wojciech Chajec, Critical Flutter Speed of Sailplanes Calculated for
High Altitude - Examples of Computation [Aerodynamics], page 69

Technical Soaring, Vol 18, nr 4, October 1994
Walter Stender, Fritz Kiessling, and Joachim P. Kuettner,
Possibilities of High Altitude Flutter During Wave Flights
[Aerodynamics], page 114

I don't have either copy immediately at hand. Back copies are usually
available from OSTIV at www.ostiv.fai.org. OSTIV normally has a booth
at the convention. Bernald Smith and his wife, Mark Maughmer often
staff it, but Loek Boehrmans frequently attends. They bring many back
copies to sell.

See http://en.scientificcommons.org/17836871 for a cite.

Do you know the OAT at 18K on the day?

Frank Whiteley