Troubling story and some questions

On Jan 9, 4:49*pm, Andreas Maurer wrote:
On Wed, 9 Jan 2008 11:59:29 -0800 (PST), wrote:
I think the concern is more that when you open the spoilers you load
up the wing outboard of the spoilers and might create bending moments
that would break the spar - especially above Vne.

Never.
As long as you don't pull really high g-loads (as it was the case in
that Nimbus 4 crash), this is not going to happen.

It's always a good
idea to be familiar with this part of the operating manual for the
specific sailplane type you're flying as you won't habe time to look
it up when you need to know. In any event it would be a wild ride.

This is why I asked - so far I haven't met a glider yet whose POH
didn't allow airbrake extension up to Vne.

Bye
Andreas

Sorry for the confustion Andreas - that's what I meant. If you are
over Vne (or at any speed really) you will need to pull some G's to
get then nose up and he airspeed down. But the bending moment for any
given G-load is higher with the spoilers deployed because only the
outer 2/3 of the wing is lifting. This is why you have different G-
limits with the spoilers out, as I recall. I will need to get my POH
out this winter and read it again. I think you are right that you can
deploy the spoilers up to redline for most gliders, but I think there
are warnings in my POH about what a violent a maneuver it can be. I'll
have to check.

I think there was a thread on the topic of the Minden Nimbus 4 crash a
while ago and in it there was discussion as to whether under certian
conditions (like a steep spiral dive) you are better off pulling the
spoilers first or using the bigger G-envelope with the spoilers closed
to get the nose up first. I don't think there was a final resolution.

9B

On Jan 9, 2:28*pm, wrote:
On Jan 9, 12:52*pm, wrote:





On Jan 8, 10:07*pm, wrote:

On Jan 8, 8:29*pm, wrote:

On Jan 8, 6:09*pm, Tony Verhulst wrote:

If you need to go into controlled airspace without permission

[CFI mode]
I fly in controlled airspace all the time and rarely get permission.

Andreas Maurer wrote:
On Wed, 9 Jan 2008 11:59:29 -0800 (PST), wrote:

This is why I asked - so far I haven't met a glider yet whose POH
didn't allow airbrake extension up to Vne.

Dave was well above Vne, so slowing down to Vne before opening the
spoilers might be a very good idea.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

IN A SPARROWHAWK. Those things weigh like 145 pounds
empty not exactly the aircraft I want to use for testing
aeroelastic theory. He has his transponder on so ATC
sees him. He is monitoring Reno Approach so he would
be aware of traffic reporting in an area of concern
to him.

In a previous post the orginal poster commented that
the FAA regards his glider as an ultralight. Could
someone please clarify if Daves Sparrowhawk is
operated as an ultralight or a certificated aircraft?

On Dec 31 2007, 6:03 am, "
wrote:

VNE at various altitudes

I have looked at a number of posts on this thread. May I attempt a
sort of summary?

At 40,000 ft, the ratio of True Airspeed to Indicated Airspeed is
approximately two (using the
ICAO ISA). This is why an airliner can fly at, say, 200 knots "on the
clock" and yet travel over
the ground at 400 knots. Since drag and therefore fuel consumption is
approximately
proportional to IAS, this is great for jet airliners. However, it's
less great for gliders.

Looking at flutter and stability, aerodynamic stability is
approximately proportional to IAS
whereas inertia is approximately proportional to TAS. Aerodynamic
stability provides restoring
moment(s) after a disturbance, that is what things like dihedral and
the vertical and horizontal tail
surfaces are for. Also, movements like pitch and roll produce changes
of angle of attack that in
themselves are (slightly) stabilising. The overall effect should be
that the aircraft is stable to
disturbances such as due to turbulence. The other side of the coin is
that "Inertia" implies that
any divergence will tend to continue, and needs to be damped out by
restoring moments before
an unstable situation develops such as what is commonly called
"flutter" that has claimed the lives
of several pilots over the years. So Vne in terms of IAS is clearly
not constant with altitude, if
divergent flutter is to be avoided. The only question is, by how much
it should reduce?

In many gliders, the protocol for Vne with altitude is one which I
understand was originally
formulated by the German certification authority, the Luftfahrt
BundesAmpt (LBA). It is also
used in JAR 22, the European airworthiness requirement for gliders
(now operated under the new
European Airworthiness and Safety Authority, EASA).

The protocol says: "For gliders, Vne IAS is assumed to be constant
from Sea Level to altitude
2000m, then decreases with altitude at constant TAS".

The idea was that this was a reasonable assumption, maybe a bit on the
cautious side, that could
be accepted by the LBA and JAR22 in the absence of real flutter
testing at high altitudes. If you
look at your flight manual (if you fly an European-produced glider),
you may well find that the
Vne table with altitude uses this protocol. Mine certainly does.

In numerical terms, to take an easy figure, if your glider Vne was 100
knots at sea level (where
IAS and TAS are the same), it would still be 100 kt IAS at 6562 ft
(2000m). Using the ICAO
ISA, IAS then reduces at altitude such that at:
10,000 ft it is 94.8, then:
15kft = 87.5
20kft = 80.5
25kft = 73.8
30kft = 67.5
35kft = 61.4
40kft = 54.7

For a real glider, multiply these figures by the ratio of your Sea
Level Vne to 100 knots. If 130
knots at SL, assuming above protocol, at 20kft the Vne IAS will be
104.7knots. I have a MS
Excel spreadsheet that does this, you enter your glider's Sea Level
Vne and the table with altitude
is shown (if you want a copy, email me).

However, the "official position" is that you must still use what it
says in your own glider's
Flight Manual, in case it is different to the above.

The manuals for older gliders may not allow for this reduction in Vne
IAS with altitude, and
advice should then be sought. In the USA I guess that this would be
from the SSA and/or the
FAA, in the UK is would be the BGA because we have delegated technical
powers from our CAA
and the matter would be dealt with in the first instance by the BGA
Technical Committee.

Background to Flutter Testing.

Unlike expensive powered aircraft, glider testing does not include
real flutter testing at altitude.
In powered aircraft, vibration is provoked in flutter testing by small
"bangers" or "kickers" that
artificially produce motion in wings, tail surfaces and so forth, so
that damped motion can be
proved from the sensors in the test aircraft. In my earlier
incarnation as a military test pilot, I have
been involved in high level flutter testing for a number of
aircraft.

This is not done in gliders for obvious reasons of cost and the
difficulty of taking prototype gliders
up to altitude with the correct "kickers" and instrumentation
sensors. Therefore, the above
protocol was produced.

I am sorry that this post is long. But it may review some of the
ground ...

Ian Strachan
Lasham Gliding Centre, UK

On Thu, 10 Jan 2008 02:36:00 -0800 (PST), Ian Strachan
wrote:

However, it's
less great for gliders.

I'm not sure that Klaus Ohlmann would agree...



I am sorry that this post is long. But it may review some of the
ground ...

Great posting!


Bye
Andreas

Martin Gregorie wrote:

I noticed the same thing in a Libelle 201 when I tried using the brakes
at high speed.

Out of curiosity, do you remember the speed at which you tried that?

The fastest I've opened them to date was 70 kts. Mine's a 201 (not B
series). They opened as easily as usual (mine has a pretty fierce over
center even when stationary) but the deceleration was immediately
noticeable - I thought that wasn't bad at all for a glider thats famous
for having weak brakes!

I tried at 80 and 100 knots. 80 was OK, but 100 was stiff enough to
require a serious pull that made it difficult to not snatch the brakes
open. I didn't try any faster.

On the opposite side, I like Duo Discus brakes. They can be operated
at high speed with a little care.

--
Philip Plane _____
|
---------------( )---------------
Glider pilots have no visible means of support

On Jan 9, 11:51 pm, Soarin Again
wrote:
IN A SPARROWHAWK. Those things weigh like 145 pounds
empty not exactly the aircraft I want to use for testing
aeroelastic theory. He has his transponder on so ATC
sees him. He is monitoring Reno Approach so he would
be aware of traffic reporting in an area of concern
to him.

In a previous post the orginal poster commented that
the FAA regards his glider as an ultralight. Could
someone please clarify if Daves Sparrowhawk is
operated as an ultralight or a certificated aircraft?

The SparrowHawk may be either operated as an ultralight vehicle or
an experimental aircraft - choice of owner. There are advantages and
disadvantages in either category. I operate my SparrowHawk as an
ultralight but have it equipped probably better than many gliders with
EDS O2, a transponder and a ballistic parachute. Since I still belong
to USHPA (US Hang Gliding Paragliding Association) I am covered for
$1,000,000 liability insurance for only $60. Also because there is no
N number the SparrowHawk falls into the same category as hang gliders/
paragliders and there are no local property taxes to be paid. Since I
have 10 years of sailplane experience and most operators know me in
this part of the world I have no problems getting a tow from the local
FBOs. For me the obvious choice was ultralight category. For others
there may be good reasons for experimental category. These may include
getting hull insurance and the requirement from the FBO have a
registered aircraft if you want a tow.
Because the FAA never envisioned a SparrowHawk when Part 103 was
generated there are almost no operating restrictions on an unpowered
ultralights - no pilot license, no air worthiness certificate, no
pilot flying experience, no stall speed requirements, no maximum speed
restrictions, no O2 requirements and the list goes on. The only
restrictions are weight (155lbs without installed safety equipment),
one person, no flying over populous areas and keeping out of ATC
controlled airspace (A, B,C and D) except with permission. I still
have yet to land the SparrowHawk at Reid Hillview Airport (D airspace)
in San Jose, CA which is a very busy towered GA airport, but they are
quite comfortable with me landing the Stemme as a glider that I am
sure after a couple of questions and clarifications I would be given
permission.
Dave

Dave,

The chance of your airspace infringement causing a
midair or even an airprox is virtually nil; the base
levels of airways are generally not used (at least
in the UK) and airways aren't the busy highways we
are led to believe, but the main reason a midair would
not have occurred is because you were transponder equipped.

If the controllers were working traffic at your level,
in your vicinity, they would have noticed your squark.
If they didn't, and you were going to cause a loss
of separation (1000' or 5nm), then a conflict warning
would have been triggered . If this visual warning
failed to attract the controllers attention then TCAS
(which virtually all airways traffic is equipped with)
would have provided the other pilot with advice on
collision avoidance.

Calling prior to entering CAS was obviously not possible
and I don't think there was any need to make a call
until everything was back under control and you were
outside CAS. As you had exceeded VNE your climb was
essential and could probably be considered an emergency;
therefore it may have been appropriate to select 7700
on your transponder as you climbed. This would have
definately alerted ATC to your presence, although you
would have needed to call ASAP to let them know everything
was ok and explain your predicament.

Philip Plane wrote:
Martin Gregorie wrote:

I noticed the same thing in a Libelle 201 when I tried using the brakes
at high speed.

Out of curiosity, do you remember the speed at which you tried that?

The fastest I've opened them to date was 70 kts. Mine's a 201 (not B
series). They opened as easily as usual (mine has a pretty fierce over
center even when stationary) but the deceleration was immediately
noticeable - I thought that wasn't bad at all for a glider thats famous
for having weak brakes!

I tried at 80 and 100 knots. 80 was OK, but 100 was stiff enough to
require a serious pull that made it difficult to not snatch the brakes
open. I didn't try any faster.

Thanks for the information.


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