"Interesting" wind yesterday

"Morgans" wrote
No, I think the post above yours got it pretty much right..Vne is
significant, in that it demonstrates itself by nasty things like
flutter, or control reversal.

Nope! Mike got it right.


"Jim" wrote
Another "coffin corner" I have heard discussed is the convergence of
Vne and Vs as altitude increases.

Nope! Mike got it right.

Coffin corner
From Wikipedia
Coffin corner is a dangerous portion of the flight envelope that must be
carefully approached by high altitude high subsonic speed aircraft, such
as the Lockheed U-2 aircraft.
Mach Limit
A subsonic aircraft must not exceed its Mach limit, some fraction of the
speed of sound near, but not at 1.0. At the low air densities encountered
at high altitude the speed of sound is lower. Exceeding the Mach limit
can cause loss of control and/or structural failure.
Stall Limit
At high altitudes the low density air is less capable of supporting the
aircraft and so the stall speed increases (as expressed in true air
speed).
The Corner
At some limiting altitude these speeds converge, and the aircraft cannot
be flown, as a slight pitch down will cause the Mach limit to be exceeded
while a slight pitch up will cause an aircraft stall with a subsequent
pitch down.


I've been to "coffin corner" in a Navy T2-V and very near to it in a
Boeing 707 and neither time was I close to Vne..Critical Mach
Number..yes, but not Vne.


Bob Moore
ATP B-707 B-727

"Bob Moore" wrote

Nope! Mike got it right.

Ok, so what is the thing that Bruce , in the Exxon Tiger experienced? I'm
quite sure that is what he called it, and could look back in the Magazines,
to the interview.

Some of my descriptions may have been off, but those were his words.

I have no doubt that what you described is accurate, but am also as
confident that there are other ways, in other aircraft, to get there.
Possible?
--
Jim in NC

"Morgans" wrote in message
...

"Mike Rapoport" wrote

I always thought that the "coffin corner" was where stall speed met the
Mach
limit. I didn't think that it even applied to non-jet aircraft.

Mike

No, I think the post above yours got it pretty much right..Vne is
significant, in that it demonstrates itself by nasty things like flutter,
or
control reversal. Pull back on the stick to maneuver, or slow down, and
stall, or at least buffet like hell.

It is true, however, that it is pretty tough for a non jet aircraft to get
to the coffin corner. The Exxon tiger (can't think of the guy's name)
that
has been trying to get the piston altitude record, has said that he is
really close to getting into coffin corner.
--
Jim in NC



I've never heard of Vne being related to TAS, only IAS. It makes no sense
to me. Could you provide a reference?

Mike
MU-2

On Wed, 09 Mar 2005 14:58:38 GMT, "Mike Rapoport"
wrote:


"Morgans" wrote in message
...

"Mike Rapoport" wrote

I always thought that the "coffin corner" was where stall speed met the
Mach
limit. I didn't think that it even applied to non-jet aircraft.

Mike

No, I think the post above yours got it pretty much right..Vne is
significant, in that it demonstrates itself by nasty things like flutter,
or
control reversal. Pull back on the stick to maneuver, or slow down, and
stall, or at least buffet like hell.

It is true, however, that it is pretty tough for a non jet aircraft to get
to the coffin corner. The Exxon tiger (can't think of the guy's name)
that
has been trying to get the piston altitude record, has said that he is
really close to getting into coffin corner.
--
Jim in NC



I've never heard of Vne being related to TAS, only IAS. It makes no sense
to me. Could you provide a reference?

Mike
MU-2



I'm not sure this is addressed to me, but just in case it is:

I guess the notion about Vne as a TAS is that Vne may be specified for
a given aircraft as an airspeed that depends on altitude. I guess it
could as easily be specified as an IAS at sea level and gross weight,
with a written notice to the pilot that Vne would then be at a lower
IAS as altitude increases. Does this make any sense?

"Jim" wrote in message
...
On Wed, 09 Mar 2005 14:58:38 GMT, "Mike Rapoport"
wrote:


"Morgans" wrote in message
...

"Mike Rapoport" wrote

I always thought that the "coffin corner" was where stall speed met the
Mach
limit. I didn't think that it even applied to non-jet aircraft.

Mike

No, I think the post above yours got it pretty much right..Vne is
significant, in that it demonstrates itself by nasty things like
flutter,
or
control reversal. Pull back on the stick to maneuver, or slow down, and
stall, or at least buffet like hell.

It is true, however, that it is pretty tough for a non jet aircraft to
get
to the coffin corner. The Exxon tiger (can't think of the guy's name)
that
has been trying to get the piston altitude record, has said that he is
really close to getting into coffin corner.
--
Jim in NC



I've never heard of Vne being related to TAS, only IAS. It makes no sense
to me. Could you provide a reference?

Mike
MU-2



I'm not sure this is addressed to me, but just in case it is:

I guess the notion about Vne as a TAS is that Vne may be specified for
a given aircraft as an airspeed that depends on altitude. I guess it
could as easily be specified as an IAS at sea level and gross weight,
with a written notice to the pilot that Vne would then be at a lower
IAS as altitude increases. Does this make any sense?

Yes and no. What you are describing is Mmo which is the limiting Mach
number. It is not Vne. Vne is a fixed mark on the airspeed indicator and,
as such, doesn't move. Mmo is a red "barber pole" on the airspeed indicator
which moves down as altitude increases.

Mike
MU-2

On Wed, 09 Mar 2005 16:29:46 GMT, "Mike Rapoport"
wrote:


"Jim" wrote in message
.. .
On Wed, 09 Mar 2005 14:58:38 GMT, "Mike Rapoport"
wrote:


"Morgans" wrote in message
...

"Mike Rapoport" wrote

I always thought that the "coffin corner" was where stall speed met the
Mach
limit. I didn't think that it even applied to non-jet aircraft.

Mike

No, I think the post above yours got it pretty much right..Vne is
significant, in that it demonstrates itself by nasty things like
flutter,
or
control reversal. Pull back on the stick to maneuver, or slow down, and
stall, or at least buffet like hell.

It is true, however, that it is pretty tough for a non jet aircraft to
get
to the coffin corner. The Exxon tiger (can't think of the guy's name)
that
has been trying to get the piston altitude record, has said that he is
really close to getting into coffin corner.
--
Jim in NC



I've never heard of Vne being related to TAS, only IAS. It makes no sense
to me. Could you provide a reference?

Mike
MU-2



I'm not sure this is addressed to me, but just in case it is:

I guess the notion about Vne as a TAS is that Vne may be specified for
a given aircraft as an airspeed that depends on altitude. I guess it
could as easily be specified as an IAS at sea level and gross weight,
with a written notice to the pilot that Vne would then be at a lower
IAS as altitude increases. Does this make any sense?

Yes and no. What you are describing is Mmo which is the limiting Mach
number. It is not Vne. Vne is a fixed mark on the airspeed indicator and,
as such, doesn't move. Mmo is a red "barber pole" on the airspeed indicator
which moves down as altitude increases.

Mike
MU-2


Well, yes Vne is marked on the ASI, and as such a mark it does not
move.

On the other hand, for several of the gliders I fly the manufacturers
make a point in the POH of directing the pilot to reduce the marked
Vne as flight altitude increases.

So I take the marked Vne as relating to sea level and adjust it
downward at increasing altitudes.

"T o d d P a t t i s t" wrote in message
...
"Mike Rapoport" wrote:

I've never heard of Vne being related to TAS, only IAS. It makes no
sense
to me. Could you provide a reference?

Vne is a fixed mark on the airspeed indicator and,
as such, doesn't move.

Despite the Vne mark on the altimeter, it definitely is not
a fixed IAS (or CAS) number. Nor is it always a fixed TAS
number. It is the number defined by the manufacturer that
is usually found in the flight manual. My sailplane has a
Vne that drops with altitude, and while it's closer to a
fixed TAS than IAS, it's not exactly either.

A fixed TAS makes sense because it is often flutter that
sets the Vne limit, and flutter is a timing related issue
that relates to TAS more closely than IAS.

"It is possible to fly without motors, but not without knowledge and
skill."
Wilbur Wright

So what is the mark on the airspeed indicator supposed to mean then? I have
never seen anything in any of the flight manuals that I have (four)
referring to Vne going down with altitude. I am not disputing that it does
but I am mystified as to why it isn't better explained in flight manuals.
Similiarly, Vmo is given as a single IAS number. In the MU-2 Vmo is 250kts
IAS at any altitude up to about 22,000' where the Mach limit takes over.
This is a large range of TAS. Is it perhaps actually related to Mmo rather
than Vne as gliders don't have airspeed indicators with barber poles? Can
you give some examples wth real numbers and altitudes?

Mike
MU-2

"Mike Rapoport" wrote

I've never heard of Vne being related to TAS, only IAS. It makes no sense
to me. Could you provide a reference?

Mike

True. My mistake.
--
Jim in NC

On Wed, 09 Mar 2005 21:52:58 GMT, "Mike Rapoport"
wrote:


"T o d d P a t t i s t" wrote in message
.. .
"Mike Rapoport" wrote:

I've never heard of Vne being related to TAS, only IAS. It makes no
sense
to me. Could you provide a reference?

Vne is a fixed mark on the airspeed indicator and,
as such, doesn't move.

Despite the Vne mark on the altimeter, it definitely is not
a fixed IAS (or CAS) number. Nor is it always a fixed TAS
number. It is the number defined by the manufacturer that
is usually found in the flight manual. My sailplane has a
Vne that drops with altitude, and while it's closer to a
fixed TAS than IAS, it's not exactly either.

A fixed TAS makes sense because it is often flutter that
sets the Vne limit, and flutter is a timing related issue
that relates to TAS more closely than IAS.

"It is possible to fly without motors, but not without knowledge and
skill."
Wilbur Wright

So what is the mark on the airspeed indicator supposed to mean then? I have
never seen anything in any of the flight manuals that I have (four)
referring to Vne going down with altitude. I am not disputing that it does
but I am mystified as to why it isn't better explained in flight manuals.
Similiarly, Vmo is given as a single IAS number. In the MU-2 Vmo is 250kts
IAS at any altitude up to about 22,000' where the Mach limit takes over.
This is a large range of TAS. Is it perhaps actually related to Mmo rather
than Vne as gliders don't have airspeed indicators with barber poles? Can
you give some examples wth real numbers and altitudes?

Mike
MU-2


It is confusing. Because the high end of the red arc on the ASI is
described as Vne, it certainly would suggest Vne is an IAS and can
be flown as such. But this is not what many glider POH instructions
state.

I don't have a POH here at work. I'll try to remember to give you an
example from one of the ones I have.

On Wed, 09 Mar 2005 21:52:58 GMT, "Mike Rapoport"
wrote:


"T o d d P a t t i s t" wrote in message
.. .
"Mike Rapoport" wrote:

I've never heard of Vne being related to TAS, only IAS. It makes no
sense
to me. Could you provide a reference?

Vne is a fixed mark on the airspeed indicator and,
as such, doesn't move.

Despite the Vne mark on the altimeter, it definitely is not
a fixed IAS (or CAS) number. Nor is it always a fixed TAS
number. It is the number defined by the manufacturer that
is usually found in the flight manual. My sailplane has a
Vne that drops with altitude, and while it's closer to a
fixed TAS than IAS, it's not exactly either.

A fixed TAS makes sense because it is often flutter that
sets the Vne limit, and flutter is a timing related issue
that relates to TAS more closely than IAS.

"It is possible to fly without motors, but not without knowledge and
skill."
Wilbur Wright

So what is the mark on the airspeed indicator supposed to mean then? I have
never seen anything in any of the flight manuals that I have (four)
referring to Vne going down with altitude. I am not disputing that it does
but I am mystified as to why it isn't better explained in flight manuals.
Similiarly, Vmo is given as a single IAS number. In the MU-2 Vmo is 250kts
IAS at any altitude up to about 22,000' where the Mach limit takes over.
This is a large range of TAS. Is it perhaps actually related to Mmo rather
than Vne as gliders don't have airspeed indicators with barber poles? Can
you give some examples wth real numbers and altitudes?

Mike
MU-2


Here is the information from the Flight Manual for the DG-500 glider.

Section 4.5.9 Flight at high altitude and at low temperatures:

...

2. Attention must be paid to the fact that at higher
altitudes the true airspeed is greater than the
indicated airspeed.
The max. speed Vne is reduced. See the
following table:

...

Altitude in ft. 0-6600 10000 13000 16000 20000
Vne IAS kts. 146 138 131 124
117

Hope this helps.