Speed of Heat

Is there a rule of thumb for 'speed of heat'? Meaning the speed in
knots where ice will not form on the leading edges of a wing. For
example, the Saberliner had no de-ice or anti-ice system, just speeding
up would remove or prevent ice build up.
Thanks.

I don't know the formula but Saberliners are too slow to offer reliable
deicing from speed alone although, like anything else, they change temp with
velocity. I recall reading that you need 400kt indicated for complete
protection.

Mike
MU-2


"vlado" wrote in message
ups.com...
Is there a rule of thumb for 'speed of heat'? Meaning the speed in
knots where ice will not form on the leading edges of a wing. For
example, the Saberliner had no de-ice or anti-ice system, just speeding
up would remove or prevent ice build up.
Thanks.

In the Citation the temp difference is about 4 degrees. I think it goes
up exponentially as you approach the speed of sound. You have to get
pretty close to the speed of sounds before you get much difference (I
think).
-Robert

Don't you eventually have to slow down? )


Trip



In article .net, says...

I don't know the formula but Saberliners are too slow to offer reliable
deicing from speed alone although, like anything else, they change temp with
velocity. I recall reading that you need 400kt indicated for complete
protection.

Mike
MU-2


"vlado" wrote in message
oups.com...
Is there a rule of thumb for 'speed of heat'? Meaning the speed in
knots where ice will not form on the leading edges of a wing. For
example, the Saberliner had no de-ice or anti-ice system, just speeding
up would remove or prevent ice build up.
Thanks.

On 14 Mar 2005 21:23:47 -0800, "vlado" wrote:

Is there a rule of thumb for 'speed of heat'?

I don't have a CR-2 with me, but it seems like the ram rise at M.82 is
about 7 deg C.

Icing conditions don't occur at flight levels for cruise anyway, so a
jet aircraft will only ice during climb, decent, or holding. If the
old gray matter serves me, I think Rockwell proved the aircraft could
fly acceptably with any ice load it was expected to encounter. The
type certificate for the military versions show them as VFR only when
operating in the civil system. I doubt seriously it could pass the
testing now required for certification. I seem to remember some de-ice
mods to later versions, but I'm not sure. They did de-ice the engines
and the windscreens are heated. Most of these aircraft are in the
scrap yard by now I would imagine.

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In article ,
Don Hammer wrote:

On 14 Mar 2005 21:23:47 -0800, "vlado" wrote:

Is there a rule of thumb for 'speed of heat'?

I don't have a CR-2 with me, but it seems like the ram rise at M.82 is
about 7 deg C.

The Mach heating temperature rise ratio (T_t / T_s) at M0.82 is .13348
referenced to absolute temperature regardless of altitude and other
atmospheric conditions. For example, if the static air temperature
(T_s) is -40F, then the total temperature (T_t) is +16F. The Mach
heating formula is:

TAU = T_t / T_s = 1 + ((gamma-1)/2)M^2

For a typical atmospheric gamma value of 1.4, the equation reduces to:

T_t / T_s = 1 + .2M^2

Converting -40F to absolute:

-40 + 459 = 419R

Insert temperature and Mach into the formula:

T_t / T_s = 1 + .2 * .82^2 = 1.13448

And:

T_t = T_s * 1.13448 = 419 * 1.13448 = 475R = 16F

So, if the outside air temperature is -40F ambient (zero velocity), then
at M0.82 the total temperature would be +16F.


Icing conditions don't occur at flight levels for cruise anyway, so a
jet aircraft will only ice during climb, decent, or holding.

This is not correct. Icing conditions can and do occur at any altitude
in which visible moisture is present.

If the
old gray matter serves me, I think Rockwell proved the aircraft could
fly acceptably with any ice load it was expected to encounter. The
type certificate for the military versions show them as VFR only when
operating in the civil system. I doubt seriously it could pass the
testing now required for certification. I seem to remember some de-ice
mods to later versions, but I'm not sure. They did de-ice the engines
and the windscreens are heated. Most of these aircraft are in the
scrap yard by now I would imagine.

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----------------------------------------------------------
** SPEED ** RETENTION ** COMPLETION ** ANONYMITY **
----------------------------------------------------------
http://www.usenet.com

--

Kurt Todoroff


Markets, not mandates and mob rule.
Consent, not compulsion.

In article ,
(TripFarmer) wrote:

Don't you eventually have to slow down? )


Trip



In article .net,
says...

I don't know the formula but Saberliners are too slow to offer reliable
deicing from speed alone although, like anything else, they change temp with
velocity. I recall reading that you need 400kt indicated for complete
protection.

Mike
MU-2


"vlado" wrote in message
oups.com...
Is there a rule of thumb for 'speed of heat'? Meaning the speed in
knots where ice will not form on the leading edges of a wing. For
example, the Saberliner had no de-ice or anti-ice system, just speeding
up would remove or prevent ice build up.
Thanks.




By the way, in the jet fighter business, we referred to the speed of
sound (Mach) as the "speed of heat".

--

Kurt Todoroff


Markets, not mandates and mob rule.
Consent, not compulsion.

All of the others talk of temperature rise do to compressibility based on
mach number, but no one really addressed the speed accounting for friction
of air molecules on the sheet metal which warms the aircraft. War story
time, low level over the plains of eastern Montana, near Conrad and Havre
Bomb Plots (Radar Bomb Scoring sites) and the outside air temp was
about -15F, however, we were moving along at about .88mach at 500ft AGL, and
the skin temperature was about 100F, not a worry about accumulating icing.

Some one else referred to "Speed of heat" as being Mach 1, because most
aircraft need after-burner or "heat" (reheat) as the Brits would say.. to
make Mach1. BTDT


BT

"vlado" wrote in message
ups.com...
Is there a rule of thumb for 'speed of heat'? Meaning the speed in
knots where ice will not form on the leading edges of a wing. For
example, the Saberliner had no de-ice or anti-ice system, just speeding
up would remove or prevent ice build up.
Thanks.

I found this formula:

http://williams.best.vwh.net/avform.htm#Mach

Which shows a temp rise pretty close to what the MU-2 flight manual shows.

Mike
MU-2


"vlado" wrote in message
ups.com...
Is there a rule of thumb for 'speed of heat'? Meaning the speed in
knots where ice will not form on the leading edges of a wing. For
example, the Saberliner had no de-ice or anti-ice system, just speeding
up would remove or prevent ice build up.
Thanks.

In article R5QZd.71896$Tt.15712@fed1read05,
"BTIZ" wrote:

All of the others talk of temperature rise do to compressibility based on
mach number, but no one really addressed the speed accounting for friction
of air molecules on the sheet metal which warms the aircraft. War story
time, low level over the plains of eastern Montana, near Conrad and Havre
Bomb Plots (Radar Bomb Scoring sites) and the outside air temp was
about -15F, however, we were moving along at about .88mach at 500ft AGL, and
the skin temperature was about 100F, not a worry about accumulating icing.

Some one else referred to "Speed of heat" as being Mach 1, because most
aircraft need after-burner or "heat" (reheat) as the Brits would say.. to
make Mach1. BTDT


BT

Hi BT,

What were you flying? Most of my time is in the F-111D and the EF-111A.
I've also flown the F-15, C-130, C-141, KC-10, E-3. Did your aircraft
have a skin temperature indicator or a total temperature indicator?
Aircraft component heating is due to Mach compressibility, not skin
friction. I'm confident that your 100F value reflected total
temperature which is based on Mach compressibility.

The "speed of heat" received it's colloquial name because the speed of
sound is based only on the static temperature of the fluid medium, not
on pressure or density as is often mistakenly believed.

--

Kurt Todoroff


Markets, not mandates and mob rule.
Consent, not compulsion.