Aircraft Takeoff speeds

why does it seem that most modern jet aircraft unstick at around 160kts?
Fighters, bombers, transports all of them frequently seem to takeoff at
160kts, is it a tire speed limit kind of thing?

Tires may be a factor as are brakes. The Space Shuttle touches down at
200mph and puts a lot of stress on both areas requiring significantly more
maintenance (and a drag chute) than would be acceptable for most
planes....although airliners/transports also rely on reverse thrust to
decelerate.......but aerodynamics probably has at least as much to do with
it. All these aircraft most frequently operate in the high subsonic
regions and therefore have similar wing loading.


"boomer" wrote in message
...
why does it seem that most modern jet aircraft unstick at around 160kts?
Fighters, bombers, transports all of them frequently seem to takeoff at
160kts, is it a tire speed limit kind of thing?

"Mark T. Evert" wrote in message
...
Tires may be a factor as are brakes. The Space Shuttle touches down at
200mph and puts a lot of stress on both areas requiring significantly more
maintenance (and a drag chute) than would be acceptable for most
planes....although airliners/transports also rely on reverse thrust to
decelerate.......but aerodynamics probably has at least as much to do with
it. All these aircraft most frequently operate in the high subsonic
regions and therefore have similar wing loading.


As I understand it, the rotation speed is invariably decided by a tailscrape
condition (this is certainly the case for transport/bomber aircraft with a
tricycle undercarriage) - it is the speed at which the aircraft can
successfully unstick from the runway without the rear of the aircraft
stiking the ground. The angle is determined by the aircraft's geometry (most
important is the longitudinal placement of the u/c), although the specific
aerodynamics such as the lift curve slope, anticiapted rate of rotation and
the wing set incidence are key parameters that determine Vlof. A safety
margin is included, typically a reserve factor of 1.2.

This can really be quite crucial to the aircraft's performacnce: the B-52
with its high wing has to have a bicycle u/c configuration to accomodate the
large bomb bay. The bicycle undercarriage really hinders rotation on
take-off and so the wing must therefore be set to an incidence angle
governed by take-off and not cruise-drag considerations. This is a real
problem from the performace engineer's perspective.

"boomer" wrote in message
...
why does it seem that most modern jet aircraft unstick at around 160kts?
Fighters, bombers, transports all of them frequently seem to takeoff at
160kts, is it a tire speed limit kind of thing?


Modern radial ply tyres (Type III and IV), especially those for military
use, are nominally rated to at least 200 Kts.

"Jim Doyle" wrote in message
...

Modern radial ply tyres (Type III and IV), especially those for military
use, are nominally rated to at least 200 Kts.

The space shuttle used carbon tires, as rubber burns in the upper
atmosphere.

thanks guys,I'm developing flight models for an upcoming flight simulator
for next year, to say the leaste it will knock the world back a bit as
nothing like this has really been done before. ANY information along the
lines of real world flight envelopes for modern day warplanes (from say F-4
onwards) from around the world would be GREATLY appreciated and likely even
credited if the info was in large quantities and of a usefull quality.
Takoff speeds, landing speeds, distances for TO and landing. If the holy
grail of G charts should become known unto me( I already have one for F-4)
you shall be knighted! (ok not really BUT if I could) Thanks for any
upcoming help. If you have info you can post it here or(preferably to
prevent me from missing it on this server) send direct to me at
with the subject "Flight Envelopes" (even if it isnt
quite to do with the envelope) so it doesnt get spam filtered out. Records
will be kept as to who sent what, and you may choose to be annonymouse if
you wish. Thanks again all :-)

"Tarver Engineering" wrote in message
...

"Jim Doyle" wrote in message
...

Modern radial ply tyres (Type III and IV), especially those for military
use, are nominally rated to at least 200 Kts.

The space shuttle used carbon tires, as rubber burns in the upper
atmosphere.

It's the takeoff weight, wing airfoil and incidence, lift devices and
ability to rotate to a given angle (tail clearance) that determine
liftoff speed (not taking into account air density, determined by
ambient conditions). From these factors the tire limit speed is
determined and tires manufactured to support that airplane. Note that
three airplanes, at least, are limited to a higher liftoff speed than
they could actually use because of tail drag - F102, F106 and F15. All
three can fly at a much higher angle of attack than te design limits.
I suspect the 757/767 are in the same boat. BTW I think the touchdown
speed on the Shuttle is higher than 200 mph. That's only about 173
Kts, less than some fighters. Tires are built for much higher speeds -
and you can buy them for your car. A waste of money unless you have
the right car, though.
As I remember the tire limit speed on the DC10-30 was 217 knots. A
no-slat no-flap touchdown was right on that limit, too.
Our F104As with three external tanks and the dart tow rig rotated at
205 Kts and about 5000 feet of roll. That was the heaviest we flew at.
The F4E carrying dispensers for the CBU38 (? antitank munitions) on
the inboard pylons rotated at 196 but that was a CG problem. FWIW we
got one batch of F104 tires that were built and designed to someone's
erroneous specifications (built to a newly specified design) and we
were throwing treads off brand new tires on a light-loaded zipper -
only gun ammo and 2xAIM9s aboard. That was interesting . . . Shortly
thereafter the specs were changed to a performance criterion and the
problems disappeared.
Walt BJ

"WaltBJ" wrote in message
snip
Tires are built for much higher speeds -
and you can buy them for your car. A waste of money unless you have
the right car, though.

I don't think so, do you have a reference for the car tire?

Elemental oxygen is some pretty nasty stuff and the shuttle does not have
car tires.

On Fri, 30 Jan 2004 03:36:14 -0600, "boomer"
wrote:

why does it seem that most modern jet aircraft unstick at around 160kts?
Fighters, bombers, transports all of them frequently seem to takeoff at
160kts, is it a tire speed limit kind of thing?


Tires for aircraft can certainly be produced for higher speeds than
160 Kts. Probably not classified anymore as a "modern" jet aircraft,
but we have had mention of the F-4 and F-104 in the thread, so I'll
add that the F-105 at max gross take-off weight still had a ways to go
with all three wheels firmly on the ground accelerating through 160.
Common combat rolls out of Korat in '66 exceeded 6000 feet on the roll
and had nose-wheel-lift-off at 196 and takeoff speed of 204 KIAS.

The tires were good to 230 kts.

An interesting limit was at the other end of the flight. Heavyweight
landing or an emergency necessitating a no-flap landing could result
in roll-ons at speeds in excess of 200 kts. The limiter was the drag
chute max deployment speed of 200. When you needed the braking the
most, you had to slow a bit before you could use it!


Ed Rasimus
Fighter Pilot (USAF-Ret)
"When Thunder Rolled"
Smithsonian Institution Press
ISBN #1-58834-103-8

Speaking of a/c wheels...

On the 1950s FJ-4B ( a Navy fighter-bomber version of the USAF F-86) the
main mount wheels were in two pieces since the sixteen ply tires could never
have been stretched over the wheel rims. The two wheel pieces were bolted
together facing each other against the respective tire rims. The bolts
required washers that had one edge beveled to fit the curvature of the
wheel.

An inexperienced mech put a wheel tire combo together with the sharp edge of
the washers facing the wheel instead of away. He mounted the wheel on the
plane and pressurized it to the required 600 psi for carrier landings. As he
walked back to the line shack there was a tremendous explosion. The plane's
drop tanks had been ruptured by wheel debris and the plane was on fire,
becoming a total loss.

Like the poem said "For want of a nail the shoe was lost...". When all else
fails, read the instructions!

WDA



end

"boomer" wrote in message
...
why does it seem that most modern jet aircraft unstick at around 160kts?
Fighters, bombers, transports all of them frequently seem to takeoff at
160kts, is it a tire speed limit kind of thing?

great start guys, all has been saved for use. Hopefully we can get some
pilots willing to reveal some stuff. Especially need stall speeds at 1 G at
various altitudes/weights, I can build on higher Gs if I can just get a
start at 1G, but obviously higher G info would be great too. Keep it coming
fellas :-)

"W. D. Allen Sr." wrote in message
...
Speaking of a/c wheels...

On the 1950s FJ-4B ( a Navy fighter-bomber version of the USAF F-86) the
main mount wheels were in two pieces since the sixteen ply tires could
never
have been stretched over the wheel rims. The two wheel pieces were bolted
together facing each other against the respective tire rims. The bolts
required washers that had one edge beveled to fit the curvature of the
wheel.

An inexperienced mech put a wheel tire combo together with the sharp edge
of
the washers facing the wheel instead of away. He mounted the wheel on the
plane and pressurized it to the required 600 psi for carrier landings. As
he
walked back to the line shack there was a tremendous explosion. The
plane's
drop tanks had been ruptured by wheel debris and the plane was on fire,
becoming a total loss.

Like the poem said "For want of a nail the shoe was lost...". When all
else
fails, read the instructions!

WDA



end

"boomer" wrote in message
...
why does it seem that most modern jet aircraft unstick at around 160kts?
Fighters, bombers, transports all of them frequently seem to takeoff at
160kts, is it a tire speed limit kind of thing?