Flanker vs F-15

Jeff Crowell wrote:

Yabbut, isn't that a case of a Lawn Dart pulling max G and
then hitting turbulence, etc.?

I could see too high of an onset rate, or pulling a turn as you
decelerated through the sound barrier. The latter case would be a very
good candidate if pulling a turn close to the limiter because of the
forward shift in the aerodynamic center going from supersonic to subsonic.


Jeff

Michael Kelly, Bone Maintainer

R Haskin wrote:
Actually fly-by-wire aircraft can be over-Gd -- it happens to F-16s all the
time.

Agreed. The Bone is a 2 channel FBW on one side with a hydromechanical
stability augmented system on the other side. There are no limiters on
the FBW or stability aug so over G's happen all the time. Limiters on
the 16 make it harder to over G but not impossible.

The F-15, while not "fully" fly-by-wire, has a primary flight control system
that is FBW (called the CAS, or Control Augmentation System) and a
hydromechanical backup system.

IIRC my F-15 test pilot former colleague described the F-15C as fully
hydromechanical and the Echo's as you did. BTW saw you the other day on
the history channel. Good interview.

Cheers,
Michael Kelly, Bone Maintainer

On Thu, 25 Mar 2004 05:41:52 -0500, "R Haskin"
wrote:


"Michael Kelly" wrote in message
m...

John Mullen wrote:

The Su has a pull-through fuction on the fbw ISTR. Might be a factor?

Probably not since the the F-15C isn't FBW and only has an overload
warning function. You can over G a F-15C.

Michael Kelly, Bone Maintainer

Actually fly-by-wire aircraft can be over-Gd -- it happens to F-16s all the
time.

The F-15, while not "fully" fly-by-wire, has a primary flight control system
that is FBW (called the CAS, or Control Augmentation System) and a
hydromechanical backup system.

All modern FCSs are electronic, not mechanical or hydraulic, but we
don't consider them to be FBW. We just consider them to be analog or
digital FCSs. However, it's possible to have hydraulic or mechanical
FCSs.

The point is that FBW is strictly between the pilot and the control
surfaces. That's it. Nothing to do with the feedback control in the
flight control system. After all, the SR-71 was summing electric
inputs from the FCS with the push-rod and cable inputs from the pilot
back in the '60s.

You can have FBW without having a feedback control FCS, not that
anyone does, and you can have an FCS without having FBW, which the
F-15 does and the SR-71 did. Or you can have both, which the F-16 and
F-18 do.

Mary

--
Mary Shafer Retired aerospace research engineer

"Mary Shafer" wrote in message
...
On Thu, 25 Mar 2004 05:41:52 -0500, "R Haskin"
wrote:


"Michael Kelly" wrote in message
m...

John Mullen wrote:

The Su has a pull-through fuction on the fbw ISTR. Might be a
factor?

Probably not since the the F-15C isn't FBW and only has an overload
warning function. You can over G a F-15C.

Michael Kelly, Bone Maintainer

Actually fly-by-wire aircraft can be over-Gd -- it happens to F-16s all
the
time.

The F-15, while not "fully" fly-by-wire, has a primary flight control
system
that is FBW (called the CAS, or Control Augmentation System) and a
hydromechanical backup system.

All modern FCSs are electronic, not mechanical or hydraulic, but we
don't consider them to be FBW. We just consider them to be analog or
digital FCSs. However, it's possible to have hydraulic or mechanical
FCSs.

The part that makes the system FBW is a distinction between cable tripped
valves, or electric valves. (current, or hydraulic)

The point is that FBW is strictly between the pilot and the control
surfaces. That's it. Nothing to do with the feedback control in the
flight control system. After all, the SR-71 was summing electric
inputs from the FCS with the push-rod and cable inputs from the pilot
back in the '60s.

The 747-200 and the DC-10 are termed "hybrid FBW" for having cable driven
hydraulic valves controlled electrically.

You can have FBW without having a feedback control FCS, not that
anyone does, and you can have an FCS without having FBW, which the
F-15 does and the SR-71 did. Or you can have both, which the F-16 and
F-18 do.

An the Boeing 717.

Boomer wrote:

I'm no aerodynamicist but I've been running some numbers and noticed some
interesting things.
The SU-27 is credited with being more manueverable than F-15 and yet F-15
has a higher TTW number (except at gross) and a lower wing loading by a
large margin (again except at gross). The SU should develope more body lift
than Eagle, but at best it looks like a wash at low altitudes, with Eagle
turning better than SU at altitude.
Any thoughts? Am I missing something large here? The Su's lerx's and higher
aspect wing should make a positive differance at low level and low speeds
but I dont think it would make up for the other numbers. Eagle should have a
20% better wing loading and about a 14% better TTW number.

My guess would be that in addition to the LERX it's the auto LEF, vs. a fixed
LE, high-camber wing. The latter is lighter, but you'll note that every
maneuverable fighter designed after the F-15 has gone with LEF. McAir's
designers considered LEF, but decided against them on cost/weight grounds, and
maybe on performance grounds in a certain part of the envelope. I've always
wanted to ask whoever made the decision if, given the benefit of hindsight,
they'd have gone the other way.

Guy

excellent point about the LEF I hadent thought of that.
Does anyone know if these devices help more at high or low altitude?

--



Curiosity killed the cat, and I'm gonna find out why!
"Guy Alcala" wrote in message
.. .
Boomer wrote:

I'm no aerodynamicist but I've been running some numbers and noticed
some
interesting things.
The SU-27 is credited with being more manueverable than F-15 and yet
F-15
has a higher TTW number (except at gross) and a lower wing loading by a
large margin (again except at gross). The SU should develope more body
lift
than Eagle, but at best it looks like a wash at low altitudes, with
Eagle
turning better than SU at altitude.
Any thoughts? Am I missing something large here? The Su's lerx's and
higher
aspect wing should make a positive differance at low level and low
speeds
but I dont think it would make up for the other numbers. Eagle should
have a
20% better wing loading and about a 14% better TTW number.

My guess would be that in addition to the LERX it's the auto LEF, vs. a
fixed
LE, high-camber wing. The latter is lighter, but you'll note that every
maneuverable fighter designed after the F-15 has gone with LEF. McAir's
designers considered LEF, but decided against them on cost/weight grounds,
and
maybe on performance grounds in a certain part of the envelope. I've
always
wanted to ask whoever made the decision if, given the benefit of
hindsight,
they'd have gone the other way.

Guy