How indicative of agility are max G numbers?

"monkey" wrote in message
om...
"Dudley Henriques" wrote in message
hlink.net...
"Hobo" wrote in message
...


How indicative of maneaverability are the max G numbers of fighter
aircraft?

You can pull max g all the way out to the structural limits of the
airframe.....but at what turn rate?.....radius? And where does that put
you
in relation to the adversary? (Delta Ps)
In order to determine maneuverability, the g ability to pull g has to be
married into an overall performance graph; then this graph must be
compared
to other aircraft. You can't just use one specific to determine a
fighter's
performance, or ability to maneuver. It takes the integration of many
different factors, all interfaced into the flight envelope to determine
maneuverability. The ability to pull g is inherent in every
fighter......what you do with that g, and WHERE in the envelope you pull
that g are much more pertinent to maneuverability than the fact that you
CAN
pull g.
Then, after you determine all this, there's roll rate, stability, axis
coupling limits, and a whole slew of other good stuff to feed into the
equation.
It's a complicated process. G, and the ability to pull g, are simply
factors
in this HUGE overall process of determining maneuverability.
Hope this helps a bit.
Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/ CFI Retired
For personal email, please replace
the z's with e's.
dhenriquesATzarthlinkDOTnzt

G is not really important from a tactical perspective, what is
important in a turning engagement is turn rate or turn radius; which
of these should be maximized depends on the situation (eg defensive,
offensive, 2 vs 1 circle fight). I won't get into the specifics except
to state that g is not a very significant measure of fighter
performance.

monkey
canadian fighter pilot

I can't tell if you are trying to add to what I said, or trying to correct
what I've said in some way? From what I'm reading, I believe what you are
saying is EXACTLY what I just said....which is correct!
:-)
Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/ CFI Retired
For personal email, please replace
the z's with e's.
dhenriquesATzarthlinkDOTnzt

There's a mix here involved. Max G available, G onset (how fast can
you load it up) and corner velocity - the minimum speed do you need to
generate the lift necessary attain max G. A lot of limitations pop up
now. Higher the G, teh stronger tha irplane must be, and therefore the
weight goes up, so the wing has to be bigger. Also to sustain the G
you need more thrust because induced drag (drag due to generating
lift) goes sky-high.
Generally the design working G limit has been either 7 1/2 or 9 - and
with a 50% safety factor that means the structural yield limit ( bent
and won't 'unbend' either 11 1/4 or 13.5 G. Human G tolerance depends
a great deal on training fitness and 'want to'. I have seen 10.5 on a
G-meter whena student 'dug in' an F4 decelerating through the Mach -
my forward push stopped it from going even higher. My G tolerance came
from flying the F102 sans G-suit and hasseling with anything that came
along. It could pull 3G at 200 KIAS, 7G at about 325, though not for
long (delta wing at airspeed!) FWIW I have a friend who was conscious
and talking to the doctors on USC's centrifuge at 11 G sustained. He
is about 6-2 and 180. Also, I know of two incidents were the pilots
recovered their aircraft pulling 12 (F106) and 13 G (F86D)
respectively after getting the nose buried close to the ground. Yes,
the aircraft were severely bent, but the pilots survived. Adrenalin is
a wonder drug in these cases - special cases of 'want to'.
Walt BJ

"WaltBJ" wrote in message
om...
There's a mix here involved. Max G available, G onset (how fast can
you load it up) and corner velocity - the minimum speed do you need to
generate the lift necessary attain max G. A lot of limitations pop up
now. Higher the G, teh stronger tha irplane must be, and therefore the
weight goes up, so the wing has to be bigger. Also to sustain the G
you need more thrust because induced drag (drag due to generating
lift) goes sky-high.
Generally the design working G limit has been either 7 1/2 or 9 - and
with a 50% safety factor that means the structural yield limit ( bent
and won't 'unbend' either 11 1/4 or 13.5 G. Human G tolerance depends
a great deal on training fitness and 'want to'. I have seen 10.5 on a
G-meter whena student 'dug in' an F4 decelerating through the Mach -
my forward push stopped it from going even higher. My G tolerance came
from flying the F102 sans G-suit and hasseling with anything that came
along. It could pull 3G at 200 KIAS, 7G at about 325, though not for
long (delta wing at airspeed!) FWIW I have a friend who was conscious
and talking to the doctors on USC's centrifuge at 11 G sustained. He
is about 6-2 and 180. Also, I know of two incidents were the pilots
recovered their aircraft pulling 12 (F106) and 13 G (F86D)
respectively after getting the nose buried close to the ground. Yes,
the aircraft were severely bent, but the pilots survived. Adrenalin is
a wonder drug in these cases - special cases of 'want to'.
Walt BJ

Yeah, it's a multiples thing all right, especially if you throw corner in
there . Below corner you're aerodynamically limited and above you're
structurally limited; go high enough and you're thrust limited as well......
but just considering g alone which was his question, and forgetting rate and
radius, you can pull max g all the way out to the right side of the envelope
until either you or the airplane starts complaining :-)
But I agree with you. You can't even begin to discuss fighter performance
using a one aspect only condition. There's just too much involved, and the
whole thing has to be integrated into the discussion for anything to make
sense at all.
Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/ CFI Retired
For personal email, please replace
the z's with e's.
dhenriquesATzarthlinkDOTnzt

On Fri, 21 Nov 2003 04:47:47 GMT, "Dudley Henriques"
wrote:


"WaltBJ" wrote in message
. com...
There's a mix here involved. Max G available, G onset (how fast can
you load it up) and corner velocity - the minimum speed do you need to
generate the lift necessary attain max G. --snip--
Walt BJ

Yeah, it's a multiples thing all right, especially if you throw corner in
there . Below corner you're aerodynamically limited and above you're
structurally limited; go high enough and you're thrust limited as well......
but just considering g alone which was his question, and forgetting rate and
radius, you can pull max g all the way out to the right side of the envelope
until either you or the airplane starts complaining :-)
But I agree with you. You can't even begin to discuss fighter performance
using a one aspect only condition. There's just too much involved, and the
whole thing has to be integrated into the discussion for anything to make
sense at all.
Dudley Henriques

I was going to jump into this yesterday, but delayed and "lo" I've
developed insight. I was going to dump my usual tirade about tactics,
training, weapons, mutual support, etc. Then, I returned to the
question.

It isn't about "fighter", it's about agility. "How indicative of
agility are max G numbers?"

I'd have to say, only minimally indicative. The 105 had a max positive
G of 8.67--a structure limit which was virtually impossible to attain,
except instantaneously. Airspeed bleedoff, if you get anywhere up to
those kinds of numbers meant you couldn't sustain for long at all.

The F-4, conversely had a 7.33 max, much lower, but no one will
challenge that the F-4 had greater agility than a 'Chief.

Clearly there's a "critical mass" sort of minimum G required to get
you into the A/A game. You don't go hassling with a 2.5 G limit MiG-25
even though you have weapons, thrust and airspeed. Corner velocity is
a consideration, attainable onset rates, sustainable G-loads,
rate/radius numbers, roll rates, all are players.

And, who can quantify that elusive "experience" factor. Doing
instructor continuation training in AT-38s at Fighter Lead-In, I
couldn't begin to pull the sustained G while twisted around in my seat
looking at my own rudder, but I could get the "big picture" of where
the battle was going and kick the young guys' butts at much lower G.

Sort of the old and young bull metaphor---young bull sees the herd and
says "lets run down and screw one." The old bull says, "lets walk down
and screw them all."

Mr. Rasimus,

MiG-25 has sustained 5g limit with half fuel stated in every source I've
ever seen. Where did You get 2.5g? That was a limit for A-12/SR71 Blackbird.

Also, I have read article in which test pilot states that one MiG-25 went to
10.5g(!), the MiG-25 airframe got deformed but landed safely.

Maybe Mr. Cooper knows better than I do?

--

Nele

NULLA ROSA SINE SPINA
Ed Rasimus wrote in message ...
On Fri, 21 Nov 2003 04:47:47 GMT, "Dudley Henriques"
wrote:

snip
I was going to jump into this yesterday, but delayed and "lo" I've
developed insight. I was going to dump my usual tirade about tactics,
training, weapons, mutual support, etc. Then, I returned to the
question.

It isn't about "fighter", it's about agility. "How indicative of
agility are max G numbers?"

I'd have to say, only minimally indicative. The 105 had a max positive
G of 8.67--a structure limit which was virtually impossible to attain,
except instantaneously. Airspeed bleedoff, if you get anywhere up to
those kinds of numbers meant you couldn't sustain for long at all.

The F-4, conversely had a 7.33 max, much lower, but no one will
challenge that the F-4 had greater agility than a 'Chief.

Clearly there's a "critical mass" sort of minimum G required to get
you into the A/A game. You don't go hassling with a 2.5 G limit MiG-25
even though you have weapons, thrust and airspeed. Corner velocity is
a consideration, attainable onset rates, sustainable G-loads,
rate/radius numbers, roll rates, all are players.

And, who can quantify that elusive "experience" factor. Doing
instructor continuation training in AT-38s at Fighter Lead-In, I
couldn't begin to pull the sustained G while twisted around in my seat
looking at my own rudder, but I could get the "big picture" of where
the battle was going and kick the young guys' butts at much lower G.

Sort of the old and young bull metaphor---young bull sees the herd and
says "lets run down and screw one." The old bull says, "lets walk down
and screw them all."

Generally the design working G limit has been either 7 1/2 or 9 - and
with a 50% safety factor that means the structural yield limit ( bent
and won't 'unbend' either 11 1/4 or 13.5 G. Human G tolerance depends

Great post, as usual, Walt. My favourite present day example is the F/A-18.
It is limited by the FCS to 7.5 G, but it maneuvers like a SOB!
_____________
José Herculano