How indicative of agility are max G numbers?

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

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

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

If your measure of "maneuverability" is the radius of the airplane's
circle, the anwer is No. A Sopwith Pup could turn a very tight circle
while pulling very few Gs.

I realize you were no doubt thinking of modern fighters when you asked
the question, but the above example should tell you something about
agility and Gs.

vince norris

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

Somewhat. Of course the A-4 Superfox (A-4F with J-52P408 and stripped of
humpback et al) was an aluminum assassin in the adversary role and rarely
exceeded 6G.

Also, most new aircraft have reported max of 9Gs. Why are they all
coming out at this same number?

Structural design starts getting to be a small problem above 9G (which
implies 13.5G prior to overload), but 9G is about it from the operator
standpoint. You can endure more for a short while, but not while performing
actions other than enduring the G. Even the fittest of the Viper drivers
don't pull max G for long periods.

R/ John

A section of the videotape of the Paris Airshow of (around) 1987 or so
includes the HUD display of an F16 flown by a company demo pilot. You
can hear him grunting to combat the G forces as he pulls up to 9G (all
the way around a 360 turn). You can also hear him sigh in relief as he
plants the thing on the ground after his workout. (It's the airshow
where the MiG29 does a lawn-dart.)
Pulling G like that is work. Doing it for three missions a day is hard
work. Doing it without a G-suit is bloody hard work!
Walt BJ

After an exhausting session with Victoria's Secret Police, John
Carrier blurted out:

Structural design starts getting to be a small problem above 9G (which
implies 13.5G prior to overload), but 9G is about it from the operator
standpoint. You can endure more for a short while, but not while performing
actions other than enduring the G. Even the fittest of the Viper drivers
don't pull max G for long periods.

Down at the centrifuge at Brooks AFB, they had a picture of a gal that
had the "honor" of receiving the "elephant award." She held the record
for 15 Gs and not going to sleep, 15Gs was computed to be the
equivalent of having an elephant stand on your chest.

They also showed a video of a viper guy spinning at 9 Gs carrying on a
simulated air-to-air dialog...this guy was a squatty body.

The day before I got to ride the spin-n-puke, two FWS F-16 IPs both
went to sleep during their rides. Too much fun in San Antonio the
night prior.

Pulling 9 Gs was the least favorite part of the FCF profile for me.
Few years back (10 away from the F-16) I was surprised that 3-4 Gs in
a T-6G felt "heavy."

Juvat