How indicative of agility are max G numbers?

"Yeff" wrote in message
...
On Thu, 20 Nov 2003 19:19:12 GMT, Dudley Henriques wrote:

Flying something like the F16 or the Flanker is a whole different
ballgame
with g. These airplanes can deliver more than you can handle unless
you're
EXTREMELY careful.

I remember seeing some video taken in an F-16B (I believe). It was a
student and instructor pilot who'd just done a loop and the student went
to
sleep. You can see the Viper heading towards the ground with the
instructor calmly saying over and over, "Recover. Recover." I guess he
finally takes the stick and pulls up. Made the hair on the back of my
neck
stand up.

-Jeff B.
yeff at erols dot com

Yup. We used that clip in safety meetings more than once.
It pays to be in shape!!
DH

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."

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

"Mark Irvine" wrote

"Anonymous" wrote

Hobo wrote in message ...


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

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

Modern aircraft are capable of higher G turns; however, in order to
stop the pilots from blacking/redding out and/or dying in their
seat, the computer controlling the fly-by-wire / fly-by-light
systems stops the turns going any higher.

I think

Cheers
Graeme


It could also be because they do not want to release into the public
domain
the exact performance of the aircraft? A few years ago all aircraft
seemed
to be listed as Mach 2.2 at altitude??

There are real physiological limits for piloted aircraft and "9G" designs
press that limit. Designing an airframe to greatly exceed the limits of the
wet-ware controller means that you are carrying structure that you will
never use. Unpiloted aircraft of course don't have that limitation, so
expect UCAVs to open that number up.

As far as Mach 2.2 is concerned, that number comes from the stagnation
temperature associated with the Mach number and the fact that most of the
fighters of that generation were aluminum. Aluminum airplanes get soft when
they dwell above M2.2 or so. Composites have better high temperature
characteristics than do Aluminum based alloys so if there is
a_requirement_for operation at higher Mach numbers then it's technically
possible to do so. Apparently there_is_no requirement, rather there is a
requirement for supersonic persistence in the M1.5 or so speed range.

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."

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