Forum: F-35 versus XYZ

I saw this video about the F-18 performing a 7 G turn to the left here it is... http://www.youtube.com/watch?v=rJ7ocBFnDQI

And i was wondering if the F-35 (at least the A varient) could perform a high g mauver like that. If it could, that could actually give it a good antee up in a dogfight if it could perform such a steep turn. Usually I would think any jet could, but with all the negative views toward the F-35, it left me puzzled, let me know what you think!

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The F-35 has already been flown to 9.9G.

If and when Canada gets their F-35A's they should be able to turn inside the F-18's turn radius as Canada's F-18's are limited to 7.5 G turns.

alloycowboy wrote:

If and when Canada gets their F-35A's they should be able to turn inside the F-18's turn radius as Canada's F-18's are limited to 7.5 G turns.

Actually not. There is a significant difference between instantaneous turn rates and sustained turned rates. I won't contest that the F-35 probably has an equal or better instantaneous turn rate than the F-16, but the F-16 can sustain a 9g turn indefinitely. Although the F-35's body generates lift, that lift factor is lost in sustained turns. According to the chief test pilot, the F-35C actually has a better turn rate than the F-35A due to its enlarged wings.

So it's quite premature to say that the F-35A will do circles around other fighters when all it's got to its advantage is instantaneous turn rates. I highly doubt that an F-35A can outperform an F-16 in a sustained turn.

Last edited by johnwill on Apr 29, 2012 - 04:15 AM; edited 1 time in total

battleshipagincourt,

I know you know the difference, but for those who do not, sustained g means the g level that can be held without losing speed or altitude.

The F-16 can indeed sustain a 9g turn, but certainly not in all flight conditions. The 9g sustained envelope is at medium speeds, at medium and low altitudes. The F-35A will be able to sustain 9g at some conditions, but the envelope may or may not match the F-16. I suspect the F-35 sustained g envelope will be larger than F-16 or any other airplane while both are carrying a heavy weapon load. I may be wrong, but I understand the F-35 is designed for 9g with a loaded weapon bay, while other airplanes cannot exceed 5 or 6g with heavy weapons.

I'm not sure where you got the idea that fuselage lift goes away during a sustained g turn. Fuselage lift is a function of AoA and airspeed, just like wing lift.

The F-35C may have a better turn rate then the A under some low speed conditions, where the big wing is enough to overcome the added drag and lower g limit of the C. At any condition where the A can exceed 7.5g, I promise you the A will have a higher turn rate than the C, which is limited to 7.5g.

alloycowboy's posted photo was taken during the YF-16 / YF-17 competition. The two airplanes in the photo are a YF-16 and an F-4 at 30,000 feet. It should be obvious which is which. I was lucky enough to be standing next to the photographer.

battleshipagincourt wrote:

alloycowboy wrote:

If and when Canada gets their F-35A's they should be able to turn inside the F-18's turn radius as Canada's F-18's are limited to 7.5 G turns.

Actually not. There is a significant difference between instantaneous turn rates and sustained turned rates. I won't contest that the F-35 probably has an equal or better instantaneous turn rate than the F-16, but the F-16 can sustain a 9g turn indefinitely. Although the F-35's body generates lift, that lift factor is lost in sustained turns. According to the chief test pilot, the F-35C actually has a better turn rate than the F-35A due to its enlarged wings.

So it's quite premature to say that the F-35A will do circles around other fighters when all it's got to its advantage is instantaneous turn rates. I highly doubt that an F-35A can outperform an F-16 in a sustained turn.

You'd be hard pressed to find an F-16 these days that can sustain 9Gs in a useful configuration. At sealevel in a clean configuration maybe, but you start sticking pods and other modern essentials on the outside and you get some significant Ps and G-limit restrictions.

Also its not just what G you are pulling, but what airspeed you are at when you're doing it. A high G turn flown at a high speed can be much worse than a lower G turn flown at a slower speed. For example a 9G turn at 400kts givesyou a 3 percent slower turn rate and a 38 percent larger turn radius than a 7G turn at 300 kts.

EDIT: Beaten to the punch...

I'm guessing the YF-16 held more altitude in that turn than the F-4(E?).

Both were supposed to hold altitude and speed. Who knows? It was supposed to be a sustained g turn comparison, but with a competitive fly-off going on, a PR style photo couldn't hurt. Perhaps it was accidental the test point happened to be flown right over the base and a photographer was ready and waiting.

The photo eventually made it to an F-16 program logo.

battleshipagincourt wrote:

alloycowboy wrote:

If and when Canada gets their F-35A's they should be able to turn inside the F-18's turn radius as Canada's F-18's are limited to 7.5 G turns.

Actually not. There is a significant difference between instantaneous turn rates and sustained turned rates. I won't contest that the F-35 probably has an equal or better instantaneous turn rate than the F-16, but the F-16 can sustain a 9g turn indefinitely. Although the F-35's body generates lift, that lift factor is lost in sustained turns. According to the chief test pilot, the F-35C actually has a better turn rate than the F-35A due to its enlarged wings.

So it's quite premature to say that the F-35A will do circles around other fighters when all it's got to its advantage is instantaneous turn rates. I highly doubt that an F-35A can outperform an F-16 in a sustained turn.

I could believe the C outperforming the A at low speed, but at high speed I think the A would come out ahead. Lift isn't all that matters, there is drag as well, and the C's larger span will probably hurt it when speeds get high.

What do you mean when you say that the F-35's lift factor is lost during sustained turns? The advantage of body lift never goes away.

I don't see why the F-35 wouldn't match the F-16 in sustained turns, but I have yet to see the flight envelope, so I can't say it's fact yet.

exorcet wrote:

battleshipagincourt wrote:

alloycowboy wrote:

If and when Canada gets their F-35A's they should be able to turn inside the F-18's turn radius as Canada's F-18's are limited to 7.5 G turns.

Actually not. There is a significant difference between instantaneous turn rates and sustained turned rates. I won't contest that the F-35 probably has an equal or better instantaneous turn rate than the F-16, but the F-16 can sustain a 9g turn indefinitely. Although the F-35's body generates lift, that lift factor is lost in sustained turns. According to the chief test pilot, the F-35C actually has a better turn rate than the F-35A due to its enlarged wings.

So it's quite premature to say that the F-35A will do circles around other fighters when all it's got to its advantage is instantaneous turn rates. I highly doubt that an F-35A can outperform an F-16 in a sustained turn.

I could believe the C outperforming the A at low speed, but at high speed I think the A would come out ahead. Lift isn't all that matters, there is drag as well, and the C's larger span will probably hurt it when speeds get high.

What do you mean when you say that the F-35's lift factor is lost during sustained turns? The advantage of body lift never goes away.

I don't see why the F-35 wouldn't match the F-16 in sustained turns, but I have yet to see the flight envelope, so I can't say it's fact yet.

He has to go away and see if Bill Sweetman (sorry I mean the user - Low Observable, there's no "proof" it's Bill) can come up with another reason he can use as to why body lift is a myth, so don't expect a response soon...

Why did the conversation switch from the F-18 to the F-16?
I thought the F-18 was significantly less maneuverable than the F-16 -- 7.5 g's vs 9 g's.

count_to_10 wrote:

I thought the F-18 was significantly less maneuverable than the F-16 -- 7.5 g's vs 9 g's.

Not from what I've seen. Shocked

yes, but as stated above, G limit is not everything. Loaded roll can also be a very important factor, as can climb rate while turning. The F/A-18 has always been a great "angles" fighter allowing it to point it's nose rapidly, but it loses speed rapidly too. The F-16 has always been a great "energy" fighter. The special G-limiter on the F-16 actually takes away from it's maximum instantaneous turn rate, but it means that at a full pull from the pilot the F-16 will not bleed speed as rapidly, which also gives the pilot the option of trading that retained speed for extra altitude.

Ah, okay. Different design strategies cause performance to project differently onto the various performance metrics.
Thanks.

Last edited by avxva on Apr 29, 2012 - 10:20 PM; edited 3 times in total

SpudmanWP wrote:

The F-35 has already been flown to 9.9G.

What were the circumstances of that feat? We always hear "the F-35 has already been flown to 9.9G," but the details are always (conveniently?) missing. I'm beginning to suspect the F-35 pulled a calculated 9.9 G's for 1/1000th of a second during some miscellaneous flight event and when the airplane landed the engineers got to looking at the accelerometer load data and someone, said, "Hey look!" Then, when the sales force / propaganda team heard about it, a press release went flying out the door saying, "We flew this thing to 9.9G's"

So what are those details exactly...?

Al

Forum: F-35 versus XYZ

Can the F-35 perform this F-18 maneuver?