Forum: General F-35 Forum

fat_cat wrote:

wrightwing wrote:

megasun wrote:

What if F-35 faces an opponent capable of both supersonic and stealthy in future?
For example for USN, who has no F-22 but F-35C to face such a challenge.

You mean post PAK FA/J-20? By that time, you'll likely see F-35 successors arriving in service

You don't really think there's a good chance the F-35 successor will actually be on time do you??? Unless they're building it right now then there's not a hope in hell of it being ready to coiunter J-20's.

I think that you need to reread what I wrote. I didn't say that the F-35's successor would be ready before PAK FA/J-20s. I DID say that by the time a foe had an aircraft that would do what Megasun was worried about, that it would be about the time for a follow on aircraft to be coming along.

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Quote:

Its not doing a high alpha turn in those videos though, its doing high alpha departures. That was a bad movie to make a point IMO, every one of those maneuvers turned it into a brick. Was that prototype using the 117S engines, because if so, I'd be willing to bet the aircraft doing the rounds at airshows lately has been massively weight reduced? Either that or combat configuration completely destroys its performance.

Is there anything available where it does a high aoa turn and actually sticks the turn like in this example?

The strain on the airframe here are considerable eighter way. Which i belive was his point.

If there are any vids of Su-27SK with heavy load.. i don't think so.
The Su-27SK was loaded with six A2A missiles(normal mission config).
Nothing like in this vid.
It was in early 2000 with the Su-27M, in England.
With the AL-31FP engines.

haavarla wrote:

The Su-27SM have the same airframe improvments as the Su-27SKM.
The SKM has stengting in wings and airframes, which make your figures go up in smoke.
Any reason you pick the SK version?

Su30MK, then?
3k flight hours airframe life...
It's still less then half what F15 does!

F15C is 1979 plane, so I wanted to make contemporary comparison and couldn't find data on models prior to beginning of the '90s.

Quote:

Your claims about the F-15C comes with higher Ps ended at the very early 2000. The first operational Su-27SM entered service in Dec2003.

Well, Russians don't seem to think so...

Yes, it's very impressive for a millionth variant of Su27 to finally beat 25 years old Eagle, in 2003.
Too bad it wasn't 1979, anymore...

Look this is getting pointless.
Said all I had on the subject (and some things several times over), but for some strange reason you remain adamant in your misconceptions.
Well, you're free to believe whatever you wish, but I just wanted to point out that your beliefs are wrong and made arguments...that's all.

Cola,

Lots of good info in this thread but I want to play devil's advocate. Is it possible that the Su design was necessary to get the internal fuel capacity needed to function as a long range aircraft?

Or do you consider that a mistake as CFT and EFT could get it done without the issues you cite above?

May be interesting for this thread?
A lot of the report (2001) handles dropping of external fuel tanks as well and how these tanks can damage a jet as the F16.
The report shows a few post-flight pictures of ventral fins of a orange wired test F16 after dropping external fuel tanks.
(As far as I know this F16 is the only test F16 of this kind in Europe. The jet does testing for the US Airforce and LM as well)

Nationaal Lucht- en Ruimtevaartlaboratorium
National Aerospace Laboratory NLR

NLR-TP-2001-327
RNLAF/NLR flight test for certification of
Lockheed Martin Overseas Corporation
Enhanced Targeting Pod and
BAe Systems Falcon Owl Navigation Pod
Maj. Tj. Haringa (RNLAF),
J.J. Meijer (NLR) and K.R. Rijzebol (NLR)

This report is based on a presentation held at the "2001 Aircraft-Stores Compatibility
Symposium", Destin, Florida, USA, 5-8 March 2001.

http://www.nlr.nl/id~4395/l~en.pdf

For someone to claim an aircraft is more dragier than other.
They have to know the figures of:

Form drag of wings and airframe. (Sweep back angle of wing, tickness of wing, even the intakes and engines, and the overall shape of airframe.)

Wave drag (As an aircraft approaches the speed of sound, shock waves are generated along the surface. There is an additional drag penalty (called wave drag) that is associated with the formation of the shock waves.)

Induced Drag (There is an additional drag component caused by the generation of lift. Aerodynamicists have named this component the induced drag. This drag occurs because the flow near the wing tips is distorted spanwise as a result of the pressure difference from the top to the bottom of the wing.)

Then we have the formula like Power (Pd) The power required to overcome the aerodynamic drag. = T/D ratio.

There are so many figures to add and sum up before on can claim that on fighter design are more draggy then the other.
Just as one fighter design may have a lower figure in one area does not mean the over all figures makes it a better design(less draggy).

Then we have stuff like Wing lift, body lift, total lift.
And T/W ratio.

So for Cola to claim the Su-27 design are more draggy vs F-15 and by that its inferior design. I would very much like to se some figures to back this up.

haavarla wrote:

So for Cola to claim the Su-27 design are more draggy vs F-15 and by that its inferior design.

Where did I say that?
I said something else, but I can't be responsible for the way you interpret things, though.
It'd be good for you to stick to the points in question and avoid baseless paraphrasing.

@shingen,
external tanks have numerous advantages.
However, different sub-requirements may tip the balance into another direction, as in Su27/F35's case.

I'm not gonna get into why someone decided to make this and that KPP, but F15 has higher SEP over Su27, due ~4 tons lighter empty airframe, among other things.
Weight increase is flight killer and to counter it you need larger lifting surfaces, but then drag builds up and you need stronger engines and those need more fuel and extra fuel builds up weight and around we go...

I wouldn't waste your time with him Cola as when you prove a point, as you have been doing, he either refuses to accept it or ignores it. Just like he did with me when he claimed the Serbian Mig-29 pilots were greenhorns and was shown evidence that says otherwise, he didn't apolagise but simply ignored it.

Seperated engines with a tunnel between is more draggier than the conventional fighter design, I am sure about this. You have three body elements, no matter how much bleeding, streamlining (or whatever the correct term is) etc you do, it can not be like one fuselage.

Pls. note that here I'm comparing designs not two aircraft such as a Sukhoi and an F-15.

haavarla,

IMO you are giving too much importance to body-lift (by a tunnel?) concept. Yes, it is implemented both by Eastern and Western aircraft but it must have been used in favor of different advantages (or aircraft specific requirements). Surely not because of an ''ample lift it offers'' case.

Another factor that increases drag in the tunnel / separated engine design is simple skin friction. That design has more surface area for skin friction to develop, called "wetted area".

"Induced drag" has little to do with flow distortions near the wing tips. It is related to lift generation, since increased lift at a particular flight condition requires increased angle of attack. That higher AoA presents more frontal area to the airstream, thus more drag, induced drag.

cola wrote:

haavarla wrote:

So for Cola to claim the Su-27 design are more draggy vs F-15 and by that its inferior design.

Where did I say that?
I said something else, but I can't be responsible for the way you interpret things, though.
It'd be good for you to stick to the points in question and avoid baseless paraphrasing.

@shingen,
external tanks have numerous advantages.
However, different sub-requirements may tip the balance into another direction, as in Su27/F35's case.

I'm not gonna get into why someone decided to make this and that KPP, but F15 has higher SEP over Su27, due ~4 tons lighter empty airframe, among other things.
Weight increase is flight killer and to counter it you need larger lifting surfaces, but then drag builds up and you need stronger engines and those need more fuel and extra fuel builds up weight and around we go...

Would you be willing to go into the KPP etc in another thread?

I want to start one in modern military aircraft.

To all:

Lots of interesting stuff here. I want to start a thread in the modern military aircraft for stuff like one design vs another or why one design chose one thing over another.

maus92 wrote:

Tell that to a Tomkitty pilot - with the wings swept, the effective wing area / lower loading made it an surprisingly agile turn fighter - better than a F-15.

Back in the 70s the Israelis evaluated the F-14 and F-15 in DACT against A-4s and F-4s. The F-15 was chosen largely because of superior WVR performances. IAF evaluation pilot Assaf Ben Nun:

"I found it hard to believe that the F-14 had no edge whatsoever over the A-4 in WVR combat". [Israeli F-15 Eagle Units in Combat, p. 16].

Until the arrival of the B+ and the D, the Tomcat always suffered from the limits of the TF-30. However, A-4s persisted as aggressors because they were generally much, much better than what many expected of a 50s-era design --particularly when they put the 408s in them. Sustained turn performance in the 220-260 KCAS range below 20K' was very good -- and when flown by experienced hands they remained competitive with 4th gen players for a long time.

Having fought them both many times, WVR there was little to distinguish between the B+/D Tomcat and the Eagle -- except, of course, who was flying it.

Forum: General F-35 Forum

JSF High Wing Loading: why?