Forum: General F-35 Forum

Tanks that can be jettisoned if need be.

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at what cost? When a squadron is flying dozens of sorties a day the idea of dropping tanks because things got a little scarey becomes a logistical nightmare. Say a squadron of 24 planes is flying 3 sorties a day for each plane with 3 tanks per sortie. That's 216 tank-sorties PER DAY! How many spare tanks do you think a squadron brings? A dozen of each in case of mechanical failure? Tanks are not simply disposable. When being shot at the last thing a pilot is thinking about is "Hmm, should I drop the tanks? What if I do and get a butt chewing? What if I don't and get blown up?" He's thinking "there's the missile 2 o'clock, roll, pull, beam, countermeasures, don't black out, reverse, pull, countermeasures, don't black out"

The advantage of stealth is that you see radar tansmissions from further away than they see you. So you've got plenty of warning to drop the external tanks. (Assuming that doesn't mess up your stealth. In a well designed fighter this wouldn't be a problem, but that's not our lovable screeching baby seal, now is it?)

hcobb wrote:

The advantage of stealth is that you see radar tansmissions from further away than they see you. So you've got plenty of warning to drop the external tanks. (Assuming that doesn't mess up your stealth. In a well designed fighter this wouldn't be a problem, but that's not our lovable screeching baby seal, now is it?)

If the F-35 is a "baby seal" what's that make the Eurocanards and F-teens? LMAO

The Eurocanards are our Chum, er I mean chums.

http://en.wikipedia.org/wiki/Chumming

destroid wrote:

Tanks that can be jettisoned if need be.

You're talking about 1 fighter in 1 situation...

What about when you've got 40+ jets all now with greatly reduced fuel capacity? And not enough tanker support to nurse them all home? I'd like to see 72 F-16s jettison their fuel tanks over #### and then need to tank up every hour to get back to Italy. Possible - yes. Logistically a nightmare. Not too mention if weather doesn't permitting taking up. Then you're screwed. If the situation arises that you need to throw a hail mary by dropping stores, then things have gone terribly wrong with the mission and jettisoning tanks is grasping as straws.

So the -35 hits a little speed bump in the transonic region. By how much? Let's toss out LO and all that goes into -35s flexibility by basically in same configuration for each and every mission, and having the same performance in each and every mission just so it can keep up with a clean (unusable) F-16 in the dash from M.9 to M1.2 below 20k and in standard atmospheric conditions.

Comparing the empty weights and thrust to weight ratios is not "worthless" especially "assuming similar specific fuel consumption". Here is how it goes. The F-35 has to have internal weapons bays, while those help with the stealth, their complete role in the aerodynamics is substantially more complex to see, they increase the width of the fuselage and from a purely volumetric point of view they increase the volume more than the volume of the weapons (empty spaces within the bay). So, the parasite drag of the F-35 could be better (or not) than a comparable aircraft of similar size, it is not that easy to see. Induced drag is also probably similar (Similar span of the F-35c and the Super Hornet, the Super Hornet has actually higher aspect ratio which would seem favoring the SH, but the induced drag is affected not only by the aspect ratio but also by the square of the Lift Coefficient in the numerator of the equation which helps the F-35C since it has a lower wing loading, so I would expect their induced drag to be similar. So, Similar empty weights, similar parasite drag, similar induced drag and similar specific fuel consumption will lead you that the loaded weight is also similar and then, the thrust to weight ratio empty is not "worthless" because it constrains a lot how much the loaded thrust and weight ratio. Furthermore Lockheed engineers have to work the very difficult task of including the low observables technologies which probably leads for compromises and potential inefficiencies (Maybe the area ruling is affected, I don't know, my point is that it is hard to optimize all those tasks at the same time).

The more surface of external tanks and external weapons contribute a lot to zero-lift (parasite) drag for a fighter that does not have weapons bay , but the volume and frontal area also contribute against the fighter that does have internal weapon bay system. My point is that if you think that there are brilliant engineers at both Boeing and Lockheed this means that it is really hard to improve much the drag conditions of modern jet fighters, especially below the transonic region, so the comparison of the empty weight to the thrust is not "totally worthless", that empty weight constrains a lot the total weight of the aircraft. No matter how much I like the F-35, I still think that some extra thrust could be necessary because it seems to be underpowered compared to current aircraft and I hope that the engine thrust is closer to 50K than 43K.

A simpler, but absolutely worthless comparison. An empty SH (Not just clean, but empty? Seriously?) is not going to be flying anywhere.

I know it is not going to be flying, that is pretty obvious for a pre schooler, but the empty weight constrains the loaded weight, in particular "assuming similar specific fuel consumption"as I said. Please see my longer answer below.

Actually my longer answer appeared above (as a "Newbie" I am learning to use the forum)

Quote:

But unlike the Hornet or the F-16, the F-35 has the same configuration unloaded as it does loaded with weapons and fuel, Burbage said. When an F/A-18 or F-16 is encumbered with weapons, pylons and fuel tanks, those jets are robbed of much of their performance.

“What is different is that this airplane has accelerational characteristics with a combat load that no other airplane has, because we carry a combat load internally,” Burbage said, the F-22 Raptor notwithstanding.

Even fully loaded, the F-35’s performance doesn’t change from its unencumbered configuration, he said.

I don't get it, how is this a problem for the F35? You're never going to send an F16 or F18 into combat without weapons.

Last edited by geogen on Jan 21, 2012 - 12:10 AM; edited 1 time in total

Other than the F-22, and maybe the F-15C/D, I'm wondering if the majority of time a USAF fighter (including F-35A) will probably enter into supersonic flight is more for defensive reasons, and not offensive? If such a case is true, then it's probable that such a defensive oriented acceleration (eg running for home for tactical reasons, or evading direct enemy attack) would include a 'clean configuration' with possible exception of a couple AAM. If so, one could argue that this is the advantage and requirement with respect to Mach .8 to Mach 1.4 (or whatever it is) acceleration in question.

In the case of F-16s in particular, I know that European AF F-16s have indeed operated at supersonic speed loaded with tanks and at least 2 AAM as part of an intercept sortie of an unknown bogey. I guess an interesting question to ask in this scenario would be; how would an F-35 with a couple AAM perform acceleration wise to M 1.2, compared to an F-16 with say, 2x tanks and 2x wing-tip AAM?

As far as comparing acceleration to a Euro-Fighter with 4x semi-recessed AAM and probably even a center-line tank (as there seems to have been some Euro-canard paranoia stirred up in this thread), there would likely be no comparison in terms of acceleration regardless of F-16 or F-35.

edit note... come to think of it, I'm sure a few enthusiasts would personally love to see a supersonic acceleration contest between an F-16XL with 4x semi-conformal AAM + 32k lb class engine and a Euro-Fighter with equivalent load-out. Thumb

edit for Spazs: Cheers

Have a good weekend

"(as there seems to have been some Euro-canard paranoia stirred up in this thread)" that's a canard geogen. Very Happy

destroid wrote:

Tanks that can be jettisoned if need be.

So tell me how the pilot gets to use all the gas that was in those tanks when they where jettisoned? What good is a plane with "unprecedented" (thats Eurocanard fan boy speak by the way) performance if you run out of gas?

Ponder that one and get back to me.

Well before the Euro-Canard boys get all excited, the reason why the canard design was not choosen for the JSF was becaue of the extra wave drag the canards produce.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890000646_1989000646.pdf

Forum: General F-35 Forum

F-35 Does Not Match Predecessor's Acceleration Specs