Forum: General F-35 Forum

Another clue about variable afterburner:

The New Front Office By John Kent Posted 15 June 2006

http://www.codeonemagazine.com/article.html?item_id=35

"...“The throttle uses the active controls to a greater degree,” Beesley continues. “The internal motors allow the throttle to be moved back automatically when the pilot has an auto throttle connected or in some of the STOVL modes allows the option to input soft stop detents and afterburner detents at will.”

One unique feature of this active throttle is that it does not have an engine cutoff position. It has, instead, a single toggle switch to cut the engine. The use of the active stick and throttle and a cutoff switch was introduced on the JSF demonstrator, the X-35...."

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So what's so neat about the variable arfterburner? Less wear and tear and better efficiency? Have to say i'm completely clueless on this as it's the first i've heard of it. And is it 100% accurate to cliam this is a first thats never been done before?

For starters (as indicated in preceding info) it is useful to have the variable afterburner on the catapult.

Yeah I noticed that but surely they didn't implement this new tech just to ease the heat load on the jet blast deflectors so i'm just curious as to what other benefits it might bring.

increase of exhaust velocity for higher dynamic thrust (relative to full mil) with a 2X increase in fuel flow instead of a 4X increase to engage (current) minimum burner?

shep1978 wrote:

southernphantom wrote:

Second impression: expensive, semi-LO F-16 with tiny payload before becoming a more-expensive Desert Falcon.

Semi-LO? How can you claim that when it has 'all aspect' stealth?

Tiny payload? I take it you're not aware that it can carry munitions externally as well as internally and is actually capable of carrying more than an F-16 of any block.

All-aspect? To quote an old Weasel pilot, YGBSM. It's better than a SHornet or a Rafale, sure, but it's nowhere near the F-22 level, and the size of the F-135's IR exhaust plume is probably going to guarantee a hit by an AA-11.

I mean tiny payload by its internal bays (until the GBU-39 comes online Twisted Evil

). If it begins to use its external hardpoints, the increase in radar cross-section means that the F-35 is effectively a really fancy F-16, since it loses its major advantage (LO).

southernphantom wrote:

If it begins to use its external hardpoints, the increase in radar cross-section means that the F-35 is effectively a really fancy F-16, since it loses its major advantage (LO).

are you insisting that F16 + external stores will have the same RCS as F35 + external stores?

pissflaps wrote:

southernphantom wrote:

If it begins to use its external hardpoints, the increase in radar cross-section means that the F-35 is effectively a really fancy F-16, since it loses its major advantage (LO).

are you insisting that F16 + external stores will have the same RCS as F35 + external stores?

Not quite, but there's a reason the F-35 will fly internal-only for the first stages of a war: external just ain't survivable against a good IADS.

The same goes for the F-22, T-50, and J-20. No VLO airframe is going to risk itself by needlessly strapping on external stores in a high threat IADS environment.

southernphantom wrote:

All-aspect? To quote an old Weasel pilot, YGBSM. It's better than a SHornet or a Rafale, sure, but it's nowhere near the F-22 level, and the size of the F-135's IR exhaust plume is probably going to guarantee a hit by an AA-11.

So what if it's not on par with the F-22? Even something ten times its RCS is orders of magnitude smaller than most jets flying today. Even if it can't get through a dense electronic fortress without detection (in a worse cases scenario) it's still a very difficult aircraft to locate or bring down with missiles. At least compared to LO targets, something which appears no larger than a golf ball can very seriously make your life hell if you're flying something with a less powerful radar and larger RCS.

I could say more about its AESA radar not being as good as an F-22's for airborne targets, but it's at least good enough for its overarching mission. Unlike the F-22, which was intended to be the best at everything in terms of performance, they compromised for something practical. The F-35 is not a showpiece, but a war bird. Even without its vaunted VLO defense, it's still comparable to most fighters flying today.

southernphantom wrote:

I mean tiny payload by its internal bays (until the GBU-39 comes online Twisted Evil

). If it begins to use its external hardpoints, the increase in radar cross-section means that the F-35 is effectively a really fancy F-16, since it loses its major advantage (LO).

At least the F-35 HAS a VLO capability. Even the F-16, F-18E, and Typhoon can't match the F-35's LO characteristics without a warload. The F-35 is optimized for carrying two smart weapons and two AIM-120's internally... external stores come at a cost, just as for any fighter. They might even have the option to jettison those stores and pylons if it must quickly revert to the VLO configuration.

Can any other fighter do that?

pissflaps wrote:

southernphantom wrote:

If it begins to use its external hardpoints, the increase in radar cross-section means that the F-35 is effectively a really fancy F-16, since it loses its major advantage (LO).

are you insisting that F16 + external stores will have the same RCS as F35 + external stores?

Because God forbid the real world be more complicated than Completely OMG Super Stealth or B-52-size.

shep1978 wrote:

So what's so neat about the variable arfterburner? Less wear and tear and better efficiency? Have to say i'm completely clueless on this as it's the first i've heard of it. And is it 100% accurate to cliam this is a first thats never been done before?

First, thanks spazsinbad for the info; I wasn't even aware of the catapult requirements.

As far as I know, it's accurate to claim it's never been done before (at least on a production aircraft). If it has, on what plane? I'm not even aware of a one-off X-plane that had it. It doesn't prove nothing else has had it, but...

Now, this is all speculation on my part, but as to the advantages, for one thing, it may be better than supercruise. A supercruise engine has to be designed entirely to supercruise, leading to a lot of compromises. It's kind of amazing the F119 is as good as it is in so many other ways, considering. But remember, even though the F119 can supercruise, it still has/needs an afterburner. The main purpose of an afterburner (except on an SR-71) has generally been for acceleration/energy recovery, not speed. The Concorde cruised without afterburner but needed the burners to get up to speed. However, an engine that can pick an afterburner setting anywhere between 0% and 400% extra fuel consumption (I'm not sure the F135 is quite that fine-tunable, but even in 5% increments) can be designed to cruise very efficiently under almost any flight conditions you want. And then you can go to high burner to accelerate, dial back the burner once you're out of the very high drag of the transonic regime, and for a few % extra fuel over subsonic cruise, you can cruise supersonic. And without the low-speed/low-altitude compromises inherent in a true supercruise (or even burner-accelerated/supersonic cruise optimized) engine. There may also be safety/reliability advantages in an afterburner that can adjust itself automatically to differences in altitude, temperature, engine state, etc. And service life advantages to an engine that can replace some heat on the expensive turbines with a lower turbine power setting augmented with a little more heat in the afterburner where there are no moving parts to wear or be difficult to cool. Plus everything everyone else has suggested.

southernphantom wrote:

All-aspect? To quote an old Weasel pilot, YGBSM. It's better than a SHornet or a Rafale, sure, but it's nowhere near the F-22 level, and the size of the F-135's IR exhaust plume is probably going to guarantee a hit by an AA-11.

I mean tiny payload by its internal bays (until the GBU-39 comes online Twisted Evil

). If it begins to use its external hardpoints, the increase in radar cross-section means that the F-35 is effectively a really fancy F-16, since it loses its major advantage (LO).

Mmm, actually it's much closer to the F-22 than Super Hornet/Rafale(~-30 to -40 dbSM), and any fighter would provide an attractive IR signature if the missile were in a tail chase. The SDB is already online(it would seem that there are a number of topics that you haven't been following too closely). The ability to carry 5000lbs of munitions stealthily, is hardly a tiny load, and the RCS of an F-35 with externals, would still be well below an F-16.

Don't forget that the F-35 can carry the big 5k bunker busters (1 per inboard external hardpoint) which the F-16 can NEVER carry and the F-15E can only carry one (centerline).

[quote="wrightwing"][quote="southernphantom"].... tiny payload by its internal bays ..

Quote:

..The ability to carry 5000lbs of munitions stealthily, is hardly a tiny load, ...

The average B-17 bomb load dropped in World War II was between 4,000 lb and 5,000 lb....a bomber!

The 5,000lbs represents 8 SDB. Each SDB can destroy a tank similar to the M1A2 Abrams Main Battle Tank. No "Tiny" feat.

Forum: General F-35 Forum

How have your opinions of the JSF changed over the years?