F-16XL

darkvarkguy · by **darkvarkguy** » 16 Mar 2009, 00:47

Thanks, those are great! Some have said here it carried a bigger weapons load than an F-15E. I guess I can't see it visually. I mean I've seen pictures of a Strike Eagle with about a dozen Mk-20s, Aim-9s and 120s. I see the XL has a lot of hardpoints but can those stations carry multiple bomb racks too?

johnwill · by **johnwill** » 16 Mar 2009, 04:00

The photos just posted show the XL carrying 12 Mk-82, 4 AIM-120, and 2 AIM-9. I believe that's essentially the same as what you attribute to the F-15E.

The XL did not carry multiple-bomb racks, as the single-bomb rack loadings were lighter and less draggy.

darkvarkguy · by **darkvarkguy** » 16 Mar 2009, 04:53

12 Mk-82s are a lot less weight and size than 12 Mk-20s (CBU-100).

geogen · by **geogen** » 16 Mar 2009, 05:38

darkvarkguy,

Hmmm, are you sure about that? A Wiki search notes 490 lb CBU-100? Also, there would have apparently been one heavy wet/dry station under each wing, so those could have hypothetically carried a multi-rack? And if the cranked-arrow was ever indeed constructed, perhaps an SDB twin-rack could attach to each underwing point. Otherwise, while the 15E/K could probably carry more 2k class ordnance, Johnwill pretty much summed it up: 'the XL would have more sleekly carried a similar requirement of 12 500lb class munitions + 4 + 2 AAM' (emphasizing asset of a less draggy/lower profile aircraft).

Given that, I wouldn't necessarily protest F-15Es one day turned over to NASA for a little 'crank-arrow', (possible tailless), Reverse-thrust Vectoring GE-132 surgery. That's another forum, I know :drool:

plant#4 · by **plant#4** » 16 Mar 2009, 09:15

darkvarkguy wrote:Does anybody have any pictures of an XL fully loaded out with weapons?

and another view....

johnwill · by **johnwill** » 16 Mar 2009, 15:31

In design load analysis of Mk-20 loadings, we (General Dynamics) used approximately 500 lb, same as Mk-82.

darkvarkguy · by **darkvarkguy** » 16 Mar 2009, 16:34

I guess you're right. CBU-100s just seemed heavier because of their size but I then again they are hollow. The XL may have been cleaner fully loaded aerodynamically but the 'E' has twice the thrust. As you can see by my quote I am a big proponent of Strike Interdiction.

StolichnayaStrafer · by **StolichnayaStrafer** » 16 Mar 2009, 17:27

Yeah- cool as the F-16XL is, it is pretty easy to see why they went with the Strike Eagle. The twin engines and the conformal tanks option from before made a real easy start for conversion from fighter to interdictor.

Did they ever compare the F-16XL to a regular F-16 in a strictly Air to air comparison before? I'm very curious to hear how the XL version performs in that aspect.

Guysmiley · by **Guysmiley** » 16 Mar 2009, 18:07

I love the "which way'd he go?" camo in that first pic with the fake canopy/refueling markings/v-stab shadow!

johnwill · by **johnwill** » 16 Mar 2009, 23:35

darkvarkguy wrote:I guess you're right. CBU-100s just seemed heavier because of their size but I then again they are hollow. The XL may have been cleaner fully loaded aerodynamically but the 'E' has twice the thrust. As you can see by my quote I am a big proponent of Strike Interdiction.

There were good reasons for choosing either airplane. But the XL could haul 12 MK-82 downtown faster and much cheaper than the F-15E. Twice the thrust means twice the fuel among other things.

StolychnnayaStrafer wrote:Did they ever compare the F-16XL to a regular F-16 in a strictly Air to air comparison before? I'm very curious to hear how the XL version performs in that aspect.

Of course. Results were mixed. XL generally had a better initial pitch rate, so could make the first turn into the target better. But, like deltas in general, it had lower sustained g capability. XL had 9g turn capability, same as F-16, but had higher rolling g capability, 7.2 vs 6 for F-16. It also had a flight control refinement which allowed the pilot to command a max roll at any g level, all the way to 9g. Roll rate was automatically reduced above 7.2g. On the F-16, max roll commands are allowed up to 6g only. The XL had a higher maximum speed than the F-16, but slower acceleration.

It was never allowed to go to its max speed at or above 50k for fear of embarrassing others. Remember the wing was based on NASA work for SST development. You know where they cruise.

StolichnayaStrafer · by **StolichnayaStrafer** » 16 Mar 2009, 23:54

Very interesting- thanks for the enlightenment, johnwill! :thumb:

cywolf32 · by **cywolf32** » 17 Mar 2009, 05:09

What a view!! Its just too bad we didn't buy any......

viper1234 · by **viper1234** » 17 Mar 2009, 07:58

It was never allowed to go to its max speed at or above 50k for fear of embarrassing others. Remember the wing was based on NASA work for SST development. You know where they cruise.

I'm curious if you remember its theoretical top end at high altitude. I'm sure the low altitude limits remained unchanged since the canopy and inlet appeared unchanged. I would be surprised if actual top end was much higher (in practice) than the current Vipers due to the poor high altitude performance of the inlet/engine.

Can you remember any Air-Air missile testing from the inner stations? It sure looks like there was a potential for substantial interference issues (missile exhaust to engine) from those positions assuming they were rails rather than ejectors (which I assume based on bomb clearance)

Cheers

geogen · by **geogen** » 17 Mar 2009, 09:41

StolichnayaStrafer wrote:Very interesting- thanks for the enlightenment, johnwill!

Copy that..

I'd be further curious: what performance enhancements, e.g., improved sustained G and acceleration, could be estimated from say a GE-132 power upgrade? If any at all? Perhaps they would have had to put a 'max speed limiter' on it at half-throttle though?

Thus an XL-derivative would arguably be even more feasible today (ahem), Air-Air wise, than in the 80s-90s standards with regards to lower relative 'sustained' turn performance as stated., given HOBS/helmet system and better longer-range ordnance?

Imagine that... an overall superior, cheaper, higher speed, longer-ranged air-superiority fighter + superior strike. Go figure. :shock:

johnwill · by **johnwill** » 17 Mar 2009, 15:37

viper1234 wrote:I'm curious if you remember its theoretical top end at high altitude. I'm sure the low altitude limits remained unchanged since the canopy and inlet appeared unchanged. I would be surprised if actual top end was much higher (in practice) than the current Vipers due to the poor high altitude performance of the inlet/engine.

Can you remember any Air-Air missile testing from the inner stations? It sure looks like there was a potential for substantial interference issues (missile exhaust to engine) from those positions assuming they were rails rather than ejectors (which I assume based on bomb clearance)

Cheers

I don't know of any work done to determine the max speed/altitude capability. 810 kcas/2.0 mach was the structural design limit. The airplane exceeded 2.0 at 50k and had more available. The powers that be were correctly reluctant to go much beyond what could be supported by analysis, even though everyone wanted to see what it could really do.

There was no missile launch work done from the inner stations. I have mentioned on another thread, those missiles were complete dummys, bolted in place with no launchers installed. A production XL would have had ejector launchers.

The aft missiles inadvertantly led to an inflight structural failure of the left speedbrake. The missile was mounted directly in front of the lower speedbrake panel. What no one realized was the missile blocked airflow on that panel. The speedbrake mount is designed for a maximum 60/40 distribution of load between the upper and lower panels. Wih the lower panel blocked, that ratio was more like 80/20 and the mount failed at 1.6/30k when the speedbrake was extended. That knocked out one hydraulic system too, so the airplane landed safely on one system.

geogen wrote:I'd be further curious: what performance enhancements, e.g., improved sustained G and acceleration, could be estimated from say a GE-132 power upgrade? If any at all? Perhaps they would have had to put a 'max speed limiter' on it at half-throttle though?

Sustained g can only be improved two ways, less drag or more thrust. So going to a higher thrust engine , whether GE or PW, would benefit sustained g.