F-16XL

Always wondered why the F-16 has a tailhook, or how big a bigmouth F-16's mouth really is ? Find it out here !
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darkvarkguy

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Unread post17 Mar 2009, 15:38

The plans for an FB-22 included a design evolution that resulted in a delta wing configuration where the horizontal stabs were replaced with incorporated elevons so you would think an evolving design for the Viper would be (would have been) the XL. Woulda, coulda, shoulda.
FB-111A Pease AFB 82-87
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vin

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Unread post08 May 2009, 16:55

I am one of the XL crew chiefs at Nasa/DFRC. I have read some (not all) of the posts regarding XL. Please, let me tell you all a few things about it. The F16XL does not have a true delta wing design. The wing on XL is called a "cranked arrow" shape. XL carries 12000 lbs of fuel and it has 19 store stations. It is stretched 54 inches longer than a standard F16, and the engine bay angle is configured 3 degrees lower than a standard F16. It has LEF's but no PDU to drive them. XL2 was the F16 that tested the Laminar Glove concept. It has not flown for years and will not ever fly again. Its sitting on our ramp waiting to be ripped and stripped. The reason why Uncle Sugar never purchased XL for production is because of this: Back in the day, under contract, GD was required to produce so many of each model of F16 for FMS. Due the the cranked arrow wing desing the Gov't didnt want anyone else to have the acft. There were numerous factors driving the decision not to purchase XL models, but the main driver was the wing. To date, XL's cranked arrow wign design is the most aerodynamically efficient wing design ever. It is still so advanced in its design that (until early 2009) Boeing was considering rebuilding XL1 for its wing shape. They were going to lengthen the nose a few feet, cut the vert in half and tee-tail it, install a GE129, install an upgraded avionic system, and modify the drag chute compartment to provide an extra 10 feet off the back. Why?... Boeing is considering a new supersonic airliner concept and they wanted the XL to test this concept. Anyway when the "powers that be" sat down to calculate the $$$ involved, they decided that XL needed too many TCTO's and upgrades to make it financially worth the effort. Well, that was XL1's last chance to ever fly again folks. XL1 has not flown for approx 10 years. Last year we defueled it, repaired the engine bay fuel leaks, performed initial service of the LDG, stuffed an F15 engine in it, and ran thru hyd ops checks (no hyd leaks on the entire acft after 10 yrs sitting). Then we taxi'd the plane around Edw just to prove we could get it up and running. XL ship 1 is now a done deal. It will be end up "popsickle sticked" somewhere on Edw. Sad... its the last of a one-of-a-kind generation of acft.
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cywolf32

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Unread post08 May 2009, 17:19

Wow Vin,

Thanks for the info!! Never would have crossed my mind that the wing technology in itself would be a major kill to the XL program. Interesting indeed. Sad, sad, sad.
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Goodwin

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Unread post08 May 2009, 18:50

What it would be nice to do is to take XL-2 and transport it to the Udvar Hazy Museum where its cranked wing would be most appreciated if it were hung up in the rafters for all to see. That is a lot better than simply scrapping it.
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Goodwin

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Unread post08 May 2009, 19:02

Politics may well have been the US State Department's concerns about the range of the F-16XL as they knew the Israel Air Force would want several F-16XL squadrons vice Block 52 F-16C/D's first procured in 1986. Having those capable planes on hand would have enabled them to mount a successful air strike against the Iranian nuclear program much earlier than 2006 and to be able to do the missions whenever needed. Yes, I would have rather have the XL to nicely complement the Strike Eagle. About FMS requirements to produce sufficient numbers of each type, Congress forbade the sale of F-22's to close allies and it would not have been a problem for us to simply keep the XL for our own use.
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johnwill

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Unread post08 May 2009, 23:30

The reasons stated above for not producing rhe XL are pure speculation. I was on the program, and was told by the USAF flight test team leader that the AF liked the XL very much, but needed to keep the F-15 production line open. There was no money for both.

As far as being the most efficient wing design ever, you'd better qualify that by saying, "for supersonic cruise", as it wouldn't be true for all flight conditions.

And, to clarify the LEF drive statement, XL did not have a PDU because the LEF were far out on the wing and were driven by motors just inboard of each LEF segment.
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whynot

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Unread post09 May 2009, 00:39

Hey wassup y'all? I am not trying to start anything here and I usually just read these posts and kinda chuckle at whats being said. The one thing I've noticed though is there is always some who "Has all the answers" and always is there to correct what they think is wrong! Now mind you I'm not the smartest F-16 guy on here, 24 years worth, and maybe more so then others but thats not the point. The point is, if "You're" so smart then why you on here trying to impress us? Whats your day job? If your the "Answer Man" Then give us proof, show us evidence and make us believe!! Don't just verbally regurgetate to sound smart. I know everyone thinks they know the"Real Deal" but honestly, do they???

If that Vin guy is crewing the XL at Edwards then show us pics, if Johnwill was there on the program then cut and paste documents to show us. From what I know, based on the current aircraft I work on, the LEF statement sounds to be true. Believe me it's possible! Oh and they are PDU's (Power Drive Units)

Anyway lets just have fun, talk about the Viper and not be so uppity with each other. (You may think your the smartest guy on here but theres always someone who thinks their smarter)

Peace Out, Raptors rock!! :cheers:
Last edited by whynot on 09 May 2009, 16:18, edited 1 time in total.
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F16guy

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Unread post09 May 2009, 09:04

whynot wrote:Now mind you I'm not the smartest F-16 guy on here



Uh...Somebody call me? And are they saying I'm not smart or they are not smart? And why should I have to prove anything anyway?


Bluto: Kroger, your Delta Tau Chi name is Pinto.
Pinto: Why "Pinto"?
Bluto: [belches] Why not?
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popcorn

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Unread post09 May 2009, 11:33

I'm assuming that the XL was going to be a single-seater whereas the F-15E had 2 guys in the cockpit. I'd read somewhere that this gave the latter an edge when evaluating both designs as the workload of flying the airplane and operating the weapons systems was shared. Would the avionics at the time have allowed for effective operationof the aircraft with only a single pilot?Obviously tech has advanced significantly in the decades that followed making possible the F-35 and F-22.
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whynot

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Unread post09 May 2009, 16:16

F16guy wrote:
whynot wrote:Now mind you I'm not the smartest F-16 guy on here



Uh...Somebody call me? And are they saying I'm not smart or they are not smart? And why should I have to prove anything anyway?


Bluto: Kroger, your Delta Tau Chi name is Pinto.
Pinto: Why "Pinto"?
Bluto: [belches] Why not?


Sorry if I offended you! Remember, No blood, No foul! :wink:
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Gums

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Unread post09 May 2009, 16:23

Salute

Re-read the thread.

For life of me I can't remeber John "wolfman" 's last name. he was one of us from Hill that went down for the fly-off. Also was the guy that showed us why we had the FLCS power supply problem from uncommanded EPU start-up. He saw the green "run light" just before the plane went end over end.

We got a few briefings and were impressed with the jet as a mud-beater.

From my memories:

- The thing could sit at 600 knots on the deck using about 90% power while hauling 12 x 500 pounders. Apparently, the semi-recessed store stations really made a difference on drag.

- The internal fuel load was awesome, so range was really, really good. Once expended, you could grab alt and zoom home real fast using lots less gas than the Eagle.

- The FLCS had a feature to help from getting into the classic "delta" drag problem at high AoA. As with original Viper limiter, you could pull all you wanted, but when you got slower the AoA was more limited than the A/B models we were flying then. Initial pitch rate was better, but as you slowed down you were limited more than you would like. Having made my bones in the Deuce, I am very familiar of the delta's nose-pointing ability and the horrendous drag rise if we held the stick back too long. I don't think the XL would be as good as the A/B was back then for air-to-air.

- John-boy and others answered a question I had about the gear. We all knew that the gear had to be stronger to handle the weight. Hell, one reason we never saw a Navy Viper was the wimpy gear. Even the Hornet designers beefed up theirs from the YF-17.

+++++++++++++

I always liked neat-looking jets, and the XL fit the bill.

I always liked carrying a lot of eggs and going fast, and the XL fit the bill just fine.

I always liked not having to worry about running outta gas, and my SLUF experience was awesome. I would have felt the same way in the XL.

As with our current procurement decisions, we can't have a zillion different planes that are too specialized. And the more you can make of the same basic design, then the lower the unit cost and overall cost. Politics and a better air-to-ground radar system in the Strike Eagle made a big difference in the source selection.

The 'vark was still viable then and LO was not the "driver" in designs. We were all surprised that USAF was looking at a replacement for it at the time. Hell, I only had one joy ride in the thing down at Cannon and it was a delight to fly and could go real fast low using min gas for such a big plane. Landed the thing on first approach with all of my 2 hours of "experience" racing over New Mexico at low alt, heh heh. Sucker was like on a rail coming down final, so pilot let me land it.

Gums sends...
Gums
Viper pilot '79
"God in your guts, good men at your back, wings that stay on - and Tally Ho!"
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johnwill

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Unread post09 May 2009, 16:46

Whynot,
Thanks for your comments. I agree we should not be "uppity", and I apologize if I sound that way. But, If I see something I don't agree with, or know for a fact is wrong, you can be sure I'll tell you my opionion. If that's "uppity", so be it. As far as people providing proof of who they are, I'll take your word and Vin's word that you are both who you say, and expect you to do the same. I don't need to give you proof, as the proof is in the answers. I'm not here to play games or impress anyone, don't need to. My "day job" is being retired from General Dynamics/Lockheed Martin following forty years as a structural flight test engineer.

popcorn,
XL number 2 was in fact a two-seater, and the production proposal included one and two seat versions.
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plant#4

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Unread post09 May 2009, 18:41

Interestingly enough, the wing jigs for the Xl were kept for over 20 years on the west lot at Fort Worth. That's not saying a lot, because they kept tooling for the F-111 for over 25 years before it was scrapped out.....
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geogen

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Unread post10 May 2009, 05:21

Salute to the XL concept, indeed... along with the -AT, the -X and the like 'woulda shoulda couldas'. With CFT, IRST, 32k class power, LOAN, AESA and 4 semi-recessed AMRAAM (among other upgrades), the interceptor role alone would have been re-invented and kept superior for decades.
The Super-Viper has not yet begun to concede.
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cywolf32

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Unread post10 May 2009, 08:05

Thought you all might enjoy this clip:

http://www.youtube.com/watch?v=ecM1-ISN ... annel_page

Cheers
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