For more than forty years, the F-16 Fighting Falcon has served as the backbone of the U.S. Air Force’s fighter fleet, but one year before the first F-16 entered service, the team behind its development had already developed a better F-16, in the F-16XL. The fighter was so capable, in fact, that it went from being nothing more than a technology demonstrator to serving as legitimate competition for the venerable F-15E in the Air Force’s Advanced Tactical Fighter program. Ultimately, it would lose out to the F-15E based on production cost and redundancy of systems, but many still contend that the F-16XL was actually the better platform.
While that assertion may be subject to debate, there’s little debate as to whether the F-16XL could have been one of the most capable 4th generation fighters on the planet.
You can watch the full rundown on the F-16XL here, or read the rest of the story below!
SCAMP: The Supersonic Cruise And Maneuver Prototype
In 1977, some three years after the first F-16 took to the skies and one year before it would enter service, its designer began work on what would come to be called the F-16 SCAMP, or the Supersonic Cruise And Maneuver Prototype. The effort wasn’t about fielding another production fighter–General Dynamics had no intention of trying to sell SCAMP once it was complete. Instead, the entire premise behind the program was to quickly (and cheaply) field a platform they could use to test the concept behind supersonic cruising, or as we’ve come to call it today, “supercruising.”
While that may sound like a capability found only on Transformers or Harleys so expensive only lawyers can buy them, the idea behind supercruising was simple, even if its execution was complex. Modern fighters like the F-16 all come equipped with afterburners they can use to dramatically increase the amount of thrust their engine produces, but it comes at a serious cost. Using the afterburner to break the sound barrier and then sustain that speed depletes an aircraft’s fuel very quickly, but if a jet could kill the afterburner at supersonic speeds and still maintain them, it would mean covering more ground at high speed, while still having enough fuel left over for a fight and the return trip home.
“I remember flying in an F-16 in afterburner while supersonic over the Yellow Sea and looking down to see a fuel-flow rate of over 50,000 lbs per hour,” F-16 and F-35 pilot Justin “Hasard” Lee explained in a piece for Sandboxx News.
“To put that into perspective, that’s similar to a fire-hose operating fully open—and that’s just a single engine. A twin-engine jet such as the F-15 or F-22 can double that. The problem is, topped off, I could only carry 7,000 pounds of fuel which was enough for me to fly at that fuel-setting for less than 10 minutes.”
In order to accomplish their goal, the F-16 design would require a pretty thorough revamp. First, the wings were modified to incorporate a cranked-arrow wing shape, creating 25% more lift while allowing for effective control at both high and low speeds. Working in conjunction with NASA (and using the company’s own funds), engineer Harry Hillaker, the same man responsible for the original F-16 design, experimented repeatedly with slightly different iterations of the wings until they came to a version they referred to as Model 400.
This new wing design, which saw a 50-degree angle near the root of the wing for supersonic performance and a 70-degree angle where the wings extended for subsonic handling, offered more than double the surface area of the F-16’s wings. Incredibly, Hillaker and his team were able to manage that without any increase in drag on the airframe–thanks to more than 3,600 hours of wind tunnel testing.
This new design wasn’t necessarily practical, with all-moving wingtips and an all-moving vertical tail meant for control that performed poorly at low speeds. The wing design also didn’t allow for any hardpoints to mount bombs or missiles.
However, impractical as it may have been for a tactical fighter, the new wing design led to a significant increase in fuel range–and that increase could be further bolstered by leveraging the massive amount of internal space these new wings offered.
The F-16 SCAMP becomes the F-16XL
Citing the promising results of the F-16 SCAMP effort, the U.S. Air Force chose to buy into the idea of an even-more capable version of the F-16. They provided Hillaker with two early F-16 airframes for conversion into a SCAMP-like design they dubbed the F-16XL. Although this new jet would be largely based on the existing F-16, the changes were dramatic, including two fuselage sections added near the front and back of the aircraft, increasing its length by some 56 inches. The cranked-arrow wings that had proven so effective in SCAMP were also added, along with a new form of wing skin made using carbon fiber that saved some 600 pounds in the design.
Those massive wings, now fully realized, gave the F-16XL a nearly doubled fuel capacity, and the additional lift coupled with 633 square feet of underwing space to leverage allowed for the addition of an astonishing 27 hardpoints for ordnance. Remarkably, the F-16XL seemed to outperform its smaller predecessor in nearly every way, prompting the Air Force to take an interest in the idea of actually building this new iteration fighter.
“To say that Hillaker’s design team achieved its objectives is an understatement,” wrote F. Clifton Berry Jr. in 1983. Berry was an Air Force veteran and the editor-in-chief of Air Force Magazine at the time.
As Berry pointed out, an F-16XL conducting an air-to-surface mission could carry twice the payload of the standard F-16 and still fly as much as 44% further–all without external fuel tanks and while carrying a full suite of air-to-air weapons (four AMRAAMs and two AIM-9 Sidewinders) for the fighter to defend itself. If you were to equip the F-16XL with the exact same payload as an F-16A on such a mission, the F-16XL could fly nearly twice as far as its predecessor.
But it wasn’t just about extended range and added payload. The F-16XL was capable of supersonic speeds at high or low altitudes, all while carrying its mighty payload, and had no trouble climbing quickly with bombs underwing. And even despite the added wing, fuel, and ordnance loads, the aircraft still somehow managed to fly 83 knots faster than the F-16 using military power at sea level, and more than 300 knots faster on afterburner at high altitudes, even while carrying a full bomb load.
“With the heavy bomb load aboard, the F-16XL is cleared for maneuvers up to +7.2 Gs, compared with 5.58 Gs in the F-16A,” Berry wrote. “This demonstrates how the designers were able to increase the aircraft weight while maintaining structural integrity and mission performance.”
All that time in the wind tunnel clearly paid off for the F-16XL design.
The F-16XL takes on the F-15E
General Dynamics ultimately built two prototype F-16XLs for testing, but as testing progressed, it was clear that this new iteration of the F-16 design was worth more than simply demonstrating technology. In search of a useful place to put the new jet’s capabilities, the Air Force decided to enter it into the Enhanced Tactical Fighter (ETF) competition, which aimed to field a capable replacement for the F-111 Aardvark.
“The F-16XL flight-test program has conclusively demonstrated that the XL performs as predicted. This performance level represents a significant increase in mission capability for USAF,” D. Randall Kent, Vice President and Program Director for the General Dynamics F-16XL program, said at the time.
“Coupling this with the affordability and low risk of the F-16XL presents USAF with a viable way to increase mission capability while simultaneously growing to a forty-wing TAC force structure.”
Soon, the ETF program changed names to the Dual-Role Fighter program–but despite the shift in titles, the goal was the same: To field an aircraft capable of penetrating deep into enemy airspace for interdiction missions without the need for fighter escorts. The F-16XL, with its significant fuel range, good performance, and hardpoints for 27 weapons, seemed like a perfect fit for the job… But it wasn’t the only aircraft competing for the contract. Standing between the F-16XL and operational service was another highly capable platform: The F-15E Strike Eagle.
Like the F-16XL, the Strike Eagle was a modified version of an existing fighter: The F-15 Eagle. The Eagle represented America’s top-of-the-line air superiority fighter, boasting an undefeated record in dogfights that holds to this very day. Unlike the F-16XL, however, the F-15E shared the vast majority of its design with the two-seater F-15D that was already in production.
There was no doubt that the F-16XL would likely be the more expensive option, thanks to its significant design departure from the F-16 it was based on. But it also offered a great deal of capability. Its massive wings made it more stable than the F-16 it was based on, while its wind-tunnel-tested design made all that wing area serve no detriment to the fighter’s handling.
“We climbed at more than 20,000 feet per minute, leaping from 4,000 to 27,000 feet in sixty-seven seconds. Jim eased the power back while turning into the supersonic corridor and getting cleared by Edwards Control to begin a supersonic run,” F. Clifton Berry wrote after riding in the F-16XL.
“Jim applied afterburner and the aircraft accelerated smoothly from Mach 0.95 through 1.0 and to 1.2 in seconds. Even with the heavy bomb load aboard, the aircraft went supersonic without a tremble. Handling characteristics at mach 1.2 with the heavy ordnance load were remarkably similar to those of the standard F-16 without bombs.”
The F-15E, on the other hand, offered only 15 hardpoints–which it’s important to note, is still a lot. The F-15E also delivered a higher top speed (Mach 2.5 versus 2.05) and a higher service ceiling at 60,000 feet (compared to the F-16XL’s 50,000). Most importantly, however, the F-15E leveraged not one, but two engines. Because these aircraft were intended to fly deep into enemy airspace without much support, the Air Force believed it was likely that these planes would see a great deal of anti-aircraft fire. Having two engines meant one could be damaged by enemy fire, but the aircraft could still limp home on the other.
The F-16XL may have been one of the most capable fighters to never make it into production
It was likely the perceived survivability of two engines, in conjunction with the lower cost of development, that saw the F-15E win the contract. But many within the Air Force saw the F-15E’s win as bittersweet. The Strike Eagle was indeed an incredibly capable platform, but the F-16XL’s fans felt as though the fighter wasn’t meant to compete with the Strike Eagle, so much as support it–much like the F-16 and F-15 support one another today. Like the YF-23 that lost to Lockheed Martin’s F-22 Raptor, the F-16XL has since been remembered as an aircraft that might have been better than the jet we ultimately got… with concerns about dollars and cents making the decision, rather than maximum capability.
Of course, that may not be an entirely fair assessment. The F-16XL was indeed a capable aircraft, but the F-15E has since proven itself in combat time and time again. The Strike Eagle was clearly not a bad choice, but with the F-16XL’s incredible chops in mind, there could be little doubt that the Air Force would have been better off with both of these capable fighters in their stable… if only money truly were no object.
Instead of fighting alongside the Strike Eagle as many hoped, the F-16XL program found its way to NASA, where both prototypes participated in a number of aeronautical research projects. In fact, some of the tests conducted using the F-16XL would go on to play a role in developing the supercruise capability for America’s top-tier air superiority fighter of today, the F-22 Raptor.
To anyone who frequents military nerd sites like this, the XL is a funny case, because usually American military nerds tend to dismiss and deride delta wing designs, but the same people will call the F-16XL the best thing since sliced bread.
It is a lot like with German WW2 tanks and the Merkava.
Everybody knows that German WW2 tanks were garbage, because they had the transmission in the front and were thus front heavy and easily mobility killed, but on the Merkava having transmission and engine at the front is the greatest idea ever.
lol
I got to sit in the cockpit of one of the two F-16 XL prototypes while training to fly Phantoms. While the initial development cost was high, as noted, what went unsaid was that had they REPLACED some of the future F-16 build with the XL version the capability would have been greatly increased but the operating costs would have been similar – thus making the difference in purchase price far less than at first it might seem.
I never understood why NOBODY bought the XL. As an air defense bird for countries with large geographical areas to defend, the supercruise would have been a huge tactical advantage and, even if the F-15 with conformal tanks could match the range, put it on target 30% faster. It also makes me wonder why the decision to buy F-15EX to fill the production backlog for the F-35 – the XL was a lot more stealthy, and new radars which can fit in the F-16 nose now are far more capable than they used to be. Plus, had they REALLY wanted a missile mule platform, the wing on the XL could have been modified a bit further to add more AAMRAM wells.
I say add vector thrust and add smaller wings at the front to improve turning to the F- 15.
You, my friend, would be looking for the F-15 STOL/MTD (Short Takeoff Or Landing/Manuverability Technology Demonstrator). 2D, and later 3D thrust vectoring and Canards. https://en.wikipedia.org/wiki/McDonnell_Douglas_F-15_STOL/MTD
Why should the USA. buy the best available fighter at the most economical price, when we can buy the most mediocre fighter at the most inflated possible price, so the defense industrial complex can maximize profits at our country’s expense? Isn’t that the formula? Buy the cheapest pos to manufacture, regardless of the endless defects and performance failures l, do the contractors can maximize their profits.
Dear Olivia, I am glad that you and your husband are back together. Sounds like you went through a helluva time with all your troubles. Although your story had a happy ending, I fail to see how your feedback applies to the article I’ve read. Good luck with your future.
PLEASE !!!!!!
HOW COULD YOU POSSIBLY THINK THAT CHINA AND RUSSIA WERE AHEAD OF US IN THE FIFTH GENERATION AIRCRAFT!!!!
You are absolutely clueless!
They both have made their best effort to come close to us …… And failed
As a devil’s advocate, the F-16XL may be the secret aircraft LM is building? Fast construction in less than a year with stealth features and advanced controls installed.
I certainly hope so!
There were many studies performed by the US Air Force at the time and truthfully the decision was made that in the Air to Surface role (the primary criteria for the Dual Role Fighter), two engines and two crew members were necessary in order to meet mission goals. It was thought at the time the best way to defeat point Air Defense Systems was to engage targets fast and at very low altitudes. There was a lot of discussion associated with having two engines in case one flamed out at low altitude flight. Also unfortunately at the time the technologies associated with providing Sensor based Automatic Target Recognition did not exist. It was a common belief at the time that even with Automated Target Cueing a Pilot had enough on his plate just flying the Plane. Therefore a crew of two would be preferred which the F-15 had and the F-16XL didn’t. I agree the F-16XL was a hell of a machine, it just didn’t meet the requirements of the day.
Personally, if there’s a conflict involving using either F-15s & F-22s or F-16s & F35s, I’d feel a hell of a lot safer with the twin engine fighters smoking the enemy. They’re just faster and look way better, which doesn’t mean much but I have more faith in a twin engine design.
Incorrect. The F-16XL could supercruise with a load of missiles, something neither the F-15 nor F-35 can do.
I really enjoy watching those Jet fighter’s and knowing that they have air superiority over Russia and China!!
Wow…..heavy duty. Dialogue! Just don’t get me started on the topic of ‘delta wings n stealth, n low level abilities.
From a past history standpoint. The ‘Convair’ company, their F-102, F-106, AND the best of ’em all, the CONVAIR B-58 HUSTLER. I hate politics, especially when it affects non-experts, performance, and survivability,
I’ll ALWAYS DESPISE Johnson’s n Kennedy’s sec of defense..
I personally, never liked the delta wing’s look. When I see a picture of the D-Wing, I always think it looks like a flying squirl. I think personally that the top requirement of a fighter jet is that it should look cool. Maybe that sounds childish, but there are some strange looking fighter jets out there. Thankfully, we went with the jet we have now.
Yeah, we went with the one with a Delta wing.
I also like a great looking airplane, but that doesn’t have much to do with the purpose of them. Military aircraft are meant to deliver the most bang for the buck and keep it’s crew protected, and if it happens to look like one of Piccaso’s weirdest paintings, so be it.
I worked on the F-16 and also took both F-16XL and prep. Them for NASA. I worked Flight Test Instrumentation for GD. The best of the best. I worked on F-22 and F-35 proto types I think the F-16 is still the best.
Matt
27 hardpoints on the F-16XL vs 15 hardpoints on the F-15E doesn’t tell the whole story. With MERs & TERs, I believe a single F-15E can carry nearly the same amount of ordnance as a four-ship of today’s F-16 fighters. Your words about the XL vs the F-16 said “twice the load”…that would mean a fully loaded F-15E with conventional weapons might be twice the F-16XL load. Am I correct? Anyway, it doesn’t much matter since most loads are with fewer smart bombs on board. Most of my 3,000+ hours in the Eagle were in the A/B/C/D models with only about 30 hours in the E. So, my F-15E knowledge is sketchy. I enjoyed your presentation on the F-16XL. I wish dollars were unlimited in the military budget. The XL would have been a great addition.
Very SAAB Draken-ish, isn’t it?!
100%
Astute observation
Yes!!! 100% and also with the super-cruise and the beauty.
I have always wondered why the XL didn’t make it. Now we know twin engines would have made it even better and probably the aircraft the USAF would be using today.
It never had to be an either-or consideration, which is why it is so tragic. The XL mod would have added about 10-15% to the purchase cost, but almost nothing to operating costs. Had every future F-16 been built with the XL wing, we’d have had almost double the capability for the F-16s roles for perhaps a 5% increase in total lifetime costs, or at the cost of a couple of units.
Extremely poor trade-off, IMHO. Especially now that they are wanting an aircraft to act as “missile mules” for the F-35/F-22 for air defense/air superiority. The XL could have carried more, had a smaller radar cross section than the F-15EX, and been able to supercruise in and out to deliver them.
….and it was fun to fly!
And it was fun to crew.
1. This New Fighter is 5thy gyration Fighter call the F-16XLtoo. It will be Lot Faster then the Re-genial F-16 Fighter is 4th gyration to be replace soon for retired soon too. This Fighter is a lot Faster too. It speed is mack 2.4 Plus too. Top Speed is Classified too.
Saab like characteristics
We likely stole the technology for this F16 just like we stole the F35 from China and Russia.
Obviously you’re either Russian or an agent.
THEY stole those designs F-22 & F-35 from US Which is WHY “their copies” are NOT AS CAPABLE as our originals.
Clearly the story of a jet made for non-DU bombs. Can travel fast but not with big heavy warheads that would destabilize it highly. So the plane got pushed out of the Air Force…
Clearly, this should be a heavy drone program version. The supercruise and extended range design would be even more effective without the needs of a cockpit. Furthermore, the single engine version for a drone that may be lost is better than losing two.
I got to see it fly twice with the GE F110 engine while at GD/FW. Amazing airplane.
I would’ve thought the Israelies would buy up half a dozen F-16XL squadrons with a licence to make parts.
Upgraded, updated F-16XL … perhaps a leading contender for the MR-X program ?
Very impressive research and great article thank you
Excellent article. I was unaware of the XL.
Yes, does look a lot like the Saab J35 draken.
Would it be possible to retrofit or upgrade the existing USAF F-16 fleet by putting new wings and perhaps new or rebuilt engines? Newer avionics could possibly be added including an electronic warfare pod with Artificial Intelligence or remote control so ground or air-based commanders could start multi-level efforts over several frequencies.
I asked about that in 1983, when I got to sit in one. They said no, there were structural differences which had to be addressed at build time.
Alex, an excellent article. After all these years where were you able to dig up the information? I was associated with the XL development and am one of those strongly in the camp believing the best aircraft did not prevail.
They also developed an FB-22 along the same lines as the F-16XL. It was canceled with the F-22 production. That particular design had an issue in that it lacked internal storage, but it’s performance increase as an interdiction aircraft was impressive.
Comparing the F-22 FB-22 ∆
Speed Mach 2.25 Mach 1.92 85%
Max TO weight 38,000 kg 54,500 kg 137%
Combat Radius 1,093 km 3,300 km 302% (subsonic)
Max g-limits +9g 6g
https://en.wikipedia.org/wiki/Lockheed_Martin_FB-22
https://en.wikipedia.org/wiki/Lockheed_Martin_F-22_Raptor
FB-35 Concept:
In similar fashion to the “FB-35” would extends the aircraft about 6 to 8 feet (12%) and uses a delta wing for more fuel and lift. This is based on two preceding experimental aircraft, the F-16XL and the FB-22. Scaling range and payload of from their fighter versions, you end up with 2,300 miles (2,000nm, 2,680 km) combat radius and capable of carrying two Tomahawk missiles internally. This is a critical distance for striking regional targets out of NATO and allied countries.
Comparing the F-35A FB-35 ∆
Speed Mach 1.6 Mach 1.36 85%
Max TO weight 31,751 kg 43,500 kg 137%
Combat Radius 1,239 km 3,742 km 302% (subsonic)
Max g-limits +9g 6g
https://en.wikipedia.org/wiki/Lockheed_Martin_F-35_Lightning_II
Removal of the two stabilizers might require vector thrusting for yaw and pitch. Given the F-35B has this already for 90 degrees, a variation for flight control should be achievable.
It would need to be able to internally carry the larger ordinance that the F-35 cannot, including current and future long range cruise and hypersonic missiles. As an example, a Tomahawk is 2,900 lb. (1,300 kg), 18 ft 3 in (5.56 m) long 20.4 in (0.52 m) diameter. In addition, two rotary bomb/missile rack capable gives you a formidable weapons platform, yet full stealth. The internal bay either side of the engine would be lengthened to, say, 25’ (7.5 m) and increased in depth about 50%
Given common parts with the F-35, the development, production, training and maintenance costs the FB-35 “Lightning Strike” would be affordable in significant quantities for a middle power already equipped with the F-35. My gut-feel, based on specialty development and numbers produced, and increased size a FB-35 would cost about twice that of a F35A, => about US$165 million. That’s about 28% of a B-21.
this aircraft is still today a truly capable platform to compliment both the f-35 and f-22. this plane and it’s potential weapons loadout will be needed in the event of a conflict with China. at this point it is problematic that our current air assets would be quickly overwhelmed by the sheer numbers that the chi-coms would deploy against our forces. the air force is looking for a economical platform to compliment its current 5 gen fighters and the solution is staring them right in their technology obsessed bureaucratic faces……
this aircraft is still today a truly capable platform to compliment both the f-35 and f-22. this plane and it’s potential weapons loadout will be needed in the event of a conflict with China. at this point it is problematic that our current air assets would be quickly overwhelmed by the shear numbers that the chi-coms would deploy against our forces. the air force is looking for a economical platform to compliment its current 5 gen fighters and the solution is staring them right in their technology obsessed bureaucratic faces……
Crazy to see Justin list those numbers, and see very similar in DCS with the Block 50. When I first saw those numbers, at around 60K pph full mil, with only internal fuel, rough calc yielded 10 mins and you were done! The fact that the XL could double that, supercruise, and carry ordinance while beating the (some block 16) is just astounding. Yet another program I was in the dark about, thanks Alex. Also, that wing surface area seems significant, the F-22 has some serious wing surface area, do you think from lessons learned with the XL? Lifting body design seems to incorporate some that also??