F-16XL

kitplane01 · Thu Jul 07, 2022 6:00 am

The F-16XL was supposidly the ever best F-16 airframe ever made. It was faster than the F-16, and on internal fuel could carry the same payload twice as far, or double the payload 44% further. It had a smoother ride down low.

It ended up competing for and losing a contract against the F-15E.

But why didn't it replace later varients of the F-16? How come later varients of the F-16 didn't use this airframe instead of the standard airframe? Were there any disadvantages compared to the F-16, except airframe parts incompatability with the normal F-16? (It could have used the same engine, avionics, radar, and ejection seat as the normal F-16)

RJMAZ · Thu Jul 07, 2022 6:54 am

First problem was agility. There is a reason the Rafale, Eurofighter and Gripen have canards at the front. A cranked arrow wing isn't much better than a Delta wing without canards and they have very poor sustained turn rate.

Second problem was a low thrust to weight ratio. The Rafale C is lighter than the F-16XL yet has significantly more thrust. The F/A-18C is only 500kg heavier yet has 22% more engine thrust than the F-16XL. So sustained turn rate would be even worse.

Third problem is its small size when competing against the F-15E. Take a small/medium/large fighter aircraft that weighed 5,000kg, 10,000kg and 15,000kg. Add 5,000kg of weapons to each. The small fighter would see its range drop by 60%. The medium fighter would see its range drop by 40%. The large fighter would see its range drop by 20%. No fancy wing can make up for a lack of size. The F-15E was 50% heavier, had 50% more fuel and had 60% more thrust. Remember the job was to replace the massive F-111. The F-16XL never stood a chance against the much bigger F-15E.

Forth problem was radar size. The intake under the nose doesn't give much room for a large diameter radar. But compared to a normal F-16 they are the same.

Though let's say the JSF program never started. The F-16XL with a F119 engine from the F-22 would make up for the lack of thrust and give it Mach 1.4/1.5 supercruise. A 3D thrust vectoring nozzle like on the X-31 or Russian aircraft would make up for the lack of ability.

texl1649 · Thu Jul 07, 2022 11:11 am

It really wouldn’t have been a great dog fighter as mentioned, though as avionics/AESA advanced and the -229 version of the F100 as well became more available the issues of net power might not have been as big a deal. The loitering ability/payload would ultimately have proven useful in an interceptor/CAP role; there’s a reason F-16’s tend to carry a lot of drop tanks. The turn rate/ability to get there was actually quite incredible for the planform;

https://www.airforcemag.com/article/1183f16xl/

https://nationalinterest.org/blog/reboo ... gle-181073

It’s one of the late-20th century what-if’s to me (along with the YF-23); had it gotten thrust vectoring ability and been fully developed it would have further cemented the F-16’s true dominance in production/market popularity in the 80’s-early 2000’s, with many likely to have then adopted it as a ‘family’ with the ‘standard’ model.

Throw in later block 80 upgrades and wow, what an evolution. It also could have then been a basis for a navalized variant to supplant the later super hornet program, at much lower development costs.

kitplane01 · Thu Jul 07, 2022 7:55 pm

texl1649 wrote:
It really wouldn’t have been a great dog fighter as mentioned, though as avionics/AESA advanced and the -229 version of the F100 as well became more available the issues of net power might not have been as big a deal. The loitering ability/payload would ultimately have proven useful in an interceptor/CAP role; there’s a reason F-16’s tend to carry a lot of drop tanks. The turn rate/ability to get there was actually quite incredible for the planform;

https://www.airforcemag.com/article/1183f16xl/

https://nationalinterest.org/blog/reboo ... gle-181073

It’s one of the late-20th century what-if’s to me (along with the YF-23); had it gotten thrust vectoring ability and been fully developed it would have further cemented the F-16’s true dominance in production/market popularity in the 80’s-early 2000’s, with many likely to have then adopted it as a ‘family’ with the ‘standard’ model.

Throw in later block 80 upgrades and wow, what an evolution. It also could have then been a basis for a navalized variant to supplant the later super hornet program, at much lower development costs.

Nice find!

Quote about manuaverability ... "it can attain five Gs in 0.8 seconds, on the way to nine Gs in just a bit more time. That’s half the time required for the F-16A, which in turn is less than half the time required for the F-4. The speed loss to achieve five Gs is likewise half that of the F-16A."

kitplane01 · Thu Jul 07, 2022 8:01 pm

RJMAZ wrote:
First problem was agility. There is a reason the Rafale, Eurofighter and Gripen have canards at the front. A cranked arrow wing isn't much better than a Delta wing without canards and they have very poor sustained turn rate.

I would have also thought manuaverability would suffer, especially something like sustained turn rate. Yet the quote of "The speed loss to achieve five Gs is likewise half that of the F-16A."

RJMAZ wrote:
Second problem was a low thrust to weight ratio. The Rafale C is lighter than the F-16XL yet has significantly more thrust. The F/A-18C is only 500kg heavier yet has 22% more engine thrust than the F-16XL. So sustained turn rate would be even worse.

A fully loaded F-16XL can carry a lot! But an empty F-16XL only weighs 22,000 lbs, and an empty F-16A weighs 16,300 lbs. The difference in weight is 34% when empty, and less when carrying an equal fuel and pay load. And a F-16XL goes further on the same fuel.

RJMAZ wrote:
Third problem is its small size when competing against the F-15E. ...

In real life it did lose a contract to the the F-15, but I was wondering why it also lost to the F-16.

RJMAZ · Thu Jul 07, 2022 10:35 pm

kitplane01 wrote:
I would have also thought manuaverability would suffer, especially something like sustained turn rate. Yet the quote of "The speed loss to achieve five Gs is likewise half that of the F-16A."

The quote is instantaneous turn rate. They are talking about speed loss in the 0.8 second it takes to hit 5G. Of course it will lose less speed than a normal F-16 that takes say 1.6 seconds to hit 5G.

The quote does not mention how fast air speed is dropping once at 5G and then sustaining 5G. The F-16XL would be a bit of a brick.

Also I expect once the F-16XL is at a slight angle of attack the roll performance slows right down like a 1960's delta. The eurocanards maintain excellent roll performance.

kitplane01 wrote:
And a F-16XL goes further on the same fuel.

No it doesn't. The F-16XL only has a better lift to drag ratio. A 787 also has a better lift to drag ratio than a 737 but obviously the heavier 787 burns much more fuel.

The F-16XL improved lift to drag ratio doesn't make up for the extra weight increase so it doesn't go as far on the same fuel. The F-16XL goes further because it has 83% more internal fuel.

I dare say a normal F-16 with conformal tanks would still be lighter and now have very similar fuel burn per hour. A clean F-16XL might now only be carrying 20-25% more fuel. So the F-16XL has a small advantage in range and speed at the expense of dogfighting ability.

The F-16 with conformals can carry 3 drop tanks when in bomb truck mode and then drop the 3 tanks to regain dogfighting ability. The F-16XL is stuck with poor dogfighting ability.

A lot of the F-16XL G limit comparisons were done against the F-16A with the lower thrust engines. The Block 60 F-16 have considerable strengthening and extra thrust. So the advantages mostly disappear.

LyleLanley · Thu Jul 07, 2022 10:50 pm

RJMAZ wrote:
The F-16 with conformals can carry 3 drop tanks when in bomb truck mode and then drop the 3 tanks to regain dogfighting ability.

“Bomb truck”? You mean “Bomb Honda CRX”?

Where are you gonna fit bombs when your rails are loaded with tanks? And at what point will the weight of the jet, loaded conformals, 3 externals tanks, and any weapons exceed max T/O or max inflight GW?

kitplane01 · Thu Jul 07, 2022 11:41 pm

RJMAZ wrote:

kitplane01 wrote:
And a F-16XL goes further on the same fuel.

No it doesn't. ...
The F-16XL improved lift to drag ratio doesn't make up for the extra weight increase so it doesn't go as far on the same fuel. The F-16XL goes further because it has 83% more internal fuel.

Maybe you're right. Wikipedia says 11% reduction in lift-drag ratio. But the F-16XL weighs about 30% more.

On the other hand, carrying around several drop tanks reduces the F-16a's lift-drag ratio by some unknown-to-us percent. So maybe you're right.

RJMAZ wrote:
I dare say a normal F-16 with conformal tanks would still be lighter and now have very similar fuel burn per hour. A clean F-16XL might now only be carrying 20-25% more fuel. So the F-16XL has a small advantage in range and speed at the expense of dogfighting ability.

Were there conformal fuel tanks in 1982?

RJMAZ wrote:

A lot of the F-16XL G limit comparisons were done against the F-16A with the lower thrust engines. The Block 60 F-16 have considerable strengthening and extra thrust. So the advantages mostly disappear.

And the F-16XL could also use the improved engines.

These days, payload, range, and endurance are move valuable than dogfighting. These days, what the F-16XL offers would be better than the F-16normal.

But my question is ... why did they continue to build F-16normals when they could have built F-16XLs? Was dogfighting so important in the 1980s?

texl1649 · Fri Jul 08, 2022 12:56 am

Kitplane, they did build a handful, but developing that into a production aircraft would have involved a lot more testing/validation (things like weapons integration, refueling certification, fatigue life validation, bringing spare parts into inventory etc), and that all costs money and requires…well a large customer (USAF). The costs to move, for example, from the LWF YF-16 to the F-16 were also substantive, but helped by the fact that it used the same F-100 engine that was in service by then with the F-15.

RJMAZ · Fri Jul 08, 2022 1:16 am

kitplane01 wrote:
Were there conformal fuel tanks in 1982?

The F-16 conformal tanks first flew in 1994.
The F-15E entered service in 1989. It is doubtful the F-16XL would have entered service before the F-15E.

So really a 5 year gap. Any air force who was looking at a long range F-16 in 1995 would have picked a normal block 50/52 with conformals over the F-16XL. Both would have the same engine and the F-16 block 50/52 now had similar payload G limit restrictions.

Most strike fighter aircraft spend 99% of the time subsonic. Even the supercruising F-22 would spend 90+% of the time subsonic as the range is still much greater. So the best fuel efficient subsonic wing is a straight one like the commercial airlines. So the wider span and lower swept F-16 normal is better for subsonic transit. The Mitsubishi F-2 had an even better subsonic wing. I would say this is a better evolution of the F-16 than the F-16XL.

The F-2A Super Kai proposed version had conformals tanks fitted. This would have been the ultimate F-16 but Japan opted for the superior F-35.

While the F-16XL does have a good advantage at supersonic speeds on a long range strike mission it would still cruise subsonic. So the high speed advantage is not very valuable here. In the interception role the high speed wing is now very valuable but then this is one of the few missions where agility is also deemed important.

kitplane01 wrote:
But my question is ... why did they continue to build F-16normals when they could have built F-16XLs? Was dogfighting so important in the 1980s?

The F-16XL wouldn't have been ready until 1990. So the normal F-16's were the only cheap option in the 1980's.

In the missions that required supersonic speeds they also required dogfighting. The cranked arrow wing could only provide the speed.

744SPX · Fri Jul 08, 2022 1:40 am

F-16XL as is had superior maneuverability at altitude to the F-16 and F-15. It never needed canards or thrust vectoring, just more thrust. Also, the current F-16 blocks 50 and above weighs only 500 lbs less than the XL. Talk about a pig.

kitplane01 · Fri Jul 08, 2022 2:11 am

744SPX wrote:
F-16XL as is had superior maneuverability at altitude to the F-16 and F-15. It never needed canards or thrust vectoring, just more thrust. Also, the current F-16 blocks 50 and above weighs only 500 lbs less than the XL. Talk about a pig.

Where did you learn the F-16XL has better maneuverability? Can you provide a link that says this?

kitplane01 · Fri Jul 08, 2022 2:13 am

RJMAZ wrote:

Most strike fighter aircraft spend 99% of the time subsonic. Even the supercruising F-22 would spend 90+% of the time subsonic as the range is still much greater. So the best fuel efficient subsonic wing is a straight one like the commercial airlines. So the wider span and lower swept F-16 normal is better for subsonic transit. The Mitsubishi F-2 had an even better subsonic wing. I would say this is a better evolution of the F-16 than the F-16XL.

From Wikipedia: These changes resulted in a 25% improvement in maximum lift-to-drag ratio in supersonic flight and 11% in subsonic flight..

Yes, the F-16XL weighs more and carries more fuel (it's a bigger airplane) ... but it's wing is more effecient in both subsonic and supersonic.

RJMAZ · Fri Jul 08, 2022 2:25 am

744SPX wrote:
Also, the current F-16 blocks 50 and above weighs only 500 lbs less than the XL. Talk about a pig.

You are comparing apples to oranges. The F-16XL would have also experienced the same weight growth and it would no doubt be pushing 11,000kg. So roughly same weight as a Eurofighter.

Higher fatigue life. Increased MTOW. Higher G limits with heavy payloads. Extra sensors. These all add weight and all would have applied to any F-16XL variant.

The F-16XL is longer than the Eurofighter and has more wing area and fuel capacity. 11,000kg is totally realistic for an F-16XL built today. What a pig that would be. The Eurofighter has 180kn of thrust. The most powerful F-16 engine maxes out at around 140kn.

GDB · Fri Jul 08, 2022 7:15 am

RJMAZ wrote:
kitplane01 wrote:
Were there conformal fuel tanks in 1982?

The F-16 conformal tanks first flew in 1994.
The F-15E entered service in 1989. It is doubtful the F-16XL would have entered service before the F-15E.

So really a 5 year gap. Any air force who was looking at a long range F-16 in 1995 would have picked a normal block 50/52 with conformals over the F-16XL. Both would have the same engine and the F-16 block 50/52 now had similar payload G limit restrictions.

Most strike fighter aircraft spend 99% of the time subsonic. Even the supercruising F-22 would spend 90+% of the time subsonic as the range is still much greater. So the best fuel efficient subsonic wing is a straight one like the commercial airlines. So the wider span and lower swept F-16 normal is better for subsonic transit. The Mitsubishi F-2 had an even better subsonic wing. I would say this is a better evolution of the F-16 than the F-16XL.

The F-2A Super Kai proposed version had conformals tanks fitted. This would have been the ultimate F-16 but Japan opted for the superior F-35.

While the F-16XL does have a good advantage at supersonic speeds on a long range strike mission it would still cruise subsonic. So the high speed advantage is not very valuable here. In the interception role the high speed wing is now very valuable but then this is one of the few missions where agility is also deemed important.

kitplane01 wrote:
But my question is ... why did they continue to build F-16normals when they could have built F-16XLs? Was dogfighting so important in the 1980s?

The F-16XL wouldn't have been ready until 1990. So the normal F-16's were the only cheap option in the 1980's.

In the missions that required supersonic speeds they also required dogfighting. The cranked arrow wing could only provide the speed.

Off the top of my head, there was the modification to the bomb bay (it rotated) exterior of the Buccaneer, done in the early 1970’s to enhance it’s already impressive range.

studedave · Sat Jul 09, 2022 5:29 pm

texl1649 wrote:
IIt also could have then been a basis for a navalized variant to supplant the later super hornet program, at much lower development costs.

'Cept for one thing~
there's a laundry list of reasons the F-16 was not used as the basis for what became the F-18.
As 'neat' as the improved bird you speak of would be- it would NEVER happen.

might be cool to see it used as an aggressor, though..... :scratchchin:

StudeDave 8-)

GalaxyFlyer · Sat Jul 09, 2022 7:02 pm

Navalizing a land-based plane isn’t easy, landing gear, the tail hook and all the support structure is only the beginning. And that’s if the basic layout meets USN standard.

texl1649 · Sat Jul 09, 2022 8:10 pm

studedave wrote:
texl1649 wrote:
IIt also could have then been a basis for a navalized variant to supplant the later super hornet program, at much lower development costs.

'Cept for one thing~
there's a laundry list of reasons the F-16 was not used as the basis for what became the F-18.
As 'neat' as the improved bird you speak of would be- it would NEVER happen.

might be cool to see it used as an aggressor, though.....

StudeDave

Well, it didn’t happen, and now of course it never will, so yes.

You might look up the F-16N though, and before that…the Vought Model 1600. The arrester hook, landing gear, and strengthening had been proposed/preliminary designs already done.

https://en.wikipedia.org/wiki/Vought_Model_1600

For the XL it could have then been adapted in lieu of the super bug (really an all new aircraft) probably for a lot less had…the XL made it into USAF service is my theory. The 1600 really just lost out to the…F/A-18 due to the USN’s then-commitment to twin engines. Fine and all, but by the late 80’s/early 90’s when the super hornet vs. Tomcat 21 etc. decisions were being made, the reliability of the F100/F110’s probably had reached a point the requirement wasn’t the end of the decision (see: the F-35).

RJMAZ · Sun Jul 10, 2022 12:08 am

texl1649 wrote:
For the XL it could have then been adapted in lieu of the super bug (really an all new aircraft) probably for a lot less had…the XL made it into USAF service is my theory.

No chance.

First reason. The F-16XL fuselage extension was at the back. The rear overhang was too big causing tail strikes and they had to remove the F-16's ventral fin.

Second reason. Delta wings land at a very high angle of attack. They don't have flaps.

Third reason. Delta wings land at high speed again they don't have flaps.

Forth reason. The Tejas had to get canards added and the Rafale is Delta canard.

Adding canards and pushing the landing gear back you now have a cleansheet F-16. If we are talking crazy the US Navy should have licence built French Rafales with F404 engines. The first Rafale prototypes had F404 engines fitted.

889091 · Sun Jul 10, 2022 12:58 am

GalaxyFlyer wrote:
Navalizing a land-based plane isn’t easy, landing gear, the tail hook and all the support structure is only the beginning. And that’s if the basic layout meets USN standard.

Wasn't the USN also pushing for (at that time) dual engined planes for redundancy purposes as well?

kitplane01 · Sun Jul 10, 2022 1:12 am

RJMAZ wrote:
texl1649 wrote:
For the XL it could have then been adapted in lieu of the super bug (really an all new aircraft) probably for a lot less had…the XL made it into USAF service is my theory.

No chance.

First reason. The F-16XL fuselage extension was at the back. The rear overhang was too big causing tail strikes and they had to remove the F-16's ventral fin.

Second reason. Delta wings land at a very high angle of attack. They don't have flaps.

Third reason. Delta wings land at high speed again they don't have flaps.

Forth reason. The Tejas had to get canards added and the Rafale is Delta canard.

Adding canards and pushing the landing gear back you now have a cleansheet F-16. If we are talking crazy the US Navy should have licence built French Rafales with F404 engines. The first Rafale prototypes had F404 engines fitted.

The Mirage 2000, the Douglas F4D-1 Skyray, and probably a bunch I cannot think of are pure delta wing, carrier based aircraft.

889091 · Sun Jul 10, 2022 1:25 am

kitplane01 wrote:
RJMAZ wrote:
texl1649 wrote:
For the XL it could have then been adapted in lieu of the super bug (really an all new aircraft) probably for a lot less had…the XL made it into USAF service is my theory.

No chance.

First reason. The F-16XL fuselage extension was at the back. The rear overhang was too big causing tail strikes and they had to remove the F-16's ventral fin.

Second reason. Delta wings land at a very high angle of attack. They don't have flaps.

Third reason. Delta wings land at high speed again they don't have flaps.

Forth reason. The Tejas had to get canards added and the Rafale is Delta canard.

Adding canards and pushing the landing gear back you now have a cleansheet F-16. If we are talking crazy the US Navy should have licence built French Rafales with F404 engines. The first Rafale prototypes had F404 engines fitted.

The Mirage 2000, the Douglas F4D-1 Skyray, and probably a bunch I cannot think of are pure delta wing, carrier based aircraft.

Was the Mirage 2000 ever certified for carrier ops? The landing gears look way too flimsy for a 'controlled crash' on a flat-top...

GalaxyFlyer · Sun Jul 10, 2022 1:26 am

889091 wrote:
GalaxyFlyer wrote:
Navalizing a land-based plane isn’t easy, landing gear, the tail hook and all the support structure is only the beginning. And that’s if the basic layout meets USN standard.

Wasn't the USN also pushing for (at that time) dual engined planes for redundancy purposes as well?

Yes.

FGITD · Sun Jul 10, 2022 1:31 am

kitplane01 wrote:
RJMAZ wrote:
texl1649 wrote:
For the XL it could have then been adapted in lieu of the super bug (really an all new aircraft) probably for a lot less had…the XL made it into USAF service is my theory.

No chance.

First reason. The F-16XL fuselage extension was at the back. The rear overhang was too big causing tail strikes and they had to remove the F-16's ventral fin.

Second reason. Delta wings land at a very high angle of attack. They don't have flaps.

Third reason. Delta wings land at high speed again they don't have flaps.

Forth reason. The Tejas had to get canards added and the Rafale is Delta canard.

Adding canards and pushing the landing gear back you now have a cleansheet F-16. If we are talking crazy the US Navy should have licence built French Rafales with F404 engines. The first Rafale prototypes had F404 engines fitted.

The Mirage 2000, the Douglas F4D-1 Skyray, and probably a bunch I cannot think of are pure delta wing, carrier based aircraft.

This got me curious…

Mirage 2000 wasn’t carrier based. Marine Nationale used the etenard pretty much until Rafael showed up

There have been a few pure delta wing carrier based aircraft, but not a bunch. The F4D, F7U, Tejas, and I think I might be missing 1 or 2, but that seems to be it.

RJMAZ · Sun Jul 10, 2022 4:37 am

FGITD wrote:
This got me curious…

Mirage 2000 wasn’t carrier based. Marine Nationale used the etenard pretty much until Rafael showed up

There have been a few pure delta wing carrier based aircraft, but not a bunch. The F4D, F7U, Tejas, and I think I might be missing 1 or 2, but that seems to be it.

Mirage 2000 is a no. Tejas had to get Canards/Levcons added and even then it probably will never be operational on a carrier. It would have to land so light that it probably wouldn't be able to land with anything more than a pair of missiles. No wonder it has been rejected.

The F-4 skyray and F7U were extremely light and didn't have high wing sweep.

There is no chance an F-16XL could ever land on a carrier. It would need Canards and the landing gear moved back at the very least.

kitplane01 · Sun Jul 10, 2022 5:55 am

889091 wrote:
kitplane01 wrote:
RJMAZ wrote:
No chance.

First reason. The F-16XL fuselage extension was at the back. The rear overhang was too big causing tail strikes and they had to remove the F-16's ventral fin.

Second reason. Delta wings land at a very high angle of attack. They don't have flaps.

Third reason. Delta wings land at high speed again they don't have flaps.

Forth reason. The Tejas had to get canards added and the Rafale is Delta canard.

Adding canards and pushing the landing gear back you now have a cleansheet F-16. If we are talking crazy the US Navy should have licence built French Rafales with F404 engines. The first Rafale prototypes had F404 engines fitted.

The Mirage 2000, the Douglas F4D-1 Skyray, and probably a bunch I cannot think of are pure delta wing, carrier based aircraft.

Was the Mirage 2000 ever certified for carrier ops? The landing gears look way too flimsy for a 'controlled crash' on a flat-top...

I'm so wrong. I remember the Mirage 2000N, but that's nuclear not naval. Thanks for the correction.

But yes, there have been pure delta carrier based aircraft.

RJMAZ · Sun Jul 10, 2022 7:50 am

kitplane01 wrote:
But yes, there have been pure delta carrier based aircraft.

I'm not sure what one subsonic (with afterburner) aircraft from 70 years ago has to do with the F-16XL being carrier capable.

texl1649 · Sun Jul 10, 2022 2:14 pm

The handling qualities observed (later) by NASA test pilots of the XL aircraft don’t support the generalized assertions/conclusions above as to the planform, imho.

https://ntrs.nasa.gov/api/citations/199 ... hment=true

It was able to take off and land in 2/3 the distance of a standard F-16A.

https://www.globalsecurity.org/military ... 6ef-xl.htm

A fairly comprehensive history of development/testing is here;

https://www.nasa.gov/sites/default/file ... flight.pdf

This I think shows that it rotated quickly at only 150 knots, for takeoff. I don’t believe it is true that the type was unsuitable to future navalized development on the basis of that work done by Vought as well for the 1600 variant, but, fine if some want to posit that.

On landing;

A straight-in approach to landing was performed to a full stop land- ing. The aircraft was trimmed to 12-13 deg. AOA (155 KCAS) for the approach and provided a solid platform to perform the land- ing. At one mile from landing some turbulence was experienced and AOA decreased intentionally to approximately 11 deg. (165 KCAS approx.) for the final phase. A constant pitch attitude with no flare landing was performed which resulted in a smooth but faster than optimum touchdown. Concern for the pitch sensitivity noted on takeoff rotation prevented any significant aerodynamic braking attempt. Once the nose wheel was lowered to the runway, aircraft deceleration without wheel braking was not appreciable and the drag chute was deployed to keep from overheating the brakes. Deceleration from the drag chute was excellent. Aircraft directional control with the drag chute deployed (no crosswind) was no problem.

Now, let’s compare that to the king of carrier tac-air of the time (all time?), the great Tomcat. It took a battle with Grumman to avoid going to 26+ degrees AOA for carrier landings;

https://theaviationgeekclub.com/taming- ... units-aoa/

Of course, loaded with more stores, and no other modifications, I am sure the XL would not be ideal, yet that is again just a theoretical configuration never matured (or formally proposed). It seems clear to me that there was a capacity in the type to meet such requirements about 10 years after the XL program was initially laid out by GD.

RJMAZ · Sun Jul 10, 2022 2:56 pm

texl1649 wrote:
The handling qualities observed (later) by NASA test pilots of the XL aircraft don’t support the generalized assertions/conclusions above as to the planform, imho.

Actually it fully supports the conclusion that it can't operate off a carrier.

texl1649 wrote:
The aircraft was trimmed to 12-13 deg. AOA (155 KCAS) for the approach and provided a solid platform to perform the land- ing. At one mile from landing some turbulence was experienced and AOA decreased intentionally to approximately 11 deg. (165 KCAS approx.) for the final phase.

165 knot landing speed with 11 degrees angle of attack? :lol:

Say Hello to the Super Hornet landing at 125 knots with only 8.1 degrees of angle of attack.

Even with with half a tank of gas and decent bomb load the Super Hornet still lands at 140 knots with 8.1 degrees angle of attack. The F-16XL at 165 knots was clean. It would definitely exceed 180 knots landing speed with a light weapon load.

The Hornet lands 5 knots slower than the Super Hornet.

texl1649 wrote:
Now, let’s compare that to the king of carrier tac-air of the time (all time?), the great Tomcat. It took a battle with Grumman to avoid going to 26+ degrees AOA for carrier landings;

Source? You just made that up. The F-14 only hits 13 degrees angle of attack at a super slow 115 knots. It lands at below 10 degrees AOA.

You fail to mention the F-14 flight manual also states a carrier landing speed between 122 and 137 knots. This is 40-50 knots slower than the F-16XL.

https://info.publicintelligence.net/F14AAD-1.pdf

Now add the stronger landing gear and hook to the F-16XL and with the increased empty weight it will be crashing into the carrier at 200 knots.

Kinetic Energy formula
K.E. = 1/2 m v2

F-16XL: 180 knots at 15,000kg = 64MJ
F-14: 130 knots at 25,000kg = 55MJ
Super Hornet: 130 knots at 20,000kg = 44MJ

The tiny F-16XL would have more kinetic energy hitting that carrier than a F-14 at max landing weight.

Russia had to add Canards to the SU-33 and larger wing despite the original SU-27 having great low speed characteristics.

studedave · Sun Jul 10, 2022 4:58 pm

GalaxyFlyer wrote:
Navalizing a land-based plane isn’t easy, landing gear, the tail hook and all the support structure is only the beginning. And that’s if the basic layout meets USN standard.

exactly.

889091 wrote:
Wasn't the USN also pushing for (at that time) dual engined planes for redundancy purposes as well?

Yes, that too.

texl1649 wrote:
You might look up the F-16N though,

Well aware of the -16N.
They were off the shelf land based birds with stronger wings.
That's it.
The first batch only lasted ten years before cracks started showing up....

StudeDave
USN (retired)

kitplane01 · Sun Jul 10, 2022 10:31 pm

RJMAZ wrote:
kitplane01 wrote:
But yes, there have been pure delta carrier based aircraft.

I'm not sure what one subsonic (with afterburner) aircraft from 70 years ago has to do with the F-16XL being carrier capable.

The original claim was that a pure delta wing cannot be carrier based. This was an example of a pure delta wing being carrier based. This does not speak to the other claim, about the F-16 being navalizable.

texl1649 · Mon Jul 11, 2022 2:43 pm

This went into a very personal/ego driven discussion somehow (?), but the XL was clearly capable of being further developed per the links I provided above, including for USN purposes. Whatever, Vought obviously did a lot of the early work (and was a naval aviation expert at that point as was the case with Grumman/McD), and the -16N I posted as a response to someone asking about adversary USN role for the -16.

The very first take off/flight showed it could handle lower speed rotation, and more work could/would be done (reason for citing the excerpt). Canards/modified planform could also have been done for a serious ‘super bug’ competitor/derivative. The -16 and the -18 competed with each other from their respective conceptions through to the present day (see: India etc). There were other negatives too, though I still profess/believe a ‘compromise’ of sorts between the 1602 and the XL and the F-2 (JASDF) wings might/could have worked well;

https://www.19fortyfive.com/2022/03/we- ... t-carrier/

The XL is an intriguing what-if that certainly could have been superior to the Super Eagle in service but as per the designer the USAF wanted the -15 to stay in production. Sometimes politics matter, inarguably, in procurement decisions of all sorts.

The V-1602 was the greatest departure from the F-16A. With the heavier GE F101 engine, the V-1602 also had a redesigned and reconfigured wing, and the fuselage was widened behind the wing to the same width as the leading edge extensions ahead of it. Wing area was 399 sq.ft., with a span of 38 ft. 11 in., and the aircraft was 53 ft. 11 in. overall length.

The Navy, however, favored the Northrop/McDonnell Douglas development of the twin-engined YF-17. It didn’t want the V-1600, nor any of the other proposals based on the F-16. Most accounts state that a primary reason for rejection of the F-16 was that the Navy preferred its aircraft to have two engines, because of the added over-water safety factor. Some say the Navy thought there was more growth potential in a scaled-up YF-17, and that it had superior range to the F-16. Others have brought up the fact that the F-16’s jet intake was just above the nosewheel, posing a greater than usual hazard for the catapult crew, but apparently these were not the only reasons, or the most important.

In his book Aircraft Carriers at War: A Personal Retrospective of Korea, Vietnam, and the Soviet Confrontation, former Chief of Naval Operations Adm. James L. Holloway explained how he fought for the F/A-18 the Navy preferred. Holloway wrote that he had already fought members of Congress who wanted to force the F-16 on the Navy: “I had testified that the Navy wasn’t interested in a fighter that could only get on and off of a carrier by means of a crane, no matter how little it costs.”

Holloway appealed directly to Schlesinger for a meeting to explain the Navy’s position. The admiral was told he could bring only two other people to the meeting because of the size of the room, but when he walked into Schlesinger’s office that day in April 1975 he found more than a dozen people from OSD, who proceeded to argue at length for their preferred F-16-based choice.

When Holloway’s turn finally came, he explained first that “… naval test analyses indicated the F-16 would bang the tailpipe on the deck with unacceptable frequency,” during carrier landings, and even a cursory look at the geometry of the main gear lends credence to those analyses. OSD personnel countered with the claim that the problem could be solved with faster landing speeds and better pilot technique (preach that to the naval aviator landing on a dark and stormy night, with the deck pitching 20 feet or more), and then went on to make even more lengthy arguments for the F-16.

Holloway, however, had saved his best argument for last.

“I pointed out that the F-16 carried only AIM-9 Sidewinder air-to-air missiles and they were clear-air-mass missiles. In clouds, a radar missile like the AIM-7 Sparrow III was required. This capability, with the necessary radar guidance system and heavier pylons, had been incorporated into the F-18 design, but the F-16 would not accommodate an all-weather missile system without extensive redesign and added weight.” The V-1600’s increased size and weight, even in a paper proposal, clearly demonstrated this.

https://forums.spacebattles.com/threads ... -that-wasn’t.343069/

Of course, the -16’s would get Sparrows/AMRAAMs but that was the end of it. Ultimately, I think it’s good the USN didn’t muck up the -16 early on, though again I think the cost for the Super Hornet, which is really a new aircraft vs. the classics, warranted a different outcome potentially (be it a Tomcat 21 or some sort of F-16 derivative).

LightningZ71 · Mon Jul 11, 2022 3:57 pm

kitplane01 wrote:
744SPX wrote:
F-16XL as is had superior maneuverability at altitude to the F-16 and F-15. It never needed canards or thrust vectoring, just more thrust. Also, the current F-16 blocks 50 and above weighs only 500 lbs less than the XL. Talk about a pig.

Where did you learn the F-16XL has better maneuverability? Can you provide a link that says this?

Of note, when the F-15 was first replacing the F-106 in the interceptor role in the USAF, comparative fly offs and combat training showed that the F-106 retained superior maneuverability at high altitude over the F-15 A/B. Aerodynamically, the lower wing loading in the thinner air was the main factor. However, in USAF combat philosophy at the time, interceptor tasks would be handled at BVR or at extreme WVR situations and maneuverability at high altitude was not a leading factor.

The F-16XL had a more modern wing and a better engine than the F-106 with better overall aerodynamics. It's not shocking to believe that it would have been superior at altitude.

None of this is to say that it would be the all-around better fighter, only that in that one case, it should be the better aircraft.

The F-16XL was designed as a competitor for the F-15E and optimized for that role. It wasn't supposed to be a top-end dog fighter, a high speed interceptor, nor any other type of thing. For the role that it was intended, it would have been sufficient to the request at a lower price, but keeping the F-15 line open was an important strategic objective. The F-16 line didn't need extra support and enjoys good volume to present day.

As to why the F-16XL is the way that it is, the design focused on increasing its range and load carrying capability. To achieve that, it needed larger wing area and larger fuel tanks. This required the additional fuselage length. If the goal was to improve on its ability to dog fight, the fuselage wouldn't be longer, and the internal tankage wouldn't have been increased. They likely wouldn't even have fitted a delta wing at all. Instead, as was the case with the offered F-16 Agile Falcon which lent a LOT to the Mitsubishi F-2 derivative design, they opted for a revised, larger version of the existing wing instead.

GalaxyFlyer · Mon Jul 11, 2022 5:54 pm

To paraphrase Adm Thomas Connolly,

“There’s not enough engineering changes in Christendom to make the F-16 a shipboard fighter.”

744SPX · Mon Jul 11, 2022 6:12 pm

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.

https://www.sandboxx.us/blog/f-16xl-the ... the-fight/

...and the F-16A had lower wing loading than the C/Block 50+

RJMAZ · Tue Jul 12, 2022 12:36 am

texl1649 wrote:
This went into a very personal/ego driven discussion somehow (?), but the XL was clearly capable of being further developed per the links I provided above, including for USN purposes.

Of course if you put a wing on the F-16 shaped like a Hornet then it would clearly be capable. But that is why the Hornets are slower than the F-15 and F-16. The Hornet wing has less wing sweep and is designed for high lift at low speed not low drag at high speed.

A navalised F-16 would have ended up being just as slow as a Hornet.

But this was discussion about the F-16XL. The articles you link to actually counter your argument. First one had the crazy high landing speeds. Now this one states:

texl1649 wrote:
When Holloway’s turn finally came, he explained first that “… naval test analyses indicated the F-16 would bang the tailpipe on the deck with unacceptable frequency,” during carrier landings, and even a cursory look at the geometry of the main gear lends credence to those analyses. OSD personnel countered with the claim that the problem could be solved with faster landing speeds and better pilot technique

This is saying that despite extensive modifications Tmthe F-16 is not capable of carrier use. That was with a conventional mid wing and not the cranked arrow delta that makes it even less carrier suitable.

That is like saying analysis indicates an SR-71 can't land on a carrier. But I counter that claim that they could just land at 300 knots and then use the barrier net for when the SR-71 rips in half.

spudh · Tue Jul 12, 2022 12:48 pm

Some of the above F-16XL carrier arguments are meaningless. The reality is that a big part of Navy fighter design is the max weight landing speed, as in how much unused ordnance can a fighter land with. The F-14 was originally intended to be able to land with 6 phoenix missiles but it failed that requirement due to AoA/approach speed constraints. Its loadout was reduced to 4 AIM54, 2AIM7 and 2 sidewinders.
If the XL needed 165kts to land it would have been a totally different airplane by the time they could get that down to the 140 the Phantom came in at let alone the Hornet.
Just look at the F-35 A versus C planform to see what navalising a fighter entails.

st21 · Tue Jul 12, 2022 5:36 pm

spudh wrote:
Some of the above F-16XL carrier arguments are meaningless. The reality is that a big part of Navy fighter design is the max weight landing speed, as in how much unused ordnance can a fighter land with. The F-14 was originally intended to be able to land with 6 phoenix missiles but it failed that requirement due to AoA/approach speed constraints. Its loadout was reduced to 4 AIM54, 2AIM7 and 2 sidewinders.
If the XL needed 165kts to land it would have been a totally different airplane by the time they could get that down to the 140 the Phantom came in at let alone the Hornet.
Just look at the F-35 A versus C planform to see what navalising a fighter entails.

Not true. The F-14 could absolutely land on a carrier with six AIM-54s. It was a question of weight and with a light fuel load, it could be done.

It was a very impractical loadout for routine ops though. Realistically, six AIM-54s would only have been carried if the Cold War had gone hot hence the nickname "Doomsday Loadout".

spudh · Tue Jul 12, 2022 10:52 pm

st21 wrote:
spudh wrote:
Some of the above F-16XL carrier arguments are meaningless. The reality is that a big part of Navy fighter design is the max weight landing speed, as in how much unused ordnance can a fighter land with. The F-14 was originally intended to be able to land with 6 phoenix missiles but it failed that requirement due to AoA/approach speed constraints. Its loadout was reduced to 4 AIM54, 2AIM7 and 2 sidewinders.
If the XL needed 165kts to land it would have been a totally different airplane by the time they could get that down to the 140 the Phantom came in at let alone the Hornet.
Just look at the F-35 A versus C planform to see what navalising a fighter entails.

Not true. The F-14 could absolutely land on a carrier with six AIM-54s. It was a question of weight and with a light fuel load, it could be done.

It was a very impractical loadout for routine ops though. Realistically, six AIM-54s would only have been carried if the Cold War had gone hot hence the nickname "Doomsday Loadout".

I'd have to go dig out old books but I'm pretty sure that the 6 phoenix loadout required excess AoA on the approach to the carrier. As you said it was available for launch but I don't think they could recover without breaching SOP.
I am open to correction here, someone with the F-14 Navop s will surely chime in to set the record straight.

Tugger · Tue Jul 12, 2022 10:57 pm

kitplane01 wrote:
But my question is ... why did they continue to build F-16normals when they could have built F-16XLs?

I think this is/was the crux of your initial question and the simple answer is: Someone would have needed to pay, upfront, for all the developmental work needed to actually get it to be volume production ready. Building two demonstrator prototypes is easy part. Add in the possibility of it not working out as well as envisioned and that cost was too great.

It would have needed to well outstrip available options except it had its own existing version competing against it with any improvement.

Now I am wondering just how much that development would have been...

Tugg

kitplane01 · Wed Jul 13, 2022 1:54 am

Tugger wrote:
kitplane01 wrote:
But my question is ... why did they continue to build F-16normals when they could have built F-16XLs?

I think this is/was the crux of your initial question and the simple answer is: Someone would have needed to pay, upfront, for all the developmental work needed to actually get it to be volume production ready. Building two demonstrator prototypes is easy part. Add in the possibility of it not working out as well as envisioned and that cost was too great.

It would have needed to well outstrip available options except it had its own existing version competing against it with any improvement.

Now I am wondering just how much that development would have been...

Tugg

I'm sure it would have been more than $22.15, but on this scale it should have been very cheap. They already had the airframe, engines, radar, missiles, and avionics. All of these things had been proven to work together.

In fact, in what way was the F-16XL prototype not already combat ready?

GalaxyFlyer · Wed Jul 13, 2022 3:42 am

It’d be cheap from today’s view, but then, it was a new plane with lots of development to go. Plus Congress and the usual budget battles.

889091 · Wed Jul 13, 2022 8:15 am

spudh wrote:
st21 wrote:
spudh wrote:
Some of the above F-16XL carrier arguments are meaningless. The reality is that a big part of Navy fighter design is the max weight landing speed, as in how much unused ordnance can a fighter land with. The F-14 was originally intended to be able to land with 6 phoenix missiles but it failed that requirement due to AoA/approach speed constraints. Its loadout was reduced to 4 AIM54, 2AIM7 and 2 sidewinders.
If the XL needed 165kts to land it would have been a totally different airplane by the time they could get that down to the 140 the Phantom came in at let alone the Hornet.
Just look at the F-35 A versus C planform to see what navalising a fighter entails.

Not true. The F-14 could absolutely land on a carrier with six AIM-54s. It was a question of weight and with a light fuel load, it could be done.

It was a very impractical loadout for routine ops though. Realistically, six AIM-54s would only have been carried if the Cold War had gone hot hence the nickname "Doomsday Loadout".

I'd have to go dig out old books but I'm pretty sure that the 6 phoenix loadout required excess AoA on the approach to the carrier. As you said it was available for launch but I don't think they could recover without breaching SOP.
I am open to correction here, someone with the F-14 Navop s will surely chime in to set the record straight.

In theory - possible
In reality - don't think it was ever attempted

https://theaviationgeekclub.com/us-navy ... t-carrier/

[edited]
Did some further digging, and here is an unverified post:
"Posted November 28, 2020
AFAIK CVW-11 did fly with the 6x Phoenix loadout on their cruise on the USS Enterprise in the mid 80s, when Robert L. "Crazy Bob" Leuschner was the skipper of the Enterprise and made the Tomcats do that to "train as you fight". Hence the 6x Phoenix loadout is sometimes referred to as the "Crazy Bob loadout".

He was reliefed of command when he drove the Enterprise onto a rock in 1986 though."

https://forum.dcs.world/topic/254210-di ... 95824_menu

ELBOB · Mon Aug 15, 2022 12:53 pm

RJMAZ wrote:
Second reason. Delta wings land at a very high angle of attack. They don't have flaps.

Third reason. Delta wings land at high speed again they don't have flaps.

F-16XL landing approach: 13 deg AoA, 195 kts. Source: AvWeek test flight, 23 September 1986

F-16C landing approach: 13 deg AoA, 160 knots light to 180 knots heavy

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