F-16XL Images

[Old Viper Tester]

I had previously submitted some F-16XL images to Pappy's Skunk Models F-16XL WIP

 

Unfortunately, with the Photobucket third party posting debacle, all of those image links have been broken. Anton K55 asked if I would repost them for reference in his build. Here is my best guess of what was posted earlier - I'm still working on cleaning up my XL slides for a more coherent posting. 

 

I had been posted as a flight test engineer to the F-16XL Combined Test Force after graduating from the USAF Test Pilot School. Made a right pest of myself with my camera from mid-1982 to early 1984...

 

 

 

T-lug suspension in the stores pylons, hence no sway braces

 

Underside of XL-1 showing shadows of pylon locations. That's a spin recovery parachute quadrapod and canister mounted above the exhaust nozzle

 

XL-1 with BDU-38s. Note the brackets fore and aft of the mid-body fins of the AMRAAM shapes. The ARAAM dummies were bolted to the airframe as there was no missile suspension/launcher equipment installed in the airframe.

 

XL-1 with CBU-58s.

 

Most of the CBU store load outs used what were then call Tactical Munitions Dispensers, later became the CBU-87 series of canisters, which were painted gloss OD

.

XL-2 tucking in with the T-38 safety chase

 

XL-2 aerial refueling

 

Belly shot of XL-2 in Heater-Ferris scheme

 

Some detail shots

 

 

XL-1 inlet antennas

 

XL-2 UHF antenna relocated near the tail hook 

 

Total Temp probe and raked cooling inlet - this intake is vertical on stock F-16s

 

Two left-side AOA probes on the XLs

 

This shot was after the aircraft was repainted in overall camo, the shadow of the blue spine remaiins

 

Thanks for looking 

Sven

Edited February 26, 2018 by Old Viper Tester

[Giorgio N]

Great shots, thanks for sharing !

XL-2 has long been one of my favourite modelling subjects, one day I'll finally manage to build a model of this aircraft

[Vingtor]

Thanks for sharing the photos, Sven!

3 hours ago, Giorgio N said:

XL-2 has long been one of my favourite modelling subjects, one day I'll finally manage to build a model of this aircraft

So will I. I have the Skunk Works kit as well as a Kitentic F-16D.

 

Do you know the FS colours for the markings? I might possibly do a new set....

 

Nils

[Old Viper Tester]

3 hours ago, Vingtor said:

Do you know the FS colours for the markings?

Nils,

General Dynamics Drawing No. 400N002 lists the grays as:

 

Light Ghost Gray, FS 36375 
Intermediate gray #1, a 25/75% mix of FS 36118 and 36375 
Intermediate gray #2, a 50/50% mix of FS 36118 and 36375 
Gunship Gray, FS 36118

Lt gray, 36270 tail serial

Lt gray, 36320 radome

 

Unfortunately, the reproduction of the black and white drawing isn't very good and the way I read it, a different gray was to be used on the vertical tail above the base structure, but none of the photos (or my memory) show anything like that.

 

Of course this is what was proposed but may have varied when it got to the paint barn.

 

Sven

Edited February 27, 2018 by Old Viper Tester

[Britman]

Thank you for reposting . My favourite F16 and I wish it had gone into production. Many moons ago I made the Monogram F16XL as a six squadron what if with wrap around camouflage with all hard points occupied , just wish I could remember what  I did with it! 

[Robert]

Great set of photos. Thanks for posting them.

 

Was the only reason it lost to the F-15E was that it only had one engine ?

 

Robert

[Old Viper Tester]

2 hours ago, Robert said:

Was the only reason it lost to the F-15E was that it only had one engine ?

A lot of discussion about the driving factors for the decision, but I don't remember the number of engines being a deciding factor.

 

One of the things that the XL team commented on was that it seemed the rules changed in the middle of the competition. The program started out as the Derivative Fighter. The XL kind of went beyond the definition of 'derivative' with the obvious enhancements to the airframe. The XL pretty much kept the legacy F-16 avionics which already met the requirements for a multi-role mission.

 

McAir went a different way, the airframe changes were minimal considering that they had already proposed mission unique conformal tanks as far back as 1976 - Fuel And Sensors Tanks (FAST Packs) - one even suggesting a turret beneath the left tank for a directed energy (laser?) weapon. The F-15C already had the conformal tank capability, and whether anyone liked to admit it in the early Eagle days of "Not a pound for Air-to-Ground", there was already basic air-to-ground capability in the stores management system and HUD. McAir's big derivation was in the cockpits, the rear being "missionized" with added displays and controls for sensor management and targeting. The USAF really liked that and the competition went from "derivative" to "dual-role" fighter. The XL had a basic F-16B cockpit with GD promises too change it to meet USAF desires in Full-Scale Development.

 

The other major consideration was payload, with the low fuselage and all of those individual pylons all over the wings was tough to envision a weapons capacity/variety close to what the F-15E looked to be capable of. No one even envisioned conformal fuel tanks for the F-16 back then, so range, even with the bigger wing and fuselage extensions, was a concern.

 

I was off the XL program by the time the final decisions were being made, so maybe there were other factors, but these were the issues that I heard.

 

Sven

[Vingtor]

10 hours ago, Old Viper Tester said:

Nils,

General Dynamics Drawing No. 400N002 lists the grays as:

 

Light Ghost Gray, FS 36375 
Intermediate gray #1, a 25/75% mix of FS 36118 and 36375 
Intermediate gray #2, a 50/50% mix of FS 36118 and 36375 
Gunship Gray, FS 36118

Lt gray, 36270 tail serial

Lt gray, 36320 radome

 

Unfortunately, the reproduction of the black and white drawing isn't very good and the way I read it, a different gray was to be used on the vertical tail above the base structure, but none of the photos (or my memory) show anything like that.

 

Of course this is what was proposed but may have varied when it got to the paint barn.

 

Sven

Thanks, Sven!

 

On photos, it seems that XL-2 had all four star-and-bars in a light grey colour (possiblly FS 36375). Unfortunately only three are included on the Skunk Works decal sheet.

 

Nils

[Phantom726]

Thanks a lot for sharing....

 

 

[Vingtor]

On 2/26/2018 at 4:52 PM, Old Viper Tester said:

XL-2 tucking in with the T-38 safety chase

Sven, do you by chance happen to know the colour for the stencils and national insignia on XL-2 in in the Ferris scheme? Or have a guess.

 

Is it one colour on all, or several? It seems that the walkway line is in two greys here, as well as some of the forward fuselage stencils.

 

Nils

[Old Viper Tester]

2 hours ago, Vingtor said:

do you by chance happen to know the colour for the stencils and national insignia on XL-2 in in the Ferris scheme? Or have a guess.

Nils,

 

None of my references specify the grey for the markings. Pretty sure from the markings below the cockpit that at least two greys are used. My guess would be 36320 and 36375.

 

Interestingly, the only marking that was specified in the General Dynamics paint spec was the tail serial to be in 36270. Maybe the darker shade is 36270 instead of 36320?

 

Sven

[Vingtor]

The tail number seems to be a lighter colour. Nearly, but not quite, white. At least on some photos.

 

Do you know if it had "fake" (or extra) national insignia on the lower fuselage? It seems there might be so on the belly shot in your original post, just behind the turbine stripe. Very vague, as the colour is nearly the same as the background Ferris colour. You say nothing about this in the Quarterly article many years ago. The extra insignia are shown on the Skunkworks fictitious Ferris XL-1 drawings, though.

 

Nils

[Old Viper Tester]

31 minutes ago, Vingtor said:

 

Do you know if it had "fake" (or extra) national insignia on the lower fuselage? It seems there might be so on the belly shot in your original post, just behind the turbine stripe.

TBH, I don't know that I ever noticed them. The contrast seems to be very low and I can't see it on most of my images but you are correct, there are mirror national insignia on the lower fuselage.  Here is a GD image (GD31-28347) where I can make out the national insignia on both sides immediately aft of the turbine warning stripe

 

Enlarged

 

yet on my image, below, I can't make them out. I can convince myself there is something there, but it is not distinct.

 

As for the tail number, my original impression was that someone went to the trouble to mask the white serial number, then after the Ferris scheme was applied, the white was toned down. Not the first time a spec wasn't followed.

 

Sven

[Vingtor]

Great photos! Thanks.

 

It seems that the lower side wing roundel could be the same colour as the palest Ferris colour- i.e. 36375.

 

Nils

[Vingtor]

Having studied the photos a bit more in detail, there is something brownish between the forward missiles and the fuselage....

[F-32]

Great shots, always loved that jet

[Hook]

Great stuff. That's the first time I noticed the fake AAR markings on her belly.

 

Cheers,

 

Andre

[Aardvark]

On 2/27/2018 at 2:02 AM, Old Viper Tester said:

The other major consideration was payload, with the low fuselage and all of those individual pylons all over the wings was tough to envision a weapons capacity/variety close to what the F-15E looked to be capable of. No one even envisioned conformal fuel tanks for the F-16 back then, so range, even with the bigger wing and fuselage extensions, was a concern.

 

But how I reading in my Russian sources (It's TcAGI magazine. It's magazine was in USSR not for mass sale, only for aircraft scientific and military):

F-16XL have cruise supersonic without external  loads

and cruise sonic with 6 AAM & 12 bombs on maximum without

afterburner engine mode. Besides, as I read, F-16XL have  maneuverability with 6 AAM - 9,1G an 7,2G with  6 AAM & 12 bombs.

It's very impressive characteristics!

I doubt that the F-15E can boast the same!

Probably there was an underestimation of the characteristics of the MiG-29 and Su-27 in matters of maneuverability?

 

B.R.

Serge

[Old Viper Tester]

21 hours ago, Aardvark said:

F-16XL have cruise supersonic without external  loads

and cruise sonic with 6 AAM & 12 bombs on maximum without

afterburner engine mode. Besides, as I read, F-16XL have  maneuverability with 6 AAM - 9,1G an 7,2G with  6 AAM & 12 bombs.

It's very impressive characteristics!

I doubt that the F-15E can boast the same!

True, as the TSaGi comparisons show (I can't remember the last time I really looked at a PsubS chart!), in many ways the XL design had many advantages over the basic F-16. And some of the performance points were better than the F-15E.

 

XL-2 did 'super-cruise' in Mil power with the GE engine, but just barely. I'm sure with the F110-GE-129 version the super-cruise performance would be better. And maneuverability with the weapons configuration cited was also very good.  But these are point design considerations. A DoD source selection often takes into account a lot more than the aircraft performance. The ins-and-outs of many source selections have been the subjects of post-graduate courses, and, as I noted above, I probably don't know all of the factors in the XL vs. F-15E decision. I'll offer for consideration:

 

  The rules did change when the evaluations moved from a "Derivative Fighter" to a "Dual-Role Fighter". The F-15B Strike Eagle test bed already offered more of what the USAF was looking for than the XL at the end of the competition - though General Dynamics promised a lot more if the design went into Full-Scale Development.

 

  By 1983, the USAF was not only looking for an F-4 multi-role replacement, which the F-16A was already taking on, but also an F-111 replacement for the tactical penetration, AKA strike, mission. I've already mentioned the range issue for the latter mission, but there was also the payload and variety of weapons required. Twelve Mk 82s for a Warsaw Pact scenario were not always going to fill the bill. Consider that if the load called for any of the 2000-lb class weapons, the XL was immediately at a disadvantage, add to that the logistics issue of having to change out all of those "tangential carriage" pylons when going from 500-lb to 2000-lb weapons.

 

  Then there is the tangential carriage arrangement itself. The spacing of all of those pylons was optimized for the Mk-82, after all, that was one of the original specifications for the DRF. That arrangement allowed for the oncoming airflow to wend its way around and between the bombs with little drag penalty. But then the evaluation started looking at weapons dispensers... The CBU-58 added considerable drag and they didn't even try to carry 12, it was bad enough with three in tandem on each side. Then came the Tactical Munitions Dispenser (TMD), or SUU-65 dispenser, what eventually became the dispenser for the CBU-87 series of weapons. The flatter nose of the TMD added considerably more drag and the proximity to the wing with the stub pylons did not help. General Dynamics went so far as to try this:

 

That's an aerodynamic cone that shields the nose of the TMD - note the cutout to allow the nose-fuse assembly to clear - though I'm pretty sure they never tried weapons separation with these things. And once you did drop the weapons, there is a base drag penalty for having that open space behind that cone that was supposed to help the drag situation. Granted, the F-15E has similar, but not as great a drag penalty carrying twelve CBU-87 and all the follow-on CBUs, but the weapons spacing is better and the F-15E is a brute rather than the elegant solution that is the XL.

 

In addition to the TMD aero fairing, there were also mentions of a "fin fairing" in the XL test plan, but I never saw it or if it ever even showed up at Edwards.  In any case, any unique logistics pieces associated with an aircraft are more points against it in a source selection.

 

And finally a word about radar: all other factors being equal, the amount of radiated power coming out of the front end is proportional to the size of the dish, or the aperture for electronically-scanned arrays. This is one of the reasons the F-15 was so large to begin with for the air superiority mission. The more power radiated, the better the range and resolution capability. For the strike mission, the APG-70 with added air-to-ground modes offered much better performance over the APG-66/68. The XL design would always be restricted to a smaller radar than the F-15.

 

There were a lot more comparisons that swung the decision to the Strike Eagle, but it would fill a book.

 

vr,

Sven

 

Edited May 24, 2018 by Old Viper Tester
correcting auto-correct, added data