F-16XL

codeonemagazine · by **codeonemagazine** » 17 Jul 2010, 04:02

New Code One site just posted about twenty XL photos in high-res. Have more, but need to scan them first. Some show aircraft under construction.

geogen · by **geogen** » 17 Jul 2010, 05:41

codeonemagazine wrote:New Code One site just posted about twenty XL photos in high-res. Have more, but need to scan them first. Some show aircraft under construction.

Thank's for the head's up. Two pretty dynamic images in particular, if I can list them here:

strykerxo · by **strykerxo** » 18 Jul 2010, 15:43

Shot this video @ Edwards AFB 2009 Test Nation airshow

The F-16XL video is at the 1:45 mark, she is a beauty.

http://www.youtube.com/watch?v=NM5swD4iHlE

mlk32170 · by **mlk32170** » 19 Dec 2010, 14:42

The XL required considerably more development and cost. Canards on any 16 would require a redesign of the forward fuselage. Space for actuators doesn't exist on the present configuration. The structure of the nose section would could not handle the loads, forcing more redesign.

johnwill · by **johnwill** » 19 Dec 2010, 16:43

Canards were considered and rejected for a production version of the XL, but you are correct about more development and cost. The winning F-15E also required considerable redesign, development, and cost.

F16VIPER · by **F16VIPER** » 19 Dec 2010, 21:07

The -XL was suposed to be a supersonic cruise aircraft. Did it ever achieve it and what was the maximum speed, and if not, what was the issue.

johnwill · by **johnwill** » 20 Dec 2010, 01:50

It had no significant supercruise capability in mil power, about like any other F-16. However, max speed was never reached, due to political considerations and lack of analytical and wind tunnel support for those speeds. It was not allowed to exceed 2.05 mach. Let us say that at 2.05 there was lots of climb rate and acceleration available.

Flight control, flutter, loads, propulsion, and heating could have been problems, because no analysis or testing had been done to support anything above 2.0.

johnwill · by **johnwill** » 20 Dec 2010, 02:04

mlk32170 wrote:The XL required considerably more development and cost. Canards on any 16 would require a redesign of the forward fuselage. Space for actuators doesn't exist on the present configuration. The structure of the nose section would could not handle the loads, forcing more redesign.

Another comment is that finding space for canard actuators and strength for canard loads was not a big problem for the CCV YF-16 nor for the AFTI F-16. So if canards had been beneficial, you can be sure our designers and engineers could have made it work.

For example, the leading edge extensions were totally empty and could have easily accommodated canard actuators and loads. In addition, there was a 26 inch plug between the wing front spar and the cockpit. That area could also have acted as canard mounts if needed.

F16VIPER · by **F16VIPER** » 20 Dec 2010, 04:08

It had no significant supercruise capability in mil power, about like any other F-16. However, max speed was never reached, due to political considerations and lack of analytical and wind tunnel support for those speeds. It was not allowed to exceed 2.05 mach. Let us say that at 2.05 there was lots of climb rate and acceleration available.

Flight control, flutter, loads, propulsion, and heating could have been problems, because no analysis or testing had been done to support anything above 2.0.

Thanks John. Does it mean that the "S" side of SCAMP was just wishful thinking or aerodynamic impediments were discovered. What was the main impediment for supercrise not being possible with this plane given its more efficient ? aerodynamic shape.
Re max speed: would you please elaborate what the political aspects were.

geogen · by **geogen** » 20 Dec 2010, 11:41

Hey, it's great to see this thread pop back up from time to time!

Instead of traditional canards, I've wondered if the front AMRAAM pair could have been set back 2 feet or so, in order to allow for LCA Tejas-Naval style LEVCON controls above from where the front AMRAAM pair poke out their noses? Or would that have obstructed w/ the landing gear? If the case, maybe AF could have just accepted writing off the two front points altogether and make them up elsewhere in an air defense/Intercept sortie loadout. Perhaps in place, a couple 6' - 9', conformal EW arrays (or some other component/system) of similar width to the AMRAAM but set back allowing an effective LEVCON type control? (w/ controls possibly enabling lower approach speeds, faster low-level speeds and better instantaneous pitch/higher AoA?)

And great observation, johnwill, about F-15E requiring substantial development work too prior to becoming operational! Wise guy, lol :wink:

Anyhow, an F-16XL concept could have been just the starting point with so many plausible spiral developments and growth - possible in later blocks - as requirements became justified and the airframe/systems technology available.

One could continue w/ some conceptual ideas on that, but to save the boredom and in the interest of not conjecturing on various sensitive areas of discussion, I'll leave it here. Although one final point... I'm almost certain that someday LM will be kicking themselves they didn't partner up around the time block 60 was being studied and separately develop the XL which could have been available today at a discount to the still kicking F-15E class. Surely Congress would be having a field day with it at least - taking into account today's mode for contingencies...

If I could have the honor then to propose an hypothetical name for the woulda been operational example, I'd vote for: F-16 6G Strategic Falcon. imho.. :thumb:

johnwill · by **johnwill** » 20 Dec 2010, 15:25

F16VIPER wrote:
It had no significant supercruise capability in mil power, about like any other F-16. However, max speed was never reached, due to political considerations and lack of analytical and wind tunnel support for those speeds. It was not allowed to exceed 2.05 mach. Let us say that at 2.05 there was lots of climb rate and acceleration available.

Flight control, flutter, loads, propulsion, and heating could have been problems, because no analysis or testing had been done to support anything above 2.0.

Thanks John. Does it mean that the "S" side of SCAMP was just wishful thinking or aerodynamic impediments were discovered. What was the main impediment for supercrise not being possible with this plane given its more efficient ? aerodynamic shape.
Re max speed: would you please elaborate what the political aspects were.

SCAMP was a clever name, but I don't think anyone expected XL to truly supercruise given the engines of the day. The wing didn't really start to show its capabilities until higher machs were reached. Today might be different with the latest F-16 engines and possibly TV for better trim. It did not help pitch trim for the 30 inch longer aft fuselage (and engine of course) to be tilted up 3 degrees for runway clearance.

I can only give you an opinion, that of a mid-level engineer, not a manager type. It seemed to many people that the AF was dead set on the F-15E winning the competition, mainly to preserve the production line. The F-16 line was assured for many more years, but F-15 was nearing it's end. That was understood and accepted. We knew we had to be a lot better to win. A dramatic increase in XL top speed, while tactically useless, could be embarrassing.

geogen,

The XL AMRAAMs were total dummies, scabbed on to the lower wing and fuselage surface, with no troughs. So there were lots of possibilities for production mounting.

My proposed solution for the pitch control problem was to ditch the elevons and replace them with standard horizontal tails, nested well into the wing planform, similar to the F-22. More area, plus no aeroelastic loss from wing twist. The elephants weren't interested in a flight control proposal from a structures engineer.

I've mentioned before how the aft AMRAAMs almost caused us to lose one of the airplane. They were mounted directly in front of the lower speedbrake panels and shielded them from much of their normal airflow. That was not a problem at lower speeds, but at the first really high speed usage (1.6/30k), the upper door had its normal load, while the lower door had about half of its. That caused an big imbalance and the door mount structure failed. The door mount structure was also the hydraulic actuator, on system B I think. The pilot, hearing and feeling the the failure, retracted the brake. Chase couldn't see any problem, so the operation was rather unwisely repeated. This time the pilot felt and heard another failure, then saw the master caution and system B lights come on. A safe landing was made, but the failure was not our proudest moment.

ViperDude · by **ViperDude** » 20 Dec 2010, 15:49

JohnWill,

As I remember the XL AMRAAMS were made out of wood? I also remember the first time I ran a flight control bit and was surprised to see L, E, A, F lights in the cockpit instead of P, R, and Y lights. I will say that the flight control troubleshooting tester for the XL was very cool because it hooked up down below as I remember and I think you could use it with engines running. (I can't remember anymore..lol)

Cheers,

ViperDude

johnwill · by **johnwill** » 20 Dec 2010, 16:05

Yes, wooden AMRAAMs, with sheet metal nosecones and fins.

Looking back, I see I've told that speedbrake story more than once. Forgive me. My wife is probably right. She says I'm getting senile.

madrat · by **madrat** » 20 Dec 2010, 17:38

johnwill-

Can you give a rough drawing of your standard horizontal tails idea and missile mounting ideas? They sound interesting. And who in the hierarchy is an elephant? I am not familiar with that term.

Like this?

johnwill · by **johnwill** » 20 Dec 2010, 19:14

Your drawing is exactly what I proposed. I don't have any insight for missile mounting. What they had could probably have been made to work.

Elephants were just our term for any heavy weight manager. Big Dog, Honcho, whatever. The rest of us had to be careful not to get stepped on by an elephant, even inadvertently. Elephants don't always see where they step.