The F-15 has long been a legendary fighter, but NASA’s ACTIVE program aimed to make it even better. Faced with the looming threat of nuclear war with the Soviet Union, the United States began testing next-generation capabilities before the 10th F-15 even rolled off the assembly line.
In the 44 years since the F-15 Eagle first entered service, the air superiority fighter has proven its combat mettle time and time again, racking up an astonishing 104 kills against enemy fighters without ever losing a bout. Today, the twin-engined F-15 remains the fastest fighter in the American stable — with a top speed of Mach 2.5 that eclipses both its super-computing younger sisters, the F-22 and F-35.
Related: WHY IS AMERICA BUYING THE F-15EX INSTEAD OF MORE F-35S?
There’s no doubt that the F-15 is among the world’s most capable dogfighters, but that doesn’t mean nothing on the aircraft could be improved by throwing a bit more money and research at it–and that’s precisely what NASA chose to do with its Advanced Controls Technology for Integrated Vehicles (ACTIVE) program (among some others). In order to explore new possibilities, the Air Force decided to take a prototype for what would have been the two-seater F-15B and use it as a one-off technology demonstrator in a series of advanced efforts.
What resulted was a Frankenstein fighter with a variety of components and systems that managed to make the legendary F-15 even better.
F-15 STOL/MTD (Short Takeoff and Landing/Maneuver Technology Demonstrator)
In 1984, the Flight Dynamics Laboratory out of the Air Force Aeronautical Systems Division awarded a contract to McDonnell Douglas to begin development on an F-15 concept that would allow these highly capable fighters to take off and land on short or damaged runways. The concept was fairly straightforward: In the event of a war with the Soviet Union, airstrips would likely be among the first targets. As a result, the Air Force wanted to ensure they could still get fighters in the air even after such a bombardment.
These efforts to modify the F-15 to take off from water-soaked, damaged runways were bolstered by the introduction of thrust vectoring technology. Thrust vector controls allow the pilot to literally aim the outflow of thrust from their aircraft’s engines (independent of the fuselage itself).
In more advanced thrust vectoring platforms like Russia’s Sukhoi Su-35, thrust vector controls allow the jet nozzle to move in any direction, whereas the experimental F-15 STOL/MTD utilized a simpler two-directional thrust vector control that allowed the pilot to orient the outflow of thrust up to 20 degrees up or down.
Related: THAT TIME AN F-15 LANDED WITHOUT A WING
That vector control of the engine outflow was further supported by the addition of canards in 1988, just in front of the F-15’s traditional wings. The canards themselves were actually modified horizontal tail surfaces stolen from the F/A-18 Hornet.
By using these additions, the F-15 tech demonstrator managed to take off at speeds as low as 42 miles per hour, and reduced the length of runway required for takeoff by 25%. In order to shorten landing requirements, the program leveraged reversible thrust from the aircraft’s engines in conjunction with its canards and thrust vector control to reduce landing roll by a whopping 78%. While a standard F-15 Eagle needed more than 7,500 feet of clear runway to land, the F-15 STOL/MTD could do it in just 1,650.
The front canards also served to increase maneuverability at lower speeds. A similar approach has since been adopted by China’s Chengdu J-20, the nation’s first stealth fighter.
NASA’s F-15 ACTIVE
In 1993, the Air Force handed the keys to their F-15 STOL/MTD to NASA for the purposes of their new ACTIVE program, which was short for Advanced Control Technology for Integrated Vehicles. Building off of their previous digital flight control programs like HIDEC and Performance Seeking Control (PSC), NASA opted to retain the unusual wing layout of their new F-15 in the ACTIVE program, hoping to use the fighter as a testbed for a whole swath of systems that could come to find use in the next generation of fighters.
However, the F-15 ACTIVE did test some flight systems that would go on to find a home in the forthcoming F-15E Strike Eagle, or a variant of the F-15 intended for air-to-ground engagements. In fact, during the ACTIVE program, the cockpit of the testbed F-15 was modified to match that of the F-15E.
Another important change NASA made in their F-15 ACTIVE testbed was the introduction of Pratt & Whitney pitch-yaw balance beam nozzles (PYBBN) on a new set of engines; the F100-PW-229. Unlike the previous thrust vector control apparatus under the STOL/MTD program, these new nozzles offered a full 360-degree arc in which the nozzles could redirect outflow.
Related: HOW AN F-15E SHOT DOWN AN IRAQI GUNSHIP WITH A BOMB
Combined, these systems produced a new aircraft that bore only a passing resemblance to the F-15 it started out as, and according to Air Force and NASA observations, was actually a better performer in the air.
“The F-15 ACTIVE flying qualities are significantly improved over production F-15 aircraft. Aircraft response is crisp and heavily damped throughout the research flight envelope.“NASA Active Flight Research Program Report
NASA officials estimated that stability at supersonic speeds was improved by a factor of more than 100% by the addition of the new front canards,
Still an F-15, but no longer ACTIVE
The F-15 that found a home in both the STOL/MTD and the ACTIVE programs (serial number USAF S/N 71-0290) would go on to continue serving as a technology testbed for programs like IFCS (Intelligent Flight Control System) and others. Throughout all of its testing iterations, the front canards and thrust vectoring power plants remained on the aircraft, which, along with its spectacular paint job, make it hard not to notice just how different this incredible fighter really was.
The intent behind these efforts was never truly to add to the capabilities of the F-15, but rather to test what capabilities the United States could develop for further generations of fighters, but in doing so, NASA and the Air Force also proved that the F-15 was, and remains, much more than the sum of its parts.
The F-15 used for these programs was ultimately retired on January 30, 2009.
Read more from Sandboxx News:
- The Air Force’s F-15E ‘bomb truck’ can now carry 15 JDAMS
- Retired F-117 Nighthawks show up in Fresno to train against F-15s
- Air Force’s new F-15EX makes dogfighting debut in Alaska war games
- The USAF once intercepted a pilotless MiG over Europe
- The Air Force wants a new fighter to fill in for the F-35
This article was originally published 12/7/2020
Feature image: NASA
The F-15SMTD could fly at 42 knots. Twenty degrees nose up, on a blow torch of burner. It could not take off at those speeds. It would scrape.
The F-15SMTD mod added 2-3,000lbs (part of me wants to say 5,000) of structure to the back end of the jet. So much that it had to be ballasted out at the front. Added to this, it was using either the PW-100 or early PW-220 engine. It did not have the power to be Ps ‘maneuverable’ let alone point-and-click /agile/.
It was almost entirely oriented around a false ATF assumption (for a jet with an 800nm combat range, half of which was supposed to be at supercruise) that the ability to operate from damaged roadways was necessary or wise on a jet which, optimally, would have had 25,000lbs of fuel and could launch from Lakenheath, fly to a tanker orbit outside the Kattegat and then head East.
Pulling 10% of the ATF KPP performance target saved what was, at that time, a failing for weight program and the design element which went was the heavy, non-stealth thrust vectoring/reversing nozzles which were made from single units of chemically milled titanium and were devastatingly expensive.
And so, when the SMTD flew in 1987-88, only two years before the YF-22/23 CD demonstrators, it was as a hollow, ‘aero sciences’ demonstrator, the capabilities of which could not and were not transitioned on to the YFs let alone the production ATFs.
What the SMTD could and did do was demonstrate the ability of an F-15E level avionics suite to (APG-70) take SAR pictures of a runway, choose the aimpoints ‘between craters’ to land on.
And then fly an auto tactical orbit and controlled glideslope approach, with the pilot monitoring via the (AAQ-13 LANTIRN Navpod) HUD FLIR and the aircraft via a ladder into a very tightly controlled scatter as manual or auto flare. The vanes were set to kick as soon as weight came onto the nose gear and these plus canard deflection slowed the jet, in a shake-rattle-roll hurry from 120-140 knots. Like a nightmare carrier approach.
An excellent idea, avionics wise, for something like an ESTOL special forces insertion aircraft, landing sneakily on a road someplace in the back of beyond. But not something a fighter wants to do, especially as part of a dispersal-to-roadbase adventure, simply because of the 18,900lbs+ fuel that even the productionized F-22 still carries. That’s a semi-truck worth of gas, per jet, per sortie folks. Try maintaining convoys of fuel hauling all that gas, covertly, into the boondocks as a flood of refugees head >>>>>>>Elsewhere in all lanes.
Now try the alternative: Flying in from outside the immediate combat theater, using a real MOB with 500,000lbs of gas in underground bunkerage. Keep your HAS farm, your weapons igloos, your hush house and clean room, and your BOQ/Command Condo safe behind walls of IAMDS and concrete.
The real advantage of an SCM fighter’s ‘supercruise’ lies in the transit phase.
The canard installation blocked the gun, so you’d have to find a new place for that.
kevin r says
With a stall speed of 42 kts, it would be able to operate off of those USMC semi-carriers. It can’t land vertically, but if the boat’s going 20 kts, you’re only going to need a couple hundred feet to land. Yes, those canards are extra parts, but it’s a lot less than the contraption the F-35 is using.
Those canards are horizontal stabs from the F-18
I’m not sure of your source of, “IFCS (Intelligent Flight Control System)”. When I worked the jet the program was called IFFCS (Integrated Flight and Fire Control System). Not sure if we’re talking two separate programs.
Why are you still on Russia asare real enemy is China! Russia at most 3/10 the power it was. Yet still play with us with air and sea parades. China is are real enemy! This f-15b could be the future as they cost less to build and maintain readiness.
Devin Hill says
I’d rather not, with the articles and comments in addition makes it complex..
Seems such a waste.. they kept making F15s.. if this was the design of the EX with the current EX avionics, it would be am amazing 4.5 gen able to go toe to toe in a dog fight with any of Russian or China’s jets.
Bud Jenschke says
Thanks for the short trip down memory lane. I was the Air Force project test pilot for the S/MTD. It was an excellent test bed for its maneuvering and short field landing capabilities, but also for its fully digital flight controls, thrust vectoring/reversing technologies, and self-contained, autonomous precision landing capability. Let’s give Pratt and Whitney kudos for the engine technologies and both them and MCAIR for integrating the flight and engine controls. It went a long way toward proving the technologies we now find in firth generation aircraft.
BTW — I never heard it called a”Frankenstein” fighter, it is such prettier!
Andrew Toth says
I’d love to get your take on the experience of flying this beautiful machine. I was the lead software developer for the nozzle controller, and we may have met. You’d remember me as the 26 year old with the deer in the headlights look on his face when we shook hands. Scared the crap out of me to connect a real person to the ultimate user of the software. That project shaped my outlook for the rest of my life.
Graham Dicken says
The USA should use all available technology to kick those chink bitch slimmy cunts out the ball park .and smash there J20 creepy dragon peice of crap out of the sky
We never built these F-15s because those canards are just extra moving parts that will break eventually. We have been using our F-15s well past their design time lives. This never would’ve happened with more mechanically complicated F-15s. And for what? To shoot down obsolete Iraqi aircraft and to bomb caves in Afghanistan? There was no need.
In an active shooting war with a neer peer adversary then they would have been produced by the thousands till the advent of a stealth fighter. But without that dire threat, the ACTIVE served America no real purpose.
You don’t know till you try. It’s called aeronautics research. Lots of things are tried, and 837 was worth doing on many levels software, propulsion self healing flight controls etc
The F15 active can take off at 42 mph??!! WTF?
Don Winslow says
We should have continued to upgrade the F-15 to the F-15 Active level with thrust vectoring, front canards etc. Look at all the advanced models the Russians developed from the SU-27. The Air Force was afraid if they improved the F-15 too much Congress wouldn’t see the need for the F-22.
The F-15 is an outstanding jet, but it’s really misleading to state, “ Today, the twin-engined F-15 remains the fastest fighter in the American stable — with a top speed of Mach 2.5 that eclipses both its super-computing younger sisters, the F-22 and F-35.”
First of all, I’m not sure we actually know the top speed of the F-22. Publicly released figure is Mach 2.25. In reality it could be more or less.
Second, for an F-15 to hit mach 2.5 it has to be clean (e.g. not in combat configuration), with limited fuel, and at high altitude, and it can only hold Mach 2.5 for a very short amount of time.
The F-22 can reportedly supercruise with combat load at Mach 1.6, which means it can supercruise at the MAX speed of a F-36 and close to the MAX speed of an F-18. I’ve heard an F-15 can sort of supercruise for a little bit of time at just over Mach 1. Therefore in practical terms the F-22 is faster than both the F-15 (and the F-14).
edit: F-36 was typo, meant to type F-35
Jermel A Clark says
We don’t need no leaks with China looking at these articles and reading comments.
Andrew Thomas says
Man, the F-15 continues to impress me every time I learn more about it. Regardless of your feelings on warfare, this thing is no small feat of human ingenuity. With airframes like the F-15 and Su-35, we grow closer all the time to true science fiction fighter craft.