Where YF-16 #72-1568 begins to stand out and helped change the fighter world are the innovative advantages the jet had over previous fighter models.
A New Fighter is Needed
Bigger, faster, and with a longer range, American airpower strategy in the Vietnam War focused on penetrating enemy territory from further distances and taking out aircraft before they ever entered the sky. Fearing a repeat of the Chinese entrance into the Korean War, the Air Force shaped this strategy to target enemy air bases such as Phuoc Yen and Gia Lam near Hanoi and those north of the Yalu River in China.
The Air Force shaped their forces for a war that did not happen. Orders came down to wage a limited war against the communist in Vietnam, and the bigger, less maneuverable, and more costly jets the service had focused their efforts in developing became ineffective in the soon-to-be air-to-air combat.
To make matters worse, the F-4 Phantoms’ AIM-7 and AIM-9 missile systems had success rates below 20 percent. Without an effective weapon for the F-4 to fight against the quicker and nimbler MiG-17, MiG-19 and MiG-21 fighter jets, the highly trained US pilots were left frustrated, empty-handed, and unable to protect their assigned bomber groups.
It was during this crossroads in fighter development and limited warfare that the “Fighter Mafia” formed. This informal group of experienced military aviators, technical experts, and defense analysts passionately fought to catch up US technology with Russian MiGs.
John Boyd, a pilot and engineer set out to prove it. As a result, he ended up creating what is now known as the Energy Maneuverability Theory, which quantified the performance variables of jets based on thrust, weight, aerodynamic drag, wing area, etc. for the first time. Most importantly, it proved to top Air Force brass that the MiG-21 was able to outmanoeuvre every single jet in the U.S. arsenal, and, in 1972, the Lightweight Fighter Jet Program was born.
Contest
The Lightweight Fighter Program set out to develop a smaller, cheaper, and less complicated fighter jet that could create and maintain dominance in hostile skies.
The program put out a set of baseline objectives, requesting a 20,000lb fighter with high maneuverability, quick acceleration, long range, and specialized to compete at combat speeds between .6 and 1.6 Mach at an altitude range of 30,000 to 40,000 feet. But it came with a kicker that each jet had to cost under $3 million – a cool $18.5 million in 2020.
Five companies entered designs which were quickly whittled down to two, the General Dynamics YF-16 and the Northrop YF-17. Although they never flew head to head in simulated combat, they did fly against other fighters in the U.S. arsenal plus some “acquired” Mig-21s. Within two years the Air Force had chosen the innovative YF-16, purchasing an initial 650 aircraft and four NATO countries vowing to buy an additional 348.
Sharing Parts and Cutting Costs
The General Dynamics YF-16 development offered a unique high-performance capability for an extremely low initial cost.
One of the most cost-effective practices used to build YF-16 #72-1568 was using parts from other aircraft with active production lines. Sharing the same supply lines was a dual benefit for the Air Force by becoming less threatening to the ongoing F-15 program, and enhanced its attractiveness to other countries.
The YF-16 utilized the power plant production lines building the Pratt & Whitney F-100 turbo fan used in the F-15’s development. The single engine cut cost per flight hour nearly in half while using a proven power plant that did not threaten the beloved F-15.
Another critical item taken was the Escapac ejection seat. This would later be replaced with the ACES II model used in the F-15 and A-10. The ACES II was slightly modified by moving the firing control handles from the sides of the seat, to a single “D” ring in the middle between the pilot’s legs saving testing and production time.
Not to overlook smaller details, even the tires were taken from the B-58 Hustler. Lastly, for the gunslingers in the sky, the M61A1 6 barrel 20mm Vulcan Cannon was mounted on board. Before being chosen for the YF-16, the Vulcan had nearly 20 years of proven performance on six different fighter and even two bomber platforms!
The YF-16 #72-1568 was originally designed with a wing area – 20 square feet smaller and a mind boggling 26 inches shorter than expected, but new requirements came as the mission set became expanded. Since General Dynamics only designed the aircraft for fair weather day fighting, there was originally no need for the Westinghouse APG-66 radar. Fitting this in mandated that the nose cone be extended. Production models were extended 10 inches in the middle to allow for greater fuel capacity and 16 inches in the radome to fit the large radar.
Cockpit and Egress Systems
Where YF-16 #72-1568 begins to stand out and helped change the fighter world are the innovative advantages the jet had over previous fighter models.
It has the ability to pull 6.5 Gs with a full internal fuel load and an astounding 9 Gs with a smaller fuel and weapons payload. This was only made possible because of three main changes in aircraft design – fly by wire, a new G-suit, and a greater slope for the ejection seat.
The most obvious change for pilots was the new fly by wire system which removed the control stick from between the pilot’s legs and mounted on the right-hand side of the cockpit. While the first digital fly by wire system was used by NASA in the space capsule and in an F-8 test jet, the two YF-16s were the first to use the slightly more reliable analog fly by wire. The system took the physical load of pulling a traditional floor mounted stick off the pilot by processing the side-mounted control stick input through a quad computer system, then using the hydraulic system to make the desired adjustments. This decreased the reaction time and allowed the pilot to get inside an opponent’s reaction cycle. This fly by wire system also allowed the engineers to move the center of gravity aft with the computers making up the difference in controls.
To reduce the enormous stress of the G forces placed on the human body, the engineers tilted the ejection seat from the original 13 degrees which can be seen in the F-15, A-10, F-4, etc. to 30 degrees.
To further decrease the likelihood of a blackout during high-G maneuvers, a new G-suit regulator was incorporated which would inflate more rapidly.
Unlike production models, unlocking and raising the canopy were two separate systems. Mounted on the internal forward canopy frame were two levers that, when pulled aft, unlocked the canopy hooks. These two levers were connected to flexible screw drives that were built into the canopy frame. The task of raising the canopy was done by an electrical switch which activated the pneumatic actuator mounted in what is now the avionics bay behind the cockpit bulkhead. When activated the actuator raised the canopy by rotating the torque tube which was co-located in the avionics bay. This enormous torque tube spanned the width of the jet and bolted directly to the canopy hinges externally.
During an emergency, the pilot had explosively fast options at his disposal, but none of them were redundant. If the pilot had to eject during flight, he had to first eject the canopy via the internal canopy jettison handle. This connected to a single canopy thruster on the left side of the fuselage which would unlock the hooks and push the canopy into the wind stream, ripping it back with enough force to break free of the torque tube. The pilot could then pull the ejection control handle on the seat to eject. With the solid polycarbonate transparency, it would have been impossible for the pilot to eject should the canopy hooks get stuck.
Externally, there was a lever on the left-hand side of the canopy that would pull out and rotate up to unlock the hooks and raise the canopy. Jettisoning the canopy on the ground was risky prospect as well. There was a single emergency canopy jettison handle on the right-hand side of the forward fuselage, the same spot where it is on production models. This handle however activated a single canopy thruster on the fuselage side that unlocked the hooks – manually raising the canopy would be necessary to rescue the pilot. This system did not have the capability of forcefully ejecting the canopy while on the ground from either canopy jettison handle, wind speed was required.
After Winning
Winning the Air Day Fighter Fly-Off was just the beginning of the Lightweight Fighter Jet Program.
The YF-16 #72-1568 was used for testing weapons like the AIM-7, ATLIS II laser targeting pod, and helmet mounted sight systems to name a few. When the aircraft was not testing it was used for air shows and static displays. At one point it was painted with a blue navy scheme to compete in a separate fly off, but due to the single engine and numerous modifications which added weight, the YF-17 (what is now the F/A-18) was selected by the US Navy instead for both the fleet service and the famous “Blue Angels.”
Sadly on May 8th 1975, during a practice flight for the Paris Air Show, the main landing gear got stuck. The pilot troubleshot the issue in flight until his fuel was nearly empty, and without time to scramble a tanker, was forced to belly land in the grass next to the Carswell, AFB runway. Upon inspection it was apparent YF-16 #72-1568 had significant damage on the inlet, a cracked bulkhead and radome, and other issues, the aircraft was put into storage for what appeared to be good.
The YF-16 #72-1568 would not be put to work again for another five years. In 1980, it was shipped from Fort Worth to the Air Development Center in Rome, New York to be used in testing. The aircraft was modified to mimic a production model by chopping the plane in half to insert a 10-inch plug behind the cockpit, fitting the larger nose radome, adding spacers inside the wings, stripping out all of the internals, and fitted with objects to be tested. YF-16 #72-1568 would be used to test everything from new antennas to external fuel tank to radar signatures at different angles.
In 2019, after 48 years and unimaginable number of tests, the Fort Worth Aviation Museum partnered with the National Museum of the Air Force and brought her back home, on loan, to be completely restored to the original condition and proudly displayed to the public. It is only with the help of knowledgeable volunteers from the Fort Worth Aviation Museum, Lockheed Martin, the 24th Fighter Squadron, and a host of local aviation experts that this restoration was possible.
Photo credit: U.S. Air Force, Lockheed Martin and Fort Worth Aviation Museum
