In our previous videos, we
have looked at several experimental U.S. aircraft pushing aeronautical limits
but never saw service the F-15 STOL MTD the F-16XL and the F-18 HARV to name a few. But there is one experimental aircraft
that stands out above all the others for its cutting edge design. The F-22 Raptor is often credited
as the most capable fighter aircraft today, although it remains
largely classified in its abilities. The Air Force considers it a top of
the line fighter for air superiority. However, as many are aware, the F-22 was not the only fighter
to compete for the position it now holds. In 1990, another 5th-gen fighter,
the Northrop YF-23, was also proposed. Today, many consider it an equal
and in some cases a superior design to the F-22. The history of the Northrup YF-23
dates back to 1981. The Air Force had released a request
for information (or RFI) to some of the top aircraft companies. Seven responded, and over the following
months, many proposals, 19 in all, were presented. These varied greatly in design
and predicted capability. The Air Force were after a design
that was stealthy, highly agile with superior radar, avionics
and the ability to supercruise, that is, to sustain supersonic flight
without using afterburner. In 1986, the two winners
of the initial program were announced: Lockheed with its YF-22 design
and Northrop with its YF-23 design. Rather than sending the other
five companies home, the prime contractors were given the
opportunity to partner with one of them. Lockheed chose Boeing
while Northrop chose McDonnell Douglas. Over the next four years, both Lockheed
and Northrop would have the opportunity to develop
their concepts into working designs. This would be part of the advanced
tactical fighter competition. Whatever they developed would be judged
against the competing demonstrator, and the winner would have that aircraft become the Air Force's preeminent
air superiority fighter. Unlike the Lockheed YF-22 design,
which put much emphasis on thrust, vectoring, the Northrop YF-23
would use no such technology. Northrop engineers
believed that thrust vectoring benefits could be achieved through other means and that thrust vectoring nozzles
without too much weight to the airframe. Rather, the aircraft would use
Single Expansion Ramp Nozzles, (or SERNs). Thrust from these engines flow through troughs
lined with transpiration cooled tiles. This method, similar to that
used on the B-2 bomber, dissipates heat, thus reducing infrared image and lowering
that chance of an IR missile lock. The unique shape of the SERN nozzle also hinders ground
launched IR missiles from achieving lock. The overall airframe shape itself
was also unique. Diamond shaped wings and
a V-tail provided better stealth capabilities
without negating aerodynamic performance. It also made it
lighter and faster than the F-22, although the latter point
remains a matter of debate. Two test aircraft were produced: nicknamed Gray Ghost
(or PAV 1) and Spider (or PAV 2).
up to two different engines would be used. Two different engines would be used; One would use the
Pratt & Whitney YF119, and the other would use
the General Electric YF120. Both the YF-22 and the YF-23 prototypes
were almost equally matched. Both had similar engine
performance of 35,000 pounds, top speeds of Mach 2.2 and
similar combat operating ranges. However, there were some differences. For instance,
the YF-23 was a lighter aircraft and its maximum range
could extend out to 4800km. Whilst the production F-22
had a range of 3200km. The YF-23s airframe design
is said to have had a near invisible radar cross-section matching
the stealth abilities of the B-2 bomber. It could be argued that it had superior
stealth capabilities compared to the F-22, offering unique possibilities
for a stealthy aircraft. In terms of speed, the airframe
demonstrated excellent performance when flying transonic. In modern beyond visual range
engagements (or BVR), such capability is important,
particularly at higher altitudes. The characteristics of the airframe
allowed for supercruise up to Mach 1.6 (that is, without the need for afterburner). This capability would have allowed for better BVR performance
for longer periods of time without burning through massive amounts
of fuel while remaining stealthy. With afterburners engaged, however,
the aircraft was said to achieve a top speed of Mach 2.6,
slightly faster than the F-22 Mach 2.2, although there is no publicly available
information to verify the top speeds of either aircraft. In terms of agility,
the F-22 ultimately won the competition. Northrop's decision
to remove thrust vectoring came at a cost and this was reduced
performance at lower speeds. Although the YF-23 was lighter, at near stalling speeds thrust vectoring could do what the airframe of the YF-23 could not; and that was to generate
the necessary movements for maneuvering. A common source of data about the YF-23s capability comes from
test pilot Paul Metz. A Vietnam veteran, Metz would be selected to fly the YF-23 during the Advanced
Tactical Fighter program. Here he got to see just how capable the
aircraft was, albeit as a demonstrator. Later, he would fly a pre-production
variant of the F-22, which by then had been commissioned following its victory in the Advanced
Tactical Fighter competition. Having flown
both aircraft, Metz offers important insight into just how good the YF-23 was. In terms of performance, he remembers the YF-23
as being particularly capable in high AOA situations, operating at trimmed
angles of attack up to 60 degrees. The F-22 could also achieve this, albeit
with the aid of thrust vectoring. He concluded that the YF-23 not only matched but potentially
outperformed the F-22. This judgment came after Metz began flying
pre-production models of the F-22, which would have been more advanced than
the demonstrator used in the competition. The exact reasons for his judgment
remain unclear, and we can only assume classified data about both aircraft
played a part in his final verdict. According to Metz, the Northrop engineers
were perhaps the best in the business, but they were engineers and presented
everything in technical terms, as you'd expect engineers to do. In contrast, Lockheed knew that marketing
and lasting impressions were important - potential purchasers
may not be technically astute. Thus, a focus was placed on
showmanship directed toward acquisition decision makers. The competition would technically begin
with the rollout of the two competing airframes. Northrup would present the YF-23
for the first time at a ceremony at Edwards Air Force Base
on June 22nd, 1990. This first YF-23
(Gray Ghost or PAV 1), would undergo a series of ground tests
over the following weeks before taking to the sky
for the first time on August 27th. Paul Metz recalls that the flight was good,
the aircraft was solid, and the F-16 escort plane
had to use afterburner to keep up with his Pratt & Whitney powered aircraft. The day after this successful test, Lockheed rolled out their YF-22 prototype. Speeding up production, Northrop then approved a mid-air
refueling test on the YF-23s fourth flight. Trailing a KC-135, the YF-23 would spend 3 hours
connecting and disconnecting at various speeds, proving it was capable. Flight number 5 saw the first supersonic test
this to prove successful. And by flight number 11,
the final pilot checks had been completed. The second aircraft, Spider or PAV 2, would emerge on October 26, 1990. Using the GE engines, test pilot Jim Sandberg would
take it for its first flight. However, it was at this point that the Northrop team
began experiencing difficulties. On October 30th, 1990, test pilot
Bill Lowe witnessed the outer layer of his windscreen shatter on Gray Ghost
while flying at Mach 1.5. Fortunately,
the polycarbonate layer remained in place and the aircraft returned safely. Not long after the same issue
occurred on the Spider. This was a major problem. Not only was it a potentially fatal flaw,
but any integrity breach to the specially designed windscreens
would increase radar cross-section, decreasing its stealth characteristics. PAV 2s second flight
would also prove troublesome. After taking off, one of the GE
engines experienced problems and would not accelerate and a single
engine landing had to be made. During flight 3,
there was an almost fatal incident when a plugged line resulted in the fuel
tanks over pressurizing. Luckily, this was picked up before the aircraft climbed too high
and a safe landing was achieved. Both PAV 1 and PAV 2 would undergo
maintenance to prevent further issues. And for the most part,
this appears to have succeeded. Both Gray Ghost and Spider
would fly together for the first and only time on November 29th, 1990, piloted by Metz and Sandberg
over the Mojave Desert. The next day, PAV 1
would be taken for its last flight and then retired. With funding running out
as the program neared its end, focus was placed on PAV 2
for the following month. New supercruise
capabilities were supposedly tested with the speed results
remaining unreleased to the public. Things would soon wrap up for PAV 2 as well. On December 18th, PAV 2
would be sent up with Lockheed's YF-22 prototype for a 15 minute
photo shoot. This would be the only time
the two aircraft would fly together. Later that same day, test pilot
Ron ‘Taco’ Johnson would take the aircraft on its final flight,
a two hour test mission. For the months following this, both YF-23s
would remain on the ground. Except for a number of taxi runs
to keep the aircraft in flyable condition, they would never be used again. The end of the YF-23 program
would come on April 23rd, 1991, with the YF-22 becoming the aircraft of choice. The Air Force contracted
Lockheed to produce the F-22 Raptor, establishing the aircraft
as the premier American fighter. The F-22 was using proven design
principles and technologies, which had been integrated
into other designs, very different to the more radical YF-23 that may have been perceived
as too much of a risk. After all,
this was to be the top line fighter, and risk mitigation
would have been a high priority. The YF-23 also lacked a demonstration-ready weapons bay, not being a requirement
for the competition. This omission may have raised concerns
about the concepts reliability and stealth capability. Thus, both YF-23s were put
into storage and later sent to museums. Other offshoots from the program,
including schematics for the production F-23 variant and the proposed
Navy variant (the NATF-23), were shelved. Today, the YF-23 remains
a legendary aircraft among enthusiasts. Its unique design, cutting edge technology
and overall ability to hold its own against the F-22, at least on paper,
has only added to its reputation. No doubt hypothetical comparisons
between the F-22 and the YF-23
will continue for years to come, or at least until all
available data is released. The YF-23 may not have been
as polished as the F-22, but it remains, according to the only pilots
who have tested both aircraft, a formidable dogfighter with great potential.
