Update – The FX Fighters

The FX concept was broadly based upon a fighter aircraft falling somewhere between the Northrop F-5E and the General Dynamics F-16A in overall performance and cost. The fad that FX had been mooted back in 1977 was apparent in that both GD and Northrop were off and running with their various entries the day FX was announced in Washington. As the funding for such a project was to come totally from within that company’s resources, the development of an all-new purpose-built FX fighter was ruled out from the beginning. Locally then, both GD and Northrop were the two manufacturers best suited to be able to field a contestant for what is generally considered a minimum 1000 aircraft market through the next fifteen years.

Northrop opted for another upgrade of their immensely successful F-5 program to produce the GE F404-powered F-5G. General Dynamics decided to field a less powerful version of their potent F-16A and thus chose the well-established GE J79 turbojet to power their F-16/79. In order to better understand the two types, let’s take a closer look at them separately.

General Dynamics F-16/79

An interesting feature of FX, when comparing the two types on offer, is that Northrop chose to utilise basically an “old” airframe with an all-new advanced technology powerplant, while GD chose the opposite route with an all-new airframe utilising what is a 1950s technology engine.

From the US State Department’s point of view, the standard F-16A was simply too potent to sell off the shelf to many overseas nations. More importantly; following the Iranian debacle, there had to be safeguards instituted to prevent the Pratt & Whitney F-100 engine from becoming. Russian property. Therefore, GD had one path to follow – change the powerplant. In this case, the obvious choice was GE’s proven J79 turbojet which gave sufficient thrust to ensure that the F-16 was still competitive with MiG-21 and 23 threats while ensuring that the new FX derivative generally performed less spectacularly than its more powerful brother. The J79, of course, was in service with a large number of operators, maintenance skills were well-honed and most operators had well-stocked and technically competent overhaul facilities. Therefore GD considered the J79 would become an asset to marketing the F-16/79 worldwide.

To the purist, placing a 30-year-old design comparatively fuel-inefficient engine in such an advanced airframe as the F-16 was a bitter pill to swallow; yet in many instances, the J79-powered aircraft will outperform its turbofan brother and is actually faster in max Mach number owing to the different operating characteristics of the turbojet and a two-stage variable air intake.

The version of the GE J79 chosen for the F-16 is designated the – 17C and produces 11,810Ib thrust dry and 18,700 lb with afterburner at sea level. The J79 is 830 lb heavier than the F100 it replaces and thus requires an additional 300 lb of ballast against the nose avionics bulkhead to balance the critical C of G. Total weight increase over the F-16A is just 2000 lb in a dry configuration while the voracious appetite of the turbojet ensures that while the internal fuel capacity remains unchanged at 6970 lb, the endurance is somewhat reduced over that of the F-16A.

Apart from shorter legs, the F-16/79 can undertake an identical mission profile to that of its hotter brother. Avionics remain unchanged and a full range of PGM weapons can be carried including Maverick and various laser-guided bombs. With full internal fuel, two 370-gallon drop tanks, full ammunition for the 20 mm Vulcan and two Sidewinders the F-16/79 is able to climb to altitude, loiter for one hour, participate in a three-minute dogfight and return to base over a radius of 250 nautical miles. This is roughly half that of the F-16A under similar conditions. In addition to this range limitation imposed by the relatively thirsty turbojet, the F-16/79 is not equipped for in-flight refuelling to further “detune” the basic design. Carrying a load of six 1000 lb bombs plus the above payload results in a hi-lo-hi ground attack profile of again 250 nm.

The F-16/79 comes supplied with the standard Westinghouse APG-66 radar which offers four air-to-air and seven air-to-surface modes which provide the aircraft with a comprehensive clear weather attack capability far in excess of such past export notables at the Mirage, F-5E, MiG-21 and Starfighter.

Program status is virtually complete with GD’s product being first flown in October last year, just 10 months after the announcement from Washington which is positive proof of the relative ease in which the basic F-16A design was converted for the FX role. The intensive 70-hour two-month flight test has long been completed and the aircraft is now available for demonstration as required. Future interest was shown from Austria and Taiwan, though at the time of writing the former had virtually washed its hands of a fighter force. Taiwan is, as always, a political ham in _ the sandwich, though from GD’s point of view, their familiarity with the J79 in the F-104 is an ace in Fort Worth’s favour. Likewise Hawthorne-based Northrop can claim the same advantage from the fact that Taiwan operates over 200 F-5s. The flyaway cost of the F-16/79 is said to be $1. 5 m lower than that of the F-16A or about $9 m in 1980 figures.

Northrop F-5G

My good friend, Roy Braybrook, once mused to me over lunch in a Surrey inn that the company that produced an F 15 replacement was destined to line its bank vault with gold. I don’t know if Roy had the FX concept in mind at that time but as time passes it becomes more apparent that the F-5 replacement might Well in fact be another F-5, at least in the same vein as the F-5E Tiger II replaced the F-5A tomorrow the “G” will ultimately supersede the current E model. With over 2300 F-5s of all marques in worldwide use by some 27 operators, one must say that Northrop has the edge over GD in already “being there” as an operational entity.

The heart of the F-5G, of course, is its exceptional engine. I say exceptional, as more than ever, this is the very heart of a modern combat aircraft. Endurance, climb, acceleration and sustained turn rate depend so much upon an engine combining both high f\lel efficiency, lightweight and brute power coupled with a minimum number of moving parts and a low Mean Time Between Failure (MTBF) – the GE F404 is just such an engine.

If there are any tangible differences between the two rival FX contenders the arguments begin and end with the form of motive power. The F404 has only 14,300 parts as against 22,000 for the vintage J79 while both reliability and component Time Between Overhaul (TBO) improvements mean that the F404 requires vastly fewer maintenance manhours than the engines it replaces in front-line service. Fuel efficiency is such that the F-5G can go much further than the F-16/79 despite it having a greatly reduced internal fuel capacity.

An idea of just how the F404 transforms the F-5 is that the increase in installed thrust lines out around 60 per cent, enough to give the lightweight F-5G performance that leaves the F-4E Phantom in the dark. For instance, the F-5G climbs to 40,000 ft 18 per cent quicker than the F-4E, accelerates from Mach 0. 9 to 1. 2 24 per cent faster and has a 21 per cent better sustained turn rate than the hulking Phantom. For all this, the cost of operating a squadron of 18 F-5Gs at 20 flying hours per month for 15 years is around one-third that of the same F-4E unit. In an age of high fuel and manpower costs, even if qualified maintenance manpower can be found and retained, the advantages of the F-5G over such aircraft as the Mirage Ill, F-104, F-4, F-5NE, and even the MiG-21 where politics allow, are obvious.

The F-5E is powered by twin GE J85 turbojets of 5000 lb thrust each with an afterburner. The fact that even without afterburner the F-5G develops as much thrust as the F-5E in full afterburner is a significant statement to the potential of this lightweight fighter. Northrop would have done well to have developed a larger and more advanced wing for the new aircraft. This would have reduced drag at high angles of attack and increased turn performance substantially but would have not only exceeded the allowable limits of the original FX concept but would have also boosted per unit aircraft cost through the need for a lengthy development program of what would have been virtually a new design aircraft rather than a mere derivative. Just as the F-5E is more than a match for the MiG-21 the “G” will be able to remain competitive against such threats as the MiG-23 Flogger and the Sukhoi SU-22.

Like the F-16/79 the Northrop product carries a wide range of weapons ranging from dumb bombs through to various marques of laser-guided bombs and Maverick missiles. The “G” retains the twin 20 mm cannons of the Tiger II in addition to wingtip mounted Sidewinder MMs and is also cleared for the 30 mm GE podded cannon. Radar is the standard F-5E Emerson unit which falls far short of Westinghouse’s APG-66 though if the current parameters of FX are dropped in the future then Northrop will no doubt be offering export versions complete with a significant radar update (limited only by available space in the small nose) combined with an all-weather attack capability and AMRAAM missiles. Such an aircraft will certainly ensure that the F-5 family remain in production till the turn of the centurv.

If the F-5G can outperform the F-4E, then what is its field performance like? Here again, both FX fighters provide startling performance with the F-5G at gross takeoff weight requiring a mere 1500 ft for takeoff and 3600 ft for the landing run, a stark reminder of the inherent deficiencies of the previous generation of export fighters in an age where the damaged runway assumed a very low probability in the minds of defence planners. How times, and weapon systems, have changed!

In the ground attack mode the F-5G, carrying seven 500 lb bombs, two Sidewinders, cannon ammunition and two underwing 275 gl drop tanks has a combat radius in a hi-lo-hi profile of around 360 nm. This includes an allowance for air combat once the target has been hit. Radius in the air combat role is similar except that an allowance exists for one hour’s loiter at altitude, something the F-5G excels at with its fuel-frugal turbofan engine. Max Mach number is 2. 0 as against 1. 6 for the F-5E while the “G” is cleared for 9G manoeuvres (like the F-16/79) for an airframe life of 8000 hrs which should see most competent operators flying the aircraft for a quarter of a century or more without major airframe problems.

While market analysts generally see a market for upwards of 1000 FX sales through the next decade (there have already been more than 1000 F-5E Tiger tells sold) Northrop tends to see the F-5G filling a long-term requirement for a true lightweight fighter with up-market performance. The fact that a 1990 radar will be much smaller yet far more capable than the current generation of 1970s radars is indisputable and it is this fact more than anything else that will tend to give Beyond Visual Range capabilities to small-sized fighters of the nineties. As FX fades into the Congressional history books, Northrop will be quick to exploit their established F-5 design with enhanced radar, BVR missiles and perhaps a new wing. Either way, both the F-16 and the F-5 family of aircraft will be around for a long time, thanks to the revolution in solid-state circuitry and the silicon chip. Northrop planned to fly the first of four F-5G prototypes in October 1982 with customer deliveries being made during 1983.

The shining point of the entire F-5G marketing effort revolves around price. Northrop claim a flyaway price in 1980 dollars of $6 m for the F-5G which when stacked up against the numbers is quite a bargain. Furthermore, Northrop is quick to point out that the “G” features a fuel-efficient engine of modern design coupled with an airframe that is both proven and relatively viceless in handling and maintenance. The fact that all current operators could convert to the “G” (State Department willing) with a minimum of fuss and expense must certainly be in Northrop’s favour.

In conclusion, one can list the major assets of the General Dynamics F-16/79 as a modern airframe with relatively capable avionics and attack systems, a comprehensive weapons-carrying capability and a powerplant that many potential operators are familiar with. The negative aspects of this aircraft would revolve around the fact that it is essentially a high-performance design that has been forcibly detuned by using a very dated (by modern standards) engine requiring relatively vast amounts of maintenance manhours and is known for its high fuel consumption by modern standards. This crucial aspect could also turn off many potential clients who feel they would be buying a “second-string” aircraft. There is always a lot of romance and flag-waving in buying a fighter force and it might just be too difficult for a politically sensitive government to opt for a detuned aircraft in such an environment.

From Northrop’s point of view, their aircraft does not have the air-to-air or air-to-ground combat operations envelope of the F-16/79 though it does have longer legs, costs far less to operate and acquire and will certainly be of great interest to those 27 operators of earlier Northrop marques.

If anything, the emergence of FX, and in particular the F-5G, certainly will recapture much of the lost ground in US lightweight fighter export sales from the Carter era. Something that will certainly affect the international marketing efforts of Dassault or any rival European manufacturer endeavouring to produce a comparative lightweight fighter for the coming generation.