|Last Updated: Mon Jan 27 11:18:09 UTC 2014|
Douglas F-15 Eagle
The Ultimate MiG-Killer
The F-15 Eagle was born as FX or Fighter eXperimental and just like its nominal predecessor, the F-111, it was another child of the USAF Tactical Air Command (TAC). The Vietnam war was a very rude awakening for TAC, which eventually bore the brunt of the sustained air war. TAC was originally equipped fo rtactical nuclear strike, with a fighter force built around the Republic F-105 Thud (see Profile, June 1984) and future plans revolving about the GD F-111. Both of these aircraft were primarily nuclear bombers, by design optimised for low level penetration and precision strike.
Thoroughly steeped in the nuclear strike oriented doctrine of the late fifties, TAC only very reluctantly accepted the F-4C Phantom into its inventory, as the US government re-oriented its strategy toward conventional rather than nuclear warfare. Vietnam provided the US with an opportunity to exercise its new approach toward lesser than global conflicts. TAC was very rapidly involved flying sorties both within South Vietnam and against the North. Rolling Thunder in the 1965-68 period and subsequently Linebacker in the 1970-73 period were both major air offensives directed against the North's infrastructure and military facilities. Both offensives demonstrated that something was radically wrong with TAC's inventory and aerial combat tactics.
The air-air kill ratio in the first offensive was only 2.3:1, however Linebacker even bettered that with a mere 2:1 exchange rate. The MiG-17s and MiG-21s were unsophisticated and crude aircraft in comparison with the F-105 and F-4, but many were well flown and this, coupled with their better turning ability and gun/heat-seeking missile armament, accounted for TAC's inability to effectively assert itself (the USN managed a 12.5:1 kill ratio in Linebacker I/II).
This was further exacerbated by the shocking unreliability and performance limitations of the early AIM-9 and AIM-7 missiles (65% of the AIM-9s and 45% of the AIM-7s failed). Of the TAC's 137 kills 42 were made with guns, significant as only the very late F-4E had the opportunity to effectively use the weapon. Virtually all kills were in dogfight engagements. It was this major problem which provided the USAF with a reason to justify the development of a dedicated air superiority fighter.
The idea of an air-air fighter was under consideration as early as 1965, but the subsequent FX study generated by USAF Systems Command created the concept of a 60,000 lb swing wing machine much like the F-111, already under criticism for its inability to do what it wasn't built for.
At this stage a Major John Boyd was appointed to rework the FX study and generate a workable solution. Boyd was an outstanding air combat tactician and the originator of the concept of energy manoeuvrability. The concept revolves about the necessity for an aircraft to maintain a maximum amount of kinetic/potential energy in a dogfight, to be able to retain as much agility as possible.
Aircraft which 'bleed' energy quickly due to drag and lift induced drag in turns will quickly run out of speed and invariably lose the initiative in the engagement (the reason for the MiG-17 being more successful than the MiG-21 over Hanoi was due to its lower energy bleed). The aircraft most successful in a dogfight (pilot ability aside) is the aircraft with the highest thrust to weight ratio, lowest wing loading and thus the ability to out-accelerate and out-turn its opponent.
Boyd rapidly sunk the idea of a swing wing, on grounds of extra weight and complexity. He then proceeded to optimise the engine (turbofan being then the in thing) bypass ratio concluding that a turbojet is best, but accepting 1.5 as a reasonable compromise (later reduced).
By early 1967 Boyd had a very agile 40,000 lb fighter on paper. Requests For Proposals were released to industry in August 1967, one month after the Russians exposing the Mach 3 Foxbat. Boyd and his supporters tried to further improve FX, creating FX^2, a 33,000 lb machine with 40% better turning and 90% better acceleration performance than FX/F-15, but this was rejected as TAC was unrelenting in its demands for range and avionic capability (note that were the F-18L fitted with more powerful engines, it could fall into this class).
Study contracts on FX were awarded to McDonnell Douglas and General Dynamics, the former winning the design contract in December 1969 after 10,000 hours of wind tunnel testing on the MCAIR 199/F-15. The 199 flew 900 hours of dogfights against known and projected threats, using the two-dome simulator at the MDC St Louis facility. The design was extensively evaluated at high angles of attack, resulting in a very simple wing with no leading edge devices and high camber. Structurally, high emphasis was placed upon survivability with a titanium wall between the engines, fire resistant blankets in the engine bay, no aft fuel stores, redundant load bearing structural elements and a redundant hydraulic and control system.
The engine battle was fought over by General Electric and Pratt & Whitney, as it was to provide a common core for the 22,000 lb FX engine and the 28,000 lb F-14B engine. The PW F-100 was subsequently selected.
The new F-15 was to carry several important new systems. The trusty M-61 20 mm Gatling gun was to yield to the new 5 barrel Philco Ford 25 mm GAU-7, firing faster and heavier caseless ammunition. The AIM-9 Sidewinder was to yield to the new all aspect AIM-82 IR missile, with a 50 degree off-boresight lock-on ability. A new digital pulse doppler radar, heavily automated, was also selected after competition between Westinghouse and Hughes. The former two flopped, the latter lived on.
The first F-15A took to the air on July 27, 1972, flown by MDC's Irv Burrows.
(Right) This photo dramatically illustrates the size of the conformal FAST packs which still allow provision for four AIM-7F Sparrow missiles. On just two underwing racks alone this aircraft is carrying a total of 12 500 lb bombs and four AlM-9L Sidewinders. (Left) MDC have fitted a canard installation to a standard F-15 in addition to variable incidence exhaust nozzles in. an attempt to further improve manoeuvrability and STOL performance.
McDonnell Douglas F-15A/B Eagle
The flight test program progressed remarkably well, prototypes F-1 up to F-10 entering use during the 1972-74 period. Initially some problems were found in the computer controlled inlets and Control Augmentation System (CAS/FCC) but these were easily corrected.
The stabilators also misbehaved, with a flutter problem which
was removed by introducing the now characteristic 'dog-tooth' . Where
the designers were caught out was with a severe buffet problem in the
very critical 0.9 Mach/6G manoeuvre area - this required a major change
which led to the raked wingtips, producing the unique planform of the
fifteen. The speedbrake was also modified to eliminate buffet and
increase drag. The only major problems were associated with the
F-100 turbofans, which experienced numerous hot end failures and fires.
These problems continued well into the operational life of the machine.
Functionally and assembly-wise the aircraft may be divided into several
areas, each with many unique features.
Structurally the F-15 is segmented into several major sections, both for convenience in assembly and survivability. The fuselage is divided into three sections. The forward fuselage houses the APG-63 radar, the central computer, electronic warfare equipment and the spacious cockpit area (90% of the avionics 'live' in this space). This makes it more accessible for maintenance and more survivable (statistically most AAA damage occurs to the rear of a fighter). The cockpit area is elevated and fitted with a bulging bubble canopy, the pilot is exposed nearly down to his waist and this provides superb 360 degree visibility. The centre fuselage structure mounts the wings and surrounds the four large reticulated foam-filled fuel cells, containing a considerable part of the 11,100 Ib of JP-4 fuel, the remainder of which fills the wing tanks.
The wing carry-through frames absorb the wing loads and support the fuel cells and main undercarriage. The forward section is mainly aluminium, the centre section is of the same material aside from three bulkheads and some critical members, which are titanium. The M-61 gun neatly fits in the starboard glove, the inflight refuelling equipment in the port. The inlet nozzles have a 'nodding' geometry and were necessary for the 2.5 Mach dash performance, though of little importance at dogfight speeds. These and the bypass doors are computer controlled. The aircraft's wing was optimised for dogfighting at 550 kts and apparently is rather draggy at transonic speeds. Three of its four main spars are of titanium together with part of the skinning, most of which is aluminium. The structure is built for +9/-3 G loads, though in practice this is limited.
The aft fuselage section is mainly of titanium and utilises two rigid tail booms which support the stabilators and tails, these have titanium spars, aluminium honeycomb fillers and boron epoxy composite skins. The airframe has four times the fatigue life of an F-4 airframe. The rear section also has a titanium keel which serves to separate the engines, constraining fires or accelerated turbine blades to the affected bay only.
The F-15A is fitted with two F100-PW-100 afterburning turbofans, the source of its spectacular performance and most of its reliability problems. The P & W F-100 was built around the core of the JTF-22 demonstrator and represented the ultimate in its class, performance attained at the expense of exceptional complexity.
The engine has a three-stage fan providing a bypass ratio of 0.72, a ten stage axial compressor, separate two-stage turbines for each and a five stage afterburner. Turbine entry temperature is in the region of 1320 deg C and requires air-impingement cooling for the compressor-turbine's blades. The overall pressure ratio is 23:1, the engine delivers around 16,000 Ib in military power and 23,800 Ib in full reheat. The choice of a turbofan may not be optimal for dogfighting, but the low fuel consumption on dry thrust improves the aircraft's combat radius considerably.
The engine has an analogue Electronic Engine Control system that controls fuel flow. Like all turbofans, the F-100 is sensitive to airflow disturbances and is thus prone to stalls. Unfortunately as the engine is operating close to its limits repeated stalls cause repeated overheating of the turbines, many of which have failed directly due to overspeed or overheating, and this drastically cuts the lifetime of the units. A further problem was discovered as it was found that the pilots tend to cycle the engines from low to high power more often than was anticipated, further aggravating these problems. Most of the aircraft lost to date have experienced engine fires.
The F-15A was unique in having several firsts in the area of avionics. The AN/APG-63 radar was one of these. Designed for use in a single seat aircraft this radar had to perform both as an air superiority sensor and air defence system, both missions having specific requirements. For the air defence role the radar employs its all aspect look-down/shoot-down capability, 130 nm+ range and track-while-scan (8 targets), range-while-search, AIM-7 Sparrow illumination modes and it couples to an IFF interrogator.
For its period the radar had excellent ECCM ability, though this was necessary as the synthetic computer generated symbology displayed on the head-down ANMI scope conceals a lot of the observable effects of jamming.
Targets are adaptively tracked in ground clutter with Kalman tracking filters and the APG-63 has been known to lock onto fast moving road vehicles, outside of legitimate bogies. Early models were sensitive to Jet-Engine-Modulation (JEM) of radar returns, which affected the tracking filters when a target was illuminated up its tailpipe.
A FAST pack (now CFT) is fitted onto an F-15E, an
which this photo shows can easily be handled by just one man. FAST
allow an additional maximum of 10,000 lb of fuel without the usual drag
penalties suffered with traditional large volume underwing tanks.
MDC's demonstrator F-15B in this photo totes no less than 22 500 lb bombs in addition to an extra 10,000 lb of fuel. The demonstrator F-15E gave an indication of its capabilities when it flew alone without the aid of a tanker or navigational escort across the North Atlantic armed in the air superiority mode. An ultra long range escort capability of this type would be very useful in escorting civil and military transports across the Atlantic in time of hostilities.
As an air superiority radar the APG-63 represented a quantum leap with its semi-automatic dogfight modes. In Boresight mode the pilot flies the F-15's longitudinal axis onto the target and the radar locks on, in Supersearch the pilot manoeuvres the target into the 20 degree HUD field of view, which is scanned by the radar, after lock-on the radar places a square box over the target to facilitate visual acquisition. The radar supports the gun and Sparrow/Sidewinder launch in these modes, all of which are selectable by throttle and stick buttons.
The APG-63 is fully modular, uses an X-band planar array antenna and a gridded TWT transmitter, the whole system weighing in at 494 lb. The aircraft has a single IBM built 32-bit 'Central Computer', which controls the weapon system, displays and radar; for its period its 3.4x10^5 instr/sec / 16 kword RAM capability was considerable. The F-15 also had the first self contained internal electronic warfare system in an air-air fighter. The core element is the large Loral ALR-56 Radar Homing And Warning System (ESM), supported by the ALQ-128 launch warning system, ALQ-154/155 tail warning system and AAR-38 infra-red rear warning system. These were complemented by the ALQ-135 internal jammer, all EW data is displayed on the head-down Tactical EW System (TEWS) scope. Precision navigation reference is provided by the AN/ASN-109 inertial system, with 1.5 nm/hr drift and a TACAN receiver is fitted. The F-15 has a conventional head up display (HUD), which eases workload considerably.
The F-15A's cockpit was built for the fighter pilot, providing not only excellent visibility but also an ergonomic environment for air combat. The HUD provides continuous attitude reference, altitude, heading, airspeed and targeting symbols for weapon launch. In gun mode the radar and HUD function to display target range, position and closure rate, while displaying the F-15A's Mach number, G-loading, ammunition count and target status (e.g. jamming).
Similarly in Sparrow mode it displays missile count and after launch counts down seconds to missile impact. All weapon and radar modes are controlled by a set of selector switches on the control stick and throttles, a configuration termed HOTAS (Hands on throttle and stick) which allows the pilot to keep his head out of the cockpit throughout an engagement, without having to release his controls. Contrary to MDC's assertions it apparently requires considerable practice before a pilot is proficient, but is well worth the effort.
Some aircraft are also fitted with HUD frame mounted Eagle Eye rifle style 6X telescopic sights for target recognition beyond visual range (a useful idea for the RAAF F-18As). The control panel layout is dominated by a radio/IFF/HUD control panel, flanked by a CRT Air Navigation Multiple Indicator (ANMI) to the left and TEWS CRT to the right. Armament control is via a dedicated panel below the ANMI scope. The pilot sits on an MDC ESCAPAC IIC zero-zero seat, effective up to 600 knots.
The F-15 handles very nicely and is described as 'a real pleasure to fly', this is to a considerable degree due to the CAS, using blended normal acceleration and cancelled pitch rate feedback in pitch and co-ordination (roll-rate X AOA) feedback and a yaw rate canceller in yaw. The CAS will alter its control law subject to undercarriage position, as it decouples yaw and roll for dogfighting and this causes problems in landing and approaches. The control surfaces are driven by a dual hydraulic system, with an additional utility system to back up the tail controls, the dual system isolates leaks automatically. The rudders and stabilators are fed with control signals from the CAS, the ailerons are mechanical.
The very low combat wing loading of 60 lb/sq ft results in superb 14 degree/sec sustained turning, the aircraft pays a penalty though, both in rough low altitude ride and in a massive 608 sq ft wing area, a large contribution to the 1050 sq ft planform. This size problem has increased detectability and forces the use of low visibility paint, initially air superiority blue supplanted later by more effective two tone greys. The F-15A accelerates well, with a combat thrust/weight of 0.9 in military power and a full 1.3 in reheat. Fully loaded with four AIM-7F Sparrows and four AIM-9L Sidewinders it will reach up to Mach 1.78 in level flight and is allowed up to 7.33 G in combat configuration.
The F-15A and its two-seat F-15B derivative have been superceded in production by the C/D models, but are still effectively used by the USAF for air defence, and by Israel's Heyl Ha'Avir. The Israelis put the aircraft to excellent use in the 1982 strike on the Bekaa Valley in Lebanon, flying in under E-2C control for a veritable turkey shoot (to use the American term). Prior to the conflict the Israelis killed 141/z Syrian aircraft, mainly MiG-21 Fishbeds, and used the F-15 for top cover on the Osirak reactor raid. The F-15As shot down forty Fishbeds and Floggers in the Lebanese conflict, mainly using AIM-9Ls and Shafrir and Python missiles (IR), and also a photorecce Foxbat B which was downed with an AIM-7F (the film clip of the spinning Foxbat on international television was quite spectacular). The F-15A has three Foxbat kills to its credit, to date.
The Israelis are very enthusiastic about the F-15s, which are flown by their elite pilots, No 133 squadron, and the aircraft are meticulously maintained. Israel has 40 A/3 models ordered under Peace Fox and as it appears will soon acquire some C/Ds. USAF F-15As may undergo considerable upgrading under the MSIP I (Multi-Stage Improvement Program), program, but many of the aircraft are otherwise occupied in research programs.
The IFFC fire control integration program was one of these (see TE September 82), yielding spectacular results when an F-15B carved up an F-102 drone with its 20 mm gun in a head-on engagement closing at 800 kts +. The gun was fired by the central computer for only two seconds (see AWST, April 11, 1983) while the pilot manoeuvred onto the drone.
The F-15 cockpit is a vast improvement on the highly complex F-4 but not as advanced as the F-18 which almost totally replaces analogue instruments with multi-function CRTs.
Another F-15A put up a spectacular performance in 1975. The Streak Eagle, stripped of everything non essential including paint, took eight time-to-height records from both the F-4 and the Foxbat. An F-15B was also used as a testbed for developing the two-seat F-15E, that aircraft is currently being used to evaluate a chin mounted pod for housing a TV telescope, Flir, or alternately an APR-38 EW system. Fitted with the AN/APR-38 HARM, and FAST packs the F-15B/D would become a formidable defence suppression platform, replacing the F-4G Wild Weasels.
The F-15's robust design has led to its use in a number of research programs and it is likely this trend will continue, as the aircraft has the space to accommodate a lot of test equipment.
Probably one of the most fascinating roles assigned to the F-15A is that of a satellite killer. TAC is planning to retrofit 40 F-15A/Bs with interface hardware to enable them to launch the USAF's antisatellite (ASAT) missile. The ASAT is a two stage weapon, which utilises a Boeing AGM-69 SRAM rocket motor as a first stage and a Vought Altair as a second stage. The ASAT armed F-15 will be directed to an intercept position against a low flying (recce) satellite, where it will enter a full power climb.
Upon reaching the peak of its climb it then fires the ASAT at the satellite. The ASAT climbs, successively burning out and dropping stages under the control of an inertial guidance system (laser gyro). Just prior to separation from the Altair, the actual homing vehicle spins up to 20 revs/sec to stabilise itself. Using then liquid helium cooled infra-red sensors it locks on to the satellite and steers itself to impact with miniature solid rocket thrusters. The concept of this weapon system is quite elegant, as the ASAT F-15s may deploy worldwide, the Russians have no direct way of identifying the ASAT equipped aircraft and finally the system may be used for rapid reaction strikes.
Operationally the aircraft has not been quite the success one would anticipate; though its performance is universally praised its reliability up to recent times has been a serious problem. In spite of the built in test (BIT) capability, its complex avionic system is quite difficult to troubleshoot and the F-100s apparently go through a lot of spares. Some sources suggest an availability as low as 65% with some units (generally improving, though the first TFW was down to 35% in late 1979) and this has forced the increasing of spare levels and test equipment levels on deployments.
Though the Israelis have been very successful with the aircraft, some US parties have misgivings about its ability to survive in a high density scenario. The argument centres on the results of the extensive AIMVAL/ACEVAL tests during 1977, which suggested that although the aircraft repeatedly chalks up scores up to 18:1 in 1 vs 1 combat, its exchange ratio drops below 1:1 in many vs many (e.g. 10 vs 10) engagements. This is mainly due to its size, though partly due to tactics built around 1 vs 1 combat.
It is interesting to note that the Israelis have used the
aircraft quite successfully in many vs many engagements, though the
Russians are trying to capitalise on the inconclusiveness of the USAF's
evaluations by deploying large numbers of Floggers in Europe (one may
assume they would attempt to saturate the battle zone with aircraft to
wear down the F-15 force, irrespective of own losses).
McDonnell Douglas F-15C/D Eagle
The F-15C and its two-seat brother, the F-15D, entered production in 1979 replacing the A/B after 383/60 deliveries. Though externally identical to the A/B, some of the internal changes to the systems have been considerable. The internal fuel capacity was increased to 13,455 Ib under the MDC PEP-2000 (Production Eagle Package) program and provisions were made for fitting FAST pack conformal fuel tanks. The FAST packs can accommodate an additional 9750 Ib of fuel with a minor increase in empty weight (and an apparent, questioned by many, drop in subsonic drag).
The undercarriage was strengthened accordingly. The biggest change is in the radar which has been improved by the use of a Programmable Signal Processor (PSP). In the early APG-63 the tracking filters and remaining signal processing hardware were hardwired to particular mathematical operations - this meant that the ECCM and functional performance of the radar was frozen at production. The PSP is a high speed digital computer that is software programmable to perform the functions of the hardwired signal processor, and thus may be instantly changed by reloading its software whenever an algorithmic improvement is developed.
Due to the use of a more powerful processor this has allowed the inclusion of further modes. For air defence missions, a raid assessment (RAM) mode can separate out several distant targets otherwise fused in one return, a velocity search mode provides a bar graph of velocity vs azimuth on incoming targets and a Non Co-operative Target Recognition (NCTR) mode which identifies target types from JEM effects in the radar returns. The PSP provides flight status and tracking information for each tracked target, indicating climbing or other manoeuvring to evade interception. The pilot may also transfer lock between tracked targets. For dogfighting, the radar gained a vertical acquisition (VACQ) mode, in which it sweeps up and down in elevation. In a tight turn, the pilot aligns a U symbol on his HUD with the target overhead and the radar locks on as in Supersearch or Boresight, for Sidewinder launch. The APG-63 PSP is compatible with the current Sparrow version, the AIM-7F which has limited shootdown capability but is far better than its doubtful forerunners. The F-15C/D also has improvements to its air-ground capability.
Though the F-15A/B had the software and electronics for bombing (e.g. CCIP or Automatic Release) it is not used for the task. The C/D has a Doppler beam sharpened groundmapping ability, ground Moving Target Indicator (MTI) and fixed target tracking, all of which are tactical strike modes.
TAC's requirement for ground attack capability followed as a result of the Rapid Deployment Force intervention oriented restructuring, though currently only the F-15Cs of the 1st TFW (Langley, Va) actually practice strike sorties. In support of the RDF TAC would deploy FAST pack fitted F-15Cs supported by KC-10 tankers to potential or actual trouble-spots in hours.
The C/D may be fitted with BRU-2GA 6X bomb racks which are cleared for supersonic release; typically the aircraft would carry 18 cluster bombs or 500 lb Mk 82s on two wing racks and one centreline rack. The gross weight limit is set at 68,000 lb.
Japan is one of three export customers for the Eagle. This particular aircraft is one of the early St Louis built aircraft and is configured with three 600 gal ferry tanks following its delivery flight from the US.
The F-15C/D also equips the Japanese and Saudi air forces.
Japan opted for the F-15 to replace its ageing F-4EJs, no doubt intending to counter the strong Soviet Foxbat and Fencer force in the Far East. Other than 12 F-15DJs, the 100 strong F-15J force will be built by Mitsubishi in Japan, differing from USAF C/Ds in the use of local J/APR- and J/ALQ-8 in preference to the US EW equipment. The F-15J will also carry a datalink to tie into a GCI network.
The Saudi RSAF acquired three squadrons under the Peace Sun program, the 45/15 aircraft order being subsequently lifted to 62. Though final deliveries were scheduled for this year, the current instability in the Persian Gulf may lead to a follow-on order of two squadrons. Saudi aircraft carry AIM-9L, FAST packs (in spite of Israeli protests), bomb racks and have in-flight refuelling capability. The RSAF F-15Cs can take credit for killing two of Khomeini's F-4s, intercepted over the Gulf in early June this year and shot with AIM-7F missiles.
McDonnell Douglas F-15 C/D MSIP II
The MSIP II program is a further systems upgrade, both to 306 existing and 260 scheduled production aircraft, currently budgeted at $274.4 million. The Phase 2 aircraft will have an improved APG-63PSP with increased range, improved raid assessment mode, improved ECCM ability and AMRAAM capability. The PSP computer will have triple the speed of its forerunner at 1.4 million instr. sec' and five times the memory at 1 Mword. The IBM mission computer will be upgraded, with three times the speed and four times the memory size of the original. The MSIP II will also result in an upgraded stores control system, using a MIL-STD-1553 communication bus linking the mission computer, weapon stations and a new 5" colour CRT screen, which replaces the earlier stores panel. The colour screen will also display BIT data, FLIR imagery and JTIDS symbology, aside from stores data. The aircraft will carry JTIDS (Joint Tactical Information Distribution System) Class 2 terminals, linked to the 1553 bus. Further improvements involve the fitting of Global Positioning System satellite navigation equipment, Mk.15 IFF equipment, upgraded ALR-56C TTWS, Pave Mint EW equipment, flare and chaff dispensers. The HUD and radar scope acquire colour CRTs.
The implications of these mods are significant. The radar and stores control upgrade will enable the carriage of the monopulse shootdown AIM-7M, the new AIM-9M and above all, the multishot AMRAAM. The aircraft will then be able to simultaneously attack up to eight aircraft with up to eight AIM-120A AMRAAMs, ripple launched, while the radar is operating in track-while-scan mode. AMRAAM uses midcourse datalink guidance, decoding pulse trains appended to each transmitted radar pulse, then employing an active radar seeker for the kill.
JTIDS (Joint Tactical Information Data System) then provides a secure voice and data communication network, linking the F-15 to an E-3A/C AWACs. The JTIDS Network can generate symbolic colour maps on the stores screen, showing the edge of the battle zone, hostile aircraft and surface units, waypoints and messages (e.g. drawing a line from the F-15 to a hostile, accompanied by kill; Hostile, 25,000 ft 550 kt). Using this network, an F-15 pilot can notify all other units as to which targets he has locked his weapons onto, alternately he may use it to transmit tactical situation data to a particular aircraft with a known callsign. JTIDS is claimed to be jam-resistant.
The combination of AMRAAM and JTIDS is to help generate an air defence barrier capable of handling the high density central European theatre, likely to become Flogger and Fulcrum saturated in the next half decade. The F-15s will be tasked with both air defence CAP and air superiority or MiGCAP over Warpac territorial airspace, the latter a highly demanding mission. One area of uncertainty in the MSIP II program is however, propulsion, as the USAF will now award engine contracts annually and thus the F100 may be replaced with the GE F110. The F110-GE-100 is heavier than the F100 at 3750 lb vs 3054 lb but delivers well over 28,000 lb in reheat and is more durable than the F-100-PW-100 (5000 tactical cyles vs 1800 or less) though only slightly (-20%) better than the newer F100-PW-220 (PW1128) engine of similar thrust rating (both have digital control). Both durability and cost will decide the issue, the USAF showing little concern in the thrust differences. Fitting 28,000 lb engines would provide adequate growth in thrust/weightto counter both Flanker and Fulcrum with a generous margin, though the relative capabilities may strongly depend on the weapon systems used.
Another area of uncertainty concerns the use of digital engine and flight controls, both offering a growth option to IFFC capability. MCAIR have test flown an F-15 fitted with an MDC/Lear Siegler digital flight control system structured around four Z-8002 micro processor chips (conceptually much like the F-18 FCS) and expect to integrate the unit with NASA's digital electronic engine control (DEEC) system. Using the DEEC system improves both engine thrust and response time, while broadening the operating envelope.
On the more conventional side, the air to ground abilities of the F-15C/D are to be eclipsed by the F-15E, selected early this year over the F-16XL/E in the USAF's quest for a deep strike fighter.
McDonnell Douglas F-15E Dual Role Fighter MSIP III
The F-15E was developed to fulfil a growing USAFE need to effective hit second echelon Warpac ground forces. The F-111E/F wings based in the UK were overcommitted with both all weather Close Air Support (CAS) and deep strike missions, the problem growing further as the Russians increase the density of their defences and deploy look-down/shoot-down fighters. It was apparent that the dwindling F-111s could no longer meet both missions, so the USAF initiated a flyoff for the Dual Role Fighter (DRF), an air superiority aircraft configured for precision all weather medium/deep strike.
McDonnell Douglas offered the F-15E, a growth version of the F-15D, and General Dynamics offered the cranked delta F-16E (XL). Though the F-16E was an excellent long range fighter, it simply could not match the payload range performance and sensory fit of the larger F-15E, which easily won the DRF contest.
The F-15E DRF was developed from an MDC/Hughes system
a modified F-15B called the Advanced Fighter Capability Demonstrator or
Strike Eagle. This aircraft was fitted with a dedicated rear cockpit
a specially modified APG-63PSP, together with a Pave Tack Flir
and FAST packs. The key to the DRF's special capabilities lies in the
radar signal processor, which is configured for synthetic aperture
groundmapping. To date synthetic aperture groundmapping has been used
only in side looking radars (e.g. OV-1D Mohawk) using photographic
non-real time (one must develop film cartridges) techniques to achieve
extremely high resolution images.
in Saudi Arabia during
Desert Storm (US Air Force).
The DRF will use the PSP to 'number-crunch' the radar information and generate the high resolution image, dwelling for 3 to 6 seconds on a patch of terrain. Typically the back-seater will lock the radar on to a known target area (e.g. containing an armoured formation) as the F-15E approaches and generate a high resolution patch map. The map is then frozen on the screen, as the operator searches for targets. Once located, the Nav-attack system is locked on, the pilot receives cueing symbols on his HUD and the Flir pod is cued. The F-15E then hits the target, running in at 500 feet or less.
The synthetic aperture patch maps are coarser with range, though at a short range of 10 nm a 0.67 x 0.67 nm map has a resolution of 8.5 feet, which is more than adequate for resolving most classes of target. The actual F-15E DRFs will be modified from 392 F-15C/Ds and the modifications are quite extensive (the F-15E will be extensively reviewed in the next issue of Australian Aviation).
The rear cockpit receives four CRT screens, the forward cockpit three and a new HUD. The conformal FAST packs will be modified for tangential (snug against the skin) low drag bomb carriage and the structure will be beefed up to handle an 81,000 lb take-off weight and 9G manoeuvring with a large payload. The aircraft will be fitted with Lantirn pods for targeting and terrain following, and will carry an interface for the JTACMS standoff surface attack missile (see TE on PGMs). Flying a typical Hi-Lo-Hi strike mission with 100 nm dash radius and 8000 lb bombload / 4 x AIM-120 the DRF has a tactical radius over 750 nm. Flying air superiority missions (30% of its projected workload) the F-15E will carry AIM-9M, AIM-7M and in particular AIM-120A, together with its gun.
Though it will be slightly heavier than the C/D its performance will suffer very little, as it will be fitted with 28,000 lb class powerplants. The F-15E DRF is expected to enter service in 1988/89.
The F-15 has found a very special place in aviation history, being the first ever fighter designed to a scientifically formulated recipe for air superiority. It has anything but disappointed its creators in St Louis, or its various users throughout the Free World, proving again and again its absolute superiority over any opponent. Even the newer Russian Fulcrum and Flanker, to a large degree influenced by the concept of the F-15, will find the Eagle a very tough customer in years to come. Progressive updates will see improvements in propulsion, control systems and avionics, these will enable the F-15 to maintain its prominent position until superseded by the Advanced Tactical Fighter.
The Eagle is the fighter pilot's aircraft and will always
remain that above all; its combat record convincingly proves it. It is
the Ultimate MiG-Killer.
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