In the late 1970s, McDonnell Douglas and Hughes Aircraft collaborated in a privately-funded study of the feasibility of adapting the basic F-15 Eagle to the air-to-ground role. Back in the late 1960s, the F-15 had originally been conceived as a multi-role aircraft, but the fighter role had become paramount, and in 1975 the air-to-ground role had been set aside.
As part of this program, the McDonnell Douglas company converted the second F-15B (71-0291) under a project known as Strike Eagle. The aircraft first flew on July 8, 1980. It was equipped with a modified APG-63 radar that equipped to use synthetic aperture radar techniques to do high-resolution ground mapping. The back seat was configured for a Weapons System Officer (WSO) who would operate the weapons delivery systems. The aircraft was equipped with the FAST conformal fuel tanks that had been introduced on the F-15C/D. The aircraft was equipped with six stub pylons on the lower corners and on the bottoms of each of the FAST packs for the carriage of bombs.
The Strike Eagle prototype was later equipped with a centerline gun pod and was provided with a Pave Tack laser designator pod (as carried by some F-4Es and F-111Fs) carried on the port side of the forward air intake. This made the aircraft capable of delivering "smart" laser-guided bombs without the assistance of a separate designator aircraft.
The Strike Eagle aircraft was displayed at the September 1980 Farnborough air show in the hope of attracting foreign customers. In the meantime, the USAF had begun studying possible concepts for an Enhanced Tactical Fighter (ETF) that would replace the General Dynamics F-111. The USAF wanted an aircraft which could conduct the strike mission alone, without any need for fighter escort, electronic jamming aircraft, or AWACS support. In the interest of cost containment, the Air Force decided to explore the possibility that conversions of existing aircraft such as the F-15 or F-16 could meet the ETF requirement rather than to try and develop an entirely new aircraft. One of the aircraft initially considered was the Panavia Tornado, but it was ruled out fairly early in the game because of its short range and its obvious political disadvantage of not being made in the USA.
The ETF studies led to a fly-off competition between the F-15 and the cranked arrow-wing F-16XL (sometimes known as the F-16E). McDonnell Douglas provided four Eagles for the flyoff, one of them being the Strike Eagle demonstrator. F-15D serial number 80-0055 flew weapons separation tests at Eglin AFB. The Strike Eagle demonstrator aircraft flew tests at Edwards AFB evaluating the efficiency of the Synthetic Aperture Radar. F-15C serial number 78-0468 flew sorties from Edwards AFB to studyfully-instrumented performance and flying qualities. F-15D 81-0063 completed 36 operational evaluation flights from Edwards AFB. General Dynamics provided two cranked arrow-winged F-16XLs for the competition.
The F-15 was named the winner of the Dual-Role Fighter competition on February 24, 1984, partly on the basis of cost estimates. The production version of the Strike Eagle was designated F-15E. Full scale development of the F-15E began in 1984, with the first production F-15E (86-0183) flying on December 11, 1986, with test pilot Gary Jennings at the controls.
The F-15E is externally and dimensionally similar to the two-seat F-15D. However, the F-15E is internally redesigned with a stronger structure so that it can safely operate at takeoff weights as great as 81,000 pounds. The structure is cleared for 16,000 hours, double the lifetime of earlier F-15s. Space for additional avionics is provided at the expense of a slight decrease in internal fuel capacity to 2019 US gallons. The entire rear fuselage pod is manufactured from superplastic-formed and diffusion- bonded titanium, which results in a neater, lighter, and more capacious engine bay.
The heart of the F-15E's electronics suite is the AN/APG-70 radar. It is intended to be used without being detected by an enemy's air defenses. The radar supposedly can be quickly switched on to obtain an single-sweep synthetic aperture radar image of a target area located as much as 45 degrees to either side of the aircraft's flight path, then rapidly switched off seconds later, making it difficult for an enemy to pick up the emissions and track the F-15E's location and flight path. The radar map can be "frozen" on the screen, and updated periodically by new sweeps as the aircraft gets nearer to the target. The radar display terminals process the radar signals received and can provide a bird's eye view of ground targets that are of higher resolution and taken from further away than the images produced by previous radars. Roads, bridges, and airfields can be identified as far as 100 miles away, and as the F-15E nears the target image resolution becomes progressively sharper and smaller targets such as trucks, aircraft, and tanks can be distinguished.
Another key element of the F-15E's weapons delivery system is the Martin Marietta LANTIRN (which is an acronym standing for Low-Altitude Navigation and Targeting, Infra-Red for Night) system, which is tied to the AN/APG-70 radar. The LANTIRN consists of two pods, one carried underneath each air intake. The starboard pod is known as AAQ-13 and is used for navigation. It contains a FLIR (Forward-Looking, Infra-Red) which can be used to display a high-quality video image of the oncoming terrain on the pilot's heads-up display, enabling high-speed low-level flights to be made at night under clear weather conditions. The navigation pod also carries a terrain-following radar which is also effective in bad weather. The pilot can manually respond to cues from the system or can couple the system to the flight controls for "hands-off" automatic terrain-following flight at altitudes as low as 200 feet off the deck. The port pod is known as AAQ-14 and is targeting pod which contains a high-resolution tracking FLIR, a missile boresight correlator, and a laser designator. The boresight correlator is used to guide the Maverick air-to-surface missile and the laser designator is used for weapons such as laser guided bombs that home in on reflected laser light.
Front and rear cockpits are upgraded with multi-purpose cathode ray tube displays for improved navigation, weapons delivery, and systems operations. The pilot's cockpit has redesigned controls, a wide field of vision heads-up display, and three cathode ray tubes which provide multi-purpose displays of navigation, weapons delivery, and systems operations. The rear-cockpit weapons system officer has four cathode ray terminals for radar, weapons selection, and monitoring of enemy tracking systems.
The WSO has at his disposal an updated ALQ-135 electronic warfare system which features a new broadband jammer. The forward fuselage was rearranged to incorporate the internal ALQ-135B electronic countermeasures system, which was not used in the F-15B/D. This system has two rather than just one tailboom antenna. The antennae for this system are located at the trailing edge root of the left horizontal atablizer and in the leading edge roots of both wings. This replaces the blade antennae located under the nose of the A, B, C, and C versions.
The F-15E retains the conformal fuel tank of the F-15D. The air-to-ground weapons load is raised to a maximum of 23,500 pounds by adding six tangential stubs on the corner of each conformal fuel tank for the carriage of external ordnance. The F-15E retains the 20-mm M61A1 cannon of the F-15D, although the ammunition capacity is reduced to 512 rounds. However, the F-15E retains the full air-to-air capability of the F-15D version, and can carry AIM-7M Sparrow medium-range missiles on the conformal fuel tank stubs and AIM-9M Sidewinder short-range missiles on the underwing pylons.
The F-15E is powered by the F-15C/D's pair of 24,000 lb.s.t. afterburning Pratt & Whitney F100-PW-220 turbofans. However, the engine bays were adapted so that these engines could eventually be replaced by more powerful turbofans in the 30,000 pound thrust class. The first 134 F-15Es were fitted with the -220 turbofans. Plans to deliver F-15Es with the twenty-percent more powerful F100-PW-229 Increased Performance Engine rated at 29,100 lb.s.t with afterburner beginning in August 1991 were delayed slightly. The -229 turbofans were duly installed in the 135th and succeeding F-15Es, beginning with 90-0233.
In June 1990, the F-15E experienced its first competition with other aircraft in the USAF's Long Rifle gunnery meet. It scored first and second in the contest.
The low-altitude ride in the F-15E can be quite a bit rougher than that in the F-111 because of the lower wing loading and the higher gust response. The F-15E is better in diving attacks and low-level high-speed dash than it is in sustained low-level high speed flight. High-speed weapons separations trials performed at low level over the Nevada desert where vicious thermals are common, provided some crew discomfort. However, the accuracy and precision of the delivery of weapons in all-weather conditions was excellent.
Following completion of operational test and evaluation at Edwards AFB and Seek Eagle weapons carriage and separation tests carried out at Eglin AFB, F-15Es were first delivered to the 425th TFTS, 405th TTW at Luke AFB for crew training. The first operational F-15E squadron was the 336th TFS, 4th TFW at Semour Johnson AFB in North Carolina, which received its first planes in early 1989. Limited operational capability was obtained with the F-15E in October 1989, with full operational capability being projected for August 1990.
Integration of the LANTIRN system with the APG-70 radar proved to be much more difficult than expected, and the F-15E was still not fully compat-ready by the time of Desert Storm. The F-15E had only just begun to operate with the LANTIRN navigation pod and did not yet have the system's targeting pod installed, so it was at least temporarily capable of delivering only "dumb" bombs. Although the F-15E was still not fully combat-ready, 48 F-15Es flew in the Gulf War. F-15Es joined other Coalition aircraft in searching for and attacking Iraqi "Scud" missile launchers. These Scud hunt missions were largely unsuccessful, but the F-15Es attacked many other Iraqi targets of opportunity. Most of these sorties were flown at medium altitudes, and the F-15E did not get much of a chance to demonstrate its low-level capabilities. The full LANTIRN system was not available until near the end of the Gulf War, and even then the targeting pod still experienced problems and was not employed in combat to its full capability. Although only some of the F-15Es were equipped with their LANTIRN targeting pods by the end of the Gulf War, pilots claimed that 80 percent of the laser-guided bombs dropped by F-15Es hit their targets.
Wartime experience with the F-15E was handed on to the F-15 Combined Test Force (CTF) at Edwards AFB, which is doing work on F-15E engine, software, radar, weapons, and LANTIRN development. Even after the Gulf War was over, work still had to be done to clear the F-15E for the full set of weapons it could carry, including the Mk 20 Rockeye and CBU-87 cluster bombs, Mk-82 and Mk-84 500-lb and 1000-lb bombs, AGM-65 Maverick missiles, and GBU-10 and GBU-15 laser-guided weapons.
The 200th and last F-15E was delivered to the USAF in June of 1994. However, some attrition replacements were ordered in FY97 and FY98.
In mid 1994, there was a prolonged grounding of many F-15Es because of problems with their F100-PW-229 engines. The problem seems to be with stress-related cracking of the engine's fourth-stage turbine blades. This affects 75 F-5Es at Elmendorf AFB, RAF Lakenheath, and Lellis AFB. Another grounding of F-15Es based at RAF Lakenheath took place in January of 1998 because of complaints about compressor stalls and an unexpectely-rapid deterioratin of some vital engine parts.
Because of reliability problems with the F100-PW-229 engines, in June of 1998 the USAF began an evaluation of the General Electric F110-GE-129 IPE (Improved Performance Engine) as a possible alternative powerplant for the F-15E. The afterburning thrust of the F110 engine is 24,000 lb.s.t. The 422nd Test and Evaluation Squadron at Nellis AFB had actually carried out series of flight tests of the F110 engine fitted to F-15Es 87-180, 86-189, and 88-1678.
The F-15E will probably remain in service through 2030, and there is no replacement currently being contemplated.
71-291 McDonnell Douglas F-15B-4-MC Eagle Used for evaluation of FAST Pack conformal fuel tanks and LANTIRN pod. Also became development aircraft for F-15E Strike Eagle 86-183/184 McDonnell Douglas F-15E-41-MC Strike Eagle 86-185/190 McDonnell Douglas F-15E-42-MC Strike Eagle 87-169/189 McDonnell Douglas F-15E-43-MC Strike Eagle 87-190/210 McDonnell Douglas F-15E-44-MC Strike Eagle 87-211/216 cancelled contract for McDonnell Douglas F-15E 88-1667/1687 McDonnell Douglas F-15E-45-MC Strike Eagle 88-1688/1708 McDonnell Douglas F-15E-46-MC Strike Eagle 89-471/488 McDonnell Douglas F-15E-47-MC Strike Eagle 89-489/506 McDonnell Douglas F-15E-48-MC Strike Eagle 90-227/244 McDonnell Douglas F-15E-49-MC Strike Eagle 90-245/262 McDonnell Douglas F-15E-50-MC Strike Eagle 91-300/317 McDonnell Douglas F-15E-51-MC Strike Eagle 91-318/335 McDonnell Douglas F-15E-52-MC Strike Eagle 91-0600/0605 McDonnell Douglas F-15E-53-MC Strike Eagle 92-364/366 McDonnell Douglas F-15E-53-MC Strike Eagle 92-607/608 McDonnell Douglas F-15E Eagle These may have been cancelled. 96-200/205 McDonnell Douglas F-15E-58-MC Strike Eagle c/n 1327/E210, 1331/E211, 1335/E212, 1339/E213, 1341/E214, 1343/E215 97-217/222 Boeing F-15E-61-MC Strike Eagle c/n E216/E221 98-131/135 Boeing F-15E-62-MC Strike Eagle c/n E222/E226 00-3000/3004 Boeing F-15E-63-MC Strike Eagle 01-2000/2004 Boeing F-15E-64-MC Strike Eagle
Engines: Two Pratt & Whitney F100-PW-229 turbofans, each rated at 17,800 lb.s.t. dry and 29,100 lb.s.t. with afterburning. Performance: Maximum speed Mach 2.54 (1676 mph) at 40,000 feet (short-endurance dash), Mach 2.3 (1520 mph) (sustained). Maximum combat radius 790 miles. Maximum ferry range 2765 miles. Weights: 31,700 pounds empty, 81,000 pounds maximum takeoff. Dimensions: wingspan 42 feet 9 3/4 inches, length 63 feet 9 inches, height 18 feet 5 1/2 inches, wing area 608 square feet. Armament: One 20-mm M61A1 rotary cannon with 512 rounds. A maximum ordnance load of 24,500 pounds can be carried on the centerline and two underwing stations plus four tangential carriers attached to the conformal fuel tanks. In the air-to-air mission, up to four AIM-9L/M Sidewinders can be carried on the underwing stations and four AIM-7F/M Sparrow missiles can be carried on the conformal fuel tank attachments. Alternatively, up to eight AIM-120 AMRAAM missiles can be carried.