McDonnell Douglas F-15E Strike Eagle
The McDonnell Douglas 'F-15E Strike Eagle' is an American all-weather multirole strike fighter derived from the McDonnell Douglas F-15 Eagle. Intended for the Dual-Role Fighter program, the F-15E was designed in the 1980s for long-range, high-speed interdiction without relying on escort or electronic-warfare aircraft. United States Air Force F-15E Strike Eagles can be generally distinguished from other US Eagle variants by darker aircraft camouflage, conformal fuel tanks and LANTIRN pods mounted behind the engine intake ramps and a tandem-seat cockpit.
Initially designed and manufactured by McDonnell Douglas, the F-15E first flew in 1986 and production continued under Boeing following the companies' merger in 1997. The aircraft became the USAF's primary strike fighter/interdictor starting near the end of the Cold War, gradually replacing the F-111 Aardvark. The Strike Eagle has been deployed for military operations in Iraq, Afghanistan, Syria, and Libya, among others. During these operations, the strike fighter has carried out deep strikes against high-value targets and combat air patrols, and provided close air support for coalition troops. It has also been exported to several countries. The F-15E is expected to remain in USAF service until the 2030s. Enhanced versions of the design, called the F-15 Advanced Eagle, remain in production.
Development
Origins
The McDonnell Douglas F-15 Eagle was introduced by the USAF to replace its fleet of McDonnell Douglas F-4 Phantom IIs. Unlike the F-4, the F-15 was designed for air superiority with little consideration for a ground-attack role; the F-15 Special Project Office opposed the idea of F-15s performing interdiction, giving rise to the phrase "Not a pound for air to ground." In service, the F-15 has been a successful fighter, scoring over 100 aerial combat victories and zero losses in air-to-air combat as of 2007.Despite a lack of official interest, McDonnell Douglas had quietly included a basic secondary ground attack capability in the F-15's design since the beginning and worked on an F-15-derived interdictor fighter. The company envisaged the aircraft as a replacement for the General Dynamics F-111 and the remaining F-4s, as well as to augment the existing F-15s. In 1978, the USAF initiated the Tactical All-Weather Requirement Study, which looked at McDonnell Douglas's proposal and other options such as the purchase of further F-111Fs. The study recommended the F-15E as the USAF's future strike platform. In 1979, McDonnell Douglas and Hughes began a close collaboration on the development of the F-15E's air-to-ground capabilities.
To assist in the F-15E's development, McDonnell Douglas modified the second TF-15A prototype, AF serial number 71-0291, as a demonstrator. The aircraft, known as the Advanced Fighter Capability Demonstrator, first flew on 8 July 1980. It was previously used to test conformal fuel tanks, initially designed for the F-15 under the designation "FAST Pack", with FAST standing for "Fuel and Sensor, Tactical. It was subsequently fitted with a Pave Tack laser designator targeting pod to allow the independent delivery of guided bombs. The demonstrator was displayed at the 1980 Farnborough Airshow.
Enhanced Tactical Fighter
In March 1981, the USAF announced the Enhanced Tactical Fighter program to replace the F-111. The program was later renamed the Dual-Role Fighter competition. The concept envisioned an aircraft capable of launching deep air interdiction missions without requiring additional support by fighter escort or jamming. General Dynamics submitted the F-16XL, while McDonnell Douglas submitted the F-15E. The Panavia Tornado was also a candidate, but since the aircraft lacked a credible air-superiority fighter capability, coupled with the fact that it was not American-made, it was not seriously considered.The DRF evaluation team, under the direction of Brigadier General Ronald W. Yates, ran from 1981 through 30 April 1983, during which the F-15E logged more than 200 flights, demonstrated takeoff weight of more than, and validated 16 different weapons-carrying configurations. McDonnell Douglas, to assist 71-0291 in the evaluation, added to the program other F-15s, designated 78-0468, 80-0055, and 81-0063. The single-engined F-16XL was a promising design, which with its radically redesigned cranked-delta wing, greatly boosted performance; if selected, the single- and two-seat versions were to be designated F-16E and F-16F, respectively. On 24 February 1984, the USAF chose the F-15E; key factors in the decision were the F-15E's lower development costs compared to the F-16XL, a belief that the F-15E had future growth potential, and possessing twin-engine redundancy. The USAF was initially expected to procure 400 aircraft, a figure later revised to 392.
Construction of the first three F-15Es started in July 1985. The first of these, 86-0183, made its maiden flight on 11 December 1986. Piloted by Gary Jennings, the aircraft reached a maximum speed of Mach 0.9 and an altitude of 40,000 feet during the 75-minute flight. This aircraft had the full F-15E avionics suite and the redesigned front fuselage, but not the aft fuselage and the common engine bay for more powerful Improved Performance Engine variants of the Pratt & Whitney F100 or General Electric F110. The latter was featured on 86-0184, while 86-0185 incorporated all the changes of the F-15E from the F-15. On 31 March 1987, the first officially completed F-15E made its first flight.
The first production F-15E was delivered to the 405th Tactical Training Wing, Luke Air Force Base, Arizona, in April 1988. Production continued into the 2000s with 236 produced for the USAF through 2001.
Upgrade programs and replacement
The F-15E was upgraded with the Raytheon AN/APG-821 Active Electronically Scanned Array radar after 2007, and the first test radar was delivered to Boeing in 2010. It combines the processor of the APG-79 used on the F/A-18E/F Super Hornet with the antenna of the APG-633 AESA being fitted on the F-15C; it was named APG-634 until it received the APG-82 designation in 2009. The new radar is to be part of the F-15E Radar Modernization Program, which also includes a wideband radome and environment control and electronic warfare improvements. In 2015, Boeing and BAE Systems were awarded contracts to comprehensively upgrade of the electronic warfare system of all USAF F-15s, including the F-15E, with the AN/ALQ-250 Eagle Passive/Active Warning Survivability System. The first F-15E retrofitted with EPAWSS was delivered in 2022.Having a sturdier airframe rated for 8,000 hours of service life or up to 16,000 hours with proper depot maintenance programs, twice the lifetime of earlier variants, the F-15E is expected to remain in service past 2025., the USAF's F-15E fleet had an average age of 21 years and an average airframe flying time of 6,000 hours. In 2012, the USAF was reportedly considering future options, with no replacement for the F-15E being slated at that time.
The F-15E design would see some export success and Boeing continued developing upgrades for international customers. More radical upgrades to the air vehicle design resulted in the F-15 Advanced Eagle family that began with the F-15SA for the Royal Saudi Air Force, which first flew in 2013. It replaces the older hybrid electronic/mechanical system with a digital fly-by-wire control system that opens up two additional wing pylons and a revised wing structure for increased service life. The Advanced Eagle would have further developed variants with the F-15QA for the Qatar Emiri Air Force and the F-15EX Eagle II for the USAF. In FY 2020, USAF began procuring the F-15EX to replace the aging fleet of F-15C/D and supplement the F-22 Raptor to maintain air superiority fighter numbers, taking advantage of the existing export production line to quickly and affordably bring additional fighters into service; the F-15EX is also an option to replace the F-15E at a later time. Another choice is the F-35 Lightning II, set to replace other aircraft such as the F-16 Falcon; an F-35E variant was studied. Adding a second seat to the F-35 is complex and costly, especially to preserve its stealth profile; providing for greater range and payload would also be difficult tasks. Alternatively, the role could be covered by a combination of fighter and bomber aircraft, such as the B-21 Raider. The F-15E may also be replaced by a clean-sheet sixth-generation aircraft design.
ALASA
On 24 March 2014, Boeing won a $30.6 million contract from DARPA as part of the Airborne Launch Assist Space Access program. The goal of the program is to cut the cost of putting microsatellites into orbit by 66% through advances in launch systems. Under the 11-month contract, Boeing will build twelve launch vehicles, each with a payload capability up to. An ALASA vehicle is to be fitted under an F-15E, which will climb to 40,000 ft, then be released and fire its four engines to reach low-Earth orbit. Awarding the contract to Boeing would make use of the F-15E as the carriage vehicle, as previous design contracts had been given to Lockheed Martin to use the F-22 Raptor and Virgin Galactic to use their SpaceShip Two aircraft. DARPA had previously insisted they wanted to select an aircraft they would not need to modify heavily to carry and launch the ALASA payload. The project was terminated in late 2015.Design
Overview
The F-15E's deep-strike mission is a radical departure from the original intent of the F-15 since it was designed as an air-superiority fighter under the mantra "not a pound for air-to-ground." The basic airframe, however, proved versatile enough to produce a very capable strike fighter. The F-15E, while designed for ground attack, retains the air-to-air lethality of the F-15, and can defend itself against enemy aircraft.The F-15E prototype was a modification of the two-seat F-15B. Despite its origins and retaining the same aerodynamic shape, it includes significant structural changes as well as more powerful engines. The aft fuselage was designed to incorporate the more powerful engines with advanced engine bay structures and doors, which incorporate superplastic forming and diffusion bonding technologies. The back seat is equipped for a weapon systems officer to work the air-to-ground avionics via multiple screens; these view the radar, electronic warfare, or thermographic cameras, monitor aircraft or weapons status and possible threats, select targets, and use an electronic moving map to navigate. Two hand controls are used to select new displays and to refine targeting information; displays can be moved from one screen to another using a menu of display options. Unlike previous two-place jets, whose back seat omitted flying controls, the F-15E's back seat is equipped with its own stick and throttle so the WSO can take over flying, albeit with reduced visibility.
For extended range, the F-15E is fitted with two conformal fuel tanks that hug the fuselage to produce lower drag than conventional underwing/underbelly drop tanks. They carry 750 U.S. gallons of fuel, and house six weapons hardpoints in two rows of three in tandem. Unlike conventional drop tanks, CFTs cannot be jettisoned, thus increased range is a trade-off for increased drag and weight compared to a "clean" configuration.