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McDonnell Douglas F-15 Eagle

Single-Seat Air Superiority Fighter with Secondary Attack Capability

Figure 1: F-15 Eagle. United States Air Force 081922-F-8732E-201.

Development

In the mid-1960s, the U.S. Air Force was concerned. Vietnam was showing that the F-4 could barely take on second-generation Soviet fighters such as the MiG-19 and MiG-21. At the same time, it was known that the Soviet Union was testing superior third-generation fighters. At the low end, the MiG-23 “Flogger” appeared to be a superior fighter to the F-4.[1] At the high end, the speedy MiG-25 “Foxbat” was a trisonic interceptor and reconnaissance aircraft, although the U.S. mistakenly believed the MiG-25 was an agile fighter. After briefly considering and rejecting the F-14, the Air Force released specifications in 1968 for a no-holds-barred air superiority fighter with minimal air-to-ground capability. It would be a modern counterpart to the P-51 Mustang of World War II and the F-86 Sabre in Korea. Although air-to-ground proponents argued for adding air-to-ground capability, the “fighter mafia” held firm with the motto “not a pound for air-to-ground.” Ironically, when the Air Force later sought a replacement for the F-111A in the air-to-ground role, it chose an Eagle variant, the F-15E.

Figure 2: F-15Es with Mustang and F-86. USAF 080307-F-8769K-205 and 080307-F-8769K-062. Taken at Davis-Monthan.

McDonnell Douglas won the contest to create the F-15 and the aircraft it designed was a beauty. It was large, weighing about 40,000 pounds in combat trim (less than the F-4 Phantom II that it replaced). Its two Pratt and Whitney F100-PW-100 engines each produced 14,670 pounds of thrust at military power and 23,800 pounds in full afterburner. The F-15 in most configurations could accelerate vertically and under certain fuel conditions it could exceed the speed of sound while zooming vertically from takeoff.[2]

 

Figure 3: F100-PW-100 Low-Bypass Turbofan with Afterburner. Pratt and Whitney.

Unfortunately, the early F100-PW-100 engines did not respond well to rapid throttle changes at high angles of attack—especially when turning on the afterburner.[3] In some cases, the afterburner ignition would put out the engine flame and backfire heat into the engine. Starved of normal cool air the engine would rapidly lose power and stall, causing the aircraft to yaw because power from the two engines was now imbalanced. This would disrupt airflow and cause the other engine to stagnate. Eventually, Pratt and Whitney gradually found ways to regulate afterburner ignitions to reduce this — at the loss of power.

 

Figure 4: F-15 Taking Off. USAF.

For air-combat maneuvering, this power was supplemented by enormous wings with a surface area of 608 square feet. For this reason, it was sometimes called the “flying tennis court.” The wings were rather conventional, with a 45 degree sweep in front and rear inboard flaps and outboard ailerons. Its two large tails and all-moving tailerons gave incredible bite for turning and the aircraft could quickly snap into 9g turns[4]. In level flight, the wing has a zero angle of incidence to the air stream. This unusual feature reduces drag. In tests against the F-4, conducted at 385 knots, the F-15 could complete a full 360 degree turn in 24 seconds—half the time of the F-4.[5]

 

Figure 5: Firing a Missile in a Turn. USAF 021105-O-9999G-037.

The most impressive thing about the Eagle is its array of electronics. The APG-63[6] fire control system was specifically designed for offensive air-to-air combat. This pulse Doppler radar was equally effective at normal-altitude threats, high-flying high-speed threats, and adversaries flying nap of the earth. It also had the highly sophisticated defensive Tactical Electronic Warfare Suite (TEWS) systems to warn of threats, execute -electronic countermeasures, and deploy chaff and flares.[7]

 

Figure 6: F-14s Firing AIM-7 Radar-Guided Missiles. USAF 021105-O-9999G-049.

Once the F-15 located a threat, it was able to take it out. Like the F-4, the F-15 Eagle typically carries four AIM-7 Sparrow radar-guided missiles placed conformally against the body and four AIM-9 infrared Sidewinder missiles on pylons under the wing.

 

Figure 7: F-15 Showing Positions of Missiles. USAF.

 

Figure 8: AIM-7 Missiles (Below) and AIM-9 Missiles (Above). USAF 820815-F-9876J-002.

There was no debate on whether the F-15 would have a gun. It was given the widely used 20mm M61A1 six-barrel Vulcan cannon firing 6,000 cannon shells per minute. The F-15 usually carried enough ammunition for about 10 seconds of firing.

 

Figure 9: M61A1 Vulcan Cannon in Right Wing Root. Source: Wikipedia Commons.

The first F-15 prototype flew in 1972, two years after the MiG-23 and MiG-25 reached operational status. The F-15 entered operational service in 1976.[8] Soon, both sides were rushing third-generation fighters to field units as rapidly as possible.

The first production versions were the single-seat F-15A and the dual-seat F-15B. The latter was a trainer but it was also a fully capable fighter and avoided a trainer designation. Although the fighter-control radar, ECM, and other electronics were almost beyond the state of the art, the cockpits were filled with old “steam gauge” dials. However, the F-15A/B models did introduce HOTAS (hands-on throttle and stick) which placed most control buttons on the throttle or stick to save the pilot the distraction of looking away to hit switches.

In 1978, McDonnell Douglas switched production to the F-15C and F-15D models. These were again single-seat and dual-seat version of the same aircraft. This time, the aircraft had glass cockpits built around color video displays, and the processing speed of the aircraft’s computer was increased by a factor of three. Improvements were also made in the aircraft’s ECM and command-control-communication suites.

 

Figure 10: 20 mm Gun Ammunition. USAF 051018-F-2636B-051

In addition, support was added for the new AIM-120 AMRAAM radar-guided missile. The newer versions could carry 1,855 more pounds of fuel internally and could also carry two conformal fuel tanks beneath the fuselage. Each of these conformal tanks could carry 750 gallons (4,900 pounds) of fuel. Maximum take-off weight was raised considerably to 68,000 pounds. The first C/D models became operational in 1979, with McDonnell Douglas producing many more C/D models than A/B models.

In early testing on the F-15A in air combat against smaller and agile adversaries,[9] it was found that the F-15 could score 18:1 from a position of advantage and 3:1 from any position—but only in a 1-on-1 engagement. With more aircraft in the furball, the APG-63 lacked the processing power to scan for other aircraft while it was engaging a target. It also needed the new AIM-120 AMRAAM (Slammer) fire-and-forget missile so that the F-15 could quickly move from one engagement to another.

Beginning in 1986, the Air Force began to run its F-15s through a multi-step improvement program (MSIP). This program greatly improved the electronics in the aircraft.

Several years after the C/D models entered service; the Air Force realized that it needed an all-weather bomber that could deliver payloads day or night even if targets were covered by clouds or smoke. Its only aircraft capable of doing this job was the aging F-111 bomber. After trials between extended versions of the F-15 and the F-16, the USAF selected the extended F-15 design. It became the F-15E and entered service in 1989—ten years after the first C/D models. By this time, the state of the art in electronics had advanced greatly. Synthetic aperture radar allowed the pilot and weapons system officer to get virtual maps of targets. In addition, F-15Es could carry a LANTIRN (Low Altitude Navigation and Targeting Infrared for Night) pod to help it find targets.  The aircraft was tentatively called the “Strike Eagle” during its early development but this never became an official designation. These aircraft were simply called F-15E Eagles, although they got some pet names such as the “Beagle” (bomb Eagle). McDonnell Douglas began production of F-15Es in 1989.

 

Figure 11: F-15E Dropping Multiple Bombs. USAF F-15E 020510-F-9999J-007.

 

Figure 12: F-15 Dropping a GBU-28 Bunker Buster. USAF 030805-F-7709A-004.

Japan built its own F-15s, which were designated the F-15J (one-seater) and the F-15JD (two-seater). Overall, more than 1,500 F-15s of all versions were built.

Combat History

The F-15 is arguably the most successful fighter in history with 92 claimed kills and no known losses in air combat. Initially, all combat missions were flown by the Israelis.[10] From June 1979 to July 1981, they scored 12.5 kills, with one kill shared. In the Lebanon War of June 1982, Israeli F-15s had 33 kills. Between then and November 1985, they scored 4.5 more kills. Overall, Israeli F-15 pilots have so far scored 50 kills without suffering a loss.

In 1984, Saudi Arabian F-15s shot down two Iranian F-4 fighters in a border confrontation. Later, in the 1991 Gulf War, USAF C/D Eagles shot down 33 aircraft and an F-15E destroyed a helicopter in flight by dropping a smart bomb on it. Saudi Arabian F-15s added two more kills. In the campaign against Serbia, American F-15s shot down four MiG-29s. In the Iraq War of 2003, no Iraqi fighters took to the skies, so there were no further kills in Iraq. Nor has there been any aerial combat in Afghanistan.

Although this kill ratio is almost unprecedented, neither the Israelis nor Coalition forces faced Soviet fighters flown by Soviet pilots and backed by Soviet air defense and guidance systems on the ground. Hopefully, the F-15 will never be forced to fight more-equal adversaries, although U.S. pilots are confident they would establish air dominance almost immediately.

Specifications: F-15A

Type

F-15 A/B/C/D: Single-seat air superiority fighter with secondary attack capability.
F-15E: Two-seat fighter/bomber

Length

63.75’ [19.44 m][11]

Wingspan

42.8’ [13 m][12]

Height

18.45’ [5.6 m][13]

Wing Area

608 sq ft[14]

Empty Weight

31,700 lbs[15]

Weight, interceptor takeoff

40,900 lb

Combat weight (50% fuel)

34,500 lb

Maximum Takeoff Weight

56,000. (With third fuel tank, must go without two AIM-7 Sparrows)[16]

Engine

 

Static thrust (military) each

14,670 lb

Thrust on full afterburner each

23,820 lb

Thrust to weight air-to-air configuration

1.4:1

Speed

1,678 mph at 47,000 ft[17],[18]

Ceiling

60,000 ft.[19]

Gun

M61 20 mm cannon with ammunition for about 10 seconds of firing time.

Radar-guided missiles

AIM-7 Sparrows or AIM-120 AMRAMs on C/D/E models (typically four)

Heat-seeking missiles

AIM-9L Sidewinders (typically four)

 

This Aircraft (76-063)

Our aircraft is an F-15A (Serial Number 76-063). It was manufactured in St. Louis, Missouri and was accepted by the Air Force in September 1977. It flew with 49th Tactical Fighter Wing in New Mexico and Nevada until 1978. It then went to the 1st Tactical Fighter Wing in Langley, Virginia. It shifted to the 405th Tactical Training Wing in Luke Air Force Base in Arizona in 1982. In 1988, it returned to the 49th Tactical Fighter Wing in New Mexico.[20]

In 1992, the aircraft went to the 199th Tactical Fighter Squadron of the 154th Composite Group (Air National Guard) at Hickam Air Force Base in Hawaii.[21] In 1987, Hawaii became one of the earliest units to get F-15As.[22] In 1992, the 119th got 26 newer F-15As upgraded with MSIP improvements.[23] Ours is one of these. The “063” defended Hawaiian skies until it was demilitarized and transferred to Pacific Aviation Museum Pearl Harbor. It now sits in Hangar 79, although it is frequently brought outside for some fresh air.

Notes

* The front of the engine intake dips between 4 degrees and 11 degrees for smoother airflow.

* There is a strake in front of rear radar missile to improve aerodynamics.

* The A model could carry three 600-gallon fuel tanks. However, if it did, it could only carry two radar missiles.

* The yellow strips at the front, back, and wingtips are dim yellow lights, like night lights, to aid in formation flying in darkness.

* McDonnell Douglas built 373 F-15As and 59 F-15Bs up to 1978.

* McDonnell Douglas produced 684 F-15Cs and 114 F-15Ds between 1978 and 1992.

* Today, it has built over 330, and it will build about 40 more for the Republic of Korea.

 

References

Aloni, Shlomo. Israeli F-15 Eagle Units in Combat, Osprey: Botley, Oxford, UK, 2006,

Davies, Steve and Dildy, Doug. F-15 Eagle Engaged, Osprey: Botley, Oxford, UK, 2007.

Rininger, Tyson V. F-15 Eagle at War, Zenith Press: Minneapolis, 2009.

Williams, Ted and Williams, Amy E. The American Fighter Plane, Metro Books, New York, 2002.

Winchester, Jim. Fighter. Paragon: Bath, UK, 2005.



[1] In secret tests only recently revealed, F-15s trained against “obtained” MiG-23s. In simulated combat, F-15s won 92 contests with no losses. Davies and Dildy, 2007.

[2] Williams and Williams, 2002.

[3] Davies and Dildy, 2007.

[4] Under rare conditions, there was a restriction to 7.33 gs. Pilots had no way of knowing when it was getting into these conditions. Consequently all turns on the A were restricted to 7.33 g turns. The F-15C/D models added an overload warning system to warn of g overload. This allowed 9 g turns under most conditions. Davies and Dildy, 2007.

[5] Davies and Dildy, 2007.

[6] “A” indicates that this unit is in a piloted aircraft; “P” indicates that this is a radar unit (“R” is for radio); “G” indicates that this is for fire-control. Sometimes, equipment designation is preceded by “AN,” as in AN/APG-63. This simply indicates that the designation is taken from the joint Army/Navy designation system.

[7] Davies and Dildy, 2007.

[9] Davies and Dildy, 2007.

[10] Data on Israeli kills from Aloni, 2006.

[14] Williams and Williams, 2002.

[16] Rinninger, 2009.

[17] Williams and Williams, 2002.

[18] The speed is sometimes listed as Mach 2.5. However, an armed Eagle’s maximum speed is 1.78. Speeds near Mach 2.5 can only be achieved with a special VMAX setting, and engines must be removed and inspected afterwards. Winchester, 2005.

[19] Williams and Williams, 2002.

[20] All dates in this paragraph courtesy of the U.S. Air Force.

[21] Date courtesy of the U.S. Air Force.

[22] Davies and Dildy, 2007.

[23] Davies and Dildy, 2007.

 

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