by Tom Clancy
Another important part of the Eagle’s avionics is the communications suite. In addition to the new Have Quick II radios (jam and intercept resistant), there is one of the new Joint Tactical Information Data System (JTIDS) terminals, which allows the “linking” of any aircraft so equipped to an aerial local area network. This secure (i.e., unjammable and untappable) data link allows the sharing of information from a plane’s sensors and other systems with other aircraft, ships, and ground units. JTIDS terminals are currently on the E-3 Sentry AWACS, as well as new E-8 Joint-STARS ground surveillance aircraft. Even U.S. Army Patriot SAM batteries, U.S. Navy Aegis cruisers and destroyers, and NATO units have the capability to tap into the JTIDS data link system. Now, while data links are nothing new, what makes JTIDS special is that it transmits a full situational report, including radar contacts, sending aircraft position, altitude, and heading, and even fuel and armament status (counting gun, bomb, and missile rounds onboard) to anyone with a terminal equipped to receive it. The major problem with the early JTIDS terminals was that they were extremely expensive; but later versions have been re-engineered to reduce their size, cost, and complexity. Luckily, the rapid march of technology has made this both possible and reasonable, and the new terminals should be in service within a year or two. Currently, only the F-15Cs assigned to the 391st Fighter Squadron of the 366th Wing at Mountain Home AFB, Idaho, are equipped with JTIDS.
It is always vitally important that the pilot know where he or she is; thus the inclusion of a highly accurate inertial navigation system (INS) in the Eagle’s avionics suite. The Litton ASN-109 INS is a “black box” that uses laser beams moving in opposite directions in rings of fiber-optic cable. Any motion of the aircraft causes tiny shifts in the wavelength of the light, which is sensed and analyzed to determine position, velocity, and acceleration. Before takeoff, the system is “aligned” and fed the geographic coordinates of the starting point (usually the aircraft parking ramp, where a sign is posted with the surveyed coordinates) and a series of “waypoints.” Since INS positional fixes tend to “drift” over the course of a mission several hours long, there are provisions to update the navigational fix with inputs from ground-based aids such as the TACAN system (a series of ground-based electronic navigation stations), as well as visual and radar map fixes. A future avionics upgrade for the -C will add a super-accurate Honeywell system combining a GPS receiver with a ring laser gyro in a single box.
Another system directed from the pilot’s HOTAS controls is the defensive countermeasures system. To survive today in a high-threat environment, you need a radar jammer. In the Eagle, this system is the internally mounted Northrop ALQ-135(V), which operates automatically, requiring only that the pilot turn it on. To alert the pilot to electronic (i.e., radar guided) threats, there is a Loral ALR-56C Radar Warning Receiver (RWR), with the display mounted just below and to the right of the HUD. This display shows both the type of threat and the bearing to the enemy radar. It also can tell the pilot whether the enemy radar is just scanning, or if it has actually fired a SAM. As might be imagined, this information is vital for a pilot to survive in the modern aerial battlefield. Antennas for the ECM and RWR systems are mounted in pods on top of the twin tail fins. Should the ECM system fail and there’s an incoming missile on your tail, the pilot also has a Tracor ALE-45/47 chaff and flare decoy dispenser, with the release button mounted on the left side of the throttle column.
The only reason for the existence of a combat aircraft is to deliver (or at least threaten to deliver) ordnance (the technical term for weapons) onto an enemy target. As we stated earlier, the original design of the Eagle was for a no-compromise air-to-air (the USAF term for this is “air superiority”) fighter. Thus, the F-15C weapons suite was optimized for taking on and rapidly defeating a large number of air-to-air targets. For the designers of the Eagle, their starting point was the original weapons loadout of the aircraft that it replaced, the eight air-to-air missiles of the F-4 Phantom. In addition, they decided to add a gun to the package, since the lack of such a weapon had cost American pilots so many MiG kills over North Vietnam. Unlike guided missiles, guns have no minimum range, and can also be used against ground targets, should that be required. While originally it was planned to fit the F-15 with the new Philco Ford (now Loral Aeronutronic) 25mm GAU-7, it was eventually decided that the F-15 would be equipped with the older, more dependable General Electric M-61 Vulcan 20mm six-barreled rotary cannon. Used on USAF aircraft since the mid-1950s, it is something of a classic on its own, and is on every air superiority fighter currently in the U.S. inventory. The cannon muzzle is located in the starboard wing root, well behind the engine intake, so there is no risk of ingesting gun gas, causing an engine flameout. A drum magazine behind the cockpit holds 940 rounds, but you better fire short bursts, since this is just enough for 9.4 seconds of firing. (The M61 fires over six thousand rounds per minute!) Today, the big news about the Vulcan is that there is a new kind of ammunition for it to fire—the PGU- 28, which has armor piercing, explosive fragmentation, and incendiary effects, all in a single round. This new bullet has greatly improved the capabilities of the M-61, which is still one of the finest airborne cannons in the world. In the F-15C, the gun is angled up about 2°, so that it “lofts” the rounds towards the target, allowing a better view before you lose sight of the target under the nose of the aircraft. There also is a new gunsight—or more properly, gunsight symbology for the HUD—which greatly eases the task of aiming. When the GUN mode is selected (from a switch on the throttle), what looks like a funnel appears on the HUD. Once you have the enemy aircraft centered between the two lines of the funnel, a squeeze of the trigger on the front of the control stick sends a stream of cannon shells toward the target. According to F-15 pilots, the new sight symbology has radically improved gunnery accuracy and makes the gun a much more dangerous weapon.
Good as the gun is, the most powerful weapons on the Eagle are its eight air-to-air missiles (AAMs). Originally, the F-15’s primary AAM was the Raytheon AIM-7 Sparrow, four of which could be carried on racks tucked neatly on the underside of the fuselage. These have since been replaced by the Hughes AIM-120 Advanced Medium Range Air-to-Air Missile (AMRAAM), which is known as the “Slammer” by pilots. Underwing pylons also can carry up to four AIM-9 Sidewinder AAMs or AMRAAMs.
All these systems and weaponry have made the Eagle the most powerful air superiority fighter in the world for over two decades now. This has translated to a modest degree of success in the export market, despite the relatively high cost of the Eagle compared to the F-16 Fighting Falcon, the Mirage F-1 and -2000, and the MiG-29. Several generations of Russian, British, and French fighters have tried to get the better of the Eagle, but regular upgrades and the superb training of the USAF pilots have kept the F-15 at the top of the worldwide fighter hierachy. Currently, there are more than 1,300 F-15s of all models in service with the U.S. Air Force, the Israeli Air Force (F-15A/B/I models), the Japanese Air Self-Defense Force (F-15J), and the Royal Saudi Air Force (F-15A/B/S models). The Japanese F-15J is built by Mitsubishi on license from McDonnell Douglas.
The ultimate test of any military aircraft is combat, and the Eagle has an undefeated record. The Israelis scored the Eagle’s first kill, a Syrian MiG-21 in June of 1979. Later on, in February 1981, they provided the ultimate proof of the Eagle’s superiority by downing a Syrian MiG-25 Foxbat, the very aircraft it had been designed to defeat. Israeli F-15s also escorted the force of F-16s that destroyed an unfinished Iraqi nuclear reactor outside Baghdad in 1981. The Saudis also have scored with their force of Eagles, with at least one kill of an Iranian Phantom over the Persian Gulf in 1988, and two kills by one pilot of a pair of Iraqi Mirage F-1Qs armed with AM-39 Exocet anti-shipping missiles during Desert Storm. In fact, Eagles shot down at least thirty-five of the forty-one aircraft that Iraq lost in air-to-air combat during the 1991 conflict. The record book currently credits the F-15 with a career total of 96.5 confirmed air-to-air kills for no losses.
With the coming of the F-15’s designated replacement, the Lockheed F-22, further production of the Eagle for the USAF and a few foreign governments will be limited to the Strike version. The remaining USAF -C and -E model aircraft will all be fitted with GPS receivers, as well as the follow-on version of the JTIDS data link terminal. There is also a radar upgrade program, designed to replace some of the “black box” components of the APG-63/70 system with newer units from the APG-73 radar used on the F/ A-18 Hornet fighters now being delivered to the U.S. Navy. This upgrade will allow for faster processing of information, as well as a larger memory module. It is also likely that before it goes out of service, the new model of the venerable Sidewinder AAM, the AIM-9X with its helmet-mounted sighting system, will be integrated into the Eagle. Whatever happens to the Eagle fleet, the taxpayers of the United States can be pleased with the value that they received for their investment in the Eagle, which held the line in the air for the last years of the Cold War and the beginning of the new world order.
MCDONNELL DOUGLAS F-15E STRIKE EAGLE
I had never flown an eighty-one-thousand-pound jet before, and we were surprised when we started taxiing. We felt a thump, thump, thump underneath us, and we were concerned until we realized that all that weight standing on the tires had molded a temporary flat spot on them.
—F-15E PILOT, DESERT STORM, JANUARY 17, 1991
The F-15E Strike Eagle is an almost perfect balance of structure, power plant, sensors, weapons, and avionics, controlled by the finest cockpit design in the world today. Now you might wonder why I’m describing it separately from the air-to-air version of the Eagle. The truth is that while the two birds share a common heritage, they really are different aircraft, both inside and out. In fact, the crews that fly this powerful beast say there are two kinds of USAF crews: those that fly the Strike Eagle, and those who wish they did. Given what I’ve learned about this machine, they may be right.
It is surprising that an aircraft originally designed as a pure air superiority machine should give rise to one of the greatest fighter-bombers in aviation history. Nevertheless, by the early 1980s, with the fleet of F-111 fighter bombers aging rapidly, and the F-117As just coming into service, there was a severe shortage of all-weather strike aircraft in USAF service. Thus, the USAF leadership began to kick around the idea of an interim strike aircraft, which could bridge the gap between the older F-111 and the new stealth types that were being planned.
The F-15E was not a plane the Air Force requested directly per se; it began as a private venture funded by McDonnell Douglas. This is because the contracting rules of the U.S. Department of Defense (DoD) do not allow the services to “ask” a contractor directly to make them something. They can, however, “suggest” that a company put together an “unsolicited proposal” to offer certain goods and services. Such dialogues are common, and were apparently conducted by General Wilber Creech, USAF, then commander of the Tactical Air Command, and several aircraft companies concerning strike variants of existing fighter designs. Thus, General Creech might well be considered the USAF “father” of the Strike Eagle. The effort began when a production F-15B (originally a two-seat trainer version) was converted for ground attack by adding extra underwing pylons and bomb racks on CFTs. Demonstrations of the prototype at Edwards and Eglin AFBs in 1982 and 1983 were sufficiently impressive that the Air Force decided to hold a competition between the F-15 and an improved version of the General Dynamics (now Lockheed) F-16 with a cranked delta wing, the F-16XL. The McDonnell Douglas entry won the competition, and in 1984 they were awarded a contract to begin full-scale development, with an original goal of 392 production aircraft. But budget cuts at the end of the Cold War chopped this number down to two hundred by 1994, plus a few replacements for aircraft lost in Desert Storm and training mishaps.
A McDonnell Douglas F-15E Strike Eagle of the 366th Wing’s 391st Fighter Squadron flies over the Nevada desert during Green Flag 94-3. It is armed with the training versions of Sidewinder and AMRAAM air-to-air and Maverick air-to-ground missiles.
Craig E. Kaston
The first flight of the Strike Eagle was on December 11th, 1986, with deliveries to the Air Force beginning on December 29th, 1988. The 4th TFW, with three squadrons, reached an initial operational capability (IOC—first squadron service) in October 1989 at Seymour Johnson AFB, North Carolina.
A cutaway drawing of the forward fuselage of the McDonnell Douglas F-15E Strike Eagle.
Jack Ryan Enterprises, Ltd., by Laura Alpher
That change was more than just cosmetic. Although the F-15E is externally very similar to the F-15D (the two-seat trainer model of the F-15C), about 60% of the F-15’s structure was redesigned to accommodate its new role as a strike aircraft. These changes were designed to strengthen the airframe, extending the certified fatigue life to sixteen thousand hours, and allowing sustained 9-G maneuvers, like its smaller partner, the F-16. The extra strength is important, because the huge fixed-geometry wing of the F-15 can make for a rough ride at low altitude for both the airframe and the crew, even when nobody is trying to kill you. Also, since low-altitude, high-speed flight can be a dangerous thing, the F-15E’s windshield is specially strengthened against bird-strikes, which are more common than you might think. The basic F-15 is an enormously tough airplane—after a midair collision, one F-15 pilot safely landed his craft with only 14 in./35 cm. of wing remaining on one side—and the modifications to the -E model have only made it tougher. Maximum takeoff weight was increased from 68,000 lb./30,845 kg. to an astounding 81,000 lb./36,741 kg.! Of this total, up to 24,500 lb./11,100 kg. can be ordnance, in almost any mix of air-to-air and air-to-ground weapons imaginable.
The two-man cockpit of this Mc-Donnell Douglas F-15E Strike Eagle is shown to advantage, with the wide-field-of-view Heads-Up Display (HUD) at the bottom, in front of the pilot. Craig E. Kaston
The greatest strength of the Strike Eagle is the two-man cockpit, which allows for the increased workloads of low-level, day and night strike missions. Historically, two-seat fighters have usually gained the advantage in combat against single-seat types, because the situational awareness benefit of an extra set of eyes and brains is greater than the weight penalty of the extra ejection seat. The benefit is even greater in ground attack missions, because the backseater can concentrate on precise delivery of weapons and managing the defensive-countermeasures systems (jamming, chaff, and flares), while the pilot concentrates on flying the plane. Though Weapons Systems Officers (WSOs) are not trained as pilots, they do tend to become skilled at flying and “staying” the pilot; and both crew positions have a full set of flight controls.
A cutaway drawing of the Lockheed Martin AAQ-13 LANTIRN navigation pod.
Jack Ryan Enterprises, Ltd., by Laura Alpher
The division of labor in the Strike Eagle between the pilot (in the front seat) and WSO (or “wizzo,” in the backseat) is nearly perfect, thanks to another excellent design effort by Eugene Adam and his team at McDonnell Douglas. In the front seat, the pilot has a wide field-of-view HUD and three Multi-Function Displays (MFDs), two monochrome/green and one full-color, in addition to the normal controls you would encounter in an F-15C. Each MFD functions like a computer monitor that can show data clearly even in bright daylight, and has an array of selection buttons mounted on all four sides of the bezel. The HOTAS controls have been upgraded to support the extra capabilities of the -E model’s APG-70 radar, as well as the Low Altitude Navigation and Targeting Infrared for Night (LANTIRN) system pods (which we will look at later). To the right of the HUD is the display for the Improved Data Modem (IDM), a sort of low-speed data link which is tied to the onboard Have Quick II radios and the weapons delivery system. It is designed to be part of the joint-service Automatic Target Hand-Off System (ATHS), which allows the F-15E to automatically send and receive targeting coordinates to and from a number of other U.S. Army, Marine, and Air Force systems, including the F-16C, the OH-58D Kiowa Warrior, the AV-8V Harrier II, the AH-64A Apache,
and the Army’s TACFIRE artillery control system. In lieu of a JTIDS terminal (which is planned for installation later), it is a capable little device for getting targeting information from a variety of sources. In the rear cockpit, delivery of air-to-ground ordnance is the WSO’s main job, and the best tool for this is the same Hughes APG-70 radar that is on the -C model Eagle, though it has a number of added features unique to the Strike Eagle. The radar data, as well as data from the onboard LANTIRN pods, are displayed on four MFDs—two color and two monochrome/green—in the rear cockpit. An onboard videotape recorder serves as the “gun camera,” recording whatever appears in the HUD, or on any of the selected MFDs.
