sustain a hellish 2,460degF/1,349degC. In full afterburner, the basic F100 produces 25,000 lb./11,340 kg. of thrust — nearly eight times its own weight! A skilled ground crew can remove and replace an engine in thirty minutes; just try that on your Oldsmobile! In service, F100 engines have worn out much faster than expected, principally because the Eagle's advanced airframe allowed pilots to fly on the 'edge of the envelope' at throttle settings and angles of attack that stress the engines severely. But the edge of the envelope is where pilots win air battles, so the price has been paid to maintain the awesome capability that the F100 delivers.
One of the realities of modern jet fighters is that they burn gas faster than teenagers drink diet soda — a lot faster. While the F100 turbofan is more efficient than the older turbojet fighter engines, they still burn a huge load of fuel, especially in afterburner. To feed the two big turbofans, the Eagle carries a huge load of fuel internally, in the fuselage and wings. In addition, all F-15s can carry up to three external 610 gallon/2,309 liter drop tanks, one on the centerline and one under each wing. To extend the Eagle's unrefueled range even further, McDonnell Douglas developed the Fuel and Sensors, Tactical (FAST) Pack, a pair of bulging 'conformal' fuel tanks (CFTs) that fit tightly against the sides of the fuselage below the wings. These are designed to minimize drag and actually generate some lift, so the Eagle's performance is only slightly affected. Holding 750 gallons/2,839 liters of fuel, each CFT can be installed or removed in fifteen minutes. In addition, there are fittings on each CFT for mounting bomb racks or missile rails. CFTs are not carried on the current fighter version of the Eagle, the F-15C, because the normal internal fuel load, as well as that in the drop tanks, is usually adequate for the missions the Eagle drivers fly.
The business end of the Eagle is the cockpit, which is topped with a large bubble canopy. It provides exceptional panoramic visibility, which is critical to survival in a dogfight. F-15 pilots talk about a feeling of riding 'on' the aircraft rather than 'in' it. By slightly extending the canopy, the design left sufficient room behind the pilot for a second seat, making it relatively simple to build the F-15/D operational trainer, and ultimately the F-15E Strike Eagle.
The pilot sits in a McDonnell Douglas ACES II ejection seat, which is one of the best in the world. When you sit in one, you are held by a lap belt and shoulder-harness system, and the cushions contain the parachute and rescue packs that deploy when the seat separates. All you need to do to escape from a stricken aircraft is to pull one of the two sets of ejection handles (one on either side of the seat) while sitting firmly in the seat, and you are on your way. Pyrotechnic charges blow off the canopy, and then a rocket motor fires and blasts you free. At that point, everything, including the parachute deployment, is handled automatically. Even the release of the parachute in the event of a water landing is handled by sensors that detect the presence of water and cut the riser lines loose to keep the survivor from fouling the chute and drowning.
While the instrument panel directly in front of the pilot is crammed with a mix of dial gauges, most of what he actually uses centers around just three things, the Heads-Up Display (HUD), the control stick, and the throttles. Earlier we saw how the HUD presents the most vital flight and sensor data to the pilot, without the pilot having to move his gaze down into the cockpit. This is critical, because the last thing you want to do in a dogfight is take your eyes off the target. Most of the controls that an F-15 pilot needs for fighting in the Eagle are located on the control stick; engine throttles are on the left side of the cockpit. Both are studded with small switches and buttons, each shaped and textured differently, so that after a short time, a pilot can rapidly identify a particular switch just by feel. This system — known as Hands on Throttle and Stick (HOTAS) — was developed by a brilliant McDonnell Douglas engineer named Eugene Adam, who is a legend in the business of cockpit design, having also been behind the 'glass' (using computer MFDs instead of dials and gauges) cockpits in the F-15E Strike Eagle, the F/ A-18 Hornet, and many other combat aircraft in service today. The HOTAS switches control almost everything a pilot needs in a fight — the radar mode, radio-transmit switch, decoy launchers, and of course the weapons release, which can be controlled by the movement of a finger and a flip of a switch.
While I've never flown in the front seat of an actual Eagle, I spent some time on the domed full-motion simulators operated by McDonnell Douglas at their St. Louis facility. When you sit down in the seat of an Eagle, the first thing you notice is that your hands just naturally move to the HOTAS controls and your eyes to the HUD. It takes a while to sort out all the switches and buttons, though you rapidly identify the really important ones. When they start it up and you're actually 'flying,' the first thing you notice is that your aircraft seems to wobble all over the sky, because the controls are so sensitive. You quickly learn that the trick to maintaining a smooth flight path is to loosen your grip on the control stick and let your right hand just 'kiss' it with a light touch. When you start maneuvering the Eagle, the control system is just so quick and responsive to even the smallest control inputs that you feel you're 'behind' the airplane. Even the twin F100 power plants are quick to accelerate and idle, thanks to the digital engine control system.
I mentioned earlier that the Hughes-built radar of the Eagle has been a standard for air intercept (AI) radars since it came into service in 1975. Originally designated the APG-63, it has been updated to the APG-70 standard in the F-15E and the last block of F-15C Eagles. The reason for having a radar so powerful and agile (i.e., able to discriminate and hold lock even on small targets during the high-G maneuvers of a dogfight) on the Eagle was that the designers wanted to be able to scan and attack targets in a vast volume of airspace in front of the new fighter. This requires a
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
