STRIKE EAGLE

SYSTEMS

ENGINES

The Strike Eagle is powered by either the Pratt and Whitney F100-PW-220 engine or the F100-PW-229 engine. Since 1991, the Dash 229 version of the Pratt & Whitney F100 has powered the F-15E starting with the 135th production aircraft (90-0233). Currently all Strike Eagles at Seymour Johnson AFB, NC, and Mountain Home AFB, ID, are equipped with PW-220 engines.  All aircraft at RAF Lakenheath, UK, and Elmendorf AFB, AK, are equipped with PW-229 engines.  Both of these engines are low bypass, high compression ratio, dual spool, turbofan engines with augmented thrust.  The engine is a modular design which means that major sections of the engine can be changed without depot level repair.  The five modules are: the fan, core, turbine, gear box, and augmenter modules.

The fan and core sections also contain variable geometry vanes to optimize airflow.  The variable vanes are stators with a movable trailing edge section.  The fan has one set of compressor inlet variable vanes (CIVVs) that make up the first stage stator vanes.  The core engine has three stages of rear compressor variable vanes (RCVVs), these consist of the rear compressor inlet guide vanes and the fourth and fifth stage stator vanes.  The engine has 13 stages of compression -- three low pressure and ten high pressure.  The fan module has three stages making up the N₁ compressor.  The core module mounts to the back of the fan section and has the remaining ten stages, making up the N₂ compressor.  The core module is smaller than the fan module allowing a small percentage of air to pass between the core and outer ducts.  This air is used to cool the core and afterburner section and provides fresh air for augmenter combustion.  The turbine module is uses hot exhaust gases to provide rotational power to the fan module.  The augmenter module (afterburner) is a variable geometry nozzle that provides optimum air pressure through the engine to give maximum thrust.  The PW-220 has 5 stages of afterburner while the PW-229 has 7.

The gear box module provides a central mounting point for engine accessory components. Engine accessories are contained in the airframe-mounted accessory drive (AMAD) rather than on the engine itself. As a result, any engine can be mounted in either the port or starboard engine bays. This provides greater ease to maintenance crews while at the same time eliminating what could be a logistical nightmare during times of war. Engines are removed by sliding them out the rear of the aircraft on rails built into the airframe. Each engine needs disconnection from only ten attachment points before it may be removed. From that point, it is slid out onto an elevated trolley for transport or immediate maintenance.

The engines are separated by titanium walls between engine bays to minimize the possibility of damage to both engines when one is hit or damaged. Between the two barriers, there is a pressurized extinguisher bottle which can release fire-suppressing Halon into either engine bay or into the void between the firewalls. Power for engine start is provided by a Jet Fuel Starter (JFS) manufactured by AlliedSignal. This unit also generates limited electrical and hydraulic power on the ground when the engines are not operating.

FLIGHT CONTROLS

The Strike Eagle's flight control system consists of two independent systems -- a direct Hydromechanical (HM) connection between the control stick and the control surfaces, and a "fly by wire" electrical system called the Control Augmentation System (CAS).

The HM system is made up of primary (ailerons, rudders, and stabilators) and secondary ( laps and the speed brake) flight controls, and the flight control actuators which hydraulically boost the stick movement.  In the HM system, stick movement directly corresponds to flight control movement.  The HM inputs are modified by the Control Stick Boost/Pitch Compensator, which ensures that stick forces and control surface movement are constant throughout the flight envelope.

The CAS is a triple-redundant digital fly-by-wire system by Lear Astronics that senses the amount of force applied to the stick and sends an electrical signal to the stab and rudder actuators to augment the HM system.  The CAS only controls the stabs and rudders (the ailerons are not involved in this system) and roll control is provided by differential movement of the stabs. When force is applied to the control stick,  the stick force sensor located just below the stick grip uses electronic spring gages to measure the amount of force applied.   All commands from the stick force sensor are routed through the flight controls computers, the electrical signal is then sent by wire to the stab and rudder actuators. If the mechanical outputs from the cockpit were completely severed, the pilot probably wouldn’t notice.  The pilot could also fly the aircraft quite well with the stick welded in place. 

FUEL

The F-15E fuel system is a fully automatic system that gages and transfers fuel to maintain balance and CG without any crew input. The fuel system provides the engine with pressurized fuel under normal conditions and gravity feeds fuel for limited engine operation without hydro or electric power.  The fuel system consists of three internal tanks, two internal wing tanks, and conformal fuel tanks (CFTs), which provide approximately 23,000# of total fuel.

All internal tanks are filled with porous foam to fill air spaces when the tanks are empty and also helps inhibit explosion should the tank get punctured by a bullet.  The Strike Eagle's conformal fuel tanks (CFTs) are flush mounted and fit tightly in the area where the wing meets the fuselage.  They are fully foamed and divides into 3 sections to prevent fuel sloshing and aid in maintaining center of gravity.  CFTs can hold 4,900# (753 gallons) of JP-8. The major advantage to CFTs is their low drag -- CFTs increase aerodynamic drag by 25% while external tanks increase drag by 65%.  Each CFT also features six stub-pylons for the mounting of ordnance. The stubs are placed tangentially, causing less drag than would be present with the use of the standard Multiple Ejection Racks mounted to the wing stations. Their placement arranges the bombs in two rows along the sides of the aircraft. This reduced drag translates into slightly higher speeds and increased range.  External wing tanks can be carried on pylon stations 2, 5, and 8 and carry 4,100# (610 gallons) of fuel and are not foamed.

The Strike Eagle is fully able to be air refueled via tankers equipped with a boom.  The aerial refueling receptacle is at the top of the left wing root below a hydraulically actuated slipway door.  When the slipway switch in the cockpit is set to open the door falls in to form a slipway for the refueling boom.  An external floodlight and internal slipway lights come on for night refueling.  The ready light in the cockpit goes out when the boom makes contact.  If the boom and aircraft become separated the ready light comes on.  The receptacle will not relatch for 5 seconds to keep from damaging the boom.

The aircraft can be ground refueled with or without electrical power through a single point refueling receptacle (SPR) in the right wheel well.  The aircraft can be suction defueled through the defuel receptacle also located in the right wheel well.

HYDRAULICS

The F-15 Hydraulic system consists of three independent systems that are further divided into four subsystems and seven total hydraulic circuits. The two power control (PC) systems primarily operate the flight controls.  The utility system supplies all other components requiring hydraulic pressure, and serves as a backup for the flight controls.  Through a system of redundant backups and reservoir level sensing the aircraft can safely maintain enough control to reach home station with only one of three hydraulic systems operating.

The aircraft utilizes Reservoir Level Sensing (RLS) on all three systems.  All three systems are divided into A and B circuits.  Reservoir level sensing isolates the effected system in the event of a leak.  The Utility hydraulic system is also divided into Utility A and B circuits.  In addition it has a utility Non-RLS circuit.  The Non-RLS circuit does not  pass back through the reservoir for sensing.  The Non-RLS system is a last ditch system designed to provide fluid under pressure to the emergency generator and horizontal stabilators and the rudders.  In the event all three hydraulic systems were lost, the aircraft could be flown with only the horizontal stabilators and the rudders.

The PC system has a total capacity of 4.6 gallons.  The Utility hydraulic has a total system capacity of 14.5 gallons.  The hydraulic reservoirs store fluid to supply the pumps.  There is one pump for each PC system, each is mounted to the aircraft mounted accessory drive (AMAD) through the pump manifold.  The PC 1 pump is mounted on the left AMAD and the PC 2 pump is mounted to the right AMAD.  The PC pumps operate at 46.8 Gallons Per Minute (GPM) and 3000 PSI.

There are two separate utility pumps, left and right.  The reason for the dual pumps is the 20 MM gun,  it has a very high demand on the hydraulic system.  A pilot maneuvering for a gun shot will place a big demand on the aircraft hydraulic systems.  When the gun is fired the additional demand will cause the utility system to sense a pressure drop and allow the right pump to contribute.  The utility pumps operate at 53.7 GPM  and 3000 PSI.

ELECTRICS

The F-15 uses both Aircraft Alternating Current (AC) and Direct Current (DC) electrical power.  Electrical power is provided by a Lucas Aerospace generating system featuring constant-speed drive units rated at 60/75/90 kVA.  AC electrical power is supplied by a left and right 115 Volts AC (VAC), 400 (HZ) generators.  The DC system provides 150 amp 28 vDC by using the left and right transformer rectifiers.  As the engine starts the AMAD turns the Integrated Drive Generator (IDG).  The IDG consists of the Constant Speed Drive (CSD) and a generator.  The CSD turns the generator at a constant speed. If the speed is incorrect to the CSD it goes into an underdrive or overdrive condition to maintain the proper rpm.  The current then goes to the GCU which ensures the current is proper.  The DC side is supplied by the left and right transformer rectifiers which convert 115 VAC, 3 phase energy, to 28 VDC 150 amp energy.

The external electrical power system consists of an external power receptacle, external power monitor, and the external power contactor.  The external power system is used for ground maintenance when the generators are not used.  When external power is applied, and the external power switch is set to on, power is applied to the external power monitor which tests the power and sends it on to the external power contactor.  The power then goes to the de-energized line contactors of the normal electrical system to provide the aircraft with full power.

The emergency power system is an integrated system that provides in flight power in the event one or both main generators fail, both transformer rectifiers fail, or fuel system boost pump pressure is too low.  The emergency electrical system consists of a hydraulically driven emergency generator which provides 115 VAC or 28 VDC to the emergency essential bus, the emergency bus, and the emergency fuel boost pump.   

EGRESS SYSTEM (EJECTION SEAT)

Both crew members sit in McDonnell Douglas ACES II ejection seats.  The ACES II is a "zero-zero" capability seat, meaning the seat can safely put a crewmember under an open parachute at "zero" altitude and "zero" airspeed.  The ACES II is one of the most advanced capability ejection seats in the world.  The seat can determine what speed and altitude you are at and, using that data, deploy parachutes automatically for maximum crewmember protection and survivability.  It provides three modes of ejection depending on the airspeed and altitude of the ejection seat when it departs the aircraft.

• Mode one ejection is a low speed,  low altitude ejection. It’s generally at speeds less than  250 knots and altitudes below 15,000 feet.  During this mode of ejection the pilot parachute is deployed when the mortar is fired. The pilot chute then pulls out the recovery chute to bring the pilot down safely.  All this happens almost immediately after the seat departs the aircraft.  The entire sequence from pulling the handle to hanging in the parachute takes less than two seconds.

• Mode two ejection is a high speed,  low altitude ejection. It’s usually at speeds between  250 and 600 knots and altitudes below 15,000 feet.  In this mode a drogue gun is fired which pushes out the extraction chute.  The extraction chute pulls put the drogue chute which is deployed to slow the seat down and prevent damage to the personal (or recovery) chute.

• A mode three recovery is an ejection that occurs at speeds or altitudes greater than mode two parameters.  When this situation occurs the seat waits to deploy any parachutes until the seat falls within mode two parameters to ensure the pilot has sufficient oxygen during descent. In the event of an ejection above 600 knots the parachutes deployed to save the pilot would be ripped from the seat.

The aircraft contains a primary and secondary escape system,  independent of each other.  Both systems are activated when the ejection control handles on the seat are pulled.  The secondary system has a time delay to allow the primary system to work first.  In a single seat aircraft it is a .75 second delay.  For the dual seat aircraft  (or family model) there is a 1.5 second delay for the back seat and a two second delay for the front seat.  In the event that both systems fail to eject the canopy, the secondary system ejects the seats through the canopy  using the canopy buster (small metal horn) on the top of the seat

LANDING GEAR

The F-15E's landing gear is a hydraulically retractable tricycle type, with single wheel on each gear. All units retract forward. Cleveland nose and main units, each incorporating an oleo-pneumatic shock absorber. Nosewheel and tire by Goodyear, size 22 x 6.6-10, pressure 17.93 bars (260 lb/sq in). Main wheels are manufactured by Bendix, with Goodyear tires size 34.5 x 9.75-18, pressure 23.44 bars (340 lb/sq in).  Wheel brakes are carbon heat-sink type by Bendix .  The wheel braking anti-skid control system is by Hydro-Aire.

STRUCTURE

The Strike Eagle features a max airframe load increase over it's C-model brothers up to +9G.  The Eagle's wing structure design is based on a torque box with integrally machine skins and ribs of light alloy and titanium.  The wingtips, flaps, and ailerons are aluminum honeycomb, the speedbrake panel is titanium, and the skin is aluminum honeycomb and graphite/epoxy composites.  The wing airfoil design is a NACA 64A section with conical camber on leading-edge and 38º sweep.   The wing is 42' at quarter-chord with a thickness/chord ratio 6.6% at the wing root and 3% at the tip.  Wing angle of incidence is 0º with anhedral of 1º. The twin vertical tails are positioned high and aft to receive vortex off wing and maintain directional stability at high angles of attack. Straight two-dimensional external compression engine air inlet each side of fuselage. The Strike Eagle's air inlet controllers (AICs) are by Hamilton Standard with the hydraulic air inlet actuators by National Water Lift.