Navy Advancement Career Guide & NPC News

202 Propulsion Systems



Referring to a standard illustration of this system or the actual equipment, identify the following system components and component parts and discuss the designated items for each.

a. What is its function?

b. Where is it located?

202.1.1. Secondary power systems

a. Auxiliary Power Unit (APU) - to provide pneumatic air for motoring over/starting a main engine or to drive an AMAD, can also be used for ground check out of the ECS. Located in door 52.

b. Airframe Mounted Accessory Drive (AMAD) - each AMAD drives a hydraulic pump, generator and motive flow boost pump. Located in door 53 L/R.

c. Secondary Power Compressed Air - provides pneumatic power for operating the air turbine starter or the environmental control system. An air connection is located in the right well wheel and allows use of an external air source for system operation (huffer starts).

202.1.2 Power Plant and related systems

a. Engines - F404-GE-400 or F404-GE-402 - axial-flow turbo fan engine with afterburner.

b. Ignition - alternator, electrical control unit, ignition exciter, main igniter and after burner igniter. Remains on until engine reaches 45% or throttle is moved to off, A/B ignition comes on when A/B is selected and remains on until light off is detected.

c. Lubrication - self contained oil system, supply tank, combination lube and scavenge pump, filters, oil cooler, gear box, engine sumps, scavenge screens, magnetic chip detectors, pressure transducer and inter connecting tubes. MIL-L-23699.

d. Main fuel - throttle movement is mechanically transmitted through the power lever control (PLC). The PLC acts as a power booster and positions the main fuel control.

e. Afterburner fuel - when throttle is moved to AB the ECA positions the AB metering valve to a minimum (pilot) flow and holds this until light off is sensed.

f. Variable Exhaust Nozzle (VEN) - automatically controls the throat area (A8) for the exhaust gases from the turbine and AB.

g. Variable Geometry - Automatically positions the fan and compressor inlet guide vanes and compressor variable stators to the most efficient position for engine operation.

h. Anti-icing - uses fourth stage high pressure compressor bleed air to prevent build up of ice on the front frame struts, inlet guide vanes and inlet center body.

i. Engine instrument - Integrated fuel - engine indicator (IFEI) - displays compressor speed, exhaust gas temperature, fuel flow, variable exhaust nozzle position, oil pressure and fuel quantities.

j. Throttle - movement is transmitted by mechanical linkage and airframe mounted throttle boost actuators to the Power Lever Control (PLC).

202.1.3 Fuel Systems

a. Fuel storage - fuel is carried internally by four interconnected fuselage tanks and two wing tanks. External fuel can also be carried on three 330 gallon tanks.

b. Refuel/ Defuel - can be done with or without electrical power. Maximum supply pressure is 55 psi. Re-fueled through a single point pressure receptacle in door 8 or the IFR probe. De-fuel is done by applying suction pressure at the refuel/ defuel receptacle.

c. Internal Fuel Transfer - keeps the feed tanks (2 and 3) full and controls the sequence of tank to tank transfer.

d. Center of Gravity (CG) Control - the signal data computer monitors the amount of fuel in tanks 1 and 4, therefore, if fuel in tank 4 becomes excessive the computer will close the valves in the effected tank to prevent an aft CG problem.

e. Hot Fuel Re circulation - cools the fuel, which is used to dissipate heat from the AMAD and hydraulic system.

f. Fuel Pressurization and Vent - provides regulated engine bleed air to all internal tanks. Pressurization prevents boil off at high altitude and provides positive pressure to tank bladders and to external tanks for fuel transfer. The internal tanks vent into a vent tank which in turn is vented through the outlets in each vertical fin.

g. Fuel Quantity and Gauging - Integrated Fuel-Engine Indicator is the primary fuel quantity display. Normally, total fuel and internal fuel will be displayed in pounds. The QTY push button switch will change the amounts in pounds to :

Tank no. 2 and no. 3

Tank no. 1 and no. 4

Left wing tank and right wing tank

External left and external right

Centerline (external)

The IFEI will also display BINGO.


202.2.1 State the components driven by the Airframe Mounted Accessory Drive (AMAD)

Hydraulic pump, generator and motive flow boost pump.


None to be discussed.


202.4.1 How does the AMAD interface with the APU and engine?

The AMAD is pneumatically connected to APU through the air turbine starter (ATS). The AMAD transmits power from the ATS to the engine for starting and motoring. Power to drive the AMAD accessories is provided by the engine during normal operation and by the APU in the ground maintenance mode of operation.


202.5.1 What safety precautions must be observed during engine ground turn-up?

-Operation of APU or engines to test for fuel leaks in the engine, AMAD or APU areas is not authorized.

-Do not operate engine with TTU-205 test set connected. Engine may go to high power due to N2 lock-up function.

-Do not enter area of 9 foot radius of engine inlets while engines are at idle and 25 foot while at MIL or MAX power.

-On engines equipped with Viton coated outer bypass ducts, combustion can produce toxic fumes of hydrogen floride and carbonyl floride.

-To prevent damage to newly installed engines, service oil system.

-To prevent damage to newly installed engine, motor at 29-35% rpm for 3 minutes and ensure oil pressure gets to 10 psi within 30 seconds and fuel flow is zero.

-If ambient temperature is 45 deg F or below and dew point is within 7 deg F of ambient temperature, the ground run up screen may be used with continual observation for ice build up on the air inlet leading edge and screen. If ice forms shut down.

-To prevent engine damage, if temperature is below 45 deg F engine anti-ice must be turned on.

-If ambient temperature is below 32 deg F or below and precipitation exists, ground run up screens are not recommended.

-To prevent engine damage do not try to start or motor engine after emergency shut down until the malfunction has been corrected.

-To prevent fuel spillage, if two starts are tried on one engine or previous starts/shutdowns since flight or tank draining is unknown, drain fuel dump catch tank before attempting another start.

-If visible tailpipe fire occurs, chop throttle to off. If fire continues, push left or right engine fire warning light. Be sure APU ready light is on or external air or crossbleed air is available to motor engine. When engine speed drops to 20 % N2, move engine crank switch of affected engine. Allow to motor for up to 5 minutes to extinguish fire. Move engine crank switch to off. If fire continues, discharge ground extinguisher into tail pipe.

-Normal brake pressure is not available with out right engine operating. To maintain aircraft control, make sure parking brake is set.

-To prevent damage to fuselage formers if stabilator is to be operated, doors 68 L/R must be closed, top row of fasteners installed and lockset assemblies secured.

202.5.2 What special safety precautions apply to?

a. Fueling

b. Defueling

-Never refuel during aircraft maintenance.

-Aircraft with suspected hot brakes shall not be refueled.

-Make sure aircraft and fuel servicing equipment are grounded.

-Make sure fire fighting equipment is available.

-Inspect refueling nozzle locking device to make sure aircraft ground refuel/defuel receptacle is serviceable.

-Make sure vent outlets on each vertical stabilizer and pressure relief vents on each external tank are not obstructed.

-Make sure refueling is not done within 100 feet of operating airborne type radio or radar equipment or within 300 feet of ground radar equipment.

-Make sure refueling is not done within 50 feet of other aircraft with engines operating.

-Operation of auxiliary power unit (APU) is prohibited during refueling.

-Loose metal objects, such as knifes, keys, or other objects which might produce sparks, should not be carried or worn.

-Never refuel during electrical storms.

-Do not carry matches or cigarette lighters.

-Shoes with exposed nails, metal plates or hobnails shall not be worn.

-All ordnance shall be safetied.

-Fuel pressure from servicing equipment shall not exceed 55 psi. If all foam in a wing tank has been replaced, the first fueling pressure should not exceed 25 psi.

-All persons involved in refueling shall dissipate static potential by touching or gripping an approved static ground often during refueling operation.

-When defueling is done using truck, a person will be stationed on top of truck to observe fuel level in truck and to signal defueling operator to avoid an overflow.