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P-3C ORION

The P-3C is a four engine, low wing aircraft designed for patrol and antisubmarine warfare. It is in the 135,000 pound GW class and is powered by four T56-A-14 turboprop engines. Each engine provides 4600 shaft horsepower (maximum rated), for takeoff.

Dimensions

Wing span..............................................99 ft, 8 in.
Length.................................................116 ft, 10 in.
Height to top of fin...................................33 ft, 8.5 in.
Props......................................Hamilton STD 54h60-77
Fuel Grade.................................JP-4
Fuel density...............................6.5 lb/gal
Ceiling....................................FL28,5
V speeds (Courtesy, Mike Cantin) ...........Under construction
Range......................................2383 Miles

APU
The auxiliary power unit provides pneumatic and electrical power necessary to make the aircraft self sufficient. Self-sufficiency is considered to include 1)Main engine starting without external power, 2)Aircraft air conditioning without external power or without the main engines operating, and 3)a 60 KVA source of ac electrical power without the main engine generators operating. The gas turbine engine of the APU is a self-contained power source which requires only the aircraft battery for starting. The main output drive pad powers a 60 KVAac generator. Pneumatic power is available as clean compressed air to supply the aircraft air-conditioning and engine starting system.

The engine develops power by compressing ambient air witha two-stage centrifugal compressor. Compressed air, mixed with fuel and ignited, drives a radial inwardflow turbine wheel. The rotating shaft of the turbine wheel drives the compressor, accessories,and the output shaft to the ac generator. Compressed air is obtained by bleeding air from the compressor.

Fuel for the APU gas turbine engine is normally supplied from the No. 2 fuel tank, although it may be supplied from any tank through the crossfeed system. It is routed to the APU through a manual shutoff valve, a fuel filter, and a solenoid-operated shutoff valve. The solenoid fuel shutoff valve is opened automatically when the APU control switch is positioned to START. The APU consumes about300 Lbs/hour when operating a normal electrical load and the airconditioning system.

The guarded APU control switch, located on the APU overhead control panel, is labeled OFF, ON, and START. It is used for startingand stopping the unit. It is spring loaded to the ON position fromSTART. Placing the switch to the on position (only) opens the inlet and exhaust doors for preflight inspection. In the OFF position, the APU will shut down and the inlet and exhaust doors will close after about a one minute time delay.

Generator Switch
The APU generator switch is identical to the engine driven generator switch in operation. The switch is located on the electrical power control panel and is labeled ON, OFF, and RESET.

In-Flight Arming Switch
The guarded APU in-flight arming switch located on the APU control panel has two positions. OFF and ARM. In the ARM position the nose landing gear uplock switch is bypassed, energizing the ground dc bus to allow APU operation during in-flight emergencies. If this switch is positioned to ARM while the aircraft is on the ground, air conditioning, engine starting, and bomb bay heating will not be available from the APU.

APU Start Checklist

NORMAL-SAFE switch.............NORMAL
All circuit breakers on APU essential bus circuit breaker panel and onAPU protion of ground operation dc bus circuit breaker panel........IN (E)
APU arming switch-OFF (In flight-ARM).
APU fire detector..............CHECKED.
APU control switch-START, then release to ON. Actuation of this switchcauses the following sequence to occur:
- a. Intake and exhaust doors open.
- b. APU starter is energized.
- c. At approximately 10 percent RPM, ignition occurs and fuel flow is initiated.
- d. As RPM increases to approximately 35 percent, starter is deenergized.
- e. RPM increases to 100 percent.
- No.2 fuel boost pump...........AS REQUIRED (to maintain RPM within limits)
Auxiliary power is now available on the ground for starting the mainengines, air conditioning, bomb bay heating, and ground electrical requirements as needed. In flight, only electrical power is available. Ensure a minimum of 1000 pounds of fuel in tank No. 2 to provide adequatehydraulic oil cooling during APU operation. With low fuel level in tankNo, 2, crossfeeding of the APU is recommended.
APU Limits
- EGT.....715 degrees C, MAXIMUM PEAK
- ........710 degrees C, MAXIMUM PEAK (10 Seconds)
- ........677 degrees C, MAXIMUM CONTINUOUS
- RPM.....98-102 percent, GROUND
- ........106 percent MAXIMUM
Stopping the APU
1. GRD AIR COND switch..........OFF (E) or if EDC is operating,
2. APU AIR OVRD switch..........ON (E)
  After exhaust temperature has stabilized:
3. APU control switch ..........OFF (E)
  - Exhaust temperature should drop.
  - RPM should drop immediately.
  - Intake and exhaust doors should close after 1 minute.

Additional Related Links

Lets lookat the P-3C Checklist.

Emergency Procedures for the P-3C Orion

The Emergency Checklist

Glib's P-3 Orion Page

RadarStorm Images from the NSSL P-3 Orion Storm Chaser.