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Boeing B747-400 ATA 49 Auxiliary Power Unit (APU)

• The document is a training manual
• It provides information on the Boeing B747-400 ATA 49 Auxiliary Power Unit
• The document is for training purposes only and internal use
• Copyright is held by Lufthansa Technical Training (LTT)
• Any reproduction or use outside of training is prohibited
• Mention of EASA Part-66 B1 is included

Pratt & Whitney Canada PWC 901A

• The APU is a Pratt & Whitney Canada PWC 901A
• The manual provides specifications for this particular APU
• It's a document for training purposes only

Engine Dimensions (Approximate)

• Length: 76.90 inches
• Width: 43.33 inches
• Height: 51.54 inches
• Weight (wet, without generators): 889.5 lbs
• Weight (dry, without generators): 846.5 lbs

Engine Ratings (Approximate)

• Fuel flow: 896 lbs/hr
• N1 at 100%: 24,625 RPM
• N2 Speed: 31,200 RPM
• Generator output speed: 8,000 RPM
• Maximum shaft horsepower: 286 SHP
• No-load airflow at 60°F (16°C): 254 lb/min
• Max-load airflow at 60°F (16°C): 444 lb/min
• No-load bleed pressure at 60°F (16°C): 25 PSIA
• Max-load bleed pressure at 60°F (16°C): 42 PSIA
• Bleed air temperature: 380-450°F (195-232°C)

Exhaust Gas Temperature

• Maximum rated temperature: 641°C (1186°F)
• Maximum temperature (auto shutdown): 700°C (1292°F)

Oil Temperature

• Normal operating temperature: 180°F (82°C)
• Maximum temperature (auto shutdown): 275°F (135°C)

APU General Description

• The APU is a self-contained unit for electrical and pneumatic power during ground operations
• It has a twin spool turbine engine, two AC generators, and controls for safe operation
• It provides compressed air for air conditioning, main engine starting, and hydraulic pumps

APU Drain

• APU drains remove fuel, oil, and water
• Discharge overboard via a drain mast and other fittings
• Intake plenum and oil filler scupper drain directly into the APU compartment

APU Fuel System

• The fuel supply line extends from the aircraft's No. 2 and 3 main fuel tanks
• Includes a DC fuel boost pump, fuel shutoff valve, pressure switches to monitor system operation.
• Fuel flow is controlled by the APU controller and a fuel metering unit (FMU) for metered fuel

APU Cooling Air System

• The load gearbox drives a fan for cooling AC generators and cooler
• The exhaust air from the accessory cooling system is expelled into the APU compartment