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Illustrated technical information covering Vol 2 Over 800 multi-choice systems questions Close up photos of internal and external components Illustrated history and description of all variants of 737 Databases and reports of all the major 737 accidents & incidents History and Development of the Boeing 737 - MAX General flightdeck views of each generation of 737's Technical presentations of 737 systems by Chris Brady Detailed tech specs of every series of 737 A collection of my favourite photographs that I have taken of or from the 737 Press reports of orders and deliveries Details about 737 production methods A compilation of links to other sites with useful 737 content Study notes and technical information A compilation of links to major 737 news stories with a downloadable archive A quick concise overview of the pages on this site



B737-200 Adv Study Notes by Anton Jordaan.

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All of the information, photographs & schematics from this website and much more is now available in a 374 page printed book or in electronic format.

*** Updated 14 Nov 2021 ***

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B737-200A APU

  • The APU consists of a 2-stage compressor and a turbine.
  • APU fuel is suction fed from the LH Fuel Manifold and is automatically heated to prevent icing.
  • During start-up, the fuel solenoid valve is opened by an oil pressure switch.
  • APU Starting limits:
  • 2 starts/hr :           in-flight
  • 4 starts/hr :           on the ground (all starts after the 2nd start to be monitored by ground personnel in the event of a fire).


APU limits:

  • 0-10,000 ft:                                  Pneumatics & Electrics
  • 10,000 – 17,000 ft:         Either Pneumatics or Electrics
  • 17,000 – 35,000 ft:         Only Electrics.
  • 35,000 ft:                                      Max altitude for APU start-up
  • APU max air demand:   90 lbs/min on the ground (restricted by APU bleed valve).

80 lbs/min in the air.

  • APU fuel consumption:              90 kg/hr (no load)

115 kg/hr (under load)

  • APU bleed valve is an electro-pneumatically operated solenoid valve.
  • When electrical load and bleed air extraction combine to raise the EGT above acceptable levels, the bleed air valve will modulate towards the closed position. In the event of an EGT overtemp, the bleed air valve will close rapidly but the APU will continue to run.
  • APU turbine speed:                   @ 100% RPM:          41,800 RPM

@ 110% RPM:          46,000 RPM (overspeed shutdown)

  • APU generator speed   @ 100% RPM:            6,000 RPM
  • APU generator’s rating:                        40 KVA in-flight (can only supply one of the Gen Buses)

45 KVA on the ground.

  • APU will automatically shut down for:
  • Low oil pressure                  
  • High oil temp                                    (157°C)
  • Overspeed                             (110% or 46,000 RPM)
  • Fire indication
  • Battery switched OFF.


  • APU oil tank capacity:                                                               1.5 US Gal.
  • APU low oil quantity light illuminates @       1.5 US Qts
  • APU max EGT constant running:                               710°C
  • APU max EGT:                                                                                       760°C
  • Max APU generator load – ground:                125 amps
  • Max APU generator load – air:                                                111 amps
  • Engine starting requirement:                                       30 psi @ SL reducing @ ½ psi per 1,000 ft.


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