APU Start

[Guest Jason210]

This is a very minor point, and I ask it just out of interest :-)I noticed that the APU will start when all the fuel pumps are off. My understanding of these type of aircraft was that one of the fuel pumps needed to be on in order to get fuel up to the APU. That was the case on the 747-400 anyway. There was an electric fuel pump that could be run from stand-by power (I think it was number 3).I might be wrong though.Anyone got any comment on this?

[scoob 18]

not required. from the 737 technical site -[blockquote]The fuel source is normally from the No 1 main tank and it is recommended that at least one pump in the supplying tank be on during the start sequence (and whenever operating) to provide positive fuel pressure and preserve the service life of the APU fuel control unit. Boeing responded to this need by installing an extra DC operated APU fuel boost pump in the No 1 tank on newer series 500 aircraft which automatically operates during APU start and shuts off when it reaches governed speed. You can quickly tell if this is installed by looking for the APU BAT position on the metering panel and the APU BAT OVHT light on the aft overhead panel.source: http://www.b737.org.uk/apu.htm[/blockquote]--

[Guest Jason210]

Thanks ....Nice answer!!!!Jason

[CF104 0]

On the 737-200 series the APU can be started without a main fuel boost pump running. The APU Fuel Control has enough suction to get a good start under most conditions and once AC power is established, turn on a #1 tank boost pump. There were several operators who ordered their 737-200's with an optional APU DC fuel pump that greatly improved starting performance when cold. I've worked on both types of APU fuel system and found the DC pump very beneficial.Cheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.sstsim.com/images/team/JR.jpgwww.SSTSIM.com