Question about 747-400 GE engines start procedure

[AdiR 27]

In manuals we have (for non-automatic ignition):

 

Engine “START” switch .................................................. Pull
Verify that the N2 RPM increases. Verify that the oil pressure increases.
FUEL CONTROL switch.........................................RUN

In 737-800 we must wait until ~25% N2 to switch fuel control lever to idle.

 

And what about 747-400? As soon as both N2 RPM and oil pressure increase (as quoted above) or maybe from specific value not shown in manual?

 

T.Hanks!  :smile:

[Tatave 57]

There are no specific values in the 744- same deal with the 777. All you look for is an increase in oil pressure and N2. 

[AdiR 27]

There are no specific values in the 744- same deal with the 777. All you look for is an increase in oil pressure and N2. 

 

Thank you Kevin!

[F16_Driver 25]

On a manual start there is a minimum level N2. It's marked by a magenta line. I can recommend this video originally made for PSX about the topic.

https://www.youtube.com/watch?v=hhM4KcxKxUM

[Qavion2 39]

There are no specific values in the 744- same deal with the 777. All you look for is an increase in oil pressure and N2.

 

 

What F16 driver said. You can potentially destroy an engine if you put the fuel lever on below the magenta line. In Engineering, for a manual start, we run the starter until it doesn't go any faster, then put on fuel. It's the same deal with 777s (at least from the engineering side). The 777 Maintenance Manual for the Trent engine, says spin the engine to 25% N3 or max motoring, then put on the fuel.

 

Cheers

JHW

[serviceceiling 135]

Ok, that's an easy one. If AUTOSTART is installed on your aircraft (AUTOSTART button on the engine start panel on the overhead) then you simply look for N2 movement and oil pressure on the engine display before you engage the fuel control switches. The FADEC will then manage the engine start on its own. If however, AUTOSTART is not installed you'll wait for around 25% N2 or max motoring and then introduce fuel with the respective fuel control switches, monitoring the engine parameters until the engine is stabilzed. It's still a turbofan engine, there's nothing different about how it works on a 737, CRJ or A380. 

[Captain_Al 66]

For a manual start, the Boeing procedure is to bring the Fuel Control switch to RUN at the Fuel On Command Indicator, which is the magenta tick mark on N2.

 

On the 747-400 that is at 15% N2. Most airlines, assuming they do not have autostart, will modify this procedure to go to max motoring, like 25% N2 + 5 seconds, and then introduce fuel, or if you can't get to 25%, then whatever max is plus 5 or some other number of seconds. This is generally better for the engines, at least according to performance engineering at a now defunct airline.

 

The early P & W did not have Autostart, but most operators have Autostart with the GE or RR engines and only do a manual start if autostart is not working. The 747-8 is a full time autostart jet with no manual start capability.

[Qavion2 39]

Ok, that's an easy one. If AUTOSTART is installed on your aircraft (AUTOSTART button on the engine start panel on the overhead) then you simply look for N2 movement and oil pressure on the engine display before you engage the fuel control switches.

 

 

I don't know where you guys come up with these procedures .... The N2 should not move if you only pull the start switch and the Autostart Switch is ON. If it does move on a CF6 or PW4000.. call an engineer immediately. If it happens on an RB211... check for strong headwinds.

 

Cheers

JHW