steveng
12-20-2004, 01:02 AM
Hello,
According to the manual, essentially the start procedure requires the Fuel Cutoff switches to be in the 'Cutoff' position, (=no fuel to engine),then the Engine Start switch moved to 'Ground' should open the pneumatic starter valve to allow compressed air to crank the engine and energise the ignition circuits. At this point the engine should begin to crank regardless of fuel pressure or the position of the Fuel Boost Pump switches. When the required N2 value is reached, the Fuel Cutoff switch should be moved from 'Cutoff' to 'Idle' to allow fuel to begin flowing to the engine and the engine should 'light up'.
The DF 727 appears to require that ALL Fuel Boost Pumps are turned on before the engine start switch will begin to crank the engine (increase N2/N1 etc.) This appears to be an anomaly, I believe the engine should crank regardless of the Boost Pump status, just the engine will not 'light up' if there is insufficient or no fuel pressure. (Incidently, real world 727 manuals I have suggest that one Fuel Boost Pump on per tank should be sufficient for engine start.) I am aware that the DF manual indicates that all Boost Pumps should be on before starting the engines, but to improve simulation the engines should at least crank regardless of the Boost Pump status.
In summary, the engines should crank up to whatever rpm the starter is capable of irrespective of the Fuel Boost Pump status. If there is fuel pressure when the Cutoff switch is moved to 'Idle' the engine should start, otherwise if no fuel pressure, the engine remains cranking with no startup.
Best regards,
Steven.
According to the manual, essentially the start procedure requires the Fuel Cutoff switches to be in the 'Cutoff' position, (=no fuel to engine),then the Engine Start switch moved to 'Ground' should open the pneumatic starter valve to allow compressed air to crank the engine and energise the ignition circuits. At this point the engine should begin to crank regardless of fuel pressure or the position of the Fuel Boost Pump switches. When the required N2 value is reached, the Fuel Cutoff switch should be moved from 'Cutoff' to 'Idle' to allow fuel to begin flowing to the engine and the engine should 'light up'.
The DF 727 appears to require that ALL Fuel Boost Pumps are turned on before the engine start switch will begin to crank the engine (increase N2/N1 etc.) This appears to be an anomaly, I believe the engine should crank regardless of the Boost Pump status, just the engine will not 'light up' if there is insufficient or no fuel pressure. (Incidently, real world 727 manuals I have suggest that one Fuel Boost Pump on per tank should be sufficient for engine start.) I am aware that the DF manual indicates that all Boost Pumps should be on before starting the engines, but to improve simulation the engines should at least crank regardless of the Boost Pump status.
In summary, the engines should crank up to whatever rpm the starter is capable of irrespective of the Fuel Boost Pump status. If there is fuel pressure when the Cutoff switch is moved to 'Idle' the engine should start, otherwise if no fuel pressure, the engine remains cranking with no startup.
Best regards,
Steven.