Boeing 737 Center Pumps INOP: Fuel Really Unusable?
Thread Starter
Join Date: May 2003
Location: The Roman Empire
Posts: 831
Likes: 0
Received 0 Likes
on
0 Posts
Boeing 737 Center Pumps INOP: Fuel Really Unusable?
Everybody knows that if both center tank pumps are INOP the center tank fuel is not usable anymore.
Or is it?
CENTER TANK SCAVENGE JET PUMP.
When both Center Tank Fuel Pump Switches are turned OFF, the fuel scavenge shutoff valve opens. This allows...
You have already got my point!
After both center tank pumps failure, couldn't we use this feature to transfer fuel to N.1 tank?
After the 20 minutes cycle, couldn't we start more cycles by turning the center pumps ON momentarily then OFF?
LEM
Or is it?
CENTER TANK SCAVENGE JET PUMP.
When both Center Tank Fuel Pump Switches are turned OFF, the fuel scavenge shutoff valve opens. This allows...
You have already got my point!
After both center tank pumps failure, couldn't we use this feature to transfer fuel to N.1 tank?
After the 20 minutes cycle, couldn't we start more cycles by turning the center pumps ON momentarily then OFF?
LEM
Join Date: Oct 2003
Location: OZ
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
LEM
1)The rate of fuel transfer will not be enough to support the fuel flow rates required by the engines,as it uses a small jet pump
2)The scavenge jetpump will only operate after a centre tank pump is switched off and will run for 20min to remove residual fuel in the centre tank
3)If you cycle the centre pump swictches every 20min you will have the scavenge jet pump running .
However you do run a risk of cavitating both the centre tank pumps as the inlets will be no longer sumerged(scavenge pump has done its job for 20min removing fuel),the reprime line for the centre tank boost pumps will be drained of fuel and be full of air.
By doing this the next time someone operates the centre tank pumps they will cavitate and destroy themselves as to reprime the centre tank reprime lines requires a minimium of 3000 to 4000kg of fuel in the centre tank.
Regards,DDG
1)The rate of fuel transfer will not be enough to support the fuel flow rates required by the engines,as it uses a small jet pump
2)The scavenge jetpump will only operate after a centre tank pump is switched off and will run for 20min to remove residual fuel in the centre tank
3)If you cycle the centre pump swictches every 20min you will have the scavenge jet pump running .
However you do run a risk of cavitating both the centre tank pumps as the inlets will be no longer sumerged(scavenge pump has done its job for 20min removing fuel),the reprime line for the centre tank boost pumps will be drained of fuel and be full of air.
By doing this the next time someone operates the centre tank pumps they will cavitate and destroy themselves as to reprime the centre tank reprime lines requires a minimium of 3000 to 4000kg of fuel in the centre tank.
Regards,DDG
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
Unless our Pilots' Tech manual is wrong, these references to 'problems' with the centre tank pumps are not relevant, since my understanding is that it is No 1 Main tank pump that scavenges? The only time scavenge will not work is when this pump is u/s? No need to touch the ctre switches! I still think it will take all day!
Thread Starter
Join Date: May 2003
Location: The Roman Empire
Posts: 831
Likes: 0
Received 0 Likes
on
0 Posts
This scenario calls for a center tank with loads of fuel, so the pumps will not be exposed to air.
I agree the transfer rate is very small, I was wondering if the logic of the 20 minutes could be restarted indefinitely, and if some engineer could provide the exact transfer rate figure...
I agree the transfer rate is very small, I was wondering if the logic of the 20 minutes could be restarted indefinitely, and if some engineer could provide the exact transfer rate figure...
Join Date: Oct 2002
Location: uk
Posts: 166
Likes: 0
Received 0 Likes
on
0 Posts
Transfer rate approx 100-200 KGS per hour.Fuel scavenge jet pump motion is provided by #1 tank FWD boost pump.However.the scavenge shut-off valve [float operated] will not be open until #1 main tank fuel qty is below 1900 KGS.
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
However.the scavenge shut-off valve [float operated] will not be open until #1 main tank fuel qty is below 1900 KGS