Center Fuel tank mininum 800-900's?

[vonmar 123]

Center Fuel tank mininum 800-900's?Will the 737-800/900 NG fuel tank pumps run it dry or shut off when 2000 remains.I read the center tank pumps must always be submirged.So, trip fuel would always be 2000 lbs more than trip + hold + alternate + reserve to keep the center tank wet.Is this correct?

[downscc 1,327]

The policy depends on operator, I've seen values less than 2,000 lbs mentioned here so I guess that is as good a value as any.

[Big_Duke 11]

The following is excerpted from Airworthiness Directive 2002-24-51 (available on FAA website):Airplane Flight Manual (AFM) Revision: Model 737-600, -700, -700C, -800, and -900 (B) For Model 737-600, -700, -700C, -800, and -900 series airplanes: Within 4 days after receipt of this AD, revise the Limitations Section of the AFM to include the following (this may be accomplished by inserting a copy of this AD into the AFM): Certificate Limitations The center tank fuel pumps must be OFF for takeoff if center tank fuel is less than 5,000 pounds (2,300 kilograms) with the airplane readied for initial taxi. Both center tank fuel pump switches must be selected Off when center tank fuel quantity reaches approximately 1,000 pounds (500 kilograms) during climb and cruise or 3,000 pounds (1,400 kilograms) during descent and landing. The fuel pumps must be positioned Off at the first indication of fuel pump low pressure.The center fuel pumps on the PMDG do not shut off automatically; you must manually shut them off in accordance with the above limitations. "I" believe the fuel remaining in the center tank counts as part of your final reserve (30 minute hold at alternate), so you would not have to plan extra fuel for covering the center tank fuel pumps as long as your final reserve is greater than 1000 pounds.

[vonmar 123]

Thanks Dan and Jerry for the information.I did a short flight from KSAN to KRNO with about half payload and could not get 3000 lbs (pilots extra) for the center tank without being overweight on landing. But I was ok with 2000 lbs.And yep, the center pumps did use it all .. I will do as instructed in the Airworthiness Directive from now on!

[Spin737 102]

I've flown for two different operators on the NG, and they had different techniques. Currently, we follow the AD. At my previous operator we would run the tanks dry and switch the pumps off when the Low Pressure lights illuminated. We may have had an Alternate Method Of Compliance or different pumps/switches for that, I don't remember.Either way, if you get a low fuel warning, don't think that you can't use that center tank fuel (I.e. don't flame out the engines and crash with 1000# left in the center tank).

[vonmar 123]

Matt,Thanks for the additional information.Ok, .. low warning = look at stickie note on dashboard .. turn all pumps back ON!Good point indeed.I do watch the Progress pages a'lot also, it helps.

[victorlima01 2]

Hii Vaughan, in 2006 I asked the same question and the thread turned out to be very informative. You can checking it out here http://forum.avsim.net/topic/118899-737-should-there-always-be-fuel-in-center-tank/page__p__785008__fromsearch__1#entry785008turns out some NGs may be retrofitted with a system that decreases the parcial pressure of O2 in the center wing tanks, reducing it to make that atmosphere more inert and less prone to ignition. Apparently this system allows operators to not load the tank with those 500kg whe flyog short hops where center wing fuel loading is not really necessary. When I load fuel for my flights I subtract 500 from the total figure and divide the result by 2 and load fuel to the tanks accordingly. For example if I need 5500kg total fuel I'll load 500 on the center tank and 2500 on each wing tank. I've never had to use the 500 kgs in the center tanks, but like Matt said, I wouldn't hesitate turning those pumps back on in an emergency. Perhaps one of the airlines Matt flew for had the nitrogen system installed and that exlains why he didn't have to load fuel in the center tank.

[Spin737 102]

Perhaps one of the airlines Matt flew for had the nitrogen system installed and that exlains why he didn't have to load fuel in the center tank.

A few of the -800s we had had the Nitrogen Generating System, but most did not. We had some where the center tank pump switches would turn off automatically, and some that did not. There was a placard on the fuel panel on some planes. The captains actually had a card they kept handy that had a matrix of plane modification and fuel panel operation specifics. Captains always ran the fuel panel, so I don't remember why it was different from the AD.

[Jack_C 1]

Hi Vaughan. At our company, we are slowly installing the NGS systems for the tail numbers that don't have them. All our newer planes have them. For now, we keep the SOPs the same regardless of tail number just to keep things uniform. Always use the 1000 lbs in the centre tank if you NEED it. As well, lets say you are taking over a tail number that just landed. You are going on a short flight. So you jump in the plane and their is full main tnaks but only 300 lbs in the centre. You do NOT have to fill the centre tank up past 1000 lbs. But of course you would not turn the centre tank pumps on fo rthe entire flight either.Jack C

[vonmar 123]

Well,Base on what everyone said .. I just might say my 800 has the inert substance in center tank and run it dry on those short flights. But then again, having a little extra weight on those windy day approaches also helps.

[Tabs 2,790]

Btw, pretty sure the 1000lbs policy was the result of an AD after TWA800 exploded... their center tank was completely empty and it allowed the sparking from wiring in the tank to ignite the fuel vapor. Not possible if the pump and its wiring are still submerged.