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737 what is Fuel Tank Capacity Limited Weight?

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737 what is Fuel Tank Capacity Limited Weight?

Old 4th Dec 2019, 04:12
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737 what is Fuel Tank Capacity Limited Weight?

my airline's OFP has column for TCAP that stands for Tank Capacity Limited Weight and it is always same as MTOW. For example, MTOW is 155000, TCAPs same as well. As you all know, we cant put that much of fuel onboard 737 and I am not sure what that means.

If anyone knows about this please feel free to post and share the ideas!
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Old 4th Dec 2019, 20:35
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Maybe post us the company definition of Tank Capacity Limited Weight, as it does not come across as a standard used frequently in those words.

Fuel Tank Location and Capacities (Usable Fuel):
TANK / GALLONS / POUNDS* / LITERS / KILOGRAMS*
1 / 2888 / 8630 / 4876 / 3915
2 / 2888 / 8630 / 4876 / 3915
C / 4299 / 28803 / 16273 / 13066
TOTAL / 6875 / 46063 / 26025 / 20896

AUX tanks can be used to increase capacity, but not to 155000...
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Old 5th Dec 2019, 01:42
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The definition from fom is as follow:-

The weight limited by maximum tank capacity.
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Old 5th Dec 2019, 03:17
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Never heard of this designation, but Iím assuming your company is just counting it as one of the limiting takeoff weights.

Why not just ask them?
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Old 5th Dec 2019, 06:12
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Maybe a value internal to the OFP calculation, and found its way to FOM years ago by someone just copy-pasting the user manual of the SW?

If the ZFW is low, then ZFW + Fcap(kg) becomes the numerical maximum. Does not sound like an operational limitation.
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Old 5th Dec 2019, 07:37
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Originally Posted by Skyjob View Post
Maybe post us the company definition of Tank Capacity Limited Weight, as it does not come across as a standard used frequently in those words.

Fuel Tank Location and Capacities (Usable Fuel):
TANK / GALLONS / POUNDS* / LITERS / KILOGRAMS*
1 / 2888 / 8630 / 4876 / 3915
2 / 2888 / 8630 / 4876 / 3915
C / 4299 / 28803 / 16273 / 13066
TOTAL / 6875 / 46063 / 26025 / 20896

AUX tanks can be used to increase capacity, but not to 155000...
I guess this is for the new Dual fuel version with Hydrogen on tanks one and two and good ole kerosene on the Centre?

TANK / GALLONS / POUNDS* / LITERS / KILOGRAMS* / kg per Gal
1 / 2888 / 8630 / 4876 / 3915 / 1.36
2 / 2888 / 8630 / 4876 / 3915 / 1.36
C / 4299 / 28803 / 16273 / 13066 / 3.04
TOTAL / 6875 / 46063 / 26025 / 20896 / 3.04

OH! That doesn't add up either cos the Total would be wrong for that case?
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Old 5th Dec 2019, 11:35
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Does or did your airline operate multiple types, where another type has a TCAP that is different from MTOW? Perhaps that's how it ended up in the OFP. Another thought I had is that a 737 with aux tanks might end up being weight limited in this way, but I don't have any data to back that up.
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Old 5th Dec 2019, 16:06
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Originally Posted by Jhieminga View Post
Another thought I had is that a 737 with aux tanks might end up being weight limited in this way, but I don't have any data to back that up.
That is not possible, 70 tons of fuel do not fit into a 737 unless you attach underwing mounted tanks as well, very large ones at that...
Besides, the MTOW will be horrendously exceeded.

155000lb is in the region of a 767-300ER with nearly full tanks...
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Old 5th Dec 2019, 18:21
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Originally Posted by FlightDetent View Post
Maybe a value internal to the OFP calculation, and found its way to FOM years ago by someone just copy-pasting the user manual of the SW?

If the ZFW is low, then ZFW + Fcap(kg) becomes the numerical maximum. Does not sound like an operational limitation.
That's the only explanation that I can think of, too.
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Old 5th Dec 2019, 18:21
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Originally Posted by Jhieminga View Post
Does or did your airline operate multiple types, where another type has a TCAP that is different from MTOW? Perhaps that's how it ended up in the OFP. Another thought I had is that a 737 with aux tanks might end up being weight limited in this way, but I don't have any data to back that up.
This sounds like a good explanation. It doesn't affect the 737, but maybe it's added for sake of standardization with another airframe.
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Old 5th Dec 2019, 22:22
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Originally Posted by Skyjob View Post
Maybe post us the company definition of Tank Capacity Limited Weight, as it does not come across as a standard used frequently in those words.

Fuel Tank Location and Capacities (Usable Fuel):
TANK / GALLONS / POUNDS* / LITERS / KILOGRAMS*
1 / 2888 / 8630 / 4876 / 3915
2 / 2888 / 8630 / 4876 / 3915
C / 4299 / 28803 / 16273 / 13066
TOTAL / 6875 / 46063 / 26025 / 20896

AUX tanks can be used to increase capacity, but not to 155000...
Not on the B737, but just based on ratio, some of those numbers can't be right:
Jet-A: 6.7 P/G or 0.8 K/L, 2.2 P/K 3.8 L/G

TANK / Gallon / ......Pounds / ....Liter / .......Kilograms*
1....... / 2888 ........ / 8630 ....... / 4876....... / 3915 . . . if P/L/K are correct (and their ratios are correct) G should be around 1283
2 ......./ 2888 ........ / 8630 ....... / 4876 ......./ 3915. . . .same
C ......./ 4299 ....... / 28803 ..... / 16273 ....../ 13066. . .all possibly correct, ratios are correct
TOTAL / 6875 ...... / 46063 ....../ 26025 ....../ 20896. . same

All vertical columns add up except Gallon, 1283 + 1283 + 4299 = 8687, so I think the error is in the 2888 numbers.
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