0

Being a passenger, I usually will have view from only one side of these planes and hence don't know if same thing is happening on other side of the plane. I have observed hoses connected to wings, but there are always many connections to plane when its on ground and never sure which one is for fueling.

Looking at the answers for fuel tank description here or here, when they are filling fuel, do they connect hoses to each tank individually or just connect to one tank? Or is it per side - fill up each side individually.

Also suge/vent tank at the tail end of a380 seems to too high. Do they fill in those tanks too?

After fuel calculations are done, is there a standard fuel distribution that has to be done to every tank for weight/balance reasons?

Ralph J
  • 51,356
  • 17
  • 157
  • 249
user871199
  • 1,817
  • 2
  • 15
  • 21

2 Answers2

4

My answer is limited to commercial type aircraft (e.g., B737/757/767, etc.). There is variance between aircraft types.

Question: when they are filling fuel, do they connect hoses to each tank individually or just connect to one tank? Or is it per side - fill up each side individually.

  1. For most large commercial aircraft (e.g., B757, B767 etc.) single-point fueling is done from one location underneath one of the wings. This single-point fueling system allows fuel to be loaded to all tanks, e.g., Left/Right Main wing tanks and the Center tank (if necessary) from a single location. The switches on the single-point refueling panel operate pumps and cross-feed valves to allow all tanks to be fueled from this single location.

Question: Also suge/vent tank at the tail end of a380 seems to too high. Do they fill in those tanks too?

  1. A "surge" tank (or similar notation) is normally dry but is designed to hold fuel that passes through the main fuel vents (due to expansion or overfilling) in the normal tanks so that the fuel does not spill out (on the ground) and cause a fuel spill. This fuel ultimately works its way back to the normal tanks through gravity.

Question: After fuel calculations are done, is there a standard fuel distribution that has to be done to every tank for weight/balance reasons?

  1. Generally speaking Yes. The location of the fuel tanks in an aircraft is designed (again, generally speaking) to be near the center of gravity (CG) for the aircraft. So, as fuel is burned during the flight the aircraft does not find itself outside of the appropriate weight/balance envelope. However, calculations are done to ensure this and verify that the fuel loading at the beginning of the flight results in the CG being within limits and that the CG is within limits at the end of the flight after the anticipated amount of fuel is burned. Generally speaking (again), the aircraft is designed to stay within limits for most types of operations considering possible fuel, cargo, and passenger loads that may be encountered during normal operations.

FYI - If the single-point fueling system is inoperative for some reason over-wing fuel points allow for manual filling of the main tanks. Also, should the Fuel Quantity Indicating System (FQIS) system fail and the total amount of fuel in the tanks cannot be determined, fuel quantity can be measured using measuring sticks (with a reference chart available to determine (manually) how much fuel is in each tank.

Below from ABXtranet.com is a picture of the fueling procedures for a B767 and a picture of the Fuel Control Panel (B767 Single Point Refueling):

enter image description here

enter image description here

Here is the link to ABXAir's B767 Fueling Procedures Manual: refuel procedures ABXAir

3

when they are filling fuel, do they connect hoses to each tank individually or just connect to one tank? Or is it per side - fill up each side individually.

They typically connect to a fueling duct that connects to all tanks. The details vary for different aircraft makes, but a typical arrangement is to have a fueling console next to an under-wing fueling port. The console has a gauge for each tank and switching that allows the fueler to open valving that will allow fuel into each tank from the pressurized fueling duct until the tank is filled to the desired level. Some aircraft will have two fueling ports—one under each wing—that will allow fueling from a second source simultaneously, but they both feed the one pressurized duct.

There is no standard fuel distribution scheme that works across all aircraft models. However, there is great similarity in how it's done, and typically for the same model of aircraft, the tanks will be filled per the same schedule almost every time for a given amount of fuel.

is there a standard fuel distribution that has to be done to every tank for weight/balance reasons?

That it be done right is critical for proper weight & balance, and sometimes fuel is used for balance purposes. For example, let's say you had a tail-heavy load in a 747 freighter such that the zero fuel weight c.g. exceeded the aft limit. If you put fuel in the center tank and consider that fuel as ballast, you could bring the zero fuel weight c.g. within the limit since the 747 center tank c.g. is the most forward of the 747 tanks. And, of course, you have to be careful to not burn that ballast fuel.

If you want to explore fuel loading on a 747-400, go to 747.terryliittschwager.com, select the first aircraft, N402YY, and give it fuel.

Terry
  • 39,137
  • 5
  • 109
  • 184