Edwards air show B-1 speed record attempt

"B2431" wrote...
On C-130s we had the SPR (single point refuling panel) where they hooked up
the
nozzel. It had indicators reading pounds for each of the integral tanks.

That's a common arrangement. Tactical aircraft with SPR may not have any
indicator at the panel; simple lights indicating a full/not full tank (closing a
float switch) may be used instead. If a partial fuel load is desired, it must
be selected by fully fueling specific tanks and/or monitoring the cockpit fuel
gauges. In the case where over-the-wing fueling is used (in the past, commonly
done with the wing drop tanks on the A-4), either the tanks are filled
completely or a specific quantity in gallons specified. Even though the A-4
fuel system indicated in pounds, the 300-gallon (2000 lb nominal) drop tanks
were filled with 150 gallons for a "half drop tanks" load, regardless of fuel
type or density. Minor weight discrepancies due to fuel type (JP-4 vs JP-5) or
temperature were disregarded, since fuel planning assumed the worst case (low
density or weight) and performance effects due to slightly higher gross weight
with high-density fuel were negligible.

For the SPR systems with indicators on the panels, the person doing the
refueling needs to know little more regarding the specific fuel upload than the
final total fuel load (or sometimes the load in each tank). By manual or
automatic tank selection and shutoff valves, the tanks are fueled until the
final load is achieved. The fueler does not need to monitor or convert volume
(gallons or liters) to weight or mass (pounds or kilograms) -- he simply uses
the indicators in the aircraft fuel system to directly read the fuel on board in
the airplane's native units.

Sometimes, e.g. when several trucks may be required to refuel a large airplane,
an estimate of required fuel may be given to the fuel company dispatcher so
[s]he can dispatch the appropriate number of trucks. In commercial aviation
this figure is seldom, if ever, used as an "order" for a specific quantity; it
is only a planning guideline.

For example, when arriving at a station in a 747, I will notify the ops center
of the estimated fuel remaining (in Kg) on shutdown. They will then estimate
the fuel load required for the next leg and notify the fuel dispatcher. When
the refueler comes to the airplane, he never knows the number of gallons/liters
required. The airline ramp ops people will tell him the preliminary or final
fuel load in Kg, and the fueler will set that figure on the airplane refueling
panel (the 747-400 is almost completely automatic; once a total fuel load is
set, the airplane system automatically controls the feed to individual tanks).
The fueler has no idea how many gallons, liters, or Kg the airplane will
require -- only the final load. He records the gallons or liters delivered,
after the fact, on the receipt for billing.

The bottom line is that conversion of units is seldom a critical problem in
refueling modern commercial airplanes.