Question

# In 1923, the United States Army (there was no United States Air Force at that time)...

In 1923, the United States Army (there was no United States Air Force at that time) set a record for in-flight refueling of airplanes. Using two refueling planes, an Airco DH-4B biplane was able to remain in flight for 39 h. During the flight, the refueling planes were able to air-transfer a total of 687 gallons of fuel to the plane in 9 refueling transfers. Assume that the refueling nozzle had a diameter of 1.75 in and each refueling took 2.45 min to perform. Calculate the velocity of the fuel through the nozzle. Assume that the fuel filled the entire cross-sectional area of the nozzle.

Total volume of fuel transfer = V = 687 gallons = 2.6 m3

Diameter of refueling nozzle = d = 1.75 in = 4.445 x 10-2 m

Number of refueling transfers = n = 9

Time taken for one refueling transfer = t = 2.45 min = 147 sec

Velocity of fuel through the nozzle = v

Cross-sectional area of the nozzle = A

A = d2/4

A = (4.445x10-2)2/4

A = 1.552 x 10-3 m2

The total volume transferred is equal to the volumetric flow rate times the total time taken.

V = (Av)(nt)

2.6 = (1.552x10-3)v(9)(147)

v = 1.266 m/s

Velocity of the fuel through the nozzle = 1.266 m/s

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