What is the average airspeed velocity of an unladen swallow

10 meters/second.

Explanation:

Unladen swallow consists of two species are Hirundo domicella and the Hirundo spilodera.

The average speed of unladen swallow comes out to be 10 meters/second. The maximum speed can go upto 13-14 meters/second. The speed of unladen swallow can be calculated by the formula given by Graham K. Taylor. According to graham the speed of unladen swallow is 3 times of the product of frequency and amplitude. (v = 3fA, v is velocity, f is frequency and A is amplitude).