Beginner's Guide to Aerodynamics is a "textbook" of information prepared at NASA Glenn Research Center to help you better understand how airplanes work. Click Beginner's Guide Index to access the list of slides. Open the slide called Relative Velocities (with text) and read the explanation on how relative velocities are used to calculate airspeed required for aircraft launch.

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In airport takeoff situations, the ground speed of the aircraft and the wind speed are the only factors in airspeed. The U.S. Navy has an additional variable. Its airports (aircraft carriers) move on the ocean at speeds that can be in excess of 35 mph. Airspeed in this unique situation is a sum of the ship's speed through the water, wind speed, and the speed of the aircraft over the deck of the ship provided by the ship's catapult.

A catapult is like a huge rubber band and is used to propel an aircraft to higher speeds over a short distance in a few seconds. For more information on aircraft carriers and catapults, click on Aircraft Carriers (http://www.chinfo.navy.mil/navpalib/allhands/ah0197/pg08-09.html).

Assume that a typical catapult can propel an aircraft from 0 to 150 mph in 2 seconds. The aircraft carrier problem is pictured graphically in the following illustration. (Note the airspeed equation at the bottom.)

 

Catapult Speed (Vc) mph	Ship Speed (Vs) mph	Wind Speed (Vw) mph	Airspeed	Go/No Go (>170 mph)
150	20	-10
150	20	10
150	30	-30
150	0	20

Airspeed = Ship Speed (Vs) + Catapult Speed (Vc) - Wind Speed (Vw)

Questions 

1. With no wind, what should the speed of the ship be to launch an F-14?

   Vs = ____________________

    

2. On launch any aviator wants to maximize lift. What would you do as Captain of the ship any time you launch aircraft?

    

3. Are wind direction and ship speed factors in landing as well?

    

4. Convert the completed table above to metric units (to the nearest kph). 

Catapult Speed (Vc) mph	Ship Speed (Vs) mph	Wind Speed (Vw) mph	Airspeed	Go/No Go (>274 km/h)