Aircraft carriers use catapults and arresting gear because a flight deck is much shorter than a normal runway. A jet must gain takeoff speed in only a few seconds, then later lose huge kinetic energy in a very short landing distance. These systems turn the carrier into a moving airfield at sea and depend on careful control of force, energy, and timing.
Understanding them shows how physics makes extreme launch and recovery operations possible.
Key Facts
- Average acceleration during launch: a = Δv / Δt.
- Net launch force can be estimated by F = ma.
- Kinetic energy of the aircraft is KE = 1/2 mv^2.
- Work done by a catapult or arresting gear is W = Fd.
- For stopping on deck, average deceleration can be estimated by v^2 = 2ad.
- Aircraft carrier launch and recovery depend on relative wind: airspeed = deck speed plus wind over deck.
Vocabulary
- Catapult
- A launch system that accelerates an aircraft along the carrier deck until it reaches takeoff speed.
- EMALS
- The Electromagnetic Aircraft Launch System uses linear motors to pull the aircraft forward with controlled electromagnetic force.
- Steam catapult
- A steam catapult uses high pressure steam to drive a piston connected to the aircraft launch shuttle.
- Tailhook
- A tailhook is a strong hook on the rear of a carrier aircraft that catches an arresting wire during landing.
- Arresting wire
- An arresting wire is a heavy steel cable stretched across the flight deck that transfers the landing aircraft's energy into braking machinery.
Common Mistakes to Avoid
- Thinking the catapult lifts the jet into the air. The catapult mainly increases forward speed so the wings can produce enough lift.
- Using mass and weight as the same quantity. Mass is measured in kilograms, while weight is a force measured in newtons and depends on gravity.
- Assuming the arresting wire stops the jet instantly. The wire pays out through braking equipment so the aircraft slows over a short but finite distance.
- Ignoring the carrier's motion and wind direction. Launches and landings are planned into the wind because wind over the deck increases useful airspeed.
Practice Questions
- 1 A 25,000 kg jet is launched from rest to 75 m/s in 3.0 s. Find its average acceleration and the average net force during launch.
- 2 A 20,000 kg aircraft lands at 65 m/s and is stopped by arresting gear in 95 m. Estimate the magnitude of its average deceleration and the average braking force.
- 3 Explain why an aircraft carrier turns into the wind for launch and recovery, and describe how this changes the required work done by the catapult or arresting gear.