Everything to Know About Airplane Speed
Airplane speed is much more complicated that many think. This guide discusses the types of speed, and how it affects takeoffs and landings.
Airplane speed is simply how fast an airplane goes, right? Not necessarily. Student pilots spend some time learning about the different aspects of speed in aviation. It is always important to balance the speed capabilities of an aircraft against its weight, fuel consumption, the altitude at which the airplane is flying, and the density of the ambient air. There are many factors to take into consideration, and aeronautical engineers and pilots, as well as those concerned about the economics of fuel consumption and keeping potential commercial clients happy, have a great deal to think about. Here is a primer on airplane speed.
Types of Airplane Speed and V Speeds
There are four types of speed to understand. They all apply to different aspects of flying.
- Indicated Airspeed: An airplane’s cockpit contains an airspeed indicator; this is where a pilot gains information about indicated airspeed. It measures the dynamic pressure the airplane is experiencing, which is necessary for knowing an airplane’s stall speed. This refers to the slowest speed at which an aircraft can move and still maintain lift.
- True Airspeed: True airspeed is defined in a number of ways, but it is generally referred to as the speed of the aircraft adjusted for altitude and the air through which it is moving. True airspeed is important in navigation, and pilots must include true airspeed in their flight plans.
- Calibrated Airspeed: Think of calibrated airspeed as “corrected” airspeed. It is the speed of the airplane after accounting for instrument error. Under certain conditions, calibrated airspeed is equal to true airspeed.
- Equivalent Airspeed: Pilots crewing airplanes which can fly at supersonic speeds must pay attention to equivalent airspeed. This is calibrated airspeed adjusted for the effects of compressed air.
- Groundspeed: This is what most people think of when discussing the speed of an airplane. It is how fast the airplane is going relative to the Earth below. Groundspeed includes an accounting for either a tailwind or a headwind.
Aviation also has a number of terms referencing what is known as V speed. These usually deal with more specific forms of speed, typically having to do with airplane configuration or phase of flight. These are important to understand in making calculations regarding flight, as well as within the context of aeronautical engineering. Here are a few:
- VNE: The airplane’s designated “never exceed” speed
- VF: Intended flap speed
- VC: Cruise speed
- VB: Maximum speed for gusts
- V3: Retraction of flap speed
There are many more V speeds to understand for safe and efficient aviating. While some might seem complex, most pilots can easily calculate them with apps or glass cockpit instrumentation.
There is no one answer to “How fast is supersonic speed?” other than “very fast.” Supersonic speed is only attainable by jets and rockets. It is going faster than the speed of sound. However, the speed of sound is dependent upon temperature, altitude, and other factors. Generally, at sea level, the speed of sound is 1215 kilometers an hour.
Supersonic flight is measured in Mach numbers. Once the sound barrier has been broken, an airplane is said to be travelling at Mach 1. Other than the Concorde—a former passenger jet service over the Atlantic Ocean–and military fighter jets, most airplanes cannot reach supersonic speeds.
When an aircraft breaks the sound barrier, it generates a sonic boom. This is created by the shock waves the airplane leaves in its wake as it speeds through the atmosphere. It is a continuous phenomenon with can cause structural damage on the ground and a loud crack or explosion-like noise.
When the Space Shuttle launched, as well as when it returned to Earth, its airplane-like shape caused a sonic boom. The slower speeds at which it re-entered the atmosphere usually meant that one sonic boom was experienced by observers for the nose of the orbiter, quickly followed by a second for the craft’s vertical stabilizer. An aircraft’s shape can exaggerate or dampen the effect of a sonic boom.
Speed at Takeoff
There is no leaving the ground without appropriate airplane speed. Large passenger jets leave the ground, for example, at approximately 170 miles per hour, but the size and weight of the airplane dictate how fast the plane is going when it leaves the runway.
Here are some V speeds regarding takeoff which are important to know:
- V1: Highest speed during takeoff after which the takeoff must take place; the airplane can no longer stop safely in an abort situation; “decision speed.”
- V2: A safety measure—the speed when a multiengine airplane can climb with only one engine
- VR: Rotation speed, or the speed when the airplane should begin to take off (the nose pitches up)
- VFTO: The airplane’s final takeoff speed
- VLOF: Speed at which the aircraft lifts
Pilots must pay close attention to an aspect of speed the general public usually does not take into consideration how fast an airplane can go: The takeoff roll. The pilot must ensure that the runway is long enough for him or her to achieve the necessary speed for takeoff. Attempting to do lift the nose to soon can result in a stall.
Speed at Landing
When the cruise phase of flight is completed, the pilot must slow the aircraft for a safe landing. The optimal speed for landing varies as much as takeoff speed does—it all depends on the aircraft, its weight, performance capabilities, and environmental factors. Pilots raise the airplane’s flaps, if it has any, in order decrease lift and slow the aircraft. The nose of the aircraft is lowered to bleed off speed until final approach, when the nose is raised again. It is important to slow as much as possible without stalling.
Here are some V speeds relating to landing:
- VLE: Fastest speed at which an aircraft should go with its landing gear down
- VS0: Minimum speed of flight when the airplane is in a landing configuration
- VTD: Touchdown speed
Experience and careful planning help pilots to know which speed is the safest for completing the landing roll.