Climb
The climb is the phase of the flight in which a gain in altitude is achieved. The increase in altitude per unit of time is called the rate of climb . The variometer in the cockpit displays this in the units “ feet per minute” (fpm), “knots” (kts) or “m / s”.
Maneuvers
The climb typically follows the take-off (exception: paragliders etc.). Commercial aircraft only pivot on the course of the departure procedure from a minimum height of 500 feet above ground. For most commercial airports, similar to the approach procedures, there are also standardized departure procedures, the so-called standard instrument departure routes , SIDs for short, which require navigation according to instrument flight rules . At the request of the pilots or air traffic controllers, departure can also take place visually.
Climb in other maneuvers :
- Adjusting the cruising altitude (cruise climb, step climb)
- Dodge on a collision course
- contour flight close to the ground
- Aerobatics , aerial combat
- Transfer of speed at height when reaching thermals, see Chandelle
- Gain in altitude in thermals
For noise protection reasons and for reasons of "clearing" airspace, commercial aircraft from large airports often take off at a steep angle of inclination, around 20 ° (depending on the specifications of the manufacturer, the load, the wind conditions and the controller). The climbing angle is usually reduced as soon as the airport area has been left.
Physical aspects
In order to initiate the climb, a dynamic lift must be generated which is greater than the weight of the aircraft. In the case of fixed wing aircraft ( fixed-wing aircraft ), a larger angle of attack of the wings is temporarily necessary than in level flight. During the stationary climb, the necessary lift is then somewhat smaller than in level flight, since the engine thrust bears part of the weight. In the extreme case of vertical ascent, the engine alone carries the thrust. A temporarily reduced lift ends the climb; the effect in parabolic flight is particularly impressive .
Angle of attack: The optimal angle of attack is the same as for the slightest sink .
Energy: During a climb, kinetic energy can be converted into potential energy , the aircraft climbs and therefore slows down. This also applies to helicopters .
Power: For a steady (acceleration-free) climb, increased propulsion power is necessary. Since the entire drive power is needed to overcome air resistance at top speed, high rates of climb can only be achieved at comparatively low speeds. This also applies to gliders in thermal or slope updrafts . The climb performance (maximum rate of climb independent of updrafts) characterizes motorized aircraft. This corresponds to the least sink in glider pilots . The speed at which the maximum rate of climb is reached is called V y . It sinks with increasing flight altitude. The altitude dependence is due to the reduced density of the air, which affects lift, engine performance and thrust.
Climbing angle: At an even lower speed, the climbing rate drops again. At first only a little, so that the angle of climb increases. It depends on the type of aircraft whether the maximum climb angle is achieved with or without a buoyancy aid . The associated speed is called V x and increases with altitude. In the case of aircraft that are capable of vertical ascent, this information only makes sense from a height at which they no longer have this ability.
The same applies to the minimum speed at which the aircraft can stay in the air (flying horizontally). All of these speeds are the same at the top . The aircraft will sink at both higher and lower speeds.
Risks when climbing
Due to the low speed and the high angle of attack when climbing, there is a risk of stalling with loss of control over the flight attitude. In turbulent air ( wake turbulence from an aircraft flying ahead, clear air turbulence , flying through clouds), the angle of attack varies, which increases the risk. The pilot must note that the critical stall speed increases in the event of overloading, turning and icing.
Even bird-strike provides for fast airplanes represent a risk to climb as long as the aircraft is at a height that use even large birds.
