Types of Climb
Aircraft Climb Performance
Most aircraft accidents occur during the take-off or landing phase of the flight. Collisions with obstacles during climb out, runway overruns on landing do occur every now and then. In this section of the site we will take a look at the various factors contributing to the performance of the aircraft in this part of the flight.
There are a number of speeds defined for aircraft where it has a certain predictable performance. These are: best rate of climb speed and best angle of climb speed. Both are used by the pilot to reach an altitude in the minimum amount of time or distance traveled.
The climb performance of an aircraft is influenced by factors as: amount of applied power, airspeed, drag in the form of flaps or landing gear and weight. We are going to examine these factors to show the effects they have.
This can be measured as the climb angle (VX) or the rate of climb (VY) and certain factors will influence these, although these speeds will remain more or less the same, the result (climb rate or angle) will change.
Power and Speed
The amount of power used during the climb over the power required directly results in a different climb performance. If your aircraft is not climbing as expected, check if full power (or recommended climb power) is set or anything else is producing drag (flaps).
Flying with a higher or lower airspeed (than used for best climb angle or rate) will result in a lower climb performance compared to the optimum speeds from the POH.
A heavier aircraft decreases the climb performance as the power required to maintain a given speed in level flight increases with all up weight. There is less excess power available to climb. So climb performance and service ceiling will suffer.
Flaps and landing gear
Extending the flaps will decrease the climb performance as L/D ratio is reduced and the power required increased. The best rate-of-climb and angle-of-climb is always reached with flaps up. Hence the need to retract flaps after a go-around if there are obstacles in the climb out path. Some aircraft are not able to climb if full flaps are selected due to the amount of drag they create. For example: a C-172 with full flaps does not climb like a homesick angel during a full power go-around.
Some aircraft manufacturers recommend a take-off setting for flaps during a short field or high performance take-off. Although L/D ratio will suffer and drag is increased by the flaps it will permit the aircraft to fly off the runway sooner, but the climb out performance will be somewhat less.
Just remember to not to prolong the climb at the maximum angle of climb speed as this speed is relatively low, engine cooling is poor and overheating and detonation could be the result. Lower the nose and increase the airspeed as soon as possible after clearing the obstacles to enhance cooling and forward view. Maintain airspeed at cruise climb speeds.
Aircraft with retractable gear should retract as soon as no more usable runway is available and a positive rate of climb is established. The drag caused by the gear reduces climb performance. Aircraft with a fixed gear have no choice in retracting but to have the gear as much as streamlined by fairings as possible. See Lancair for some good examples.
This consist of air temperature, altitude and are influenced by ambient pressure. Any change in one of these factors influences the density altitude and climb performance of any aircraft.
An increase in altitude reduces air density and a decrease in engine power and wing and propeller (airframe) performance. Power available reduces with altitude, unless the engine is turbo- or supercharged. Power required goes up with altitude and at one point these two will be the same. The aircraft then has reached its absolute altitude. The definition of service ceiling is where the aircraft vertical speed is reduced to 100 ft/min.
Temperature and QNH
These two have a direct effect on air density and thus climb performance. At any altitude where OAT is higher than standard ISA temperature climb performance will be reduced. If QNH is lower than ISA then aircraft climb performance is affected too.
Turbulence and maneuvering
Any change in the aircraft attitude due to maneuvering, turbulence and turning reduces the climb performance somewhat as part of the excess power is needed to compensate for the maneuvers.
With exactly the same power settings and climb speeds, in a headwind the result will be that the distance traveled over the ground is reduced whereas with a tailwind the distance over the ground is increased. It can be seen that climbing into the wind has an distinct advantage when obstacles are in the climb out path.