Climb performance is a measure of excess thrust which generally increases lift to overcome other forces such as weight and drag
This is true for most aircraft although some high performance aircraft can function like rockets for a limited time, utilizing thrust to lift away from the earth vertically, with no lift required
Excess power or thrust, terms that are incorrectly used interchangeably, allow for an aircraft to climb
Power vs. Thrust:
Power and thrust are not the same, despite their use as such
Power is a measure of output from the engine while thrust is the force that actually moves the aircraft
In a piston aircraft, power is converted to thrust through the propeller
In a jet aircraft, the engine produces thrust directly from the engine
When you are moving the throttle controls inside of the aircraft, you're controlling the engine and that is why they are referred to as power levers
Therefore the best angle of climb (produces the best climb performance with relation to distance, occurs where the maximum thrust is available
The best rate occurs where the maximum power is available)
Propulsion vs. Drag:
The relationship between propulsion and drag is such that it takes a certain amount of power/thrust to overcome drag both on the high end (the faster you go) and also the low-end (the slower you go)
This is noticeable during slow flight where you find yourself adding extra power to overcome all the increases in drag that are necessary to sustain lift
If you fall "behind the power curve" however, you're in a position where you cannot generate immediate performance by simply increasing power
The increase in power must first overcome the increased drag and then the expected performance will occur
Ultimately, it is because of excess power (or thrust) that an aircraft climbs
For the purpose of initial climb however, we are concerned with our aircraft's performance in order to get away from the ground
Certain conditions will call for a specific climb profile, generally best rate (Vy) or angle (Vx) of climb
Best Angle-of-Climb:
Max excess thrust results in the best angle of climb
Occurs at L/Dmax for a jet
Occurs below L/Dmax for a prop
Best Rate-of-Climb:
Best rate of climb, or Vy, maximizes velocity to obtain the greatest gain in altitude over a given period of time
Vy is normally used during climb, after all obstacles have been cleared
It is the point where the largest power is available
Occurs above L/Dmax for a jet
Occurs at L/Dmax for a prop
Provies more visibility over the cowling
Increases airflow over the engine while at high power
Provides additinoal buffer from stall speeds
Airplane Flying Handbook Best angle of climb verses best rate of climb
Factors Impacting Climb Performance:
There are several factors which can impact climb performance:
Aircraft Weight:
One of the most basic considerations with regard to aircraft performance is weight, as it is a principle of flight
The higher the weight of an aircraft, the more lift will be required to counteract
Temperature:
Ambient air temperatures impacts your aircraft performance based on their physical properties
Engines don't like to run hot and if they do then reduced throttle settings may be required
Temperature is also a leading factor in determining the effect of air density on climb performance
Air Density:
Air density, and more specifically, density altitude, is the altitude which the aircraft "thinks" it is at
Performance does not depend on the physical altitude, but rather the density altitude, and the higher the temperature, the higher that altitude
Winds:
Headwinds increase performance by allowing wind flow over the wings without any forward motion of the aircraft
Tailwinds do the opposite
Aircraft Condition:
Smooth, parasite free wings produce the best lift
Anything to interrupt the smooth flow of air or increase drag will require additional forward movement, or thrust, to overcome
Conclusion:
Climb performance is governed by FAR Part 23, depending on aircraft weight
Pilots may always deviate from climb numbers for factors like cooling or ability to locate and follow traffic
Remember when flying under instrument conditions, minimum climb gradients are expected unless a deviation is communicated and authorized, as applicable
