[Ref RPL Instruction Kit (502) 8th Edition P. 77-80,  Pilot’s Handbook of Aeronautical Knowledge, FAA-H-8083-25B Page 5-24]

4 Forces in a Climb (Climbing Maneuver)

  1. Lift is titled and which should still be perpendicular to the flight path through the CP.
  2. Weight acts vertically downwards toward the earth
  3. Thrust acts forward along the propeller shaft – acts forward and parallel to the flight path
  4. Drag acts to the rear parallel but opposite to the flight path

During the transition from straight-and-level flight to a climb, lift is momentarily increased due to back elevator pressure causing AoA increased.

Source: FAA-H-8083-25B Page 5-24

If the climb is entered with no change in power setting, flight path is inclined upward, a component of the aircraft’s weight acts in the same direction as, and parallel to the total drag of the aircraft. Consequently, the total drag (effective drag) is greater than the power, and the airspeed decreases.

Concept of steady flight is suitable for climb still!

After the airspeed stabilizes, it is a steady climb, in which the forces of thrust and drag, and lift and weight again become balanced – sum of 4 forces is zero, BUT at a value lower than in straight-and-level flight at the same power setting.


Climb performance

  1. angle of climb (Vx)
  2. rate of climb (Vy)
  3. cruise climb (Vcc)

Vx   <   V L/Dmax   < Vy   < Vcc

– related to excess thrust available
– best obstacle clearance
– worst cooling and poor vision

– related to excess power available
– maximum height in given time

– maximum groundspeed
– best cooling and good vision


Factors affecting Climb performace  x11
Notes: Key factors are related to weight, drag as well as excess thrust (Power) available!

  1. Weight
    • higher weight which means its component downward flight path is larger. Then, more thrust (power) is used to against the drag plus the component of weight. Eventually, maximum angle and maximum rate of climb is reduced.
  2. Power
    • any setting less than the specified power will decrease both the angle and rate of climb.
  3.  Airspeed
    • Higher or lower airspeeds than recommened (Vx,Vy) decrease both the angle and rate of climb.
  4. Flap deflection
    • any flap deflections (flap down) will usually reduce the L/D ration and so drag increased. This causes excess thrust (power) available reduced and so the maximum angle and rate of climb decreased.
  5. Altitude
    • Higher Altidue, engine performance is reduced – excess thrust (power) reduces and this causes angle and rate of climb decreased.
  6. Temperature
    • Temperature related to Air density and Density Height/Altitude (DH/DA)
      Climb higher, air density decrease or High DA cause engine performance decrease – angle and rate of climb decreased
  7. Angle of Bank (AoB)
    • Higher AoB, more lift is need to maintain level flight – more life causes more induced drag – excess thrust (power) decrease. Therefore, angle and rate of climb decreased.
  8. Wind (Head/ NIL/ Tail)
    • At a constant airspeed case : rate of climb is unaffected by the wind ; angle of climb (and ground distance covered) will be affected – steeper climb angle with a headwind and shallower climb angle with a tailwind.
  9. Windshear
    • At an increase airspeed case : both angle and rate of climb increased;
    • At a decrease airspeed case : both angle and rate of climb decreased
  10. IGE / OGE
  11. Aerofoil contamination (e.g Ice, Frost)

p.s  Density Height – is the altitude (Pressure height) adjusted for temperature. (details ref Ch 6.3)



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