Climbing is the process whereby an aircraft gains altitude.
Objectives of the lesson
Knowing how to climb:
- At recommended normal climb speed.
- At recommended best rate of climb speed.
- At recommended best angle of climb speed.
- At various airspeeds (en route climb).
Levelling off at specified altitude.
Each time we go in flight we use these different speeds to take off and climb.
In addition of pitch nose up attitude (see last lesson “straight and level flight”) we are going to gain altitude this time.
Review questions: attitude and movement
- If the nose of the airplane is above the horizon (reference datum) we say that the aircraft is?
- If it’s below we say?
- How the wings are if the aircraft is in cruise attitude?
- When backward pressure is applied to the control column the nose……?
- When forward pressure is to applied to the control column the nose….?
- When the aileron control is moved to the right the aircraft roll to the….?
- What are the causes of yaw?
- What is the main control to counteract the yaw ?
Forces acting on the aircraft
Lift opposes Weight
Thrust opposes Drag
In straight, unaccelerated flight,
Lift = Weight
Thrust = Drag
- Lift: created by pressure differential around wing. High pressure on lower surface and low pressure on the upper surface – low pressure caused by increased airflow velocity over top of airfoil.
- Weight: downward force of gravity
- Drag: rearward retarding force
- Thrust: forward force propelling airplane through air
Angle of Attack
is the angle that is formed between the chord line of an airfoil and the Relative Wind.
How an aircraft climb ?
- An aircraft can climb only if it can produce excess thrust.
- A climb is carried out by increasing the lift of airfoils (wings) supporting the aircraft until their lifting force exceeds the weight of the aircraft. Once this occurs, the aircraft will climb to a higher altitude until the lifting force and weight are again in balance.
- If the climb is entered with no change in power setting (just by increasing the angle of attack) the airspeed gradually diminishes because the thrust required to maintain a given airspeed in level flight is insufficient to maintain the same airspeed in a climb.
Normal climb speed
Normal climb speed is the speed at which the aircraft is climbed under normal circumstances.
Normal climb speed is higher than best rate of climb and best angle of climb speeds and is recommended for routine climbing situations because:
- Forward visibility is better.
- Cooling is more effective.
- Easier control.
Best rate of climb
- Is the airspeed that will afford the greatest gain in height in a given time.
- If it’s important to reach a given altitude quickly, then this is the airspeed to use.
- Vy: 78 kts for cessna 172 (check P.O.H).
Best angle of climb
- Is used to achieve the greatest gain in height in a given distance.
- For example if there are obstacles in the take off patch, the aircraft should be climbed at the best angle of climb speed so that within the shortest possible ground distance the aircraft will be well above the height of the obstacles.
- Vx: 64 kts for cessna 172 (check P.O.H).
En route climb
- are carried out at various airspeeds between normal climb and normal cruise speed.
- For example: To gain altitude slowly under a gradually upsloping cloud cover.
- Convenience and comfort are the prime factors, since no climb time or climb distance limitation are assumed to apply.
Procedures to climb
Look out !!!, clearing the airspace around your airplane and particularly in the area ahead.
APT: ATTITUDE (PITCH)- POWER- TRIM.
- Apply back pressure on the yoke to establish the aircraft in a nose up attitude.
- Add power to the recommended setting for a normal climb (2500 rpm-cessna 172)
- Add right rudder to compensate for the left-turning tendencies which result from the increase in pitch attitude and decrease in airspeed.
- Trim (up wheel) elevator. (AND MAINTAIN BACK PRESSURE)
Rule of thumb: 100 rpm = 5 kts = 100 feets per minute.
- Trim is not a control device – fly with elevators and use trim only to relieve pressure
Procedures to Level off
APT: ATTITUDE (PITCH)- POWER- TRIM.
- Attitude: Apply forward pressure on the yoke to establish the aircraft in the normal cruise attitude.
- Let the plane accelerates to cruise speed.
- As the airplane accelerates, less right rudder pressure will be needed.
- Power: Reduce power to the cruise setting when the desired speed is reached.
- Trim: (down wheel) to relieve the control pressures.
Rule of Thumb
- Start leveling off at 10% of your rate of climb.
Exemple: If you are climbing at 500fpm start your level off 50ft prior to your desired altitude
Factors Effecting Climb
- Performance of the aircraft depends on the density of the air in which it flies.
- Density altitude is pressure altitude corrected for nonstandard temperature.
With low air density (high density altitude):
- The engine develops less power.
- The propeller produces less thrust.
- The wings produce less lift.
This results in:
- Longer takeoff run
- Poorer climb performance
- Longer landing distance
- Flaps increase lift but also increase drag and thus increasing drag effectively reduces the rate of climb.
- also increases drag and thus reduces available excess thrust. To maximize climb performance with a retractable gear aircraft, let’s get that gear up.
- A lighter loaded wing will have a superior rate of climb compared to a heavier loaded wing as less airspeed is required to generate the additional lift to increase altitude.
- The carburetor heat reduces power output from the engine and so reduces climb performance, it should be cut off except if there are a risk of carburetor ice.
Also decreases performance of the aircraft.
- Lookout – During the climb the aircraft is a nose up attitude and forward visibility is limited.
- During prolonged climbs, lower the nose momentarily or change heading at regular intervals to search the sky for other traffic.
- Conduct cockpit (mixture full rich, Carb heat off, Temperature and Pressure Gauge : green).
- What’s the difference between the best rate of climb and the best angle of climb ?
- Why using normal climb speed ?
- What does APT stand for?
- Which factors affect the climb performance ?
- When leveling off why do we wait before we reduce power?