Before we get started in going over over the different charts and how to understand them we need to cover a few things.
Definitions
Factors
And more.
Rate of Climb definition
Angle of Climb (AOC) - most altitude gained over a short distance. Used to clear a 50ft obstacle. These is referred to as the V-speed of (VX).
Rate of Climb (ROC) – altitude gained relative to the time needed to reach that altitude. These is referred to as the V-speed of (VY).
For example, in a maximum Angle of Climb (VX) profile, an aircraft takes 30 seconds to reach 1,000 feet AGL, but covers only 3,000 feet over the ground.
Whereas for a maximum Rate of Climb (VY) profile, the same aircraft climbs to 1,500 feet in 30 seconds but covers 6,000 feet across the ground.
Climb Performance Factors
An increase in altitude also increases the power required and decreases the power available. Therefore, the climb performance of an aircraft diminishes with altitude.
As altitude is increased, these various speeds finally converge at the absolute ceiling of the aircraft.
Absolute ceiling – No excess power available and only one speed allows level flight. The aircraft can no longer climb.
Service ceiling – The altitude at which the airplane is unable to climb at a rate greater than 100 feet per minute (fpm).
Interpolating tables
Interpolating table type charts is required to calculate numbers that are not listed on the table. It works for all tables, numbers, altitude, weight, temperature etc.
How do we interpolate?
To interpolate this equation is used:
Value 1 + Value 2
2 = ?
Takeoff Distance - To find the takeoff distance for a Pressure Altitude (PA) of 2,500 feet at 20°C. We need to first locate 2,500 feet between the 2,000 feet and 3,000 feet in the 'Press ALT (ft)' column.
Next, we need to locate the ground roll numbers under the 'Grnd roll (ft)' column for 20°C, which will be 1,115 and 1,230.
To find the ground roll for takeoff at a PA of 2,500ft., we add the two numbers and divide by 2.
Example Equation: 1,115 + 1,230
2 = 1,173 feet
Remember:
Absolute ceiling – No excess power available and only one speed allows level flight. The aircraft can no longer climb.
Service ceiling – The altitude at which the airplane is unable to climb at a rate greater than 100 feet per minute (fpm).
To interpolate this equation is used:
Value 1 + Value 2
2 = ?
References:
Aircraft POH charts
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