The power needed to maintain level flight at best climb speed.
Maximum Rate of Climb
0 fpm
0 m/s
Excess Horsepower
0 HP
function calculateRateOfClimb() {
// Get input values using var
var weightInput = document.getElementById('aircraftWeight');
var bhpInput = document.getElementById('brakeHorsepower');
var effInput = document.getElementById('propEfficiency');
var reqInput = document.getElementById('powerRequired');
var resultBox = document.getElementById('resultDisplay');
var errorBox = document.getElementById('errorDisplay');
var weight = parseFloat(weightInput.value);
var bhp = parseFloat(bhpInput.value);
var efficiency = parseFloat(effInput.value);
var powerReq = parseFloat(reqInput.value);
// Validation
if (isNaN(weight) || isNaN(bhp) || isNaN(efficiency) || isNaN(powerReq)) {
errorBox.style.display = 'block';
errorBox.innerHTML = "Please enter valid numbers in all fields.";
resultBox.style.display = 'none';
return;
}
if (weight <= 0 || bhp <= 0 || efficiency 100 || powerReq < 0) {
errorBox.style.display = 'block';
errorBox.innerHTML = "Please check your inputs. Efficiency must be between 0-100% and weight/power must be positive.";
resultBox.style.display = 'none';
return;
}
errorBox.style.display = 'none';
// Calculation Logic
// 1. Calculate Thrust Horsepower Available (THP_a)
// Efficiency is percentage, convert to decimal
var thpAvailable = bhp * (efficiency / 100);
// 2. Calculate Excess Horsepower
var excessPower = thpAvailable – powerReq;
// 3. Calculate Rate of Climb (RoC)
// Formula: RoC (fpm) = (Excess HP * 33,000) / Weight (lbs)
// 1 HP = 33,000 foot-pounds per minute
var roc_fpm = (excessPower * 33000) / weight;
// 4. Convert to Meters per Second (m/s)
// 1 fpm = 0.00508 m/s
var roc_ms = roc_fpm * 0.00508;
// Display Logic
resultBox.style.display = 'block';
// Handle negative climb (descent) cleanly
if (roc_fpm < 0) {
document.getElementById('mainResult').style.color = '#dc3545';
document.getElementById('mainResult').innerHTML = Math.round(roc_fpm) + " fpm (Descent)";
} else {
document.getElementById('mainResult').style.color = '#28a745';
document.getElementById('mainResult').innerHTML = Math.round(roc_fpm) + " fpm";
}
document.getElementById('metricResult').innerHTML = roc_ms.toFixed(2) + " m/s";
document.getElementById('excessHpResult').innerHTML = excessPower.toFixed(1) + " THP";
}
Understanding Maximum Rate of Climb
The Maximum Rate of Climb Calculator is an aerodynamic tool designed for pilots, aeronautical engineering students, and aviation enthusiasts. It estimates the vertical speed of an aircraft based on its weight, engine power, propeller efficiency, and drag characteristics.
Rate of climb (RoC) is defined as the vertical component of an aircraft's airspeed. The maximum rate of climb is achieved at a specific airspeed known as Vy. At this speed, the aircraft gains the most altitude in the shortest amount of time.
Key Concept: Climb performance depends entirely on Excess Power. This is the difference between the power the engine can produce (Power Available) and the power needed just to keep the airplane flying level (Power Required).
The Physics of the Climb
To climb, an aircraft must overcome gravity and drag. The mathematical relationship governing the rate of climb is derived from the conservation of energy. The formula used in this calculator is:
RoC = (Excess Power × 33,000) / Weight
Where:
RoC: Rate of Climb in feet per minute (fpm).
Excess Power: (Power Available × Propeller Efficiency) – Power Required.
33,000: Conversion factor (1 Horsepower = 33,000 foot-pounds per minute).
Weight: Gross weight of the aircraft in pounds.
Input Definitions
To use this calculator effectively, you need to understand the required inputs:
Aircraft Gross Weight (lbs): The total weight of the airplane, including fuel, passengers, and cargo. Heavier aircraft require more power to climb at the same rate.
Engine Max Power (BHP): The rated Brake Horsepower of the engine. Note that this decreases as altitude increases (for non-turbocharged engines).
Propeller Efficiency (%): Engines produce rotation, but propellers convert that into thrust. Typical fixed-pitch propellers have an efficiency between 75% and 85%.
Power Required (BHP): This is the aerodynamic drag penalty. It is the power needed to maintain level flight at Vy. This value is derived from the aircraft's drag polar.
Factors Affecting Climb Performance
Several variables can drastically change an aircraft's ability to climb:
Density Altitude: As air density decreases (due to high altitude or high temperature), engine power output drops, and propeller efficiency decreases. This reduces Excess Power, resulting in a lower rate of climb.
Weight: Increasing weight not only increases the power required to maintain lift but also increases the denominator in the climb formula. A 10% increase in weight can result in a disproportionately larger loss in climb performance.
Configuration: Flaps and landing gear increase parasite drag, which increases the Power Required, leaving less Excess Power for climbing.
Example Calculation
Let's look at a typical single-engine trainer aircraft scenario:
Weight: 2,400 lbs
Engine Power: 160 BHP
Propeller Efficiency: 80% (0.80)
Power Required at Vy: 65 BHP
Step 1: Determine Thrust Power Available
160 BHP × 0.80 = 128 Thrust Horsepower (THP).