When going through the rigorous training schools on the way to becoming a pilot, there are many lessons that teach the safety protocols of flying and the ins-and-outs and basic and advanced aviation.
Yet, one of the most popular questions we get asked is how to calculate the top of the climb and have to measure the top of descent.
This might be due to the fact that this is not the most exciting topic in flight school, and oftentimes this gets overlooked because let’s face it, there are more interesting topics to study.
Yet, it’s a vital component of the aviation process and something that needs to be understood.
What Is Top Of Climb?
The top of the climb is the point where you’ll reach your cruise altitude for the day.
It is the climbing phase of the flight to the cruise phase and at this point is the moment when the planned climb to cruise altitude has been completed successfully.
This can be important if your goal was to fly the most efficient route possible.
For example, if you’re flying from New York City to Chicago and you want to save fuel, you would want to go as high as possible before descending into the Windy City.
In order to do this, you’d need to calculate the top of the climb and know what the highest point you will be able to safely fly to while still being able to descend back down again later on.
Top of descent is the reverse opposite of this and is the point at which the aircraft begins its descent to the next airport. This is especially useful if you’re planning on landing at multiple airports during your flight.
If you’ve flown all day long and are now about to land at your destination, you’ll want to begin your descent in order to make sure that you don’t overshoot the runway.
In order to calculate the top of descent, you reverse engineer the process as you would with the top of the climb.
How To Calculate Top Of Climb
In order to calculate the top of the climb, there are a few things to consider and which you will need to know before being able to definitively know your top of the climb.
First off, you need to know the current airspeed that you are traveling at. You should always use an actual speed instrument such as a Pitot tube or Air Data Computer (ADC) to determine the current speed that you are flying at.
The reason why you might want to use an ADC or Pitot tube is so that you can account for wind effects.
Winds vary depending on the time of year and location and they can affect the amount of thrust that an engine produces.
When calculating the top of the climb using these factors, you must also take wind into consideration in order to accurately calculate the top of the ascent.
You may also be wondering how far away you are from your destination airport. This is very similar to knowing the current airspeed that is running through the engines.
You can then add that to the difference in longitude divided by 15 degrees.
So, in order to calculate the top end of the climb, you first need to know the current speed that you’re flying at, the distance you are from the destination airport, and the wind speed.
All of these numbers must be entered into an equation and subtracted from each other.
Once you have the answer, you can round up or down to the nearest tenth of a mile. For example, if the answer is 3.5 miles, rounding up to 4 miles means that you’ve just calculated the top of the climb!
Is There A Quick Way To Estimate Top Of Climb?
Yes, there is. It’s called the “Rule of Three.”
The Rule of Three states that when you divide the total distance between two points by three, you will get the average rate of climb.
For example, let’s say that we are going from Point A to Point B. We know that the distance between them is 100 miles. In order to find the average rate of climb, we simply divide 100 by 3. That gives us 33 feet per minute.
Now, let’s say that you were flying at 40 knots and wanted to know what the top of the climb would be. Using the rule of three, you would divide 40 by 3. That gives you 13 knots.
Now, if you were flying at 20 knots and wanted to know the top of the climb rate, you would divide 20 by 3. That gives 5 knots.
This is a simple method to estimate the top of the climb but it does not take into account any wind conditions.
It’s not hard to calculate the top of climb and descent when you know how to do it.
It’s important to be able to calculate the height at which you plan to begin a descent because you don’t want to lose too much altitude while doing it.
And even though the calculation isn’t difficult, it helps to keep track of where you are in terms of altitude.
If you ever found yourself lost in the sky, you could look at the altimeter display and see exactly how close you are to the ground (see also “How Does Heads Up Display Work“).
Nowadays, we have GPS systems that provide us with some degree of safety and accuracy, but without having to rely solely on those devices, we can still use our heads to help us stay safe.
Frequently Asked Questions
What Is Density Altitude?
Density altitude is simply the altitude at which the atmospheric pressure is equal to the standard sea level pressure of 1013 mbar.
How Do Headwinds And Tailwinds Impact The Descent Rates?
The higher the wind speed, the faster the plane descends. If the wind is coming directly toward the nose of the aircraft, the pilot should increase power to maintain the desired flight path angle.