engineering

Rate of climb

Rate of climb is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Rate of climb rather than just read about it. In short: In aeronautics, the rate of climb (RoC) is an aircraft's vertical speed, that is the positive or negative rate of altitude change with respect to time. In most ICAO member countries, even in otherwise metric countries, this is usually expressed in feet per minute (ft/min); elsewhere, it is commonly expressed in metres per second (m/s).

Key takeaways

Rate of climb belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Rate of climb to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Rate of climb from memory before moving on to harder problems.

Reference excerpt

In aeronautics, the rate of climb (RoC) is an aircraft's vertical speed, that is the positive or negative rate of altitude change with respect to time. In most ICAO member countries, even in otherwise metric countries, this is usually expressed in feet per minute (ft/min); elsewhere, it is commonly expressed in metres per second (m/s). The RoC in an aircraft is indicated with a vertical speed indicator (VSI) or instantaneous vertical speed indicator (IVSI). The temporal rate of decrease in altitude is referred to as the rate of descent (RoD) or sink rate. A negative rate of climb corresponds to a positive rate of descent: RoD = −RoC.

Speed and rate of climb There are a number of designated airspeeds relating to optimum rates of ascent, the two most important of which are VX and VY. VX is the indicated forward airspeed for best angle of climb. This is the speed at which an aircraft gains the most altitude in a given horizontal distance, typically used to avoid a collision with an object a short distance away. By contrast, VY is the indicated airspeed for best rate of climb, a rate which allows the aircraft to climb to a specified altitude in the minimum amount of time regardless of the horizontal distance required. Except at the aircraft's ceiling, where they are equal, VX is always lower than VY. Climbing at VX allows pilots to maximize altitude gain per horizontal distance. This occurs at the speed for which the difference between thrust and drag is the greatest (maximum excess thrust). In a jet airplane, this is approximately minimum drag speed, occurring at the bottom of the drag vs. speed curve. Climbing at VY allows pilots to maximize altitude gain per time. This occurs at the speed where the difference between engine power and the power required to overcome the aircraft's drag is greatest (maximum excess power). Vx increases with altitude and VY decreases with altitude until they converge at the airplane's absolute ceiling, the altitude above which the airplane cannot climb in steady flight. The Cessna 172 is a four-seat aircraft. At maximum weight it has VY of 75 kn (139 km/h) indicated airspeed providing a rate of climb of 721 ft/min (3.66 m/s). Rate of climb at maximum power for a small aircraft is typically specified in its normal operating procedures but for large jet airliners it is usually mentioned in emergency operating procedures.

Variometer

See also ICAO recommendations on use of the International System of Units Climb (aeronautics) Descent (aeronautics) V speeds

References

Illustrations

Rate of climb: The vertical speed indicator from a Robinson R22. This is the most common type used in aircraft, showing vertical speed in feet per minute (ft/min). — The vertical speed indicator from a Robinson R22. This is the most common type used in aircraft, showing vertical speed in feet per minute (ft/min).

Worked examples

Example 1 — a first encounter with Rate of climb

Start with the simplest possible case. Write down what Rate of climb claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Rate of climb before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Rate of climb ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Rate of climb

In research: Rate of climb appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Rate of climb in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Rate of climb is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aerospace engineering, Aircraft aerodynamics, Temporal rates, so understanding it makes those chapters shorter.
In everyday life: Look for Rate of climb outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Rate of climb in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rate of climb means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Rate of climb out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rate of climb in simple terms?

Why does Rate of climb matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Rate of climb?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Rate of climb.