An Air Canada Captain Answers Your Questions on Engines, Takeoffs and More

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Your aviation questions answered: on starting airplane engines, takeoffs vs. landings and rumbling noises.

An illustration of a keychain with a key and an airplane charm hanging on it.

Do airliners have keys? 

Keys are not required to start an airliner’s engine, nor are they needed to open aircraft doors. Only small airplanes, like a Cessna, require keys and the only key I have is for the aircraft’s medical kit. Instead, switches and levers in the cockpit start the engines using compressed air, supplied by the Auxiliary Power Unit (APU), a small gas turbine engine located in the aircraft’s tail. Exception: In the Boeing 787 I fly, engines are started electrically without compressed air from the APU. 

February 16, 2022
An illustration of a marshaller, wearing a safety vest and holding signs, gesturing to direct traffic on the airplane runway.

Who starts the engines and taxis the airplane? 

This depends on the airline. At Air Canada, engine start‑up was once the captain’s duty, but now it’s the first officer’s task. However, the captain taxis the aircraft and is responsible for releasing and setting the parking brake. On the ground, airplanes can be steered using hand tillers, which are levers that adjust the direction of the nose wheel. 

Related: How Does Flight Planning Work?

An illustration of an airplane wheel touching down on the landing strip.

Which is more challenging: takeoff or landing?  

The short answer is landing, but both have inherent challenges. During takeoffs, pilots focus on airplane performance both in terms of mechanics and the environment. For every takeoff in larger aircraft, flight crews reference a decision speed called V1. Think of it as a yellow light in the decision‑making process – do we stop or continue? We practise these decision‑making procedures in the flight simulator. For landings, the biggest challenge is the weather. Low visibility, low clouds, slippery or short runways and crosswinds top the list of things we need to think about.   

Related: How Air Traffic Control Works

An illustration of an airplane's fuel gauge, with clouds scattered around the top.

Do airliners use full power for takeoff?  

Modern jet engines are so efficient that they can produce thrust beyond what’s necessary to get airborne, which means we rarely use full takeoff thrust. Decreasing thrust is achieved by inputting a faux temperature greater than the outside temperature into the flight management computers. The faux temperature commands the engines to mimic thrust produced as if the outside air pressure is less dense. Also, reducing thrust prevents wear and tear on the engines, saves fuel and minimizes noise.

An illustration of an overhead view of an airplane with a blue sky in the background.

What is that rumbling heard at cruising altitude? 

You might hear a slight rumbling when the engines increase thrust (known as spooling up) to climb. Generally, the higher an aircraft is flying, the more efficiently it burns fuel. If the aircraft is heavy, pilots must wait until enough fuel has been consumed to lighten the aircraft, enabling it to ascend in altitude – called a “step” climb. For an airliner flying a long‑haul flight, this process can take hours before the plane reaches its maximum altitude.\

Related: How to Read Clouds (and Flight Conditions) According to an Air Canada Captain

An illustration of an old fashioned gas pump, with an airplane symbol on the top.

Are the fuel tanks always full?  

To fly from A to B in a jetliner, the fuel required is the A‑to‑B fuel plus reserve fuel of 30 minutes to go to an alternate destination (fuel is carried inside the aircraft wings). We rarely fly with full fuel tanks as you would when embarking on a road trip because, when flying, an airplane’s fuel is weight. So carrying extra fuel requires burning more fuel: An extra tonne of fuel requires about 100 kilograms of fuel to carry it.

Ask the Captain

Do you have questions about another facet of air travel? Send your aviation and operations queries to: douglas.morris@aircanada.ca

Portrait of Air Canada's Captain Doug Morris
Photo: Reynard Li

Doug Morris is an author, meteorologist, instructor and Air Canada captain on the Boeing 787.