How do Airplane Engines Start? (Including Startup Sounds)

And did you know...
1. An important job of the ground crew is to ensure that on very windy days, the engine is orientated into the wind. A strong rear wind would turn the fan blades in the opposite direction, and if it's very strong, could result in a poor airflow through the engine. This increases the combustion chamber temperature which can burn out and shorten the lifespan of the turbine. This is known as a hot start.

2. The APU delivers air at around 45 PSI. That's similar to the pressure in a well-inflated mountain bike tire!

3. A lot of aircraft will also use a ground cart to start up. This is a motor which is substituted in instead of the APU to provide high-flow air to the engine. It's often cheaper to maintain and thus saves on maintenance cost of the APU.

4. For military engines, the requirement is a little more straightforward. You want to start your engines unassisted as quickly as possible. This is to ensure your response time to an emergency is at a minimum. A pilot might find himself in the middle of an airfield which quickly turns hostile. The F-22 uses a pressured cartridge to blast high pressure air onto the APU turbine blades. This kickstarts the APU and starts it much more quickly than an electrical motor. However this is only used in an emergency.

5. Many smaller business jet engines are also directly started using their electrical motor, which serves as the generator for on-board electricity once the engine is running.

6. Single-shot Pyrotechnic cartridges (also known as fireworks!) are used almost exclusively for expendable RPVs such as missiles or decoys which are started in flight and need no re-start capability. This is low weight and economical and starts an engine in less than 10 seconds.

7. It's also worth mentioning that newer engines are electrically started. For example, the GEnx and RR Trent 1000 engines on the Boeing 787 Dreamliner have electrical motors mountain directly on the engine shafts. This motor is powered by the APU and aircraft batteries. It reduces the overall weight of the starter system since the motor acts as the generator during engine operation, providing electrical power to the aircraft.

Keep On Going by Joakim Karud / joakimkarud
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[pabloarvelo]

I was a gas turbine tech in the US Navy. The engine starting sequence was one is the most challenging topics to explain to junior technicians. This video simplifies kindergartens it. Thanks you!!

[PH-mdxp]

Excellent explanation!
The jet engine is an amazing invention. I recently flew back from Dubai, direct to Seattle, 15 hour flight, on an Airbus A-380. The endurance and thrust those engines deliver day in and day out is just incredible. 280, 000 pounds of thrust across 4 engines, provide these massive aircraft with enough velocity and air moving across the wings to lift an aircraft weighing up to 580 tons off the ground. It’s just awe inspiring.
Hundreds of passengers and all their luggage. Inside the aircraft, I could hear the engines, but just barely. Have to respect the engineers that design these engines.

[sensitiveissues]

Why do I find the sound and sight (and smell in a real setting) of a jet engine starting up so satisfying? Thanks for this walk-through.

[aravintakzun]

One of the best explanations out there. Students need teachers like you

[norodom]

I’m thankful for all these smart people moving humanity forward. Imagine what we will come up with in 50-100 years.

[KingdaToro]

Using one engine to start another is a cross-bleed start. It's only done if the APU is down, since the engine providing the starting air needs to be throttled up significantly, using a lot more fuel than the APU. This is done after starting the first engine at the gate with a "start cart", an external air source. Normally, the APU starts both engines, then is shut down once both engines are running.

[denheer]

I've always been curious about the specific sounds an airliner jet engine makes during startup. Now, I've finally learned what that particular sound is just before fuel injection in the main engine: it's the speeding up of both pressure shafts. Each shaft has a different RPM and can sometimes go out of harmony with each other.

[somelad]

God the sound of the engine starting up is a pure eargasm!

[Slarti]

Absolutely fantastic description on the air-starter clutch.

[davecrupel]

0:40 "By a large onboard battery"

Commercial jet technician here.
Its only marginally larger than the battery in your car. Though they throw out twice as much voltage. And there are two of them in narrowbody jets, and 4 of them in most widebody jets.

[sigmafastener]

Thanks. The explanation is simple and straight forward. Just in case the starter system fail, the pilot need to engage the clutch pedal, put to second gear, ask ground crew to give a little push to the aircraft, and pop the pedal..😄

[RZ-eyjk]

Great overview, just one comment from an engineer at Rolls-Royce: the fuel is not self igniting due to the high air pressure, you need a sustained flame in the combustion chamber. So if you have a flame-out you need to re-ignite.

[proton]

VERY professional presentation with clear audio and without irrelevant jargons.
Diagrams are to the point and step by step logical approach.

hope you do another video on all the sounds we typically hear within the cabin during the flight.
Thanks

[bobrice]

It is very rare for engines to be started from another as you need to spool up to gain the 40 psi needed. It is only the HP spool that is driven. The LP rotates as the airflow generated by the rotatating HP drives its turbine.
The 20% mentioned is HP speed as you only need to check you have rotation of N1.
Other than that good description.

[rvamark]

Good video, very accurate. I spent 43 years in the aircraft design industry, and was always impressed by that start-up sequence.

[robertheinkel]

The SR-71 used an external V-8 engine, connected thru a driveshaft, to the engine. Once started, the shaft was removed.
On the KC-135R, it has two large APUs on board, so it can start multiple engines at once.

[DigitalAndInnovation]

First video on this topic that actually combines every element of the startup into a easy to follow package!

[maurice]

As a passenger I have always wondered what the sounds were as the engines made as they (spooled) up and now I know, thank you very much !!!

[sanandaallsgood]

With the exception of misidentifying engines 1 and 2, this was an informative video. Engine 1 is always the one on the left wing.

[LucasAlmeida-dzxh]

Finally the startup explained by a human voice instead of a goddamn ai