How do Airplane Engines Start? (Including Startup Sounds)

How do aircraft fly? • How Does Lift Work? (H...
How do jet engines work? • How Does a Jet Engine ...
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.
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[@PH-md8xp]

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 lift those engines deliver day in and day out is just incredible. 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.

[@andydouglas2108]

Yes Sir, it is an amazing age in which we live! Long may it last👍

[@pabloarvelo5969]

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!!

[@Negev-Israel]

Do you know why they use an air starter instead of an electric starter?

[@twwc960]

@@Negev-Israel In the past, electric motors and generators were heavier than the components used to carry the high pressure air (called "bleed air") from the APU or engine to where it is needed. Improvements in motor and generator technology have changed this balance, and newer aircraft, such as the Boeing 787 dreamliner, use electrical starters and virtually eliminate the use of bleed air in all their systems.

[@ChapaLipar]

We use air starter instead of electrical starter for many reasons. The first one is that an air starter of an A320 or B737 is a 150 HP turbine. An electric equivalent would be heavier and you have to carry it for all the flight when you only use it for less than 1 minute. Also an electric starter would require energy that you find in heavy batteries. Same thing. The weight to power ratio is not in the advantage of the electric starter. As described in videos the APU which is a small turbo engine is started by the battery of the aircraft or a ground cart when available. But when power is required the electric solution is too heavy yet 😊

[@Negev-Israel]

@@ChapaLipar makes more sense

[@ChapaLipar]

@@twwc960yes it’s true. On bigger aircraft such as 777 they use alterno-generators which are used as electrical motors during start and as generators during the flight, providing electrical power to the aircraft. They are heavy but they replace the generator and the starter. That provides a weight benefit over two separate systems.

[@aravintakzun]

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

[@sensitiveissues3671]

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.

[@energeticvids]

Agreed. It's a full orchestration of sounds also including the ding, ding-dong of chimes, pumps and motors and constant 400Hz electrical hum. I even featured that start-up sound in one of my music videos. /watch?v=U1Q5KohVfsw

[@iTz_JLAR]

Here's an engine start for you. Best sounding engines I've ever worked around kzbin.info/www/bejne/qn-vq2d-pdh-h7csi=5l3I10u_hWmzoMdW

[@TruthInAdvertising987]

At 2:48 there is a minor suggested change. It's not the pressure of the air that ignites the incoming fuel. It's the existing flame in the chamber. An excellent video. Nice job.

[@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.

[@user-bc5qz3mt5h]

My understanding is that there are many variables at play here which will determine the starting procedure that (commercial) pilots use. Options e.g.: APU bleed air to start both engines separately, an APU start for one engine to then cross-bleed another, and ground-cart air used in place of an APU for engine starting. If an aircraft is going to be sitting around after taxiing away from the terminal, waiting for take-off permission, it can be more economical to start a single engine via the APU, shut-down the APU to conserve fuel, and then shortly before take-off, cross-bleed to start the other engine. I always thought it was pretty much up to the airline policy to determine whether it's an APU or cross-bleed start for the final engine...

[@KingdaToro]

@@user-bc5qz3mt5h Unless there's a single-engine taxi procedure in place, you'd normally start the APU and shut down both engines if you're going to be sitting still for a while. On a 737NG, for example, the APU will burn 240 lb/hr under load, but a single engine at idle will burn 850 lb/hr while putting out the same amount of electricity as the APU and significantly less bleed air.

[@foofghtr]

Cross Bleed Start was a new Airframes Change in 1986 when I was in VF-101 for Tomcat training. Before that the huffer and power cord had to stay connected until both engines started.

[@memcrew1]

I was looking for this comment. The APU is used to start both engines. A crossbreed start is usually done if the APU is not available.

[@chacehart7286]

The 737 starting procedure-Aft left fuel on, APU start, APU bleed on, selector switch to engine 2, engine 2 start switch to GRD, wait for 25% N2, fuel selector switch behind throttles all the way up. Repeat process for engine one. APU does all of the work.

[@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..😄

[@HitMeWith]

Haha! The absolute fail safe method 👌

[@OrianaBiggs-xz1oq]

Bloody true, sounds like you fix what pilots break😂

[@OrianaBiggs-xz1oq]

PS when I did my apprenticeship on Beechcraft, I have been ask a question similar to that. 😂

[@ImperrfectStranger]

If second gear doesn't work, try reverse (thrust) 😜

[@planaproject]

The cool thing about this procedure is that its in flight!

[@somelad346]

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

[@davecrupel2817]

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.

[@rv6amark]

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

[@Slarti]

Absolutely fantastic description on the air-starter clutch.

[@HitMeWith]

Glad it was helpful!

[@norodom2074]

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

[@DigitalAndInnovation]

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

[@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.

[@ChapaLipar]

In fact, during the start sequence it’s mainly the air exiting the starter and the HP compressor spooling up that you hear. When the starter provides the maximum HP speed, around 20% of the maximum, the LP spool ( Fan in the front and low pressure turbine in the rear) are only rotating at 4-5% of their maximum by the air going out of the engine. So you don’t hear it. When fuel and ignition are turned on you may hear a little clic noise (and if you can see the back of the engine, a small fume) and then you hear the engine spooling up to idle ( around 60% of the maximum) the GE90 of the B777 has a double annular combustion chamber which gives a specific growling noise when the ignition begins until it stabilizes at idle. This shows that the engine is not designed to run in this condition. It’s a little weird, but it’s perfectly normal. Then everything becomes quiter.

[@user-bc5qz3mt5h]

This was super interesting. I always wondered what those sounds were when I'm waiting for my plane to take-off. Now I know. Thanks HMW! Love this channel - subbed

[@HitMeWith]

Glad you enjoyed!

[@philipgotay7314]

closest thing to riding a fighter jet, except for the catapult launch...😊

[@raphaministriesworld7777]

GREAT INFO. FOR US OLD PROP PILOTS. I KNEW THE PROCESS IN THE OLD 707 DAYS. I HAVE HEARD THIS NEW PROCESS MANY TIMES. NOW, I KNOW WHAT I HEAR. THANKS.

[@robertheinkel6225]

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.

[@M3dicayne]

So the Blackbird wouldn't be able to even start its engines without on any other airfield than that with that kind of engine?

[@robertheinkel6225]

@@M3dicayne correct. It could only land where full support is available.

[@Bellboy40]

Actually, the start carts for the SR71 had two 400 hp Buick engines connected together to start the jet engines. Later on the start carts used two 460 hp Chevy 454 ci engines. Those engines had to be revved up to their red line to spin the jet engines over fast enough to start. Those things sounded awesome when they were spinning up to start the jets. Link to video of start cart in action: kzbin.info/www/bejne/gJvHqoSmerqMsKs

[@sanandaallsgood673]

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

[@markburckhard553]

I noticed that, too. Good eye.

[@bobrice3957]

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.

[@dehypnotizerz]

Yup! Actually, I haven't heard about rotating the LP fan during the start-up.

[@stephenholland5930]

You would only use bleed air from the first engine to start the second engine when doing a cross-bleed start. This would be required when the APU was unable to supply bleed air, and a ground airstart unit is used to start the first engine.

[@ChapaLipar]

@@stephenholland5930 or if you have to restart an engine in the air. As the APU is generally turned off.

[@tajwarchowdhury22]

Iv been searching for videos like this since I was a child. But never found one. This was very educational and fun to watch. Make more please

[@thatoneguyRyan1]

4:40 you got the engines mixed. Left engine is #1 and right engine is #2

[@zolo111]

Yup, looking from back to front, count engines from left to right. Great video though.

[@bikingmoments]

Thank you . This is the best illustration video about aviation technicals I’ve watched!

[@elcaballopapi]

One of the best videos explaining this.

[@hansolovelander342]

Thank you for the lesson!❤

[@6thdayblue59]

Just found your channel. Really enjoyed it, and I hope you do more as they are genuine and honest as well as interesting and informative. Thank you

[@Luuuugn]

Thank you! love that you included the startup sounds also.

[@maurice5977]

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 !!!

[@joesimonetti]

Same here...was a pretty cool illustration...

[@dominikg.5619]

Thats one of the best videos on KZbin. A great thanks to the creator🎉

[@TheAstroguypasa]

I have been looking for explanations as to where the sound comes from during startup. Thank you for making such an amazing and educative video.

[@23for82bigs]

I work on cars and always wanted to know how jet engines start but never got to researching it, after this amazing video I now understand exactly 👍

[@proton9551]

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

[@twwc960]

That annoying crying sound is the baby in the seat behind you.

[@don-music]

I learned so much in 5 minutes here that I've never known.... thank you! fascinating!

[@mystisith3984]

Didn't realize it was that complex. Thanks for teaching us.

[@cameronk4582]

Loved this video! Thank you

[@cliffdodson1592]

Thanks!! I work at LAX and LOVE LOVE LOVE watching the engines start when we push back. I do the mechanic headset sometimes and instruct the pilots when it’s clear to start engines Right to Left on a 777, or 4,3,2,1 in a 747. 🎉 ✈️ 😎

[@kevingould6725]

It’s even better when you get to carry out engine tests. Last test on a Tornado engine set up test is The Slam . We take the engine from idle to combat through afterburner. We slam the throttle from idle position to combat and the computer does its magic. We still have control of the engine via the throttle.

[@DardanellesBy108]

For our maintenance engine runs we use the APU for both engines. I’m certain the pilots usually do the same. A cross bleed engine start is done when the APU is inop. The first engine is started with a high pressure air cart. (In the Navy we called them huffers). Then they start number two with cross bleed. Great video!

[@rwjolley]

That was fantastic!!!! The use of graphics really helped me understand the physical process of the engine working. Excellent work!!

[@azfan10]

Cool video! But we start the second engine exactly the same as the first one, so with the help of the APU. A crossbleed start, where you use bleed air from the other engine instead of the APU, is only used when the APU is unserviceable. The rest of the video is very accurate!

[@steveprisby3043]

really enjoyed your explantions - just great !

[@GX33Official]

This is 10/10 content, very nice explanation. Thank you

[@Kebab4523]

Very clear info thank you 🎉🎉❤❤

[@Liberator74]

I loved this video - thanks!

[@LucasAlmeida-dz5xh]

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

[@musicforaarre]

Most excellent ! I didn't know all of these steps before. Gorgeous. Aarre Peltomaa

[@user-ug4cp5nl9d]

Thanks a lot for the piece it's interesting to note the plane also uses the clutch.

[@LexaBukreev]

Thanks for a great video! Now i know how it works!

[@FDXFilms]

I already knew how they start. So I watched this to waste my time. but I learned something new today and that is what do the different type of sounds created by the engine mean. Thanks so much!

[@FDXFilms]

u got a like btw

[@husniyeaksut9902]

Thank you so much for your excellent explanation. Waiting for more videos

[@billmartin3198]

I sell toilets for a living. This level of engineering & design blows my mind.

[@edutaimentcartoys]

Very useful video and adds to my knowledge about airplanes

[@opathe2nd973]

Spot on video! Thanks for the lesson!

[@sukhmanbhullar2772]

Best explanation I've ever seen

[@rafaeldelafuente4787]

Amazin explanation. Thank a lot.

[@zuniga0331]

that was sick!

[@dandurban9123]

Now I know how those engines whine first and then roar; fascinating sequence of startup!😘🤷‍♂

[@twotalljones4790]

That was an excellent explanation.

[@user-pm5os7rx6i]

Very fantastic description vidéo of starting jet engine

[@bc-guy852]

Oh Yeah... I think we'll be seeing and hearing a lot more from this channel!! At least I hope so! Excellent production in all ways: camera, B-roll and audio all great! A very interesting topic, well-demonstrated, brilliantly detailed with diagrams and a good script. In My Opinion. An easy: subscribe, like, notifications on and a comment for the creator. YES - more like this please!

[@sandipghosh3792]

Nicely explained.

[@willtrent3077]

Excellent video, thank you. Concise explanation and description.

[@MinhajMalik]

Always wondered how it was done, now I know. Thank you so much.

[@swipekonme]

i am liking the FLOW in enunciation

[@scratchy523]

Awesome video. I learned so much from it.

[@manikandanganesh5952]

terrific video,,always luved the jets

[@Ryan-hd6um]

finally figured out what makes the rumbling sound, as ground staff i love it

[@PeterNGloor]

the older jets with a smaller bypass ratio sounded different. They spooled up much faster, the onset of fuel burn was very audible, and there was no rumble as on today's big engines.

[@timothypharmd]

Thank you 🙏.

[@theKhumbaguy]

Amazing. I always thought that first sound was the first engine starting. Now I know it's the APU. And I remember that deep grumble when the engine is fired up from my last flight.

[@KoolHandJuke]

I thought the same exact thing! 😅

[@KoolHandJuke]

That low grumble is awesome. The power gets the old testosterone flowing. 🤜💥🤛

[@ChapaLipar]

The low grumble is very noticeable ina B777 with GE90 engines. It sounds like the engine is not willing to start a new business day 😊 Just like me with the alarm clock on monday morning 😖

[@markallen8226]

Excellent, thank you.

[@pv.unmesh3203]

Thanks 🙏

[@andrewbennett7756]

Omg I never new it had a clutch amazing

[@RZ-ey9jk]

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.

[@m3photo726]

Yep. That’s the case for diesel.

[@symbionese2348]

Thank you. I jolted when he said that, too. What he should have said is that the engine sustains combustion in the correct direction. Yes?

[@PeterNGloor]

The ignition is switched on when it's time to light the fuel, then the flame burns like on a welder's torch. But I understand that in certain weather conditions the ignition is set to continuous in case of a flame-out.

[@ChapaLipar]

@@PeterNGloor that’s correct. In normal circumstances during engine start you use only one of the two igniters. If the engine start fails, then you make a second attempt with ignition selected on ‘both’ . When the engine is spooling up to idle, the starter disengages and the ignition is switched off. During the flight in severe conditions like heavy rain, ice, or freezing temperatures on the ground when landing the procedure is to turn the ignition on to prevent any flameout.

[@ChapaLipar]

And in ‘continuous’ position the ignition is on for both igniters.

[@stevenkaskus6173]

Great video, hope to see more

[@Sabotage_Labs]

Engineering... Its what makes the world work! Gotta love it. And...High Fidelity. Good movie and...great track when he hits that play button. American treasure, Stevie Wonder and I beleive when I fall in love. Great....great track!

[@PW-qy8mf]

Interesting video, but allow me one minor correction: in NORMAL operation, we do start BOTH engines by using APU bleed air. Only if the APU is inoperative, we use an external air starter unit to start the first engine and then apply the "cross-bleed start procedure" to start the other one with the air bleed pressure from the first engine ;-)

[@railroad6601]

Would it be more efficient and quicker to Cross-bleed to start second engine? Because you can shut off the APU earlier and first large engine produces more flow/pressure for second large engine than the APU. Also the two larger engines could be closer to each other that long run from APU.

[@jacksonwanyoko273]

I have been waiting for someone to make this video. Thanks man👊🏾

[@Sowhat300]

I had a ‘70 Volkswagen Beetle that started the same way, only I had four friends provide the forward movement.

[@paulmoor595]

Great video...I've been around aircraft for years and never knew this information. Well done..

[@arcus_aro8584]

I’ve read wiki pages and seen many videos of how plane engines start and finally I have a sort of surprising and informative answer. Thank you very much!?😁

[@747driver3]

Here’s how they start: You hook the burner section to your corporate or personal bank account and the jet engine sucks money out and burns it.

[@FutureAIDev2015]

That reminds me of a comic that I saw making fun of the concept of the four forces of flight. Instead of lift, gravity, thrust, and drag, though, there was ambition, reality, money, and the FAA. 😂

[@PH-md8xp]

😂😂

[@dennisnewman678]

That's actually a pretty good description. 😂😂😂

[@ramadhanisme7]

Thank you for your super simple yet very easily to understand video

[@Bugsworth]

Very good sir. Subscribed!

[@danylosokolov2085]

Cool, thank you

[@brianligat9493]

When you said you had a birds-eye view of a jet engine I thought ... ouch!

[@RickyD1968]

Very cool !!!

[@WhiteMouse77]

Happy to know how it's invened. ....but then (and also?) for what purpose is that truck with big generator-like cube on chassis usually connected with massive cable into airplane belly? Battery recharging?

[@LuciferCelebrimbor]

Perfect explanation complemented by outstanding visual graphics.

[@mikehutchins1364]

Cool ...... Thank you ! .....

[@BucharestRO]

First video i see that actually explains this. A lot of videos about " how a jet engine works " but never mention how it starts for some reason. That should be the first thing they say

[@cooltube]

Best explanation I’ve seen 👍🏻🇬🇧

[@roberttirado4569]

Wow. That was awesome. Thanks

[@DropBear69]

This was very interesting! You should not leave such a long gap between delivering videos - you do a great job! Subed.

[@Zero_Narrative]

Such a great video

[@thaddaeuswilson3248]

Interesting!! V he Ave heard these sounds from outside znd ad a passenger. Now I know what all the sounds are. Thanks!!

[@Stormrider-Flight]

Nice and simple. Now i'd like to hear about how a JFS system works different.

[@anton74624]

I was a technician for 36 years and it still amazes me how a ton of air can pass through the 15th stage hpc blades only an inch in length in 45 seconds at take off power.

[@SoFlaSooner]

Very interesting video. Thanks!

[@faimum2634]

Great explanation. Nice to watch.

[@robertbenoit5374]

They can also use what is called an Air start cart. Military uses these more than Civilian Aviation because they lack the APU but if the APU is not functioning that is what they would use in Civilian aviation.

[@rinsedpie]

Learnt something; cheers

[@adriankohli4870]

Top Video 👌🙏