How do Airplane Engines Start? (Including Startup Sounds)
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- Опубликовано: 14 май 2024
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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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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!!
Do you know why they use an air starter instead of an electric starter?
@@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.
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.
Yes Sir, it is an amazing age in which we live! Long may it last👍
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.
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
Here's an engine start for you. Best sounding engines I've ever worked around
ruclips.net/video/tNLz4HpsKQU/видео.htmlsi=5l3I10u_hWmzoMdW
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.
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.
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...
@@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.
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.
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.
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.
One of the best explanations out there. Students need teachers like you
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..😄
Haha! The absolute fail safe method 👌
Bloody true, sounds like you fix what pilots break😂
PS when I did my apprenticeship on Beechcraft, I have been ask a question similar to that. 😂
If second gear doesn't work, try reverse (thrust) 😜
The cool thing about this procedure is that its in flight!
I’m thankful for all these smart people moving humanity forward. Imagine what we will come up with in 50-100 years.
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.
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.
God the sound of the engine starting up is a pure eargasm!
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.
Yup! Actually, I haven't heard about rotating the LP fan during the start-up.
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.
Good video, very accurate. I spent 43 years in the aircraft design industry, and was always impressed by that start-up sequence.
First video on this topic that actually combines every element of the startup into a easy to follow package!
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.
So the Blackbird wouldn't be able to even start its engines without on any other airfield than that with that kind of engine?
@@M3dicayne correct. It could only land where full support is available.
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:
ruclips.net/video/JjdyQpEUYzI/видео.html
With the exception of misidentifying engines 1 and 2, this was an informative video. Engine 1 is always the one on the left wing.
I noticed that, too. Good eye.
4:40 you got the engines mixed. Left engine is #1 and right engine is #2
Yup, looking from back to front, count engines from left to right. Great video though.
Absolutely fantastic description on the air-starter clutch.
Glad it was helpful!
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 !!!
Same here...was a pretty cool illustration...
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.
Yep. That’s the case for diesel.
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?
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.
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
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.
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. 😂
😂😂
That's actually a pretty good description. 😂😂😂
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
Glad you enjoyed!
closest thing to riding a fighter jet, except for the catapult launch...😊
Thank you . This is the best illustration video about aviation technicals I’ve watched!
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.
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
One of the best videos explaining this.
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.
I thought the same exact thing! 😅
That low grumble is awesome. The power gets the old testosterone flowing. 🤜💥🤛
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
Thank you for the lesson!❤
Thank you! love that you included the startup sounds also.
Finally the startup explained by a human voice instead of a goddamn ai
I learned so much in 5 minutes here that I've never known.... thank you! fascinating!
Didn't realize it was that complex. Thanks for teaching us.
Thats one of the best videos on RUclips. A great thanks to the creator🎉
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.
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!
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 👍
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
That annoying crying sound is the baby in the seat behind you.
Loved this video! Thank you
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!
u got a like btw
really enjoyed your explantions - just great !
i am liking the FLOW in enunciation
Now I know how those engines whine first and then roar; fascinating sequence of startup!😘🤷♂
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.
🎉 ✈️ 😎
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.
This is 10/10 content, very nice explanation. Thank you
Brilliant! Now I want to know what the startup sequence for the APU is!
Most excellent ! I didn't know all of these steps before. Gorgeous. Aarre Peltomaa
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!
Very useful video and adds to my knowledge about airplanes
When you said you had a birds-eye view of a jet engine I thought ... ouch!
That was fantastic!!!! The use of graphics really helped me understand the physical process of the engine working. Excellent work!!
finally figured out what makes the rumbling sound, as ground staff i love it
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.
Nicely explained.
I dont why I watched this, I can barely understand how a regular 4-stroke engine runs and sometimes I think thats a miracle.......
I loved this video - thanks!
I have been waiting for someone to make this video. Thanks man👊🏾
Thanks a lot for the piece it's interesting to note the plane also uses the clutch.
I sell toilets for a living. This level of engineering & design blows my mind.
Thanks for a great video! Now i know how it works!
Spot on video! Thanks for the lesson!
that was sick!
Thank you for the turbine engine startup process. Could you do a similar video for jet prop systems, and a third with liquid fuel gas propeller engines? Excellent graphics, easy to follow, fun to observe and extremely informative. Bob C Clearwater, Fl former AIR FORCE Veteran 🇺🇸👍
If by "jet prop" you mean turboprop engines, then the startup process will be very similar, if not identical: The only difference between a turbojet and turboprop is that the latter has a free power turbine bolted onto the back, which converts the high pressure, high velocity turbojet exhaust into mechanical torque, which is then utilised (via a separate driveshaft and step-down gearbox) to spin the propeller.
A turbofan engine works the same way as a turboprop, the only difference being that the free power turbine drives the big fan instead of a propeller. In older turbofans, the free power turbine drives the fan directly, with both rotating at the same speed. Newer turbofans use a step-down gearbox to spin the fan at a slower speed than the free power turbine. This is necessary for large diameter high bypass turbofans to prevent the fan blade tips exceeding the speed of sound, which would otherwise produce more noise and be less efficient.
The other variant is the turboshaft engine, which again works the same way as turboprop or turbofan, except that the free power turbine drives an output shaft coming out of the back of the engine, which is known as a "hot end drive". Turboshaft engines are most commonly used in helicopters, though they can also be used to make electricity (by connecting the output shaft to a generator), or in marine applications to drive a ship propeller, again most likely through a step-down gearbox.
Whether you are using a turbojet, turboprop, turbofan or turboshaft, the core of the engine is going to be the same - a compressor, combustion section and a turbine driving the compressor. The starting method largely depends on the size of the engine: Electric motors can be used on smaller engines, such as the 1950s era J47 turbojet, which used a big, beefy starter motor, consuming 400 amps at 30 volts DC, which is 12 kilowatts or about 16 horsepower. To put this into some perspective, this is about 10 times more powerful than the electric starter motor used in the average car.
Larger engines are usually started with an air-turbine starter, which is essentially a weight-saving measure: An electric motor powerful enough to start a modern turbofan engine (a Rolls-Royce Trent 1000 for example) would be impractically large and heavy, as would the batteries needed to power it. The combination of the APU and an air turbine starter is much lighter. An added advantage is that an air turbine starter can be powered for as long as you like, provided you have an adequate supply of compressed air to run it. Those 12 kilowatt electric starter motors could only be powered for a maximum of about 90 seconds before they would overheat, after which they needed at least an hour to cool down before being used again.
@@lloydevans2900 One thing perhaps worth noting from a passenger perspective is that a turboprop can have another major change in sound once the startup is complete and the blade pitch is adjusted. The ones I often ride in seem to start up fully feathered and then pitch to provide thrust when they're ready to move - although I don't know whether this is universal.
Incidentally I didn't realise that turboprops ran off a secondary turbine - I always assumed the prop was on a (geared) shaft from the turbojet core. Glad to be corrected :-)
@@simonwaldman5497 There are some older turboprop designs which do work as you originally assumed, with the power output shaft spinning at the same speed as the rest of the engine, then going through a step-down gearbox before driving the propeller. To achieve this, the turbine section has to extract more power than is necessary to run the compressor, so is either larger than the equivalent turbojet would be, or more likely just has extra stages added. The drawback of this design is that whatever the engine is driving will necessarily have to also be spun up while the engine is being started, which places an extra load on the starting mechanism, whether that is an electric motor or some kind of air turbine starter. Also, this design cannot be used to drive anything where there is a possibility of the mechanism seizing up or significantly slowing down, because that would stop or slow down the engine core itself.
Hence the development of engines with free power turbines, because then the core and the power turbine can be mechanically independent and spin at their own optimum speeds, which also makes the system far more efficient. The most well known and popular engine which works this way is the P&W PT6, used on a lot of light aircraft, either as a single engine right up the front, or wing-mounted for some larger twin-engine aircraft. It is also built as a turboshaft variant for helicopters. A curious aspect of the PT6 is that it often gets installed "backwards", with the air intake behind the exhaust - if you ever see a single engine light aircraft with a pair of exhaust pipes curving backwards just behind the propeller, you can be pretty certain that the engine is a PT6.
@@lloydevans2900but it's the starter we are interested on.
@@simonwaldman5497I think they start up in beta range as this might mean the smallest air resistance that the prop has to overcome. To taxi the prop pitch shifts to high pitch for best efficiency, and to brake the plane in taxi, the prop can be shifted to beta again, with no forward pull. Some turboprops taxi out from a gate backwards, with the props set to reverse pitch.
terrific video,,always luved the jets
That was an excellent explanation.
Nice and simple. Now i'd like to hear about how a JFS system works different.
Awesome video. I learned so much from it.
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?
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!?😁
Amazin explanation. Thank a lot.
Great video, hope to see more
Excellent video, thank you. Concise explanation and description.
Fascinating to see a GenX engine starting with an air starter. Takes so much time compared to an older engine
That was a RR not a GE.
I blame it on the enormous fan, and the huge load it puts on the core, even at low speeds like this.
@@thomasburke7995sorry for the misunderstanding. I meant in general, a genx is impressive to see.
Fyi .. RR uses a rubber tipped steep angle cone for thier engines.. its unique to RR and the theroy is that it will deflect moisture away and the rubber tip will prevent ice forming due its flexibility
@@thomasburke7995 yes, I knew about this 😊 it’s an old RR trick, also used on the RR Tay on the Fokker aircraft
Omg I never new it had a clutch amazing
Very fantastic description vidéo of starting jet engine
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.
Excellent explanation, I was aware of the basics but not the use of a centrifugal clutch
Same
Thank you so much for your excellent explanation. Waiting for more videos
Very clear info thank you 🎉🎉❤❤
Very good sir. Subscribed!
Interesting!! V he Ave heard these sounds from outside znd ad a passenger. Now I know what all the sounds are. Thanks!!
Excellent, thank you.
Great video...I've been around aircraft for years and never knew this information. Well done..
Thats so cool the engine the vibration you feel as the plane pulls out is the engine start up because you miss out on how the plane functions because what you hear is a safety demo will all this is happening outside
As an Engineer, Pilot (Recip), and Car Nut, the factoid I found most interesting is that the Heat of Compression was enough to keep things lit!!! In Diesels, 17:1 compression is needed for that to happen! Just a buncha Whirling Vanes makes 17:1??? Wow!
I'm always fascinated by those engines. Your comment made me looking for the actual value and mordern jet turbines reach up to about 50:1! So, maintaining enough compression to keep it burning doesn't seem to be an issue.
That's actually not accurate. The combustion is self sustaining from the constant flow of air and fuel, which is ignited by the heat of the flame. The pressure has nothing to do with it. Piston engines need an ignition source, either a spark or heat from pressure, because there isn't any combustion already happening. They use a batch process, while a jet engine uses a continuous process.
My dumba$$ thought the turbines just started like flipping the switch on a desk fan 😂
Always wondered how it was done, now I know. Thank you so much.
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!
This was very interesting! You should not leave such a long gap between delivering videos - you do a great job! Subed.
A few errors: The APU has its own battery, it does not use aircraft battery. Starter air first goes thru a starter valve (not mentioned), then the air turbine starter connected to the HP section by an overrunning clutch (not necessarliy a centrifugal version) much like in your car. As the engine begins to pull on its own and Exhaust Gas Temperature (EGT) reaches a certain amount, the starter clutch disengages naturally and the starter valve closes.
Minimum sustained speed for engines is around 50%N, not 20%.
Thanks for this explanation. I was hoping you would also explain how the Rpm is controlled. I'll search your other videos.
Thanx for that . Now I know how they are started. I remember back in the 1970s going to my local airport and seeing DC8s starting. The always seem to give off a cough as the engine fired up.
I think only the '50 series of the Eight made this whooshing sound, which might have come from the starter. The start air used to come from ground vehicles with a diesel air compressor.
the part with the APU delivering compressed volumes of air to the Air Turbine Starter to the engine, reminds me of a child blowing on a pinwheel..the harder you blow the faster the pinwheel will turn.
Perfect explanation complemented by outstanding visual graphics.
The 777 starts both engines simultaneously using APU bleed air by the method described in this video. The 787 starts both engines simultaneously using two APU generators providing electrical power to two starter generators on each engine.
Can be ..but not advisable.. these engines create a tremendous amount of when nearing ignition when using the ground cart or the APU. IF YOU have a failure to start you switch to the other to allow for the original one to cool.. plus the start air coming from the running engin is double the volume but not the pressure..
@@thomasburke7995 All 787 Pilots are taught, by Boeing and their respective airlines, to start BOTH engines at the same time in normal circumstances. Airplane & engines were engineered with this in mind. It hurts nothing and has no associated risks or issues. 787 starters are only ELECTRIC. The only Bleed air system on a 787 is the Engine intake anti-ice system.
The 787 has one APU, with two generators, since the 787 uses more electrically driven motors vs. a hydraulic system.
I believe the 747-400 used to start both engines on the same wing at the same time, 1&2 - 3&4 at the same time
@@stevew8614 Boeing dose not make the engines and using the start up procedures that the engine manufacturers prefer ensure longevity and minimal damage that will shorten TBO'S.. also airlines typical modify recommended procedures to best fit thiere operation.. just because you can dual start an engine does not mean you should.
Fascinating video . As a suggestion , could you cover the different types of false starts, like compressor stalls etc and how to rectify these, please?
Mitch you could also teach us.
Very interesting video. Thanks!
@4:50 Shout out for using "High Fidelity"....a little known movie with Jack Black and John Cussack, Lisa Bonet and others.
I had a ‘70 Volkswagen Beetle that started the same way, only I had four friends provide the forward movement.
Great explanation.
Nice to watch.