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 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.
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 😊
@@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.
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
Planes fly over my house at 10,750' and the planes always make some kind of a thrust back noise. I don't know what it is. It's usually 8-10 minutes before they're landing in Charlotte. Sounds like gearing down. Don't know.
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
Yes, I’m afraid every indicator I can think of is pointing towards rapid regression. Government losing territorial control, decreasing standards of living, rapidly rising crime, interruptions to supply chains, rising indolence among the upcoming generations, quality standards slipping across the board from healthcare to policing to politicians to emergency services, next will be food supply chains being interrupted, rapidly increasing food prices, widespread, lawlessness, anarchy, disease, plague, starvation and cannibalism. 10,000 years of progress gone in two generations.
Finally some recognition for the maintainers. Without them the Pilots who fly them and the passengers who fly in them are grounded. Aircraft require far more servicing/maintenance than a car. Most large commercial aircraft can only go 1 flight before the engines need to be serviced with oil (as an example)
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!
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.
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.
@@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.
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
Thank you indeed, very instructive, helpful understanding and following the succession of steps, and perhaps somewhat reassuring. Access to royal family members' attitudes and reactions: priceless...
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...
@@RebeccaJackson-w2v 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.
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.
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.
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.
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.
@@sudhanwankumar2269 The proper title for my profession is "Airframe & Powerplant Technician." It's a govt issued license. How you get it varies from country to country.
I've only been on a jet maybe 4 times in my life, but I've always been impressed by how quickly they accelerate on the runway just as they're taking off- pretty much in the muscle-car range of acceleration.
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!
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.
@@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.
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 ;-)
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.
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..😄
Thank you very much Match. I take plane very often and I always wonder how the air compressor of the main engine starts? Electrically or what? And finally now I know how it starts and then starts the turbine. APU is the key 💡 Respect engeneers!!
Thanks, and good question! Using an APU is the most common method, but the Boeing 787 Dreamliner engines use electrically started engines (no ATS). Fighter jets can use high pressure gas cartridges to quickly spin up the turbine and start fast! More information in the description :)
@@HitMeWith I've worked with many of the different 4th gen fighters in the US. There are 2 types of starters. APU & JFS. APUs use bleed air to spin an impeller that spins over the engine during start. Some fighters that use an APU are A-10 Warthog (Not a fighter but attacker), F-22 Raptor, & F-35 Lightning. Other Fighters use a JFS (Jet Fuel Starter). It uses PTO shafts through a gearbox to mechanically spin over the engine. Some fighters that use a JFS are F-15 Eagle & F-16 Falcon/Viper. Some fighters don't have a starter at all. They require ground assist to start the engines. This is generally done with a jet powered start cart. Some aircraft that this apply to are the F-4 Phantom, F-5 Tiger, & T-38 Talon.
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.
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 😖
The APU is usually started well before passengers even get on board. At the gate that is what supplies electrical power and air for the airconditioning
this explanation is extremely well done!!! concise and easy to understand yet detailled enough to really grasp the very basics. could listen to your video much,longer
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.
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.
Piston engines seem less complicated that jets. AFAIK the generators on the engines are used as starter motors that spin the engines. Same as on a car. Power can come from the onboard batteries or a GPU, or even from an APU.
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.
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: th-cam.com/video/JjdyQpEUYzI/w-d-xo.html
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.
Its actually stagnation in the compressor airflow I believe, which disappears as the compressor speeds up, (shout out if that's wrong I'm airframes not engines) if it goes on too long the jet pipe temperature starts to rise (fuel starts burning in the jet pipe) and you have to shut down to prevent an overheat, then you have problems with a possible wet start when you try again.
As an airline mechanic of over 30 years, we almost never cross blead air from one engine to start another unless using a ground air supply in the event of an inoperative APU. An example of that would be an inop. APU, the airplane is located off in a remote area with no ground power available, and using an air start piece of ground equipment, you could use the emergency battery bus and fire the engine ignitors with the battery. Spin the starter, then fire the engine ignitors with the battery power, once you have an engine generator on line, the airplane is powered, then cross bleed and start the remaining engine/ engines. Other wise the APU's installed in most airliners were more than able to start any engine you chose. Good video, great explanation. On the B-52 though standard engine start up was to get #4 engine running, cross bleed air to start #5 engine, then use those two engines to start the rest on their respective wing. Really fun.
GREAT VIDEO!! One I would like to see is thrust power. In other words....what percent of engine thrust is needed to start the plane taxing, what percent used in take off, climb, cruise, descent, reverse thrust.
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!
Not quite! A flamed out engine will still be spinning due to the air rushing past it. This is known as windmilling. Once it is up to the required speed, fuel flow re-starts and the ignitors fire to combust it
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.
I was interested to read about the "start cart" which is used when the APU is inoperative. Apparently, it's not that unusual for a plane to be considered airworthy without a functioning APU.
ATC here. "Cross-Bleed Starts" are not uncommon. I'd get a request maybe once every week or so. They use a start-cart, then push back, then throttle up the single engine and cross-bleed the other one. It often requires ATC approval as starting an engine on the bay is really uncommon and presents hazards as compared to doing it in the push-back.
Commercial jet technician here. They can be allowed to fly without a working APU, but the plane cant go to as many destinations. Only ones that have start carts. Or "huffer carts" as we call them.
Ramp agent here. Nothing to add just want to be included 😂 although we call the “starter carts” an “Air start”, have also had to keep ground power connected for an engine to start up on stand because of an inop APU, but yeah isn’t uncommon. Nice to know what the sounds are when I’m telling the pilots it’s clear to start engine 1
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.
@@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.
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!
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.
Awesome video, I am an engineering student and we have just finished up the Brayton cycle/propulsion cycle in Thermodynamics 2 and I was wondering how these jet engines first get started, I felt like a traditional electrical starter might not be practical enough to exceed these engines stall speeds.
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. 😂
At 4:30 the engine numbering is mirrored. The number one engine is always on the left side of the airplane (when looking forward), shown correctly at 1:31.
@@justing42 Typically the engine-driven hydraulic pumps are left on between flights, so they will pressurize the hydraulics once the engines are started without the pilots having to do anything.
Brought back lots of memories as a USAF crew chief. But many military aircraft the APU is an external unit that must be connected. Watched one disintegrate once. Glad nobody was in the redline blade area.
@@snorttroll4379 It's a small jet engine. It's built into a roll cart, that is marked with usually 2 red lines on both side marking where the turbine blades are. If in the rare instance the blades break or separate in any way, it will shoot through the cart sides like a hot knife through butter possibly in all parallel directions.In the hundreds of APU's I've worked with or seen, I've only scene one fail that way. Although in training school they showed it in films to let crew chiefs know some of the daily dangers of the job.
Were your -60s self propelled? We had a -60 lose the main shaft bearing, lock up and shell out during ops checks. You could hear it bog down and then... Boom.
@@iTz_JLAR I've worked with both. Hated the self propelled. Mostly had manual ones. I would rather either pull them (as long as the tires were fully inflated and not low) or find a tug to hitch it to.
God damned amazing CG explanation !.... Keep up the good content creation ! (greeting from Jakarta.) Does each airplane have the APU unit onboard?! ....or....do they need from external APU unit for some other airplane model?
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?
Boeing is working on an electric motor that is placed inside the front nose wheel - airplane can taxi to runway , engines started minutes before take off . The electric motor powers all essential on board computers . ✈️🇺🇸✨$ Millions of dollars of Jet A are saved , price of seats comes down .
Your description of an engine start isn’t accurate. I haven’t flown every turbine aircraft flying today, so there may be exceptions, but I’ve flown the CRJ as welll as every model of the 737 since the classic -300 and we start both engines using APU air. We don’t start the first engine using the APU and the the second using the first engine as described in your video. I know there are aircraft such as the 777 which can start both engines at the same time using bleed air from the APU as long as atmospheric conditions allow (low pressure altitude). We can start the second engine of a 737 using bleed air from an already running engine, but we’d only do that if the APU was inoperative and we had to start the first engine using an external air start cart to provide the necessary air pressure to turn the starter on the first engine. And even then, we’d have to run the thrust up on the first engine to get enough bleed air pressure to start the second engine, which would require us to coordinate with ground control to find a location in n the airport to run up the first engine without damaging anything behind us. In general jet airliners use the APU to start both engines and then shut it down to save fuel. I’d love to hear if there are newer airliners such as the 787 or Airbus 359 which start engines as you describe, but I haven’t heard that they start their second engine that way.
You're correct. On the 747-400 for example, the APU puts out a higher bleed air pressure than the idling first engine, so the check valves on the first engine close, shutting off the engine air supply. If the APU wasn't operating, you'd have a ground start unit to start the first engine, then push back. Only then would the first engine start the other engines. You will probably have to go up on power on the first engine to achieve sufficient bleed air to start the other engines.
@@arthurhardy Sorry, I don't understand what you are trying to say. What is so hot? Are you saying main engine bleed is hotter than APU bleed? Are you saying the bleed temperature is the main issue and *not* the temperatures caused by the high rotational speed of the starter? Or are you talking about starter time limits on any start? Or something else?
When I pulled alert duty on the KC-135A, we would load one starter cartridge to get one engine started. That engine would then go to full power, to start the other three engines at the same time.
Oh. Such wit. Excuse me while I stop my sides exploding. I have emptied the honeycart, I have marshalled. I have towed. I have stood outside on headset whilst the engines are run. I have sat in the cockpit and talked to the guy outside while I ran the engines. I've ground run fighter jets in reheat/ afterburner. The last course I went on took 2 days to explain the computer controlled starter system to allow me to make the decisions to allow me to fix it and get the aircraft safely into the air. How long was you trolling course?
Probably a lot longer than your video critique course. Your earlier job description "groundcrew" was also bland Disney style, but thanks for your full resume'. @@chrisfox3161
Pretty good starter turbine explanation. especially how the starter disconnects, although it's a very much simplified version. However, the second engine also (normally) uses (bleed) air from the APU, not from the first engine. Air from the first engine is used for second engine start when APU is inoperative. That's called Cross-Bleed Start. When APU is inop, first engine is started with a GTSU (Gas Turbine Starter Unit), basically a ground cart supplying air. Great video though.
Question: during landing, before the point of tires touching runway, have the wheels been spun up so that when the tires touch down, there is less friction at the surface thus easing into the braking stage and saving tire wear? Motors in the wheels may cost more than tire replacement cost but what is the actual tradeoff? Thanks for the great detail.
The answer is no they aren't spun up, various methods have been tested over the years including motors and vanes on wheels or tyres, but basically it isn't done because there is no real point. Tyres lose some tread every time they touch down but can last from 1 to several hundred landings, it just depends on the aircraft type, (size and weight) landing speed, braking forces, runway conditions,(wet/dry/rough/smooth) wind direction, ordinary landing or emergency, so they are checked after every landing and a decision is taken by the ground crew whether it goes again or does it get changed.
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.
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 😊
@@ChapaLipar makes more sense
@@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.
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
th-cam.com/video/tNLz4HpsKQU/w-d-xo.htmlsi=5l3I10u_hWmzoMdW
Because you know how much engineering and thought went into this beautiful piece of machinery to work flawlessly
we are gear heads , thats why !! awesome !!
Planes fly over my house at 10,750' and the planes always make some kind of a thrust back noise. I don't know what it is. It's usually 8-10 minutes before they're landing in Charlotte. Sounds like gearing down. Don't know.
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.
One of the best explanations out there. Students need teachers like you
just a #student:
drive.google.com/drive/folders/1-e0jFYBkWAEVm8jspdxpuxwWDjeN54xQ
I’m thankful for all these smart people moving humanity forward. Imagine what we will come up with in 50-100 years.
Until we break away from the crutch of fossil fuels, there may not be a future of progress.
Well…considering that there’s a growing segment of the population that believes the earth is flat…
A nuclear wasteland
I hope humanity is gone by then
Yes, I’m afraid every indicator I can think of is pointing towards rapid regression. Government losing territorial control, decreasing standards of living, rapidly rising crime, interruptions to supply chains, rising indolence among the upcoming generations, quality standards slipping across the board from healthcare to policing to politicians to emergency services, next will be food supply chains being interrupted, rapidly increasing food prices, widespread, lawlessness, anarchy, disease, plague, starvation and cannibalism. 10,000 years of progress gone in two generations.
Nothing can’t beat the air start of a DC8. It was music to my ears when I use to watch those United freighters use to depart.
Thanks to all the men involved in this invention and those who mantained it every day.
Finally some recognition for the maintainers. Without them the Pilots who fly them and the passengers who fly in them are grounded. Aircraft require far more servicing/maintenance than a car. Most large commercial aircraft can only go 1 flight before the engines need to be serviced with oil (as an example)
Dont forget the aircraft mechanics that are women. I know several that are right up there with the best of them.
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!
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
Absolutely fantastic description on the air-starter clutch.
Glad it was helpful!
First video on this topic that actually combines every element of the startup into a easy to follow package!
Good video, very accurate. I spent 43 years in the aircraft design industry, and was always impressed by that start-up sequence.
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...
I love the sound and smell of an engine starting. Such a great video! Thank you!!!
I already knew most of this, but the clutch disengage action of the air turbine starter was illuminating!
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.
@@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.
And in ‘continuous’ position the ignition is on for both igniters.
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 indeed, very instructive, helpful understanding and following the succession of steps, and perhaps somewhat reassuring.
Access to royal family members' attitudes and reactions: priceless...
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...
@@RebeccaJackson-w2v 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.
God the sound of the engine starting up is a pure eargasm!
I've replayed it 6 times!
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.
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.
@@stephenholland5930 or if you have to restart an engine in the air. As the APU is generally turned off.
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.
hey there
how did yoy become a jet tehcnician?
@@sudhanwankumar2269 The proper title for my profession is "Airframe & Powerplant Technician."
It's a govt issued license. How you get it varies from country to country.
I've only been on a jet maybe 4 times in my life, but I've always been impressed by how quickly they accelerate on the runway just as they're taking off- pretty much in the muscle-car range of acceleration.
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!
One of the best explaining Videos i've ever seen. Thank you!
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.
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 ;-)
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.
@@railroad6601 it is about PRESSURE....it doesnt care where it gets it, as long as it has it
@@railroad6601no it’s more efficient to start all engines from the APU
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 👌
If second gear doesn't work, try reverse (thrust) 😜
The cool thing about this procedure is that its in flight!
😂😂😂😂😂😂😂😂😂 from Malaysia 🇲🇾🇲🇾🇲🇾🇲🇾🇲🇾
On my motorcycle, I just point it downhill, no need to bother a friend. Downhill should work for an airplane, right?
Thank you . This is the best illustration video about aviation technicals I’ve watched!
Thats one of the best videos on TH-cam. A great thanks to the creator🎉
Thank you very much Match. I take plane very often and I always wonder how the air compressor of the main engine starts? Electrically or what? And finally now I know how it starts and then starts the turbine. APU is the key 💡 Respect engeneers!!
Thanks HMW! Great to get these insights from an aerospace engineer. Are there any big differences in this process across different types of planes?
Thanks, and good question! Using an APU is the most common method, but the Boeing 787 Dreamliner engines use electrically started engines (no ATS). Fighter jets can use high pressure gas cartridges to quickly spin up the turbine and start fast! More information in the description :)
Awesome, thank you!
@@HitMeWithor a jet fuel starter
@@HitMeWith I've worked with many of the different 4th gen fighters in the US. There are 2 types of starters. APU & JFS. APUs use bleed air to spin an impeller that spins over the engine during start. Some fighters that use an APU are A-10 Warthog (Not a fighter but attacker), F-22 Raptor, & F-35 Lightning. Other Fighters use a JFS (Jet Fuel Starter). It uses PTO shafts through a gearbox to mechanically spin over the engine. Some fighters that use a JFS are F-15 Eagle & F-16 Falcon/Viper. Some fighters don't have a starter at all. They require ground assist to start the engines. This is generally done with a jet powered start cart. Some aircraft that this apply to are the F-4 Phantom, F-5 Tiger, & T-38 Talon.
@@HitMeWiththose cartridges were used on improvised air bases that lacked electric starters on the ground.
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. 🤜💥🤛
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 😖
The APU is usually started well before passengers even get on board. At the gate that is what supplies electrical power and air for the airconditioning
@2:50 I don’t believe that the fuel self ignites. The fuel has already been ignited by the igniters, combustion just continues
That’s what he meant by the way.
this explanation is extremely well done!!! concise and easy to understand yet detailled enough to really grasp the very basics. could listen to your video much,longer
One of the best videos explaining this.
This is very interesting and great to watch for someone who has no aircraft engine technical knowledge!
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.
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.
there are no "pressure shafts"
Show us the start up of a Pratt and Whitney R 2800-500 The ßame engine in the F6F, F4U 1 to 4 and P47.
Piston engines seem less complicated that jets. AFAIK the generators on the engines are used as starter motors that spin the engines. Same as on a car. Power can come from the onboard batteries or a GPU, or even from an APU.
@@PeterNGloor I love the sound of Radial engines the bigger the better.
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.
This is 10/10 content, very nice explanation. Thank you
Finally the startup explained by a human voice instead of a goddamn ai
Very interesting, now I know what usually happens when the engine sound pitches each time. Thanks for the explanation.💯
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:
th-cam.com/video/JjdyQpEUYzI/w-d-xo.html
The SR-71 has fascinated me since I was a kid what a magnificent aircraft
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.
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.
Agreed. He also calls them spark plugs, all the engines I work on they are called igniters
Thanks. I always wondered how airliners started their engines. Very informative and easy to understand.
@1:42 That is S & S Turbine Services in Ft. St John, BC ... if I am not mistaken :)
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.
I sell toilets for a living. This level of engineering & design blows my mind.
You sell toilets? No shit😅
@billmartin3198::: Toilets are different , they are powered by Gas .
@ 😆🤣😀..😳.😆
Dumb question. Why does the low rumble at 6:00 go away if combustion is continuous? Is the exhaust drowning it out?
Its actually stagnation in the compressor airflow I believe, which disappears as the compressor speeds up, (shout out if that's wrong I'm airframes not engines) if it goes on too long the jet pipe temperature starts to rise (fuel starts burning in the jet pipe) and you have to shut down to prevent an overheat, then you have problems with a possible wet start when you try again.
As an airline mechanic of over 30 years, we almost never cross blead air from one engine to start another unless using a ground air supply in the event of an inoperative APU.
An example of that would be an inop. APU, the airplane is located off in a remote area with no ground power available, and using an air start piece of ground equipment, you could use the emergency battery bus and fire the engine ignitors with the battery.
Spin the starter, then fire the engine ignitors with the battery power, once you have an engine generator on line, the airplane is powered, then cross bleed and start the remaining engine/ engines.
Other wise the APU's installed in most airliners were more than able to start any engine you chose.
Good video, great explanation.
On the B-52 though standard engine start up was to get #4 engine running, cross bleed air to start #5 engine, then use those two engines to start the rest on their respective wing. Really fun.
GREAT VIDEO!! One I would like to see is thrust power. In other words....what percent of engine thrust is needed to start the plane taxing, what percent used in take off, climb, cruise, descent, reverse thrust.
This is a great idea. I've put it on the list!
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
And is it the same for a flamed out engine restart in flight?
Not quite! A flamed out engine will still be spinning due to the air rushing past it. This is known as windmilling. Once it is up to the required speed, fuel flow re-starts and the ignitors fire to combust it
@@HitMeWith Thank you very informative!
This was very interesting! You should not leave such a long gap between delivering videos - you do a great job! Subed.
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.
I was interested to read about the "start cart" which is used when the APU is inoperative. Apparently, it's not that unusual for a plane to be considered airworthy without a functioning APU.
No, but only for 10 days.
ATC here. "Cross-Bleed Starts" are not uncommon. I'd get a request maybe once every week or so. They use a start-cart, then push back, then throttle up the single engine and cross-bleed the other one.
It often requires ATC approval as starting an engine on the bay is really uncommon and presents hazards as compared to doing it in the push-back.
Commercial jet technician here.
They can be allowed to fly without a working APU, but the plane cant go to as many destinations. Only ones that have start carts. Or "huffer carts" as we call them.
Ramp agent here. Nothing to add just want to be included 😂 although we call the “starter carts” an “Air start”, have also had to keep ground power connected for an engine to start up on stand because of an inop APU, but yeah isn’t uncommon. Nice to know what the sounds are when I’m telling the pilots it’s clear to start engine 1
@@markcrawford8651 Hey, you rampies have important jobs. You're more than welcome!
great video, animation, graphs and commentary.. well done
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.
Great explanation of the start sequence on the ground. What about the engine restarting process in the air?
Thank you so much for your excellent explanation. Waiting for more videos
I learned so much in 5 minutes here that I've never known.... thank you! fascinating!
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!
What a great explanation of the start up process. Not what I thought at all!
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.
Awesome video, I am an engineering student and we have just finished up the Brayton cycle/propulsion cycle in Thermodynamics 2 and I was wondering how these jet engines first get started, I felt like a traditional electrical starter might not be practical enough to exceed these engines stall speeds.
Very clear info thank you 🎉🎉❤❤
What a simple and effective system.Genius!
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. 😂😂😂
Engines are called money to noise converters by some.
❤j
that’s the tax people if you don’t pay taxes
Thanks for this video and for keeping it easy to understand and follow.
When you said you had a birds-eye view of a jet engine I thought ... ouch!
At 4:30 the engine numbering is mirrored. The number one engine is always on the left side of the airplane (when looking forward), shown correctly at 1:31.
Suck, Squeeze, Bang, Blow! 26 year USAF JET MECHANIC. That's all that you need to know!
Fully agree. On modern engines I use Suck, Squeeze, Burn, Blow. This is level 1, but enough 😀
That was fantastic!!!! The use of graphics really helped me understand the physical process of the engine working. Excellent work!!
Its usually always
1. Batteries
2. Fuel Pumps
3. APU
4. Engines
5. APU Off
6. Fly
So no hydraulics…got it
@@justing42 Typically the engine-driven hydraulic pumps are left on between flights, so they will pressurize the hydraulics once the engines are started without the pilots having to do anything.
Nice video! So that cross-blerd of air is why you get a faint waft of fuel smell in the cabin?
5:37 I liked this video until the royal family photo. What a shame.
What is ur problem with the royal family? Also not everyone cares about ur respect or opinion
@@Pfor_PodiI don’t care for your opinion either, so fvck off
Whiles I don't like them their as they are just rich snobs it's just a silly picture and isn't gonna do eny harm c:
@@Pfor_Podialso calm my brother
Very helpful
And the best explanation video
Thank you sir.
The 787 Dreamliner has left the chat 😂
Best illustration I have seen!!!
Brought back lots of memories as a USAF crew chief. But many military aircraft the APU is an external unit that must be connected. Watched one disintegrate once. Glad nobody was in the redline blade area.
why did it didintegrate and why was it not containted?
@@snorttroll4379 It's a small jet engine. It's built into a roll cart, that is marked with usually 2 red lines on both side marking where the turbine blades are. If in the rare instance the blades break or separate in any way, it will shoot through the cart sides like a hot knife through butter possibly in all parallel directions.In the hundreds of APU's I've worked with or seen, I've only scene one fail that way. Although in training school they showed it in films to let crew chiefs know some of the daily dangers of the job.
The -60 was a mediocre air cart at best, but better than using cartridges.
Were your -60s self propelled?
We had a -60 lose the main shaft bearing, lock up and shell out during ops checks. You could hear it bog down and then... Boom.
@@iTz_JLAR I've worked with both. Hated the self propelled. Mostly had manual ones. I would rather either pull them (as long as the tires were fully inflated and not low) or find a tug to hitch it to.
God damned amazing CG explanation !....
Keep up the good content creation ! (greeting from Jakarta.)
Does each airplane have the APU unit onboard?! ....or....do they need from external APU unit for some other airplane model?
Airplanes have centrifugal clutches??? wow thats literally like a moped
Chainsaws too!
Some reel type power mowers had centrifugal clutches too. My folks had one such lawnmower.
If it works ,it works
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?
Fascinating and very educational - but we can do without the bloody Royals poking their unwanted noses into the scene
Why do think anyone wants to read your childish bile.
lol yeah what was that about?
That confused me too. What’s the link? I don’t associate them with compressed air. 😃 Although that could describe the way they speak…
@@RobManser77 The Royals were photographed watching an RAF flyover, probably during the Queen's Jubilee.
Worse still; they destroyed a beautiful Citroen 2CV!!!!!😢😖
Very useful video and adds to my knowledge about airplanes
0:29 am I the only one that finds that hilarious 😂😂
Pretty good video. You do have some of your animations running in reverse though, including at 1:53 and 2:14
I was wondering if I was the only one that noticed that!
Close enough. I’m an aircraft engineer/mechanic. There are some inaccuracies.
Wrong turbine rotation
Shannon how to get connected to you please your email or any other way please
Thank you! love that you included the startup sounds also.
Boeing is working on an electric motor that is placed inside the front nose wheel - airplane can taxi to runway , engines started minutes before take off . The electric motor powers all essential on board computers . ✈️🇺🇸✨$ Millions of dollars of Jet A are saved , price of seats comes down .
Boeing cutting corners to save millions of dollars... Where have I heard that before? 🤔 🤔 🤔
One correction, minor but no one does x bleed starts on the second eng. It’s done with the APU, x bleed starts are only if something is MEL’d.
Your description of an engine start isn’t accurate. I haven’t flown every turbine aircraft flying today, so there may be exceptions, but I’ve flown the CRJ as welll as every model of the 737 since the classic -300 and we start both engines using APU air. We don’t start the first engine using the APU and the the second using the first engine as described in your video. I know there are aircraft such as the 777 which can start both engines at the same time using bleed air from the APU as long as atmospheric conditions allow (low pressure altitude). We can start the second engine of a 737 using bleed air from an already running engine, but we’d only do that if the APU was inoperative and we had to start the first engine using an external air start cart to provide the necessary air pressure to turn the starter on the first engine. And even then, we’d have to run the thrust up on the first engine to get enough bleed air pressure to start the second engine, which would require us to coordinate with ground control to find a location in n the airport to run up the first engine without damaging anything behind us. In general jet airliners use the APU to start both engines and then shut it down to save fuel. I’d love to hear if there are newer airliners such as the 787 or Airbus 359 which start engines as you describe, but I haven’t heard that they start their second engine that way.
Nah 787 doesn't have a pheumatic start, just electric, and an a350 starts like how a 737 would
You're correct. On the 747-400 for example, the APU puts out a higher bleed air pressure than the idling first engine, so the check valves on the first engine close, shutting off the engine air supply. If the APU wasn't operating, you'd have a ground start unit to start the first engine, then push back. Only then would the first engine start the other engines. You will probably have to go up on power on the first engine to achieve sufficient bleed air to start the other engines.
Also when starting using a main engine bleed air, It is Hot so there is a time limit that you can use it.@@ImperrfectStranger
@@arthurhardy Sorry, I don't understand what you are trying to say. What is so hot? Are you saying main engine bleed is hotter than APU bleed? Are you saying the bleed temperature is the main issue and *not* the temperatures caused by the high rotational speed of the starter? Or are you talking about starter time limits on any start? Or something else?
When I pulled alert duty on the KC-135A, we would load one starter cartridge to get one engine started. That engine would then go to full power, to start the other three engines at the same time.
That was an excellent explanation!! Good job! :)
I was groundcrew . This is a very bland disney style explanation.
That was a very bland job description. What kind of groundcrew? "Honeycart" operator? 😅
bs. you were a janitor or something
Oh. Such wit. Excuse me while I stop my sides exploding. I have emptied the honeycart, I have marshalled. I have towed. I have stood outside on headset whilst the engines are run. I have sat in the cockpit and talked to the guy outside while I ran the engines. I've ground run fighter jets in reheat/ afterburner. The last course I went on took 2 days to explain the computer controlled starter system to allow me to make the decisions to allow me to fix it and get the aircraft safely into the air.
How long was you trolling course?
Probably a lot longer than your video critique course. Your earlier job description "groundcrew" was also bland Disney style, but thanks for your full resume'. @@chrisfox3161
Pretty good starter turbine explanation. especially how the starter disconnects, although it's a very much simplified version.
However, the second engine also (normally) uses (bleed) air from the APU, not from the first engine. Air from the first engine is used for second engine start when APU is inoperative. That's called Cross-Bleed Start. When APU is inop, first engine is started with a GTSU (Gas Turbine Starter Unit), basically a ground cart supplying air. Great video though.
Question: during landing, before the point of tires touching runway, have the wheels been spun up so that when the tires touch down, there is less friction at the surface thus easing into the braking stage and saving tire wear? Motors in the wheels may cost more than tire replacement cost but what is the actual tradeoff? Thanks for the great detail.
I believe this has been considered long ago, but the weight and size of the motors have no room there.
Also you have to consider the extra fuel burn to carry the weight of these motors in the wheels.
To fly, weight is the enemy !
The answer is no they aren't spun up, various methods have been tested over the years including motors and vanes on wheels or tyres, but basically it isn't done because there is no real point. Tyres lose some tread every time they touch down but can last from 1 to several hundred landings, it just depends on the aircraft type, (size and weight) landing speed, braking forces, runway conditions,(wet/dry/rough/smooth) wind direction, ordinary landing or emergency, so they are checked after every landing and a decision is taken by the ground crew whether it goes again or does it get changed.
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 👍