Helicopter Gear Reduction

This video shows how a helicopter drive system transfers power from the high speed output of a gas turbine engine to a helicopter's rotors
00:00 Intro
01:15 Engines
02:10 High Speed Shafts
02:36 Freewheeling Units
03:32 Combining Gear
03:52 Bevel Gear
04:37 Planetary Gear
05:26 Tail Rotor Gears
06:05 Tail Rotor Drive Shaft
06:24 Intermediate Gears
06:48 Tail Rotor Gears

[@polka23dot70]

I like this video - lots of explanation and no annoying "music."

[@bzig4929]

Thanks! Appreciate the tip. I also find music, over the top of a voiceover, really annoying.

[@DieCastoms]

I also very much appreciate that it is not a robot voice. robot voices are an acceptable way for someone who doesn't speak English to produce an English spoken narration, but after a couple minutes I have trouble paying attention to the content instead of noticing all the translation, inflection, and 'grammar errors' (pauses where there shouldn't be any, etc.) I am by no means a grammar nazi, mine is terrible too, but some of those robot voices are worse >.

[@urbanturbine]

makebaa makebaa would have worked fıne :)

[@1islam1]

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[@wesleydeer889]

@@bzig4929 I have wondered for years how in the hell helicopter gearing works with the high rpm engines. When I saw the thumbnail I was like, no effing way. Could you shed some light on why turboshafts spin so much slower than turbines? I thought turbine engines operated near 100k?

[@flyonbyya]

These modern animations, together with superior step by step, logically presented, exploded, then reassembled by clear narrative is a game changer! Great work !

[@HanZie82]

Couldnt have said it better!

[@JRJunior8624]

Tis indeed

[@coptertim]

I've had many people ask me to describe how turbine engines work in helicopters. It's easy to explain but not often easy for them to visualize how the dynamic components work together. This is one of the best descriptions and animations I've seen yet. Well done!

[@dalethomasdewitt]

is there a difference between centrifugal pumping or turbine

[@fredsalter1915]

Bro's got mad CAD ability!!! Unreal. Thank for creating this!!!!!!

[@bzig4929]

I love the comment! But I'm a CAD noob... Just having fun.

[@DieCastoms]

@@bzig4929 I would like to see what you can do when you've has some more practice if you are considering this noobish!

[@claudevieaul1465]

​@@bzig4929I'm by no means a noob - been designing in 2D and 3D professionally for decades, but I'd be hard put to show this marvel on my usual software... 🤣🤣 Well done, sir! 🙏

[@bzig4929]

Thanks!!

[@Klimbo93]

if you dont know CAD dont give acknowledgements hiding parts and whole assemblies is easier than alt-tab to another window

[@user-us3dp7tb3m]

I have always wondered how this functioned. Watched with sound off and still understood it. We are grateful for the hard work you have put in for us.

[@bzig4929]

Thanks for the nice words!

[@RandoWisLuL]

Little more detail on the engines: These turboshaft engines are gas turbine engines and work on the same principle as all gas turbines do, the same as turboprops, turbo fans, turbo jets and natural gas turbines. The "gas generator" as you call it in this video is split into 3 turbine stages connected together with a hollow shaft. It consists of an axial fan stage in the front to draw air in, a centrifugal compression stage (some turbine engines have axial compression stages, like in an airliner engine) to compress the air, and an axial combustion stage to drive the fan and compression stages. This whole set makes up the N1 turbine. these are marked in silver. The N1 stage can run all by itself with no power stage installed, it just won't have any load to it. The rear black turbine stage is the "power stage". it consists of 1 set or more ( in this case 2 sets) of turbine blades to scavenge the power made by the N1 turbine stages. It takes what the combustion stages don't use and convert it into rotational power. This is the N2 turbine. This N2 turbine has a smaller shaft that runs through the N1 turbine's shaft which makes it independent from the N1 turbine set. In most aircraft, the N1 and N2 stages are represented independently on the RPM gauges of the engine itself so you can see what each turbine set is doing independently. This setup is the same in power plants, pumping stations, natural gas compression stations, air liners or turboprops. In those cases, the N2 turbine powers a giant fan in the front (in the cast of Turbofan engines found on airliners. It's that huge fan you see in front when they are parked at the terminal) or a propeller (as seen turbo props), or an electric generator (gas turbine/jet turbine power plants), pump (jet turbine pumping stations) or a natural gas compressor (jet turbine compressors). Machines like jet powered snow blowers on trains, old military aircraft and snow melters use "turbojet" engines. These simply use that jet blast coming off of the N1 turbine as a heat source/blower source to blow and melt snow/push the old jet fighters along. These machines/planes do not have that N2 turbine (power turbine) since there is nothing for them to power but the snow itself. Old fighters simply had a nozzle at the end to focus the jet blast. modern fighter jets use low-bypass turbofan engines, which DO have a N2 power turbine and a fan in front like a jetliner. Early jet powered airliners also used turbojets. Jet power plants (for example) are typically a quarter of the size compared to its diesel counterparts, which is why gas turbines are usually used for stuff like this, due to its high power to weight ratio. 1 more fun fact, Turbines are just about as efficient at near full throttle as they are at idle with a 70% efficiency gain when going from idle to full throttle. One of the major reasons why you don't see them in trains or cars. Plus, in train tests, they melted bridges. No one liked the vacuum sound of the Chrystler Turbine made in the 1960s compared to a V8, even though it needed far less maintenance and could run on anything from diesel to Taquila with no issues, since timing is nonexistent. So they never released it past the test market. Due to heat collectors that used exhaust heat to aid the combustion process, the exhaust temp of a Chrystler Turbine never exceeded 180 degrees F. It made 130hp and the engine was the size of a couple of watermelons. The turbine is TINY in that car, 1 centrifugal compression blade, 1 axial combustion blade and 1 axial power blade. No "fan" blade here at all. the single blades made up the N1 and N2 turbine sets. It ran at its maximum of 60,000 rpm and 20,000 at idle. It has a pressure(compression) ratio of 4:1 and a gear reduction ratio in that car is around 22.5:1!!

[@bzig4929]

Wow, awesome details! Here's a fun fact about V-22 Osprey exhaust... there have been in-service issues with hot exhaust gas impingement on ship flight decks and concrete surfaces. This doesn't really impact the aircraft, but causes issues for ships and airports. You also reminded me of my favorite jet engine joke. What's the difference between a pilot and a jet engine? The jet engine stops whining when the flight is over.

[@RandoWisLuL]

@@bzig4929 haha nice joke and that makes sense. When they tested trains, they worked very well when cruising but when idle, they sucked with fuel economy and trains idle A LOT. They would sometimes idle under bridges or had too for whatever reason. Bridges would do the same thing, so it wasn't really a "melt" but more as you described it. Unfortunately, it was usually bad for the bridge's structures, and they had to repair them quite often because of the jet blast.

[@caty863]

If gas turbines have no efficiency gain going from idle to full throttle, then they are better used in hybrid cars where their role would be to charge the battery. In that case, they are either on full throttle or off, no need for cumbersome gear reduction kits, runs on any fuel, have small size and weigh less, etc...

[@RandoWisLuL]

@@caty863 funny you mention that. In the 90s, Toyota made a hybrid concept that used a Power-split or series hybrid design where an RC sized gas turbine in the trunk charged batteries for the electric drivetrain on the car. It fit in the corner of the trunk/boot, out of the way, due to how small turbine engines can be with lots of power. It ran at near full throttle when charging. They ditched the idea due to its lack of serviceability in the consumer/repair markets. They were afraid it would cost more to implement and train people on. They then opted to go with the Power-split or series-parallel hybrid designs you see in the first generations of the Prius, where both the engine and electric motor do work to make the car go. The original mainstream hybrid, the Honda Insight, used a similar Parallel system in favor if the Series ones that were in development at the time. With the advent of plug-in hybrids, manufactures went back to using Series hybrid systems but with ICE engines as the generator instead of turbine engines.

[@caty863]

@@RandoWisLuL forgive me the pedantry but gas turbines are also ICEs. maybe you meant reciprocating engines?

[@byronharano2391]

As a former AD2 in our United States Navy. I appreciated your video

[@CardanoETF]

HM3 agrees

[@ImplodedAtom]

Clear narration at reasonable pace, elegantly structured script, animation that shows you exactly what you need to see when you need to see it. Have a sub, good Sir.

[@ISmellLikeBeefandCheese]

Redditor

[@ImpendingJoker]

This is what I did on helicopters in the Army as a Helicopter Drivetrain Technician MOS 68D. I was responsible for everything that wasn't the powerplant(engines), and I did a lot of bearing work on other parts of the helicopters. Like wheel bearings and stabilator bearings for the UH-60 and the spider mount brackets for the AH-64's main landing gear attachments. So this is a very cool and familiar subject for me.

[@JerkerDahlblom]

What are the parts that require most maintenance on a helicopter? How are those gears lubricated?

[@bzig4929]

thanks for watching an not calling me out on the parts that look janky. Those clutches are way to big compared to the real things ;) I've looked at a bunch of gearboxes in my life, but I'm not that savvy on what's inside of them.

[@new.handle]

​@JerkerDahlblom go to 5.01 the planetary gear is the most complex due to many moving parts and high torque. It is lubricated by an oil pump that cycles oil through gear assembly and is attached also to this gear set as well (self lubricating in a way). The author/creator didn't put it here since it is a separate system and it would only add additional detail that will overcomplicate everything. Presentation/video is really good, and shows a fair amount of detail. ;)

[@JerkerDahlblom]

@@new.handle thank you!

[@new.handle]

@JerkerDahlblom you're welcome. The complexity comes from torque as I wrote above since there is a heavy rotor system above (in our case is 3 bladed main rotor, but it can go up to 8 as in Mi-26) that produces drag (generated as opposite force to lift and forward motion) making it even more challenging to rotate. The second part is torque from engines/turbines that drives all. This is why planetary gear reduction is needed: to get a big turn ratio in a small and light gearbox. And then, of course, torque generates friction, and friction generates heat, hence lubrication. The transmission system (engines-main rotor-tail rotor-pumps) also generates heat and torque, but it is a bit bigger, and gear ratios are smaller, so a bit less heat. Hope this helps. ;)

[@CidavuKK]

As a helicopter pilot I found it great in explanation and also visualization 👏🏻 I think it will be very helpful for pilots in training. Thank you❤

[@sferg9582]

I love this. Beautiful presentation, excellent explanations... and yes, there's no annoying music.

[@michaelfields8793]

Right...exactly what you said.

[@briankeirns9936]

I worked HH-60’s for a couple years in the Air Force as an engine troop. Great video and break down of how gear reduction is accomplished. Love the exploded views with clear, concise explanation. Great video

[@heinzriemann3213]

It's not just that we are interested in the matter. It's that you present it so brilliantly.

[@JeremyZao]

This helped me wrap my head around the transmission system. And bonus on the gas generator and power turbine coupling. This is really a one-stop masterclass on a turbine helicopter powertrain.

[@nicholaskoh206]

This video popped up randomly on my feed and I watched it from start to finish. I teach for a living and I really appreciate and commend you on your clear voice, excellent breakdown and methodical explanations. The on-screen text when mentioning anything mathematical allows your viewers and myself to follow along easily. Subscribed and looking forward to more interesting content!

[@thehilltopworkshop]

Fellow geek here. I can't believe you just answered so many questions I've had about helicopters for so long, but never knew where to start looking for the answers. Absolutely love your videos. These are seriously close to what most would consider a professional training product.

[@shprite781]

Can't help but admire the people who put these animations together for the sake of sharing knowledge with others.

[@frankgrisdale4513]

Informative visuals without annoying music. Keep up the excellent work!

[@cepaasch]

Excellent illustration of power from the engines to the TGB!!!

[@paulaxford6754]

Nice renderings. I was involved in commissioning a gearbox R&D test facility at Westland in the early '80s and gained some unforgettable knowledge from their engineers who would be using it. The test rig could provided 3x 3,500 hp from 11kV electric motors geared up to about 25,500 RPM with an overhead arrangement for absorbing power and moment-loading the output flange. They explained to me in detail about how their gearboxes worked and what tests they would undergo, including operating life after loss of oil.

[@IO-zz2xy]

At last, I have finally seen the insides of helicopter reduction gearboxes. I have seen the enormous grey gearbox on a turbine Bell 47. It's just incredible how they manage to reduce turbine to prop/rotor speeds. Thanks for a superb and simple explanation video. Regards from South

[@Pthrust]

I sat still for 7 minutes, you explain things very nice and calm.

[@charleswetzel1250]

I'm quite grateful to see the internals of the main transmission, I've only ever helped haul the thing out, never actually seen how they operate. Cheers for the solid video.

[@fross1203]

Your video is a work of art. I know quite a bit about rotary craft. Did not realize that the slanted tail rotor also provided lift.

[@davidbrohede]

Marvellous animation, very clear and focused without disturbing background soundtrack. Thank you, instant sub!

[@ramishrambarran3998]

Excellent ! I never imagined how complex this drive system was ! Thank you very much. Trinidad & Tobago. West Indies.

[@samspade8612]

Hands down the best video I've ever seen on turbine helicopter operation!

[@glenstribling6123]

Thank you so much. Very good job. I've heard many different views on why the tilted tail rotor. Thank you for setting me straight.

[@rodin4429]

Wow. You went way beyond answering my questions on just how is a 'typical' helicopter' geared! Super interesting but also you gave some numbers which just made it come alive and be real, instead of just a diagram!

[@mountain3301]

Thanks for the delightful description and visuals

[@kurtnowak8895]

Always wondered how this worked. Watched with sound off and still understood it.

[@esnevip]

Flawless explanation, clear and concise with no music. Very clean modeling as well, subbed!

[@bzig4929]

Awesome, thank you!

[@dennisg-ski7829]

Outstanding graphics and introduction to the subject matter. It would've been awesome during my training. As the gas compressor and power turbine spools aren't mechanically coupled, as you mentioned, the power turbine is known as being a free power turbine. A design feature for this configuration is that the engine's efficiency is optimized, lessening the need for an additional reduction gearbox. Respectively referred to as Ng and Nf (or Np). Ng/Nf produce power for the rotor system measured as Nr. A turboprop is coupled, so its measurements are expressed more commonly as N1/N2 and add in prop speed. Gas turbine thrust engines N1, N2, and power output are measured/expressed as Engine Pressure Ratio (EPR). You described freewheeling, which is critical to disengaging a failed powerplant from the powertrain/drivetrain of the rotor system. Verses a turboprop that can feather the propeller to reduce its drag coefficient. Awesome work!

[@b43xoit]

I take it the ring gear is fixed. A consequence of the overall design would appear to be that if one engine goes out but the other keeps working, you still have some power and so I suppose you would have more leeway in finding a place to land, compared to what you would have with autorotation.

[@quebec0909]

for visual learners, this is a great presentation ! easy to follow and seamless to learn this complex topic. i am fascinated how this model is also very similar to navy blackhawks

[@voltz53]

This is a great video. It gives you an appreciation for how crucial gear alignments and overall strength of gears and components are to maintain safe operation. I imagine finding the right gear reduction involved a lot of trial and error in early helicopter development. A balance of rigid and flex connections all while rotating at high speed and torque.

[@bzig4929]

And... Gearbox monitoring systems, pressure, temp, debris and vibrations are super important in helicopters. Thanks for watching and commenting!

[@PhunkyChikin]

Excellent video! Thanks for the clear explanations and graphics.

[@crazyralph6386]

Wish we had these incredible visual aids back in flight school many moons ago.

[@andreyzhavoronkov6746]

Insanely good representation of the helicopter drive. Thank you!

[@user-wl1oz3vi4w]

This is the clearest explanation of this topic I have seen, well done 👍

[@Harkarajrai-si6wo]

Being in Nepal and NEPALI I would like to thank you for sharing science theroy +technology to presenter and modern science.

[@BoogeyBryan13]

I worked on H-60s for years and watching this video brought me back some good memories

[@CS_247]

Nicely explained, thank you! As a helicopter engineer, I get asked thus all the time, and it is hard to explain to laymen. This is brilliant.

[@patrickpafarnis5798]

Thanks for showing this explanation. Given your comments at the end of this video and after seeing many other videos on this subject on your channel, I draw the conclusion that you are a very knowledgeable person in this matter, and especially concerning helicopters. Thanks again for this clear explanation.

[@nathanwalsh6837]

Thank you for better helping us all understand the inner workings of a helicopter!

[@molotovdk]

A+ content. Simple breakdown and explanation, high quality work and no dumb music. I hope you make more.

[@bzig4929]

I will. I'll publish one today on how helicopter controls work. Thanks for watching!

[@oldergeologist]

Excellent video. Such a complicated drive train, a bit scary too.

[@Idrinklight44]

I crewed CH-53 and S-58 helos, this is a really good explanation of the drive systems!!!!

[@bzig4929]

Semper Fi! I couldn't make out the logo but it looks jarhead-ish.

[@tonybilco1317]

Amazing break down and explanation commentary thankyou ❤

[@msontrent9936]

Absolutely awesome. Clear with great animations. Great work.

[@jonhare392]

Awesome explanation dumbing it down for us laymen. I now have a very good idea of what’s going on inside the airframe.

[@zulucharlie5244]

Phenomenal tutorial. Outstanding, thank you.

[@richjageman3976]

This is how these types of videos should be made!

[@satyamsharma-qm4yb]

thanks for creating such wonderful visualizations and lucid explanations. subscribed.

[@aquilaz56]

Great job! I've always wanted a good explanation of this transmission system. You nailed It!!!

[@ME262MKI]

A better explanation you can't get, love it

[@wasihunwubishet3406]

clear explanation about a helicopter transmission 👏 thank you sir.

[@newklear2k]

Man, I wish you could explain other things to me too. Like… taxes or quantum physics. Your calm monotone instils a level of confidence in your information, and the animations being so pro definitely doesn't hurt either.

[@bzig4929]

Thank for the really nice comment!

[@Filmpilot]

I’ve got around 22,000 hours in helicopters maybe more; I’ve been to virtually every company‘s factory school that manufactures helicopters have never seen anything so succinctly explained as this; some of the RPMs are obviously model and make contingent but it still makes absolutely perfect sense for any of us that have been fine-tuned to any of the, harmonious, synchronous melodies that are finely tuned in machines that’s working properly. it certainly is a cacophony of harmony that most of us that our pros have learned that if anything out of sync we can hear it we can feel it before anything goes wrong; those that get in aircraft as opposed to those that wear them know what I’m talking about about and we use them as an extension of our body.

[@Hans_Magnusson]

Yeah, that is how I was taught too. Use your ears… It a winner

[@AdamWarwicker]

Top quality illustration! I knew the gear reduction system was complex, but never saw any representation. The friction loss must be crazy for helicopter drive systems and so many more points of mechanical failure, especially at those bevels.

[@patrickvillers6454]

Thank you you've made me appreciate helicopters even more and what amazing machines they are.

[@space1commander]

Beautifully explained. This Video got some gears spinning in my brain. Thank You Sharing.

[@alexanderk2121]

Just awesome! thank you for such detailed and well illustrated and organized explanation! I wish all my early mech engineering studies were like that!

[@SYoung-kk9od]

Very well described, animated and explained - thank you

[@fivestar2227]

3 days ago I watched a model rc turbine helicopter video and it got me wondering how the drive system worked in both models and full scale applications then the youtube algorithm somehow read my mind and dangled this informative video in front of me. Now it makes sense to me while there are soo many tail rotor accidents with all those possible points of failure.

[@Flopsaurus]

It's clear that you really are knowledgeable about helicopters, and that makes the video much much better

[@llwellyn1]

This presentation is beyond awesome. Nice job !!!

[@Rhinozherous]

Awesome explanation and graphics! Thank you very much!

[@86locomotivebreath]

Thank you for taking the time to explain this so well. It’s truly appreciated

[@michaelchownyk5255]

What an excellent graphical representation and explanation

[@lyndavichi5938]

Remarkable video. Beautiful work and narration. Well done.

[@TheSwanies]

I love that I can hop on KZbin at 10pm and watch a proper video on how helicopter gears work.

[@dwightprzybilla6477]

This is fantastic! Good information that is presented in an accessible format to the average viewer. Please keep them coming!

[@user-tq8pi8vq3f]

Thank you!! For some reason I always thought the tail rotor changed its speed relative to the main rotor, rather than the pitch of the blades being controlled to vary the anti-torque properties.

[@TheScottbb1]

I think you’re up for big things. KZbin recommended this to me and I love this content. Keep up the good work. Subscribed!

[@VenturiLife]

These are pretty intricate systems. Interesting and detailed explanation.

[@julybliss4440]

Definitely great work on your video really interesting, but also i could get this excited with a pop out or toddler picture book as long as it was talking abouts gears and especially helicopter systems. Something significantly better about your video explanation than the other helo system videos i have came across recently.

[@Like_Ike]

This is the video ive been looking for since my interests in engines began all the years ago as a young boy. Thank you

[@michaelabraham2635]

Weldone dude. This is my first time seeing clearly how a helicopter drivetrain works...

[@glowplug4762]

Great visual explanation! Thanks for the info!!

[@richwaight]

Fantastic video! Love how you brought that to life! 🙌

[@4stringmanagmaildcom]

I'm a 67 YO aviation nut Boeing retiree and I've never heard this explained. I never did work on helos but I have ridden in them and I work with the Navy SAR unit in my area on a volunteer basis. Excellent piece. Will share with my team members. Thank you!

[@rollbot]

absolutely amazing! love this! MOAR PLZZ!!!

[@rickwilson9747]

Outstanding! Thanks for a great explanation.

[@Kelly-oq9nh]

Wow! Excellent presentation. Fascinating!

[@Grzybo93]

This is quality content, lots of work, perfect voiceover with detailed explanation. You deserve 1M+ subs bro.

[@CupidStunttz]

I've never in my life watched a KZbin video and felt like I was in class studying for a test... AND ENJOYED IT. Please sir, do an indepth video just like this one on women.... Then send me your venmo information because I'm sending you everything I own. 😂

[@foadrightnow5725]

Fascinating and informative! Well done!

[@PauloOliveira-str]

Thank you, very clear and concise. I've learned something today.

[@He_that_has_eyes]

This explanation tops anything else I’ve seen.

[@gawwad4073]

Extremely well presented.

[@jeffwest6479]

thanks for helping me to understand. looking forward to more.

[@yippikiyay197]

I've been building an eVTOL so this is very helpful

[@chrisbeauchamp5563]

Great video mate. I’m a helicopter pilot. This video was detailed but not overly complex, well done

[@joshb6993]

Really high quality content here sir! Thanks a lot

[@joebond5012]

Thank you for an interesting explanation. I look forward to more.

[@ratratrat59]

Beautiful engineering! Thank you.

[@OVRxNxOUT]

Omg, wish I’d seen this channel long time ago cuz “geek out” is in my blood. *_SUBSCRIBED!!_*

[@martyb3783]

Wow this is a fantastic representation of how this works. I always wondered about this. Great video and 3d animation. Well done!

[@backpages1]

Despite the fact that I play with r/c helicopters, I am blown away at the level of engineering that goes into the real thing. Now if I were a machinist, I could miniaturize all that and stick it in one of my helicopters! But then I’d have to shrink a pilot down and stick him in there to fly the thing. And where’s the fun in that… (great work on the graphics and math!)