Why the Inline 6 Engine Disappeared From Aviation - History & Technical

[@LetsGoAviate]

WWII Aero V12 Engines Design Explained : kzbin.info/www/bejne/iqubp4ekoZKjd7c Deltahawk's Jet Fuel Piston Engine Explained : kzbin.info/www/bejne/q32zqqBrjdKmpdk V8 Aero Engine History & Design : kzbin.info/www/bejne/rXqunKNrhsljaNE

[@anac3652]

Reminds me a lot of gregs channel. Love the videos and keep it up I think your presentation is fantastic

[@LetsGoAviate]

Thanks, appreciate it.

[@peterlastrucci324]

Well researched and presented, your vids are always interesting!

[@LetsGoAviate]

Thanks so much!

[@oxcart4172]

I hope your channel grows as well as it deserves to

[@LetsGoAviate]

Thanks!

[@acebacker1]

Fantastic 😊. Well done - Great content and delivery 👍

[@josephpacchetti5997]

After watching the first video I saw, I subscribed with all upload notices, thank you for your time & effort.👍🛩

[@yoursoulisforever]

Excellent video. Thank you!

[@frank-y8n]

I understood long ago that engines are more important for the performance of aircraft than their design. Your videos make that a lot clearer.

[@ethanmckinney203]

The MS.406 puts the lie to that, unfortunately. I swear that I'll do a video about it some day.

[@Cuccos19]

Czechoslovakian and Czech aero engine manufacturers made (or still make) engines after WW2, in their light civil aviation aircrafts (trainers, light utility, aerobatic aircrafts as well).

[@ivansemanco6976]

Yes, Im still flying planes with those engines. Noisy, inefficient but very nice.

[@thebadmindreader]

Yes, walter mikron, m137/337ak. Best sounding engines!

[@harryspeakup8452]

Thank you for this. As someone with a lot of time behind Gipsy Majors, and in between pairs of Gipsy Queens, I'd love to put a LOM six into something the general size and mission of a Vans RV-8.

[@Steven-p4j]

Dual wing aircraft maintain a lot of advantages, with a faster climb rate and manuaverability, as well as superior stall recovery. Largely because of the larger wing area. Once more powerful engines were developed, however, the disadvantage of far higher drag had become a significant issue. This was the reason for aircraft manufacturers to move to the single wing, and further developments were then encouraged also. Items such as the monocoque frame and stressed metal skin with runners were made possible.

[@JohnDalton-n6l]

As an aircraft mechanic, I have a different perspective. One big reason for air-cooled, opposed, pushrod engines is that individual cylinders can be removed and repaired with relative ease. This makes them far cheaper to operate in the long term. The lower end ot these engines generally is very durable and long-lived. Piecemeal cylinder repairs are cost efficient. An overhead (or underhead) cam makes working on one cylinder far more involved, difficult, and time-consuming. The same with liquid cooling. Air-cooled engines seem to have more problems with individual cylinders than en block, water-cooled engines. This may be because they are more durable designs for other reasons.

[@danbenson7587]

The I6 long crankshaft is torsionally flexible. This can lead to vibration problems. Indeed it can be so severe engine timing is affected. Second, while the 6 is balanced, un-counter weighted throws pound out bearings. Not a problem at the low rpm these engines run (

[@LetsGoAviate]

Very valid, thanks. The higher revving I6's usually have crankshaft counterweights. There are some photos of the Mercedes D.III and D.IV crankshaft online (copyrighted, so couldn't use in the video), and as you suspect, zero crankshaft counterbalance weights! One sturdy-looking crankshaft though.

[@danbenson7587]

@@LetsGoAviate FYI. The early Allison V12 did not have CWs. To get more hp out of last models, Allison increased RPM and added CWs. Don’t know about RR, Jumo, and DB engines. Some 6 cylinder Lycomings and Continentals have articulated CWs serving as bifilar damper.. An airplane engine crank does not have to be fully CW’d, just enough. Cheers

[@ArneChristianRosenfeldt]

@@danbenson7587opposed engines still need the crank to be symmetrical to be balanced in itself. Why would any manufacturer not do this? Save weight? That is when you game KPIs .

[@danbenson7587]

@@ArneChristianRosenfeldt Not sure of your point. Early I engines (Model T)did were not CWd at all and early Allison WW2 V12s were not CWd Aircraft H engines are balanced by the offset crank pin pairs w/o CWs. However due to resonance problems, some aero H engines have CWs/bifilar dampers. Aircraft H engine cranks are relatively long because of finned cylinders causing wind up, and the crank zig zag’s flex. Far from ideal but gets the job done.

[@ArneChristianRosenfeldt]

@@danbenson7587 yeah, but even steam locomotives have cw in their wheels. I would understand if a cw needs too much space in the crankcase or blocks air flow. How many mains does Ford have? I mean if only two, then the crankshaft is balanced anyway before it touches a bearing.

[@philipfreeman72]

How heavy was the juke opposed piston diesel ? 6 in line is well balanced . I think flathead engines have a place too .

[@Steven-p4j]

From personal experience, the smoothest and most at ease engines to live with are straight six engines. Also, very large amounts of power can be drawn from them with great reliability. Any further developments appear to be concentrating on more effective air screw design.

[@billymania11]

Designing a sport aircraft with an inline six powerplant and inline seating would be an interesting plane. It would have superior performance and good fuel economy. Being a two seater though, limits its market potential. It would make for a decent long-distance aircraft I would think.

[@chippyjohn1]

Already have designed one. Far better than current offerings.

[@clc2328]

What about a 3/4 scale ME109, Spitfire or Mustang?

[@toddsculley2710]

I have a one of a kind junkers jumo super charged one cylinder two piston engine from 1936

[@joemerican5781]

For engines to review/research how about small gas turbines in General Aviation? With the question, “Why aren’t there more?”

[@danbenson7587]

The air flowing thru the gas turbine has a boundary layer whose thickness is nearly constant regardless of engine size. In small GTs, the BL is proportionally thicker and chokes the engine. A source of GT inefficiency is air leakage around the blade tips. Again the clearance is say .001 in a small or big GT, but is a much bigger proportion in the small GT. GT efficiency is related to pressure ratio….and improving yields compressor complication and expense. Generally simple GTs run at PR of 3.5 and airliner engines over 100! (PR is similar to compression ratio) GT turboprops have gears, and these are very high quality and of course expensive. Technology marches on, maybe someday!….. cheers D

[@Dave5843-d9m]

The blunt nose of a radial engine has less overall negative effect than the shape suggests. There is no radiator drag and the blunt nose is really not as bad as it looks. P-47 Thunderbolt and F4U Corsair were extremely fast machines.

[@DoktorBayerischeMotorenWerke]

Not really, their design was very poor in terms of aerodynamic drag which is revealed in their low continuous cruising speed.

[@codyweaver706]

The P47 and F4U made up for their drag with sheer horsepower. Perhaps the best example of an aerodynamically efficient application of an air cooled radial is the Focke Wulf 190, all the air the aircraft needs enters in the relatively small opening in the front of the cowling, supplemented by a cooling fan at low speeds when ram air is insufficient.

[@DoktorBayerischeMotorenWerke]

@@codyweaver706 Not really... at max. continuous horsepower the P-47 could only maintain a speed of 300 mph at sea level. F4U was even worse with its high drag design it could only maintain a speed of 215 mph at sea level. Pilots preferred in-line engines because of the superior forward visibility, very important in a fighter aircraft.

[@codyweaver706]

@DoktorBayerischeMotorenWerke because pilots do most of their flying at sea level. Also many pilots preferred radials for sheer durability. One hit to a coolant line or radiator will tank a liquid cooled engine. P47s and F4Us would return with entire cylinders blown off and not a single drop of oil left, but still got their pilots home.

[@DoktorBayerischeMotorenWerke]

@@codyweaver706 Radials are still slower, and in the fighter game speed is everything... Jets rendered them both obsolete because of the huge speed advantage.

[@Dudeface167]

13:55 no single underhead cam

[@RulgertGhostalker]

"any other engine types" question: I did contact a glider company in Europe with the idea of a water-less Glider with an integrated H2O2 rocket Range Extender and braking rocket ....as range extender in a glider, the instant solenoid controlled on / off would lend to Automated Stall Protection, ( for a Glider pilot, the difference between life and death )....it has high power to weight also. I don't see the drawback of H2O2's high fuel, and catalyst, costs as any problem not offset by the benefits, in that application, ( though feel "self launch" should be out of the question )...it also can be considered zero emission, which also makes it seem a good match for a Glider. of course the braking rocket would allow for landing the water-less design....replacing the water weight with a lower drag design.

[@38midside85]

I am Vietnamese, experimenting with building an airplane with a BMW s1000r engine, reinstalling a transmission. Can you see it?

[@confederatenationalist7283]

Logical deduction says a V12 will generally fit where an inline 6 will fit and will provide twice as much power for a similar crank case size and weight all else being equal. Luckily for the free world.

[@Steven-p4j]

The flat 4 and 6-cylinder engines of today, enable the heat to be dispersed more evenly than an inline 6 as the banks are fat shorter, allowing more air cooling over a shorter area. Even in the air cooled regime, I put it to you that the flat six engine is still very popular for private aircraft. 'Lycoming' and 'Continental' engines spring to mind.

[@chippyjohn1]

Liquid cooling has far better and more uniform heat dissipation.

[@Steven-p4j]

@@chippyjohn1 True in every respect, however there have been some notable exceptions, as mentioned. Water cooling is always more efficient as it spreads the cooling ability.

[@mjoelnir1899]

I would assume, that Germany loosing the wars, had a bigger influence on the demise of the inline six, than all technical reasons. In regards to air cooling, there are solutions to get all cylinders equally cooled. The dominance of the USA aircraft industry, not producing inline six, is also a reason.

[@LetsGoAviate]

The USA did produce the Liberty 6 - probably in direct response to the success of the German inline sixes - but yes ofcourse this would have played a part.

[@Flies2FLL]

Inline 6 engines are simple, cheap, and very smooth. Where they fall down is in the area of weight. V6 engines are lighter overall due to the "box" design and the crankshaft is way lighter as well. In fact, American automotive inline 6 engines were often times heavier than the cast iron optional V8's that were usually offered! Also, the long heavy engine means that the section of fuselage aft of the CG has to be built longer, which also adds weight. Modern light aircraft use horizontally opposed designs because these are not only lighter, but are way easier to cool with air cooling.

[@chippyjohn1]

If you compared two identical engines except that one was an inline 6 and other vee 6, the weight would be similar. Inline also has more room for bearings and has better balance, allowing it to rev higher, whereas a vee engine would have a stiffer crank but smaller bearings. Less exhaust piping on inline if turbo, less coolant hoses, less timing associated parts. In the end, they are very similar.

[@Flies2FLL]

@@chippyjohn1 Completely wrong. Inline 6 engines do not efficiently use metal. The block is very heavy because it has to be stronger than the V6, which forms a "box", enhancing strength. The long crankshaft of an inline 6 can weigh upwards of 60-70 pounds, and the length causes vibration nodes, rendering it vulnerable to breakage at certain RPM's and requiring extra strength. This means that it doesn't like to rev out, thus ALL high powered inline 6 engines use force induction instead, which increases horsepower by increasing torque. Finally, the inline 6 is far harder to package due to its length. The V6 is much easier to fit longitudinally or transversely in an engine bay. The advantages of the inline 6 are perfect primary and secondary balance, but the big advantage is that it is simply cheaper to build. This is the main reason why it exists at all.

[@chippyjohn1]

@Flies2FLL it sounds as though you are referencing a specific engine rather than inline engines. The average crank from an inline 6 today would be around the 10-15kg not 25-30 you mention. We are talking about modern engines I hope and not engines from ww1.

[@Flies2FLL]

@@chippyjohn1 Wrong again-

[@jiroyamamoto2878]

@@Flies2FLL lets focus on aircraft applications.

[@anvilsvs]

Weight is major issue. V or boxer engines are almost always lighter than inlines of equal strength by a significant amount due to the shorter, stiffer crankshaft and block. The linger motor mounts required also work against the inline as does the rotational inertia of the longer heavier crank which slows maneuvering. BTW, inline 6s are NOT perfectly balanced. they do have a secondary imbalance. But that imbalance is so slight as to be basically unnoticeable. And overall balance if an inline six is better than that of a 90 degree V8. But there's a very good reason why most light aircraft engines are flat fours or sixes. They are perfectly balanced. And, IF all other things are equal, are lighter than an inline. Also usually more expensive to build than an inline due to having two heads particularly if they are OHC.

[@ExceptionallyCleverUsername]

Any of those boxer engines will have a rocking couple, since one bank of cylinders is forward of the other. It's not as noticeable as the buzziness of an inline four, but just like that buzziness the only way to engineer it out is with balance shafts.

[@chippyjohn1]

A BMW K1600, M54 or especially an M57/B57 would put all the air cooled engines to shame. Air cooled horizontally opposed engines are the same as imperial measurement. It Was obsolete a long time ago but the US continues to force it on the rest of the world. Its not just engines that are old designs, but the aircraft are designed for the old engines.

[@cmbaileytstc]

Many car engines will put typical aircraft piston engines to shame in terms of displacement to horsepower ratio, until you realize that plane motors are expected to spend their entire operating lives between overhauls at between 100% and about 70% cruise power, hours on end for many trips, and not fail to keep running even one time. Your road car engine has to output whatever dynamite full power number it possesses for brief periods passing, merging with traffic etc before it goes back to using about 10% of full power for hours on end to cruise. A race car engine gets overhauled frequently. And neither vehicle is likely to kill the driver and all passengers if they lose power, merely inconvenience them. Homebuilders have tried auto engines, sometimes it works out, but there’s a reason aircraft type piston engines continue to exist even though mass produced car engines would have economy of scale heavily on their side. And liquid cooling inevitably introduces multiple additional failure points which can’t be justified in an airplane engine unless it’s WWII and you need every last ounce of performance to win dogfights. There’s many a man who likely wouldn’t have had to replace the motor in his wife’s car if said engine has been air cooled instead of cooled with an additional fluid prone to leaking out. But again, getting stuck on the side of the road isn’t trying to land with a stopped prop. Over mountains. At night. Etc.

[@chippyjohn1]

@@cmbaileytstc What engine did you use in your experimental aircraft?

[@cmbaileytstc]

@@chippyjohn1 Never built one. Dad had a Cessna 175 (NOT 172) and a Piper TriPacer and we went a lot in them whole time I was growing up. Worked on them too. To give you an example of how conservative the airplane community can be, lots of pilot don’t like the geared engine in the 175. Whew, 3000 RPMS!!! LOL But there’s reason to be an extreme conservative with an airplane engine, again it’s job is just not like any auto engine. The most popular auto engine to convert for airplane use used to be the Volkswagen air cooled number from the old Beetle. On paper it was a lot of power for the weight. But again it required a stepdown gearbox to turn a prop with that power, and the engine was never really designed to run at 70-100% of its maximum power all day long.

[@chippyjohn1]

@@cmbaileytstc I'll tell you something. You are wrong. You tell me why a smaller modern engine can't make reliable power. No offence, but Inhave heard it many times, people saying how aircraft engines in a Cessna are something special, but they can't explain why. The truth is they are not, and some modern, liquid cooled, smaller engines can reliably output more power for just as long. It is tiring hearing people say the same thing when they don't actually understand engines.

[@cmbaileytstc]

@@chippyjohn1 I just explained to you exactly why car engines are not plane engines in simple English. But it didn’t take, so here is the dumbed down version for semi-illiterates: The aircraft engines are both as simple as they can be made and not working very hard. These engines could be “hot-rodded” to make significantly more power…for a little while. See WWII. But because they have as few failure points as possible and are so understressed, they WILL run for their TBO hours, barring bad maintenance or very, very bad luck. There is a small but non-zero chance that your car will have a loss of power or complete stoppage due to one of the sensors or other electric doohickeys that make it so efficient. That chance is a non-issue in driving but way too high for flying. Now, go find a way to operate your street car at 70-100% of its rate power without stopping ALL DAY, with absolutely no slowdown. I dare you. I’m not sure how you will do this practically TBH. I guess rent a track and drive around at or near your ungoverned top speed all day. Spoiler: Your car won’t be able to complete the challenge for even for one day. Fortunately, almost certainly the coolant will overheat and force you pull back before anything worse happens to the car. So you’ll put in a highly upgraded cooling system and try it again. Then something worse will fail, and you’ll begin to learn why racing is a good way to make a small fortune out of a large fortune.

[@massmanute]

Problem for inline 6: Torsional vibration!

[@RulgertGhostalker]

all in the reduction there. the I-6 can rev.

[@ВладимирБутенко-х6ч]

👌👍👍👍👍👍👍👍

[@margarita8442]

its due too cooling, cant air cool a str8 six

[@44hawk28]

Please, do not ever pronounce the word ducting like that again. The letter T in the word Duct, is silent period and the proper word, I did sheet metal work 441 years, is ductwork. The T is still silent in that word as well .

[@chippyjohn1]

The T is in fact pronounced, it is not silent.

[@Ron-j3t]

44hawk28 I hope he does it the way u don't like forevermore. Let's cu pronounce words in another language other than American, right?

[@jiroyamamoto2878]

Where did you grow up? Everywhere I have lived in the US the t in duct is what distinguishes it from birds that live on the water, aka, ducks.

[@edgarpryor3233]

Hard to argue with nearly 4 and a half centuries of knowledge.

[@Dudeface167]

Who in the heck pronounces it duck 🦆🤨🤣

[@HeavensGremlin]

DeHavilland were of course, great exponents of the inline six. What killed these engines for them, as Bristol-Siddeley, was fuel consumption, which is one aspect that you omitted from your otherwise excellent video.