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Comment by redis_mlc | Hacker News Reader

The A220 is a certificated airliner. Neither China or Japan has done that.

And don't forget the Avro Jetliner. Interestingly, in terms of missed opportunities, this may well have been bigger than the Arrow.

https://en.wikipedia.org/wiki/Avro_Canada_C102_Jetliner

Wow and they cancelled that for the arrow!? Yikes.

No, they cancelled that to focus on the Canuck as per the article.

False. https://en.wikipedia.org/wiki/NAMC_YS-11

That's a turboprop...Aren't those much less safe than jet engines?

No. My understanding is that they are generally even safer. The public doesn't seem to like them as much, though.

A turboprop is a jet engine. The propeller moves a large mass of air, increasing efficiency ... like the current turbo fan engines! lol.

Pax hate turboprops because of the noise and a misconception that they're not jet engines.

There's no inherent safety difference, except that there used to be regional airlines flying with inexperienced pilots like cough Colgan.

https://en.wikipedia.org/wiki/Colgan_Air_Flight_3407

There’s more moving parts, since each prop has to rotate on its own axis in addition to rotating in line with the aircraft. Jets are stupidly simple, but turboprops are more complex due to these requirements of the props. Turboprops also can’t go as high or fast as jets, because they need a certain amount of air density to operate.

They can provide fine-controlled reverse thrust, so they have that going for them. And they’re less complicated (and lighter) than a traditional piston engine, making them a win over normal engines in mid-sized aircraft.

EDIT: "Jets" in the above is a poor reference to turbofans, as pointed out by replies. Thanks for the clarification.

A Turbofan still has a turbine being powered by a jet engine, similar to a turboprop, but it does not have the complexity associated with being able to change the pitch of the props.

Is there any modern airliner plane that still uses jets? IIRC all modern passenger plane engines are turbofan engines. Turboprops win at slower speed, while turbofans excel in the fast-but-still-subsonic range.

There aren't any modern planes still using turbojets. I think the Concorde might have been the last (ceased operation in 2003.)

Combat jets often have very low-bypass ratio turbofan engines though. A true turbojet has a 0 bypass-ratio; a lot of turbofan fighter jets have bypass-ratios under 1, while the engines on a 787 have a bypass-ratio of 10.

https://en.wikipedia.org/wiki/Bypass_ratio#Engine_bypass_rat...

I should clarify, when I'm saying "jet", I do mean turbofans. And turbofans still include a jet engine, but the output turns a turbine which rotates the fans.

Turbojets, turbofans, and turboprops all use gas turbines. The "jet" in this context refers to the action of the exhaust, not the mechanism creating the exhaust (which is the gas turbine.) Turbojets and Turbofans both create jets of hot exhaust gas to produce thrust. Turbojets produce thrust exclusively with this jet of exhaust gas, while turbofans produce some [often most] of their thrust by using some of the turbine's output to turn a ducted fan. Turboprops don't produce any meaningful jet of exhaust gas, instead using the output of the gas turbine to turn a propeller.

Related to turboprops are turboshaft engines, which turn a power transmission shaft instead of a propeller directly. In some cases, like the V-22 Osprey, the line between a turboprop and a turboshaft is blurred. But some clear examples of turboshaft engines are in modern helicopters and Abrams tanks.

There are some kinds of jet engines that don't use turbines. Ramjets and scramjets don't use turbines, but have 'jet' in the name because they produce their thrust using a jet of hot exhaust gas. Rocket engines produce jets of hot exhaust gas, but aren't called jet engines because.. reasons.

> jet: A collimated stream, spurt or flow of liquid or gas from a pressurized container, an engine, etc.

(Note that this makes turboprop engines not jet engines, but turbojet and turboprop engines are both gas turbine engines.)

"Jets are stupidly simple" Haha :D I don't know where that comes from. Jet engines are fiendishly complicated.

If they are so simple can you explain to me how interlaced rows of stator and rotor blades turn pressure into gas speed? That one always stumped me. Or how do I make monocrystalline blades, and how can I QA them? Or what exactly a FADEC do during startup, and how do the controlled parameters change depending on atmospheric conditions? Also I heard that the injectors and the air flow in the combustion chambers is designed such that there is an outside layer of incomplete combustion creating a colder laminar gasflow to protect the chamber wall itself. How do I go about designing that? How do I cool the bearings? How does one get the rotational energy out from the centre shaft to drive an oil pump on the side of the engine?

I mean these are just the first questions which pop up in my mind when I think about jet engines. And I'm not even a jet mechanic. If you truly think that jet engines are simple, then I envy your intellect.

I was referring to the operational complexity of the final product, not in the design or manufacturing. They have two main moving parts - the jet turbine, and the turbine connected to the fan (or prop). This is in comparison to the hundreds of moving parts your average ICE has for the drive train alone, not including the electrical system that lives alongside it to facilitate timed fuel ignition.

Jet engines are used on some older oil pumps because they can run for decades with minimal maintenance.

[1] https://en.wikipedia.org/wiki/Geared_turbofan

This Genius Invention Could Transform Jet Engines, 2015, 3m51s, Bloomberg QuickTake Originals

[2] https://www.youtube.com./watch?v=8aPIEsnKb6o

Rolls-Royce UltraFan technology, 3 shaft geared turbofan jet engine, 2018, 2m29s, MDx media

[3] https://www.youtube.com./watch?v=6zD4uEdCkAk

The initial comparison was turboprops vs. turbojets, so switching the comparison to the undoubted complexities of internal combustion piston engines is beside the point.

The 'jet' engines used on oil pumps etc. are actually not jet engines: they are gas turbines in which an additional turbine or turbine stage is used to extract rotational power - in other words, they are more like turboprop engines than jet engines.

Nevertheless, I do disagree with the suggestion that turboprops are much less safe than turbojets, and I suspect that the author of that comment was confusing them with piston engines, which also (almost always) use propellers (increasingly, we are seeing turboprop singles replacing piston twins.) Finally, piston engines themselves have become much more reliable since the days when they were the only option.

> each prop has to rotate

Pedant.

Turboprop/turbine engines are quite reliable. Will gladly put my trust in a single engine Pratt and Whitney (Canada) PT6. Piston on the other hand.

It's a fair point and simultaneously does a disservice to what China is very obviously about to accomplish with the C919.

There is every reason to anticipate China taking a big share of that industry away from Boeing and Airbus. They only need to buy their own supply (which they will) to do that.

Further, Japan is also very obviously about to successfully unleash the Mitsubishi SpaceJet.

It's like people that were still pointing out up to the last moments in May that the US had no human space launch capability, trying to wring that last bit of satisfaction from the context.

Here how I've been told the story of the C919 by people working at Airbus. Airbus wanted to sell planes to China. China said OK, but you must build a factory in Tianjin and assemble the planes there, with Chinese workers and engineers. So Airbus did that.

They then built the factory for the C919 in Shanghai, and there went most of the people who previously worked at the Airbus factory. :)

> about to accomplish with the C919.

not certified, a decade late

> about to successfully unleash the Mitsubishi SpaceJet.

wasn't that cancelled last week?

https://www.avweb.com/aviation-news/mitsubishi-pulls-back-sp...

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