Discussion about the engine idea that was way ahead of its time.
Now that we see a future need for lower fuel consumption, is the idea of bringing the propfan back on the table? IIRC the only con was the cabin noise, but that can easily be fixed a la the Q400.
Not just cabin noise, but noise in general. They're loud as shit.
Also more complex maintenance.
>>903191
Do you have a video where the noise can be heard? I can't seem to find one.
>>903198
Wouldn't matter anyways. Video doesn't capture the magnitude of the sound.
Propfan AN-70
>>903190
Except that's wrong. The future is increased bypass ratio turbofans.
What exactly is the difference between a propfan and a turboprop?
>>903245
The swept nature of the blades on a propfan has them acting as, you guessed it, fans like in a turbofan.
It's really just the swept propellers.
>>903249
Would the Airbus A400M engines count as propfans?
>>903251
No. A400 use single propeller for each of its engines. Propfan has dual propeller
>>903190
found the guy that never sat in the back of a 727
"cabin noise" hah
>>903190
I made a thread a bit ago about the Kuznetsov NK-12MA contra-rotating turboprop, the powerplant that the TU-95 uses. I really like the idea of these contra-rotating turboprops/propfans. There are a couple issues with the concepts though.
1. The noise
Noise is a huge factor when creating engines today. An engine has to follow strict noise limitations for the airport environment, as well as cabin noise. These coaxial propellers/fans are naturally loud because of constructive interference between the props, and often because the size of the propeller/fan is enormous.
2. The gearbox
This was one thing I couldn't quite justify. These engines normally have a planetary gear setup to both slow the prop and allow for coaxial operation. The problem is that these gear configurations are a weak link in the operation, because these engines are putting out thousands and thousands of horsepower (15000 shp in the NK-12MA), and that is a hell of a lot of force to put through a gearbox. Secondly, the complexity of these gearboxes is a big maintenance headache, and can be a bit costly.
Overall, I'm definitely for them. They are way more efficient than a turbofan (for a similar thrust output) and typically cheaper. It is proven to be a viable design, but frankly, the industry is focused on turbofans at the moment. Everyone wants to compete in a market that has a future, and turbofans are the hot thing right now. The coaxial turboprop/propfan is more or less a design many would consider to be experimental, and in the long run isn't worth it to companies such as GE, Rolls-Royce, etc. to develop a design many people wouldn't invest in. Maybe it'll catch on one day, I hope.
The only currently commercially viable propfan designs I've seen are the ones with the depressed rear fuselage with U or H tail setups that have the props up and to the rear, so the end of the fuselage and tail surfaces and the tailcone/platypus tail area shields the ground from noise. Otherwise there's no way in hell they'll meet stage 3 noise requirements reasonably and not deafen the passengers.
>>903190
still waiting for this piece of shit
>>903660
Because fuck maintainers?
>>903508
>more efficient than a turbofan
For what application though? Long-distance, high altitude flights? Short-distance flights? Heavy or light aircraft?
