Unducted fan: weren't propeller airlines obsolete? ...maybe no...

"Grindintosecond" (Grindintosecond) 09/16/2013 at 12:07 • Filed to: planelopnik

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early 80's: The "Unducted Fan", showed huge potential in saving fuel on large jet airliners. The fuel prices in 1989 fell like that 'Life is a Highway' band off of the Billboard charts and with cheap gas, the program ended. (LOTS more + videos after jump)

I mean, at bulk sale into the wing tanks at 30 cents a gallon, saving 30% of fuel burn makes little difference compared to the cost of new expensive engines. But now, at a present day holy balls $3 a gallon into the wing, the UDF props on large commercial airliners is a genuine idea again!

This all started with the oil crisis in 1973. OPEC shut us off and we learned how much of life was run on fuel. in the 70's, 1/4 the cost of an operating airline was fuel cost. It shot up to 50% or more and the UDF project began, it matured and became visual art. sort of like watching a Steam train made for the modern era! We could see everything happening to make it go. They even had a product ready to be produced and showed it at Farnbourough in 1988 for the world to see and start ordering.

(theres a nice f-18 demo at the end of this)

It all ended with crazy Tracy Morgan oil price volatility. Now, suddenly or not-so-suddenly depending on how you look at world events, the airline cost of fuel in the US is collectively $2 to $5 billion a month (inflation corrected, that's 50% higher than it got in the early80's!)...enter fuel saving ideas again! Remember how nobody cared about hugging trees and hugging hybrid cars until it became cost effective and profitable? That's the only thing that drives such a change. Can you profit more using that device? Now it makes sense. So thoughts have begun on UDF work; however, It does have competition! Noise limits at airports will require further efforts on the noise signature, (you could hear it in that video) and the Geared turbofan is presently being produced for the new market planes on the horizon, using mostly present day available parts in current engines. (=cheaper)

Geared? how? Well that huge high bypass turbofan engine has a tranny inside. Oh yes, but it can only work one way. a nice planetary gear reduces the core engine to that big fan and now they don't need so much core engine to drive it, so a smaller more efficient inside drives a huge giant fan outside....effectively, they just made a UDF style engine with one fan and put ducting around it. That makes it much quieter and overall 20% more cost efficient than the engines on today's Airbus and Boeing products. The new style design of the geared turbofan engine flew TODAY on the first test flight of the new Bombardier C-series airliner (737 sized) !!!error: Indecipherable SUB-paragraph formatting!!!

So that fancy awesome looking UDF with even more fuel economy? It could come back to the front if fuel gets even nuttier, let's say not so Tracy Morgan silly but perhaps Jack Nicholson Shining insane, but with the geared turbofan (a less efficient ducted unducted fan) in production) and noise legality, well i guess that's good enough for now...

Photo credits: GE, Pratt&Whitney, Bombardier

Jayhawk Jake > Grindintosecond 09/16/2013 at 12:19

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I don't think the UDF will ever make a come back, it's too loud. More GTF's will show up though, it will be a popular choice for future airliners.

BoxerFanatic, troublesome iconoclast. > Grindintosecond 09/16/2013 at 12:20

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They have a term for that.

Turboprop.

Maybe a dual, contra-rotating, or a dual-stage multi-rate same-direction turboprop, but a turboprop when it comes right down to it.

turboprop = airscrew or multiple airscrews attached to a jet engine.

turbofan = ducted fan or multi-stage ducted fan attached to a jet engine.

turboshaft = ouput shaft to some sort of unattached, driven device, attached to a jet engine, rotor, fan, prop, generator, hydraulic pump, whatever...

Grindintosecond > Jayhawk Jake 09/16/2013 at 12:23

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GTF's will be very popular. UDF's were loud. The prop manufacturer on the test aircraft then say that today, they could make it much quieter (Look at the Q400 turboprop now...it's very quiet) but also the interior cabin electronic noise cancelling has matured as well so that will be used for passenger comfort. (also used in the Q400....when it works) so if there's a need for a more efficient engine, I would imagine with todays technology, even 20% savings over the GTF isn't unreasonable should they really need it against stupid high oil prices.

Grindintosecond > BoxerFanatic, troublesome iconoclast. 09/16/2013 at 12:26

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there seems to be semantics over what a prop is vs. what a Fan is. How many blades do we need to call something a fan? I have a table top fan with 3 blades....I used to fly a turboprop with 3 blades. I would suppose they used alot of terms to get people excited by it. Noone wnats to fly on a turboprop but a fan-jet? sounds bitchin'

BoxerFanatic, troublesome iconoclast. > Grindintosecond 09/16/2013 at 12:35

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Less about the number of blades.

More about whether it provides primary thrust, IIRC.

If you are talking about an un-ducted 'fan' that provides primary thrust through the air... and the airscrew action propels the aircraft directly, it would thus be a *propeller*.

A desktop fan doesn't propel itself across your desk, it provides cooling airflow.

If it is ducted... it is a fan. If it it provides less thrust percentage than the engine's exhaust, it is likely a fan, whether ducted or not, and likely is used at least somewhat for engine cooling bypass air.

Jayhawk Jake > Grindintosecond 09/16/2013 at 12:40

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Maybe, but the real issue is sound to the ground. People already complain about how loud airplanes are, with a UDF it would be much worse especially if we get a few years with GTFs ruling the skies.

Grindintosecond > BoxerFanatic, troublesome iconoclast. 09/16/2013 at 12:43

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well, the manufacturers of all engines in that configuration call it a fan. Even the AN-70, about the most modern version that achieved the most widespread use, refers to it as a prop-fan. Even tho it is indeed an air-screw and working it's action as such. I would prefer the actual names be used but I can't fight the actual makers and program managers of these things. Some planes I flew I would have rather been named POS but I can't make them see the light

BoxerFanatic, troublesome iconoclast. > Grindintosecond 09/16/2013 at 12:46

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Marketing speak is indeed marketing speak.

I can't get people to stop calling cars with four side doors, as coupes, just because of a little less rear head room.

Grindintosecond > Jayhawk Jake 09/16/2013 at 12:48

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And yet, after the airport has been there for 75 years, providing a very large tax infusion into the community, they move right next door and then start to complain about how loud it is. There's a reason the house was cheap. Yet they gripe about the noise. Stage 4 noise limits are very strict and working very well. If they complain about a Stage 4 compliant airplane overhead, they just moved into the wrong neighborhood and honestly have no room to complain. Let's go move next to railroad tracks and start complaining to Union Pacific and the Government and see how that works. Multiple blades do quiet things down a bit and further modern design would help alot. Even if they create a stage 4 compliant UDF, that old lady in her house 24/7 would complain about it because it sounds different so it must be breaking the law.

Grindintosecond > BoxerFanatic, troublesome iconoclast. 09/16/2013 at 12:51

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Oh god yeah, Pontiac did that didn't they? The wide-track coupe?...shiver...

Jayhawk Jake > Grindintosecond 09/16/2013 at 12:56

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Don't get me started on that one...the worst example that always comes to mind is Santa Monica. Residents have been trying to get rid of the airport for YEARS....the airport has been there for nearly a century, if you didn't want airplanes flying over your house you shouldn't have moved in next to an airport.

Grindintosecond > Jayhawk Jake 09/16/2013 at 12:59

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100% agree. It's got such history to the place and the money it generates for the community is irreplaceable. A park does not have landing fees. Apartment complexes don't generate fuel tax revenue. The sad part is that when an airport looses the battle, there is one less place for an emergency aircraft to land. Or even a plane to divert to when another airport closes due to fog or other weather.

BoxerFanatic, troublesome iconoclast. > Grindintosecond 09/16/2013 at 13:09

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Pontiac Grand Prix was actually a coupe and a sedan pairing, for a while, and the Grand Prix was the car they advertised as having a wide track.

The first I remember really, deliberately calling a 4-door car as a coupe, is Mercedes Benz, when the original CLS debuted...

Bluecold > Grindintosecond 09/16/2013 at 13:12

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Has CROR's, or Counter Rotating Open Rotors. Makes a really strange noise, since the interaction of the two props provide a higher pitched harmonic through the standard turboprop noise. It's quite something.

Slave2anMG > Grindintosecond 09/16/2013 at 13:28

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I like MD80s...but they're noisy in the back with regular engines. It would have been deafening with these suckers...

Grindintosecond > Bluecold 09/16/2013 at 14:57

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video of the noise