I live near ANC, which may well be one of the best places in the world for plane-spotting. We still fly DC-6 aircraft up here, along with a few Grummans, and there are a host of airframes within easy driving distances stretching from the C-119 to a AN-2 being restored. Looking at all these old prop-planes, it lead me to wonder what a modern large prop aircraft would look like.

Modern large aircraft have swept wings and sloping tails, developed for high speed jet service. If there were a modern replacement for the Bristol Britannia/Yukon, would it share these features, perhaps looking more like a Russian Bear Bomber than the Brabazon? If it were a slower creature, would it have straighter wings?

I'd imagine the speed limitations on long-haul flights would kill any possibility of developing a new long range turboprop so that would probably eliminate any sort of swept-wing design. They simply aren't fast enough to justify long flights.

Now, regionally centered aircraft might work. I don't think we'd see any drastic wing or fuselage changes. I think the engines and propellers would be the game changer here. Maybe high density?

NameOmitted wrote:

I live near ANC, which may well be one of the best places in the world for plane-spotting. We still fly DC-6 aircraft up here, along with a few Grummans, and there are a host of airframes within easy driving distances stretching from the C-119 to a AN-2 being restored. Looking at all these old prop-planes, it lead me to wonder what a modern large prop aircraft would look like.

Modern large aircraft have swept wings and sloping tails, developed for high speed jet service. If there were a modern replacement for the Bristol Britannia/Yukon, would it share these features, perhaps looking more like a Russian Bear Bomber than the Brabazon? If it were a slower creature, would it have straighter wings?

For passengers or cargo? Because here's a large prop plane (MTOW >300k lbs) designed today. It's got a mission-specific design, though, like a high wing and a T-tail and a cargo ramp.



The jets win for passengers because they can go fast and high, and sometimes passengers don't like the big spinny things. As long as you don't care about that stuff, a prop wins. A prop-driven passenger airplane meant to get near-jet performance would look like a Tu-114 (and sound like a thousand freight trains), and one optimized to medium-haul would look like an Electra. Short-haul would look like an ATR or dash-8.




If you're into this sort of stuff, you might enjoy a book called "The Road to The 707", by William Cook.

Than you, I'll check it out!

A modern large prop aircraft would have to (and is able to) at least match current narrowbody levels of speed (Mach 0.78), so the wings wouldn't appear very different from those on a B737 or A320. The engines would probably have to be mounted near the back of the fuselage instead of on the wings, which means the aircraft would have a T-tail design.

Progress in Open Rotor Research: A U.S. Perspective (NASA, 2015)

Would love to see a civilian variant of the A400m.

I look at option / technology a decade ago, but I haven't seen much innitiative since then.

Fuel went (relatively) low & noise became more important, which probably didn't stimulate investment..
http://aviationweek.com/commercial-aviation/drop-oil-prices-means-airline-profitability-boost-now

Great work... a decade ago, but where is the fly?

NameOmitted wrote:

I live near ANC, which may well be one of the best places in the world for plane-spotting. We still fly DC-6 aircraft up here, along with a few Grummans, and there are a host of airframes within easy driving distances stretching from the C-119 to a AN-2 being restored. Looking at all these old prop-planes, it lead me to wonder what a modern large prop aircraft would look like.

Modern large aircraft have swept wings and sloping tails, developed for high speed jet service. If there were a modern replacement for the Bristol Britannia/Yukon, would it share these features, perhaps looking more like a Russian Bear Bomber than the Brabazon? If it were a slower creature, would it have straighter wings?

There will be new turboprop freighters. Ayres worked on this concept for a while:

viewtopic.php?t=551407


That didn't pan out, but Fedex did recently order 50 new Cessna 408s:

https://about.van.fedex.com/newsroom/fe ... -aircraft/

CowAnon wrote:

A modern large prop aircraft would have to (and is able to) at least match current narrowbody levels of speed (Mach 0.78), so the wings wouldn't appear very different from those on a B737 or A320. The engines would probably have to be mounted near the back of the fuselage instead of on the wings, which means the aircraft would have a T-tail design.

Progress in Open Rotor Research: A U.S. Perspective (NASA, 2015)

I'm not an engineer but I don't believe the wings need to be swept for high levels of speed as this is not their mission

BobbyPSP wrote:

CowAnon wrote:

A modern large prop aircraft would have to (and is able to) at least match current narrowbody levels of speed (Mach 0.78), so the wings wouldn't appear very different from those on a B737 or A320. The engines would probably have to be mounted near the back of the fuselage instead of on the wings, which means the aircraft would have a T-tail design.

Progress in Open Rotor Research: A U.S. Perspective (NASA, 2015)

I'm not an engineer but I don't believe the wings need to be swept for high levels of speed as this is not their mission

I'm no (aeronautical) engineer either, but my understanding is that you'd need swept wings if you wanted to match speed with a 737 or 320. And I think that extra speed (compared to traditional turboprops) would be required for its mission, because the lack of speed compared to other narrowbodies seems to be one of the reasons why there aren't more turboprops in the sky. (Although the news links in the Airbus A340 Laminar Flow Demonstrator To Fly In 2017 thread indicate that a smaller {20-degree} wing sweep may be used for an M0.78 airliner, compared to the 25-degree swept wings of the 737/320.)

Why not pusher turboprops, couldn't such designs share quite a bit of common components with rear engined regional jets?

WPvsMW wrote:

Great work... a decade ago, but where is the fly?

see that little spec in the corner? Hadn't hatched yet

CowAnon wrote:

because the lack of speed compared to other narrowbodies seems to be one of the reasons why there aren't more turboprops in the sky.

I don't think that short- / medium-haul airlines give one moment's consideration to speed, other than when planning block-time and crewing. What they really want is capacity + economy; if a 180-seat turboprop could cut fuel-burn by 40% with a 20% reduction in speed, what airline would decline on the basis that it wasn't fast enough. More significant is climb rate, getting up the flight levels and en route quickly.

It's just that we don't have 180-seat turboprops, largely for legacy reasons. Jets were prestige in the 1960s and have become the default for medium-capacity aircraft for little other reason.

IMO, hybrid turboprops will eventually cover all the 200 seat and below space (not saying totally replace, just that there will be types with such capacity on the market). We might eventually see hybrid turbofans. An evolution analogous to cars. Hybrids provide the range full electrics can't (at present). Eventually fuel-cell hybrids. The hybrids will be perfect for market-pairs with noise curfews. Electric on TO and Landing, switching to fuel for climbout and cruise. Will be nice to have "instant" rather than "spool up" power on approach.

WPvsMW wrote:

IMO, hybrid turboprops will eventually cover all the 200 seat and below space (not saying totally replace, just that there will be types with such capacity on the market). We might eventually see hybrid turbofans. An evolution analogous to cars. Hybrids provide the range full electrics can't (at present). Eventually fuel-cell hybrids. The hybrids will be perfect for market-pairs with noise curfews. Electric on TO and Landing, switching to fuel for climbout and cruise. Will be nice to have "instant" rather than "spool up" power on approach.

It's not like spool-up time is much of an issue anymore, even in large turbofans.

The energy density of batteries is an order of magnitude less than jet fuel. That's a massive gap to bridge. Two more things: With a hybrid you need both electric motors and gas generators so you're just adding weight, and with jet fuel weight decreases over time.

Not saying it will never happen, but barring some revolutionary advancement, transport planes will be jet fuel only for a long time to come.

Valid points that will indeed delay hybrids, but I had in mind hybrids as a solution to noise curfews. Imagine LHR, LGB, etc., operating hybrids during noise curfew hours.

WPvsMW wrote:

Valid points that will indeed delay hybrids, but I had in mind hybrids as a solution to noise curfews. Imagine LHR, LGB, etc., operating hybrids during noise curfew hours.

The noise from a modern turbofan doesn't come from the core (much). The noise is from accelerating air in the engine overall, and from dirty configuration on approach.

Electrically driving the fan will not decrease noise significantly because you still have to accelerate the same amount of air for a given aircraft weight.

The jury is still out on "perceived noise". Imagine a helicopter without the core noise, only the rotor. Even the experts (as in Thales and Mancunian wizards) don't know what "propeller without core" noise sounds like. Here's an interesting, but non-conclusive paper based on the Q400s of FlyBE at MAN.
https://www.researchgate.net/profile/An ... r-data.pdf

There definitely is a propeller component, which is instantly apparent when you're overflown by an Osprey, but I perceive the Osprey's core noise to be much louder than the propeller noise.

ELBOB wrote:

CowAnon wrote:

because the lack of speed compared to other narrowbodies seems to be one of the reasons why there aren't more turboprops in the sky.

I don't think that short- / medium-haul airlines give one moment's consideration to speed, other than when planning block-time and crewing. What they really want is capacity + economy; if a 180-seat turboprop could cut fuel-burn by 40% with a 20% reduction in speed, what airline would decline on the basis that it wasn't fast enough. More significant is climb rate, getting up the flight levels and en route quickly.

It's just that we don't have 180-seat turboprops, largely for legacy reasons. Jets were prestige in the 1960s and have become the default for medium-capacity aircraft for little other reason.

I'm not sure. McDonnell Douglas came close to putting GE's unducted fan on their narrowbodies (presumably including the 187-seat MD-90-55) in the late 80s/early 90s, but didn't do it despite the UDF approaching that level of fuel burn reduction with lesser or no loss of speed. When you think of the additional amounts of money spent on fuel that could have been saved industrywide since that period, it really is a shame.

Starlionblue wrote:

WPvsMW wrote:

Valid points that will indeed delay hybrids, but I had in mind hybrids as a solution to noise curfews. Imagine LHR, LGB, etc., operating hybrids during noise curfew hours.

The noise from a modern turbofan doesn't come from the core (much). The noise is from accelerating air in the engine overall, and from dirty configuration on approach.

Electrically driving the fan will not decrease noise significantly because you still have to accelerate the same amount of air for a given aircraft weight.

I can assure you that, up close, the noise from an ATR in "hotel" mode is deafening. Even without the propeller turning. So I guess there is some room for improvements.

I would also expect distributed propulsion systems to have less noise, or at least different noise. Compare for example the noise of a large multicopter with a conventional helicopter. Even if the noise pressure is identical at the source, the higher frequencies are attenuated much faster in air than the lower ones. When an aircraft is far away, you only hear a low rumble, or the distinctive chopping sound of helicopters.

As to the noise emanation source, the quoted study was inconclusive.