[HN Gopher] The next steps for Airbus' big bet on open rotor eng...
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The next steps for Airbus' big bet on open rotor engines
Author : CGMthrowaway
Score : 58 points
Date : 2026-02-03 15:31 UTC (7 hours ago)
(HTM) web link (aerospaceamerica.aiaa.org)
(TXT) w3m dump (aerospaceamerica.aiaa.org)
| inhumantsar wrote:
| > Airbus is also assessing shielding the area of the fuselage
| closest to the engines to minimize the risk of a blade off -- one
| or more composite blades breaking, which could dent or puncture
| the fuselage and, in the worst-case scenario, strike a passenger.
|
| sightly terrifying
| roboror wrote:
| Yeah I'd think you'd need some serious shielding to prevent a
| puncture
| in_a_hole wrote:
| I had a sharp intake of breath after reading this and then
| clicking through to see the header image of the article.
| KolmogorovComp wrote:
| not more terrifying than sitting in any turboprop airplane.
| mapt wrote:
| The cowling of the current turbines serves the same purpose,
| but needs to cover 360 degrees of rotation, so it's heavier and
| draggier. The blades have a bit more angular momentum in the
| propfan than in a high bypass turbofan, but there's fewer of
| them.
| dameyawn wrote:
| Instead of reinforcing the fuselage, I wonder if just having
| a 1/4 nacelle that shields the passenger side would work.
| fsckboy wrote:
| > _The cowling of the current turbines serves the same
| purpose, but needs to cover 360 degrees of rotation_
|
| this doesn't make sense. if you are not worried about fan
| blades flying off in directions other than the fuselage, why
| cover 360 degrees? (and if you are worried 360, then why open
| rotor?)
| somewhereoutth wrote:
| The cowling is its own structural support, so needs to be
| strong all around, otherwise it would fail on the other
| side and you'd get blade+cowling approaching the fuselage
| at high velocity.
| pavon wrote:
| The impact area of the fuselage looks much larger than an
| unrolled cowling, and thus significantly heavier to
| reinforce. The smaller cowling will save drag through.
| csours wrote:
| High bypass turbo fans do this as well, it's just in the
| fan/engine housing, not the fuselage.
| bob1029 wrote:
| I am assuming the target market for this is European short haul
| flights?
|
| On something like a New York <-> Los Angeles flight I cannot
| imagine the turboprop beats a 737 in any performance or comfort
| category.
| micwag wrote:
| The article is not about turboprop but about open-rotor engines
| which are a modern variation of propfan engines.
| 4fterd4rk wrote:
| Everything old is new again... McDonnell Douglas looked into the
| propfan thing. Boeing looked into the propfan thing. Now it's
| Airbus' turn. IIRC the technology has been ready for years but
| the passengers are freaked out by it.
| cherryteastain wrote:
| Real problem was noise, not passengers. Immense advances in
| aeroacoustics over the past 40 years thanks to CFD is the main
| enabler here.
| dcrazy wrote:
| I think it's a cool idea but I also know that the nacelles have
| a safety function of containing the rotor blades in the event
| of disintegration (e.g. from a bird strike).
|
| If these fans have blades with anywhere near the same kinetic
| energy, I would be nervous.
| txru wrote:
| Southwest 1380[0] is a case where the cowling _didn 't quite_
| contain the thrown rotor blade.
|
| They were very lucky that only one person died.
|
| [0]
| https://en.wikipedia.org/wiki/Southwest_Airlines_Flight_1380
| filleduchaos wrote:
| Turboprops have already existed for decades, so perhaps you
| should already be nervous.
| drivebyhooting wrote:
| Won't this be absurdly loud?
| Etheryte wrote:
| This is discussed in the article, was there a specific part
| that was ambiguous?
| drivebyhooting wrote:
| It was glossed over and buried.
| xattt wrote:
| TFW does say there is an opportunity for reduced noise.
| However, conventional turboprops are very loud compared to
| their jet counterparts.
|
| Each revolution of a prop blade sends out a shockwave of air
| against the airframe. The strength of the shockwave is likely
| proportional to the instantaneous thrust of the engine, and
| more blades are likely to weaken or smooth it.
|
| A turbofan has a nacelle to contain the shockwave, and avoid
| the whole noisy mess.
| ufmace wrote:
| It's only discussed in a similarly ambiguous way - like that
| they know noise is a potential problem that they're working
| on. Though to be fair, the designers probably have no idea
| themselves, since apparently nobody has built a prototype
| engine that could be run at the rated thrust level in a way
| they could check the real-world noise and vibration on.
| rgmerk wrote:
| I would assume that these days you can simulate that
| increasingly accurately before you need a full-scale
| prototype.
|
| They could also use active noise cancellation, which is
| already used in some turboprops like the Q400.
| xattt wrote:
| Just an opportunity to sell premium quiet seats at the back,
| and pleb seats at the front.
|
| With all seriousness, I am thinking whether there are parallels
| between this proposed plane and the Q400.
| JorgeGT wrote:
| I talked with one of the aeroacoustic engineers working on it,
| she says they expect to match noise levels of current engines.
| AnotherGoodName wrote:
| It's part of the tradeoff between momentum and energy that you
| should aim to move as high of a mass of air at as low of a speed
| as possible for efficiency.
|
| When you put energy into a mass of air you impart energy of 1/2
| MV^2, the kinetic energy equation, which you can think of as the
| energy you're leaving in the air as it's accelerated to a given
| velocity on exhaust from the engine. The V^2 part is a killer.
| This does not translate directly into momentum at all and the
| most energy efficient way to gain momentum is with a large mass
| that's accelerated to a low velocity. You can actually see this
| with the wings which keep the plane itself up. The wings impart
| enough momentum to hold the weight of the aircraft up by moving a
| lot of air at relatively low velocity which sacrifices very
| little energy for the upwards momentum gained.
|
| So engines in aircraft have been getting bigger and bigger as
| well as slower and slower. It's basic physics, aiming to move as
| high of a mass at as low of a practical velocity as possible. The
| 737 max issues were an example of adding giant engines to an
| airframe not originally built for them due to the drive to move
| as much air at as low of a velocity as possible while still
| keeping the plane moving forwards. Passenger aircraft have been
| getting slower over the years, the 747 was faster than the newer
| 787's because we're looking for efficiency above all else these
| days. Going open bladed makes a lot of sense as we go further
| down this path.
| Gibbon1 wrote:
| I'm curious about using a hybrid system where you have multiple
| electric fans. For instance 2 turbines and 4 fans. Advantage is
| smaller diameter for the same mass flow. And more redundancy. A
| negative is the weight of the electric motors and generators.
| If you added a battery you have some other advantages. Less
| pucker when you lose an engine. And better throttle response.
| pedrocr wrote:
| Another advantage is you can place the fans all along the
| wing getting you better stall resistance as the flow doesn't
| detach as easily. There's already a prototype of a hybrid
| plane that does this:
|
| https://www.electra.aero/
| aceofspades19 wrote:
| This isn't true though, the 747's cruise speed is the same as
| the 787's at 0.85 mach. The 747 has a slightly faster max speed
| but that's not relevant for actual travel. The 777 has a slower
| max speed and cruise speed than the 787 despite being older. I
| don't think you can realistically draw a correlation between
| older/newer being faster or slower on wide body aircraft.
| enopod_ wrote:
| Sounds like a helicopter is not very efficient?
| AnotherGoodName wrote:
| Less efficient than an aircrafts wings over a long distance
| but very efficient for an aircraft with engines pointing
| straight down.
|
| The blades are massive, push a lot of air relatively slowing
| compared to smaller engines. There's a reason most planes
| will stall when pointing straight up, despite in theory
| having more power to weight. Their prop efficiency is worse
| than a helicopters rotors.
| zabzonk wrote:
| Isn't this like turboprops (already very efficient) with bigger
| propellors? I couldn't tell from the article, but quite possibly
| missed something.
| nickff wrote:
| This website has some nice explanations and GIFs:
| https://s2.smu.edu/propulsion/Pages/variations.htm
| game_the0ry wrote:
| The inner nerd in me is so satisfied. Thanks for the link.
| jiehong wrote:
| That website it gold!
| Ajedi32 wrote:
| So the "open rotor" engine is actually a propfan engine?
| nickff wrote:
| Essentially yes, different engine companies have used
| different nomenclature over time. It seems that the "open
| rotor" terminology is being used to emphasize the
| improvements which have been made to blade design, noise,
| and general efficiency.
| somewhereoutth wrote:
| I think it is the stators fixed to the engine nacelle, judging
| by the article image.
| Stevvo wrote:
| The Antonov An-70 has been in service with "open rotor" engines
| for 30+ years. It's superior to its western counterparts in every
| way. i.e. greater speed and payload with less fuel consumption
| than a C-130 or A400M.
| nradov wrote:
| Huh? Only two An-70 prototypes were ever built so it's not
| really "in service". The early propfan designs, while
| efficient, were too loud for widespread civil use. Newer open
| rotor designs are much quieter.
| vel0city wrote:
| You know what makes the C-130 or the A400M superior? The fact
| there's more than one operational today.
| cpursley wrote:
| Russia has also just modernized their IL-114s and got an order
| from India.
| micwag wrote:
| Those are turboprop like the A400m or C-130. The article is
| about open-rotor engines which are a modern variation of
| propfan engines.
| direwolf20 wrote:
| Is this not... a propeller? A turboprop engine?
| idontwantthis wrote:
| I'm not an expert but I think the distinction is that the blade
| tips in these reach supersonic speeds like in turbofans. That
| is a hard problem to fix because you don't have the duct to
| contain the noise and catch the blades if one were to break.
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