Active turbulence cancellation makes bumpy flights smoother
newatlas.com
newatlas.com
Todays airframes have a lifespan measured in flight hours, and an estimation is done as to how much turbulence will be hit per hour of flight. At the lifespan limit, the plane is typically scrap.
If this tech can reduce the flexing of the airframe during flight by 80%, you can probably get 5x the flight hours from the airframe before it becomes too weak to be safe (or more - half the flexing typically more than doubles the lifespan)
Alternatively, you can make the airframe thinner and lighter for the same number of operating hours (and that's what is likely to happen, since aircraft manufacturers don't want to put themselves out of business). Thinner and lighter airframe saves fuel and makes the aircraft cheaper.
Secondly, the turbulence prediction is extremely hard for an airliner because it’s traveling so fast - you’d need sensors extended comically far forward and at that point you’ve got real risk of them breaking off mid flight meaning you would have to add significant amounts of weight to strengthen them (assuming you could). You’ve also got the problem that you need to retract this stuff on landing probably which adds more weight and complexity. Adding even more problems, generating sudden thrusts to counteract turbulence for a commercial airliner seems really difficult since that’s not how the engines work (eg you probably can’t generate a countervailing force quickly enough).
This is a neat concept but keep in mind this is a PoC on a very lightweight craft going relatively slow. It’s not clear how big/fast an aircraft it can scale up to. An easier turbulence reduction would be to mount the passenger area in something that could actively mechanically stabilize like optical image sensors. If you could decouple things so that the airframe could be repaired/replaced cheaply independent you everything else in the aircraft, that would be much more cost effective. However I suspect the mechanical stabilization itself would add a lot of weight/also need replacement and you wouldn’t see fuel savings I think, just a more comfortable ride.
That's exactly, what i imagined, at least.
This article is about a PoC where they put sensors extended out of the airframe of a small slow moving aircraft and demonstrated a 60% prediction accuracy for a 10% fuel savings. It’s unlikely this approach would scale up to an airliner. The sensor problem might be but I have big questions about the adjustments an airliner moving at 600-900 mph can make to successfully counteract the prediction.
It's designed to work at Mach 0.85, and was meant to increase the lifespan of the airframe during low-altitude penetration flights where lots of turbulence could be expected.
It seems like a system like this would need to respond very quickly to changes in the air mass, and the weight and slow response of an airliner might make this system less feasible unless you could somehow measure airflow a reasonable distance in front of the plane.
This could be a few extra control surfaces, like a canard or actuated slat, or it could be through something like Active Flow Control -- https://www.scientificamerican.com/article/the-next-darpa-x-... -- where puffs of bleed air or electrostatics adjusts airflow rapidly.
I think systems-- like the B-1 Lancer highlighted by a sibling comment-- show it's not completely impractical for larger aircraft.
Given how slow and cautious the industry is (and for good reason), even if someone has been working on this for a decade already, I don't expect to see anything like that before 2030.
Obviously this impacts engine efficiency, so not 100% sure how great it would be for cruise, but doesn't seem entirely impractical?
The lighter airframe is really interesting, too, given the ongoing cost savings
The old clunkers still around are mostly used in sanctioned countries, or where a market failure has failed to provide a decent equivalent (757/767)
Not sure who still flys 757/767s so, at least for pax. Most shoupd have been replaced by 777/787/A350s by now.
Edit: Totally forgot about Delta.
A whole lot of weird, or just simply old planes still operate in Canada for this reason. Until this year you could still find 737-200 flights in the north.
No other 737 got the gravel kit
Will be interesting to look at fatigue of the control surfaces though, if they get used many times more per flight to adjust for minor turbulences.
This is true--- these days. We've been tending to replace planes before the airframe life limits are met.
> I can't remember an accident of a major airliner as a result of the airframe failing post the 1970s.
Well, on the other hand, this is mostly true because airframe life limits and expensive inspection programs that we established after horrific accidents.
And things like https://en.wikipedia.org/wiki/Aloha_Airlines_Flight_243 (1988).
> Will be interesting to look at fatigue of the control surfaces though, if they get used many times more per flight to adjust for minor turbulences.
Control surfaces are on bearings and have, in general, a lot of excess strength to minimize internal deflection. Even if there were a trade in wearing out control surfaces faster, they are a more easily inspected and replaced part of the airplane.
Isn’t the lifespan related to the number of cabin pressurizations (not flight hours).
Which is why long haul planes like 787 have longer lifespans than a 737, because 737 are doing way more quick turn trips (more pressurizations) than a long haul international flight plane.
For general aviation, yes. For pressurised cabins, life is measured in pressure cycles. A long flight wears the structure about as much as a short one; it's the inflating and deflating that counts.
- Stockton Rush
Self tuning and active predictive PID controllers are also a thing aided by the 'ye olde' faithful Kalman-Filter. At least I remember reading about them in research papers.
Now what exactly from those has materialized in commercial applications, I have no idea, since it's not like they publish such in depth info in the public facing spec sheet.
2.65m */ 0.1 seconds = 60 mph.
Airliners fly about 500 mph, so something about this math is far off...
They are not targeting airliners for the current generation.
Like someone else said in the comments, (if true) this tech seems to have already been used in military bombers for a long time now, so to me it's weird it hasn't made it to civilian aircrafts already from the civilian arms of military contractors, and instead needs to be reinvented by a start-up.
[1] https://www.wildbergair.com/registrations/C/OE-CRG_1_01.htm
So the class of technology they need to make this works already exists in production. So the real problems will be how they’re sensing, and can they make them survive hundreds of thousands of air miles.
A shower of something like nuts or cherries halls a few feed past a bright area and the bad ones just magically sort themselves out into a different stream away from the main flow.
I’d love to see one in person.
One test aircraft used 2.65m poles extending off the front of the wing. One test aircraft used a boom extending off the nose. The model airplane used a big rig sticking out front and teeing off to the sides.
If this can achieve more fuel-efficient adjustments, it'll be extremely valuable.
Based on the article it looks like their fuel savings claims are due to not having to avoid turbulence by rerouting around it.
If it could directly impact fuel economy much compared to a plane flying directly through the turbulence I would think they would call that out too.
Still, if you’re operating an airline fuel saving is fuel saving.
https://link.springer.com/article/10.1007/s13272-021-00512-y
I fly a ton and have only experienced bad turbulence a handful of times in the last 5 years.
It's actually astounding to me how little turbulence there seems to be now.
Maybe I'm just getting lucky?
If drink service wasn't suspended on others, it wasn't very bad turbulence. A rule of thumb is that if your seat belt isn't hurting you, it's moderate or lower intensity.
My rule of thumb is if the drinks didn't fly into the air and spill, then turbulence is minor.
Also pilots largely avoid microbursts now:
https://www.aerotime.aero/articles/microbursts-the-danger-th...
They also created a 3D microphone array that they used to map the sound inside the airplane and spend the dampening budget in the places that will get the most impact.
Nothing super memorable. I'm sure it happens, but seems very rare and/or route dependent.
The longer the plane, the further between the nose and the leading edge of the wing. So the more time you have.
also aren’t turbulent more likely when you are lower than at final cruise altitude? Wouldn’t the plane be going slower than anyway for fuel savings in the denser air?
Even if it would only work on longer/larger jets it could still be very helpful.
> "Climate modelling studies have indicated that the volume of airspace containing moderate-or-greater clear-air turbulence on transatlantic flight routes in winter will increase by 40%–170%, relative to pre-industrial times, when the CO2 is doubled"
https://link.springer.com/article/10.1007/s00376-017-6268-2
The CO2 doubling point is expected to arrive in ~60 years at current fossil fuel combustion rates, but I'd expect by that time a very large fraction of short-distance air travel will have moved to (electrified) high-speed rail as it's far cheaper per distance traveled. Also, as others note, this technology doesn't seem applicable to trans-oceanic jet travel.
From https://www.defensemedianetwork.com/stories/naca-the-jet-age...
In 1951, Kraft issued NACA Technical Note 2416 that proposed a theoretical solution to the problem. Tests first on a modified DC-3 and later on a C-45 validated the theory, and by 1955 the system was perfected.
Can be downloaded from here.
https://digital.library.unt.edu/ark:/67531/metadc64927/m2/1/...
I'm not suggesting gyros are the correct way to do this. But I can say the difference is night and day.
A gyro large enough to counter turbulence in an airliner would be too heavy to fly and too the fuselage apart
The technology in the linked article is even different, they put a sensor far in front of the wing and preemptively control the surfaces to counteract turbulence.
It’s certainly going to be easier to replace hydraulic cylinders or something for the control services than the entire wing (which I’m assuming no one does).
So it may still be a net win in maintenance terms.
I mean, they do anyway, but eventually it leads to refunds, and fines from the FAA. Actually on second thought it’s probably not physics or logistics, it’s the FAA.
"Nobody likes to fly through turbulence"
Thats not true! There are dozens of us! (Actually, quite a big more, I read a stat that we're about 5% of the fliers)
[1] kids be kids, of course - as a kid I once ran up and down the aisle during take off, so Im cool w/ kids.
There have been five fatalities of US airline passengers in the last 10 years. That’s billions of passengers. It’s incredibly safe.
https://www.iihs.org/topics/fatality-statistics/detail/yearl...
When you say driving is also safe, it doesn't really seem like a reasonable comparison when 85,878 died in motor vehicle crashes for every 1 person that died from flying.
Right now the FAA is bragging about serving 2.9 million passengers a day. I had no idea it was that high. That’s almost 1% of the population. The IIHS death rate works out in the neighborhood of 1 in 8-10k. But I think that’s per driver, not per trip. So we are stuck on the per trip bit again.
Meanwhile 5 fatalities in 10 years (~3652 days) is less than 10.5 billion person trips (assuming passenger rates climb over time) which is around 1 in 2 billion. So unless we are living in a statistical fluke that’s about two orders of magnitude off.
It has a chart normalizing by trip. Someone posted this on HM a few days ago.
Also, the statistical difficulties of this, and therefore large error, are significant. I see at least two:
1. 5 fatalities in ten years in the US neglects the 346 fatalities of passengers who died in two 737 Max flights before being recalled - flight deaths that, being 100% Boeing's fault, aren't on the US' tally by stat fluke (lookin at you Southwest).
2. actually its not luck that the hundreds of 737 dead didn't end up in the US' tally. Airline deaths are rare enough that there are not enough flights to sample the death rate properly.
There are orders of magnitude more driving than flying by mile and number of journeys.
https://en.m.wikipedia.org/wiki/Aviation_safety
Scroll down to "transport comparison" and look at the journey normalization.
Safety calculations are hard.
Even on a gut level, feeling the plane bounce against the "road" gives you a confirmation that, yes, in fact, it is bouncing against something (even if that something is just air under the wings).
Flights are boring, the rocking around is fun!
IMHO, the second accident had a better chance of survival, but it wasn't enough. IIRC, the flight before the first accident also had erroneous MCAS activation, and the flight crew did turn off electric trim and did it manual, but it wasn't treated as a must fix maintenance item, because MCAS was hidden.
There really should have been a separate shutoff for MCAS apart from the electric trim switches. Limited activation authority will hopefully be sufficient, but doesn't satisfy my airchair aerospace engineering demands.