This is my biggest concern with this concept as well. Towing things is challenging because the tow plane's center of gravity can change drastically depending on the forces on the glider it is towing -- if the glider deploys its spoilers / crabs in a crosswind / gets in your wake turbulence you're not going to be able to predict how it changes your CG (and your control authority) without training or experience. Also, with gliders, the tow plane is traveling at around 60MPH to 90MPH, with a decision window of 2-3 seconds. Commercial planes travel at ~500 MPH... The concept seems like a hard sell to the pilot unions. I bet they've thought about this though.
Would this not be trivially solvable with a system that detects the situation (e.g. by measuring the forces acting on the towing plane's attachment point) and detaches the tow? If in the final concept the towed plane would be unmanned and wouldn't contain fuel, even a crash would not be particularly catastrophic.
As for a system that measures forces, that’s not likely to work either. Transient forces are OK, but the same force over a little bit of time is enough to force a nose down attitude that is unrecoverable. Attempting to draw the line unequivocally between the two is difficult because it depends on conditions, weights, centers of gravity, and many other things.
Read linked NTSB report
(i understand it well - have been flying planes for over 13 year now)
You might not say that if it hit your house or your person. It is going to have a lot of kinetic energy.
- the weight of either airplane.
- the performance of the engine on that particular day (varies by altitude / airspeed / temp / mixture / type of fuel / ...)
- the instantaneous weather conditions
- the performance characteristics of either plane.
- slack in the rope (no tension to two times the weight of the glider)
- the glider's towing position (below / above wake)
- crosswinds
- the glider's preferred towing position (depends on visibility from the cockpit, e.g. if someone has a phone or a tablet on the dash, the towing position will be different)
So it isn't really a trivial problem, especially when false positive or false negative will lead to a crash.
Oh btw, it needs to be able to react in milliseconds (so no AI, unfortunately). Here's an example of what an early release looks like btw: https://youtu.be/Gu0mZC2mLEg?si=dzVMxG-rW5624T_m
notice how he's always on the stick. Also notice how fast it goes from stable to unstable positions.
> even a crash
Recklessness is never the answer in aviation (or coding matter of fact). Practically, good luck convincing insurance to cover a 100 ton (any appreciable cargo load) plane that might fall out of the sky on any property in the general vicinity.
In order to make such a contingency safe, we'll need swathes of ground that are clear of any population so that these things can crash without collateral damage.
If you have a corridor of land that's void of population between your origin and destination, then you might as well, you know, lay down some tracks or tarmac and get rid of the whole flying business altogether.
Now, if you have a body of water between your points this might be a better suited plan I think.
https://en.wikipedia.org/wiki/Messerschmitt_Me_323_Gigant#Me...
How are they planning to handle aborted takeoffs of towing plane, for example?
How does it integrate with ATC? During towing? During landing of glider?
This video claims that trailer is landing separately and autonomously. Obscure of details. https://www.aerolane.com/news/florida-2025-q1-tests
I sure wouldn't want to be on a Boeing 7XX flight with one of these things in tow. Just imagine the possibility for human and machine error, the plane in tow could cause all manner of issues for the leader.
Ever tried riding a bike and towing someone on another bike or a skateboard? It's perilous. Now do it in the air. Gutsy.
Probably a lot, but I'd assume it is by less than the fuel that 1-2x more planes would use, otherwise there wouldn't be a point to doing this.
A winched glider implements flight with renewable electricity and it does so efficiently because the power and motor never leave the ground!
A glider can climb up to 5000 feet and travel 50x that before making a landing. Wouldn’t it be glorious to see cargo being autonomously slung from site to site across the world, powered entirely by green electricity?
https://youtu.be/A-RfHC91Ewc?si=uMjPf00zqbJHfSwn
We are so smart that we can take good things and modify them in stupid ways to make bad things. This is, in fact, very smart of us.
Winch launching is already a thing https://youtu.be/U3ztaJ0yfxE?si=1AjAS8F8-pCaUFZI
I can see a big winch glider being worthwhile in some very limited circumstances.
Is a glider basically joinked into the air by a large and fast winch, and then detached and the glider glides on it's own "power" back to the landing? Or is the winch at the destination, with a cable going _all_ the way across the landscape to where the launch point is, so that it can pull the glider over?
I'm a tad confused.
On a day with a decent breeze, it is possible to "kite" a glider up to very high altitude by letting the wire out again. But this is highly frowned upon because it means there is a very long (and nearly invisible) wire dangling right through the airspace used by other aircraft!
Cable falls can be a problem. A cable falling over power lines causes all sorts of fuss!
Cable breaks can be terrible. The cable will spring back, whip around, and is incredibly destructive - hence the cage around the winch operator. I would not have been standing anywhere nearby and certainly not next-to or behind the drum.
Edit: so yes, your first thought is correct. :) It's somewhat similar to an aircraft carrier launch except that the glider can get a lot more altitude out of it.
Truck, you can load and send it much further than any glider can ever glide, any time, any day. Also throughput of highways is much bigger than airports, and you can deliver it literally to the target doors.
Not a very practical fantasy it seems.
Thinking on, specifying the weak links and managing failed winch launches (which happen fairly regularly) is interesting to consider. Recreational gliders are light enough to be manoeuvred by hand, although old farm tractors are used to move them more than a few dozen feet. How would all that work?
(Now that I mention it, why don’t carriers combine both catapult and ski jump?)
(Don't worry, reader, I never intended to get a pilot's license.)
I'm not sure if simple descriptions of the phenomenon that glide ratio is independent of weight are missing an asterisk or if I'm just wrong...
A decent glider has a ratio of 1:40, an A320 1:17. Is the A320 a "bad plane" or is it optimized for higher speed with the corresponding worse glide ratio? (It also has engines that produce a lot of drag when gliding)
On another hand, there are CFIs, the FAA, books, etc.
I've only found one search result that agrees with you, so far, and at least a dozen that disagree, but the one that agrees with you has no math in it, and the ones that disagree mostly seem to depend on the same source info, so that doesn't feel conclusive in either direction.
The Wikipedia page on lift-to-drag ratio also believes weight does not matter to the ratio.
As a side note, your 200km/h example also sounds like it's just not the correct angle of attack or airspeed for the aircraft, so I'm not sure if that example applies?
The Laminar profiles perform better, but only when uncontaminated (no bugs or rain). Contaminated turbulent profiles perform better than contaminated Laminar profiles. Since regulations state that you should carry fuel for the worst case scenario, it does not yet make sense to design airliners with Laminar profiles.
Naturally, manufacturers are looking for ways around this.
Eg: you wouldn't build a glider out of heavy material that gives you huge speeds but also huge sink rates.
So I think the entire glide ratio conversation mostly fits in the "your plane is fully loaded" vs "your plane is empty" scenario, and the point is that your best glide ratio will be constant, but you'll be gliding at higher speeds if you have more weight.
Here are a couple of many posts on the topic:
- https://gronskiy.com/posts/glide-ratio-lift-to-drag-and-weig...
NB/ spherical cows are unable to glide in a vacuum.
I guess another thing worth noting is that "glide ratio" isn't the same as "gliding" in the "flying a glider" context.
The space shuttle is probably the most famous glider, and was described as "a flying brick" and getting it to the ground at the right spot was very much a matter of glide ratio. Worth noting the space shuttle's speeds started off as hypersonic.
By comparison, a typical glider's built to be able to take advantage of air currents to regain altitude, and I'm not sure how weight affects that.
You can glide faster with the same L/D, so that might be worth it if you try to optimize for speed.
The minimum speed, at which the critical aoa is reached, increases. And therefore the take off and landing speeds.
It does sound unlikely, and it's not like the comment is saying "no f'ing way!!" It's about as polite a way to say "that's weird" as anything.
And if you had a track for the cable to run in or a carriage holding the winch to drive travel along, then you would just make it rail freight.
If you're really in a hurry you need a helicopter. Then pay your indulgences to some politician's shady "carbon credit" corporation if you feel guilty about your climate sin, or use a carbon-neutral manufactured kerosene for it, and then you're even greener and still cheaper than the unpowered spruce goose idea.
This means the consist is capable of taking off on the same runways and with similar climb profiles as the primary tow plane is alone."
This is just denying basic physics. Ask any glider pilot how the climb out on aerotow varies based on the weight of the glider being towed.
For many planes under good conditions (high density, high headwind) acceleration to takeoff speed isn't the limit, but only airframe strength. Under those conditions, you could tow significant extra weight. The existing fleet of older planes includes many that have had engine upgrades, so they can pull a lot more weight than their MTOW.
Runway length has to include room for a rejected takeoff, for when the engine loses power just before you get to rotation speed. I don't think it'd be fun to try to reject a takeoff with a heavily loaded cargo trailer behind you. The trailer must have its own brakes, but it sounds scary.
If you can leave all the endurance for cruise and main climb to the lead plane, electric becomes almost trivial.
Airbus concepts like fello'fly[1] and GEESE seem significantly safer. I could see using something like a lead aircraft with several drones following in formation and breaking off for takeoff and landing operations. Reliable Robotics is already working on autonomous small cargo aircraft for these types of regional cargo operations.
[1] https://www.airbus.com/en/innovation/future-aircraft-operati...
"When towing Aerocarts, planes instantly double or triple their payload capacity. This is because their capacity is limited by the takeoff / landing weight – not what they can safely pull through the air."
But later, on "How it works" section it is apparent that the main plane still has to tow the cart behind it when taking off. What's the trick that makes this work? Extra set of wings?
________
* - someone who has an interest in aviation, but no professional background or training therein
Case 1) how are you handling potential rapid TCAS climbs/decent? You're making the targets a lot larger and less responsive. If TCAS commands a decent and slow down, you will be overtaken by the tow.
Case 2) landings thay require rapid braking, such as short runways for emergencies or engine fires (rapid brakes used so emergency vehicles don't have to chase 2km to get to you)
Case 3) aborted take offs. Brakes will need to be more performant and reactive than the ones we have on the main aircraft
Case 4) taxiing across active runways now has reduced margins.
Case 5) go-around performance is diminished. Already sometimes tight margins on that, what happens if you need to do a go around but the landing gear on the glider collapsed and is now a ground anchor?
I'm no aerospace engineer but it seems like it would be more efficient to fly one single bigger plane than to tow a second one behind it. I suppose this might appeal to certain groups where they already own a plane, and want to increase capacity without buying a whole new plane. But the idea that it's 65% more efficient just seems pretty sketch. I could totally imagine some drug cartels using these though...
Your towing plane is going to have to accelerate the same mass to takeoff speed before it can get off the ground, no?
Plus there's an interesting wrinkle here: a lot of the media on the site show the tow plane as one with engines, and not a glider. I'm sure that's because those are the aircraft they could get their hands on, so that's what they made it work with, but the option is there to have the towed plane powered on takeoff. Doing that safely, with the two aircraft tethered... that sounds like a mess. But it's an option!
Even assuming a full size one doesn't fatigue off the tail of the lead plane, presumably any time a plane towing one gets into difficulty, the first thing they'll do is cut the towed thing free.
Also the website sounds like it was written by an over-caffeinated estate agent.
“Oh sh1t!” at 35K feet.
It mentions it has a form of automated control in the tow with "Aerolane's patented Pilot Positioning Assist systems"
* what's the point of landing in tow? The safety aspects and the failure modes are enormous
* it's unclear where the 65% fuel saving comes from. Riding the wingtip vortex on the inside produces downward momentum. In order to generate positive lift from the wingtip vortex, the follower has to be outside of it (e.g., gaggles of geese in wedge formation)
* taking advantage of wake flows, while possible (although 65% is highly improbable), would always be less efficient than optimizing a single airframe so that it minimizes the wake generation in the first place
* the site is missing footage of real flights. The 3 clips 10-seconds long are not showing what they claim to be showing. Also, does the "see flight tests" link work for anybody?
65% are almost easy to achieve, with a bit of clever accounting: you'd look at fuel per ton-mile (that much is clear and perfectly fine) and then you just pick a tow plane that's maybe a bit overpowered but doesn't have much cargo capacity. If you look at fuel saving through that lense, the sky is the limit.
The contingency page in the pitch deck for when the "bigger plane is always more efficient" argument comes up would be looking at big end of the hypothetical size spectrum: when you want efficiency, a bigger plane means bigger wingspan. Air travel is in something not too dissimilar to the "panamax" situation on the oceans, everything on the ground stops at 747-sized (the A380 was carefully squeezed to mostly fit that profile). A formation can get a similar effect as a larger wingspan without exceeding runway dimensions.
(and as for landing in tow: perhaps some stupid legal angle, "it's all fully automated, but technically this is not autonomous because the lead aircraft pilot is in charge"?)
If the tow plane lands second then it needs to loiter, gliding autonomously, for as long as it takes for the lead plane to land and get out of the way. And that sounds like a much harder problem to do safely, particularly with the lead plane's pilot having to pay attention to landing and unable to control the tow plane if it gets into a dangerous state.