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Aerocart cargo gliders

aerolane.com

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Re: Aerocart cargo gliders

#41

Post by gervwyk »

cirrus3 wrote: post #25
bigwheels wrote: post #24

Earlier quoted context omitted.

Also, how much does it decrease the fuel economy of the towing plane? 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.

> how much does it decrease the fuel economy of the towing plane 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.

I did a masters on design a autopilot to optimize fuel consumption in formation flight. What is interesting about the aerodynamics is that if placed in the upwash wake of the leader, you are essentially increasing the wing aspect ratio of the system, resulting in gains for both the leader and the follower aircraft. Feels very unintuitive but basically the donut spool is larger and the combined wing is bigger in the spool.

Re: Aerocart cargo gliders

#42

Post by aseg »

tgsovlerkhgsel wrote: post #27
aseg wrote: post #21

Earlier quoted context omitted.

In gliding, tow upsets are pretty common and, in rare cases, can be fatal. An out-of-position glider out can _easily_ and very quickly overcome the tow planes elevator authority (ability to pitch up or down) which leads to accidents like this. This video does a good job explaining explaining the root causes and potential dangers ( https://youtu.be/5cpqFzhM9dY?si=J7GxP1dI9Xopy3xu ). Also read the comments from testimo…

> An out-of-position glider out can _easily_ and very quickly overcome the tow planes elevator authority 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.

The force at the attachment point is constantly changing and depends on several factors.

- 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.

Re: Aerocart cargo gliders

#44

Post by eptcyka »

gorgoiler wrote: post #35

This product is for towing behind another aircraft, but what about winch towing? 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…

Traditionalcgliders are incredibly light, I doubt anything careying sufficient cargo will be able to do a 50:1 distance to altitude ratio.

Re: Aerocart cargo gliders

#45

Post by roeles »

eptcyka wrote: post #44
gorgoiler wrote: post #35

This product is for towing behind another aircraft, but what about winch towing? 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…

Traditionalcgliders are incredibly light, I doubt anything careying sufficient cargo will be able to do a 50:1 distance to altitude ratio.

Glide ratio and weight are not related. Weight shifts the glide Polar to higher speeds and theoretically improves it slightly due to Reynolds effects.

Re: Aerocart cargo gliders

#46

Post by tdeck »

jayde2767 wrote: post #18
drpixie wrote: post #2

Really? Those who have had anything to do with gliders know there is plenty that can and will go wrong. Landing on-tow !?!? And what's the benefit - they might save a little in cruise, but they've got to get there (safely) first?

Not to mention, what happens in the event of damage to the towed aircraft rendering flight operations impaired such that it affects the towing aircraft? “Oh sh1t!” at 35K feet.

Better there than at 200 feet.

Re: Aerocart cargo gliders

#47

Post by rkomorn »

roeles wrote: post #45
eptcyka wrote: post #44

Earlier quoted context omitted.

Traditionalcgliders are incredibly light, I doubt anything careying sufficient cargo will be able to do a 50:1 distance to altitude ratio.

Glide ratio and weight are not related. Weight shifts the glide Polar to higher speeds and theoretically improves it slightly due to Reynolds effects.

"Weight doesn't affect glide ratio" is one of these things I learned why taking flying lessons that still feels counterintuitive every time I read it.

(Don't worry, reader, I never intended to get a pilot's license.)

Re: Aerocart cargo gliders

#48

Post by usrusr »

chimpontherun wrote: post #33

This concept raises more questions than the site answers: * 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…

Taking an "optimist's advocate" position here (I share your scepticism):

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"?)

Re: Aerocart cargo gliders

#49

Post by stinkbeetle »

wiml wrote: post #38
stinkbeetle wrote: post #37

Earlier quoted context omitted.

Do you mean laying out 50 mile long cables from place to place with big engines on the ground that pull in a cable at a couple hundred miles per hour after a plane attaches to it? That wouldn't work. Not even if you skipped tow out a cable from your departure point so it could be reused. 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 r…

No. Winch glider launches (which are not a new thing) use a ground-based winch to give the glider an initial impulse, and the glider uses that to gain altitude and then glide for a much longer distance. https://glidingschool.com/briefing-winch-launch/

Well then it's even simpler, carrying any worthwhile amount of cargo in a winch launched glider is not going to work.

Re: Aerocart cargo gliders

#50

Post by Ruarl »

gorgoiler wrote: post #35

This product is for towing behind another aircraft, but what about winch towing? 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…

I'm the wrong kind of engineer to work it out, but I'd be interested to know what the implications for the strength of the cable and specifications for the winch would be for a heavy cargo glider.

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?

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