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Aerocart cargo gliders

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Re: Aerocart cargo gliders

#81

Post by satiated_grue »

dmitrygr wrote: post #12

Tow-plane pilot for gliders is a dangerous profession. A simple mistake by the glider pilot can kill the tow plane pilot, with not enough time to react. I saw this happen in person once ( https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/G... ). Gliders and towing them is neither easy nor safe.

I was always amazed that the idea of towing a plane with three other planes (the "Troika-Schlepp") was not only conceived, but performed.

https://en.wikipedia.org/wiki/Messerschmitt_Me_323_Gigant#Me...

https://ww2talk.com/index.php?threads/glider-towing.22518/

Re: Aerocart cargo gliders

#82

Post by rkomorn »

roeles wrote: post #74
rkomorn wrote: post #69

Earlier quoted context omitted.

I assume it is a relevant enough concept to flying an aircraft (which also happens to be the context of TFA) that you learn about it while flying. 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…

Weight affects speed with minimum sink. That affects the diameter of the circle you fly. Since thermals have more lift towards the center (assuming perfectly circular thermals), you are not able to circle in the strongest lift. So you climb more slowly. You can glide faster with the same L/D, so that might be worth it if you try to optimize for speed.

Intersting! Thanks for chiming in. :)

Re: Aerocart cargo gliders

#83

Post by rkomorn »

hermitcrab wrote: post #58
rkomorn wrote: post #47

Earlier quoted context omitted.

"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.)

So, 2 gliders with identical geometry, one standard and one made of lead will have the same glide angle? That sounds unlikely.

I don't get why this got some downvotes.

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.

Re: Aerocart cargo gliders

#84

Post by jmiskovic »

I don't understand?

"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?

Re: Aerocart cargo gliders

#85

Post by beAbU »

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.

So now we are dropping shipping containers with wings out of the sky when things go south with the towing.

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.

Re: Aerocart cargo gliders

#86

Post by wildzzz »

jmiskovic wrote: post #84

I don't understand? "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?

Yes, the wings of the glider provide lift that otherwise would not be present. The engines still need to produce more thrust to pull the glider but that's expected, the extra cargo doesn't come free.

Re: Aerocart cargo gliders

#87

Post by xhkkffbf »

plasticchris wrote: post #78
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.

Traditional gliders also carry ballast for cross country flights, which increases their speed without negatively impacting their glide ratio.

Really? That seems counter intuitive.

Re: Aerocart cargo gliders

#88

Post by wildzzz »

hermitcrab wrote: post #67
rkomorn wrote: post #65

Earlier quoted context omitted.

There is an asterisk that you have to be at the right glide velocity, but yes: they'll have the same glide angle. The leaden one will just go significantly faster. And yes, it does sound unlikely. That's why I made my previous comment. Here are a couple of many posts on the topic: - https://gronskiy.com/posts/glide-ratio-lift-to-drag-and-weig... - https://skybrary.aero/articles/glide-performance

Thanks for the links. Weight may cancel out of the equations, but (being a bit pedantic) I suspect 'glide angle in independent of weight' only holds up to a point. Taking things to extremes, if the glider is heavy enough that you are going to have to go supersonic then I suspect a lot of the assumptions become invalid. NB/ spherical cows are unable to glide in a vacuum.

Make a paper airplane and drop it. It likely won't go much further than your feet. Throw it gently and it will go some distance. Throw it harder and it will go further. Glide ratio is the horizontal distance over vertical distance. The vertical distance is the product of (lift - mass)*t^2 where lift is a function of the shape of the wings and the airspeed. So given a higher mass and the same lift, the time to hit the ground will be less when the glider is dropped at 1000ft. Increase the airspeed and you'll have more lift to negate the higher mass. The increased airspeed also means your horizontal distance will be covered faster. The lead glider will travel the same path as the normal one but will be going a lot faster. The reason why gliders are built as light as possible is reduce the work required to lift them, the speed at which to release them, and the interia required to turn them. You also have the benefit of being able to land them at a lower airspeed without injury.

Re: Aerocart cargo gliders

#89

Post by wildzzz »

stinkbeetle wrote: post #49
wiml wrote: post #38

Earlier quoted context omitted.

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.

It would work fine for sending small payloads short distances but unless you're in a hurry, it would be much easier to just send more mass by truck or train. One big benefit is having a truck or train being able to return to its origin without requiring another launch facility and also being able to travel in nearly all weather. There may be some use cases where drone gliders could airdrop payloads and return to their origin. But again, this requires very specific circumstances like good weather, a lack of roads, unavailability of av gas or jet fuel, and enough cleared space to launch a glider. I do see winches as a good way to launch lightweight fixed wing drones to reduce the amount of fuel and engine size required to deliver payloads. You'd only need to account for the fuel and power required to sustain cruise if you could winch a drone into the sky. You'd get even more distance if the drone was never intended to return like a kamikaze weapon. A small clearing in a field in Ukraine could launch cheap fixed wing kamikaze drones all day long.

Re: Aerocart cargo gliders

#90

Post by renewiltord »

bombcar wrote: post #70
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…

The we simplify it by putting the winch on rails, and give the glider wheels, then we can chain them together and then we’ve reinvented the railroad, badly.

Yes, then we could put wheels on my grandmother and we would have invented a bicycle badly

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

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