JBee
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- JB
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Regarding inertia on a plane. To range extend our EVTOL UAV fleet we use climb and glide to add around 10-15% range. For a winged aircraft propulsion is only required to maintain altitude and velocity, if the motor is switched off you can maintain velocity with the glide angle alone at the expense of altitude. Unlike motor propulsion through a prop, inertia is 100% efficient in glide. Further best motor and prop efficiency equals most efficient climb rate, which on most aircraft is not the same as its cruise speed.
This means that by using a climb and glide flight profile you can add potential inertia by converting stored energy through the motor/prop at the most efficient climb rate. Then you can use that inertia to glide until the next climb. Prop folds back to reduce drag in that period and there is absolutely no regen required. Its basically bunny hopping.
Regen for autorotation is possible, but unlikely to yield meaningful energy on a rotorcraft as the intention of autorotation is to land safely in a motor failure emergency, which is very short range and is not to charge your battery up.
Likewise regen for a forward flight winged aircraft will also convert more energy into turbulent air losses than recover in battery energy. You're better off using the stored energy of altitude to propel your flight in glide to extend your range, by simply starting your decent earlier, and therefore not convert energy back and forth and simply keep the energy stored instead.
Another way to visualise the energy flow is to imagine an ebike on a hill, would the rider get further by letting it roll, or regen down the hill and using the recouped energy to drive along the straight?
Airline flights typically start their decent a few hundred km from their destination for this reason, its only in the last phase when they are at low altitude (and low energy potential) and preparing for landing that they deploy flaps, primarily to increase lift at lower speeds which they require to land without ripping off their undercarriage. Air brakes are typically only used to increase their glide angle so they don't overshoot the runway threshold on approach because they stuffed up the decent phase or because of local wind. Typically its preferred to use the motors on approach to reach the threshold, simply because motors are not limited to extend the glide slope but air brakes are. Using regen is like air brakes.
Therefore one would assume that the only meaningful use of regen on a aircraft is to artificially increase glide slope for a steep landing decent and approach, for a space constrained landing (terrain or noise related - regen might be noisier tho?) but not in any way to improve efficiency or range.
(PS Essentially, for all intents and purposes, altitude can be considered energy storage in itself with very high conversion efficiency to useful range)
This means that by using a climb and glide flight profile you can add potential inertia by converting stored energy through the motor/prop at the most efficient climb rate. Then you can use that inertia to glide until the next climb. Prop folds back to reduce drag in that period and there is absolutely no regen required. Its basically bunny hopping.
Regen for autorotation is possible, but unlikely to yield meaningful energy on a rotorcraft as the intention of autorotation is to land safely in a motor failure emergency, which is very short range and is not to charge your battery up.
Likewise regen for a forward flight winged aircraft will also convert more energy into turbulent air losses than recover in battery energy. You're better off using the stored energy of altitude to propel your flight in glide to extend your range, by simply starting your decent earlier, and therefore not convert energy back and forth and simply keep the energy stored instead.
Another way to visualise the energy flow is to imagine an ebike on a hill, would the rider get further by letting it roll, or regen down the hill and using the recouped energy to drive along the straight?
Airline flights typically start their decent a few hundred km from their destination for this reason, its only in the last phase when they are at low altitude (and low energy potential) and preparing for landing that they deploy flaps, primarily to increase lift at lower speeds which they require to land without ripping off their undercarriage. Air brakes are typically only used to increase their glide angle so they don't overshoot the runway threshold on approach because they stuffed up the decent phase or because of local wind. Typically its preferred to use the motors on approach to reach the threshold, simply because motors are not limited to extend the glide slope but air brakes are. Using regen is like air brakes.
Therefore one would assume that the only meaningful use of regen on a aircraft is to artificially increase glide slope for a steep landing decent and approach, for a space constrained landing (terrain or noise related - regen might be noisier tho?) but not in any way to improve efficiency or range.
(PS Essentially, for all intents and purposes, altitude can be considered energy storage in itself with very high conversion efficiency to useful range)
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