mdrejhon

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Everything posted by mdrejhon

  1. The million dollar question is what “very short time” means. There are some lithium batteries, where upon short circuiting it, it takes a long time before it becomes a conflagration — the chemistry, the construction, etc. Whereas, others (some unprotected lipos) will just simply expand / explode almost right away. If you have any experience watching some of the battery tests of the more slow-cascading lithium battery designs, you’d realize that it is possible to design it in a way that it would take long enough before temperatures/expansions raised to structure-failure levels. There are designs that give enough time for landing before structural failure, at some cost of battery density. Lithium battery self-destruction rapidity varies all over the map. Sometimes a Tesla screen have displayed a warning more than half an hour before the first flames occurs; so there is some precedent to the ability to warn in advance of a potential impending battery fire as well; those are often reported more often than fuel fires which also happens to airplanes as well; (also consider many vehicle lithium batteries — not just Tesla — apparently has had way, way more active monitoring of all the battery sensors than the lithium battery in the first flawed A380 design). But yes, this will probably be a major item of FAA approval. The fire incidence must be acceptably low with a wide margin of safety for the public to accept electric aviation — both from a frequency perspective and also a warn-in-advance perspective.
  2. That's going to be a big purpose of advocacy. We need more accountants, pilots, mechanics, etc, working on this -- testing out scenarios, crunching the numbers, visiting Magnix, monitoring the news, etc. Then that way, I can shut up, and let everybody's numbers speak for themselves. P.S. (edit) One thing to keep in mind is that jump capacity scaleback, if any, is likely temporarily minor. For a "trial" it is probably only 1 electric jump plane at a major dropzone such as Perris or Deland. Preferably 2025 intead of 2030. By the time a whole jump plane fleet goes electric, it would be long into the 2040s or beyond where there is no longer notable capacity compromises.
  3. That's fair. Let's get more data over the coming months/year to back up this better. I agree that we need a lot more data. The other point I want to point out is it's not exactly that irresponsible to say this, is that at $6 per load, one can scale back the skydvers quite a bit to restore a lot of climb performance and then still make a profit. Still hugely more proftiable than a C182... A 9-person slightly-slower climb (11-minute instead of 8-minute) Electric Caravan could perhaps work just fine on dropzone accounting if the fuel-up is only a few dollars (whether $6 or $30). Yes, slower turnover than an avgas carvan that way -- but sooo much cheaper operationally when also considering the lower maintenance. The goldilocks spot is simply calculated by the cost vs time, which might turn out to be a number similar to that -- less than max load, but quite usable. Something that climbs fast enough with those Early Version 1 Jump Batteries. Which can be later be replaced in five years (in subsequent ePlanes, and in battery replacements in a decade) with a lighter Version 2 to increase jump capacity later. The improved profits can be saved towards such inevitabilities, in theory. By 2030 it looks highly probable that no skydiver-load-scaling-back is necessary.
  4. This is a good point. That said, keep in mind that battery fires start more slowly than fuel fires -- enough time for people to exit the car many minutes before exiting the airplane. Regardless, the design of a battery fire should be sufficient to allow the plane to quickly glide to landing before the battery fire consumes the plane. They will likely avoid lithium polymer (lipo) for an electric airplane because they can be more explosive. Most other lithium batteries (the Li-On ones used by Tesla) slowly heat up and smoulder gradually, so it would take more than 10-20 minutes of smoldering before fires. Design of a battery fire safety will be important. [replying to the other points out of sequence, keep tuned]
  5. Lithium batteries are already highly modular and this is probably a shoo-in feature. Left wing battery, right wing battery. (Ooops, forgive the political puns -- I know this ain't Speaker's Corner). Keep in mind that a Tesla car has more than 1,000 separate laptop batteries in it, and a charge controll activates/deactivates each and every one of them based on imminent failures. An airplane will need more partitioning/firewalling of this, but a large lithium battery is already automatically modular -- they just will have to tree-subdivide it appropriate for aviation: - Cell level & individual cell sensors - Pack level & individual pack sensors - Cluster level (cluster of packs) & their emergency cutoff switches It's only a simple architectural detail for modern large lithium batteries nowadays, as a simple subdivision matter. Three clusters is probably ideal -- left wing, right wing, and underfloor. The underfloor could be a reserve battery. Also, the Magnix motor can theoretically be used as generator for regen descents, recovering between 5%-10% of the energy. The electric trainer already can capture up to 13%, although student pilots find it scary to dive that deep. But jump pilots don't mind doing steep descenbts, so wouldn't mind a bit of regen (if the location's electricity rates are expensive). The kicker: The Magni500 consumed about $6 worth of electricity during the Grand Caravan’s 30min test flight, he adds. At those prices, we could essentially forget about regen. Even a 6-skydiver Caravan load can already be profitable -- since motor longevity is stellar, assuming good battery longevity. But by the end of this decade, I don't think we even need any capacity reductions.
  6. I'm not surprised. Weight is a super-fast moving target. It's not a problem to have a light battery but you want a long-lasting battery, so you need a great cooling system. A 750kW-output capable battery needs great longevity. The technology for such lonevity has finally arrived, but the devil is in the details. The point being -- supercar electric cars are already racing at sustained 750kW on the racetrack using a battery lighter than the fuel load of a fully loaded Caravan!!! The first megawatt supercars came out six years ago. (One megawatt = 1340 horsepower). Since then, they've finally found ways to sustain-output more than half a megawatt for many minutes (>10 mins) -- long enough for a jump lift! The "C" problem a solvable problem; the problem is making the battery longevity good through creative cooling systems and heat monitoring systems (Tesla has succeeded in durable 1C-3C batteries on the racetrack, but we need twice that for sustained Magnix operations). The Tesla battery has more advanced temperature monitoring and charge monitoring than the Airbus A380 battery does. It's quite dismal how Airbus designed that first version compared to Tesla did to their batteries -- several thousand temperature sensors & several thousand charge controllers -- in those older 18650-based Teslas. The safety industry standard is 1 temperature sensor per cylindrical battery AND 1 temperature sensor per battery pack, as a double-redundancy, and always leaving a healthy SoC at the top/bottom ends of the range. And a Tesla (original) consists of thousands of 18650 laptop battery cells -- so that's thousands of temperature sensors. The Tesla charge controller quickly isolates bad cells in a best-effort. Also, there were some major charge management mistakes done in the A380 batteries. Now Tesla's moved to 2170's and soon 4680's. Other battery manufacturers are finally copying the incredible battery monitoring breakthroughs that Tesla paved, and will be important for ePlane safety. It's amazing how beat-up Tesla batteries are; no wonder they catch fires (but less often than gas fires of gas cars). Airplanes are treated more gently than cars, not having to deal with shocks of potholes and curb-bumps as often -- so just like electric cars catching fire less often than gasoline cars -- but, yes, they need to design electric airplanes to catch fire less often than avgas planes -- for trust of the public. Given length of aviation approvals, it will take time, and one will have to migrate to safer lithium chemistries, and build enough safety margin. However, experimental trials should proceed sooner than later in preparation for the incredible economics of an electric jump planes so advocacy should begin sooner than later. We don't have to use Tesla batteries but we have to compliment the brilliance Tesla brought to the table for other lithium battery manufacturers. You can already cram the weight of 2 Tesla batteries including cooling weight equivalent (~200 kWh for 1.5 megawatt surge output, easily 750 kilowatt sustained) for the same weight as a fully tanked Caravan load. Obviously, we would use something else other than Tesla, as not as much cooling weight is needed due to cold altitudes -- but it all mathematically checks out already. Supercar batteries are often lighter for higher power output, since their longevity doesn't matter as much as a Tesla, I simply use Tesla as a gold standard since they're pretty long-longevity batteries. Now, power-wise, if we assume full max throttle 750kW for 8 minutes for a hurry-to-altitude, that will consume ~50% of a 200 kWh battery that fits within the weight of fully fueled caravan assuming we go by the latest weight data (lighter 4680 based architecture, under 2200lbs for 200kWh including water cooling -- unlike 2760lbs for the 18650 based architecture at 2x1380lbs for a Tesla P100D battery doubled-up). That leaves 100kWh for emergency reserve. This is only napkin math at this stage -- but it shows this is all really within a stone's throw already, with even the lower capacities. That's today's technology, only 200kWh per kilogram, including cooling. We haven't begun talking about tomorrow's 300-400kWh per kilogram implementations, yet. Consequently, I'm pretty confident a long-lasting jump battery is a very solvable jump lift problem before 2030 -- the writing is on the wall. Yes, the battery weight is a fast moving target due to many variables (chemistry, cooling, etc)
  7. On this point, I agree, more information from the industry will be welcome to execute better mathematics. Are there any pilots here that would be willing to help me run the mathematics on various types of battery packs (Tesla scenario, LiFePo4 scenario, current 250kWh/kg scenario, future 300kWh/kg scenario, future 400 kWh/kg scenario) I will get partial data from Magnix but because battery technology is an amazingly rapidly moving target (Thanks to Tesla lighting a fire under everybody who makes lithium batteries), we will have to do calculations separately on the hypothetical battery packs. On this point, I disagree it is inconsequential because the mass difference will become much more major as 2020 progresses towards 2030, as explained in three previous posts -- In a "Designbattery for one skydive + 30min reserve" scenario (between-jump fast-recharging), the amount of battery for one skydive will become smaller/lighter, as an increasingly tinier percentage of a fully fueled load. Yes, it will still be heavier than the equivalent fuel for one skydive (partially fueled plane), but regardless, a full or near-full flight with full load of jumpers should be achievable, in this "design for one skydive" scenario. The sufficiently powerful motor is already here, and there likely should be advocacy / trials even before the expected battery improvements that dramatically changes the mass savings. This isn't nuclear fusion perpetual "won't happen for another 20 years" fantasyland stuff.
  8. That assumes sustained average (steady highway speed, like level flight) A Tesla pack can discharge at approximately 5C to 10C in Ludricious acceleration mode, and typically discharges at 2C-3C during brisk acceleration starts by regular drivers. Yes, you heard me right -- a Tesla 100 kWh battery output more than half a megawatt! And that's using the laptop batteries they used before the 4680 battery. It's mainly the battery temperatures you have to worry about but the climb to altitude is short enough, with plenty of cooling opportunity afterwards during the descent. Teslas are also used at the racetrack now, with the Racetrack Package (on the existing battery pack), which allows sustained high-C operations far longer than a jump lift. Besides, Magnix already confirms that output is not the weak link for a fast climb to altitude. The descent also allows enough time for the battery to cool down before being charged, assuming the use of battery cooling mechansims including good heatsinking to the wings. The Tesla Model 3 Racetrack Package allows a Tesla to do sustained >1C output, typically 2C-3C output with automatic battery heat management -- color coded battery heat is shown on the screen during racetrack use. That's the same Tesla battery, unmodified. The Racetrack Mode pushes the battery very hard for much longer than a Magnix will need. For a faster climb, you will have to size the battery for more frequent sustained 750hp (500kW) to use the full power of the Magnix, but it's quite within the realm of today's batteries. A Cessna Caravan accomodates about 2224lbs of fuel. One Tesla battery pack (capable of 750 kW surge output) is only 1000lbs-1400lbs. (List of Tesla battery weights, including cooling systems). The older P100D (100kWh) battery pack was 1380 pounds using the laptop 18650 batteies capable ot outputting half a megawatt aggregate in Ludricious Mode -- but the 2170 battery based ones were lighter, and now newer Tesla 100kWh batteries using the 4680s are reportedly far closer to 1000 pounds for 100 kilowatt hours including cooling. Obviously, it is not an apples-vs-apples, but the point being is -- batteries lighter than the fuel load is capable of fully powering a Magnix motor -- including the weight of water cooling. Now that specific doubt out of the way: If they design to instead heatsink to the airframe with a bit lighter water cooling, then some weight savings can be had, given the higher airspeeds of colder air at altitude (precisely where the battery begins to heat up -- a while after takeoff and on a fast climb to cold altitude). Perhaps it pushes today's batteries hard, but 750kW is definitely within the envelope of "Tesla style" battery architectures -- though one may want to upsize by 2x while including the water cooling that Tesla battery packs use -- to allowed about 5 minutes of sustained 750kW. But even airplanes don't always sustain maximum horsepower for 100% of the climb, as pilots often taper that of a bit after the takeoff roll, for turbine longevity purposes (so not all 900hp is all in use for the entire duration of climb to altitude). But you see, the "C" problem is already actually mostly solved -- however, battery longevity might be down (e.g. like maybe too few flights -- i.e. only 3-5 years of flights) until upsized a bit -- though the improvements made by 4680's longevity and other similar lithium battery technologies by others (competitors propelled by Tesla innovations). One problem is that Tesla is a bit ahead of competitors in charge management and battery heat management. It's a bit hard to get large off-the-shelf lithium batteries that can charge/discharge as fast as a Tesla battery (multiple C) without longevity-shortening effects. With the great battery management they use to detect and isolate bad cells within packs -- the Tesla battery management systems behaves like many thousands of concurrent battery chargers. Such technology is now being introduced into other batteries The cooling tech is part why batteries last longer in many electric cars longer than the batteries in R/C airplanes. That said, battery technology is improving extremely rapidly. Over the course of 2020-2030 will solve any remaining "C" problem (heating, cooling, supercharging, easier to downsize battery, etc) of a one-skydive-sized battery that doesn't need to be bigger/heavier than it needs to be. However, the suitable jump plane electric motor is already here, and it should be tested/experimented by pilots for simulated jump ops. Tests can be done while the skydiving world awaits jump operations. See my Advocacy post.
  9. I never said that -- you remember incorrectly: Scroll back to the post, and re-read: "That battery, today, already appear to weigh less than a full fuel load, for some aircraft specifications" So repeating the points: We only need between-load recharging of the batteries between loads; We only need one skydive's worth of batteries, plus 30 minutes reserve; Yes, the partial-batteries will weigh more than the equivalent partially-fueling; However, the partial-batteries will weigh less than a fully fueled airplane. For more concrete numbers, there are questions I need to ask the electric aircraft makers. Roei (CEO of Magnix) has agreed to be interviewed for the Parachutist electric jump aircraft article I want to collaborate on -- so before I send them, I have to discuss with co-authors if they're good questions. Don't worry, I won't be publishing anything unsubstantiated in that article. (Additional coauthors and proofreaders welcome, contact me)
  10. ...I should also add that the fuel weight lightens as you burn, the battery weight does not. But the efficiency gains over the short time period of getting to altitude are apparently significant enough to overcome that variable. It is a big factor for longer flights, rather than the few minutes to altitude where plane lightening is often only essentially a low single-digit percentage of plane total mass, and in many cases under 1% for some fully loaded airplanes. For the short 8 minutes to 10 minutes to altitude, plane-fueload-lightening is sufficiently small enough (as % of plane mass) that the sheer efficiency of an electric plane motor wins out, by affording pilot more flexibility to milk the airframe/prop settings instead. A turbine can go much less efficient at certain airframe settings despite being physically airflow efficient, but RPM/torque inefficient for the turbine (burning more fuel). Thus, the goldilocks airframe/prop settings range is smaller on the same airframe for a turbine than for an electric re-engining on the same airframe. The electric stays efficient at a wider range of torques & RPMs, so you can work the propulsion efficiencies more physically (pitch, flaps, etc) than worrying about hitting the motor-efficiency sweet spot. Worry about milking the laws of physics of your airplane, more than worrying about fuel buen. The efficiency gains of optmium settings far exceeds the 1% airplane mass lightening from fuel load burn over the short timescales we’re talking about. We lose out over avgas for longer flights, but this becomes a mathematical win-win for jump operations which are just short flights. The assumption made for longer flights is silly as the sheer shocking short-flight efficiency of an electric flight wins out. So battery deadweight is far less of an issue for a smaller 1-skydive-designed (+30min reserve) battery than for trying to mimic a fully 100% fueled airplane.
  11. Scientific fact: It’s worth noting — ignoring airplanes — that the energy required to lift a mass X against gravity Y from height A to B — is mathematically a fixed amount of energy in the ideal case regardless of the velocity of lift from altitude A to altitude B. Things like friction (air friction, water friction, rolling friction, etc), acceleration/deceleration differences (at beginning/ends of the gravity journey, if acceleration energy is not recaptured), and also motor efficiencies make the gravity-lift math less ideal. Also, for simplicity, we can effectively ignore gravity gradients (high altitudes have a tiny bit less gravity) or theory of relativity as they are not meaningful error margins at current physical speeds and current altitudes being discussed. Now in the case of airplanes — improve the variables (e.g. efficient flexibility of motor at all power settings) so absolute airframe & propeller efficiencies can be better milked. A plane cannot solve all weak links breaking the ideal (friction is always with us) but it also explains the concept of less battery differential versus fuel differential — getting a tiny bit closer to the ideal formula dictated by laws of physics. This may not be significant for some airframes but is more for others, but regardless, it’s generally possible to achieve a smaller consumption difference (% difference of slow-vs-fast altitude gain) for an electric for a given altitude gain A to B on the exact same airframe.
  12. (re: noisefloor = I meant “lost in the midpoint of the varying time-to-altitude statistics of all dropzones worldwide”. I should not have tried to summarize that into one word, apologies) For the specific 10%-20% (yes, wholeheartedly unscientific estimate) is based on previous world experiences in other electrifications — electric cars, radio control airplanes, etc. They drive similar speed and fly similar speed and climb similarly performant at similar weights. In lots of cases, the electrics outperform in raw performance (witness the electrics beating petrol speed records in some domains). Also, skydivers will become impatient if the plane climb noticeably slower than other planes in the fleet. 10% slower climb isn’t really noticed by everyone in the load, but a 50-100% slower is definitely noticed by the whole load. But here’s some scientific observations, that actually brings credence to the point I’m making: The math is a sudden viability line: Change the battery numbers a bit, and things suddenly go from “Can’t meet MTOW” to “I can fly quickly to full jump altitude”. Given the small envelope of a single jump lift, the fuzz region is actually much smaller than many people think, since a slow-vs-fast climb isn’t that terribly a large watts-hour delta in the Magnix tests (you consume less power but consume longer ... It is less variable in “power-consumed-per-foot-gain-of-altitude” with electric than with avgas, simply by virtue of the electric motor being efficient at all RPMs. (Yes, you have to correctly set your flaps and optimal prop pitch and all, to avoid wasting power in an inefficient climb, but once optimal, it is more balanced than for avgas. A slow optimal climb vs fast optimal climb isn’t as much battery watt-hours consumed differences as the fuel-consumed differences because of the efficient-at-all-RPMs behaviors that make it easier to dial the optimal climb. Putting more of the motor’s energy more efficiently into the climb — Turbines are most efficient at a specific settings, while electrics are efficient at nearly all settings, giving pilot more flexibility to focus more on adjusting the plane’s surfaces to optmium prop/airframe settings, rather than optimizing the plane to meet the efficiency at the performance settings of a specific turbine motor. So, the slow-vs-fast climb matters less since it’s a fixed altitude gain, you’re paying energy a more stabilized amount of energy per foot of gain, you’re paying energy a more stable amount of power for a given altitude gain, thanks to the brilliant efficiency of the electric motor in virtually its entire performance range. There is still a difference (it’s not linear) but the watt-hours difference is not as big as the fuel difference of a fast-vs-slow climb. For the first plane, if it climbs too slow, you remove passengers or wait for battery tech to become viable. The power difference of a fast climb versus slow climb from altitude X to Y (0feet to 13500feet) isn’t going to double the battery size. The napkin numbers are touchy: A minor improvement in battery tech suddenly allows the electric airplane to have no disadvantage. The “fuzz” between not practical and suddenly fully practical (at no climb performance degradation or jump capacity loss), is actually rather a tight twilight zone that may last only a few years, possibly only a year. So the moral of the story is when the battery gets good enough, it only needs a little more refining to quickly zero out the remaining performance-related disadvantage. But a dropzone will bite the ePlane bait a bit before that, i.e. tolerate a 10-20% climb performance decrease to decrease the size of the battery, to gain the other advantages (like major cost savings). But yes, replace the “10%-20%” unscientific numbers with your favourite low-percentage threshold where somebody bites the ePlane carrot. I would bet DZOs also won’t bite at 100% slower climb performance. That’s what we saw happen in other electrifications. Anyway, the point being is that the tech fuzz zone between “Not practical” and a “ePlane climbing at full velocity to jump altitude” is actually shocking small, because of the reasons above described. Improve the tech just enough and — bam — it’s practical without a compromise. If we’re going to have compromises, it will only be very short-term like removing 1 or 2 or 3 passengers to meet volume/weight envelopes, but only for as long as battery tech improves even a few percent in a “we-only-need-a-battery-for-1-skydive-plus-reserve” scenario. Anyway, I just heard back from Magnix CEO he’d be happy to be interviewed for the Parachutist article. Now to formulate the right questions. (which may also answer some of these questions too, as well as correct any details in some of my answers, I’ll admit to being wrong sometimes. But really, there are a lot of details people don’t realize about electric motors, like “high-efficiency-at-all-power-settings” behaviors).
  13. True, but that may not be a problem — it assumes the lighter motor & other factors don’t fully cancel-out. Also — depending on plane — many dropzones don’t always absolute-max throttle their jump ship. Backing off a bit, especially after takeoff, to a mutually-agreed redline indicator on the dial, for climb performance that makes it easier for the airplane maintenance department & dropzone accountants for avgas consumption. Some do push it beyond, especially if you’re trying to push loads fast on a busy day, but that can be brutal on the engines of some planes if you’re near the performance envelopes. In reality, if slower, we are probably nitpicking only tiny percents (e.g. 10% or 20% slower climbs for same plane type) which is within the noise floor of the jump ship variances between dropzones. And even that assumes we’re using today’s batteries, not tomorrow’s. Fortunately, from the early tests, it already looks like we’re not going to be seeing 22-minute Cessna 182 style climbs with electric airplanes.
  14. Actually, probable reduced flight time. The Magnix can actually climb to altitude faster than the original turbine because you don’t worry about the redline as much — the battery difference between a slow climb and fast climb isn’t too terribly major for the current small envelopes asked of a 1-skydive battery sizing. At full 750hp throttle, a >93% efficient Magnix generates only 35 kilowatts of waste heat which is easily cooled by sheer airspeed, and I heard it climbs more vertically than a 900hp for the same weight because of less HP loss (direct shaft drive, no differential). But yes, the extra battery weight may cancel this out. Battery heating is also a factor but the quick climb moots this out; electric car have output more wattage than a Magnix doing a full Nurburgring Loop in Germany. For practical purposes, I expect no difference between turbine and Magnix electric for a typical jump plane climb. HP for HP, electrics can outperform avgas, as noticed by R/C hobby airplane pilots. Electric R/C airplanes perform spectacularly. Sure, the battery capacity is an issue, but you only need to size for a fast climb for 1 skydive load + 30min level flight reserve, which will still weigh less than a full fuel load. The kWh per kilogram may need to improve a bit more, but that’s just details from 2020-2030 at this stage — the fast climbing electric jump motor is already here...
  15. True in that this “seems” more apples vs apples. On the other hand, a Magnix electric direct drive engine (297lbs) is smaller and weigh less than the original turbine (of apparent lesser performance, despite same or slightly higher horsepower). And a lot less than piston engines and older turbines (and their respective gearbox/differential that are no longer needed thanks to gearless direct drive). This frees up a portion of weight for the minimal 1-skydive fast-10min-charge battery + 30min reserve flight capacity, with potentially zero loss of skydiver passenger capacity. The battery undoubtedly will weigh more than the fuel load of one skydive, but looks like a one-skydive battery can still now fit within max-takeoff with a full load of skydivers. Extra “fuel” weight is vastly far more than compensated by the massive cost savings. ($300 of avgas cut by 90% to 98% in cost to just $6 to $30 depending on your commercial electricity rates) (DZO accountants.,,. yes..... potentially under $1 “fuel“ per skydiver to 13500 feet!!!!) With the good instant rev torque that Magnix-trying pilots go wow at — even a near-MTOW load does not feel as dicey as with in a turbine. I think the napkin math is starting to look impressive this decade.
  16. Short Answer: They said year 2018 dollars, inflation adjusted. Watch the Tesla Battery Day video, which quoted the future numbers.Currently cutting factory costs faster than inflation. Long answer below: Tesla is treating it as a technology cost-cutting problem; reducing cost via incredible Thomas Alvas Edision style technique ("Lighbulbs ought to be cheaper than candles") and Henry Ford technique (faster moving assembly lines). It's literally jaw dropping how fiercely Tesla is brutally chopping the cost of lithium battery manufacturing, as if it was just a technology-getting-cheaper problem. Prices are falling more than 10x faster than inflation. Reputable battery researchers were impressed; they gave it 10 stars out of 10 stars. Panasonic is now adopting this. Tesla found out ways to "Henry Ford Style" further automate the manufacturing of lithium batteries at 10x-100x speed. Running large-scale-battery assembly line like soda pop bottles in a continuous high velocity assembly line -- with one factory eventually able to manufacture terawatt-hours of batteries per year. Multiple reputable news sources: Battery Day Video Tesla's new 'tabless' cell design is 'brilliant,' said a top battery researcher Tesla’s 4680 battery cell is 'brilliant' according to industry experts Battery Tech Researcher Says Tesla Batteries Could Last Over 2-Million Miles Tesla patents a new battery cell that Elon Musk hypes as ‘way more important than it sounds’ High Speed Assembly Line for cheap lithium batteries like flashlight batteries They want to ramp up battery manufacturing by multiple orders of magnitude. Multiple terawatt hours of batteries being manufactured per year. Making these lithium batteries almost cheaper than flashlight batteries used to be! This fits inside an airplane wing: Here is a YouTube video of Tesla batteries now being manufactured like soda pop bottles in a high-speed assembly line. Click play to see the assembly line: They even said they were inspired by soda pop manufacturing (52:04 into video). Combining "battery factory + printing press technology" to roll batteries faster. Combining "battery factory + soda bottle manufacturing" to zoom the entire batteries faster through the assembly line. Redesigning the battery to be quicker and easier to automate-manufacture as flawlessly as soda bottles. Etc. And they are making lithium batteries cheaper (1:06:51 into video) There's enough lithium in Nevada alone to electrify all of America's cars (plus a lot of grid batteries too), and they're even removing conflict minerals such as cobalt from the batteries. Reducing cost, making future battery cars eventually cheaper than similar gas cars, etc. You have to hand it to Elon Musk for the low lithium battery prices -- in making electric jump airplane conversions viable this decade. Even ardent petrol users have to acknowledge these Henry Ford and Thomas Edision techniques in the brutal price reductions of lithium batteries far more than 10x faster than inflation! Battery manufacturers that need to survive, are now adopting the new Tesla manufacturing techniques to manufacture lithium batteries more than 10x more cheaply. This battery factory video is amazing for electric airplanes: Look at the aggressively roboticized lithium battery manufacturing tech! There was no reason to manufacture terawatt-hours of lithium batteries until recently. Now lithium batteries are used in grid-scale storage batteries because it's a cheap way to reduce electricity prices during peak = more profit for electricity utilities. If you see New Tesla Grid Battery Delivers Stunning WIndfall Profits For Electric Utility Company in Australia. Near gigawatt-size batteries for their electricity utilities are now viable now that battery prices have fallen enough to be profitable as storage batteries for an entire city! Even without subsidies. Just like 1980s $5000 laptops became $500 today (even before inflation adjusting) -- Tesla has found ways to brutally slaughter the cost of lithium battery manufacturing profitably far faster than inflation. The blue bargraph chart I posted earlier is real -- Tesla is single-handedly to blame for industry-wide price drop of $1183/kWh to only $156/kWh at-factory cost, in less than a decade. They found out a path of how to manufacture batteries 75% cheaper at 10x manufacturing rate for the same factory floor space. A single factory will eventually manufacture 1 terawatt-hour of lithium batteries per year! Packaging and retail costs extra (profit), but we clearly see Tesla treating battery manufacturing just like a technology problem, shaking up old manufacturing assumptions.. Simple first-year Economics 101 and Business 101 if one went to university... ____ P.S. The inventors of lithium ion batteries, just got a Nobel Prize in Chemistry in 2019 .. Originally invented in the early 1970s, lithium batteries are now powering the world's economy in applications originally undreamed of.
  17. Fortunately, we don't need that much battery weight for electric skydiving aircraft. We only need enough permanently-built-in battery for one skydive plus 30 minute level flight emergency reserve capacity. That battery, today, already appear to weigh less than a full fuel load, for some aircraft specifications. This can be designed into a 25%-50% SoC discharge. The emergency reserve capacity in a battery also doubles as a battery-longevity-increaser (20-year lithium battery) since you don't want to deep-discharge most lightweight lithium chemistries, unless you have to. Chargers are now fast enough to replace 25% of a SoC by recharge in only 10 minutes between loads -- which is feasible battery recharging time from a future cheap modified electric road-truck charger, being installed at the dropzone. Sure, those "superchargers" still can take 40-50 minutes for a 100% charge, but if you design the battery small for a 25%-discharge for only skydive, then you can slam the 25% back into the battery between jump loads. You can strap down human-carryable suitcase batteries (large 5kWh - 10kWh lithium power banks) under bench seats for deadheading the electric airplane to faraway dropzones. You don't need deadweight during regular jump operations. Ferry flights, no problem. Those suitcase batteries will be cheap in 10 years, basically larger versions of existing kilowatt camping batteries. Such future batteries will be within 70 pounds (5kWh at conservative 200kWh/kg = 55 pounds, plus 15 pounds of battery frame/protection, for 70kg). But battery tech has already improved past that. Strap down a few cheap "battery baggage" under jumpship's bleacher seats, then only one or two charging stops is needed, and Skydive Perris can lend their future e-Caravan or e-Otter to Skydive Deland for the 2032 POPS record attempt, if they wish. Now, throw in the low-maintenance nature of an electric airplane, as well as the improved safety of happy instant stable torque for more comfortable emergency go-arounds (zero engine-spool up, it just instantly revs on a throttle slam-forward very stable without sounding bad, direct shaft drive, no gear box, less wear and tear). Get out of stall risks faster. With a 750hp Magnix outperforming a 900hp Garret becase of direct shaft drive + instant torque, both pilots & maintenance centres are going to be raving about electric airplanes. Regardless of your preferred political stripes -- the new administration will be very pro-electric -- some things at FAA will accelerate electric initiatives. Background buzz says SpaceX-style behind-the-scenes networking is already quickly occuring to eventually lubricate FAA introduction to the point where it's quickly cheaper (ETA 2030) for a dropzone to re-engine to electric than a replacement turbine. Many stakeholders will be anxious to trial electric in many markets, to the point where one early dropzone (ETA 2025?) will succumb to the irresistible carrot temptation of an electric trailblazer trial given Magnix CEO is a skydiver. The micdrop of this matter is Magnix found that an electric flight normally requiring $300-$400 of fuel cost only $6 of electricity. Even if off by an order of magnitude, $60 still represents an 80% savings on fuel even at current depressed fuel prices. Jump tickets could fall by half, while still more than doubling profits for the DZO? Anyone else who wants to co-write a Parachutist article from the skydver perspective -- see my offer in earlier post -- I have been published in skydiving magazines before. I have one tentative co-writer/proofreader already, but I would like additional for Google Docs. Purpose is to educate and mythbust incorrect preconceptions. Maybe can also interview the Magnix CEO together via email or Zoom/Skype. And interview others too. I'm just a super enthusaic pro-electric with no profit or stake in all of this except to keep skydiving alive without becoming unafforable.
  18. I think they'll come first via conversions -- like the Electric Caravan C208 conversion, and the founder of Magnix is a skydiver. We can just replace the battery more cheaply than a re-engining. Also, by 2025-2030, electric conversions are rapidly going to become cheaper than a turbine re-engining. Short-haul Twin Otters, too, will likely be electrified too. Lots of airframes need to be re-engined in ten years sooner than electric hand-me-downs. Estimate is $62/kWh by 2030 and $30/kWh by 2040. Assembled cost is more, but you get the picture...
  19. Even better. I think one dropzone will be doing electric jump ships before this decade is out, now that electric transportation initiatives is going to get a big boost. I dare say 2027 or 2028 as my guesstimate. Could even be earlier. I hear whispers of 2025 for the "first" jumpship ops. It will be 20-30 years before widespread probably, but the first dropzone will be sooner than many expect. Electric conversions are likely to quickly become cheaper than re-engining before year 2030. In other news, an electric-propelled 300mph wingsuit BASE jump was successful just mere days ago!
  20. Year 2020: Advocacy. Random simple things like the maintenance people subscribing to electric-plane news/sites. Or the DZO emailing a turbine supplier about their future plans of ePlane conversions later in decade. Or participating in aviation (FAA/airport/etc) public information centres where they're asking for comments on new regulations. Or attending a Magnix test or another ePlane vendor's test if they're happening within a few hours drive of you. Ask them questions. Bring a skeptic friend. Write a Parachutist article about your personal experience attending Magnix tests and also corroborate lithium battery industry observations into the same article. Ask for an interview with the point contact of your power company's new battery farm. Even personally test drive a Tesla car (or electric Ford F150, or electric Hummer, when they come out) with one of your skeptic aviation friends. Convince your electric-doubting mechanic coworker. Contact your aviation-nut congressperson. Talk to your friend at FAA. All kinds of random advocacy steps to lower the laughingstock background noise down to a quiet din. Baby steps. Advocacy. Dispel myths. Learn. Disbelieving people can inject years of delays in pushing the gearwork (slower advocacy, slower FAA rules, slower convincing, less ePlanes knowledge, etc). The live-under-rock factor is strong. Flap those butterflies so the Chaos Theory so dominoes can fall sooner. Random Theoretical Examples: - [2020-Begin] Hypothetically, seven DZOs asks three turbine vendor about future ePlane plans, three turbine vendors contacts Magnix or another ePlane motor/battery supplier, Magnix realizes there's a jumpplane market, Magnix contacts FAA about theoretical jumplane rules, Magnix goes into the jumpplane conversion biz [2030-End] - [2020-Begin] Hypothetically, somebody's brilliant Parachutist article causes 3 people do a Tesla test drive, 5 people to research Magnix, 2 exhibition jumpers to ask if they can test-jump the magnix eCaravan, 2 DZO accountants to do the math only to suddenly get surprised and speeddial all FAA friends. Then, say, 7 FAA readers, prodded by articles/dropzones to start writing draft documents on time to become final when those good jump-capacity aviation batteries arrive, a dropzone finally buys an ePlane conversion a couple years sooner when they are mature earlier than expected, etc. [2030-End] - Or whatever, etc. Infinite number of theoretical dominoe paths. Other dominoes to tip. Many dominoes take 5-10 years to finish falling. Yes, Some advocacy steps are ridiculous and longshots, but a lot of mudane skydiving innovations over the last 70 years sometimes came from surprisingly simple advocacy or manifest watercooler talk or pilot/instructor lounges. And now are instructor/SIM material. Lots of Chaos Theory Butterflies happened there already... Also, in another industry (gaming industry, since I operate a research laboratory on high-performance display screens), some of my discussion forum posts incubated an invention that are now in a peer reviewed science journal & my ideas were implemented in certain virtual reality headsets and gaming monitors, with confirmed credit. Just in September, Samsung Electronics cited me; I now have over 20 research papers that cited either me or my business (Blur Busters / TestUFO), and a few that I am even co-author of (in one paper that included a NIST.gov researcher in a U.S. government-funded peer-reviewed conference paper that I am a co-author of), from something originally incubated in a forum. From something more casual than this forum thread, that progressiely dominoed all the way there. So, this is not my first tango at online advocacy (in a different high-skill industry)... In a sense, just doing these dropzone.com falls under the "Advocacy" umbrella. Make a few in the skydiving industry a smidge more aware, recruit people who agree, etc. I've written a few times for CanPara and Parachutist before (e.g. Canada Big Way, Rainbow Boogie, etc). Happy to co-write a Parachutist article, I would want help from at least 1 co-author working with me in Google Docs and at least 3-4 proofreaders, maybe even one or two bleeding edge pilots/dropzone accounts/jumpdrivers/DZOs to review, add useful commentary, and fix errors in the article. So it's a proper electric jump plane wake-up-call article in a national skydiving magazine instead of 1-person speil. If you also have writing experience, and movement is desired on a Parachutist article, Google my full name (Mark Rejhon) and reach me through any channel (LinkedIn, email, etc -- I have rarely visited here after the forum upgrade so that's why I still am at 0 rep despite 2766 posts since rep system didn't exist before then).
  21. On the note about the pilots I talked to that disbelieve the rapidity of ePlane practicality, think about this: Suggested Napkin Sketch Timeline (replace dates with whatever seems more realistic, but you get the idea: start ASAP) 2021: Turbine re-engine vendor partners with ePlane vendor 2022: Somebody proposes FAA draft rules for theoretical ePlane jump ops 2023: Test jump plane conversion, reduced capacity, novelty skydives (like heli or biplane). Possibly, it would be a 50% trainer plane, 50% novelty skydive plane as a partnership between multiple airport stakeholders as a risk-sharing trial; 2025: First official-kit expensive conversion (i.e. Skydive Dubai, Perris) 2025: Full FAA approval as easy or easier than turbine kit. 2030: Capital Cost Parity: ePlane kit as cheap or cheaper than turbine kit, including cost of batteries. Making possible jump tickets cheaper than turbine planes while simultaneously keeping bigger DZO profit. Planning clearly begins now for 2030. Anybody who doesn’t begin planning now is already too late to be first. Push the dominoes. Lots of dominoes to tip (FAA, mechanics training, test ahead of battery improvements — the outperforming airplane electric motor’s already ready, Test today before too many people re-engine to another turbine, many are going to get buyer’s remorse in 2030) One more thing. Actual tests showed $300-$400 avgas replaced by $6 to $30 of electricity. Magnix tests showed cost-savings scales better in aviation than for cars. And that’s even ignoring much less maintenance. Actual number from Magnix electric converted Cessna Caravan. Any dropzone laughing at electric? This is the microphone drop below: Apparently, $300-$400 of avgas is what many skydiving dropzones tank up with (approximately) for a sufficiently generous jump altitude. But it’s in that territory for many common jump planes of the Caravan / Twin Otter variety to non-skimpy altitudes with a full load. Now, instead of about 2.5c/kWh for locally sourced renewable, and your industrial/commercial rate of your electricity is 12-15c/kWh in other states — then, yes, it’s closer to $30 than $6 per jump lift, and probably cheaper than that since most jump planes fuel less than $300-$400 avgas. At the most expensive end, 10x savings and literally pennies of fuel per jumper — well under a dollar of fuel per jumper to 13500 feet if you’re getting good rates for your electricity. And if electricity later goes crazy in your state, just build a solar farm or pay some farmer 10 miles away to build a wind turbine (safely far away from dropzone), and deliver the power to the dropzone cheaply. Some rural airports have built their own megawatt-scale solar farms as a side business, and that’s unintentionally accidentally convenient for ePlanes. You’re more 1973-proofed and 2008-proofed than with avgas. You can’t easily manufacture your own avgas onsite, but you can manufacture your own electricity — The freedom to choose to do so! Combined with the far reduced motor-related maintenance, the savings easily pay for the initially high capital cost; a DZ can even keep the tickets the same price initially to payoff capital faster; and drop them later. Also, due to various reasons (no gears, direct drive motor!!), the 750hp electric may outperform a 900hp diesel for climbs — less horsepower needed for a specific climb rate, because no horsepower is lost in a fully direct-drive propeller. So there’s an electric dividend that reduces battery size somewhat for a same-time climb to jump altitude. Or find the sweet-spot climb rate (which might be just only 1 minute slower) — the battery might be downsized slightly more too. The sweet spot climb rate can be discovered in ePlane experiments. One might find you need less battery than expected to do 1 jump (in a 25-50% battery discharge) + 30 minute reserve level flight. The minimum battery weight numbers may almost fits the weight difference of a lightweight Magnix vs original engine already. With fast 10-to-15 minute between-loads charging increasingly looking potentially feasible, you only need to size battery for 1 jump load with zero passenger loss. Electric jump plane problem solved in nearer future than expected? Start planning and thought exercising for the DZ business...Maybe the weight numbers don’t work just quite yet for zero-passenger-loss Caravan but they will very soon. That’s no reason to avoid planning for electric jump ops now. With skydiving being too expensive for many, economical electric jump planes will simultaneously raise DZO profits + lower jump ticket prices — we all need it by 2030. Read again: $300-$400 of avgas in an electric Cessna Caravan only costs $6 to $30 of electricity. 10x to 50x fuel cost savings. Donkey, meet carrot. Carrot, meet donkey. Which DZ wants to be first?
  22. Today’s Announcement of a Hummer EV Truck Today’s release of the 1000 horsepower electric Hummer truck/SUV and its 200 kWh battery going 350 miles and can fast-charge at 0.4 megawatts to refuel 100 miles in just 10 minutes. Much as we can thank Apple for the ability to buy a terabyte SSD for $100 (Even if the flash is manufactured by someone else), and that we can thank NVIDIA/AMD for kickstarting 3D GPU graphics innovations that now fit in a mobile phone/smartwatch (Even if the GPU is manufactured by someone else) — we have to blame Tesla for turning crazy expensive luxury $500 laptop batteries into viable cheap profitable gigawatt-output electric utility grid batteries (Even if the batteries are manufactured by someone else). Now about that official Hummer EV... While the Hummer EV is more expensive than a Model 3 Tesla, since it is using some more proprietary higher power battery than standardized form factors (18650, 2170s, etc)... the audacity of a Hummer EV out-Hummering a petrol Hummer (longer range than most gas Hummers, more horsepower, better offroading, fastest 0-to-60 in 3 seconds, etc, etc). This continues to portends the unexpected trojan horse of lithium to vehicles formerly never dreamed of going officially electric in our lifetimes. But it’s there, GMC.com website, prototypes already on road, and ready to preorder today! The audacity that something like that exists today for purchasing..... Hummer? EV? In the same sentence? And drives further than most gasoline Hummers? Doubletake. I truly think that people who disbelieves ePlanes are THAT far behind need to look again — even a kick in their behind to really run the numbers again on the fast-moving target — just a little more engineering left to click all the checkboxes for a lightweight ePlane conversion kit with a 10-minute between-loads recharge — I am starting to now think zero passenger jump capacity loss may actually be possible by 2030 for Caravans/Otters, since the electric motor replacing original old turbines are much lighter and may be all the weight savings you need for battery for just 1 load + 30 min level flight reserve capacity with ZERO jumper passenger loss, possibly... In a recent conversation — too many pilots still disbelieve that ePlanes are hurtling towards real-world practicality for short-range ops and jump-plane ops. I have to wave a neon checkered flag “yoo-hoo”, to look closer... Someone needs to write a Parachutist article about this to get the word out since a turbine re-engine is no longer as rubberstampable as IBM in the 1960s and 1970s (“You never got fired for choosing IBM”...until someone did). So many planes are approaching re-engine dates in 2025-2030 and many re-engine vendors are ignoring electric (at peril) given the recent surprising performance statistics of this year’s Magnix trials (including the Magnix 750hp having superior go-around rev-up performance than a 900hp Garrett from what I heard — the electric “instant spoolup” factor). I think vendors need to look at the engine & battery separately; the engine is here now, but the battery is “just about barely” not good enough for jump ops at zero passenger loss (yet), but the rapidity of Tesla means appropriate batteries for jump ops will fit in the necessary profitability no-compromises (except 10-minute between-loads recharge) envelope sooner than later. In the trials, the motor apparently is already good enough for skydiving operations; the battery just needs a few more years to catch up. So approaching the problem at different angles; the motor and the battery(capacity/weight). And watching Tesla/Hummer/etc — the writing is on the wall... At first, it might require a more well captialized dropzone (e.g. a Skydive Dubai or a Skydive Perris) to do the headway of being the first (with more expensive lightweight proprietary lithium batteries) and reap the profit/rewards of low-cost jump ops after the high capital cost of being first — gradually chainsaw all the FAA red tape down to get specific conversions kits approved — then the floodgates open as a competitive alternative to normal re-engines, and the cost of ePlane conversion kits really fall (with more commodity Tesla-style batteries). We’ve been ignoring ePlanes/electric conversions with disbelief for so long, until the Hummer EV / Tesla EV / Magnix wake-up call. A conversation with disbelieving aviation stakeholder is why I started making a lot of noise in this thread — not because I want to advertise or troll anything — but a big aviation operational cost-savings opportunity red button is flashing. Texas Turbine should put Magnix on speed dial and get into the electric jump plain conversion business before someone else beats them to the market by 2030...!
  23. I was looking at wind turbine power charts elsewhere and noticed that because of minimum wind speed (before the blades spin), it gets a little jumpstart on the power of cube early in the curve. The formulas are fairly complex though and I certainly could have overlooked some variables such as: Touché. That's a good observation! Still, even 5-10% regen return is still free cash. Resistance on the propeller will cause some weird flight dynamics but nothing an approved ePlane jump pilot couldn't handle since they already do frequent dives and well versed on the dynamics of an open jump door and sudden weight shifts. Regen ops will be much tamer than those mudane plane-bouncy factors... Some tests and training might be needed for FAA approval of regen, which might later have rules about regen approvals (like no regen below 1000 feet or such).
  24. Riggerrob, you wrote this in year 2017. Any comments on the 750hp Magnix electric conversion kit that's lighter weight and reportedly more powerful than the 900hp Garrett conversion in some aspects? It apparently reportedly has faster and smoother rev-up torque (good for takeoffs, go-arounds and emergency manoevers), reports are that it is very "slam-the-throttle-forward" friendly compared to avgas powered motors -- doesn't lurch or do any weird rev-releated vibrations and never sounds damaging to the motor -- it just instantly and surprisingly smoothly revs up to max power almost instantly, suddenly spooling-up much faster than any piston or turbine engine -- with no hint of needing maintenance afterwards. Now that an electric Cessna Caravan has been converted, I think it kind of changes the ballgame when a potential ePlane conversion might have better economics for jump pilots, especially future implementations with 10-15% regen recovery (refuel on descent). Considering that with the new Tesla 4680 battery format, for the capacity required of a single jump flight, a 12 minute partial charge times (one loadful at a time) are now possible between loads! So you don't need a full day's charge, and now you only need a much lighter battery. The ability to design a battery size to deplete only 25% for a typical jump + hopefully FAA mandated reserve for more than 30 minutes of level flight, it is now completely unnecessary to preinstall a battery larger load than one jump + reserve. Multiple spare human-liftable standardized cargo batteries -- 10kWh now fits inside a suitcase smaller than checked baggage -- in human-liftable military boxes that can be strapped down under the bench seat for ferry flights such as loaning to other dropzones. or doing specialized jumps such as HALO. Store them (and use them as hangar Powerwalls) when not in use. With Tesla hurtling batteries to $62/kWh by 2030 and $30/kWh by 2040, the numbers starts to compete with normal conversion kits. So many solutions are happening that ePlane conversion kits likely will quickly become as economical as the usual re-engining -- I now expect inexpensive electric jump plane conversions around 2030-ish based on what I now know.
  25. In reality, it scales a bit better than 8x+ power at double wind speed, because many blades tend to become more efficient at faster speeds, up to their sweet speed. Some ground wind turbines typically generate 9x better power approximately, at doubled wind speeds. Basically the cubed bonus plus the higher-windspeed efficiency bonus (overcome inertia/friction/stiction/momentum), same reasons wind turbines can't spin anymore at half wind speeds -- blades don't spin until wind speed is fast enough. Beyond a specific point, it tends to follow the cube, but there's a particularly large bonus-above-cubed speed magnitude above minimum windspeed to spin the blades. Most airplane propellers are designed to be efficient at fast speeds, so the regen power (in theory) should scale better than cubed powers. Thusly, what regens at 50mph will be more than 64x regen power at 200mph in an airplane. And, thusly, you can turn 10 kW regen to a megawatt regen simply by slightly more than quadrupling wind speed. A plane will have to respect approved airspeeds though, say, ~200mph, and the whole airplane has its own terminal velocity for idled dives too. And regen will add slight more air resistance (a few percent less terminal velocity). So terminal velocity or maximum approved air speed may be reached before max regen capability depending on airframe design and propeller design. Then by all means, the existing jump plane return dives, are already at optimal regen angle -- it is quite possible. Although I am not sure what the optimal regen pitch for propellers is; the blade pitch adjustment range might or might not need to be much wider than a regular propeller -- so electric replacement propellers optimized to also have a regen envelope -- might (or might not) need a pitch not available in existing pitch-adjustable propellers. Efficiency for takeoff and powered flight is far more important than regen, so some compromises will happen for regen. If current blade geometry is hugely suboptimal for efficient regen, then a double propeller system (theoretical foldable or idled-by-default regen-optimized blades behind the regular blades) might someday later play a role, if regen outweighs the weight cost (which I doubt at this time). Long term (cleansheet designs), possibly ultra-lightweight regen-optimized blades folded flush against fuselage could automatically latch onto the shaft when it unfolds (via a clutch mechanism that occurs only when unfolded to allow it to spin up safely after an interlock ensures the main propeller is idled), allowing the same shaft to double as a RAT (ram air turbine) with little weight penalty. Blade geometry, obviously, will be optimized for powered operation. But adjustable pitch range improvements might in theory be beneficial for regen capabilities. But for now, realistically, existing propellers will just undergo minor modifications (if any) to properly accomodate "bonus-regen" only as a secondary priority after max-efficiency powered use. The propeller engineers of ePlanes will know better than I on regen requirements. Regen is already accomplished on an electric airplane (Pipistrel electric trainer at Pitt Meadows, and also I think in Vancouver too) and was claimed to recover 13% of energy of the ascent. But it didn't work as well in normal use by students, except in steep dives scary to students, where you need to use speed brakes. BUT....steep dive regen is what you want for experienced skydiving jump planes! 13% is a lot of money savings. Imagine in-flight manufacturing 13% of your avgas... Regenenerative capability should be a part of any electric jump plane retrofit (Texas Turbine style) for quite obvious economic reasons...