mdrejhon

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  1. 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).
  2. 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?
  3. 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...!
  4. 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).
  5. 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.
  6. 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...
  7. You meant “wouldn’t be used anyway”, but with that correction, you are correct. Yes, the battery reserve can double as SoC management AND a rarely used reserve. Regen is usually a freebie feature (no extra weight) in proper EV design, since inverters are bidirectional capable in some vehicles. Might as well have it handy on your descent, it’s extra landing / go-around power. An electric skydiving plane that’s not in a huge hurry (slower manifest) can just descend at optimal regen glide, which might be a specific shallowness or steepness. Could maybe be a 20% time-save in battery charging wait. Turning a 12-minute charge wait into 10-minute charge between loads, in theory. Even 5% or 10% would be 5% or 10% cash savings in electricity per jump! Who knows, maybe a dollar more profit per jumper... Split the profit with the dropzone pilot as a quid pro quo to incentivize regen descents. The slower descend time also allows a shorter between-loads charge time. There likely be a “sweet spot” balance, on time-cost and electricity-profit, for a specific propeller’s efficiency and flight stall safety (aka maximum regen capacity). Beyond a certain descent rate, is just wasted gravity when regen exceeds motor/battery limits and propeller efficiency given airplane propellers are not as big as wind turbines. Although the fast steep-glide airflow compared to ground wind makes up for a lot of that deficit, the rules of the exponential curve (Double wind speed creating 8x+ power, quadruple wind speed creating 64x+ power...). Dive hard enough and you may match that truck megawatt charger on the ground you’d normally use to recharge the plane with. Yes, thanks to the law of exponents, sheer speed can make a (custom electric-regen-optimized blade-tiltable) Twin Otter propeller generate as much power as a full size wind turbine! At some sufficient steep descent rate, the regen may exceed charge controller capacity and the motor simply throttle speed by its own sheer increased magnetic resistance (from throttled regen current flow), or electronics auto-idling the propeller to keep regen envelopes. Optimal regen glide angles will be part of a DZO profit planning of the electric 2030s/2040s when some slower days pushes profit-per-jumper instead of jumpers-per-day. Who can say no to converting time into free electricity? (when profitable enough).
  8. Also, battery reserve conveniently can double as the same “reduced battery wear and tear” SoC charge cycle and battery sizing planning. Skydives never going below 30-50% battery bar. Whatever is below 30% battery can be designed to be enough power for level flight for 30 minutes. Also, it can potentially do some regenerative (gliding downwards recharging battery a bit) as battery motors typically cam double as generators.
  9. Yes. True. The weight of a 750 horsepower electric Magnix airplane motor is only 297 pounds, so there’s still extra battery haulage opportunity of an electric conversion. In some respects 750hp electric outperforms 900hp turbine because of more instant spool-up torque. Much briefer brake hold-down for a leaping start on short runways, it’s more immediately apparent to the pilot the motor confidently and safely leaped to full power, in an uncannily smooth near-instantaneous spinup. This can be useful in getting you out of tight situations, the ability to instantly rev for a go-around. The horsepower per pound is also improving on the electric motor front. So, still extra battery haulage without sacrificing much passenger load (if any) for right-sizing wing battery to regular skydiving ops. — BTW, for other readers, there is now a 100 watt charger for a specific model of a cellphone — which injects 50% back into the battery in just a few minutes and a full battery charge in 17 minutes. It tapers wattage safely based on charge progress and temperature monitoring. Tesla uses massive parallelized charging like that, like thousands of separate fast chargers for each cell in each battery pack — just by plugging in one Supercharger connector. It’s incredible engineering of concurrency to speed-charge, and this can also be done to future electric aircraft needing frequent cycles, like jump planes. (Charge controllers are often built into cells or modules) A 50% refuel in under 10mins, so the 12-15min estimate are cheaper/more realistic, given well-engineered battery design optimized for gentler ultrafast shallow-cycle charging from a future aftermarket truck megawatt recharger retrofitted to recharge future jump planes. Realistically, like partially filled wing tanks, it increasingly appears unnecessary to perm-install more battery than needed for one jump lift for a 25-50% discharge. One might need more weight in partial battery than equivalent partial avgas, but the weight envelope freed by lighter powerful motor enables that without much sacrifice (if any) to jumper capacity, and the charging ends up still much cheaper than avgas for many airports. Assuming they can pull off the upcoming near-term economics, the numbers starts to check out, surprisingly so — cheaper jump tickers and bigger DZO profits is something rare simultaneously.
  10. Electric Deadheading / Repositioning Operations The Harbour Air electric tests have a removable in-cabin battery that will later be integrated into the airframe (presumably the wings). Now, it was discussed among electric airplane engineers that an optional removable in-cabin battery can be used only for deadheading/repositioning the airplane across the states (NYC-to-California), in operational practice, you only need one jumpship load of built-in battery in the wings. The ruggedized deadheading battery modules are modularized to hand-liftable (~30-60lbs each) out of the airplane door, and can be stored at the dropzone (at ~50% storage SoC) that airplane is leased/loaned/stored at, until the electric airplane needs to be moved to a different airport/dropzone. The thought exercise, is that optional extender batteries just looks like small strap-down cargo boxes -- like upcoming bigger aviation-standardized many-kWh sized versions of electric camping batteries - some of them have high power AC outlets built into them + high-amperage car booster outputs. With the new Tesla 4680s, it is increasing possible to fit almost 10 kWh in a 50 pound "suitcase" small enough to fit under skydiving bench seats and be strapped down during repositioning flights. And by 2030, more capacity is possible. A DZ be able to load up the whole cabin full of these, strapdowns-permitting. A few hundred kWh worth of cheap human-carryable modules! (Remember: lithium batteries is quickly hurtling to $62/kWh by 2030, and $30/kWh by 2040. Even if you double/triple that for module assembly and profit margin, this becomes affordable to dropzone electric aviation by 2030s-2040s) Suitcase sized supersized equivalents of cellphone battery banks. With lift handles on them metal boxes with rubber corner bumpers. To resist bumps of loading/unloading/storage, with strap attachments for the existing floorbottoms of existing airplanes -- treating the extender batteries like cargo. Flexible daisychainable connectors allow you to attach a variable number of modules to the airplane's built-in supplemental-power outlet in the cabin to supplement the in-wing battery. And you can load as few/as many extender batteries you want up to the cabin space + cabin load limits + MTOW -- at projected 300-400 kWh/kg plus weight of battery pack casings -- almost megawatt-hour worth of battery for an electric Twin Otter for repositioning, and still be below MTOW. If theoretically approved for use during skydiving operations, you might be able to do 30,000 feet HALO operations with fewer skydivers + some extender batteries strapped down under the bench seat. But they'll likely mainly be used for long-haul repositioning. And when the deadheading batteries are not in use, they can also conveniently double as backup batteries during DZ power outages or boost other turibne Otters replacing existing battery wagons. There's no need for long-haul deadheading batteries during regular commercial operations. It's a brilliantly simple idea -- strap-in batteries for passenger cabin only used for longhaul deadheading operations -- and right-sizing the in-wing battery for your revenue service (i.e. one jump load discharging 25-50% of a battery that can be replenished in about 12-15 minutes between loads using a fast-charger installed at an airplane dropzone). The borrower dropzone would just hand-remove the normal looking cargo boxes (extension batteries) set them aside in the hanger. The borrower dropzone just trickle-recharges them from the hanger's regular AC outlets at 1875 watts (115V/15A) to finish charging them within 3-4 days (the common time period of a bigway/boogie/record attempt). Then put the battery-cargo back into the electric jump plane for the repositioning flight back to Skydive Perris, with enough weight leftover for three or four DZ-employee passengers and their luggage. Longer flights might need one quick-charging stop at some intermediate dropzone, but that's not the end of the world. So yes, in year 2035, Skydive Perris can still loan their future electric Twin Otter or electric Caravan to Skydive Spaceland or Skydive Deland's big boogie or record attempt.
  11. Ooops, that was the Otter (the Garrett upgrade by Texas Turbine Conversions), not the Twin Otter. Memory slipped there, it's been a long time. Doh. Texas Turbines advertises "Our conversion will allow your airplane to haul more, take-off shorter, climb faster, cruise farther, and burn less fuel.". Haul more! Just what you need for battery weight. They do Twin Otters and Caravan upgrades too that defacto allows you to milk your airframe's approved MTOW. Much of the points stand -- including unofficial DZ-specific MTOW downratings (whether be load quirks, power limits due to maintenance department edict or DZO edict, and mudane factors like that) -- like moving the redline marker lower and mandating the pilot not to exceed that mark, forcing loading decisions on extreme days (hot, winds, etc). The horsepower differences of the various horsepower upgrdes (turbine-replace-turbine upgrades) that are made to underpowered turbine-engined Twin Otters turning them into 900hp Super Otters. Like the ones at Skydive Perris, of which I frequently jumped bigways from. Electrics can redline more frequently than turbines can before it needs maintenance, so that's another bonus, too. Terminological issue too -- when I say MTOW increases, I mean removal of power downratings / MTOW downratings (including the unofficial DZ specific ones) and being able to push all the way to the approved MTOW without reducing manifest by 1 or 2 skydivers on hot-weather days due to bad specific air density for an older engine whose maintenance department recommended a lower redline for. In BEV research, it was found that strategic fast-discharge/charge cycling of battery doesn't really wear the battery any differently from slower charge of that specific battery cycle, as long as it's within the 80%-to-30% SoC (battery bar) envelope and within thermal criteria. Fit one skydive load in that SoC envelope, and quickly becomes a sealed deal economically. Both the Texas Turbine upgrade & the Magnix electric upgrades includes a more efficient propeller and what appears to be stronger engine mounts. In other words, Texas Turbines makes legal MTOW easier with less risk Imagine, the electric equivalent of a Texas Turbines Upgrade (maybe they'll get into that market too, purchasing electric motors from vendors like Magnix, if they want to franchise them later this decade!) It can make it comfortable to move the DZO/maintenance-prescribed lowered voluntary redline marker back up higher. Giving pilots more pillow-comfortable freedom with frequently safely reaching FAA approved MTOW happily going near vertical, with tons of stall safety margin, sooner on the runway, on worse summer days, without as much maintenance wear-tear and without an early trip to the Tucson boneyard.
  12. AFAIK, the certification standard for MTOW includes performance requirements.... to a certain point. Please correct me if I am wrong, but... We've got skydiving planes that use original engines and original propellers, versus upgraded engines and upgraded propellers -- that kind of slightly affects MTOW approval, up to the approved structural limits of the airframe. When an airplane is refurbished with completely upgraded engines (e.g. turbine upgrade + better propeller on a formerly piston aircraft), it can remove the performance-derived MTOW downrating if the airframe structural MTOW is not the limiting factor. There are Twin Otters with piston engines, and Twin Otters with turbine engines upgrades paid for by dropzones. And propeller design have improved over the lifetime of the Twin Otter. The piston engined Twin Otter is underpowered relative to the Twin Otter structural ratings. It is a very strong airframe designed for rough bush landings. In actual practice, dropzones usually load the turbine Twin Otters a little bit more without needing longer runway + climb faster. Yes, some MTOW downratings are internal/unofficial (DZO-mandated) because of their airport-specific risks ("It climbs like a grandma on hot days, I'm nervous of this squirmy jump load to keep plane safe during takeoff"), that are then removed when they do their turbine upgrade ("Go safely nuts on the throttle, up to the marked redline, we have tandems to push!"). Your DZ's maintenance department may thus also request a recommended MTOW, to save maintenance costs. See? A redlined piston engine will need maintenance sooner than a redlined turbine engine. And a redlined electric needs even less maintenance than a redlined turbine engine. By 2030, dropzones will probably have a choice between a turbine upgrade or an electrific upgrade. FAA is already working on regulations on such upgrades, thanks to the Magnix work. I have frequently jumped out of many Twin Otters of different engine powers, at multiple dropzones in multiple countries. Dropzones pilots generally babies them very differently. Anything else?
  13. Perhaps from a structural/regulatory perspective, yes. But many aircraft can’t even reach the airframe’s MTOW without a turbine engine upgrade. So many old jumpships out there that are being generally run below airframe MTOW rating.... the MTOW can be downrated by an older, less powerful engine already extant on the aircraft, and other variables like runway lengths and air density. While electric doesn’t fix all, it’s no longer hard to max out an approved airframe MTOW rating with electric without reducing passenger capacity much (for favourable conditions, low altitude with great runway). You only need enough battery for one trip to jump altitude with a reserve margin, and that’s all the battery weight you need. By 2030, strategic battery sizing may be lighter than the avgas it replaces. The point is horsepowerage is no longer the limiting factor. The electric supercars now can do 1300 horsepower with a battery now lighter than the weight of the avgas of a full caravan fuelup!! But that can be skipped, and the battery right-sized for one or two loads at 50% or 25% discharge per full-throttle load, and heat is no longer an issue with the low internal resistance and new heatsink-friendlier battery heat-radiating design (just heat-conduct to airframe, little extra cooling-related wright). Just a little more time and the weight math checks out. Those dropzones with old engines, by 2030, will be deciding between turbine refreshes versus cheap electric conversion kits (and tolerating the 12-minute recharge between loads).
  14. Yes, a cleansheet design is better, though the first electric jump plane will probably be a cheap Caravan/Otter conversion kit (compared to turbine), circa 2030-2035. 1000+ horsepower electric motors are now being invented that are lighter than a 600 horsepower airplane engine + associateds (differential gears, fuel piping, etc). Electric motors are direct propeller drive and modern inverters are miniaturized (like wallwarts vs iPhone chargers). Thanks to horsepower, battery weight haulage is no problem at the Caravan scale, if the airplane frame can support the weight and enough capacity to jump altitude in under 10 minutes using only 25-50% battery + fast 12 minute charge between loads. It’s now all within the envelope of circa 2030 DZ economics. “Do I buy a new plane, or do a turbine re-engine, or do an electric conversion? Those electric conversion kit prices are tempting...”