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  1. Dusan

    Two Pitch Angle for The Same Cruse Speed ?

    Same power, different AoA, different speeds. E.G. by the graph here, at 65Hp you could be at 50 or 83kts, and respectively, a high AoA close to stall at 50, but very small AoA at 83.
  2. Dusan

    HELP in aircraft design

    To design an aircraft is hard. You need to understand new concepts that are not intuitive. I created a primer on basic aircraft aerodynamics for students to acquire those concepts. Primer on basic aircraft aerodynamics
  3. Dusan

    How does lift *actually* work?

    Is it Newton, or Bernoulli? Mabe is Kutta-Joukowski, or Prandl. No, there are no people lifting the wing up! Joking aside, Newton, Bernoulli, Kutta-Joukowski, and Prandl are mathematical models that predict lift produced, but do not explain the physical cause of aerodynamic forces. We know air...
  4. Dusan

    Design challenge: world's smallest airplane.

    Maybe something like this, a modern combination between hiller platform and the Wee-Bee
  5. Dusan

    Is it a bird? Is it a Plane? Is it a Helicopter? Nope - I'm building one of those new drone thingy's!

    Idk, maybe they are still experimenting, or for other markets.
  6. Dusan

    Is it a bird? Is it a Plane? Is it a Helicopter? Nope - I'm building one of those new drone thingy's!

    I assisted to one of the Jetsons presentation, as far as I remember they are saying in Europe is certified as a hovercraft, software limited to altitudes under 6m
  7. Dusan

    FAA: Wrestling with Appropriate Pilot Rating for EVTOLs

    Err.. No - A multicopter does not auto-rotate, and cannot glide. It cannot "have equal or better reliability and safety than a conventional helicopter" since is lacking an inherent safety mechanism. A parachute is not an inherent safety mechanism. It needs to be deployed, it takes time and can...
  8. Dusan

    Jack Norris books on propeller design & theory of flight

    Definitely the books are hard to read. Anyway, propeller efficiency is a subject very acute today. Electric propulsion makes it so - The electric motor, controller, battery, wiring, all together have more than 90% efficiency - the weakest link is the efficiency of propellers.
  9. Dusan

    Hydraulic Hybrid Multicopter Design Takes Flight

    Interesting concept, but I have seen other 'heavy lift drones' using mechanical transmission to the 4 propellers and using electrically controlled variable pitch for stability and control. I think those systems are more efficient, lighter, and having better control response. One of the problems...
  10. Dusan

    Redundant / Failsafe engine control project

    Sorry KeithO, I didn't want to sound negative or to kill your enthusiasm. I'm designing electronics for a living and using 3mm slot type opto-sensors a lot. One particular project has quantity of millions of boards/year, have two of these sensors per board, and sometimes they fail much sooner...
  11. Dusan

    Redundant / Failsafe engine control project

    I would not use optical sensors - they are not reliable enough. The light output of the IR LED decreases over time, the effect is very temperature dependant. At 100C the transfer ratio will drop much faster than specified in the datasheet, the solution is to use lower current or/and replace the...
  12. Dusan

    Why battery-powered aircraft will never have significant range

    Thanks BJC!
  13. Dusan

    Why battery-powered aircraft will never have significant range

    Losses at high loading are mostly I2R, and not entering into details, max power is transferred when total power is twice the losses, so efficiency is 50%. This is regardless of motor type; Would you care to explain if you have other opinion?
  14. Dusan

    Why battery-powered aircraft will never have significant range

    You're right. 50% efficiency at max power is a theoretical number, never achieved in practice, but good motors are very close to it. Anyway it's a moot point since no motors can operate at that loading. I can vouch for that. The convenience of charging at home means for me not freezing at -25C...
  15. Dusan

    Rotor revolution

    VTOL history is long and full of imaginative aircraft concepts that even on paper failed, concepts that went to prototyping and failed. Most of these aircraft are represented in the famous - VTOL wheel of mis-fortune published by vertical flight society. From hundreds of configurations only 3...
  16. Dusan

    Why battery-powered aircraft will never have significant range

    The efficiency at max power of any motor is 50%, and no motor can operate at that point without burning out, regardless of time and cooling. Usually this max power is not stated in the datasheet, but 'peak power' which is less, but achievable for a limited time. This 'peak power' seems to be the...
  17. Dusan

    Why battery-powered aircraft will never have significant range

    As I stated in my previous post, the electric propulsion performance is augmented a lot by the electric motor's large power-to-weight ratio. For the same shaft delivered power the electric motor and controller weight is about 1/4 the weight of the piston ICE, leaving a lot of room for the...
  18. Dusan

    Why battery-powered aircraft will never have significant range

    Overheat is created when the cooling system does not manage to remove heat produced. This could happen even if operating the motor under the rated power if operated at a regime of lower efficiency, (e.g. more torque, less rpm). Overboosting is always on the downwards efficiency slope, so more...
  19. Dusan

    Why battery-powered aircraft will never have significant range

    Specific energy of gasoline is at about 12900 Wh/Kg and best lithium batteries have 240 Wh/Kg (wikipedia), so the theoretical ratio is about 53. Taking into consideration that only about 25% of that gasoline chemical energy is converted into mechanical shaft power, vs about 75% for the chemical...
  20. Dusan

    The concept of a flying car will eventually succeed

    Air transport is so interesting because of potential 3 benefits: 1. Speed. Time is precious for everyone. Minimizing time lost for transportation I think is the best benefit air transport provides, but the current commercial model makes this true only for long distances. VTOL has the potential...
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