Human powered ornithopter design
 

Following a discussion in the engine-powered human carrying thread, I think it is a good time to launch a thread to focus particularly on the challenges and opportunities peculiar to human-powered ornithopters. The discussion raised the question of automated repetition of flapping strokes versus stroke-by-stroke reflex adjustment.

While it is true that models fly OK using the automatic incidence properties of a membrane wing, you cannot say they fly with an energy efficiency approaching that of an albatross or a rigid-wing glider. There are many interesting things you can do with an inefficient aircraft (like an aerobatic Pitts for example) but they are irrelevant to my interest in human powered ornithopters.

Following the success of the Gossamer, Daedlus etc. aircraft in human powered flight we know the requirements very well. Their glide performance, particularly sink-rate, cannot be compromised by short span or sub-optimal airfoil profile. Unless somebody can prove otherwise, I believe this rules out single-surface sail wings.

Stability too is a feature we can take for granted only through built-in inefficiency such as the down-thrusting long-boom tail and fin, neither of which has found a place in avian body shape, despite the enormous diversity of birds.

A human powered aircraft has such a tiny margin of power over level flight requirements that it must operate at close to the optimum in every phase of takeoff, climb and level flight. Propeller driven aircraft use variable pitch to achieve some flexibility. In exchange for the modest improvement in propulsion efficiency that we hope to achieve with an ornithopter, we must incorporate an analogous method of dealing with variable airspeed, ground proximity, manoevering and wind gusts ( or puffs) etc. I think the most promising approach is through continual optimisation of flapping parameters rather than simply turning the handle. I anticipate that we will require adjustment of amplitude, force rhythm and timing for each wing panel and stroke, using the kind of trained reflexes that athletes learn in other sports such as rowing, jumping or running etc.

This is not only a unique challenge for human powered ornithopters but a unique opportunity since no automatic system, whether mechanically or computer mediated can apply such subtle sensing, power control and adaptive learning as an animal can. Human animals are no exception.
Murray Scott

Efficiency
 

I believe that man powered flapping flight is in reach and the key to achieving it is efficiency. Efficiency in wing design and drive mechanics, as far as the mechanics goes I believe that I have that. But wing design I am still working on. I have seen many ornithopter designs that are to bulky an heavy, as if the human body isn't heavy enough. In the 1800's Otto and others had successful glides using wing spans of 20 feet with a wieght of 35- 40 pounds.
As I look around me today at some of the designs for human powered ornithopters, they are huge; even if they worked I personally wouldn't want one. We should think small light and efficient, material technology in todays world is on our side.

One thing about that though: you need a lot of wing area to minimize the power requirement. An ornithopter might not need as much wing area as an airplane, but it will still need a lot. Instead of a giant 100 pound aircraft, you might have a much smaller 50 pound aircraft. However, when you include the pilot weight, this becomes perhaps 250 pounds compared with 200 pounds . Not a very large weight savings, compared with the reduction in wing area. I don't mean to minimize the importance of saving weight. Clearly you are right! But don't do it at the expense of proper wing area.

Wing area.
 

At the moment I am at 192 lbs down from 205 lbs and on my way to 185 lbs. I 've calculated that the mechanics including functional wings will be in the 45 - 55 lbs and my wing span is going to be about 18 ft by 4' 1/2ft. Now if this will be enough to get me up to speed I do not know but right now I am just in the testing phase.
For a 185 lbs person what wing area do you think I will eventually need ? I spent a couple of years at airforce school in florida but mechanics is more my field, wings are not my thing, yet. I am building a wing style after that of Karel Pustka, his design seems to be the best for my application. I wish he spoke english, but that is another story.


Thanks !

Like a bird,
Karel Pustka has passed away. Willi

Wow
 

I had no Idea, we lost a great one in him. Wow, wow I am glad that he chose to share his work with all of us on his web site. Stunned !

very nice, i to feel like whats the point of all of this unless we can come up with an ornithopter that we can strap on, take off runnin and flappin like a do do bird and fly. it can and will be done.

Nathan

Obviously Like a bird places a different emphasis on weight savings than you do. Anyone that diets so he can better pilot his orni is very keen. With a weight saving of 20lbs by starving, he will jump at the chance to save another 50lbs (if he is not too dizzy from his diet :). The best mindset to have regards weight saving for these ornis is natures approach - every tiny bit of excess material should go! View 1 percent as a huge saving and iterate down constantly.

Regarding takeoff for a human powered orni I see this as a non-event, requiring no ability except to seek out the higher ground and face the right way. I think that a 10-15ft relief in ground clearance should be ample to launch, with a head wind 5-10 kts. A simple ramp with tiny runway would do. If (when) an orni becomes a reality, much like the hang-glider, launch sites will dot the country side :) A 15 ft high X 15 ft diameter silo with flat top would only leave the challenge of climbing it first. I cant wait!!!!