17 Feb

While searching through old emails yesterday for one related to a gift I recently gave to my niece, I stumbled across two that had come in about a year ago and had somehow escaped my attention.   One was from John Bailey in the UK and the other from a new contact in South Africa.   John Gibbs is a technical writer in the Durban area and, as he describes himself, ‘a backstreet aeronautical engineer’.   He had found the Great Blue Machine and was motivated to write a detailed description of his informed views on the future of human powered aviation.  I’m going to write him back and request permission to post his letter in the correspondence section, because I hope it will prompt some discussion from John Bailey and Tom Phillips and perhaps others as well.   While I was glad to see that we agree on essentially every aspect of innovative aircraft design,  John feels that ornithopter R & D is going to waste lots of time, and I feel that it is the area in most dire need of exploration.   True, some supplemental power is needed to gain altitude under many conditions but then with a decent glide ratio (which all birds possess), the need for power would be diminished except possibly at landing when a significant amount of flapping would be required for breaking.   A bit called “Why don’t airplanes have flapping wings” by Robert Lamb on the Blow Your Mind blog cites the work of Jim Usherwood at the Structure and Motion Laboratory, Royal Veterinary College, University of London.  Robert Lamb takes a similar view to John Gibbs when he states that birds are just not very efficient.   As a Biology teacher who has spent more than twenty years studying and watching birds, I must disagree.   Nature cannot afford to be wasteful and our best way forward as a species is to emulate this principle first.  We must ultimately come to understand that the entire infrastructure needed to support the automobile, – including all roads, bridges filling stations, tunnels and manufacturing plants is killing this planet and its riotous biodiversity.   With a clear focus on intentional, biologically inspired design, we can learn to travel in the water as the sharks and whales do and take to the sky as the birds, bats and insects do.   John and I agree that birds have power to spare and that humans cannot generate an equivalent amount for our size.  We can generate some though, and super-capacitors can be used to make up the difference.   Birds, Bats, and Bugs are WAY more versatile and maneuverable than anything we have some up with so far.   They bulk up at the end of the summer and routinely fly thousands of miles non-stop through all manner of environmental conditions.     John and I agree that a radically novel approach to personal flight is needed, it’s just that we see different ways to get there and that is good.   The more people looking carefully at the problem, the more likely we are to resolve it!

My interest is in creating ornithopters of increasing mass and demonstrating their inherent air-worthiness.  The engineers at FESTO have been able to realize significant improvements in efficiency with their bio-inspired designs.   Digitizing actual bird parts and using a combination of 3D printing and carbon fiber milling is already yielding an increasing diversity of smaller mass flying robots.  We have swifts, penguins, hummingbirds and gulls.   It won’t be long until other bird families are represented and the employment of artificial feathers should lead to a substantial increase in both thrust and lift generating capabilities.   From there, flapping winged fliers will quickly gain mass / size.

3 Responses to “”

  1. Tom Dunlap February 17, 2014 at 1:14 pm #

    Hi Karl. I have to agree that inefficiency is selected out of the natural world where flight is concerned. Birds developed their hollow bones because birds with lighter bones did better than birds with heavy bones for example. It’s likely that each species evolved to a point that was ‘just good enough’ for it’s niche, That is not to say that our own ‘directed’ evolution of flight won’t come up with ‘better’ solutions. Jet engines are obviously better if what you want is speed. But if your goal is to emulate the versatility of a certain species of bird, you can’t go wrong by studying that bird and using it’s structure and modes as a starting point.

    For myself, I want the soaring capability of an inland raptor or vulture so that is where I’d start. Others may want to be able to do what a hummingbird does or as you have indicated, the Great Blue Heron would be your model.

  2. John Gibbs February 18, 2014 at 1:37 am #

    Birds are as efficient as they can be, for all that they are.
    It pays to bear in mind that birds are not optimised for flight alone – and THAT is the issue.

    Speak of the devil…

    Yes, it’s John Gibbs – I am a Technical writer, and before that I was an Electronics Engineer.

    While I have no formal aerodynamics training, I have filled countless spread sheets with lift and drag calculations, I have run a great many aerofoil sections through the JavaFoil analysis – including multiple foil arrangements. I have built and flown many models.

    I have a passion for physics – especially Newtonian mechanics and a good feel for fluid dynamics.

    There is just too much to say here in one bleat – I have studied this whole issue in great detail for close on twenty years, and it won’t stop until I have my own practical human powered plane, or I get old and die…

    Just for starters:

    The best performing aircraft are specifically designed and optimised for extremely limited operational requirements. There is no bird that can compare with the L/D performance of typical modern sailplanes simply because birds have too many other features that unavoidably compromise their design:

    Built-in mechanical maintenance
    Wing-morphing
    Super-fast and convenient wing stowing arrangement
    Ability to reproduce
    Made from biological, living material
    Able to get wet and still fly
    Able to dive into water and swim underwater – and then still fly again
    Sufficiently resilient to survive a considerable battering

    OK, some of these we don’t need, but in reality we simply can’t afford ANY of these “bells and whistles” – as they all compromise the machine’s efficiency (flying ability for the power available).

    (For those thinking about it, no, a vasectomy won’t help)

    The only reason birds flap is because of limits imposed by biology.
    Flapping (like a bird) is not the most efficient way to implement powered flight – I will discuss the finer details with those willing to partner with me.

    With all due respect to those who have done incredibly good work, present day Human Powered Aircraft are still as clumsy as all heck, they are fragile beyond belief and need constant love and care, a huge budget, perfect weather, a deserted field, etc, etc, etc.

    They require a super-athlete to remain airborne for any reasonable duration.

    Birds have a phenomenal power:weight ratio
    Humans are stuck with a comparatively feeble power:weight ratio

    Being a large-scale, biological machine, rotating parts and conservation of momentum is not possible in a bird – and the bird makes up for this very lossy arrangement by having power to spare, a fast metabolism – and an enormous appetite.

    Practical wings that allow for easy take-off from the ground are only possible when there is a significant excess or power available – but we want to do this with human power.

    We do not have the luxury of power to spare, so we cannot afford to adopt a method that is as wasteful of power, we want to get good returns on every bit of energy we expend.

    We need to devise a system that makes full use of conservation of momentum – the only losses that we can afford to have are the drag of the airframe through the air, and the friction in the bearings of the system. I agree that we need to move away from using a propeller. Ground clearance issues result in a spindly, compromised arrangement and the huge propeller ruins any hope of gliding.

    Long, flapping wings (with sprung, pre-loading?) CAN be made very efficient, but dammit, we really want to be able to take off from a level field under our own power – without the need for a whole backup crew and equipment.

    I do not believe that electric motors or super capacitors are needed – all this will add to the all-up weight and entirely destroy hope of any endurance.

    If you want an effective energy storage system… just climb!

    I have a design approach that I believe has a darn good chance – and I am looking for somebody who has the time and finances to partner with me to develop the next generation HPA.

    I believe that this aircraft has the potential of being commercially viable – and with a performance capability that will make Human Powered Flight the next sporting fad.

    Take off at ~ 38 km/h
    Fly on most days without rain – tolerant of moderate winds
    Cruising at 47 km/h on power output that can be sustained by a normal healthy person
    Capable of soaring (pedal, rest, pedal, rest) – with no propeller drag to worry about
    Thus capable of cross-country flights of potentially hundreds of km
    Wing span… far smaller than many thought possible
    No wing handlers needed
    Manoeuvrable – able to turn far more easily than present HPA

    The aircraft should be capable of winning both the Cremer Marathon and Sports Plane prizes (50 000 and 100 000 pounds, respectively, if I remember correctly).

    If the design is as robust and as practical as I think it can be, then people will want it, very much.

    Tooling up for mass production could then bring per unit price down, and HPA ownership to the middle class.

    All I ask for my contribution is a 30% share of any prize money – and mutually agreeable royalties from any production.

    I would naturally prefer that such persons lived near Durban, South Africa – but am not averse to taking on overseas partners in this quest, as I am only to aware of how rare these folk are!

    In a field such as this, there are those with the resources and the ability, and there are those with the vision and strength of conviction to keep chipping at an idea… it is seldom that one person has both.

    Anybody know someone really good at building things, who may be itching to give it a go?

  3. John Gibbs February 18, 2014 at 7:22 am #

    “Nature cannot afford to be wasteful”

    But “wasteful” only has meaning when resources are limited.
    Birds have power to spare – and an abundant supply of fuel.
    They have no need to be frugal!

    For birds it is not a question of efficiency, it is rather a question just being good at what they do.

    Compared to the birds, we are close to bankrupt when it comes to power output.

    Even a “pathetic” little white dove can explode from zero to 80 km/h flight in what looks like under a second. All the hideous, power-gobbling turbulence is no concern at all, when the alternative is being eaten.

    That is not efficiency at work – it is a demonstration of hideous power to spare.
    That is a bird whose power system is analogous to the WWII Thunderbolt – no, actually far more.

    The thunderbolt was certainly not an efficient aircraft.
    But it was great for its intended purpose: Travelling some distance at good speed and bringing big guns to fire on the enemy.

    Just like the Thunderbolt, Birds are not efficient either.
    BUT they are very good at what they need to do!

    They have powerful engines and they gobble plenty of fuel – of which there is great supply.

    Humans, quite simply, do not.
    We are nowhere near their league.

    Yes the little white dove is a “monstrous example”, I know that there are more sedate birds

    But when you do a cold and scholarly assessment of their their power/weight, you will find that even they are orders of magnitude more powerful than humans.

    I agree that Human Powered ornithopters are certainly achievable – but they could never be a practical solution, as they bring with them far greater problems than the 3-metre propeller that they replace.

    In an example such a Daedalus, all flight surfaces (and the propeller blades) were operating close to their optimum – this is simply not possible with flapping wings – go and ask any aeronautical engineer who knows his stuff.

    It only gets worse with flapping wings – not better, and then you have ground clearance issues…Birds only manage because they are so darn strong.

    It is tempting to observe the gracefulness of bird flight and conclude that because it appears effortless that it is.

    The reality is that birds are incredibly powerful animals, with high fuel consumption – even the “gentle” fliers.

    I believe that the present state of the art of HPA design is close to its practical limits and it is time for a bold departure from the “conventional” approach.

    Time for the next stage in HPA progress, something that will deliver PRACTICAL HPAs with better performance that will open up a whole new category of sport and recreation.

    Not conventional, not ornithopter…

    I have a design approach that I am convinced can do it.
    Anybody game?

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