ETLB Squawk Forums — Archive

Hi
Is it at all reasonable to presume one can build an AirBike, either total scratch built or kit or partial kit, that makes u/l weight with any engine that can actually safely perform normal flying activities? (190 pound pilot) I believe the airbike website suggests it is possible, I am more looking for actual instances where someone was legally u/l.  Thank you for your time in this matter.
Kim Brown
New Hampshire

Hi Kim,
For a pilot under 200lbs it is possible to get very close to the ul weight with a lightweight engine such as the hirth f33. It has been done before with the Zenoah g25b and rotax 277 but you have to eliminate every ounce you can when building. in the end you will have a plane that barely makes weight, cruises 40mph, and climbs 200fpm, very minimalistic performance.

The average 447 powered airbike weighs around 350lbs empty for reference. The 1100R and 1030R minimaxes can both be built under 254lbs with 28hp engines and will cruise 50-55mph and climb 400fpm, much better performance.

If you are set on a high wing and steel tube fuselage, look at the legal eagle. It is a great flying bird and can handle engines up to 60-70lbs while making weight

Chris

And I guess now you can get folding wing feature with the Legal Eagle.  Have not seen an LE in person but from the photos it always struck me that one's legs were crammed/cramped into a short front end area.  You are suggesting less weight with LE versus Airbike, I will have to do a little internetting to see wherein lies the weight saving.  Thank you

I agree with Chris, it CAN be done but I think you would be disappointed in its performance and the limited conditions in which you could fly. If you really want to build an AirBike, which is a cool plane, go Light Sport then you can mount a 40 or 50 hp engine, put in an extra fuel tank, and maybe brakes and you will then have something that performs well and is fun to fly with confidence.

Paul Fiebich
aka. AirBike Ace

Kim,

The weight savings lies in the materials used, The legal eagle was designed from the onset as an ultralight, therefor thinner wall thickness tubing is used in its construction. The airbike was designed as an experimental amateur  built aircraft around the popular rotax 447 and 503 engines. The prospect of mounting a 130lb, 50hp engine requires a stronger airframe to deal with the weight and higher speeds / g loading that a more powerful aircraft is capable of.

Chris

Quoted from BlueMax tal amateur  built aircraft around theKim,

The weight savings lies in the materials used, The legal eagle was designed from the onset as an ultralight, therefor thinner wall thickness tubing is used in its construction. The airbike was designed as an experimen popular rotax 447 and 503 engines. The prospect of mounting a 130lb, 50hp engine requires a stronger airframe to deal with the weight and higher speeds / g loading that a more powerful aircraft is capable of.

Chris

If that is so it sure doesn't line up with my memory bank!

The first Airbike I saw was at Oshkosh in the middle 90s.  It had a Rotax 277 and not an N number in sight.  This was the TEAM factory prototype Airbike. They changed to the Rotax 447 but didn't do anything different to the design. I'm pretty sure it continued to fly as an ultralight. I flew my 447 Airbike for years with no N number and no one ever asked me to prove it wasn't an ultralight.  I'm sure more Airbikes have been flown under Part 103 than as E-AB.

The Airbike used .035 tubing which is pretty light.  What does the Legal Eagle use?  Paul has already demonstrated that a 503 will break some of the structure of the Airbike.

Video of early 447 Airbike flown under Pt 103.  
https://youtu.be/MlhjEFFqvZs

Quoted from kfb Hi
Is it at all reasonable to presume one can build an AirBike, either total scratch built or kit or partial kit, that makes u/l weight with any engine that can actually safely perform normal flying activities? (190 pound pilot) I believe the airbike website suggests it is possible, I am more looking for actual instances where someone was legally u/l.  Thank you for your time in this matter.
Kim Brown
New Hampshire

Mine weighed 305 with a Rotax 447.  Remove the fiberglass cowl and wingtips, the windshield, the brakes, the padded seat, most of the paint, and go with a lightweight engine and I'm sure it can be done.  You can save 30 lbs by using something like a 35 hp Poloni Thor 250 and still have plenty of power.  My 447 Airbike would climb at 700 fpm on 40 hp and that was at a gross weight of about 550 lbs.

Legal Eagle also uses .035" tubes.  I was building one years ago. Had empenage, wings, fuse, on gear etc.
Mounted the wings and was horrified at the amount of fuselage flex/racking in the cabin area. Had no trust in it, sold it.
Now I see the Airbike uses cables from the wings to the fuse for this. Had I known that then I would have added cables to the Legal Eagle.  
Legal Eagle weight savings that comes to mind, alum tail, lightning holes in nose ribs, and spars.  Dont let anyone on the LE forum fool ya', its certainly "highly influenced" (putting politely) by the AB. I dont have a problem with that. I have a problem with them not admitting it, or giving Wayne Ison the credit he deserves.   The AB has an engineering stress analysis that proves its safe. The LE?   Of course there are a few flying and I have not heard of any structural failures so maybe its nothing to worry about.