Page 2 of 2 FirstFirst 12
Results 11 to 17 of 17

Thread: Air bike Tandem- getting started

  1. #11

    Join Date
    Feb 2018
    Posts
    26
    All good info. What I meant to say was, 2-stroke motorcycle engines were (are) virtually bomb-proof. Very reliable, and easy to service and maintain. The drawback: super polluters!

  2. #12

    Join Date
    Sep 2011
    Posts
    144
    Some consideration of engine choices should include safe landing risk if engine stops. I fly in San Bernardino mountains out of Big Bear where there is no place to put down if engine fails.
    If you fly around flat farm fields with plenty of open spaces, survival risk may be higher. But if you routinely fly in rough terrain where put down means a non-survival crash, you want an engine with high reliability and
    cost is secondary. I fly a Pulsar with a 912 with 1170 hrs and no engine issues...yet.

  3. #13
    Norman Langlois's Avatar
    Join Date
    Jul 2011
    Location
    Northwood ,N.H. USA
    Posts
    173
    I did not base my comment on statistics . On the observed only. and plain logic . The ultra light era gave many individuals opportunities to create . The fly. Your own data shows a decline in incident. Sudden stoppage always has a root . Most will lead to a user error. water ,over rev, improper oil, poor maintenance. Its not the 2 stroke its that 2 strokes need a strict user guideline. That beginning era was indeed experimental with many failures. The answer is obvious ly Yes there are more reliable than before. But still no more reliable than in comparison to 4 stroke. Nether power plant is any better with poor human interaction. If one engine design has been improved to the point it is bullet poof only then would you lift your condemnation of 2 strokes. And that will take another 10 years of statistics and only if all aircraft going forward with 2 strokes are of that design. I do not expect to change your mind if you have a condemnation of 2 stroke use . If you feed your 4 stroke water and let the sump go dry it will stop also.

  4. #14

    Join Date
    Mar 2018
    Posts
    2
    I agree with Norman. These engines are great for the small aircraft we fly (less expensive, light weight, use of auto fuel, etc.) but they do have operational limitations and they must be maintained and inspected in accordance with the published procedures. I have had two engine-out events and both have been caused by something that could have been corrected had the proper attention been paid to proper procedures. I have almost 50 hours on my Air Bike since its first flight with no unexplained problems and I feel confident that this 447 Rotax will continue to perform reliable fashion ( of course, I still have that landing site picked out all through the flight, just in case...).

  5. #15
    Sam Buchanan's Avatar
    Join Date
    Nov 2011
    Location
    KDCU
    Posts
    436
    It is my experience (and the experience of many others) that a primary difference in reliability between two and four stroke engines is their failure modes. The engine failures I had with two-strokes resulted in sudden stoppage of the fan with no warning. Four strokes are more likely to fail gracefully, usually with ample warning that they are not feeling well if the pilot is paying attention. Two strokes generally operate on the margins of reliability in order to achieve high output with light weight, four strokes often are less stressed for a given percentage of power.....but heavier.

    Here is a simple question: Which engine would you prefer to fly at night over hostile terrain......two stroke or four stroke?
    Sam Buchanan
    The RV Journal RV-6 build log
    Fokker D.VII semi-replica build log
    YouTube Channel

  6. #16
    DaleB's Avatar
    Join Date
    Sep 2015
    Location
    KMLE
    Posts
    469
    Quote Originally Posted by Sam Buchanan View Post
    Which engine would you prefer to fly at night over hostile terrain......two stroke or four stroke?
    Turbine.

    Personally, my experience with 2-stroke engines has been limited to R/C engines, a very early 1970s Lawn Boy mower, a '55 Vespa scooter, and a few weed whackers. I think that probably holds true for a lot of people, and trying to mentally translate that experience into something to fly behind (or in front of) can be a challenge. Although, now that I think of it, all of those examples have been extremely reliable as long as they get good gas, enough (but not too much) oil, and the carbs and reed valves don't gum up. When that's happened I don't think I've ever gotten one to run again. Of course that's a perfect example of what happens when someone tries to "fix" something they know next to nothing about.
    Measure twice, cut once...
    scratch head, shrug, shim to fit.

    Flying an RV-12. Building a Fisher Celebrity.

  7. #17
    Norman Langlois's Avatar
    Join Date
    Jul 2011
    Location
    Northwood ,N.H. USA
    Posts
    173
    My original comment was for HAPPYDAN .In considering going Ultralight with his plane. The 2 cycle engines that are being produced for use in aircraft are improved. Liability has made this happen. One can still build and fly a 103 with any engine they choose. But that wont be true for certified. That will require a few more hoops to jump through.
    I was at Oshkosh and Sun and fun this year. I stopped by the Hirth booth. I was impressed by the specs for the Hirth F33. This engine was not doing well when first introduced, but has now become one of there top sellers. EXPENSIVE for a 2 stroke option yes. If it is as reliable as projected ,the cost would be worth it. I'm not trying to sell there product.
    The one statement made to me, was in answer to my Question how long at full throttle. The reply, was till you run out of gas. That reflects a very reliable mechanical sound engine design. Something to consider about the past use of 2 cycle engines. In an experimental application, engine loading ! The back yard builder would need help with this, but did they in the past 30 yrs. I suggest that over the last 15 yrs we have better recommended prop to engine data. The loading is as important as the fuel mixture . The data that has been gathered has made the choice more reasonable.
    Last edited by Norman Langlois; 01-06-2019 at 09:56 AM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •