Page 4 of 4 FirstFirst ... 234
Results 31 to 34 of 34

Thread: Ultralight engine options

  1. #31

    Join Date
    Nov 2013
    Location
    Redding, CA
    Posts
    11
    Quote Originally Posted by aeroschmitz View Post
    A very neat bird! I did a search for the 20-20 episode but could not find it. Thanks for the link, it clearly shows how the engine is mounted upright in the open. this is what I wanted to do with my challenger to get away from the inverted engine issues. what climate did your fly in? I had researched the F33 hirth (spendy) and they do make a pretty slick kit to mount on a challenger. I think this is probably a better way to go since that engine is in use in a pusher.

    I fly in Northern California. Never gets really cold here but it can get really hot in the summers. The engine originally had an aluminum air scoop on the head to improve the cooling. It cracked from the vibration. I made another one. It cracked from the vibration. I made another one out of thicker aluminum. It cracked from the vibration. I gave up and just ran the engine as rich as it would stand without a scoop and found I could keep the temps in range. Carbon build up was a little more than before but decarboning a free air 277 takes all of about an hour. A scoop fabricated out of composites might hold up to the vibration. Aluminum won't.

    After the second piston seizure, I had the cylinder bored out about 0.002 larger than spec to provide more clearance for the piston. I managed to avoid any further seizures but it was always a worry. The CHT would get down below 250 on the descent to landing. Whenever I was doing touch and go, I was at risk of a cold seizure, which is when the aluminum piston heats up and expands faster than the cast iron cylinder and seizes in the bore.

    I think the F33 would be a better option than the 277, but it is spendy. It has a Nicasil cylinder so it's not nearly as prone to cold seizure as a steel-sleeved Rotax. In my experience and from experience of others I know, Hirth engines often require a lot of fiddling to get them set up right. Rotax did their homework and provided charts with the proper carb jetting for different altitudes. Hirth just seems to send engines out with a random selection of carburetor jets installed. They often will barely run when received straight from the factory, so you should plan on buying a selection main and needle jets, and jet needles and spending some time get it running right before you attempt to fly it. Once he got it set up properly, my friend has had very good service from his F33 engine and he wouldn't trade it for a Rotax. He's got it mounted on a ultralight trike and frequently shuts down the engine for soaring. He has the electric start which is real boon for air starting when the thermals give out. An F33 weighs a lot less and runs smoother than a 277, but probably doesn't put out quite as much thrust. I think it would probably get a Challenger in the air, but don't expect spectacular climb rates. Mounting the engine upright should give you the room to swing a big prop, which is key to getting high thrust out of low HP. I was getting over 200 pounds of thrust from my 277 with a 60" IVO prop. I felt pretty good about that until I read that the Wright Flyer produced about 130 pounds of static thrust from 12 hp. It was turning two 102" propellers at only 300 rpm. I doubt if there's been any airplane since that time that's had a better thrust to HP ratio. Static thrust is a pretty good indicator of performance for slow flying ultralight aircraft. Maybe not so much for faster airplanes.

  2. #32

    Join Date
    Mar 2016
    Location
    Rockford, IL
    Posts
    30

    20/20

    Quote Originally Posted by VFR-on-top View Post
    15 minutes on google & youtube resulted in no transcript or youtube videoor "Ultralights: Flying or Dying". Other writers stated their own difficulties in finding that video as well.
    Roughly what was filmed (this was 33 years ago so memory might not be completely accurate) was a reporter came to an ultralight dealer and wanted to film himself flying an ultralight. He'd told the dealer that he was an experienced pilot (he had no training) and refused to wear the supplied shoulder harness because it clashed with the shirt he was wearing on camera (dumb). Ended up with him doing repeated dives and recoveries until he fell out of the plane (no shoulder harness) and died. All on film and on TV. Pretty much killed the industry.

    Please correct any inaccuracies.

    Bill H.

  3. #33

    Join Date
    Mar 2016
    Location
    Rockford, IL
    Posts
    30

    follow up

    Quote Originally Posted by griffin800 View Post
    Roughly what was filmed (this was 33 years ago so memory might not be completely accurate) was a reporter came to an ultralight dealer and wanted to film himself flying an ultralight. He'd told the dealer that he was an experienced pilot (he had no training) and refused to wear the supplied shoulder harness because it clashed with the shirt he was wearing on camera (dumb). Ended up with him doing repeated dives and recoveries until he fell out of the plane (no shoulder harness) and died. All on film and on TV. Pretty much killed the industry.

    Please correct any inaccuracies.

    Bill H.
    http://www.rotaryforum.com/forum/showthread.php?t=29957

    A long ago review of what happened.

  4. #34
    Dana's Avatar
    Join Date
    Jul 2011
    Posts
    928
    Mark Smith at Tri-State Kites (former Quicksilver dealer, still scratch builds them and sells parts) has a copy of the 20/20 video. He will show it to any visitor who asks, but will not allow copies to be made (I guess I don't blame him). From what I've heard, the pilot was instructed to make it look crazy and dangerous (typical muckracking "journalism"). Combine that with a pitch sensitive aircraft that could easily exceed Vne in level flight, and an unbuckled harness, well, the outcome is unsurprising.

Posting Permissions

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