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Hirth F33 Reliability

Posted: Sun Sep 17, 2017 9:42 am
by HAPPYDAN
I just received a September copy of SPORT AVIATION, in which there is an excellent article regarding the Aerolite 103. As I have become frustrated with the Sport Pilot licensing route, but still enjoy flying, this presents new possibilities. Maybe I'm falling prey to the hype, but this one sounds good. It can be a kit or complete, and standard comes with a Hirth F33 2-stroker. My question is, how reliable is this engine? In the '70s I grew up with 2-stroke road and dirt bikes, and found those (Yam and Zuki) to be strong and reliable, although smoky. Plugs fouled regularly, and exhaust ports needed to be cleaned now and then, but sooo easy to work on, not a problem. Get the oil mix right and keep the revs inside the redline and everything worked fine. Research on the INET produced very little useful information; a few swear by them, and just as many swear at them. Knowing the frustrated are more likely to sound off than the satisfied, I'm asking any and all to respond with info, facts, or anecdotes regarding the Hirth aircraft engines, especially the F33.

Re: Hirth F33 Reliability

Posted: Sun Sep 17, 2017 4:43 pm
by chicagorandy
No help from me other than to suggest a different forum to search - non sport pilot that is- I know I've seen postings regarding the Hirth and other ultra-light engines over at the EAA Forum groups -

http://eaaforums.org/forumdisplay.php?9 ... ight-Strip

Re: Hirth F33 Reliability

Posted: Mon Sep 18, 2017 8:50 am
by Jim Hardin
I read the Aerolite article too and was impressed. But I think chicagorandy's response is the best idea.

Keep in mind that aviation and marine use involve mostly steady throttle/rpm conditions which add a lot to reliability. Aircraft mechanics I have talked to feel that if you stick to the maintenance schedules for them, 2 cycle engines are reliable. (I have never flown one)

The other important thing is your attitude. If you are casual with preflight and before flight testing indications, you should go back to dirt bikes. Also find yourself a grass strip and keep up practice for engine out landings. Plan your flight route, even a fun hop, that keeps usable landing spots under your tires.

Keep us updated on your research and progress :wink:

Re: Hirth F33 Reliability

Posted: Mon Sep 18, 2017 9:23 am
by rsteele
Learn as much as you can about 2 strokes. If you treat one like a four stroke, you are guaranteed to have problems. I expect at least some of the difference of opinion is because some people take time to understand 2 strokes and some don't. That said, I've never flown one, but did the same sort of research you are starting on now, a few years ago.

Ron

Re: Hirth F33 Reliability

Posted: Mon Sep 18, 2017 12:24 pm
by HAPPYDAN
So I'm intrigued and inspired by the whole "Part 103" aspect. I guess the NTSB and the FAA doesn't really care if I endanger myself, so long as I don't endanger anyone else. But this old dog knows that advertising "hype" can cover up a lot of defects, hence my concern. U-Fly-It (current builder of the Aerolite 103) offers several engine options, and I wouldn't mind paying a little extra for a solid mill.

Re: Hirth F33 Reliability

Posted: Mon Sep 18, 2017 12:32 pm
by chicagorandy
It 'seems' to be often posted that with a small 2-Stroke, it's not 'if' it will shut down during flight, but 'when' it will? I can appreciate that they require more attention to maintenance than other engines.

Re: Hirth F33 Reliability

Posted: Mon Sep 18, 2017 12:52 pm
by rsteele
chicagorandy wrote:It 'seems' to be often posted that with a small 2-Stroke, it's not 'if' it will shut down during flight, but 'when' it will? I can appreciate that they require more attention to maintenance than other engines.


That's certainly an often heard sentiment. Another thing to look at TBO. I think it's on the order of 300hr for some of the 2 strokes.

Re: Hirth F33 Reliability

Posted: Mon Sep 18, 2017 1:30 pm
by TimTaylor
HAPPYDAN wrote:So I'm intrigued and inspired by the whole "Part 103" aspect. I guess the NTSB and the FAA doesn't really care if I endanger myself, so long as I don't endanger anyone else. But this old dog knows that advertising "hype" can cover up a lot of defects, hence my concern. U-Fly-It (current builder of the Aerolite 103) offers several engine options, and I wouldn't mind paying a little extra for a solid mill.

Usually, you people complain about over-regulation by the FAA. I think this is the first complaint I have seen on one of these aviation sites about under-regulation. It never stops.

Re: Hirth F33 Reliability

Posted: Mon Sep 18, 2017 5:30 pm
by 3Dreaming
TimTaylor wrote:
HAPPYDAN wrote:So I'm intrigued and inspired by the whole "Part 103" aspect. I guess the NTSB and the FAA doesn't really care if I endanger myself, so long as I don't endanger anyone else. But this old dog knows that advertising "hype" can cover up a lot of defects, hence my concern. U-Fly-It (current builder of the Aerolite 103) offers several engine options, and I wouldn't mind paying a little extra for a solid mill.

Usually, you people complain about over-regulation by the FAA. I think this is the first complaint I have seen on one of these aviation sites about under-regulation. It never stops.


I didn't take it has him complaining.

Re: Hirth F33 Reliability

Posted: Wed Sep 20, 2017 7:58 am
by Jim Hardin
One impression I have gained from being around the Part 103 crowd is the striking lack of knowledge about aircraft and engines :? Combine that with a lack of respect for safe operating practices and it is little wonder that they have issues with 2 stroke engines...

I am not knocking the people and it is understandable that without being in the regulated side of aviation their approach is from never having worked in the discipline.

If a 103 guy recommends a can of diet coke per 5 gallons of premix, others will either try it or pass along that 'good advice'.

2 strokes do require a more rigid maintenance scheduled without any room for a, it will probably be ok attitude.

Re: Hirth F33 Reliability

Posted: Wed Sep 20, 2017 8:44 am
by MrMorden
I don't know anything about the Hirth engines, but last year I did get a chance to walk around the Aerolite at Oshkosh. It was pretty neat. I like that the covering is sail cloth that is zipped on -- easy and cheap replacement and access to the structure. I didn't love that it has a yoke instead of a stick, but that's just personal preference.

Overall it looked like a very nice Part 103 machine.