ULPower engines?
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Capt. Geoffrey Thorpe
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Light and Sporty Guy
This guy has one in his Zenith and seems to like them... https://www.youtube.com/c/KitplaneEnthusiast1/featured
wanttaja
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Small sample size; my 1998-2020 database has about 4,550 total homebuilt accidents, but only 11 of aircraft powered by ULPower engines. Two Sonexes, one RV-12, the rest on Zeniths. Six are on Zenith CH-750s. All of the 11 accidents involved fixed-wing aircraft.
Of those 11 accidents, six were due to loss of engine power. None of the six cases were pilot-induced (e.g., no one ran them out of gas). Six out of eleven is about 54%. In comparison, the overall rate of engine failures is about 33%, with the Lycoming O-320 at 27% and the Rotax 912 at 22%.
The reason for the loss of power in one of the six cases was not discovered due to "The airplane was not made available during the investigation" (CEN17LA329). The airplane landed in a field, not sure why the engine wasn't examined. Sounds like the pilot just took his football home.
Of the other five cases, two were due to losing power to the electronic ignition. One I assessed as Builder Error, as the NTSB found faulty installation of the Engine Control Unit (ERA09CA162), the other was due to a loss of power to the ECU (WPR19LA222). In this second case, the NTSB specifically called out that the aircraft lacked a backup ECU.
One case was due to "....air or fuel vapor entering the fuel system, which prevented fuel from reaching the engine cylinders" (WPR18LA120). Another was fatigue failure of the crankshaft (WPR21LA049), and the last was a stuck exhaust valve (CEN19LA199).
AGAIN, though, I have to highlight that this is a small sample size. I normally don't assess engine or aircraft types unless I have 40-50 accidents in my database.
This is raw output from my database, comparing a number of engine types. "Primary" means the initiator of the accident was engine-related, "Sec" stands for "Secondary"; the mechanical issue was brought on by another reason such as builder error. The highlighted row ("Engine Mechanical Either") is usually the first place I look at when comparing engine types.
Ron Wanttaja
wanttaja
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Part of that is my own analysis process. When I started doing this work ~22 years ago, I was concerned that mechanical faults in homebuilt aircraft were being obscured by "Probable Causes" that reflected the pilot's problems when dealing with the emergency. This chart from one my presentations sums it up:
Same circumstances, one investigator attributes the accident to a failure of an oil line, while the other feels the pilot is at fault since he should have been able to safely force-land the aircraft.
So... I don't use the Probable Cause in my analysis. I read the narratives to find what I call the "Initiator;" the first major event that precipitated the accident. I flag the Initiator, and any other factors that might have been at play that day get tagged as "secondaries." Each accident in my database has one Initiator, and as many Secondaries as appropriate. I cross-check with what the NTSB investigators tag as the "Probable Cause," and, if my Initiator differs, I carefully examine the accident to make sure. Almost always, if an accident sequence begins with a mechanical issue, it gets an Initiator based on that. If my database attributes the accident to the pilot's actions, then the aircraft itself was in 100% condition.
In any case, this is a long-winded explanation that isn't really needed here. In this accident, the exhaust valve failure was tagged as the reason for the total engine failure by the NTSB. The pilot reported a total loss of power, and the NTSB report said...
An engine examination revealed the No. 3 exhaust valve was stuck open. A borescope inspection of the No. 3 cylinder did not reveal any mechanical issues or interference between the piston and the stuck exhaust valve. A borescope inspection of the crankshaft and camshaft did not reveal any anomalies or mechanical damage.
The airplane was equipped with an experimental reciprocating engine equipped with an electronic fuel injection and ignition system. The engine control unit (ECU) continuously controls the air-fuel mixture and ignition timing based on readings from multiple sensors, including a crankshaft position sensor that provides the engine speed and position of each cylinder’s piston and valves. It is likely that the stuck No. 3 exhaust valve adversely affected cylinder compression, engine timing, and fuel delivery to the cylinders. (CEN19LA199)
Ron Wanttaja
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http://www.myulpower.com
This website gives one person's opinion, to the issues he had with his ulpower
engine.
This website gives one person's opinion, to the issues he had with his ulpower
engine.
Well, this certainly gives me pause.
They are pushing it pretty hard. It's their default engine for the Cruzer.
It seems like the FADEC on the ULP should be a huge positive, but from what I'm reading it's a negative. Nobody seems happy with the way it's tuned, and apparently there's no tweaking it within the warranty. The fact that it can shut the engine off if the readings confuse it is a hard pass for me. Redundancy won't solve that problem.
I think the fact that the vast majority of certified SLA's are using Rotax is making me lean towards Rotax. I liked the fact that the UL was direct drive, but if it's still failing as much as a Rotax, that doesn't mean much. My take after a whole day of research is the UL is a good engine for someone that wants to be constantly tinkering with the engine. This is not me. I'm not afraid of tinkering, but only to meet my primary goal of flying, not as a primary hobby itself.
Warmi
Line Up and Wait
To me personally Rotax is now gold standard for reliability for experimental and LSA planes … all engines fail but as far as reliability Rotax is not worse ( imho actually better ) than certified engines.
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wanttaja
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I recently completed an analysis of the Rotax 912 vs. other small engines in the same HP range, such as the Continental A65 through O-200, the Lycoming O-235, the Jabiru, and a couple of auto engines. The Rotax 912 has the best record, as far as mechanical issues are concerned.
Direct comparison with the small Continentals looks pretty good, too....
The installed base for the Rotax 912 in the homebuilt aircraft world was large, as well. The FAA registry shows about 1800 A-65s through O-200s vs. about 1400 Rotax 912s. However, there are another 2300 aircraft identified as having "Rotax" engines without specifying what model number, so the installed bases are probably pretty close.
In short, I found the Rotax 912 has the best safety record of any of the small homebuilt engines, including Lycomings or Continentals.
Should be a KITPLANES article coming out on this, in the upcoming months....
Ron Wanttaja
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Not just experimental by the way, tecnam uses them in some their certified aircraft, 912s3, with 2K TBO
Rotax is the way to go
Grum.Man
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Issues with UL engines aren’t terrible from what I’ve seen. At least not to the level of other newish engines like Jabiru or Rotec. I enquired once about their aerobatic engines as a possible candidate for one of my Pitts projects. The rep kind of shot him self in the foot when he recommended I look them up on YouTube. The very first video was of an aerobatic team crash as a result of engine failure. Upon further googling it seemed like there were a lot of issues with that engine so it certainly turned me off in an application as unforgiving as a Pitts. The price delta of a UL and Lycon new engine keeps growing though so not completely off the table in the future.
Capt. Geoffrey Thorpe
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Light and Sporty Guy
With gold plated prices for parts.
Kenny Phillips
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Isn't that what Zenith uses on the SuperDuty? You could ask Roger how it's working out, should have many hundreds of hours now.
Warmi
Line Up and Wait
With gold plated prices for parts.
Yeah but still cheaper than damn avionics and people seem to have no problem putting 30-40k worth of avionics into their VFR experimental planes and then “save money” on their engines by installing something odd like Viking or other auto conversions …
Tantalum
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Given the choice I'd take a simple steam setup, mount the iPad, and spend the $$ on a reliable engine..
Granted, auto-conversions be ragged on but the Corvairs seem to do okay.. and Rotax found a way to make a reliable gearbox. The whole "but the gearbox?!?!?!" argument is crap to me. Just about every turboprop has a gearbox on it and we're always told how much more reliable turboprops are
I digress
Granted, auto-conversions be ragged on but the Corvairs seem to do okay.. and Rotax found a way to make a reliable gearbox. The whole "but the gearbox?!?!?!" argument is crap to me. Just about every turboprop has a gearbox on it and we're always told how much more reliable turboprops are
I digress
wanttaja
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Well... Corvairs are not as common or as reliable as some might think. Here's a tally of engine types from the January 2022 FAA registration database. Only engines with 50 or more examples are shown.
Some of the AMAT/EXP entries and the "No Engine Listed" entries are undoubtedly Corvairs. But then, they're just as likely to be VWs, Fords, Chevies, Rotaxes, Continentals, etc.
To me, a better indicator of the popularity is the number of accidents. Because regardless of engine, the more airplanes flying, the more are going to crash. The total number Corvair-powered homebuilt crashes in my 1998-2020 database is 24, still well below my desired threshold for full analysis. But the rate of engine failure is running about the same as the ULPower results I shared earlier. Vs. the ULPower engines, there are proportionately fewer "engine internal" cases, more "Undetermined engine failures."
Ron Wanttaja
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Such a treasure trove of data you've got. Love it
Daleandee
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Dale Andee
I'm certainly a one off example but my engine, assembled by Dan Weseman of Sport Performance Aviation (Panther Aircraft) to the specifications of William Wynne (The Corvair Authority), has given good performance with excellent reliability. Plenty of power and a very smooth air-cooled flat 6!