Zenith 750 stol

Housedr

Filing Flight Plan
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Housedr
I’m at a point in my build where I need to pick an engine.
The Viking guys love theirs, the rotax guys love theirs, the UL guys etc.
Everyone tells me 130 hp.
Any advice? I have a hard time believing the 750 wont perform well with 100 hp.
Feel free to give your opinion.
Rotax is just costly but they are really light compared to anything else.
It just seems to me that adding weight in the nose would make power off flair challenging.
Any thoughts?
 
I can’t comment on Hp but if you can afford it go with the rotax out of the three choices. UL is still relatively new and a nice engine but I would be concerned with long term parts availability. Viking looks good on paper but I wouldn’t give the owner a dime. You should be aware that many of the Viking forums are highly moderated with negative posts and issues quickly deleted and users removed. Talk to actual owners n person before going with the Viking. Rotax seems to be the gold standard for many experimentals with the only downside being the cost to buy one.
 
I'm building a Zenith with a partner and he's gung ho on the Viking. I have the reservations kmacht points out. We're not to the decision point yet, but he's wearing me down a little on it with merits of the Viking. For example, as much as it chaps my ass, if you didn't do business with a company only because the CEO is an *******, you wouldn't do much business.
 
I'm building a Zenith with a partner and he's gung ho on the Viking. I have the reservations kmacht points out. We're not to the decision point yet, but he's wearing me down a little on it with merits of the Viking. For example, as much as it chaps my ass, if you didn't do business with a company only because the CEO is an *******, you wouldn't do much business.
I know nothing about Viking or its owner. A CEO or owner who's an a$$ on his/her own time doesn't affect me. A CEO or owner who's an a$$ in how (s)he directs the company to deal with customers, especially if there are issues that need to be resolved...that affects me.

I just had a not-insignificant issue on a five-figure home improvement project. It had to do with a miscommunication somewhere between me, the prime contractor, and their sub. I wasn't entirely sure I was blameless. The prime's owner decided I was and is fixing the issue with no argument or hassle.

I'm glad the owner wasn't an a$$.
 
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I'm building a Zenith with a partner and he's gung ho on the Viking. I have the reservations kmacht points out. We're not to the decision point yet, but he's wearing me down a little on it with merits of the Viking. For example, as much as it chaps my ass, if you didn't do business with a company only because the CEO is an *******, you wouldn't do much business.
The guy who owns the company is the company. If he retires or simply decides to wrap it up ( as he has done in the past ) what are you gonna do in terms of maintenance ? Rotax has been around for 100 years and selling this particular line of engines since 1980s - nothing is ever certain but but some things are a lot more certain than others ….
 
Consider resale value or if partnership has to switch hands, which will be more sellable and retain more value?

Is serviceability away from home a consideration? Go with the engine that has more mechanic familiarity and parts availability.
 
The guy who owns the company is the company. If he retires or simply decides to wrap it up ( as he has done in the past ) what are you gonna do in terms of maintenance ? Rotax has been around for 100 years and selling this particular line of engines since 1980s - nothing is ever certain but but some things are a lot more certain than others ….
An example is the recent death of the owner of Titan aircraft. Last I heard, no one was answering the phone at the company.

The installed base for the Viking is too small for an accurate assessment of the safety record. A lot of Rotaxes out there, and the safety record on the four-stroke versions is good.

Ron Wanttaja
 
I’m at the same point on my 750. Leaning heavily to Viking, but haven’t ruled out UL yet. Both sets of actual owners seem very happy.
 
The guy who owns the company is the company. If he retires or simply decides to wrap it up ( as he has done in the past ) what are you gonna do in terms of maintenance ? Rotax has been around for 100 years and selling this particular line of engines since 1980s - nothing is ever certain but but some things are a lot more certain than others ….
They are common Honda engines. Pretty much any auto mechanic can work on them.
 
Completely disagree than Jan is anything but a highly respected well liked individual.

There are a few people who got burned 20 years ago on his Subaru conversions but even then he tried to make it right.

There are a few more recent yahoos that have tried to blame him for the problems they created AFTER he advised them not to - like running 100LL in the engines and or trying to do their own tuning.

Or the loudmouth who recently took off with zero light sport training, and against Jans advice, and also on a very windy day, and didn't get out of the pattern before he crashed the plane. Then tried to blame Jan for his own incompetence.

The only people Jan may screen are these idiots who refuse to accept responsibility for their mistakes.

Jan and Alyssa are great people who now have hundreds of Viking Aircraft engines flying throughout the world in every conceivable experimental aircraft.

If your considering Viking spend some time on their Facebook page and following them. Or talk to Jan or Alyssa yourself and form your own opinion. And maybe learn the real story behind the very few detractors.
 
Completely disagree than Jan is anything but a highly respected well liked individual.

There are a few people who got burned 20 years ago on his Subaru conversions but even then he tried to make it right.

There are a few more recent yahoos that have tried to blame him for the problems they created AFTER he advised them not to - like running 100LL in the engines and or trying to do their own tuning.

Or the loudmouth who recently took off with zero light sport training, and against Jans advice, and also on a very windy day, and didn't get out of the pattern before he crashed the plane. Then tried to blame Jan for his own incompetence.

The only people Jan may screen are these idiots who refuse to accept responsibility for their mistakes.

Jan and Alyssa are great people who now have hundreds of Viking Aircraft engines flying throughout the world in every conceivable experimental aircraft.

If your considering Viking spend some time on their Facebook page and following them. Or talk to Jan or Alyssa yourself and form your own opinion. And maybe learn the real story behind the very few detractors.
Again, talk to actual owners and their experiences. Jan’s Facebook group and the Viking forums are highly moderated and you will not get a true picture. I know at least two sonex builders who gave up on their Vikings and are now putting in Rotax engines. You don’t want the internet to be your sole and single point of data.
 
They are common Honda engines. Pretty much any auto mechanic can work on them.
It is not the engines thats the problem, it is the custom stuff like gearbox and other add ons.
 
Again, talk to actual owners and their experiences. Jan’s Facebook group and the Viking forums are highly moderated and you will not get a true picture. I know at least two sonex builders who gave up on their Vikings and are now putting in Rotax engines. You don’t want the internet to be your sole and single point of data.
I get involved in a lot of discussions about homebuilt aircraft safety. Online forums such as this, the post-presentation Q&As after my EAA Homebuilt Week presentations, Facebook groups, or talking at local EAA chapters.

I get queried about Viking engine accident statistics more often than any specific homebuilt item...including that of Van's aircraft. I sense a considerable animus out there, beyond just one or two people. It may not be warranted, but the suspicions are obvious.

If you look at engine types in the FAA registration database, you'll see about 110 homebuilt aircraft listed with Viking engines. They're not all that prevalent... there are six times that many Volkswagens in the homebuilt fleet, five times as many Jabirus, ten times as many Rotax 912s. They're not that common.

It is not the engines thats the problem, it is the custom stuff like gearbox and other add ons.
It's difficult to track the safety record of Viking engines, because we don't know how many NTSB investigators just enter "Honda" as the engine type, vs. "Viking."

There are twenty confirmed accidents where Viking engines were installed on homebuilt aircraft (1998-2022 data). None of the accidents involved the internals of the engine. Only one case (WPR17LA156) involved the gearbox. The NTSB report on this accident states, "Two days after the accident, the engine manufacturer recalled the flywheel drive assemblies and stated they would be replaced with heavier flywheel drive assemblies." So the manufacturer is reactive to problems found in the field.

There are two cases involving the engine internals where the NTSB said merely "Honda" instead of "Viking". One pre-dated the start of Viking aircraft, the other appeared to be a conversion by the aircraft company. CEN13LA103, interesting case.

Of those twenty accidents, five were related to engine issues. Four the issues involved either the engine controller or an electrical system fault that meant the controller lost power. These are usually builder-related. But it's certainly true that if the builder had installed a traditional magneto-ignition engine, those accidents probably wouldn't have happened.

There are twenty times as many Rotax 912 accidents in my database than Vikings. Yet only three accidents involved the ignition system or controller. What is Rotax doing that gives the users a lower chance of error?

Ron Wanttaja
 
Biggest issue with the Rotax is you have to go big bucks to get more than 100 HP. The viking 130 HP is kinda the sweet spot.
 
Biggest issue with the Rotax is you have to go big bucks to get more than 100 HP. The viking 130 HP is kinda the sweet spot.
The age old dillema - how much you are willing to pay to minimize your risk and how to define the sweet spot for this tradeoff - I am afraid there is no a collective answer here that works for everybody …
 
The age old dillema - how much you are willing to pay to minimize your risk and how to define the sweet spot for this tradeoff - I am afraid there is no a collective answer here that works for everybody …
I happen to agree with you, but my partner is not there.
 
Completely disagree than Jan is anything but a highly respected well liked individual.

There are a few people who got burned 20 years ago on his Subaru conversions but even then he tried to make it right.

There are a few more recent yahoos that have tried to blame him for the problems they created AFTER he advised them not to - like running 100LL in the engines and or trying to do their own tuning.

Or the loudmouth who recently took off with zero light sport training, and against Jans advice, and also on a very windy day, and didn't get out of the pattern before he crashed the plane. Then tried to blame Jan for his own incompetence.

The only people Jan may screen are these idiots who refuse to accept responsibility for their mistakes.

Jan and Alyssa are great people who now have hundreds of Viking Aircraft engines flying throughout the world in every conceivable experimental aircraft.

If your considering Viking spend some time on their Facebook page and following them. Or talk to Jan or Alyssa yourself and form your own opinion. And maybe learn the real story behind the very few detractors.
Agreed, my conversations with them have been very informative.
 
I’m at a point in my build where I need to pick an engine.
The Viking guys love theirs, the rotax guys love theirs, the UL guys etc.
Everyone tells me 130 hp.
Any advice? I have a hard time believing the 750 wont perform well with 100 hp.
Feel free to give your opinion.
Rotax is just costly but they are really light compared to anything else.
It just seems to me that adding weight in the nose would make power off flair challenging.
Any thoughts?

Without knowing your priorities, it can be tough to make a recommendation. So this is more my thoughts based on my priorities.

Based on the performance of the factory built planes at LSA weights, an O-200 offers impressive performance so unless I plan on doing something that requires better than the O-200 performance, 100hp is a reasonable floor.

If money is tight, and I am looking to fly quickly, I would likely be shopping for a used O-200 (there is a 1500 hr O-200A listed on Barnstormers right now, at a price that is in line with the 90hp Viking, is better documented, and will be easier to get A&P support on if you need to farm out maintenance and inspections once its flying. But personally that would not be my first choice.

Once we accept that performance is covered by most options, I would focus on 3 realities: 1) Most EAB aircraft are flown less than 100 hours per year (so that high time O-200, is likely looking at 3+ years before it hits TBO, if you plan to rebuild at that point), 2) If I am building a STOL plane, its because I want to go anywhere, and the last (often overlooked) concern 3)Anywhere includes airports.

Based on those realities (assuming any major engine choice will be reliable), I would look for something well documented, easy to work on, has the fewest calendar time based services, and (because I want to go anywhere) can run on the widest variety of fuel. Personally, I would not build a plane right now that cannot run on 100LL, because even though I hate the stuff, I don't want to be stuck at an airport wondering what impact the fuel will have on my engine. For that reason I would not choose a Viking and would shy away from Aeromomentum (I don't find any info on how well they handle 100LL). This is a bit of an annoying requirement for auto conversions, because many pilots take for granted that the engine can run on 100LL, but modern car engines are not designed to handle it. I'm guessing landing at airports was not the plan when you chose the STOL version of the 750 and for that reason running E15 would also be a requirement. Being able to land at a backcountry strip (or rural road in places its legal) and refuel at the nearest gas station fits my dreams of a STOL plane. That requirement would eliminate all older aircraft engines, most Corvair conversions and most VW (due to limited documentation that I have seen on long term ethanol exposure in these aircraft conversions).

Personally, my first choice would be a mid-time Rotax, its the most cost effective option that addresses my concerns. If I am buying new, especially with backcountry flying, I like the simplicity of a direct-drive, air-cooled engine. Time spent in the shop for work like Rotax's 5 year rubber replacement, maintaining/bleeding the cooling system and inspecting the gearbox is time that isn't spent flying. So, unlimited funds, I would go with a UL power engine.

Last, I want to address why I would go used, I think in 5-10 years the fuel situation in the US will be very different, I personally fear that the 100LL phase out will go really slowly then all at once, but I don't know what the timeline will actually look like. Both the Rotax and the O-200 can handle 100LL and Unleaded alternatives, but if 100LL was phased out tomorrow, I would look at using a modern auto conversion (I personally like what I have seen of the Aeromomentum, but I have no hands on experience with any of them.)

A final note, this is based on what I have read and I am generally unqualified to have an opinion. I am just some dude at his computer.
 
Another input that slipped my mind: Have you talked to your insurance provider? The engine mounted could have a significant impact on premiums.
 
An example is the recent death of the owner of Titan aircraft. Last I heard, no one was answering the phone at the company.

The installed base for the Viking is too small for an accurate assessment of the safety record. A lot of Rotaxes out there, and the safety record on the four-stroke versions is good.

Ron Wanttaja
Basically, what happen with the Super Stallion https://www.aircraftdesigns.com/ from Martin Hollmann
 
Have you looked at Aeromomentum?
The AM15 (https://aeromomentum.com/am15-117hp-to-147hp/) or AM15T (https://aeromomentum.com/am15t-160hp/) would be good candidates for a 750.

I have talked with the owner multiple times, he has an engineering background and is willing to share a lot of information and work with you on the install. Also, if you read the Zenith forums, you'll see that he's been a lot more civilized and didn't resort to some of the language and insults Jan threw around.
I know a couple people who got burned by Jan. I would never give him any of my money.
 
I'd listen to the safety guy (@wanttaja). Rotex is expensive, but you get what you pay for.

You want 130 hp to be to get into and more importantly out of Anywhere. I would avoid a traditional engine like the 0-200 because of the weight. Getting out of Anywhere is harder at higher gross.
 
I fly a Corvair conversion. They are lighter than an O-200 and can be built up to 125-130 hp but they certainly are not the lightest choice available. A friend at our airport has a Zenith 701 STOL with a 100 HP Corvair conversion and it will get up and gone very quickly. Cruise is not spectacular but that is true for most STOL designs.

Years ago at Sun-N-Fun watching these planes take off with a 100 HP Rotax was pretty thrilling ...

 
I am looking into Highlanders. Rotax seems the way to go. If you go Used a big bore mod might be an option for extra performance. Some the the Highlanders use Apex snowmobile engines (160HP normally aspirated)
 
I’m at a point in my build where I need to pick an engine.
The Viking guys love theirs, the rotax guys love theirs, the UL guys etc.
Everyone tells me 130 hp.
Any advice? I have a hard time believing the 750 wont perform well with 100 hp.
Feel free to give your opinion.
Rotax is just costly but they are really light compared to anything else.
It just seems to me that adding weight in the nose would make power off flair challenging.
Any thoughts?
That airframe performs better with large prop diameter as opposed to lots of pitch. That rules out the VW conversions with direct drive (small diameter, big pitch).. depending on CG go with Rotax or Cont O-200.. Rotax is lighter but you may NEED the weight up front
 
That airframe performs better with large prop diameter as opposed to lots of pitch. That rules out the VW conversions with direct drive (small diameter, big pitch).. depending on CG go with Rotax or Cont O-200.. Rotax is lighter but you may NEED the weight up front

VW would be ruled out because it will overheat in an attempt to make enough power & would give extremely anemic performace at best. Some may suggest a turbo on a VW conversion but that just makes the over heating issue worse.
 
Based on the aircraft's purpose, a reduction gearbox engine with minimal weight is the only rational choice. It provides enormous thrust in the required speed range, and in this regard, the 912ULS is unmatched. As for the price, no matter what it is, life is still more valuable. Furthermore, Rotax engines are always in demand on the secondary market.
We are currently capable of providing propellers for any of the chosen options. However, you are still paying for thrust and reliability, and in the case of Rotax, both of these parameters will be at an acceptable level. Leave everything else to those who dream of being test pilots in every flight.
 

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