HP rating??

[Russellmn]

So the Patrol is rated for between 115 and 210hp... what's the limiting factor on the 210hp? Just weight? Torque? Something I don't understand (quite likely)? My reason for asking is that I like tinkering, and like hp, and am quite interested in ULPower's work on the Yamaha Apex snowmobile engine. I know how powerful and reliable these engines can be, and 250-300hp is pretty easy and relaxed for that platform. Also, weight is pretty low, right around 200lbs with gearbox, alternator, turbo, etc...

edit: please don't let this drop into a discussion of the viability of this engine platform. I'm just curious what the limiting factor is in the Patrol keeping it to 210hp. If weight were the same, would 225hp be ok? Or what would it do to the flying characteristics? 300hp???

[whee]

It is a weight thing. I think the Apex motor might even be a little too light.

Oops: you must have edited your post while I was typing. My thoughts on the Apex platform removed.

[Cguy]

One thing to consider when thinking of a lighter engine then the plane was designed around: loss of forward viz due to a longer cowl. This has been something I have been thinking about if I put a Rotax 912 in a LSA. I'm not talking inflight, but landings, especially off airport, kind of a big deal.

[Russellmn]

Cguy, I kinda figured I'd compensate for the weight loss by mounting the battery on the firewall and probably a 3-5 gallon header tank as well. I'm also looking pretty closely at running the PSTOL double slotted Fowler flaps that will help pitch the nose down considerably.

[whee]

Usable CG range is what you need to be considering. If your empty CG is already half way aft in the CG envelope then you'll be severely limiting the usefulness of the plane. It seems you recognize this but I wanted to make sure since you mentioned using PSTOL flaps to help. The flaps won't do anything to help keep your CG within the envelope.

I'd suggest taking the W&B info from a flying Patrol and running some numbers. It would be easy and would tell you what you need to know. For example: each battery on my firewall moves my empty CG forward .25". A 5 gallon header tank mounted on the firewall would move the empty CG forward .5".

Worth noting, the FAA requires that any nose mounted fuel tanks must be separated from the engine by a firewall. So if you put a tank up there you'll need to add another firewall unless you can find a DAR that will look the other way.

One thing to consider when thinking of a lighter engine then the plane was designed around: loss of forward viz due to a longer cowl. This has been something I have been thinking about if I put a Rotax 912 in a LSA. I'm not talking inflight, but landings, especially off airport, kind of a big deal.

I don't think you'll have any problem with a Rotax on a LSA. Installed weight of a 100hp Rotax 912 is typically very near 200lbs. Bob built the proto type LSA with a non-electric A65. Those have an installed weight of 185-190 lbs.

[Rollie]

It's probably best to call Bob (the designer) and ask him. All any of us can do is speculate on why he listed 210 as the max. My personal guess would be that is the biggest hp you normally see published on Lycoming 4 cylinders and those were the engines he expected to be used primarily, but that is purely a guess.

[keefer66]

remember the apex might make 300 ponies but it is only for short duration's. normal usable hp out put is in the 150 hp range (follow yamaha aircraft conversions on book of faces)

[Russellmn]

Only need full power for a few minutes typically. Two or three minutes of full power climb gives plenty of altitude...

[Gerd Mannsperger]

I would suggest save extended cruise power for the Yamaha to be 100 HP or bellow. We never ever had a issue with the motors when normally aspirated turbos will make them wear much faster but we only use 20% power while cursing down a trail and 100% very seldom. For example the snow bike engines are bullet proofed on a dirt bike , one just never has a issue with the Yamaha 450s on wheels where typical max power use is very sporadic, on a snow-bike where guys run them at 100% for extended periods they need new pistons every 100 hrs. The magic mark is 110 hours and the pistons crack simple metal fatigue. So 200 - 300 hp for a few seconds on take of or for a stol drag race but bellow 100Hp for any extended periods in cruise. I hope people will not fool themselves with putting a apex in a airframe that requires any more for cruise == I would go as far as saying it is a LSA motor no more than 1320 gross weight to keep ion save.

[Russellmn]

Edge Performance is saying about 1500 hrs TBO and around 140hp at cruise power, and up to 450-500hp wide open for short bursts. I REALLY should have started a second thread for the Apex, this is not what I wanted this thread to be about...

[keefer66]

Russellmn remember the patrols weights are 950 empty 2000 gross , where as the Just Highlander where the yamaha engine is making the news is 615 empty 1320 gross. takes more continuous power for the heavier a/c

[Russellmn]

As I said in my original post, I don't really want to get into a debate about WHICH engine I may use, just the potential effects of the higher HP output. But to reply to your comment anyway... 3 minutes at max power should allow for AT LEAST 3000' of altitude gain. Probably more. I don't know about you, but I tend to reduce power after 1500' or so and go into a "cruise climb" setting...

[PaulSA]

Could be all sorts of reasons. For the VANS aircraft, it is normally so that you don't raise the potential of exceeding Vne - they are slippery airframes and it's easy to do at higher levels as Vne is based on TAS. I don't suspect that is a problem with the Bearhawk family.

My feeling is that it is all about matching the engine to the airframe - so it's a recommendation rather than a limit. Sure, put 300hp in a Patrol but you end up with the law of diminishing returns. All that extra power only equates to a few extra knots cruise speed vs all the extra weight/fuel consumption/cost etc.

I've built an RV-10 and am 1/2 way through my Bearhawk. Everything I have read leads me to 2 conclusions. First, stick to the recommended power for the airframe. Second, use a Rotax/Jabiru/UL/Lycoming/Continental. I know it's "experimental" but I've heard of so many horror stories with auto conversions that if you really want a relatively cheap and reliable aircraft, stick with something you know.

I have an Aerosport IO540 in my -10 and it is sweet as .... Runs smoothly, efficiently and makes a great sound (guess that last one doesn't really count .....). I have just built and taken delivery of their IO375 200hp for my Bravo. Matching it to a 3-blade MT prop and looking forward to more great things!

[schu]

So the Patrol is rated for between 115 and 210hp... what's the limiting factor on the 210hp? Just weight? Torque? Something I don't understand (quite likely)? My reason for asking is that I like tinkering, and like hp, and am quite interested in ULPower's work on the Yamaha Apex snowmobile engine. I know how powerful and reliable these engines can be, and 250-300hp is pretty easy and relaxed for that platform. Also, weight is pretty low, right around 200lbs with gearbox, alternator, turbo, etc...

edit: please don't let this drop into a discussion of the viability of this engine platform. I'm just curious what the limiting factor is in the Patrol keeping it to 210hp. If weight were the same, would 225hp be ok? Or what would it do to the flying characteristics? 300hp???

The limiting factor on aircraft engine power is weight, supporting systems, fuel consumption, and Vne. If you have an engine that's too heavy, then your airplane will have odd CG limitations or limited useful load. If the engine puts out way more power than you need to beef up the engine mount and airframe to support it or you might need a much larger prop that would require landing gear changes. If the engine consumes too much fuel then you will have a limited range or too much weight in fuel. If the engine is strong enough to pull the airplane past its Vne in level flight, then you could run into flutter, which very much could kill you.

As for your comment about engines: aircraft engines are not the best place to tinker. Seriously, if you don't know a bit about torsional vibration, propeller harmonics, P factor, gyroscopic forces, and the complexities of gearboxes, then you don't know what you don't know.

Your comment about ULPower's work on the Yamaha engine causes me to wonder how familiar you are, as ULPower makes its own engine and isn't related to Yamaha. You were almost certainly talking about Edge Performance.

I am also quite familiar with the apex engine, and while getting 300hp is pretty easy with boost, calling 100hp per liter "relaxed" is stretching it. Some people say that you would only run at 300hp for a limited duration. I would say, when? Takeoff? That's the worst time to have engine failure.

Everybody is looking at STOL drags and Steve Henery and thinking, I could do that. And you can, but Steve has walked away from a lot of engine failures. He is comfortable gliding off a cliff without any engine at all. Bottom line, if you aren't absolutely comfortable with an engine blowing up 400 feet in the air a 1/2 mile from the runway, then you have no business tinkering to the tune of 300HP per liter.

I know you said you said, "please don't let this drop into a discussion of the viability of this engine platform" so you probably don't want to hear what I just said, but hey, this is the Internet, and the last thing any of us want to see around here is you or your Bearhawk strike the ground in an uncontrolled fashion.

Least you get the impression that I'm against the Yamaha platform or against innovation, here is what I think it would take to get the Yamaha going in a patrol:

1. Figure out a safe tune that doesn't stress the engine too much. The patrol is a lot of airplane on 180HP, 200 is plenty. I'd probably setup for turbo normalized at the 215hp level. That should keep your fuel consumption, range, speed, and prop size all pretty reasonable while at the same time having a very high-performance airplane that won't run the risk of blowing up. Yes, Steve runs it at 300hp, but that is a competition plane where reliability comes second to performance.

2. I would try to figure out exactly what it weighs and do what you must to make a longer nose/engine mount to get the CG where you want it. You might get lucky, or you might have to build a few different mounts and rebuild the nose until you get it right.

3. Figure out how to make the fuel system work. I can't remember what Steve is doing for a fuel system, but in order to have cool fuel up front, you will probably want a return to tank fuel system and dual pumps. This causes new issues such as pumping faster than the engine consumes can cause the pumps to bring air into the system when you are low on fuel. A stock bearhawk fuel system probably won't work for this engine, and fuel system design isn't as simple as it sounds.

4. Figure out cooling. You will need to figure out all of the radiator stuff and how to cool that engine. It's not super hard but will require a bit of experimentation.

5. Figure out the prop. Some airplanes are bigger, some are draggier, some have ground clearance issues. From what I understand you will need to have an electric constant speed prop. The ones I've seen aren't that large, and may not work that well on a patrol. I suppose you could bolt a large fixed pitch to it, or perhaps a ground adjustable, but you will give up some ground roll or cruise speed.

6. Engine mount. This is not as simple as it sounds. A lot of people in this space just weld something together and roll with it, but I don't think that's very safe. Overbuilt can cause problems just as fast as underbuilt. One fellow on the facebook group mocked up a mount and built a rig to stress cycle it. That's a much better way to do it.

[Russellmn]

Thanks for at least starting with the question I had. I was mainly curious about the flight characteristics issues I may anticipate with a higher HP setup, and you at least touched on them. I probably shouldn't have even mentioned the Yammy power in my post, it just caused digression. And yes, I meant to type Edge Performance, not sure why I said ULPower instead...

200-225hp is likely where I'll end up (or I'll go cheap and grab a local's 160hp O-320...), I just was curious what the limitations were that put the rating where it is...

[schu]

I think it's great to mention Yamaha power, I'm also very interested in that platform, but you need to be completely in the know as you are now both an aerospace engineer and a test pilot.

A lot of people want to conceal what they are really doing so that they don't experience criticism, but please know that my thoughts are not meant to criticize from the perspective of don't do it, but from the perspective of doing it right and being safe.

[Russellmn]

I just think I should have started a separate thread for it as I was really more interested in why the numbers are what they are for this question.

[Cguy]

Russellmn remember the patrols weights are 950 empty 2000 gross , where as the Just Highlander where the yamaha engine is making the news is 615 empty 1320 gross. takes more continuous power for the heavier a/c

Henry's bird is close to 800 pounds FWIW, all those mods. That 615 was "optimistic" to start with.

[zkelley2]

The one thing not mentioned is rudder size. I don't think you'd have an issue with anything you suggested, but if you went off the deep and and put a TIO-540 or R-985 up front(and we for a moment ignore the weight issue), you'd probably have a control issue on takeoff, with the airplane quickly darting left into the weeds even as you have full right rudder in. Some warbirds are know for this and you have to slowly bring the power in and as you get some airspeed over the tail can finally get to full power. Not ideal imo.

[stinger]

I think this subject has gone off the deep end . Yes weight is very important. Horse power and cubic inches important but thrust is where it's at . We don't land a airplane looking over the nose we use peripheral vision . Try flying a Stearman airplane and look over the nose or even a Cub. Stinger

[Gerd Mannsperger]

On the Yamaha -- I build and raced several turbo and supercharged RX1 and Latter Apex engines( on snowmobiles running straight av Gas), they are a great engine if you run them in safe perimeters up to 200 Hp for stock engines on boost and up to 300 Hp on mod engines with stronger Carrillo rods and Head studs low compression pistons etc. They are perfect for stol drags and similar events for continues power it should be limited to around 100 hp about 65% of stock engine power to run reliably.. This would make it a great engine for the LSA 150 HP on take of and 75 to 100 Hp for cruise flight and you will have a engine that will serve you well for Years to come. A Lycoming will cruise at 75% hp output all day long with little issues a turbo Yamaha 200 to 300 hp or even 914 not so much.
Same with the highly modified Lycomings, they just wear out very quickly if you have a race spec io360--390 putting out 230 Hp and start using it for cross country flights and Cruise it at 75% of 230Hp they wear out and have all sorts of issues. Cruise at 75% of the 180 Hp with the same motor and they last just as long as a stock motor.

The biggest limitation for HP is the weight of the rotating Mass of the engine and propeller assembly. This huge Gyroscope does not like to move in turbulence or on bumpy take off and stresses the engine mount and attache points more than HP and weight alone. A lighter engine like the Apex or rotax 914 with a lightweight carbon propeller go a long way to reduce that effect over a heavy crank lycoming with a heavy aluminium constant speed propeller.

Gear reduction to reduce propeller speed help -- that is the largest gyroscope high revving engines also ad to the gyroscope effect, it is all a game of give and take .

I would love to try the Apex normally aspirated stock engine 150 hp in the LSA airframe

For the Patrol a Build 320 The experience i have with them in cubs they just run sweet and with porting and high compression pistons on a good exhaust they easily pull 175 to 180 Hp while running much smoother with lower fuel burn than a 360.

And on the 4 place, how can one even argue with the 540s Ported and high compression pistons make the O540 into a solid 260+ hp motor
without the weight and complexity and initial cost of fuel injection. Not that I dislike the fuel injection, just love the simple nature of the O540 I spend many thousands of hours flying behind them and that builds trust --- they just never let me down.

[Bcone1381]

Hey Gerd; I like reading your posts. Your depth of knowledge and experience is deep. I see lots of wisdom and I curious if you might consider writing up a short biography of yourself and post it on the "New Member" section.

[zkelley2]

My biggest concern with the yamaha engines is resonance. Almost no one does gearbox, prop, engine resonance testing. Which, to me, makes them unsuitable for aircraft over anything but the most hospitable landscape. Or as a toy that doesn't really do much. Maybe if you had 2 of them, the chances of them tearing themselves apart at the same time is rather low.

Other people's risk tolerance is greater.

[Gerd Mannsperger]

First of all harmonics are real and a big issue with large displacement GA engines and heavy aluminium propellers. No doubt about it not even a discussion there.
Also any Large displacement engine (big power pulse) with a PSRU and a heavy aluminium propeller have huge harmonic potential to destroy the PSRU.

On this particular engine making 150 Hp at about 10000 + rpm going through a internal reduction drive with rubber dampeners and after that to a PSRU the power pulses are so small , about 1/4 of a comparable lycoming 320/360 and factory dampened on top of it. I see much less potential for harmonics. My experience with these engines is they are silky smooth.
The next factor is the composition propellers have much less harmonic potential over a heavy aluminium tuning fork propeller.
The chances of harmonics are as low as they can be in this case anyway.

All this said this is very much a experimental set up and I would only consider it for max performance and stol fun flying applications. Not for everyone.

If you need a serious reliable back county hauler I would suggest that a Patrol with a O 320/360 would be the better tool for the Job.

[zkelley2]

You're correct that the dampers and carbon prop make it much less likely, but you're still counting on pure luck, with no data at all.
Also, you cannot necessarily feel harmonics. It does not matter how "smooth" an engine is, that has literally nothing to do with resonant frequencies.
Also it doesn't need to have a PSRU to have this problem. Most all the aluminum props for aircraft engines and almost all the carbon props that have been tested have RPM bands to avoid on direct drive engines as well.

[svyolo]

To me it looks like Rotax has been around long enough, and it is BIG enough in numbers, that I think they have the 60-130 hp gear reduction/prop combos sorted out. They require a very light prop, and I think they are almost all composite. I also think the torsional vibration/resonance is mostly metal props as well. I think Hartzell says their composite CS props don't have any limitations. I am not sure about MT.

I think the Viking engines still had some gearbox issues for a while.

I don't think the gearboxes on larger HP motors are as well sorted, but the smaller ones seem to be. Some of the APEX conversions use the Rotax "C" drive.

[Battson]

210 hp is enough in the 4-place to perform admirably. Planes like the Patrol would be overpowered above at 210 hp in my opinion, you are giving up landing performance and balance and not getting any useful gains.

Extra power is a good thing, but I suspect it becomes unwieldy in a small aircraft, above a certain point. Such as the 330hp 4-place from Florida, they are an impressive machine at 260hp, 330 would be more impressive, but no more useful.

The best balance is probably 160hp, in the same way the best balance is for a Supercub between T/O and landing.
The best power is probably 160-180hp I suppose, hard to comment without flying a range of planes.