Request for 10,000,001st engine choice discussion

[MidGenerationAL]

I know there are tons of existing discussions on this topic, but none of them specifically get at my considerations.

Lots of detail here. If you don't have time for all the detail just skip down to the main question in bold below.

My daughter will start flight training in the Spring of 2026 and I am starting this Spring.
Now before everyone's heads explode, we are optimistically 3 years away from the Bearhawk being completed and realistic is probably longer than that. And even if the plane was already finished, neither of us will fly it until experienced pilots/CFIs say we're ready AND we've have had some Bearhawk flight time (BTW if anyone here is a CFI and owns a Bearhawk, I'd love to talk to you in a year or two or three).
We will both start training in a Champ and stay in the Champ until we're ready to move on - and even then do not plan to jump right in to the Bearhawk. One great resource for us is my brother and brother in law are both CFI's with immediate access to a 180 (probably most relevant), a Bonanza, and if somehow it became relevant, a Baron.

We have an IO-540 core and my father built the engine mount and cowling around this (these can obviously be revised/replaced).

My main consideration right now is whether the 540 is the right choice for relatively new pilots.
Her career plan as of now (albeit, remember, 14 year old career plans) is to go to one of the many aviation training schools in our area after high school and study as both a mechanic and a pilot, aiming for a career as a missionary bush pilot. So yes, eventually, flying fully loaded and STOL and operating in high DA could be a thing for her.
But if this makes the plane significantly more challenging for less experienced pilots, i'd be inclined to move down to a 4-cyl and put the 540 engine mount and the cowling back in the barn for possible future use.

FYI operating cost is a lower concern. The 540 core we have runs on automotive pump gas and she has some nontrivial funding from her grandparents. She's not a Paris Hilton kabillionaire heiresss, but she's not in a position where fuel efficiency has to drive the bus.

[Dpearson]

There’s no replacement for displacement.
I can’t imagine any reasonable situation where the choice of the 540 would make the plane less safe, and there are many obvious situations where additional power can be a life saver (high density altitude go-around, escaping downdrafts, etc….).
If you want to save fuel, pull back the power on the 540. There’s of course some efficiency loss associated with 2 more cylinders, and a useful load trade off to consider too.

[gregc]

A 540 will be fine. Go with what you have.

[jaredyates]

Much respect for your wisdom here Greg!

[jaredyates]

I have owned and operated a plane with the small engine and also one with the big engine. I have also been lucky to have some flight experience with a few very different Bearhawks. I have also had the good fortune of watching a handful of pilots from all experience levels do their first takeoffs and go-arounds in a BH.

I do not see much threat for the engine size and pilot hours. Just ensure that those hours are good quality instruction, and learn to use finesse on the throttle. If you take a pilot with 10k hours in Cessna trainers and put them in an empty Bearhawk with 250hp with no training, that could be way more scary than your daughter with 10 hours of good quality pattern work in the BH after 50 hours of fundamentals in the Champ. Your insurance company might not agree! But that is what it is unfortunately. I have flown non-commercial hops with several dozen non-pilots and Cessna-pilots and they are all offered stick time after a 30-second talk about how to steer. I can tell you that experience can be a barrier to the stick and rudder aspects of flying a plane like a high-HP Bearhawk.

Most folks would have a hard time finding someone who can teach her well. Finding an instructor with experience in any tailwheel or any high-performance airplane, or especially both, is not trivial. I think this decision pivots on having your family members available to teach her.

Regarding engine choice more generally, first, I totally agree with Greg's post right above this one. But I also don't agree with a common sentiment that more is always better. If you want to read more about that, carry on at your own risk, realizing these may not all be consensus views.

When it comes to handling and performance, yes horsepower is a factor. But also, gross weight is a major factor. If you could have a 1100-pound empty weight and 300hp, then there is no replacement for that. But until that is possible, realize that there are Bearhawks with an empty weight over 1750. That is still an airplane, but not as useful of one, for most missions.

The advice that I would give, and have for a while, is that the ideal engine compromise should be driven by the most common mission. If you are routinely going to fly at max gross weight and/or above 6-7000', you will want the bigger engine.

The lighter the plane is, the more delightful it is to fly. Some folks don't care about this, which is ok. But a dog of an airplane can be created just as much by underpowering as it can by overweighting.

Consider two planes. The first has an empty weight of 1100 pounds and 170hp, which is in round numbers the original prototype's specs. The second plane has an empty weight of 1600 and 300hp.

Put one pilot and 50 gallons of fuel, and which plane is "better"? Well, that depends on what "better" is. The approach speed will be noticably slower on the lighter plane. One will take off in 600 feet and the other in 300. If you are using a 500' gravel bar runaway, then that really matters. If you are using a 5000' municipal runway, not so much.

On the climb out, the first plane will have a fuel flow in the. High teens gph and 1000 fpm. The second will be 30gph and 2000 fpm. You'll get to altitude faster, maybe fast enough that you save fuel, maybe not, depending on technique.

In cruise, you can set either engine to 9-10gph and get very similar cruise. You can bump the big engine plane up to 12gph and pick up another 7 knots. The light plane probably won't be able to do it at WOT, depending on the environmental factors. Most operators that I have spoken with don't cruise much over 12gph, regardless of available HP.

But now let's change it up and carry some load. Say 800 pounds of people and 100 pounds of luggage. Well, the second plane is now 300 over gross (zfw is at max-gross) so that isn't going to work. The lighter plane is 200 under max-gross, with full tanks. It is going to need 1000' of takeoff roll and will be climbing at 500fpm for the first few thousand feet. Is that good enough? It depends on your mission. It will climb to 12000' but it will take half an hour. Is that a dog? Again, it depends. There are missions for which these numbers are not safe or acceptable.

I flew the Five with 320-ish HP, ballasted to 3000 pounds, on the same wing, and it was outperforming those numbers in both takeoff roll, climb rate, and ceiling. This is one reason that I would recommend that a new builder committing to a big engine should build a Five instead of a 4-Place.

How about a cargo load? With the heavy plane we have 1600 empty, 300 fuel, 200 for the pilot, leaving 400 pounds to reach max-gross takeoff weight. Depending on the type of load, you may run out of legal weight before you run out of space. There is a slight complication here in the CG, because if you had the room up against max gross weight, you could actually do better by carrying a second pilot, because at heavier loads, the front seats are forward of the CG. But if you add another 200 pounds of second pilot, you are down to 200 pounds of payload (or, "education-and-recreation-load"). Here, you will almost certainly reach max-gross weight before you run out of cabin space.

Now let's consider the lighter plane's cargo load. 1100 empty, 300 fuel, 400 for two pilots, leaves 700 pounds to reach max gross. Yikes, what a difference. Unless you are carrying concrete or moose meat or something, good luck fitting more than 500 pounds into the back seat and baggage area. (Here again you can see the very real utility of an extra foot of cabin length and an extra 500 pounds of gross weight afforded by the Five). This is another reason that I wouldn't initiate a large-engine build on a 4-Place when the Five is an option.

So with all of that said, how can you make the best plane without transcending reality? Keep it light! If you are going to use the 540, make it a parallel valve. Minimize the fluff and be relentless about weight reduction as you build. Rework all of the above numbers with a 1400 pound empty weight and 250hp and you can still have a very useful airplane. Don't embrace the idea that the 180hp Bearhawk is a dog (it doesn't have to be) and don't accept that a bigger engine is always better. If you go from 230-300hp you will either take a loss on reliability or a gain in empty weight, and you won't have the cabin to put it to work.

We can talk about ideals and optimums but if you build a Bearhawk as-designed, including the engine choice, and keep it light, you will have a very fine airplane that is better than a whole lot of the rest of the GA fleet.

[Nev]

A lot of wisdom in that post !

[MidGenerationAL]

other thoughts below but I did want to say I love the classic paint scheme on your plane

[gregc]

I'll add one thing to Jared's excellent summary - I took Bearhawk transition training from him and we practiced a few take-offs in his 540 powered 4 place at less than full power to simulate what I might expect from my O-360 powered Companion. I'm in phase 1 testing now and it turns out that due to the weight difference between the two airplanes, a full power take-off is is pretty similar in both. As he points out, there are a lot of factors that enter into an engine choice but I don't think that pilot experience or the learning process is one of them.

[MidGenerationAL]

All these thoughts are helpful and much appreciated.
Although early in our aviation journeys neither of us will really feel the different performance limits, my daughter's (current) career path could certainly take her in that direction.
I'd like to be able to fly with my wife for short easy VFR cross country trips when I'm at that proficiency - but probably either engine would work for that.

As long as there are no daunting new pilot challenges I think we will go with a rebuild on the core we have.

We do have a ways to go before we are ready for an engine so there is no immediate pressure.

Progress report: once we prime the wing ribs and rivet... every... single ... rivet..... on the main wing skins, we will be about at the place a quick build kit starts.

PS - it is a parallel valve engine.

PPS - what you say about the five makes sense - and if they'd had the five when my father started this project he probably would have gone that route - but unless the A model Four can do time travel so I can go back with a set of five plans - well, as you said, transcending reality isn't an option ;-)

PPPS - the model 540 we have is quoted at 374 lbs and 250 hp. So I suspect we would be somewhere between the two power and weight examples you described.

[rv8bldr]

This is pretty much exactly what I have in my Bearhawk 4A for an engine. I haven't flown it yet although the aircraft is essentially done. Just going to wait for decent weather in the spring before getting my final inspection. I just sold my Maule M5 which had, strangely enough, a 250hp, parallel valve O-540. I loved the performance and smoothness. I personally don't need a 300hp fire breathing dragon, but I know I will loading the Bearhawk up to gross at least once a year (Oshkosh), probably more often, and having the ponies up front to deal with that weight in the summer heat is reassuring. As gregc said above when training with Jared, you don't need full throttle in every situation.

One final thing to consider is that with the larger engine and a CS prop, you'll almost certainly run out of gross weight room before you exceed the aft CG.