4 Place Cruise Speeds at 10 GPH

[OBP]

I almost hijacked the 200 HP thread but figure this is a slightly different question...

What kind of cruise speeds are you guys getting from the various setups?
I am looking for efficiency. Would it make zero sense to build a 180 horse mogas friendly 4-seater? I hear you can throttle back a 540 and see similar fuel burns as a 360, but I'm stuck thinking I want to build the lightest plane I can (with starter and constant speed prop).

Maybe it's possible to ask this way:
What speed do you fly at 10 gallons per hour? (What is your engine and compression)

My home strip is a 1000 foot cow pasture with bad approaches (low elevation). I will have to use at least 26" tires most of the year. If any of you guys with 360s and a similar setup can give me advice I'm all ears.

I will still have an S7 beater plane for super slow solo flight and Aerocross activities so maybe I should just use a 540 if the main mission is to cross country?

Fuel burn might be a personal question, and if so feel free to email a curious guy--gregswingle at gmail.

I still *thinking* of building (haven't sold my S7 yet). Don't hate me if I trade for a 180.

[whee]

Think I've told you before that I was happy with the performance of the 180hp BH I was flying. It was a bit slow but I think fairings would have fixed it. 118mph at ~9gph. I can't remember what the compression was but it was low enough to burn regular mogas.

Thing that was a bit frustrating is Balckrock can throttle back his 540 and fly faster on less fuel and he is missing the same fairings. If your keeping the S7 I'd go with a 540. A super light 540 BH will out perform a super light O360 BH except in landing distance.

[tailwind]

180 hp O 360A1D with mt prop. 2500 rpm 22 inches about 10gph 107 kts 850 wheels no fairings 1394 empty weight

[N942VT]

Mine is similar to what you're describing Swingle, O360 A1A, Bob built with angle valve cylinders, 8.5:1, 190(?) HP, Hartzell constant speed, 26" Goodyears in the off season, 31" Bushwheels the rest of the time. I don't have a fuel totalizer but the Lycoming manual puts an A1A at 10.5 gallons / hr at 2450 rpm or 75% power. My numbers are 24 inches and 2300 rpm = 118 knots, 19 inches and 2200 rpm = 90 knots with the Goodyears. I'm at 1350 lbs and if I built it again could easily loose 100 lbs. Not trying real hard take offs are 250 ft, down and stopped in 600' of runway moderately loaded. Bushwheels mess with these numbers, subtract 10kts, add 50 ft to the take off but the landings are sweet. A light four place is a nice plane, but I've seen some heavy 540's that do just fine, Tyson has one in southern NH and I don't think he gives up anything to me on landing and his take offs and speed are better by 10%, he's probably a better pilot though. All told, I wouldn't change a thing, it's just such a nice flying airplane.

[Zzz]

Dave, where would you lose those 100 lbs?

[N942VT]

Zzz - Lighter floor boards (.040 with Deco Dot cover), skylight area (overbuilt), thinner plex for skylight and windows, lots of redundant wiring and conduit, landing light set up, carbon prop, Earth X battery, lighter cables, less paint or Oratex (maybe), Vans style air intake, bottom sump intake, B&C alternator, rear mount oil cooler (shorter hoses), lighter mounts for avionics / magnetometer / antennas etc, etc. It all ads up a little at a time. I weighed mine with 8 qts of oil and some fuel in the tanks, back seat in, baby bushwheel on and 26' Goodyears so my weight is generous.

[Baloo]

What length prop are you using and what kind of climb rates are you seeing?

[Battson]

A fun question!

My setup:
IO-540 standard compression 260hp, Avgas or Mogas compatible, with 82" CS two blade MacCauley prop (at least 1% faster than a three blade Hoffman prop, tests have shown)
Vortex generators installed
All fairings installed
26" tires and 12" tundra tailwheel, empty weight about 1490.

My performance:
10 GPH at 7000ft yields an average 120 KTAS all day long, and 108 KIAS near sea level.

I can get the same efficiency (distance covered per gallon burnt) at 11 GPH which produces 130 KTAS at 7000ft. I run 2350 RPM and 25" MAP for cruise.

My tests showed the fairings only make a measurable difference right at the top end of the speed range, >115kts you can measure a very small benefit. Similarly, we didn't measure a loss with the VGs or tires, but the combination of the two was *just* measurable.

My most efficient setting, in terms of fuel burn per distance travelled, is quite slow at ~100 kts and about 8 GPH. That works best at about 23 squared. I don't like flying those settings, it's not good for the engine idling along at 50% power for hours, and I can go a lot faster for very little incremental cost.

So that's my plane's performance.

You say your airstrip has difficult approaches? If you want to fly in and out of a difficult place at full gross, with a comfortable safety margin in any ambient weather, I would recommend a 250hp engine. I regularly fly into airstrips of that size with difficult approaches - I am always happy about the extra power. At gross it's a close-cut affair even with 260hp. Power to weight ratio is the most important factor in terms of take-off and climb performance. I see little value in a super-light plane which you can land shorter than you can take-off. I think one needs to strike a balance between weight and power. After 400 hours PIC time, I have learned how to land my plane as short as I can take-off, which has changed my viewpoint on the weight of the -540. More practice won't make an underpowered plane accelerate or climb faster, it's at the mercy of it's engine limitations and ambient conditions.

I think the -540 is at the heavier / overpowered end of the spectrum, but still strikes the right balance between weight and power. Taking off last Saturday, a regional airliner was taxiing for the runway as I rolled. I did a max performance T/O and climb, just for practice. The airliner's pilot exclaimed "wow" over the radio, then asked tower what type of plane that was. That kind of reaction is not unusual The Bearhawk's high performance is impressive, but being able to throttle back and cruise fast and very efficiently re-doubles people's surprise at what the plane is capable of.

[whee]

Ya'll just wait till I get my TCM IO360 BH flying...you'll be truly amazed then😋

[marcusofcotton]

Ya'll just wait 'til I get my 0-320 BH flying... so I can catch up!

[OBP]

Thanks guys! This gives me a lot to chew on. It's a brave new world. i have to cross reference wikis and Google when reading about all of the choices. It's cool how there are so many options. The airframe seems versatile. So, I guess nobody has made the multiengine Rotax 912 Bearhawk yet? I was just starting to figure that thing out.

[Baloo]

4 Place BH
1567lbs Empty
Typical Mission Load 2100lbs
Typical operating altitude 500 - 2000ft MSL
Engine 200hp io-360
Prop Hartzell 80" CS
26" Goodyears (Shopping for 31" ABWs)
STOL Speed VGs Wings Only

8GPH = 96-100 KIAS
10GPH = 100-105 KIAS
11.4 GPH = 105-110 KIAS

Never had it above 4000ft ASL

No Wind Takeoff Pavement @ 2000lbs SL = 400-450ft
No Wind Landing Pavement @ 2000lbs SL = 400ft
No Wind Takeoff Gravel Bar @ 2000lbs SL = 500-600ft
No Wind Landing Gravel Bar @ 2000lbs SL = 400-500ft

Initial rate of climb @ 2000lbs 65kts = 680-800fpm

[Wayne Massey]

Your strip is a 1,000 foot cow pasture with bad approaches? If I were operating out of a rough 1,000 foot strip with a difficult approach I’d consider a -540 mandatory. Operating off a short rough cow pasture you’ll want to get airborne as quick as possible. Ground roll on rough terrain is uncomfortable. You’ll want the muscle of the 540 to pull you off quick (and it will).

Another advantage of the -540 is high altitude performance. Even if you are a flat lander there are advantaged to high altitude performance. High altitude cruise being one of them. There is the power and speed advantage operating above 7,000’ with the excess power of the -540’s while burning 9-11 gph. Think of a long cross country flight on a summer day and climbing to 8-10,000 feet to get above the scattered cumulus clouds and smooth air cruising at 130 kts burning 9-10 gph. I don’t mind bouncing around below the clouds when I’m flying by myself but when I have passengers on cross country flights I always climb to altitude until it is smooth.

[Wes Helm Bearhawk 1209]

I will be operating out of a thousand foot Runway also. I had talked to Bob some time back about the best engine for this type of operation he suggested the - 360. But if you guys with the - 540 s don't have any problems getting stopped and that distance. I would love the cruise speed. I may have to rethink my engine choice

[Battson]

A 1000ft runway is ample with the -360, if you can use all 1000ft every time. Add trees at each end, and things are very different.

[Bdflies]

A couple of things come to mind. Stopping a 2000+ lb aircraft, on a 1000' strip, with less than good approaches, I'd want the biggest, baddest brakes I could fit on the axles. Maybe a tailhook, too. Departing that same strip, on a hot day, with a couple of trusting butts, sitting in the plane, I'd want all the horsepower I could bolt on the nose. A PT-6 maybe? Fuel flow be damned!
A good wing, big tires and awesome brakes, paired with great technique, will get you into small spaces. All that stuff helps, but there's nothing like a big honking motor to get you out of that spot, day after day.
Just an opinion.

Bill

[DemoDollCate]

When I was ferrying/flying Marks BH around the country I would typically cruise at 120mph indicated and see 9 gph. It was always loaded to the gills when ferrying. You can always pull the throttle back when you want but you can only get so much when everything is full IN. I would always lean towards the 540.

I miss flying that great plane and am now sniffing around the forum again.

[Chris In Milwaukee]

Nice to see you back! My first Bearhawk ride was with you a number of years back. I was hanging out in the back seat while someone else was flying, but it was still pretty cool. :-)

[kestrel]

MHO- If you're so light that the -360 is the better choice, go fly the S-7 instead. You already have it.

If you are getting a Bearhawk because you want to put stuff in it and go somewhere, get the -540. I do want to shave some weight off mine, but I have no interest in giving up my -540 to do it. I'll look elsewhere for weight savings. It is fantastic being able to load the thing up to the gills and "just take-off and climb".

[Battson]

In the weekend, I was out hunting and the Bearhawk had to lift:

three men in winter gear
enough gear for a three days self-sufficient in the snow
enough fuel to get home
three red deer stags worth of meat (think three small bull elk)
we were at ~2600lbs & aft CG limit

All of the above, from a 650ft airstrip, overgrown with looong autumn grasses standing dead in seed, soaked in melted hoar frost (extremely heavy dew). Winds light and variable, no help whatsoever. We needed 500ft to get airborne, and both passengers remarked how that felt SLOW for the Bearhawk.
Racing towards a wall of forest at 40mph will do that to people.... she dragged her heels in the grass for a long time, while the speed built.
I wanted every last horsepower I had hidden under the cowl.

[Mark Moyle]

Some day...I'll finish my BH....and some day I hope to be able to mimic Dave Roberts take off and landing ability. Marv Haught, Dave and I piled into his O540 powered BH... Good 650 pounds of meat, tanks 1/2 full. Dave taxied to his mowed grass 300 foot practice strip... We were airborn in less than 300'. Landing on a couple dirt roads to move irrigation pipe...Dave would land three point then use the brakes to bring the tail up...just as we stopped he'd give a burst of power to softly let the tail down. When we landed back at his practice strip....he landed a bit long...stopped 50 beyond the mowed end of the strip... That O540 was really impressive! Low and slow....then full throttle....like launching a 68 Shelby cobra powered by a twin 4 bbl 428 cid!


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