Bearhawk 4-place cruise speeds

[Battson]

I am wondering whether my plane is a little out of rig, and wanted to hear what airspeeds people are seeing. Worth having a thread on this.
To make it useful, it would be good to include all relevant factors, like whether it's IAS/TAS/GS, altitude if GS / TAS, fuel flow, throttle/prop settings, etc.

I am seeing a consistent 108 KIAS running LOP with 2300 and 22", at 35 L/h (9.25 Gal/h), or 125 KIAS with 2400 and 24" ROP for about 55 L/h (14 Gal/h).

[Mark Goldberg]

You do seem a little slower than my BH Jonathan. When I flew with 700x6 tires, I saw consistent 130 kts at 2300/22" burning around 12 GPH. The bigger tires seem to have cost me 5-7 kts. 122-123 kts is what I see now at the same power settings. Mark

[Battson]

Hmm, I got that feeling... I haven't got lower fairings for the wing struts yet - can we get fibreglass ones from somewhere?

I am really keen to hear from the other guys too! What airspeeds are you seeing?

[Enewton57]

Bob Barrows sells them

[Battson]

Got those fairings from Bob...

Bump - what speeds are others guys seeing?

[whee]

The scratch-built O360 BH I was flying cruised at ~123mph on the GPS 2400/20" (WOT) at 9000MSL. ~9gph, almost no fairings, tiny tires (600x6). I know it was a little out of rig and had a couple minor things that added some drag.

[Gavin Chester]

The BearHawk's max speed for any given weight etc, will be the fastest with a aft c of g

[Battson]

I agree - the trouble is, by the time you've added enough weight to a -540 BH to get an aft CG, all the extra weight has eroded any extra airspeed benefits you might have otherwise enjoyed. I am always about 4kts slower with a heavy load on, i.e. 4 people + gear.

[Gavin Chester]

That surprises me. When I fly full gross 2700 lbs +, I can get a consistent 118-120 kts gps, Density altitude 5000'. at 24 square, LOP.
Me and the Dog ( right seat ) full fuel in mains the best I can do is 105 kts.Throw the dog in the back 40lbs he will sleep against the back wall,And I will pick up 5 kts.

[Battson]

That is at the same fuel burn in each case? Just to ask the obvious.
I guess I do have my H-stab set at incidence of -3 instead of -4, and I also have the profiled stabiliser, so I might be different in that respect.

On a totally different subject, 24 square is a very high power setting for LOP operations... that's ~72% power at sea level, ~77% at 5000ft, which is right on the hairy edge for any leaning of a Lycoming. The manual says always full rich above 75%. Sorry - I don't mean to be rude and tell you how to run your engine, I just wouldn't want to hear about a blown cylinder.

[Gavin Chester]

I believe your h-stab would make the difference.Sorry I prefer LOP. You may want to give this article a read. just click on the link and select articles then experts are everywhere.

[Battson]

Yes, I've read & re-read basically everything I can find about LOP!
I run LOP almost everywhere I go, I even use it to cool the engine down gradually prior to closing the throttle for landing.
I was just surprised to see you're running LOP at such high power settings, that's all.

Sorry - back on topic - if anyone flying a BH -540's is reading, please post your cruise speed!

[Phil]

Battson, do you have any fairings on your plane yet? They will make a difference. Also, I just picked up a copy of the book "Speed with Economy" By Kent Paser. It's got a lot of good info that may help you get your cruise speed up without changing your fuel burn.

[Battson]

I have the fairings from Bob now, they were the last ones I needed (hard to make myself!).
I suspect the larger 10" tail wheel also makes a difference - the tail wheel has to be one of the most un-aerodynamic part of the plane.