Bearhawk First Flight

[Helidesigner]

Early this morning I performed a successful first flight on N83ME. Overall it went well. It needs a little bit of right rudder trim and the left wing is a little heavy. It was a very calm day and my weight on the left side may be the reason for the slight left roll. On takeoff I applied the power slowly. I was shooting for full power in about 4 seconds. The plane took off before I got to full throttle.

The biggest issue is that my airspeed system is way off. I estimate it is reading over 20% faster than I am actually going. My round dial AS indicator and EFIS were only a couple knots different. I was reading ~140 kias at 3500 ft at about 60% hp. Great, but I do not beleve it. Up and away I stalled at 51 kias at 2000 lb gross weight. Way too fast. I strongly suspect it is the static port location. I have a static port on each side of the boot cowl about 8 inches above the forward landing gear strut attachment. I have a small trip strip in front of each port. Where are other people placing their static ports? Has anyone else seen such an error?

My brakes are working but are weak. They are single puck Matco units. Has anyone else had difficulty working in brake pads? I have done about 30 mintues of start-stop taxiing. They are not spongy, there is plenty of pressure.

Most of the flight was done between 55% and 60% power. I need to review the engine log data. All the head temps were 325F or lower. My oil temp at takeoff was 80F, It steadily rose to about 195F mid flight and reached 204F in the pattern. That seems kind of high for a partial power setting and relatively low cylinder temps. I have a new Positech P10634C cooler. I'm pretty sure it is the right size for my IO-540. It looks like it. The engine is freshly overhauled to new specs. It may have been working itself in and making some extra heat on the cylinder walls and not the heads. I burned less than a half quart on the flight. Any thoughts here?


Mark
BHQB73

[DRLPatrol]

Fantastic, good job. Great looking also.
Doug

[N3UW]

congratulations.

[Battson]

Congratulations on the first flight - sounds like you've had no more issues than anyone else. Perfectly normal!

Almost every machine I've seen photos of has the static port in the fuselage, at the last station before the horizontal stabiliser's front cross-tube.

I have single piston Grove brakes, and yes they are reasonably pathetic. With a full gross load on, in a crosswind, they are basically useless. Ok that is a bit harsh, but they don't exactly raise the nose when taxiing.

Are you running new cylinders in your overhauled engine? You need to run over 75% power and minimise ground running if so, at least for the first few hours - they are the most critical. Once the oil consumption stabilises, then you can run 50-65% (or less) safely without risk of glazing the cylinders and doing permanent damage.

That oil temp does sound much too high. I have my redline at 205F and have never gotten anywhere close to that. I have the big 11 pass Positech oil cooler, and it normally sits around 140 at the most. What oil pressure are you seeing?

[Helidesigner]

Oil pressures looked good, 60 on the ground, mid 80's climbing, 70 in cruise.

[Enewton57]

Congratulations on the first flight of your Bearhawk Mark. I had my static ports (2) mounted at the first bay aft of the baggage door and my airspeed was spot on. I did the same on the patrol. Some thoughts on the cooling issue. Where is your oil cooler mounted and how many rows? Also, the exit area needs to be large and fairly unobstructed. In almost every case of overheating on Bearhawks that I have heard of, the cowling air exit are near the tunnel is either too small, or too obstructed, or the lip is too small to get a smooth high volume of air flow out. The lip around the exit area looks a bit small. It is important that the lip be about 2" long and hang down at about a 45 degree area. Some things to look at anyway.

[Battson]

Eric - this may interest you,

ZK-NJB has no lip around the exit area when the cowl flaps are closed, and she cools like a dream - in fact it runs too cold (260*F CHT & 120*F oil) in autumn and I am increasing the size of the shutters on the cowl flaps to warm it up, before winter. I have 100 square inches tunnel area (flaps closed).

The only reason I can figure is I put a smooth 0.5" radius transition at the sharp corner of the firewall to boot cowl tunnel transition. I figure that must be at least partly responsible for the extra efficiency; the flaps (when closed) aren't the point of difference. This was a very simple mod which just screws on, using the forward tunnel attachment screws. Took about an hour to fabricate and install.

Also as you say, my exit area is not obstructed.

[jaredyates]

Great work Mark! I also had a heavy wing. I don't find that cabin weight distribution matters very much in roll trim. The best way to fix it was to add washers at the front of the aileron hinge mounts. I mounted my two static ports in the fuselage tail section like the others, using pop rivets through the stringers, and a little L-shaped bracket. As for the temperatures, I don't think you have a cooling problem. When you have temperatures approaching 230 or 240°, then it would sound like you have a cooling problem. For now with an engine so new, I wouldn't worry about it yet.

[DRLPatrol]

Jared,
Can you elaborate on the "washers at the front of the aileron hinge mounts"?

Doug

[John Massaro]

Congratulations !
Nice looking ride-

[bearhawk2015]

Congratulations,

Before you move your static port try removing the small strip in front of your static port, it may be creating an area of low pressure behind it where your port is which would cause a higher than normal indicated airspeed.

My static port is also on the boot cowl and it is pretty accurate.

[jaredyates]

Doug, when you shim the aileron hinge mount at the bottom, it raises the height of the aileron a little and makes a roll correction that lifts that wing. I ended up with a full-thickness washer on the heavy side and also a half-thickness washer on the top legs of the hinge mounts on the light side. The washers go through the fore-aft running bolts that hold the hinge mounts to the rear spar, with the washers going between the steel and the rear spar cap strip. Does that make sense?

[Helidesigner]

I will be trying a deflector in front of the static ports. I'm pretty sure that will work. The engine CHT's were low. I paid a lot of attention to the cooling. I have baffling behind the propeller, fairings behind the air inlets to improve efficiency (like RV's), good baffeling seals, a rounded lip at the tunnel-firewall intersection (like RV's), and cowl louvers both sides. I have a 3/8 in ~30 degree lip on the cowl exit.My exit area not including the baffels is about 90 sqin. With the louvers I'm over 100 sqin.

I'll count the rows on my cooler and report back.

Jared, please tell us about the washer trick.

[Mark Goldberg]

First of all, congratulations of your first flight Mr. Scott. Placing 1/8" washers between the aileron attach weldments and the rear spar where it is bolted - this is what you would do on the three UPPER "legs" of the weldments. Two "legs" on the weldment where the pushrod comes out and the one on the outboard weldment. This in effect lowers the aileron a little helping "lift" the heavy wing slightly. If that isn't enough, then you can place the same 1/8" washers under the lower attach points of the weldment for the aileron on the "light" wing.

Lowering the flap a little on the heavy wing might be enough on your plane, but it wasn't on my BH. I would certainly try that first. Mark

[Battson]

How did you mount your oil cooler? Directly onto the baffles, or with a remote mount?
If remote, what size tube and diffuser have you used? A photo would help if it's remote.

Sorry to state the obvious below.... just trying to help:

> There could be a blockage in your oil cooler. This is not uncommon.
> It is possible some crud is trapped inside your oil cooler hoses, obstructing the flow of oil through the cooler.

Obviously you've already:
> checked nothing could be obstructing the airflow over the oil cooler (?).
> chosen the right grade of oil for running in a new engine (?) e.g. Phillips 20W50
> checked if the engine has a defective thermostatic bypass valve, if installed (?)
> checked that the temperature gauge is working properly (?)

I notice you didn't reply about the run in process you followed.
I hope that means you don't have new cylinders, or that you already knew it through and through

But, forget to follow a proper run in process and the cylinders will be glazed by too much low power running e.g. medium power cruise and/or ground running. Then excessive blow-by from the combustion chambers can/will increase the oil temperature, just as you describe. The other give-away of that problem is oil consumption failing to stabilise within published limits. You can check for this with a compression test.

[DRLPatrol]

So if I understand, you are raising the pivot point of the aileron. I will have to think about that for a while, don't understand how that would pick up a wing.

Doug

P.S. I always picked up a heavy wing with flap linkage, except on a rag wing where you can twist the wing with the rear strut. The patrols flaps are so big you would never see the change.

[Battson]

Doug, I used the flap linkage too - very quick and easy to adjust - and as you say, they are so big you never need much. Basically impossible to notice.

[jaredyates]

If you have a very small change, then the flaps may work out ok- but in my case with the 1" deflection, the flap flex caused the trim effect to diminish as speed increased. When I placed a straight edge across the top of the aileron, I noticed that there was a slight difference in height on the two- less than 1/16" and not easy to measure, but still visible. This prompted me to wonder whether the difference in aileron height was the source of the roll issue in the first place. It seems that aileron height is one of the most critical dimensions for roll trim. My first choice was of course to address the source of the problem, as to not have a flap fighting the aileron and creating drag. I suspect that the reason for the aileron height being so critical is how the airflow changes the position of the aileron, causing deflection sort of how a trim tab or trailing edge radius would. So I think of it less as a matter of total wing lift and more a matter of the airflow powering the aileron.

[Enewton57]

If you run out of options, try a 2" lip at the cowl outlet. 3/8" is a little small. Eric Newton - Long Beach, MS http://mybearhawk.com