N62588 Phase 1 Flight Testing

[Bcone1381]

Phase one flight testing. I am following the EAA Flight Test Task Based. But that program by the letter does not address Engine Break-in. So when Engine break-in is complete, then the program gets implemented in earnest. The first flight was about 45 minutes with the goal of running the engine hard and returning to check things over for pending infant mortality issues.

Issues we found in flight
-Prop RPM needs adjusting
-Rigging - needs slight left rudder in cruise, and has slight L heavy wing.
-ADS-b failed to record anything.
-IAS seems to read slow ~ 10 kts.

The next two flights were dedicated to fixing ADS-b issue as the aircraft is based in ADS-b airspace. This was fixed thru adjustment of settings of the Trig Transponder. In those two flights a ground test found that Prop low pitch stop was set perfectly by Hartzell and so a govenor adjustment was made. The rudder rigging is being addressed. Once that is good, we will address the roll rigging. A trim tab is commonly installed to fix this.

With my focus on Engine Break-in I am not spending much time playing with stuff at various airspeed, then stopping, adjusting, then seeing what effect it has. I flew a 2+ hour flight yesterday and do one thing at a time. I am also going to test out a simple rudder trim device that uses an adjustable bungee to apply some rudder pressure. This is what my colleague calls a MPV design.... "Minimally Viable Product".

Airspeed. The pitot/static tube I installed is from Steen Aero Lab. It sticks out about 10" from the leading edge. We are getting low airspeed readouts....Data says about 14 kts slow. The Husky has a very very similar pitot static tube and they have had the same issue and have a fix for it. I am on there group and getting some good data/ideas that we will implement to improve the error. I might end up getting it fixed with modifications to the pitot tube or move the static port to the fuselage. Right now I see 97 KTAS on the Garmin G5. When I fly a GPS box pattern and average the speed of the four legs I get 111 kts ground speed. I think the compression of the air as it runs into the leading edge of the wing is increasing the pressure at the static holes in the probe, so the airspeed reads low. I will play with various treatments ahead of and behind those holes just aft of the pitot tube "nozzle" and see what happens.
Screenshot 2025-02-25 at 7.43.28 PM.png

[rodsmith]

Good job working through the issues Brooks!

[svyolo]

There are terms used in rigging that I was/am not familiar with. The biggest being "heavy wing". I had a slight left roll tendancy, that I tried to fix with a "heavy wing" fix. That caused a heavy wing.

So what I think is a "heavy wing", is the aircraft will roll some set amount, in my case 10-15 degrees. Hands off the ailerons, and the ailerons are displaced into that roll. The aileron displacement causes adverse yaw in the opposite direction. The plane reaches equalibrium, and just sits there, one wing down, yawing in the opposite directions.

Is that an accurate description?

I fixed the roll with the flaps. I undid most of what caused the "heavy wing", and most of it went away. Right now I have a small trim tab, but will still try to get rid the small amount of heavy wing without the tab. Flies hands off.

[jaredyates]

Hey John it is great to hear that you are out putting hours on your plane! There can be some complexity to the roll trim, because there are lots of things that can impact it. Since there is coupling between the yaw and roll controls and their axes, that doesn't help either. Sometimes what seems like a heavy wing (out of trim in the roll axis) is actually a rudder thing rather than a wing thing. Asymmetry in the flaps at their full-up position can cause a roll, but the ailerons can too, for a few different reasons. A very slight height difference in the ailerons is a common trim point. This is accomplished by adding washers under the aileron mounting points at the rear spar, either at the bottom, or the top, to raise or lower the aileron accordingly.

The key to happiness is figuring out what the cause of the roll is, and fixing that. In my case it was aileron related. I adjusted a flap, and that would fix it at one speed, but if I was faster or slower than that speed, the uncommanded roll input was still present.

[svyolo]

The roll tendency was definitely fixed with flaps (ball centered manually). It does appear to be a slight height difference in the flaps.

The ailerons were more "fun". A slight height difference caused the neutral position(not neutral) of the ailerons to cause a slight left roll, and adverse yaw the other way. When they reached equilibrium, the airplane would just sit 10-15 degrees left wing down, and yawed to the right. I am thinking that is what is called "heavy wing". If I am wrong with that I hope someone sets me straight.

I created the heavy wing by misdiagnosing a rolling moment as a heavy wing, and trying the washer under the aileron hinge. I have almost completely eliminated that.

I have a fixed rudder trim tab, with little deflection. And a temporary small aileron trim tab, but I think I will be able to zero out the heavy wing without the tab.

Right now it flys hands off at normal cruise, just needs rudder if going slower or faster. Small amount of fine tuning required.

[Bcone1381]

Seems like the Weather has been IFR or windy so no more flights since #4. I enjoy the discussion on rigging.

John; I don't know what i'm looking for to help trouble shoot my rigging. I jump in and fix it before it gets that far. Feet on the floor with hands off the stick I think it yaws right. Not sure about roll. If I center the ball with left rudder I need right stick to keep the wings level.

What does it mean in my wings are level, the ball is centered, and I study my hood ornament (my kids may not know what a hood ornament is). my heading does not stay on target....it drifts to the right. I suspect that might mean my ball indicator on my G5 needs adjustment, but I'm not sure. I think if I release a bit of R rudder so the ball shows 1/3 ball left then the aircraft holds a heading and the ornament stays on target.

Another data point... I talked with Mark Goldberg a few days ago. He said another check that could effect roll was the H-stab rigging. I checked mine and the R & L H-stabs are identical....with one exception. My R. outboard incidence was about 1/16 bubble off using a old fashion bubble level. The H-stab spar checks good. The H-stab has a stream lined strut that rigs the outboard leading edge of the H-stab up/down. I adjusted mine, raised the Leading edge a bit by lengthening the strut end one turn and have it nailed now. I also rigged up an internal rudder trim because I woke up in the night with an idea, and I did not like the shape of my trim tab.

My plan is to rig this like we use to trim the 727. Start with the tail (rudder) and move forward to the wing. But I'm open to advice from the experts. That means I'd trim out the rudder so it stays on target, note the G5 ball indication so I can change the setting when I land. Then I would work on trimming out any roll that I still have.

[svyolo]

I have never rigged an airplane before, but my thinking is similar. Use your feet to center the ball, and then see what the airplane wants to do in roll. Included in the "what does it want to do in roll", is release the stick and see where the ailerons sit with no pressure on the stick. If they are not neutral, the will induce a roll AND adverse yaw. If they stay neutral, and you still have a roll, it is "something" else. On mine, I fixed that with the flaps. After I sorted the roll out, I set the rudder trim tab to be neutral at normal cruise, which for me I think will be 115-120 knots IAS, at least for now on small tires.

Interesting about your yaw on the G5. I had a bad remote magnetometer. It did not effect yaw, but it showed up as the heading changing, but visually, my heading was not changing. That was an easy diagnosis and fix. I still have one minor issue that I believe is the Left to Right accelerometer built into the internal IRS in my GRT Horizon 10.1. Airspeed, groundspeed, TAS all seem good, referenced against an external GPS. Crosswind component seems off, and a bit erratic. Sort of like checking your IRS's after a flight and seeing 15 knots. It is displayed to me as erratic crosswind indication, and flight path marker displacement. Vertical is good. I can fly and navigate no problem. I will work with GRT to figure this out next month.

[huntaero]

Hi Brooks Make sure you ball is exactly level by leveling the airplane and adjust the gage to read level first, then go out and work from the rudder forward you could be chasing an instrument error.

[Bcone1381]

I have been thinking that same thing huntaero. Today I leveled it in the hangar (a level says my floor is level) and re-did the attitude set-up but did not check the slip-skid ball indicator. I'll do that tomorrow.

[jaredyates]

Just a refresher on some of the content that we have in the ecosystem on these topics:

https://bearhawk.tips/3537

https://bearhawk.tips/3722

If you don't have access to these just let me know and I'll send a pdf.

[Nev]

What does it mean in my wings are level, the ball is centered, and I study my hood ornament (my kids may not know what a hood ornament is). my heading does not stay on target....it drifts to the right. I suspect that might mean my ball indicator on my G5 needs adjustment, but I'm not sure. I think if I release a bit of R rudder so the ball shows 1/3 ball left then the aircraft holds a heading and the ornament stays on target.

My understanding is that this is known as a steady heading sideslip. If the heading is kept steady then the ball will indicate out to one side. If the ball is kept centered then a gradual heading change will occur. On my Bearhawk it was indicative of a "heavy wing", and corrected by installing washers under the affected hinge to raise or lower the hinge line as required.

[Bcone1381]

I've got 10 hours on the aircraft now and so I am scaling back engine break-in focus and moving towards Rigging. Kevin D's Beartrack Articles from 2018 were brought to my attention yesterday. I read thru them and fabricated some tools and a set of instructions.

One H-stab's streamline strut was adjusted one turn on the fitting to get it lined up. I also checked the H-stab's angle of incidence against the wing's. It is within .100" of being exact. In cruise flight with me and 40 pounds in the rear seat the elevator is displaced out of neutral 1 inch nose up. So when it gets loaded up it will be less. It will be interesting to see how it changes.

I made headway on my airspeed indication. The Husky group had me install an oring on the pitot tube. The IAS : TAS difference with the oring improved from 14 kts to 4 kts. WIth this modification a dynamic static test was performed, where I took off, stayed just above the runway and watched the altimeter. The altitude went down 40' at 100 kts.
Screenshot 2025-03-05 at 6.25.29 PM.png
I want to get the IAS nailed so I decided to enlarged it a bit more. I tried to taper the approach to the oring and make it look pretty with shrink tubing.

Screenshot 2025-03-05 at 6.25.53 PM.png

Kevin D's article says my first task is to take measurements, then start with some pitch tests to expose the aircrafts pitch stability and this reveal if the h-stab's incidence is righteous or not. Before reading Kevin's article I was nosing around and found that I should retract my R flap 1 degree to match the left flap. That may be the cause of the rudder and aileron issue. But its windy and rainy. My local body shop will be painting my engine cowl. I drop it off tomorrow so I have a list of things I'll do with the cowl off.

[svyolo]

Here is a <2 minute youtube on pitot/static testing on the ground. There are longer ones but the technique is the same. Worked for me.

https://www.youtube.com/watch?v=DN-74HluxC0&t=514s