Sunday, September 25, 2011

Worked on improving the nose gear. First a a piece of phenolic material was installed underneath the nose strut stop. This reduced the friction of the nose strut while in flight. Next the v-notched channels were ground down and polished. The nose strut no longer touches the extrusion in normal flight, but rides when the rudder is at extreme positions.

The friction in the rudder pedal bearings was also reduced by changing the bolt tension down a bit to 25lbs from 30lbs.

In flight the rudder slowly returns to position, but is still not as loose as I would like due to the nature of the nose bearing surfaces.

A new lower nylon bearing had been fabricated and installed last week. The old bearing had shown some signs of wear and had a 2-3mm gap in it. This new bearing was intended to reduce the amount of forward and back shake on landing. Overall the change was successful. The shake is still visible, but it is no longer detectable in the pedals. This may be the nose strut flexing.

I ended up making a side-by-side comparision video of my 701 & 150 taking off and landing. The takeoffs are on the same runway and almost identical conditions. The winds, pilot, amount of fuel, ect were almost the same. What was not the same was how I flew the 701. This was a normal takeoff, not a short field takeoff. For the 150 I did a short takeoff.

The landings were similar in wind. Obviously the runways were different. The 150 land land short. Just drop 40 degrees of flaps and use power to keep from falling out of the sky.

Sunday, September 18, 2011

The weather was bad on Saturday and I took it as a chance to try to reduce the friction in the rudder system and reduce nose gear shake on landing.

For the shake I fabricated a new lower nylon bearing. This one has a tighter fit than the original, so the forward\back motion is limited.

To install it the old lower bushing had to be removed. This was an incredible pain. Reaching the bolts is complicated by the nose strut and the muffler. While the nose bearing was out I removed the v-notch channels and machined them down to create a smoother ride. the new shape is a semi-circle instead of t notch.

I also experimented with the strut cap. New pieces were fabricated out of nylon and phenolic to attempt to reduce the nose gear friction. Once all the pieces were re-installed some reduction of friction was made, but not much. In addition new friction was added by the new lower bearing. The lower nose gear needs to be removed again as I found the new machining of the notches allows for full left rudder deflection, but not full right deflection.

There is still too much friction in the rudder system. After much experimentation I can say the friction is mostly from the nose strut. The rudder by itself is free of perceivable friction. Some friction is being added by the rudder pedal assembly bearings. Grease, teflon, lithium, ect does not seem to reduce the pedal friction.

With the nose gear push rods removed, it obvious that the nose gear is the cause of my troubles. By placing washers under the nose strut cap, I tried lowering the nose strut to allow the cross tube to rub the newly machines angle. This was more friction than the strut cap, despite having less contact surface. The addition of a nylon or phenolic piece under the strut cap adds some reduction in friction, but not as much as expected. One idea I have is to place a matching nylon piece on the firewall shelf so the bearing is nylon to nylon. This would require removing\accessing the bolts holding the upper nylon bearing and may be impossible with the nose strut in place.

The final attempt will be to perform the roller bearing mod. Adding the bearings will require removal of the nose strut or the exhaust system. It will also require some way of adding additional material on top of the lower nylon bearing to allow for full deflections.

The roller bearing mod was originally found here:

The proper bolt length appears to be AN3-37 and the bearings are "DPP4-FS464" from ACS.

Monday, September 12, 2011

Tested gross weight and aft most CG limits. To test the aft limit I flew off the fuel to only 6 gallons and then loaded the baggage compartment with 40lbs shoved to the far back. This is as close to the aft limit as I could get given the baggage hold limits.

Handling at rear CG was slightly lighter. Power-off and powered stall attempts, takeoffs and landings were about the same as solo/no gear.

Next I added 200lbs of sand bags and fueled up to 16 gallons. Starting DA was 2000'. This was also the most forward CG I could obtain according to the numbers.

Takeoff roll was about 300' and climb out was ~700~750FPM. Power-off stall attempts resulted in a lower nose attitude when the elevator lost authority. Poweron stall attempts also resulted in a lower nose attitude.

Landings were very different. The added mass gave the plane much more momentum and was harder to slow. With my standard final approach speed of 60 MPH, the sink rate was higher and the plane felt "faster".

On Sunday I found an issue with the control system. The baggage area was loaded, but in a slightly different way. This caused the piece of nylon I installed underneath the baggage area to shift. The end result was a snag that I felt in the controls check. It took about 30 minutes to locate it and then a few more minutes to fix it.

Tuesday, September 06, 2011

Lots of flying over the Labor Day weekend. The big item was getting N701GV up to 17990 and running out of VFR airspace. The climb took 38 minutes and 100+ FPM of climb was still left at 50MPH indicated.

Parts were ordered for the roller-bearing mod on the nose gear. This should improve the feel of the rudders in the air. I will also adjust the lower strut bearing to see if it can be tightened and remove the V-notches the nose strut sits on.

Thursday, September 01, 2011

Reached 10 hours in the air. Changed the oil and did another under the cowl inspection.

All indications from the magnet filter and oil look good, break in is going well.

Found some evidence of an oil cooler fitter rubbing against the engine mount. This was more flex than expected. The filter was moved and secured down additionally to stop this.

After adjusting the turnbuckles more, it appears that 18lbs tension is the magic number. The slight left turning bias on the ground was traced back to a trailing \ not yet broken in brake pad.

There is still more friction that I would like in the rudder system, so I will install the rolling bearing mod on the nose strut.

The airframe now has about eleven hours in the air.