Before the first flight on my KR-2, my EAA Chapter 478 Flight Advisor had
arranged for me to take a series of flights with other owners of similar low
wing tri-gear aircraft. Each aircraft was different, but reasonably similar
to my KR-2. The idea was to get me experience in these aircraft so that
when I made my first flight in my KR-2 that would be just another different
aircraft with different characteristics. Those other aircraft were a
Cherokee 160, Grumman Yankee, T-34B, RV-8, Lancair 320 and Pulsar XP. I got
6.1 hours in the Pulsar XP to qualify for insurance coverage with Falcon
Insurance.
As to malfunctions on the first flight: At lift off the Elevator Trim Tab
went to full nose up and stayed there the entire flight. That resulted in a
huge PIO right off the runway. The Dynon g meter recorded +0.3 to +1.7 g
excursions. I got that under control in 2 cycles. The pull-out from the
first dive was about 6 feet off the ground according to observers on the
taxiway. I had to hold about 10 pounds forward pressure on the stick the
entire flight.
The second problem was an aft CG which tended to make the aircraft unstable
in pitch. That was controllable, but the aircraft would hunt up and down in
pitch.
The third problem was dropping oil pressure and runaway high oil
temperature: 240 degrees F and rapidly climbing. I thought the engine was
about to seize.
The fourth problem was oil leaks. The bottom of the fuselage and stub wings
were well oiled. Don't know how, but a few spatters got on the canopy also.
At the time I thought I had lost all my oil.
I created another problem on the high speed landing by bending the nose gear
strut on the third touch down bounce by hitting nose wheel first.
On the first flight I did not have time to explore slow flight or stall
situations. With aft CG conditions stalls are very dangerous. Slow speed
touch down will result in tail strikes and loss of pitch control. The
center of lift will move forward with decreasing airspeed and increased
angle of attack. Stalls will produce a pitch up in those conditions instead
of the expected pitch down.
I fixed the Elevator Trim Tab by securely fastening the sheath of the Nyrod
cable at the horizontal stabilizer. The fix for the aft CG was to add 30
pounds of ballast attached to the cowl just behind the spinner. The fix for
the high oil temperature was to throw away the old cooler and install a
Revmaster oil cooler to the bottom of the 2180 VW. I am still fixing oil
leaks one at a time. The technique is to secure a shop cloth around the
suspected location then run the engine. If oil is on the outside and not on
the inside of the cloth, the leak is elsewhere. If it is wet on the inside,
the leak is there. I fixed the nose strut with a replacement strut and
swivel bolt assembly.
I have made a total of 4 flights on my KR-2 and still chasing this aft CG
problem. I have moved the engine 2 inches forward from plans call-out. I
found a transcript of an interview with Stu Robinson done about 25 years
ago. He implied that the center of lift for the RAF 48 airfoil may be about
2 inches further forward than he had assumed when he was designing the KR-2.
This prompted the design of the new airfoils for the KR-2S. So, when I weigh
my KR-2 and come up with a ready to fly with me and half fuel at a CG of
12.6 inches, the reality is the airplane will behave as if the CG was at
14.6 inches.
As Larry says, "Your results may vary."
Sid Wood
Tri-gear KR-2 N6242
Mechanicsville, MD, USA
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Questions to Sid Wood;
You wrote about your First Test Flight, that you had 4 malfunctions on your
KR, which may have
lead you to fatal, would you tell me, just about what they were and what
were the " Test pilot Training ", like
stall recover, slow flight, uncontrollable situations ??
I`m going to have it soon with my KR, so, that may be the fatal help,,,!!
Thousand Thanks !!
Yoshio, Hamburg
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