| Adam. This is so weird as it is almost a clone of my first KR. I agree with your tables except the measurement on fuel should be 64. At least that is what I used.
Thanks Mark Jones Tampa, Fl
N771MJ “WunderBird” www.flykr2s.com Mark,
You didn't provide the measurement to the fuel tank, but using the leading edge to tank measurement for my KR2 with wing tanks installed aft of the spar, here is the result. I've also calculated the CG for your oops flight and you with full fuel for a normal test flight. Provided these weights and measurements are accurate and on these calculations, your incident flight CG should have been slightly forward of the forward limit and should not have resulted in the experience you had with not being able to lower the nose. If anything it should have felt very nose heavy. It would possibly indicate that there is something else wrong outside of CG or you data is incorrect. Let me know if you have any questions.
Sincerely,
Adam Deem
| Date: |
5/20/2026 |
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| A/C Type: |
KR2S |
Serial #: |
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| Registration
#: |
N771MJ |
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| Owner Name: |
Mark Jones |
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| Address: |
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| Datum: |
Front edge of prop crush plate |
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| Allowable CG: |
54.5"-60.5" |
Max Weight: |
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| EMPTY WEIGHT &
CG |
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| Description |
Station |
Weight |
Moment |
|
|
| Left Wheel |
67.5 |
319.0 |
21532.5 |
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| Right Wheel |
67.5 |
325.0 |
21937.5 |
|
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| Nosewheel |
21.5 |
259.0 |
5568.5 |
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| Empty Wt/CG |
54.31 |
903.0 |
49038.5 |
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| ADJUSTMENTS |
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| Description |
Station |
Weight |
Moment |
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| Full Fuel |
75.5 |
-145.2 |
-10962.6 |
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| |
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|
0.0 |
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| |
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|
0.0 |
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| |
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0.0 |
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| |
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0.0 |
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| Adjusted
Weight/CG |
50.25 |
757.8 |
38075.9 |
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| OOPS FLIGHT CG 1/4
TANKS |
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| Description |
Station |
Weight |
Moment |
|
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| Empty Wt |
50.2 |
757.8 |
38075.9 |
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| Pilot |
65.0 |
178.0 |
11570.0 |
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| Passenger |
65.0 |
0.0 |
0.0 |
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| Fuel |
75.5 |
36.0 |
2718.0 |
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| Baggage |
100.0 |
0.0 |
0.0 |
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| Loaded Wt/CG |
53.9 |
971.8 |
52363.9 |
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| CG WITH PILOT &
FULL TANKS |
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| Description |
Station |
Weight |
Moment |
|
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| Empty Wt |
50.2 |
757.8 |
38075.9 |
|
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| Pilot |
65.0 |
178.0 |
11570.0 |
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| Passenger |
65.0 |
0.0 |
0.0 |
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| Fuel |
75.5 |
145.2 |
10962.6 |
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| Baggage |
100.0 |
0.0 |
0.0 |
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| Loaded Wt/CG |
56.1 |
1081.0 |
60608.5 |
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| NOTES: |
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| CG range is listed as 8-16" aft of stub wing leading edge
by Rand Robinson build manual, however flight testing has shown operation in
the aft 2" is undesirable due to insufficient stability. The range listed on this sheet excludes the
aft 2" as recommended. |
I don't know if it got through but I calculated 56.07"... Assuming his station measurements and weights are correct.
Jerry Pryce On May 20, 2026 10:11, Chris Pryce via KRnet < [email protected]> wrote: What are you getting for a calculated CG for the aircraft in flying configuration? I would hope that it is 54.5 to 60.5 based on your Datum for your leading edge.
HELP......I am so confused. My new KR WunderBird is ready to fly except for the weight and balance. I have made many runs down the runway and on one run I lifted the nose and she shot straight up to about 100' and I could not push the nose down and she stalled on me. I was fortunate enough to cut power and get her flat before she contacted the ground very hard. Bent the main landing gear brackets and had to make more. I did some w&b adjustments, repaired the gear and tried again. Still tail heavy. I am very lucky I did not destroy the plane on that first flight attempt. So, here is my challenge to anyone who wishes to figure a weight and balance on this bird. I just want to compare others with my calculations. Here are the parameters.
Weighed with FULL FUEL: 12 gallons each wing. Left Main 319 lbs Right Main 325 lbs Nose wheel 259 lbs Datum measuring point: Front side prop Crush plate Datum to nose wheel: 21.5" Datum to Mains: 67.5 Datum to leading edge stub wing: 46.5 Datum to Pilot: 65" with pilot weight 178l lbs
Thanks for any help.
Mark Jones KR2S (N771MJ) Cessna 140 (N1856C) Tampa, FL
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