PGLong said:
Help.......I have an RV-4 and am experiencing landing problems with a rear seater present. I installed a Landoll Harmonic Balancer and according to weight and balance, should be able to tote a 225 pounder and stay within CG limits with correct fuel loads. Even with a 120-150 pound person in the rear seat, the elevator controls are so light it's almost like moving nothing.
The aft CG limit should be set to where ever
your flight testing shows it needs to be. The number from Van's is just a recommendation. There are valid reasons why Van's recommended aft CG limit may not work for you, with your current weight and balance data:
1. The weighing may have been done incorrectly, so you have the wrong empty CG. E.g., the aircraft may not have been correctly leveled. Or the scales may not have been accurate, etc. If your aircraft has an inaccurate empty weight and/or CG, the calculated CG limit (based on the inaccurate starting point) will need to be different than if you had an accurate starting point.
2. Your aircraft may have some difference to a standard RV-4 that could degrade the handling at aft CG. Extra power degrades aft CG handling. Extra friction in the controls may degrade aft CG handling.
3. Each pilot will have a different threshold at which he will declare the longitudinal stability is no longer acceptable. Maybe your personal threshold is set differently than Van's threshold.
Flying with a passenger is not the best way to open up the aft CG envelope. This is something to do with ballast to simulate a passenger. Move the CG back in nice easy steps, adding a few pounds of ballast each flight. Assess the static and dynamic longitudinal stability, with flaps up and flaps down, at idle power and with full power. Do stalls, wings level and in a 30 deg bank turn, with idle power, and with high power. Do takeoffs and landings. Determine where you consider the aft CG limit should be. If that doesn't allow enough weight in the rear seat, then look at what changes you can make to the aircraft to move its empty CG forward.
But first, maybe review the weight and balance. Did you do the weighing? Was the aircraft properly leveled? Did you properly account for the tare weight (chocks, shims, etc)? Were accurate scales used? Check the calculations. If in doubt, weigh the aircraft again.