Phase 1 Questions

Hi all,

I am in the early to mid phases of Phase 1 flight testing. This airplane is amazing to fly. Nimble, responsive but not at all squirrely. Definitely worth the ten years it took me to get to this point.

I have been following FAA AC90-89 as my primary guide to testing. I was going to do the stability testing next. The guide says:
"Start all tests with a forward center of gravity and at a low cruising speed"

This will seem llike a dumb question, but what do you suppose a low crusing speed means in an RV 8? My bird seems very comfortable at 120 kts. I know that is a common aerobatic entry speed. Does 120 kts seem reasonable or should I go with 100 or 110?

I did the VyVx testing last week. Had a heck of a time getting a really good curve. I will plan to repeat the test a couple more times and again at gross but I am getting about 110 Kts Vy and and about 85 kts Vx. That jive with what others have been getting? I know there is some variation with engine, prop, weight, etc.

I am:
IO360 M1B
3-blade Catto Fp
Full fuel and me:
Weight 1579
cg: 81.61

Any other pointers anyone would care to offer would be greatfully accepted.

120 kt is a good speed to start from. Then go up and down from there. Then put 50 lb or so in the rear luggage bay, and do it all again. Keep adding weight in the back until you get to Van?s recommended aft limit, or you decide you are not happy with the handling and choose to move the aft limit forward for your aircraft.

You should have excellent static stability at forward CG, but you will notice the stick forces get lower, and the static stability gets worse, as the CG goes aft. The stability is also worse with power on.

At aft CG, during climb at Vy, my aircraft has negative stick free static longitudinal stability. If I trim at Vy, get a bit slow, then release the stick, the airspeed will keep reducing until the stall. This is a good thing to discover during the flight test phase, rather than during an IFR departure.

Testing speeds

Thanks, Kevin

I am quite sure that Phase 1 is as much about training the pilot as testing the plane.