Balance for first flights

> When I compare where I would balance out on Checkoway's RV7 vs my own RV8, flying solo with half full tanks I would balance out 32% aft off the fwd CG range on the 7 while only 5.7 % aft in my 8.
> If I put 25 pounds in the rear baggage shelf I would still only be 21.5% aft of the forward CG range.
> We don't have a Flight Tech counseler in our group so I'm wondering what the consensus is of people who fly the heavier angle valved engine/hartzell prop especially.
> I get 27 - 28 degrees of upelevator throw and when solo. Do I *need* to get that up to the max recommended of 30 or is a couple of degrees a non-factor?
> thx,
> lucky


Lucky,
I would make sure you get the full 30 degree up elevator travel. With an angle valve, and no doubt a Hartzell, you'll need all the up elevator you can get when landing solo. I can't say what the effect of 27-28 would be relative to the specified 30, but I would want to give myself every advantage in a known forward CG bias situation. I don't have the Van's documentation here, but isn't there a range on the elevator travel stops like 30-32? Also, be sure to check the deflection range on your trim tab and make sure you're getting the Van's specified values.

Regarding your first flight, I would recommend putting 25-50 lbs in the baggage compartment. Go with the 50 if you can secure it reasonably. RV-8's simply fly better when more toward the center of the range. That's not to say it's unsafe with it when more forward, just don't plan on doing any 3-point landings. Are you going to make the first flight yourself? Have you been through transition training? As more new RVs going the fleet it seems like more and more guys are having more experienced RV drivers do their first flights. Not a bad idea depending on your own experience and situation. Plan ahead insurance-wise though, make sure whomever does the duties is covered. Regardless of whe makes the actual first flew flights, you should take responsibility for the flight plans and what gets checked and noted... you are the manufacturer and the owner.

BTW, one of the parameters that should be tested, not necessarily on the first flight, is what is the slowest speed that can be trimmed to when in landing configuration (full flaps, idle power, hands off the stick). My guess is you won't be able to trim for your desired (~80 mph) approach speed but will need to hold additional back stick.

Danny or Kevin, any further advice?

Randy Lervold

EAA Tech Counselor
EAA Flight Advisor
www.rv-8.com
www.rv-3.com

randylervold said:

BTW, one of the parameters that should be tested, not necessarily on the first flight, is what is the slowest speed that can be trimmed to when in landing configuration (full flaps, idle power, hands off the stick). My guess is you won't be able to trim for your desired (~80 mph) approach speed but will need to hold additional back stick.

Danny or Kevin, any further advice?

Click to expand...

Given all the reports about people running out of elevator when trying to do a three-point landing at forward CG, I would prefer to have 30 degrees of up elevator travel. Is it needed? Probably not, in the strictest sense of the word. I adjusted my up elevator stop to get 30 degrees of up elevator. I had to do a bit of filing on the stop to get the travel I wanted.

I would use ballast as required to get the CG near the middle of the allowable range. Of course the ballast must be well secured.

I agree that it would be interesting to do a test of the minimum trim speed. Keep in mind that the minimum trim speed will vary with CG, power and flap angle. You should also check the ability to trim at aft CG, flaps up, maximum cruise speed. If you have more than enough down trim for the aft CG high speed case, you could rerig your trim control to move the trim tab travel a bit more towards the nose-up direction. I.e. reduce the travel in the nose-down sense, to get more travel in the nose-up sense. Just be sure to have enough nose-down travel for the high speed aft CG case.

Do the 8's and 8A's have a similar empty weight center of gravity? I'm wondering if an 8A would also benefit from 25-50 lbs. of ballast when flown solo.