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Handling at increased gross weight

G

gerrychuck

Well Known Member
I have been searching and reading a great deal here on the board on the subject of flying RV-6's at gross weights above those recommended by Van's. I'm familiar with all the wing loading calculations, etc, so I'm comfortable with th concept from a structural point of view. I also understand that an increased gross requires a higher approach speed due to higher stall, etc. and that CG is frequently a major limiting factor.

My question is a simple one (hopefully): If an RV-6A is flown at 1800 lbs (the normal recommended gross for the 7A) will it's flying qualities be substantially different than those of a 7 at the same weight?

Thanks in advance.
 
Keep in mind that the RV-7 has one more foot of wing span than the RV-6 (assuming the same style wing tips on both models). Most RV-6s have the original wing tips, and newer RV-7s likely have the newer wing tips which have an extra 6" of span each, for an extra foot of wing span overall just due to wing tips. So, newer RV-7s have two more feet of wing span and 10% more wing area than most RV-6s.

A 1800 lb RV-6 would have the same wing loading as a 1980 lb RV-7, assuming old style tips on the RV-6 and new style tips on the RV-7. There is a good chance that the CG locations will not be the same either. Thus, you shouldn't expect the two aircraft to handle identically at any given gross weight.

Assuming you add enough extra approach speed to account for the increased stall speed, the biggest handling effect of the higher weight will be due to the aft movement of the CG (assuming that the high weight is due to lots of weight in the baggage compartment). Of course take-off, climb and landing performance will be significantly affected by a weight increase.
 
As mentioned, the most noticeable difference will be handling, as weight is moved back. Other than that, my 6A ( 180HP) still performs very well at it's 1850 gross weight. It will still climb faster, and out run a 9 with a 160HP and lighter weight. It's still light on the controls. And it's slower than the six cylinder F1, that I sometimes fly with.....

L.Adamson --- RV6A/ Hartzell CS
 
Welcome Gerry...

We flew our -6a at increasingly heavier weights and the most noticeable change at gross, was the very light elevator during the landing flare. The CG obviously moves rearward as fuel burns off but unless you're ham-fisted, not a big deal.

We had the -7 batwing tips because I preferred their looks and the added wing area, so we were only 1' shorter than the -7's. Our lightweight Skytek starter and Catto prop also added to the aft CG at gross and the firewall mounted Oddysee (sp?) battery helped offset that.


Best.
 
Thanks to all respondents (and thanks to Pierre for the welcome!). Much appreciated on all counts, and improves my understanding tremendously.
 
Incremental Build-Up

I'd like to endorse something that Pierre said in his post:

"We flew our -6a at increasingly heavier weights and..."

One of the first things that I learned in flight testing is the Golden Rule of incremental build-up. If you're planning to fly at a higher than normal gross weight, I suggest that you do it in small increments and then thoroughly assess the effect at each step. You seem aware of the effects of gross weight upon structure, so the effects of weight upon handling and performance can be assessed from experience...careful, incremental experience.

Let us know how it goes.

Rob
 
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