Question concerning operation at rearward CG

I'm contemplating a trip with a heavier than standard friend. With light bags, our CG at landing will put us at 76.25 with the rear CG limit being 76.8

I'm still pretty new to flying the 6A, and am trying to anticipate what kind of handling surprises I might find. I've owned several different planes in the past. Some of them were perfectly fine anywhere within the allowable CG range. Others were downright scary once you got towards the rear limits. Where does the 6A fall? Thanks in advance for any advice and recommendations.

Pitch force gets VERY light at aft cg limits in the -6/6A, especially at lower speeds. At landing speeds, stick force is so light, it's very easy to over flare.

Make sure you figure the CG with the fuel burned down as well as full. In the -6, as you burn down the fuel, since it is forward of the spar, the CG will move back.
In my -6, with a heavy passenger and a rear CG, it was more difficult to land since the tail wheel wanted to hit first. Also, what Mel says is correct.
I really noticed this on a trip at GW with a friend. We ended up putting some luggage just ahead of the spar behind our legs and it made quite a difference in handling.

I agree with Mel, in that the stick forces do get much lighter. At the end of a long flight, my CG is much closer to the aft limit than you are proposing (some times within .3 of an inch). I have to limit my baggage to 70 lbs in order to stay within CG at 8 gal remaining (this is why my personal limit is min 10gal). Although it is more sensitive, it is still very controllable and not a concern.

Same consideration with -9/9A?

I know this is a -6/6A forum, sorry for veering off but I'm curious-
is this why the baggage limit on the -9/9A was dropped from 100 lbs. to 75 lbs.? Do the -9s get scary when they move toward aft CG?

sf3543 said:

Make sure you figure the CG with the fuel burned down as well as full. In the -6, as you burn down the fuel, since it is forward of the spar, the CG will move back.
In my -6, with a heavy passenger and a rear CG, it was more difficult to land since the tail wheel wanted to hit first. Also, what Mel says is correct.
I really noticed this on a trip at GW with a friend. We ended up putting some luggage just ahead of the spar behind our legs and it made quite a difference in handling.

Click to expand...

The 76.25 figure I quoted (worst case) was burned down to 10 gallons. If I put my toolbag and one of out other bags in front of the spar, the CG will move up to 75.92.

Thanks for all the advice listed so far. I had a feeling it would be much lighter in pitch, but wanted to be relatively sure it would still be controllable. Headed up to Canon City, CO for the 4th of July. 3 1/2 hour trip in the RV versus 11 hour drive. I'd much rather fly if at all possible.

Craig...

As the previous owner of several different birds (recall, I met you years ago over in the C120/140 forums), what are your initial impressions of the glorious RV's?

I was just curious how you measured the performance, thrill, and/or overall capabilities of the RV thusfar? I know you've been from the 140, to the 170 (? I think) to the Citabria.......or something like that.....

Thanks in advance for the synopsis/thoughts.

You might consider ballasting your airplane for a more aft C.G. position than you are currently acustomed to flying at, and then shoot a few landings. This should be standard practice for a builder during phase 1 flight testing (though it seems that very few people do it) so why not you to help you get familiar with e new (to you) airplane.
This would be much more desirable than trying it the first time at an unfamiliar airport after posibly being pounded by bumps for 3 1/2 hrs.
Don't start at the aft limit, work your way towards it a couple landings at a time and see how it feels.

Gary - the RV blows away anything I have flown so far in terms of performance, speed and out-and-out fun factor. It is MUCH more sensitive in pitch that all the ragwing taildraggers I had been flying. The Mooney M10 was the only thing I've flown that even approached it in pitch sensitivity. It too got VERY light in pitch as you progressed towards the rear CG limits. I'll miss landing on rough 1000ft dirt strips for awhile, but the RV certainly makes up for that in other ways. I've only got about 5 hours in the plane so far (including my transition training) so I'm still kind of feeling here out. It took me a couple landings to remind myself I wasn't in a taildragger. I was trying to over rotate in the flare.

Scott - we're planning to do just what you suggested; a series of test hops with CG progressing rearward as we go along. First we'll just fly with me, my friend and full fuel. Then we'll add the bags. Then we'll burn off an hour's worth of fuel and try landings there. Then we'll burn off another hour and try again. I'm planning maximum 2 hour legs on the trip to keep as much fuel in the tanks as possible. That seems to be the easiest way to keep the CG as forward as possible.

CraigH@KRPH said:

I'm contemplating a trip with a heavier than standard friend. With light bags, our CG at landing will put us at 76.25 with the rear CG limit being 76.8

I'm still pretty new to flying the 6A, and am trying to anticipate what kind of handling surprises I might find. I've owned several different planes in the past. Some of them were perfectly fine anywhere within the allowable CG range. Others were downright scary once you got towards the rear limits. Where does the 6A fall? Thanks in advance for any advice and recommendations.

Click to expand...

Scrapping the tail on touchdown was one for me. When aft CG I carry another 10 knots on touchdown to prevent the tail strike on the 6A. Other than that, the other comments about being pitch sensitive was absolutely true especially slow and in the flare. It can really feel like its some other plane your flying at that particular point in time. Add the speed and the tail will not be a factor on touchdown. Definatley not scarey, but worth your undivided attention.

Best,

Don't do anything with a pax that you haven't done solo

A flight test program isn't mandatory for people who purchase flying aircraft, but it certainly is a very good idea. The flight test program is more than just a way to find and fix problems. It is also a way for the pilot to learn how the aircraft handles and performs across the full spectrum of conditions.

It would be wise to not do anything with a passenger that you haven't already done solo, including flying at the extremes of the weight and CG envelope. Use ballast as required. Fly all the various flight manoeuvres at each corner of the weight/CG envelope.

A good flight test program should also include a full assessment of the various systems and avionics on the aircraft, including various expected abnormal conditions. For example, if you run a fuel tank dry, do you know what the best procedure is to get the engine restarted? How long does it take, and how much altitude is lost? It is far better to find the answers to these questions on a deliberate test, overhead an airfield, than it is to conduct the experiment on the fly on the day you forget to change tanks.

If anyone is interested in the outcome of the tests here they are:

Take-off was pretty normal, with a little less back pressure on the stick required to hold the nose wheel up.

Cruise required more quite a bit down elevator trim than solo or no baggage flight.

Landing was also stable, but required much less nose-up trim once the flaps were deployed. Once the nose settled on landing, pitch sensitivity made it diffucult to pull the nose up and hold it there. Definitely handled a little different, but very nothing that felt unstable.

Stick forces.

I can ditto comments on the stick forces. At the aft CG, especiall a heavy aft CG, stick forces approach nil. Over flaring, and possible turn to final stalls are a concern. Just keep your heads up, watch out even more for the "RV sink" and add a few knots for the wife and kids.
At our grass strip while testing a 6a at aft CG, I actually banged the tail skid on the ground while taxing at a slow speed on a bumpy taxiway. read...High power setting on grass, aft elev. and big bumps.