Cg causing landing issues

[farmflyer]

I think Gman talked about this a while back. Iv tried to search it out but couldn't find it. The discussion was about nose heavy cg causing a bounce on landing. I'm looking for the explanation why this would happen.

[seaviper]

Probably because when you have a nose heavy Cg, you have to keep your speed higher on touchdown otherwise your elevator wont be effective enough to round out before touchdown. You will probably touch down at flying speed (higher than Vso) so any little rebound from the struts or bump in the runway or even small change in elevator will hop the bird back into the air.

[wrongroad]

G'day farmflyer,
seaviper is on the ball here but may I add that the nose heavy configuration also will put you in a nose down attitude and, PERHAPS, a steeper approach leading to a tennis ball reaction.
It is all about action and reaction.
I see a lot of pilots at my club make a near perfect approach only to rip in up elevator to flare instead of a gentle easing back on the stick. The result is a the three time landing as opposed to a three point landing.
Now, and am I sure that SV with concur here, nose down CG is relative. I fly with a bit of nose down in all my models [except the FMS Olympus that I try to have a neutral as possible] and, I add nose down trim on my landing approach to set up a positive rate of descent. Then I balance with elevator and throttle to control the rate. If I let go of the sticks, my machines go nose down rapidly, indeed! If you were to fly my models, there is every chance that you would hate my set up. [It is a good way of keeping the 'can I fly your model ?' brigade away;)]
With this set up, I very rarely bounce a landing as I go for the flatter approach. Now having said that, guess what I did today?
Now, I do not subscribe that nose down CG will cause the bounce, it is the fact that the pilot does not control the nose down set up.
It is just as SV puts it.
Once you have the aircraft two feet of the deck, ease back on the throttle and control the rate of sink and 'hey presto' next to perfect landings all the time.
Regards and respect
Daryl

PS
If you want to look at my club field check out

https://www.graftonmac.com

look at the forums and find the video links to see some good footage of the field.
It is in much better condition two years on.

[Grossman56]

Hey guys:
What was happening in my case was that the Pitts was extremely nose heavy. I took everyone else's advice and jammed the battery all the way forward, and trimmed the forward piece out in anticipation of pushing it even further. I took in to R/C Flight School and had Dave fly it. He diagnosed it as being extremely nose heavy so we played around with the cg and brought it back to a point where the rear battery strap was just over the battery. Huge difference as now she doesn't do this crunch on landing then bounce into the air again. As you lose airspeed, the weight of the nose cause the plane to come down hard on the mains then bounce back up. You can see it has pushed the L/G out quite a bit in this pic. This is with the battery all the way forward before I cut the inside of the fuse to allow even more forward movement. Never did go that far, although every video I've watched, tells me that's what I have to do.

Grossman56

[starcop]

Also, a Cross-wing can cause a bounced landing. This is for obvious reasons, but it can be missed. (y)

Matt

[F106DeltaDart]

You mean a Cross-wind? I had a few close calls with those shooting approaches with my Tomcat on the weekend.

[StormyDog1962]

Remember also the the CG in the manual is a recommended starting point and from there you can adjust it to suit your flying style. Case in point Mark prefers a bit nose heavy however Tom likes em a bit tail heavy therefore each has issues flying the others planes. But their own set ups work well for them individually so don't be afraid to move it a bit in small increments until it feels right to you not necessarily what feels right to others.