Effect of CG on flight characteristics?
02-18-2003 | 10:24 PM
#2
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From: north palm beach,
FL
CG Effects
My experience is this:
If too nose heavy, it'll require a fair amount of UP trim to fly level. And you'll also find that you will run out of "UP" upon flairing to land. At such a slower speed, the nose wants to drop requiring more UP to counter. However, a CG that slightly favors nose heavy makes for much more a stable flying airplane.
On the other side of the coin, an aft CG creates more instability and pitch control becomes ultra sensitive as compared to being nose heavy. Snap stalls are relatively common depending on the type and spins will tend to flatten out becoming much more difficult to recover from.
Hope that answers some of your questions.
Ted
If too nose heavy, it'll require a fair amount of UP trim to fly level. And you'll also find that you will run out of "UP" upon flairing to land. At such a slower speed, the nose wants to drop requiring more UP to counter. However, a CG that slightly favors nose heavy makes for much more a stable flying airplane.
On the other side of the coin, an aft CG creates more instability and pitch control becomes ultra sensitive as compared to being nose heavy. Snap stalls are relatively common depending on the type and spins will tend to flatten out becoming much more difficult to recover from.
Hope that answers some of your questions.
Ted
02-19-2003 | 12:24 AM
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From: Glencoe, Minnesota
Effect of CG on flight characteristics?
02-19-2003 | 03:00 AM
#4
Effect of CG on flight characteristics?
Ted covered most of it. Also with a nose heavy model the up trim needed to balance the model will result in a very strong pitching up tendency with added speed either from power or diving. It will basically hate to be very far off it's best trim airspeed.
As it gets back closer to neutral the pitching up tendency from extra airspeed is greatly reduced.
In my experience any bad snap tendencies would be more due to the airfoil and planform of the wing along with the wingloading. I've flown a fair number of models that were very close to neutral stability and had no unwanted snap tendencies.
On the other hand an ARF Cub would snap and spin at the drop of a hat. It died on it's third or fourth flight. Good riddance.
The moral is that it doesn't always make sense but it does happen when you least expect it.
As it gets back closer to neutral the pitching up tendency from extra airspeed is greatly reduced.
In my experience any bad snap tendencies would be more due to the airfoil and planform of the wing along with the wingloading. I've flown a fair number of models that were very close to neutral stability and had no unwanted snap tendencies.
On the other hand an ARF Cub would snap and spin at the drop of a hat. It died on it's third or fourth flight. Good riddance.
The moral is that it doesn't always make sense but it does happen when you least expect it.
02-25-2003 | 12:30 AM
#5
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Re: Effect of CG on flight characteristics?
Originally posted by Splais
Could someone take the time to give me a short primer on what effect the CG has (to far back - to far forward) on flight in a pattern/sport type plane.
Could someone take the time to give me a short primer on what effect the CG has (to far back - to far forward) on flight in a pattern/sport type plane.
A nose heavy plane doesn't fly too good. A tail heavy plane doesn't fly too long.
Dan
02-25-2003 | 09:30 AM
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From: Kfar Vradim, ISRAEL
Effect of CG on flight characteristics?
One more thing:
When shifting C.G Backward (nose direction)
Rotation speed on Take-Off will be higher,
So Take-Off ground roll will be increased.
Explanation:
The elevator will have to overcome the
increased wing pitch-down moment
(wing moment arm was extended due to C.G shift)
When shifting C.G Backward (nose direction)
Rotation speed on Take-Off will be higher,
So Take-Off ground roll will be increased.
Explanation:
The elevator will have to overcome the
increased wing pitch-down moment
(wing moment arm was extended due to C.G shift)
