upright and inverted flight

[Sam Laughery]

Probably a stupid question but we had this discussion at our field today an I got an array of answers.  Assume for a moment that your plane such as a cardinal or vector is trimmed perfectly.  Should the handle be at exactly the same angle (90 degrees) when flying upright and inverted?  Most of mine seem to need a little down when flying inverted.  Is my handle out of adjustment or could the flap and elevator be out of allignment?

Sam

[rustler]

I would have thought when flying level upright you need the lift necessary to keep the plane in the air. If you have the handle at exactly the same angle when inverted, flying surfaces would be at exactly the same position and you would get lift acting towards the ground, hence need to change handle angle slightly.

[Wayne Collier]

Speculative opinion only -- don't take this for science.  It would seem to me that while most of us depend on sight and feel while flying some of us may rely slightly more on one or the other.   For a person who has a feel  preference, handle position is very important.  When their arm and wrist are in a particular position they want the plane behaving in a corresponding way.  I've never seen someone fly blindfolded, but we've all heard of people who can.  That is a testimony to the effectiveness of getting trim and feel "worked out" and "right on."  People who tend to rely more on sight than feel may not even be aware of their exact arm and wrist position at any particular point during a flight.  They are watching the plane and the "reflex" motions of the body are in responce to what they see.  These people are in real trouble if "sun blinded" for a moment but almost instantly and nearly unconsciously compensate for things like wind changes or obstacles like birds.

[minnesotamodeler]

I would have thought when flying level upright you need the lift necessary to keep the plane in the air. If you have the handle at exactly the same angle when inverted, flying surfaces would be at exactly the same position and you would get lift acting towards the ground, hence need to change handle angle slightly.

Our symmetrical airfoils are "neutral lift"--require a slight positive angle of attack to maintain level flight.  So...a touch of "up".  Handle is generally adjusted at that point to be level.  Invert it, and to achieve that required positive AoA requires a touch of "down".  Handle can NOT be held in exactly the same position, but slightly "down".  Perception notwithstanding, that is the aerodynamic reality of upright vs. inverted flight. 

Think of a flat-bottom or undercambered high-lift airfoil--it will fly upright at a truly 0 d. angle of attack.  Inverted, if it flies at all, it is with a considerable AoA with lots of "down" to counteract the negative lift it's producing.  Handle can NOT be in the same position both ways.  Different airfoil but same principle.

--Ray

[Ron King]

Probably a stupid question but we had this discussion at our field today an I got an array of answers.  Assume for a moment that your plane such as a cardinal or vector is trimmed perfectly.  Should the handle be at exactly the same angle (90 degrees) when flying upright and inverted?  Most of mine seem to need a little down when flying inverted.  Is my handle out of adjustment or could the flap and elevator be out of allignment?

Sam,

The short answer to these questions is "No" and "Maybe not."  

Your Cardinal or Vector or most stunt ships all have symmetrical airfoils - as mentioned by the folks who can type faster than me.     These generate no lift unless you give them some angle of attack (AoA). It's hardly noticeable, but when upright, your plane will be flying with a slight upward AoA and when inverted, you will have to give it some down elevator to produce a negative AoA.

It's hardly noticeable at the handle on a well trimmed and balanced plane, but it's there. I feel it in the difference of finger pressure on my handle more than any visible wrist movement.

You will notice it more if the plane is nose heavy. You get used to the wrist position and finger pressure flying upright and it takes more movement and pressure to fly level when inverted. It's no big deal if you like your planes a little nose heavy.

Hope this helps,

Ron

[john e. holliday]

Sam,  I am no expert by a long way, but,  I have been paying attention to my flying the last decade or so of trying to fly stunt.  If someone helps me set up a new plane in which all flaps/elevator is neutral and handle is verticle I find I am feeding in a little up at the handle while flying.  So when I land I adjust the handle with a little more up.  I have trouble getting enough down if I don't do it this way.  That is why I am starting to have one handle and set of lines for each of my stunt planes.  Now when I go out to just play it doesn't matter as I fly by sight most of the time.  Have fun,  DOC Holliday

[Ted Winterman]

       Sam,

       Everyones hand bone structure is different. When my flaps/elevators are all neutral
and leadouts are equal in length, in order for me to fly level upright or inverted, I need
alot of up-bias. I do not have much wrist up movement.

       Ted

[Bill Little]

Hi Ted,

I have the opposite set up.  I get a LOT of "down" with my wrist compared to "up".  Since I have gone to a vertical hand set up, it has helped the symmetry of my control inputs for some reason.

As to the difference in upright and inverted trim, I have not noticed it lately in my planes.  maybe I just do the "subconscious deal" and give a little pressure to the handle when I am flying the inverted laps.

Kinda like asking a golfer as he's getting ready to hit his first tee shot: "Do you breath in or out during your backswing?"   

[Sam Laughery]

Thanks everyone.  That helps a lot.    y1Sounds like with a symetrical airfoil perfectly trimmed you need a little up flying upright and a little down flying inverted.  That makes sense.  It also means that the handle cannot be in exactly the same position inverted and upright.  You just need to get it as close as you can.  My Cardinal seems to need the most down inverted.  That is probably because I built quite a bit of 'slop' in the controls.

Sam

[Jim Thomerson]

I think most people change hand position between upright and inverted flight.  So it is hard to say if the handle is being held the same or different in terms of how much up and down is put in.  I adjust my handle so that the airplane flys at the required level flight level both upright and inverted when I just hang on and think about other things.   

[Steve Helmick]

If you pull your hand in and up, in front of your chest, you'll find that you get more up and less down in wrist movement. This also takes the load off your tendons and instead loads your muscles with the task of absorbing the pull.  If you have a hard pulling model, it will help your shoulder and elbow. Bill and Ted have the same identical problem...it's normal. Don't fly that way!  Steve

PS: What Jim said!

[Howard Rush]

I would only change the elevator pushrod length (flap position relative to elevator position) if the pitch angle is different right side up than upside down or if there's a limit cycle ("hunting") oscillation that can be fixed by changing elevator pushrod length.  If the handle setting feels OK otherwise, you'll get used to holding what feels like a bias when flying inverted. 

[Leo Mehl]

If you fly at the Salem Oregon circle in October none of this is an issue!

[Bill Little]

Bill and Ted have the same identical problem...it's normal. Don't fly that way!  Steve

HI Steve, what did I miss here??