rcworld2000

wanna see what everyone here thinks happend to my control of a plane w/ expo set wrong . me and the guy that trained me at my club took out my top flite cessna 182 for the first time the other day he was taking it up first to help trim it out for me..


ok on low rates it seemed like he had very little control so we swithed on the high rates and it was better . he got it trimmed out and then i flew for a while. i am very good pilot with my trainer and i have flown a few others like a four star 60 . and this plane was way (looser) seemed like it was very touchy but we were on high rates.

then he landed it because i wasnt comfortable. he had a little rough of a landing and bent nose gear no biggie.

but when we brought to the pit i decided to look at something i the radio and i saw that i some ow had the plane set up for 60% expo which is way high and on top of that it was set for + not - like it should be.

i fixed that but couldnt get another flite in with bad gear. so i took it home. gear is fixed.

MY QUESTION IS what does + expo do ?

would that have made the plane fly the way i described...

TomCrump

post # 19 http://www.rcuniverse.com/forum/begi...bout-expo.html

rcworld2000

yep i had a bear. it really wasnt that bad.. just made a cessna which i told was a lazy flyer. felt like a a 3d plane...

jetmech05

JR + expo makes for a softer center on the sticks. Futaba - makes for a softer center on the sticks. If that was reversed then it would be more sensitive at the center.
Expo doesn't do anything for the amount of throw. If you didn't have expo let's say that if you moved the stick 25% the control surface would move 25%. Stick hard over and you have full throw. Now with expo let's say you move the stick 25% and the control surface moves 10%, but hard over is still full throw. The airplane would seem less sensitive.
Those numbers I gave are just random to help explain.

rcworld2000

I figured having the expo wrong is what made it way to sensitive.

JohnBuckner

My Feedback: (1)

Yes exactly and as noted the total throw, endpoint or travel volume (three different methods of expressing the same thing) does not change. In effect when you use expotential your controls are no longer proportional.

Most radio systems it is very easy to scroll rapidly from a minus figure right on into a a plus figure (or vice versa) without even realizing the mistake therefore its important when ever setting or resetting expo to always double check that the plus or minus remains whichever is appropriate for your system. Futaba/Hitec use negative for what JR used to call soft center and JR/Spectrum use positive, Can't remember what Airtronics uses.

Depending upon a lot of variables with many types of airplanes using the wrong expo setting can certainly be fatal.

John

52larry52

My Feedback: (1)

I just don't see the need for expo on a nice flying scale plane like the Top Flite Cessna 182. Maybe it's just me but this is a case where "KISS", keep it simple stupid, applys. Set your throws according to the instructions, Top Flite is a trusted quality kit builder and they aren't going to give you bad set up specs. Don't try to out engineer the guys who know what they are doing, follow their specs, fly the plane and then make minor changes to suit your style. This is extra true if you are new to RC flying and don't have a lot of information in your "knowledge bank" yet. Just because your TX has expo doesn't mean you should use it on all your planes. Top Flite gives you high and low rate specs and I know following them produces an honest, sweet flying scale Cessna. Too many new guys try to reinvent the wheel and" dial themselves out" in the process. Wild 3-D planes may need expo but not this plane. But, of course that's just my opinion, others may disagree.

speedracerntrixie

My Feedback: (29)

I started out in 1977 no expo, no nothing. Fast forward to today and I use expo on everything right down to the kids trainer. Granted the trainer only runs 15% while the competition aerobatic airplanes get as much as 35%. The idea is to get a soft feel around center but not so much that the model feels sluggish. IMO most airplanes are set up with too much throw but that's a whole different thread.

dspeers

My Feedback: (22)

I thought that the primary purpose of expo was primarily to counteract the Ackermann effect inherent in the geometry of most control linkages. Thoughts?

FlyEng

My Feedback: (5)

If expo is eliminated as the culprit, double check the center of gravity and make sure it is per the instructions. A plane that has a cg rearward of its intended position can be a handfull to fly. Planes that are just slightly tailheavy can still be flyable but the controls become very sensitve. This is especially true in the pitch axis.

52larry52

My Feedback: (1)

I agree with speedracesntrixie that the trend today is to set up most planes with too much throw and then use expo to cover the fact that too much throw was used to the point that the plane is not comfortable to fly. You shouldn't try to make a scale Cessna into a 3-D plane using excessive throws then tone it down with expo. What you end up with is a Cessna that is not fun to fly. If you like a little expo to soften the center feel, that's personal preference, and not covering for poor set up choices. I guess my point is to match the set up of the control throws to the skill of the flyer, the type of aircraft in question and it's intended flight mission. In the case of the OP, he ended his original post by asking "what does + expo do ?". If you don't know what it does, why in the world would you include it in your set up? I think rcworld2000 is fairly new just coming off his Hobbistar 60 trainer, ready to move up to his next plane and the T.F. Cessna is a good step up choice but should be set up for now to fly on the gentle side. Simple easy flying set ups would benefit him most at this point.

rcworld2000

yes 52 larry im new. i agree im just looking for good easy flying bigger plane. but i am also flying a 40 size ultra stick very well.


i was sure that plus expo would make plane control to sensitive just wanted others thoughts.

and i have cessna throws set to instructions do you have a better settings in mind?

Charlie P.

Not at all. Only control surfaces that have two attachment points (i.e. pull-pull, two-wheel steering, etc.) have any involvement with the Ackerman effect. With a single control rod there is no Ackerman at all.

52larry52

My Feedback: (1)

rcworld2000, I have a T.F. Cessna 182 that is an older kit built version (I assume yours is the newer ARF version) that I bought used about 11 or 12 years ago. I was at a similar stage in my RC learning curve as you are now, good on the Hobbistar 60 and looking to move up. I set the Cessna up using the high rate and low rate settings in the T.F. build instructions. I found them to be very easy to learn to fly this plane with, staying mostly on low rates as I flew this plane mostly in a scale fashion. A few non scale loops and rolls to "stretch my wings" now and then and for learning fun . Your ARF version and my kit built a the same aircraft offered in different formats. The set up specs should be very close if not the same. My book calls for: Elevator 1-1/16" up and down on high rate, 3/4" up and down on low rate. Rudder 1" left and right on high rate, 5/8" left and right on low rate. Ailerons 5/8" up and down on high rate, 1/2" up and down on low rate. Flaps 1" down on take off and 2" down for landing. My plane was built with no flaps but yours will have them. Compare the settings to your printed specs and the control throws and each surface of your plane. This should give you a good comfortable base set up to get used to this faster less self righting scale plane. Take offs and landings should always be on low rates and I would advise not using the flaps for while if your runway is long enough to land without them. This plane will float a long ways on landing and use up a lot of runway. If you have the runway room to learn with, practice making pretty scale like soft landings before adding flap use to the learning curve. One step at a time. Get good with each new step before adding more stuff. I still have my T.F. Cessna and flew it three weeks ago for the first time in about 3 years. It is still a pleasure to fly and makes great realistic landings. Use your stick as your "hotrod" and the Cessna as a tool to perfect your scale flying skills and you will have this plane to enjoy for years to come. If after getting comfortable flying on the low rate specs for a while and you decide you want to try a little expo, that's personal preference. It's OK, just go slowly and take it one step at a time.

rcworld2000

its a older kit model. i bought off a 80 year man. he flew it two times. i dont know how old. but it was a kit.

rcworld2000

no flaps heres some pictures

52larry52

My Feedback: (1)

OK, very much like I came to own my Cessna. I bought mine dirt cheep from one of the older members of my club. I went to his house to buy a great Planes Slow Poke plane and saw the Cessna sitting damaged in a corner, the main landing gear had been torn off. Took both planes home with me and did the necessary repairs. Yours look very nice, much nicer than mine did. Over the years I did many up grades, lighting system and cosmetic improvements but mine is still a good looking "20 footer". With no flaps to deal with you have already seen how this plane floats forever landing. Looks like you're flying from grass and in wide open spaces so you must have a good long runway. Yours looks very nice but the nose gear looks out of alignment. Maybe that's from the first day's hard landing you referred to. I see a Super Tiger decal on it. What's under the cowl? Mine has a Super Tiger 75, plenty of power and with the pitts exhaust it makes good noise too. Well good luck with that pretty plane. I think if you check and adjust the throws as I suggested and don't get ahead of yourself you will do just fine.

speedracerntrixie

My Feedback: (29)

Sometimes even the manufacturers throws can be excessive. I think this derives from most manufacturers have you set up a CG that is forward simple because the general opinion is that a forward CG is safe. To compensate the elevator throw is increased. If you have an airplane that needs a lot of back stick on final or won't slow for landing then chances are it's nose heavy. The same would apply for an airplane that wants to roll out of a loop.

Muttdog

I would say to first check and see the difference between pos and neg expo on your radio as they can be different amongst brands. The easiest way to see this is to set your expo so it is activated by a swtich. Then move your stick just a little off of center and hold there while activating the swtich. If your control surface moves more when you activate the expo then it is the wrong way and will make it more sensitive. It should reduce the throw at those low stick positions when you activate the expo to make it more controllable. I do agree with others here in that you should need very little to no expo in that type of plane. I just don't see how you could possibly need 60% expo. I run 45-55% on my 3D aerobat with huge control surfaces and 50+ degrees of throw so something is clearly wrong.

rcworld2000

landing gear was from the hard lading. it has a 61 super tiger ... (the old guy said it was the itailan made motor)

rcworld2000

yes 60% is way to much. i am still not sure how that setting came to be.. i fly with 30% on my hobbico trainer.

i am going to start off with 20% on this plane

stu48

+1 - Futaba uses -% Spektrum and a lot of others use a +%. If set 60% in the wrong direction would make the controls very sensitive around neutral.

Radical Departure

My Feedback: (13)

Been there, done that. Typically I'm switching between a Spektrum and JR. Both are opposites in how they adjust expo, as stu48 mentions. Had a new plane, a big Wilga, maidened ok but needed some tweaking to tone down a couple squirrels. Using the JR, I dialed in as I would with Spektrum, so I was actually dialing it up, the expo that is. Got it in the air, man.. that thing was all over place.. got in back in one piece, then took off my 'failed to pay attention' hat.. flew great with the right settings!

Bozarth

My Feedback: (15)

Ackerman is not a factor

Muttdog

I just maidened a plane for a fellow club member that had this same issue. There is no question he would have crashed it as it needed a lot of trim on top of the expo issue. Then later that day I maidened another plane for someone else and he did not tell me there was a gyro in it. No problem except for the fact that the Gyro was reversed in all directions! After the rollercoaster takeoff no one thought I would get it down in one piece but luck prevailed and we got her down safe. I was more nervous on that flight then maidening my 35% a few months back. It's funny because we were all pulling our hair as to the problem until he remembered it had a gyro...DOH!!!