Ok I bought a used but never flown P-51 mustang, I took it out this evening after the wind died back a bit.

Checked her all out best I could but it had no instructions or anything it has an OS 46 LA engine I added my RX and batt, with no instructions I balanced at the spar about 4.5 inches from LE.

Took it up, trimmed it out, WONDERFUL level flight at half throttle, roll left add elevator....it bounces through the turn....level off throttle up try an inside loop.. It starts up tries to level off, up a little more tries to level off over and over all the way through the loop. Does this anytime I use the elevator, banked turns loops etc..

It will perform outside loops tight but smooth, aileron rolls, snap rolls all thumbs up.

Landed well, checked the throws, moved 2 holes closer to surface on the horn, took it back up, same thing just more violently..


I am thinking it is a CoG problem, nose heavy..any ideas ??

How much elevator movemant do you have up VS down? If you are performing smooth outside loops but
chopping the insides, there is a chance you have too much up elevator. Moving the clevise closer to
the surface increases overall travel. Try moving out on the surface horn or in on the servo horn.

Guess I don't know what an inside roll is? Think perhaps you meant to say inside loop and it is rolling out? Believe you have too much elevater throw it's stalling and starting to snap. reduce elev. throw and believe you will be good.

Well at first it was all the way out. It did not have a lot of throw at all, little more then a half maybe 5/8 each way.

So I moved 2 holes closer to increase the throws just to see if it made a diff, it did it just bounces harder...

I applied pressure to the servo it does not give a bit so it is not stripped or failing once its in position it is there to stay.

It does this even in a light banked turn. My first thought was the servo was junk..

yes I meant loops.

Yeah................ just looked up throws for similar planes......all of em are like 1/4 elevator in each direction....... this thing would have been trying to turn in and bite its own arse with the throws it had...thanks guys

Phoenixangel,

Post some pictures of the plane, give wingspan and length. Maybe someone knows who makes it (if arf)
or who designed it. that way you might get some help in the setup area.

It is this thing http://www.hobbytron.com/P-51Mustang...CAirplane.html $200 dollars got everything but the RX and battery already built, been in storage for a few months, the OS engine is very used though it runs well. I, nor Matt errrr the guy I bought it from can find a manual. but as stated above similar P-51 models show the throws at like 1/4 With the throws it has now I could have flown it with the trim :P

Phoenix, I think you need to check out the elevator push rod. If it is like most planes it is pulling when you give it down elevator such as when your doing an outside loop but when doing an inside loop your servo is pushing and the rod is probably bowing and changing the amount of throw/movement according to the air pressure pushing against the elevator.
Fred

A 6lb plane with a .46 LA engine is going to be relatively UNDERPOWERED.

The LA may not have enough OMPH to get the plane through the loops.

A .46 LA is about equal to a .32 GMS or FX engine in power, which I would use on a 3lb sport plane at most.

It's fine for a .40-.50 trainer though, which is not expected to do things like loops from level flight.

reset throws, checked pushrods , the thing flew great, thanks for the help

I am running a 10x6 prop on this thing the LA seems just fine to me 80+ mph and plenty of vertical without stall, so I am happy

Somehow I doubt a 6lb plane is going to do 80mph on an 1.2hp, OS LA engine unless you go into a high speed dive.


I have an OS .46 AX with a tuned MACs pipe pulling a 4.5lb Polecat around at that speed using an APC 10x7 prop.

At best the LA will turn at best around 12000 RPM loaded which works out to about 60mph and that's w/o allowing for inefficiencies.

The AX is more powerful at a rated 1.65hp and will turn a consistent 13.5K+ RPM in the air.

I have my .46 LA engine on a .32 sized Megatech Extra at 3lbs also turning a 10x7 prop which tends to run into the 72mph range on level flight, and that's about right for this plane... Higher pitch degrades performance and decreases velocity.

I did not say anything about level flight at 80 just that the engine/airframe was capable.

yes its in a dive

Glad to hear it flies better, it's amazing how little elevator can be too much. For Pattern we usually use about
12-15 degrees of elevator and aileron, and 40+ rudder, and they do loops and rolls quite well.

I left the ailerons snappy fast just used expo to keep them easily manageable, It was windy today but I took her up anyway it is so much better I have the throw set right at 5/16

a little more then recommended for other P-51 models like my strega but I like the way its flying.

I really like these warbird style aircraft I am quite addicted to them. I am going to be looking for a good P-40. P-38, Corsair something soon. LOL the wife will love it !!

I was not going to fly the Strega yet I have a lot of hours solo time with my trainer but it is still a trainer, the guy that taught me to fly said "quit being a wuss and just fly it, take it up to pucker factor 1 height, slow it stall it get used to everything it will do and when".

So he stood beside me we took it up flew the crap out of it and I landed it and never looked back I have 7 flights on it now and its my favorite plane out of the bunch.

I ordered a http://www3.towerhobbies.com/cgi-bin...?&I=LXNMD1&P=0 and some 12x7 props for it the other day.

A couple of things for you to comtemplate. First, someone had suggested the linkage bowing.. which is a very good possibility, even though you have it flying to your satisfaction. The way to find out is to hold the servo with one hand and then try to flex the elevator with the other. If it moves, then it will move during flight, usually trying to center itself with the pressure against it in loops, for instance. The way to fix that is to use stronger linkage rods, or pass the linkage rods through tubes that have been secured to the fuselage formers. That's what I had to do with one of mine a while back that was behaving exactly as you described.

This is, of course, if you want to find the original problem. What you did was ok if you are satisfied with it's performance.

The other thing, well, a prop with a 6" pitch will do approximately 5000 feet per minute (theory based on prop size and 10,000 RPM) which is just under 1 mile per minute or just under 60 miles per hour. This is under perfect conditions, of course.

CGr.

I checked the pushrods they are not flexing I made sure.

last time I ever mention the speed of a plane in this forum, guessing or not.

no offense, it is just not worth it..thanks for the help guys