High Speed Turn Problem!!!Help Needed
 

https://cimg6.ibsrv.net/gimg/www.rcu...95a443f37c.png
So i have decided to set up again my Fly Eagle F-100, the jet is one of the first generation jets, no issues what so ever about breaking apart in the air. About five or six years ago i built the plane with ALL new stuff servos, wires, smart fly, Rhino etc. First flight went great with a few clicks of trim needed, second flight was absolutely horrific!!! after a few laps and filling comfortable with the way the plane handle, i started pushing the throttle and this is when Sh@@ hit the fan!!! every time i was about to turn, as soon as i apply elevator to compensate, the plane did not want to come back, turns were so wide that by the time the plane will actually turn i was way out of bounce and so far that i can barely see the airplane, i literally had to trust my fingers just to know which way i needed to move the sticks in order to bring the plane back in sight. When i slow the plane down i regain full control of the elevator like nothing happen. Needles to say after this experience i took the airplane apart and started changing things, wires, elevator servos and batteries. The EXACT something happen again!! fist flight fine, second flight same issue!! i got so frustrated i took the plane apart and used the parts on other airplanes and figure that perhaps the issue was on the actual structure of the airplane. I have decided to put the plane back together again for the third time thinking how can it be a structural issue if it flys slow ok it should fly fast also (unless of coarse it breaks up) maybe i overlooked something. Im getting ready to test fly the airframe again and was just wondering if anyone could make anything out of this issue that i explain. Any advice will be greatly appreciated.

I remember reading it was a common problem with the early kits. The elevators are getting pushed back under load. Several were lost because of it.

Requires re engineering of the linkage and perhaps the piviot point on the stab was wrong. Do a search perhaps

Check the pivot points of the stabs
Gary

What am i looking for?

Thanks

Chris

The pivot points need to be at like 20-25% MAC. If you don’t know what that means, time to put that model up for static display. Don’t fret, I have a beautiful $6k Fly Eagle F-14 on static display that is really pretty to look at.

Why do I say such a thing? There are just a whole bunch of things that could be going on in your F-100: loose stab pins, formers that flex under a load, Servo mounts that flex under a load, wings could be flexing, etc...

With Fly eagle, you just don’t know and every flight is a new discovery at airborne Russian roulette. *Bang

Can you explain 20-25% MAC mean? it might be a stupid question because i don't know but i bet ya I'm a really good pilot hehe..... BTW i already check for loose stab pins and servo mount flex.

Thanks in advance

The shaft going into the stabs is in the wrong spot. That is what Raf is talking about with 25% mac.

Also I've seen on one like others said the shafts bend backwards underload and can rub on the fuselage to the point they wont work. Its the same old flyeagle issues everyone talked about back in the day.

Can you explain 25% MAC? From what i can see there is no shaft bending or stab rubbing anywhere. Im just trying to narrow possibilities here.

Thanks

Great!!

Thanks

Slow down.

I guess you can say it's your elevator pivot point and geometry servo setup for max torque.
http://www.rcwingcog.a0001.net/V3_te...index.html?i=1

https://www.airfieldmodels.com/infor...amic_chord.htm

Woops Basimpson beat me too it and his is better.

Haa...sorry man...But if he have to learn MAC to fix his F-100 I think he better off cut his loss and get another airframe.

Thanks for all the info gang, i now starting to understand the whole MCA thing, looking at it from the bright side i now have a bunch of good stuff to put on another airframe, i think i want a Hawk. In the mean time ill fly what i have :)

Just to add to this for others benefit to think about maintenance , I don't need to rehash about "Fry Eagle"! :p

A couple a weeks ago at my event one of the guys brought out a beautiful BVM F100 that he purchased from a very famous scale modeler.
The model was test flow earlier this year by a very competent Jet flyer with no issues.

Anyhow he proceeded to fly and he was having tremendous issues at high speeds turning the model, so he throttled back and brought it in for a successful landing.

He proceeded to remove the tail section to inspect the servos and linkages, what he discovered sent chills down his spine.

With the BVM there are two servos driving a common shaft for the flying stab, the servos were high torque JR types more than up to the task.
The issue was one the 4-40 threaded rods that was epoxied into the carbon fiber shafts broke at the threads, so only one servo was driving the stab.
Long story short, the air frame was talking to him, luckily he listened and avoided a major crash!

Boxes are all secure, however when i move the stick full up or down and use my finger as force on the trailing edge of the stab, the stab stays still and of coarse the servos buzz with no movement.

One last thing, so in order from the problem to go away the pivot point will have to move aft correct?

Page 19 of this document has a diagram that may help you.

Attachment 2265329

Page 19 of this document has a diagram that may help you.

AMA Document 520A Large Model Airplane Requirements

Thanks Viper

Great Info

All true. I lost two from structural failures. Would never go back, even if someone paid me.

This is your problem. Fix the linkage, get better servos, etc. It should NEVER do that.