Flight Deck

March 2009

Control systems for the AMA Carrier plane

By Eric Conley

My feelings on the subject of control systems for carrier competition is to go with what is being used in the field at the time you are competing. In other words today (2009) you would use a Brodak J. Roberts 3 line system that consists of a 3-line handle and a matched Brodak 3 line bellcrank. There is only one 3-wire handle by Brodak and it comes in 3 different colors. There are eight different Brodak 3 wire bellcranks to choose from and their major difference is upright, inverted, long span, short span, which side of the fuselage you're using, and whether the pushrod for the elevator goes next to the fuselage or is away from the fuselage. There are hundreds of different ways these units can be used and only time and experience with them will let you take full advantage of the choices you have.

NOW, if you decide to fly carrier and you have no or limited experience with 3 wire systems or if you haven't used a 3 wire system sense the 1960s but have this old box of stuff that you can probably find in the attic DON'T look for it, just order a new system from Brodak Manufacturing & Distributing Inc. I have watched people try to work with old mismatched handles and bellcranks and I've tried to help them and it's just not worth the effort as these systems are all different and can be seldom mixed with good results and don't let anyone tell you different. Life is short, and I hope you don't want to spend your vital limited time learning that these mixed systems do not work well very often.

When I build my Bf-109T or F2G-1 (low wing) carrier planes I use a C-22 - BB-376 2.5'' Upright Short Span bellcrank. I place this bellcrank behind the fuel tank on the outside wing panel next to the fuselage and either internally or on the wing, centered between the spar and the trailing edge. The control lines are routed internally (.15 and Skyray 35) or on top of the wing (AMA Profile). On the AMA Profile 109T the lines are on the surface of the wing or just as close as I can get them to reduce drag. On the F2G-1 the lines come off the bellcrank and go out over the bent wing and make contact with the wing at the tip where the line guide is located. The lines are close to 3/4'' off the surface of the wing at the mid point of the inside wing so there is minimal drag created between the lines and the top surface of the wing. Reminder if at all possible the lines should exit the plane at its horizontal center of gravity.

When I build a CL-1 or 2 MO-1 I use a C-24 - BB-378 Inverted Short Span bellcrank. I locate this bellcrank on the bottom of the wing at its midsection where it is enclosed by the fuselage. I run the throttle pushrod along the outside of the fuselage to the carburetor. On my planes this places the HS needle on the bottom of the plane, which is not a good place when trying to adjust the needle. At this time I'm experimenting with a remote NVA and if it works will use them on all of my planes. If the remote NVA doesn't work I will use 2 control horns and a vertical shaft at the rear of the engine to rout the carburetor push rod to the bottom of the engine compartment.

I dedicate a set of flying lines to each carrier plane I build. After my first MO-1 that had leadouts and then watching my fellow carrier fliers fumble with theirs at the contest field I decided to dedicate lines to each plane. I have 3 Brodak handles and have adjusted the leadouts on them to be all the same so I can trade them around my planes. I better clarify and say that the leadouts on the handles have longer up and down wires and the throttle wire is shorter than the up and down ones.

Dedicated lines make your overall plane and equipment lighter, cleaner as far as drag is concerned, and there are fewer variables to trip you up on contest day. I can't stress enough that when I arrive at a contest the only thing I want on my mind is how well I'm going to fly each event that I am entered in. I don't want to fumble around getting the right lines on the plane that they belong too. I don't want to tie someone else up trying to adjust the handle and lines so the throttle works OK and the controls are neutral. Many entrants arrive at the contest alone and if they have several planes with them they shouldn't tie up other fliers while they try to sort out there equipment and get their planes ready to compete. We are always glad to help another flier if he needs it but "set up" should be the last thing we should be called upon to do.

When you dedicate a set of lines to each plane you don't have to have leadouts on the plane. You can install the flying lines directly on the bellcrank of the plane. I do this with 2-56 bolts and 3 2-56 blind nuts. I put medium brass thimbles on the end of each line at the bellcrank and crimp them with aluminum tubing. I use aluminum tubing because you have less chance of damaging the flying lines with the softer metal. I run the lines first through the aluminum tubing then around the brass thimble twice, and then go back through the aluminum tubing and back around the outside of the aluminum tubing and then back though the aluminum tubing and then crimp each line three times. The crimping force (I use round nose pliers) should be firm but not balls out hard. I base this on experimenting with copper, brass, and aluminum tubing for the crimps. I found that the copper and brass tubing resulted in the flying wire breaking inside of the crimped tubing and with the aluminum tubing the flying line broke outside of the tubing.

Currently I'm using .057 OD music wire for the elevator pushrod. I run the wire through a piece of carbon fiber tubing that has an ID of .060 and an OD of .125 for stiffness. I use Z bends at both ends (at the bell-crank and at the nylon control horn on the elevator) of this push rod for lightness and simplicity. I'm pretty sure that the Z bend puts a lot of stress on the music wire but so far I have never had a failure.

I always use a nylon control horn on my elevators. They are light, strong, easily available in different sizes, and seem to wear well over a long period of time. The only time I have seen a nylon control horn break at the pushrod hole is after a crash on a very old stunt model.

When it comes to hinges for the elevator I'm now sewing mine. It is so simple, strong, free to move, and you end up with a better air seal along the hinge line.

SLIDERS anyone? The word either brings a smile or raises the hackles when brought up in carrier circles. It was already there when I arrived and I never gave it a thought. I soon found that many of the people that were flying carrier up to the mid-1970s can have a whole other take on the slider. My experience with carrier for the last 14 years has proven to me that its one the great things to come along in this event. First and foremost the planes equipped with sliders just about never wear out or get torn up. You have to give the planes away to make room for your next venture. It's the ability to slow down for the landing that gives the slider-equipped plane its longevity. I have watched the no-slider pilots tear their planes to pieces time and time again and then turn around and cuss the slider planes.

Another great thing is how the low speed portion is flown with slider-equipped planes. In a full size plane as you slow down while holding an even altitude the nose slowly is raised and as the nose comes up and the plane slows down and you have to add power to hold your altitude. You reach a point where the plane has slowed down to just above its stalling speed and you are carrying quite a bit of power, and as you hold your attitude (pitch) and hold your altitude (power) you find that power can be varied and the plane doesn't seem to do much except hold the altitude. Actually the plane is doing something as you vary the power, its going up or down. In carrier we call this the hang. Of course our carrier plane was stalled the minute we went into the hang so I guess it's the holding attitude (pitch, 60 degrees) and maintaining altitude by varying the power that's so much like the real plane.

If your plane wasn't equipped with the slider you would be throttled back somewhat (not all that much) and gaining or losing altitude while you nursed the plane around the circle. When it came time for you to land you would swoop (dive?) down onto the deck usually in a nose down tail up attitude and take your chances of nailing an arrested landing in that 18 feet of deck. Now don't tell me that is how a planes flies and the heck with that stupid looking hang thing. Our model airplanes just don't fly like the real ones. They are proportionately much heavier and much more powerful than a real plane. Another thing is that damn carrier is sitting still when in reality it should be moving into the wind at around 30 knots.

So there is plenty of controversy to go around. My feeling is that the hang gives you a better feel (pitch, and power) for the plane (more like the real thing) and allows you to land on the deck instead of exploding on the deck.

You do not need hinging rudders, flaps, or ailerons on the AMA carrier planes. They add nothing but more problems and weight. I suppose if we were talking about Nostalgia carrier and you copied a nostalgia plane you might want to duplicate the same working control surfaces that were on the original model.

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This page was upated March 19, 2009