by: Fred Cronenwett

Profile, Sport, Designer and F4B-FAI

Control line scale is an event that can be simple or complex as you want it to be. There are several AMA events and also include 1/2a scale that is flown as a club event. In general there are very few kits advertised as CL scale models, so CL scale pilots take radio control kits, plans and models and convert them over to CL scale. Brodak is the only source that I know of that advertises a CL scale kit. The events can be very simple to the extremely complex that require extensive research and building experience. Throttle control is expected in all events except for 1/2a scale. The AMA rules were changed in 2013 to allow 2.4 Ghz to be used in CL scale competition. You can still use 3-line and other forms of “Down the wire” electronic controls so there are lots of options when it comes to throttle control and other features. The best way to stated is to get a scale ARF that you can document, 2.4 Ghz controls and try a fun scale contest. Get some input from an experienced CL scale pilot on some pointers on the documentation and the flight portion and you will do well. Once you have added the leadout guide and the bellcrank to control the elevator you have converted the RC scale model to a CL scale model.

1/2a Scale
This event uses .061 or smaller engines such as the cox or other .049 and .061 motors that are on the market. These models do not have throttle control and tend to be small. This event is currently flown in Milwaukee, Tucson, St Louis, Muncie (Nats & FCM contest) and at the Brodak contest. Check with the contest CD for a set of rules before you build a model for this event. In general you start your motor(s) and takeoff and then land. This is a simple and fun event. Rules can be found on the Brodak web site and on the Tucson club web site (

Fun Scale
This event does not have Builder of the Model rule. This event also has very few points for static and the bulk of the points are with the flying portion of the event. The documentation for fun scale does not have to be as extensive as compared to profile or sport scale. The flight portion is the same as profile and sport scale where you have to takeoff, 10 level laps, 6 options, realism and landing. This is the only event you fly an ARF in. You will find beginners and experts flying this event because it is a fun event. To do well you would need to have throttle on the model. Look on the AMA web site for the rules for fun scale.

Profile Scale
This is where the fuselage and any nacelles are no more than 1” thick. You will find this to be an event that is very popular and competitive. Static judging in this event is100 points (max), then your flight points are another 100 points (max), so you need to do well in both to place in this event. The flight portion is the same as fun scale that require takeoff, 10 level laps, 6 options, realism and landing. The documentation will need to be done to the same level as sport scale. Outline is judged with a critical eye, also markings and color are also judged just like in sport scale at 15 feet.

Sport Scale
This event is where you build a full body fuselage and nacelles. Throttle is expected to do well and if the full size had retracts you will be expected to have retracts on the model if flown at some contests. The flight portion is the same as profile scale and the static judging is done from 15 feet. The cockpit is not judged and the judges will be critical of any changes in the outline, color and markings.

FAI (F4B) Scale
F4B is the international scale event that has very high standards and some consider this event to be “Museum” scale where every detail is expected in the cockpit and surfaces. This event is no longer flown at the world championships so the USA no longer sends a team for this event. However the NATS still hosts a F4B competition for those who want to enter the event. You will need to get hold of the FAI rules before building a model for this event. They have lower model weight limitations and other differences as compared to the AMA rules that you would need to understand.

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