Indoor Free Flight Scale Competition Classes Explained in Brief

Classes flown at the BMFA Indoor Nationals are currently as follows.

Open Rubber

Maximum weight 250 grams, maximum wing loading 15 g/,  powered by rubber strip.

For scale judging the minimum documentation required is a 3-view drawing with a minimum wingspan of 150 mm, three separate photos showing the entire aircraft, one of which has to be of the aircraft modelled, plus evidence of the colour of the subject aircraft and its markings.  It’s worth noting that the highest factored marks in the static judging are for outline accuracy

The model must fly for 15 seconds to qualify and flights are judged on realism with the flight split into the following phases: take-off, initial climb, cruise, descent and landing approach, landing and realism.  Flying at a scale speed will increase the realism mark.  The cruise part of the flight has the largest proportion of the marks.

Marks for static and flying are split 50/50. As usual for free flight scale models, there is a trade-off when it comes to how much detail to add to the model – more detail will achieve a higher scale mark but a lighter model will fly more slowly and realistically (and generally be easier to trim).  A simple, lightweight model with accurate scale outlines that flies well can place very highly in the Open class, so don’t be put off by the apparent difficulty of this flagship class.

Open Electric/CO2

Rules are exactly the same as for Open Rubber, but model power source can be either CO2 or electric (with on-board battery).  The use of electric power opens the door to interesting multi-engined types that would not be practical using rubber motors.  As encouragement, a multi engine model gains a 10% bonus to its flight score.

Indoor Kit Scale

Maximum weight 250 grams, maximum wing loading 15 g/,  power can be rubber, electric or CO2

The kit scale class differs from the Open classes chiefly in that scale documentation requirements are much more relaxed and more emphasis given to how the model flies.  The event is open to any scale design that has been available as a model kit, though you don’t have to build the model from a kit – you can use a kit plan and your own wood.  Static judging is against the kit plan, which has to be produced as documentation.  Significant deviations from the plan are penalised.  Some evidence should be supplied to support the chosen colour scheme – this can be a photo, drawing or painting (e.g. box art from the kit).  To encourage models with a coloured tissue finish, a Painted model will incur a penalty.

Flights are judged on realism, similar to the open classes, but equal marks are applied to each phase of the flight.  A 10 second flight must be made to qualify.  The best two flights out of four count towards the final score, meaning the flying scores make up approximately 2/3 of the total marks.

Peanut Scale

This class is open to rubber powered scale models with a wingspan of maximum 13” or fuselage of not more than 9” (excluding propeller).  Unlike the Open classes the flight score is based on duration and not realism.  A successful take-off from the ground adds 10 seconds to the recorded flight score.  You are allowed to make up to 9 official flights with the best two counting towards the flight score total.

For scale judging the minimum documentation required is either a 3-view of minimum 2“ wingspan plus a photo or printed reproduction of the subject aircraft with proof of colour if you only have a black and white photo, or alternatively a coloured 3-view of the subject aircraft to a minimum of 1:144 scale.  Profile Publications are a useful source for these illustrations.

The Peanut scale class is one where you really have to balance the aim of building the most realistic model possible against obtaining a reasonable flight duration.  Extra static marks can obtained for a painted finish, complex markings, scale rib spacing, separate control surfaces etc, but these will generally increase model weight, hence reduce flight performance.  It is worth noting that there is a 9 point scale bonus for a low winged model or biplane – a significant amount considering that 100 points is a decent scale score.

Unlike in the Open classes, final placings are not calculated by simply adding static and flight scores together.  Instead, static scores and flying scores are ranked separately with the best placed models getting 1 point, second 2 points etc.  Competitors’ scores for flying and static are then added together with the lowest total placing first, second lowest total second and so on.

Pistachio Scale

This class is broadly similar to Peanut scale, but with a maximum wingspan of just 8” or maximum fuselage length of 6” excluding prop.  Flight scoring is the same, but there is no 10 second bonus for a take-off.

Documentation for scale judging is the same as Peanut scale.  Scale judging is along the same lines as Peanut but somewhat simplified.  Again there is a bonus for biplanes and low wing types.  One interesting aspect is that in Pistachio scale there is no penalty for using wings covered on the upper surface only – wings like this can work very efficiently at this small size.

If you want to know more about indoor free flight scale competition, or have any queries, please do not hesitate to contact Mike Stuart on 07922 596491 or by email at