Internal Combustion Ducted Fan Models

1. ICDF Rules

1.1   The intention of these additional rules is to provide an incentive for modellers to build jet-outline models with a prototypical sound, performance and appearance

1.2  Apart from these specific rule additions, ALL OTHER current Class 1 and BCD rules remain applicable to ICDF models



2. Definitions

2.1   An internal-combustion ducted fan (ICDF) power plant is defined as an integrated unit comprising an impeller (fan), a shroud and an internal combustion engine, which together provide the means of propulsion for a model representing a full-sized jet-propelled aircraft.

2.2 The shroud must be a tube surrounding and containing the fan.

2.3  The shroud perimeter must be solid, except for essential holes for engine and fuel management. A full-bodied model’s fuselage or engine nacelle(s) may be used as the shroud.

2.4  The ICDF fan can be of any size, but must be completely enclosed by the shroud and driven directly by the Internal Combustion (IC) engine

2.5   Any type of I/C engine may be used.

2.5.1  For single-engined models the ICDF engine’s cubic capacity must not exceed 0.46 cubic inches (7.54 cubic centimetres) in design displacement

2.5.2 For multi-engined models, the total of the ICDF motors’ design displacement must not exceed .50 ci (8.19cc)

2.6    The ICDF unit(s) must be located in the same general position on the model as the full-sized aircraft’s jet engine(s)

2.7   If an ICDF unit is used in the model, no additional power unit (eg conventional propeller/glow motor) may be used as well unless the prototype featured dual power sources (e.g. Ryan Fireball), in which case the rules for multi-engined models will be applied,



3.      Class 1 Carrier-Deck Models

3.1  The current .40ci maximum capacity limit is increased to 0.46 ci

3.2  Auxiliary airflow-diverter devices may be used within the model’s jet-pipe to assist low-speed control, provided that they are invisible when the model is viewed from the side and above

3.3  The model’s exhaust jet-pipe dimensions may be increased by up to 30% from scale size to compensate for the essential airflow needs of ICDF units.



4.     Basic Carrier Deck (BCD) Models

4.1   Tuned pipes may be used for ICDF-powered models

4.2  The maximum engine displacement MUST NOT exceed 0.46 ci



5.      Notes on the Changes

5.1   The .046 ci maximum engine size reflects the availability of appropriate ICDF engines and fan units

5.2   The increase in maximum capacity for Class 1 is offset by the additional complexity of incorporating ICDF in a Class 1 model

5.3   The increased jetpipe diameter in Class 1 is an offset against the concession for allowing engine cylinder heads on propeller-driven models to protrude

5.4   The restriction on the engine capacity for BCD is offset by allowing the use of a tuned pipe, which is essential for the proper function of an ICDF engine

5.5   The Contest Director’s decision on the eligibility of any particular model will be final

5.6   Revised rules for Electric Ducted Fan (EDF) models will be added to this section if and when it is deemed necessary