The FAI code covering attempts always has a paragraph about

detached parts:

“When part of the model becomes detached during the launch

or during the flight time”. (FAI porting Code part 4a: paragraphs

3.1.5 (c), 3.2.5(a), 3.3.5(b) for F1A,B and C respectively).

No one I have contacted knows the rule’s historic reasoning.

The core justification for an attempt seems to be events a flier

can’t control - such as splitting wooden propellers or a front

end falling off when the front portion of a rubber motor suddenly

blows up. One can argue that the phenomena of a detached

engines, which might have been caused by vibrations and the

impact of stopping the engine, might also fall under this category.

All these are failures of a model’s propulsion system.

Since the attempt rule does not qualify the detached part,

the rule has been used for incidentals such as the famous

Wakefield’s back peg o-ring, falling rudder tabs and timer’s

hatch doors. It’s not clear why these events should justify an

attempt, since they fall into maintenance and properly setting

up the model before flight.

The rule has been applied to cases where major structural

failures caused parts to fall off. But neglecting to rubber band

a wing properly - resulting with a complete wing separation -

would also qualify as an attempt. On the other hand, dangling

major parts such as dihedrals, fins or portions of a stab don’t

justify an attempt under the attempt rule.

Should we qualify the parts that fall off?

If we decide that detachments of incidentals don’t justify an

attempt, then the model’s time will be counted, provided it was

still legal. For example, suppose a timer hatch door detaches.

The flight time would be counted if the rest of the model

remains above the minimal weight.  And if we decide to include

the failure of major structural components, then dangling parts

should also justify an attempt.

The difficulty of throwing out the incidentals while including

major structural failures lies in defining what they are exactly.

This is not easy! Should a major structural failure include the

main spar, the D-box, the trailing edge or a combination of two

or more components? It would be very difficult to reach a

consensus definition.

Personally I think most of the propulsion system detachments

are beyond the control of the flier and should justify an attempt.  

That the incidentals and major structural failures should be

simply be left out.

And yes, timers should be explicitly required to observe the

part(s) falling off the model in the first place.