Is it not possible to idle a rotary?
No! That's exactly the point!
A rotary behaves rather like a simple model glo-plug engine in that it either runs or it doesn't according to mixture. There's no throttle, it's either on or off.
Due to the considerable inertia of that big wooden prop and several cylinders plus crankcase all whirling round it has huge inertia so stopping the combustion does little to slow the rotation.
There are two ways of robbing a rotary of it's 100% power, either shut the fuel (lever) off or cut the magneto (blip switch). Thus to achieve an average power level between 100% or more than zero the pilot needs to modulate the engine between "off" and "100%" by means of either the fuel lever or the magneto switch.
Hence "blipping". I assume one sets up a high approach with the engine inhibited - i.e. dead via the blip switch or fuel control at "off", which approach is reduced by the characteristic sideslip but interspersed with a burst of engine (by necessity at 100% intermittently - or as soon after restoration of sparks or fuel the damn thing chooses to respond) Watch videos of rotaries taxying - blaaaa! pause - Blaaa! pause, Blaaaa!
It's a pretty blunt way of controlling power by today's standards and as described in the video above each individual engine seems to have it's own way of responding - or not - or maybe.
Even so, smoke and engine noise on short finals shows that the engine is trying to light up again if not actually giving its all just yet.
It is a two-stroke after all. If it is running it'll smoke like hell - and smell like Heaven, of course!
Do the Tiger Club have their Stampes still? They were fitted with a basic "injector" fuel system that was allegedly based on Sir William Cobham's full inverted system (1920's) , derived from a rotary set-up using a fuel lever and an air lever only. You changed over from the nice but blue-side-up only carburettor to this devious two lever contraption that just gave you engine on or off - and then only if you had fuel and air levers precisely balanced (fugall power if you didn't) , tho regardless of attitude which made the Stampe nicely aerobatic. Still, it sure was a bit of a blunt instrument and one that astonishingly had lasted well into the late '80s when I last saw it. It impressed the heck out of me, I can tell you!
Magenta Line it isn't!