If you mean the iris vanes behind the spinner then this was not a fan. Whilst not a true iris motion they are triangular segmental vanes that open and close in unison with the exhaust flap valve to control airflow over the engine.
These were adjusted manually. For true emergency / combat power setting they were trimmed fully closed so that no (or very little) air flowed thru the engine compartment. When fully open the additional drag was said to reduce the top speed of the La5FN by some 55km/hr
