Singapore legislation
Regulation 44
of Air Navigation (91 — General Operating Rules) Regulations 2018
Regulation 44
Flight crew communication
A person assigned duty as a flight crew member for any flight mentioned in regulation 3(1)(a) or (b), and who is required to be on flight deck duty for the aircraft, must communicate through a boom or throat microphone if the aircraft is —
(a)
an aeroplane that is operating in accordance with the Instrument Flight Rules below transition level or altitude; or
(b)
a helicopter.