Other-standby CS FTL.1.225(b)(2), (see also CAT.OP.MPA.210(a)(3)): Would using a controlled rest procedure while the flight crew member is at his/her assigned station break the 18-hour awake time?
No. Controlled rest procedure is a countermeasure to manage unexpected fatigue, whilst the 18-hour awake time target is part of the operator roster planning procedures.
According to CAT.OP.MPA.210 (a)(3) controlled rest organised by the commander, if workload permits, shall not be considered to be part of a rest period for purposes of calculating flight time limitations nor used to justify any extension of the duty period.
Under CS FTL.1.225 (b)(2), the operator designs standby procedures in a way that makes unexpected fatigue unlikely by avoiding excessive awake times.
The frequent use of controlled rest after having been called from other-standby could indicate that the standby procedure does not fulfil the expectation to avoid excessive awake times.
Controlled rest procedure to manage unexpected fatigue should be described in the operations manual. (ref. AMC3 ORO.MLR.100).
The operator should be able to monitor the use of controlled rest to evaluate effectiveness of mitigation strategies.