Note: This question is based on previous ECQB TK Syllabus versions and its corresponding EASA AIR OPS. However, it seems that this question still appears in some CAA exams, according to student's feedback.

According to CAT.POL.H.215 - En-route - Critical engine inoperative (PC1):

The mass of the helicopter and flight path at all points along the route, with the critical engine inoperative and the meteorological conditions expected for the flight, shall permit compliance with the following:

(1) When it is intended that the flight will be conducted at any time out of sight of the surface, the mass of the helicopter permits a rate of climb of at least 50 ft/minute with the critical engine inoperative at an altitude of at least 300 m (1 000 ft), or 600 m (2 000 ft) in areas of mountainous terrain, above all terrain and obstacles along the route within 9,3 km (5 NM) on either side of the intended track.

(2) When it is intended that the flight will be conducted in VMC with the surface in sight, the flight path permits the helicopter to continue flight from the cruising altitude to a height of 300 m (1 000 ft) above a landing site, without flying at any time below the appropriate minimum flight altitude. Obstacles within 900 m on either side of the route need to be considered.

Note: According to CAT.POL.H.320-En-route - Critical engine inoperative, the fore-mentioned rule is also valid for Performance Class 2 helicopters.