When a departure route requires a turn more than 15° off the alignment of the runway centerline, a turning area is constructed. Turns may be specified at an altitude or height, at a fix, and at a facility. Straight flight is assumed until reaching an altitude or height of at least 400 ft (120 m), or 300 ft (90 m) for helicopters, above the elevation of the departure end of the runway. Where the location and/or height of the obstacle precludes the construction of a turning departure that satisfies the minimum turn height criterion, the departure procedure should be developed on a local basis in consultation with the operator concerned. A turn is prescribed upon reaching a specified altitude or height to accommodate the situation.