Meeting the minimum certification standard does not, in itself, provide any capability other than allowing compliance with the limitations of the RFM. It is the operations manual that needs to specify the performance standard for PC1 – normally, in conformance with a State’s Code of Performance.
(Depending on the speed specified for the type/procedure, the minimum required performance for the first segment might only provide a climb gradient of 1.6% or 0.9°- which is almost indistinguishable from level flight. Minimum performance in the second segment is almost as bad at 1.8% or 1.06°. The shallowest available slope at a PC1 heliport is 4.5% or 2.58°.)
It should therefore be clear that minimum Category A performance standards are not, in themselves, sufficient to provide obstacle clearance; that is why, in many performance presentations, it is stated that PC1 is a Category A procedure plus application of (obstacle) clearance to the local environment.
Minimum Category A climb performance is not really applicable to any known obstacle environment, it is performance in a semantic bubble. This is not just true of helipads, it also applies to runway-type heliports.
It is only possible to take-off in PC1 from a heliport when the following are known and/or accounted for (or standard company procedures assuring obstacle clearance are in place):
For a runway procedure: the rejected distance, continued take-off distance (which may, or may not, include a clearway), and take-off climb slope;
For a helipad procedure (including one within a limited area): the size of the helipad surface (for reject), the elevation and dimension of the clearway, and take-off climb slope;
Whatever profile is used, two things are necessary (which are in themselves obvious): (1) when flying to the TDP it must be possible to keep the rejected area in sight at all times; and (2), sufficient space must be available to allow the rotorcraft to accelerate from TDP to Vtoss prior to commencing the initial climb.
For other than a runway-type procedure, (2) above will inevitably require a vertical procedure where completion of the acceleration to Vtoss is conducted outside the boundary of the heliport - in most cases over obstacles.
In order for the pilot to ensure that min-dip remains (the required height) above obstacles in the continued take-off, the provision of an elevated clearway is necessary. The elevated clearway provides: a level datum for establishing the height of the TDP, at a length sufficient to allow completion of the acceleration to Vtoss.
For those who have not read the whole thread, here is a pointer to a number of slides that illustrate the above:
https://www.dropbox.com/s/i5am5zyg5a...sion.pptx?dl=0
The required procedure will be found in the Category A supplement; the take-off mass should, as well meeting the WAT, allow the required climb gradient (normally 4.5%) throughout the first, level and second segments (as constructed in the RFM supplement).
Almost all modern helicopters provide a suite of Category A (vertical) procedures; most can achieve take-off at a practical operating mass even when the clearway is elevated to a substantial height above the take-off surface (to raise it, and the take-off climb surface, above all obstacles). Power reserve provided by the 30 second and 2 minute settings (or 2.5 minutes if no 30 second setting is stipulated) can provide access to heliports (and required climb performance) in even the most complex obstacle environment (i.e. city centres with high rise buildings).