Performance class two enhanced (offshore)

[JimL]

Just a couple of other points that should be made:

There was considerable pressure put on the working group by some NAAs and those oil companies who wanted an elimination of the risk of engine failure that, theoretically, a move to PC1 should have provided.

Before NPA-38 was written, there was a time when existing profiles were being considered and risks/benefits quantified. Profiles included those from manufacturers and those resulting from the HAPS modelling – one was for the Bell 212 which I shall return to later in this post.

Further work on the quantification of the exposure periods resulted from examination of the Power-loss Exposure Risk Reports (PERRs) produced by the manufacturers - although some of these PERRs included the HAPS profiles, some did not. (You will remember that the HAPS profiles were intended to reduce risk – one of which results from the degraded FOV that occurs as a result of inappropriate landing procedures. A number of manufacturer’s profiles did not have this as their primary consideration - this might have been as a result of previous certification regulations, the re-use of onshore profiles or a concentration on payload over FOV.)

In order to estimate the effect on payload of the move to HAPS profiles with mass calculations; further modelling was undertaken, using first the HAPS model, and then EUROPA (remember that HAPS is a two-dimensional model whereas EUROPA is three dimensional – the third dimension being required to model the sidestep manoeuvre on landing). Once wind was factored into the modelling, it became clear that the effect on payloads would not be severe except, perhaps, in nil wind conditions and specifically, for drop down. To estimate the effect of environmental conditions on the whole solution, several years of wind data were downloaded from the INTOPS data base (along with temperature and pressure) and conclusions reached.

One disappointment that resulted from the modelling was the realisation that it was extremely difficult to come up with a single metric (from existing data) to provide ease of calculation; the data was presented using ’OEI ratio’ as a common metric but with the three types (a medium, a larger twin and a triple), the ratio for take-off at MUAM in nil wind conditions was respectively 1.36, 1.29 and 1.16 – clearly too wide to provide a basis for the solution. (It was probably the length of fuselage that caused the wide spread).

The output from modelling was collated and the results were presented to all working groups, operators, manufacturers and Authorities – it looked extremely promising. It was agreed to go ahead and replace the requirement for PC1 in 2010 with PC2 (and PC2e); NPA-38 was produced, accepted and the rest is history.

To return to the Bell profile; Bell were one of the first manufacturers to provide a CAT A Helideck procedure. They decided that the best solution (addressing operational constraints) was to utilise an upwards and sideways acceleration. This provided two benefits: the FOV to/from the deck would not be an issue; and the TDP would be positioned at the same point as the LDP. In the event, the procedure was ahead of its time and was not extensively used. It does continue to be used at Bell and evidence of it can be seen in the CAT A procedures for the B427 and B429 (and a very comfortable procedure it is - as those who have flown it will testify)

However, now that examination of the wind data shows that about 37% of the total departures could occur when the helicopter is facing into the 150° obstacle sector, it might be time for operators to revisit the merits of the Bell 212 take-off on those occasions. No, this is not an answer to issues with turbulent winds from the 150° sector (some of which are addressed in the HLL) but, as has already been explained, this is not a process that always has a deterministic outcome – and explains why the authors of AL5, quite righty, put PC2e in the Exposure loop.

In addition, this profile (or a form of it) can be used for departures from a well-head platform – particularly when flown with more powerful helicopters. With an engine failure before RP in the departure, the deck will remain in sight and a reject can be quite easily undertaken. This is a matter of training only – the performance figures should not be substantially altered (in fact it may assist because I am informed that there is a penalty applied by some operators)

None of this affects the 80% - 90% of departures which could now be undertaken without exposure.

Oh, and I still have not had the answer the question “how much endurance does the EC225 have with a take-off mass of 10,875 and 19 passengers”. Perhaps one of you can PM me the answer to that.

Jim