S76 C++ and 5 x 10 to the minus 8

[pjohnson]

Hi All

Would you happen to know anything about the following from a Request for Tender:

“4. Performance Class 2 Helicopters have been requested. Can the Bidder demonstrate that the probability of power unit failure during the exposure time at take off and landing from elevated helidecks is no greater than 5 x 10-8 (that’s 10 to the minus 8) per take off or landing “

I've read all about it at:

JAR OPS in Plain English: JAR OPS 1 ... - Google Book Search (http://books.google.com/books?id=hff1s-HxWksC&pg=PA215&lpg=PA215&dq=power+unit+failure+during+the+exposure&source=bl&ots=tQ-v2XRPOz&sig=Tt-zXOCVS44vWwcvRx38wnctPRE&hl=en&ei=9cswSujwA4zU7AOBkeW9BA&sa=X&oi=book_result&ct=result&resnum=1#PPA215,M1)

but I'm at a loss as to where I can find out if the C++ meets these requirements. All suggestions gratefully accepted. Thanks.

[JimL]

It does - check with Sikorsky who will provide you with the engine reliability data (revised data for all types has recently been issued).

They will also provide you with the EHA Risk Assessment that established that if the engine reliability meets a target of 1 x 10^-5, the 5 x 10^-8 is achieved for each take-off or landing event.

Jim

Perhaps I should also have added that there is no such thing as a Performance Class 2 helicopter. A helicopter certificated in Category A can be operated in Performance Classes 1, 2 or 3 depending upon the operational requirements.

[Shawn Coyle]

JimL
Where is this engine reliability data available?

[pjohnson]

Thanks Jim. Sikorsky are going to get something to me that shows the C++ meets the 5 x 10 to the minus 8 parameter. With the oil companies now asking for this information, it would be nice if they could put it on their web site somewhere.

[212man]

Sikorsky issued AOLs to the operators in 2006 and February of this year that covered this. I'm assuming they will be using the Arriel 2S1 data in the 76 C+ to provide the figures for the 2S2 in the C++, as the data covers a 5 year window that precedes the C++ entry to service?

Shawn, I can e-mail you the AOLs if you wish - drop me an address.

[JimL]

Shawn et al,

Firstly I do not speak for Sikorsky or any other manufactuer - the information below is based upon knowledge of previous and present methods of compliance with JAR-OPS (and the proposed methods for EASA OPS). Sikorsky is used as the example only because the question was asked about one of their types.

The reliability data is not raw IFSD data (a term which itself requires interpretation), it has been produced for showing compliance with JAR-OPS (and EASA OPS) in accordance with the methodology contained in ACJ-1 to Appendix 1 to JAR-OPS 3.517(a) - specifically paragraph 5.5.

Use of this data for operations with Exposure also depends upon the implementation of additional precautions which include the full panoply of engine monitoring and operational procedures that are described in ACJ-2 to Appendix 1 to JAR-OPS 3.517(a).

If at first sight of the Sikorsky information you are tempted to think 'no-way - this can't be correct', let me assure you that if you had sight of the detailed analysis (available to NAAs) you should be convinced.

Before the question is asked, the information (and analysis) takes account of both core engine (Engine TCH) and installation (Airframe TCH) power-loss events in the provision of the final reliability figure - i.e. it is both engine and helicopter installation dependent.

The methodology permits credit to be taken for modification - to resolve failure modes - in providing the reliability figures (of course only if the modifications have been applied and have shown to be effective).

As 212man has implied, new engines are dealt with on a case-by-case basis. As most engines are derivative, the reliability of previous marks can be taken into account (the requirement should not prevent the introduction of new and improved engines because of lack of statistically significant data).

The statistical analysis is based upon a five year moving window and the results are expected to be updated every year.

The Offshore Risk Assessment was provided by the EHA in co-operation with the manufacturers; it took advantage of the data/information contained in the manufacturer's initial Powerloss Exposure Risk Reports (PERR) for engine reliability and departure and arrival profiles.

Each manufacturer is responsible for the maintenance of its data/information and will have established the method of distribution of reports and detailed analysis. They should be the first port of call for provision of this information. Sikorsky provide their report via AOLs and hold the full analysis available for NAAs.

Jim

[Shawn Coyle]

JimL:
Thanks for the info- how can us lowly mortals who aren't in an NAA get some of this data?

[JimL]

Hi Shawn,

212man has already offered to send you the Sikorsky AOL information (in effect the reliability index); I could send you the detailed methodology and offshore Risk Assessment but I am not aware of any mere mortal who has access to the detailed IFSD analyses.

Jim