HC:
You are quite correct to point out that wave height alone is not sufficient. The wavelength and period, leading to the steepness of the waves are just as important, if not more so. However, such data is not measured offshore so cannot be transmitted to the crews before flight planning. This is a similar situation to the question of heave. As offshore pilots we all knew that actual heave was not the real problem – it was/is heave rate. How many years did it take to finally get heave rate data introduced? How many years will it take for the ‘authorities’ to act on accurate sea state reporting?
Probability – what is the probability of having to ditch? 1 in 10 to power 7? 10 to 8? 10 to 9? Since 1989, there have been 5 separate incidents of G-reg helicopters ditching around the North Sea:
Apr 1989 G-BGKJ Bo105 Oil pollution flt near Scacsta 1 passenger
Jan 1995 G-TIGK AS332L Crew change flt near Brae A 16 pax
Nov 2006 G-JSAR AS332L2 Crew change? Dutch sector 13 pax
Feb 2009 G-REDU EC225 Crew change flt near ETAP 16 pax
May 2012 G-REDW EC225 Crew change flt near Aberdeen 12 pax
5 incidents in 23 years, all different reasons, but with the same end result – 60 pax in the sea. How does that stand up against the level of ‘probability’? Based on Aberdeen Airport’s latest figures, there are approx helicopter 500,000 passengers per year. That would amount to around 11.5 million in 23 years. 60 pax out of 11,500,000 – that’s about 1 in 200,000. I wonder how
they feel about being just a ‘slim probability’. How do the oil workers perceive that probability? Let us not forget that these guys
are just going to work. If they are late, so what? And perception is the key word here. Why are there no Chinooks flying offshore oil support today? Should the oil workers, your passengers, lose faith in the EC225 or the basic survivability of ditching, what then?
So, let’s look at what the ‘authorities’ have to say. A gentleman by the name of David Andrew Howson of the CAA SRG, issued a paper titled “RESEARCH INITIATIVES FOR IMPROVING THE SAFETY OF OFFSHORE HELICOPTER OPERATIONS” – link
www.ihst.org/Portals/54/Partners/India/3_Howson.doc
Page 4 makes interesting reading.
Further suggested reading is HOSS/WP-99/8.5, (link
http://www.jaa.nl/secured/Operations...20Survival.pdf) extracts below:
“Taken on their own, the FAR/JAR would require the designer to select a reasonably severe wave condition for the area in which he expects the helicopter to operate and to demonstrate that the probability of a capsize has been minimised. FAA and JAA however, have adopted an interpretation (AC29-2A para 337(a)(3)) which states that Sea State 4 is considered to satisfy the reasonably probable requirement.”
“Although sea keeping qualities vary from one helicopter type to another, most types currently in use will capsize in sea states in the range 4 to 5 and above. A recent study of wave climates along a representative selection of main helicopter routes in the northern North Sea and West of Shetland (regarded in JAR-OPS 3 as a Hostile environment), indicates that Sea State 4 will be exceeded on 26-36% of occasions over the whole year (Ref. 1). During the winter period between December-February, this increases to between 51-65%. If the certification requirement was raised to Sea State 6, the risk of exceedence would fall to a maximum of approximately 3% over the whole year and 3-7% in the winter months.”
The history of North Sea oil support helicopters has been one of continuing safety improvements. In the early days, neither pilots nor passenger had survival suits or even lifejackets. Offshore survival training didn’t exist. No HUMS systems, single engine helicopters, single pilot operations, DECCA moving maps. I could go on, but you should get my drift. The industry must continue to improve safety
and the perception of safety.
bondu
Edited to correct figures - thanks John