View Full Version : S92 start/shut down wind question.
dakarman
7th Mar 2018, 07:29
Hi,
As a regular in the back of N Sea flights, I hope you dont mind me asking a question but a situation came up yesterday I cant find an accurate answer for.
Thanks to multiple flights, triggered lightning and a VIP visit to the rig I am on yesterday a situation occured where the S92 could have shut down n deck but was unable due to the wind. I know its a startup shutdown windspeed issue to avoid blade flap and resultant really loud banging noises from the tail boom but my question is, is there a stated windspeed value for S92 in oilfield N Sea operations above which startup shutdown is forbidden?
Thanks
budgie2007
7th Mar 2018, 07:49
In a nutshell, yes, the maximum wind speed for a planned offshore startup or shutdown is 35kts for the S92, arguably this includes gust, which yesterday were quite severe.
The crew also need to consider the turbulence coming off the rig or is the deck sheltered from the wind. In yesterdays conditions they would make a dynamic risk assessment of whether shutting down or remaining rotors running is the safest option, they will always go for the safest option. If they elect to shutdown they need to consider how long they may be shutdown and if they can tie the blades down, this may require a working at height permit which can take time. If you have a technical issue and the rig has fuel, it will often be safer to remain rotors running while troubleshooting the issue and speaking to the engineers onshore.
Next time I would advise asking the pilots, they will always be willing to chat to the passengers about their decisions.
dakarman
7th Mar 2018, 08:26
Thanks for the answer, unfortunately i was not in a position to ask the pilots as i was not lucky enough to be departing yet myself but more in a position wondering when the vips would leave.......
Interesting info though, ta.
the maximum wind speed for a planned offshore startup or shutdown is 35kts for the S92, arguably this includes gust,
35kts, that's not quite much...
skadi
212man
7th Mar 2018, 13:00
35kts, that's not quite much...
skadi
I'm assuming it's an operator limitation imposed with a buffer to cater for unexpected increases in speed that then put the aircraft outside limits for start. I remember an operator shut an S76 down in the SNS, and the wind pick up so quickly that the crew were unable to get to the aircraft from the restroom before a blade had been bent up and written off.
HeliComparator
7th Mar 2018, 15:40
Yes there is a big difference between planning to shutdown - ie departing base to visit a rig to shut down for hours, versus having to shut down on the spur of the moment due to a problem and then restarting. The former has to have a big buffer as funnily enough, the offshore weather forecast is not always totally accurate! The latter can be based on the actual conditions of the moment and RFM limits.
albatross
7th Mar 2018, 16:30
We carried a 2 part aluminium pole with slots cut in the end that allowed us to install the tiedowns without "working at height". Worked well when required, which was not very often.
In a nutshell, yes, the maximum wind speed for a planned offshore startup or shutdown is 35kts for the S92, arguably this includes gust, which yesterday were quite severe.
The crew also need to consider the turbulence coming off the rig or is the deck sheltered from the wind. In yesterdays conditions they would make a dynamic risk assessment of whether shutting down or remaining rotors running is the safest option, they will always go for the safest option. If they elect to shutdown they need to consider how long they may be shutdown and if they can tie the blades down, this may require a working at height permit which can take time. If you have a technical issue and the rig has fuel, it will often be safer to remain rotors running while troubleshooting the issue and speaking to the engineers onshore.
Next time I would advise asking the pilots, they will always be willing to chat to the passengers about their decisions.
Yes there is a big difference between planning to shutdown - ie departing base to visit a rig to shut down for hours, versus having to shut down on the spur of the moment due to a problem and then restarting. The former has to have a big buffer as funnily enough, the offshore weather forecast is not always totally accurate! The latter can be based on the actual conditions of the moment and RFM limits.
Ok, thank You
skadi
helimutt
7th Mar 2018, 18:48
35kts?
Thats a lot more restrictive than others I know.
S76
60kts engagement
75kts departure
;)
212man
7th Mar 2018, 19:13
35kts?
Thats a lot more restrictive than others I know.
S76
60kts engagement
75kts departure
;)
60 for engagement - are you sure? 75 for departure is just rotors running so no rotor limits involved.
Fareastdriver
7th Mar 2018, 19:49
60 for engagement
When the first 76As came out in 1981 we used to start both engines against the rotor brake. When you released it it was controllable almost immediately. Come the problems with the spindles we then went to one engine start and then released the rotor brake. Offshore with a high and gusty wind blowing we could do a double engine start even though the 76 had sweepback on the tips to stop it picking up the helideck net.
60 knots seems a bit high, the brain cells suggest 45 knots.
It was certainly 60 knots for operating on a deck with an enroute wind of 75.
35 knots is an ops manual planned offshore shutdown 'limit'. The RFM obviously allows start and stop at higher speeds with the appropriate procedure. But you don't plan to shutdown offshore at more than 35 knots.
On the 92 in my company.
ShyTorque
7th Mar 2018, 20:11
I'm fairly sure the max wind speed for rotor engagement on the S-76s I flew (A, A++, B, C, C+, about 4,400 hours in total) wasn't as high as 60 kts.
It's well over ten years since I last flew the type but I think the manufacturer's limit was 40 kts. It would be a brave operator who disregarded that.
Edit: Just found my old SK-76 question bank, as issued by Flight Safety International. 40 kts was the rotor engagement wind speed limit.
212man
7th Mar 2018, 21:26
I'm fairly sure the max wind speed for rotor engagement on the S-76s I flew (A, A++, B, C, C+, about 4,400 hours in total) wasn't as high as 60 kts.
Yes, I was being polite
It was certainly 60 knots for operating on a deck with an enroute wind of 75.
That was post G-TIGH/Cormorant A, prior to that 75 kts on the deck was allowed. I recall flying nearly 3 hours to the Murchison and the windspeed was gradually increasing. As we got final clearance we were told the wind was 80 kts and my crusty old captain said "what's 5 knots, we're here now?" We'd parked a few degrees out of wind to give a few degrees of tilt to maximize the gravity refuel, so initially I was in the lee, and as I walked around the baggage bay I walked into the full force of the wind and my zipneck suit immediately inflated and I became airborne heading towards the Tail Rotor and the deck edge. Bunching into a ball got me back on deck and then I clambered with the net to the sponson and clung on. I learned about wind from that!
The RFM limit is 55 knots, as long as the wind is +/- 45 degrees of the aircraft nose.
Fareastdriver
8th Mar 2018, 08:06
Around 1980 the helideck crews where told to stop attaching ropes between the access stairway and the helicopters structure so that the passengers had something to hold onto crawling across the deck.
SASless
8th Mar 2018, 11:13
Quite frequently used the attached safety line routine....but that was in the Cowboy Days of the North Sea.
Some commonsense has crept into and out of Ops since then it appears.
More than a few aircraft got damaged while shutdown and tied to the decks during the early days of offshore shuttle operations where the aircraft lived on an open deck.