Question for any offshore North Sea pilots from a curious passenger

[GCSSC]

Good morning ladies and gentlemen,

I was wondering if anyone could enlighten me as to the operational limits of the S92 in calm conditions from offshore installations, ships and rigs.

The main point I would like to explore is if there is a reduction in load capacity of the S92 in calm/no wind conditions. I ask as on several occasions we have had passengers and cargo removed from flight in what would appear to be perfect flying conditions; clear skies, good visibility, short hop ashore etc. The only common denominator is the lack of wind.

Are there any fixed rules regarding this or does it vary from company to company/come down to pilot discretion etc.

Any information would be most appreciated by this item of self loading cargo.

Many thanks in advance.

[Mustapha Cuppa]

The main point I would like to explore is if there is a reduction in load capacity of the S92 in calm/no wind conditions. I ask as on several occasions we have had passengers and cargo removed from flight in what would appear to be perfect flying conditions; clear skies, good visibility, short hop ashore etc. The only common denominator is the lack of wind.

Wind, pressure altitude, outside air temperature, deck edge clearance and available dropdown height from the helideck to the surface of the sea are all factors that affect aircraft performance hence available payload.

Are there any fixed rules regarding this

Yes. The tables and graphs in the performance section of the flight manual predict performance in accordance with the conditions mentioned above.

or does it vary from company to company/come down to pilot discretion

An operator can impose more stringent requirements than those found in the flight manual should it choose to do so. So can the customer.

​​​​​​​And the commander always has the final say.

[GCSSC]

Many thanks for the prompt response.

I ask this as I work on floatels and we often have persons or cargo removed from flights in calm weather and yet the same aircraft will come out with a full POB and cargo hold on another day when windspeeds are greater.

I have been informed that it has to do with greater translational lift being provided by wind across the helideck permitting better performance at take-off.

I'd be interested to hear more on limits in low wind conditions.

Once again, many thanks for the information.

[helicrazi]

There is also Centre of Gravity issues.

The days you mention, were there few passengers and a heavy cargo load?

More passengers on board allows better use of the cargo hold

your HLO should have a copy of the cargo hold limits with numbers of passengers

[SimonK]

Probably Performance Class 2e restricted. I won’t go into the boring details but I think this May have been the issue in the days in question. All valid points raised above though aswell.

[GCSSC]

You guys are sharp with the replies! Thank you.

On days where there is less than max POB, the crew do tend to prevent passengers from sitting in the after-most seats so I've always assumed that was to do with CoG.

The variables that baffles us is how on one week, the crew change will happen: 18 pax and the usual luggage (no "cargo" in that there's nothing more than the usual passenger luggage) with no issue. The next day or week the same crew change occurs but we are informed that X number of people have been bumped due to wind (or lack thereof). This was occurring even when located close to shore (25 mins flying time, OSE Norwegian sector) so its not like range was an issue.

[gulliBell]

As helicopter airspeed increases from zero to best rate of climb speed the power required reduces.

So, with the helicopter hovering, as the wind continues to increase from zero, less power is required to hover. Meaning, more power is available to achieve the required departure performance as wind across the deck increases. Meaning you can carry more stuff with more wind across the deck. It's not quite as simple as that, but for layman explanation purposes, that's good enough.

[212man]

All valid points above, although the S92 is not that CofG critical. Flotels tend to have low helideck heights compared to platforms, which means less ‘dropdiwn’ to accelerate to an airspeed that will allow higher mass, so are particularly impacted. Don’t forget, too, that the arriving aircraft will probably have a lower fuel load than when it departs, so that will create a difference in available payload. In case not clear - these considerations are related to accounting for having an engine failure at a critical point in take off and landing.

[helicrazi]

Actually there's a few times we are over cargo hold limits for given number of passengers. It crops up about 2 times a month for me personally which I didn't expect.

Other limit to beware of is Table 2 and restricted sector, however this is for stronger winds than the scenario queried above.

Other possibilty is weather at destonation requiring an alternate, which granted has nothing to do with wind, but passengers will see a chance in capacities.

also fuel available at the offshore installation, again not wind related but changes a payload somewhat.

although you may have been told it's due to wind, I know of a few occasions passengers have been told something completely different to the actual reason. Chinese whispers.

[industry insider]

GCSSC

Do you work on a TOTAL installation using a TOTAL contracted helicopter? Total has additional performance restrictions over and above the Flight Manual. With a lower drop down available from a Floatel, it may lead to a restriction in your case.

[GCSSC]

Our rig hasn't been at a Total platform recently but some of our sister vessels have. We have mostly dealt with AkerBP, BP, Premier and Statoil/Equinor.
​​​​​​
Just last trip we were told that we had to move across to the fixed installation for our crew change rather than use our own helideck. It was a cool, clear day with barely a breath of wind. I'm guessing the sweat lost through lugging our bags up and down several flights of stairs while wearing the bulkiest flight suits ever invented, was enough to account for any threat to the MTOW.

[Ennio]

Agree with a previous poster above. Destination weather most likely reason in North Sea region with S92.
It may seem strange to pax on arrival at Aberdeen to nice weather but knowing a colleague got bumped.
Short story, if weather at destination may need either 1. Appoach fuel or 2. Due to possibility of not being able to land due weather below minima, enough fuel to see you on your way to Dundee or Inverness etc. If the forcast weather at either of those is iffy, then you could find Edinburgh is the alternate airport with weather to allow landing. The further away from Aberdeen the alternate airport is then more fuel required and less payload available.
NS pilots honestly don't bump pax for fun and no pilot likes to do it but if you need the fuel its got to be in the tanks even if you are confident that the weather will be fine at destination
If the Met Man forecasts weather that says the destination needs an alternate then you must put in fuel to allow this. This also explains why crews ask for the latest weather updates from the Offshore Radio Op. and why crews sometimes sit on deck a while if the time is coming up to a new forecast being issued.

[helicrazi]

Our rig hasn't been at a Total platform recently but some of our sister vessels have. We have mostly dealt with AkerBP, BP, Premier and Statoil/Equinor.
​​​​​​
Just last trip we were told that we had to move across to the fixed installation for our crew change rather than use our own helideck. It was a cool, clear day with barely a breath of wind. I'm guessing the sweat lost through lugging our bags up and down several flights of stairs while wearing the bulkiest flight suits ever invented, was enough to account for any threat to the MTOW.

it's difficult to comment on this accurately without all the facts of the day. As I've found, sometimes it's not the pilots choice it's easier logistics by your offshore admin.

if you were connected to the platform then with certain wind directions landing can he prohibited and literally 1 degree in change of direction makes all the difference.

also depending if you were joined then the wind direction could have a limitation in take off weight from one helideck but not the other, so it allows more payload to be used by transferring you to the other platform.

as the poster above said, we don't do it to be a pain, I would much rather take everyone home, I've been stuck offshore, it's not fun. If I can get everyone home and offer a full payload then I certainly will.

[industry insider]

Hi GCSSC

I can’t add much to my fellow professionals above, but it’s not nice having to offer a lower payload and to bump passengers. As an aviation advisor for an oil and gas company in an area where there are long distances, high temperatures and large seasonal weather variations, I would work with the offshore roster coordinators to plan simple pax number monthly payloads.

Planning was outbound and inbound by installation and deck with attention paid to low bow deck vessel crew changes and seasonal Flotel position relative to the installation. In cyclone season, we would meet weekly and adjust scheduled pax numbers further as additional fuel is required when there are storms forecast. With Total as a JV partner we implemented many of its rules, including aircraft performance requirements.

Meeting with planners is an important part of the job because the roster coordinators can plan schedules in advance based on the payload predictions. As a company, we may have have flown with some empty seats when we planned for events which didn’t materialise. Likewise, we needed to ad hoc the occasional extra flight to catch up if we had to cease operations for a couple of days during cyclone season.

Pilots will always do their best operating within the rules but expectations start with management and planning. Management should know it’s business well enough to ensure that unfair expectations are not placed on aircrew, it’s not right to use crews to mask poor company planning.

[GCSSC]

Well I must say, a massive thanks to all who have replied in this thread. Your information is greatly appreciated and well put across.

As a worker, we all understand that there will always be situations outside your control and whether people are bumped or flights cancelled or delayed, in over 13 years offshore I've never heard anyone criticise the chopper crews. Quite the opposite actually. We realise as much as anyone that situations regarding weather and mechanical issues are always dynamic and that it doesn't take much to throw a spanner in the works. You guys went the extra mile in 2017 and got us ashore just in time to allow us to get home for Christmas despite some horrendous weather and delays.

The only slight issue is the questionable taste in in-flight music some of you boys and girls have :ok:

Seriously though, a massive thanks for taking the time to let this regular passenger and aviation enthusiast (I've got ~10 hours on C152+172 so far. Slowly but surely :O) have a better insight into how you guys operate.

Thank you all.