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Heli weather north sea

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Heli weather north sea

Old 28th Apr 2012, 19:48
  #1 (permalink)  
Thread Starter
 
Join Date: Apr 2012
Location: North sea
Age: 45
Posts: 3
Heli weather north sea

Hi guys,

Just a short introduction: I'm a roughneck working on a drilling rig a small hours flight out of Aberdeen,

I've always had a passion for flying helis but never made the career change and as I'm gettin towards the end of my 30's now I'm quiet comfy in my current job, I am also very interested in the weather that develops around the north sea and always haves great respect to the pilots that fly us to work and back.

I was hoping if someone could explain what kind of weather limitations there are for flying around in the north sea? I sometimes hear the pilots say that they have to perform an airborne radar approach to the rig and sometimes they do get in and other times they return back to Aberdeen, and what kind of weather limits(feet/visibility) are there for Aberdeen airport? Do you always need plenty of fuel to reach another airport or what are the weather limits (feet/visibility) if the wether is marginal.

I've also spoken to a few pilots out there and heard terms like "Coastal and land heliports" but never understood what this involves?

It probably does not concern me, but I'd really like to learn a bit more and i even asked my OIM for more info about this, but the best advise he'd gave me was 'visit PPRuNe and just ask it straight up'.

Thanks in advance

James
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Old 28th Apr 2012, 21:26
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Join Date: Jun 2007
Location: Left of the middle
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There's basically two methods of making an approach offshore by day (rather than complicate the issue with night).

An en-route let down leads to a visual approach at the rig and uses the weather radar to ensure a clear path ahead of you whilst you descend to 500 feet above the sea. Weather minima would need to be greater than 600 feet cloud ceiling (more than half the sky covered by cloud) and 1500 metres visibility and you need to miss all radar contacts by 5 nautical miles.

Otherwise, the airborne radar approach (ARA) is a published*instrument approach using the weather radar to track to the rig down to a minimum descent height of 200 feet (in to wind approach) and with a decision point at 0.75 nautical miles. If the target isn't visible at this point, a go around would be necessary up to the minimum safety altitude. The ARA is a specific procedure that is documented on an approach plate and can start from overhead the rig.

That's the basic form, but it should be said that there are other minima and factors for the crew to consider depending on whether they are shuttling in field or making an approach to a nearby rig and transiting to the destination visually. And in respect of the ARA, if the approach is out of wind by more than 30 degrees then higher minima would be used.

As for onshore approaches, the lowest minima is 500 metres visibility on the ILS because you get lateral and vertical guidance down to the runway. The decision point is 200 feet and again if the crew aren't visual at that point, they would climb up to the safety altitude (to either hold or divert).

There are universal stated limits for when you need to carry diversion fuel for an alternate airport, for example if the cloud height and/ or visibility are forecast to be at or below a certain limit. There are also stated limits for when an aircraft may be able to depart without carrying alternate fuel (depending on the individual operators limits).

Carrying coastal airport fuel is somewhere in the middle and allows an aircraft to depart without carrying full alternate fuel, but enough to perform an instrument procedure back at the airport or an 'en-route let down' over the sea to become visual before reaching the coast. The stated weather minima for coastal airport fuel is high enough to expect to be able to do a visual arrival at the airport but allows enough scope that if the weather deteriorates an instrument approach is still possible.

Hope this helps

TTT
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Old 29th Apr 2012, 07:17
  #3 (permalink)  
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Join Date: Apr 2012
Location: North sea
Age: 45
Posts: 3
Thanks TTT, much appreciated! I must admit there are lots of guys I know offshore that would be interested in knowing more about these weather limits (especially the 'ARA' limits, as this is a phrase we here lots from you guys)

What does the 'land heliports' stand for though?

Thanks again for your reply

James
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Old 29th Apr 2012, 08:13
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Join Date: Mar 2009
Location: Beside the seaside
Posts: 670
Helicopters departing a land base for an offshore installation must carry enough fuel to make an approach at the offshore destination and (if a landing is not possible) then have sufficient fuel for an onshore diversion where the weather at the ETA must be above certain limits.

A coastal airfield is one which is invariably near the coast and so long as it is approved as such then it is possible to nominate it as a destination airfield without an alternate if the weather limits are >600 foot cloud base and >4km vis by day at the ETA. This is obviously preferable as alternate fuel does not have to be carried allowing a greater payload for the customer.

ARA limits as TTT said are 0.75nm and if the rig is not visible then a missed approach must be carried out. If there is sufficient fuel then another can be attempted. Minimum descent is usually a radalt height of 200 feet during the day and 300 feet at night but each company sets their own.

Other limits to be considered in rough weather are the pitch, roll and heave limits of the rig deck for each helicopter type. These are relayed to the crew before the approach can begin. If they are out of limits then it is a waste of time making the approach as a landing is prohibited.
Epiphany is offline  
Old 29th Apr 2012, 10:38
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Join Date: Mar 2006
Location: Behind the curve
Posts: 275
Hi roughneck

For a little more insight into ARA procedures, the principle is that both pilots first use a map we carry of offshore installations, combined with looking at the radar picture and the wind reported at the helideck, to discuss and agree a safe approach path into the wind. One pilot carefully briefs the other as to headings, heights, speeds, ranges and missed approach procedures.

The path must be planned to reach the helideck avoiding other obstructions including boats in the final approach path. Normally the pilot who is going to do the deck landing uses the radar and acts as a talk-down controller, while the other pilot concentrates solely on flying the aircraft accurately according to his colleague's instructions and the flight instruments.

When the pilot doing the talkdown sees the helideck and is confident that he has adequate visual references, he says "I have control" and takes over the handling of the aircraft to perform the landing. If he never sees the deck by 0.75nm or isn't comfortable with the visual picture, he says "Go around" and the handling pilot turns to a safe direction away from the helideck while climbing to a safe altitude.

Now to ask you a favour; I've used your thread to serve as a "plug" for mine. In case you haven't seen it, please would you read mine: Attention offshore passengers. Engine failures ! and pass it on as widely as you can.

Last edited by Senior Pilot; 29th Apr 2012 at 11:19. Reason: Keep to the weather discussion
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