Offshore Platform PBN/RNP

[212man]

Thanks Shawn - I was going to ask the same question, as I consider myself reasonably au-fait with most offshore CFITs that have occurred in the last 25 years or so, and don't recall many being ARA related. The one that does spring to mind, involving an AS32 L2, was not related to the approach per se, but a mishandled missed approach.

I'm fully in favour of automated, simple to use, approach procedures that bring the aircraft close to the platform - preferrably with AFCS systems that then allow continued coupled flight to close to the commital point. I fully agree that these provide an enhancement to help prevent CFITs, particularly at night and in DVEs. SAC and ECF are both developing such capabilities using elements of their SAR AFCS systems. What I am not in favour of is the assumption that an approach can be designed that does not rely on real time obstacle information using, as a minimum, the radar.

[FlightPathOBN]

With IFR procedures, you are not at elevations where there would be an obstacles other than other aircraft, until you are on final, and within .5nm to .3nm of the rig. This allows the crew to spend the workload on flying the helo, rather than trying to determine offset distances from the rig using a weather radar.

As with any instrument procedure, radar is still actively used to avoid obstacles.

There are many instances on approach to the rig, where, especially at night, the crew becomes disoriented during the offsets, a search on the internet picks up quite a few...but I will hazard this one.

http://www.aaib.gov.uk/cms_resources...9%20G-REDU.pdf

[C.C.C.]

Originally Posted by FlightPathOBN

There are many instances on approach to the rig, where, especially at night, the crew becomes disoriented during the offsets

Originally Posted by AAIB G-REDU

At a range of approximately 13 nm, the commander could also see the platform and the crew agreed to descend to 500 ft asl and conduct a visual approach using the weather radar to assist with range information.

So this crew stopped using the ARA technique at approx 13nms, and not the offset point as you are infering. As a direct result of this accident there have been significant changes to our SOPs for Night/Poor Visibility Operations to Offshore Installations. During this training it was commented that no-one could recall any CFIT incidents/accidents following the visual segment at the end of an offset night ARA on the North Sea.

I agree with 212man about obstacles. The minimum safe operating altitude for poor visibility (not IMC) offshore operations in Nigeria was raised after a Bell 212 got a bit close to a 3-legged jack-up rig (possibly Trident IX with 518' legs) which had its legs extended whilst under tow in Harmattan and it's movement had not been previously notified to the crew.

[FlightPathOBN]

The MSA, in all of the standards, for ARA is 1500', until on final approach, descend to 1200' when 4.5nm away from the rig. You then descend to the level segment 2nm away from the rig...
It also states that if you observe and obstacle within 4nm of the rig, raise the MDA 200' to 550' (min)

The 1500' is a minimum per the criteria, min segment altitudes are a design, they are not automatic. If there is another rig within 11 nm, the MSA is raised. This MSA assumes 500' ROC (req obstacle clearance), so it plans for obstacles 1000' high...if you have floating platforms taller than this, (I know, virtually impossible, but as soon as I state it, an internet ref will show up!) the design would raise the MSA. Another option would be to issue a NOTAM for the mobile platform with dates, and temporary MSA.

The IFR procedures code in the location of the waypoints with min segment altitudes as a navigation aide. Use the weather radar for spotting uncharted obstacles, there is enough clutter already on the screen..the crew still needs to aviate.

http://www.caa.co.uk/docs/33/2010001.pdf

Here is an accident report compilation for 2000, note page 25 (FITWO/CFIT)
http://ihst.rotor.com/portals/54/ind...try%202000.pdf

According to Eurocontrol, since 1976, there have been 7 fatal accidents, with a loss of 94 lives, and 34 non-fatal accidents while on ARA type approach.



Safety Council.

http://easa.europa.eu/communications...20Brochure.pdf

[JimL]

FlightPathOBN,

I'm sorry, your statement:

According to Eurocontrol, since 1976, there have been 7 fatal accidents, with a loss of 94 lives, and 34 non-fatal accidents while on ARA type approach

cannot go unchallenged. Is it possible for you to point us at the source of that information.

Jim

[FlightPathOBN]

Jim,

I have it as a handout from a working group, GIANT (GNSS Introduction in the Aviation Sector...)

"A new offshore approach procedure"

It is a modified SOAP using GPS....much more user friendly with a closer offset and a 15 degree bank to deck instead of 30 degrees in SOAP.

I will see if I can locate an online copy....

[212man]

A trawl through the GIANT website doesn't seem to show this statistic - which I agree sounds slightly incredible. Do you really think that anyone with more than a passing interest in the offshore industry would be unaware of 41 accidents in the last 35 years?????

GIANT

Has some good links showing some of the project work to date. One of this forum's contributors was/is involved in the project (and is named in the flight test summary document) so perhaps he might step in and explain?

[FlightPathOBN]

The document speaks for itself...
Would there be such an emphasis on approach procedures if there were not significant issues?
Helo operators need to evolve with aviation. The accident rates for helo ops are far above acceptable limits.

GPS navigation is here to stay, and has significant safety, navigation, fuel savings, access, and bottom line ramifications.

Evolve, or become a casualty of evolution.

[industry insider]

I am with you as well 212 and Jim L. I think if we put our heads together, we could almost name all the CFIT accidents resulting from an ARA and I don't think its as many as Flight Path is suggesting.....?

[JimL]

FlightPathOBM,

You are mixing apples with oranges; yes there have been a number of accidents associated with visual approaches - some with limited visibility as a causal factor - but I am only aware of one recent accident (in Malaysia) that was associated with the ARA (that is not to say that there are not others).

A number of us have the safety of offshore operations as one of our concerns - we monitor such accidents. You still need to justify your statement with some data/information.

You might wish to search back and find the thread on this subject following the REDU accident. It was quite illuminating and provided a great deal of thought on offshore approaches.

Jim

[212man]

Evolve, or become a casualty of evolution.

Interesting to see your presumptions. As I write I'm sitting in the back of a simulator watching a crew fly an FMS driven RNP APCH approach using a 4-axis autopilot! Fewer assumptions and more facts might be useful in this discussion.....

I guess what might be quite interesting would be to know to what extent your proposals differ from either the GIANT procedure or the FAA OSAP with parallel offset, and why the differences if any? Also, whether you are targeting a particular aircraft and equipment fit, or just generic procedures. what receiver TSO fit are you assuming, for instance?

[C.C.C.]

Like JimL, 212man & industry insider, when I read your statistic of 41 accidents on an ARA type approach I was very surprised having used the technique since 1981 and never heard of that many ARA related accidents.

Whilst there were a couple of poor weather related accidents, none were on an ARA in the CAA HARP report - http://www.caa.co.uk/docs/33/CAP641.PDF

In the Helios ARA Hazard Analysis there is only one ARA accident - http://www.luftfartstilsynet.no/mult...ment_1861a.doc

I look forward with professional interest to reading about the other 40 ARA accidents in due course.

[JimL]

Thanks CCC; the 1981 accident at Alerk Island cited in the 'helios' report was not exactly flown to exemplary standards:

AFTER WAITING 7 HOURS FOR THE WEATHER TO IMPROVE THE HELICOPTER WAS FINALLY DESPATCHED AT NIGHT IN IFR TO BE POSITIONED AT AN OIL RIG. DURING THE INSTRUMENT APPROACH TO THE OIL RIG THE CREW DESCENDED BELOW COMPANY MINIMUMS IN ICE/FOG. THE RADIO ALTIMETER WAS UNSERVICEABLE. TO SIGHT THE OIL RIG LIGHTS THROUGH THE ICE/FOG THE PILOT DESCENDED TO 150FT AGL ON HIS ALTIMETER. THE HELICOPTER STUCK THE SEA ICE AND CRASHED. TEMP CORRECTION NOT APPLIED.

at the very least, the RADALT being unserviceable should (under European regulations) have prevented a descent to below MDH + 200ft - based upon the lowest regional setting. It also does not say whether this was an ARA procedure.

This accident says more about the operator/pilot than any procedure.

Jim

[FlightPathOBN]

212,

There are, or can be differences, depending on the level of optimization needed.

The best method is to code the procedure with waypoints, so that the procedure is in the box, and the flight plan can reflect the the instrument procedure. This very easy, using the procedure template, with a fixed rig. Obstacles within the 11nm circle are charted on the plate. Floating platforms require a slightly different design and coordination.

The main difference is the performance real-time MDA, given real time climb gradients. The standard assumes the climb gradient at 2.5% for the missed, so if you have a climb grad of 4 or even 12%, the MDA will be significantly lower, as will the vis requirements.

Using a coded procedure that includes the land based location, the operator knows that the obstacle evaluation has been done, and that the containment area is cleared. The example of Karratha overlaying the RNP approach, the operator knows that Air Services is maintaining the corridor for obstacles and equipment.

The track miles are fixed, so that a rising cost of fuel, can be directly calculated on the bottom line.

Australia is getting set to enact the carbon tax on fuel, so fuel saving ill become very important.

Once one has a chance to see the glass cockpit in action, it really is impressive. I have some GBAS procedures that are rated for CAT III autoland...that is very impressive.

In regards to the stats, I dont know the specifics, other than what what shown in the handout, that were used to justify the GIANT procedure design vs SOAP vs ARA.

Didnt mean to offend...

[zalt]

CCC

Thanks for that Helios link. A very interesting report.

JimL

This accident says more about the operator/pilot than any procedure.

I'm afraid I have to agree. Sadly the local regulations have not advanced as they have in the North Sea countries either.

[C.C.C.]

Just found that the above Helios report was also incorporated into a Paper issued by the CAA - http://www.caa.co.uk/docs/33/200906.pdf

In the Norway version the above Bell 212 accident is listed under ARA Related (page 52), but in the CAA paper it is listed under Other (Page 189).

[FlightPathOBN]

CCC,

Thanks for that reference.

As much as I just love studies....

Good reference for ARA, and good ref for GPS, but certainly a disconnect.

If you were using GPS for nav, you would not likely code in an ARA approach, but a PinS or a SOAP. SOAP directly overlays an ARA but with only one offset, so yes, the study is correct that there are no coded ARA's at that point in time, but there were many coded SOAP's and PinS's.

It is a criteria foundation, that an operator cannot enter an instrument procedure, which is why the Rig Approach system will not likely get approval.

There is no reason that the same procedure cannot be pre-loaded, and this would be approved for use.

The procedure design can account for uncompensated baro-vnav, rad-alt or better both, which both is the current standard for MOS charts. (although with baro, the coldest temperature of the location is used, which is why one sees such a difference in MDA between rad-alt and baro)

I am starting to see the point that many of you have made about incidents attributed directly to ARA, especially differences between the regulators and operators. Incidents appear more focused on the operational errors, using FITWO as a catch-all...and given assumptions that there havent been choices, the definitions have not been addressed between approach types in the incident reports.

[jonseagull]

I am doing a small amount of research into offshore approach's, nothing so high brow as the majority of the discussion you learned gentlemen are having here, I hasten to add, and have come across the following document:-http:[URL="http:////www.caa.co.uk/docs/33/200906.pdf"]

With reference to the discussion about CFIT, I would draw your attention to the Part 2, Annex B CHIRP Events. This does indicate that although, thankfully, there have not been many cases DIRECTLY attributable to the ARA procedure, there is certainly room for improvement. I have been in the fixed wing world now for many years and so much of my rotary experience is now out dated, but, having flown many CAT 3 B auto lands in <200m and flown numerous rig-radar approaches, I know when I felt more comfortable!

I only post this to suggest that just because you can't quote a CFIT accident, it doesn't mean you are immune.

[212man]

JS,
you make an entirely valid and reasonable point, but could I just point out that the majority of the reports are clearly very old - more than 25 years - and refer to ARAs with the earlier minima (0.5nm and 150 ft.) There are also a couple of clear breaches of SOPs....

[FlightPathOBN]

While the CFIT, etc incidents while ON the ARA procedure are minimal....technically my point is,
that if you are on and maintain an ARA procedure, you will never land...

It is only when you disconnect from the ARA, can you go visual and land.

Look at the incidents on visual from the ARA....