Offshore performance planning (merged threads)
 

Could anyone tell me what performance graphs should be used when planning a flight to an offshore platform in a twin, and how do you work out your MAAUW?

Thanks.......

Basically when operating under OPS3 and class of performances 2 (applicable to most of light and medium twins) the MTOW is determined by the 150 ft/mins at 1000 ft above heliport (or helideck)
When operating to/from helidecks it is advised to use the OGE limitation since the ground effect is very limited here. (on a relatively small surface)

If we operate under PC1 (class of performance 1) V1 , VTOSS, and RTOD will determine the MTOW.

If we forget OP3 and operate under other regulations, I think it makes sense to check the out of ground effect performances when operating on elevated helidecks.

In which offshore area are you planning? It makes a huge difference, and "a galaxy far, far away" isn't specific enough to enable a correct reply.

GLS:

I, like you, would like to join the fray on this but am unwilling to until we have some ground rules.

We could wait for Sandy Helmet to come back down to earth and state that which he desires or, alternatively, we could do the thread a service and set out the comparative offshore performance standards for all to see and compare.

What do you think?

Well, I only know of one area. Down here in the GOM, we just load up to max gross. For most types, the weight isn't limited at all until the temp approaches ~30deg C, then it is only slightly lower. We just plug the temp and altitude into the computer & get a number, which is the maximum allowable takeoff weight. Pulling out the POH and going through charts while the SLF in the back has a heat stroke isn't the best solution. We don't do Cat A, or OPS3, or any of the other JAR stuff over here. I realize things are different in Europe, but I'm not there. Try reducing the loads to that extent over here & you won't be employed long.

That's why I asked for the area in my first post - it's not the same in the UK as in Canada as in Oz as in Mexico as in..........

What about Canada, Australia and Mexico - what do you guys do?

Another KOS,

I can hear the sound of silence - anything we should infer from this?

Its a little slow as we have just been down that road......but I am sure there are some lessons to learn if you spark it up again.

http://www.pprune.org/forums/showthr...threadid=90224

We Canucks use the same charts/limits as our North Shore brethern. Its quite complex to get into in detail, but in short, we can maintain OEI stayup at our MOCA, and we assure we can get there as well (Cat A). We may be exposed to a water reject for a short spell after takeoff, but its not really an issue with our high decks. Depending on sea state/vis/day-night we more often than not have fly-away weights at rotation.

Old Man Rotor:

Thanks - I watched that debate from the sidelines but it was more concerned with the carriage of return fuel than the calculation of performance.

Bladestrike:

Is it CARs that require operations in Performance Class 2, or some other regulation (OpSpecs or something)?

I guess you are also at risk from a deck-edge strike as well as a water reject (or ditching in plain language) - both on the landing and the take-off.

Where does Cat A come into this debate on calculation of weights?

Now you Aussies - what calculation do you do?

Cat A weights are determined from charts in the AFM, and assure that you can meet a predetermined rate of climb OEI, and directly affect your take-off weight. Temps/DA go up, weights go down, if you want to be able to meet that rate of climb should you lose a can.

While the CARs have not yet adapted the Class 1/2 criteria, and the AFM for older aircraft do not have the charts, we have SOP's determining our takeoff weights that are much more stringent than required by the CARs. If the pilot determines that achieving flyaway at rotation is a must (night, rough seas, heavy fog....), he'll apply the more stringent weights from our SOP's, but its not a regulatory requirement.

At the very least, the CARs do require us to be able to maintain a MOCA OEI. By limiting ourselves to Cat A weights, we assure we can get to our MOCA (generally 1000 feet IFR offshore, CAT A weights assure 150 fpm at Max Contingency OEI to 1000 feet).

Bladestrike:

Thanks for the explanation. My interest was sparked because of your use of the term Cat A.

Although agreeing with what you have said, what you have not said is more important. Cat A isn't just a calculation of weight for en-route performance, it is the application of a take-off to landing trajectory to ensure adequate space is available for rejects, and distances are available to ensure that obstacles are cleared by the appropriate margins - in all phases of flight.

What you have described might more accurately be termed operations in Performance Class 2.

I am more interested in what you have said about company SOPs, do I understand that you have a method of calculating take-off masses to assure deck-edge miss and minimise drop down? How was the data derived? Does it give an assurance of engine failure accountability on and off the rig?

If you do not wish to broadcast, please do it by PM.

Getting myself in trouble trying to be vague.

Yes, what I described is a Performance Class 2 helicopter should we chose to be exposed to a reject for a period after rotation. As such, I guess the CARs 704 requirement is for a Performance Class 2 Helicopter. We attempt to have Class 1 weights if the marine enviroment is considered "hostile".

Yet we sort of need to fly Cat A to assure meeting Performance Class 2 critieria with any certainty. It depends on how you interpret the regs, you could probally get away with simply being at a weight where you could maintian a zero rate of climb at your MOCA, and this would give you better than Cat A take-off weights. It would just take you longer to get up there. On a nice VFR day with calm seas I don't see it as a problem.

Cat A is indeed a specific take-off and landing profile, and if flown correctly, and WITHIN THE CHARTED WEIGHTS, will assure a reject within a certain amount of distance OR a rate of climb of 100 fpm at Vtoss, accellerating to Vbroc, yielding 150 fpm climb to 1000 feet, at max contingency OEI power, depending on where you are within the profile when the engine quits. You cannot just apply the profile and stopping distances if you are not within the charted Cat A weights for your OAT/DA.

If you do not meet Cat A, are you still Performance Class 2? The CARs are vague, and I don't know if its spelled out in the JARs. We apply them regarding on prevailing conditions, beit day VFR, night, IFR....

Cat A
 

Oh come on Guys [Gals]......Why try to confuse the two different Certification Standards.........

You are either flying CAT A.......or you are flying to CAT B......but you can't fly both at the same time.

CAT A and Offshore is ridiculous.......no company, even the conservative UK Oil Companies do not insist on CAT A Offshore...its a nonsense.

Red Wine, thanks for that post it will do nicely…No confusion Red Wine:

The two terms Category A and Category B are used for the certification of helicopters:

• 'Category A' means multi-engine helicopters designed with engine and system isolation features specified in JAR-27/29 or equivalent and Helicopter Flight Manual performance information based on a critical engine failure concept which assures adequate designated surface area and adequate performance capability for continued safe flight in the event of an engine failure.
• 'Category B' means single-engine or multi-engine helicopters which do not fully meet all Category A standards. Category B helicopters have no guaranteed stay-up ability in the event of engine failure and unscheduled landing is assumed.

However for operations, the use of these two terms alone is too constricting for a machine that is as flexible as a helicopter.

Absolutely Red Wine, now do you see the limitation of those two terms – we can’t exactly describe how we operate!

So what are Performance Classes

• Performance Class 1 operations are those with performance such that, in the event of failure of the critical power unit, the helicopter is able to land within the rejected take-off distance available or safely continue the flight to an appropriate landing area, depending on when the failure occur.
• Performance Class 2 operations are those operations such that, in the event of critical power unit failure, performance is available to enable the helicopter to safely continue the flight, except when the failure occurs early during the take-off manoeuvre or late in the landing manoeuvre, in which cases a forced landing may be required.
• Performance Class 3 operations are those operations such that, in the event of a power unit failure at any time during the flight, a forced landing may be required in a multi-engined helicopter but will be required in a single engine helicopter.

Yes Red Wine, and that is why we use performance Class 2.

Flights to helidecks in the North Sea (and noting the comments of Bladestrike – Offshore Canada), operate in Performance Class 2.

A helicopter certificated in Category A may be operated in Performance Class 1, 2 or 3 – but a helicopter certificated in Category B may only be operated in Performance Class 3. Now can you see the flexibility of language and the potential for risk assessing an operation and prescribing the Performance Class such that it meets the perceived risk profile.

Finally, we have seen over other threads that modern twins have the potential to give engine failure accountability at MUAM (even the S76C+ has a Category A rig take-off profile at 11,700lbs).

Consider this; at the time when the installed power gives HOGE OEI at MUAM, we will be performing operations to helidecks in Performance Class 1 – no chance? Check the flight manuals of the latest clever twins - and hopefully the AB139.

Forgive me for hogging the thread and posting two replies - it was easier this way

Bladestrike:

In the absence of regulations prescribing the operating standard, that is an extremely well considered approach. You have also correctly identified that rig operations in Performance Class 2 may have an exposure to deck-edge strike and ditching (depends on the strength and direction of the wind).Operations in Performance Class 2, by definition, meet the requirements of Performance Class 1 just after the take-off phase. This is achieved by specifying that the second segment climb performance must be met (as you have said - climb performance of 150'/min at 1000' above the take-off site).

The way that you operate appears to be analogous to operations in Europe - the difference is that it is spelled out in JARs but not in CARs.

Try and avoid the term Class 2 helicopter - as you will have seen, it is not appropriate language for certification or operations.

Good luck.

Bladestrike:

Now your dilemma can be seen, CAR 704.48 prescribes flight at the MOCA for offshore operations when IMC and at night; and at 500ft for day VFR; but does not populate the Standards in CAR 724 Division IV (I hope the terminology is correct).

It is a credit to the operator that a Standard is incorporated in the Operations Manual. Is there some protocol between the operators in Canada that facilitates these safe practices - or do oil companies require them as part of their contractual agreements?

How often are offshore conditions hostile ?

Hostile conditions are deemed whenever a ditching would be "high risk", beit night or high seas. High seas being common 200 miles out.

Our SOP's are stricter than any CAR's requirement, and the oil companies seem to vary from district to district on their requirements and standards, so I'd hazard to say its more of a protocol among operators. While Canadian's may have a reputation of "bush ops- getting the job done" mentality, I have seen a significant swing towards safety over the past two decades, specifically in the offshore industry. No doubt driven by fear of litigation, but I don't think we are up to JAR's standards yet.

Is there a big difference under the JAR's? Do Brits do things differently than Norwegians differently than the Danish?????

Uh Oh! The can of worms just got opened! Do the Brits do things differently? I cannot wait to see where this thread goes now!

With all of the discussion above.....and very articulate and informative it was.....what is the difference in the accident rates in the various areas for the situations under discussion? I dare say.....besides the odd BO-105 fluttering into the GOM after a single engine failure in cruise....the real accident rates are the same all over the world for post engine failure accidents.

Any takers?

Bladestrike:

My understanding is that the the Brits, the Norwegians, the Dutch, the Danes and the Irish (all of those with offshore operations in the North Sea plus the Irish) apply the Standards of JAR-OPS 3. Therefore in the context of this thread, they all apply Peformance Class 2 (as expressed in JAR-OPS 3 - i.e. with exposure).

SASLess:

I'm really surprised at you dumping on a safety discussion when your campaign for improvement in safety standards is well known.

The OPG statistics show that there is a similar accident rate for the (offshore) oil industry (with a few blips here and there) worldwide. The important thing about these statistics is that they only measure that which is undertaken. There are no engine failures for singles in the North Sea as none are operated there. Why, because the environment is hostile. Engine failures in the North Sea are a reasonably foreseeable event - mitigated by the operational rules.

It would appear to me that the message that comes loud and clear from the OGP statistics is that, where equipment and standards - appropriate to the environment - are: contracted by the oil companies; or are prescribed by regulations; or are as the result of SOPs facilitated by protocols, the accident rate is ALARP.Yes for the reasons stated above.

When quoting from my PM you omitted the second part of the sentence:It is clear that the accident record for the GOM this year so far does not make for pleasant reading.

I for one applaud the Canadian operators and pilots for understanding that hostile environments should be treated with respect.

I shall now dismount from my high horse.

Thanks to Bladestrike, GLSNightPilot and Another KOS we are starting to form a picture of what the Performance Standard is for offshore operations - as requested by Sandy Helmet:

all of whom use the AFM data to provide the RTOM.

With the exception of the comment from Red Wine, we have no information from areas other than those stated.

As the Australians have everything from extremely tropical to downright hostile, is it possible that they could join us in this thread - it would be interesting to see how they manage their offshore performance with such a varied range of climates.

Another question that might be interesting to answer is - do the oil majors have a Standard which they themselves apply by use of contractual agreements. I have heard a rumour that deepwater GOM might be the subject of such a standard in the near future.

When we have done this subject to death, we might attempt to have a similar discussion on equipment for overwater operations (ditching approval, floats, liferafts, lifejackets, survival suits etc) - for both hostile and non-hostile environments (always supposing that we have a common understanding of those terms).