Performance class two enhanced (offshore)
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[. If a take off or landing profile is 'certified' (accepted by the authorities as Cat A compliant) then it cannot by definition conflict with a mandatory (listed in the 'Limitations' section of the RFM) HV envelope.
2. My AW 139 has a Vertical Helipad profile with optional TDPs between 35 and 70 feet and a Short Field Take Off (vertical ascent to TDP) with TDPs between 85 and 400 feet ATS, published as Cat A compliant.
3. These profiles are clearly in conflict with the HV envelope.
4. The size of the HV envelope is variable according to WAT inputs but the TDP options are not WAT-dependent.
]
Geoff
I wonder how you can make statements like these. A Cat A profile, by definition and by certification rules, can never interfere with the H-V area because if this would happen, the fundamental requirement of a safe landing, could not be achieved.
Since you have to demonstrate that at any point of the take off profile before TDP you can safely land after engile failure or you can carry out a Continued Take Off after an engine failure at or after TDP, there is no way H-V can interfere with Cat A.
The AW139 Cat A profiles (6 different techniques) have been certified and are compliant with these rules.
I strongly reccomend you to carefully study RFM Supllement, this will avoid to rush to not correct conclusions.
2. My AW 139 has a Vertical Helipad profile with optional TDPs between 35 and 70 feet and a Short Field Take Off (vertical ascent to TDP) with TDPs between 85 and 400 feet ATS, published as Cat A compliant.
3. These profiles are clearly in conflict with the HV envelope.
4. The size of the HV envelope is variable according to WAT inputs but the TDP options are not WAT-dependent.
]
Geoff
I wonder how you can make statements like these. A Cat A profile, by definition and by certification rules, can never interfere with the H-V area because if this would happen, the fundamental requirement of a safe landing, could not be achieved.
Since you have to demonstrate that at any point of the take off profile before TDP you can safely land after engile failure or you can carry out a Continued Take Off after an engine failure at or after TDP, there is no way H-V can interfere with Cat A.
The AW139 Cat A profiles (6 different techniques) have been certified and are compliant with these rules.
I strongly reccomend you to carefully study RFM Supllement, this will avoid to rush to not correct conclusions.
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Geoff,
you are not an attentive reader of your AW139 Flight Manual.
I explain why.
If you compare the Cat A weights, obtained from the Cat A WAT charts for the procedures you mentioned in your post i.e. Vertical Profile and Short Field, with the weight for which there is no H-V you will see, unbelievable, that the CAT A weights are always lower than the weights for NO H-V.
Some examples.
PA:0ft, OAT=40°C
Cat A weight ( Page S12-A32 and S12-B16 of the Suppl.12 to the 139 RFM):6400 Kg
NO HV weight (Page 1-17 of the basic RFM): HV does not exist
PA:5000 ft, OAT:20°C OAT :0°C
Cat A weight : 5880Kg Cat A weight: 6220 Kg
NO HV weight : below 6000Kg HV weight: HV does not exist
PA :10000ft , OAT:0°C
Cat A weight : 5220Kg
NO HV weight : below 5400Kg
You can continue the exercise by checking different procedures and environmental conditions but the results will be always the same i.e:
Cat A weight are always lower than the NO HV weight.
And this is obvious because this is the prerequisite that makes possible to reject the TO after an engine failure.
If you don’t trust me and you want to know more about the H-V and the way in which is determined I suggest to read the AC29 Page B-92 (it may be downloaded from http://http://www.faa.gov/regulation...TopicID/107) .
You will realize that the HV is not always defined by failing the engine in steady flight.
This is true for the cruise region of the HV envelope.
The Take off region is defined by failing the engine along the TO profile at various height and speed. Therefore in a dynamic condition.
Keep off the HV. Remember its nickname.
gmrwiz
you are not an attentive reader of your AW139 Flight Manual.
I explain why.
If you compare the Cat A weights, obtained from the Cat A WAT charts for the procedures you mentioned in your post i.e. Vertical Profile and Short Field, with the weight for which there is no H-V you will see, unbelievable, that the CAT A weights are always lower than the weights for NO H-V.
Some examples.
PA:0ft, OAT=40°C
Cat A weight ( Page S12-A32 and S12-B16 of the Suppl.12 to the 139 RFM):6400 Kg
NO HV weight (Page 1-17 of the basic RFM): HV does not exist
PA:5000 ft, OAT:20°C OAT :0°C
Cat A weight : 5880Kg Cat A weight: 6220 Kg
NO HV weight : below 6000Kg HV weight: HV does not exist
PA :10000ft , OAT:0°C
Cat A weight : 5220Kg
NO HV weight : below 5400Kg
You can continue the exercise by checking different procedures and environmental conditions but the results will be always the same i.e:
Cat A weight are always lower than the NO HV weight.
And this is obvious because this is the prerequisite that makes possible to reject the TO after an engine failure.
If you don’t trust me and you want to know more about the H-V and the way in which is determined I suggest to read the AC29 Page B-92 (it may be downloaded from http://http://www.faa.gov/regulation...TopicID/107) .
You will realize that the HV is not always defined by failing the engine in steady flight.
This is true for the cruise region of the HV envelope.
The Take off region is defined by failing the engine along the TO profile at various height and speed. Therefore in a dynamic condition.
Keep off the HV. Remember its nickname.
gmrwiz
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Bpaggi
I think you have misunderstood my views. If you go back a few posts you will see that I agree 100% with your assertion.
Maybe I should have said 'apparently in conflict'
Shawn and I are arguing the point that certified Cat A profiles are ALWAYS safe to use if you apply the WAT curves correctly.
It's MrWizz that seems to be having a problem with this.
G.
Maybe I should have said 'apparently in conflict'
Shawn and I are arguing the point that certified Cat A profiles are ALWAYS safe to use if you apply the WAT curves correctly.
It's MrWizz that seems to be having a problem with this.
G.
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"The Bell 212 CAN be operated Cat A and PC1. Just reduce payload"
In Dubai, that will allow you one passenger. The max weight in Summer is around 8500 lbs!
It's only 10,000 max Cat A anyway.
Phil
In Dubai, that will allow you one passenger. The max weight in Summer is around 8500 lbs!
It's only 10,000 max Cat A anyway.Phil
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PC1 Operations
I'd like to add some more thoughts to this discussion.
PC2e has been invented most likely because most of the helicopter used in offshore can not afford PC1 operations at a decent weight/payload.
Furthermore I keep hearing that PC1 operations are not possible offshore due to several constraints and too variable weather/environment conditions.
At AW we think differently and we worked hard to provide several Cat A procedures one of which is specific for offshore operations.
We realized the peculiarity of this environment and we understand that in several situations PC1 is not possible. But we also think that in several scenarios this is possible and it is much safer if this actually carried out.
The AW139 Cat A offshore procedure (EASA certified) provides not just full protection from engine failure but allows much greater obstacle margins than most of the current procedures.
It has been constructed based on operation requirements and with pilot work load in mind.
This procedure does not implies pitch variations greater than -10° and +5° during the take off profile regardless there is an engine failure or not. The take off maneuver has a delta TQ application that is proportional to the hover performance in order to keep the RTO ballooning at the same height.
The TDP is the lowest possible (20 ft) but rotation point is at 30 ft in AEO and OEI.
The deck edge clearance is at least 100 m in the worst conditions with take off from the center of the deck.
The biggest drop down you can ever experience is 50 ft at max weight (6800 kg) during take off and not lower than 0 ft for a balked landing.
All this is at zero wind.
There is very little weight penalty in most of the hottest ambient conditions and almost no penalty with just 5 kts of factored wind.
This is not meant as sale pitch but an attempt to provide evidence that safety is not just performance but also obstacle clearance, power margins, controllability margins, easy to fly and a good pilot confidence.
I hope that PC1 offshore (and on shore) will be used all the times this will be feasible and I hope operators will give us all the necessary feedbacks in order to make the operations safer.
PC2e has been invented most likely because most of the helicopter used in offshore can not afford PC1 operations at a decent weight/payload.
Furthermore I keep hearing that PC1 operations are not possible offshore due to several constraints and too variable weather/environment conditions.
At AW we think differently and we worked hard to provide several Cat A procedures one of which is specific for offshore operations.
We realized the peculiarity of this environment and we understand that in several situations PC1 is not possible. But we also think that in several scenarios this is possible and it is much safer if this actually carried out.
The AW139 Cat A offshore procedure (EASA certified) provides not just full protection from engine failure but allows much greater obstacle margins than most of the current procedures.
It has been constructed based on operation requirements and with pilot work load in mind.
This procedure does not implies pitch variations greater than -10° and +5° during the take off profile regardless there is an engine failure or not. The take off maneuver has a delta TQ application that is proportional to the hover performance in order to keep the RTO ballooning at the same height.
The TDP is the lowest possible (20 ft) but rotation point is at 30 ft in AEO and OEI.
The deck edge clearance is at least 100 m in the worst conditions with take off from the center of the deck.
The biggest drop down you can ever experience is 50 ft at max weight (6800 kg) during take off and not lower than 0 ft for a balked landing.
All this is at zero wind.
There is very little weight penalty in most of the hottest ambient conditions and almost no penalty with just 5 kts of factored wind.
This is not meant as sale pitch but an attempt to provide evidence that safety is not just performance but also obstacle clearance, power margins, controllability margins, easy to fly and a good pilot confidence.
I hope that PC1 offshore (and on shore) will be used all the times this will be feasible and I hope operators will give us all the necessary feedbacks in order to make the operations safer.
bpaggi
Its well known that the 139 has very good OEI performance, making an engine failure in nearly any phase of flight a non-event.
However the penalty for that is large engines with poor cruise fuel consumption, resulting in an aircraft that has poor range-payload.
When the manufacturers can produce a helicopter with good OEI performance AND good range-payload, it will be a good helicopter indeed. In the mean time, personally I prefer the low stress of good range-payload in my 225 rather than the elimination of one way to crash (engine failure during exposure) which is very far down on the list of ways to crash in terms of occurrance rate.
HC
Its well known that the 139 has very good OEI performance, making an engine failure in nearly any phase of flight a non-event.
However the penalty for that is large engines with poor cruise fuel consumption, resulting in an aircraft that has poor range-payload.
When the manufacturers can produce a helicopter with good OEI performance AND good range-payload, it will be a good helicopter indeed. In the mean time, personally I prefer the low stress of good range-payload in my 225 rather than the elimination of one way to crash (engine failure during exposure) which is very far down on the list of ways to crash in terms of occurrance rate.
HC
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HeliComparator
You're right on the low occurrences of crashes due engine failures. My point is another.
The huge difference in flying aircraft like the 139 is not in the OEI performance (that are anyway outstanding) is the daily operation carried out in AEO conditions as I stressed in my post.
Safety in operations on helidecks are also provided by good AEO power margins, aircraft controllability, cross wind capability (45 kts at all azimuth for the 139) and possibility to carry out approaches, landing and take offs with the best obstacle clearance possible.
At AW we did not traded safety with range, on the contrary we have provided the highest safety standard with the best range capability in its class.
I hope you'll never brief your passengers that the aircraft are flying in has a very good range but some exposure in the most critical part of the flight!
You're right on the low occurrences of crashes due engine failures. My point is another.
The huge difference in flying aircraft like the 139 is not in the OEI performance (that are anyway outstanding) is the daily operation carried out in AEO conditions as I stressed in my post.
Safety in operations on helidecks are also provided by good AEO power margins, aircraft controllability, cross wind capability (45 kts at all azimuth for the 139) and possibility to carry out approaches, landing and take offs with the best obstacle clearance possible.
At AW we did not traded safety with range, on the contrary we have provided the highest safety standard with the best range capability in its class.
I hope you'll never brief your passengers that the aircraft are flying in has a very good range but some exposure in the most critical part of the flight!
bpaggi
To me your post seemed primarily about CAT A which is surely mostly about engine failure accountability? But I totally agree that good AEO performance is important for safe day-to-day operations. I have never flown the 139 and I don't know what its AEO performance is like. I do seem to recall that AEO max gross weight has recently been increased and this is surely only to improve the range-payload, not to improve safety, so AW is not totally saintly in this regard!
A safe helicopter has the attributes you mentioned, but also others such as good visibility from the cockpit, carefree handling including intuitive automation, and a good HMI. Those are the bits that help reduce operational accidents, but of course there is also the design of the mechanical bits - eg failure modes all identified and allowed for, good VHM system etc. and just plain high reliability of critical bits!
I don't know where the 139 stands on these points, but I do notice that it hasn't had much market share in terms of offshore helicopter sales. Why do you think that is?
HC
daily operation carried out in AEO conditions as I stressed in my post
A safe helicopter has the attributes you mentioned, but also others such as good visibility from the cockpit, carefree handling including intuitive automation, and a good HMI. Those are the bits that help reduce operational accidents, but of course there is also the design of the mechanical bits - eg failure modes all identified and allowed for, good VHM system etc. and just plain high reliability of critical bits!
I don't know where the 139 stands on these points, but I do notice that it hasn't had much market share in terms of offshore helicopter sales. Why do you think that is?
HC
bpaggi
That's about 180 aircraft for offshore then, which is a lot. There are none that I can think of in N N Sea, not aware of any in SNS maybe 1 or 2 in Holland, so out of curiosity, where are they all? (yes, I know its a big world outside of UK waters!).
Oh just thought - do you mean "options" or "ordered" or "delivered" when you say "sold"?
HC
That's about 180 aircraft for offshore then, which is a lot. There are none that I can think of in N N Sea, not aware of any in SNS maybe 1 or 2 in Holland, so out of curiosity, where are they all? (yes, I know its a big world outside of UK waters!).
Oh just thought - do you mean "options" or "ordered" or "delivered" when you say "sold"?
HC
In providing the analysis of exposure on one of the first pages of this thread, I inadvertently placed the 20kts wind into the >20 and <30 grouping. This had a substantial effect on the outcome of the analysis because that was the mean wind. This was pointed out by HC but it did not immediately sink in at the time.
I apologise for those who were mislead - I have corrected the original post and have put it 'in quotes' in this post. In fact, the effect of the revision of the analysis shows that I overestimated the amount of flights that would still be exposed when complying with the regulations.
Jim
I apologise for those who were mislead - I have corrected the original post and have put it 'in quotes' in this post. In fact, the effect of the revision of the analysis shows that I overestimated the amount of flights that would still be exposed when complying with the regulations.
Jim
Here is an attempt to quantify the benefit of the extant regulation with respect to the reduction in Exposure; in order to do this it is necessary to establish those operations which are potentially:
INTOPS provided us with 39,131 North Sea wind data points (reports) for a four year period. Using this data we established that:
Using the figures shown above, we are able to estimate the likely proportions of: non-exposed; potentially non-exposed; and potentially exposed, operations.
Non-Exposed
Wind at or below 20kts in all sectors:
However, each aircraft has a zero drop down mass that is associated with an unfactored wind - if we assume that this wind is 30kts (not an unreasonable assumption given the figures provided in the calculated masses) then PC2e (without exposure) can be flown for an additional (30/360 x 20%) 1.7% of flights – i.e. when the wind is > 30kts and in the (30°) LOS (no obstacles above deck height).
This raises the non-exposed operations to 80.7%.
Potentially Non-Exposed
Wind >30kts and in the 150° obstacle sector
The exception to this occurs on those decks with turbulent sectors; this is, and should continue to be, dealt with in the HLL.
Potentially Exposed
Wind is >20 and <30 and in the 180° sector
Operations without exposure are likely to be 80.7% of the total.
Operations where exposure tends to zero is likely to be 8.3% of the total.
Operations with exposure is likely to be 11% of the total.
Conclusions
Whilst there are operations in the North Sea where there is de facto no exposure, this has never been quantified (apart from operations with the AW139). Using the actual wind data and the examples of masses shown previously this can now be done.
We continue to base the take-off and landing masses on the clear area WAT just so we can establish the second segment climb – this is no longer satisfactory.
There were several reasons why there were change to the regulations, the most important of which was to provide a signal to manufacturers that future aircraft should be capable of providing exposure free operations.
To do nothing but justify what is already done will result in the continuation in operation of existing underpowered models and hold out the prospect of no change in the future.
without exposure; and
where exposure might remain.
Firstly we need a reasonable basis for assessment. During the modelling of PC2e, access was provided to an operator’s database of weather reports (INTOPS).where exposure might remain.
INTOPS provided us with 39,131 North Sea wind data points (reports) for a four year period. Using this data we established that:
Wind <= 20kts occurred in 22,725 reports or 58%
Wind >20kts but <30kts occurred in 8,577 or 22%
Wind >30kts occurred in 7,829 reports or 20%
The following assessment assumes a helideck which is compliant with Annex 14 Volume II – as implemented in Cap 437. The orientation is not assessed but it is assumed that, if the CAP 437 recommendations have been followed, the Obstacle Free Sector is oriented into the prevailing wind; if this is the case, the figures shown below will be pessimistic.Wind >20kts but <30kts occurred in 8,577 or 22%
Wind >30kts occurred in 7,829 reports or 20%
Using the figures shown above, we are able to estimate the likely proportions of: non-exposed; potentially non-exposed; and potentially exposed, operations.
Non-Exposed
Wind at or below 20kts in all sectors:
Pure PC2 can be flown in 58% of all take-off or landing cases
Wind in excess of 20kts occurring in the 180° sector: PC2e can be flown in 21% of all take-off or landing cases
This accounts for 79% of take-off and landings.However, each aircraft has a zero drop down mass that is associated with an unfactored wind - if we assume that this wind is 30kts (not an unreasonable assumption given the figures provided in the calculated masses) then PC2e (without exposure) can be flown for an additional (30/360 x 20%) 1.7% of flights – i.e. when the wind is > 30kts and in the (30°) LOS (no obstacles above deck height).
This raises the non-exposed operations to 80.7%.
Potentially Non-Exposed
Wind >30kts and in the 150° obstacle sector
PC2e with zero drop down occurs for (150/360 x 20%) 8.3% of flights
In these cases, exposure is undefined but is tending to zero. As the wind increases all aircraft reach the point where OEI HOGE is achieved (just below the lowest Vtoss). The exception to this occurs on those decks with turbulent sectors; this is, and should continue to be, dealt with in the HLL.
Potentially Exposed
Wind is >20 and <30 and in the 180° sector
We have 11% of flights where, potentially, there would be exposure.
In SummaryOperations without exposure are likely to be 80.7% of the total.
Operations where exposure tends to zero is likely to be 8.3% of the total.
Operations with exposure is likely to be 11% of the total.
Conclusions
Whilst there are operations in the North Sea where there is de facto no exposure, this has never been quantified (apart from operations with the AW139). Using the actual wind data and the examples of masses shown previously this can now be done.
We continue to base the take-off and landing masses on the clear area WAT just so we can establish the second segment climb – this is no longer satisfactory.
There were several reasons why there were change to the regulations, the most important of which was to provide a signal to manufacturers that future aircraft should be capable of providing exposure free operations.
To do nothing but justify what is already done will result in the continuation in operation of existing underpowered models and hold out the prospect of no change in the future.
Last edited by JimL; 29th Mar 2010 at 13:32. Reason: Spelling and grammar
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Deck size / FAA Approval
Do you see the CAT A offshore TO/LDG profile being FAA approved in the near future? Also someone at Augusta needs to talk to Gulf of Mexico operators and understand a different enviroment than other areas in the world. The biggest concern, deck size, the current deck size, 72x72' only on a few floaters coming into the gulf. 50'x50' deck are more common while 40'x40' decks even more popular. Augusta needs to talk to GOM operators and get the certification and for the smallest deck the operators operate from.
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The US needs to outlaw under size decks!
The shake up after Deepwater Horizon and the replacement of the lax MMS regieme will only increase the chances of rigorous enforcement of sensible, internationally compatible, requirements.
The shake up after Deepwater Horizon and the replacement of the lax MMS regieme will only increase the chances of rigorous enforcement of sensible, internationally compatible, requirements.
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139GOM: Are you talking about Augusta, Georgia? Who in Augusta, Georgia cares about the GOM?
Call me cynical, but I don't think much is going to change. The oil companies care about only short-term profits, because that's what management bonuses are based on. They will resist to end anything which might lower those, and won't spend money on new heliports unless forced to by regulation. New regulation, after the investment of a few hundred thousand dollars in campaign contributions, is unlikely.
Call me cynical, but I don't think much is going to change. The oil companies care about only short-term profits, because that's what management bonuses are based on. They will resist to end anything which might lower those, and won't spend money on new heliports unless forced to by regulation. New regulation, after the investment of a few hundred thousand dollars in campaign contributions, is unlikely.
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Just read the October 15th inputs to this thread. Looking backward, there was a flurry of activity in the February-March timeframe, but nothing between then and October 15th.
Back in February-March it was stated that PC2e is a quasi-PC1 procedure that provides zero-exposure engine failure accountability, but apparently with a reduced useful load. The ensuing debate discussed the merits of pure PC2 vs PC2e, even speculating that for various reasons pure PC2 might be safer than PC2e.
It was also mentioned that the implementation of PC2e had slipped from January 1st to July 1st 2010. July 1st has passed, so does anyone know the current status of PC2e? Is it now implemented or has the implementation been further deferred?
Back in February-March it was stated that PC2e is a quasi-PC1 procedure that provides zero-exposure engine failure accountability, but apparently with a reduced useful load. The ensuing debate discussed the merits of pure PC2 vs PC2e, even speculating that for various reasons pure PC2 might be safer than PC2e.
It was also mentioned that the implementation of PC2e had slipped from January 1st to July 1st 2010. July 1st has passed, so does anyone know the current status of PC2e? Is it now implemented or has the implementation been further deferred?
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ZALT PC1/PC2e is an essential part of 7/7=1 which Shell launched nearly 6 years ago. Obviously it took time for the OEMs to put procedures in place and to get higher performance machines in place, but such an important part of 7/7=1 was high priority and helped drive many fleet renewals around the world with EC225, S-92, AW139. EC155, EC135 etc.