Performance class two enhanced (offshore)
Just a couple of other points that should be made:
There was considerable pressure put on the working group by some NAAs and those oil companies who wanted an elimination of the risk of engine failure that, theoretically, a move to PC1 should have provided.
Before NPA-38 was written, there was a time when existing profiles were being considered and risks/benefits quantified. Profiles included those from manufacturers and those resulting from the HAPS modelling – one was for the Bell 212 which I shall return to later in this post.
Further work on the quantification of the exposure periods resulted from examination of the Power-loss Exposure Risk Reports (PERRs) produced by the manufacturers - although some of these PERRs included the HAPS profiles, some did not. (You will remember that the HAPS profiles were intended to reduce risk – one of which results from the degraded FOV that occurs as a result of inappropriate landing procedures. A number of manufacturer’s profiles did not have this as their primary consideration - this might have been as a result of previous certification regulations, the re-use of onshore profiles or a concentration on payload over FOV.)
In order to estimate the effect on payload of the move to HAPS profiles with mass calculations; further modelling was undertaken, using first the HAPS model, and then EUROPA (remember that HAPS is a two-dimensional model whereas EUROPA is three dimensional – the third dimension being required to model the sidestep manoeuvre on landing). Once wind was factored into the modelling, it became clear that the effect on payloads would not be severe except, perhaps, in nil wind conditions and specifically, for drop down. To estimate the effect of environmental conditions on the whole solution, several years of wind data were downloaded from the INTOPS data base (along with temperature and pressure) and conclusions reached.
One disappointment that resulted from the modelling was the realisation that it was extremely difficult to come up with a single metric (from existing data) to provide ease of calculation; the data was presented using ’OEI ratio’ as a common metric but with the three types (a medium, a larger twin and a triple), the ratio for take-off at MUAM in nil wind conditions was respectively 1.36, 1.29 and 1.16 – clearly too wide to provide a basis for the solution. (It was probably the length of fuselage that caused the wide spread).
The output from modelling was collated and the results were presented to all working groups, operators, manufacturers and Authorities – it looked extremely promising. It was agreed to go ahead and replace the requirement for PC1 in 2010 with PC2 (and PC2e); NPA-38 was produced, accepted and the rest is history.
To return to the Bell profile; Bell were one of the first manufacturers to provide a CAT A Helideck procedure. They decided that the best solution (addressing operational constraints) was to utilise an upwards and sideways acceleration. This provided two benefits: the FOV to/from the deck would not be an issue; and the TDP would be positioned at the same point as the LDP. In the event, the procedure was ahead of its time and was not extensively used. It does continue to be used at Bell and evidence of it can be seen in the CAT A procedures for the B427 and B429 (and a very comfortable procedure it is - as those who have flown it will testify)
However, now that examination of the wind data shows that about 37% of the total departures could occur when the helicopter is facing into the 150° obstacle sector, it might be time for operators to revisit the merits of the Bell 212 take-off on those occasions. No, this is not an answer to issues with turbulent winds from the 150° sector (some of which are addressed in the HLL) but, as has already been explained, this is not a process that always has a deterministic outcome – and explains why the authors of AL5, quite righty, put PC2e in the Exposure loop.
In addition, this profile (or a form of it) can be used for departures from a well-head platform – particularly when flown with more powerful helicopters. With an engine failure before RP in the departure, the deck will remain in sight and a reject can be quite easily undertaken. This is a matter of training only – the performance figures should not be substantially altered (in fact it may assist because I am informed that there is a penalty applied by some operators)
None of this affects the 80% - 90% of departures which could now be undertaken without exposure.
Oh, and I still have not had the answer the question “how much endurance does the EC225 have with a take-off mass of 10,875 and 19 passengers”. Perhaps one of you can PM me the answer to that.
Jim
There was considerable pressure put on the working group by some NAAs and those oil companies who wanted an elimination of the risk of engine failure that, theoretically, a move to PC1 should have provided.
Before NPA-38 was written, there was a time when existing profiles were being considered and risks/benefits quantified. Profiles included those from manufacturers and those resulting from the HAPS modelling – one was for the Bell 212 which I shall return to later in this post.
Further work on the quantification of the exposure periods resulted from examination of the Power-loss Exposure Risk Reports (PERRs) produced by the manufacturers - although some of these PERRs included the HAPS profiles, some did not. (You will remember that the HAPS profiles were intended to reduce risk – one of which results from the degraded FOV that occurs as a result of inappropriate landing procedures. A number of manufacturer’s profiles did not have this as their primary consideration - this might have been as a result of previous certification regulations, the re-use of onshore profiles or a concentration on payload over FOV.)
In order to estimate the effect on payload of the move to HAPS profiles with mass calculations; further modelling was undertaken, using first the HAPS model, and then EUROPA (remember that HAPS is a two-dimensional model whereas EUROPA is three dimensional – the third dimension being required to model the sidestep manoeuvre on landing). Once wind was factored into the modelling, it became clear that the effect on payloads would not be severe except, perhaps, in nil wind conditions and specifically, for drop down. To estimate the effect of environmental conditions on the whole solution, several years of wind data were downloaded from the INTOPS data base (along with temperature and pressure) and conclusions reached.
One disappointment that resulted from the modelling was the realisation that it was extremely difficult to come up with a single metric (from existing data) to provide ease of calculation; the data was presented using ’OEI ratio’ as a common metric but with the three types (a medium, a larger twin and a triple), the ratio for take-off at MUAM in nil wind conditions was respectively 1.36, 1.29 and 1.16 – clearly too wide to provide a basis for the solution. (It was probably the length of fuselage that caused the wide spread).
The output from modelling was collated and the results were presented to all working groups, operators, manufacturers and Authorities – it looked extremely promising. It was agreed to go ahead and replace the requirement for PC1 in 2010 with PC2 (and PC2e); NPA-38 was produced, accepted and the rest is history.
To return to the Bell profile; Bell were one of the first manufacturers to provide a CAT A Helideck procedure. They decided that the best solution (addressing operational constraints) was to utilise an upwards and sideways acceleration. This provided two benefits: the FOV to/from the deck would not be an issue; and the TDP would be positioned at the same point as the LDP. In the event, the procedure was ahead of its time and was not extensively used. It does continue to be used at Bell and evidence of it can be seen in the CAT A procedures for the B427 and B429 (and a very comfortable procedure it is - as those who have flown it will testify)
However, now that examination of the wind data shows that about 37% of the total departures could occur when the helicopter is facing into the 150° obstacle sector, it might be time for operators to revisit the merits of the Bell 212 take-off on those occasions. No, this is not an answer to issues with turbulent winds from the 150° sector (some of which are addressed in the HLL) but, as has already been explained, this is not a process that always has a deterministic outcome – and explains why the authors of AL5, quite righty, put PC2e in the Exposure loop.
In addition, this profile (or a form of it) can be used for departures from a well-head platform – particularly when flown with more powerful helicopters. With an engine failure before RP in the departure, the deck will remain in sight and a reject can be quite easily undertaken. This is a matter of training only – the performance figures should not be substantially altered (in fact it may assist because I am informed that there is a penalty applied by some operators)
None of this affects the 80% - 90% of departures which could now be undertaken without exposure.
Oh, and I still have not had the answer the question “how much endurance does the EC225 have with a take-off mass of 10,875 and 19 passengers”. Perhaps one of you can PM me the answer to that.
Jim
Last edited by JimL; 22nd Apr 2010 at 06:38. Reason: Correction of the proportion of exposed flights
Join Date: May 2002
Location: tomorrowland
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
HV curve
Geoff,
what you say about the HV curve, is wrong.
CS29.59(a)(1) "Take-off path:Category A" establishes the requiremnts .
If a Cat A profile penetrates the "true" HV envelope a Rejected Take-off /Landing can not be carried out.
The "true" HV envelope is a family of variable HV envelope as a function of the Take-off/Landing Mass and density altitude.
Quite often, manufacturers do not spend to many efforts in defining the HV curves but simply presents the biggest envelope valid for the maximum density altitude and Maximum Take off/Landing mass.
In this case a Cat A vertical TO/Land procedure, carried out at a specified mass and at a specified DA, migth cross the HV.
But if it has been demonstrated that in those condition a RTO/OEI Land can be carried out, no doubt that the trajectory is outside the HV.
The region outside the HV envelope is a safe OEI reject take off and landing area. And this is also the requirements defined by Cat A.
gmrwiz
what you say about the HV curve, is wrong.
CS29.59(a)(1) "Take-off path:Category A" establishes the requiremnts .
If a Cat A profile penetrates the "true" HV envelope a Rejected Take-off /Landing can not be carried out.
The "true" HV envelope is a family of variable HV envelope as a function of the Take-off/Landing Mass and density altitude.
Quite often, manufacturers do not spend to many efforts in defining the HV curves but simply presents the biggest envelope valid for the maximum density altitude and Maximum Take off/Landing mass.
In this case a Cat A vertical TO/Land procedure, carried out at a specified mass and at a specified DA, migth cross the HV.
But if it has been demonstrated that in those condition a RTO/OEI Land can be carried out, no doubt that the trajectory is outside the HV.
The region outside the HV envelope is a safe OEI reject take off and landing area. And this is also the requirements defined by Cat A.
gmrwiz
Just to round up the data that was shown on the earlier posts, I have added the S92 masses to those which have already been provided.
Just in case you do not wish to read the other posts, the figures are:
For the S-92:
Taking ISA SL conditions the following masses are provided by the graphs:
Take-off:
Jim
Just in case you do not wish to read the other posts, the figures are:
For the S-92:
Taking ISA SL conditions the following masses are provided by the graphs:
Take-off:
The Pure PC2 mass is 26,250lbs
The PC2e mass with an unfactored wind of 20kts is:
Landing:The PC2e mass with an unfactored wind of 20kts is:
26,500lbs for a 50ft drop down
Zero drop down is achieved with an unfactored wind of 30ktsThe Pure PC2 mass is 26,500lbs
The PC2e mass with an unfactored wind of 20kts is:
The answer to my question about the endurance of the 225 with 19 passengers appears to be about 2:18 endurance (plus 10% and final reserve fuel).The PC2e mass with an unfactored wind of 20kts is:
26,500lbs for zero drop down
Zero drop down is achieved with an unfactored wind of 20ktsJim
Join Date: Dec 2001
Location: Philadelphia PA
Age: 73
Posts: 1,835
Likes: 0
Received 2 Likes
on
2 Posts
gmrwiz:
The Category A profiles will have been flown and tested to be safe. There will be a statement in the front of the Category A supplement (if there is a supplement) that the HV curve is no longer applicable when using the performance and procedures for Category A.
Mixing apples and oranges.
The Category A profiles will have been flown and tested to be safe. There will be a statement in the front of the Category A supplement (if there is a supplement) that the HV curve is no longer applicable when using the performance and procedures for Category A.
Mixing apples and oranges.
Join Date: Oct 2003
Location: UK
Posts: 510
Likes: 0
Received 0 Likes
on
0 Posts
JimL,
Thanks for the insight into PC2e which I thought was dead as far as the North Sea is concerned?
Alot of what you have put on here shows how much impact PC2e would have over the current status quo.
Some observations:
Whilst new decks have to be designed according to CAP 437 (IIRC) there are plenty of existing decks out there which don't seem to comply according to my layman's eye. These are the decks which will (should) really feel the impact of PC2e and to be honest, we would be better served by a new deck rather than new paper work.
You sight seastate 4 as a limit for what can be considered a "safe" ditching. Surely that is aircraft specific (stability and float fit and so on). To limit PC2e to SS 4 might be a disincentive to offer/buy SS5 or SS6 float kits. Also evaluation of seastate is location specific (which wave spectrum to use) and subjective - who is qualified to judge?
It is going to be interesting to see how PC2e will be introduced and what training will be required to fly it.
Thanks for the insight into PC2e which I thought was dead as far as the North Sea is concerned?
Alot of what you have put on here shows how much impact PC2e would have over the current status quo.
Some observations:
Whilst new decks have to be designed according to CAP 437 (IIRC) there are plenty of existing decks out there which don't seem to comply according to my layman's eye. These are the decks which will (should) really feel the impact of PC2e and to be honest, we would be better served by a new deck rather than new paper work.
You sight seastate 4 as a limit for what can be considered a "safe" ditching. Surely that is aircraft specific (stability and float fit and so on). To limit PC2e to SS 4 might be a disincentive to offer/buy SS5 or SS6 float kits. Also evaluation of seastate is location specific (which wave spectrum to use) and subjective - who is qualified to judge?
It is going to be interesting to see how PC2e will be introduced and what training will be required to fly it.
Droopystop,
The issues should not be confused; an existing deck which does not fully meet CAP 437 compliance will/should be limited by the HLL - this will not change with compliance with the requirement (i.e. no real change there).
It is not clear to me (from the numbers that have been posted) that the impact would be severe for modern aircraft. Look again at the operating masses for your particular aircraft and see what the impact would be. For example, if you are operating the EC155 in zero wind the Pure PC2 mass is 4,750kg - the restricted operating mass with less than 5 kts wind is 4,620kg (which should continue to be applied) and with up to 10 kts, 4,770. In this case the problem is with the aircraft not the system.
There is no Sea State limit on PC2e; the regulation permits Pure PC2 when a Safe-Forced-Landing can be carried out. It is generally accepted (borne out by the ditching approval which mandates the SS4 requirement for all helicopters - and sets the parameters) that a SFL can be achieved in SS4.
For Sea States over 4, PC2e should (in the majority of cases - see my post on the effect of compliance) provide engine-failure accountability. The hard break of 20kts wind between PC2 and PC2e (should it be accepted) will make this transition seamless.
If you have been flying the HAPS procedures (as described in JARs) there should be no substantial change in procedures.
Jim
The issues should not be confused; an existing deck which does not fully meet CAP 437 compliance will/should be limited by the HLL - this will not change with compliance with the requirement (i.e. no real change there).
It is not clear to me (from the numbers that have been posted) that the impact would be severe for modern aircraft. Look again at the operating masses for your particular aircraft and see what the impact would be. For example, if you are operating the EC155 in zero wind the Pure PC2 mass is 4,750kg - the restricted operating mass with less than 5 kts wind is 4,620kg (which should continue to be applied) and with up to 10 kts, 4,770. In this case the problem is with the aircraft not the system.
There is no Sea State limit on PC2e; the regulation permits Pure PC2 when a Safe-Forced-Landing can be carried out. It is generally accepted (borne out by the ditching approval which mandates the SS4 requirement for all helicopters - and sets the parameters) that a SFL can be achieved in SS4.
For Sea States over 4, PC2e should (in the majority of cases - see my post on the effect of compliance) provide engine-failure accountability. The hard break of 20kts wind between PC2 and PC2e (should it be accepted) will make this transition seamless.
If you have been flying the HAPS procedures (as described in JARs) there should be no substantial change in procedures.
Jim
Last edited by JimL; 22nd Apr 2010 at 06:36. Reason: Correction of 155 masses
Join Date: Aug 2001
Location: Cornwall
Age: 75
Posts: 1,307
Likes: 0
Received 0 Likes
on
0 Posts
Deck Design
Excuse me but I could not help but chuckle when I read the assertion that all new decks are built to CAP 437. My experience is that the first time anyone gets to look over 437 is when it's being towed out to the field and the oil company rep is scratching his head wondering how the vent stack ended up in the 210 sector. And that's in Europe - You should take a look at what goes on elsewhere - and no HLL either. When I see pictures of some of the GoM decks I wonder if we are on the same planet.
G.
G.
Join Date: May 2002
Location: tomorrowland
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Shawn,
I am not mixing anything.
I am just pointing out what the airworthiness code (european and american) requires:
[QUOTE CS 29.59 Takeoff Path: Category A
(a) The takeoff path extends from the point of commencement of the takeoff
procedure to a point at which the rotorcraft is 305 m (1000 ft) above the takeoff surface and compliance with CS 29.67 (a) (2) is shown. In addition:
(1) The takeoff path must remain clear of the heightvelocity envelope established in accordance with CS 29.87.[/QUOTE]
And this is logic because 29.87 establishes:
[QUOTE 29.87 Heightvelocity envelope
(a) If there is any combination of height and forward velocity (including hover) under which a safe landing cannot be made after failure of the
critical engine and with the remaining engines (where applicable) operating within approved limits, a heightvelocityenvelope must be established for:
(1) All combinations of pressure altitude and ambient temperature for which
takeoff and landing are approved; and
(2) Weight, from the maximum weight (at sealevel) to the highest weight approved for takeoff and landing at each altitude. For helicopters, this weight need not exceed the highest weight allowing hovering out of ground
effect at each altitude.[/QUOTE]
In other words the Cat A and the H-V requirements prescribe to carry out a safe landing after an engine failure.
The only difference is that H-V does not require to reject on the take-off area while Cat A requires.
By the way I have never seen in the Flight manual Cat A Supplement the statement you mention that H-V is not applicable to Cat A.
gmrwiz
I am not mixing anything.
I am just pointing out what the airworthiness code (european and american) requires:
[QUOTE CS 29.59 Takeoff Path: Category A
(a) The takeoff path extends from the point of commencement of the takeoff
procedure to a point at which the rotorcraft is 305 m (1000 ft) above the takeoff surface and compliance with CS 29.67 (a) (2) is shown. In addition:
(1) The takeoff path must remain clear of the heightvelocity envelope established in accordance with CS 29.87.[/QUOTE]
And this is logic because 29.87 establishes:
[QUOTE 29.87 Heightvelocity envelope
(a) If there is any combination of height and forward velocity (including hover) under which a safe landing cannot be made after failure of the
critical engine and with the remaining engines (where applicable) operating within approved limits, a heightvelocityenvelope must be established for:
(1) All combinations of pressure altitude and ambient temperature for which
takeoff and landing are approved; and
(2) Weight, from the maximum weight (at sealevel) to the highest weight approved for takeoff and landing at each altitude. For helicopters, this weight need not exceed the highest weight allowing hovering out of ground
effect at each altitude.[/QUOTE]
In other words the Cat A and the H-V requirements prescribe to carry out a safe landing after an engine failure.
The only difference is that H-V does not require to reject on the take-off area while Cat A requires.
By the way I have never seen in the Flight manual Cat A Supplement the statement you mention that H-V is not applicable to Cat A.
gmrwiz
Join Date: Aug 2008
Location: Aberdeen
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
"The answer to my question about the endurance of the 225 with 19 passengers appears to be about 2:18 endurance (plus 10% and final reserve fuel)."
As per my PM to you, in the 225s I fly you can lift with 4800lbs of fuel plus 19 pax and around 500lbs of baggage, if not more. At a burn rate of 1400lbs per hour this is 3 hours 25 minutes to tanks dry. (BTW, this is how I have always calculated endurance; if I am supposed to take off final reserve fuel and 10% then it is news to me).
As per my PM to you, in the 225s I fly you can lift with 4800lbs of fuel plus 19 pax and around 500lbs of baggage, if not more. At a burn rate of 1400lbs per hour this is 3 hours 25 minutes to tanks dry. (BTW, this is how I have always calculated endurance; if I am supposed to take off final reserve fuel and 10% then it is news to me).
Thanks Paul,
Perhaps I ought to have set out my thinking; I was trying to establish whether take-off mass of 10,875kg would be limiting - i.e. if I had to move 19 pax and their bags, would such a mass result in me flying with less fuel.
It wasn't so much endurance that I was looking for but the length of leg (plus any alternate) that could be flown. If this were to be planned, then it would consist of (simplistically):
I'm not sure that any of this matters too much now because it is becoming clear that compliance with the rule does not result in additional risk due to either: a limitation on the amount of fuel that can be carried; or, a reduction in passenger loads such that additional sectors would have to be flown.
Jim
Perhaps I ought to have set out my thinking; I was trying to establish whether take-off mass of 10,875kg would be limiting - i.e. if I had to move 19 pax and their bags, would such a mass result in me flying with less fuel.
It wasn't so much endurance that I was looking for but the length of leg (plus any alternate) that could be flown. If this were to be planned, then it would consist of (simplistically):
Leg fuel (and alternate if one were required)
Contingency fuel of 10%
Final reserve fuel of 30 minutes
Subtracting my FRF and then 10% contingency provided the maximum fuel for the leg(s) which was 2:18 (the useful time that could be planned for any leg(s)). The only difference was that I used a fuel burn of 1440lbs/hr.Contingency fuel of 10%
Final reserve fuel of 30 minutes
I'm not sure that any of this matters too much now because it is becoming clear that compliance with the rule does not result in additional risk due to either: a limitation on the amount of fuel that can be carried; or, a reduction in passenger loads such that additional sectors would have to be flown.
Jim
Jim
A few thoughts, though insufficient time for a comprehensive post:
1) The figures I have for INTOPS wind bear no relation to what you posted earlier. Its much more common to have wind <20kts
2) Even if we assume that your gentleman's agreement that SS4 is acceptable for SFL, how do we the pilots know what the current SS is? Do all offshore installation have such measuring equipment? Would it be accepted by the regulator?
3) If I could always takeoff in my 225 at 10875kg then this reg would not be much of an issue, but you are chosing your data carefully to make the best of it.
4) You are using graphs from EC that require 30' TDP for deck edge clearance, this is getting dangerously high for night (or even day with my flying)
Finally, if you are saying that the impact of this reg is insignificant in terms of fuel, payload etc, then what you are equally saying is there will be no change in the general risk from engine failure compared to now (since you will not be making us fly any lighter), and what you are doing is introducing a huge level of additional complexity (viz EC PC2e supplement running to 49 pages) that you expect pilots to comply with "in anger" eg during the normal in-flight route changes, weather changes etc. Pilot A - heads down trying to read the graphs at night whilst pilot B flies into the water! As I said previously, an overall reduction in safety.
HC
A few thoughts, though insufficient time for a comprehensive post:
1) The figures I have for INTOPS wind bear no relation to what you posted earlier. Its much more common to have wind <20kts
2) Even if we assume that your gentleman's agreement that SS4 is acceptable for SFL, how do we the pilots know what the current SS is? Do all offshore installation have such measuring equipment? Would it be accepted by the regulator?
3) If I could always takeoff in my 225 at 10875kg then this reg would not be much of an issue, but you are chosing your data carefully to make the best of it.
4) You are using graphs from EC that require 30' TDP for deck edge clearance, this is getting dangerously high for night (or even day with my flying)
Finally, if you are saying that the impact of this reg is insignificant in terms of fuel, payload etc, then what you are equally saying is there will be no change in the general risk from engine failure compared to now (since you will not be making us fly any lighter), and what you are doing is introducing a huge level of additional complexity (viz EC PC2e supplement running to 49 pages) that you expect pilots to comply with "in anger" eg during the normal in-flight route changes, weather changes etc. Pilot A - heads down trying to read the graphs at night whilst pilot B flies into the water! As I said previously, an overall reduction in safety.
HC
Join Date: Mar 2009
Location: UK
Age: 43
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
You should take a look at what goes on elsewhere - and no HLL either. When I see pictures of some of the GoM decks I wonder if we are on the same planet.
Join Date: Aug 2001
Location: Cornwall
Age: 75
Posts: 1,307
Likes: 0
Received 0 Likes
on
0 Posts
Too much complexity?
In my CP days we would have looked at the problem, found a suitable 'rule-of-thumb' that met the ambitions of the regulators and written that into our SOPs in 'simplespeak.
In the 80s we circumvented the prospect of line-joes mis-reading the RFM and its acres of similar looking and sometimes obscurely drawn graphs by simply stating that if you were operating from airport A, B or C (the only places we were contracted to work from/use as alternates) and you operated with 2000 feet of runway then you could use cAT A Clear Area profile every time up to 25 degrees C.
Surely if the normal procedures are followed and the risk management requirements are thereby met there is no need to get into complex pre-landing or pre-TO computations. In Risk Management terms such endeavours may actually increase risk. I think the acronym is K.. I.... S....S!
G.
In the 80s we circumvented the prospect of line-joes mis-reading the RFM and its acres of similar looking and sometimes obscurely drawn graphs by simply stating that if you were operating from airport A, B or C (the only places we were contracted to work from/use as alternates) and you operated with 2000 feet of runway then you could use cAT A Clear Area profile every time up to 25 degrees C.
Surely if the normal procedures are followed and the risk management requirements are thereby met there is no need to get into complex pre-landing or pre-TO computations. In Risk Management terms such endeavours may actually increase risk. I think the acronym is K.. I.... S....S!
G.
Join Date: Aug 2001
Location: Cornwall
Age: 75
Posts: 1,307
Likes: 0
Received 0 Likes
on
0 Posts
Mr Wizz, Shawn
I am no Test Pilot but seems to me we are talking in circles.
1. 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.
Maybe somebody who knows how this apparent conflict can fit into our understanding can explain it to me and not just quote isolated bits of the FARs/JARs without sufficient explanation.
Thanks and sorry for the minor thread-drift.
G.
1. 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.
Maybe somebody who knows how this apparent conflict can fit into our understanding can explain it to me and not just quote isolated bits of the FARs/JARs without sufficient explanation.
Thanks and sorry for the minor thread-drift.
G.
Join Date: Jul 2006
Location: Ban Don Ling
Posts: 244
Likes: 0
Received 0 Likes
on
0 Posts
Geoffers
Couldn't agree more about KISS - no-one stops to determine such data other than a RTOM/W or different rotation point. Whereas I thank JimL for his elegant elucidation of the points in question, on the line or answering the even more baffled client, we need to end up with simple reasoned profiles and procedures backed up by relevant training and supervision - and not complicate it with hypothetical gobbledeespeak forced upon us by the regulators.
Join Date: Mar 2010
Location: North America
Posts: 107
Likes: 0
Received 0 Likes
on
0 Posts
Category A Vertical Takeoffs and the H-V Curve
Geoffersincornwall and Shawn Coyle are right on target, citing “the dynamics of the situation” and that “the Category A profiles will have been flown and tested to be safe.” A helicopter climbing vertically through a 100 ft TDP is in a substantially different energy state than a helicopter hovering at 100 ft.
Subsequent to single engine failure during vertical climb through 100 ft the pilot can lower the collective stick to contain the rotor droop while the helicopter continues to ascend to its peak height. By the time the descent begins, the remaining engine will have spooled-up and the rotor speed set to just below the governed speed thereby providing that OEI maximum contingency power is available throughout the descent. That’s why helicopters like the EC155 with Certified Category A helipad procedures can climb vertically to a TDP on the order of 100 ft, and successfully land back. This will have been demonstrated at up to the maximum helipad takeoff weight for altitude and temperature by both the helicopter manufacturer and the certificating authority prior to achieving Category A certification approval.
I have not seen the EC155 Category A Helipad Flight Manual Supplement, but it’s hard to believe that it doesn’t address this issue. This is addressed for other helicopter models. For instance, in the Limitations section of the S-76C+ Category A Helipad Supplement it states that “using the procedures and gross weights described in this supplement, it has been demonstrated that safe operation within the avoid area of the height-velocity diagram can be maintained if a single engine failure occurs at any point along the takeoff and landing flight paths.”
Subsequent to single engine failure during vertical climb through 100 ft the pilot can lower the collective stick to contain the rotor droop while the helicopter continues to ascend to its peak height. By the time the descent begins, the remaining engine will have spooled-up and the rotor speed set to just below the governed speed thereby providing that OEI maximum contingency power is available throughout the descent. That’s why helicopters like the EC155 with Certified Category A helipad procedures can climb vertically to a TDP on the order of 100 ft, and successfully land back. This will have been demonstrated at up to the maximum helipad takeoff weight for altitude and temperature by both the helicopter manufacturer and the certificating authority prior to achieving Category A certification approval.
I have not seen the EC155 Category A Helipad Flight Manual Supplement, but it’s hard to believe that it doesn’t address this issue. This is addressed for other helicopter models. For instance, in the Limitations section of the S-76C+ Category A Helipad Supplement it states that “using the procedures and gross weights described in this supplement, it has been demonstrated that safe operation within the avoid area of the height-velocity diagram can be maintained if a single engine failure occurs at any point along the takeoff and landing flight paths.”
HeliComparator,
Equally short:
1. The INTOPS winds are those supplied for the PC2e modelling and had a mean of 20kts (there has been no untoward manipulation). The winds shown were for the Northern and Central North Sea; if the winds for the Southern NS are included, then the mean will reduce to below 20kts. With a mean wind <20 kts, the number of exposure free operations will increase because more operations can be flown within the 180 obstacle free sector.
2. The suggestion is that the hard break (between Pure PC2 and PC2e) should be related to reported wind (at SS4), with high sea states taken into consideration only when they are at odds with the reported wind - i.e. wind has dropped but the sea is still running high (using rule of thumb). Getting this wrong (at the margin) has no serious consequence. It is also understood that a number of companies would apply PC2e at night - particularly in Norway.
3. I would agree with you that there will be little change for the EC225 (or the S-92) - because of this, simpler metrics could be applied. For the AW139 there will be no change.
3. Yes the helideck CAT A take-off profiles have been used.
When PC2e was conceived, it was not intended to add complexity to operations. The work was done in the face of the pressure to move to operations in PC1 by 2010. The alternative (PC2e) was provided to show that the 'bar' could be raised by providing a safety-net to reduce exposure ALARP - i.e a removal of unfettered exposure offshore.
Yes the EC Supplement runs to 49 pages but it is based upon two graphs with many, many examples.
It was fully accepted that the modern types that were just about to appear on the North Sea would have no problem meeting the standard (as has been demonstrated). It was also accepted that there would be an effect on older types but it was projected that most of these would have left the North Sea by 2010 (remember that this work was started in about 2002).
There were also secondary objectives. It was felt that mass growth should be tied to a performance standard - the second segment climb performance was seen as as weak metric (that is why the AEO HOGE was brought from guidance and put into the rule - for all operations with exposure). There was a need to ensure that future aircraft had a built-in level of performance for offshore operations. (The working group were mindful of a remark that had been made at the time of the introduction of exposure that, in future, installed power could be reduced accordingly.)
A number of these objectives have already been met but some have not. The introduction (of most) of the modern types has improved the situation - this is in no small part due to the introduction of the new requirement with an implementation date of 2010. Manufacturers have strived to provide aircraft that meet the 2010 standard and they are to be congratulated for that.
Jim
Equally short:
1. The INTOPS winds are those supplied for the PC2e modelling and had a mean of 20kts (there has been no untoward manipulation). The winds shown were for the Northern and Central North Sea; if the winds for the Southern NS are included, then the mean will reduce to below 20kts. With a mean wind <20 kts, the number of exposure free operations will increase because more operations can be flown within the 180 obstacle free sector.
2. The suggestion is that the hard break (between Pure PC2 and PC2e) should be related to reported wind (at SS4), with high sea states taken into consideration only when they are at odds with the reported wind - i.e. wind has dropped but the sea is still running high (using rule of thumb). Getting this wrong (at the margin) has no serious consequence. It is also understood that a number of companies would apply PC2e at night - particularly in Norway.
3. I would agree with you that there will be little change for the EC225 (or the S-92) - because of this, simpler metrics could be applied. For the AW139 there will be no change.
3. Yes the helideck CAT A take-off profiles have been used.
When PC2e was conceived, it was not intended to add complexity to operations. The work was done in the face of the pressure to move to operations in PC1 by 2010. The alternative (PC2e) was provided to show that the 'bar' could be raised by providing a safety-net to reduce exposure ALARP - i.e a removal of unfettered exposure offshore.
Yes the EC Supplement runs to 49 pages but it is based upon two graphs with many, many examples.
It was fully accepted that the modern types that were just about to appear on the North Sea would have no problem meeting the standard (as has been demonstrated). It was also accepted that there would be an effect on older types but it was projected that most of these would have left the North Sea by 2010 (remember that this work was started in about 2002).
There were also secondary objectives. It was felt that mass growth should be tied to a performance standard - the second segment climb performance was seen as as weak metric (that is why the AEO HOGE was brought from guidance and put into the rule - for all operations with exposure). There was a need to ensure that future aircraft had a built-in level of performance for offshore operations. (The working group were mindful of a remark that had been made at the time of the introduction of exposure that, in future, installed power could be reduced accordingly.)
A number of these objectives have already been met but some have not. The introduction (of most) of the modern types has improved the situation - this is in no small part due to the introduction of the new requirement with an implementation date of 2010. Manufacturers have strived to provide aircraft that meet the 2010 standard and they are to be congratulated for that.
Jim
Jim
1) Mean of 20kts I can believe, but you said earlier that wind was 20+ for 81% of the time.
Two graphs but repeated 3 times for 3 possible values of Nr. The Nr value not surprisingly has a significant impact on deck edge clearance. So the pilots have first of all to work out what the hover Nr will be (based on density altitude and using a graph in the main part of the RFM). Assuming they are not lucky to have the Nr exactly as in one of the graphs, they then have to go into 2 sets of the graphs for 2 of the Nr values, then interpolate the answers. IMHO this is unrealistic to do in flight.
HC
1) Mean of 20kts I can believe, but you said earlier that wind was 20+ for 81% of the time.
Yes the EC Supplement runs to 49 pages but it is based upon two graphs with many, many examples.
HC
Thanks HC.
I have looked back at my text - the post with the distribution of wind is fairly clear; however, I am not an error free zone.
I could have sworn that the graphs in the Complementary Flight Manual were identical - are they different in the RFM? I agree that this should not be done in flight - haven't EC provided an EFB yet.
Going back to the text of the rule; the wording is much more flexible than it is for PC1; I can't see how it could have been more operator/pilot friendly unless it had said 'please yourself'.
Now that we have shouted ourselves hoarse, perhaps we could just sit down and make it work to everyone's advantage. Explain to me why we didn't do this over the phone or on email! Perhaps because it is not just you and I who have to understand and work with this but other operators, pilots and regulators.
This can't be more difficult than trying to establish the best Vtoss to get over that 14ft mast on the end of 14 can it?
Jim
I have looked back at my text - the post with the distribution of wind is fairly clear; however, I am not an error free zone.
I could have sworn that the graphs in the Complementary Flight Manual were identical - are they different in the RFM? I agree that this should not be done in flight - haven't EC provided an EFB yet.
Going back to the text of the rule; the wording is much more flexible than it is for PC1; I can't see how it could have been more operator/pilot friendly unless it had said 'please yourself'.
Now that we have shouted ourselves hoarse, perhaps we could just sit down and make it work to everyone's advantage. Explain to me why we didn't do this over the phone or on email! Perhaps because it is not just you and I who have to understand and work with this but other operators, pilots and regulators.
This can't be more difficult than trying to establish the best Vtoss to get over that 14ft mast on the end of 14 can it?
Jim