Helicopter Performance IFR

[Vertolot]

Hi,

Is there anybody out there who could give me some more information about the required "helicopter performance" ie. ROC for planning of an IFR flight.

As I have understand, If you are operating PC1 you will comply with an Cat A mass that will provide you with a minmum of 100 FPM/Vtoss ROC until 200 feet and 150 FPM/Vy until 1000 feet, OEI. If you are cmplying with PC2 you will have a mass that gives you 150 FPM/Vy @ 1000 feet.

If you then comply with a SID the requirements for fixed wing is 3,3% PDG (2,5% OIS + 0,8% MOC) and for helicopters 5,0% PDG (4,2% OIS + 0,8% MOC), or if an excess of standard PDG is required it should be promulgated on the SID. All these according to ICAO DOC 8168 Volume II. It also states that an emergency contingency procedure is the responsibility of the operator.

My questions are:
Q1. If you are flying an fixed wing SID with a helicopter should you comply with the requirement of 3,3% PDG?

Q2. If you have an published Copter contigency procedure, single engine. Lets say that for one runway there is a published required single engine climb gradient, but for the other runway there is no publised requirement. If there is no published minimum climb gradient, what should your minima planned climb gradient be?

Thanks in advance:ooh:

[212man]

Under JAR Ops there are no IFR minimum climb rates for the departure and en-route phases, other than those you mention and a nominal rate of climb which is effectively a 'stay level' guarantee for the en-route phase. This is 50 ft/min for PC1 and PC2.

However, you have to respect the obstacle clearance during a SID -or the oft forgotten Missed Approach - and it is up to the operator/pilot to do the calculations.

If you consider a typical minimum gradient of 2.5%, this is approx 1.5 degrees and using the 1:60 rule of thumb this gives G/S (kts) divided by 400 to give the required RoC (ft/min.) So with a Vy of 80 kts you would need to maintain 200 ft/min to achieve the profile. Of course, the logical way to do this would be to calculate the restricted mass at top of climb that equates to the minimum climb performance. You also need to be aware that this gradient is based on ground speed, and with the very low Vy KIAS values that helicopters have, relative to FW, the wind will have a huge impact on the subsequent gradient, hopefully in a positive way with a headwind.

Either way, the glaringly obvious thing taht stands out is that in general terms, operating at the Cat A RTOM you will almost certainly be unlikely to achieve the required gradient and will need to reduce the RTOM accordingly - either for the SID or the en-route mass at MSA.

AEO there is never a problem. I'm sure JimL can elaborate on the above if necessary.

FW Airlines have performance departments who look at all their destinations and calculate whether they can comply with the SIDS. Often they will devise an 'engine out SID' which may also be based on the premise of an early return, as well as performance. For an example, look up the video of the Thompson B757 with the bird strike on departure from Manchester Airport - the subsequent Mayday includes detailks of the revised departure they are following. It would be a Company Engine Out SID and likely in the secondary flight plan on the FMC.

Current FW pilots may like to correct/expand on this (Thriddle Op Des?) but I believ the gist of it to be true.

[Thridle Op Des]

Correct 212, we have two options for an EFATO, either standard EOP which is ignore the SID and climb straight ahead - MAN is a particularly good example since the SID is based on Noise Abatement and not Obstacle Clearance, of course once we had done the AN bit we could C communicate with ATC to tell them we are continuing straight ahead which is exactly what the birdstrike crews did. We also have to consider Approach Climb Gradient for an arrival which despite it's confusing title describes the Missed Approach profile with the loss of a critical engine. If the Approach Climb Gradient requirement is high as is required in HGK we have a couple of options, either raise the MDA so the obstacle is no longer limiting, or use the EOSID lateral requirement to navigate around the obstacle.

For places like ZRH the EOSIDS can be quite demanding. Our performance departments do the calculation for us and they are presented to us on the Take-Off performance computer. We then tend to construct a couple of lines in the Navigation Displays as a reminder of what to do should the engine stop which are not picked up by the NAV system but have to be flown in selected modes. Some operators have EOSIDS programmed into the FMS to call upon should the occasion arise. Just as a flavour the ZRH EOSID on RWY16 was: At KLO 2.2D, left TRK 128, Intercept KLO 141R Outbound, at KLO 4.6D, Left (190 KIAS) to KLO, Intercept KLO 253R. Hold S/W at KLO 21.0D 073 Right Turns 1 min legs.

Another issue which is largely ignored is the lateral navigation issue. Wind will help helicopters achieve excellent gradients however the same wind can easily take the helicopter out of the protected Take-Off Flight Path, this is surprisingly small, starting at 90m from the runway centre line at the end of TODA, then expanding at 12.5% until a corridor of 300m from the runway extended centre line (with sufficient navaid accuracy). Since the G/A is typically done before the threshold of the runway, straying out of the protected area is 'dead' easy. I have had direct experience with this when conducting a instrument training exercise at SUM we did a G/A, ATC instructed us to maintain RWY HDG and the 50 kt crosswind got us interestingly close to Fitful Head.

BTW only 1 'd' in Thridle!

[JimL]

Vertolot,

You have already quoted the correct documents and appear to have a reasonable idea of what is required by reading DOC 8168. Firstly for the benefit of others we probably should explain the acronyms and the use of some terms:

PDG used in 8168 means the Procedure Design Gradient - i.e the climb gradient that is required to clear all obstacles and provide the sufficient reserve divergence in height to ensure that, eventually, you will have achieved the 1,000ft (2,000ft in mountains) clearance from all obstacles (these are the two figures you provided in brackets).
Gradient is used (as opposed to a rate of climb) in order to 'normalise' the requirements and so they can be applied by any aircraft. Unlike fixed wing, most helicopter performance is provided in Rates of Climb (or height gained over distance); this will have to be converted to a gradient for your helicopter in order to satisfy the requirement of the SID.
Gradients are gradients - it does not matter to the procedure whether the aircraft on the SID is a helicopter or a fixed wing.
The PDG is either the default specified in 8168 - i.e. the 3.3% mentioned, or one that has been specified by the procedure designer. As is stated in 8168 "Unless otherwise published, a PDG of 3.3% (5% for helicopters) is assumed".
It can be assumed that the procedures are AEO because as stated in 8168:1.7 ABNORMAL AND EMERGENCY OPERATIONS

1.7.1 The design of procedures in accordance with this section assumes normal operations and that all engines are operating.

1.7.2 It is the responsibility of the operator to conduct an examination of all relevant obstacles and to ensure that the performance requirements of Annex 6 are met by the provision of contingency procedures for abnormal and emergency operations. Where terrain and/or obstacle considerations permit, the contingency procedure routing should follow that of the departure procedure.

1.7.3 It is the responsibility of the State to make available the obstacle information described in Annexes 4 and 6, and any additional information used in the design of departures in accordance with this Section.
In my view then and for Q1; if you are flying a SID you should comply with the gradient specified; if not specified you should assume the default for the type of procedure.

For Q2 (much more complicated); if you have a contingency procedure you have to adjust your performance to meet the PDG OEI. If you do not have a contingency procedure and wish to fly the SID, you should, as part of any risk assessment (which might conclude that the probability of engine failure is low enough not to require a procedure) specify the actions to be carried out in the event of an engine failure on departure.

Remember when applying an adjustment to mass to meet a PDG, the gradient is applied from the end of the runway; this can be used to your advantage because you should reach the TODRH well before the end of a fixed wing runway. Conversion of FM ROC (or height gained in a set distance) to a required gradient is a matter of simple arithmetic - but best not done in the air.

I have never been involved in providing such procedures but, if asked, I might break the departure into segments (easiest points would be at first and second climb segments) and specify actions in case of a power-unit failure at, or before, those points.

You have to remember that most of the procedures in 8168 assume a simplistic obstacle environment (the type that is usual in a fixed wing runway environment); because the Vy of a helicopter is slow compared to a fixed wing, advantage can be taken of better climb gradients (but take note of Tod's advice with regard to wind applicability - 8168 provides advice in this as well). However, the performance of the helicopter degrades much more than a fixed wing with height and some power settings are very limiting - you should be aware of these limitations and try to arrange that the strategy for an engine failure in the climb is worked out, and provided in the OM, before operations start.

This is an unusual question and one I have not heard for about 10 years - the last time was with respect to IFR departures from the southern runway at ABZ

Jim

[Vertolot]

Thanks for all the replies. These are questions I have been asked during the last OPC´s, but sometimes I feel that there is more questions than answears:O

Thanks

[Phil77]

Last edited by Thridle Op Des : 17th April 2009 at 14:09. Reason: cos pprune doesn't allow you to see the original message when you reply, so I always forget something!

Psst! just scroll down... its all below the reply box in reverse order! :ok:

[212man]

Don't mind him Phil - he's an A340 pilot, so is used to everything being brought to him by young ladies,nowadays :E

[JimL]

Vertolot,

DOC 8168 Volume II (PANS OPS) is a 'procedure writer's manual'. Only those who wish to discuss, or propose amendment of, IFR arrival or departure procedures need to be familiar with the contents.

Whilst this discussion was interesting (to some of us), it cannot be expected that the average pilot would have a knowledge of the presence - let alone the contents - of PANS OPS.

The procedures that are discussed/followed during an OPC should be those which are enumerated in the Operations Manual (OM). That a SID is constructed/flown AEO is something that should be known to pilots but it should also be set out in the OM - as should alternative OEI contingency departure procedures (EOSIDS) if they are considered necessary. In the absence of EOSIDS, there should be a statement of policy within the OM; as mentioned earlier, this might just consist of a statement of actions to be taken following an engine-failure at or before the some clearly defined elements of the CAT A procedure - when IMC. (Remember that before entering IMC, the aircraft must be operating in PC1 - i.e. there must be a transition from PC2 to PC1 at or before 200ft; the conditions for PC2 at 200ft are identical to PC1 - hence from that point, Subpart H points to Subpart G and does not contain requirements.)

The one thing that is perhaps not clear is whether (your) SIDs contain the specified gradient. If not, it might be appropriate for you to recommend that the OM is amended to include this information. When doing that, it might also be advisable to ensure that the other basic elements of SIDs are contained within an informational narrative.

Jim

[Geoffersincornwall]

I found this thread fascinating and somewhat revealing. In more than 40 years of IFR helicopter ops I cannot remember ever flying a standard SID or STAR. Certainly I have flown helicopter SIDS/STARS (Aberdeen, Bergen) which are designed for helicopters coming and going from offshore. My experience of major airports is that they wont let you anywhere near a SID or a STAR - they take you under radar and probably join the airway at a convenient point so you can occupy the lowest levels without screwing up their fixed wing traffic. Likewise Radar-To-ILS is the normal arrival.

Now that we have a sophisticated FMS I am teaching SIDS and STARs so I have had to rely on my FW colleagues to provide the vital data on how to use them correctly - and then try and pass it on. Until this thread the performance side of SIDs and Missed Approaches was a mystery to me and I am grateful to know more, however I wonder if I am shamefully ignorant or do my fellow SFIs/TRIs/IRIs share this lack of awareness?

I have never seen any data in any OM that I have previously used on special OEI SIDs. Am I alone or are there OMs for Helicopter Operators out there with such data with guidance on how to use the kind of information that has now come to light. It's one thing to micro-study your main operating bases but what happens on a ferry or a positioning flight into strange territory?

More threads like these please - thought provoking stuff!

G
:ok:

[Thridle Op Des]

First of all any more abuse from the darker swamps of Brunei will result in much toy-throwing-out-of-cot! Secondly the last two tea bearers were sadly not of the fairer sex but some hairy ex rugby 7's supporters so don't get too excited about our supposed salubrious surroundings. Thanks to Phil for the hint about where to see posted content, 212's excessive penchant for the letter 'd' was somehow glossed over. However readers will note the number of posting I have against my name compared with some which I hope is indicative to those who care ;) as to how much harder life is in the plank world and we don't have hours of time to while away at our computers until the wee hours of the morning!

On to more relevant comments concerning the thread, interesting comment on SID's & STAR's from Geoffers. The only time I recollect ever finishing a SID or completing a STAR to seamlessly transition to an approach is at Osaka. The Japanese have spent ages constructing intricate noise abatement procedures so the turning energy of the aircraft is managed really well in achieving the wall-of-death profile around the Osaka bay. In Europe, ATC slam you straight onto a heading so they can drop the separation from 5 to 3 miles, once clear of descending traffic we then get a direct to an appropriate waypoint.

Also interesting comment about the use of FMS in helicopters as well, I have been having a side discussion in this context with another ex colleague and while RNP and Navigation Accuracy are normal SOP in the FW world, the idea of using the FMS for IFR SID's & STAR's is meeting with surprising resistance in the higher echelons.

Sorry for the thread creep, but another small but interesting note is the difference between PDG of 3.3% and the certified engine out climb gradient FW have to achieve in the Second Segment (ie after the gear is retracted) is 2.4% for a twin and 3.0% for a quad, at a typical V2 of approximately 160KIAS, versus the rotary 5% requirement at a Vy of about 100 KIAS less, hence the frequent requirement for an EOSID.

TOD (1 'd')

[212man]

Geoff,
no I don't think you are alone. Generally the opportunity to fly SIDs and STARs will be restricted to ferry flights or similar as most rotary operating bases will have local procedures or Copter procedures. Ferry flight srae also likely to encounter non-radar environments where the procedural concepts are more relevant.

Historically, even twin engined performance was such that many helicopters could not even contemplate flying such procedures, particularly to any significant altitude, and their presence would be very unwelcome in a busy terminal area attempting to do so.

However, modern aircraft have not dismiliar performance to some light FW piston twins, and certainly the equal of the Twin Otter, and with their FMS and autopilots the use of these procedures is entirely viable.

One thing to bear in mind with the performance side is that an OEI missed approach is automatically in the second segment climb (except for a Cat II ILS, but that's rare) and so the notion of pulling 30 second power or max contingency/2 minute power during a missed approach is somewhat dubious, but often taught. It makes for an interesting discussion point with crews (and other TREs!)

[Vertolot]

This probably is more like a "simulator/OPC/check ride" problem and of course the "performance" procedures/requirements/climb gradient compliance should be outlined and explained for the pilot in the company OM.

On the other hand many modern helicopters with de-icing could fly an "fix wing" SID. I don´t know what the criteria for designing an helicopter contingency procedure OEI are, but they seem to be design for an OEI event very early in the departure. So, the problem could still be that you encounter OEI well into the SID (and you can not comply any more with the published contingency procedure). Specially if you should be IMC and with de-icing ON your climb performance OEI is very poor even in the most powerful helicopters.

Therefore should you plan to be able to fly the SID OEI (de-icing ON/OFF)??

(Sorry if I'm repeating myself to much:ouch:)

[212man]

I don´t know what the criteria for designing an helicopter contingency procedure OEI are, but they seem to be design for an OEI event very early in the departure. So, the problem could still be that you encounter OEI well into the SID (and you can not comply any more with the published contingency procedure). Specially if you should be IMC and with de-icing ON your climb performance OEI is very poor even in the most powerful helicopters.

Well, you either devise an operator specific OEISID for failure early on, that respects the terrain clearance requirements, or you do the performance planning required to comply with the published SID/MAP - with the emphasis on achieving MSA. If your climb performance is very poor with anti-icing on, and a failure means you will not be able to ensure terrain clearance, then you should not be operating in that environment with passengers. The RTOM should be adjusted accordingly. Most RFMs I've seen have the required data to produce relatively simple tables, or even remain as graphs but with you emphasisng the required gradients or RoCs to determine RTOMs.

Bear in mind also, that you can legally operate from an airport which you cannot legally make an approach back into, so you will need to consider how you will achieve the en-route MSA for the (60 minute) alternate you have selected.

Sorry for the thread creep, but another small but interesting note is the difference between PDG of 3.3% and the certified engine out climb gradient FW have to achieve in the Second Segment (ie after the gear is retracted) is 2.4% for a twin and 3.0% for a quad, at a typical V2 of approximately 160KIAS, versus the rotary 5% requirement at a Vy of about 100 KIAS less, hence the frequent requirement for an EOSID

TODDD,
the 5% for rotary is only in relation to a Cat H PDG - if you are flying a Cat A procedure you only need comply with the gradient specified.