Helicopter Performance Performance Class 2 - The Concept Jim Lyons
Aim of the Presentation Establishes the derivation of PC2 from the ICAO Standard and explains the necessary extensions Examines the basic requirements; discusses the limits of operation; and considers the benefits of the use of PC2 Contains examples of PC2 in specific circumstances, and explains how these examples may be generalised to provide the operators with methods of calculating landing distances and obstacle clearance HEMS Seminar 2
Purpose of Presentation This presentation considers Performance Class 2 as established in JAR-OPS 3. It has been produced for the purpose of: discussing the underlying philosophy of Operations in PC2; showing simple methods of compliance; and explaining how to determine - with examples and diagrams: the take-off and landing masses; the length of the safe-forced-landing area; distances to establish obstacle clearance; and entry point(s) into PC1 HEMS Seminar 3
What Defines Performance Class 2? HEMS Seminar 4
What Defines PC2 - Definition 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. HEMS Seminar 5
What Defines PC2 The Requirements Certification in Category A A PC3 take-off or landing - meeting PC1 requirements for the climb, cruise and descent For the purpose of minimum performance the following is required (at the appropriate power settings): Category A second segment climb performance - 150ft/min at 1,000ft (at Vy); and, depending on the choice of DPATO: For occasions when early entry into IFR is required, first segment climb performance 100ft/min up to 200ft at a nominated Vtoss HEMS Seminar 6
What Defines PC2 A Comparison of Profiles AEO profile PC2 profile PC1 profile DPATO between these two points PC1 TDP 2nd segment climb 150ft/min at Vy 1st segment climb 100ft/min at Vtoss 200 ft Reject takeoff/safe-forced-landing HEMS Seminar 7
PC1 requires: What Defines PC2 Obstacle Clearance OEI obstacle clearance in all phases of flight (engine failure accountability) PC2 requires: AEO obstacle clearance to DPATO OEI obstacle clearance from DPATO PC3 requires: AEO obstacle clearance in all phases of flight HEMS Seminar 8
PC1 requires: What Defines PC2 Discontinued Take-Off A prepared surface on which a rejected take-off can be undertaken (no damage) The surface (FATO) must be under the control of the heliport (within the boundary) PC2 and PC3 require (except when operating with Exposure): A surface on which a safe-forced-landing can be conducted (some damage can be tolerated but reasonable expectancy of no injuries to occupants or third parties) The surface does not need to be under control of the heliport HEMS Seminar 9
Benefits OF Performance Class 2 HEMS Seminar 10
What Are the Benefits of PC2? Operations in Performance Class 2 permit advantage to be taken of an all-engines-operating (AEO) procedure for a short period during takeoff and landing whilst retaining engine failure accountability in the climb, descent and cruise. The benefits include: Ability to use (the reduced) distances scheduled for the AEO - thus permitting operations to take place at smaller heliports and allowing airspace requirements to be reduced HEMS Seminar 11
Requirement for Scheduled Distances Short Field Procedure (Class 1) 200 ft 2nd segment climb 1st segment climb Reject T/O distance Distance to Vy at 200 ft HEMS Seminar 12
Requirement for Scheduled Distances Short Field Procedure (Class 1 v Class 2) 200 ft 2nd segment climb 1st segment climb Reject T/O distance Distance to Vy at 200 ft Distance required for Class 1 Distance required for Class 2 HEMS Seminar 13
What Are the Benefits of PC2? Operations in Performance Class 2 permit advantage to be taken of an all-engines-operating (AEO) procedure for a short period during takeoff and landing whilst retaining engine failure accountability in the climb, descent and cruise. The benefits include: Ability to use (the reduced) distances scheduled for the AEO - thus permitting operations to take place at smaller heliports and allowing airspace requirements to be reduced Ability to operate when the safe-forced-landing distance available is located outside the boundary of the heliport Ability to operate when the take-off-distance available is located outside the boundary of the heliport HEMS Seminar 14
Distances All Outside Heliport (PC1 Helipad) HEMS Seminar 15
Distances All Outside Heliport (PC1 Helipad) HEMS Seminar 16
What Are the Benefits of PC2? Ability to use existing Category A profiles and distances when the surface conditions are not adequate for a reject but are suitable for a safe-forced-landing (for example when the ground is waterlogged). Additionally, following a Risk Assessment when the use of exposure is permitted by the Authority: Ability to operate when a safe-forced landing is not assured in the take-off phase. Ability to penetrate the HV curve for short periods during take-off or landing. HEMS Seminar 17
Helipad Without SFL (Ground Level Exposure) HEMS Seminar 18
Implementation of PC2 in JAR-OPS 3 HEMS Seminar 19
Does ICAO spell it out? ICAO Annex 6 does not give guidance on how DPATO should be calculated nor does it require that distances be established for the takeoff. However, it does require that up to DPATO AEO, and from DPATO OEI, obstacle clearance be established HEMS Seminar 20
Annex 14 Provisions DPATO HEMS Seminar 21
Annex 6 Requirement HEMS Seminar 22
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Does ICAO spell it out? Note: Annex 8 Airworthiness of Aircraft (Part IV, Chapter 2.2.1.3.4) requires that an AEO distance be scheduled for all helicopters operating in Performance Classes 2 & 3. Annex 6 is dependent upon the scheduling of the AEO distances, required in Annex 8, to provide data for the location of DPATO. As can also be seen from the next Figure, flight must be conducted in VMC until DPATO has been achieved (as the OEI climb gradient will not have been established)). HEMS Seminar 24
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What is the Function of DPATO HEMS Seminar 26
Function of DPATO a. Obstacle clearance before DPATO; the helicopter shall be able, with all engines operating, to clear all obstacles by an adequate margin until it is in a position to comply with b. below. b. Obstacle clearance after DPATO; the helicopter shall be able, in the event of the critical power-unit becoming inoperative at any time after reaching DPATO, to continue the take-off clearing all obstacles along the flight path by an adequate margin until it is able to comply with enroute clearances. c. Engine failure before DPATO; before the DPATO, failure of the critical power-unit may cause the helicopter to force land; therefore a safe-forced-landing should be possible (this is analogous to the requirement for a reject in Performance Class 1 but where some damage to the helicopter can be tolerated.) HEMS Seminar 27
Function of DPATO From the preceding paragraphs it can be seen that DPATO is germane to PC 2. It can also be seen that, in view of the many aspects of DPATO, it has, potentially, to satisfy a number of requirements which are not necessarily synchronised (nor need to be). HEMS Seminar 28
Three Elements of a PC2 Take-Off DPATO AEO PC2 profile 150ft/min OEI TDP Pilot s pre-considered actions in the case of an engine failure between these two points Safe-forced-landing The calculation of re-landing distance from this point would be irrational! HEMS Seminar 29
Establishing the Take-Off Mass HEMS Seminar 30
Establishing the Take-Off Mass For the purpose of minimum performance the following is required (at the appropriate power settings): Category A second segment climb performance - 150ft/min at 1,000ft (at Vy); and, depending on the choice of DPATO the first segment climb performance 100ft/min to 200ft (at Vtoss) - may be required As with PC1, if the minimum climb performance does not provide OEI obstacle clearance, a modified mass might be required to clear obstacles HEMS Seminar 31
Three Elements of a PC2 Take-Off OEI modified climb gradient AEO VFR 10.7 IFR 10.7 0.01 DR DPATO TDP 150ft/min OEI Safe-forced-landing HEMS Seminar 32
Do Distances Have to be Calculated? HEMS Seminar 33
Do distances have to be calculated? Distances do not have to be calculated in VFR when, by using pilot judgement or standard practice, it can be established that: A safe-forced-landing is possible following an engine failure (notwithstanding that there might be obstacles in the take-off path); and Obstacles can be cleared (or avoided) - AEO in the take-off phase and OEI in the climb. HEMS Seminar 34
Calculating Distances DPATO Based On AEO Data (IMC) If early entry (in the sense of cloud base) into an IMC departure is required - calculations should be carried out. However, standard masses and departures can be used when described in the Operations Manual. In the simplest case and if provided, the scheduled AEO to 200 ft at Vy can be used Otherwise, and if scheduled in the HFM, the AEO distance to 50ft (V50) determined in accordance with FAR/JAR 29.63 - can be used Note: Where this distance is used, it will be necessary to ensure that the V50 climb out speed is associated with a speed and mass for which OEI climb data is available this will either be the Vtoss for the Clear Area procedure or Vy HEMS Seminar 35
Entry into IMC Using AEO Data DPATO AEO 200ft and Vy OEI obstacle clearance (AEO to DPATO) OEI obstacle clearance (AEO to DPATO) DPATO at V50 RFM Distance RFM Distance Entry into cloud possible at 200ft 50ft HEMS Seminar 36
Calculating Distances DPATO Based On Cat A (IMC) It is not necessary for specific AEO distances to be used (although for obvious reasons it is preferable); if they are not available, a flight path (with OEI obstacle clearance) can be established using Category A distances - which will then be conservative Note: the apparent DPATO is for planning purposes only in the case where AEO data is not available to construct the take-off flight path. The actual OEI flight path will provide better obstacle clearance than the apparent one (used to demonstrate the minimum requirement) - as seen from the firm and dashed lines in the following diagram. HEMS Seminar 37
Entry Into IMC at Vtoss (Real and Apparent Distance) Real DPATO AEO to Vtoss PC2 PC1 Apparent DPATO TODRH RFM Distance Entry into cloud possible when Vtoss is reached HEMS Seminar 38
Entry Into IMC at Vy (Real and Apparent Distance) Real DPATO AEO to Vy PC2 PC1 Apparent DPATO Vy distance to Vy RFM Distance Entry into cloud possible when Vy is reached HEMS Seminar 39
Safe-Forced-Landing Distance HEMS Seminar 40
Safe-Forced Forced-Landing Distance Unless the use of PC2 is based upon the surface conditions and can therefore take advantage of PC1 distances, the calculation of the relanding distance could be problematical A method that could be used is the combination of the CAT B V 50 and the CAT A landing distance from the RFM HEMS Seminar 41
SFL Distance (V 50 + Cat A Landing Distance) V50 AEO distance to V 50 Cat A landing distance Safe-Forced-Landing distance HEMS Seminar 42
PC2 Landing Procedures HEMS Seminar 43
PC2 Landing Considerations Apart from operations to elevated sites, landing at a location (where a take-off has been conducted) has to satisfy two sets of criteria: for an engine failure at or before 200ft when the helicopter must be able to perform a baulked landing meeting the same obstacle clearance required for the take-off procedure. at or after 200ft AEO; all obstacles have to be avoided OEI; be able to perform a safe forced landing. HEMS Seminar 44
PC2 Landing Procedure 200ft Vtoss & +ROC Flight path meeting The Category A take-off climb criteria HEMS Seminar 45
Obstacle Clearance Regardless of the procedure described in the Flight Manual, clearance from all obstacles in the baulked landing sector has to be shown; this sometimes requires that the landing mass be reduced to improve the climb gradient. HEMS Seminar 46
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Operations in PC2 with Exposure HEMS Seminar 48
Operations in PC2 with Exposure JAR-OPS 3 offers an opportunity to discount the requirement for an assured safe-forced-landing area in the take-off or landing phase - subject to an approval from the Authority. The following sections deal with this option As stated above, Performance Class 2 has to ensure AEO obstacle clearance to DPATO and OEI obstacle clearance from that point. This does not change with the application of exposure It can therefore be seen that operations with exposure are concerned only with alleviation from the requirement for the provision of a safeforced-landing The absolute limit of exposure is 200 ft - from which point OEI obstacle clearance must be shown HEMS Seminar 49
The Application of Risk Assessment The ICAO Helicopter and Tiltrotor Study Group, is engaged in an ongoing process to amend Chapter 3 to take account of current practices following this process the proposed text is likely to be: 3.1.2 In conditions where the safe continuation of flight is not ensured in the event of a critical power unit failure, helicopter operations shall be conducted in a manner that gives appropriate consideration for achieving a safe-forced-landing Although a safe-forced-landing may no longer be the (absolute) Standard, it is considered that Risk Assessment is obligatory to satisfy the amended requirement for appropriate consideration Risk Assessment used in this paper for fulfilment of this proposed Standard is consistent with principles described in AS/NZS 4360:1999 HEMS Seminar 50
The Application of Risk Assessment in JAR-OPS 3 Where possible, operations in Performance Class 2 should be conducted in accordance with the non-alleviated requirements contained above Under circumstances such as: operations to an elevated heliport (deck edge strike); or operations from a site where a safe-forced-landing cannot be accomplished because the surface is inadequate; or where there is penetration into the HV curve for a short period during take-off or landing Provided such operations are Risk Assessed and can be conducted to an established safety target - they may be approved HEMS Seminar 51
Elements of a Risk Assessment Any Approval process consists of an operational Risk Assessment which includes four principle elements: A Safety Target An airframe/engine reliability assessment Continuing airworthiness Mitigating maintenance and operational procedures HEMS Seminar 52
The Safety Target The main element of the JAA Risk Assessment was an assumption that turbine engines in helicopters would have a failure rate of about 1:100,000 per flying hour; which would permit (against the agreed safety target of 5 x 10-8 per event) an exposure of about 9 seconds for twins during the take-off or landing event (this has been established as an acceptable Residual Risk) Note: Residual Risk is considered to be the risk that remains when all mitigating procedures - airworthiness and operational - are applied HEMS Seminar 53
Reliability Assessment The JAA reliability assessment was initiated to test the hypothesis that the majority of turbine powered types would be able to meet the safety target. This hypothesis could only be confirmed by an examination of the manufacturers power-loss data. Note: The Powerloss Exposure Risk Report (PERR) that has been produced by manufacturers is discussed in a later presentation. HEMS Seminar 54
Mitigating Procedures (continuing airworthiness) Mitigating procedures consist of a number of elements: the fulfilment of all manufacturers safety modifications; a comprehensive reporting system (both failures and usage data); and the implementation of a Usage Monitoring System (UMS). Each of these elements is to ensure that engines, once shown to be sufficiently reliable to meet the safety target, will sustain such reliability (or improve upon it). The monitoring system is felt to be particularly important as it had already been demonstrated that when such systems are in place it inculcates a more considered approach to operations. In addition the elimination of hot starts, prevented by the UMS, itself minimises the incidents of turbine burst failures. HEMS Seminar 55
Mitigating Procedures (operations) Operational and training procedures to mitigate the risk - or minimise the consequences - are required of the operator. Such procedures are intended to minimise risk by ensuring that: the helicopter is operated within the exposed region for the minimum time; and simple but effective procedures are followed to minimise the consequence should an engine failure occur. HEMS Seminar 56
Performance Requirement - Ground Level Exposure The take-off mass is obtained from the more limiting of the following: the climb performance of 150 ft/min at 1000 ft above the take-off point; or AEO hover out of ground effect (HOGE) performance at the appropriate power setting Note: AEO HOGE is required to ensure acceleration when (near) vertical dynamic take-off techniques are being used. Additionally for elevated heliports/helidecks, it ensures a power reserve to offset ground cushion dissipation; and ensures that, during the landing manoeuvre, a stabilised HOGE is available - should it be required HEMS Seminar 57
Summary We have established the derivation of PC2 from the ICAO Standard and explained the necessary extensions We have examined the basic requirements; discusses the limits of operation; and considered the benefits of the use of PC2 We have shown the application of PC2 in specific circumstances, and explained how these examples may be generalised to provide operators with methods of calculating landing distances and obstacle clearance PC2 is difficult to explain but simple to use provided safety targets are applied, it gives an opportunity to take advantage of the flexibility provided by modern helicopters HEMS Seminar 58
Any Questions HEMS Seminar 59
Helicopter Performance Performance Class 2 - The Concept Jim Lyons