602 601(g)(1) Data reporting AMC §J36.111 [ETM AMC A4 6.0]
(1) Reporting requirements Noise certification data reporting requirements are detailed in J36.111 of part 36. Compliance with stabilized test conditions, including test airspeed, average rotor speed and flyover height, should be reported for the 10 dB-down period. If an acoustic data recording is made, information about the recorder, including frequency bandwidth and sample rate and operating mode, should be recorded.
(2) Lateral position flight track data There is no requirement to determine the lateral off-track position directly above the noise measurement point, since it is necessary to show only that it is within the requirements defined in J36.105(b)(3) of part 36. Even so, an applicant may find merit in determining and reporting the lateral off-track distance, with the height information that is required, as a way to show compliance.
EQUIVALENT PROCEDURES INFORMATION [ETM 6.2] 602(a) General [ETM 6.2.1] The objective of a noise certification demonstration test is to acquire data for establishing an accurate and reliable definition of a helicopter’s noise characteristics. In add ition, part 36 establishes a range of test conditions and procedures for adjusting measured data to reference conditions.
602(b) Procedures for the Determina tion of Changes in Noise Levels [ETM 6.2.2] Changes in noise levels determined by comparison of flight test data for different helicopter model series have been used to establish certification noise leve ls of modified or newly derived versions by reference to the noise levels of the baseline or “flight datum” helicopter model. These noise changes are added to or subtracted from the noise levels obtained from individual flights of the “flight datum” helicopter model. The confidence intervals of the new data are statistically combined with the “flight datum” data to develop overall confidence intervals (see 305 of this AC).
602(b)(1) Modifications or upgrades involving aerodynamic drag changes [ETM 6.2.2.1] The use of drag devices, such as drag plates mounted beneath or on the sides of the “flight datum” helicopter, has proven to be effective in the noise certification of modi fications or upgrades involving aerodynamic drag changes.
External modifications of this type are made by manufacturers and aircraft “modifiers”. Considerable cost savings are realized by not having to perform noise testing of numerous individual modifications to the same model series. Based on these findings, it is considered acceptable to use the following as an equivalent procedure:
a) for helicopters to be certificated under Appendix J of part 36, a drag device is used that produces the aerodynamic drag calculated for the highest drag modification or combination of modifications;
b) with the drag-producing device installed, a flyover test is performed by using the appropriate noise certification reference and test procedures;
c) a relationship of noise level versus change in aerodynamic drag or airspeed is developed by using noise data, adjusted as specified in Appendix J of part 36, of the “flight datum” helicopter and of the “high drag” Page 245
configuration;
d) the actual airspeed of the modificati on to be certificated is determined from performance flight testing of the baseline helicopter with the modification installed; and
e) using the measured airspeed of the modification, certification noise levels are determined by interpolation of the relationship developed in item c).
602(b)(2) Testing of light helicopters outside Appendix J temperature and humidity limits [ETM 6.2.2.2] With the approval by the FAA, it may be possible to cond uct testing of light helicopters in compliance with the temperature and relative humidity test limits specified in H36.101(c) of part 36 (see Figure 51) instead of the limits specified in J36.101(c)(2) of part 36 . Temperature and relative humidity measurements must be made between 4 ft
(1.2 m) and 33 ft (10 m) above ground as specified in J36.101(c)(2) of part 36 and within 30 minutes of each noise measurement as required by H36.101(c)(7) of part 36. In such circumstances , it will be necessary to conduct a onethird octave band analysis of a noise recording of each flyover. The measured value of SEL must be adjusted from the test values of temperature and relative humidity to the re ference conditions defined in J36.3(a) of part 36. The adjustment procedure must be similar to that defined in H36.205(f)(2) of part 36 with the propagation distances QK and QrKr, respectively replaced by H, the height of the test helicopter when it passes ov er the noise measurement point, and the reference height, 492 ft (150 m).
Appendix 2 test window Reference condition (25°C; 70%) 12 dB/100 m Relative humidity (%) Temperature (°C) Figure 51. Optional Appendix H T emperature/relative humidity test window Page 246
Chapter 7 GUIDELINES FOR TILTROTOR AIRCRAFT EVALUATED UNDER APPENDIX K OF 14 CFR PART 36
CHAPTER TABLE OF CONTENTS
701 EXPLANATORY INFORMATION247
701(a) Background247
701(a)(1) Applicability247
701(b) General Information249
701(b)(1) Terms used in tiltrotor noise certification procedures249
701(c) Information on Specific Appendix K Texts249
701(c)(1) Definitions250
701(c)(2) Applicability250
701(c)(3) Noise evaluation measure250
701(c)(4) Reference noise measurement points250
701(c)(5) Maximum noise levels and trade-offs250
701(c)(6) Noise certification reference procedures251
701(c)(7) Test procedures252
701 EXPLANATORY INFORMATION [ETM 7.1] 701(a) Background [ETM 7.1.1] 701(a)(1) A pplicability GM §36.1(5) [ETM GM ATT F 1]
(1) Intent of Appendix K requirements The prescribed test requirements for the noise certification of tiltrotor aircraft is presented in Appendix K of part
36. It was adopted in the USA following the ICAO development effort by the CAEP5 Tiltrotor Task Group that specifically addressed the noise certification of the Bell/Agusta BA609, the first example of a civil tiltrotor aircraft, which was renamed the AW609 in 2011. Initially developed as ICAO guidelines, it is becoming the basis for noise certification of tiltrotor aircraft in the USA. The explanatory material in this chapter is intended to provide an insight as to how the guidelines were developed. Its use is anticipated for AW609 noise certification and will become an ICAO standard within the Annex after its initial application.
(2) Scope of Appendix K In anticipation of the AW609 becoming the first civil tiltrotor aircraft, these guidelines are being adopted in the USA as applicable standards. The ICAO Annex 16, Volume 1, Attachment F guidelines, published in 2002, provides a noise certificati on compliance testing methodology for tiltrotor aircraft that pr omotes uniform and consistent environmental protection for aviation.
When Working Group 1 (Noise) was originally task for developing tiltrotor guidelines, it was decided after careful deliberations, that the current Standards of Chapter 8 for helicopter in Annex 16 would offer a good basis for the guidelines since the helicopter configuration would characterize the worst case (noisiest) condition.
a) The noise from tiltrotors will be most prominent during departure and approach. In these situations tiltrotors will normally operate in or near the “helicopter mode”.
b) In the development of the guidelines, the noise of the Bell XV-15 tiltrotor aircraft (a prototype of the AW609) was observed. It was concluded that the char acter of the noise of this aircraft was much like that of a normal helicopter.
c) In horizontal flyover, the “helicopter mod e” will normally be the noisiest configuration.
d) The proposed guidelines are confined to tiltrotors th at can only take off vertically, excluding those with STOL characteristics. They will operate much like normal helicopters, with relatively steep takeoff and approach paths.
e) The level of available noise abatement technology for tiltrotors is considered to be the same as for helicopters.
f) Tiltrotor operations will often mi x with helicopter operations from the same heliport. Therefore there will be a desire to compare the noise from tiltrotors and helicopters.
(3) Transition phase noise-test point evaluation One item of strong interest is the tr ansition from one nacelle angle to the other, which may be associated with particular noise-generation mechanisms. For example, wh en one considers the tiltrotor transition from airplane mode to helicopter mode while decelerating, there is a ph ase in which the component of the speed vector that is perpendicular to the rotor changes from “top to bottom” to “bottom to top”. It would be conceivable that sometime during the transition phase, blade vorti ces would be ingested or another non-stationary effect would create additional noise.
A number of flyovers of the Bell XV-15 were listened to, one of which was especially set up to study the noise during transition. In this run, the tiltrotor (Bell XV-15) passed overhead at 492 ft (150 m) while transitioning from airplane to helicopter mode. No special phenomena were heard during this flight. In addition, during the other runs, in which there were demonstrations of hover, hover turns, sideward flight, takeoff, level flyovers at various speed/nacelle angle combinations, and approaches at 6° and 9°, no particularities were heard other than normal blade vortex interaction noise during both the 6° and 9° approaches. During the procedures to set the aircraft up for the various runs, several transitions were made from helicopter to airplane mode and back, which were listened to from different positions relative to the aircraft. No particular noise was heard.
Based on this experience and the arguments stated as follows, it has been decided not to attempt to define a special test point aimed at catching transition noise of tiltrotors.
The arguments for this are:
a) Experienced observers from industry claim they have never noticed any particular noise phenomena associated with the transitional phase. This was backed up by the specific observations of the Bell XV-15 referred to above.
b) The conversion rate is relatively slow, which means that during the whole conversion process, the flow field also changes very slowly.
c) If there were to be a transitional noise, it would probably be related to some form of blade-vortex interaction.
This phenomenon is covered under the approach procedure, and it might be hard to justify adding a measurement point to get some additional information.
d) Defining a reproducible and practicable procedure to catch the transition noise which nobody has ever noticed is virtually impossible.
e) If in the future there is a design that has clear tr ansitional noise characteristics, the effect could be studied and, if deemed necessary, an amendment to the guidelines could be proposed.
701(b) General Information [ETM 7.1.2] 701(b)(1) Terms used in tiltroto r noise certification procedures GM §36.1(i) [ETM GM ATT F 6] Airplane mode means a configuration with nacelles on the down stops (axis aligned horizontally) and rotor speed set to cruise revolutions per minute (RPM).
Airplane mode RPM means the lower range of rotor rotational speed in RPM defined for the airplane mode cruise flight condition.
Fixed operation points mean designated nacelle angle positions (“gates”) selected for airworthiness reference. These are default positions used to refer to normal nacelle positioning operation of the aircraft. The nacelle angle is controlled by a self-centering switch. When the nacelle angle is 0 degrees (airplane mode) and the pilot moves the nacelle switch upwards, the nacelles are programmed to automatically turn to the first default position (for example, 60 degrees) where they will stop. A second upward move of the switc h will tilt the nacelle to the second default position (for example, 75 degrees). Above the last de fault position, the nacelle angle can be set to any angle up to approximately 95 degrees by moving the switch in the up or down directio n. The number and position of the fixed operation points may vary on different tiltrotor configurations.
Nacelle angle is defined as the angle between the rotor shaft centerline and the longitudinal axis of the aircraft fuselage.
Tiltrotor means a class of aircraft capable of vertical takeoff and landing, within the powered-lift category, with rotors mounted at or near the wing tips that vary in pitch from near vertical to near horizontal configuration relative to the wing and fuselage.
Vertical takeoff and landing (VTOL) mode means the aircraft state or configuration having the rotors orientated with the axis of rotation in a vertical manner (i.e., nacelle angle of approximately 90 degrees) for vertical takeoff and landing operations.
VCON is defined as the maximum authorized speed for any nacelle angle in VTOL/Conversion mode.
VMCP is defined as the maximum level flight airspeed for airplane mode corresponding to minimum specification engine power corresponding to maximum continuous power available for sea level pressure of 1013.25 hPa, at 77 F (25 C) ambient conditions at the relevant maximum certificated weight.
VMO is defined as the maximum airspeed in airplane mode that may not be deliberately exceeded.
VTOL/Conversion mode is all approved nacelle positions where the design operating rotor speed is used for hover operations.
VTOL mode RPM means highest range of RPM that occur for takeoff, approach, hover, and conversion conditions.
701(c) Information on Specific Appendix K Texts [ETM 7.1.3] Page 249
701(c)(1) Definitions GM §36.K1 [ETM GM ATT F Note 1]
(1) Definition The definition was proposed by the International Coordi nating Council of Aerospace Industries Associations (ICCAIA). It focuses on the fundamental difference between tiltrotors and other aircraft.
701(c)(2) Applicability GM §36.K1 [ETM GM ATT F Notes 1 and 2 and Section 1]
(1) Applicability An applicability section promotes uniform application of the guidelines. The reference to derived versions means that no measurements are required on ai rcraft that are quieter than their pare nt aircraft due to the definition of derived versions though addressed as an acoustical change. The regulation is effective upon completion of the US rulemaking.
701(c)(3) Noise evaluation measure GM §36.K2 [ETM GM ATT F Section 2]
(1) Noise evaluation measure In view of the commonality with helicopters, the same units used in Appendix H of part 36 are proposed. It is proposed that no new appendix for tiltrotors be created, since the current Appendix H of part 36 is considered to be appropriate.
The FAA encourages that additional data be made available for land-use planning purposes. With the exception of flyovers in airplane mode discussed later in this chapte r, the intention of this section of the guidelines is to require only data that can be gathered through additional analysis of the data that have already been measured for certification purposes. Which data should be provided is to be determined between the FAA, or other authorities, and the applicant, since the needs of different authorities in this respect may differ. As a minimum, data in units of SEL and LAmax as defined in Appendix 4 of part 36 should be made available for approval by the FAA. This data may be presented in the noise section of the RFM as supplemental information (see 201(d) of this AC discussing §36.1581(b) of part 36).
701(c)(4) Reference no ise measurement points GM §36.K3 [ETM GM ATT F Section 3]
(1) Reference noise measurement points In view of the desired commonality w ith helicopters, the same reference noise measurement points used for Appendix H of part 36 are prescribed.
701(c)(5) Maximum noise levels and trade-offs GM §36.K4 and §36.K5 [ETM GM ATT F Sections 4 and 5]
(1) Maximum noise levels and trade-offs In view of the desired commonality with helicopters, it was determined that the Stage 2 limits of H36.305(a)(2) and the trade-offs of H36.305(b) of part 36 would serve as a good starting point for use in this regulation. In the helicopter mode, both the lift technology and operating environment are similar to those of a helicopter. For the flyover case, a limit is specified only for the helicopter mode, since this is normally the noisiest configuration Page 250
and also the configuration most likely to be used when flying the circuit pattern.
(2) Noise levels in airplane mode There is no maximum noise level for the tiltrotor in airplane mode. However, it is recommended that noise levels be measured as per the reference procedures defined in 36.K6 and reported as supplemental data in the noise section of the RFM as this configuration will be used when transiting between points.
701(c)(6) Noise certificat ion reference procedures GM §36.K6 [ETM GM ATT F Section 6]
(1) General The capability to change the nacelle angle and the two (possibly more) different rotor speeds required additional criteria relative to the current helicopter reference procedures of Appendix H of part 36.
(2) Rotor speed In Appendix H of part 36, the rotor speed required is linked to the corresponding flight condition. This means that for takeoff, approach and flyover in the helicopter mode, the higher rotor speed will have to be used, while for the flyover in airplane mode, the lower rotor speed has to be used.
(3) Nacelle angle
a) Takeoff During takeoff, the choice of the nacelle angle is left to the applicant. This is in line with the philosophy of part 36 where the choice of the configuration is left to the applicant. It is also in line with the requirement in Appendix H of part 36 to use the aircraft’s best rate of climb speed, Vy, since the applicant will normally choose the nacelle angle that is close to the nacelle angle which corresponds to the overall best rate of climb. Note that for each nacelle angle there is a speed that gives the best rate of climb, which is normally not the same numerical value for different nacelle angles. There will be one nacelle angle that gives the highest overall rate of climb, but this is usually not an angle that corresponds to a fixed operation point.
b) Flyover in helicopter mode In the case of flyover in helicopter mode, the definition of the nacelle angle to be used was one of the more difficult problems. Initially it was proposed to use a nacelle angle of 90°, comparable to a helicopter. This was however unsatisfactory because a tiltrotor will normally not fly at this angle at the high speed required for noise certification. Normally the rotor will be tilted to get more forward thrust without tilting the fuselage forward, and to do this, a nacelle angle of approximately 80° is selected. It was agreed that this unique capability of the tiltrotor should be incorporated into the reference procedure. On the other hand the requirement should prevent the applicant from choosing a nacelle angle that would be close to 0° since this would give unrealistically low noise figures. Note that tilting the rotor will reduce the advancing blade tip Mach number. After long deliberations, a satisfactory solution was found. For a tiltrotor there will normally be a nacelle angle below which hover is no longer possible and for which flight with zero airspeed is not permitted. It was decided to fix the nacelle angle for the flyover in helicopter mode to the fixed operation point closest to that angle.
c) Flyover in airplane mode In flyover in airplane mode, the nacelle angle is defined as on the down-stop, the position that will normally be used for cruise and high speeds. Two conditions are measured:
— one is with the high rotor speed and the same speed as used in the helicopter mode flyover. This Page 251
condition is intended to make it possible to make comparisons between the helicopter mode and airplane mode flyover; and — the other condition is with the cruise rotor speed and speed V MCP or VMO, as defined in 701(b), which is intended to represent a worst-case cruise condition.
d) Approach For the approach reference configuration, the nacelle angle for maximum approach noise should be used. This is consistent with the philosophy of Appendix H and other parts of part 36 that require the noisiest configuration for approach. This will normally require testing several different nacelle angles in order to determine which is noisiest.
In the tiltrotor aircraft design, the flap angle varies with airspeed so the pilot may manually set flaps or may use auto flap control in order to reduce the pilot’s workload. In this latter case, the flap angle for noise certification will be the flap angle that is normal for the approach configuration and approach condition flown. For a design with pilot-controlled flap angle, the applicant should use the flap angle designated for approach and will have to prove that the noisiest configuration is used for noise certification.
701(c)(7) Test procedures GM §36.K7 [ETM GM ATT F Section 7]
(1) Test procedures The test procedures are the same as in Appendix H of part 36. Where appropriate, the helicopter guidance provided in Chapter 4 of this AC is equally applicable to tiltrotors.
Note that this means that, as a minimum, all noise measurements are taken and evaluated with the microphone at 4 ft (1.2 m), including any voluntary data taken for land-use planning purposes. This is proposed in order to maintain commonality with Appendix H numbers and to reduce costs for the applicant. If, for land-use planning or other purposes, the gathering of data at other microphon e positions (i.e., at ground plane) were desired, this would of course be allowed but would have to be agreed between the applicant and the FAA.
Chapter 8
GUIDELINES ON FLIGHT TEST WINDOWS AND
ADJUSTMENT OF LAND-USE PLANNING NOISE DATA MEASURED IN ACCORDANCE WITH ATTACHMENT H TO ANNEX 16, VOLUME I
CHAPTER TABLE OF CONTENTS
801 EXPLANATORY INFORMATION253
801(a) Background253
801(a)(1) General253
801(b) Test Windows254
801(b)(1) Alternative constant airspeed and flight path conditions254
801(b)(2) Multi-segmented flight path conditions at constant airspeed — no climb segments256
801(b)(3) Multi-segmented flight path conditions at constant airspeed with climb segments256
801(b)(4) Non-constant airspeed and flight path conditions256
801(b)(5) Approaches with constant deceleration and flight path conditions256
801(b)(6) Other non-constant airspeed and flight path conditions256
801(c) Reference Conditions258
801(c)(1) General258
801(c)(2) Predefined constant flight path and constant airspeed259
801(c)(3) Derived constant flight path259
801(c)(4) Derived constant airspeed259
801(c)(5) Multi-segmented flight path conditions at constant airspeed259
801(c)(6) Guidance for multi-segmented flight paths with climb segments259
801(c)(7) Non-constant airspeeds and/or flight path conditions260
801(c)(8) [Approaches with constant deceleration and flight path conditions]260
801(c)(9) Other non-constant airspeeds and/or flight path conditions260
802 EQUIVALENT PROCEDURES INFORMATION260
803 TECHNICAL PROCEDURES INFORMATION260
803(a) Adjustments to Reference Conditions260
803(a)(1) Constant airspeed and flight path conditions260
803(a)(2) [Measurements processed using the procedures of Appendix J of part 36260
803(a)(3) Measurements processed using the procedures of Appendix J of part 36262
803(a)(4) Multi-segmented flight path conditions at constant airspeed264
803(a)(5) Non-constant airspeed and flight path conditions264
803(a)(6) Approaches with constant deceleration and flight path conditions264
803(a)(7) Other non-constant airspeed and flight path conditions265
801 EXPLANATORY INFORMATION [ETM 8.1] 801(a) Background [ETM 8.1.1] 801(a)(1) General [ETM GM ATT H 1] At CAEP/6, guidelines for the provision of rotorcraft noise data for land-use planning (LUP) purposes were approved as Attachment H to Annex 16, Volume 1. The objective of Attachment H is the provision of noise data, in metrics suitable for LUP purposes, at the noise certification flight conditions and/or at alternative flight conditions representing normal operating procedures or other flight procedures for noise abatement or heliport-specific requirements.
Detailed guidance on flight test windows and adjustments of LUP data to reference conditions for alternative flight procedures specifically designated for LUP data provision is provided in this chapter. To be consistent with noise certification data and provide comparable accuracy, the detailed guidance is based, to the fullest extent practical, on the flight test windows and data adjustment procedures utilized for noise certification flight procedures.
In developing these flight test windows and data adjustment procedures, the needs associated with LUP data provision have been balanced against the test costs in acquiring LUP data, with the intent of encouraging additional optional flight testing and measurements by applicants.
The guidance on test windows for alternative flight procedures is provided in 801(b). Guidance on adjustment of LUP data to reference conditions is provided in 801(c) and 803(a), with 801(c) addressing reference conditions and 803(a) providing specific guidance on adjustment procedures.
Note.— The test windows and adjustments to data provided in this chapter address constant airspeed and flight path conditions only. Varying airspeed and flight path conditions may require additional guidance not yet provided in this chapter.
801(b) Test Windows [ETM 8.1.2] 801(b)(1) Alternative constant airs peed and flight path conditions [ETM GM No. 1 ATT H 2.1 and 2.2] The flight test windows and procedures for alternative constant flight conditions for LUP are provided in Table 16 together with the existing requirements for noise certification. “No change” in Table 16 denotes the recommended use of the corresponding test window or procedure of Appendix H or J of part 36.
Table 16. Flight test windows and procedures for alternative constant flight conditions for LUP Annex 16/Doc 9501 reference Test window/procedure Noise certification LUP f light conditions
8.7.4 Total adjustments Takeoff: 4 EPNdB/2 EPNdB No change for integrated Approach and flyover: 2 EPNdB noise metrics
8.7.5 Rotor speed (Nr) ±1 percent No change
8.7.6 Airspeed ±5 kt (±9 km/h) ±7 kt (±13 km/h)
8.7.7 Flyovers with headwind/tailwind Equal numbers No change
8.7.8 Angle from the vertical ±10° or ±65 ft (±20 m) No change
8.7.9 Flyover height at overhead ±30 ft (±9 m) No change
8.7.10 Approach angle ± 0.5° “Wedge” No change
8.7.11 Weight 90 percent to 105 percent No change App 2, 2.2.2.2 b) Temperature at 10 m (33 ft) 14F to 95°F (–10C to 35C ) No change App 2, 2.2.2.2 b) RH at 10 m (33 ft) 20 to 95 percent No change App 2, 2.2.2.2 c) 8 kHz sound attenuation coefficient 12 dB/100 m No change App 2, 2.2.2.2 e) Wind at 10 m (33 ft) 10 kt (5.1 m/s) No change App 2, 2.2.2.2 e) Crosswind at 10 m (33 ft) 5 kt (2.6 m/s) No change Page 254
Annex 16/Doc 9501 reference Test window/procedure Noise certification LUP f light conditions App 2, 3.5.2 Microphone height 4 ft (1.2 m) 4 ft (1.2 m) (Note 1) App 2, 5.4.2 Number of test runs 6 4 App 2, 5.4.2 90 percent CI — 3 microphone average ±1.5 EPNdB ±1.5 dB SEL (Note 2) 90 percent CI — each metric at each N/A To be reported microphone Doc 9501, 4.2.3.2.1 No adjustment window Equivalent to <0.3 dB delta No change (Note 3) Doc 9501, 4.2.3.2.2 Airspeed for equivalent Mach number 3 kt (±5.5 km/h) No change Doc 9501, 8.1.2 Airspeed (VT and V(x)) — decelerating N/A ±7 kt (±13 km/h) of reference airspeed schedule
11.6.5 Total adjustments 2 dB(A) No change
11.6.6 Rotor speed (Nr) ±1 percent No change
11.6.7 Airspeed — constant ±3 kt (±5.5 km/h) ±5 kt (±9 km/h) (Note 4)
11.6.4 Headwind/tailwind Equal numbers No change
11.6.8 Angle from the vertical ±10° No change
11.5.2.1 a) Height at overhead ±50 ft (±15 m) No change Approach angle N/A ±0.5° “Wedge”
11.6.9 Weight 90 percent to 105 percent No change App 4, 2.2.2.2 b) Temperature at 33 ft (10 m) 14 ºF to 95ºF (–10°C to 35°C) No change App 4, 2.2.2.2 b) RH at 33 ft (10 m) 20 to 95 percent No change App 4, 2.2.2.2 b) 8 kHz sound attenuation coefficient 10 dB/100 m No change App 4, 2.2.2.2 c) Wind at 10 m (33 ft) 10 kt (5.6 m/s) No change App 4, 2.2.2.2 c) Crosswind at 10 m (33 ft) 5 kt (2.6 m/s) No change App 4, 4.4.2 Microphone height 1.2 m (4 ft) 1.2 m (4 ft) (Note 1) App 4, 6.3.1 Number of test runs 6 4 App 4, 6.3.2 90 percent CI ±1.5 dB SEL No change 90 percent CI — each metric at each N/A To be reported microphone Doc 9501, 4.2.3.2.1 Equivalent Mach number ±3 kt (±5.5 km/h) No change Doc 9501, 8.1.2 Airspeed (VT and V(x)) — decelerating N/A ±7 kt (±13 km/h) of reference airspeed schedule
1. LUP measurements at other heights should be adjusted to 1.2 m (4 ft) using an approved method.
2. The three-microphone average is based on the three noise certification measurement points.
3. No change for Appendix H noise certification measurement points. Other measurement points to be evaluated.
4. Can use ±7 kt (±13 km/h) if velocity term, 2, of Appendix H is used.
Many of the flight test windows and procedures currently used for noise certification testing can be applied when acquiring noise data for LUP purposes. Thus the flight test windows and procedures detailed in Table 16 make as Page 255
much use of current adjustment procedures of Appendix H and J of part 36 as practical. In addition, it should be noted that the “zero attenuation adjustment window” as defined in 402(c)(2)(A), may be used.
Table 16 includes, relative to the noise certification requirements, an expanded airspeed tolerance of ±7 kt (±13 km/h) for Appendix H helicopters and ±5 kt (±9 km/h) for Appendix J helicopters (or ±7 kt (±13 km/h) if the Appendix H 2 adjustment is used), and a minimum number of 4 test runs. The 90 percent confidence interval limit of ±1.5 EPNdB currently applied to the three-microphone average of EPNL in Appendix H is also applied to the corresponding threemicrophone average of SEL. In the case of Appendix J helicopters, the current 90 pe rcent confidence interval requirement for SEL at the flight track microphone is retained. In addition, the 90 percent confidence interval calculated for each time-integrated and maximum noise level metric at each microphone should be reported.
These guidelines primarily address the balance between LUP data needs and test costs for applicants providing data under Attachment H. In particular, increasing the airspeed test window by 2 kt (3.7 km/h) will reduce test costs while having little impact on the final results. Reducing the required minimum number of test runs from 6 to 4 also reduces test costs while the needed accuracy of the data is maintained by the 90 percent confidence interval limit.
801(b)(2) Multi-segmented flight path conditions at constant airspeed — no climb segments [ETM GM No. 2 ATT H 2.1 and 2.2] The flight test windows and procedures provided for alternative constant flight conditions for LUP in Table 16 can be applied for the case of approaches with multiple referenc e flight path segments, each having a different constant descent angle or level flight condition. In particular, the test tolerances in Table 16 for total adjustments, rotor speed, airspeed, angle from the vertical, height at overhead, approach angle and test weight are applicable to each flight path segment as appropriate.
Note.— Changes in reference flight path angle between two segments should be completed as quickly as possible in order to remain within flight path tolerances for each flight segment. This may necessitate initiating the transition prior to the reference transition point.
801(b)(3) Multi-segmented flight path conditions at constant airspeed with climb segments [ETM GM No. 3 ATT H 2.1 and 2.2] (Reserved) 801(b)(4) Non-constant airspeed and flight path conditions [ETM GM No. 4 ATT H 2.1 and 2.2] (Reserved) 801(b)(5) Approaches with constant deceleration and flight path conditions [ETM GM No. 5 ATT H 2.1 and 2.2] The flight test windows and procedures provided for alternative constant flight conditions for LUP in Table 16 can be applied for the case of approaches with constant deceleration and flight pa th (glide slope) cond itions with some adjustments to account for the constant variation of airspeed with time. Specifically, a reference airspeed “schedule”
(i.e., reference airspeed as a function of position along the reference flight track) needs to be derived from the reference deceleration rate for the reference condition of zero wind speed. The airspeed tolerance of ±7 kt (±13 km/h) should be applied both to airspeed as a function of time and as a function of position along the reference flight track as illustrated in Figure 52 and Figure 53.
801(b)(6) Other non-constant airs peed and flight path conditions [ETM GM No. 6 ATT H 2.1 and 2.2] (Reserved) Page 256