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
0 10 20 30 40 50 –7 kt +7 kt 60 70 80 90 100 –800 –600 –400 –200 0 200 400 600 Flight track position (m) Aispeed (kt) 10-dB down period V is the reference airspeed at X 0 0 Potential X d0 efinition points x = ½ at + V t + V = at + V 2 0 0 X0 Overhead of flight track microphone Figure 52. Example of a reference airspe ed profile versus flight track position for a constant deceleration from 80 kt to 50 kt at 1 kt/s Page 257
0 10 20 30 40 50 60 70 80 90 100 –20 –15 –10 –5 0 5 10 15 20 Time (s) [= 0 seconds at overhead] –7 kt +7 kt Aispeed (kt) Overhead of flight track microphone 10-dB down period Constant deceleration = linear airspeed profile Figure 53. Example of a reference airspeed profile versus time for a constant deceleration from 80 kt to 50 kt at 1 kt/s 801(c) Reference Conditions [ETM 8.1.3] 801(c)(1) General [ETM GM No. 1 ATT H 2.3] Flight procedures designed to represent normal or noise abatement operations can vary from simple fixed flight path and airspeed procedures similar to noise certification test conditions to complex non-constant flight path and/or nonconstant airspeed procedures. The resulting reference flight procedures and data adjustment procedures should be submitted to the FAA for approval.
The primary reference test conditions that affect adjustments to the noise data are the reference atmospheric conditions, the reference helicopter flight path, and the reference helicopter airspeed. For acquiring noise data for LUP purposes, the reference atmospheric conditions should be the same as those specified in H36.3(a) and J36.3(a) of part 36.
In the process of developing flight profiles for LUP and noise abatement procedures, a reference flight path and/or reference airspeed procedure may not have been determined prior to obtaining a set of noise data suitable for LUP purposes. In such cases, the flight path and airspeed test data may be used to derive appropriate reference values. The method used should be approved by the FAA.
801(c)(2) Predefined co nstant flight path and constant airspeed [ETM GM No. 2 ATT H 2.3] If a predefined reference constant flight path and constant speed conditions similar to, but different from, those defined for noise certification testing under Appendix H of part 36 are used, the same adjustment procedures defined in Appendix H can be used with the new reference conditions substituted in the adjustment procedures as appropriate and the adjustment procedures modified as necessary to give results in terms of adjusted sound exposure level, L AE, and any other metrics selected by the applicant.
801(c)(3) Derived cons tant flight path [ETM GM No. 3 ATT H 2.3] If a reference flight path is not predefined, a reference path needs to be derived or otherwise determined from the flight test data. One method to define the reference path is to determine the mean of the test runs by calculating the path of each test run using a least-squares linear fit of the aircraft position data, defined in terms of X, Y and Z coordinates, between the 10 dB-down points and averaging the calculated results.
An example is the case where, as a result of flight testing multiple glide slopes, a fixed glide slope approach is deemed appropriate for pilot acceptability. If the selected flight path is repeated as necessary to obtain a statistically valid set of noise levels, the flight path data can be averaged to define the reference flight path.
801(c)(4) Derived constant airspeed [ETM GM No. 4 ATT H 2.3] If the reference airspeed, V r, is not predefined, a value of V r needs to be derived or otherwise determined from the measured data. One method to define V r is to determine the mean of the test runs by averaging the true airspeeds (TAS) of each test run that meets the test window criteria.
An example of this is the case where the sensitivity of noise level with airspeed and rate of descent is of interest. The test program might incrementally test a range of fixed IAS for one or more rates of descent, with the reference airspeed for a LUP flight profile subsequently defined after the flight test program.
For the special case of determining Vr for the flyover condition when using the equivalent Mach number method (see section 10 of 401(h)(8), 402(c)(2)(B) and J36.105(c) of this AC) to adjust for source noise, a separate method is described in 801(c)(7).
Note.— The reference ground speed, VGr, can be derived from true airspeed data since, by definition, the true airspeed and ground speed are identical for the zero wind reference condition.
801(c)(5) Multi-segmented flight path conditions at constant airspeed [ETM GM No. 5 ATT H 2.3] This guidance applies to multi-segmented approach profiles at a single constant reference airspeed, with each segment having a different reference descent angle or level flight condition.
Note.—An alternative procedure for supplying LUP data for multi-segmented flight profiles at constant airspeed is possible by combining segm ents from constant profile data sets. The applicant should be aware, however, that directivity effects can be important in propagating acoustic data to the flight paths for each segment, necessitating the use of additional microphones to provide greater geometric resolution of the recorded noise data.
801(c)(6) Guidance for mult i-segmented flight paths with climb segments [ETM GM No. 6 ATT H 2.3] (Reserved) Page 259
801(c)(7) Non-constant airspeeds and/or flight path conditions [ETM GM No. 7 ATT H 2.3] (Reserved) 801(c)(8) Approaches with constant deceleration and flight path conditions [ETM GM No. 8 ATT H 2.3] The deceleration phase of the reference flight profile should span the entire 10 dB-down period for each of the noise certification measurement points as illustrated in Figure 52 and Figure 53. If not, the reference approach procedure should not be treated as a single flight segment. It is also advisable that the deceleration phase be initiated as close as possible to the start of the 10 dB-down period in order to ensure that the airspeed is as close as possible to the reference airspeed at the first 10 dB-down point. This will be useful in minimizing the potential effects of wind on meeting both airspeed tolerance requirements.
Note.— Practice flights may be advisable to establish and/o r confirm a reference flight profile that meets these criteria.
If a reference deceleration or airspeed schedule is not predefined, its value needs to be derived or otherwise determined from the measured data. One method to de fine reference deceleration or airspeed schedule is to determine the mean of the test runs by averaging the deceleration or airspeed profile of each test run that meets the test window criteria.
801(c)(9) Other non-constant airspeed s and/or flight path conditions [ETM GM No. 9 ATT H 2.3] (Reserved) 802 EQUIVALENT PROCEDURES INFORMATION [ETM 8.2] (Reserved) 803 TECHNICAL PROCEDURES INFORMATION [ETM 8.3] 803(a) Adjustments to Reference Conditions [ETM 8.3.1] 803(a)(1) Constant airspeed and flight path conditions [ETM GM No. 10 ATT H 2.3] Helicopter noise data acquired for constant airspeed and f light path conditions are typically adjusted to reference conditions using standardized procedures such as provided in Appendices H and J of part 36.
803(a)(2) [Measurements processed using th e procedures of Appendix J of part 36 [ETM GM No. 11 ATT H 2.3] The following adjustments to noise data assume corrected as-measured one-third octave and aircraft position time history data and are available in Appendix J of part 36.
Note.— Corrected as-measured noise data are data corrected as per the requirements of A36.3.9 and A36.3.10 of part 36.
If a reference flight condition with a fixed flight path and/ or fixed airspeed different from those defined for noise certification testing under Appendix H of part 36 is measured, the same data adjustment procedures defined in Appendix H of part 36 can be used with the new referenc e conditions substituted in the adjustment procedures as appropriate and the adjustment procedures modified as necessary to give results in terms of sound exposure level (LAE) and any other metrics selected by the applicant.
The adjustments to be applied to time-integrated noise metrics (e.g., LAE or EPNdB) should include:
a) band-sharing correction for tone corrected metrics such as EPNL;
b) 1 adjustment for sound attenuation;
c) 2 duration adjustment for time-integrated metrics; and
d) 3 source noise adjustment for Flyovers.
Note.— The band-sharing correction, the 1 adjustment and the 3 adjustment should also be applied, as appropriate, to the maximum noise level (e.g., PNLTM, LAmax) if the value is to be published.
1 can be calculated for LAE and LAmax as follows:
a) determine the aircraft position at the time that the noise at L Amax was emitted and the slant range to the microphone diaphragm;
b) determine the reference aircraft position based on the reference flight path and th e reference slant range to the microphone diaphragm;
c) calculate a new reference L Amax from the one-third octave spectrum as adjusted using the equation in H36.205(f) of part 36;
d) calculate 1 by subtracting the test LAmax from the reference LAmax as in H36.205(f) of part 36.
Note 1.— Use of the 1 adjustment derived for EPNL and PNLTM is acceptable for application to LAE and LAmax noise data.
Note 2.— If the temperature and humidity meteorological conditions are within the zero attenuation adjustment window, the reference and test slant ranges may be replaced by the reference and test distances to the helicopter when the helicopter is over the center noise measuring point (see 402(c)(2)(A) of this AC). This assumes that the measurement points are the same or close to the locations used for noise certification testing, and the aircraft slant ranges are similar to those seen during noise certification testing. If additional measurement points are used that are significantly further from the flight path, consideration should be given to the increased error that is inherently added by the increased distances.
The 2 adjustment is applied only to time-integrated noise metrics. The measured and reference distance values used in determining 1 adjustments to the test data may be used to determine the distance term of the 2 adjustment.
An example of calculating 2 for LAE is:
a) determine a mean ground speed, V G, for each test run;
b) if a reference ground speed, V Gr, has not been predefined, determine a reference ground speed from the test results to be used as VGr in the 2 adjustment; and Page 261
c) calculate 2 as in H36.205(g) of part 36 from the slant ranges determined from the 1 adjustment procedure, mean ground speed, VG, of the test run, and the reference ground speed, VGr.
During noise certification testing, an accepted source noise adjustment procedure for flyovers is the method described in H36.205(e) of part 36. This adjustment is normally made using a sensitivity curve of the maximum PNLTM versus main rotor advancing blade tip Mach number. For time-integrated metrics other than EPNL, the corresponding maximum noise metric should be used in place of PNLTM.
An alternative method, the equivalent Mach number test procedure, is to calculate an adjusted reference true airspeed based on the pre-selected reference airspeed and/or test airspeed and the test-day outside air temperature (see 401(h)(7), section 10 of 401 (h)(8), 402(c)(2)(B) and AMC J36.105(c) of this AC). Either method is acceptable for adjusting flyover data for LUP purposes at other speeds when the reference airspeed is known beforehand.
Note.— Use of the source noise adjustment derived for EPNL and PNLTM is acceptable for application to LAE and LAmax noise data.
For some flyover tests without a predefined reference airspeed, Vr, for which the equivalent Mach number method is intended to be used, test runs may be flown at selected airspeeds without first adjusting the airspeed for test-day outside air temperature. In this case, the reference airspeed, V r, may be derived from the test data so that it includes the adjustment for source noise. This can be achieved by the following process:
a) calculate a main rotor advancing tip Mach number, M T, for each test run from the test true airspeed, VT, the main rotor blade tip rotational speed, V TIP, and the speed of sound, c T, calculated from the on-board measurement of outside air temperature:
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b) calculate the mean of the test Mach numbers;
c) set the reference Mach number, M R, equal to the mean of the test Mach numbers;
d) calculate V r from the reference Mach number, M R, the main rotor blade tip rotational speed, V TIP, and the speed of sound, c, at 25C (77F):
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e) calculate the adjusted reference airspeed V ar and 2 for each test run as in the normal manner (see 401(h), section 10 of 401(h)(8) of this AC of and H36.205(g) and J36.205(c) of part 36).
Note.— A value of Vr can be selected that is different from that calculated above, with Var adjusted accordingly, as long as each test run used to determine the mean noise level for the chosen Vr is within the test window for airspeed.
803(a)(3) Measurements processed using the procedures of Appendix J of part 36 [ETM GM No. 12 ATT H 2.3] Note 1.— Appendix J applicants are encouraged to record the sound pressure signals and/or one-third octave data and, if possible, aircraft position time-history data in addition to the requirements of Appendix 4 of the Annex.
This will enable additional analysis and provision of data, including additional sound metrics.
Note 2.— In addition to the center microphone required by Appendix J, applicants should give consideration to acquiring data using two additional measurement points symmetrically disposed at 492 ft (150 m). The adjustments Page 262
in this section can be applied to the noise levels measured at those locations. This requires the calculation of the slant range distance from the aircraft position at the overhead point to the sideline location.
The following adjustments assume corrected as-measured data obtained from an integrating sound level meter and aircraft position at the overhead point and are available in Appendix J of part 36. When as-measured one-third octave data are used to calculate LAE, the method described in 803(a)(2) can be used if aircraft time-history position data are also available.
Note.— Corrected as-measured noise data are data corrected as per the requirements of J36.109(d)(ii) of Appendix J of part 36.
The adjustments to be applied to time-integrated noise metrics (e.g., LAE) should include:
a) 1 adjustment separated into spherical spreading and duration terms (see example below); and
b) 2 adjustment.
Note 1.— The separation of the 1 adjustment into spherical spreading and duration terms is based on the terms specified in Appendix 2 of the Annex.
Note 2.— The spherical spreading term of the 1 adjustment should be applied to the maximum noise value (e.g., LAmax) if the value is also to be provided.
An example of calculating 1 is:
a) determine the slant range distance, SR , from the aircraft to the microphone using the measured aircraft height, H, when the helicopter is over the center noise measur ing point; for the flight track microphone, SR will equal H;
b) determine the reference slant range, SR REF, to the microphone using the reference flight path; and
c) calculate spherical spreading term of 1SS as follows:
1SS = 20 log (SR/SRREF) The duration term of the 1 adjustment need be applied only to the time-integrated metric and is calculated as follows:
1D = –7.5 log (SR/SRREF) The 2 adjustment need be applied only to the time-integrated noise metric. For flyovers, the equation described in J36.205(c) of part 36 for J3 and reproduced here should be used to calculate 2.
2 = 10 log (Var/Vr) where Var is the adjusted reference true airspeed.
To calculate the 2 adjustment for takeoff and approach flight conditions, the ground speed of each test run is required.
However, Appendix J of part 36 requires measurement of the ground speed, V G. If each test run is performed with a headwind component, then it is considered acceptable that a 2 adjustment need not be calculated. Note, however, that the resulting noise level will be higher than if adjusted. If ground speed is measured, then 2 should be calculated using the following equation:
2 = 10 log (VG/Vr) Page 263
where Vr is predefined or calculated as in 801(c)(7).
803(a)(4) Multi-segmented flight path conditions at constant airspeed [ETM GM No. 13 ATT H 2.3] Because of the multiple flight segments, determination of Q r to define a Q rKr distance may not be feasible.
Alternatively, if QrKr cannot be located on the reference flight profile, the minimum distances to the test and reference flight profiles can be used to approximate the ratio of Q rKr to QK in determining the 1 and 2 adjustments. The determination of minimum distances should be made to ensure that the adjustments to data are based on distances from the corresponding flight segment on both the test and reference profiles.
803(a)(5) Non-constant airspeed and flight path conditions [ETM GM No. 14 ATT H 2.3] (Reserved) 803(a)(6) Approaches with constant deceleration and flight path conditions [ETM GM No. 15 ATT H 2.3] If a predefined constant reference flight path equivalent to or similar to that defined for noise certification testing under Appendix H is used, the 1 adjustment and the first (distance) component of 2 adjustment defined in Appendix H of part 36, can be used with:
a) the new reference conditions substituted as appropriate; and
b) the adjustment procedures modified as necessary to give results in terms of adjusted sound exposure level, LAE, and any additional metrics selected by the applicant.
For the constant reference airspeed conditions of noise certification under Appendix H of part 36 the second term of the 2 adjustment uses a ground speed ratio to effect a duration adjustment to the measured noise levels. Because the reference airspeed is constant, this ground speed ratio is a time ratio. With a non-consta nt reference airspeed due to deceleration, however, a single reference ground speed is not available and the second term of the 2 duration adjustment is better determined directly from reference and test-time deltas defined for each test run. In this case, the 2 adjustment is modified to:
Δ2 = –7.5 log (QK/QrKr) + 10 log (Δtr,j / ΔtT,j) where tr,j is the reference flight path time interval between the test run 10 dB-down time points and tT,j is the test time interval of the 10 dB-down period for test run j.
Times for the first and last 10 dB-down points on the reference profile can be determined by the following procedure:
a) distance along the reference flight profile can be represented by:
Xr = ½ at2 + V0t + X0, where a is the reference deceleration, V0 is the reference airspeed at X0, and X0 is the selected reference flight track coordinate, typically at the initiation of the deceleration, overhead of the flight track microphone, or at the termination of the deceleration;
b) for each measurement point for each test run, j, time t can be incremented until the calculated X r coordinate agrees with the X T coordinates of the first and last 10 dB-down points to determine the corresponding times on the reference flight profile; alternatively, the solution to the quadratic equation Page 264