(viii) Spectral irregularities;
(ix) Cutback thrust (power) application;
(x) Instrument and equipment calibrations;
(xi) Pseudo-tones.
(7) Manufacturer’s Data: Adjustment of noise values from test to reference conditions should be based on FAA-approved manufacturer's data. Manufacturer's data may include:
(i) Reference flight profiles during take-off with maximum gross weight;
(ii) Flyover, lateral, and approach engine thrust (power) or thrust settings at reference conditions;
(iii) Engine cutback thrust (power) requirements at reference flyover conditions;
(iv) Data defining negative runway gradients;
(v) Reference airspeeds during flyover, lateral, and approach tests at maximum gross weights.
c. Procedures
(1) Applicant’s Responsibility: The applicant is responsible for:
(i) Developing and obtaining FAA approval of noise data including those associated with equivalent procedures.
(ii) Obtaining FAA approval of noise data adjustment procedures and analysis methods.
(iii) Applying approved noise data adjustments used to determine values of EPNLr.
(iv) Documenting adjustment procedures not specifically identified in part 36.
240. Section A36.9.1.2
The “integrated” method of adjustment, described in section A36.9.4, must be used on takeoff or approach under the following conditions:
(a) When the amount of the adjustment (using the “simplified” method) is greater than 8 dB on flyover, or 4 dB on approach; or
(b) When the resulting final EPNL value on flyover or approach (using the simplified method) is within 1 dB of the limiting noise levels as prescribed in section B36.5 of this part.
a. Explanation
None.
b. Supplemental Information
(1) Simplified and Integrated Methods: When testing is conducted at other than reference conditions, noise data must be adjusted to reference conditions by one of the following methods:
(i) The simplified analysis procedure, whereby the PNLTM value of the lateral, flyover, and/or approach noise measurement is adjusted to reference conditions
(ii) The integrated analysis procedure whereby, each half-second spectrum of noise measurements throughout the 10 dB-down period is adjusted to reference conditions. The noise emission angle is kept constant in determining the reference emission time that corresponds to the test emission time. The use of the integrated procedure is not required by part 36 for adjustment of lateral noise data.
c. Procedures
(1) NPD Equivalent Procedures: Applicants that propose the use of NPD databases may be required to use the integrated method as part of an equivalent procedure approval process. Appropriate noise data adjustments from test to reference conditions must be incorporated into the integrated method prior to comparing values of EPNLr to the limits specified in Appendix B.
241. Section A36.9.2 Flight profiles
As described below, flight profiles for both test and reference conditions are defined by their geometry relative to the ground, together with the associated airplane speed relative to the ground, and the associated engine control parameter(s) used for determining the noise emission of the airplane.
242. Section A36.9.2.1 Takeoff Profile
Note: Figure A36-4 illustrates a typical takeoff profile.
(a) The airplane begins the takeoff roll at point A, lifts off at point B and begins its first climb at a constant angle at point C. Where thrust or power (as appropriate) cut-back is used, it is started at point D and completed at point E.
From here, the airplane begins a second climb at a constant angle up to point F, the end of the noise certification takeoff flight path.
(b) Position K1 is the takeoff noise measuring station and AK1 is the distance from start of roll to the flyover measuring point. Position K2 is the lateral noise measuring station, which is located on a line parallel to, and the specified distance from, the runway center line where the noise level during takeoff is greatest.
(c) The distance AF is the distance over which the airplane position is measured and synchronized with the noise measurements, as required by section A36.2.3.2 of this part.
a. Explanation
This section specifies the take-off flight test profiles for flyover noise measurements.
b. Supplemental Information
(1) Take-off Tests: The reference take-off configuration selected by the applicant must be within the approved airworthiness certification envelope. Special flight crew procedures or aircraft operating procedures are not permitted. The following figures explain the approved takeoff procedures used during noise certification flight testing for subsonic transport category large airplanes and jet airplanes.
(2) Take-offs with Thrust (Power) Reduction: Take-offs with thrust (power) reduction are permitted to be included in the reference flyover noise certification procedure (and in the reference lateral noise certification procedure for tests conducted before August 7, 2002) for subsonic transport category large airplanes and jet airplanes, regardless of category (see Figure A36.4). Maximum average engine take-off thrust (power) must be used from the start of take-off roll to the minimum altitude for initiation of thrust (power) reduction as specified in section B36.7(b); see the table below. Section B36.7(b)(2) limits the thrust (power) reduction to the greater of:
(a) that required to maintain one-engine-inoperative level flight, or (b) that required to maintain 4 percent climb gradient with all engines operating. After thrust (power) reduction a slight decrease in the climb gradient may occur due to the thrust lapse that results from increased altitude during the 10 dB-down period. Figure 2 illustrates an example of the effect of thrust (power) reduction on the PNLT time history.
Figure A36-4. Typical Takeoff profile
(3) Minimum Altitude for Thrust (Power) Reduction: During take-off, the engine thrust (power) may be reduced after the minimum altitude has been reached. The minimum thrust (power) reduction altitudes are given below:
Stage Number of Engines Bypass Ratio Minimum Thrust (Power) Reduction Altitude 1 a. More than 3 turbojet engines
b. 3 or fewer turbojet engines
c. Not powered by turbojet engines
a. All bypass ratios
b. All bypass ratios
c. Not applicable
a. 700 ft (214 m)
b. 1,000 ft (305 m)
c. 1,000 ft (305 m) 2 a. More than 3 turbojet engines
b. 3 or fewer turbojet engines
c. More than 3 turbojet engines
d. 3 turbojet engines
e. Fewer than 3 turbojet engines
f. Not powered by turbojet engines
a. Less than 2.0
b. Less than 2.0
c. 2.0 or more
d. 2.0 or more
e. 2.0 or more
f. Not applicable
a. 700 ft (214 m)
b. 1,000 ft (305 m)
c. 689 ft (210 m)
d. 853 ft (260 m)
e. 984 ft (300 m)
f. 1,000 ft (305 m) 3 a. More than 3 engines
b. 3 engines
c. Fewer than 3 engines
a. Minimum cutback altitude for Stage 3 airplanes is not dependent on bypass ratio.
b. Minimum cutback altitude for Stage 3 airplanes is not dependent on bypass ratio.
c. Minimum cutback altitude for Stage 3 airplanes is not dependent on bypass ratio.
a. 689 ft (210 m)
b. 853 ft (260 m)
c. 984 ft (300 m)
PNLT
POINT OF THRUST (POWER) REDUCTION TIME
B ALONE
A ALONE
FLYOVER NOISE TIME
HISTORY WITH THRUST (POWER) REDUCTION SPOOL DOWN
FULL POWER 10d 2(A) TAKE-OFF NOISE TIME HISTORY
POINT OF THRUST (POWER) REDUCTION
FULL TAKEOFF THRUST (POWER) FLIGHT PATH ENGINE SPOOL- DOWN PERIOD
REDUCED THRUST (POWER) FLIGHT PATH
NOISE MEASURING POINT 2(B) TAKE-OFF FLIGHT PATH OVER FLYOVER
MEASURING POINT WITH THRUST (POWER) REDUCTION
Figure 2: Noise Time History with Thrust (Power) Reduction
(4) Full Thrust (Power) Take-offs: Full Thrust (power) take-offs are also permitted as the reference flyover noise certification procedure and are required for the lateral noise certification procedure for tests conducted on or after August 7, 2002 (see sections B36.3 and B36.7(b)(3)). Maximum approved take-off Thrust (power) is to be used from the start of roll (Point A) at one end of a runway (Figure 3). Liftoff from the runway is at Point B, after which the landing gear is stowed, and flap positions adjusted. At Point C, the stabilized climb angle and airspeed are achieved while maintaining full take-off thrust (power). The airplane continues to climb until sufficiently past (Point F) to ensure that the 10 dB-down time noise value is measured at point K. Between Points C and F, the thrust (power), flight path and aircraft configurations are to be kept constant.
Altitude BR LOF Test Start
PT A PT B PT C PNLTM-10dB PNLTM PNLTM-10dB Test End PT F PT M PT K Flight Path Microphone PNLT Time 10dB-down Period PNLTM C F 10dB 21,325 ft (6,500 m)
Figure 3: Normal Full Thrust (Power) Take-Off
(5) Flight Path Intercept Take-off: The flight path intercept procedure is permitted as an equivalent procedure for take-off noise certification testing (Figure 4). Under this equivalent procedure, noise certification test runs may be conducted with the airplane “intercepting” the relevant portion of the noise certification flight test path. This procedure is used in lieu of performing an actual landing and takeoff for each test run. When using the flight path intercept procedure, the airplane test flight path, pitch, airspeed, thrust (power), etc., are to be identical to those that would have existed had the applicant conducted the take-off noise certification test from a static condition on the runway. See sections 2.1.1 and 3.1.1 of the appended ICAO TM.
Altitude 0 PT B PT C PNLTM-10dB PNLTM PNLTM-10dB Test End, Initiate Go Around PT F PT M PT K Flight Path Microphone 10dB down periodDistance Power Advance Stabilized Conditions PNLT PNLTM Time C F 10dB
(6) Flight Path: Figure 5 illustatrates the flight path tolerance for envelope within which the flight crew can fly between Points C and F. The FAA permits a + 20 percent tolerance in overhead test altitude and a + 10° lateral tolerance relative to the extended runway centerline. These tolerances permit the applicant to conduct testing during most wind conditions with minimal risk of re-testing being required due to off-target flight paths. In conjunction with the climb gradient and approach angle, these flight path deviation limitations define the takeoff “flight path” through which the aircraft is to fly during and throughout the noise measurements (during 10 dB-down period). During flyover and lateral noise measurements, the extended centerline is not visible and it may be more difficult to conduct flight within the approved flight path, especially during conditions of anomalous winds aloft. Several methods have been devised to assist, and provide direction to the flight crew in order to stay within the required flight path envelope. Indicators located in the airplane cockpit can provide flight path direction and indicate deviations from the extended runway centerline. Transmissions from the airplane position-indicating system (e.g., microwave position system, precision DMU, or DGPS) can also provide useful inputs.
Figure 4: Flight Path Intercept Take-Off
Allowable Vertical Deviation Flight Path Test End Microphone Location Test Begin PT C PT F
PT K PT M PNTLM-10dBPNTLM-10dB Extended Runway Centerline Overhead Test Target Altitude Allowable Lateral Deviation Overhead Test Window
Figure 5: Take-Off Flight Path
c. Procedures
(1) Target Test Conditions: Target test conditions are established for each noise measurement.
These target conditions specify the flight procedure, aerodynamic configuration to be selected, airplane weight, engine thrust (power), airspeed, and, at the closest point of approach to the noise measurement point, airplane altitude. Regarding choice of target airspeeds and variation in test weights, the possible combinations of these test elements may affect the airplane angle-of-attack or airplane altitude and therefore possibly the airplane noise generation or propagation geometry. See sections 2.1.2.1 and 3.1.2(a) of the appended ICAO TM for guidance on the choice of target airspeeds and variation in test weights.
(2) Simulated Thrust (Power) Reduction Evaluation: When thrust (power) reduction, as permitted under section B36.7(b), is used in conjunction with establishing the flyover noise certification level (or lateral noise certification level for tests conducted before August 7, 2002), a commonly used equivalent procedure allows for the noise certification level to be determined through the coupling of the NPD database with the approved engine spool-down data. As long as the minimum thrust (power) reduction height requirements specified in section B36.7(b)(1) are met, the thrust (power) reduction initiation height may be selected to ensure stabilized thrust (power) reduction conditions before the initial 10 dB-down point. As discussed in section 2.2.1.2 of the appended ICAO TM, this procedure can be implemented using constant stabilized thrust (power) throughout the 10 dB-down period. Flyover noise levels with thrust (power) reduction may also be established from the merging of PNLT versus time measurements obtained during constant thrust (power) operations. The 10 dB-down period may contain portions of both the full thrust (power) and reduced thrust (power) noise time histories. Section 2.2.1.1 of the appended ICAO TM describes the establishment of the flyover noise certification level when the 10-dB down PNLT noise time history contains portions of both full thrust (power) and reduced thrust (power). The FAA must
witness and approve all engine spool-down testing. See section B36.7(b)(1) for additional information regarding engine spool-down testing.
(3) Flight Test Procedures: Before the start of noise testing the FAA must approve flight path tolerances (see Supplemental Information Item 6 under this section). Between Points C and F (Figure 5), the engine thrust (power), airplane flight path and aerodynamic configuration must be kept constant during each approved certification flight test (except when take-offs with thrust (power) reduction are being demonstrated).
(4) Invalid Test Data: Noise measurements obtained when the airplane flies outside the approved flight path envelope between Points C and F (Figure 5) during a noise certification test are considered invalid, and the noise measurement is to be repeated.
243. Section A36.9.2.2 Approach Profile
Note: Figure A36-5 illustrates a typical approach profile.
(a) The airplane begins its noise certification approach flight path at point G and touches down on the runway at point J, at a distance OJ from the runway threshold.
(b) Position K3 is the approach noise measuring station and K3O is the distance from the approach noise measurement point to the runway threshold.
(c) The distance GI is the distance over which the airplane position is measured and synchronized with the noise measurements, as required by section A36.2.3.2 of this part. The airplane reference point for approach measurements is the instrument landing system (ILS) antenna. If no ILS antenna is installed an alternative reference point must be approved by the FAA.
Figure A36-5. Typical Approach profile
a. Explanation
This section provides illustrations and explanations of approach flight test profiles .
b. Supplemental Information
(1) Approach Tests: Figures 6 and 7 depict the types of approved approach flight test procedures used during noise certification testing for subsonic transport category large airplanes and jet airplanes. The approach angle (steady glide angle) for this condition is 3° ± 0.5°, and the target airplane height vertically over the noise measurement point is 394 feet. Figure 8 illustrates the allowable approach flight test path deviations.
Maximum PNLT may occur before or after the approach noise measurement point.
(2) Normal Approach Flight Tests: Part 36 specifies a full landing following each approach noise measurement (Figure 6). This type of flight test is less efficient than the flight path intercept equivalent procedure that is used by most noise certification applicants. See sections 2.1.1 and 3.1.1 of the appended ICAO TM for more guidance on the use of the flight intercept procedure.
Altitude PT P PT J PNLTM-10dB 6562’ Distance PT G PT H PT I Stabilized Conditions End of Test Flight Path Touchdown Microphone PT N PNLTM-10dB 10 dB-down Period PT O Glide Slope = 3°±0.5°
Figure 6: Approach With Full Landing
(3) Flight Path Intercept Approaches: When the flight path intercept procedure is used for approach, the airplane does not land, but following the determination that the 10 dB-down time requirements have been satisfied, initiates a go-around maneuver and returns to the in-flight setup location for the next test condition
(Figure 7). Most applicants use the flight path intercept procedure for approach flight testing. This procedure permits the applicant to remain flying during acceptable atmospheric conditions without the delays associated with landings and take-offs.
Altitude 0
PT P PT J PNLTM-10dB 6562’ Distance PT G PT H PT I Stabilized Conditions Initiate Go-Around Flight Path Simulated Normal Touchdown Microphone PT N PNLTM-10dB 10dB-down Period PNLT PNLTM Time G I 10dB Go-Around End of Test PT O Glide Slope = 3°±0.5°
Figure 7: Flight Path Intercept Approach
(4) Flight Path Deviations: Approved altitude and centerline deviations along the extended runway approach flight path (Figure 8) define an approved flight path envelope within which the flight crew can fly between Points G and I (see Supplemental Information under Item 6 section A36.9.2.1). Since the flight crew has a clear view of the airport runway during approach conditions, it is normal for the crew to consistently fly within the approved flight path envelope. Therefore, the approved centerline and altitude deviations for approach conditions may be smaller than during take-off conditions.
Extended Runway Centerline Allowable Altitude Deviation Flight Path Test End Microphone Location Test Begins PT I PT G
PT N PT O PNTLM-10dB PNTLM-10dB PT H Test Target Altitude = 394 ft Allowable Lateral Deviation PT P 10 dB-down Period
Figure 8: Approach Flight Path Deviations
c. Procedures
(1) Noise-Power-Distance Database: By developing an approach noise-power-distance database, the applicant can obtain noise certification data to cover a range of airplane weights and engine thrust (power) settings. The NPD method is an equivalent procedure and must be approved by the FAA prior to its use. In developing an NPD database, noise data may be obtained with a series of different engine thrust (power) settings down to in-flight idle thrust (power). The NPD database can then be used to determine reference condition approach noise levels. Stabilized thrust (power) (Point G in Figure 7) is set before the initial 10 dB-down point and maintained until the subsequent 10 dB-down point has passed (Point I). The applicant must take care to obtain enough thrust (power) settings to permit a second or third order curve fit through the generalized data, and to define data shifts that may be caused by engine internal compressor bleed operations. In creating an NPD database, it will not be possible to maintain all of the constant constraints of weight, airspeed, thrust (power), configuration glide path, and height over the microphone. The critical test parameters to be maintained are constant thrust (power) and configuration during the test condition. The glide angle during the NPD test shall be that which results from the aircraft conditions (i.e., weight, configuration, airspeed, and engine thrust (power)).
See sections 2.1.2 and 3.1.2 of the appended ICAO TM.
(2) Target Test Conditions: Target test conditions must be established for each noise measurement. These specify the selected aerodynamic configuration, system operation, airplane weight, flight procedure (such as complete landings or flight path intercepts), altitude, thrust (power), and airspeed during each overflight. The applicant is required to select the approved airworthiness configuration for the approach noise certification that produces the highest noise level (i.e., the most critical from the standpoint of noise). Airspeed is generally held to within ± 3.0 percent of the average airspeed during the 10 dB-down measuring period. The airplane configuration (e.g., flap setting, A/C, and/or APU system operation) is to remain constant during the noise measurement period. Airspeed variations are measured in indicated airspeed determined by the pilot’s airspeed indicator.