Variable speed helicopter airworthiness certification noise equivalent test device and method

Abstract

The application provides a variable speed helicopter airworthiness qualification noise equivalent test method, which comprises the following steps: determining a reference test condition; obtaining a test and measurement condition; performing a flight state test under the reference test condition, the test and measurement condition, meteorological condition, take-off test condition, horizontal flight test condition and approach test condition; meanwhile, the application also provides a variable speed helicopter airworthiness qualification noise equivalent test device; through the above equivalent test method, the forward rotor tip Mach number during the test is kept consistent with the forward rotor tip Mach number under the reference test condition, so that the variable rotor speed helicopter noise airworthiness qualification is ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of helicopter noise and airworthiness, and particularly relates to a variable speed helicopter airworthiness certification noise equivalent test device and method. BACKGROUND

[0002] The Aircraft Type and Airworthiness Certification Noise Regulation (CCAR-36) makes clear provisions for the reference test conditions, test and measurement conditions, test equipment, noise evaluation and calculation, etc. of the noise airworthiness certification of civil helicopters. In order to obtain the type certificate of a civil helicopter, the applicant must carry out noise certification tests in accordance with the relevant requirements of the regulations, obtain the external noise level of the helicopter, and show that it meets the relevant requirements of the regulations to the airworthiness authority.

[0003] However, the airworthiness regulations have provisions for noise testing of constant speed helicopters, but do not clearly define the noise testing method for variable speed helicopters. SUMMARY

[0004] To solve the above technical problems, in a first aspect, the application provides a variable speed helicopter airworthiness certification noise equivalent test method, the method comprising:

[0005] determining reference test conditions;

[0006] obtaining test and measurement conditions; meteorological conditions, take-off test conditions, level flyover test conditions, approach test conditions

[0007] conducting a flight state test under the reference test conditions, test and measurement conditions.

[0008] Preferably, the determination of the reference test conditions comprises:

[0009] determining reference atmospheric conditions, reference take-off profiles, reference flyover profiles, and reference approach profiles.

[0010] Preferably, the obtaining of the test and measurement conditions comprises:

[0011] obtaining meteorological conditions, take-off test conditions, level flyover test conditions, and approach test conditions.

[0012] Preferably, the conducting of the flight state test under the reference test conditions, test and measurement conditions comprises:

[0013] conducting a take-off state test under the reference test conditions, test and measurement conditions.

[0014] Preferably, the conducting of the flight state test under the reference test conditions, test and measurement conditions comprises:

[0015] The horizontal flight state test is performed under the reference test condition, test and measurement condition.

[0016] Preferably, the flight state test is performed under the reference test condition, test and measurement condition, including:

[0017] The approach state test is performed under the reference test condition, test and measurement condition.

[0018] In a second aspect, the application also provides a variable speed helicopter airworthiness qualification noise equivalent test device, the device comprising:

[0019] A determination unit is configured to determine a reference test condition.

[0020] An acquisition unit is configured to acquire test and measurement conditions, including meteorological conditions, take-off test conditions, horizontal flight test conditions and approach test conditions.

[0021] A test unit is configured to perform a flight state test under the reference test condition, test and measurement condition.

[0022] Preferably, the flight state includes a take-off state, a horizontal flight state and an approach state.

[0023] The application has the following advantages: the above-mentioned equivalent test method ensures that the forward rotor tip Mach number during the test is consistent with the forward rotor tip Mach number under the reference test condition, thereby ensuring the noise airworthiness qualification of the variable speed helicopter and meeting the relevant requirements of the Aircraft Type and Airworthiness Qualification Noise Regulations (CCAR-36). BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a reference take-off profile schematic diagram provided by the embodiments of the application;

[0025] Figure 2 is a reference flight profile schematic diagram provided by the embodiments of the application;

[0026] Figure 3 is a reference approach profile schematic diagram provided by the embodiments of the application;

[0027] Figure 4 is a schematic diagram of the relationship between the rotor speed and the pressure altitude and atmospheric temperature (below 50 kt true airspeed);

[0028] Figure 5 is a schematic diagram of the relationship between the rotor speed and the pressure altitude and atmospheric temperature (above 70 kt true airspeed);

[0029] Figure 6This is a schematic diagram of the climb rate calculated based on the tip Mach number provided in the embodiments of this application;

[0030] Figure 7 This is a schematic diagram of the approach speed calculated based on the tip Mach number provided in the embodiments of this application. Detailed Implementation

[0031] Please see Figures 1-7 The solution provided in this application is as follows:

[0032] I. The baseline test conditions in the noise equivalence test method for airworthiness certification shall adopt the baseline test conditions specified in the "Noise Regulations for Aircraft Type Certification" (CCAR-36), as follows:

[0033] 1. Baseline atmospheric conditions

[0034] (1) Sea level pressure: 1013.25 hPa;

[0035] (2) Atmospheric temperature 25℃;

[0036] (3) Relative humidity 70%;

[0037] (4) No wind.

[0038] 2. Baseline takeoff profile

[0039] like Figure 1 As shown, the baseline takeoff trajectory begins 500m ahead of the central noise measurement station A, at an altitude of 20m above the ground, with a climb angle β and a V under baseline atmospheric conditions. Y The aircraft climbs steadily, flying over a straight line from station A, with its ground projection perpendicular to the line connecting the noise measurement stations. The climb angle β is limited by the climb power under reference atmospheric conditions and V. Y Sure.

[0040] 3. Benchmark flyover profile

[0041] like Figure 2 As shown, the reference overflight trajectory begins 150m above the ground in front of the central noise measurement station A, and flies steadily at the reference airspeed across the straight line of station A. Its ground projection is perpendicular to the line connecting the noise measurement stations. The reference airspeed is 0.9V under reference atmospheric conditions. H 0.9V NE 0.45V H +120km / h and 0.45V NE The minimum value within +120km / h.

[0042] 4. Reference Approach Profile

[0043] like Figure 3The reference approach path is shown as a straight line from the front of the center noise measurement station A, with an approach angle η = 6° and a steady glide Vy under the reference atmospheric conditions, flying at a height of 120 meters above ground when passing the station A, and its ground projection is perpendicular to the line connecting the noise measurement stations.

[0044] II. Test and Measurement Conditions for Noise Equivalent Test Method of Airworthiness Certification The test and measurement conditions for noise equivalent test method of airworthiness certification are as follows:

[0045] 1. Meteorological Conditions

[0046] (1) No precipitation;

[0047] (2) Atmospheric temperature between -10℃ and 35℃ (inclusive);

[0048] (3) Relative humidity between 20% and 95% (inclusive);

[0049] (4) Atmospheric sound attenuation on one-third octave band of 8 kHz center frequency is not more than 12 dB / 100m;

[0050] (5) Wind speed is not more than 19 km / h (10 kt), and crosswind is not more than 9 km / h (5 kt).

[0051] 2. Take-off Test Conditions

[0052] At least six take-off noise tests are completed, and the tests are measured simultaneously at three noise measurement stations. The weight of each test must be between 90% and 105% of the maximum certified weight, and at least one test must be conducted at or above the maximum certified weight. The landing gear position in the test is consistent with the airworthiness certification test for determining Vy, and the following tolerance limits must be maintained within the 10 dB drop period:

[0053] (1) Flight trajectory lateral deviation is not more than ±10° or ±20m, taking the larger value;

[0054] (2) Airspeed deviation from the reference airspeed is not more than ±9 km / h (±5 kt);

[0055] (3) Rotor speed deviation from the normal working speed is not more than ±1.0%.

[0056] 3. Horizontal Flight Test Conditions

[0057] At least six flyover noise tests are completed, and the number of tests against the wind must be equal to the number of tests with the wind, and the tests are measured simultaneously at three noise measurement stations. The weight of each test must be between 90% and 105% of the maximum certified weight, and at least one test must be conducted at or above the maximum certified weight. The landing gear is in the retracted position during the test, and the following tolerance limits must be maintained within the 10 dB drop period:

[0058] (1) Fly over A at 150 ± 9 m;

[0059] (2) Lateral deviation of flight path not more than ± 10° or ± 20 m, whichever is greater;

[0060] (3) Airspeed deviation from reference airspeed not more than ± 9 km / h (± 5 kt);

[0061] (4) Rotor speed deviation from normal operating speed not more than ± 1.0%.

[0062] 4. Approach test conditions

[0063] At least six approach noise tests must be completed, with simultaneous measurements at three noise measurement stations. Each test must be conducted at a weight between 90% and 105% of the maximum certified weight, and at least one test must be conducted at or above the maximum certified weight. The landing gear must be in the down position during the test, and the following tolerance limits must be maintained during the 10 dB drop period:

[0064] (1) Approach angle η = 6° ± 0.5°;

[0065] (2) Fly over A at 120 ± 10 m;

[0066] (3) Lateral deviation of flight path not more than ± 10° or ± 20 m, whichever is greater;

[0067] (4) Airspeed deviation from reference airspeed not more than ± 9 km / h (± 5 kt);

[0068] (5) Rotor speed deviation from normal operating speed not more than ± 1.0%.

[0069] III. Variable rotor speed characteristics

[0070] The certain type of civil helicopter has the following variable rotor speed characteristics: the reference rotor speed of 100% is 279 rpm, and during actual flight, the rotor speed is automatically adjusted between 97% and 105% based on real-time true airspeed, pressure altitude, and atmospheric temperature. Figure 4 and Figure 5 The relationship between rotor speed and pressure altitude and atmospheric temperature is given for true airspeeds below 50 kt and above 70 kt, respectively. For true airspeeds between 50 kt and 70 kt, the rotor speed is linearly interpolated from Figure 4 and Figure 5 .

[0071] Due to the above-mentioned variable rotor speed characteristics, when the helicopter is flown at reference airspeed for flight testing, the rotor speed varies with the pressure altitude and atmospheric temperature at the time of testing, and the corresponding rotor speed under the reference test conditions cannot be maintained.

[0072] Taking the horizontal flight noise test as an example, the reference atmospheric condition is a pressure altitude of 0 m and an atmospheric temperature of 25°C, the reference airspeed is 131 kt, and the corresponding rotor speed is 281.4 rpm, and the forward blade tip Mach number is 0.749. Assuming that the test atmospheric condition is a pressure altitude of 150 m and an atmospheric temperature of 5°C, the corresponding rotor speed is 277.8 rpm when the true airspeed is 131 kt, and at this time, due to the deviation of the rotor speed, the rotor forward blade tip Mach number deviates from the test state required by the regulations.

[0073] In other embodiments of the present application, three flight states are provided:

[0074] The test method provided by the present application comprises the following steps:

[0075] In the take-off state:

[0076] Step 1, determine the rotating blade tip speed Vr of the rotor under the reference condition according to the following formula: 基准 is 218.1 m / s; wherein the rotor speed n 基准 is 281.4 rpm, the rotor radius R is 7.4 m, and:

[0077] Vr 基准 = n 基准 πR / 30

[0078] Step 2, determine the sound speed c under the reference condition according to the following formula: 基准 is 346.1 m / s, wherein T0 is 293.15 K, and T 基准 is the absolute ambient temperature under the reference condition;

[0079] c 基准 = 343.2 (T 基准 / T0) 1 / 2

[0080] Step 3, determine the forward blade tip Mach number MAT of the rotor under the reference condition when taking off according to the following formula: 爬升 is 0.749; wherein Vr 基准 is the rotating blade tip speed 218.1 m / s under the reference condition calculated in step 1, Vy is the best climb rate speed 80 kt of the helicopter in the take-off state, and c 基准 is the sound speed under the reference condition determined in step 2.

[0081] MAT 爬升 = (Vr 基准 + 0.5144 Vy) / c 基准

[0082] Step 4: During flight testing, based on the pressure altitude and atmospheric temperature of the area where the test helicopter is located, by... Figure 4 Interpolation yields the rotor speed n under the current weather conditions. 测试 The corresponding rotating blade tip speed Vr during the test is obtained. 测试 ,as follows:

[0083] Vr 测试 =n 测试 πR / 30

[0084] Step 5: During the flight test, the speed of sound c during the test is calculated based on the atmospheric temperature of the area where the test helicopter is located. 测试 As shown below, where T0 is 293.15K, T 测试 It is the absolute ambient temperature during the experiment.

[0085] c 测试 =343.2(T) 测试 / T0) 1 / 2

[0086] Step 6: During flight testing, the area where the test helicopter is located may not be consistent with the baseline conditions, causing changes in rotor speed and atmospheric sound speed. To ensure that the advancing blade tip Mach number is consistent with the baseline conditions during actual flight testing, the following formula is used to adjust the climb rate V during actual flight testing. 测试 To change the forward propeller tip Mach number; where MAT 爬升 Vr is the forward tip Mach number at takeoff under the baseline conditions determined in step 3. 测试 c is the Mach number of the rotating blade tip during the test, determined in step 4. 测试 The speed of sound during the test is determined in step 5.

[0087] V 测试 =1.9438 (MAT) 爬升 ·c 测试 -Vr 测试 )

[0088] Step 7: Due to the takeoff state, the helicopter needs to climb from an altitude of 20m to an altitude of over 200m. Figure 6 The climb rate V is given at temperatures of 5℃, 7.5℃, and 10℃, to maintain a consistent tip Mach number due to pressure and altitude variations. 测试 The changes show that, taking a temperature of 5℃ as an example, to ensure a consistent rotor tip Mach number during takeoff, the climb rate should be adjusted to 69.8 kt at an altitude of 20 m and to 66.5 kt at an altitude of 200 m.

[0089] Step 8, from step 7, at ambient temperature 5°C, the helicopter climbs from the height of 20m to the height of 200m, to ensure the consistency of the forward flight tip Mach number, the climb speed should be changed by 3.3kt, the pilot needs to adjust the climb speed at any time during the take-off process, which greatly increases the pilot's control load; if the climb speed V 测试 is used at the height of 20m, the speed will deviate from the climb speed V 测试 at the height of 200m determined in step 6 by 3.3kt. The regulations require that the airspeed deviation from the reference airspeed during take-off should not exceed ±9km / h (±5kt), and the 3.3kt speed deviation caused by the change of pressure altitude during take-off leaves only 1.7kt margin, which is too stringent to ensure the validity of the test data. Therefore, the climb speed V 测试 at the height of 100m determined in step 6 is taken as the stable climb speed, which not only reduces the pilot's control load, but also ensures the validity of the data.

[0090] In the horizontal flight state:

[0091] Step 1, the rotating tip speed Vr 基准 of the rotor under the reference condition is determined according to the following formula, where the rotor speed n 基准 is 281.4rpm, the rotor radius R is 7.4m, and:

[0092] Vr 基准 = n 基准 πR / 30

[0093] Step 2, the speed of sound c 基准 under the reference condition is determined according to the following formula, where T0 is 293.15K, T 基准 is the absolute ambient temperature under the reference condition:

[0094] c 基准 = 343.2(T 基准 / T0) 1 / 2

[0095] Step 3, the V H of the test helicopter under the reference condition is 148kt, and V NE is 178kt, therefore the reference airspeed V m is determined to be 0.45V H +120km / h, i.e. 131kt.

[0096] Step 4, the forward flight tip Mach number MAT 平飞It is 0.825, where Vr 基准 Given the reference blade tip velocity of 218.1 m / s calculated in step 1, c 基准 V is the speed of sound under the reference conditions determined in step 2. m The speed of this type of helicopter during horizontal flight, determined in step 3, is 131 kt.

[0097] MAT 平飞 =(Vr 基准 +0.5144Vy) / c 基准

[0098] Step 5: During flight testing, based on the pressure altitude and atmospheric temperature of the area where the test helicopter is located, by... Figure 4 Interpolation yields the rotor speed n under the current weather conditions. 测试 The corresponding rotating blade tip speed Vr during the test is obtained. 测试 ,as follows:

[0099] Vr 测试 =n 测试 πR / 30

[0100] Step 6: During the flight test, the speed of sound c during the test is calculated based on the atmospheric temperature of the area where the test helicopter is located. 测试 As shown below, where T0 is 293.15K, T 测试 It is the absolute ambient temperature during the experiment.

[0101] c 测试 =343.2(T) 测试 / T0) 1 / 2

[0102] Step 7: During flight testing, the area where the test helicopter is located may not be consistent with the baseline conditions, causing changes in rotor speed and atmospheric sound speed. To ensure that the advancing blade tip Mach number is consistent with the baseline conditions in the actual flight test, the following formula is used to adjust the level flight speed V of the actual flight test. 测试 To change the forward propeller tip Mach number, where MAT 平飞 Vr is the forward tip Mach number during horizontal flyby under the baseline conditions determined in step 4. 测试 c is the Mach number of the rotating propeller tip during the test, determined in step 5. 测试 The speed of sound during the test, as determined in step 6.

[0103] V 测试 =1.9438(MAT·c 测试 -Vr 测试 )

[0104] In approaching state:

[0105] Step 1: Determine the rotor tip speed Vr under reference conditions using the following formula. 基准 The speed is 218.1 m / s, where the rotor speed n 基准 The speed is 281.4 rpm, and the rotor radius R is 7.4 m.

[0106] Vr 基准 =n 基准 πR / 30

[0107] Step 2: Determine the speed of sound c under the reference conditions using the following formula. 基准 The velocity is 346.1 m / s; where T0 is 293.15 K, T 基准 It is the absolute ambient temperature under the baseline conditions;

[0108] c 基准 =343.2(T) 基准 / T0) 1 / 2

[0109] Step 3: Determine the advancing tip Mach number MAT of the rotor under reference conditions during approach using the following formula. 进近 It is 0.749; where Vr 基准 The rotor tip speed, calculated in step 1, is 218.1 m / s under the baseline conditions. Vy is the optimal climb rate of 80 kt for this type of helicopter during approach. 基准 The speed of sound is the speed of sound under the reference conditions determined in step 2.

[0110] MAT 进近 =(Vr 基准 +0.5144Vy) / c 基准

[0111] Step 4: During flight testing, based on the pressure altitude and atmospheric temperature of the area where the test helicopter is located, by... Figure 4 Interpolation yields the rotor speed n under the current weather conditions. 测试 The corresponding rotating blade tip speed Vr during the test is obtained. 测试 ,as follows:

[0112] Vr 测试 =n 测试 πR / 30

[0113] Step 5: During the flight test, the speed of sound c during the test is calculated based on the atmospheric temperature of the area where the test helicopter is located. 测试 As follows; where T0 is 293.15K, T 测试 It is the absolute ambient temperature during the experiment.

[0114] c 测试 =343.2(T) 测试 / T0)1 / 2

[0115] Step 6, during the flight test, the area where the test helicopter is located does not necessarily conform to the reference condition, thus causing the change of the rotor speed and the atmospheric sound speed, in order to ensure the consistency of the forward blade tip Mach number in the actual flight test and the reference condition, the following formula is used to change the forward blade tip Mach number by adjusting the approach speed V 测试 of the actual flight test, wherein MAT 进近 is the forward blade tip Mach number during the approach under the reference condition determined in step 3. Vr 测试 is the rotating blade tip Mach number during the test determined in step 4, c 测试 is the sound speed during the test determined in step 5.

[0116] V 测试 = 1.9438(MAT 进近 · c 测试 -Vr 测试 )

[0117] Step 7, due to the approach state, the helicopter needs to be lowered from the ground height of 180m to the ground height of 60m, Figure 7 The change of the approach speed V 测试 is given when the temperature is 5℃, 7.5℃ and 10℃ respectively, in order to ensure the consistency of the blade tip Mach number due to the change of the pressure height, it can be seen from the table that, for example, when the temperature is 5℃, in order to ensure the consistency of the blade tip Mach number during the approach, the approach speed should be adjusted to 66.9kt at the ground height of 180m, and the climb speed should be adjusted to 69.1kt at the ground height of 60m.

[0118] Step 8, as can be seen from step 7, when the environmental temperature is 5℃, the helicopter is lowered from the ground height of 180m to the ground height of 60m, in order to ensure the consistency of the forward blade tip Mach number, the climb speed should be changed by 2.2kt, and the pilot needs to adjust the approach speed at any time during the approach, which greatly increases the pilot's control load; if a stable speed approach is performed at the ground height of 180m with the approach speed V 测试 determined in step 6, the speed will deviate from the approach speed V 测试 determined in step 6 at the ground height of 60m, and the deviation reaches 2.2kt.

[0119] According to the regulations, the airspeed deviation from the reference airspeed during the approach should not exceed ±9km / h (±5kt), due to the 3.3kt speed deviation caused by the change of the pressure height during the approach, only the remaining 2.8kt margin is too strict, and it is difficult to ensure the effectiveness of the test data, therefore, the approach speed V 测试As the speed of stable approach, both the pilot's control load and the data validity are ensured.

[0120] The technical solution of the present application: the forward flight tip Mach number helicopter affects the external noise of the helicopter. During the noise test, the tip Mach number may deviate from the test state required by the airworthiness regulations due to the influence of the pressure altitude and atmospheric temperature of the flight area where the civil helicopter is located, resulting in invalid noise flight test.

[0121] During the noise airworthiness qualification of a certain type of civil helicopter, for the variable rotor speed characteristic, on the basis of the reference test method given by the airworthiness regulations, the following equivalent test method is adopted for the characteristics of variable rotor speed:

[0122] According to the pressure altitude and atmospheric temperature of the flight area where the civil helicopter is located during the test, the current helicopter adjustment airspeed is determined, so that the forward flight tip Mach number during the test is consistent with the forward flight tip Mach number under the reference test condition, thereby ensuring the validity of the test data.

Claims

1. A noise equivalent test method for airworthiness certification of a variable-speed helicopter, characterized in that, include: S1: Determine the baseline test conditions and calculate the corresponding baseline forward tip Mach number (MAT_baseline). Determining the baseline test conditions includes: determining the baseline atmospheric conditions, baseline takeoff profile, baseline overflight profile, and baseline approach profile. S2: Acquire test and measurement conditions and flight status, wherein acquiring test and measurement conditions includes acquiring weather conditions, takeoff test conditions, level flyby test conditions and approach test conditions, and flight status includes: takeoff status, level flyby status and approach status; S3: Based on the weather conditions and flight status during the actual test, calculate the flight speed required to maintain the forward propeller tip Mach number consistent with the reference forward propeller tip Mach number; S4: Control the helicopter to perform a noise test flight at the stated flight speed under the stated baseline test conditions, test and measurement conditions.

2. A noise equivalent test apparatus for airworthiness certification of a variable-speed helicopter, used to implement the noise equivalent test method for airworthiness certification of a variable-speed helicopter as described in claim 1, characterized in that, The device includes: a determining unit for determining baseline test conditions; an acquiring unit for acquiring meteorological conditions and flight status during actual tests; and a testing unit for conducting flight status tests under the baseline test conditions, test conditions, and measurement conditions.

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