Flight airworthiness verification method for 30-minute full-engine power cooling of transport helicopter engine

Abstract

The invention belongs to the technical field of aircraft design, and discloses a flight airworthiness verification method for 30-minute full-engine power cooling of a transport helicopter engine. Carrying out a hovering cooling flight test; the cooling system is in the most harsh test condition; the helicopter takes off in a plain airport according to a normal program: the helicopter wheel is 3m above the ground, all engines carry out ground-effect hovering at the power not greater than the maximum continuous power, hovering is kept for 5 minutes after the lubricating oil temperature of a transmission system and the engines is stable, or hovering is kept for 5 minutes after the highest lubricating oil temperature appears; the hovering height is increased till no ground effect hovering is achieved till the power of all the engines reaches the rated power of all the engines for 30 minutes, normal landing is conducted when the conditions are met, and all the engines and an auxiliary power device are shut down; after the vehicle is stopped for 15 minutes, a data acquisition system on the vehicle is turned off; the step aims to ensure that the change trend of the temperature of all the power device parts can be collected during the period that the fairing is closed after the power device parts are parked. And carrying out data processing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aircraft design, and discloses a method for verifying the airworthiness of a transport helicopter engine full-power 30-minute cooling flight. BACKGROUND

[0002] A certain type of civil helicopter applies for type certificates of A and B type transport helicopters, and the engine has 2.5-minute single-engine emergency power, 30-minute full-power, take-off and maximum continuous rated power state. The design requirement of the engine 30-minute full-power is to facilitate hovering at a higher power to perform search and rescue tasks, and the rated power value is equal to the rated take-off power, which allows the helicopter to hover in this state for no more than 30 minutes after take-off, and the number of uses is not limited during flight.

[0003] The airworthiness regulations CCAR-29 of the Civil Aviation Administration of China and the relevant airworthiness standards of FAA and EASA all put forward the requirements of the cooling flight test of the transport helicopter, including the requirements of the test procedure, but as for the cooling test method of the engine 30-minute full-power, since the power state exceeds the maximum continuous power required in the hovering cooling test procedure of CCAR29.1049, no specific test method and technical scheme document can be found for implementation, and a special cooling flight airworthiness verification method needs to be developed. SUMMARY

[0004] The application aims to provide a method for verifying the airworthiness of a transport helicopter engine full-power 30-minute cooling flight, which supports the A and B type airworthiness certification of the transport helicopter.

[0005] TECHNICAL SCHEME A method for verifying the airworthiness of a transport helicopter engine full-power 30-minute cooling flight, the method comprising: Performing a hovering cooling flight test; The test method is as follows: Step 1.1; make the cooling system in the most severe test condition; in order to examine the cooling capacity under the maximum power, usually, the accessories such as alternator engine, air conditioning components, etc. work at 100% power.

[0006] Step 1.2; take off at a normal procedure at a plain airport: the helicopter wheel off the ground height is 3 meters, all engines are in ground effect hovering at not more than the maximum continuous power, and the hovering is maintained for 5 minutes after the transmission system and engine oil temperature is stable, or the hovering is maintained for 5 minutes after the highest oil temperature appears; the purpose of this step is to ensure that the power plant components and liquid temperature can reach stability before entering the state of each flight stage; Step 1.3; increase the hover altitude to unground effect hover until all engine power reaches the 30 minute full power rating, normal landing when any of the following conditions are met, all engines and APUs are shut down; Condition one: oil temperature stabilizes for 5 minutes; Condition two: maximum oil temperature is reached during hover and remains for 5 minutes; Condition three: the 30 minute full power rating is reached for the maximum time allowed; Step 1.4; shut down the on-board data acquisition system after 15 minutes of shutdown. This step is to ensure that the temperature trends of all power plant components are captured during the time the nacelles are closed after shutdown.

[0007] Step 1.5; data processing.

[0008] Further, if the engine power cannot reach the 30 minute full power rating after increasing the hover altitude to unground effect hover in step 1.3, then take off from an airport at high altitude and repeat steps 1.3 and 1.4.

[0009] Further, the high altitude airport is an airport with an elevation of 3000 meters or higher.

[0010] Further, the method further comprises: performing a take-off cooling flight test; For an aircraft meeting the A class performance, the take-off cooling flight test method is as follows: Step 2.1; place the cooling system in the most severe test condition; Step 2.2; take off according to the A class take-off procedure in the flight manual: the wheel lift-off height is 3m, all engines are in ground effect hover at no more than maximum continuous power, and the oil temperature of the transmission system and the engine is stabilized for 5 minutes, or the maximum oil temperature is reached during hover for 5 minutes, and the engine torque during hover is recorded; Step 2.3; confirm that all parameters are normal and there is no warning information; push the stick to accelerate the helicopter to the critical decision point, set the critical engine power selection switch to "ground slow"; adjust the pitch angle, accelerate to the take-off safety speed V TOSS , turn into climb, adjust the total distance, control the rotor speed Nr within the normal range, and use the single engine failure maximum power state; climb at V TOSS to 60m above ground level, accelerate to the best climb speed V Y , use the single engine failure maximum continuous power state, adjust the total distance, control Nr within the normal range, and climb at V YStable climb to 300m above ground level; this step is to verify that the power plant components surface temperature and its surrounding environment temperature, liquid temperature are in the safe operating range, when the power plant is in the critical operating condition, which is usually the single engine inoperative take-off climb; Step 2.4; stable climb at speed V Y , maximum continuous power state stable climb to 0.75m / s climb rate, then level flight, to the transmission system and engine oil temperature stable continue to climb or level flight for 5 minutes, or after the highest oil temperature recorded, continue to climb or level flight for 5 minutes; Step 2.5; normal landing, all engines and auxiliary power units are turned off, after 15 minutes of parking, the data acquisition system on the aircraft is turned off.

[0011] Further, the single engine inoperative maximum power state is: the maximum power of the single engine in the type design characteristics, for example, OEI 2.5min power, OEI 30min power, the use of single engine inoperative maximum power state cannot exceed the use time limit.

[0012] Further, for the aircraft that does not meet the performance of class A, the take-off cooling flight test method is as follows: Step 3.1; make the cooling system in the most severe test condition; Step 3.2; take off according to the class B take-off procedure in the flight manual: the wheel is 3m above ground level, all engines are in ground effect hover at no more than maximum continuous power, and are kept for 5 minutes after the transmission system and engine oil temperature is stable, or are kept for 5 minutes after the highest oil temperature appears during hovering, and the engine torque during hovering is recorded; Step 3.3; the push rod makes the helicopter low head acceleration, the total distance is increased to make the engine torque 7% higher than the hovering torque, and the engine power does not exceed the take-off power, the helicopter accelerates to 80km / h, then the attitude is adjusted to enter climb, when the height above ground is 15m, the indicated airspeed is 100km / h, and the speed is continuously increased to the best climb speed V Y , the power is no more than the maximum continuous power of the full engine, and the V Y speed is kept; Step 3.4; stable climb at speed V Y , maximum continuous power state stable climb to 0.75m / s climb rate, then level flight, to the transmission system and engine oil temperature stable continue to climb or level flight for 5 minutes, or after the highest oil temperature recorded, continue to climb or level flight for 5 minutes; Step 3.5; normal landing, all engines and auxiliary power units are turned off, after 15 minutes of parking, the data acquisition system on the aircraft is turned off.

[0013] Further, the method further comprises: performing a climb cooling flight test; Step 4.1: Place the cooling system under the most severe test conditions; Step 4.2; Take off according to normal procedures, at speed V Y The engine can stably climb to the smaller of the maximum continuous power state, either the maximum height with a climb rate of 0.75 m / s or the engine's critical height. Step 4.3; Descend 305m and fly level at that altitude until the transmission system and engine oil temperature stabilize; Step 4.4; Set the critical engine power selection switch to "ground slowness" at speed V. Y When the maximum continuous power of OEI is stable and the climb rate is 0.75m / s, switch to level flight and continue to climb or level flight for 5 minutes until the lubricating oil temperature stabilizes, or continue to climb or level flight for 5 minutes after the highest recorded lubricating oil temperature is reached. Step 4.5: Land normally, shut down all engines and auxiliary power units, and shut down the onboard data acquisition system 15 minutes after stopping.

[0014] Furthermore, keep the power compartment fairing closed until data acquisition is complete.

[0015] Furthermore, step 1.5 also includes: correcting the data from the external test environment temperature using a "degree-to-degree" correction method to obtain a set of data for the +50℃ operating environment temperature; the correction formula is as follows: T 修正 =T 测量 +〔50-0.0065 ×(Pressure Height)- T 外界环境温度 ] In the formula: temperature is in °C, and pressure and height are in meters.

[0016] Furthermore, the most stringent test conditions for the cooling system refer to: requiring the cabin cooling system to be activated and set to "high speed" during flight; and ensuring that the variable frequency generator in the engine room is under the most stringent heat dissipation conditions, with all the electrical power required by the aircraft's DC loads being provided by a single variable frequency generator.

[0017] In summary, the beneficial effects of the present invention are as follows: This invention provides a method for airworthiness verification of a transport helicopter engine during a 30-minute full-power, cooled-down flight, supporting Category A and Category B airworthiness certification for transport helicopters. This invention establishes a complete, detailed, and implementable method for airworthiness verification of a transport helicopter engine during a 30-minute full-power, cooled-down flight. It comprehensively covers the airworthiness requirements for cooled-down flights under airworthiness regulations and supplements the novel requirement of 30 minutes of full-power engine operation with a cooled-down flight test, providing a conformity verification method for the airworthiness certification of relevant civil transport helicopters. Attached Figure Description

[0018] Figure 1 A flowchart of a method for verifying the airworthiness of a transport helicopter engine by 30 minutes of full-power cooling flight. Detailed Implementation

[0019] A method for airworthiness verification of a transport helicopter engine with full-power cooling for 30 minutes during flight, such as... Figure 1 As shown, the specific steps are as follows: Step 1: Conduct a hovering and cooling flight test. This test is applicable to both Category A and Category B transport helicopters for airworthiness certification. The test method is as follows.

[0020] Step 1.1 To put the cooling system under the most severe test conditions, the cabin cooling system must be activated and set to "high speed" during flight. To put the variable frequency generator in the engine room under the most severe heat dissipation conditions, all the electrical power required by the onboard DC loads must be provided by a single variable frequency generator.

[0021] Step 1.2 Take off from a plain airport according to normal procedures: The helicopter wheels are about 3 meters off the ground. All engines hover with ground effect at no more than the maximum continuous power. Hover until the lubricating oil temperature of the transmission system and the engine stabilizes, and then hold for 5 minutes. The temperature is considered to be stable when the temperature change rate is <1.1℃ / minute, or after the highest lubricating oil temperature occurs during hovering, hold for another 5 minutes. Step 1.3 Increase the hovering height to ground effect-free hovering until all engines operate at full power for 30 minutes, maintain this position for 5 minutes after the lubricating oil temperature stabilizes (temperature change rate < 1.1℃ / min), or maintain this position for 5 minutes after the highest lubricating oil temperature is reached during hovering, or exceed the 30-minute full-power rated power usage time limit (whichever comes first). Land normally, and shut down all engines and auxiliary power units; Step 1.4 After stopping for 15 minutes, ensure that the temperature no longer rises, then shut down the onboard data acquisition system. Keep the power compartment fairing closed until data acquisition is complete.

[0022] Step 1.5 If a 30-minute no-ground-effect hovering and cooling test flight with the engine running at full power cannot be conducted at a plain airport, take off from a high-altitude airport (approximately 3000m) according to normal procedures: At a suitable altitude, the helicopter hovers at full power for 30 minutes without ground effect, maintaining the hover until the lubricating oil temperature (transmission system and engine) stabilizes, then maintaining it for another 5 minutes (temperature change rate < 1.1℃ / minute), or until the highest lubricating oil temperature is reached, then maintaining it for another 5 minutes, or the 30-minute no-ground-effect hovering time limit (whichever comes first); land normally, shut down all engines and auxiliary power units, stop for 15 minutes, then shut down the onboard data acquisition system, keeping the engine compartment fairing closed until data acquisition is complete.

[0023] Step 2 involves conducting a takeoff cooling flight test. The method for a Category A takeoff cooling flight test is as follows. Step 2.1 To put the cooling system under the most severe test conditions, the cabin cooling system must be activated and set to "high speed" during flight. To put the variable frequency generator in the engine room under the most severe heat dissipation conditions, all the electrical power required by the onboard DC loads must be provided by a single variable frequency generator.

[0024] Step 2.2 Take off according to the Category A takeoff procedure in the flight manual: The wheels are 3m off the ground. All engines hover with ground effect at no more than the maximum continuous power. Hold the hover until the lubricating oil temperature (transmission system and engine) stabilizes (temperature change rate < 1.1℃ / minute) and then hold for 5 minutes, or hold for 5 minutes after the highest lubricating oil temperature occurs during hovering. Record the engine torque during hovering. Step 2.3 Confirm all parameters are normal and there are no alarm messages; accelerate to the critical decision point using the push rod, and set the critical engine power selection switch to "ground slow" (one engine not operating). Adjust the pitch angle and accelerate to V. TOSS (Takeoff safe speed), transition to climb, adjust collective pitch, control rotor speed Nr within the normal range, and use OEI (single engine failure) power mode for 2.5 minutes. (V) TOSS Climb to 60m above the ground, accelerate to V-shaped speed during level flight. Y (Optimal climb speed), using OEI 2.5min power status, adjust collective pitch, control Nr within the normal range, and achieve a speed V Y Stable ascent to an altitude of 300m above the ground; Step 2.4 at a speed V Y When the maximum continuous power state is stably climbed to a climb rate of 0.75m / s, switch to level flight. After the lubricating oil temperature (transmission system and engine) stabilizes (temperature change rate <1.1℃ / minute) or the highest recorded lubricating oil temperature is reached, continue climbing or level flight for 5 minutes.

[0025] The method for Category B takeoff cooling flight test is as follows.

[0026] Step 2.1 To put the cooling system under the most severe test conditions, the cabin cooling system must be activated and set to "high speed" during flight. To put the variable frequency generator in the engine room under the most severe heat dissipation conditions, all the electrical power required by the onboard DC loads must be provided by a single variable frequency generator.

[0027] Step 2.2 Take off according to the Category B takeoff procedure in the flight manual: The wheels are 3m off the ground. All engines hover in ground effect at no more than the maximum continuous power. Hold this position until the lubricating oil temperature (transmission system and engine) stabilizes (temperature change rate < 1.1℃ / minute), or until the highest lubricating oil temperature is reached during hovering. Hold this position for another 5 minutes and record the engine torque during hovering. Step 2.3 Push the stick to pitch the helicopter down, while gently increasing collective acceleration (using torque higher than hovering torque, but not exceeding takeoff power); after accelerating to 80 km / h, adjust the attitude to begin climbing, and when the altitude is 15m above the ground, indicate an airspeed of 100 km / h; continue to increase the speed to V. Y (Optimal climbing speed), power not exceeding maximum continuous power, maintain V Y Speed ​​increase; Step 2.4 at a speed V Y When the maximum continuous power state is stably climbed to a climb rate of 0.75m / s, switch to level flight. After the lubricating oil temperature (transmission system and engine) stabilizes (temperature change rate <1.1℃ / minute) or the highest recorded lubricating oil temperature is reached, continue climbing or level flight for 5 minutes.

[0028] Step 3: Conduct a climb-and-cool-down flight test, which is applicable to airworthiness certification for both Category A and Category B transport helicopters. The test method is as follows.

[0029] Step 3.1 To put the cooling system under the most severe test conditions, the cabin cooling system must be activated and set to "high speed" during flight. To put the variable frequency starter generator in the engine room under the most severe heat dissipation conditions, all the electrical power required by the onboard DC loads shall be provided by a single variable frequency starter generator.

[0030] Step 3.2 Take off according to normal procedures at a speed of V. Y The engine can stably climb to its maximum height with a climb rate of 0.75 m / s or its critical height (whichever is smaller) when the three engines are at maximum continuous power. Step 3.3 Descend 305m and fly at that altitude until the lubricating oil temperature (transmission system and engine) stabilizes (temperature change rate < 1.1℃ / min). Step 3.4 Set the critical engine power selection switch to "ground slow" (one engine is not working) at speed V. Y When the OEI maximum continuous power state is stably climbed to a climb rate of 0.75m / s, switch to level flight and continue climbing or level flight for 5 minutes until the lubricating oil temperature stabilizes (temperature change rate <1.1℃ / min) or the highest recorded lubricating oil temperature is reached.

[0031] Step 4: Data Processing. Record test data during the cooling flight, and analyze the data after the flight. Perform a "degree-to-degree" correction on the temperature data. Temperature Correction Explanation: A certain type of helicopter has an operating ambient temperature requirement of +50℃. To ensure this requirement is met, the temperature in the flight test results should be corrected to the helicopter's maximum ambient temperature (+50℃). A "degree-to-degree" correction method can be used. The correction formula is as follows: T 修正 =T测量 +〔50-0.0065 ×(Pressure Height)- T 外界环境温度 ] In the formula: temperature is in °C, and pressure and height are in meters.

[0032] A dedicated cooling flight airworthiness verification method was developed for the engine at full power for 30 minutes. A cooling-flight airworthiness verification method applicable to Category A and Category B airworthiness certification of transport helicopters is proposed. This invention provides strong guidance for the airworthiness certification of transport helicopters and can effectively verify whether the power unit components of transport helicopters have sufficient cooling capacity to ensure the continuous safe operation of the helicopter.

Claims

1. A method for verifying the airworthiness of a transport helicopter engine during a 30-minute full-engine power-cooled flight, characterized in that: The method includes: Conduct hovering and cooling flight tests; The test method is as follows: Step 1.1: Place the cooling system under the most severe test conditions; Step 1.2; Take off from a plain airport according to normal procedures: The helicopter wheels are 3 meters off the ground, and all engines hover with ground effect at no more than the maximum continuous power. Hold the hover until the lubricating oil temperature of the transmission system and the engine stabilizes, or hold the hover for 5 minutes after the highest lubricating oil temperature is reached. Step 1.3; Increase the hovering height to ground effect hovering until all engine power reaches the rated power of the engine for 30 minutes at full power. When the following conditions are met, land normally and shut down all engines and auxiliary power units. Condition 1: Maintain the lubricating oil temperature for 5 minutes after it has stabilized; Condition 2: Maintain the position for 5 minutes after the highest lubricating oil temperature is reached during hovering; Condition 3: The engine reaches its rated power within 30 minutes of full-load operation, thus meeting the usage time limit. Step 1.4; After parking for 15 minutes, shut down the data acquisition system on the machine; Step 1.5: Perform data processing.

2. The method according to claim 1, characterized in that: In step 1.3, if the engine power still cannot reach the rated power of the engine for 30 minutes after raising the hovering altitude to ground effect-free hovering, then take off from a high-altitude airport and repeat steps 1.3 and 1.

4.

3. The method according to claim 2, characterized in that: Plateau airports are airports with an altitude of over 3,000 meters.

4. The method according to claim 1, characterized in that: The method also includes: conducting takeoff cooling flight tests; For aircraft that meet Category A performance requirements, the takeoff cooling flight test method is as follows: Step 2.1: Place the cooling system under the most severe test conditions; Step 2.2; Take off according to the Category A takeoff procedure in the flight manual: The wheels are 3m off the ground, and all engines are hovering in ground effect at no more than the maximum continuous power. Hold the hovering position until the transmission system and engine oil temperature stabilizes, and then hold it for 5 minutes, or until the highest oil temperature is reached, and then hold it for 5 minutes. Record the engine torque during hovering. Step 2.3; Confirm all parameters are normal and there are no alarm messages; push the stick to accelerate the helicopter to the critical decision point, and set the critical engine power selection switch to "ground slowness"; adjust the pitch angle and accelerate to the safe takeoff speed V. TOSS Enter climb mode, adjust collective pitch, control rotor speed Nr within normal range, and use single-engine failure maximum power mode; with V TOSS Climb to 60m above the ground, accelerate to the optimal climb speed V during level flight. Y Using the maximum continuous power state of single-engine failure, adjust the collective pitch and control Nr within the normal range, at speed V Y Stable ascent to an altitude of 300m above the ground; Step 2.4; at a speed V Y When the maximum continuous power state is stable and the climb rate is 0.75m / s, switch to level flight. Continue to climb or level flight for 5 minutes until the lubricating oil temperature of the transmission system and engine stabilizes, or continue to climb or level flight for 5 minutes after the highest recorded lubricating oil temperature is reached. Step 2.5: Land normally, shut down all engines and auxiliary power units, and shut down the onboard data acquisition system 15 minutes after stopping.

5. The method according to claim 1, characterized in that: The maximum power state for single-engine failure is: the maximum power of a single engine in the model design features, which is the OEI 2.5min power or OEI 30min power. The use of the maximum power state for single-engine failure shall not exceed the usage time limit.

6. The method according to claim 4, characterized in that: For aircraft that do not meet Category A performance requirements, the takeoff cooling flight test method is as follows: Step 3.1: Place the cooling system under the most severe test conditions; Step 3.2; Take off according to the Category B takeoff procedure in the flight manual: The wheels are 3m off the ground. All engines hover with ground effect at no more than the maximum continuous power. Hold the hover until the transmission system and engine oil temperature stabilizes and then hold for 5 minutes, or until the highest oil temperature is reached and then hold for 5 minutes. Record the engine torque during hovering. Step 3.3; Push the stick to make the helicopter pitch down and accelerate, increasing collective pitch so that the engine torque is 7% higher than the hovering torque, and the engine power does not exceed the takeoff power. After the helicopter accelerates to 80 km / h, adjust its attitude to begin climbing. When the altitude is 15m above the ground, the indicated airspeed is 100 km / h, and the helicopter continues to increase its speed to the optimal climb speed V. Y The power output should not exceed the maximum continuous power output of the entire generator, maintaining V. Y Speed ​​increase; Step 3.4; at a speed V Y When the maximum continuous power state is stable and the climb rate is 0.75m / s, switch to level flight. Continue to climb or level flight for 5 minutes after the transmission system and engine oil temperature stabilizes, or continue to climb or level flight for 5 minutes after the highest recorded oil temperature is reached. Step 3.5: Land normally, shut down all engines and auxiliary power units, and shut down the onboard data acquisition system 15 minutes after stopping.

7. The method according to claim 1, characterized in that: The method also includes: conducting a climb-cooling flight test; Step 4.1: Place the cooling system under the most severe test conditions; Step 4.2; Take off according to normal procedures, at speed V Y The engine can stably climb to the smaller of the maximum continuous power state, either the maximum height with a climb rate of 0.75 m / s or the engine's critical height. Step 4.3; Descend 305m and fly level at that altitude until the transmission system and engine oil temperature stabilize; Step 4.4; Set the critical engine power selection switch to "ground slowness" at speed V. Y When the maximum continuous power of OEI is stable and the climb rate is 0.75m / s, switch to level flight and continue to climb or level flight for 5 minutes until the lubricating oil temperature stabilizes, or continue to climb or level flight for 5 minutes after the highest recorded lubricating oil temperature is reached. Step 4.5: Land normally, shut down all engines and auxiliary power units, and shut down the onboard data acquisition system 15 minutes after stopping.

8. The method according to any one of claims 1-7, characterized in that: Keep the engine compartment fairing closed until data acquisition is complete.

9. The method according to claim 1, characterized in that: Step 1.5 also includes: correcting the data from the external test environment temperature using a "degree-to-degree" correction method to obtain a set of data for the +50℃ operating environment temperature; the correction formula is as follows: T 修正 =T 测量 +〔50-0.0065 ×(Pressure Height)- T 外界环境温度 ] In the formula: temperature is in °C, and pressure and height are in meters.

10. The method according to any one of claims 1-7, characterized in that: The cooling system being subjected to the most severe test conditions refers to: requiring the cabin cooling system to be activated and set to "high speed" during flight; and ensuring that the variable frequency generator in the engine room is subjected to the most severe heat dissipation conditions, with all the electrical power required by the aircraft's DC loads being provided by a single variable frequency generator.

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