Test flight verification operation method for civil aircraft windshield anti-fog capability

Abstract

The invention relates to a test flight verification operation method for the anti-fog capability of a windshield of a civil aircraft. The method comprises the following steps: heating all glass in a windshield when an airplane takes off, and adjusting the target temperature of an air conditioner to be the lowest selectable temperature so as to reduce the temperature of air in contact with the inner surface of the glass as much as possible; when the airplane reaches the specified height, the airplane flies flatly, heating of one piece of glass in all the pieces of glass is stopped, and the piece of glass is cooled and soaked until the temperature of the inner surface of the piece of glass is reduced and stabilized at the lowest actual temperature; the aircraft rapidly descends at the maximum descending rate; when the airplane descends to a lower height, the emergency ventilation system is opened to introduce external high-humidity air; whether the cold-soaked glass and the non-cold-soaked glass have the fogging phenomenon or not is verified; heating the cold-soaked glass, and observing whether the windshield has enough demisting capability or not until the fogging phenomenon disappears; the emergency ventilation state of the emergency ventilation system is kept, the aircraft is landed normally, and it is verified that the anti-fog capacity of the windshield is sufficient during descending landing. According to the method, fogging inside the windshield of the airplane can be effectively realized in a high-temperature and high-humidity environment, and the anti-fogging capability of the windshield can be verified.

Description

Technical Field

[0001] The present invention relates to a flight test verification operation method for anti-fogging capability of a civil aircraft windshield, and more specifically, to a flight test verification operation method for anti-fogging capability of a civil aircraft of CCAR 25 category under a high temperature and high humidity environment. Background Art

[0002] During the certification test flight of CCAR 25 civil aircraft, according to the requirements of CCAR-25 airworthiness clauses, it is necessary to carry out test flight verification of windshield anti-fog capability. The main verification contents include:

[0003] (i) Verify that the windshield heating system functions properly;

[0004] (ii) Verify that the operation of the windshield heating system control panel, the indicator lights, the CAS information display / warning / control logic, etc. are normal;

[0005] (iii) Verify that the anti-fogging performance of the windshield heating system meets the requirements under high temperature and high humidity conditions;

[0006] (iv) Verify that the pilot is able to remove fog from the inside surface of the side windshield without significantly increasing the pilot's workload.

[0007] The windshield anti-fog flight test verification is mainly to verify whether the aircraft windshield anti-fog system function can work normally when the windshield is fogged up inside, and whether it has sufficient defog capability. The windshield anti-fog flight test verification requires that the aircraft be able to fog up inside the windshield, then turn on the windshield heating to defog, and verify whether the defog capability is sufficient. Since civil aircraft are generally equipped with dual air-conditioning components, the working principle of the air-conditioning components themselves causes them to remove most of the moisture contained in the gas introduced from the engine when cooling it. Therefore, the dew point temperature of the air in the aircraft cabin is usually very low, and under normal flight conditions, it is difficult to fog up the inside.

[0008] Therefore, it is necessary to find a complete and effective flight test verification operation method to complete the verification of the windshield internal fogging and defogging capabilities under special environments such as high temperature and high humidity. However, in this field, there is currently no flight test verification operation method or procedure that can be directly used for CCAR Part 25 civil aircraft to perform windshield anti-fogging capabilities under the above special environments.

[0009] To this end, the industry is currently in urgent need of designing a flight test verification operation method for the anti-fogging ability of civil aircraft windshields, which can effectively achieve fogging inside the aircraft windshield in a high temperature and high humidity environment and verify the anti-fogging ability of the windshield. Summary of the invention

[0010] The purpose of the present invention is to provide a flight test verification operation method for the anti-fogging ability of a civil aircraft windshield, which can effectively achieve fogging inside the aircraft windshield glass and verify the anti-fogging ability of the windshield in a high temperature and high humidity environment.

[0011] The invention discloses a flight test verification operation method for the anti-fogging capability of a civil aircraft windshield, the method comprising the following steps:

[0012] (i) During takeoff, heat all glass in the windshield and adjust the air conditioning target temperature to the lowest selectable temperature to minimize the temperature of the air that the inner surface of the glass contacts;

[0013] (ii) when the airplane reaches the required altitude, the airplane turns to level flight, the heating of one of the windows is turned off and the window is cold soaked until the temperature of the inside surface of the window decreases and stabilizes at the lowest practical temperature;

[0014] (iii) Descend the airplane rapidly at the maximum rate of descent;

[0015] (iv) when the aircraft descends to a lower altitude than the minimum safe altitude, open the emergency ventilation system to introduce outside air;

[0016] (v) Verify whether fogging occurs on both the cold-soaked glass and the non-cold-soaked glass;

[0017] (vi) Heat the cold-soaked glass and observe whether the windshield has sufficient anti-fogging ability until the fogging disappears;

[0018] (vii) Maintain the emergency ventilation system in its emergency ventilation state to allow the aircraft to land normally and verify that the windshield’s anti-fogging capability is adequate during descent and landing.

[0019] Preferably, prior to step (i), a suitable season and test airspace are selected so that the absolute humidity near the ground in the specified test airspace on the test day is greater than or equal to a specified value within one hour while the aircraft is preparing for rapid descent, to ensure that the air at altitude near the ground has sufficient humidity.

[0020] Preferably, in step (i), the cockpit temperature and the cabin temperature are set to lower limit values ​​at takeoff.

[0021] Preferably, in step (iii), the aircraft descends rapidly according to the aircraft emergency descent procedure.

[0022] Preferably, the lower altitude is 1500 meters above the ground.

[0023] Preferably, in step (iv), when the aircraft descends to a lower altitude, the aircraft is leveled and the dual air conditioning components, trim air and recirculation fans, cargo hold ventilation are turned off, the air drying system of the passenger cabin or cockpit is turned off, and the pressure difference between the inside and outside of the cabin is adjusted to be less than a specified value.

[0024] Preferably, in step (v), during verification of fogging of the cold-soaked glass, the pilot performs a wiping action and comments on the workload.

[0025] Preferably, in step (vii), during the descent and landing, it is observed whether the glass is fogged again.

[0026] In the above embodiment, the aircraft may be a CCAR 25 civil aircraft.

[0027] In the above embodiments, the method can be performed under a high temperature and high humidity environment.

[0028] The above-mentioned test flight verification operation method for the anti-fogging capability of the windshield of civil aircraft has been verified during the certification test flight of a domestic civil aircraft of 25 categories. The test was successful in the surface compliance test flight of the windshield anti-fogging in the airspace of a certain place in the south where negative high pressure is controlled in summer and the ground water network is dense. Among them, the inside of the aircraft windshield glass was fogged smoothly, and the anti-fogging capability of the windshield was effectively verified. The verification result also shows that the anti-fogging capability of the aircraft windshield heating on hot and humid days is sufficient and meets the requirements of the airworthiness clauses. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to further illustrate the technical effect of the flight test verification operation method for the anti-fogging capability of a civil aircraft windshield according to the present invention, the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, wherein:

[0030] Figure 1 The windshield area of ​​a civil aircraft during a flight test is schematically shown, in which four glass panels are installed, and the reference numerals of these glass panels are 1, 2, 3, and 4 respectively. DETAILED DESCRIPTION

[0031] The steps, working principle and technical effects of the flight test verification operation method for the anti-fogging capability of a civil aircraft windshield according to the present invention are described below in conjunction with the accompanying drawings.

[0032] It should be clear that the embodiments described in this specification only cover some embodiments of the present invention, not all embodiments. Based on the embodiments recorded in the specification, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The terms "including" and "having" in the specification and claims of the present invention and the above-mentioned accompanying drawings and any variations thereof are intended to cover non-exclusive inclusions. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0034] The present invention discloses a flight test verification operation method for the anti-fog capability of a civil aircraft windshield, referring to Figure 1 As shown, the method comprises the following steps:

[0035] (i) When the aircraft takes off, turn on the windshield heating device to heat all the windshield glass 1, 2, 3, 4, adjust the air conditioning target temperature to the lowest selectable temperature, set the cockpit temperature and cabin temperature to the lower limit value, take off and climb according to normal procedures, so as to minimize the air temperature that the inner surface of the windshield glass 1, 2, 3, 4 contacts;

[0036] (ii) After the aircraft climbs to the ceiling or to a sufficiently low altitude, it turns to level flight (i.e., leveling off), turns off the heating function of one of the windshields to be verified (e.g., glass 1), so that the windshield 1 is soaked in cold, and the aircraft maintains level flight at a level altitude not lower than the current altitude and at a relatively low speed until the temperature of the inner surface of the windshield 1 drops and stabilizes at the lowest actual temperature (usually, the lowest actual temperature should be higher than the air conditioning target temperature, i.e., the lowest selectable temperature), wherein a temperature sensor attached to glass 1 is used to measure the temperature of the inner surfaces of windshields 1, 2, 3, and 4;

[0037] (iii) Maintain the flight altitude, adjust the aircraft to a suitable position as quickly as possible, and descend rapidly in accordance with the aircraft emergency descent procedure or at the maximum achievable descent rate;

[0038] (iv) When the aircraft descends to about 1,500 meters above the ground (preferably to a lower altitude that is higher than the minimum safe altitude), turn the aircraft to level flight and quickly shut down the dual air conditioning components, trim air and recirculation fans, cargo hold ventilation, shut down the cabin or cockpit air drying system, and adjust the cabin pressure difference to less than the specified value to ensure fast and smooth emergency ventilation. At this time, open the emergency ventilation system to introduce outside air, and wait and observe whether the main windshield and side windshield on both sides are fogged;

[0039] (v) While verifying the fogging of the cold-soaked glass 1, the pilot performs the wiping action and comments on the workload, and continuously observes whether the side windshields 2, 3, and 4 that are not cold-soaked will fog due to the high humidity;

[0040] (vi) heating the cold-soaked side windshield 1 to observe whether the windshield has sufficient defogging or anti-fogging capabilities, and maintaining this state until the fogging disappears;

[0041] (vii) Maintain the emergency ventilation system in its emergency ventilation state and allow the aircraft to land normally. During this period, observe whether fogging occurs again to verify that the anti-fogging capability of the windshield is sufficient during descent and landing.

[0042] Prior to step (i) of the above method, a suitable season and test airspace may be selected so that the absolute humidity near the ground in the specified test airspace on the test day is greater than or equal to a specified value (in high humidity weather, an absolute humidity greater than a specified threshold) within one hour while the aircraft is preparing for a rapid descent, to ensure that the air at a height near the ground has sufficient humidity.

[0043] There are certain risks associated with the above flight test verification operation method. To this end, the inventor has developed a series of measures to reduce the risks.

[0044] Although the verification object of the windshield anti-fog test flight is the cockpit windshield, the humid air introduced by the emergency ventilation system will eventually spread to the entire cabin space (i.e., the pressurized area). Since the fuselage structural frame and skin in the pressurized area are in direct contact with the outside air, their temperature is lower than the inner surface of the windshield. Therefore, after the emergency ventilation system is turned on, fog and condensation will soon appear on the inside of the skin and the fuselage frame, and dripping and flowing water will soon appear in some areas. The impact of the above phenomena on the aircraft's onboard systems, cables, power supply equipment, including test modification systems, should be evaluated before the test. Protection should be implemented for the parts that need protection, and the aircraft's drainage capacity in the relevant areas also needs to be verified or evaluated in advance.

[0045] After the emergency ventilation system is turned on during the windshield anti-fog test flight, the cockpit is connected to the outside atmosphere, the cabin altitude is the aircraft pressure altitude, and the aircraft descent rate is the cabin altitude descent rate. Since Part 25 civil aircraft generally have high performance, the descent rate can easily reach several thousand feet per minute. The windshield anti-fog test flight requires emergency ventilation to be maintained during descent and landing, so a large descent rate may endanger the health of the test personnel on board. Therefore, during the test, it is necessary to keep the descent rate at a small value when descending after the emergency ventilation is turned on.

[0046] The above-mentioned test flight verification operation method for the anti-fogging capability of the windshield of civil aircraft has been verified during the certification test flight of a domestic civil aircraft of 25 categories. The test was successful in the surface compliance test flight of the windshield anti-fogging in the airspace of a certain place in the south where negative high pressure is controlled in summer and the ground water network is dense. Among them, the inside of the aircraft windshield glass was fogged smoothly, and the anti-fogging capability of the windshield was effectively verified. The verification result also shows that the anti-fogging capability of the aircraft windshield heating on hot and humid days is sufficient and meets the requirements of the airworthiness clauses.

[0047] Although the steps and working principle of the flight test verification operation method for the anti-fogging capability of the windshield of a civil aircraft according to the present invention are described above in combination with the preferred embodiments and the accompanying drawings, it should be recognized by those skilled in the art that the above examples are only for illustration and cannot be used as limitations of the present invention. Therefore, the present invention can be modified and varied within the spirit of the claims, and these modifications and variations will fall within the scope required by the claims of the present invention.

Claims

1. A flight test verification operation method for the anti-fogging capability of a civil aircraft windshield, the method comprising the following steps: (i) when the aircraft takes off, heating all the glass (1, 2, 3, 4) in the windshield, and adjusting the air conditioning target temperature to the lowest selectable temperature to minimize the air temperature contacted by the inner surface of the glass; (ii) the aircraft turns to level flight when reaching a specified altitude, turns off the heating of one glass (1) among all the glass (1, 2, 3, 4) and allows the glass (1) to be cold soaked until the temperature of the inner surface of the glass drops and stabilizes at the lowest practical temperature; (iii) causing the aircraft to descend rapidly at a maximum rate of descent; (iv) when the aircraft descends to a lower altitude than the minimum safe altitude, opening the emergency ventilation system to admit outside air; (v) verifying whether the cold-soaked glass (1) and the non-cold-soaked glass (2, 3, 4) all produce fogging; (vi) heating the cold-soaked glass (1) to observe whether the windshield has sufficient anti-fogging ability until the fogging phenomenon disappears; (vii) Maintain the emergency ventilation system in its emergency ventilation state, allow the aircraft to land normally, and verify that the anti-fogging capability of the windshield is sufficient during descent and landing.

2. The flight test verification operation method for the anti-fogging capability of a civil aircraft windshield as claimed in claim 1, characterized in that: Prior to step (i), a suitable season and test airspace are selected so that the absolute humidity near the ground in the specified test airspace on the test day is greater than or equal to the specified value within one hour while the aircraft is preparing for rapid descent, to ensure that the air at the height near the ground has sufficient humidity.

3. The flight test verification operation method for the anti-fogging capability of a civil aircraft windshield as claimed in claim 1, characterized in that: In step (i), the cockpit temperature and the cabin temperature are set to lower limit values ​​at takeoff.

4. The flight test verification operation method for the anti-fogging capability of a civil aircraft windshield as claimed in claim 1, characterized in that: In step (iii), the aircraft descends rapidly according to the aircraft emergency descent procedure.

5. The flight test verification operation method for the anti-fogging capability of a civil aircraft windshield as claimed in claim 1, characterized in that: The lower altitude is 1,500 meters from the ground.

6. The flight test verification operation method for the anti-fogging capability of a civil aircraft windshield as claimed in claim 1, characterized in that: In step (iv), when the aircraft descends to the lower altitude, the aircraft is turned into level flight and the dual air conditioning components, trim air and recirculation fans, cargo hold ventilation are turned off, the air drying system of the passenger cabin or cockpit is turned off, and the pressure difference between the inside and outside of the cabin is adjusted to be less than a specified value.

7. The flight test verification operation method for the anti-fogging capability of a civil aircraft windshield as claimed in claim 1, characterized in that: In step (v), while verifying the fogging of the cold-soaked glass (1), the pilot performs a wiping action and comments on the workload.

8. The flight test verification operation method for the anti-fogging capability of a civil aircraft windshield as claimed in claim 1, characterized in that: In step (vii), during the descent and landing, observe whether the glass (1) is fogged again.

9. The flight test verification operation method for the anti-fogging capability of a civil aircraft windshield according to any one of claims 1 to 8, characterized in that: The aircraft is a CCAR 25 category civil aircraft.

10. The flight test verification operation method for the anti-fogging capability of a civil aircraft windshield according to any one of claims 1 to 8, characterized in that: The method is carried out under a high temperature and high humidity environment.

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