An access cover for a nacelle

Abstract

The present invention relates to an access cover for a nacelle. The access cover for the nacelle includes a track disposed on the fan wall panel of the nacelle; an access cover plate slidably engaged with the track; a stopper, and the access cover plate is disposed on the fan wall panel through the stopper. In the open state of the stopper, the access cover plate can slide relative to the fan wall panel, and in the locked state of the stopper, the access cover plate is fixedly engaged with the fan wall panel. The present invention provides an access cover for a nacelle, and the overall structure occupies a small space, facilitating maintenance and repair inside the nacelle.

Description

Technical Field

[0001] The present invention relates to the technical field of machining of nacelles for aeroengines, and particularly to an access cover for a nacelle. Background Art

[0002] Commercial aero turbofan engines are generally equipped with nacelles. In order to facilitate the maintenance of components inside the engine, an access cover is usually provided on the outer casing of the nacelle. Figure 1 The structural diagram of a nacelle in the prior art is shown. Figure 2 The structural diagram of a fan cowl in the prior art is shown. As shown in the figure, an access cover 102 for the oil slide valve is provided on the fan wall panel 101 to maintain the oil sump. At the same time, the access cover 102 also has the function of pressure relief to cope with the situation of a sharp increase in the cabin pressure caused by the rupture of the internal pipeline of the nacelle.

[0003] The traditional nacelle access cover 102 adopts the configuration of a gooseneck hinge 103. To open the nacelle access cover 102 through this gooseneck hinge 103 requires a large amount of moving space, resulting in a reduction in the utilization rate of the cabin space. And with this structure, a large number of accessories need to be installed on the fan casing, and the nacelle access cover 102 is very likely to interfere with the accessories. At the same time, a pressure relief door 104 and a pressure relief lock 105 are also provided on the nacelle access cover 102. The pressure relief door 104 is fixed to the nacelle access cover 102 through the pressure relief lock 105. Once the pressure relief lock 105 is opened by the cabin pressure, the pressure relief door 104 cannot be closed during flight, posing a potential risk and affecting flight safety. Summary of the Invention

[0004] In view of the above problems of the prior art, the present invention provides an access cover for a nacelle, the overall structure of which occupies a small space and is convenient for maintenance and repair inside the nacelle.

[0005] Specifically, the present invention provides an access cover for a nacelle, the access cover comprising:

[0006] A track provided on the fan wall panel of the nacelle;

[0007] An access cover plate slidably engaged with the track;

[0008] A limiter, the access cover plate is arranged on the fan wall panel through the limiter. In the open state of the limiter, the access cover plate can slide relative to the fan wall panel. In the locked state of the limiter, the access cover plate cooperates with the fan wall panel to be fixed.

[0009] According to an embodiment of the present invention, the limiter includes a limiting base, a mounting base, a limiting pin, and a driver. The limiting base is disposed on the access panel cover, the mounting base is disposed on the fan wall panel, and the limiting pin is disposed on the mounting base through the driver;

[0010] The driver drives the limiting pin to disengage from the limiting base, and the limiter enters the open state, so that the access panel cover can slide relative to the fan wall panel; the driver drives the limiting pin to insert into the limiting base, and the limiter enters the locked state, and the access panel cover and the fan wall panel are relatively fixed.

[0011] According to an embodiment of the present invention, the limiting pin includes a nested fixed pin body and a moving pin body. The fixed pin body is disposed on the driver, and the driver can control the moving pin body to move in a relative direction with respect to the fixed pin body. A first spring is disposed between the moving pin body and the fixed pin body.

[0012] According to an embodiment of the present invention, the driver includes an electromagnetic element and a tensioner, and the electromagnetic element controls the movement of the moving pin through the tensioner.

[0013] According to an embodiment of the present invention, the maintenance access panel further includes a control button disposed on the fan wall panel. The control button is electrically connected to the electromagnetic element, and the control button is used to trigger the electromagnetic element to work.

[0014] According to an embodiment of the present invention, the maintenance access panel further includes a slide rail. The slide rail includes a slider, a connecting plate, and a first columnar telescopic device. The slider and the first columnar telescopic device are disposed on both sides of the connecting plate. The slider is slidably engaged with the track. The connecting plate is connected to the access panel cover through the first columnar telescopic device, and the access panel cover can move relative to the track through the slide rail.

[0015] According to an embodiment of the present invention, the first columnar telescopic device includes a fixed pin, a second spring, a guiding cylinder, and a limiting block. The fixed pin is disposed on the bottom surface of one side of the connecting plate and extends vertically downward. The limiting block is disposed at the bottom of the fixed pin. The guiding cylinder is disposed on the access panel cover. The fixed pin extends downward into the guiding cylinder. The second spring is disposed in the guiding cylinder and sleeved on the fixed pin. The bottom of the second spring abuts against the limiting block.

[0016] According to an embodiment of the present invention, the maintenance access panel further includes a pressure relief door and a second columnar telescopic device. The pressure relief door is fixed to the access panel cover through the second columnar telescopic device.

[0017] According to an embodiment of the present invention, the second columnar expander includes a positioning pin and a third spring. The positioning pin passes through the periphery of the pressure relief door and is fixed on the access cover plate, and the third spring is arranged between the positioning pin and the pressure relief door to enable the pressure relief door to be in sealing fit with the access cover plate.

[0018] According to an embodiment of the present invention, when the pressure in the nacelle is higher than the pressure threshold, the pressure relief door overcomes the elastic deformation force of the third spring and moves along the length direction of the positioning pin to disengage from the access cover plate; when the pressure in the nacelle is lower than the pressure threshold, the elastic deformation force of the third spring pushes the pressure relief door to fit against the access cover plate.

[0019] A maintenance access cover for a nacelle provided by the present invention adopts a track configuration, enabling the maintenance access cover to slide relative to the nacelle. The overall structure occupies a small space, facilitating maintenance and repair inside the nacelle, and thus enhancing the safety performance of the engine nacelle.

[0020] It should be understood that the above general description and the following detailed description of the present invention are both exemplary and explanatory, and are intended to provide further explanation of the present invention described. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are provided to provide a further understanding of the present invention. They are incorporated herein and constitute a part of this application. The drawings illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. In the drawings:

[0022] Figure 1 Shows the structural diagram of a nacelle in the prior art.

[0023] Figure 2 Shows the structural diagram of a fan cowl in the prior art.

[0024] Figure 3 Shows the schematic structural diagram of a maintenance access cover according to an embodiment of the present invention.

[0025] Figure 4 Shows the schematic cross-sectional view B-B of the maintenance access cover in the closed state according to an embodiment of the present invention.

[0026] Figure 5 is Figure 4 The partial enlarged schematic view of the limiter in the locked state in.

[0027] Figure 6 is Figure 4 The partial enlarged schematic view of the limiter in the opened state in.

[0028] Figure 7 Shows the simplified cross-sectional view B-B of the maintenance access cover in the closed state according to an embodiment of the present invention.

[0029] Figure 8 Shows a simplified cross-sectional view of B-B under the unlocked state of the maintenance hatch of an embodiment of the present invention.

[0030] Figure 9 Shows a simplified cross-sectional view of B-B during the opening process of the maintenance hatch of an embodiment of the present invention.

[0031] Figure 10 Shows a simplified cross-sectional view of B-B during the closing process of the maintenance hatch of an embodiment of the present invention.

[0032] Figure 11 Schematic diagram of cross-section A-A of the maintenance hatch in the closed state of an embodiment of the present invention.

[0033] Figure 12 Is Figure 11 Partial enlarged schematic diagram of the first columnar telescopic device in the locked state in

[0034] Figure 13 Is Figure 11 Partial enlarged schematic diagram of the first columnar telescopic device in the opened state in

[0035] Figure 14 Is Figure 4 Enlarged schematic diagram of the second columnar telescopic device in

[0036] Among them, the above-mentioned drawings include the following reference numerals:

[0037] Fan wall panel 101, Maintenance hatch 102

[0038] Gooseneck hinge 103, Pressure relief door 104

[0039] Pressure relief lock 105

[0040] Maintenance hatch structure 300, Track 301

[0041] Hatch cover plate 302, Limiter 303

[0042] Limiting base 304, Mounting base 305

[0043] Fixed pin body 306, Movable pin body 307

[0044] Electromagnetic element 308, Tensioner 309

[0045] Control button 310, Slide rail 311

[0046] Slider 312, Connecting plate 313

[0047] First columnar telescopic device 314, Fixed pin 315

[0048] The second spring 316 and the guiding cylinder 317

[0049] The limiting block 318 and the first spring 319

[0050] The second columnar expander 320 and the positioning pin 321

[0051] The third spring 322 Detailed implementation manners

[0052] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0053] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0054] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless otherwise clearly specified in the context, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "comprise" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0055] Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that for the convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the said technologies, methods, and devices should be regarded as part of the authorized specification. In all the examples shown and discussed herein, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that: similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0056] In the description of the present application, it should be understood that the orientation or positional relationship indicated by orientation terms such as "front, rear, upper, lower, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom", etc. is usually based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description. Without contrary explanation, these orientation terms do not indicate and imply that the device or component referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the protection scope of the present application; the orientation terms "inner, outer" refer to the inside and outside relative to the contour of each component itself.

[0057] For ease of description, spatial relative terms such as "above...", "over...", "on the upper surface of...", "upper" etc. can be used here to describe the spatial positional relationship of a device or feature shown in the figure with other devices or features. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation described in the figure for the device. For example, if the device in the drawing is inverted, the device described as "above other devices or structures" or "over other devices or structures" will then be positioned as "below other devices or structures" or "under other devices or structures". Thus, the exemplary term "above..." can include both orientations of "above..." and "below...". The device can also be positioned or rotated in other different ways by 90 degrees or in other orientations, and corresponding interpretations are made for the spatial relative descriptions used here.

[0058] In addition, it should be noted that the use of terms such as "first", "second" etc. to limit components is only for the convenience of differentiating the corresponding components. Without additional statement, the above terms have no special meaning. Therefore, it should not be construed as a limitation on the protection scope of the present application. In addition, although the terms used in the present application are selected from well-known and commonly used terms, some of the terms mentioned in the specification of the present application may be selected by the applicant according to his or her judgment, and their detailed meanings are described in the relevant parts of the description herein. In addition, it is required to understand the present application not only through the actual terms used, but also through the meaning implied by each term.

[0059] Figure 3 The structural schematic diagram of the maintenance access cover of an embodiment of the present invention is shown. As shown in the figure, the present invention provides a maintenance access cover structure 300 for a nacelle, mainly including a track 301, an access cover plate 302 and a limiter 303.

[0060] Among them, the track 301 is arranged on the fan wall panel 101 of the nacelle. In this embodiment, two tracks 301 are provided on the fan wall panel 101, and are arranged in parallel on both sides of the access cover plate 302.

[0061] The cover plate 302 can be slidably mated with the track 301. The cover plate 302 is arranged on the fan wall panel 101 through the stopper 303. When the stopper 303 is in the open state, the cover plate 302 enters the unlocked state, and the cover plate 302 can slide relative to the fan wall panel 101, and the sliding direction is parallel to the length direction of the track 301. When the stopper 303 is in the locked state, the cover plate 302 enters the locked state, and the cover plate 302 is fixedly mated with the fan wall panel 101. In this embodiment, the cover plate 302 can be made of any one of aluminum alloy, steel, titanium alloy or superalloy.

[0062] The maintenance cover structure 300 of the present invention changes the flipping and opening method using a hinge in the prior art, and adopts a sliding method to open the cover plate 302, so that the overall structure occupies a small space, is convenient for carrying out maintenance and repair work in the nacelle, and improves the safety performance of the engine nacelle.

[0063] Figure 4 Figure 7 shows a schematic cross-sectional view of the maintenance cover structure in the closed state according to an embodiment of the present invention taken along section B-B. Figure 5 is Figure 4 a partial enlarged schematic view of the stopper in the locked state in FIG. Figure 6 is Figure 4 a partial enlarged schematic view of the stopper in the open state in FIG. Figure 7 Figure 17 shows a simplified cross-sectional view of the maintenance cover structure in the closed state according to an embodiment of the present invention taken along section B-B. Figure 8 Figure 19 shows a simplified cross-sectional view of the maintenance cover structure in the unlocked state according to an embodiment of the present invention taken along section B-B. Figure 9 Figure 21 shows a simplified cross-sectional view of the maintenance cover structure during the opening process according to an embodiment of the present invention taken along section B-B. Figure 10 Figure 23 shows a simplified cross-sectional view of the maintenance cover structure during the closing process according to an embodiment of the present invention taken along section B-B. As shown in the figure, the stopper 303 includes a limit base 304, a mounting base 305, a limit pin and a driver. The limit base 304 is arranged on the cover plate 302, the mounting base 305 is arranged on the fan wall panel 101, and the limit pin is arranged on the mounting base 305 through the driver. The driver drives the limit pin to disengage from the limit base 304, and the stopper 303 enters the open state, so that the cover plate 302 can slide relative to the fan wall panel 101. The driver drives the limit pin to insert into the limit base 304, and the stopper 303 enters the locked state, and the cover plate 302 is relatively fixed with the fan wall panel 101. Specifically, the stopper 303 can be switched between the open and locked states, and correspondingly, the cover plate 302 can be switched between the unlocked and locked states. Refer to Figure 2 , in this embodiment, four groups of stoppers 303 are arranged around the cover plate 302.

[0064] Preferably, refer toFigure 5 The limit pin includes a nested fixed pin body 306 and a movable pin body 307. The fixed pin body 306 is arranged on the driver. The driver can control the movable pin body 307 to move relative to the fixed pin body 306 in a certain direction, and a first spring 319 is arranged between the movable pin body 307 and the fixed pin body 306. More preferably, the driver includes an electromagnetic element 308 and a tensioner 309, and the electromagnetic element 308 and the tensioner 309 are used to control the movement of the movable pin.

[0065] Rotate to Figure 1 The maintenance access door structure 300 of the nacelle further includes a control button 310 arranged on the fan wall panel 101. The control button 310 is electrically connected to the electromagnetic element 308 in the limiter 303. When the aircraft is in the ground state, the control button 310 can be used to trigger the electromagnetic element 308 to work.

[0066] Refer to Figure 5 and Figure 7 In the initial state, the movable pin body 307 extends into the limit base 304, the limiter 303 is in the locked state, and the limit base 304 cannot move in the direction perpendicular to the paper surface, so that the access door cover plate 302 is fixed in cooperation with the fan wall panel 101, and the access door cover plate 302 cannot move. At this time, press the control button 310, and the control button 310 triggers the electromagnetic element 308 to work. The electromagnetic element 308 controls the movable pin body 307 to move relative to the fixed pin body 306 in a certain direction through the tensioner 309, and the first spring 319 is compressed. Refer to Figure 6 and Figure 8 The movable pin body 307 disengages from the limit base 304, and the limiter 303 is in the open state. Refer to Figure 9 The access door cover plate 302 naturally disengages from the fan wall panel 101 in the direction indicated by the pointed head, the access door cover plate 302 enters the unlocked state, and the access door cover plate 302 can slide relative to the fan wall panel 101, that is, move in the direction perpendicular to the paper surface, so as to perform maintenance work on the nacelle. After the maintenance work is completed, push the access door cover plate 302 back to its original position. Refer to Figure 10 Push the access door cover plate 302 to move towards the fan wall panel 101 and move upward along the pointed head direction. Under the action of the first spring 319 and the tensioner 309, the movable pin body 307 is inserted into the limit base 304, so that the access door cover plate 302 is fixedly re-fitted with the fan wall panel 101, and the limiter 303 returns to the locked state.

[0067] Figure 11 Schematic cross-sectional view of the maintenance access door structure in the closed state according to an embodiment of the present invention along section A-A. Figure 12 is Figure 11 Partial enlarged schematic view of the first columnar telescopic device in the locked state in Figure 13 is Figure 11Partial enlarged schematic view of the first columnar telescopic device in the open state. Referring to Figure 1 As shown, preferably, the maintenance access cover structure 300 further includes a slide rail 311. The slide rail 311 includes a slider 312, a connecting plate 313, and a first columnar telescopic device 314. The slider 312 and the first columnar telescopic device 314 are arranged on both sides of the connecting plate 313, and the slider 312 is slidably engaged with the track 301. The connecting plate 313 is connected to the access cover plate 302 through the first columnar telescopic device 314, and the access cover plate 302 can move relative to the track 301 through the slide rail 311. It is easy to understand that in this embodiment, two sets of slide rails 311 are provided, corresponding to and cooperating with the two tracks 301 on both sides respectively.

[0068] Preferably, referring to Figure 12 and Figure 13 , the first columnar telescopic device 314 includes a fixed pin 315, a second spring 316, a guiding cylinder 317, and a limiting block 318. The fixed pin 315 is arranged on the bottom surface of one side of the connecting plate 313 and extends vertically downward. A limiting block 318 is provided at the bottom of the fixed pin 315. The guiding cylinder 317 is arranged on the access cover plate 302. The fixed pin 315 extends downward into the guiding cylinder 317, the second spring 316 is arranged in the guiding cylinder 317 and sleeved on the fixed pin 315, and the bottom of the second spring 316 abuts against the limiting block 318.

[0069] When the access cover plate 302 is in the closed state, the access cover plate 302 is fixedly engaged with the fan wall plate 101. Referring to Figure 12 . The fixed pin 315 is inserted into the guiding cylinder 317, the bottom of the fixed pin 315 abuts against the limiting block 318, and the second spring 316 is in a relaxed state. When the access cover plate 302 enters the unlocking state, referring to Figure 13 , the access cover plate 302 moves downward, disengages from the fan wall plate 101, and the second spring 316 is under pressure. Obviously, Figure 12 the distance L1 from the connecting plate 313 to the access cover plate 302 in Figure 13 is smaller than the distance L1' from the connecting plate 313 to the access cover plate 302 in

[0070] Preferably, referring to Figure 3 , the maintenance access cover structure 300 further includes a pressure relief door 104 and a second columnar telescopic device 320. The pressure relief door 104 is fixed to the access cover plate 302 through the second columnar telescopic device 320. In this embodiment, the pressure relief door 104 can be made of a metal material or a composite material.

[0071] Figure 14 is Figure 4An enlarged schematic view of the second columnar expander in []. As shown in the figure, 4 groups of second columnar expanders 320 are arranged around the pressure relief door 104. Each group of second columnar expanders 320 includes a positioning pin 321 and a third spring 322. The positioning pin 321 passes through the periphery of the pressure relief door 104 and is fixed on the cover plate 302. The third spring 322 is arranged between the bottom of the pin head of the positioning pin 321 and the pressure relief door 104 to make the pressure relief door 104 and the cover plate 302 in sealing cooperation.

[0072] Preferably, when the pressure in the nacelle is higher than the pressure threshold, the pressure relief door 104 overcomes the elastic deformation force of the third spring 322 and moves along the length direction of the positioning pin 321 to disengage from the cover plate 302, and the pressure relief door 104 opens. When the pressure in the nacelle is lower than the pressure threshold, the pressure relief door 104 is pushed by the elastic deformation force of the third spring 322 to fit the cover plate 302, and the pressure relief door 104 closes.

[0073] A maintenance access cover structure for a nacelle proposed by the present invention adopts an orbital configuration, avoiding the problem of large space occupation of the traditional gooseneck hinge structure, and minimizing the risk of interference between the cover plate and the in-cabin accessories to the greatest extent. At the same time, it has the function of pressure relief, and a recoverable second columnar expander is adopted, so that the pressure relief door can return to its original position after the pressure in the cabin is restored, eliminating the problem that the traditional configuration cannot be closed, and reducing the impact on flight safety.

[0074] It will be apparent to those skilled in the art that various modifications and variations can be made to the above exemplary embodiments of the present invention without departing from the spirit and scope of the present invention. Therefore, it is intended that the present invention cover modifications and variations of the present invention falling within the scope of the appended claims and their equivalent technical solutions.

Claims

1. A maintenance access cover structure for a nacelle, comprising: A track, provided on the fan wall panel of the nacelle; An access cover plate, slidably engaged with the track; A limiter, the access cover plate is provided on the fan wall panel through the limiter. When the limiter is in the open state, the access cover plate can slide relative to the fan wall panel. When the limiter is in the locked state, the access cover plate is fixedly engaged with the fan wall panel; A slide rail, the slide rail includes a slider, a connecting plate and a first columnar telescopic device. The slider and the first columnar telescopic device are provided on both sides of the connecting plate. The slider is slidably engaged with the track. The connecting plate is connected to the access cover plate through the first columnar telescopic device. The access cover plate can move relative to the track through the slide rail.

2. The maintenance cover structure according to claim 1, wherein The limiter includes a limit base, a mounting base, a limit pin and a driver. The limit base is provided on the access cover plate. The mounting base is provided on the fan wall panel. The limit pin is provided on the mounting base through the driver; The driver drives the limit pin to disengage from the limit base, and the limiter enters the open state, so that the access cover plate can slide relative to the fan wall panel; The driver drives the limit pin to insert into the limit base, and the limiter enters the locked state, and the access cover plate is relatively fixed to the fan wall panel.

3. The maintenance access cover structure according to claim 2, characterized in that, The limit pin includes a nested fixed pin body and a movable pin body. The fixed pin body is provided on the driver, and the driver can control the movable pin body to move in a direction relative to the fixed pin body. A first spring is provided between the movable pin body and the fixed pin body.

4. The maintenance hatch structure according to claim 3, characterized in that The driver includes an electromagnetic element and a tensioner, and the electromagnetic element controls the movement of the movable pin body through the tensioner.

5. The maintenance hatch structure according to claim 4, characterized in that, It further includes a control button provided on the fan wall panel. The control button is electrically connected to the electromagnetic element, and the control button is used to trigger the electromagnetic element to work.

6. The maintenance hatch structure according to claim 1, wherein, The first columnar telescopic device includes a fixed pin, a second spring, a guiding cylinder body and a limit block. The fixed pin is provided on the bottom surface of one side of the connecting plate and extends vertically downward. The limit block is provided at the bottom of the fixed pin. The guiding cylinder body is provided on the access cover plate. The fixed pin extends downward into the guiding cylinder body. The second spring is provided in the guiding cylinder body and sleeved on the fixed pin. The bottom of the second spring abuts against the limit block.

7. The maintenance cover structure according to claim 1, characterized in that It further includes a relief door and a second columnar telescopic device. The relief door is fixed to the access cover plate through the second columnar telescopic device.

8. The maintenance access cover structure according to claim 7, characterized in that The second columnar telescopic device includes a positioning pin and a third spring. The positioning pin passes through the periphery of the relief door and is fixed to the access cover plate. The third spring is provided between the positioning pin and the relief door, so that the relief door is hermetically engaged with the access cover plate.

9. The maintenance hatch structure according to claim 8, wherein, When the pressure in the nacelle is higher than the pressure threshold, the relief door overcomes the elastic deformation force of the third spring and moves along the length direction of the positioning pin to disengage from the access cover plate; when the pressure in the nacelle is lower than the pressure threshold, the elastic deformation force of the third spring pushes the relief door to fit against the access cover plate.

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