BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a sensor for detecting when a latch assembly is secured. Particularly, the present invention is directed to a sensor for detecting when a latch assembly for securing an aircraft engine cowl door is properly secured. 
         [0003]    2. Description of Related Art 
         [0004]    A variety of devices and methods are known in the art for detecting whether an aircraft latch is in a secured state. Of such devices, many are directed to determining whether an aircraft latch for securing an engine cowl door is in a secured state by using simple visual inspection conducted by aircraft maintenance personnel. Failure to secure the cowl doors after opening can lead to malfunction of the cowl doors during take-off or flight. In some circumstances, the cowl doors can be liberated from the aircraft completely. Fortunately, the loss of an engine cowl door is not generally a serious threat to an aircraft. However, it is nonetheless advantageous to reduce the number of cowl door incidents. Typically, the onus is on ground personnel to verify that all engine cowl doors are secured before an aircraft pulls away from its gate. It is believed that the prevailing cause of engine cowl door incidents is failure of ground crew to securely latch engine cowl doors prior to departure. 
         [0005]    Efforts have been made to assist ground crews in verifying engine cowl doors are secured. Commonly, a rather large and prominently colored access door is provided over the latch assembly such that the access door cannot be closed unless the latch assembly is engaged. Such an access door is easily seen when hanging down in the open position but it is a costly and heavy solution on an aircraft. 
         [0006]    U.S. Pat. No. 6,334,588 to Porte describes a system for securing fan cowls in which a maintenance crew can visually detect an unsecured fan cowl because edges of unsecured fan cowls protrude enough to allow for visual detection. Another visual technique for detecting unsecured cowls is described in U.S. Pat. No. 5,518,206 to Arnold et al., which describes an apparatus that extends a flag visible to ground crew when an engine cowl is unsecured. 
         [0007]    Such conventional methods and systems generally have been considered satisfactory for their intended purpose. However, while visual cues make it possible to verify that an engine cowl is securely latched, these techniques still rely on the ground crew to remember to check the latches. Improvements in this area, for example, to remove the “human element” from the process using electronics, have been slow due to the harsh conditions present in the engine nacelle environment. One attempt has been to use sensors to detect the state of a cowl latch, as in U.S. Pat. No. 7,131,672 to Pratt et al. (Pratt et al. patent). However, the sensors and wiring systems described in the Pratt et al. patent are prone to failure in the harsh nacelle environment. Further, wiring adds weight, complexity and components that may fail, which are undesirable in aviation applications. 
         [0008]    Other efforts have been made in creating systems to inform operators whether an engine cowl is secured or not by using sensors. U.S. Patent Application No. 2006/0038410 to Pratt et al. describes a latch having sensors to assist controlling an electrical motor, which operates to open and close a latch for a fan cowl. The sensors can also inform a controller as to the status of the latch. U.S. Pat. No. 6,279,971 to Dessenberger et al. describes a latch with a sensor. The latch includes a hook pivotally connected to a handle for engagement with a keeper. The sensor has a sensing end and a blocking end so that when the sensor is in the unblocked position, a trigger lock is allowed to engage the hook and close the handle. 
         [0009]    Despite these advances, there still remains a continued need in the art for a latch sensor that is more sensitive, reliable, able to be retrofit, and provides information to a remote area such as the cockpit. There also remains a need in the art for a system of latch detection that is inexpensive and easy to make, including retrofitting existing latches without substantially altering the latch itself. 
         [0010]    Moreover, latch assemblies are typically set to secure the cowl doors in a tight fashion. In other words, the latch assemblies serve to create a force that retains the cowl doors in the proper position to prevent rattling and chafing during flight. A typical latch keeper is provided with a star wheel or like adjustment mechanism to vary the position of the keeper and, thereby, the load on the latch assembly. Then a force gauge is used to determine the force required to close the latch, which is an indirect measurement of the load on the latch assembly. Typically, the latch assembly adjustment is only used initially when building and attaching the engine nacelle to the airplane. 
         [0011]    Based on the assumption that the force required to close the latch is the load on the latch assembly (e.g., the load between the latch and keeper), the keeper is adjusted to set the load. Since such measurements and adjustments can be cumbersome, subsequent regular readjustment is usually not made again. As a result of normal component wear and usage, the load upon the latch assembly changes. The load can become too small resulting in chafing, or too tight resulting in undue component stress and fatigue. In either case, improper pre-loading can cause premature wear and failure of not only the latch assembly but other components as well. 
         [0012]    In view of the above, a need exists for an improved remotely interrogated latch assembly, as well as a system and method that allows the aircraft mechanic to accurately pre-load the latch assembly. Additionally, a system and method suitable for subsequent maintenance and adjustments would allow maintaining latch assemblies at desired loading levels. 
       SUMMARY OF THE INVENTION 
       [0013]    The purpose and advantages of the present invention will be set forth in and become apparent from the description that follows. Additional advantages of the invention will be realized and attained by the methods and systems particularly pointed out in the written description and claims hereof, as well as from the appended drawings. 
         [0014]    One advantage of the subject technology is that it provides a sensor to effectively notify ground mechanics and cockpit crews that the cowl latch assemblies are closed while being able to withstand the harsh engine nacelle environment without reducing the aerodynamic profile or adding weight to the latch assembly. Further, the subject technology can be adapted as an upgrade for existing latch assemblies so that a direct measurement of load on the latch assembly may be made. 
         [0015]    Another advantage of the subject technology is an ability to properly pre-load the latch assembly so that components are properly closed to prevent premature wear. Such pre-load measurements are easy to make, so that maintenance adjustments can be quickly made. 
         [0016]    The subject technology is directed to a cowl assembly for an engine nacelle including a first and second cowl door mounted for movement between an open position and a closed position. A latch assembly retains the first and second cowl doors in the closed position by having a latch retained in a latch housing on the first cowl door engage a keeper retained in a keeper housing on the second cowl door. A latch pin is associated with one of the keeper, keeper housing, latch and latch housing. A sensor in an internal bore of the latch pin determines a signal indicative of a load on the pin, wherein the signal is determinative of whether the cowl doors are in the open or closed position. A transmitter, integral with the pin, conveys the signal to a location remote from the sensor. In one embodiment, the pin retains the latch to the latch housing and further includes a microcontroller in the internal bore for processing the signal and running the transmitter. In a further embodiment, the sensor is a set of three spaced apart strain gauges and a cap encloses the internal bore. 
         [0017]    The subject technology is also directed to a wireless latch detection system for determining when an engine cowl latch of an aircraft engine nacelle is secured. The wireless latch detection system includes a pin for generating a signal indicating a status of the latch. The pin has a body defining a bore, at least one strain gauge disposed within the bore, an antenna for transmitting the signal and a microcontroller operatively connected to a power source, at least one of said strain gauges, and the antenna. A transceiver is remotely located from the pin for processing the signal from the antenna. In one embodiment, the transceiver records and stores the signal. The wireless latch detection system may be selectively activated or inactivated such as when the aircraft engine is shut down, running, or in flight. 
         [0018]    The subject technology is also directed to a method for determining when a latch assembly is open or securely closed, comprising the steps of: a) providing a pin in the latch assembly such that the pin bears a first load when the latch is secure and a second load when the latch is open; b) generating a signal indicative of the load on the pin; and c) wirelessly transmitting the signal to a location remote from the pin. In one embodiment, the signal is converted into status information regarding the open or secure state of the latch assembly. The pin may bear a third load during pre-load and, in turn, generate a pre-load signal to reduce wear. In one method, a latch is retained to the latch assembly by the pin. 
         [0019]    In another embodiment, the subject technology is directed to a method for pre-loading a latch assembly comprising the steps of providing a pin in the latch assembly such that the pin bears a load when the latch is secure, using the pin to generate a signal indicative of the load and determining if the load is appropriate based on the signal. In a further embodiment, the method includes adjusting the load and rechecking the signal when the load is inappropriate. The load may be adjusted by positioning a keeper that engages a latch. 
         [0020]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the method and system of the invention. Together with the description, the drawings serve to explain the principles of the invention. 
           [0022]      FIG. 1  is a perspective view of an aircraft showing the engine nacelle cowl doors in the closed position. 
           [0023]      FIG. 2  is a perspective view of a mechanic and engine nacelle with open cowl doors. 
           [0024]      FIG. 3  is a perspective view of closed and fastened cowl doors from the interior of an engine nacelle, showing latch assemblies in accordance with the subject technology. 
           [0025]      FIG. 4  is a more detailed plan view of the latch assembly of  FIG. 3  as seen from inside the engine nacelle. 
           [0026]      FIG. 5A  is a perspective view of the latch and keeper of the latch assembly of  FIG. 3  in a closed position, showing the head of the pin. 
           [0027]      FIG. 5B  is a perspective view of the latch and keeper of the latch assembly of  FIG. 3  in an open position, showing the head of the pin. 
           [0028]      FIG. 6  is a perspective view of the hook and latch of the latch assembly of  FIG. 3  in an assembled condition, showing the head of the pin pulled out. 
           [0029]      FIG. 7  is a partial sectional perspective view of the pin of  FIGS. 5 and 6  with the cap removed and inner components visible. 
           [0030]      FIG. 8  is a longitudinal cross-sectional view of the pin, taken at line  8 - 8  of  FIG. 6 . 
           [0031]      FIG. 9  is a perspective view of the latch assembly, showing transmission of the signal to the receiver and forwarded to airplane cockpit. 
           [0032]      FIG. 10  is a perspective view of the latch assembly, showing transmission of the signal to a mechanic&#39;s transceiver. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0033]    Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. The method and corresponding steps of the invention will be described in conjunction with the detailed description of the system. The devices and methods presented herein may be used for detecting when a latch is (and is not) properly secured. The present invention is particularly suited for detecting when aircraft engine cowl doors are securely latched. 
         [0034]    In brief overview, a wireless latch detection system (WLDS) uses strain gauges, a microcontroller and an antenna integrated in a latch pin to directly ascertain a load of a latch assembly. When a latch assembly such as on the cowl doors is properly closed, the latch assembly is loaded and the WLDS transmits an indication of the closed condition. Otherwise, the WLDS transmits an indication that the latch mechanism is unloaded, e.g., in the open position. Further, the strain gauges provide a direct reading of the load so that adjustments may be made to set the load at a proper value. Although the following description is with respect to cowl doors retained by four latch assemblies, it is envisioned that the latch assembly may retain components of the landing gear, cargo doors, passenger doors, access panels and the like because the latch assembly disclosed herein is easily adapted to various applications. 
         [0035]    Referring to  FIG. 1 , an aircraft  10  showing engine nacelles  12  is shown. The engine nacelles  12  are attached to a strut  16  under the aircraft wing  14 . The engine nacelle  12  is shown being inspected by a mechanic in more detail in  FIG. 2 . The engine nacelle  12  includes two cowl doors  18 ,  20  that open to allow access to components therein for service and maintenance. The cowl doors  18 ,  20  are hinged to open and are retained closed by latch assemblies  100  (see  FIG. 3 ). It is within the subject disclosure to adapt the latch assemblies  100  to retain a single cowl door, however, the following description refers to an embodiment having four latch assemblies  100  that extend across and secure two cowl doors  18 ,  20 . 
         [0036]    Referring to  FIG. 3 , a perspective view of an interior of closed and fastened cowl doors  18 ,  20 , showing the four latch assemblies  100  is shown. Four latch assemblies  100  are shown but it is appreciated that an alternative number may be used. When properly loaded, the latch assemblies  100  will effectively retain the cowl doors  18 ,  20  closed, so that rattling, chafing and premature wear do not occur. The closed cowl doors  18 ,  20  also provide an aerodynamically smooth surface for the engine nacelle  12 , and protect components inside the cowl doors  18 ,  20  from the elements. 
         [0037]    Referring now to  FIG. 4 , a plan view of a single latch assembly  100  of  FIG. 3  is shown as seen from inside the engine nacelle  12 . The latch assembly  100  includes a latch  102  held within a latch housing  104  that is secured to the cowl door  20 . On the adjacent cowl door  18 , a keeper  106  is secured within a keeper housing  108  for engaging the latch  102  to close the latch assembly  100 . Each housing  104 ,  108  is permanently fixed to the respective cowl door  20 ,  18 . 
         [0038]      FIGS. 5A and 5B  show perspective views of a closed and open latch assembly  100 , respectively, as would be seen from inside the engine nacelle  12 . In the closed position, the latch  102  and keeper  106  are securely engaged whereas in the open position, the latch  102  and keeper  106  are disengaged. The keeper  104  has a grasp bar  110  fixed to the keeper housing  108  by a linkage such as a threaded bar  112 . The threaded bar  112  is secured to the keeper housing  108  by a plate  160 . A nut (not shown) may be used to lock the position of the threaded bar  112  with respect to the plate  160 . As can be seen, the latch  102  has a hook  114  (shown in phantom dashed lines) connected by a linkage  116  to a handle  118 . The linkage  116  allows the handle  118  to move between the closed latch position of  FIG. 5A  and the open latch position of  FIG. 5B . As the handle  118  moves along arrow “a”, the linkage  116  urges the latch  102  along arrow “b” into and out of engagement with the keeper  104 . When the latch assembly  100  is closed, the handle  118  rests within a depression (not shown) formed in the cowl doors  18 ,  20  so that an aerodynamic profile is formed. To close the cowl doors  18 ,  20 , the handle  118  is moved towards the hook  114  and, in turn, the hook  114  moves onto the grasp bar  110  of the keeper  106  and creates a retentive force. The retentive force pulls the cowl doors  18 ,  20  together. To open the cowl doors  18 ,  20 , the handle  118  is moved away from the keeper  106  and, in turn, the latch  102  moves off the keeper  106 . The handle  118  is usually painted red for extra visibility so that when moved away from the keeper  106 , the handle  118  hangs down below the engine nacelle  12  to provide visual indication that the latch assembly  100  is open. 
         [0039]    Referring to  FIGS. 5A ,  5 B and  6 , the latch  102  is coupled to the latch housing  104  so that a pin  120  connected to the linkage  116  carries at least a portion of the load on the latch  102 . Preferably, the pin  120  is configured and positioned so that the full load is directly carried by the pin  120 . The position of the keeper  106  and grasp bar  110  with respect to the keeper housing  108  can be adjusted by rotating the threaded bar  112 . By adjusting the position of the grasp bar  110  along arrow “b”, the retentive force between the hook  114  and grasp bar  110  (e.g., the latch/pin load) can be adjusted. In one embodiment, the latch housing  102  and keeper housing  108  are titanium and the body  122 , the latch  102  and keeper  106  are aerospace steel. In another embodiment, one or more pins can be used to retain one or both housings  104 ,  108  to the cowl doors  18 ,  20 . 
         [0040]    Referring to  FIGS. 7 and 8 , the pin  120  includes components to generate a signal indicative of the load thereon. The pin  120  has a body  122  defining a bore  124 . One or more strain gauges  126  to detect the pin load are bonded within the bore  124  such as taught in U.S. Pat. No. 2,873,341, U.S. Pat. No. 3,695,096 and U.S. Pat. No. 3,365,689. The strain gauge  126  can detect the operational forces on the pin  120  and convert such strain to a load signal. The strain gauge  126  can be calibrated after installation and operation of the aircraft  10  to prevent inaccurate readings. In one embodiment, the pin  120  is fixed in place so that the orientation between the force lines of the load and strain gauge  126  is known. Any type of device that generates a signal indicative of strain can be used instead of a strain gauge  126 . For example, a surface acoustic wave (SAW) device may be used to measure the surface strain on the relevant portion of the pin  120 . 
         [0041]    The strain gauge  126  provides a signal to a microcontroller  128  also housed within the internal bore  124 . The microcontroller  128  can serve to provide signal processing as necessary, as well as control the operation of the pin  120 . For example, the microcontroller  128  may turn off the pin  120  upon receipt of a signal indicating that the aircraft engine is running. 
         [0042]    An antenna  130  for transmitting the signal is also in the internal bore  124  and connected to the microcontroller  128 . In one embodiment, the antenna  130  is multiband or wideband, such as a fractal antenna commonly used in cellular telephone and microwave communication applications. In one embodiment, the signal is transmitted at a 2.4 GHz RF IEEE standard 802.15.4 modulation protocol. Alternatively, the pin  120  may be wired into the electronics of the airplane  10 . 
         [0043]    A battery  132  powers the pin components as needed. The battery  132  is preferably a small, reliable power cell located in the internal bore  124 . One exemplary battery  132  is a high temperature lithium-ion battery with an expected life span of 7-10 years. It is recognized that any power source is acceptable such as a rechargeable battery with an internal power source. The internal power source may convert light or motion into energy to recharge the battery. A cap  134  and seal ring  136  enclose the bore  124  so the components are protected from the external environment. To allow access to change the battery  132 , the cap  134  may thread into the body  122  or utilize a like arrangement. Alternatively, the battery  132  and other components are permanently and/or hermetically sealed in the pin  120 . In one embodiment, the cap  134  is configured to have beam steering qualities (e.g., a radome) so that the broadcast zone has a desired shape that aims the signal toward a reception point. 
         [0044]    Referring to  FIGS. 5-8 , the pin  120  is set in place using conventional means such as threads  140  that couple to a nut  142  and a washer  146  on one end, and a bolt head  144  on the other end. The cap  134  may be screwed, press fit, glued and the like into the bolt head  144 . Preferably, the body  122  also has a non-threaded portion  148  that carries the latch assembly load. The non-threaded portion  148  may be surrounded by narrower portions to help transmit the pin forces more effectively to the at least one strain gauge  126  mounted in the internal bore  124 . Generally, the placement of the strain gauge  126  will be to locate the strain gauge  126  near where the pin  120  carries the load on the latch assembly  100 . Thus, it is envisioned that configuration of the body  122  as well as the number and placement of the strain gauge  126  may vary greatly depending upon the particular application. 
         [0045]    In another embodiment, the hardware for generating and transmitting a signal indicative of the strain on the latch assembly  100  is housed in another component. For example, the plate  160  that anchors the keeper  106  may have the strain gauge and other components mounted therein. Additionally, one or more of the components may be mounted on an exterior as design constraints like space and effectiveness demand. Similarly, the component may be integrated to a housing, a keeper, a latch and the like. 
         [0046]    Referring to  FIG. 9 , a perspective view of the latch assembly, showing transmission of the signal to a remotely located transceiver  138  and forwarded to airplane cockpit is shown. The force or load on the latch assembly  100  is shown by force arrow “c”. In operation, the pin  120  may be activated upon receipt of a signal from the transceiver  138 . The strain gauge  126  generates a signal indicative of the load between the latch  102  and keeper  106 . The microcontroller  128  performs any necessary signal processing so that the signal is transmitted from the antenna  130  into a broadcast zone around the pin  120 . The remotely located transceiver  138  is preferably mounted within the cowl doors  18 ,  20  and the broadcast zone to receive the signal. 
         [0047]    If necessary, the transceiver  138  performs further processing of the signal such as boosting the signal, converting a raw signal into a reading of load and/or converting a load reading into a status indication of open or closed and the like. It is envisioned that the signal processing could be distributed in any practical arrangement between the microcontroller  128  and transceiver  138  or other subsequent components such as a computer in the cockpit or other area of the aircraft  10 . Further, the transceiver  138  may be configured to process the signals from a plurality of latch assemblies  100 . Similarly, if needed, multiple transceivers could be used to process and boost the signals from a single pin  120 . 
         [0048]    In one embodiment, the transceiver  138  has a Wheatstone bridge measuring circuit (not shown) with various calibration and tuning resistors. Thus, the transceiver  138  can process the pin signal, convert the signal into a reading of the load and provide an indication of whether of not the latch is closed. The transceiver  138  may have various lights to indicate open, closed or within an acceptable predetermined range. The transceiver  138  may also have an analog readout, and/or a digital readout along with on/off, and a mode selection switch. The transceiver  138  also passes the signal along, either wired or wirelessly, to another portion of the aircraft  10  so that the pilot and/or ground crew has an indication of the latch assembly status or even a numeric reading of the load. In one embodiment, the transceiver  138  is mounted on the engine fan case and hard wired to the aircraft or engine control electronics. 
         [0049]    The pin  120  in the latch assembly  100  bears a large load (e.g., 400 to 800 lbs) when the latch assembly  100  is closed and a small load (e.g., 3 lbs) when the latch assembly  100  is open. Consequently, the signal indicative of the load on the pin  120  can be wirelessly transmitted so that a pilot or mechanic, at a location remote from the pin  120 , can be aware of the status of the latch assembly  100 . Hence, by utilizing a pin  120  in each latch assembly  100 , the latch assemblies  100  can be effectively polled prior to take off to make sure each latch assembly  100  is closed. During flight, the latch assemblies  100  bear an even larger load (e.g., 4,000 to 18,000 lbs) and the pin  120  and other components are designed robustly to withstand the in-flight loading. As noted above, the active components of the pin  120  may be switched off during flight, e.g., to conserve battery strength. 
         [0050]    The microcontroller  128  and/or the transceiver  138  may function together or separately to provide various modes of operation for the pin  120 . The pin  120  may have a maintenance mode as described below or intermittent modes of operation. For example, the load signal may be transmitted when the engine  12  is not operational and the microcontroller  128  has been prompted into activation by receipt of an input signal. The pin  120  may also run according to a schedule protocol (e.g., once every two minutes), reporting on request (e.g., on demand from a base station or control area), or reporting on change (e.g., when the latch  102  is opened or closed). 
         [0051]    Referring now to  FIG. 10 , it may be beneficial to monitor and adjust the pre-loading of the latch assemblies  100  during engine build up or aircraft maintenance. By having the latch assemblies  100  apply the proper closing force to the cowl doors  18 ,  20 , chafing and undue wear is prevented. Typically, the latch pre-load force has been measured by using a force gauge to measure the force required to close the latch  102 , which is an indirect measurement of the operational force between the latch  102  and keeper  106 . By using the pin  120 , a mechanic can acquire a direct measurement because the pin  120  actually may carry the load between the latch  102  and keeper  106 . 
         [0052]    In one embodiment, the mechanic uses a separate mechanics transceiver  154  that provides additional functionality to the transceiver  138  mounted on the engine fan case. The mechanic can use the pin  120  and mechanics transceiver  154  to generate a signal indicative of the load and determine if the load is appropriate based on the signal (e.g., 500 lbs plus or minus 50 lbs). When the pre-load is inappropriate, the mechanic can adjust the position of the keeper  106  by rotating the threaded bar  112 . As a result, the pre-load on the latch assembly  100  can be adjusted until the pre-load is within tolerance. The mechanics transceiver  154  shown has a digital display  156 , an on/off button  158  and an indicator light  162 . 
         [0053]    Common airline design parameters are to incorporate additional robustness into mechanical designs. Often, a structural component is 5 or even 10 times as capable of carrying the respective working load because of the potentially catastrophic consequences of failure. As a result, many components are bulkier and heavier than is desirable. By applying the subject technology, it can be seen that monitoring of the current and accumulated strain can allow prediction of component fatigue. By predicting when a component may become likely to fail, replacement and repair can be accomplished prior to failure. As a result, the excessive mechanical robustness requirements may be loosened to allow for more compact and lighter assemblies. Additionally, if the mechanism has a secondary fail safe load path, having the subject technology in the primary load path will immediately identify a failure, e.g., an indication that the secondary fail safe device has taken over. As a result, the secondary device will not need to be designed to function between maintenance intervals. Rather, the design of the secondary fail safe device can be designed to function over shorter intervals. 
         [0054]    While the invention has been described above in the context of a latch for an aircraft engine cowl door, it will be apparent to those skilled in the art that the invention can also be used in other contexts as well. The invention can be used to sense the state of any latch. For example, the sensor can be used in various locations throughout an aircraft to sense the closing of latches, such as on any aircraft door, without departing from the spirit and scope of the invention. Moreover, while the invention has been described above with one antenna paired with one receiver, those skilled in the art will appreciate that it is also possible to use multiple antennae with a single receiver and vice versa without departing from the spirit and scope of the invention. Implementation of the subject technology also has benefits from a security standpoint, in addition to the other advantages discussed above. For example, after the cowl doors are properly closed and locked, continued remote monitoring of the transmitted load signal (by personnel either on board the aircraft or remote from the aircraft), up until the time the aircraft takes off from the runway, can provide an indication if the door has been tampered with or otherwise improperly opened. If any such tampering or opening has taken place, take-off can be delayed, and the aircraft can promptly be inspected and the cause appropriately addressed. 
         [0055]    All patents, published patent applications and other references disclosed herein are hereby expressly incorporated in their entireties by reference. It will be apparent to those skilled in the art that various modifications and variations can be made in the latch assembly and methods of the present invention without departing from the spirit or scope of the invention. For example, each claim may depend from any or all claims in a multiple dependent manner even though such has not been originally claimed. Thus, it is intended that the present invention include modifications and variations that are within the scope of the appended claims and their equivalents.
A cowl assembly for an engine nacelle including a first and second cowl door mounted for movement between an open position and a closed position. A latch assembly retains the first and second cowl doors in the closed position by having a latch retained in a latch housing on the first cowl door to engage a keeper retained in a keeper housing on the second cowl door. A pin retains the latch to the latch housing. The pin defines an internal bore. A sensor in the internal bore determines a signal indicative of a load on the pin, wherein the signal is determinative of whether the cowl doors are in the open or closed position. A transmitter conveys the signal to a location remote from the sensor. The signal can also be used to set the pre-load on the latch assembly.