Abstract:
A system including an extraction force transfer coupling link assembly is provided that extracts a cargo from an airborne aircraft with an extraction parachute and then deploys the cargo with a descent parachute. During a normal extraction the link assembly transfers a force from an extraction line to a deployment lanyard that deploys a descent parachute. In the event of a failed extraction, the assembly severs the deployment lanyard and jettisons the extraction parachute. The extraction force transfer coupling link assembly includes an ultra high molecular weight polyethylene rope that has one end of the deployment lanyard braided with the extraction line. The rope acts as both the extraction line for the cargo and the deployment lanyard for the descent parachute. By virtue of the ability to use a single rope, the link assembly is of simple construction and employs pyrotechnic cutters to effect the release of the extraction line and deployment lanyard rather than conventional mechanical interlocks.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to a system that extracts a cargo from an airborne aircraft and then deploys the cargo parachute. More specifically, the present invention relates to a system that during a normal extraction transfers a force from an extraction parachute to deploy a descent parachute and that, in the event of a failed extraction, jettisons the extraction parachute. 
         [0003]    2. Description of the Prior Art 
         [0004]    During a typical operation for the extraction and deployment of cargo from an airborne aircraft, a drogue parachute first deploys an extraction parachute which acts to extract the cargo from the aircraft. As the load leaves the ramp of the aircraft, the connection between the extraction parachute and the cargo is released. As a result, force from the extraction parachute is transferred to extract the descent parachute which, once deployed, carries the cargo during the descent. A conventional extraction assembly with cargo is illustrated in  FIG. 1 . 
         [0005]    During a normal deployment, only the connection between the cargo and the extraction parachute is released. However, an emergency situation can arise during a failed extraction, such as when the cargo platform becomes immobile or when the extraction parachute does not disconnect from the cargo. In this situation, the connections to both the extraction parachute and the descent parachute must be severed and the cargo is not deployed. 
         [0006]    Various conventional approaches are known for separating an extraction parachute from a deploying cargo during a failed extraction. For example, one approach involves manually cutting the lines that connect the extraction parachute to the cargo so as to release the parachute. The manual approach, however, can pose a substantial safety risk to aircraft personnel. 
         [0007]    U.S. Pat. No. 5,816,535 discloses an Emergency Cargo Extraction Parachute Jettison System that in one configuration eliminates the need to manually effect the release. The system includes a load transfer coupling attached to each extraction parachute for releasing the extraction parachute from the cargo container upon receipt of electrical power. A first circuit, coupled to the load transfer coupling, provides electrical power to the load transfer coupling of the next ejectable cargo container upon receiving an actuation signal to release the extraction parachute. A second circuit is used to sense when each of the plurality of cargo containers has been ejected from the aircraft and to provide the cargo container ejection signal to the first circuit upon such ejection. The actuation signal is provided to the first circuit if the ejection signal is not received within a specific time after initiation of the cargo ejection sequence. A third circuit is used to manually provide the actuation signal to the first circuit to enable immediate jettison of the extraction parachute. 
         [0008]    The U.S. Government uses a standard mechanical release Extraction Force Transfer Coupling (EFTC) as shown in  FIG. 2 . As indicated above, the EFTC is released in response to movement of an actuator arm  4  when the load leaves the ramp of the aircraft. Upon such release, the extraction line  6 , which is attached to a three-point link  8 , deploys the descent parachute. While a workable system, the U.S. Army EFTC system is limited to a 42,000 lb payload extracted weight for standard airdrop at low altitudes. 
         [0009]    The U.S. Army has also adapted an Extraction Parachute Jettison Device (EPJD) into the EFTC for payloads with a maximum extracted weight of 21,000 lb. The EPJD, however, does not incorporate any redundancy in the release unit. In addition, the Army&#39;s EFTC and EPJD are installed in series and, because of the three-point link design, necessarily include multiple mechanical assemblies. 
         [0010]    Finally, the U.S. Army&#39;s EFTC is used with a nylon concentric loop extraction line that varies in length and number of plies depending on the extraction weight and type of aircraft being used. This nylon line stretches as much as 25-30%, resulting in the storage of a considerable amount of energy during the extraction event. Consequently, the nylon line has a tendency to rebound or send a standing wave back into the aircraft during the extraction parachute deployment. 
       SUMMARY OF THE INVENTION 
       [0011]    In order to overcome the above-described drawbacks of the prior art devices, the present invention provides an electronically controlled system that extracts cargo from an airborne aircraft with an extraction parachute and then deploys the cargo with a descent parachute. During a normal extraction, the extraction parachute pulls the cargo from the aircraft via a cargo extraction line. Upon severing of the extraction line, a deployment lanyard subsequently deploys a descent parachute. In the event of a failed extraction, the assembly severs both the extraction line and the deployment lanyard so as to jettison the extraction parachute. 
         [0012]    By combining both EFTC and EPJD capabilities into a single assembly, the present invention facilitates the extraction of payloads ranging from 5,000 to 100,000 lb at both low and high altitudes. 
         [0013]    The present invention also includes an ultra high molecular weight polyethylene rope that is a braided assembly of the extraction line and the deployment lanyard. The single piece rope serves as both the extraction line for the cargo and the deployment lanyard for the descent parachute. The rope exhibits very low elongation under load, and therefore does not exhibit the standing wave phenomenon associated with conventional nylon extraction lines. 
         [0014]    Another feature of the present invention is its mechanical simplicity. By virtue of the ability to use a single rope for both the extraction and deployment functions, the link assembly is of relatively simple construction and avoids use of the conventional three-point link. 
         [0015]    Still another feature of the present invention is that by virtue of using the ultra high molecular weight polyethylene rope, the system can employ pyrotechnic cutters to effect the release of the extraction line and deployment lanyard rather than conventional mechanical interlocks. Pyrotechnic cutters are far more efficient and reliable than mechanical assemblies, especially when the tension in the load member is relatively high. Therefore, the present invention is capable of reliably deploying loads that are substantially heavier than the loads associated with conventional EFTC systems. 
         [0016]    Yet another feature of the present invention is the ability to vary the time delay of the extraction force transfer coupling, as well as the ability to jettison the extraction parachute in any type of emergency. 
         [0017]    Accordingly, it is an object of the present invention to provide an electronically controlled system that extracts a cargo from an airborne aircraft with an extraction parachute and then deploys the cargo with a descent parachute, while also having the capability to sever both the extraction line and the deployment lanyard to jettison the extraction parachute. 
         [0018]    Another object of the present invention is to combine EFTC and EPJD capabilities into a single assembly. 
         [0019]    Yet another object of the present invention is to provide a system that uses a single rope for both the extraction and deployment functions, thereby providing a link assembly that is of simpler construction and more reliable than the conventional three-point link. 
         [0020]    Still another object of the present invention is to provide an ultra high molecular weight polyethylene rope that can be severed using pyrotechnic cutters and which exhibits very low elongation under load. 
         [0021]    A further object of the present invention is to provide an EFTC assembly having variable time delay capability. 
         [0022]    A still further object of the present invention to be specifically enumerated herein is to provide an extraction force transfer coupling and parachute jettison system in accordance with the preceding objects that will conform to conventional forms of manufacture, be of relatively simple construction and easy to use so as to provide a system that will be economically feasible, long lasting, durable in service, relatively trouble free in operation, and a general improvement in the art. 
         [0023]    These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like reference numbers refer to like parts throughout. The accompanying drawings are intended to illustrate the invention, but are not necessarily to scale. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  is an illustration of a conventional extraction force transfer coupling and extraction parachute jettison system. 
           [0025]      FIG. 2  is an illustration of a conventional three-point link used in the system of  FIG. 1 . 
           [0026]      FIG. 3  is a perspective view illustrating an extraction force transfer coupling and extraction parachute jettison system in accordance with the present invention. 
           [0027]      FIG. 4  is a perspective view illustrating an extraction line and deployment lanyard rope and EFTC link assembly coupled to an extraction parachute in accordance with the present invention. 
           [0028]      FIG. 4A  is an enlarged view of portion  4 A of  FIG. 4 . 
           [0029]      FIG. 5  is a perspective view illustrating an EFTC assembly in accordance with the present invention prior to deployment of an extraction parachute. 
           [0030]      FIG. 6  is a perspective view illustrating the EFTC assembly of  FIG. 5  after the extraction line has been cut and with the deployment lanyard remaining intact as in a normal operation. 
           [0031]      FIG. 7  is a perspective view illustrating the EFTC assembly of  FIG. 5  during a parachute jettison operation in which both the extraction line and deployment lanyard have been cut. 
           [0032]      FIG. 8  is a block diagram illustrating analog control circuitry for the extraction force transfer coupling in accordance with the present invention. 
           [0033]      FIG. 9  is a block diagram illustrating microprocessor-controlled control circuitry for the extraction force transfer coupling in accordance with the present invention. 
           [0034]      FIG. 10  is a flow diagram illustrating the functional flow of the circuitry of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    Although preferred embodiments of the invention are explained in detail, it is to be understood that other embodiments are possible. Accordingly, it is not intended that the invention is to be limited in its scope to the details of constructions, and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiments, specific terminology will be resorted to for the sake of clarity. It is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. Where possible, components of the drawings that are alike are identified by the same reference numbers. 
         [0036]    Referring now specifically to  FIG. 3  of the drawings, there is illustrated an extraction force transfer coupling (EFTC) and extraction parachute jettison device (EPJD) system, generally designated by the reference numeral  10 , in accordance with the present invention. The EFTC acts to transfer the force initially applied to the extraction line by the extraction parachute, which is used to extract the platform from the aircraft, to the deployment lanyard of the cargo&#39;s main descent parachute. The EPJD releases both the extraction line and the deployment lanyard in the case of a failed extraction. 
         [0037]    The system  10  includes an EFTC link assembly, generally designated by reference numeral  20 , mounted on a load platform  70  and electrically coupled to an electronic control box  100 . The electronic control box  100  receives signal inputs from an EFTC switch box  90 , which is coupled to an EFTC actuator  80 , and from an emergency jettison box  110 , all of which are mounted to the platform. 
         [0038]    The EFTC link assembly  20  is connected to an extraction parachute  15 , as shown in  FIG. 4 , and to a main deployment parachute  25 , as shown in  FIG. 4A , by an extraction line and deployment lanyard rope, generally designated by reference numeral  40 . As shown in  FIG. 4A , the extraction line and deployment lanyard rope  40  includes an extraction line  42  and a deployment lanyard  44  which are joined to one another, preferably by braiding or other highly integrated connection, at a junction  46 . The extraction line  42  connects the extraction parachute via the link assembly  20  to the cargo that is to be deployed. The deployment lanyard  44  connects the rope  40  to the descent parachute  25  that, once deployed, carries the deployed cargo to the ground. 
         [0039]    The extraction line and deployment lanyard rope  40  is manufactured from a high-tenacity material which reduces the amplitude of the standing wave that is often associated with extraction parachute deployment using conventional extraction line material as previously discussed. A preferred material of construction for the rope  40  is ultra high molecular weight polyethylene (UHMWP). In one preferred embodiment, the rope  40  is made from a UHMWP rope such as the product sold under the trademark PLASMA by Cortland Cable of Cortland, N.Y. The PLASMA rope is constructed of high modulus polyethylene fibers produced by gel spinning ultra high molecular weight polyethylene, and has an excellent strength-to-weight ratio, the highest abrasion resistance of any fiber, and excellent dynamic toughness. The PLASMA rope also exhibits excellent flex fatigue resistance, low resistance to heat, and very low elongation, stretching only approximately 3-5% under load which results in less stored energy and reduced standing wave magnitude. 
         [0040]    In a preferred configuration of the extraction line and deployment lanyard rope  40 , the extraction line  42  is a 1⅝ inch diameter, twelve strand, PLASMA line, and the deployment lanyard  44  is a 1⅛ inch diameter, twelve strand PLASMA line that is braided into the extraction line  42  at the junction  46 . This configuration provides a rope  40  that has an ultimate tensile strength of approximately 295,000 lbs. 
         [0041]    As shown in  FIGS. 5 ,  6  and  7 , the EFTC link assembly  20  includes an extraction line pyrotechnic cutter  50  and a deployment lanyard pyrotechnic cutter  60 . The extraction line  42  connects to the EFTC link assembly  20  through pyrotechnic cutter  50 , and the deployment lanyard  44  connects to the EFTC link assembly  20  through pyrotechnic cutter  60 . Preferably, the deployment lanyard  44  has some slack when configured for deployment, such as that provided by loop  41 , to prevent the lanyard from being pulled inadvertently. As shown in  FIG. 5 , pyrotechnic cutter  50 , when activated, severs the extraction line  42  while the deployment lanyard remains intact. This occurs during a normal extraction operation. 
         [0042]    During a failed extraction, however, pyrotechnic cutter  60  is activated. If pyrotechnic cutter  50  has not already been triggered by the EFTC actuator  80 , control circuitry activating the pyrotechnic cutter  60  will first trigger the extraction line pyrotechnic cutter  50  to sever the extraction line  42  just before the deployment lanyard  44  is severed. Hence, activation of pyrotechnic cutter  60  effectively results in the severing of both the extraction line and the deployment lanyard, as shown in FIG.  7 . Thus, pyrotechnic cutter  60  functions essentially as an extraction parachute jettison device (EPJD) to release the extraction parachute  15  in the event of an emergency or abnormality in parachute deployment. 
         [0043]    Activation of the pyrotechnic cutter  50  is initiated by the EFTC actuator  80  which is connected to the EFTC switch box  90  via a control cable  85 . The actuator  80  includes an actuator arm  4  (see  FIG. 2 ) which, when tipped, results in a signal being sent over the control cable  85  to the switch box  90 . The switch box  90  generates an output which is transmitted to the control box  100  over control cable  95 . The control box  100  then initiates activation of the link assembly  20  via control cable  105 . Control cable  105  provides two inputs  111 ,  113  to the link assembly, one to initiate severing of the extraction line and the other to initiate severing of the deployment lanyard. In brief, activation of a switch mechanism  202  on the emergency jettison box  110  generates a signal to the control box  100  over control cable  75  which results in activation of the link assembly  20  to sever the deployment lanyard  44 . 
         [0044]    Block diagrams setting forth the transfer coupler control circuitry are provided in  FIGS. 8 and 9 .  FIG. 8  depicts an analog embodiment of the circuitry, while  FIG. 9  depicts a microprocessor controlled embodiment thereof. A flow diagram illustrating the functional flow of the circuitry is set forth in  FIG. 10 . 
         [0045]    To operate the control system, power is first switched on via an On/Off switch  204 . Two independent power sources  206 ,  207  provide dual redundancy, with a power management circuit  208  being configured to provide continuous power to vital components of the EFTC such as the timing circuit  210  and the test circuit  312 . Upon start up, the power management circuit  208  takes its supply voltage from a power A rail  214  by default. If there is a fault, however, then the power management circuit  208  switches to receive its supply voltage from a power B rail  215 . The power rails  214 ,  215  are constantly monitored and the power management circuit  208  has the ability to switch to either the power A rail  214  or the power B rail  215  should there be a fault. 
         [0046]    Assuming a successful start-up, the transfer coupling control circuit enters an operational mode in which the EFTC swing arm  4  and the EPJD activation switch  202  are continuously monitored. For purposes of discussion, the circuit as powered by power A rail  214  is described. However, persons of ordinary skill in the art will recognize the same discussion is equally applicable to the circuit flow as powered by power B rail  215 , as shown in parallel on the right-hand side of  FIG. 10 . 
         [0047]    While the cargo load is inside the aircraft, a circuit trigger  300  remains open and the EFTC cannot be activated. Movement  303  of the actuator arm  4  in response to load exit  302  from the aircraft  302 , however, activates the EFTC to trigger the circuit  304  which starts a first timer  306  within timing circuit  210 . 
         [0048]    Once the first timer times out at  308 , a second timer within the timing circuit  210  begins at  310 . When the second timer times out, the timing circuit  210  produces an output via control lines  115 ,  117  to a firing circuit  220  to activate the pyrotechnic cutters  50  to sever first and second bridgewires  222 ,  224  to release the extraction line  42 . In the microprocessor-controlled embodiment, the timing circuit  210  is embodied as a microprocessor  240  which provides a high output  238  to a plurality of optocouplers  242  that in turn output main power  244  to the cutters  50  to sever the bridgewires  222 ,  224 . 
         [0049]    If the EPJD activation switch  202  is activated, the timing circuit  210  or microprocessor  240  initiates a 250 millisecond time delay  246  before the respective firing circuits  220  or optocouplers  242  activate the pyrotechnic cutters  50 . During this delay period, corresponding firing circuits  221  or optocouplers  243  are activated to initiate operation of pyrotechnic cutters  60 , via control lines  119 ,  121 , which act to sever third and fourth bridgewires  252 ,  254  to release the deployment lanyard  44 . Following this release, i.e., about 250 milliseconds later, the first and second bridgewires  222 ,  224  are severed by pyrotechnic cutters  50  to release the extraction line as already discussed. 
         [0050]    As shown in  FIG. 8 , the transfer coupler control circuitry also includes a test circuit  312  including a switch comparator network  314 , a power comparator network  316  and a bridgewire comparator network  318 . The test circuit  312  allows a system operator, by pressing a pass/fail bit test switch  320  at any time, to carry out a Built In Test (BIT) of the power comparator network  316  to determine whether there is sufficient voltage in both the power A and power B rails. Another BIT then checks the switch comparator network  314  for continuity of both the EFTC swing arm  4  and the EPJD activation switch  202 . A final BIT is then performed of the bridgewire comparator network  318  to check the resistance of all eight initiator bridgewires  222 ,  224 ,  252 ,  254 ,  222 ′,  224 ′,  252 ′,  254 ′ to ensure that they have the correct resistance and are not open or short circuited. If all three of the aforementioned tests are successful, a green (Pass) Light Emitting Diode (LED) indicator lamp  262  is illuminated. If one of the tests fails, a red (Fail) LED lamp  264  is illuminated. The microprocessor-controlled circuitry with microprocessor  240  performs comparable BIT functions using a switch bit test network  414 , a power bit test network  416  and a bridgewire bit test network  418  as shown in  FIG. 9 . 
         [0051]    The present invention provides many advantages over the prior art. To summarize, the rope  40 , which is attached to the EFTC link assembly  20  with no mechanically released components, eliminates the need for the traditional three-point link mechanical interlock assembly used in the conventional EFTC system. Thus, the present invention advantageously eliminates many of the mechanical components normally associated with this type of airdrop hardware, reducing cost and simplifying operation. Instead, the system  10  of the present invention employs modern electrical controls combined with pyrotechnic cutter technology that has proved to be highly efficient and reliable. The pyrotechnic cutters  50 ,  60  are far more reliable than conventional mechanical assemblies, especially when the tension in the load member is relatively high. Therefore, the present invention is capable of reliably deploying loads that are substantially heavier than the loads associated with conventional EFTC systems. 
         [0052]    Another advantage of the system  10  according to the present invention is that the extraction line  42 , deployment lanyard  44  and extraction parachute rigging/installation will be the same as or similar to that of the current U.S. Army system. In a C-17 or C-130 aircraft, for example, the electronic control system of the present invention can be integrated with the current control system at the loadmaster station, which presently controls the U.S. Army EPJD-light, controller, and platform interfaces. 
         [0053]    It is not intended that the present invention be limited to the specific apparatus and methods described herein. The foregoing is considered as illustrative only of the principles of the invention. For example, while the various embodiments of the invention have been described in the context of deploying a single cargo, in another possible embodiment the system described herein can be used to deploy a succession of cargo platforms. 
         [0054]    In addition, while the invention has been described in the context of a single extraction parachute and a single descent parachute, in another possible embodiment the system described herein can be used with cargoes requiring a plurality of extraction parachutes and/or a plurality of descent parachutes. 
         [0055]    Additionally, while the invention has been described in the context of a rope  40  that is of braided ultra high molecular weight polyethylene construction, in another possible embodiment the rope can be of a different construction as long as it can fulfill the requirements of the service described herein. 
         [0056]    Further, numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and, accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.