AIRCRAFT WITH AN EMERGENCY FLOATATION SYSTEM

Abstract

An aircraft with an emergency flotation system, the emergency flotation system being activated upon an emergency landing of the aircraft on water, for preventing at least sinking of the aircraft, characterized in that a capsizing avoidance buoyancy system is provided, the capsizing avoidance buoyancy system being activated if predetermined activation criteria are satisfied and only after activation of the emergency flotation system upon an emergency landing of the aircraft on water, for preventing at least capsizing of the aircraft.

Claims

1. An aircraft with an emergency flotation system, the emergency flotation system being activated upon an emergency landing of the aircraft on water, for preventing at least sinking of the aircraft, wherein the aircraft being provided with a capsizing avoidance buoyancy system separate from the emergency flotation system, the capsizing avoidance buoyancy system being activated if predetermined activation criteria are satisfied and only after activation of the emergency flotation system upon an emergency landing of the aircraft on water, for preventing at least capsizing of the aircraft, and in that the at least one capsizing avoidance buoyancy device has an inflation unit that is electrically coupled to an associated power supply, wherein supplying power from the associated power supply to the at least one capsizing avoidance buoyancy device inflation unit is only enabled after the at least one capsizing evaluation unit determines that the predetermined activation criteria are satisfied.

2. The aircraft of claim 1, wherein the emergency flotation system comprises at least one float bag, the at least one float bag being inflated upon activation of the emergency flotation system.

3. The aircraft of claim 2, wherein the capsizing avoidance buoyancy system comprises at least one capsizing avoidance buoyancy device, the at least one capsizing avoidance buoyancy device being inflated upon activation of the capsizing avoidance buoyancy system.

4. The aircraft of claim 3, wherein inflation of the at least one capsizing avoidance buoyancy device is only enabled after inflation of the at least one float bag.

5. The aircraft of claim 3, wherein the capsizing avoidance buoyancy system comprises at least one capsizing evaluation unit, the at least one capsizing evaluation unit being activated after activation of the emergency flotation system upon an emergency landing of the aircraft on water, in order to determine whether the predetermined activation criteria are satisfied.

6. The aircraft of claim 5, wherein the at least one capsizing evaluation unit is electrically coupled to an associated power supply, wherein supplying power from the associated power supply to the at least one capsizing evaluation unit is only enabled after activation of the emergency flotation system.

7. The aircraft of claim 5, wherein the capsizing avoidance buoyancy system comprises at least one capsizing avoidance buoyancy device inflation unit, the at least one capsizing avoidance buoyancy device inflation unit being activated for inflating the at least one capsizing avoidance buoyancy device if the at least one capsizing evaluation unit determines that the predetermined activation criteria are satisfied.

8. The aircraft of claim 7, wherein the predetermined activation criteria are satisfied if a respective sea state is above predetermined emergency flotation system limits.

9. The aircraft of claim 1, wherein the predetermined activation criteria are satisfied if a respective inclination angle of the aircraft with respect to a vertical reference line is above a predetermined limit.

10. The aircraft of claim 1, wherein the predetermined activation criteria are satisfied if it is determined that the aircraft is comprised in a capsizing process.

11. The aircraft of claim 1, wherein activation of the capsizing avoidance buoyancy system is performed automatically and operator-independently.

12. The aircraft of claim 1, wherein a fuselage that defines a lower fuselage region and an upper fuselage region, the emergency flotation system being at least partly arranged in the lower fuselage region and the capsizing avoidance buoyancy system being at least partly arranged in the upper fuselage region.

13. The aircraft of claim 12, which is embodied as a rotary wing aircraft, in particular as a helicopter.

14. The aircraft of claim 13, wherein a main rotor, wherein the predetermined activation criteria are satisfied if operation of the main rotor is discontinued.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Preferred embodiments of the invention are outlined by way of example in the following description with reference to the attached drawings. In these attached drawings, identical or identically functioning components and elements are labeled with identical reference numbers and characters and are, consequently, only described once in the following description.

[0043] FIG. 1 shows a perspective view of an aircraft according to the invention,

[0044] FIG. 2 shows a schematic diagram of a capsizing avoidance buoyancy system actuation system according to the invention,

[0045] FIG. 3 shows an exemplary capsizing avoidance buoyancy device inflation sequence,

[0046] FIG. 4 shows an exemplary inadvertent capsizing avoidance buoyancy system activation fault tree, and

[0047] FIG. 5 shows an exemplary capsizing avoidance buoyancy system loss fault tree.

DETAILED DESCRIPTION OF THE INVENTION

[0048] FIG. 1 shows an aircraft 1 according to one aspect that is exemplarily illustrated as a rotary wing aircraft and, more particularly, as a helicopter. Thus, for purposes of simplicity and clarity, the aircraft 1 is hereinafter referred to as the helicopter 1.

[0049] Illustratively, the helicopter 1 comprises at least one multi-blade main rotor 1a for providing lift and forward or backward thrust during operation. The at least one multi-blade main rotor 1a preferably comprises a plurality of rotor blades 1b, 1c, 1d, 1e that are mounted at an associated rotor head 1f to a rotor shaft 1g, which rotates in operation of the helicopter 1 around an associated rotor axis.

[0050] Preferably, the helicopter 1 comprises a fuselage 2 that exemplarily defines a cabin 2a and a cockpit 2b. Illustratively, the fuselage 2 comprises a lower fuselage region 2c and an upper fuselage region 2d. The lower fuselage region 2c is preferably connected to a landing gear 1h, which is exemplarily embodied as a skid-type landing gear. The upper fuselage region 2d preferably defines a roof of the helicopter 1, where the rotor head 1f is exemplarily arranged.

[0051] Illustratively, the fuselage 2 is connected to a tail boom and exemplarily comprises at least one preferentially shrouded counter-torque device 4 configured to provide counter-torque during operation, i. e. to counter the torque created by rotation of the at least one multi-blade main rotor 1a for purposes of balancing the helicopter 1 in terms of yaw. The at least one counter-torque device 4 is illustratively provided at an aft section of the tail boom 3 and preferably comprises a tail rotor 4a. The aft section of the tail boom 3 preferably further comprises a vertical stabilizer 5 that is provided with a bumper 6. Illustratively, the tail boom 3 is also provided with a suitable horizontal stabilizer 3a.

[0052] According to one aspect, the helicopter 1 comprises an emergency flotation system 7 and a capsizing avoidance buoyancy system 8. The emergency flotation system 7 is preferably adapted for being activated upon an emergency landing of the helicopter 1 on water, for preventing at least sinking of the helicopter 1. The capsizing avoidance buoyancy system 8 is preferably adapted for being activated if predetermined activation criteria are satisfied and only after activation of the emergency flotation system 7 upon an emergency landing of the helicopter 1 on water, for preventing at least capsizing of the helicopter 1.

[0053] The emergency flotation system 7 and the capsizing avoidance buoyancy system 8 are preferentially implemented as two separate systems, such that the emergency flotation system 7 can be operated independent of the capsizing avoidance buoyancy system 8. In other words, an activation of the emergency flotation system 7 does not necessarily entrain an activation of the capsizing avoidance buoyancy system 8. However, in any case at least activation of the capsizing avoidance buoyancy system 8 and, preferentially, activation of the emergency flotation system 7 and the capsizing avoidance buoyancy system 8 is triggered operator-independently, i. e. automatically.

[0054] According to one aspect, the emergency flotation system 7 comprises one or more float bags 7a, in particular inflatable float bags. Illustratively, four float bags 7a are provided, from which three float bags 7a are visible in FIG. 1.

[0055] By way of example, the emergency flotation system 7 can be realized by using inflatable and inflating components that are currently already used for implementing conventional emergency flotation systems. Such components preferably comprise conventional float bags together with a pressurized gas cylinder or a gas generator including an electrical activation system located within a container. However, such conventional emergency flotation systems are well-known to the person skilled in the art, so that a more detailed description thereof can be omitted for brevity and conciseness.

[0056] The float bags 7a are preferably inflated upon activation of the emergency flotation system 7. Exemplarily, the float bags 7a are provided at least partly at the lower fuselage region 2c and, preferentially, mounted to the landing gear 1h. However, instead of mounting the float bags 7a to the landing gear 1h, they may alternatively be mounted directly to the fuselage 2 at the lower fuselage region 2c.

[0057] According to one aspect, the capsizing avoidance buoyancy system 8 comprises one or more capsizing avoidance buoyancy devices 8a, which are preferentially also embodied as float bags, in particular inflatable float bags. Illustratively, a single capsizing avoidance buoyancy device 8a is shown.

[0058] By way of example, the capsizing avoidance buoyancy system 8 can be realized by using inflatable and inflating components that are currently used for implementing conventional emergency flotation systems. As described above, such components preferably comprise conventional float bags together with a pressurized gas cylinder or a gas generator including an electrical activation system located within a container. However, as such conventional emergency flotation systems are well-known to the person skilled in the art, a more detailed description thereof as well as a more detailed description of the capsizing avoidance buoyancy system 8 as such can be omitted for brevity and conciseness.

[0059] The capsizing avoidance buoyancy device 8a is preferentially inflated upon activation of the capsizing avoidance buoyancy system 8. Exemplarily, the capsizing avoidance buoyancy device 8a is at least partly roof mounted at the upper fuselage region 2d. However, this roof-mounting is only illustrated by way of example and not for limiting the invention accordingly. Instead, the capsizing avoidance buoyancy device 8a may alternatively be mounted to the helicopter 1 at any other position that is suitable to allow preventing capsizing of the helicopter 1 upon inflation.

[0060] FIG. 2 shows an exemplary capsizing avoidance buoyancy system actuation system 9. According to one aspect, the latter comprises at least a capsizing evaluation unit 9a and a capsizing avoidance buoyancy device inflation unit 9b. The capsizing evaluation unit 9a preferably comprises one or more sensors, preferentially one or more water and/or vibration sensors. The capsizing avoidance buoyancy device inflation unit 9b is adapted for inflation of one or more capsizing avoidance buoyancy devices (e. g. capsizing avoidance buoyancy device 8a of FIG. 1) upon actuation.

[0061] According to one aspect, inflation of the one or more capsizing avoidance buoyancy devices is only enabled after activation of an associated emergency flotation system (e. g. associated emergency flotation system 7 of FIG. 1), preferably after inflation of one or more float bags (e. g. float bags 7a of FIG. 1) of the associated emergency flotation system. Accordingly, an emergency flotation system armed state detector 10 is provided for determining/indicating whether the associated emergency flotation system is ready for being activated and an emergency flotation system activated state detector 11 is provided for determining/indicating whether the associated emergency flotation system has been activated, i. e. whether the one or more float bags have been inflated.

[0062] By way of example, the detectors 10, 11 are implemented as switches, which are either turned ON or OFF. Preferably, a respective ON switch state indicates inflation resp. activation, while a respective OFF switch state indicates that no inflation resp. no activation has occurred.

[0063] According to one aspect, an emergency flotation system state evaluator 12 is provided for evaluating a respective current state of the associated emergency flotation system, i. e. the one or more float bags. Therefore, the emergency flotation system state evaluator 12 is preferably at least similarly embodied to an AND gate and preferentially analyses data provided by the detectors 10, 11, i. e. determines respective switch states thereof.

[0064] If both switch states are ON, the emergency flotation system state evaluator 12 preferably electrically couples a capsizing evaluation unit power supply 13a to the capsizing evaluation unit 9a and, thus, releases power supply from the power supply 13a to the capsizing evaluation unit 9a. Accordingly, supplying power from the power supply 13a to the capsizing evaluation unit 9a is only enabled after activation of the associated emergency flotation system so that the capsizing evaluation unit 9a is only activated after activation of the associated emergency flotation system, preferentially upon an emergency landing of a given helicopter (e. g. helicopter 1 of FIG. 1) on water.

[0065] Upon electrically powering the capsizing evaluation unit 9a, the latter starts determining whether predetermined activation criteria are satisfied. By way of example, the predetermined activation criteria are satisfied if one or more of the following conditions is fulfilled: a respective sea state is above predetermined emergency flotation system limits, a respective inclination angle of the given helicopter with respect to a vertical reference line is above a predetermined limit, the given helicopter is comprised in a capsizing process and/or operation of a main rotor of the given helicopter (e. g. multi-blade main rotor 1a of FIG. 1) is discontinued.

[0066] According to one aspect, if the capsizing evaluation unit 9a determines that the predetermined activation criteria are satisfied, the capsizing evaluation unit 9a preferably electrically couples a capsizing avoidance buoyancy device inflation unit power supply 13b to the capsizing avoidance buoyancy device inflation unit 9b and, thus, releases power supply from the power supply 13b to the inflation unit 9b. Accordingly, the inflation unit 9b is activated for inflating one or more capsizing avoidance buoyancy devices (e. g. capsizing avoidance buoyancy device 8a of FIG. 1).

[0067] FIG. 3 shows an exemplary capsizing avoidance buoyancy device inflation sequence 14, that can be implemented by means of the capsizing avoidance buoyancy system actuation system 9 of FIG. 2, i. e. with the inventive helicopter 1 of FIG. 1. The sequence 14 starts with an initial step 14a.

[0068] According to one aspect, in step 14a occurrence of an emergency situation is determined. More specifically, in step 14a it is determined whether ditching of a given helicopter (e. g. helicopter 1 of FIG. 1) on water is imminent or has already occurred.

[0069] Then, in step 14b, it is determined whether a respective emergency flotation system (e. g. emergency flotation system 7 of FIG. 1) is ready for being activated, i. e. whether the respective emergency flotation system is in armed state. Subsequently, in step 14c, it is determined whether the respective emergency flotation system has been activated, i. e. whether the respective emergency flotation system is in activated state. More specifically, step 14c may comprise a determination on whether one or more float bags of the respective emergency flotation system (e. g. float bags 7a of FIG. 1) have been inflated.

[0070] Subsequently, in step 14d, it is determined whether a respective sea state is above predetermined emergency flotation system limits. Furthermore, in step 14e, it is determined whether the given helicopter is already in a capsizing situation, i. e. whether the given helicopter already rotated or is already rotating into capsized position. Preferably, steps 14d and 14e are performed by means of the capsizing evaluation unit 9a of FIG. 2.

[0071] Finally, in step 14f, if the determinations in steps 14d, 14e are affirmative, a capsizing avoidance buoyancy device inflation unit of the given helicopter (e. g. inflation unit 9b of FIG. 2) is activated for inflating one or more capsizing avoidance buoyancy devices (e. g. capsizing avoidance buoyancy device 8a of FIG. 1). In other words, an underlying capsizing avoidance buoyancy system (e. g. capsizing avoidance buoyancy system 8 of FIG. 1) is activated.

[0072] It should, however, be noted that the order of the steps 14a to 14f, as well as respective measures that are taken at specific steps, are merely exemplary and not for limiting the invention accordingly. Instead, other measures and/or another sequential procedure is likewise possible and, therefore, contemplated. For instance, step 14b may be performed prior to step 14a or step 14e may be performed prior to step 14d. Similarly, while step 14d is only described as a determination on whether a respective sea state is above predetermined emergency flotation system limits, it may more generally be intended to detect an instability state of the given helicopter that has ditched on the water. Such an instability state is e. g. given if a respective inclination angle of the given helicopter with respect to a vertical reference line is above a predetermined limit and/or if operation of a main rotor of the given helicopter (e. g. multi-blade main rotor 1a of FIG. 1) is discontinued.

[0073] FIG. 4 shows an exemplary inadvertent capsizing avoidance buoyancy system activation fault tree 15. Fault tree 15 represents a safety assessment that is based on requirements according to FAR Part 29.1309 or EASA CS 29.1309 for a classification CATASTROPHIC of an unintended release of the capsizing avoidance buoyancy system 8 of FIG. 1. Accordingly, the capsizing avoidance buoyancy system 8 of FIG. 1, i. e. its constituent components, are preferably embodied with respect to an inadvertent release such that they provide for a qualitative function development assurance level A (FDAL-A) according to SAE-ARP-4754-A and a quantitative requirement for a failure probability of Q<10.sup.9/flight hour (Fh).

[0074] More specifically, with respect to an inadvertent capsizing avoidance buoyancy system activation by sensor, which is e. g. initiated by the capsizing evaluation unit 9a of FIG. 2 and illustratively referred to with the reference sign 15a, a qualitative item development assurance level C (iDAL-C) and a quantitative requirement for a failure probability of Q<5*10.sup.5/Fh should preferably be met. Furthermore, with respect to an inadvertent capsizing avoidance buoyancy system powering, which is e. g. initiated by the emergency flotation system state evaluator 12 of FIG. 2 and illustratively referred to with the reference sign 15b, an iDAL-A and a requirement for a failure probability of Q<10.sup.5/Fh should preferably be met.

[0075] As a result, when combining the qualitative assurance levels and the quantitative requirements according to 15a, 15b illustratively by means of an AND-conjunction 15c in the fault tree 15, a resultant FDAL-A and a resultant requirement for a failure probability of Q<10.sup.9/Fh are obtained. As described above, this resultant FDAL-A and this resultant requirement for a failure probability of Q<10.sup.9/Fh are preferably considered during design of the capsizing avoidance buoyancy system 8 of FIG. 1, i. e. its constituent components, with respect to an inadvertent release, wherein the capsizing avoidance buoyancy system 8 of FIG. 1, i. e. its constituent components is/are correspondingly configured, as illustratively indicated at reference sign 15d.

[0076] FIG. 5 shows an exemplary capsizing avoidance buoyancy system loss fault tree 16. Fault tree 16 represents a safety assessment that is based on requirements according to FAR Part 29.1309 or EASA CS 29.1309 for a classification CATASTROPHIC of a loss of the capsizing avoidance buoyancy system 8 of FIG. 1. Accordingly, the capsizing avoidance buoyancy system 8 of FIG. 1, i. e. its constituent components, are preferably embodied with respect to a possible loss such that they provide for a FDAL-A according to SAE-ARP-4754-A and a requirement for a failure probability of Q<10.sup.9/Fh.

[0077] More specifically, with respect to a damage of the capsizing avoidance buoyancy system 8 of FIG. 1, such as e. g. of the capsizing avoidance buoyancy device 8a of FIG. 1 and/or the capsizing avoidance buoyancy system actuation system 9 of FIG. 2, which is illustratively referred to with the reference sign 16a, an iDAL-A and a requirement for a failure probability of Q<5*10.sup.6/Fh should preferably be met. Furthermore, with respect to a loss of electrical chain for respective capsizing avoidance buoyancy devices, such as e. g. of the capsizing avoidance buoyancy device inflation unit power supply 13b of FIG. 2, which is illustratively referred to with the reference sign 16b, an iDAL-A and a requirement for a failure probability of Q<5*10.sup.6/Fh should preferably be met.

[0078] When combining the qualitative assurance levels and the quantitative requirements according to 16a, 16b illustratively by means of an OR-conjunction 16c in the fault tree 16, a resultant FDAL-A and a resultant requirement for a failure probability of Q<10.sup.5/Fh are obtained. This resultant FDAL-A and this resultant requirement for a failure probability of Q<10.sup.5/Fh are preferably considered during design of the capsizing avoidance buoyancy system 8 of FIG. 1, i. e. its constituent components, with respect to a potential loss of inflation capability of the capsizing avoidance buoyancy system 8 of FIG. 1, as illustratively indicated at reference sign 16d. Furthermore, with respect to a damage of the emergency flotation system 7 of FIG. 1, such as e. g. of the float bags 7a of FIG. 1, and/or with respect to a current sea state that may lead to capsizing of the helicopter 1 of FIG. 1, both of which are illustratively referred to with the reference sign 16e, a FDAL-C and a requirement for a failure probability of Q<10.sup.4/Fh should preferably be met.

[0079] As a result, when combining the qualitative assurance levels and the quantitative requirements according to 16d, 16e illustratively by means of an AND-conjunction 16f in the fault tree 16, a resultant FDAL-A and a resultant requirement for a failure probability of Q<10.sup.9/Fh are obtained. As described above, this resultant FDAL-A and this resultant requirement for a failure probability of Q<10.sup.9/Fh are preferably considered during design of the capsizing avoidance buoyancy system 8 of FIG. 1, i. e. its constituent components, which is/are, thus, correspondingly configured with respect to a possible loss, as illustratively indicated at reference sign 16g.

[0080] In summary, based on the generic fault trees 15, 16 of FIG. 4 and FIG. 5, requirements for the emergency flotation system 7 of FIG. 1 and, more particularly, for the capsizing avoidance buoyancy system 8 of FIG. 1 and its constituent components are defined. The capsizing avoidance buoyancy device 8 of FIG. 1 itself, which exemplarily comprises a roof mounted buoyancy device 8a in FIG. 1, which is preferably connected to a gas cylinder and a valve, should preferentially be designed to fulfill a quantitative requirement significant below 10.sup.9/Fh. The qualitative requirement iDAL A could be seen according SAE ARP 4754 as fulfilled.

[0081] Furthermore, the quantitative requirement for a respective electrical release is also required to be significant below 10.sup.5/Fh, which can be fulfilled by activation of the capsizing avoidance buoyancy system 8 of FIG. 1 (i. e. the roof mounted buoyancy device 8a of FIG. 1) in combination with a sensor detecting water and/or stop of rotor. A respective qualitative iDAL can be fulfilled by using a powering route and an independent release route, both iDAL-B or one of them iDAL-A and the other one iDAL-C. Simple sensors and contactors are able to fulfill these requirements. Moreover, an actuation logic, i. e. the capsizing avoidance buoyancy system actuation system 9 of FIG. 2, can be by this sufficiently developed according iDAL-C.

[0082] In addition, as described above, the capsizing avoidance buoyancy system of FIG. 1 is linked to the emergency flotation system 7 of FIG. 1. If the latter is not already activated, the capsizing avoidance buoyancy system of FIG. 1 preferably remains unpowered. For the emergency flotation system 7 of FIG. 1, respective safety figures for unintended activation are already above the CATASTROPHIC event classification described above. More specifically, there are already two different events defined, i. e. flight over water with emergency flotation system already armed and flight over land with emergency flotation system not armed. Thus, the failure probability for unintended activation of the dedicated sensor(s) of the capsizing avoidance buoyancy system 8 of FIG. 1 is below 10-5/Fh.

REFERENCE LIST

[0083] 1 rotary wing aircraft [0084] 1a multi-blade main rotor [0085] 1b, 1c, 1d, 1e rotor blades [0086] 1f rotor head [0087] 1g rotor shaft [0088] 1h landing gear [0089] 2 fuselage [0090] 2a cabin [0091] 2b cockpit [0092] 2c lower fuselage region [0093] 2d upper fuselage region [0094] 3 tail boom [0095] 3a horizontal stabilizer [0096] 4 counter-torque device [0097] 4a tail rotor [0098] 5 vertical stabilizer [0099] 6 bumper [0100] 7 emergency flotation system [0101] 7a float bags [0102] 8 capsizing avoidance buoyancy system [0103] 8a capsizing avoidance buoyancy device [0104] 9 capsizing avoidance buoyancy system actuation system [0105] 9a capsizing evaluation unit [0106] 9b capsizing avoidance buoyancy device inflation unit [0107] 10 emergency flotation system armed state detector [0108] 11 emergency flotation system activated state detector [0109] 12 emergency flotation system state evaluator [0110] 13a capsizing evaluation unit power supply [0111] 13b capsizing avoidance buoyancy device inflation unit power supply [0112] 14 capsizing avoidance buoyancy device inflation sequence [0113] 14a emergency situation occurrence [0114] 14b emergency flotation system armed state [0115] 14c emergency flotation system activated state [0116] 14d aircraft flotation instability state [0117] 14e imminent aircraft capsizing situation [0118] 14f capsizing avoidance buoyancy device inflation [0119] 15 inadvertent capsizing avoidance buoyancy system activation fault tree [0120] 15a inadvertent capsizing avoidance buoyancy system activation by sensor [0121] 15b inadvertent capsizing avoidance buoyancy system powering [0122] 15c AND-conjunction [0123] 15d inadvertent capsizing avoidance buoyancy system actuation [0124] 16 capsizing avoidance buoyancy system loss fault tree [0125] 16a damage of capsizing avoidance buoyancy device [0126] 16b loss of electrical chain for capsizing avoidance buoyancy device [0127] 16c OR-conjunction [0128] 16d loss of capsizing avoidance buoyancy device inflation capability [0129] 16e damage of emergency flotation system leading to aircraft capsizing state [0130] 16f AND-conjunction [0131] 16g loss of capsizing avoidance buoyancy system in aircraft emergency condition