Docket 06-1171 PCT - 1 -

SYSTEM AND METHOD FOR MEASURING PARAMETERS AT AIRCRAFT LOCI

BACKGROUND

Embodiments of the disclosure may be directed to aircraft testing systems, and especially to in-flight aircraft testing systems measuring conditions outside the pressurized space of an aircraft.

Large numbers of measurements in harsh environments are commonly required in conducting flight test operations. Equipping for such flight tests may incur high installation costs. Adaptability, responsiveness to emergent requirements, limited space availability, and labor resources may drive the design of flight test instrumentation. The flight test validation of a new airplane model may be the last major step prior to certification of the new airplane model for revenue flight. Lt is important for processes and tools to be accurate, thorough, complete, efficient, and cost effective during flight test operations in order to meet delivery schedules.

During an aircraft flight test program, instrumentation personnel may monitor and record thousands of test points throughout the test airplane. Aircraft flight test programs are not necessarily limited to airplane testing. Flight test program measurements may include reading of production sensors as well as reading of sensors installed specifically for the flight test program. The flight test sensors installed specifically for the flight test program and any flight-test modifications to the airplane itself that may be made specifically for the flight test program are preferably removed after testing. The test airplane is preferably reworked to a configuration suitable to being returned or delivered to the aircraft owner. Data from test measurements are preferably recorded during flight test conditions that are designed to demonstrate the safety and air worthiness of the airplane.

Measurement requirements may be defined in a computerized database that may reside on a database server called the Flight Test Computing System (FTCS). The FTCS may define what is to be measured, the sample rate, the accuracy required, and other parameters needed to acquire useful test data. From this FTCS requirements database, instrumentation personnel may design each measurement installation to provide the desired data. In order to guarantee successful data acquisition and reliability, an instrumentation engineer preferably considers many factors including, by way of example and not by way of limitation, the data system capabilities, end-to-

Docket 06-1 171 PCT - 2 - cnd measurement uncertainty, signal latency through various components of the system, and conditions under which measurements will be made.

As the complexity of measurement installations increases, the cost and impact may rise in terms of design, installation and removal, schedule and other aspects. Unique costs may be associated with items such as, but not limited to, the use of specially coated wire to reduce flammabilily, finite wire separation requirements, requirements for skilled labor to effect installation of test instrumentation, weight limitations, and penetration through pressure seal fittings. In addition, wires routed into the pressurized vessel or aircraft cabin from outside of the pressurized vessel of aircraft cabin must be electrically isolated to prevent the possibility of lightning flowing through a flight test wire into the interior of the airplane during flight or on the ground.

In a typical flight test program one may be required to install five to seven miles of wire or similar connecting medium to gather and record sensor data from 2500 to 4000 sensing loci in a tesl aircraft. Sensing may be effected, by way of example and not by way of limitation, using analog transducers. Sensors may be located inside and outside the pressurized space or pressure vessel of the test aircraft, or may be installed in remote locations of the test aircraft such as, but not limited to, a wing, horizontal stabilizer or vertical stabilizer of the aircraft. Such outside, remote or otherwise difficult-to-access loci or locations may necessitate expensive penetrations and rcfurbishmcnts of structure to install temporary test wiring. Secondary costs of wire routing may also be significant. Not only is there the cost of installation and removal and restoration of ^" any affected area of the test airplane, but there is also the cost associated with schedule disruption caused by the added steps a flight-test airplane must undergo for installation of wire and equipment during its production process. Benefits of embodiments of the disclosure may be pronounced when involving large testing programs. However, benefits of embodiments of the disclosure may also be realized even when involved in smaller testing instrumentations such as, by way of example and not by way of limitation, in smaller scale testing programs earned out between regularly scheduled operational flights by an aircraft.

There is a need for a system and method for measuring parameters at a plurality of loci associated with an aircraft that permits low-cost installation of test instrumentation and substantially quick removal of test instrumentation and return of the test aircraft to service condition.

Docket 06-1 171 PCT - 3 -

SUMMARY

A system for measuring parameters at a plurality of loci associated with an aircraft includes: (a) a central unit; (b) a plurality of communicating nodes coupled with the central unit; and (c) a respective plurality of sensing units associated with each respective communicating node of the plurality of communicating nodes; at least one selected sensing unit of at least one respective plurality of sensing units being a remote sensing unit. The at least one remote sensing unit communicates wirelessly with the respective communicating node. A method for measuring parameters at a plurality of loci associated with an aircraft includes the steps of: (a) In no particular order: (1) providing a central unit: (2) providing a plurality of communicating nodes coupled with the central unit; and (3) providing a respective plurality of sensing units associated with each respective communicating node of the plurality of communicating nodes, (b) Operating at least one selected sensing unit of at least one respective plurality of sensing units as a remote sensing unit. The at least one remote sensing unit communicates wirelessly with the respective communicating node.

It is. therefore, a feature of embodiments of the disclosure to provide a system and method for measuring parameters at a plurality of loci associated with an aircraft that permits low-cosl installation of test instrumentation and low cost, and substantially quick removal of test instrumentation and return of the test aircraft to service.

While the present description deals with flight testing, one skilled in the art of testing and test instrumentation may recognize that embodiments of the disclosure can be advantageously employed in connection with other testing programs in addition to flight testing, flight testing. By way of example and not by way of limitation, embodiments of the disclosure may be advantageously installed in a production configuration of a vehicle such as an aircraft, automobile, taick, ship, boat or another vehicular or non-vehicular system to effect such functions as health monitoring, predictive maintenance and other sensor monitoring jobs. Substantially similar issues apply to the production world of design, installation, and weight of wire and other components necessary' for non-wireless instrumentation. Further features of embodiments of the disclosure will be apparent from the following specification and claims when considered in connection with the accompanying drawings, in

Docket 06-1171 PCT - 4 - which like elements are labeled using like reference numerals in the various figures, illustrating preferred embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FlG. 1 is a schematic illustrating a representative installation of a system of an embodiment in an aircraft.

FIG. 2 is a schematic diagram illustrating a representative communicating node with associated sensor units. FIG. 3 is as schematic diagram illustrating representative overlap among wireless communication ranges of a plurality of hosting communicating nodes and respective associated sensing units.

FlG. 4 is a flow chart illustrating a method according to an embodiment of the disclosure.

DETAILED DESCRIPTION

One embodiment of the disclosure has a system configured as a wireless sensor network that can reduce wire routing and installation time required for flight test.

One challenge involved in designing the wireless sensor network the embodiment is providing local power to wireless sensor units that is safe and will operate in harsh environments. Time correlation of data over a wireless network embodiment of the disclosure is difficult when transmitting high speed data. Time stamping of data close to its origin or point of measure provided one satisfactory solution for providing desired accuracy in time correlation of collected data. Bandwidth and scalability of data is another design consideration when operating in a relatively small area with significant volumes of data being sent and received simultaneously. Bandwidth and scalability design considerations may be handled in an embodiment the system by creating independent zones or picoiicts that arc isolated from each other, and multiplexing data from the various independent zones that is time stamped close to the source of the data measurement or acquisition.

Other design considerations in designing a wireless sensing network or system may include, by way of example and not by way of limitation, managing power to limit propagation of

Docket 06-1171 PCT - 5 - wireless signals, designing antennas to optimize signal paths within a system, employing a network management tool for effecting system flexibility. By way of further example and not by way of limitation, one may employ software tools to optimize information flow within a system or to manage hardware employment, such as by selectively turning off one or more independent zones when not in use in order to manage power consumption.

In a preferred embodiment, independent zones may be advantageously configured as independent piconets. employing a plurality of Transducer Interface Modules (TlMs) in cooperation with a Network Capable Application Processor (NCAP). A TIM may be a module that performs interface functions such as, but not limited to, signal conditioning, Analog-to- Digital (A-to-D) conversion or Digital-to-Analog (D-to-A) conversion, or other interface functions to present a treated signal to the NCAP.

The system preferably employs a sensor connected to a Transducer Interface Module (TlM) by a short wire harness. The sensor may be integrally formed with the TIM. Some parameters measured by some sensors may require treatment by the TIM or other system component so as to be useful in a test program. A parameter measured by strain gage, by way of example and not by way of limitation, may require treatment such as analog signal conditioning and an A-to-D (Analog-to-Digital) conversion to produce a usable parametric signal. Such signal treatment may be carried out using circuitry provided on a daughter board in the TIM. Jn such manner, a TIM may be manufactured as a generally common system element, with changes to effect different signal treatment requirements being accommodated on custom daughter boards for use with TlMs installed at appropriate sampling loci in an aircraft. By way of example and not by way of limitation, the TlM data may be sampled, signal conditioned, digitized, converted to engineering units, buffered, or otherwise treated as required.

A group of sensors with respective TIMs may be coupled with a Network Capable Application Processor (NCAP) to form an independent zone configured as a sub-network or ^■ 'piconef. NCAPs associated with piconets may operate as a master unit in a master-slave relationship vis-a-vis TIMs in a respective piconet and may communicate with a central processing or control unit on board the test-aircraft to carry out a test program. The number of possible zones is theoretically determined by the signal propagation of each component and their relationship to other zones, as well as. the management of which zone is active at a given time. By way of example and not by way of limitation, software may manage a network to place one or more selected TlMs in a sleep mode when the selected TIMs are not needed. Such selective

Docket 06-1171 PCT - 6 - employment of TIJMS can save power and can assist in managing signal propagation issues such as signal interference, signal strength and other propagation issues.

FlG. 1 is a schematic illustrating a representative installation of a system of an embodiment in an aircraft. In FlG. 1. an aircraft 10 is configured with a test system 12 for effecting flight testing of aircraft 10. Test system 12 includes a central unit 14 communicatingly coupled with a plurality of communicating nodes 16ι, I6 ₂ , I6 ₃ , 16 _n . The indicator "n" is employed to signify that there can be any number of communicating nodes in test system 12. The inclusion of four communicating nodes I6 ₁ , I6 ₂ , 16 ₃ , 16 _n in FlG. 1 is illustrative only and does not constitute any limitation regarding the number of communicating nodes that may be included in the test system of an embodiment of the disclosure.

Selected communicating nodes such as. by way of example and not by way of limitation, communicating nodes I 6 ₂ , I 63. 16 _n may be wire coupled with central unit 14. Wire coupling may be effected, by way of example and not by way of limitation, using an Ethernet connection, fiber optic cable, or another cable or wire connection or digital data transport arrangement. Alternatively selected communicating nodes such as. by way of example and not by way of limitation, communicating node \6 _\ may be wirelessly coupled with central unit 14. By way of example and not by way of limitation, such wireless coupling may be configured according to the IEEE (Institute of Electrical and Electronics Engineers) 802.1 1 g VViFi Standard or another wireless connection arrangement. Each respective communicating node 16|. 16 ₂ , 16 ₃ , 16,, is coupled with at least one sensor unit. In representative test system 12 illustrated in FIG. 1 , communicating node I6 ₁ is coupled with sensor units I Si ₃ I S ₂ , I 8 ₃ , I 8 ₄ . I Ss, ' 8 _m . Communicating node I 6 ₂ is coupled with sensor units 20ι, 2O ₂ . 20 ₃ , 20^ ₁ 2Oj. 20 _m . Communicating node 16 ₃ is coupled with sensor units 22|, 22 ₂ . 22 ₃ , 22 ₄ , 22 ₃ . 22 _m . Communicating node 16,, is coupled with sensor units 24i, 24?. 24j, 24 ₄ , 24s, 24 _m . The indicator "m" is employed to signify that there can be any number of sensor units coupled with a respective communicating node in test system 12. The inclusion of six sensor units coupled with each communicating node in FIG. 1 is illustrative only and does not constitute any limitation regarding the number of sensor units that may be coupled with a selected communicating node in the test system of an embodiment of the disclosure. Moreover, illustrating the same number of sensor units coupled with each selected communicating node in FIG. I is illustrative only and does not constitute any limitation regarding the number of sensor

Docket 06-1 171 PCT - 7 - units that may be coupled with a respective communicating node in the test system of an embodiment of the disclosure.

Some sensor units of sensor units 18 _mj 20 _m , 22 _m , 24 _m may be wire-coupled with a respective communicating node I6 _n . Wire-coupling may be effected, by way of example and not δ by way of limitation, using an Ethernet connection or another cable or wire connection arrangement. In order to achieve maximum benefit of embodiments of the disclosure, it is preferred that sensor units 18 _m: 20 _m , 22 _m . 24 _m be wirelessly coupled with communicating nodes I6 _n , using a Bluetooth connection or another wireless connection arrangement.

FIG. 2 is a schematic diagram illustrating a representative communicating node with0 associated sensor units. In FIG. 2, a communicating node 16 _n is wirelessly coupled with sensor units 24|, 24 _2j 24 ₃ , 24 _4i 24 ₃ , 24, _n . Each sensor unit 24 _m includes a sensing module 30 _m , an interface module 32 _in . a power module 34,,, and an antenna 36 _m . Sensor unit 24| includes a sensing module 30|, an interface module 32|, a power module 34| and an antenna 36|. Sensor unit 24 ₂ includes a sensing module 3O ₂ , an interface module 32 _2j a power module 34 ₂ and an5 antenna 36 ₂ . Sensor unit 24 ₃ includes a sensing module 3Cb. an interface module 32 ₃ . a power module 34j and an antenna 36j. Sensor unit 24 ₄ includes a sensing module 3O ₄ , an interface module 32j, a power module 34 ₄ and an antenna 36 ₄ . Sensor unit 24s includes a sensing module 3O ₅ . an interface module 32s, a power module 34 _$ and an antenna 36 ₅ . Sensor unit 24 _m includes a sensing module 3O _1n . an interface module 32 _m . a power module 34 _m and an antenna 36,,,.0 Interface modules 32 _m may each be configured as a Transducer Interface Module (TIM).

Connection between a sensing module 30 _m and a TlM 32 _m may be established using a short wire harness or the sensing module 3O ₁₁₁ may be integrally formed with a TIM 32,,,. Some parameters measured by some sensing modules 30 _m may require treatment by a connected TIM 32 _m or other system component so as to be useful in a test program. A parameter measured by strain gage, byδ way of example and not by way of limitation, may require treatment such as analog signal conditioning and an A-to-D (Analog-to-Digital) conversion to produce a usable parametric signal. Such signal treatment may be carried out using circuitry provided on a daughter board in the TIM 32 _m . In such manner, a TlM 32 _m may be manufactured as a generally common system element, with changes to effect different signal treatment requirements being accommodated on0 custom daughter boards for use with TIMs 32 _m installed at appropriate sampling loci in an aircraft. By way of example and not by way of limitation, a TlM 32 _m may sample data,

Docket 06-1 171 PCT - 8 - condition signals, digitize data., convert data to engineering units, buffer data, or otherwise treat data as required.

A group of sensor units 24 _m including respective sensing modules 30 _m , TlMs 32 _m and power modules 34 _m may be coupled (preferably wirclessly coupled) with a respective communicating node 16 _n . Communicating node 16 _n may be embodied in a Network Capable Application Processor (NCAP) to form an independent zone configured as a sub-network or "piconet" 4O _n . Each NCAP 16 _n associated with a respective piconet 4O _n may operate as a master unit in a master-slave relationship vis-a-vis TIMs 32 _m in a respective piconet 4O _n . As illustrated in FIG. 1. an NCAP 16,, may communicate with a central processing or control unit 14 on board a test-aircraft 10 to carry out a test program. The number of possible zones or piconets 4O _n is theoretically determined by the wireless signal propagation of each sensor unit 18 _m , 20 _m , 22 _m . 24 _m ; each communicating node 16 _n and their relationships to other piconets 4O _n .

By way of example and not by way of limitation, a TIM 32 _tn may manage time using an internal clock as directed by a communicating node 16 _n embodied in an NCAP (Network Capable Application Processor) using periodic commands. Such a design arrangement may synchronize each respective TIM 32 _m to begin its respective data acquisition cycle. In such an arrangement, respective data acquisition cycles arc managed at the level of respective TlMs 32 _m , and data transfer cycle is managed by an NCAP.

Some of sensor units 24,,, may be situated within a pressurized space in a test aircraft (e.g.. test aircraft 10; FlG. 1 ). Other sensor units 24 _m may be situated outside of a pressurized space of test aircraft 10. As mentioned earlier herein, in order to achieve maximum benefit of embodiments of the disclosure, it is preferred that sensor units 18,,,. 20 _m , 22 _m . 24,,, be wirelessly coupled with NCAPs or communicating nodes 16 _n , using a wireless connection arrangement. In a preferred embodiment of the disclosure. TIMs 32,,, are coupled with NCAPs 16 _n using an IEEE 802.15 Bluetooth communication protocol, and NCAPs 16 _n are coupled with a parent data system or central unit 14 (FIG. 1) using an IEEE 802.1 Ig WiFi communication protocol. In its preferred embodiment, an NCAP 16,, is equipped with at least two radio communication units to facilitate using the desired two separate communication protocols. It is preferred that participating radio units be qualified for participation in a test system 12 (FIG. 1) or in a piconet 40,,. By way of example and not by way of limitation, software or other tools may be employed to preclude participation by non-qualified radios from joining a test system 12 or a piconet 4O _n .

Docket 06-1 171 PCT

- 9 -

It is especially important that at least sensor units 24 _m situated outside of a pressurized space in test aircraft 10 be wirelessly coupled with a respective NCAP or communicating node 16 _n inside of a pressurized space in test aircraft 10 to facilitate coupling while avoiding expense and inconvenience associated with traversing a pressurized boundary to establish a wire δ connection with an NCAP or communicating node 16 _n .

When requested by a respective NCAP or communicating node 16 _n . sensor units 24 _m (via respective TlM 32 _n) ) may organize data relating to a measured parameter or parameters into packets or data grams. The data grams may be time-stamped and sent to a central unit 14 (FIG. 1 ). Communication among various TIMs 32 _m , NCAPs 16 _n and central unit 14 may be carried out0 using wireless communication or wired communication. Wireless communications may use, by way of example and not by way of limitation, a Bluetooth wireless link according to an IEEE 802.15 series standard, a wireless link according to an IEEE 802.1 1 series standard or another wireless link. Connected communications may use, by way of example and not by way of limitation, a wired Ethernet link according to an IEEE 802.3 standard, a fiber optic (non-wired)5 link or another connected communication link. It is preferred to avoid wired links outside or partially outside an aircraft because of dangers associated with possible lightning strikes. It is preferred that communications across long distances or through boundaries of pressure zones be carried out using wireless communications in order that economic benefits of such an installation can be used to advantage. A wireless sensor network of the sort disclosed herein may add value0 vis-a-vis a wired-nctwork system by reducing duration of schedule interruptions and by reducing installation, removal, and maintenance costs associated with a test program, such as costs and structural changes required by prc-testing installation and post-testing removal of wires or cables. A lower total cost of a measurement and test program may result.

An architecture that supports a modular block format may also be preferred so that as5 technology in one block may change, only the affected block needs to be replaced. Using such a modular architecture, by way of example and not by way of limitation, a radio module may be changed to accommodate new technology without affecting other modules in the system.

In providing local power without the option of wired transmission of power from a centralized source, the choice comes down to designing power modules 34 _m to produce power0 locally or to store power locally and draw from the stored energy. Energy harvesting is one design approach that may have an advantage of little power storage, limited regular maintenance, and substantially unlimited use. Environmental restrictions may be built into a low cost energy

Docket 06-1171 PCT - 10 - harvesting design. Energy harvesting generally may involve: (1) Identifying an energy source. Some typical sources for energy harvesting may include, by way of example and not by way of limitation, vibration, temperature gradient, light source, or fluid flow. (2) Determining reliability of the source. That is. to inquire whether the energy source is available when needed. (3) Providing an efficient device to harvest the energy and deliver the energy to the load.

Other systems and methods for providing and storing power locally near a parameter measurement site or locus may also be employed. Local power systems such as battery systems, by way of example and not by way of limitation, enable avoiding having to install wires from a central power source to a TIM 32 _m and associated sensing module 30 _m . Having to install a power wire would negate gains made by establishing wireless communications between a TIM 32 _m and an NCAP 16,,.

One consideration in designing a wireless sensor system is providing a deterministic transport of data from a data source to a point at which the transported data can be time stamped or otherwise rendered deterministic. Determinism is closely related to the correlation of data over the entire test scope and duration because any measurement uncertainty introduced in terms of indcterminism or latency may affect correlation of events in different parts of the test. Indeterminate correlation of events in a test may reduce ability to analyze cause-and-effect relationships sought to be evaluated by a test.

The system of an embodiment of the disclosure may address determinism by tagging data with a time stamp in a respective NCAP 16 _n . Such time stamping may serve to nullify or reduce variations in the transmission time over a wireless network to a central unit 14 or elsewhere for recording because the data event time is already identified in the time stamp. Accurate time information from the data source to the location in the network where the data is time stamped is important for a useful time stamping approach. Such time information should be accurate enough to provide a desired level of determinism. An approach used in an embodiment of the system of the disclosure for providing such accuracy in time information may be carried out in a software implementation of IEEE 1588 Precision Time Protocol (PTP) standard and the Bluetooth standard. An example of such a software implementation is described in "Design Considerations for Software only Implementations of the IEEE 1588 Precision Time Protocol" by Kendall Correll, Nick Barendt and Michael Branicky; IEEE 1588 Conference; 2005.

The PTP provides a method for networked computer systems to agree on a master clock reference time and a way for slave clocks to estimate their offset from the master clock time

Docket 06-1171 PCT - 11 - through analysis of a series of time stamped packets. A clock discipline may be set up between the master and slaves using a series of clock estimates. This method, when done in the physical layer, provides sub-microsecond accuracy. By way of example and not by way of limitation, a method of accomplishing this in software, known as the Precision Time Protocol daemon (PTPd) ₃ has been developed (see Correll et al. cited above). When effective wireless communicating ranges of neighboring piconets overlap there is a need for avoiding interference among communications in overlapping piconet coverage areas.

FlG. 3 is as schematic diagram illustrating representative overlap among wireless communication ranges of a plurality of hosting communicating nodes and respective associated sensing units. In FlG. 3, a communicating network 50 includes piconets 40|. 4O ₂ , 4O ₃ . Piconet 40ι includes a communicating node 16| hosting a plurality of sensor units 18|, I S ₂ , 18 ₃ , I8 ₄ , I 8 ₅ , 18 _m . Communicating node 16 ₁ has an effective wireless communicating range T _\ . Piconet 4O ₂ includes a communicating node 16 ₂ hosting a plurality of sensor units 20|, 2O ₂ , 2Oj, 2O ₄ , 2O ₅ , 2O ₁₁₁ . Communicating node I 6 ₂ has an effective wireless communicating range r ₂ . Piconet 4O ₃ includes a communicating node 16 ₃ hosting a plurality of sensor units 22|, 22 ₂ , 22 ₃ , 22 ₄ , 22s, 22 _m . Communicating node 16 ₃ has an effective wireless communicating range r ₃ . Sensor units 18,,,. 20 _m , 22 _m may be configured substantially as described in connection with FlG. 2.

Communicating units 16ι, 16 ₂ - 16 ₃ arc situated in appropriate proximity that communicating ranges i"|. T ₂ . 1 ^* ₃ overlap. A result is that a sensor unit associated with a respective hosting communicating node 16|, 16 ₂ , I 6 ₃ may be situated within effecting communicating range of another communicating node than the hosting communicating node for the respective sensor unit.

In the representative orientation illustrated in FlG. 3. sensor unit 18| is within effective wireless communication range of its host communicating node 16ι, and also is within effective wireless communicating range of communicating nodes I 6 ₂ , 16 ₃ . Sensor unit IS ₂ is within effective wireless communication range of its host communicating node 16ι, and also is within effective wireless communicating range of communicating node I 6 ₃ . Sensor units 1 S ₃ . 18 ₄ , I 8 ₅ . 18 _m are within effective wireless communicating range of only their respective host communicating node \ 6 _\ . Sensor unit 2O4 is within effective wireless communication range of its host communicating node 16 ₂ . and also is within effective wireless communicating range of communicating nodes 161 , 16 ₃ . Sensor unit 20s is within effective wireless communication range

Docket 06-1 171 PCT - 12 - of its host communicating node lό _? . and also is within effective wireless communicating range of communicating node 16|. Sensor units 20?, 2O ₃ are within effective wireless communication range of their host communicating node I6 ₂ , and also are within effective wireless communicating range of communicating node 16 ₃ . Sensor units 2Oi . 20 _m are within effective wireless communicating range of only their respective host communicating node 16?.

Sensor unit 22s is within effective wireless communication range of its host communicating node I 6 ₃ , and also is within effective wireless communicating range of communicating nodes 16|, 16?. Sensor units 22i, 22 _m are within effective wireless communication range of their host communicating node I6 ₃ , and also are within effective wireless communicating range of communicating node 16?. Sensor units 22?. 22s, 22 ₄ are within effective wireless communication range of only their respective host communicating node I6 ₃ .

The indicator "m" is employed to signify that there can be any number of sensor units coupled with a respective communicating node in test system 12. The inclusion of six sensor units coupled with each communicating node 16|. I 6 ₂ . 16 ₃ in FlG. 3 is illustrative only and does not constitute any limitation regarding the number of sensor units that maybe coupled with a selected communicating node in the test system of an embodiment of the disclosure. Moreover, illustrating the same number of sensor units coupled with each selected communicating node 16|. 160. 16 ₃ in FIG. 3 is illustrative only and does not constitute any limitation regarding the number of sensor units that may be coupled with a respective communicating node in the test system of an embodiment of the disclosure.

Each piconet 40|. 4O ₂ , 40 ₃ should preferably be configured to prevent interference with other piconcts 40|, 40?. 4O ₃ such as. by way of example and not by way of limitation, by increasing the distance between communicating nodes 16| ₅ 16 ₂ - 16 ₃ , by tuning antennas in a piconet (see. e.g.. antennas 36 _m ; FIG. 2), or by reducing the power of the radio transmitter unit in the TIMs 32,,, (FIG. 2) in a piconet 40|. 4O ₂ . 4O ₃ . Other techniques may also be employed to reduce or avoid interference among piconets 40i, 4O ₂ , 4O ₃ such as, by way of example and not by way of limitation, frequency division multiplexing, time division multiplexing, code division multiplexing or other interference reducing techniques which may be adapted from other radio- based technologies. FIG. 4 is a How chart illustrating a method according to an embodiment of the disclosure.

In FIG. 4, a method 100 for measuring parameters at a plurality of loci associated with an aircraft begins at a START locus 102. Method 100 continues by. in no particular order: (1) providing a

Docket 06-1171 PCT - 13 - central unit, as indicated by a block 104; (2) providing a plurality of communicating nodes coupled with the central unit, as indicated by a block 106; and (3) providing a respective plurality of sensing units associated with each respective communicating node of the plurality of communicating nodes, as indicated by a block 108. Method 100 continues by operating at least one selected sensing unit of at least one respective plurality of sensing units as a remote sensing unit, as indicated by a block 1 10. The at least one remote sensing unit communicates wirelessly with the respective communicating node. Method 100 terminates at an END locus 1 12.

It is to be understood that, while the detailed drawings and specific examples given describe preferred embodiments of the disclosure, they are for the purpose of illustration only, that the apparatus and method of embodiments of the disclosure are not limited to the precise details and conditions disclosed and that various changes may be made therein without departing from the spirit of embodiments of the disclosure which is defined by the following claims: