Wireless rotating instrumentation system and methods for data collection on helicopter rotor systems

The application relates to a wireless rotating instrumentation package for collecting data from a spinning rotor head of a rotary wing aircraft. The application also relates to a method of wirelessly collecting data from a spinning rotor head of a rotary wing aircraft.

BACKGROUND

Historically, airframe manufacturers have instrumented helicopter main rotor head(s) to perform flight testing. Typically they have employed data collection systems that require slip ring assemblies to be attached to the main rotor shafts to transfer power up to the instrumentation package and pass data down.

DETAILED DESCRIPTION

The Army has funded and participated in projects to develop and test the technologies necessary to realize a wireless system concept that could be used on any type of helicopter. “Wireless” in this case refers to the lack of slip-rings or contacts or wires to pass power or electrical signals to and from the rotating assembly.

The present application realizes a workable solution for collecting data from an aircraft rotor head that is spinning. The concept uses a battery or self-powered instrumentation package on the rotor head of a rotary wing aircraft for the purpose of collecting data for post flight processing in addition to making the data available for real-time monitoring on the ground during flight testing. Embodiments were fabricated and employed for an actual successful flight test program.

Such collected rotor data need to be available after the flight for detailed computer aided data analysis. The rotor data saved for post flight processing must be lossless and time correlatable to the data collected elsewhere on the test aircraft. During the flight test, rotor data should be available real-time for analysis in a ground station in order to maintain safety-of-flight and to make flight test decisions.

The data used for real-time analysis is usable with delays and time uncertainties on the order of a small fraction of a second. It does not need to be lossless but instead it needs to be good enough to use to make flight test decisions.

A low technical risk approach was taken by selecting commercially available components from various vendors and configuring them in a manner to make a useful instrumentation package. SeeFIG. 1, which is a Wireless Rotating Instrumentation Package (WRIP) shown as a Methods Block Diagram. Also seeFIGS. 2 and 3, which are two different embodiments of a WRIP attached to two types of helicopters. The rotating components are contained in a suitable instrumentation package116/118/120/122attached to the rotor head110. Wiring extends from the instrumentation package116/118/120/122to the transducers114on the rotor head110and the rotor blades112to collect the data from transducers114on the main rotor head110. The transducers114are wired to data modules116, which in turn are connected to miniature, configurable small data collection system118. GPS signals are received for the instrumentation package116/118/120/122with a data modules GPS antenna166. A GPS receiver card (not pictured) in the data system provides time tags for the data collection. The Pulse Coded Modulation (PCM)/Frequency Modulated (FM) output of this system feeds a digital L-Band telemetry transmitter126using PCM/FM modulation. The rotating small data collection system118is attached to an instrumentation package solid state data recorder120with removable solid state media (not pictured) for collecting lossless data with micro-second Global Positioning System (GPS) derived time tags received with the data modules GPS antenna166. The instrumentation package116/118/120/122is powered with re-chargeable battery packs122. The rotor instrumentation package116/118/120/122or combination of the data modules116, the small data collection system118, the instrumentation package solid state data recorder120and the rechargeable battery packs122are often attached together to form what is hereinafter referred to as the instrumentation package116/118/120/122. In one embodiment, the instrumentation package116/118/120/122is cylindrically shaped, sitting atop a helicopter rotor head110with the axis of the cylindrical style instrumentation package116/118/120/122being collinear with the axis (A) of the rotor shaft180. Built In Test (BIT)170features for monitoring battery voltage, temperature and package vibration are connected to the instrumentation package116/118/120/122. The instrumentation package116/118/120/122may optionally be designed with power scavenging features124from the rotor head110. A first telemetry transmitter transmit antenna130and optionally a second telemetry transmitter transmit antenna132or more are placed on the rotor head110. If multiple transmit antennas are used, then, for example, the first telemetry transmitter transmit antenna130, the second telemetry transmitter transmit antenna132and so forth are connected to a transmission signal splitter128, which splits the signal between the multiple telemetry transmitter transmit antennas130,132.

A telemetry receiver receive antenna134and optionally a second telemetry receiver receive antenna136or more are placed in “line of site” (LOS) with the first and second telemetry transmitter transmit antenna(s)130,132or more. The RF signal from the telemetry receiver receive antennas134,136is fed to an airborne telemetry receiver142with bit synchronizer (not shown). The Data and Clock from the telemetry receiver142with bit synchronizer (not shown) are fed to a decommutator card (not shown) in the data merger144attached to the aircraft data collection system146. The decommutated data is thus directed to the main aircraft data collection system146and merged into specific data locations in the PCM data stream using a current value table (CVT) technique for the asynchronous data. This combined composite data is recorded with a GPS time stamp in an aircraft data collection system solid state recorder152for post flight data processing of the mainstream parameters. The aircraft data collection system solid state recorder152is in turn connected by wire to a collection system solid state recorder GPS antenna172which receives GPS signals and sends them to the aircraft data collection system solid state recorder152. The composite data stream from the aircraft data collection system146is directed to an aircraft data collection system telemetry transmitter148, and tele-metered, using an aircraft data collection system transmit antenna150to transmit data to the ground station tracking antenna154attached to a ground station156for real-time display in the ground station156. A bi-directional data link, including a maintenance computer158, and a maintenance computer antenna160, sends and receives signals via a maintenance link transmit antenna162which is connected to a ground maintenance-providing bi-directional RF data link164which in turn is connected to the small data collection system118in the rotor instrumentation package116/118/120/122. Thus by means of the maintenance computer158, using readily available data link technologies, a system can be implemented to allow easy access to the rotor instrumentation package116/118/120/122data system for programming, pre-flight checkout and maintenance functions on the ground. The combination of the airborne telemetry receiver142, data merger144, aircraft data collection system146, aircraft data collection system telemetry transmitter148and aircraft data collection system solid state data recorder152is often attached together to form what is hereinafter referred to as a receiver package142/144/146/148/152.

Antenna Link Methodology: Problems and Solutions

Antenna Geometry: The Airborne test telemetry bands include microwave radio frequencies that are directional and require line-of-sight (LOS) between the first and second telemetry transmitter transmit antennas130,132and the first and second telemetry receiver receive antennas134,136to establish adequate communications. If the configuration of the antennas is such that a LOS condition can be accommodated, then an adequate link can be established relatively easily. Such is the case with a non-limiting example of a first telemetry transmitter transmit antenna130placed on the top of the rotor head110and a first telemetry receiver receive antenna134placed on a cowling/cover176behind and below the rotor head110, as well as a second telemetry receiver receive antenna136placed high on the tail of a UH-60 helicopter with a tail rotor110, as shown inFIG. 3. In contrast, as shown inFIG. 2, in a non-limiting example, with a non-LOS arrangement on a CH-47 helicopter, with two main rotors and no tail, it is not possible to set up this configuration. There is an instrumentation package116/118/120/122atop each rotor shaft180. The RF link must be made under the rotor system. If a first telemetry transmitter transmit antenna130is placed on the bottom of the rotor system and a first telemetry receiver receive antenna134is placed on the roof of the cabin under the rotor110, then as the first telemetry transmitter transmit antenna130rotates, a situation will occur where the main rotor head110and/or shaft180will block the signal and result in an unacceptable loss of data. The solution to this problem is a second telemetry transmitter transmit antenna132and/or a second telemetry receiver receive antenna136to maintain a line of sight through the full rotation. The signal can thus be transmitted. In this embodiment, the receiver package142/144/146/148/152is located within the helicopter cab.

Alternatively, as shown inFIG. 3, in a non-limiting example, with a non-LOS arrangement, there is shown a UH-60 helicopter, with one rotor and a tail. There is an instrumentation package116/118/120/122attached atop the rotor110. The telemetry receiver receive antenna134, as well as the GPS antenna168, is placed on the engine cowling/cover176, below and behind the rotor head110. The aircraft data collection system transmit antenna150is placed below the front end of the helicopter. There is a receiver package142/144/146/148/152within the helicopter cab.

FIG. 4shows a close-up view of one of the two cylindrical/conical instrumentation core packages116/118/120/122shown inFIG. 2. These are the instrumentation core packages116/118/120/122that are perched on top of the two helicopter rotor heads110shown inFIG. 2.FIG. 2shows the helicopter rotor blades112and rotor shaft180surrounding the instrumentation core packages116/118/120/122. The axis of the rotor shafts180are collinear with the axis (A) of the instrumentation core packages116/118/120/122. InFIG. 4, on the instrumentation package116/118/120/122is shown the two telemetry transmitter transmit antennas130/132. Also shown are views of the data modules GPS antenna166and the BIT170.

FIG. 5is a close-up view of the cylindrical instrumentation core package116/118/120/122shown inFIG. 3. InFIG. 5are shown views of a first telemetry transmitter transmit antenna130, data modules GPS antenna166, BIT170as well as a rotor data transducer114.FIG. 3shows the helicopter rotor blades112and rotor shaft180surrounding the instrumentation core package116/118/120/122. The axis of the rotor shaft180is collinear with the axis (A) of the instrumentation core package116/118/120/122shown inFIG. 5.

Signal Combination: An RF transmission signal splitter128(for telemetry transmitter transmit antennas130,132) and/or receiver signal combiner140(for telemetry receiver receive antennas134,136) is used between the two types of antennas. The classical problem with multiple antennas is the cancellation of the composite signal when the two signals combined are equal amplitude and 180 degrees out of phase. One can change the phase and amplitude of the signals independently using hardware. The phase can also be changed by varying the length of the cables, whether they be transmit cables138,182or receive cables178,184. The transmit cables138,182are connected to the two telemetry transmitter transmit antennas130,132and the receive cables178,184are connected to the two telemetry receiver receive antennas134,136. The length of microwaves in a co-axial cable are on the order of a few inches, so varying the length an inch can avoid cancellation at a given rotor position. The relative amplitudes of the signals can be varied using, respectively, an RF transmission signal splitter128and/or RF receiver signal combiner140with the appropriate frequency range. These devices are currently available in a number of different ratios, for example; 50%-50%, 60%40% and 90%-10%.

Variable Power: A feature of this method is that the power of the transmitter is variable (from approximately 10 milli-Watts to approximately 10 Watts). RF link performance is a function of power available. Performance increases are not linear with increased power. A point of diminishing return can be found experimentally during ground runs. The links in this application are short and it was found that adequate performance could be realized using 10 s of milli-watts in an embodiment with an under-the-rotor antenna configuration. It was shown during the early experiments, that power on the order of 100 milli-watts would be sufficient to produce a link to a telemetry transmitter transmit antenna(s)130,132and back to the main aircraft data collection system146via a telemetry receiver receive antenna(s)134,136and an RF receive cable(s)178,184. One implementation of this used a commercially available, powered, low noise microwave amplifier (LNA) (not pictured) at the tail of the helicopter to drive the return signal RF receive cable178,184, thus lowering the power requirements at the WRIP data collection system telemetry transmitter128.

Antenna Polarization: A variable of the RF link is the polarization of the telemetry transmitter transmit antenna(s)130,132and the telemetry receiver receive antenna(s)134,136. The polarization of an antenna is fixed in the manufacturing process. Some of the variations are: Horizontal, Vertical or Circular polarization with Left or Right Hand options. Polarization of the telemetry transmitter transmit antenna(s)130,132and the telemetry receiver receive antenna(s)134,136should match the signal in order to obtain the greatest efficiency. The mounting orientation of the telemetry transmitter transmit antenna(s)130,132and the telemetry receiver receive antenna(s)134,136affects the polarization of the links. This is a complex three dimensional problem in a system that is continually changing its geometry cyclically. If bounces off of stationary and rotating components of the aircraft are included, the problem becomes very difficult to visualize. The complex geometries that constantly change during rotation also make the results very difficult to model and predict a solution. On the other hand, these messy situations also make it less likely that the perfect cancellation will occur. Limited 3-D modeling and experience has shown that experimenting with the variables outlined here will result in an “adequate” solution.

A measure of digital data link performance is Bit Error Rate (BER). The links described here can easily achieve BER in the 10E-6 range. In simplistic terms this means 1 error every 1 million bits. In the case of one embodiment, experimentation was stopped when the error rate was about 1 data error in 10 seconds. It should be noted as part of the method, that the decommutation synchronization strategy of the short link telemetry on the aircraft should be set very “loose”. This means that individual bit errors in a frame synchronization pattern will tend NOT to drop out a whole frame of data. Individual bit errors in least significant bits will not be noticeable. Bit errors in higher order bits will be easily recognized visually as errors, because the next sample will return to the correct value. If desired, wild-point routines or filtering of the data may be implemented real-time to reduce the effects of these dropout errors. A goal here would be to make it possible to automate real-time computer monitoring of data limits. As a practical matter the short RF ink has a fraction of the dropouts associated with the normal main ground link.

The following is an outline of the process to establish an adequate telemetry link:

1. Overhead Link: If geometry allows, as in the case of a conventional helicopter with a vertical tail rotor, a line of site (LOS) link is established using a single omni-directional telemetry transmitter transmit antenna130and a telemetry receiver receive antenna134. The telemetry receiver receive antenna134should be high on the tail to avoid or minimize rotor blade interference. Polarization should nominally be matched. A directional telemetry receiver receive antenna134on the tail such as a horn or slot array is advantageous to the link but may not be aerodynamically acceptable for certain flight tests. To test the link, first run the aircraft on the ground, away from large RF reflectors such as metal aircraft hangar buildings. Looking at receiver signal to noise ratios and/or Bit Error Rate (BER) tests during ground runs can help establish the first workable solution. Ultimately, real-time telemetry from the main package will be viewed in the ground station156. The power and antenna geometry should be varied on successive runs and then iterated to establish an adequate link.

2. Under Rotor Link: A telemetry link can be established under the rotor head110. When trying to use a single telemetry transmitter transmit antenna130and telemetry receiver receive antenna134, LOS will usually be compromised by the rotor head110or shaft180. The solution is to use either two telemetry receiver receive antennas134,136and/or two telemetry transmitter transmit antennas130,132, approximately placed 180 degrees around the rotor shaft180. Because of the difficulty of predicting the link performance, a physically convenient mounting scheme should be chosen that gives LOS to at least one pair of antennas at every rotor position. Experimentation on the first embodiment involved about a dozen ground runs and a few short flights. The variables in the problem, their effect and desired end state are summarized:

a. Various number and locations of telemetry transmitter transmit antennas130,132and/or telemetry receiver receive antennas134,136may be tried to maintain a line-of-site link during rotation of the rotor head110.

b. Various polarization and orientation of telemetry transmitter transmit antennas130,132and/or telemetry receiver receive antennas134,136may be tried to establish a favorable RF link through the full rotation of the rotor head110, to resolve a three dimensional visualization problem.

c. Control of RF transmit cable lengths138,182to vary the signal phasing at the transmission signal splitter128or receiver signal combiner140may be tried to control cancellations of the signal as a function of rotation angles.

d. Various ratios of the relative amplitude of the signals in the transmission signal splitter128and/or the receiver signal combiner140may be tried to control cancellations of the signal as a function of rotation angles.

e. RF transmit power may be varied to get an adequate signal to noise ratio and adequate BER. There is a point of diminishing returns that can be determined experimentally during a ground run.

Using the Methodology outlined herein to manipulate the variables that affect the telemetry link, one can improve an RF link performing real-time monitoring of data on rotors.

A defining feature and critical component of the present system is the battery power source122. The technology chosen, Lithium iron phosphate (LiFePO4), has only been commercially available for a few years. Requirements for use of LiFePO4in an aircraft application in general and this application in particular included:

A. Intrinsically safe charge and discharge characteristics, no thermal runaway;

B. Ability for fast charge and discharge, characteristic low internal impedance;

D. Rugged construction capable of withstanding the forces on a Rotor head110;

E. Commercial availability in the Amp-hour capacities and form factors for these applications, 4 to 10 A-hr at 24 Vdc.

The battery capacity can be tailored to the aircraft application. Different aircraft have different flying times available. For helicopter applications this is between 1½ and 4 hours. The power required by the package is the other variable that establishes the size or Ampere-hours required at a certain voltage.

Electrical energy storage batteries122in general and LiFePO4technology in particular can be used to power aircraft rotor package instrumentation.

Global Positioning System (GPS) Time Correlation:

Time Correlation: Time correlation of the data obtained on the rotor head110with the data collected elsewhere is critical to the concept. This system methodology uses at least one data modules GPS antenna166in the rotating package116/118/120/122and at least two independent GPS receivers168,172connected to the airframe package142/144/146/148/152to time stamp the recorded data. GPS time stamps in this embodiment were accurate to better than 20 μsec when the GPS signals were locked and collected to the micro-second resolution. Subsequent modifications to these devices yielded accuracies down to one micro-second. Two time formats are available in both packages. The first is time embedded in the PCM data stream or “time as data” (the “main stream” file) and the second is the acquisition time stamp saved in the recorded file (a .bin or RCC-106 Chapter 10 format) of the aircraft data collection system solid state recorder152. The two data systems are not synchronized. Sample rates and sample times are different in each. The two data sets can be easily plotted on the same time scale. If data analysis routines require that samples be coherent or in the same stream, then further manipulation will be required. A novel method to do this is based on the fact that the main telemetry stream is made to contain rotor data received from the instrumentation package116/118/120/122, sampled and at times synchronized to the main data stream data. The rotor data actually contained in these time slots is subject to the short telemetry link dropouts and time jitter caused by the Current Value Table (CVT) merging of the asynchronous data from the rotor head110. To solve this problem requires post-processing of the two recorder data files. First, the exact time of the rotor data needed in the time slot in the main data stream should be found. Second, the two data points in the rotor data that bracket the time required should be found. The data to the exact time needed should be interpolated. A Linear or Spline interpolation may be used here to find the data value between the two data time points. The data value in that time-slot in the main stream file should be replaced. The data may be manipulated in counts in the original Chapter 10 files of the recorded file or after date reduction in engineering units. The PCM “frame positional” time offset of each parameter should be accounted for. Note, if strict time correlation between specific measurements is a requirement, then other delays such as transducer delay and pre-sample filter delays will also have to be accounted for.

Rotating GPS Antenna: Accurate time tagging is essential to the dual stream concept. The data modules GPS antenna166on the rotor head110can be subject to interference from the digital L-band telemetry transmitter126for the telemetry link. A notch filter (not pictured) can be employed on the data modules GPS antenna166feed to minimize this effect. On the first embodiment, first and second telemetry transmitter transmit antennas130,132were spaced about a foot from the data modules GPS antenna166and the power was small that was necessary to obtain an acceptable link. Thus the problem was avoided. In another embodiment the omni-directional data modules GPS antenna166was mounted in the center of the rotor head110, so there was no apparent change in antenna location with rotation. A signal available from the GPS receiver card (not shown) that indicates the status of the airborne telemetry receiver142is monitored during flight. This indicated that the airborne telemetry receiver142rarely lost lock. If it did, it was for a small fraction of a second and the on-board phase-locked clock free-runs through this. A situation may arise where the data modules GPS antenna166cannot be placed at the center of rotation or where the rotor structure110interferes with line-of-sight to the satellite constellation during rotation. Initial experiments with this situation, with the airborne telemetry receiver142, indicate that time will stay “locked”. This may not hold true for all possible configurations or different vendors' equipment. Possible solutions would include: multiple data modules GPS antennas166or a distributed data modules GPS antenna166, or a change in GPS card programming to allow time data to pass without a GPS location solution.

The GPS receiver antennas166,168,172and time stamps (not shown) to the micro-second level can be used to accurately time correlate the data as recorded. There are independent data modules GPS antennas/receivers166located in the rotating package116/118/120/122as well as independent aircraft data collection system GPS antennas/receivers168and solid state recorder GPS antennas/receivers172located in the main aircraft data package142/144/146/148/152. Time is embedded in the data stream and the recorded date can be time-stamped in the (Ch 10) file format. If synchronous data from both sources is required in one data stream for post processing, then a specific pre-processing data merging technique, outlined above, may be implemented.

As part of the daily operation of this rotor instrumentation, a number of functions may or may not need to be performed that require interaction with the instrumentation package116/118/120/122:

a. turning the system on or off,

b. exercising the calibration modes,

c. checking the data before flight,

In the case of a small aircraft it may be easy to physically reach the rotor instrumentation package116/118/120/122to turn it on or off or hook a cable to it. In a larger aircraft such as a CH-47 it is difficult, time consuming and somewhat dangerous for instrumentation personnel to climb up to the rotor head(s)110on a regular basis. What is needed is a wireless bi-directional communications link. The requirements for this link are commercially available solutions that can be adapted to provide the necessary functionality. A 900 MHz RS-232 data modem, Blue-tooth or Wi-Fi are but a few technologies that would be satisfactory.

To realize improved maintenance, daily operations and personnel safety of a rotating instrumentation package, a bi-directional data link between a personal computer and the rotating instrumentation package can be implemented using existing technologies such as Bluetooth, Wi-Fi or a 900 MHz data modem.

Alternate Power Sources and Energy Scavenging:

The instrumentation package116/118/120/122is powered with a rechargeable battery122. The size, weight and power of this battery122is dependent on the power used by the system and the desired run time. The target in the case of the first embodiment was 3-4 hours. About 3.5 hours was achieved with a 6.6 A-hr battery122. This is somewhat dependent on the transmit power. The battery122must be re-charged or replaced with a charged battery122when depleted. The rotor110is spinning and being driven with a powerful engine. There is plenty of power available to scavenge and re-charge the battery122in flight. Any number of power generation devices should be feasible to generate all or part of the power required to operate the instrumentation package116/118/120/122. All of the schemes will need a power converter to change the energy produced to a usable form and to charge the battery122. These converter devices are becoming available commercially for this express purpose to change the energy produced to a usable form. Energy Scavenging Schemes include:

1. Airflow Driven DC generator—A direct current-producing generator can be mounted on the top center of the rotor head110. Blades112or vanes (not shown) or anemometer type cups (not shown) or a combination of both can be mounted to the generator shaft180. As the rotor110turns, aerodynamic forces on the cups and vanes will slow down the shaft180with respect to the rotating generator (not shown), allowing energy to be extracted in the form of electricity. Air flow around a rotor110is complex and varies in the different flight regimens. In a hover the higher pressure below the rotor110bleeds up close to the rotor110and will partially succeed in turning properly angled blades112attached to a generator in the opposite direction of the rotor110producing a speed difference between the spinning generator (not shown) and the blades112. In forward flight the airflow will tend to be directional, forward to aft. In this regime the anemometer type cups (not shown) will produce drag in the direction opposite the rotor-generator movement. In any case the difference in speed between the generator shaft180hooked to aerodynamic devices and the generator (not shown) driven by the rotor head110will be exploitable to produce energy.

2. Linear generator driven by rotor component motion—Most helicopters have a lead/lag damper (not shown) for each rotor blade112. These dampers (not shown) slow down a motion that is not productive to flight. They waste energy in the process. A linear generator (not shown) could be fashioned and mounted in parallel to the damper(s) (not shown) and used to remove electrical energy. The speeds and forces available here are substantial and can easily accommodate adequate energy production using direct drive of a magnet through a coil. An example of a small commercial linear generator is the flashlight that one can shake to put a charge on a battery and produce light. Other cyclical motions such as the pitch change link up and down motion could also be harnessed in this manner using the inertial mass of a magnet. A short throw, inertial mass, linear or angular rotor generator (not shown) could harness the energy in the rotor110small motion, high frequency vibration.

3. Other Methods of power scavenging: a) Piezoelectric generation from vibrations; b) Solar power—from solar cells on the top of the rotor package.

Alternate Power Schemes not Considered as Scavenging:

4. Direct Drive DC Generator—Some helicopters have a standpipe (not shown) in the center of the rotor shaft180for various reasons. This standpipe (not shown) does not rotate with the rotor head110. A DC generator (not shown) would be mounted over the top center of this standpipe (not shown). The generator shaft (not shown) would be restrained from spinning by the standpipe (not shown), thus allowing the generator to produce electrical power which could be conditioned to charge a small battery122or power the instrumentation directly when the rotor110is spinning.

5. Slip ring power—Some helicopters have rotor shaft110de-icing slip-rings (not shown) that bring power up to the rotor blades112for heating and de-icing. The slip ring assembly (not shown) power could also be used to power the instrumentation package116/118/120/122.

Energy can be scavenged from the motion naturally occurring on the rotor head110to power an instrumentation package116/118/120/122or supplement the charge on a battery122, in order to replace or minimize the size and weight of a battery122required to power a rotating instrumentation package116/118/120/122during flight test.

The present application relates to a wireless rotating instrumentation package176for collecting data from a spinning rotor head110of a rotary wing aircraft, the data being used for both real time flight testing and post flight processing, the package comprising:

b) a small data collection system118including a GPS time card (not shown) to provide time tags for data collection; and

c) an instrumentation package solid state data recorder120with removable solid state media (not shown) for collecting lossless data with micro-second GPS derived time tags (not shown);

and wherein wired devices communicate by wire to the instrumentation package116/118/120/122, the wired devices including:

c) a data modules GPS antenna166enabled to send GPS signals by wire to the data modules116;

d) a digital L-Band telemetry transmitter126using PCM/FM modulation to receive Pulse Coded Modulation (PCM) output from the data collection system118; and

e) at least one telemetry transmitter transmit antenna130,132, being connected by wire to receive a signal from the digital L-Band telemetry transmitter126;

and wherein the instrumentation package116/118/120/122is enabled to communicate wirelessly with an aircraft data collection system146, by a wireless signal being sent via the at least one telemetry transmitter transmit antenna130,132, the aircraft data collection system146including:

a) at least one airborne telemetry receiver receive antenna134,136being positioned in line of site with the telemetry transmitter transmit antenna(s)130,132, and being connected by wire to send a signal to the airborne telemetry receiver142;

b) the airborne telemetry receiver142being enabled to be fed the signal received by the at least one airborne telemetry receiver receive antenna134,136, the airborne telemetry receiver142including a bit synchronizer;

c) a decommutator card (not shown) included in a main aircraft data collection system146, the decommutator card (not shown) being enabled to receive data from the bit synchronizer (not shown) of the airborne telemetry receiver142, and the decommutator card (not shown) then being enabled to direct decommutated data to the main aircraft data collection system146;

d) an aircraft data collection system solid state recorder152in which combined composite data from the aircraft data collection system146is recorded with a GPS time stamp (not shown) for post flight data processing;

e) a solid state recorder GPS antenna172connected by wire to the aircraft data collection system solid state recorder152, to send GPS data from the solid state recorder GPS antenna172to the aircraft data collection system solid state recorder152;

f) an aircraft data collection system telemetry transmitter148to which the combined composite data is directed and telemetered;

g) an aircraft data collection system transmit antenna150connected by wire with the aircraft data collection system telemetry transmitter148by which data can be sent from the aircraft data collection system telemetry transmitter148to a ground station tracking antenna154;

h) an aircraft data collection system GPS antenna168connected by wire to the aircraft data collection system146and being enabled to receive GPS data for the aircraft data collection system146;

i) the ground station tracking antenna154connected by wire to a ground station156, the ground station tracking antenna154being enabled to receive data from the aircraft data collection system transmit antenna150which is in direct communication with the aircraft data collection system telemetry transmitter148; and

j) the ground station156which analyzes the data received to maintain safety-of-flight and to make flight test decisions.

In an embodiment of the wireless rotating instrumentation package, when multiple telemetry transmitter transmit antennas130,132are used then a transmission signal splitter128is connected by wire to the digital L-Band telemetry transmitter126and the multiple telemetry transmitter transmit antennas130,132are in turn connected by wire to the transmission signal splitter128.

In another embodiment of the wireless rotating instrumentation package116/118/120/122, when multiple airborne telemetry receiver receive antennas134,136are used then a receiver signal combiner140is connected by wire to the airborne telemetry receiver142and the multiple airborne telemetry receiver receive antennas134,136are in turn connected by wire to the receiver signal combiner140.

In yet another embodiment of the wireless rotating instrumentation package116/118/120/122, the instrumentation package further comprises a power scavenging unit124connected to the rotor head110and the battery122, and the power scavenging unit124helps power the battery122.

In still another embodiment of the wireless rotating instrumentation package116/118/120/122, the small data collection system118includes a ground maintenance-providing bi-directional RF data link164connected by wire to the small data collection system118; the ground maintenance-providing bi-directional RF data link164including a maintenance link transmit antenna162; wherein the maintenance link transmit antenna162in turn transmits data to the aircraft data collection system GPS antenna168which is connected by wire to the aircraft data collection system146.

In an embodiment of the wireless rotating instrumentation package116/118/120/122including the ground maintenance-providing bi-directional RF data link164, the maintenance link transmit antenna162transmits data wirelessly between the ground maintenance-providing bi-directional RF data link164and a maintenance computer antenna160included on a maintenance computer158, the maintenance computer158in turn controls i) turning the wireless rotating instrumentation package116/118/120/122on or off; ii) exercising calibration modes on the wireless rotating instrumentation package116/118/120/122; iii) checking data on the wireless rotating instrumentation package116/118/120/122before flight; and iv) re-programming the wireless rotating instrumentation package116/118/120/122.

In still another embodiment of the wireless rotating instrumentation package116/118/120/122, the instrumentation package116/118/120/122further comprises a Built In Test (BIT)170connected by wire to the data modules116which tests battery voltage, temperature and acceleration in the wireless rotating instrumentation package116/118/120/122.

In yet another embodiment of the wireless rotating instrumentation package116/118/120/122, the instrumentation package116/118/120/122further comprises production power slip-rings to connect with the wireless rotating instrumentation package116/118/120/122to provide electricity to heat, de-ice or power the wireless rotating instrumentation package116/118/120/122during flight.

In still another embodiment of the wireless rotating instrumentation package116/118/120/122, the instrumentation package116/118/120/122further comprises one or more additional telemetry transmitter transmit antennas132and one or more additional airborne telemetry receiver receive antennas136to maintain a line of site link during rotation of the rotor head.

In yet another embodiment of the wireless rotating instrumentation package116/118/120/122, the telemetry transmitter transmit antennas130,132and airborne telemetry receiver receive antennas134,136are polarized and orientated to establish a favorable RF link through the full rotation of the rotor head110.

In still another embodiment of the wireless rotating instrumentation package116/118/120/122including a transmission signal splitter128, the lengths of RF transmit cable138,182are varied to change the signal phasing at the transmission signal splitter128so that cancellation can be controlled as a function of rotation angles.

In yet another embodiment of the wireless rotating instrumentation package116/118/120/122including a receiver signal combiner140, the lengths of RF transmit cable138,182and RF receive cable178,184are varied to change the signal phasing at the receiver signal combiner140so that cancellation can be controlled as a function of rotation angles.

In still another embodiment of the wireless rotating instrumentation package116/118/120/122, ratios of the relative amplitude of the signals in the transmission signal splitter128and/or in the receiver signal combiner140can be varied to control cancellations of the signal as a function of rotator angles.

In yet another embodiment of the wireless rotating instrumentation package116/118/120/122, RF transmit power can be varied to get an adequate signal to noise ratio and adequate BER.

The present application also relates to a method of wirelessly collecting data from a spinning rotor head110of a rotary wing aircraft. The method comprises the steps of:

A) attaching a wireless rotating instrumentation package116/118/120/122to a rotor110of a rotary wing aircraft, the instrumentation package116/118/120/122comprising:

ii) a small data collection system118including a GPS time card (not shown) to provide time tags for data collection; and

iii) an instrumentation package solid state data recorder120with removable solid state media (not shown) for collecting lossless data with micro-second GPS derived time tags (not shown);

B) adding additional devices connected by wire to the attached instrumentation package116/118/120/122to aid in operation of the instrumentation package116/118/120/122, the additional devices including:

iii) a data modules GPS antenna166enabled to send GPS signals by wire to the data modules116;

iv) a digital L-Band telemetry transmitter126using PCM/FM modulation to receive Pulse Coded Modulation (PCM) output from the data collection system118; and

v) at least one telemetry transmitter transmit antenna130,132, being connected to receive a signal from the digital L-Band telemetry transmitter126;

C) sending data wirelessly from the wireless rotating instrumentation package116/118/120/122to an aircraft data collection system146via antennas, the aircraft data collection system146including

i) at least one airborne telemetry receiver receive antenna134,136placed in line of site with the telemetry transmitter transmit antenna(s)130,132and being connected to send a signal to an airborne telemetry receiver142;

ii) the airborne telemetry receiver142being enabled to be fed the signal received by the at least one airborne telemetry receiver receive antenna134,136the airborne telemetry receiver142including a bit synchronizer (not shown);

iii) a decommutator card (not shown) included in a main aircraft data collection system146, the decommutator card (not shown) being enabled to receive data from the bit synchronizer (not shown) of the airborne telemetry receiver142, and the decommutator card (not shown) then being enabled to direct decommutated data to the main aircraft data collection system146;

iv) an aircraft data collection system solid state recorder152in which combined composite data from the aircraft data collection system146is recorded with a GPS time stamp (not shown) for post flight data processing;

v) a solid state recorder GPS antenna172connected by wire to the aircraft data collection system solid state recorder152, data being able to be sent by the solid state recorder GPS antenna172from the aircraft data collection system solid state recorder152;

vi) an aircraft data collection system telemetry transmitter148to which the combined composite data is directed and telemetered;

vii) an aircraft data collection system transmit antenna150connected by wire with the aircraft data collection system telemetry transmitter148by which data can be sent from the aircraft data collection system telemetry transmitter148to a ground station tracking antenna154;

viii) an aircraft data collection system GPS antenna168connected by wire to the aircraft data collection system146and being enabled to receive data for the aircraft data collection system146.

ix) the ground station tracking antenna154connected by wire to a ground station156, the ground station tracking antenna154being enabled to receive data from the aircraft data collection system transmit antenna150which is in direct communication with the aircraft data collection system telemetry transmitter148;

x) the ground station156which analyzes the data received to maintain safety-of-flight and to make flight test decisions.

In another embodiment of the method, when multiple telemetry transmitter transmit antennas130,132are used then a transmission signal splitter128is connected by wire to the digital L-Band telemetry transmitter126and the multiple telemetry transmitter transmit antennas130,132are in turn connected by wire to the transmission signal splitter128.

In yet another embodiment of the method, when multiple airborne telemetry receiver receive antennas134,136are used then a receiver signal combiner140is connected by wire to the airborne telemetry receiver142and the multiple airborne telemetry receiver receive antennas134,136are in turn connected by wire to the receiver signal combiner140.

In still another embodiment of the method, the small data collection system118includes a ground maintenance-providing bi-directional RF data link164connected by wire to the small data collection system118; the ground maintenance-providing bi-directional RF data link164including a maintenance link transmit antenna162; wherein the maintenance link transmit antenna162in turn transmits data to the aircraft data collection system GPS antenna168which is connected by wire to the aircraft data collection system146.

In yet another embodiment of the method, the maintenance link transmit antenna162transmits data wirelessly between the ground maintenance-providing bi-directional RF data link164and a maintenance computer antenna160included on a maintenance computer158, the maintenance computer158in turn controls i) turning the wireless rotating instrumentation package116/118/120/122on or off; ii) exercising calibration modes on the wireless rotating instrumentation package116/118/120/122; iii) checking data on the wireless rotating instrumentation package116/118/120/122before flight; and iv) re-programming the wireless rotating instrumentation package116/118/120/122.

EXAMPLE

The technical specifications listed here are for an embodiment, successfully flown for a flight test. They are but one realization of a viable system for a specific helicopter application. The components listed can be configured, programmed or substituted for a specific air vehicle or program requirement. For instance, the data acquisition system stack may contain more or less cards and thus more or less data channels. Another vendor's miniature PCM system may be used, assuming it withstands the rotating environment, vibration, centrifugal forces, temperature, etc. The bit rate and data cycle map can be programmed to accommodate different sample rates for different rotational speeds and data requirements for specific testing. The battery122size can be tailored to the aircraft application for power and run time.

Component numbering below refers to a specific embodiment of the instrumentation package116/118/120/122including the components shown inFIG. 1. The components include: