Thermal measuring and testing – Temperature measurement – Combined with diverse art device
Reexamination Certificate
2000-06-02
2003-11-11
Fulton, Christopher W. (Department: 2857)
Thermal measuring and testing
Temperature measurement
Combined with diverse art device
C374S183000, C374S109000, C374S044000
Reexamination Certificate
active
06644849
ABSTRACT:
FIELD OF THE INVENTION
Ambient air temperature determination as a function of aircraft skin temperature.
BACKGROUND OF THE INVENTION
Many aircraft control functions require ambient air temperature information. Some of these applications require relatively accurate data. For example, U.S. Pat. No. 4,303,978, entitled Integrated-Strapdown-Air-Data Sensor System, issued to Shaw, et al on Dec. 1, 1981, the complete disclosure of which is incorporated herein by reference, discloses the use of raw air temperature signals, produced by total air temperature sensors, which are compensated and manipulated to produce signals suitable for use by the automatic flight control, pilot display, and navigation systems of the aircraft. Another, more recent example shown in
FIG. 1
, U.S. Pat. No. 5,276,326, entitled Scanning Ranging Radiometer for Weather Hazard Surveillance, issued to Philpott on Jan. 4, 1994, the complete disclosure of which is incorporated herein by ireference, discloses an in-flight windshear detection system which utilizes an externally mounted array of photoconductive infrared detectors
102
to detect the air temperature
104
in front of the aircraft
106
so as to provide a more accurate indication of windshear during approach. Placing air temperature sensors outside the skin of an aircraft requires piercing the airframe with one or more mounting and signal access holes to lead the signal back to the onboard equipment operating the application, for example, a central processing unit
108
. The need of such applications for highly accurate ambient air temperature information justifies the holes in the airframe and the consequent structure analysis effort.
Furthermore, the skin temperature of high speed commercial aircraft, unlike that of slower single-engine piston aircraft, is not directly related to the ambient air temperature. Therefore, those applications on commercial aircraft requiring only approximate air temperature data are forced to use one of the conventional airframe-piercing thermal probes and suffer the consequential expense. Examples include the density altimeter disclosed in U.S. Pat. No. 4,263,804, entitled Apparatus for Directly Measuring Density Altitude in an Aircraft , issued to Seemann on Apr. 28, 1981, the complete disclosure of which is incorporated herein by reference, which uses the ambient air temperature, pressure and humidity conditions to determine density altitude. In another example, U.S. Pat. No. 4,325,123, entitled Economy Performance Data Avionic System, issued to Graham, et al on Apr. 13, 1982, the complete disclosure of which is incorporated herein by reference, an avionic system is disclosed for producing the most economical engine and airspeed settings as a function of multiple parameters, including outside air temperature at the departure airport, which is essentially aircraft skin temperature, even in larger commercial aircraft. Still another example is the thermal navigation device disclosed in U.S. Pat. No. 4,591,111, entitled Thermal Navigator, issued to Laughter on May 27, 1986, the complete disclosure of which is incorporated herein by reference, which uses temperature sensors mounted on the right and left aircraft wings to provide a temperature differential between the wings and indicate a rate of change in ambient air temperature, whereby an ultralight aircraft, glider, or sailplane detects thermal updrafts and indicates to the pilot when and how rapidly to turn to obtain the maximum lift from the thermal updraft. Such applications, although useful on any general aviation aircraft, except perhaps U.S. Pat. No. 4,591,111, have not been generally practical on smaller aircraft because neither the expenses for equipment and installation of conventional airframe-piercing thermal probes nor the concomitant structural analysis can be justified.
However, practice of these and similar applications on ultralight aircraft, gliders, sailplanes, and slower single-engine piston aircraft depends upon the availability of a low-cost thermal sensor that need not pierce the airframe to provide an adequate measure ambient air temperature.
Some applications on aircraft also benefit by the use of an outside air temperature signal. For example, a geometric altitude computation in an Enhanced Ground Proximity Warning System (EGPWS) is more accurate when the pressure altitude component is enhanced using approximate air temperature data. The usefulness of merely approximate air temperature data in such an applications makes piercing of the airframe similarly impractical.
Thermistors are one well-known generally low-cost thermal sensor. A thermistor as defined by Webster's New Collegiate Dictionary, 1977 edition, published by G.&C. Merriam Company, Springfield, Mass., is an electrical resistor making use of a semiconductor whose resistance varies sharply in a known manner with temperature. Conventional thermistor chips are shown in
FIGS. 2A
,
2
B and described, for example, in U.S. Pat. No. 5,952,911, entitled Thermistor Chips and Methods of Making Same, issued to Kawase, et al on Sep. 14, 1999, the complete disclosure of which is incorporated herein by reference, as chips
110
formed of terminal electrodes
112
provided at both end parts of a thermistor element
114
having an oxide of a transition metal such as Mn, Co and Ni as its principal component. The terminal electrodes
112
are each formed of an end electrode
112
A formed by applying Ag/Pd or the like in a paste form and then firing and a plating layer
112
B formed on its surface by using Ni or Sn. The normal-temperature resistance value of such a thermistor chip is generally determined by the resistor value of the thermistor element
114
and the position of the terminal electrodes
112
. As shown in
FIG. 2C
, U.S. Pat. No. 5,952,911 also discloses a more recent thermistor chip
116
wherein the terminal electrodes
118
are formed of a multi-layer structure having an inner most layer
118
A in direct contact with a surface of the thermistor element
114
that affects its normal temperature resistance value.
However, thermistors have not been in use in aircraft industry for measuring ambient air temperature. Nor have either conventional thermal sensors or thermistors been used to measure skin temperature to determine ambient air temperature, without piercing the airframe. Therefore, a need exists to provide low precision ambient air temperature information in a form which avoids piercing the airframe skin and the concomitant structural analysis.
SUMMARY OF THE INVENTION
The present invention overcomes the limitations in the prior art of determining ambient air temperature using conventional thermal probes that pierce the airframe by providing a method for generating a signal representative of ambient air temperature surrounding an aircraft and supplying that signal to an avionics application by attaching a thermal sensor in contact with an interior surface of the skin of the aircraft, and with said thermal sensor, generating a signal as a function of ambient air temperature. According to one aspect of the invention, the thermal sensor is generally chosen from the class of thermal sensors known as thermistors.
According to other aspects of the invention, the thermistor is fixed in intimate thermal contact with the interior surface of the aircraft skin. Such intimate thermal contact is provided by installing a thermally conductive material between the thermistor and the interior skin surface. Preferably, the thermally conductive material is a thermally conductive bonding agent. The thermistor supplies the generated signal to one or more avionics applications capable of proper functioning using an imprecise indication of ambient air temperature.
According to still other aspects of the invention, the invention includes protecting the thermistor from an interior atmosphere of aircraft to reduce thermal effects resulting from contact with the usually warmer interior atmosphere. For example, the invention includes covering portions of the thermistor otherwise exposed to the interior
Fulton Christopher W.
Honeywell International , Inc.
Rupnick Charles J.
Verbitsky Gail
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