Detecting an incorrect altimeter setting

The disclosure is directed to techniques that use a data communication system such as ADS-B to provide an output to alert an aircraft operator of an incorrect barometric pressure setting for a pressure altimeter, and provide the correct altimeter setting. For example, the system may compile the ADS-B Out data from other aircraft operating near a first aircraft to provide the barometric pressure setting in use by the other aircraft. A system of this disclosure may identify the altimeter setting used by majority of the other aircraft in a region of airspace. If a first aircraft's current barometric altimeter setting is different from the setting of the majority of the nearby aircraft, then the system may generate an output to alert the operator of the first aircraft of a potential incorrect altimeter setting as well as provide a suggested barometric altimeter setting.

TECHNICAL FIELD

The disclosure relates to aircraft avionics.

BACKGROUND

Aircraft include numerous electronic systems, which are commonly referred to as avionics. Avionic systems include communication systems, navigation systems, aircraft management systems, and numerous other systems and sensors. One such sensor is an aircraft pressure altimeter that measures the outside air pressure to estimate the altitude of the aircraft.

SUMMARY

In general, this disclosure is directed to techniques that use a data communication system, such as Automatic Dependent Surveillance-Broadcast (ADS-B), to determine an incorrect barometric pressure setting for the pressure altimeter. In some examples, the data communication system may also provide the correct altimeter setting that the flight crew or aircraft operator should use. The techniques of this disclosure may use ADS-B Out data from other aircraft and ADS-B ground stations in the local area to provide the barometric pressure setting in use by the other aircraft. A system of this disclosure may create a sample set of other aircraft in the vicinity of a first aircraft and identify the altimeter setting used by majority, or some other measure of central tendency, of the other aircraft. If the first aircraft's current barometric pressure setting is different from the setting of the majority of the nearby aircraft sharing the same airspace then the system may output an indication of a potential incorrect altimeter setting, such as an alert to the operator of the first aircraft. For example, if the first aircraft is using 29.89 inches of mercury (in Hg) and the majority of other aircraft are using 29.86, then an alerting message may be provided to the flight crew, as well as providing a recommended altimeter setting.

In one example, the disclosure is directed to a method comprising: receiving, by processing circuitry on a first aircraft, a barometric pressure setting for a pressure altimeter on the first aircraft; receiving, by the processing circuitry and via a communications device, a plurality of barometric pressure settings from a plurality of aircraft, wherein the plurality of aircraft does not include the first aircraft; calculating, by the processing circuitry, a measure of central tendency for the plurality of barometric pressure settings; comparing, by the processing circuitry, the barometric pressure setting for the first aircraft to the measure of central tendency of the plurality of barometric pressure settings; determining, by the processing circuitry, that the barometric pressure setting for the first aircraft is different from the measure of central tendency of the plurality of barometric pressure settings; in response to determining that the barometric pressure setting for the first aircraft is different from the measure of central tendency of the plurality of barometric pressure settings, generating, by the processing circuitry, an output indicating that the barometric pressure setting for the first aircraft is different from the measure of central tendency of the plurality of barometric pressure settings.

In one example, the disclosure is directed to a system comprising: a pressure altimeter; a communications device; an output device; processing circuitry installed on a first aircraft, the processing circuitry in signal communication with the pressure altimeter, the communications device and the output device, wherein the processing circuitry is configured to: receive a barometric pressure setting for the pressure altimeter on the first aircraft; receive via the communications device, a plurality of barometric pressure settings from a plurality of aircraft, wherein the plurality of aircraft does not include the first aircraft; calculate a measure of central tendency for the plurality of barometric pressure settings; compare the barometric pressure setting for the first aircraft to the measure of central tendency of the plurality of barometric pressure settings; determine that the barometric pressure setting for the first aircraft is different by more than a threshold amount from the measure of central tendency of the plurality of barometric pressure settings; and in response to determining that the barometric pressure setting for the first aircraft is different from the measure of central tendency of the plurality of barometric pressure settings, generating an output indicating that the barometric pressure setting for the first aircraft is different from the measure of central tendency of the plurality of barometric pressure settings.

In one example, the disclosure is directed to a computer-readable storage medium comprising instructions for causing programmable processing circuitry to: receive a barometric pressure setting for the pressure altimeter on a first aircraft, wherein the programmable processing circuitry is installed on the first aircraft and in signal communication with the pressure altimeter, a communications device and an output device, each of which is installed on the first aircraft; receive via the communications device, a plurality of barometric pressure settings from a plurality of aircraft, wherein the plurality of aircraft does not include the first aircraft; calculate a measure of central tendency for the plurality of barometric pressure settings; compare the barometric pressure setting for the first aircraft to the measure of central tendency of the plurality of barometric pressure settings; determine that the barometric pressure setting for the first aircraft is different by more than a threshold amount from the measure of central tendency of the plurality of barometric pressure settings; and in response to determining that the barometric pressure setting for the first aircraft is different from the measure of central tendency of the plurality of barometric pressure settings, generating an output indicating that the barometric pressure setting for the first aircraft is different from the measure of central tendency of the plurality of barometric pressure settings.

DETAILED DESCRIPTION

The disclosure is directed to techniques that use a data communication system, such as ADS-B, to determine an incorrect barometric pressure setting for the pressure altimeter. In some examples, the data communication system may also provide a correct altimeter setting.

Outside air pressure can change significantly as weather patterns change, which may lead to inaccurate altitude readings if the barometric pressure setting is not adjusted. The aircraft altimeter has an adjustment setting to correct the altitude reading for changes in outside air pressure. The barometric pressure setting for the aircraft's pressure altimeter is the value of the atmospheric pressure used to adjust the sub-scale of a pressure altimeter so that the altimeter indicates the height of an aircraft above a known reference, e.g. sea level. Failure to set the appropriate pressure setting can result in deviation from the correct altitude, which may result in loss of separation from other air traffic and potential collision with other aircraft or with terrain. For example, an aircraft with the wrong altimeter setting may show that the aircraft is at 5000 feet, but the aircraft may actually be at 4000 feet. If that aircraft is flying in poor visibility near a mountain, a tall transmission tower, or around other air traffic, the inaccurate altimeter setting may pose a danger that the aircraft may collide with other air traffic or features on the ground. Aircraft on cross-country flights traveling below a “transition altitude,” e.g. 18,000 feet above sea level in some countries are recommended to update their altimeter setting every 100 statute miles (160 kilometers) or so by checking with a nearby weather station. Aircraft traveling above 18,000 feet may use a standard altimeter setting of, e.g. 29.92 in Hg. When an aircraft above the transition altitude descends while approaching for landing, the aircraft needs to change their altimeter setting to match the local conditions.

The techniques of this disclosure may use ADS-B Out data from other aircraft and ADS-B ground stations in the local area to provide the barometric/altimeter setting in use by the other aircraft. A system of this disclosure may create a sample set of barometric pressure settings received from other aircraft in the vicinity of a first aircraft and identify the altimeter setting used by, for example, a majority of the other aircraft. If the first aircraft's current barometric altimeter setting is different from the setting of the majority of the nearby aircraft sharing the same airspace, the system of this disclosure may determine the first aircraft is using an incorrect setting. In some examples, the flight crew, or operator of the first aircraft may be alerted of a potential incorrect altimeter setting. For example, if the first aircraft is using 29.89 in Hg and the majority of other aircraft are using 29.86, then the system may determine the first aircraft has an incorrect setting. In some examples an alerting message may be provided to the flight crew, as well as provide a recommended altimeter setting.

The techniques of this disclosure differ from other techniques of alerting a flight crew to an incorrect altimeter setting. Some example systems may display an alert to “CHECK BARO SETTING,” for example when an aircraft passes below the transition altitude, e.g. 18,000 feet, such as enroute to an airport for landing. Other existing techniques include comparing the aircraft pressure altimeter to other systems on the aircraft, such as predicted GPS altitude, or a calculated altitude from a radar altimeter. When the comparison of the pressure altitude with other aircraft systems differs, existing aircraft systems may alert the flight crew to check the barometric altimeter setting. In contrast, the techniques of this disclosure utilize aircraft operating in the same vicinity to determine a correct altimeter setting, such that when the aircraft all use the same setting, then the separation altitudes set by air traffic control (ATC) may be more accurate.

The techniques of this disclosure also provide other advantages over other existing techniques for checking altimeter setting. As one example, a system of this disclosure may alert the flight crew of the first aircraft if any of the other traffic aircraft is not using the correct altimeter setting. For example, if the first aircraft, and majority of the other aircraft, in the vicinity are using the setting of 29.86, but a second aircraft is using 29.89, then the second aircraft may be highlighted on the first aircraft's traffic display. Because the techniques of this disclosure can continuously compare the first aircraft's altimeter setting with other aircraft and advise the first aircraft of any deviations. For example, ATC may transmit a change to the altimeter setting and other aircraft in the vicinity can switch to the new setting. In case the first aircraft crew forgets to switch to the new setting, this continuously executed monitor may automatically detect and alert the flight crew of the incorrect setting. Though continuously monitored, in some examples, the alerts may be inhibited such as during critical phases like takeoff and final approach.

FIG. 1is a block diagram illustrating an example system that determines and displays an altimeter setting used by aircraft in a predefined volume of airspace, according to one or more techniques of this disclosure. Aircraft220may operate in the same region of airspace as other nearby aircraft such as aircraft232, aircraft234and unmanned aerial vehicle (UAV)235.

Aircraft220may include a system with a flight management system (FMS)210, a pressure altimeter209, one or more output devices208, and communication circuitry204coupled to one or more communication antennae206. Other aircraft systems212may also be coupled directly to communication antennae206, or via communication circuitry204. Other aircraft systems212may include a global positioning system (GPS), radar altimeter, weather radar, voice and data communication systems, attitude and heading reference system (AHRS), engine control systems and similar aircraft systems.

FMS210may include, processing circuitry202, memory214and other components not shown inFIG. 1. FMS210may include functions like navigation, aircraft systems management and monitoring such as engine status, autopilot, communication, fuel management and status, and similar functions. In this disclosure FMS210may refer to a large, complex system in a commercial aircraft, or a smaller, less complex system such as may be installed in UAV235or in a private aircraft, such as aircraft234. FMS210may be in signal communication with communication circuitry204, other aircraft systems212and pressure altimeter209. FMS210may communicate with one or more output devices208.

Processing circuitry202may receive a barometric pressure setting for the pressure altimeter on the first aircraft. In some examples, a flight crew member inputs the barometric pressure setting by touch screen, keypad, knob or other control into FMS210or directly into pressure altimeter209. The barometric pressure setting for the geographic area may come from a recorded weather update, e.g. ATIS (Automatic Terminal Information Service), data transfer via communication circuitry204, voice communication from ATC, or other means.

Processing circuitry202may receive, such as via communication circuitry204, a plurality of barometric pressure settings from aircraft other than aircraft220, such as aircraft232or aircraft234, that are operating in a predetermined volume of airspace nearby aircraft220. In some examples, it may be desirable for the predetermined volume of airspace to include a volume near an airport in which the aircraft are either inbound or outbound. ATC for the airport may be able to maintain accurate altitude separation when the inbound or outbound aircraft to the same airport, or to nearby satellite airports, are using the same pressure altimeter setting. Aircraft operating at a significant distance from aircraft220, e.g. more than 50 NM, may be experiencing different weather conditions and have a different pressure altimeter setting. Therefore, receiving barometric pressure settings from aircraft at a significant distance from aircraft220may be less desirable.

The region of airspace may include a volume around an airport, such as within a predetermined radius of a three-dimensional distance from an airport. In other examples the region may be the mode C veil (within 30 NM and up to 10,000 feet) around a large airport with a class B airspace, within the designated class B airspace volume, or other similar airspace designation, which may depend on the rules of country where the airport is located. In other examples, the region of airspace may be a predetermined distance from aircraft220. The predetermined distance may be a radius defining a cylinder of airspace around aircraft220with a predetermined bottom altitude and top altitude. In some examples the predetermined distance from aircraft220may define a three-dimensional sphere or some other three-dimensional shape around aircraft220, such as an ovoid shape with the longer dimension in the direction of travel of aircraft220.

Processing circuitry202may calculate a measure of central tendency for the plurality of barometric pressure settings from the other aircraft. In this disclosure, measures of central tendency may include arithmetic mean (i.e. the average), median, mode (i.e. a majority), or other similar measures of central tendency for a sample of data values. In some examples, processing circuitry202may determine what the majority of other aircraft nearby aircraft220are using for their barometric pressure setting and compare the barometric pressure setting for aircraft220to the pressure setting for the majority of other nearby aircraft.

Processing circuitry202may determine that the barometric pressure setting for aircraft220is different from the setting used by a majority of other nearby aircraft. Because the barometric pressure setting may be transmitted as a single value by ATIS, ATC or other means, all the nearby aircraft may have the same pressure setting within hundredths of mm Hg. For example, ATIS may broadcast that the current barometric pressure setting for specific airport is 30.02 mm Hg. Therefore, all inbound and outbound aircraft should have the barometric pressure setting for their pressure altimeter set to 30.05 mm Hg. In some examples, processing circuitry202may determine that the barometric pressure setting for aircraft220differs from the majority of other nearby aircraft by more than a threshold amount, such as ±0.02 mm Hg.

In response to determining that the barometric pressure setting for aircraft220is different from the barometric pressure setting of the majority of other aircraft, processing circuitry202may generate an output, such as via one or more output devices208. Output devices208may include a digital display, a portion of a primary flight display (PFD) or a multi-function display (MFD), an audio alert, indicator light, or other output. The output may alert a crew member of aircraft220that the barometric pressure setting for a pressure altimeter on the first aircraft may be erroneous or should be verified. In the example of a UAV, the output may alert a remote operator of the UAV, such as UAV235. In some examples, the output generated by processing circuitry202may include a display of the measure of central tendency, e.g. the barometric pressure setting of the majority of nearby aircraft. In some examples, processing circuitry202may also cross-check the altimeter setting with information received from other systems212such as the altitude received from a GPS system, radar altimeter or other sources.

In some examples, processing circuitry202may inhibit the output alerting the crew to a possible erroneous barometric pressure altimeter setting. For example, some phases of flight may require a high workload from the crew and a pressure altimeter alert may be a distraction. For example, take-off and final approach to landing may be considered a high-workload phase. Adjusting the pressure setting is less important than other actions during these phases. Processing circuitry202may have instructions setting one or more predetermined high-workload phases of flight, where the processing circuitry may inhibit an alert or at least reduce the conspicuousness of alerting the crew. For example, the majority altimeter pressure setting may be displayed near the actual altimeter pressure setting, but during high workload phases, processing circuitry202may for example, dim the displayed value, or put both values as the same color rather than turning the majority value a different color or flashing the majority value if the majority altimeter pressure is different from the current pressure setting. In some examples, processing circuitry202may inhibit an audio alert during high workload phases of flight.

Examples of processing circuitry202may include, any one or more of a microcontroller (MCU), e.g. a computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals, a microprocessor (μP), e.g. a central processing unit (CPU) on a single integrated circuit (IC), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a system on chip (SoC) or equivalent discrete or integrated logic circuitry. A processor may be integrated circuitry, i.e., integrated processing circuitry, and that the integrated processing circuitry may be realized as fixed hardware processing circuitry, programmable processing circuitry and/or a combination of both fixed and programmable processing circuitry.

Memory214may store instructions that cause programmable processing circuitry202to perform the actions described above. Memory214may also store data received from communication circuitry204, such as the barometric pressure settings from other aircraft, as well as data and measurements from other systems212, programming instructions and settings from the crew, and similar information. Memory214may be any type of computer-readable storage media such as random access memory (RAM).

In some examples, communication circuitry204may include an ADS-B transceiver. ADS-B is a surveillance technology that allows ATC and other aircraft to watch airplanes move around. ADS-B includes a network of ground stations, such as ground station230, and orbiting satellite stations (not shown inFIG. 1) to receive aircraft reports and send them back to ATC, for example, for aircraft that are outside of ADS-B communication range from an ATC facility. ADS-B data transmissions include ADS-B In and ADS-B Out. ADS-B Out includes the ability for properly-equipped aircraft automatically broadcast the aircraft position without the need for a radar interrogation. ADS-B In includes the broadcasted aircraft positions as well as data transmissions from the ground stations that include transmit weather and air traffic information. The air traffic information from the ground stations may include information received from aircraft at a different location and retransmitted via the ground station. ADS-B Out transmissions from aircraft may not only include the aircraft position, speed and direction of flight, but also include how accurate the aircraft position is, the barometric pressure altimeter setting, and other information.

In some examples, ground station230may include processing circuitry231and communication circuitry233(similar to those found in aircraft220) operable to receive the barometric pressure setting from aircraft operating in a predetermined volume of airspace, e.g. aircraft220,232,234and235. Ground station230may be near a flight service station, ATC facility, near an airport, or other location. The processing circuitry231in ground station230may perform functions similar to that described above for processing circuitry202. For example, processing circuitry231may calculate a measure of central tendency for the plurality of barometric pressure settings from the other aircraft received via communication circuitry233. Processing circuitry231may transmit the measure of central tendency to one or more aircraft operating nearby via a variety of means, including automated voice message or a datalink such as controller-pilot data link communications (CPDLC), also referred to as controller pilot data link (CPDL), which is a method by which air traffic controllers can communicate with pilots over a datalink system.

In some examples, processing circuitry231at ground station230may receive a specific barometric pressure setting to be used for a predetermined region of airspace, i.e. a directed barometric pressure setting. For example, the directed barometric pressure setting may be input to processing circuitry231via an automated input from a weather data system, a manual input from ATC, a flight service station, or a weather observer for the region of airspace, or by some other similar source. Processing circuitry231at ground station230may also receive a plurality of barometric pressure settings for the plurality of aircraft operating in the region of airspace via communication circuitry233. In some examples, various barometric pressure setting for the plurality of aircraft may be received via ADS-B In. Processing circuitry231at ground station230may determine that one or more aircraft is using a barometric pressure setting that is different than directed barometric pressure setting and identify the one or more aircraft. In some examples, processing circuitry231may determine that the barometric pressure setting for an aircraft exceeds a threshold difference from the directed barometric pressure setting. In response to determining an aircraft is using a barometric pressure setting different from the directed barometric pressure setting, processing circuitry231may alert ATC, which may then communicate with the identified aircraft via voice or datalink, such as CPLDC. In other examples, processing circuitry231may automatically send an output to the identified aircraft, e.g. via datalink, to alert the aircraft operator to check the barometric pressure setting.

FIG. 2is a conceptual diagram illustrating an example display output of air traffic in a predefined volume of airspace, according to one or more techniques of this disclosure. Processing circuitry202may cause output device208, described above in relation toFIG. 1, to display the images seen in display output250depicted inFIG. 2.

Display output250may show a depiction of a first aircraft260in which an FMS that includes processing circuitry may be installed. Aircraft260inFIG. 2may correspond to aircraft220, described above in relation toFIG. 1and the FMS installed in aircraft260may include components and functions similar to those described above for FMS210.

Display output250may include displays of terrain, e.g.262, controls or status displays, such as those along the top edge of display output250, weather (not shown inFIG. 2) and other aircraft such as aircraft252,254,256,258and270. In some examples, display output250may also include the barometric pressure setting (not shown inFIG. 2).

Processing circuitry onboard aircraft260may receive barometric pressure settings from aircraft in the vicinity of aircraft260, such as aircraft252,254,256,258and270. In some examples, aircraft260may receive barometric pressure settings via ADS-B In transmissions, either directly from the other aircraft of from orbiting satellites or ground stations. For example, in mountainous terrain, aircraft260may not be able to receive an ADS-B transmission directly from another aircraft, though the other aircraft may be in the vicinity and inbound to the same airport as aircraft260. Aircraft260may receive the barometric pressure setting from the out-of-range aircraft via retransmission from a ground station, for example. Aircraft260may also receive barometric pressure settings from other aircraft, or from ATC, via other communication systems.

In some examples, one or more other aircraft in the vicinity of aircraft260may be using a barometric pressure setting that is different from the majority of other aircraft in the same vicinity. Processing circuitry on aircraft260may cause display output250to indicate which aircraft is using a different barometric pressure setting and therefore may be at a different altitude than expected. For example, display output250may place a ring around the aircraft, such as depicted by aircraft270. In other examples, display output250may change the color or otherwise indicate that aircraft270is using a different altimeter setting.

FIG. 3is a conceptual diagram illustrating a second example display output, according to one or more techniques of this disclosure. Similar to display output250described above in relation toFIG. 2, processing circuitry202may cause output device208, described above in relation toFIG. 1, to display the images seen in display output300. In some examples, display output300may be called a primary flight display (PFD). In other examples, a display similar to display output300may be output to a heads up display (HUD). Display output300may be displayed on output device208depicted inFIG. 1. Other examples of generated outputs may include an indication shown on a multi-function control and display unit (MCDU), near-to-eye (NTE) display, heads down display, such as an MFD, or an electronic flight bag device such as a tablet computer and similar displays. In the example of a UAV, the output may appear on the operating console.

Display output300may include a barometric pressure setting302as well as an indication of the measure of central tendency (304), such as the barometric pressure setting value for the majority of other aircraft in the vicinity such as aircraft232, aircraft234or UAV235depicted inFIG. 1, as well as aircraft252-258depicted inFIG. 2. In the example ofFIG. 3, majority value304is different from the current barometric pressure setting302for the aircraft using display output300, such as aircraft220described above in relation toFIG. 1. Therefore, one or more processors that control the content of display output300, such as processing circuitry202described above in relation toFIG. 1, may cause majority value304and/or barometric pressure setting302to alert the flight crew, for example, “CHECK BARO SET: 30.35.” In some examples, one or both of majority value304or barometric pressure setting302may flash, turn a different color (e.g. red instead of green), or provide some other indication that barometric pressure setting302needs attention. In other examples, the crew may receive an audio alert, or some other generated output. As described above in relation toFIG. 1, this alert may be minimized, inhibited (i.e. canceled) during certain predetermined phases of flight.

Barometric pressure setting302may impact the value of altitude displayed on altitude indicator306. In the example ofFIG. 3, if the majority of other nearby aircraft are using 29.96 in Hg as their altimeter setting, then the aircraft with the different setting of 29.92 in Hg may have an actual separation different from the expected separation altitude set by ATC.

Other elements of display output300may include pitch indicator310, angle of bank indicator312, airspeed indicator314, and direction indicator316. In the example ofFIG. 3, display output300also includes an indication of the surrounding terrain (320). In some examples terrain indication320may be a synthetic vision depiction of the terrain. In the example of mountainous terrain, an inaccurate barometric pressure setting may lead to an aircraft colliding with the terrain or other structures such as a tower. In other words, inaccurate barometric pressure setting may lead to controlled flight into terrain (CFIT).

FIG. 4is a flowchart illustrating an example operation of a system according to one or more techniques of this disclosure. The process steps ofFIG. 4will be described in terms ofFIG. 1, unless otherwise noted.

Processing circuitry on a first aircraft, such as processing circuitry202as part of FMS210, may receive a barometric pressure setting for a pressure altimeter on the first aircraft (400). In some examples, the barometric pressure setting may be manually set by a flight crew member directly into a pressure altimeter, such as pressure altimeter209, which is in signal communication with processing circuitry202. In other examples, the barometric pressure setting may be set using input commands to FMS210.

Processing circuitry202may also receive via a communications device, such as communication circuitry204and communication antennae206, a plurality of barometric pressure settings from a plurality of other aircraft different from the first aircraft (402). The other aircraft may be operating in the same vicinity as the first aircraft, such as inbound or outbound from the same airport. Communication circuitry204may receive the barometric pressure settings over a variety of communication channels. In some examples, the communication channel may be ADS-B. Other examples of communication channels include datalink, voice messages from air traffic controllers, aviation operational control (AOC) systems, ATIS messages, traffic information system (e.g. TIS-B) messages and similar examples.

The processing circuitry may calculate a measure of central tendency for the sample set of barometric pressure settings from the other aircraft (404). Some example measures of central tendency may include an average or a majority (i.e. the mode) of the sample set.

Processing circuitry202may compare the barometric pressure setting for the first aircraft to the measure of central tendency of the sample set of barometric pressure settings from the other aircraft (406). The barometric pressure setting is selected based on the weather conditions in the area and may be broadcast to aircraft in the area by ATIS, data transmission, voice communication or other means. All aircraft operating in the same area, for example, within about 100 NM, may use the same barometric pressure setting to ensure accurate altitude above terrain features as well as accurate altitude separation from other aircraft.

The processing circuitry may determine whether the barometric pressure setting for the first aircraft is different from the measure of central tendency of the sample set of barometric pressure settings from other aircraft (408). If the values are not different, the processing circuitry may continue to monitor the barometric pressure settings for nearby aircraft (NO branch of408). In some examples, processing circuitry202may also identify other nearby aircraft that are using a barometric pressure setting that is different from the measure of central tendency.

In response to determining that the barometric pressure setting for the first aircraft is different from the measure of central tendency of the sample set of barometric pressure settings (YES branch of408) the processing circuitry may generate an output to a crew member of the first aircraft (410). The output may include a visual display, audible alert, or similar indication. In some examples, the output may include displaying the measure of central tendency on an output device, such as described for display output300in relation toFIG. 3(412). The generated output may alert a crew member that the barometric pressure setting for a pressure altimeter on the first aircraft may be erroneous and should be verified. In some examples, the generated output may be disabled or at least muted or made less conspicuous during critical phases of flight.