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PPL AGK > gnss and other systems > Flashcards

gnss and other systems Flashcards

1
Q

what is GNSS?

A

global navigation satellite system, the correct term for GPS. where GPS is the American version and other countries have their own type with GPS and Russian GLONASS being global.

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2
Q

how many satellites does GPS have and how many does GLONASS have?

A

33 with 31 active for GPS

26 with 24 active for GLONASS

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3
Q

how long does it take for a satellite to orbit the earth and what does their arrangement allow for?

A

every 11 hours and 58 minutes with the satellites passing over the same locations every orbit.

arranged so that at least six satellites are visible to anywhere on earth.

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4
Q

what are the two frequencies used for broadcasting?

A

1575.42 MHZ (L1 band signal) and 1227.6 MHZ (L2 band signal)

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5
Q

L1 signal contains what?

A

a coarse acquisition (CA) code and a P-code where the P is only used for military use and can be encrypted.

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6
Q

all GNSS rely on what?

A

accurate measurement of time to determine distance and therefore position.

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7
Q

what clocks are used for GNSS?

A

atomic clocks are used in satellites and control segments. user segments (receivers) use quartz crystal clocks.

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8
Q

GPS is maintained by the US space force and uses what? (5)

A
  • 1 master control station in colorado
  • 1 backup MC in cali
  • 16 monitoring stations around the world
  • 7 remote tracking stations
  • 4 dedicated ground antennas
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9
Q

each satellite is regularly updated with what? and what do these updates do?

A

navigational data.

synchronise the atomic clocks onboard the satellites to within a few nanoseconds of each other and adjust the ephemeris data ( current position of each satellite) of each satellites internal orbital model

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10
Q

what is almanac data?

A

information as to the orbits of other satellites which is also uploaded.

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11
Q

what is the user segment of a GNSS?

A

compromising of tens of millions of civilian, military and scientific users with receivers comprising of specially built-for-purpose devices through to the phone.

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12
Q

aviation use receivers contain what?

A

alamanac data of navigation data (waypoints, obstacles, IFR charts, radio frequencies) that requires updating regularly.

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13
Q

how does GNSS work?

A

works on the principle of trilateration. the process of finding out where you are by measuring distances with spheres.

each satellite broadcasts a radio signal which travels out in 360 degrees of every spherical direction at the speed of light.

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14
Q

what causes satellite clock error?

A

satellite clocks drift so they need correcting.

if the receiver obtains the wrong clock time the calculated position will be wrong.

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15
Q

what is ephermeris error?

A

essentially position error. if the satellite erroneously reports its position, receiver will incorrectly calculate its position.

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16
Q

what is ionospheric delay?

A

where the speed of the satellite signal is affected by the ionosphere.

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17
Q

what is the multipath effect?

A

where satellites reflect off buildings and terrain causing the signal to be received at the wrong time.

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18
Q

what is reciever error?

A

includes any issues with the reciever including placement of the aerial.

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19
Q

what is Geometric Dilution of Precision (GDOP)?

A

relates to the error caused by the relative position of satellites.

when satellites are closer together, GDOP is increased and the receiver is less able to determine your position.

20
Q

what are some failure indications of GNSS?

A
  • If a GNSS receiver is unable to compute your location or it’s having trouble it’ll display a warning message.
  • if such warning isn’t present GNSS receiver displays indications that are unlikely to be correct and should be disregarded.
21
Q

what is TAWS?

A

Terrain Avoidance and Warning System - designed to prevent controlled flight into terrain accidents.

22
Q

how does TAWS work?

A

uses a digital terrain elevation dataset and aircraft instrument values to ascertain the position of the aircraft relative to the terrain and identify if the current flight path in a calculated future position intersects with the ground.

23
Q

what usually happens in the TAWS warning?

A

an alert or visual warning or when implemented in a moving map can point terrain as different colours to indicate threat level.

24
Q

what are the characteristics of a Class A TAWS? (4)

A
  • excessive closure rate to terrain alert
  • flight into the terrain when not in landing configuration alert
  • excessive downward deviation from an ILS glideslope alert
  • terrain awareness display that shows either the surrounding terrain or obstacles relative to plane
25
Q

what are the characteristics of a Class B TAWS?

A

same as class A but no requirement for a visual display?

26
Q

what are the characteristics of a Class C TAWS?

A
  • mostly for GA and smaller turbine aircraft

- configurable system, designed more for voluntary usage

27
Q

what is an EFIS?

A

Electronic Flight Instrument System - a modern replacement for analogue instruments in older aircraft.

28
Q

what may an EFIS consist of? (4)

A
  • PFD (Primary Flight Display)
  • Engine indicating and crew alerting system
  • ND (Nav Display)
  • MFD (Multi Functioning Display)
29
Q

what is on the typical PFD layout? (4)

A
  • altitude and airspeed scale is shown on a vertical bar
  • slip indicator replaces balance ball
  • at the bottom, you can see the DI.
  • AH looks much like the analogue version and is in centre
30
Q

what does the Air Data computer do?

A

receives all inputs that are usually gathered to serve analogue instruments, including pitot pressure, static pressure and temperature.

uses this data to calculate aircraft altitude, vertical speed, airspeed, and ambient temp

31
Q

what does the signal generator do?

A

utilises information given by the pilot, signals from various sensors located in the aircraft, EFIS formats made by the pilot and any adjustments made by the pilot to produce the visual displays of the EFIS.

32
Q

what is TCAS? and how does it work?

A

Traffic Collision Avoidance System - a system designed to reduce the incidence of mid-air collisions.

it monitors airspace surrounding the aircraft for other aircraft with active transponders and displays the position and altitude of these aircraft to the pilot on the instrument screen.

33
Q

who does ICAO mandate a TCAS for?

A
  • aircraft exceeding MTOW of 5700kg

- authorised to carry more then 19 passengers.

34
Q

what is used to sense a change in velocity?

A

micro-electro-mechanical systems (MEMS)

35
Q

what is MFD used for?

A

as a backup for PFD if it fails.

36
Q

what is the function of input data sources to an EFIS system?

A

information gathered must be processed and converted into digital data before transmission to the EFIS.

they’re designed to measure the raw info and convert it to a digital signal before onward transmission.

37
Q

what occurs with the electrical failure of the EFIS and what should be done when occurred?

A
  • reduce electrical load
  • two screen efis can draw 25amps and the battery will not last long
  • most systems will automatically tun the MFD off if the alternator fails
38
Q

input issues are caused by what and what should be done?

A
  • icing
  • dealt like how it’s done without an EFIS
  • pitot or static port blockage or leak will register the same way as it would with non EFIS planes
39
Q

equipment failure procedures?

A
  • not much can be done
  • use backu instruments
  • land ASAP
40
Q

what is an Attitude heading reference system?

A

a system that provides heading and attitude information for aircraft. designed to replace gyro instruments and is more reliable and more accurate.

41
Q

how does an AHRS work?

A

a magnetometer is used for magnetic heading and MEMS is also used.

accelerometers are also used. the units and sensors within them that detect movement in pitch and roll are rigidly fixed to aircraft and retain their orientation to the airframe.

42
Q

who requires ELT’s and why?

A

aircraft for search and rescue in event of off-field landing.

43
Q

how is an ELT operated?

A

with a switch.

NZ is required to be 406 MHz, these are digital. the beacon transmits to orbiting satellites and can also broadcast unique identities so that an active beacon can be linked to specific aircraft.

Allows false alarms to be identified and reduces time window between detection and scrambling of search and rescue assets.

44
Q

what is the process for an ELT? (6)

A
  • transmitter activated automatically or manually
  • one satellite picks up transmission from the beacon
  • satellite transfers signal to a ground control station
  • station process signet and forms data including approx location to a national authority
  • authority forwards data to rescue authority
  • located beacons and commences rescue.
45
Q

How many satellites are needed for trilateration?

A

3 for a fixed position and a 4th for altitude

PPL AGK (29 decks)

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