AP4ATCO - Safety Systems
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- The following SKYbrary Articles:
21. Safety systems
a) article description Presentation of all known safety systems available in modern airliners. The IANS document presents the following systems and equipment: SSR transponder, HUD, GPWS, weather radar, windshear alert, FDS (Flight Director System) and FMS. Systems to be added to the article are: TAWS, TCAS, FDR (Flight Data Recorder), CVR (Cockpit Voice Recorder)
b) source (IANS) 4.4
c) additional sources FAA Advanced Avionics Handbook (FAA-H-8083-6) – chapters 1, 3, 4, 5 FAAInstrument Flying Handbook (FAA-H-8083-15A) – chapters 3, 7 FAA Instrument Procedures Handbook (FAA-H-8261-1A) – chapter 1 Airbus – Adverse Weather Operations – Optimum Use of the Weather Radar SKYbrary Article: “Transponder” SKYbrary Article: “Flight Data Recorder (FDR)” SKYbrary Article: “Cockpit Voice Recorder” SKYbrary Article: “Airborne Collision Avoidance System (ACAS)” _____________________________________
In addition to the flight instruments, navigational instruments and engine instruments, other instruments can be found in a cockpit of an aircraft, depending on its type and design features. The avionics and aircraft systems are continuously advancing and there are many ways in which an aircraft manufacturer may choose to set up a cockpit. However, there are few instruments that can be considered as common and not belonging to the categories already explained. This section briefly explains the use of other cockpit instruments such as:
• SSR transponder, • Head-Up Display (HUD), • Ground Proximity Warning System (GPWS) / Terrain Awareness and Warning System (TAWS) • Weather radar, • Windshear alert system, • Flight Director System (FDS) / Autopilot, • Flight Management System (FMS) • Flight Data Recorder (FDR) / Cockpit Voice Recorder (CVR)
A transponder is an on-board receiver/transmitter which provides ATC services with information about the identity (also referred to as Mode A) and altitude (also referred to as Mode C) of an aircraft.
It responds to the interrogations received from ground-based Secondary Surveillance Radar (SSR) by transmitting a digital reply on a different frequency containing a four digit code set on the unit itself (Mode A code), and altitude. The altitude information is provided by the altimeter, included in the transponder, and permanently referenced to 1013.25 hPa.
When the reply is received from SSR, in addition to the range and bearing information detected by the radar system a Mode A code is used to determine the aircraft identity. This is possible because each aircraft is assigned discrete Mode A code, and this code is entered into the radar system. A label is attached to the target displayed to the controller containing the aircraft callsign and altitude (Mode C).
The most sophisticated mode available is mode S. It gradually becomes implemented for use in new airspace parts and by more and more operators. Mode S permits selective interrogation of aircraft by means of a unique 24-bit aircraft address, thus avoiding the risk of confusion or mis-identification due to overlapping signals. Mode S has been deployed because the historical SSR systems have reached the limit of their operational capability and therefore it is a necessary SSR replacement in airspace subject to high levels of traffic density.
Mode S provides the following operational benefits: - unambiguous aircraft identification - improved integrity of surveillance data - improved air situation picture and tracking - alleviation of Mode 3/A code shortage - improvements to Safety Nets (e.g. STCA) - increased target capacity
For more information about mode S and its use in ATC please refer to: - SKYbrary’s “Mode S” article - SKYbrary’s “Use of Selected Altitude by ATC” article - EUROCONTROL Mode S Homepage - Hindsight : Mode S - Helping to reduce risk: by Andy Edmunds
As any other system Mode S transponders are subject to anomalies and technical faults. These subjects are described in:
- SKYbrary article “Surveillance: anomaly on Mode-S transponders” - SKYbrary article “Aircraft Mode S Transponders - Incorrect and Missing Data - EASA Safety Information Bulletins”
The operation of the airborne equipment is fairly simple. The transponder’s control panel has one switch controlling the mode of operation (OFF/SBY/ON/ALT/TST), one special button (ident) and code selection knobs. The pilot has to set the code assigned by ATC and select the desired mode of operation:
- OFF – the transponder is off; - SBY (standby) – the transponder is on, but is not replying to interrogations (used when a code change is taking place); - ON – the transponder is on and replying to interrogations, but only Mode A is sent in the reply (no altitude information is available); - ALT – the transponder is on and replying with Modes A and C; - TST – the transponder performs internal diagnostic checks. - The ident button is used when requested by ATC (when a controller wants to confirm the identification of a specific aircraft). Pressing the ident button on the transponder causes the flight label to blink or flash on the radar display.
By international agreement, transponder code 2000 is used for aircraft which have not been assigned a transponder code, although in some parts of Europe, 7000 is used for this purpose. Details of standard codes in different countries may be found in national AIPs. Special codes are used in emergency, as follows:
- hi-jack (7500); - loss of communication (7600); and, - general emergency (7700).
HEAD-UP DISPLAY (HUD) – THIS EQUIPMENT HAS BEEN DESCRIBED IN ARTICLE “18. ALTITUDE AND ALTIMETERS” AND, IF NOT USED SEPARATELY, THE BELOW TEXT SHOULD BE HYPERLINKED IN BOTH ARTICLES (18TH AND 21ST).
Head-Up Display (HUD)
The HUD is a display system that provides a projection of navigation and air data (airspeed in relation to approach reference speed, altitude, left/right and up/down glide slope) on a transparent screen between the pilot and the windshield.
The concept of a HUD is to diminish the shift between looking at the instrument panel and outside. Virtually any information desired can be displayed on the HUD if it is available in the aircraft’s flight computer. The display for the HUD can be projected on a separate panel near the windscreen or on an eye piece.
Other information may be displayed, including a runway target in relation to the nose of the aircraft, which allows the pilot to see the information necessary to make the approach while also being able to see out the windshield.
The main purpose of having HUD systems is to supplement or even provide an alternative to the expensive and complicated ground based systems used for landing in very poor weather conditions. Although the HUD equipment is installed in almost all modern aircraft, its full operational use and benefit is still considered as something to be expected in the future.
GROUND PROXIMITY WARNING SYSTEM (GPWS) – THIS EQUIPMENT HAS BEEN DESCRIBED IN ARTICLE “18. ALTITUDE AND ALTIMETERS” AND, IF NOT USED SEPARATELY, THE BELOW TEXT SHOULD BE HYPERLINKED IN BOTH ARTICLES (18TH AND 21ST). Ground Proximity Warning System (GPWS)
The aim of the system is to give visual and audible warning signals to the pilot when aircraft’s proximity to the terrain constitutes a potential threat to its safety. Although the system is not foolproof and perfect, it does enhance flight safety by reducing the risk of accident in case of malfunction or misinterpretation of navigational equipment, or in case of inappropriate ATC instruction.
GPWS is a radio altimetry system that detects the height of an aircraft above the ground, and gives an oral and graphical warning to the pilot at predetermined levels, depending on the phase of the flight. The system operates between 50 and 2450 feet actual height above the surface and automatically selects its mode of operation.
A recent development is the Enhanced Ground Proximity Warning System (EGPWS) or TAWS (Terrain Awareness and Warning System) which incorporates an electronic map of the world that gives terrain elevation. By comparing this data with the aircraft’s position, computed by its navigation system (usually IRS), the proximity to the ground can be calculated. The advantage of this system is that it can look further ahead than GPWS, and give earlier warning of terrain proximity to the crew, thus providing longer reaction time.
The system generates two types of messages: alerts and warnings. Alert is defined as a caution message, while warning is a command generated by the EGPWS. The response to all warnings should be positive and immediate (level the wings and establish maximum climb gradient until reaching the minimum safe altitude for that sector). Establishing the cause of EGPWS activation should come second. Although repeated experience of unwanted (incorrect) alerts/warnings may reduce confidence in the system, flight crews are required to report all of them for appropriate analysis and remedial action (if necessary). The following table gives an overview of the alerts and warnings generated by the EGPWS:
Situation Alert Warning Excessive descent rate “Sink rate” “Whoop whoop pull up” Excessive terrain closure rate “Terrain terrain” “Whoop whoop pull up” Altitude loss after take off or go-around “Do not sink” - Unsafe terrain clearance while not in landing configuration – gear not locked down “Too low gear” “Whoop whoop pull up” Unsafe terrain clearance while not in landing configuration – flaps not in a landing position “Too low flaps” “Too low terrain” Descent below glideslope “Glideslope” - Descent below minimum altitude “Minimums” Unsafe terrain clearance due to excessive bank angle “Bank angle” - Windshear - “Windshear” The visual indication is usually integrated on the navigational display showing terrain in shades of green, yellow and red. The terrain display can be selected by the pilot or may be automatically activated whenever the terrain becomes a threat. Following graphics show examples of visual alerts and warnings generated by the EGPWS:
JAR (Joint Aviation Regulations) regulations state that all aircraft with MTOW (Maximum Take Off Weight) above 5700 kg and maximum number of passanger seats of 9 have to equipped with GPWS.
Despite efforts to minimize nuisance alerts, they still occur occassionally. For this reason, most TAWS systems offer a terrain inhibit switch that allows you to silence TAWS alerts. There have been cases in which pilots have used the inhibit switch or ignored TAWS alerts, thinking they were nuisance alerts, when in fact the alerts were valid indications of a dangerous situation. For this reason a pilot should respond to TAWS alerts just as you would to any other sort of emergency and always, if in any doubt set full Power and climb at VX or VY.
Here are examples of indicents and accidents or incidents involving TAWS alerts inhibition:
- D328, Manchester UK, 2006 - on 18 January 2006, a Dornier 328 on descent into Manchester UK, avoided CFIT only by response to EGPWS following failure to capture the ILS Glideslope and a high rate of descent in IMC.
- D328, Sumburgh UK, 2006 - on 11 June 2006, a Dornier 328 operated by City Star Airlines whilst positioning in marginal visibility for a day approach at Sumburgh, Shetland Isles UK, and having incorrectly responded to TAWS Class A warnings/alerts by not gaining safe altitude, came to close proximity with terrain . The approach was continued and a safe landing was made at the airport.
- SW4, New Plymouth New Zealand, 2009 - the visual approach at destination was rushed and unstable with the distraction of a minor propeller speed malfunction and with un-actioned GPWS warnings caused by excessive sink and terrain closure rates. After a hard touchdown close to the beginning of the runway, directional control was lost and the aircraft left the runway to the side before continuing parallel to it for the rest of the landing roll.
- T154, vicinity Smolensk Russian Federation, 2010 - on 10 April 2010, a Tupolev Tu-154M was being operated by the Polish Air Force Special Transport Regiment on a pre-arranged VIP fight for the Polish President and his entourage on a flight from Warsaw to Smolensk Severny impacted ground obstacles and terrain (TAWS alerts were present prior to impact).
The practice of simply ignoring or disabling TAWS alerts based on pilot intuition is a big risk ! It is a direct cause of CFIT (Controlled Flight Into Terrain) accidents.
For more information please refer to “Controlled Flight Into Terrain” category on SKYbrary.
WEATHER RADAR Weather radar
Airborne weather radar is used to provide the pilot with information regarding weather ahead (precipitations, thunderstorms, etc).
The weather radar, which is very high frequency primary radar, is located in the aircraft's nose. It can be tuned to show more or less detail, such as fronts, and are range selectable with maximum range of over 300 NM. The antenna is gyro-stabilized in pitch and roll. Its main functions are to detect the size of water droplets and hence deduce where the areas of turbulence are within the cloud, and to determine the cloud tops by tilting the radar beam up or down.
The radar derived information (weather ahead) is presented on a dedicated unit or on the navigational display on EFIS equipped aircraft. The presentation is color coded as follows:
• Black – no or very light precipitation; • Green – light precipitation; • Yellow – moderate precipitation; • Red – heavy precipitation; • Magenta – turbulence or windshear.
Following graphic shows an example of airborne weather radar indication:
Weather radar use
The weather radar only detects precipitation droplets. How much it detects depends upon the size, composition and number of droplets. Water particles are five times more reflective than ice particles of the same size.
The radar does detect: - rainfall - wet hail and wet turbulence - ice crystals, dry hail and dry snow. However, these three elements give small reflections.
The radar does not detect: - clouds, fog or wind (droplets are too small, or no precipitation at all) - clear air turbulence (no precipitation) - windshear (no precipitation except in microburst) - sandstorms (solid particles are almost transparent to the radar beam) - lightning.
Radar echo returns are proportional to droplet size, and therefore, precipitation intensity. Droplets that are too small (fog droplets) will return no echo, whereas heavy droplets (thunderstorm droplets) will return the majority of radar waves. Reflectivity of precipitation not only depends on the intensity of the precipitation, but also on the type of precipitation. Precipitation that contains water will return a stronger return than dry precipitation. The upper level of a thunderstorm, that contains ice crystals, provides weaker returns than the middle part, that is full of water or wet hail. It is important to note that reflectivity of particles is not directly proportional to the hazard that may be encountered in a cell. Air can be very humid, when close to the sea for instance. In this case, thermal convection will produce clouds that are full of water. These clouds will have a high reflectivity, but will not necessarily be a high threat. Also snow flakes have low reflectivity, as long as they are above freezing level. As they descend through freezing level, snowflakes stick together and become water covered. Their reflectivity increases and the weather radar display may display amber or red cells, despite the fact that there is no threat. Modern weather radars are now able to apply a correction to a signal when it is suspected to have been attenuated behind a cloud. This reduces the attenuation phenomenon. However, a black hole behind a red area on a weather radar display should always be considered as a zone that is potentially very active. Some weather radars are fitted with a turbulence display mode. This function (the TURB function) is based on the Doppler effect and is sensitive to precipitation movement. Like the weather radar, the TURB function needs a minimum amount of precipitation to be effective.
The weather radar display may be wrongly disregarded by the flight crew (who may decide to enter clouds) in the following conditions:
- near the destination airport - when following an other aircraft - at night
As stated in Doc 4444 - 8.6.9 Information regarding adverse weather - 184.108.40.206, “An aircraft’s weather radar will normally provide better detection and definition of adverse weather than radar sensors in use by ATS“. Also, as stated in 220.127.116.11, “In vectoring an aircraft for circumnavigating any area of adverse weather, the controller should ascertain that the aircraft can be returned to its intended or assigned flight path within the coverage of the ATS surveillance system and, if this does not appear possible, inform the pilot of the circumstances. Note: Attention must be given to the fact that under certain circumstances the most active area of adverse weather may not be displayed.”
For more information please refer to “ATC Operations in Weather Avoidance Scenarios” article.
WINDSHEAR ALERT SYSTEM Windshear alert system
Windshear is a change in wind velocity along an aircraft’s flight path which occurs significantly faster than the aircraft can accelerate or decelerate. It is especially dangerous at very low altitudes, for example, during take-off and landing. Visual and aural windshear warnings are given when several parameters such as ground speed, airspeed, barometric height, rate of descent and radio altitude, indicate the initial conditions of entering an area of windshear.
New forward-looking detectors use the weather radar to predict upcoming weather events, including windshear. The system bounces energy pulses off the rain droplets or moisture of the upcoming region and analyzes the distance to a potential problem area by measuring the time it takes the pulse to return to the aircraft. It can even detect which way the air is moving. Although this is likely to be at very short notice (90 seconds at the best), it still allows the pilot to initiate the windshear procedure earlier, giving the aircraft time to fly according the necessary adjustments.
Following graphic shows an example of visual indication of a windshear ahead:
FLIGHT DIRECTOR (FDS) / AUTOPILOT Flight Director System (FDS) / Autopilot
The Flight Director System (FDS) was originally developed as an aid used by pilots during landing. It gave a pilot the ability to concentrate on fewer instruments and, as it gave instructions as to attitude and steering, it reduced the workload.
Basically, FDS collects information from different sources (pitot-static system, air data computer, NAV receivers, IRS, flight management system) and converts them into simple fly up or down, and fly left or right instructions (in a form of visual indications). Nowadays the signal produced by the FDS is coupled with the autopilot (FDS instructions are passed to the autopilot) allowing it to perform more complex tasks. Different modes of operation of the FDS/autopilot system can be selected by the pilot (or automatically by the FMS), depending on the phase of flight.
The FDS instructions are presented to a pilot in a form of two command bars on a PFD, one vertical (fly left or right) and one horizontal (fly up or down). These command bars (usually in magenta color), that are very similar and used in a same manner as an ILS CDI with GS indicator, are superimposed over the attitude indicator. In addition, the mode of operation of the FDS/autopilot system is presented on the PFD in an area called Flight Mode Annunciator.
On modern aircraft two FDS are fitted. Each system is used to monitor the indications of the other. The displayed command bars are removed when a difference greater than certain tolerance is sensed between the two FDS, and they will not appear until the sensed difference returns within the limits. Having two FDS also means certain amount of redundancy in the system, however if one system should fail the second will take over.
Common pilot errors in using Flight Director are:
- blindly following Flight Director cues - the convenience of flight director cues can invite fixation or overreliance on the part of the pilot. Pilots sometimes assume that flight director cues are following a route or course that is free from error and do not include navigation instruments and sources in their scan.
- confusion about Autopilot engagement - pilots sometimes become confused about whether or not flight director cues are being automatically carried out by the autopilot, or left to be followed manually by the pilot. Verification of the autopilot mode and engagement status of the autopilot is a necessary technique for maintaining awareness of who is flying the aircraft.
Having a FDS on its own is not a big advantage. The greatest benefit is when the FDS is coupled with an autopilot system (the new integrated system sometimes referred as AFDS – Autopilot Flight Director System).
The main purpose of the autopilot is to relieve the pilot of the physical and mental fatigue of flying the aircraft, especially during long flights. This results with the pilot being more alert during the critical phase of landing the aircraft safely. Because of the autopilot’s ability to react more quickly and more accurate to any disturbance than a human pilot, it also enables aircraft to fly along the prescribed routes more precise. Generally, modern aircraft fitted with FDS/autopilot systems can fly automatically for almost the entire route (the power is controlled automatically as well by separate auto-throttle servo motors). However, it should be noted that the autopilot does not carry out the take offs which have to be done by human pilots.
The autopilot system consists of sensors, autopilot computer and actuators (servo motors to move the control surfaces) that can maintain an aircraft’s stability. The autopilot is capable of producing the same actions as a human pilot but with much shorter reaction time. It detects the disturbance and then computes the corrective action which is finally applied to the control surfaces through the servo motors. Next, it detects when the aircraft has responded to the corrective action and returns the control surfaces to the neutral when the disturbance is corrected. Oversimplifying we can say that all the autopilot does is only stabilization of the aircraft, and the rest “extra” features (altitude hold, heading hold, LNAV, VNAV…) are achieved by the FDS passing corresponding (“false”) disturbance information to the autopilot sensors making it manoeuvre the aircraft into a position to achieve FDS aim.
An aircraft can be subjected to disturbance about three axes. So, the stabilization task must be controlled about the same three axes. However, there are autopilot systems that can control only the roll (sometimes referred as single axis systems) and autopilot systems that can control roll and pitch (sometimes referred as two axis systems).
A FDS/autopilot system is controlled using the mode control panel that allows the pilot to set the desired parameters and change among different modes of operation. Usually, the switches illuminate to indicate that certain mode has been selected. The following are examples of two different mode control panels.
Also refer to Hindsight “Airbus AP-FD TCAS MODE” article by Paule Botargues for more information about FD/autopilot use in automated flights.
FLIGHT MANAGEMENT SYSTEM (FMS)
Flight Management System (FMS)
A flight management system (FMS) is designed to improve navigation, fuel efficiency, and to reduce pilot workload. The system enables aircraft to fly along complex routes, using lateral guidance (LNAV) and calculates optimum cruise altitudes as well as the best combination of auto-throttle and speed during climb and descent, using the vertical guidance (VNAV). The computer calculates the optimum flight profile, both horizontally and vertically. This includes tasks such as determining descent points, calculating optimum speeds, selecting headings, and many other items. Unless ATC requests a specific profile, the pilot will allow the FMS to handle the aircraft automatically. In fact, even when a specific maneuver/profile is requested by ATC, the pilot is not usually flying the aircraft by hand; he/she uses the FMS to control the aircraft by entering commands in the system.
The task is achieved mainly by the flight management computer (the heart of FMS) that communicates or receives information from almost all aircraft systems and instruments, and handles the aircraft by passing commands to the FDS/autopilot. It also stores information in form of a database. This database, which has to be updated regularly by maintenance, is divided into two major sections: one containing performance related information (aircraft drag, engine characteristics, maximum and minimum speeds, etc), and the other containing flight plan and navigational information (location of navigational aids, waypoints, ATS routes, minimum altitudes, airports, runways, SIDs, STARs, approaches, company routes and other company selected information).
Currently, electronic navigation databases are updated every 28 days. It ensures consistency with AIRAC (Aeronautical Information Regulation And Control) cycle according to which AIPs (Aeronautical Information Publication) are revised with operationally significant changes and information. Because these changes are received well in advance, users of the aeronautical data can update their flight management systems (FMS).
Control and Display Unit (CDU)
The interface between the crew and the FMS is called a Control and Display Unit (CDU). The CDU is used to enter commands or data in the FMS or to select different modes of operation of aircraft instruments and systems. Usually, two CDUs are fitted on either side of the cockpit (one for each FMC), with one normally being the master and other being on stand by. If there is a failure, the second system takes over and operates the aircraft on its own. Following graphics show examples of different CDUs used on modern aircraft:
TRAFFIC ALERT AND COLLISION AVOIDANCE SYSTEM (TCAS/ACAS)
Traffic Alert and Collision Avoidance Systems (TCAS/ACAS)
The TCAS is an airborne system which operates independently from the ground-based ATC system. TCAS was designed to increase flight deck awareness of proximate aircraft and to serve as a “last line of defense” for the prevention of mid-air collisions.
There are two levels of TCAS systems. TCAS I was developed to accommodate the general aviation (GA) community and the regional airlines. This system issues traffic advisories (TAs) to assist pilots in visual acquisition of intruder aircraft. TCAS I provides approximate bearing and relative altitude of aircraft with a selectable range.
TCAS II is a more sophisticated system which provides the same information of TCAS I. It also analyzes the projected flight path of approaching aircraft and issues resolution advisories (RAs) to the pilot to resolve potential mid-air collisions. Additionally, if communicating with another TCAS II equipped aircraft, the two systems coordinate the resolution alerts provided to their respective flight crews.
To find out more about TCAS refer to SKYbrary article: “Airborne Collision Avoidance System (ACAS)” Also please see periodically published ACAS bulletins focusing on a different operational themes of interest to both aircrews and air traffic controllers.
FLIGHT DATA RECORDER Flight Data Recorder (FDR) Flight Data Recorder (FDR) is a device used to record specific aircraft performance parameters. The purpose of a FDR system is to collect and record data from a variety of airplane sensors onto a medium designed to survive an accident. Flight recorders comprise two systems, a flight data recorder (FDR) and a cockpit voice recorder (CVR). Sometimes, both FDR and CVR functions are combined into a single unit. According to the provisions in ICAO Annex 6 - Operation of Aircraft, Vol 1 and Vol. III, a Type I FDR shall record a number of parameters the parameters required to determine accurately the aeroplane flight path, speed, attitude, engine power, configuration and operation. Types II and IIA FDRs shall record the parameters required to determine accurately the aeroplane flight path, speed, attitude, engine power and configuration of lift and drag devices. Provision 6.3.6 of Annex 6, Vol. I states that, all aeroplanes of a maximum certificated take-off mass of over 5,700 kg for which the individual certificate of airworthiness is first issued after 1 January 2005 shall be equipped with a Type IA FDR. The recorder is installed in the most crash survivable part of the aircraft, usually the tail section. To find out more about FDR refer to SKYbrary article: “Flight Data Recorder (FDR)”
COCKPIT VOICE RECORDER Cockpit Voice Recorder (CVR) Cockpit Voice Recorder (CVR) is a device used to record the audio environment in the flight deck for the purpose of investigation of accidents and incidents. The CVR records and stores the audio signals of the microphones and earphones of the pilots’ headsets and of an area microphone installed in the cockpit. According to the provisions in ICAO Annex 6 “Operation of Aircraft”, Vol I: • Fixed-wing aeroplane and helicopters shall be equipped with a cockpit voice recorder with a recording duration of at least 30 minutes of its operation; • Fixed-wing aeroplanes with a maximum take-off mass of more than 5 700 kg and for which the certificate of airworthiness is first issued after 1 January 2003 shall be equipped with a CVR with a recording duration of two hours; and • Helicopters for which the certificate of airworthiness is first issued after 1 January 2003 shall be equipped with a CVR with a recording duration of two hours. Additional ICAO provisions in force from 1 January 2007 require that all aeroplanes which utilise data link communications and are required to carry a CVR shall record on a flight recorder, all data link communications to and from the aeroplane. The minimum recording duration shall be equal to the duration of the CVR, and shall be correlated to the recorded cockpit audio. Also, sufficient information to derive the content of the data link communications message and, whenever practical, the time the message was displayed to or generated by the crew shall be recorded.
To find out more about CVR refer to SKYbrary article: “Cockpit Voice Recorder (CVR)”
1. [Question type: multiple choice, based on AirQuestions INST-OTH/380]
Q: The altitude information provided by a SSR transponder is always referenced to A1: QNH A2: radar site pressure A3: 1013,25 hPa A4: QFE
Correct answer: A3
2. [Question type: multiple choice, based on AirQuestions INST-OTH/423]
Q: The main purpose of the flight management system - FMS is to A1: improve navigation, fuel efficiency and reduce pilot workload A2: collect information from different sources (pitot-static system, NAV receivers, IRS, FMS) and convert them into simple fly up/down and fly left/right instructions A3: relieve the pilot of physical and mental fatigue of flying the aircraft, especially during long flights A4: fly the aircraft more precisely along prescribed ATS routes
Correct answers: A1
3. [Question type: multiple choice, based on AirQuestions INST-OTH/417]
Q: The flight director system's instructions are presented to the pilots in form of command bars on the primary flight display in magenta colour A1: two horizontals, the top one (fly left/right) and the bottom one (fly up/down) A2: two verticals, the left one (fly left/right) and the right one (fly up/down) A3: one vertical (fly left/right) and one horizontal (fly up/down) A4: one on the PFD (fly left/right) and the second one on the ND (fly up/down
Correct answers: A1, A5, A6
4. [Question type: true or false]
Q: According to the provisions in ICAO Annex 6 “Operation of Aircraft”, Vol I fixed-wing aeroplanes with a maximum take-off mass of more than 5 700 kg and for which the certificate of airworthiness is first issued after 1 January 2003 shall be equipped with a CVR with a recording duration of two hours A1: True A2: False
Correct answers: True
22. Wake turbulence