Correct Answer : Stable and damped response
Explanation : The height error gain is chosen so that the frequencymax is well below the bandwidth of pitch attitude loop to ensure a stable and well damped height loop response. If the frequency is high, it might lead to oscillations in the vertical axis.
Correct Answer : Density of air
Explanation : The altitude control loop works using , Where H is the required height or altitude, θ is aircraft pitch angle and α is angle of incidence.
Correct Answer : Pitch, roll and yaw control
Explanation : The pitch attitude control loop and the heading control loop, with its inner loop commanding the aircraft bank angle, are thus fundamental inner loops in a common autopilot control mode. They are short, fast period loops which continuously control the control surfaces of an aircraft to maintain the pilot command.
Correct Answer : Autopilot
Explaination : The basic function of the autopilot is to control the flight of the aircraft and maintain it on a predetermined path in space without any action being required by the pilot. The autopilot can thus relieve the pilot from the fatigue and tedium of having to maintain continuous control of the aircraft’s flight path on a long duration flight so the pilot can concentrate on other tasks and the management of the mission.
Correct Answer : Generate commands to the inner flight control loop
Explanation : The autopilot exercises a guidance function in the outer loop and generates commands to the inner flight control loop. These commands are generally attitude commands which operate the aircraft’s control surfaces through a closed flight control loop system so that the aircraft rotates about the pitch and roll axes until the measured pitch and bank angles are equal to the commanded angles. The changes in the aircraft’s pitch and bank angles then cause the aircraft flight path to change through the flight path kinematics.
Correct Answer : Housekeeping management
Explanation : The Light Management System performs various functions such as Automatic navigation and guidance including ‘4D’ navigation, Presentation of information, Management of aircraft systems, Efficient management of fuel, Reduction of operating costs. Housekeeping management is a separate system which takes care of air conditioning, entertainment systems, etc.
Correct Answer : Instrument landing system
Explanation : ILS or instrument landing system is a radio based approach guidance system installed at major airports and airfields where the runway length exceeds 1800 m which provides guidance in poor visibility conditions during the approach to the runway.
Correct Answer : SBAS
Explanation : SBAS or Satellite Based Augmentation Systems exploiting differential GPS techniques will be able to provide reliable and accurate approach path guidance in category II visibility conditions. This will be increasingly used in the future.
Correct Answer : Localizer transmitter and glide slope transmitter
Explanation : ILS system basically comprises a localiser transmitter and a glide slope transmitter located by the airport runway together with two or three radio marker beacons located at set distances along the approach to the runway. The airborne equipment in the aircraft comprises receivers and antennas for the localiser, glide slope and marker transmissions.
Correct Answer : 1 m
Explanation : The navigation position accuracy of 1 m which can be achieved with the differential GPS technique is being exploited in the US for landing guidance with a system called the Ground Based Augmentation System, GBAS. The Ground Based Augmentation System, when installed at an airport, will be able to provide the high integrity and accurate guidance necessary for landing in Cat. III visibility conditions.
Correct Answer : 2.91 m/s
Explanation : Vertical velocity at the start of flare = approach speed x glide slope angle. Thus Vv= 66.87* x sin(2.5°) = 2.91 m/s . *[converting knots to m/s].
Correct Answer : Proportional plus integral
Explanation : The auto-flare loop is a high-order system; apart from the lags present in the filtered rad.alt. signals there are also the lags present in the response of the pitch attitude command loop. This loop controls and its response is significantly slower at the low speeds during the approach. A proportional plus integral control term is used in the auto-flare controller to ensure accuracy and some phase advance is generally provided to compensate for the lags in the loop and hence improve the loop stability and damping.
Correct Answer : 0.0033 RAD
Explanation : The beam error γ = d/R, where d is the displacement of the aircraft’s CG from the beam center line and R is the slant range of the aircraft. γ = 5/1,500 = 0.0033 RAD.
Correct Answer : Aircraft range is close to zero
Explanation : In the localizer coupling loop gain increases as range between aircraft and runway decreases. The gain reaches a point where it becomes too large and the loop becomes unstable. Thus gain scheduling with range is required.
Correct Answer : ILS Localizer receiver
Explanation : The Localizer coupling loop is integrated with the heading command loop to manage the heading of the aircraft. It is a closed loop system which continuously corrects with respect to the ILS Localizer. The error in flight path is corrected with respect to the localizer beam by means of a localizer receiver in the aircraft.
Correct Answer : Runway length
Explanation : The two basic parameters used to define the visibility category are the decision height, that is the minimum vertical visibility for the landing to proceed and the runway visual range. The length of a runway is not used to define visibility category.
Correct Answer : VHF
Explanation : The localizer transmitter used VHF range from 108-122 MHz frequency and provides information to the aircraft as to whether it is flying to the left or right of the center line of the runway it is approaching. The localizer receiver output is proportional to the angular deviation γL, of the aircraft from the localizer beam center line which in turn corresponds to the center line of the runway.
Correct Answer : UHF
Explanation : The glide slope or glide path transmission is at UHF frequencies from 329.3 to 335 MHz frequency and provides information to the aircraft as to whether it is flying above or below the defined descent path of nominally 2.5?, for the airport concerned. The glide slope receiver output is proportional to the angular deviation γV, of the aircraft from the center of the glide slope beam which in turn corresponds with the preferred descent path.
Correct Answer : Weight of the aircraft
Explanation : The height limits and visibility conditions in which the autopilot can be used to carry out a glide slope coupled approach to the runway depends on the visibility category to which the autopilot system is certified for operation, the ILS ground installation standard, the runway lighting installation and the airport’s runway traffic control capability.
Correct Answer : Category III
Explanation : Visibility conditions are divided into three categories, namely Category I, Category II and Category III, depending on the vertical visibility ceiling and the runway visual range (RVR). Category III includes zero visibility conditions.
Correct Answer : Decision Height
Explanation : This minimum permitted ceiling for vertical visibility for the landing to proceed is known as the decision height or DH. A very high integrity autopilot system is required for fully automatic landing below a DH of 100 ft – Cat. III conditions.
Correct Answer : 50 ft
Explanation : The auto flare is initiated around 50 ft where the aircraft is over or very near the runway threshold so that the radio altimeter is measuring the height of the aircraft above the runway. Low range radio altimeters are used to ensure accuracy.
Correct Answer : 75 MHz
Explanation : The marker beacon transmissions are at 75 MHz. The middle marker beacon is located at a distance of between 1,000 and 2,000 m from the runway threshold and the outer marker beacon is situated at a distance of between 4,500 and 7,500 m from the middle marker.
Correct Answer : Decision height of 5m
Explanation : The autopilot requirements and operational limits for a category III visibility conditions are a probability of catastrophic failure of less than 10−7 per hour, fully automatic landing system with flare, runway guidance required to taxi point. The decision height for a category IIIc condition is 0m. No system is yet certified for category IIIc operation.
Correct Answer : FADEC
Explanation : The FADEC or Full Authority Digital Engine Control is a system that controls all aspects of the engine performance. Since there are a lot of variables involved in the control of different engines, the workload of the pilot is increased. The FADEC system is used to reduce the workload at the same time giving full control of the engine to the pilot. It also ensures maximum engine performance at different flight conditions.
Correct Answer : Small negative height
Explanation : In the control law for auto flare, HREF is a small negative height, or bias, which ensures there is still a small downwards velocity at touchdown. This avoids the long exponential ‘tail’ to reach zero velocity and enables a reasonably precise touchdown to be achieved.
Correct Answer : Radio altimeters
Explanation : When an aircraft is about to land, accurate altitude measurements are needed. Pitot static measurements suffer from errors due to weather and generally have lag. The aircraft height above the ground is measured by very accurate radio altimeters during the landing phase.
Correct Answer : To align with the runway
Explanation : Just prior to touchdown a ‘kick off drift’ maneuver is initiated through the rudder control so that the aircraft is rotated about the yaw axis to align it with the runway. This ensures the undercarriage wheels are parallel to the runway center line so that no sideways velocity is experienced by the wheels when they make contact with the runway.
Correct Answer : To reduce airspeed and rate of descent
Explanation : The flare maneuver is the increase in pitch of the aircraft seconds before touching the ground. This is done to reduce the airspeed and the rate of descent. If the flare is not executed correctly it may result in a runway overrun, landing gear collapse or a tail strike.
Correct Answer : Automatically switch between different types of communication
Explanation : The tasks of the FMS include Flight guidance and lateral and vertical control of the aircraft flight path, Monitoring the aircraft flight envelope and computing the optimum speed for each phase of the flight and ensuring safe margins are maintained with respect to the minimum and maximum speeds over the flight envelope, Automatic control of the engine thrust to control the aircraft speed. However, the communication systems are taken care manually by the pilot.
Correct Answer : 2
Explanation : There are two independent FMS in a typical commercial aircraft’s cockpit. FMS-1 is on the Captain’s side and FMS-2 on the First Officer’s side to carry ou the flight management functions. The reason why both are independent is that when one fails the other can take over.
Correct Answer : Keyboard and Cursor Control Unit
Explanation : The flight crew can navigate through the pages of FMS and can consult, enter or modify the data via the Keyboard and Cursor Control Unit (KCCU). The Keyboard and Cursor Control Unit (KCCU) enables the flight crew to navigate through the FMS pages on the MFD and enter and modify data on the MFD and can also perform some flight plan revisions on the lateral Navigation Display (ND).
Correct Answer : Target Detection and Locking System
Explanation : The cockpit interfaces to the flight crew provided by each FMS comprise a Navigation Display (ND), a Primary Flight Display (PFD), a Multi-Function Display(MFD), a Keyboard and Cursor Control Unit (KCCU) and an Electronic Flight Instrument System (EFIS) Control Panel (EFIS CP).
Correct Answer : Control over graphical and textual FMS data
Explanation : The EFIS Control Panel (EFIS CP) provides the means for the flight crew to control the graphical and textual FMS data that appear on the ND and PFD. Control over flight plan and performance is given by MFD. Navigation through the pages is by KCCU.
Correct Answer : 3
Explanation : There are a total of three Flight Management Computers FMC -A, FMC -B, FMC -C. They are necessary to carry out the necessary functional computations. They can be reconfigured to maintain the system operation in the event of failures.
Correct Answer : Single mode
Explanation : In Single mode operating mode of the FMS two of the FMC is not in operation and this might cause one of the two FMS to fail. Hence both the FMS get information from one FMC.
Correct Answer : Kalman filter
Explanation : The FMS combines the data from the navigational sources, comprising the inertial systems, GPS and the radio navigation systems, in a Kalman filter to derive the best estimate of the aircraft position. Each navigation system has its own advantages and limits, a Kalman filter combines the resource from all the systems to provide a more accurate position of the aircraft.
Correct Answer : Aircraft position
Explaination : The final output of a Kalman filter is the best estimated aircraft position derived from various radio and inertial/GPS sensors. The direct information from the sensors ( raw data) cannot be used directly for accurate position location as their error increases with time.
Correct Answer : GPS only
Explanation : Each FMS computes the aircraft position and the position accuracy. The FMS computed position is an optimum combination of the inertial position and the GPS or radio position, depending on which equipment provides the most accurate data. This results in four navigation modes: Inertial (IRS) – GPS, Inertial (IRS) – DME/DME, Inertial (IRS) – VOR/DME, Inertial (IRS) only. The only GPS is not used as the position information is within a radius where the aircraft is flying.
Correct Answer : Position of the aircraft
Explanation : The FMS continually monitors the aircraft envelope and ensures that the speed envelope restrictions are not breached. It also computes the optimum speeds for the various phases of the flight profile. This is carried out taking into account factors such as: Aircraft weight – computed from a knowledge of the take-off weight and the fuel consumed (measured by the engine flow meters), CG position – computed from known aircraft loading and fuel consumed, Flight level and flight plan constraints, Wind and temperature models, Company route cost index.
Correct Answer : 28 days
Explanation : The navigation database is updated every 28 days, according to the ICAO AiRAC cycle, and is held in non-volatile memory. It is clearly essential to maintain the recency and quality of the database and the operator is responsible for the detail contents of the database which is to ARINC 424 format.
