Avionics Mcqs - Set 23

ANSWER: Flare

Explanation:
The flare is an exponential path tangent to a horizontal plane several feet below the runway, which ensures a positive touchdown.

ANSWER: Gain scheduling

Explanation:
The localizer gain must be scheduled to decrease as the runway is approached because the surfaces of constant DDM coverage to make the error signal more sensitive to distant displacement.

ANSWER: True

Explanation:
In the early 1970s the British Trident and the U.S. L-1011 aircraft including their autoland systems were certified for Category III A operations in revenue service using guidance information form the ILS and other on-board sensors.

ANSWER: ILS

Explanation:
The instrument landing system or ILS is a collection of radio transmitting stations used to guide aircraft to a specific airport runway, especially during times of limited visibility.

ANSWER: Depends upon density of traffic on the airspace

Explanation:
High density airports where a lots of planes land and take off typically have more than one runways with multiple ILS systems. Chicago’s O’Hare airport had an ILS installed on 12 runways in 1996.

ANSWER: ICAO standards and recommended practices

Explanation:
The ICAO Standards and Recommended Practices for the ILS, subscribed by the180 member states, standardize the signal in space for the ILS ground transmitting equipment, no matter where they are manufactured to maintain international standards.

ANSWER: Beyond the stop end of the runway

Explanation:
The localizer antenna is centered on the runway beyond the stop end to provide lateral guidance. The glide slope is located beside the runway near the threshold to provide vertical guidance.

ANSWER: Radiation monitors

Explanation:
Radiation monitors are used to detect ILS failure. They are placed at a particular distance away from the runway to check for errors in ILS transmission or drift in the frequency of radiation.

ANSWER: Horizontal polarization

Explanation:
Every transmitter in the ILS including the glide slope transmitter, localizer and the marker beacons radiate continuous wave, horizontally polarized, radio frequency energy which can be received by the on-board receiver.

ANSWER: 75 MHz

Explanation:
All the marker beacons, all around the world, operate on a single frequency of 75MHz.

ANSWER: True

Explanation:
The localizer, glide slope and DME frequencies are paired such that only the localizer frequency is required to tune by the pilot. This hard pairing reduces the pilot’s work load.

ANSWER: Crystal controlled

Explanation:
The marker beacon receiver is a dedicated crystal controlled receiver fixed tuned to 75 MHz. This is because all marker beacons use the same frequency.

ANSWER: Ground reflection

Explanation:
Mulit path Signals are created when a part of the original signal take a different path than LOS to reach the receiver. Thus a signal with same information reaches the receiver at multiple times. Multi path signals are created when the actual signal gets reflected from the ground and reaches the receiver.

ANSWER: Localizer

Explanation:
An audible Morse code identification signal is transmitted on the localizer frequency. A voice channel from the control tower may also be provided.

ANSWER: Localizer

Explanation:
The localizer establishes a radiation pattern in space the provides a deviation signal in the aircraft when the aircraft is displaced laterally from the vertical plane containing the runway center line.

ANSWER: Clearance signal

Explanation:
When the localizer CSB pattern is narrow, to reduce reflections from buildings and other aircraft, the system requires the addition of “clearance” signals to provide 35° coverage in both directions.

ANSWER: Long periodic antenna

Explanation:
Almost all of the localizer antenna is long periodic antenna. It provides unidirectional radiation, can be installed without guy cables and has good broadband characteristics.

ANSWER: False

Explanation:
Clearance Signals, when required, can be provided by a separate array antenna specifically for clearance signals. In some designs, both clearance signals and localizer signals are transmitted from different elements of the same array. Nevertheless, the same antenna cannot be used.

ANSWER: Image glide slope

Explanation:
Image array glide slope systems depend on reflections from the ground in the direction of approaching aircraft to form the radiation pattern.

ANSWER: Fan shape

Explanation:
Marker beacons provide pilot alerts along the approach path. Each beacon radiates a fan shaped vertical beam that is approximately ±40° wide along the glide path by ±85° wide perpendicular to the path.

ANSWER: Environment sensitivity

Explanation:
The main weakness of the ILS system was its sensitivity towards the environmental factors. Since the frequency used by the system is in MHz, it was more susceptible to atmospheric and weather interference.

ANSWER: Narrow beam width antennas

Explanation:
The main weakness of the ILS system is eliminated by using narrow beam width antennas which are physically small since the frequency is high. As frequency increases antenna size decreases.

ANSWER: Radar

Explanation:
A basic MLS consists of azimuth and elevation ground stations and a conventional DME for 3D positioning on approach course to 40° on either side of center line and to 15° elevation above the runway.

ANSWER: Missed approach

Explanation:
An expanded MLS system uses back azimuth stations. It is generally used for departure and for missed approaches. It provides lateral guidance to 40° on either side of the center line.

ANSWER: 200

Explanation:
The MLS station transmit both angle and data functions on one of 200 frequencies between 5031.0 and 5190.7 MHz. The relatively high number of channels allows the use of multiple MLS in metropolitan cities.

ANSWER: Bit error rate

Explanation:
The acceptable bit error rate of the differential phase shift keying (DPSK) transmissions at the 20-nmi limit determines the transmitter power needed in the ground stations.

ANSWER: False

Explanation:
Early MLS with mechanical scanned array used a varying audio tone to encode the pointing angle on the scanning beam pattern. The FAA adopted the time interval between successive passages of the unmodulated beam as an efficient means of angle encoding.

ANSWER: 20,000°/sec

Explanation:
The very high scanning rate of 20,000°/sec provides about 40 samples per second of the angle data, a rate ten times higher than that needed to control the aircraft.

ANSWER: True

Explanation:
An Electronically scanned array antenna is an array of radiating elements with a feed network incorporating variable propagation delays. These arrays cause the antenna pattern to rotate by “phase shifting” the RF signal.

ANSWER: Number of users

Explanation:
The primary reason for not using basic GPS for landing systems is because does not provide the accuracy that is required for landing, it lacks a monitoring system and the availability of a sufficient number of satellites to provide location information.

ANSWER: WAAS

Explanation:
For non-precision and Category I precision approaches, the limitations by the GPS is mitigated by the FAA’s Wide Area Augmentation System. It may be supplemented with local differential GPS stations located near runways.

ANSWER: Provide precision approaches for Category III C

Explanation:
WAAS addresses the limitations by providing Wide area differential GPS error correction, a ground integrity broadcast, and a GPS ranging function from three or four geostationary satellites providing additional availability.

ANSWER: High- integrity ground to air data link

Explanation:
To support Category II and III landing operations, the additional requirement for accuracy and monitor-response times can be achieved with a differential GPD reference station and a high-integrity ground to air data link located near the runway.

ANSWER: Multi-path signal interference

Explanation:
LDGPS operation leads to the nearly complete cancellation of errors due to satellite ephemerides, clock offset, selective availability, and ionospheric propagation, leaving mainly those errors due to multipath signal interference and receiver noise.

ANSWER: False

Explanation:
The runway reference station can supply integrity warnings within the required response time of 1 to 2 sec. These are located near the runway.

ANSWER: False

Explanation:
GPS receivers were capable of about ten solutions per second, which is sufficient for coupled flight. The accuracy of the SPS code solution without augmentation is satisfactory for nonprecision approaches.

ANSWER: False

Explanation:
The pilot has the option of coupling the autopilot to the ACLS, flying the aircraft from “needles” controlled by ACLS data, or being talked down by a shipboard controller. A manual carrier landing with ACLS resembles a land based ground controlled approach.

ANSWER: Lower

Explanation:
Jet aircraft approach the carrier deck with at airspeeds up to 125 knots. Their speed relative to the deck is lower due to the “wind over the deck,” which is normally about 30 knots.

ANSWER: 4°

Explanation:
The approach path, often called the glide slope, is in the vertical plane containing the runway center line and is inclined 3.5° relative to the sea at the touchdown point and 4° relative to the moving flight deck.

ANSWER: Steady state wake

Explanation:
Steady state wake caused by the relative wind over the ship’s deck and around the superstructure, Which causes a “burble” at the threshold and the glide path.