Technical Interview 7 Flashcards
What is a moment arm?
Moment (Balance) Arm is the distance from the datum to the centre of gravity of a mass.
What is the range of a VOR?
VOR stations are fairly short range: the signals are line of sight between transmitter and receiver and are useful for up to 200 miles.
Maximum theoretical range is calculated using:
1.23 X (√Transmitter) + (√Receiver)
How would you navigate if all VOR’s and NDB’s en route fail?
With the IRS/INS/GPS or visually.
Tell us what ranges the glideslope and localiser beams are checked out to?
Glideslope: the glideslope operates in the UHF band between 329.15 and 335MHz to provide 40 complementary channels. e.g. 329.15, 329.3, 329.45, 329.6 - 335MHZ.
The glide path coverage extends from the transmitter to a distance of at least:
10 nm (18.5km) in sectors of 8° in azimuth on each side of the centre-line.
Localiser: the Localiser operates in the VHF band between 108 and 111.975MHz to provide 40 channels. e.g.108.1 108.15; 108.3 108.35; 108.5 108.55 -111.95 Mhz.
The localiser coverage sector extends from the transmitter to distances of:
25 nm (46.3km) within plus or minus 10° from the centre-line;
17 nm (31.5km) between 10° and 35° from the centre-line;
10 nm (18.5km) outside ±35° if coverage is provided.
How does an ILS work?
An ILS (Instrument Landing System) is defined as a precision runway approach aid based on two radio beams which together provide pilots with both vertical and horizontal guidance during an approach to land.
The ILS aerials transmit two lobes. For a pilot on final, the lobe to his right is modulated at a frequency of 150 Hz and the one to his left at 90 Hz. The point where the lobes meet is the centre line of the runway. As the signals on the lobe move from the centre line to either side, their amplitude increases. This means the magnitude of their depth modulation increases. The depth modulation can be considered as a percentage. For example, if an aircraft receives a 15% depth modulated signal from the left and a 5% depth modulated signal from the right, the difference of modulation becomes 10% to the left. This electrical imbalance is sent to the aircraft and the localizer needle is designed in such a way that it will show a deflection to the opposite direction, telling the pilot to go to the right.
When on the centre line, the modulation difference is zero and the needle centres itself.
The glide slope or the glide path provides the pilot with vertical guidance. The glide slope is set such that a glide slope angle of 3 degrees is maintained by the pilot. The needle of the slope moves up, if the aircraft is too low and moves down if it is too much above the required path. The glide slope is on the UHF band (329.15 - 335 Mhz).
The glide slope operates the same way as the localizer. The only difference is that the lobes are emitted on the vertical plane. The upper lobe is modulated at 90 Hz while the bottom one at 150 Hz. Exactly the same way as before, the needle of the slope moves based on the difference in depth modulation. As like before when the modulation difference is nil, the glide needle moves to the very centre of the instrument.
If you are at the locator, on glide-scope, on localiser, but your altimeter is reading 500ft high what could be the cause of this?
False glide slope.
What is the relevance of the mass and balance document?
It’s an official document for the safety of the flight.
How would you load an aircraft for max range?
To increase range, I would load the aircraft in such a way as to attempt to position the center of gravity near its aft limit. I would use the aft cargo compartment.
What is BEM?
Basic Empty Mass (BEM) is the mass of an aeroplane plus standar items such as: unusable fuel and other unusable fluids; lubricating oil in engine and auxiliary units; fire extinguishers; pyrotechnics; emergency oxygen equipment; supplementary electronic equipment
How can you calculate the Operating Mass?
Operating Mass is the DOM plus fuel but without traffic load.
What is the purpose of a locator?
To notify the crew of the aircraft of a particular position on the approach.
Locators, often installed on an ILS approach, are sometimes co-located with Outer and Middle Marker and are used as an aid for approach procedures.
Locators have been largely replaced with Distance Measuring Equipment (DME), but they can still sometimes be found associated with Outer or Middle Markers where they are referred to as Locator Outer Marker (LOM) or Locator Middle Marker (LMM).
How does an IRS work?
Inertial Reference Systems (IRS) provide aircraft velocity and position by continuously measuring and integrating aircraft accelerations. IRS is electrical, self contained system, use no external references, are unaffected by weather, operate day/night, and all corrections for earth movement and for transporting over the earth’s surface are applied automatically. The products of an IRS are: position (Iat/long), speed (knots), distance (nautical miles) and other navigational information (e.g. true heading, true track, attitude, drift, ground speed). The basis of an operation is the measurement of accelerations in known directions. Accelerometers detect and measure acceleration along their sensitive (input) axes; the platform (accelerometers) output is integrated, first to provide velocity along the sensitive axis, and a second time to obtain the distance along the same axis. The process of integration is used because acceleration is rarely a constant value.
What errors does an NDB suffer from?
- Accuracy: The best guaranteed accuracy of NDBs is ±5°.
- Designated Operational Coverage: The designated operational coverage (DOC) of an NDB defines the maximum range from an NDB at which a pilot will receive the required level of bearing accuracy of ±5°, by day only. DOCs are typically between 15 and 50 nms. Information on the DOC of NDBs is contained in the United Kingdom, Aeronautical Information Publication (AIP) in the GEN and ENR sections.
- Precipitation static: Precipitation static is generated by the collision of water droplets and ice crystals with the aircraft. This phenomenon causes a wandering needle and a background hiss in the audio, and effectively reduces the reception range.
- Thunderstorms: The powerful discharges of static electricity in thunderstorms will cause significant bearing errors in the ADF. For this reason, caution must be exercised when using the ADF in the vicinity of thunderstorms, as the needle can actually point at the thunderstorm.
- Night effect: At night, the characteristics of the atmosphere change with respect to the transmission of radio waves. Night Effect is most marked around dawn and dusk, and is characterised by needle hunting and audio fade.
- Station interference: Due to the number of stations in the MF and LF bands, there is the possibility of interference between NDBs which are on or near the same frequency.
- Mountain effect: Mountainous areas can cause reflections and diffraction of the transmitted radio waves, leading to errors in ADF systems.
- Coastal refraction: Radio waves speed up over water compared to over land. This phenomenon leads to a bending of the waves as they cross the coast, and is the cause of errors in indicated bearings.
- Quadrantal error: The theoretical polar diagram of the loop aerial is distorted by the airframe which produces a strong electrical field along the fore and aft axis of the aircraft. Incoming NDB signals are, thus, refracted towards the fore and aft airframe axis. This is known as quadrantal error.
- Dip error: The angle of bank during a turn causes a current to be induced in the horizontal elements of the loop, thereby leading to a bearing error which is referred to as “dip” error. This error is present only when the aircraft is banked, with the ADF needle falling towards the low wing of the aircraft. This error is maximum when the beacon is on the nose/tail axis (typically up to 10º), and at a minimum when the beacon is on the wing axis.
- The Absence of Failure Indications in the ADF Display: Finally, it is important to realise that false indications due to a failure in the ADF system are not readily detectable because of the absence of failure warning within most ADF instruments.
página 311 ppl oxford navigation
What’s the temperature at FL150 according to ISA?
-15°C, because:
-2°C per 1000 feet gives -30°C.
ISA: 15°C at sea level - 30°C = -15°C at FL150
What is a VOR? What frequency range and band is it in?
VHF Omnidirectional Radio Range is an aircraft navigation system operating in the VHF band.
VOR beacons transmit in the frequency range 108 Megahertz (MHz) to 117.95 MHz.
The VOR beacon transmits two signals at the same time. One signal is a stationary pattern of signals, broadcast in all directions (i.e. omni-directionally), while the other is a rotating pattern of signals. The two signals are in phase on Magnetic North from the VOR beacon; in all other directions there is a phase difference between the two sets of signals which identify the magnetic bearing of the aircraft from the transmitter.
The VOR receiver measures the phase difference between the two signals, and displays it as a bearing on the VOR display. The bearing of the aircraft from the beacon is known as a radial.
