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Question 216-1 : How can an air traffic control unit determine the position of an aircraft without the use of radar ? [ Preparation civilian ]
By using auto triangulation provided from several vdf bearings from different stations.
Learning objective 062.02.01.02.03 explain that by using more than one ground station, the position of an aircraft can be determined and transmitted to the pilot...vdf vhf direction finding is a method of measuring the direction from which a vhf signal came. it has been used for many decades now, and is particularly useful as the transmitting aircraft only needs a standard vhf radio to ask for a vdf bearing from a suitably equipped atsu. this can give them..qdm magnetic bearing from the aircraft to the station...qdr magnetic bearing from the station to the aircraft...quj true bearing from the aircraft to the station...qte true bearing from the station to the aircraft...with this information, the pilots can plot the location of their aircraft on a chart by drawing a true radial qte outbound from each station that was used. 2 stations and therefore 2 lines can be enough to calculate the position of an aircraft, by finding the point at which they intercept. this is a process known as triangulation. it is important to get a large angle at the point of interception, as the larger the angle optimum 90º , the better the precision of the fix. more than 2 vdf stations can also be used to get a more accurate fix...distress and diversion 121.5 mhz have access to an auto triangulation feature which gives them an immediate readout of the position of any calling aircraft, due to the reception of its transmission at multiple different locations with vdf capability. the computer allows the triangulation to be done immediately...position is the only thing that can be gained from vhf direction finding though, so it is limited in that sense, but is very useful in the sense that only a vhf radio is required in the aircraft.
Question 216-2 : Which of the following options are the correct frequency band, propagation type, and range of usable frequencies for an ils localiser ?
Vhf, space waves, 108.10 mhz to 111.975 mhz.
Ils localisers operate on a frequency between 108.10 and 111.96 mhz vhf , in the bottom half of the band that is used by vors. as such, they propogate as space waves, which are line of sight radio waves. the linked glide path signals operate on a frequency between 328.6 and 335.4 mhz uhf , and also travel as space waves.
Question 216-3 : An aircraft is equipped with a dme receiver that provides a ground speed read out. it is being flown at fl70 and is currently crossing radial 090 from a vor dme station at an indicated dme range of 20 nm. the aircraft is flying in a north easterly direction. the ground speed shown on the dme display ?
Inaccurate as the aircraft is crossing the radials rather than flying an inbound or outbound radial.
Refer to figure.. some dme receivers have a setting that will read out the aircraft's groundspeed when heading towards or away from the station, as well as an estimate of the time to the station. this is calculated by the dme receiver using the rate of change of the detected distance from the station. this means that flying anywhere other than directly to/from the station causes an unusable read out, as is the case in this question, where we are crossing the radials.another thing to consider is that dme systems calculate slant range from the aircraft to the station, so the dme groundspeed calculations are more accurate when this slant range closely resembles ground distance, so when at low altitude and far away from the dme within line of sight of course.
Question 216-4 : Which of the following could give sufficient guidance to the pilot when flying a curved mls approach ?
Flight director bars
An microwave landing system mls works in a similar way to an ils, with a ground station or multiple transmitting information to aircraft on the approach, and an airborne receiver interpretting that data, and providing guidance to the pilot. an mls is a precision approach, and can be segmented, or even curved, due to its 3d design, and has far fewer drawbacks than an ils system. as it provides both horizontal and vertical guidance, it can be flown very well by an autopilot, and in some cases can be setup to provide flare guidance for an autoland, etc. as an alternative, it can also be manually flown following flight director guidance in the horizontal and vertical sense, and this is possible for all mls approaches, even the complex curved ones...it would not be possible for a cdi, rmi, etc. to provide such guidance for curved approaches, as they do not follow a straight line like an ils does, and also rmi lacks in the ability to provide vertical guidance.
Question 216-5 : A dme ground station can generally respond to a maximum of 100 aircraft at once. what is the reason for this limitation ?
Saturation of the dme ground station working on only one receive frequency and one transmit frequency.
Distance measuring equipment dme is a type of secondary radar system that provides slant range using the pulse technique. the aircraft’s interrogator transmits a stream of psuedo random omni directional pulse pairs on the carrier frequency of the ground transponder. the ground transponder then receives these, waits 50 microseconds, and repeats those pulse pairs outwards at a frequency 63 mhz above the interrogation frequency...the airborne system identifies its own unique stream of pulse pairs and measures the time of arrival electronically, between the start of the interrogation and the reception of the ground transponder's replies...as there is only one interrogation frequency and one reply frequency for each dme ground station, they can only service a certain number of pulses per second, and it ends up meaning that the dme becomes saturated with around 100 aircraft using it, and it will then prioritise the pulses with the strongest signal...aircraft attempting to search for a dme emit 150 pulses per second, but after 15000 pulses, reduce that to 60 pulses per second, and later on to 24 pulses per second when fully 'locked on'. as the dme can only handle 2700 pulses per second reliably, this ends up being approximately 100 aircraft, some searching, some locked on.
Question 216-6 : According to icao doc. 8168, an aircraft can be considered established on a vor approach when within what error margin ?
Half scale deflection.
Icao doc. 8168 part 3.3.4. an aircraft is considered established when it is. a within half full scale deflection for the ils and vor or. b within ±5° of the required bearing for the ndb.learning objective 062.02.03.04.01 define that the accuracy the pilot has to fly the required bearing in order to be considered established on a vor track when flying approach procedures, according to icao doc 8168, has to be within the half full scale deflection of the required track.
Question 216-7 : You are flying across northern canada on airway nca whiskey. you wish to cross check the irs computed position by taking a bearing from a nearby vor. you tune into the churchill vor and find you are on the 300° radial. what is the bearing to plot on a chart if the variation at the vor is 2°w and the ?
298°
Refer to figure...to cross check our position using a chart, we must find the true bearing from a known position to our aircraft. in this case the known position is the churchill vor, and we are on radial 300°. radials from vors are in magnetic, so we know the magnetic bearing from the vor to the aircraft is 300° m and also that we should use the variation at the vor to calculate our true bearing an easy way to remember this is that v is for vor and also for variation, so use the variation at the vor. there are many ways to turn this into a true bearing, one of which is the rhyme..variation east, magnetic least,..variation west, magnetic best...therefore our magnetic bearing of 300° is greater than our true bearing by the amount of 2°, so the true bearing to plot from the vor on the chart would be 298° t...note 1 another piece of information would still be required to compute the position of the aircraft, such as another vor bearing or a dme readout...note 2 in canada airspace, northern domestic airspace nda is the area of compass unreliability within which runways and navaids are oriented to true north. however churchill vor is not included in nda airspace, as they would have to specify this in the question.
Question 216-8 : A pilot is flying an ndb holding pattern. they should continuously monitor the… ?
Morse code as a means to identify a potential failure of the ndb.
Ndb failure warning..unline vor or ils systems that have failure warning indications, the ndb does not warn the pilot in the case of a failure. the ndb is a simple transmitter. the adf receives the signal and displays the direction of the radio source. since adf receivers do not have a 'flag' to warn the pilot when erroneous bearing information is being displayed, the pilot should continuously monitor the ndb's identification...when the ndb itself fails, the pilot might notice a searching needle on their display much like when it is out of range of the receiver. this is not a very reliable failure indication, so the pilot should continuously monitor the ndb's morse code identifier, which would stop transmitting in the event of an ndb failure, and would be a much more timely method of noticing a failure. this is obviously not a nice thing to do, as it is often a very annoying identifier noise, another reason ndbs are such a bad navigational aid in modern times.
Question 216-9 : In the legend of a navigation chart, a beacon is mentioned to be a tvor. which description of the tvor is correct ?
A vor station with a shorter range, used as part of the approach and departure structure at major aerodromes.
Vor applications..vors can be classified as follow... a conventional vor cvor is a first generation vor transmitter which emits a spinning limacon shaped amplitude modulating variphase signal.. a doppler vor dvor is a second generation vor transmitter with no moving parts, and sends a frequency modulating variphase signal through its many antennas which circle the beacon to use the doppler shift effect.. a terminal vor tvor is a low power beacon with shorter range, used as part of approach and departure procedures.. a broadcast vor is usually a terminal vor with a voice broadcast giving out the airfield weather atis superimposed on the carrier wave.. a test vor vot is a very low power beacon sited at some airfields. it puts out a constant phase difference of zero in all directions. this allows aircraft to test the accuracy of their equipment on the ground....it is important to note, with the other possible answers, that the tvor in question is not just for the inbound runway course, but is for all around the airfield, and is useful for both approach and departure...note do not confuse a tvor with a test vor
Question 216-10 : Which of the following statements correctly describe the principles of operation of distance measuring equipment dme 1. the aircraft's primary radar output transmits a signal that triggers a reply from the dme station.. 2. a transmission from the aircraft's interrogator triggers a reply from the dme ?
2 and 3
Distance measuring equipment dme is a type of secondary radar system that provides slant range using the pulse technique. the aircraft’s interrogator transmits a stream of pseudo random omni directional pulse pairs on the carrier frequency of the ground station receiver. the ground transponder then receives these interrogation pulses, waits 50 microseconds, and sends a reply, repeating those pulse pairs outwards at a frequency 63 mhz above the interrogation frequency...the aircraft's dme system identifies its own unique stream of pulse pairs and measures the time of arrival electronically, between the start of the interrogation and the reception of the ground transponder's replies. this then can be calculated into a line of sight distance to the ground station, known as the slant range.
Question 216-11 : Determine the distance which will be shown on a dme display when the aircraft is at fl 360 and 6 nm plan range from the dme station..for the calculation use the following assumptions/approximations..qnh is 1013 hpa..pressure altitude is true altitude. ?
8 nm
Refer to figure...the question states that we can regard pressure altitude to be the true altitude. therefore, true altitude equals 36 000 ft.... 36 000 ft / 6 076 = 6 nm approx....what we have is isosceles perpendicular triangle since plan distance and altitude are both equal to 6 nm...dme measures the slant distance hypotenuse. we already know lengths perpendicular of perpendicular sides...using the pythagoras theorem..x2 = 62 + 62..x2 = 72..x = 72 = 8.48 nm closest answer is 8 nm
Question 216-12 : A procedural vor approach using a procedure turn is to be flown. the outbound leg follows the 098° radial from the vor to a dme range of 6.0 nm, followed by a left turn onto a track of 018° m , what should the next turn be ?
A right turn onto a track of 278° m to intercept the inbound track.
Refer to figure...in a procedural approach, often an aircraft will need to perform a reversal manoeuvre, in order to get from an outbound to an inbound track. there are many different ways this can be done, and the chosen method will be dictated clearly on the approach plate. some of the available methods are the 45 180 procedure turn, the racetrack pattern, the teardrop procedure, and the 80 260 procedure turn....icao doc 8168..3.2.2 reversal procedure..b 80°/260° procedure turn see figure i 4 3 1 b , starts at a facility or fix and consists of..1 a straight leg with track guidance. this straight leg may be timed or may be limited by a radial or dme distance..2 an 80° turn..3 a 260° turn in the opposite direction to intercept the inbound track...the 80°/260° procedure turn is an alternative to the 45°/180° procedure turn a above unless specifically excluded.
Question 216-13 : After tuning the correct ils frequency, and receiving the correct ident, the pilot notice that the localiser loc and glide path gp indicators are both showing warning flags. the pilot confirms that the aircraft is within the prescribed coverage area of the ils. what is the most probable reason for ?
The aircraft receives modulating frequencies of 90 and 150 hz at a rate of 0%.
Learning objective 062.02.05.02.05 describe the circumstances in which warning flags will appear for both the loc and the gp absence of the carrier frequency absence of the modulation simultaneously the percentage modulation of the navigation signal reduced to 0...when within the coverage area of the ils, and receiving the ident, that means that the carrier wave for the correct loc is definitely being received, but showing flags for both loc and gs is not what you would expect in normal operation. when flags are shown, it is due to any of the items listed in the lo above, or possibly due to the received signal being below a certain strength. this narrows down the possible failures to a modulation problem...also, the other possible answers are wrong as... selected course does not affect ils signals or indication.. any more than full scale deflection within the coverage area shows exactly that, full scale deflection.. an aircraft ahead of yours might cause a momentary change in the ils indication due to signal reflection, but this woud be a tiny blip indeed.
Question 216-14 : After tuning and receiving a correct ident, you become established on an ils and follow the approach. on short final, the localiser loc and glide path gp indications disappear, and both show warning flags instead. what is the most probable explanation for the warnings ?
The modulation of the 90 hz and 150 hz signals is 0%.
Learning objective 062.02.05.02.05 describe the circumstances in which warning flags will appear for both the loc and the gp absence of the carrier frequency absence of the modulation simultaneously the percentage modulation of the navigation signal reduced to 0...as we have identified and followed the ils down to short final by this point, we know that this sudden appearance of flags is a fault of some kind. when flags are shown, it is due to any of the items listed in the lo above, or possibly due to the received signal being below a certain strength. this narrows down the possible failures to a modulation problem...also, the other possible answers are wrong as... the lack of loc/gp ident signals would not be a reason for showing flags. loss of both carrier frequencies would cause this to happen, but that is not one of the available answers.. there is no cone of confusion for ils transmitters, and definitely should be no similar error regions on short final.. signal strength that is too high would not cause distortion.
Question 216-15 : An aircraft is on the 290° radial from a nearby vor. the magnetic variation at the vor is 5°e and the magnetic variation at the aircraft is 7°e. what true track does the aircraft need to fly to go directly to the vor ?
115°
The aircraft is on radial 290°, which is a magnetic bearing from the vor. to turn this into a true bearing, we can use the saying variation west, magnetic best.. variation east, magnetic least.in this case, we must use the variation at the vor, as this is where the radials come from, which is 5° east. an easy way to remember this is that 'v' is for variation and vor, so we should use the magnetic variation at the vor.magnetic is least, therefore the true bearing from the vor is going to be 5° more than 290° m , so will be 295° t.the bearing from vor to aircraft is 295° t , so the true track to fly the opposite direction is 295 180 = 115° t , this is the true track to be flown direct to the vor.
Question 216-16 : An aircraft is radar vectored onto a cat i ils approach using a hsi. the final approach track is 164° and the magnetic variation is 4°w. the pilot is expecting approximately 6° right drift on final approach, what should they set the course selector to on the hsi ?
164°
An ils inbound track is based on magnetic courses, and therefore there is no need to apply variation, as the hsi horizontal situation indicator is also based on magnetic, as it is slaved to the magnetic field by the remote reading compass system...it is also important to note that the hsi display will actually not depend on the selected course, as an ils course deviation indicator cdi does not depend on selected course, and just works off the differing modulation between two localiser lobes to give fly right or fly left indications. the cdi in the middle of the hsi will just display fly left and fly right indications, no matter the selected course and can therefore reverse sense if twisted backwards...the hsi should therefore be set up with the inbound magnetic course selected, as this will give the correct indications and an aide memoir of the inbound course to the pilot all the way down the approach...the inbound heading of the aircraft accounting for wind correction angle would not be used for many important reasons.
Question 216-17 : Which of these options correctly describes the basic principles of operation of an mls ?
The time interval between the to and from scans in azimuth and elevation determines the aircraft position within the coverage area.
Refer to figure...the principles of operation of microwaves landing systems mls are actually quite simple to understand. there are 2 main and 1 extra transmitters providing information to the aircraft. the first one provides information about how far an aircraft is horizontally from the correct inbound course, called azimuth guidance similar to ils localiser. the second one provides similar information about how far the aircraft is from the correct glide path, called elevation guidance...there is a third transmitter that is used to allow curved and segmented mls procedures to take place also, called the dme/p, which is a more precise version of a standard dme. with this in use also, the aircraft can have the knowledge of its 3 dimensional position for much more complex not straight in approaches...the azimuth and elevation transmitters work in the same way, they emit a beam that scans the sky, side to side to and fro for the azimuth guidance, up and down for the elevation beam. the aircraft then detects how much time passed inbetween the beams being detected, between the to and the fro beam, for instance , and can very accurately detect its angular distance from the inbound course/glide path...the azimuth beam does not constantly scan to fro to fro..., but has a break whilst the elevation beam does it's own scan, and they alternate with each other. with data being passed also through the frequency at set intervals.
Question 216-18 : What is one of the main differences between cat ii and cat iii mls approaches ?
Only cat iii allows no decisions height.
Refer to figure...cat ii and cat iii minima are not specific to the mls microwave landing system , but are much more commonly used on ils approaches as mls approaches barely exist anymore...it can be thought of as a scale, cat i can get an aircraft down to 200ft, cat ii can get further down to 100 ft, etc. then there are 3 levels of cat iii minima, which do actually have varying rvr requirements depending on authority, but the annex above gives the basic values...as can be seen in the annex, the first time a full autoland can be completed no decision height is cat iii, meaning that this is the correct answer...both cat ii and cat iii require a radio altimeter, and both have rvr requirements except cat iiic, but this is only one section of cat iii minima , so all the other answers are incorrect...please note that this annex uses the old system. we believe that easa may be in the process of transitioning to the new system of minima. see the short explanation in the comments for more, whilst we find out what easa are currently considering is correct, thank you.
Question 216-19 : There are two primary methods of flying to or from an ndb. complete the following statement from the options below.. 1 may be used to fly 2 the ndb while 3 may be used to fly 4 the ndb. ?
1 homing 2 to 3 tracking 4 to or from
Refer to figure.. there are 2 different ways to fly using ndb's, the difference between the two is how the wind is dealt with.in the 'easiest' way to fly, homing, the pilot can simply point at the ndb relative bearing 0º and keep the needle on the nose of the aircraft. the problem is that the wind will push them off track if there is any crosswind , but the aircraft will just change its heading to point at the ndb again, meaning that they end up flying a curved path towards the beacon, ending almost completely into wind. this is not efficient, and can cause dangers with terrain clearance and other traffic. a visual representation can be seen in the annex above.tracking, on the other hand, is a more correct way to fly using an ndb, and this requires the pilot to choose an inbound or outbound course from the beacon, and maintain it by applying a wind correction angle to their heading, so that their track is always directly towards or away from the ndb, on the chosen radial. it is a little more complex to fly, but far more useful.not that homing can only take you to an ndb, whereas the tracking technique can guide aircraft to and from ndbs.
Question 216-20 : A crew is briefing for a procedural vor approach that requires a procedure turn for their destination airport. this procedure turn consists of a straight track with outbound track guidance followed by a turn of 45° left, followed by a... ?
Timed straight leg without track guidance and a 180° turn to the right to intercept the inbound track.
Refer to figures...in a procedural approach, often an aircraft will need to perform a reversal manoeuvre, in order to get from an outbound track to an inbound track. there are many different ways this can be done, and the chosen method will be dictated clearly on the approach plate. some of the available methods are the 45 180 procedure turn, the racetrack pattern, base turns, and the 80 260 procedure turn. the one in question has started with a 45º turn, so must be the 45 180 procedure turn. see the annexes above for the specific manoeuvre and the other main reversal procedures....icao doc 8168..3.2.2 reversal procedure..3.2.2.3 a 45°/180° procedure turn see figure ii 5 3 1 a , starts at a facility or fix and consists of..1 a straight leg with track guidance. this straight leg may be timed or may be limited by a radial or distance..measuring equipment dme distance..2 a 45° turn..3 a straight leg without track guidance. this straight leg is timed. it is..i 1 minute from the start of the turn for category a and b aircraft and..ii 1 minute 15 seconds from the start of the turn for category c, d and e aircraft and..4 a 180° turn in the opposite direction to intercept the inbound track.
Question 216-21 : Which of the following options states the correct frequency band, propagation path and frequency range for an ndb ?
Lf and mf, surface waves, 190 khz to 1750 khz.
Learning objective 062.02.02.01.05 state that the ndb operates in the lf and mf frequency bands...learning objective 062.02.02.01.06 state that the frequency band assigned to aeronautical ndbs according to icao annex 10 is 190 1750 khz...learning objective 062.01.03.04.02 state that radio waves in lf, mf and hf propagate as surface/ground waves and sky waves..this question involves knowledge of all the above learning objectives. there is not much more to explain, except that ndbs are only properly usable when they travel as surface waves radio waves which cling to the surface of the earth.. this is because the direction of the incoming beam matters to their accuracy by their very nature, and is much less accurate if it has been 'reflected' off the ionosphere. it is for this reason that there is a 'night effect', when the sky waves reflect much more from the ionosphere and return to the aircraft, interfering with the surface waves to cause difficulty in measurements.
Question 216-22 : A pilot of an aircraft flying in the daytime at fl80 on heading 030° m is instructed by atc to route directly towards an ndb. the adf is already tuned to this ndb and identified correctly, with a qdm of 340° m and about 8 nm away. upon banking left to start a turn, the indication on the rmi rapidly ?
Dip error
Learning objective 062.02.02.05.03 explain that the bank angle of the aircraft causes a dip error..with the way that an adf antenna picks up the direction of the incoming signal, there can be quite a significant error brought into the reading simply by banking the aircraft. this is called dip error. when tracking ndbs in real life, dip error is actually quite large, and means that the adf needle is almost useless whilst in the turn. it is also very difficult to correct for accurately.
Question 216-23 : Ils approaches are divided into facility performance categories. which of the following statements relates to facility performance category ii ?
Guidance is provided from the coverage limit to the point at which the localiser course line intersects the ils glide path at a height of 15 m 50ft or less above the horizontal plane containing the threshold.
Refer to figure...learning objective 062.02.05.04.01 explain that ils approaches are divided into facility performance categories defined in icao annex 10....icao annex 10 sets out facility performance categories in order to set out the requirements for cat i, ii and iii approaches. there are therefore facility performance category i, ii and iii instrument landing systems...the differences between the three facility performance categories are numerous, everything from the accuracy down to the monitoring is defined for all three facility performance categories, with many more variables in between. in the end, that means that they can provide increasingly good guidance to aircraft as the category goes up, and the associated minima get lower. as you can see in the annex above, taken directly from icao annex 10, facility performance category i can give guidance down to a height of 100 ft or less, category ii down to 50 ft or less and category iii down to the runway with the aid of ancillary equipment...it is important to note that the facility performance categories do not use the same altitudes at the ils categories we use in normal operations. a facility performance category i ils system is capable of providing information for a cat i ils as it gives useful information down to 100ft, which is lower than the lowest minimums of a cat i ils at 200ft. this gives some safety margin in the system, which is always useful at such extremely low heights.
Question 216-24 : What causes the dip error in an adf ?
The tilted antenna whilst banking the aircraft.
Learning objective 062.02.02.05.03 explain that the bank angle of the aircraft causes a dip error.with the way that an adf antenna picks up the direction of the incoming signal, there can be quite a significant error brought into the reading simply by banking the aircraft. by doing this, the antenna is no longer level, so is now detecting a downwards component of the signal, which effects the reading in a similar way to tilting a compass. this is called dip error. when tracking ndbs in real life, dip error is actually quite large, and means that the adf needle far less accurate whilst in the turn. it is also a very difficult eerror to correct for accurately.
Question 216-25 : Which frequency band do dmes operate within ?
Ultra high frequency uhf 300 mhz to 3000 mhz
Refer to figure.. learning objective 062.02.04.01.01 state that dme operates in the uhf band.each frequency band is effectively a logarithmic band which begins at one frequency value, and ends at the frequency value 10x higher. they all begin with the number 3, and are of different orders of magnitude.dmes operate within uhf ultra high frequency , which is the band above the well known vhf frequency band. therefore, a good way of remembering the frequency bands is having vhf as a starter band, and we can say that a well known vhf frequency of 121.5 mhz is between 30 and 300 mhz, so therefore we can create the bands above and below that, and so on.there is an acronym to remember the order, using the first letters, very lovely maidens have very useful sewing equipment.
Question 216-26 : Given the following information, what is the true bearing from the ndb to the aircraft compass heading 348º. adf indication relative bearing indicator 317º. deviation 2º. variation 22ºw. the convergence is negligible ?
101º t
Refer to figure...first, we must calculate our true heading, then we can use our relative bearing to calculate our true bearing from the ndb sometimes called a qte...to calculate our true heading, we can use the saying 'cadbury's dairy milk very tasty' which is popular within british aviation schools. also an option is tv makes dumb children which is a reversal of the other saying. there is a universal method which can be used that applies to both directions. compass deviation magnetic variation true...to get our compass heading into a magnetic heading, we apply the deviation using the rhyme... deviation west, compass best. deviation east, compass least...we must also know that a positive value is easterly, and a negative value is westerly it can be given in either format , so in this case our compass heading is 2º more than our magnetic heading, so our magnetic heading is 348º 2º = 346º...now to get true heading, we apply variation to our magnetic value using the rhyme... variation west, magnetic best. variation east, magnetic least..we now know that our magnetic heading is 22º more than our true heading, so true heading = 346º 22º = 324º....with this in mind, we can apply the relative bearing to our true heading, which is simply a case of adding the two together...true heading + relative bearing = 324º + 317º = 641º which isn't possible, so subtract 360º > 281º..281º is therefore the true bearing from the aircraft to the ndb. we want to find the opposite direction to this, so we shall simply add or subtract 180º, giving us 101º true bearing from the ndb to the aircraft...note even though this does look like a gnav or fpl question, the feedback shows that it has been asked in rnav, and the rnav learning objectives include specific references to the topics, 062.02.02.02.02, 062.02.02.02.04 and 062.02.02.02.05. everything required for this question is in the rnav syllabus.
Question 216-27 : An aircraft equipped with a vhf radio is flying within radio range of two or more ground direction finding stations. which aircraft parameter can be determined in this scenario the aircraft's... ?
Position
Learning objective 062.02.01.02.03 explain that by using more than one ground station, the position of an aircraft can be determined and transmitted to the pilot....vdf vhf direction finding is a method of measuring the direction from which a vhf signal came. it has been used for many decades now, and is particularly useful as the transmitting aircraft only needs a standard vhf radio to ask for a vdf bearing from a suitably equipped atsu. this can give them... qdm magnetic bearing from the aircraft to the station.. qdr magnetic bearing from the station to the aircraft.. quj true bearing from the aircraft to the station.. qte true bearing from the station to the aircraft....with this information, the pilots can plot the location of their aircraft on a chart by drawing a true radial qte outbound from each station that was used. 2 stations and therefore 2 lines can be enough to calculate the position of an aircraft, by finding the point at which they intercept. this is a process known as triangulation. it is important to get a large angle at the point of interception, as the larger the angle optimum 90º , the better the precision of the fix. more than 2 vdf stations can also be used to get a more accurate fix...distress and diversion 121.5 mhz have access to an auto triangulation feature which gives them an immediate readout of the position of any calling aircraft, due to the reception of its transmission at multiple different locations with vdf capability...position is the only thing that can be gained from vhf direction finding though, so it is limited in that sense, but is very useful in the sense that only a vhf radio is required in the aircraft.
Question 216-28 : A cat i ils with a decision height of 240 ft is what type of approach ?
Type b, 3d approach
Icao annex 6, part ii.. 2.2.2.2.2 instrument approach operations shall be classified based on the designed lowest operating minima below which an approach operation shall only be continued with the required visual reference as follows a type a a minimum descent height or decision height at or above 75 m 250 ft andb type b a decision height below 75 m 250 ft. type b instrument approach operations are categorized as 1 category i cat i a decision height not lower than 60 m 200 ft and with either a visibility not less than 800 m or a runway visual range not less than 550 m 2 category ii cat ii a decision height lower than 60 m 200 ft but not lower than 30 m 100 ft and a runway visual range not less than 300 m. 3 category iii cat iii a decision height lower than 30 m 100 ft or no decision height and a runway visual range less than 300 m or no runway visual range limitations this is new from 2018, and categorises instrument approaches into type a or type b depending on their decision height or minimum descent height being above or below 250ft. as the approach in question is an ils, which has both horizontal and vertical guidance, it is therefore a 3 dimensional 3d approach, and its decision height is below 250 ft, so it is type b.note this question does cross over quite heavily with air law, but feedback shows that it is being asked in rnav exams.
Question 216-29 : Which of the following statements is true ?
With an a2a modulated wave you can hear the wave in adf mode.
Refer to figures.. the first annex above contains the 4 learning objectives which relate to this question.2 different types of ndb exist, and they are categorised by their radio wave modulation. the earlier type of ndb is called n0n a1a, and the newer type is n0n a2a. the only difference between the two is that a1a signals can not be identified unless the bfo beat frequency oscillator mode is used, whereas a2a signals can be identified aurally in standard adf mode as well. the reasons behind this are slightly too complex for the syllabus, and most modern adf panels use the bfo mode automatically when required anyway.
Question 216-30 : An aircraft is equipped with a dme receiver that can provide a read out of ground speed. it is climbing on a heading of 270° t , and is crossing the 330 radial from a vor/dme station. the ground speed calculated by the dme computer is... ?
Less than the actual ground speed because the change in slant range is smaller than the change in ground distance.
Refer to figure.. some dme receivers have a setting that will read out the aircraft's groundspeed when heading towards or away from the station, as well as an estimate of the time to the station. this is calculated by the dme receiver using the rate of change of the detected distance from the station. this means that flying anywhere other than directly to/from the station causes an unusable read out, as is the case in this question, where we are crossing the radials.another thing to consider is that dme systems calculate slant range from the aircraft to the station, so the dme groundspeed calculations are more accurate when this slant range closely resembles ground distance, so when at low altitude and far away from the dme within line of sight of course.in this question, our aircraft is crossing the 330 radial, and the slant distance is increasing a small amount, but by much less than our groundspeed, therefore, the groundspeed read out on our dme will be lower than our actual groundspeed.
Question 216-31 : A pilot has selected the appropriate ils frequency for the approach that they are currently established on. which of the following scenarios would cause a warning flag to appear on both the localiser loc and giide path gp indications ?
Absence of both carrier waves.
Learning objective 062.02.05.02.05 describe the circumstances in which warning flags will appear for both the loc and the gp absence of the carrier frequency absence of the modulation simultaneously the percentage modulation of the navigation signal reduced to 0....when on the approach, the sudden appearanc of both flags must mean a fault of some kind not just being out of range , so this must be down to one of the faults listed in the learning objective above. the easiest fault to remember is correct in this case, as the sudden absence of a carrier wave is certainly going to remove loc and gp indications and will therefore show warning flags...the other answers are wrong because... the difference in depth of modulation ddm is the way an ils tells you where you are in relation to the localiser centreline or the glide path, and a ddm of zero means being exactly on the loc or gp.. 'excessive loc or gp deviations' is vague, but even when at more than full scale deflection but within the coverage area , the indicators still show the direction we are off track/glidepath.. loss of ident transmission would not show flags on its own, but there might be a common error which causes both flags to show and the ident to stop transmitting, such as a total power loss, etc.
Question 216-32 : To avoid the inaccuracies that may be caused by coastal refraction, the pilot should attempt to take adf bearings when… ?
The aircraft is on the perpendicular to the coast which runs through the ndb.
Refer to figure.. learning objective 062.02.02.04.01 explain 'coastal refraction' as a radio wave travelling over land crosses the coast, the wave speeds up over water and the wave front bends.coastal refraction affects ndb/adf equipment due to the type of carrier wave that ndbs transmit. they transmit between 190 and 1750 khz, which is partly in the lf band and partly in the mf band. these waves travel as surface waves, which are massively affected by the surface they are travelling over. water is much smoother to travel over than land, so the waves are able to travel a bit faster.this creates a change in speed when ndb carrier waves go from land to sea, which can cause a process called refraction, meaning that the beam bends away from the perpendicular called the normal and therefore creates the image shown in the annex. this means that the carrier wave arrives at our aircraft from a slightly different direction than it should, and our adf therefore reads incorrectly.the best way to stop this is to place ndbs very close to the coast thereby reducing the error , or to take adf readings when the signal crosses the coast at a right angle perpendicular. the closer to the perpendicular, the less refraction will occur, and so is less affected by the coastal effect.
Question 216-33 : Which of the following options can be used for entry into a holding pattern based on a vor/dme fix ?
The dme arc defining the fix.
Note the feedback strongly suggests that this is a question asked in previous rnav exams, even though there are no learning objectives within the rnav syllabus that pertain to it...it is more of an air law question, and even then it is on the edge of learning objective 010.06.05.01.10...the good thing is that it is a very distinctive question that will be easy to remember for the exam....refer to figures...there are a few different places a holding pattern can be constructed, over ndbs, vors, over a vor/dme fix, or over an rnav waypoint not a conventional nav aid...the most complex of those is certainly the vor/dme fix...technically a hold can be placed on 2 intersecting radials, but they are extremely rare...in the 1st annex above stockholm arlanda overview of all holding patterns , there are all the different types of holds shown...starting from the top you can see hammar hmr vor, and there is a hold there with the inbound course of 191° and left turns and 1.5 minute legs usually 1 min legs are used, but this is a higher altitude hold...below this is the erken erk ndb hold, based directly on the ndb...to the far left of the chart is the tinka hold which is simply based on an rnav/rnp waypoint...the furthest south holding pattern nilug is a hybrid, it is an rnav waypoint but with a vor/dme fix given, so that it can be flown using conventional nav aids...this is what the question is asking about...there are 3 more of these on the chart, eltok, balvi and xilan....firstly, note that all these vor/dme holds all have inbound courses directly towards the vor, this is so the inbound course can always be tracked, which is a key requirement of any holding pattern technically they can also track directly away from the vor but i have never seen one published...in the case of the nilug hold, the pilot will fly inbound on the 007° to course radial 187 towards tebby teb vor, until reaching a dme distance of 44.2 nm, then begin the right hand turn and do the rest of the procedure using timings which is very normal , until established on the inbound course again, where tracking resumes until 44.2d, etc...they are easy enough to fly, if a little inaccurate due to being so far from the vor the difficulty arrives due to the fact that they can only be joined from particular directions...as can be seen in the annex above, they can only be joined using conventional nav aids from..a the vor radial..b the dme arc where specified or..c the entry radial to a vor/dme fix at the end of the outbound leg, as published...by far the most common way and easiest is by the vor radial, but that is not one of the available options, so we have to say the dme arc defining the fix in this case 44.2 nm...see the 2nd annex for a view of the dme arc for this example.
Question 216-34 : What causes 'mountain effect' and what type of navigational aid does it affect ?
It is caused by diffraction and affects ndbs.
Learning objective 062.02.02.05.01 ndb section describe diffraction of radio waves in mountainous terrain mountain effect...because ndbs produce lf and mf radio waves, which travel primarily as surface ground waves for the purposes of directional navigation as is required for ndbs , the ground that is being travelled over matters a lot. water is flat, for instance, so surface waves travel over water faster and much further than a similar strength wave travelling over rolling hills, built up areas, and worst, mountainous terrain. basically, the more obstacles and rougher the terrain, the worse the ndb signals travel...this is most prominent in mountainous terrain as the radio waves try and follow the contours of the ground, which means going over the peaks and into the valleys. the largest problem with this is a phenomenon known as diffraction, where the wave gets scattered slightly as it crests each mountain and tries to go down the other side...reflection of the waves also could be an issue, but does not affect ndb directions received by aircraft as much as the relative diffraction of mountains.
Question 216-35 : You are established on an ils approach at 4 nm on the dme and get some signal interference. what could be the reason for this ?
Multipath interference from reflections off objects within the published coverage area.
Learning objective 062.02.05.04.08 explain that multipath interference is caused by reflections from objects within the ils coverage area...we can be sure that the aircraft is within the coverage area in this question, as it is fully established on the ils approach at 4 nm it is most likely to be descending on the glide path as well as on the localiser. this leaves only one answer available, as none of the other options happens when within the correct coverage area of the ils...reflections of the ils signals off objects can hit the aircraft at certain stages of the approach, altering the difference in depth of modulation between the 90 hz and the 150 hz lobes, and can cause a false movement of the ils needles, which in turn can affect the autopilot if one is engaged.
Question 216-36 : You are flying on radial 227° inbound to a vor. the wind is from 270° and the wind correction angle is 3°. the magnetic variation is 10°w. the obs should be set to 1 and magnetic heading should be 2 . ?
1 047° 2 044°
If we are flying inbound on the 227° radial then our track has to be the opposite, 047°. 047° is therefore what we also want to set as our obs course, as we want the needle to indicate in the correct sense as we track to the vor. the wind in this scenario is coming from 270° it does not matter whether true or magnetic , which is a partial tailwind blowing across from the left. this means that we have to turn left by our wind correction angle 3° to track 047°. this gives us a heading of 044° to fly.all our bearings and tracks are in magnetic, as this is what is used by vors, and the wind does not matter, as 10° different would still make the wind a tailwind/crosswind from the left.
Question 216-37 : A doppler vor provides usable signals up to what distance from the station and is intended for which type of traffic ?
Up to 200 nm from dvor for en route ifr traffic.
Learning objective 062.02.03.01.04 state that the following types of vor are in operation conventional vor cvor a first generation vor station emitting signals by means of a rotating antenna doppler vor dvor a second generation vor station emitting signals by means of a combination of fixed antennas utilising the doppler principle en route vor for use by ifr traffic terminal vor tvor a station with a shorter range used as part of the approach and departure structure at major aerodromes test vor vot a vor station emitting a signal to test vor indicators in an aircraft..as stated in the learning objective above, dvors are powerful enough to be used by en route ifr aircraft for reliable navigation. by looking in the enr section of an aip, the useful ranges of the vors can be seen, and the maximum is 200 nm distance and 50 000 ft altitude.
Question 216-38 : When tuned in to an ndb, when is dip error most likely to occur ?
When turning towards the ndb.
Learning objective 062.02.02.05.03 explain that the bank angle of the aircraft causes a dip error...dip error is an inaccurate reading of the bearing information when the aircraft is banked. this is because the adf system that receives and interprets ndb signals was designed to work when in horizontal flight. when a turn is initiated, the indicated bearing is modified. the needle will cause an error towards the direction of whichever wing is banked down.
Question 216-39 : When holding at an ndb, you are approaching the beacon on the inbound leg. how will you know when to initiate the turn ?
The head of the needle will be pointing to the fix and the needle will turn 180° when passed it.
Refer to figure..a holding pattern requires an aircraft to fly towards the holding fix on a certain inbound track, and when the aircraft reaches the fix vor, ndb, or a vor/dme fix , the pilots should begin a 180º turn right is standard but left turns can be used. upon the end of this turn, or passing abeam the beacon, the pilot will then fly a timed leg on the opposite track plus any wind correction to the inbound leg now called the outbound leg , then turn back onto the inbound leg to start the process again. this forms the familiar racetrack pattern.an ndb simply produces a signal of particular frequency, and the adf receiver in our aircraft picks this up, and tells us from where it came. this is very simple, and means we can follow an adf needle all the way to the beacon, when it will then become very sensitive, and go from pointing ahead of the aircraft to pointing behind it, as per the location of the ndb.this is different from a vor, which we would track inbound via a cdi course deviation indicator which flicks from to to from upon passing the beacon, and also has a cone of confusion.
Question 216-40 : You are flying the inbound course of an ndb holding pattern in an area of local thunderstorm activity. what might the adf indicate ?
The needle will point towards the thunderstorm.
Note we require further feedback about this question from the exam...in particular, we belive two of the answers are partly correct...the needle would point towards the thunderstorm very often, but would also act erratically, however it shouldn't matter whether it is night or day the night effect is to do with other ndbs which are usually out of range during the day , the effect should be the same, which makes us want to discount that erratic option....learning objective 062.02.02.05.02 state that static radiation energy from a cumulonimbus cloud may interfere with the radio wave and influence the adf bearing indication....thunderstorms can have very powerful discharges of static electricity across much of the electromagnetic spectrum including in low frequency lf and medium frequency mf...these discharges cause the most severe errors in adf receivers...a static discharge in a cumulonimbus cloud cb can be heard as a loud crackle on the audio and the needle will move rapidly to the source of the cb...if there are several active thunderstorms in the area the needle might point to them for a longer period...as thunderstorms are incredibly powerful, the electromagnetic waves they give off can easily overpower that of an ndb, especially if it is only a low power locator beacon.
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