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Question 171-1 : The lines on the earth's surface that join points of equal magnetic variation are called ? [ Practice protocol ]

Isogonals

Admin . 1425.isogonic lines connect positions that have the same variation .agonic line a line which joins all points where the value of magnetic variation is zero exemple 271 Isogonals.

Question 171-2 : An aircraft departing a n40°00' e080°00' flies a constant true track of 270° at a ground speed of 120 kt what are the coordinates of the position reached in 6 hours ?

N40°00' e064°20'

Admin .6h x 120 kt = 720 nm .720 cos mean latitude = 720 / cos40° = 940.940 / 60 = 15 66 15°39' .from longitude e080°00' flying west e080°00' 15°39' = e64°21' exemple 275 N40°00' e064°20'.

Question 171-3 : A nautical mile is equivalent to ?

1852 m

exemple 279 1852 m.

Question 171-4 : An aircraft flies the following rhumb line tracks and distances from position 04°00'n 030°00'w 600 nm south then 600 nm east then 600 nm north then 600 nm west the final position of the aircraft is ?

04°00'n 029°58'w

Admin .the aircraft flies 600 nm 600/60 = 10° south from position 04°00'n 030°00'w .it is now at 06°00's 030°00'w .the aircraft flies 600 nm east from position 06°00's 030°00'w .it is now at 10°/cos6 around 10°03' east at 06°00's 019°57'w .the aircraft flies 600 nm north from position 06°00's 019°57'w .it is now 10° north at 04°00'n 019°57'w .the aircraft flies 600 nm west from position 04°00'n 019°57'w .it is now at 10°/cos4 around 10°01' west at 04°00'n 029°58'w exemple 283 04°00'n 029°58'w

Question 171-5 : What is the final position after the following rhumb line tracks and distances have been followed from position 60°00'n 030°00'w south for 3600 nm east for 3600 nm north for 3600 nm west for 3600 nm the final position of the aircraft is ?

60°00'n 090°00'w

Admin .the aircraft flies 3600 nm 3600/60 = 60° south from position 60°00'n 030°00'w .it is now at 00°00'n/s 030°00'w .the aircraft flies 3600 nm east from position 00°00'n/s 030°00'w .it is now at 60°/cos0 around 60° east at 00°00'n/s 030°00'e .the aircraft flies 3600 nm north from position 00°00'n/s 030°00'e .it is now 60° north at 60°00'n 030°00'e .the aircraft flies 3600 nm west from position 60°00'n 030°00'e .it is now at 60°/cos 60 around 120° west at 60°00'n 090°00'w exemple 287 60°00'n 090°00'w.

Question 171-6 : Complete the following statement regarding magnetic variation the charted values of magnetic variation on earth normally change annually due to ?

Magnetic pole movement causing numerical values at all locations to increase or decrease

exemple 291 Magnetic pole movement causing numerical values at all locations to increase or decrease.

Question 171-7 : In which two months of the year is the difference between the transit of the apparent sun and mean sun across the greenwich meridian the greatest ?

February and november

Admin .apparent solar time or true solar time is given by the daily apparent motion of the true or observed sun it is based on the apparent solar day which is the interval between two successive returns of the sun to the local meridian .mean solar time conceptually is the hour angle of the fictitious mean sun the duration of daylight varies during the year the length of a mean solar day is nearly constant unlike that of an apparent solar day . true solar time duration is between 23 h 59 min 39 s et 24 h 0 min 30 s .because many of these long or short days occur in succession the difference builds up so that mean time is greater than apparent time by about 16 minutes in february and mean time is less than apparent time by about 16 minutes in november . 2474.the difference between the transit of the apparent sun and mean sun across the greenwich meridian is the greatest in february and november exemple 295 February and november.

Question 171-8 : What is the highest latitude listed below at which the sun will reach an altitude of 90° above the horizon at some time during the year ?

23°

Admin .the axis of the earth is tilted 23 5° degrees from 'vertical' this causes the northern hemisphere to be tilted toward the sun during half the year and tilted away from the sun the other half of the year . 2475.the sun is vertical perpendicular to the surface or as states an altitude of 90° above the horizon at 23 5°s and 23 5°n for solstices exemple 299 23°.

Question 171-9 : Assuming mid latitudes 40° to 50°n/s at which time of year is the relationship between the length of day and night as well as the rate of change of declination of the sun changing at the greatest rate ?

Spring equinox and autumn equinox

Admin . 2476.the length of daylight/night at a given latitude varies with the declination of the sun and the greatest rate of change of declination is when the sun is crossing the equator at the spring and autumn equinox the rate of change of the length of daylight will therefore be greatest when the rate of change of declination is greatest exemple 303 Spring equinox and autumn equinox.

Question 171-10 : At what approximate date is the earth closest to the sun perihelion ?

Beginning of january

Admin . 2477 exemple 307 Beginning of january.

Question 171-11 : At what approximate date is the earth furthest from the sun aphelion ?

Beginning of july

Admin . 2477.the aphelion is the point in the orbit of a planet or comet where it is farthest from the sun exemple 311 Beginning of july.

Question 171-12 : An aircraft at position 60°n 005°w tracks 090° t for 315 km on completion of the flight the longitude will be ?

000°40'e

Admin .315 km = 170 nm.170 / cos 60 = 340'.340' = 5° 40'.60°n 005°w 5° 40' = 60°n 000°40'e exemple 315 000°40'e.

Question 171-13 : The 'departure' between positions 60°n 160°e and 60°n 'x' is 900 nm what is the longitude of 'x' ?

170°w

Admin .distance = change in longitude x cos latitude.900 nm = change in longitude x cos 60.therefore .change in longitude = 900 / 0 5.change in longitude = 1800'.1800' / 60' = 30°.if position 'x' is west 160°e 30° = 130° .if position 'x' is east 160°e + 30° = 170°w exemple 319 170°w.

Question 171-14 : An aircraft at latitude 02°20'n tracks 180° t for 685 km on completion of the flight the latitude will be ?

03°50's

Admin .on a meridian 1° = 60 nm .we are heading south .685 km / 1 852 = 370 nm.370 / 60 = 6 16°.0 16° x 60 = 10' exactly 9 6 min .02°20'n 6°10' = 03°50's . 2478 exemple 323 03°50's.

Question 171-15 : An aircraft at latitude 10° south flies north at a gs of 890 km/h what will its latitude be after 1 5h ?

02°00'n

Admin .1° of longitude = 60 nm.ground speed is 890 km/h or 890 /1 852 = 480 kt .480 x 1 5h = 720 nm travelled .720/60 = 12°.you are 10° south of the equator you are travelling north you will reach the equator after 10° you are now in northern hemisphere and you travel another 2° to arrive at 02°00'n exemple 327 02°00'n.

Question 171-16 : An aircraft at latitude 10°north flies south at a groundspeed of 445 km/h what will be its latitude after 3 h ?

02°00's

Admin .1° of longitude = 60 nm.ground speed is 445 km/h or 445 /1 852 = 240 kt .240 x 3h = 720 nm travelled .720/60 = 12°.you are 10° north of the equator you are travelling south you will reach the equator after 10° you are now in southern hemisphere and you travel another 2° to arrive at 02°00's exemple 331 02°00's.

Question 171-17 : An aircraft is flying in the shortest possible way between point 1 and 2 and between point 2 and 3 .point 1 60°n 30°w.point 2 60°n 20°w.point 3 60°n 10°w.the track change when passing point 2 will be approximately ?

9°

Admin .the aircraft follows a great circle track which is on the polar side of the rhumb line track .givry correction = 1/2 x 10° x sin60° = 4 33.east track .depart point 1 on heading 090° 4 33 = 85 67°.at halfway between point 1 and point 2 85 67 + 4 33 = 090°.arriving point 2 on heading 90° + 4 33 = 94 33° .crossing point 2 on course to point 3 we perform the same heading change when we have left point 1 .the track change when passing point 2 will be approximately 94 33° 85 67 = 8 66° minus 9° changes . 1418 exemple 335 -9°.

Question 171-18 : At the magnetic equator when accelerating after take off on heading west a direct reading pivot suspended compass ?

Indicates the correct heading

Admin .magnetic dip is the angle between the horizontal and vertical forces acting on a compass needle toward the nearer pole . 1430.a direct reading compass has a pivoted magnet that is free to aligne itself with the horizontal component of the earth's magnetic field . 1945.the compass is pendulous and symmetrical and will sit level if there is no magnetic field or if the field is horizontal with no vertical component of the earth's magnetic force as on the magnetic equator .in fact the pendulosity helps to counteract the effect of dip trying to keep the compass card level .but because the cg is under the pivot point accelerating makes the bulk of the compass lag behind the machine and displace the cg aft of the pivot point if you were just going north or south all you would get is extra dip but if you are going east or west the north bit of the compass is pointing to the side of the aircraft and the displaced cg not being vertically in line with the pivot point ges towards north to create a couple that makes the compass turn clockwise to read less than 90° during the turn a deceleration has the opposite effect . acceleration errors are maximum on eat/west headings and near the magnetic poles and nil on north/south headings and at the equator .a mnemonic for the effect of acceleration error is the word ' ands ' acceleration north deceleration south .acceleration causes an indication toward north deceleration causes an indication toward south exemple 339 Indicates the correct heading.

Question 171-19 : The circumference of the parallel of latitude at 60°n is approximately ?

10 800 nm

Admin .360° x 60 nm x cos 60 = 10 800 nm exemple 343 10 800 nm.

Question 171-20 : Given .position 'a' n60 w020 position 'b' n60 w021 position 'c' n59 w020 .what are respectively the distances from a to b and from a to c ?

30 nm and 60 nm

Admin .at the equator 1° = 60 nm .from a to b = 1° change of longitude .distance in nm for 1° change of longitude = 1° x 60 nm x cos latitude .distance in nm for 1° change of longitude = 1° x 60 nm x cos60° = 30 nm .from a to c = 1° change of latitude .distance in nm for 1° change of latitude = 1° x 60 nm = 60 nm exemple 347 30 nm and 60 nm.

Question 171-21 : The coordinates of the heliport at issy les moulineaux are n48°50' e002°16 5' .what are the coordinates of the position directly on the opposite side of the earth ?

S48°50' w177°43 5'

Admin .on the opposite side of the earth the latitude will be the same of our position but south .on the opposite side of the earth the longitude must be west 180° 002°16 5' = 177° 43 5' .if you want to check use the funny tool tunnel to other side of the earth exemple 351 S48°50' w177°43.5'.

Question 171-22 : Isogonals are lines of equal ?

Magnetic variation

Admin . 1425.isogonic lines connect positions that have the same variation .agonic line a line which joins all points where the value of magnetic variation is zero exemple 355 Magnetic variation.

Question 171-23 : At a specific location the value of magnetic variation ?

Varies slowly over time

exemple 359 Varies slowly over time.

Question 171-24 : Parallels of latitude except the equator are ?

Rhumb lines

exemple 363 Rhumb lines.

Question 171-25 : Given .a is n55° 000°.b is n54° e010°.the average true course of the great circle is 100° .the true course of the rhumbline at point a is ?

100°

Admin .they specificaly state 'the average true course' . 2479.loxodrome track rhumb line true course between 2 points will be the same as the average great circle track orthodrome between those 2 points exemple 367 100°.

Question 171-26 : Given .position 'a' is n00° e100° position 'b' is 240° t 200 nm from 'a' .what is the position of 'b' ?

S01°40' e097°07'

Admin .on a bearing of 240°t from a to b it means the b will be south of a south of the equator and to the west of 100°e longitude less than 100°e .only one answer satisfies this exemple 371 S01°40' e097°07'.

Question 171-27 : The angle between magnetic north and compass north is called ?

Compass deviation

Admin .learn the composition of this table . 1438 exemple 375 Compass deviation.

Question 171-28 : The north and south magnetic poles are the only positions on the earth's surface where ?

A freely suspended compass needle would stand vertical

Admin . 2031.diagrammatic representation of the earth's magnetic field illustrating how field lines represented by arrows intersect the earth's surface and how inclination angle the angle formed between the field lines and the earth varies with latitude at the magnetic equator the curving line across the earth field lines are parallel to the earth's surface the field lines become progressively steeper as one travels north toward the magnetic pole where the field lines are directed straight down into the earth and the inclination angle is 90° . 1430.the force acting on the compass needle is directly proportional to the horizontal.component of the earth's field and inversely proportional to the vertical component of the earth's .at the magnetic poles the earth's magnetic field is perpendicular to the earth's surface magnetic dip is 90° at the magnetic poles a dip needle stands vertical exemple 379 A freely suspended compass needle would stand vertical.

Question 171-29 : Value for the flattening of the earth is 1/298 earth's semi major axis as measured at the equator equals 6378 4 km .what is the semi minor axis km of the earth at the axis of the poles ?

6356 9

Admin . 2062.ratio of ellipticity e = a b /a = 1/298.6378 4 6378 4 / 298 = 6356 99 km exemple 383 6356.9

Question 171-30 : Morning civil twilight begins when ?

The centre of the sun is 6° below the celestial horizon

Admin .morning civil twilight is the period in the morning from the centre of the sun is 6° below the horizon until the upper limb of the sun appears at the horizon exemple 387 The centre of the sun is 6° below the celestial horizon.

Question 171-31 : How many small circles can be drawn between any two points on a sphere ?

An unlimited number

exemple 391 An unlimited number.

Question 171-32 : An aircraft is following the 45°n parallel of latitude the track followed is a ?

Rhumb line

exemple 395 Rhumb line.

Question 171-33 : A rhumb line on a direct mercator chart appears as a ?

Straight line

Admin .on a direct mercator chart meridians are parallel equally spaced vertical straight lines. 2054.rhumb lines or loxodromes are tracks of constant true course exemple 399 Straight line.

Question 171-34 : A great circle on the earth running from the north pole to the south pole is called ?

A meridian

exemple 403 A meridian.

Question 171-35 : If you are flying along a parallel of latitude you are flying ?

A rhumb line track

exemple 407 A rhumb line track.

Question 171-36 : What is the rhumb line distance between two positions on latitude 60°n that are separated by 10° of longitude ?

300 nm

Admin .10° x 60 nm x cos 60 = 300 nm exemple 411 300 nm.

Question 171-37 : What is the length of one degree of longitude at latitude 60° south ?

30 nm

Admin .1° = 60 nm on the equator.1° = 60 nm x cos of latitude.1° = 60 nm x cos 60 = 30 nm exemple 415 30 nm.

Question 171-38 : The initial great circle track from a to b is 080° and the rhumb line track is 083° what is the initial great circle track from b to a and in which hemisphere are the two positions located ?

266° and in the northern hemisphere

Admin .we can only be in northern hemisphere if great circle track is smaller than rhumb line track for easterly tracks . 1462.conversion angle is 3° 083° 080° it is half of convergency thus convergency is 6° .our great circle track at b will be 086° .initial great circle track from b will be 086°+180° = 266° exemple 419 266° and in the northern hemisphere.

Question 171-39 : The great circle track measured at a 45°00'n 010°00'w from a to b 45°00'n 019°00'w is approximately ?

273°

Conversion angle = 1/2 g sin mean latitude.where g = change of longitude = 10°w to 19°w = 9°.1/2 x 9° x sin 45° = 3 18°.we are going west so rhumb line is 270° and the great circle track at a 270° + 3° = 273° .how to find if we have to add or retract the conversion angle correction . 1462.it's very simple look at the shape of a great circle track in north and south hemisphere exemple 423 273°.

Question 171-40 : When the time is 2000 utc it is ?

1400 lmt at 90° west

Admin .lmt local mean time .you must check all the answers .0800 lmt at the prime meridian wrong 20h00 gmt at prime meridian = 20h00 lmt at prime meridian .2400 lmt at 120° west wrong 120° 4 minutes per degree 120 x 4 = 480 minutes 8h .20h00 gmt at prime meridian going west so minus 8h it is 12h00 lmt at 120° west .1200 lmt at 60° east wrong 60° 4 minutes per degree 60 x 4 = 240 minutes 4h .20h00 gmt at prime meridian going east so plus 4h it is 24h00 lmt at 60° east .1400 lmt at 90° west correct 90° 4 minutes per degree 90 x 4 = 360 minute 6h s .20h00 gmt at prime meridian going west so minus 6h it is 14h00 lmt at 90° west exemple 427 1400 lmt at 90° west.


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