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Question 172-1 : The distance along a meridian between 63°55'n and 13°47's is ? [ Practice protocol ]

4662 nm

.1° of longitude = 1 minute = 60 nm.63°55' + 13°47' = 77°42' .77° x 60 + 42 nm = 4662 nm exemple 272 4662 nm.

Question 172-2 : In which occasions does the rhumb line track and the great circle track coincide on the surface of the earth ?

On tracks directly north south and on east west tracks along the equator

exemple 276 On tracks directly north - south and on east - west tracks along the equator.

Question 172-3 : In the northern hemisphere the rhumb line track from position a to b is 230° the covergency is 6° and the difference in longitude is 10° what is the initial rhumb line track from b to a ?

050°

The rhumb line track from a to b is 230° so the rhumb line from b to a is the opposite 050° 230 180 ..convergency and difference in longitude are useful for great circle calculation only ..remember .rhumb lines or loxodromes are tracks of constant true course .great circle is the shortest distance between two points exemple 280 050°

Question 172-4 : How many degrees has the mean sun moved along the celestial equator in 8 hours and 8 minutes ?

122°

.the earth moves around the sun at a rate of 4 minutes per degree of longitude 15°/h .8h x 15° = 120°.8 minutes = 2°.120° + 2° = 122° exemple 284 122°.

Question 172-5 : The great circle bearing of position b from position a in the northern hemisphere is 040° if the conversion angle is 4° what is the great circle bearing of a from b ?

228°

.the reciprocal of 40° is 220° and that is measured at a .for the track from b to a measured at b .convergency between a and b = 8°.great cricle track at b > great cricle track at a.great cricle track at b = great cricle track at a + convergency.great cricle track at b = 040° + 8°.great cricle track at b = 048°.reciprocal of 048° = 228° exemple 288 228°.

Question 172-6 : When flying on a westerly great circle track in the southern hemisphere you will ?

Experience an increase in the value of true track

Admin .it's very simple first look at the shape of a great circle track in north and south hemisphere and at the equator . 2051.now take an example based on our question . 2049.when flying on a westerly great circle track in the southern hemisphere you will experience an increase in the value of true track exemple 292 Experience an increase in the value of true track.

Question 172-7 : When the time is 1400 lmt at 90° west it is ?

1200 lmt at 120° west

Admin .you must check all the answers .1400 lmt at 90° east wrong it can not be the same lmt for different longitudes .1000 lmt at 60° west wrong 30° between 90° west and 60° west 4 minutes per degree 30 x 4 = 120 minutes .14h00 at 90°west going east so plus 2h it is 14h00 lmt at 60° west .0600 lmt at the prime meridian wrong 90° between 90° west and greenwich meridian 4 minutes per degree 90 x 4 = 360 minutes .14h00 at 90°west going east so plus 6h at greenwich meridian it is 08h00 lmt .1200 lmt at 120° west correct 30° between 120° west and 90° west 4 minutes per degree 30 x 4 = 120 minutes .14h00 at 90°west going west so minus 2h it is 12h00 lmt at 120° west exemple 296 1200 lmt at 120° west.

Question 172-8 : Which of the following alternatives is correct when you cross the international date line ?

The date will increase if you are crossing on a westerly heading

Admin .the aircraft is flying on a westerly heading of 270° . 2042.the international date line idl is an imaginary line on the surface of the earth that runs from the north to the south pole and demarcates one calendar day from the next it passes through the middle of the pacific ocean roughly following the 180° longitude but it deviates to pass around some territories and island groups .the international date line is on the opposite side of the earth to the prime meridian greenwich meridian the prime meridian helps to define universal time and is the meridian from which all other time zones are calculated time zones to the east of the prime meridian are in advance of utc up to utc+14 time zones to the west are behind utc to utc 12 exemple 300 The date will increase if you are crossing on a westerly heading.

Question 172-9 : The local hour angle of the mean sun at 1200 lmt is ?

000°

Admin .in astronomy the hour angle is one of the coordinates used in the equatorial coordinate system for describing the position of a point on the celestial sphere the hour angle of a point is the angle between the half plane determined by the earth's axis and the zenith half of the meridian plane and the half plane determined by the earth's axis and the given point the angle is taken with minus sign if the point is eastward of the meridian plane and with the plus sign if the point is westward of the meridian plane .the hour angle is usually expressed in time units with 24 hours corresponding to 360 degrees .the hour angle of a point on the earth's surface is the angle through which the earth would turn to bring the meridian of the point directly under the sun the earth is rotating so this angular displacement represents time .so in observing the sun from earth the solar hour angle is an expression of time expressed in angular measurement most usually degrees from the solar noon .at solar noon at the observer's longitude on earth the hour angle is 0 000 degrees with the time before solar noon expressed as negative degrees and the local time after solar noon expressed as positive degrees .the hour angle is the angular displacement of the sun east or west of the local meridian due to rotation of the earth on its axis at 15° per hour with morning being negative and afternoon being positive .for example at 10 30 am the hour angle is 22 5° 15° per hour times 1 5 hours before noon exemple 304 000°.

Question 172-10 : Location a is at 50°n 030°w and location b is at 50°s 030°w on 27th november it is noted that ?

Sunrise will be later at a than it is at b and sunset will be earlier at a than it is at b

.in winter the northern hemisphere is tilted away from the sun at this time the sun is not directly above us days will be shorter and nights longer . /com en/com061 552 jpg.in southern hemisphere this is summer and in northern hemisphere sunrise will be later and sunset will be earlier exemple 308 Sunrise will be later at a than it is at b and sunset will be earlier at a than it is at b.

Question 172-11 : An aircraft is flying a great circle track between waypoints number 4 45°00'n 040°00'w and number 5 45°00'n 030°00'w .on arrival over waypoint number 5 compared to the true track at waypoint number 4 the true track has ?

Increased by less than 10°

.the aircraft is flying a great circle track which is on the pole side of the rhumb line 45°n . /com en/com061 555 jpg.from 040°w to 030°w rhumb line is 090° true track at waypoint number 4 is less than 090° .at 035°w we are at our highest latitude and at a true track of 090° .our true track to reach waypoint number 5 is now more than 090° our true track has increased exemple 312 Increased by less than 10°.

Question 172-12 : Given .variation is 6°w isogonic lines jan 2002 .average annual increase 10' .calculate variation in 2005 ?

6 5°w

.variation 6°w in 2002 increasing 10 minutes per year .2002 to 2005 = 3 years it is an increase of 30 minutes .6° + 30' = 6°30'w 6 5°w in 2005 exemple 316 6.5°w.

Question 172-13 : Position a = 56°00 0's 163°57 2'e .position b = 56°00 0's 171°47 4'w .for the route from a to b the ?

Great circle direction at b is 080 7°

. /com en/com061 565 jpg.great circle direction at b = 090° conversion angle 1/2 g sin lm .g change of longitude approximatively 24° .lm = mean latitude 56° .great circle direction at b = 090° 1/2 x 24° x sin56° .great circle direction at b = 080° .rhumb line distance from a to b = change of longitude x cos lat.rhumb line distance from a to b = 24 x 60 x cos 56°.rhumb line distance from a to b = 1440 x 0 559 = 805 nm exemple 320 Great circle direction at b is 080.7°.

Question 172-14 : Position a = 30°00 0'n 175°23 2'w .position b = 30°00 0'n 173°48 1'e .for the route from a to b the ?

Rhumb line distance is 578 nm

. /com en/com061 566 jpg.great circle direction at a = 270° + conversion angle 1/2 g sin lm .great circle direction at b = 270° + conversion angle 1/2 g sin lm .g change of longitude approximatively 11° .lm = mean latitude 30° .conversion angle = 1/2 x 11° x sin30°.conversion angle = 2 75° 3° .great circle direction at a = 270° + 3° = 273°.great circle direction at b = 270° 3° = 267°.rhumb line distance from a to b = change of longitude x cos lat.rhumb line distance from a to b = 11 x 60 x cos 30°.rhumb line distance from a to b = 660 x 0 866 = 572 nm close to 578 nm exemple 324 Rhumb line distance is 578 nm.

Question 172-15 : The first law of kepler states ?

Planets move in elliptic orbits with the sun in one of the foci

exemple 328 Planets move in elliptic orbits with the sun in one of the foci.

Question 172-16 : What is meant by 'aphelion' ?

The point of the earth's orbit furthest away from the sun

Admin . 2477.the aphelion is the point in the orbit of a planet or comet where it is farthest from the sun exemple 332 The point of the earth's orbit furthest away from the sun.

Question 172-17 : Which statement about meridians is correct ?

A meridian and its anti meridian form a complete great circle

exemple 336 A meridian and its anti-meridian form a complete great circle.

Question 172-18 : A rhumb line from a position 86°n 30°w has an initial track of 085°t is it ?

A spiral to the north pole

. /com en/com061 664 jpg.when following a rhumb line track you fly via a spiral to the north or south pole except for track 000° 090° 180° and 270° exemple 340 A spiral to the north pole.

Question 172-19 : A great circle track crosses the equator at 30°w has an initial track of 035°t it's highest or lowest north/south point is ?

55°n 060°e

.a great circle divides earth in two equal hemispheres .the equator is a great circle meridians of longitude that cross over the north and south poles are also great circles .on this picture great circles are in black purple equator and yellow meridians . /com en/com061 611 jpg.our great circle intersects the equator in 030°w with a great circle direction of 035° t his antipodal location on the equator will be 030° w 180° = 150° e .our airplane will reach his highest latitude at halfway 030° w 090° = 060° e .we are climbing on a north track we are in northen hemisphere only one answer remains possible exemple 344 55°n 060°e.

Question 172-20 : The latitude of the tropic of capricorn is ?

23 5°s

exemple 348 23,5°s.

Question 172-21 : Which statement is true ?

The declination of the sun and the latitude of the observer will affect the duration of civil twilight

exemple 352 The declination of the sun and the latitude of the observer will affect the duration of civil twilight.

Question 172-22 : At 00h00 local mean time of an observer ?

The mean sun is in transit with the observer's anti meridian

.local mean time is solar time as measured by the position of the mean sun with respect to an observer's local meridian local mean time differs continuously with the observer's longitude and is not standardized over a time zone however a day as measured by local mean time does not vary in length throughout the year it is always 24 hours and at midnight 00h00 it will be on the observer's anti meridian exemple 356 The mean sun is in transit with the observer's anti-meridian.

Question 172-23 : Kepler's second law states that ?

The radius vector sun earth sweeps out equal areas in equal time

Admin .kepler's second law states an imaginary line joining a planet and the sun sweeps out an equal area of space in equal amounts of time .the animation below depicts the elliptical orbit of a planet about the sun . 2040.the dot pattern shows that as the planet is closest the sun the planet is moving fastest and as the planet is farthest from the sun it is moving slowest nonetheless the imaginary line joining the center of the planet to the center of the sun sweeps out the same amount of area in each equal interval of time . 2041 exemple 360 The radius vector sun-earth sweeps out equal areas in equal time.

Question 172-24 : Consider the positions 00°n/s 000°e/w and 00°n/s 180°e/w on the ellipsoid which statement about the distances between these positions is correct ?

The route via the north pole is shorter than the route along the equator

.since earth shape is an ellipsoid the distance from position a 00°n/s 000°e/w to b 00°n/s 180°e/w both located on the equator will be shorter via the poles . /com en/com061 587 jpg. exemple 364 The route via the north pole is shorter than the route along the equator.

Question 172-25 : The sr/ss sunrise/sunset table for the 23rd of february at latitude 40°n gives .sr = 06 44.ss = 17 44.at 12 00 central european time utc+1 at 40°n ?

The sun rises at 64°w

.sr and ss are given in utc so we need to know first the central european time in utc .when it is 11 00 utc it's 12 00 local time in central europe utc+1 ..now in central europe the sun rises at 06h44 utc so 4h and 16 minutes later at 11 00utc where does the sun is rising .answer we must be near the north american and canadian border close to the coast ..4h and 16 minutes = 256 minutes..what is the speed of the trace of the sunrise on the ground ..1440 minutes per day 24h per day 360° to cover for a complete turn of the sun around the earth so 1440/360 = 4 minutes par degree..256/4 = 64°..when it is 11 00 utc the sun rises at 64° west of our position exemple 368 The sun rises at 64°w.

Question 172-26 : An aircraft follows a great circle in the northern hemisphere at a certain moment the aircraft is in the position on the great circle where the great circle direction is 270° t continuing on the great circle the ?

Track angle will decrease and the latitude will decrease

. /com en/com061 594 jpg.following a great circle track in the northern hemisphere your heading will decrease track angle will decrease and the latitude will decrease too exemple 372 Track angle will decrease and the latitude will decrease.

Question 172-27 : On an oblate spheroid representing the earth's shape ?

1 minute of arc along the equator measures a greater distance than 1 minute of arc along the meridian at a latitude of 45°n/s

Admin .the earth is a tad wider than it is tall giving it a slight bulge at the equator this shape is known as an ellipsoid the diameter from the north pole to the south pole the shortest diameter is approximately 6860 nm and the equatorial diameter the longest diameter is approximately 6883 nm .the polar circumference is 21554 nm each minute of arc being equal to 0 998 nm .the equatorial circumference is 21626 nm each minute of arc being equal to 1 001 nm exemple 376 1 minute of arc along the equator measures a greater distance than 1 minute of arc along the meridian at a latitude of 45°n/s.

Question 172-28 : Given .a 56°n 145°e .b 57°n 165°w .what is the difference in longitude between a and b ?

050°

.we only want to know the difference in longitude between a and b is 50° not the distance between a and b so latitudes are irrelevant .from a longitude to reach the anti meridian 180°e/w we have 35° of longitude and then to reach b longitude we have 15° of longitude .35° + 15° = 50° exemple 380 050°.

Question 172-29 : What is the duration of morning civil twilight at 66°48'n 095°26'w on 27th of january . 2480 ?

01h 13m

Admin . 1809.at 67°n on january 26th the duration of morning civil twilight is 1h34 min .we are looking for january 27th .you can continue to interpolate with january 28th but if you look at the sunrise difference time between 26th and 28th at 66°n you gain 11 minutes now for the morning civil twilight between 26th and 28th at 66°n you gain 7 minutes .so for january 27 th 1h33 minutes sounds good exemple 384 01h 13m.

Question 172-30 : The gmt of morning civil twilight at 66°48'n 095°26'w on 27th of january is . err a 061 605 ?

1436 gmt

.the answers are all in gmt so take the time from the annex and adjust for longitude at 15°/h .95°26' / 15 = 6h 22min .as the location is west of the prime meridian the answer must be later in the day reference to gmt .0814 + 6 hrs 22 = 1436 gmt . notice 0814 is calculated by interpolation exemple 388 1436 gmt.

Question 172-31 : The gmt of sunrise at 66°48'n 095°26'w on 27th of january is . err a 061 606 ?

1549 gmt

.sunrise at 66°48'n 095°26'w on 27th of january . /com en/com061 606 jpg..interpolation between 26th and 29th january . difference at 68n is 13 minutes for 4 days so for one day is 3 25 minutes . difference at 66n is 11 minutes for 4 days so for one day is 2 75 minutes .we are looking for 66°48'n 3 minutes is a good deal .09h39 66°n to 9h45 68°n on january 26th at 66°48' it will be 09h32 and 09h49 on january 27th ..now convert local mean time lmt at longitude 095°26'w .95 4° x 4 minutes = 381 6 minutes.381 6 minutes = 6 36 hours = 6 h 22 minutes .09h49 + 6h42 = 15h51 utc exemple 392 1549 gmt

Question 172-32 : The latitude of the tropic of cancer is ?

23 5°n

exemple 396 23,5°n.

Question 172-33 : Position a is 31°00's 176°17'w .rhumb line track t from a to b is 270° .initial great circle track t from a to b is 266 2° .the approximate position of b is ?

31°00's 168°58'e

Admin .difference between the great circle track and rhumb line track is conversion angle .conversion angle = 270° 266 2° = 3 8°.1/2g sin 31° = 3 8°.g change of longitude.1/2g = 3 8° / sin 31°.1/2g = 7 38°.g = 14 76°..176°17'w + 14 76° or 14°45' = 168°58'est exemple 400 (31°00's, 168°58'e)

Question 172-34 : An aircraft departs from schiphol airport and flies to santa cruz in bolivia south america via miami in florida .the departure time off blocks is 07h45 st utc + 1 at the 10th of november taxi time before take off at schiphol is 25 minutes the flight time to miami over the atlantic ocean is 09h40m ?

21h05 10th nov

Cmarzocchini .i only did 06h45 utc off blocks + 00h45 + 09h40 + 00h45 + 02h40 + 06h30 = 26h05 .in santa cruz bolivia utc +5 so 26h05 5h = 21h05 same day exemple 404 21h05 10th nov.

Question 172-35 : Two places on the parallel of 47°s lie 757 8 km apart calculate the difference in longitude ?

10°00'

.first convert km in nm .757 8 km / 1 852 = 409 nm..distance = change of longitude x cos of latitude.409 nm = change of longitude x cos 47°.change of longitude = 409 / cos 47° = 600 minutes.600 / 60 min per degree = 10° exemple 408 10°00'.

Question 172-36 : In a sunrise/sunset table given for the 28th of june at a certain latitude sunrise is gven as 0239 and sunset is given as 2127 .what is the latitude ?

60°n

Admin .it must be in the northern hemisphere because it's summer and 28th of june it's quite a long period of daylight but at 80 degrees north you have mid summer night this is where the sun never goes below the horizon i think that's why the answer is 60 degrees north . .absolutly we are close to the longest day during summer time in the northern hemisphere .furthermore above 66 5°n in summer it is permanent daylight exemple 412 60°n.

Question 172-37 : On the earth's ellipsoid one degree of latitude near the equator is ?

Less than 60 nm

.at the equator one degree of latitude = 110 57 km or 59 7 nm .at 50°n or 50°s one degree of latitude = 111 23 km or 60 05 nm .at the poles one degree of latitude = 111 69 km or 60 3 nm .the geoid is an ellipsoidal form so a degree of latitude centered on the equator is not the same length as one degree of longitude along the equator the difference is small enough to ignore for many applications exemple 416 Less than 60 nm.

Question 172-38 : With an increase in magnetic latitude there will be a decrease in the ?

Directive force

.the directive force is the horizontal component of the earth's magnetic field the horizontal component of the earth's magnetic field is stronger at magnetic equator and very weak at the magnetic poles .thus if you are heading to the magnetic poles your latitude is increasing there will be a decrease in the directive force exemple 420 Directive force.

Question 172-39 : Which statement about the duration of daylight is true ?

Close to the equinoxes the influence of latitude on the duration of daylight is at its smallest

exemple 424 Close to the equinoxes the influence of latitude on the duration of daylight is at its smallest.

Question 172-40 : Which figure in the appendix represents the geocentric latitude of position p which is situated above the surface of the ellipsoid . err a 061 662 ?

Figure b

.geocentric latitude is measured from the centre of the ellipsoid geodetic or geographic latitude which is what is normally measured is the angle between the plane of the equator and the line which is normal to the ellipsoid at the point of interest unlike geocentric latitude this line does not typically pass through the centre of the ellipsoid whenever the unqualified term latitude is used it will normally mean the geographic latitude . /com en/com061 662 jpg.on the wgs84 ellipsoid the length of a degree of latitude increases from 110 574 km at the equator to 111 694 km at the poles geographic and geocentric latitudes can differ by as much as 12 minutes of arc an amount equivalent to a distance of more than 30 km on the ground exemple 428 Figure b.


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