Datum line and time

[Olendirk]

Hey!

I have one questions and it would be very kind if somebody could explain them to me:

1.Under which circumstances does the date of the landing lay ahead of the date of takeoff?

one example for the given answers: flight from east to west takeoff short after midnight etc...

There are several of those questions but I think I didnt understand the relation between the datum line and the passage of the sun. how can i find solutions for questions like this above?

thanks for your help!

od

[Pole Hill]

I assume that your studying gen nav theory.

The trick here is to always make sure that you pass through the Greenwich meridian, for example when working out Local times and Standard times. You will see that it becomes obvious when the date has changed from the calculated time. For example, if you calculate the time to be 26:00, then it is 02:00 the following day.
Hope this helps.
POL.

[Olendirk]

hmm, yeah, i mean i have noc clue how it works.Im always in situation of the meridian 180 where the datum is located so i make different scenarios. could you answer the question above and explain me why you choose this answer?

Would be so nice!

OD

[Pole Hill]

Olendirk,
To describe it properly, I'd need to sit down with you and draw some diagrams... The method that I described previously is the way to perform calculations without worrying about how the date line works.
I suggest that you talk to your groundschool provider.
Good luck with your exams
POL

[BobC]

posted 11th June 2004 21:19
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Olendirk

POL is right - always do the math "going via Greenwich (GMT).

The following illustrative problems may help?

Depart Japan 1000 Japan Standard Time (JST) on 12 November. Flight time to Hawaii is 8 hours 40 min. What is the arrival time in Hawaii Standard Time (HST)

To indicate the date and time together, let's write the departure as 12/1000 JST

The first step is to convert your departure time to GMT. From Air Almanac STANDARD TIMES listings, to convert JST to GMT subtract 9 hours. So:

Departure time = 12/1000 JST minus 9 = 12/0100 GMT

Now add the flight time to get the arrival time in GMT:

Arrival time = 12/0100 GMT plus 8:40 = 12/0940 GMT

Lastly, convert GMT to HST which, from the Air Almanac listings, requires you to subtract 10 hours, so:

Arrival time = 12/0940 GMT minus 10:00 = 11/2340 HST


Now let's consider a flight in the opposite direction, leaving Hawaii at 2200 HST on 12 November bound for Japan with a flight time of 9 hr 30 min. What is the arrival time in Japan in JST?

Again, convert the departure time to GMT, this time by adding 10 hours:

Departure time = 12/2200 plus 10 = 12/3200 = 13/0800 GMT

Now add flight time to get the arrival time in GMT:

Arrival time = 13/0800 plus 9:30 = 13/1730 GMT

Now convert the GMT arrival time to JST by adding 9 hours:

Arrival time = 13/1730 plus 9:00 = 13/2630 = 14/0230 JST

[Send Clowns]

My teaching is always to calculate flight times UTC (as you will when you fly). Convert the take-off time to UTC. Add the flight time to find the landing time, UTC. Convert this to whichever time reference is required by the question. That way the relative positions of the take off and landing become irrelevant.

Send Clowns
Gen Nav, BCFT