Calculation of Sunrise and Sunset Inflight

[lion-g]

Hi all,

Out of curiousity, any of you guys have a rule of thumb regarding calculation of sunrise or sunset timing inflight ?

The usual way of us doing it is by trial and error, based on the LAT and LONG along our flight path and cross reference to the sunrise and sunset tables provided.

Another way which works along the equator is to plot 2 straight lines, 1 line being the takeoff time and landing time and the other being the sunrise/sunset time at departure airport and destination airport, both on the same graph. The point where the 2 lines intercept is where the sun will rise/set.

From my understanding, as we travels up north or down south, the relationship ceases to be linear anymore. Do correct me if I am wrong.

Any better ways of doing the calculation?

Thanks for sharing,

Cheers,
lion-g

[pilotdude]

try:
Compute Sunrise, Sunset & Twilight For Cities & Airports Worldwide With Local TZ

For USA:
Complete Sun and Moon Data for One Day

[Alpine Flyer]

Sorry I can't explain the formulae, but there is a free Palm OS program called SunFly that does the calculations.

[Intruder]

I look outside and estimate when the big, bright ball disappears/re-appears from view at the horizon...

[Checkboard]

Ask one of the FAs to bring up a paper once a passenger is finished with it, and read it there.

[captjns]

Ask one of the FAs to bring up a paper once a passenger is finished with it, and read it there.

But what happens if it was yesterday's paper?

[tocamak]

The usual way of us doing it is by trial and error, based on the LAT and LONG along our flight path and cross reference to the sunrise and sunset tables provided

This sounds familiar although an iterative process sounds better whereby you estimate the position at sunrise/set and then calculate the predicted time before then refinining your postion according to the time so found (i.e trial and error!). My own experience was a bit easier as the moving platform was doing maximum 15kts but basically we used Nautical Almanac figures in the above process so as to be ready for star sights. Correction for altitude was not a factor.

[munster]

i was working as a flying spanner last year in the middle east. during ramadan it was hilarious to see the passengers suffer waiting for sunset as we departed flying west, prolonging their agony...

[lion-g]

Thanks for all the interesting comments

Well, I would like to estimate the sunrise time in flight, say I departed out of middlle east midnight and arriving South east asia in noon. Those poor FA will need the guessimated time to serve those who are going to fast. Just in case they miss the dinner, otherwise they got to wait till sunset before they can eat.

Any more pointers?

Cheers

[Pugilistic Animus]

There's also the Air Almanac

I like Old Smokey's method

[lion-g]

Old smokey method?

Care to elaborate ?

Thanks

[JAR]

Sunrise/sunset tables for major cities in the en-route supplement carried on flight deck?

[ChristiaanJ]

Now THAT must have been "fun" on Concorde flying West from LHR or CDG on the evening take-offs.

Take-off just after sunset.
All the sheiks on board heave a sigh of relief.
But, no... the sun comes up again in the West.
Cries of dismay.
"Purser, purser !"
"Yes, Sir ?"
"How long will this last ?"
"Until we're in New York, Sir..."

[sycamore]

I would have most company Ops/Planning people ought to be able to tell you for your flight plan.Most GPSs will also tell you for a selected `position ` en-route(ie user w/pt). The `Air Almanac `will also give you corrections for height.....good little task for co-pilots who are bored on long trips... anothe is `how far has a fan blade tip travelled on this leg ?`

[Pugilistic Animus]

Night = Dark
Day = Light

the OS method

[FLEXPWR]

Lion-g,

Do you mean calculating the actual time the sun rises/sets at your flight level, or the sunrise/sunset time on the ground you fly over at this point in time?

Flex

[lion-g]

The more accurate answer would be the sunrise time at our Flight Level along our flight path. But of course, if I am able to get the time on the ground for sunrise, we can deduce a pretty accurate guessimate.

The reason being some of our pax are fasting and they need to know the time so that they can either start or end their fast.

Cheers

[Intruder]

I would not attempt to provide an allegedly "correct" time for religious purposes. I have no idea what their definition of "sunset" might be! I might:

Tell them the published time of sunset at the takeoff point.
Tell them the published time of sunset at the landing point.
Tell them "It appears the sun has set" when/if that happens airborne.

[FLEXPWR]

Well, it's been a few years since I worked that one out, I'll try to remember...

We'll have to make a few assumptions in regards to where the sun stands at the time you see it rising or setting: using the formula for line-of-sight range (eg. range of a VOR, VHF...) and making the correction from a known sunrise/sunset table.

1- If you fly at, let's say FL300, that would be 1.23x(sqrt of 30000)= 213 NM. This means the sun would rise about 213NM away from your present position.

2- The earth day being 24 hours, we have 360/24=15. So 15 degrees an hour is our rotation speed, so 1 degree equals 4 minutes.

3- Next, you correct your line-of-sight distance for latitude, to obtain degrees/minutes of longitude, so if you fly along the 45N parallel for example, you apply 213NM / (cos 45)=213/0.707= 301. Attention, the 301 value is no more a distance, but is the number of minutes of angle at your present latitude (since 1 NM equals 1 minute of angle of a great circle, corrected by the cosine of latitude).

4- You then convert the result in degrees, then in minutes of time: 301 minutes of angle equals 301/60= 5 degrees. Since there is 4 minutes of time for every degree, you get 5x4=20.

The end result is 20 minutes. So the sun will rise 20 minutes earlier and set 20 minutes later at you position than what it's showing on the almanach (Jeppesen for example). Any latitude less than 30 north or south, you can disregard the Cosine correction, as the numbers change very little (cosine 30 is roughly 91%).

I have tried this method a number of times years ago when flying cargo for DHL, it works quite ok, max error I ever got was about one minute. Of course it is easier if you fly a northbound or southbound track, because you don't have to calculate the estimated position of the aircraft in regards to longitude, but with GPS nowadays, you can easily estimate any position you choose along your route.

I hope this is what you were looking for, anyhow, comments and corrections are welcome.

Flex

[Pugilistic Animus]

FLEXPWR you sound like you've had some navigator training!