How far can a pilot see?

ScouseMouse

I have a feeling you are going to laugh at me, but gonna ask anyway.

Looking up at the sky this morning, its was clear and fresh. I saw a jet, up high, and it made me curious. I used my flightradar24 AR app on my phone and it told me it was a United Airlines flight from Newark to Frankfurt at 40 thousand feet.

So. It just made me wonder, if I can see it in the sky, how far could the pilot see from up there. I originally thought he could be over Liverpool or somewhere, and could probably see Germany, but then I realised, he could be over Europe already. I live in Tallaght and he was in the sky over towards Dublin (but far beyond, if that makes any sense)

Anyone got any ideas. I know its probably mad technical, but anyone know a rough idea. I dont need any mad science triganometry formulae.

Thanks all.

Citizen2011

When looking up at a jet he's covering 1 mile every eight seconds. Your first sighting of him he will be about 30 miles away and within 4 minutes he's over your head. A jet at 40,000 feet coming from Europe over Dublin would be able to see the Irish West Coast on a clear day.

Comhrá

I'm not a pilot but I'd guess someone in an aircraft at 40,000 ft. with excellent visibility could see something in excess of two hundred miles in every direction, in other words they could see four hundred miles+ from one side of the horizon to the opposite side.

I'm open to correction here but that's my guess

Milan Cobian

On a clear night overhead the English midlands, I have seen London, Cork, Dublin, Belfast and Glasgow all visible at the same time.

shedweller

Milan Cobian wrote: »

On a clear night overhead the English midlands, I have seen London, Cork, Dublin, Belfast and Glasgow all visible at the same time.

You're not Chris Hadfield by any chance??!!

Lapin

Milan Cobian wrote: »

On a clear night overhead the English midlands, I have seen London, Cork, Dublin, Belfast and Glasgow all visible at the same time.

Did the plane have wing mirrors ?

ScouseMouse

Citizen2011 wrote: »

When looking up at a jet he's covering 1 mile every eight seconds. Your first sighting of him he will be about 30 miles away and within 4 minutes he's over your head. A jet at 40,000 feet coming from Europe over Dublin would be able to see the Irish West Coast on a clear day.

If my first sighting of him is 30 miles away, then flying away from me, he would be disappearing at 30 miles also. So, does this mean he would have been mid irish sea when he disappears from view. Or is it he would disappear due to my eyesight?

If I see a plane disappear into the horizon from Dublin, would he be over Liverpool, Sheffield or even Holland?

Is there an easy way to work this out. Just curious.

amen

When travelling over a sphere or any curved surface the distance to the horizon changes with altitude.

At 10,000m the distance to the horizon is about 357Km so a pilot can see objects that are 357Km either side of him and that are level with the Earths surface.

If the object to viewed is above the earths surface say a mountain that is 1000m then it gets a bit more complicated but you could see that even if it is beyond the 357km horizon distance.

If you were on the moon then at 10,000m the distance to the horizon would be 186Km which although a shorter distance covers more of the moons sphere.

coylemj

shedweller wrote: »

You're not Chris Hadfield by any chance??!!

Since you ask, this was tweeted by him this evening.

It's looking west from above the English midlands, you can see (starting in the lower left) North Devon, the Bristol Channel, Wales, the IOM and Ireland.

Notice the glare from the Shannon estuary, Lough Derg and Galway Bay.....

smurfjed

I would have thought that the formula for radio range would also work for this, as it is pretty much line of sight, so if i remember correctly, its 1,23 times the square root of the difference in altitude. So for 40,000 feet it should be about 246 miles.

smurfjed

Amirani

You can calculate this by drawing a vertical line and two tangential lines to the Earth to form a triangle. Then use Pythagoras' theorom to calculate the length of the tangent that forms the hypotenuse.

Dr.Rieux

NiallSparky wrote: »

You can calculate this by drawing a vertical line and two tangential lines to the Earth to form a triangle. Then use Pythagoras' theorom to calculate the length of the tangent that forms the hypotenuse.

Except the earth is curved so no right angle

lomb

smurfjed wrote: »

I would have thought that the formula for radio range would also work for this, as it is pretty much line of sight, so if i remember correctly, its 1,23 times the square root of the difference in altitude. So for 40,000 feet it should be about 246 miles.

smurfjed

Yes or another formula is square roots of (1.5xheight in feet)= distance in nautical miles. 1 nm =1.85 km. Same answer as your way

Amirani

Dr.Rieux wrote: »

Except the earth is curved so no right angle

Zirconia

Distance to horizon

At a height h above the ground, the distance to the horizon d, is given by:

d = sqrt(2*R*h/b)

b=0.8279 is a factor that accounts for atmospheric refraction and depends on the atmospheric temperature lapse rate, which is taken to be standard. R is the radius of the earth. Note that the earth is assumed smooth- likely only true over the oceans!

For h in feet and d in nm:

d =1.17*sqrt(h)

i.e. from 40000 feet, the horizon is 234nm away = 269 statute miles giving a diameter of vision of 538 miles.

amen

hmm using my way I get 394Km or 246 miles.

Of course this is in perfect conditions, no atmospheric distortion etc and doesn't allow for refraction.

Except the earth is curved so no right angle

Tangent :-)

If my first sighting of him is 30 miles away

This may not be true. If he is cruising at 40,000ft, its a clear day and there is no object between you and him such as a mountain then it maybe possible to see him at the horizon distance which could be close ~250 miles. Of course thats in perfect conditions and assuming you can resolve him. Most likely you will see him several degrees (if not 10s) above the horizon thus making him closer. It should be possible though to see him at 100 miles maybe more. On a nice clear evening in the west its possible to see planes for several minutes from the time they appear on one horizon until they disappear on the other.

Flier

This is all getting very technical!
I can see the bottom line of the snellen chart. That's good enough for me.:p

eatmyshorts

I recently exited the NAT's just west of Galway on a gin clear moonlit night at around 1am. Could see the lights of Limerick, Galway, Cork, Dublin, Belfast, Glasgow, Liverpool, Manchester, Birmingham and just about make out the glow of London.
We routed right overhead the DUB VOR and could easily pick out the Cock Tavern on Swords Main St, where a few of my friends were at that moment sitting having a few pints! Gave me an awful thirst!