Longest commercial flight from Singapore to New York - questions

[diddy1234]

Hi All

I stumbled across a video on Youtube of the longest commercial flight (non stop) from Singapore to New York and was amazed but also had a couple of questions

Video SQ22: From Singapore to New York - Longest NONSTOP commercial passenger flight with Airbus A340-500 - YouTube

Warning it is 1 hour and 46 mins long and the aircraft doesn't take off until 46 mins into the video.

Very impressive what with the duration of 18 hours, flight route and shear amount of logistics involved (like fuel and food and drink).
A couple of questions though.

1.When flying over the north pole, is it dangerous to fly at 36,000 feet as the air is less dense at the poles ?
Don't aircraft normally descend in height to play it safe ?

2. how many crew must have been on the aircraft for 18 hours ?

[taxistaxing]

I'm fresh from ATPL met so can answer '1' :ok:.

As you climb from sea level the air cools at roughly 2 degrees/1000 feet until you reach the tropopause, the layer of the atmosphere that seperates the troposphere from the stratosphere. Above this point the temperature remains roughly constant until you reach a vast altitude.

As the air at the poles is colder (and therefore denser) than at the equator, the polar tropopause is lower (and warmer) than at the equator - typically around 30,000 feet and -45 degrees, whereas the average height/temp over the whole planet would be around 36,000 feet and -56.5 degrees. At the equator it can be as high as 50,000 feet with temperatures as low as -75 degrees.

Makes sense if you think about it. The height of the tropopuase is governed by the density (and therefore temperature) of the air beneath it, which is far higher over the equatorial regions than over the polar regions.

Therefore it actually makes no difference what height you fly at once you go above 30,000 feet over the poles, the temperature will be a constant --45 degrees and density (which is proportional to temperature) will therefore also be constant.

[DaveReidUK]

how many crew must have been on the aircraft for 18 hours ?

All of them, I would expect. :O

[treadigraph]

I've noticed the return flight on FR24 a couple of times when it's routed over Croydon for whatever reason... And I thought "Jeez, they've already been airborne for six or seven hours and they are only a third of the way there..."

[Mr Mac]

I have done that route once west bound in A340 which has only business class seats, and we came up over Northern Europe not the Pole. Its a long,long way and very boring if you can not sleep (I did and it was still tyring), and you have already seen all the films you wanted to see on Kris. Had to do it that once and would not do it again by choice. Flying to Far East tonight from Man with EK but rather than Heathrow and non stop, I prefer doing DXB two step as it breaks journey up a bit. I think ULH can just be that bit too far 12-13hrs ok north of that I need a dam good reason or no choice. Also should point out that I am spoilt as all my long haul is in Business which makes life a lot more comfortable;).