NavList:

Hi Folks

Love this forum but little time to read and reply – at 71 yr I am still full time employed – why – I cannot sit still!!

Thought I might chip in with something really interesting – and where those of you who are more cognisant with the true sea mariner’s sextant of old knowledge.

I am reading numerous books on polar and Antarctic exploration  - exploration – and am 3/4s way through The Lonely Sea and the Sky – Sir Francis Chichester and his flights around the world in Tiger Moth – sort of like using a bicycle to cross the poles – anyway I read this because someone on this forum wanted to see if he could navigate in an aircraft with a mariner’s sextant – and 3/4s the way through this the answer is a definite [yes] – provisionally – sounds like hedging your bets – he did – he became a very smart amateur pilot and refined the aeronautical art of DR Navigation – “Dead reckoning” or whatever – I as an Air Force Navigator of 4000 hrs know exactly what that is in the air ( and it isn’t much different on the ground ( exploring unknown continents, Artic or Antarctic ice/land) – however, in an aircraft things are changing quickly.

In an aircraft travelling at 60 knots – every hour you have gone 60 nms – and with a 5 knot wind from due port or starboard you will be left or right of track 5 nms in 1 hr.

Translate that to navigating from the tip of the north Island of New Zealand to Norfolk Island about 766 kms ( 413 nms) – at 60 knots = 6.88 hrs and get your drift wrong say 5 knots left or right 34 nms left or right of destination – try and find Norfolk Island by DR then.

[By the way folks I have done exactly that trip in a Dakota as a final check flight on my final Navigation training flight.]

Sir Francis used a marine sextant to get sun shots – and I have read his book and without those shots being accurate he would not have found Norfolk Island.

Can we in general use a marine sextant as such, in an aircraft – NO – he was wave hopping – i.e. a few hundred feet above the sea – ALWAYS FLYINY VISUAL FLIGHT RULES ( very very different from night and instruments flying) and the other bit of info absolutely essential for this type of flying is wind direction and speed ( or drift) and at that height you can get very accurate wind directions and wind speed off the sea appearance. Useless at altitude ( except drift isn’t i.e. shove a drift sight out the side of the aircraft – and if you can see the sea at 10000, 15000 ft you can get drift = just as good – useless at night EXCEPT some big atolls could be seen from 30000 ft in an Orion)

And I once navigated a bristol freighter from Hobart to Invercargill ( 917 nms) at around 5000 using only the drift sight – it was 10/10ths clagg!!) – we didn’t hit any mountains but we were worried as no beacons, radar or anything to help – drift sight and wind off sea estimate.

So – could Sir Chichester do it – yep – and he was very skilled at it and was employed in WWII to teach fighters roaming the European war continent to do mental DR to know where they are. His techniques are still used.

DR was used by bomber command but in general was very inaccurate for getting you over a particular city for a bombing run – there was no time for Astro notwithstanding holding straight and level for 10 mins for Astro ( night fighters usually got those aircraft doing that).

So let us get back to the reason for this post – polar exploration.

I am reading "Empire of Ice and Stone" The Disastrous and heroic voyage of the Karluk – to the point – the became locked in ice in 1913/1914 when winter came early. The drift huge distances and seldom saw land – though maps were basic then.

My point was the writer Buddy Levy writes that their position was roughly known ( and whilst reading this as a navigator) I wondered was it not possible to get moon/sun/star (at dawn/dusk) position lines – very little was said about ‘knowing their position) but would not a marine sextant still be useful to give position lines relatively accurately?

But then suddenly in the book after the Karluk became crushed and the crew and scientists had to camp on the ice – which was constantly moving west ( and sometimes east) – they had been on the ice for months and the captain sends a team on a sledge to look for land that he estimated to be due south ( Herald or Wrangel Islands) – “the Captain hands Mamen a sextant and an artificial horizon ( a gyroscopic instrument designed to give an artificial horizon) to help them locate Wrangel or Herald Island” !!!!!!!!!!!!

Hey what – an artificial horizon was on board – hmmm – well that is news to me notwithstanding the pure fact that using a sextant is a skilled job not just suddenly given you when someone hands you a sextant – Mamen was a ring in crew member but not experienced but was a big strapping Nordic fellow that had become a confident and trusted crew member but not a word on being shown how to use a sextant let alone an artificial horizon out on the ice etc.

Big big questions folks – if someone can elucidate facts from the information given on how accurate COULD they have plotted their position – but from a aeronautical perspective – with an artificial horizon – still only able to shoot day shots and dawn and dusk but with long long long twilight periods I would be confident of an accuracy of 5 nms plus.

Regards HHG