Where a Twotter goes even ...
 

Hercules fear to tread ....

https://www.washingtonpost.com/news/...evening&wpmm=1

Flight aware track of one of the two ...

Impressive! But I notice that the aircraft does not seem to have moved a lot over the past day... duty time limitations perhaps? Or have they moved too far South for them to be tracked?

They are showing as in Costa Rica so definitely not too far south. I don't see why Flight Aware wouldn't be able to track them to Rothera. Only one will continue from there and the NSF's site says the earliest it could arrive is the 19th. I wonder if they are waiting for better weather, although it would seem worthwhile to head down to Chile first?

I think the KBA crews know how to do this flight in the safest, quickest way!

I've just spent a tough but enjoyable hour three layers deep in articles on the science. Again, I'll mention Smoot's book, 'Wrinkles in time'. As a page turner, it beats Geoffrey Archer.


Back to this link.


Just lots and lots of gutsy people doing science these days.

How do they manage the low fuel temps? A bit hard for a Twotter to descend to a lower level and increase mach number!

Ahem,

I'd bet a beer that a DHC7 could do it and with some 2.5 times the payload of a DHC6

Apparently the fuel is preheated before loading - one reason for choosing the Twotter over the Hercules, 2500 lbs to heat instead of 60000.

The Twotter can carry a cabin auxiliary tank, which of course is not exposed to the cold until needed. (but I presume Herky-Birds have that option also).

They'll need the reserve tank just for the outbound leg, so there must be refueling capacity at the Polar base - and that fuel can be preheated also before the return.

The DHC-6 is an impressive aircraft in many ways. A friend ferried one back from a remote field in Alaska years ago which required a single engine take-off. Not sure many twins would be capable of that but with that large vertical tail and keeping it light, it was apparently quite easy.

I don't get it...
Winter flights to NZ's Scott Base in Antarctica under way | Stuff.co.nz

Scott Base is right next to the US base at McMurdo. Its a Costal location, likely with relatively warmer weather than the South Pole base.

I think not.........

South Pole is 9,300ft above sea level, and does not have a runway - the only aircraft that operate into there are Twin Otters on skis, and Air National Guard LC-130 (ski-fitted Hercules). The LC130s operate off over 10,000ft of groomed snow (that is maintained through the short summer operating season). The Twin Otter obviously needs much less skiway.
As far as I know, the LC-130 has a minimum temperature for take-off and landing of -50C (hydraulic system limitation?). Twin Otter, with simpler systems, has been operated down to -60C. (Would have to dig out my books to check the official limit).
Year round average surface temperature at South Pole is -49C, and can get into the minus 80s. At this time of year, the average temperature is between -55 and -62C. The operating window for routine operation of the LC 130s to Pole is early November to late February. (Today looks like a warmish day there for the time of year, -51C, 1600m in blowing snow)

The flight from Rothera (British base at 67S on the Antarctic Peninsula) to Pole is about 1300nm, approximately 10 hours in a ski-fitted Twotter. Ferry tanks in the back, PNR approximately half way, nowhere else possible to land. Almost the whole route in complete darkness, including the landing on a skiway with no proper lighting. Although there have now been 3 landings at Pole during the winter, two were early or late when there was still a bit of light in the sky. I believe only one was in total darkness - this one is going to be pretty close to mid-winter.


(2500 hrs ski Twin Otter inc 5 landings at South Pole, 2000 hrs DHC7)

Any news on when they will depart Costa Rica?

AC560 can ;-)

Ant T, Hats off to you and those other bush pilots!

Yes hats off. Damned impressive.
Would seem (Very sensibly) this mid winter flight may be getting timed so as not to occur in the dark. Coordinated with a full moon that last for weeks!
https://blogs.crikey.com.au/planetal...not-done-dark/

Another nice thing about the Twotter is its performance at the other end of the limits, if a donkey quits when is is very hot and high - no worries, it still has some climb left.
Marvellous machine with very few vices other than the noisiest office in the business.

Had a Twotter one day en-route PLH/LHR with a full load, one engine disintegrated resulting in a "Mayday" and a dirty dive in to RAF Odiham.

Roo,

I'd pay scant attention to Sandilands' articles. He purports to be an Antarctic aviation expert journalist because he went there as a passenger in a herc some 37 years ago. He might know more than the standard journo, but that does not an expert make.

Many of his articles are riddled with factual errors (including the one you linked above) and big noting to suit some agenda I cannot understand.

Fuel tanks are in the belly, not the wings. Unpressurised cabin. I'm guessing there might be a way to keep the ferry tanks warm enough via normal bleed air heating of the cabin and in turn keep the main tank fuel warm, either through circulating the fuel or ducting warm air around it?

No experience with Twotter winter ops myself, but one or two hours on type in a former life. Great machine.
Anyone with proper winter experience on the Twotter around who can share info?

I first started flying back in 01 when KBA made the initial polar rescue. After watching it on TV I knew I just had to fly for these guys and I eventually did. My years there were the best of my career so far and there are times like now when I wish I could go back.

Allow me to share what I know about their operation and this trip in particular.

The twin otter is the best aircraft for this task. The USAF C-130 is only capable of operating from a groomed skiway, whereas a ski equipped twotter can theoretically be put down anywhere. That being said I imagine the main reason is cost. With a C130 burning somewhere around 4,000 lbs of fuel an hour I can't begin to imagine how much it would cost to fill up at the most expensive gas station on the planet.

The twin will be flown with two internal ferry tanks providing an additional 5,000 lbs of fuel and yielding a total endurance of 10-12 hours. I say 10-12 because the fuel burn varied between 600-700 depending on the machine. The flight from Rothera to Pole is 1,300nm and travelling at 150kts on paper it will take 9 hours. However, the winds coming down from the polar plateau can be strong (50-100kts) and extend for hundreds of miles. I imagine the boys will probably put on an additional drum or two of granny gas if they can afford the room.

There are no cold weather limits for the Twin Otters at KBA. That being said the temperatures that they will be operating at are on the extreme end of what they normally deal with. The severe cold has a tendency to accelerate the failure of any aircraft components with an underlying weakness. Once you get below -40 and into the 50's it's important to baby the aircraft in all ways possible. The engines, battery, and avionics require special care of course. But so do the lesser items like the ski bungees, fuel caps, and door handles. Any of which can easily break without much effort at all.

On arrival, once the aircraft comes to a stop it will be immediately frozen in place. Normally, knocking the skis and twisting the throttles will be enough to wiggle yourself loose but at ferry weight she will most certainly need a tug from a tractor to break free. Another interesting phenomenon at these extremes is ski friction. Normally the weight of the ski on snow melts a small layer into water which allows you to slide along. But at these temperatures that doesn't always happen, especially at low speed like taxing. The friction of the snow now becomes similar to sand. As a result gaining any sort of momentum can be quite challenging. Thankfully they have 12,000ft of groomed skiway to play with.

They most likely won't be on the ground for long. Starboard engine will be kept running to power the tip tank fuel pumps and keep the battery above board. Some hot fuel, wx check, and load'em up. They'll have tailwinds for the return trip but it will be no less challenging. Fatigue will become a factor. As will enroute icing around the coast and the ever present possibility of the weather going down at Rothera.

Plenty of factors to account for on a mission like this. I wish them all the best!!

When does jet fuel need to be heated and if heated fuel is uploaded into the belly tanks, does it retain much of its heat cause its below the heated cabin floor?
Does the wing fuel in C130 really retain useful heat exposed to those temps and insulated with a wing skin?
Also wondering if there's an approach aid into the strip @ the South
Pole or just WAAS GPS. Navigating that far south must be tricky? Is it as simple as plugging in a waypoint?
Does anyone know what other unique prep both aircraft get prior to departure?
Do they spend their summers in Antarctica?
Bunch of questions but Im fascinated..................thanks

Didn't the evac of the Doctor in 2001-ish involve an overnight at SP Station? I didn't know they did the whole trip in one go. I did get brief on the C-141 airdrop that year.

Both the 2001 and the 2003 winter medevacs involved a rest period for the crew at the Pole. About 16 hours in 2001, and 12 hours in 2003. The planned rest of 10 hours in 2001 was extended due to weather concerns, and problems thawing out the aircraft and getting the skis unstuck.

Coincidentally, both medical cases involved gallstones (plus other complications).

Gallstones can be very painful and are very serious if the gall bladder bursts.

Any sign of the Twotters moving further south?

Having Ant T and Mr. North in this thread is pretty much the reason for the internet. Hats off.

Puts the "p" back in pprune, which is most welcome after any accident thread

Plus 1.

As an ex Herc /L100 pilot; a pleasure to read and will most certainly follow the progress
Good luck

Not without risk.
 

Three Canadians from Kenn Borek Air died in January 2013 during an Antarctic flight when their plane crashed into a steep slope on the Queen Alexandra mountain range.
The crew were flying from the Amundsen-Scott South Pole Station while delivering fuel for an Italian research team when the accident occurred.

The planes are in Punta Arenas, Peru, awaiting favorable weather to fly to the British Antarctic Survey Station at Rothera.

http://www.ctvnews.ca/canada/total-d...sion-1.2952179

Plus of course the unfortunate iceberg at the end of the runway incident....

Compressor Stall, do as you wish.

However I happily take Bens point that numerous media outlets are running with headlines such as
>'Total darkness': Calgary planes fly to South Pole for risky rescue <
whilst in reality the place is not actually in total darkness ATM. This is nicely demonstrated here:
The USAP Portal: Science and Support in Antarctica - South Pole Station Webcams or here: ESRL Global Monitoring Division - South Pole Observatory

Of course if the moon is obscured by a heavy overcast on the day it might be a different story.

Could the pilots (or at least one of them) wear night-vision goggles?

G-CPTN
AFAIK Twotters are not NVG configured, ie. the cockpit lighting would swamp the goggles sensors. Aside from law enforcement ac I'm not sure any civil aviation has NVG compatible cockpits.
Whilst doing spotter duties on CC130's we had to place tape over the emergency flashlight mounted on the wall (this was in the back, near the jump doors) as the tiny red charging indicator would cause issues with our NVG's.
Cheers from CYZX.

For anyone who might be interested, charts for Rothera, where the Twin Otters will be heading as soon as weather permits, from Punta Arenas (in Chile, Matelo, not Peru....)

https://www.bas.ac.uk/wp-content/upl...era_010113.pdf

The GNSS approach is new since I was last there, (2009).
The normal flying season starts in early October and runs to early March. I did two winter flights into Rothera, in the Dash 7, one after a fatality on the base, and the other for a person with a collapsed lung. Both were in August, when there were a few hours of daylight each day, but on the first one, we were lucky to get in, as the weather deteriorated significantly after we had passed PNR and we landed with about 2000m in blowing snow.

The 2013 KBA accident happened in the transantarctic mountains, which go up to almost 15,000'. The normal route between Rothera and Pole threads its way between King George Island and the peninsula, and then over fairly featureless plateau for most of the rest of the route.

Ref. the iceberg accident at Rothera in 1994 - that is a persistent hazard at Rothera, the deep water at both ends of the runway allows bergs to float past very close. When the sea is not frozen, they tend to move on fairly quickly, but some winters they can get caught in place, and make for some interesting approaches.

(Just noticed, the aerial photo of the runway on page 8 of the approach info linked above, shows a good example, with a couple of icebergs frozen into the sea on short final to RW 18)

Hmmm - most places in the Antarctic would seem to trump even Lukla as "interesting places to fly the Twotter". Be carefull out there.

Chile, Matelo, not Peru.


I saw Chile. Read Chile. Typed Peru. :mad:

Tks for the correction.:ok:

Over a relatively flat, monochrome white land, under a relatively uniformly black sky, where do NVGs come in? I suppose they would pick up the landing area quicker, but that would be all.

In my 45 years of airline flying. (Retired last Nov) I had the pleasure of flying with two Antarctic pilots. (L & N) this was before they went "south" I have to say they were both proberbly the best pilots who I had the pleasure of sharing a cockpit with.
Respect!

The standard algorithms for moonrise/-set are a bit whacky for these extreme longitude values, but indeed between 2016/6/13 08:05:02 and 2016/6/27 12:53:52 the moon ist astronomically above the horizon: https://gist.github.com/cprior/c295bbb24d00897b73d21f574e862b2e

Fascinating!
http://i.imgur.com/oaEabL3.jpg