Kenn Borek Antarctic Cause/Speculation Thread

[co-joe]

Definitelty more questions than answers LL. I would suggest that 1300' is significant with respect to crew oxygen. Specifically did they have any, was it functioning, had they run out? To me the only reason to be at exactly 13000' that close to a 14 700' mountain and not at some higher MSA, MOCA, or otherwise would be that you have no oxygen available. If this is the case, mild hypoxia can't be ruled out. If they had working O2, why weren't they much higher?



GyvAir, very interesting read. I've never heard of using exact ground run to determine teake off weight. The way SRP told me the story he directly suggested that the crew purposely flew too close to the ice berg and then couldn't outclimb it. He used the expression "jacking around" as the cause of the crash. But then he's a bit of an asshole.

[CID]

If the scenario was that they were in IMC they would maintain MSA for that leg. That would be somewhere above the peak. The 13,000 foot number apparently comes from the SPOT so we aren't sure (yet) of that is Palt or maybe even GPS altitude. We also don't know what they may have been using for an altimeter setting or if they added cold weather correction or if their altimeter reading was altered by effects of terrain.

So...it's not all that surprising that they would be at 13,000 (SPOT reported). Why the SPOT reported a rapid descent before climb is puzzling but that could be for many reasons. One, perhaps they were prematurely aligning with a new course on the other side of the mountain range with a new MSA or the SPOT could have been in error.

For now, don't take an of the reported measurements as an accurate indication of their altitude. The CVR should shed a great deal of light on this if it was serviceable and operating.

[Cat Driver]

Earlier in this discussion I said we may know a lot more if the CVR was working and was in good enough condition that they can retrieve useful info.

It is the time frame that will be frustrating as we have no idea of what was on it or when they will release the info.

This is the 21 st. century so I am assuming it would not be very long between the retrieval of the CVR and their finding out what if anything is on it.

When I was in the aircraft repair and ferry business we generally could get parts sent to most places on earth in a very short time frame.

[ragbagflyer]

Was it an actual SPOT brand tracker or one of the other aviation specific Sat trackers? IIRC the SPOT website doesn't give you a ground speed, and it only transmits every ten minutes so you don't get instantaneous climb info either.

[CpnCrunch]

I believe it was Skytrac (Bob said in the past they were using Skytrac).

[flyinthebug]

I believe it was Skytrac (Bob said in the past they were using Skytrac).

That is what KBAL used when I was there a couple years ago.

[aviate_77]

it is strange that they crashed at 13000'... oxygen could have definitely been a factor. It was reported that they descended abruptly down a couple thousand feet, and then back up to 13000, just before airspeed read zero. Maybe the crew realized they were starting to feel the effects of hypoxia, descended abruptly, saw mountains, and quickly acted to climb back up to a higher altitude. Hypoxia is a scary thing. It really boggles my mind. Bob in his normal state of mind was.... lightyears ahead of the average. That's why I'm leaning towards hypoxia.

[sky's the limit]

I highly doubt Hypoxia was a factor.

Used to spend lots of time up that high, and 13,000ft doesn't get the average person. Skiing in Colorado will get you higher than that.

Try spending 5-6hrs at FL250 with a tube of O2 stuck in the side of your mouth... single pilot.

[esp803]

I didn't want to wade into this one... but with regards to hypoxia, I suspect most of us who fly unpressurized aircraft on a regular basis in mountainous terrain can probably spend days at 13,000 with little effect (assuming normal physical work load). Speaking from a climbing standpoint I can spend all day climbing in the 10-15k range with little difficulty, going much above that I take time to acclimatize. I am by no means an expert on hypoxia but, I have done high altitude indoctrination at Spokane Air Force Base and have been everything from mildly to very hypoxic and when I read what is known I don't think hypoxia is an issue.

E

[esp803]

I highly doubt Hypoxia was a factor.

Used to spend lots of time up that high, and 13,000ft doesn't get the average person. Skiing in Colorado will get you higher than that.

Try spending 5-6hrs at FL250 with a tube of O2 stuck in the side of your mouth... single pilot.

+1

[Lost in Saigon]

The accident site was reported as S83.9187 E168.7640 (S83 55.12 E 168 45.54)

The elevation at that point looks to be less than 13,000 feet (3960 meters)

Is there a more accurate location available? Or is the reported elevation wrong?

http://usarc.usgs.gov/drgs/dir2/c83172s5.jpg

[CID]

CVR readback takes time. The memory needs to be physically extracted from the CVR and installed in a known serviceable unit. All that while dealing with a possibly mangled unit.

[CpnCrunch]

The accident site was reported as S83.9187 E168.7640 (S83 55.12 E 168 45.54)

I think that is the location of the 406 ELT signal, which is only accurate to a few miles if there is no GPS.

[goldeneagle]

It was reported that they descended abruptly down a couple thousand feet, and then back up to 13000, just before airspeed read zero.

That part is actually quite easy to explain. Those altitude readings come in digital packets, and I'm not sure how much error correction / detection that system has. The reports I saw said 13K for one report, 88K for the next report, and back to 13K for the next one after that. If you invert bit 13 of the number representing 13,000, then you get an error of 4096 feet. If that bit error is not detected and / or corrected, then one report would be for 13000-4096 = 8904, which is very close to the reported altitude on that dip, which was reported elsewhere as a descent to 8800.

So, anybody intimately familiar with the twin, answer a simple question for those of us that have never flown it. Can a loaded twotter climb from 8800 to 13000 in a span of 3 minutes, the time difference between the reports as mentioned elsewhere.

Personally, I think the drop to 8800 is a bit of a red herring, and more likely to be a data transmission error than an accurate report. It's just to co-incidental to me, that inverting one bit in a binary number will give results that pretty much match the reports, and for the reports to be accurate, would require very rapid descent, followed by a very rapid climb. The descent is easy, but I'm doubtful of the climb profile. Another co-incidence that would have to happen, the ENTIRE descent / climb profile would have to line up precisely with the 3 minute data transmissions, a schedule that the pilots had no knowledge of. Way to much co-incidence there, to have a descent and climb, where it all lines up within the 3 minutes between data bursts, and results in altitude numbers that just happen to match precisely with what amounts to the most common type of data transmission bit error in existence, one bit inverted to a 0 instead of a 1. If there really was a descent and climb, it should show in at least TWO of the transmissions, highly unlikely the whole profile occurred within the span of just one blip.

[MUSKEG]

A loaded T/ O will not climb 3 thousand plus feet in three minutes. At least not starting at almost 9 thousand feet. Get some help from a mountain wave and maybe yes.

[lostinthebattle]

The reports I saw said 13K for one report, 88K for the next report, and back to 13K for the next one after that.

That is inaccurate, according to friend who has seen the actual Skytrac Data. There was no sudden drop to 8800'. There seems to be no climb or descent
greater than 600fmp. In fact most climbs and descents were <500fpm.

[flyinthebug]

A loaded T/ O will not climb 3 thousand plus feet in three minutes. At least not starting at almost 9 thousand feet. Get some help from a mountain wave and maybe yes.

And they wernt climbing at VY or VX...it was a casual cruise climb of 140 kts (if we are to believe the data). Not a chance in hell of getting 4000 ft back in 3 mins even with the help of an updraft/wave...especially if they were climbing at 140 kts. To me, its the lack of urgency in the climb back to 13000 that may hold a clue to what happened. Hopefully the CVR will enlighten us.

[shimmydampner]

l realize it's only natural to speculate on what happened, but this thread seems more ridiculous than most. Let's not forget that the speed readout from a sat tracker is GROUND SPEED! If in fact there was a conscious effort on the part of the crew to climb, it's much less likely that they were climbing at 140, and much more likely they were climbing at a better rate but with a tailwind.
Also, l see reference here to "a loaded twin otter" but do we actually know it's TOW? I feel like that information probably isn't public knowledge. It's certainly not out of the realm of possibility that a lightly loaded twin could manage a 1000 fpm climb, even at those altitudes.
And hypoxia at 13,000 feet? Give me a break. Any halfway healthy human being should have very little difficulty at that altitude, let alone a crew that was experienced in mountain flying and had probably spent a great deal of time at high elevations.
Speculation is one thing but use your heads people!

[flyinthebug]

l realize it's only natural to speculate on what happened, but this thread seems more ridiculous than most. Let's not forget that the speed readout from a sat tracker is GROUND SPEED! If in fact there was a conscious effort on the part of the crew to climb, it's much less likely that they were climbing at 140, and much more likely they were climbing at a better rate but with a tailwind. Also, l see reference here to "a loaded twin otter" but do we actually know it's TOW? I feel like that information probably isn't public knowledge. It's certainly not out of the realm of possibility that a lightly loaded twin could manage a 1000 fpm climb, even at those altitudes.
And hypoxia at 13,000 feet? Give me a break. Any halfway healthy human being should have very little difficulty at that altitude, let alone a crew that was experienced in mountain flying and had probably spent a great deal of time at high elevations.
Speculation is one thing but use your heads people!

shimmeydampner...

I highlighted this part of your statement to point out...is that not speculation on your part as well? How do you know its much less likely or more likely what they did or didnt do? You yourself have pointed out how ridiculous it is to speculate on an accident we know little about.

You may well be correct that the speed indicated was GS. You may also be correct and chastized those that asked if hypoxia might be a contributing factor...but to some of us, Bob was more than just a fellow aviator. He was a friend, a mentor, a leader and quite simply the BEST DHC6 driver in the world! We (his friends) are seeking out ANYTHING that seems out of the ordinary and we may be far off base...but please remember that grieving people want answers when one of our very best has an accident.

I think this thread is in particularly good taste and being treated with respect.

Im sorry if some of the speculation on a speculation thread offends you...but im more offended not knowing why or how such an experienced crew could end up as they did.

Its good to throw out ideas that people have. Most of us have ZERO experience in the Antarctic, so wouldnt most of us be out of our element to speculate at all? The thread was started with the intent to have an intelligent and respectful discussion about the loss of 3 of our own. If you ask me, we have so far achieved that.

Im not looking for an arguement, just wanted to point a few things out that maybe you overlooked before posting. It is after all a speculation thread.

Fly safe all.

[Lost Lake]

Hypoxia would not have been a problem.Not sure of base camp altitudes, but I believe it was around 6,000. Anyone who has lived at that altitude builds a tolerance.

[CID]

Hypoxia is a very real danger at the altitude(s) that the Twin Otter was flying. Of course I have no way of knowing if any of the crew was on oxygen but not only would they be required to be by regulation, failing to do so could cause even mile effects of hypoxia, namely headaches, fatigue, shortness of breath, a feeling of euphoria and nausea.

The longer you spend at those altitudes, the more severe the symptoms become. Being "healthy" has less to do with your ability to cope than being "acclimatized". And that takes a great deal of time.

So if you think that those "minor" symptoms of hypoxia are OK for a pilot to experience, I beg to differ.

[Diadem]

Also, l see reference here to "a loaded twin otter" but do we actually know it's TOW? I feel like that information probably isn't public knowledge. It's certainly not out of the realm of possibility that a lightly loaded twin could manage a 1000 fpm climb, even at those altitudes.

I don't know what the actual TOW was for the flight, but they were on their way home at the end of the season and carrying a lot of extra equipment. Again, I don't know any specifics, but usually they would be carrying wheels or wheel-skis to replace the skis before they returned to South America, possibly an extra set of skis as well, any spare parts thought necessary, all of their personal belongings, survival equipment, possibly tents and stoves if they had been working a contract that required them to overnight away from a fixed base, and ferry tanks for extra fuel. If they left the South Pole with full tanks, even without putting fuel in the ferry tanks, the aircraft would have been quite heavy. As I said earlier, KBA gets ferry permits which allow higher TOWs (I said 17000 or 17500, but now I'm wondering if it's 16500; I can't remember exactly) so they can tanker up with fuel to cross the Drake Straight from South America. I don't know if they needed it on this flight, and I don't know exactly what their weight was, but there's a possibility that they were operating at legal but still higher than normal weights.

[Doc]

Hypoxia is a very real danger at the altitude(s) that the Twin Otter was flying. Of course I have no way of knowing if any of the crew was on oxygen but not only would they be required to be by regulation, failing to do so could cause even mile effects of hypoxia, namely headaches, fatigue, shortness of breath, a feeling of euphoria and nausea.

The longer you spend at those altitudes, the more severe the symptoms become. Being "healthy" has less to do with your ability to cope than being "acclimatized". And that takes a great deal of time.

So if you think that those "minor" symptoms of hypoxia are OK for a pilot to experience, I beg to differ.

Got to disagree with you on this one.
These guys flew this height on a frequent basis. They would be more than "acclimatized" to the altitudes. There is NO way hypoxia is going to be an issue for all three crew members at 13000 feet. Grasping at straws here folks.
I don't hold much faith in the CVR answering many questions either. Frankly, I feel it might be as simple as coming to a complete stop, while being in IMC.
Lot of comments about a "loaded" Twin Otter being able to climb 4000 feet in 3? minutes? We'll have to define "loaded"? If they felt any urgency to climb, methinks they would have put "present position" into the GPS and made a circling climb remaining within a mile or two (?) from that point, until they were at a safe altitude. That's what I would do. But, I've had quite a bit of time to consider that option now, haven't I?
I have no idea what happened here.

[FICU]

And hypoxia at 13,000 feet? Give me a break. Any halfway healthy human being should have very little difficulty at that altitude...

I've spent time in Nepal and have seen very fit people show symptoms of hypoxia and develop altitude sickness at that altitude to the point where they couldn't go higher.

I think the crew would be well acclimatized since they spend so much time close to those altitudes in cruise.

[iflyforpie]

I fly all kinds of passengers (read unfit and elderly tourists) at those altitudes without O2 all of the time and I've never seen any display signs of hypoxia...

You have to remember too that you aren't standing up and walking around.. you are just sitting.