Help researching 1961 Electra crash
 

I've lurked here for some time, and recently joined so I could ask for help.

For the last year I've been researching the 1961 crash of a NWA Electra in Chicago. My dad was the captain. For background, search for N137US. A year ago I stumbled across some old press photos of the crash site, and after looking them over I realized that in certain respects the official crash reports couldn't possibly be correct.

Since then I've been digging up documentation and writing a new scenario. It's been reviewed by one person who has experience reviewing accident reports. He agrees with my reasoning and conclusions, so I think it's time to find a wider audience.

I want input from pilots, crash investigators and others in the flying community. I'm looking for critical feedback, and for ideas I haven't thought of. If I made mistakes, tell me what I got wrong.

I'm interested in hearing from anyone who has a connection to the event. My hope is that this will come to the attention of someone who has some of the original files. I'd like to find the debris maps and witness interviews and lots more pictures.

It's a 55mb PDF. If you find errors, please let me know. The link takes you to a download page, but does not start the download.

http://we.tl/4GRGZxxxEJ

Craig Hagstrom

I'm seeing many reads, some downloads, but no responses yet.

Here's the nickel tour:

The CAB report says the plane cartwheeled, slid backward and upright to a stop, and burst into flames. Multiple pictures show the plane was upside down instead of upright. Ground scars say the plane's arrival at the final site was high-energy, not a sliding stop.

The CAB and ALPA agree that the plane was slightly nose-down and gradually descending in a 90-degree right bank. Consider the likelihood of that.

The ALPA report says the number four prop left scars across a railroad embankment, which is how they calculated ground speed. But the number four engine was left lying on the track, so it must have been the number three prop that left the scars. The wing was intact nearly to engine four, which means the ground cannot be touched by the number three prop in a bank steeper than 30 degrees.

The CAB and ALPA reports are wrong. That much is a slam-dunk. The errors are partly understandable and partly unconscionable.

The puzzle is in unraveling what actually did happen. This is a 54-year-old mystery. Part of the mystery is that no one even knew there was a gap in our understanding. The other part is to figure out what the crew was doing and how the plane really went down. To me it looks like an attempted belly landing that didn't work out.

My project will be mentioned in the NWA History Center December newsletter. It's not out yet, but will be available at Newsletters. An updated PDF will be available in a couple weeks, with two new visual aids and a newly discovered picture. The current link will still work, and will show you where the new version is.

Hello Craig.

I empathize with your desire to learn as much as you can about this. I wish you the best in your quest.



westhawk

Thanks. It's a totally fascinating project.

One editor of a flying-related newsletter was dumbfounded that I could even imagine questioning an Official Report. If there were a genuflect emoticon he would have used it. To confess, it took quite a while for me to accept that the official reports had to be wrong, having believed them for so long.

A couple well-meaning pilots have said I shouldn't even think about it, and everyone died instantly, which of course was not true. One said I must still be traumatized, but I was over that 40 years ago. This is a detective story.

I'm hoping that when this hits the NWA history newsletter it will find the right people. Many remember my dad, and remember that day. Hopefully someone still has some documentation. If not, then just finding what I have has been a terrific bit of luck.

One friend was at the airport that day, but didn't see the crash. Until he saw my write-up we had no idea our paths had crossed in this way. When he took off the plane banked toward the city instead of west as it normally did, and that caught everyone's attention. He was a veteran on that route. Apparently they banked so the passengers couldn't see the wreck. Makes sense.

Craig

Lockheed L-188C Electra
 

This aircraft suffers from cracking in the wing planks, wings are not very flexible.

Capt Tech - is that a general observation, or were you responding to my question in the document about how much the wing could contribute to the final bounce? I know the wings are stiff with regard to vertical stresses. The issue I was wondering about was how it might rebound when it hit something nose-first. As I mention in the write-up, there wasn't much wing left at that point anyway.

Megan, thanks for your response.

You're right, the picture of something on the track is thin evidence. As I mention in the document, I try to do as little violence as possible to the official reports. I accept the reports up to the point that they are clearly wrong, and then I set that error (and that error only) aside. The ALPA report said that everything beyond engine four was finely shredded, so there cannot have been any large wing part left on the track. In the 2015_Image_03 picture there are some small fragments in the near distance, beyond and beside the guy standing on the left. These match the description in the ALPA report, but the object in 2014_Image_02 (whatever it is) does not. It's the right order of magnitude, but I can't prove what it is.

Exactly. That's the problem. The ALPA report said that it was the wing and not the number four engine that hit the track, and it was the number four prop that left the scars. If it was the wing, then it was a couple hundred pounds of fuel and aluminum that bent the track. I propose that that's not realistic. It seems that the track damage is likely to be engine four hitting the track or the ballast just short of the track, and it killed its forward momentum and left it lying there.

It's not impossible that engine four left the foreground scar in 2014-Image_05. It's not impossible that engine four parted at that point and went on to hit the track. It seems unlikely, but it's not impossible. The key event is not where engine four parted, but where it ended up. As you say, it looks like it would take an engine to bend the track, an object of about the right size was left there, and the prop scars remain unresolved unless they were from engine three. So the details of engine four are much less important than the remaining wing and the angle that WS 293 presents to us.

The prop scars across the embankment were the source of the speed calculation. This was not a throwaway line, but critical to the investigation. Yet the wing was intact out to WS 293, and it's impossible for prop three to touch the track in a 90 degree bank while the wing remains intact to WS 293. This is the strongest single piece of evidence for the shallow bank. You simply can't draw a line through WS 293 and prop 3 that is at 90 degrees to the horizontal axis.

You're right that the angle could be confirmed by measuring the broken power lines. But they were confident of the 90-degree bank, and laying out and measuring those broken lines would take probably several days and quite an investment. Who would bother, since there was no question? Nothing in either report says that power line measurements confirm the angle.

I agree that it would be best to see all this on the ground. But it's long gone, the area is now covered with warehouses, and all I have are these pictures. This is sort of like a paleontological dig. I'm looking for fossils, but fossils are statistically few and far between, so I'm trying to piece together the lineage using these scattered and blurry data points. That's why I'm hoping this document helps turn up some more old files.

What the crew actually intended, or thought they might accomplish, is the most elusive question. I think there's enough evidence to say this was close to a successful belly landing, but that doesn't mean the crew thought they could make it or even thought it was within the realm of possibility. I'm positive they were doing the best they could; I don't know what they thought the outcome might be.

I uploaded the revision, but people are still downloading the first version. I thought the red and yellow sign on the download page pointing to the new version would be enough. :)

The new link is http://we.tl/M88emt5L4F

The revision includes a new picture of the tail wreckage, and I've been able to understand the physics there better. It has two new illustrations to show the dymamics of the last two bounces. There is also a short discussion about why the ALPA got it so wrong.

Y'all sure are taking it easy on me. Been up a month, bunch of downloads, and no meaningful arguments. Either no one is actually reading what they're downloading, or I'm a really persuasive writer. Maybe everyone's just speechless.

Hard to solve.
 

An accident that occurred fifty some years ago has to be harder than solving most cold cases. The technology in the early 60's was very poor to what we can do today. The 1961 investigators, I'm sure did there best, but you are looking at it in todays time frame. I think your conclusion may be accurate, but will that ever change the historical outcome?


Frequently, in cases where the crew does not get to defend or tell their side of the story, the operators loose. The aircraft manufacture, maintenance crews and company are all there to deflect the fingers away from there possible contribution and point at the crew.


Just my couple of cents. Very sad but true.

As I mentioned in the first post, I got a sanity check from a guy who reviews crash reports and helps with things like requests for re-examination. I don't see any value in that, because I'm not questioning the cause of the crash, only the description of the impact. I think the breakup sequence is telling, mostly as a detective story and also as archeology - uncovering a historical record that was unsuspected.

I'm getting a feel for the crash investigators, and the more I consider it the more indignant I get over the ALPA writer. Here's what I think happened:

The ALPA writer had access to CAB documents, but it was grudging access. The ALPA and CAB did not always cooperate, and in at least one case the ALPA was more or less accused of sequestering a crew so the CAB could not get toxicology results, etc.

The CAB in one document described prop hits across the railroad embankment. In another document the CAB described how the spacing between prop hits across the ground let them calculate ground speed. I'm positive those two documents described the same sequence of prop hits, but one of them explicitly mentioned the railroad embankment, and the other mentioned only the "ground". So the ALPA writer assumed those were two different sequences, but they were simply one sequence mentioned in two documents.

So with good intentions, the ALPA writer concocted a scenario that had two sets of prop hits, and obviously that had to be engine four and then engine three. And he came up with a sequence that seemed to fit that, but without doing the geometry he was wildly off base. The result of following the ALPA scenario is that the plane had to go from a 90-degree right bank to a 150-degree bank where the number three prop hit, and then reverse and go back around to a belly landing, all in 1.4 seconds. The timing comes from 380 feet between first wingtip impact and nose impact at 160 knots. The guy didn't have a clue.

What kills me about this is that all he had to do was ask. A simple conversation with the CAB guys would have cleared it up. The ALPA writer clearly never went to the crash site, never understood the physics. And because of the prickly relationship or his personal attitude he couldn't ask the question.

This is all conjecture, you understand, but this is what I see behind the scenes.

The CAB report says the plane slid tail-first and right side up. The pictures show the plane tail-first and upside down. Do you accept the CAB report on that item?

You agreed that the railroad tracks appear to be hit by engine four. The ALPA report says the number four prop left the scars on the tracks. Do you accept the ALPA report on that item?

The ALPA report requires a longitudinal axis rotation of 60 degrees clockwise and then 330 degrees counterclockwise all in 1.4 seconds. Do you accept that scenario? (That's in the Dec 18 version, by the way.)

The acceleration and rotation forces were lethal in the forward fuselage. No one survived there longer than a half second, far as I can see, and no screams came from there. I put the forward fuselage and main fuselage discussions in separate sections so there would be no confusion about which I was discussing. I didn't contradict myself.

It's not credible that anyone heard screaming before the forward fuselage broke off. Until then there were at least two running engines. The Morning Tribune says Mrs. Trapp heard a thump and then heard screams, so that would be after the forward fuselage broke off and there were then no engines. The plane was briefly a glider, with the fuselage front open to the air. Mrs. Trapp reported hearing screams after running out into the yard, which would have taken a few seconds. So these screams would be coming from the aft fuselage after it came to rest.

The CAB report is the source of your quotation, but it doesn't assert that the lines were measured, or even strongly imply it. Whether or not they measured the lines, the wording you quoted might have been the same either way. It's not explicit.

Opposed to this position is the remaining right wing and the prop marks. It's not possible for engine three to leave prop marks while banking steeper than about 30 degrees, when the wing remains intact nearly to engine four.



I'll take geometry over witness statements any day.

I have been flying for nearly 20 years and work in the aviation business. I have a keen interest in aviation safety and have read pretty much every AAIB report published since the early 1980's and a fair few NTSB reports.

I have read your entire pdf and would be happy to make a few comments.

I can see you have spent a lot of time and effort in researching this topic. At first I couldn't work out what 'Axe you had to grind' (understandable by the way, I probably would in your position), then I realised that your principle issue was the lack of credit given to the crew in almost pulling off a successful forced landing (according to your theory).

But a good accident report would never do this regardless of how well the pilots did or didn't perform. A good air accident report presents the facts in a completely unbiased manor so as not to prejudice any subsequent legal proceedings.

As for your theory on the impact sequence I have a number of observations that counter your theory on maximum bank angle.

Firstly as already mentioned by Megan, the CAB report is clear that the power lines were severed about 70 degrees from the horizontal. The investigators on the ground at the time won't have just guessed this, it will have been measured and is a major piece of evidence as to the bank angle at impact.....when you then consider that the captains AI was at 90-100 degrees at impact (possibly unreliable but corroborates the power line evidence). This makes a very strong case for the bank angle.

If the aircraft did only attain a maximum bank angle of 30 degrees then the question has to be asked......why didn't they just keep on flying? Had they been able to limit bank angle to 30 degrees they could have climbed (slowly) to a safe altitude and trouble shooted the problem.

The fragmentation of the wreckage also indicates a high energy impact consistent with a high bank angle.



From the CAB report I will say this. The flight crew performed impeccably. In the very short time they had to react they managed to make a distress call and turn off the aileron boost to try to regain control of the ailerons (very impressive when you consider the pilots were very new to the Electra with a maximum of 314hrs on type). They were at very low altitude and airspeed so would in all likely hood not have been able to safely try other options like lots of rudder and/or asymmetric thrust as this would have probably led to an immediate stall/spin. (The Electra is particularly sensitive to loss of thrust with regard to lift due to the huge amount of prop wash over the wing). Your father had the control wheel at full left deflection and even had the presence of mind to close the throttles at the last minute in an effort to reduce the impact. Impeccable.

If you programmed this failure into a simulator and got 100 Electra crews to fly this flight, I'd bet all of them end in this outcome. There was nothing more the crew could do.

I don't know the full aftermath of this accident (I'd be interested to hear it if you are able to divulge it), but the 2 mechanics, Foreman and possibly the Inspector that replaced the aileron boost unit 2 months prior to this accident with complete disregard to procedure or even basic aviation engineering principles, should have ended up in jail along with their managers.

I'm here to get my thesis tested; I want to know how robust it is. I very much appreciate your and Megan's response. I need to know how well my scenario stands up.

No, it's become a detective story that fell in my lap, and I was fascinated as I peeled back the layers. It's an aside that the crew did better than we knew, but it's also a guess. It might be that as Megan said they really were just along for the ride, and this is simply the attitude the plane had reached when it hit the ground despite all their attempts at control. The impact looks like an approximate belly landing, but we have no way to know that the crew thought they could make such a landing.

As I said in the document, my own case is weakened by the fact that it's so easy to say I have an axe to grind. Nothing I can do about that, since I'm the one who found the pictures.

I wouldn't expect the official reports to be particularly laudatory, though the ALPA report did mention how well they performed under the circumstances. I'm not here fishing for compliments. I just want to correct what appear to be some erroneous reports in which I have particular interest. Frankly, the more I consider the errors the more indignant I get.

I believed the angle right up until last year. I had no call to question the official reports, and accepted the 90-degree bank completely. But when the CAB says the plane was right side up and it is shown upside down, suddenly there's a legitimate call for a closer look. When the ALPA says the number four prop slashed the railroad tracks but the number four engine clearly hit the tracks, again a question is raised. If such basic issues are so clearly wrong, then how much should we trust that every single other T was crossed?

The bank angle is the biggest hurdle I have to confront, as the document says. The reports cite witnesses, some of whom probably had good views. I don't know if they were cherry-picking or not. I can't explain the artificial horizon.

In support of my thesis I have the final impacts, which indicate a high-speed forward movement, not a tumble. I have the intact wing and the prop 3 marks which cannot happen in a 90-degree bank. If you can explain this one to me, I'd appreciate it, because I can't see it.

I'd think so too. This is why I wanted to hear from Electra pilots. My experience is limited to sailplanes, and I don't understand why they didn't climb. So maybe they really were just along for the ride.

I don't know the details, the punishments that might have been meted out. Many years later my sister told me that one of those held responsible committed suicide. I wasn't bitter about it and wouldn't have wished that on anyone.

As I mention in the document, one reason for putting this out is to see if I can shake some old documentation out of the tree. Some old airline employee or investigator may have something. The National Archives has nothing. Maybe some bystander with a Brownie camera has pictures. Some of this material probably still exists, but I see no path to it except this document and word of mouth.

Considering the report again, I guess the physical evidence at the crash site regarding the aileron cable disconnect may not have been sufficient for a criminal conviction......although possibly sufficient for a civil case.

I agree that it would be interesting to hear from a current Electra pilot......there are still around 20 Electras flying (I think nearly all in Canada in freight and fire fighting roles) so there must be a few on pprune.

There is an interesting diagram in the CAB report showing the crash site in relation to the runway....it appears the diameter of the turn the plane made was approx 5000ft. Someone with more expertise should be able to deduce average bank angle from this information.

Very best of luck in your search for further information.

See, that's what I'm looking for. The turn radius never occurred to me.

I have several Electra manuals, but no information on turn radius.

Aircraft Turn Information Calculator is a turn radius calculator.

Given the plane's takeoff weight of 93,000 lbs, the stall speed is 110 knots. I don't have a better speed to work with than the 160 knot estimated impact speed. The bank was said to be steadily increasing, so that throws a wrinkle in it.

At any rate, the calculator says a 43 degree bank would give a diameter under 5000 feet, and a 70 degree bank would give a 1660 foot diameter. So if the bank was as steep as the official reports say, the plane would have crashed closer to the runway.

This is fascinating, thank you very much. I'll have to follow this further.

One of the most important lessons I ever got came from this case. After the cause became known, several people told my mom she should sue NWA. But we've been an NWA family for many years, and she wouldn't do it even though it would be easy money that we really could have used in those years. She said that the fact that you could get money out of someone didn't make it the right thing to do.

Regarding finding an Electra pilot, I have a friend who's a retired NWA Electra pilot, and I can't get him to read the furshlugginer thing. It's like pulling teeth.

I agree. Those who said they heard screaming before the first impact were surely hearing the turbines. That was still new technology, and those raised on piston engine sounds would not be familiar with it.

That's why I said I'll take geometry over witnesses any day.

We can't tell what they were attempting, we can only tell what they came close to. Perhaps they thought a landing was doable, perhaps not. It's reasonable to say they were trying for it, but that's as far as we can go.

Yes, I made that point in the document. Once they had the cause of the accident, the impact sequence became trivial. From the obvious errors, it's clear that the breakup sequence didn't rate high on their scale of importance. The impact is not relevant if you're interested in preventing future accidents. It's meaningful only if you're interested in the truth as opposed to slapdash reporting.

We don't know what they knew. They're dead, and we can't interview them. We can only guess.

I set aside the root cause in the first few paragraphs, and explicitly said I don't take issue with that.

I take issue with a particular set of descriptions. They are not germane to the cause of the crash, but they are relevant if you care what the true story was. The errors in the CAB and ALPA reports are egregious and obvious. "Slapdash" is an appropriate term.

I don't accept that they are beyond question merely because the writers are probably now dead.

Ok, this is fascinating. I've been running some numbers.

There are probably formulas that would handle all this with the ability to tweak the bank angle change rate over time, but I'm a spreadsheet guy so I did it with a spreadsheet.

I divided the flight into one-second chunks, one per line. I start the plane headed 143 at zero bank, and for each second I increment the bank by an amount. Given the bank angle, I compute the radius of the turn and the number of degrees through which it turns in that second. The degrees turned gets added to the previous line heading. I run the numbers until the heading is 270, which was the heading at impact.

I also compute the distance by which the plane moves laterally from the runway axis for each second, which is the sine of the difference of the current and initial heading, convert from knots to feet per second. I accumulate each with the prior second.

The target is to end up with a lateral movement of 5000 feet when the heading is 270. It turns out a bank that increases by 1.1 degrees per second ends on heading 270-ish and 5000 feet from the runway axis at a final bank angle of 45 degrees.

I'm going to play with the numbers some more, and see what nonlinear changes to the bank angle give us.

I'm not saying this proves anything, ok?

This computation is highly sensitive to the way the incident starts out. If the plane starts to bank and then they get some control on it, you end up with a lower bank at the end.

So I started with the bank increasing by three degrees per second for four seconds. Then I increase it by two degrees per second for five seconds. Then I increase it by one degree per second for ten seconds. We're pretending the bank caught them by surprise and they got some control over it.

After 36 seconds they end up at 270 degrees 5000 feet from the runway at a bank of 33 degrees.

It isn't proof, it isn't even evidence, but what a totally charming result. :)

Hello DuBois -

Back when your father was pilot of the Electra, I was a housewife with 4 kids, and for the first time had to get a babysitter and fly to Boston from Philadelphia on Eastern Airlines. It was an Electra, the Eastern service was called the Shuttle.

My first time on an airliner (had a ride in a light plane in l944). So I felt relatively safe, with the pilots in proper uniforms, the cabin staff very professional. The engines started, we taxied hither and yon, and then before entering the runway, the pilots were revving the engines, then doing it again, then doing it again, and again, and they certainly made some peculiar noises.
People in the cabin looking at each other nervously. Presently after ten minutes of this, the captain came on the radio and said "You may have noticed one of the engines sounds a bit rough, so we are going back to the gate and get a different airplane.!"

And with that, we all trooped off, and over to the other gate...no further excitement at all. My only recollection of an Electra flight.

Do you fly yourself? I have 3,000 hours in gliders and light aircraft, but in my day women did not often become airline pilots. We were supposed to stay at home and raise a family.

But I have read a few reports, when I knew the incident described, and as many above have said, witnesses do not always understand what happened.
Those who survived and were responsible for what happened tend to be economical with the truth! It can be too painful to admit responsibility when people are hurt.

I did a little sailplane flying when I was a teenager, but had to stop so I could save money for college. Loved it, though.

The scale in the CAB site map shows the impact was about 4100 feet off the runway axis, and the CAB report says it was 3800 feet off the runway. So I'll run some more numbers through my spreadsheet. It looks like the bank can never be higher than about 42 degrees to hit that window.

The iterations were too much like work, so I wrote a routine to do the heavy lifting. One problem is I had to add the speed calcs, which changes the turn radius continuously. Now I have a routine that calcs the flight path second by second, increments the speed until it hits 160 knots, and gives the turn diameter, time to impact, heading, all that stuff. The calc terminates when the heading goes past 270 degrees, as was reported.

V2 for this plane was about 120 knots, at a weight of 93,000 lbs. To be conservative, I'll arbitrarily use 125 knots as takeoff speed. So whatever flight time the bank rate allows us, I tweak the acceleration until it hits 160 knots before impact.

The first lesson is, you just can't realistically get to a 90 degree bank. The faster you increment the bank angle, the tighter the turn gets, and the less time you have to add more bank increments. Incrementing the turn by 10 degrees per second gets you to a 90 degree bank after about 8.5 seconds under a thousand feet off the runway axis. Any linear bank increase less than 10 per second never gets you there at all.

You can get to a 70 degree bank using a linear increment of three degrees of bank per second, but it's at less than 2500 feet from the runway. The lower the increment the farther it will get from the runway, but the farther you get from the 90 degrees reported. There doesn't appear to be any linear bank increase that gets you anywhere close to the target.

The flight time is estimated by Lockheed to be about 45 seconds. The CAB said it was two minutes from clearance to impact. We need a result that's somewhere on that order of magnitude. My computation starts from when the bank commenced, not when the plane took off, so there's some fudge factor.

We get a pretty good result if we increment the bank by 1.5 degrees per second, assuming an acceleration of 1.5 knots per second. With a steadily increasing bank, we end up with an angle of 51 degrees right at 4000 feet after 34 seconds. Problem is, we have physical evidence that the bank angle was about 30-ish degrees when it hit the railroad tracks.

Using a nonlinear bank angle, as mentioned above, we end up with a final angle of 33 degrees 4000 feet away after 27 seconds. That's the right ballpark for the angle and timing. This is based on all the bank incrementing happening in the first 8 seconds, and then the crew manages to stop the bank from increasing but are unable to immediately reduce it.

The intriguing aspect to this, of course, is that the crew must have been having an effect. If they were able to stop the bank from increasing, then they weren't without control.

I've uploaded a new version which incorporates the discussion of turn radius. It has a map showing the path of a 90 degree bank turn and others. Experimenting with the turns leads to a fairly small range of possibilities that can get the plane to the observed impact point, and the possible bank angles range from about 33 to about 41 degrees. The bank increments cannot be linear to get the plane to the observed impact point, which means something the crew was doing was having an effect. Very interesting.

The new link is http://we.tl/B9288LJnjV and this is now the link that clicking the background will take you to.

I took down the latest version after doing some more thinking. My turn computations were too simplistic, and they don't have the explanatory value I first thought they did.

So I'm still stuck with an intractable problem. Everything from the right wing hit on through the sequence looks like a belly landing. I can't show good evidence that the high-angle bank was wrong, but it's incompatible with the rest of the sequence. I can show that a low-angle bank is reasonable, but can't give any hard evidence for it. If the plane came down with a high-angle bank, I have no clue how it could have transitioned to the belly landing.

More work to do.

After removing the turn radius computations, but leaving in the discussion about how the ALPA came to the wrong conclusions, I put it back up.

http://we.tl/InGXbDKkkX

I'm working on a draft that starts at the final wreckage site and works backwards. We'll see if that one works better.

The problem with the chronological approach is that it's vital to understand the bank angle, but there's not any direct evidence until the right wing impact. People seem to come to a mental halt before that, because I'm disagreeing with the official reports on what is (at that point of the crash) thin evidence. Maybe if I start with the most obvious error I'll be able to carry the reader along better.

Uploaded a new version that reworks the turn and bank discussion. My first take at it was too simplistic.

This version is the kiss of death for the high-bank hypothesis.

Part of the new discussion uses the CAB map to determine what turn radii they were representing, and shows that their map conflicts with the witness narrative. The map constrains the maximum bank angle at impact to about 47 degrees. I also noticed a hint that at least some witnesses said the bank reduced, but the report writers chose to ignore them.

Another part takes my original computations and adds a little enhancement so I can insert the emergency during the normal expected turn. A series of calc runs shows how the flight would look and where it would end up. Turns out a final bank in the low 30's works out fine, and lower is possible.

The most interesting development in this approach is that it provides clear evidence that the bank was being moderated at the time of impact. The crew had leveled the plane from a maximum bank around 45-ish degrees to one of 35-ish, and were flattening the bank at a rate somewhere near one degree per second. In other words, they were very close to pulling out of this.

Take a look, let me know what you think.

http://we.tl/1qiw9nIJlw

Buffalo Airways in Yellowknife, NT, has Electra pilots, as does AirSpray in AB.

I have no quarrel with their finding of the root cause. But their work on the impact sequence does not magically become rigorous and proper just because they got the root cause right. The work on the impact sequence was still slapdash and it's fair to call it that.

Today based on a tip from a reader I went to the Chicago Tribune archives. On the back of the Monday edition there was an artist's conception of the impact sequence. It shows the main body sliding backwards to the final site. The paper didn't make this up; it had to come from the CAB.

As an old newspaperman I can tell you that the morning edition is put to bed about 11pm. In other words, on the day of the crash the CAB had ALREADY decided that the plane slid backwards, and they never wavered from that. This goes beyond unconscionable, which is what I called it in my analysis. To put out any affirmative statement on Day One is unheard of.

At the time the CAB put their stake in the ground on the backward slide, they had absolutely no idea what the root cause was.

Evidence beyond a reasonable doubt. How many airplane crashes involve a plane sliding backwards? Ever heard of one outside of this crash? What are the odds that a reporter would make up such a story, entirely on his own? What are the odds that the CAB would match such an unlikely story with exactly the same one?

There is no need or incentive for a newspaper to posit such specifics. There's enough meat in this incident without a backward slide. Read the archives; it's dripping with pathos and tuggable heart strings.

The only way this was in the paper is because the reporter was fed it. This part, at least, I know how it works.

Having thoroughly read through the reports and reviewed the photographs, I find nothing inconsistent with the aircraft being banked at an angle of 90 to 100 degrees at the point of impact with the railway embankment.

The primary purpose of the accident report was to establish the cause and given the significant disruption and lack of flight recorder data, the investigators carried out a thorough investigation given the techniques and resources available at the time.

Given that the aircraft was at low altitude and climbing when the aileron cable detached, the description of the aircraft entering a continuously increasing bank and turn, before stalling into the ground is entirely consistant with the photographs of the scene. There is evidence that at least one control column was commanding a full left turn, presumably a full left rudder input was also commanded and the crew appear to have been attempting to control the turn with engine power, but simply didn't have the altitude to recover the situation.

I don't find anything in the official reports that suggest the crew acted inappropriately at any stage and there are definite indications that they fought to control the aircraft attitude all the way to the ground. The final radio transmission gave some pretty vital clues to the crash investigators and that is unusual in modern accidents where the emphasis is to concentrate on flying the aircraft. Perhaps one advantage of having more than two crew members in the cockpit?

The accident wasn't ever going to be survivable and I can't agree that the aircraft bank angle did anything other than continuously increase once the control cable separated.

Had the control cable separated in a high level cruise, it is possible that some measure of control over the aircraft attitude might have been regained, but I suspect that a spiral dive would probably have been the final outcome.

Given the high speed of the impact but only a modest low nose attitude, the fuselage would be expected to tumble and break up as it slid along the ground striking trees and other low level obstructions.

As far as I can tell, the crew did everything right, they just ran out of time and altitude. The official reports were as thorough as they could have been for the time. There doesn't appear to me to be any attempt to cover things up or hide any failings. It is clear that short cuts were being taken with maintenance operations, but no more than with any other similar organisations at that time. A lot of pilots and engineers had cut their teeth during World War 2 when the emphasis was in getting the job done, not getting all the boxes ticked.

Different times and different attitudes.

Sorry for your loss, but you should be proud that your dad kept trying to fly the aircraft right to the end and he was doing all the right stuff that he should to try and recover given the circumstances.

It's entirely reasonable to say the bank angle in might continuously increase given the mechanical failure. But if it had continuously increased in this case, the impact would have been southeast of where it actually hit. The path would be a tightening spiral with more movement parallel to the runway and less orthogonal. For the plane to hit where it did, it required more movement orthogonal to the runway than parallel, and that means the bank must have moderated.

But it didn't tumble. The right wing was obliterated just inboard of the number four engine, but the left wing's full (or very nearly full) length was present at the final impact site. The empennage was virtually undamaged, and only the forward fuselage broke off.

I never suggested any ill-intent, merely carelessness. The breakup sequence just didn't matter much.

The recurring problem in this puzzle is figuring out how much we have to discard for the rest of it to make sense. Clearly not all the witnesses agree, so some of them must be in error. The question is to decide which ones.

I've been reading the Chicago Tribune stories. There is (embedded in some purple prose) a clear description of three powerful bounces, as opposed to a cartwheel. I find this fascinating because the pictures seem to show three bounces as well, and that is the scenario I present in my document.

That nugget, plus the evidence that the CAB had laid out their impact sequence on the day of the crash, is going to take a while to process before I publish a new version.

ETA: Another interesting bit in the Trib is a picture of a wing fragment lying on the west pair of train tracks. It's a small fragment no more than two feet across. But the large object lying on the east rails in my document is more like seven feet across. This adds weight to the idea that it's the number four engine lying on the east tracks in my picture, and that's a lock on the shallow bank argument.

I personally think the object lying in the track is part of the wing tip and aileron structure, rather than an engine. The metal has been twisted making it appear more three dimensional than the originally flat wing structure.

Given that it was impossible to apply any corrective aileron input due to the control cable being disconnected, the only means of moderating the bank angle would be rudder and differential engine power.

The rudder alone may have been partially successful in moderating the bank angle initially. As the bank angle continued to increase, more and more engine power would have been needed to maintain lift. Once the bank angle passed 30 degrees, differential reduction of engine power to correct the bank would not have been possible. The aircraft would have immediately stalled and fallen from the sky.

The official reports are quite firm in their estimates of bank angle when the aircraft initially struck the high tension wires and the railway embankment. The wing spar alone would have been sufficient to displace the railway tracks. Railway tracks are designed to support heavy vertical loads. The sleepers linking the tracks are designed to maintain constant spacing between the rails, not to resist horizontal displacement. A certain amount of horizontal displacement occurs naturally with constant expansion and contraction of the rails due to seasonal temperature changes. So long as the relative spacing between the tracks remains constant, trains can use the line despite some quite severe looking kinks.

So I believe the debris on the track is a twisted part of the outer wing structure and the number four engine separated after passing over the embankment.

The rear fuselage and tail section are almost completely inverted where they came to rest. Whether they rolled, tumbled or spun to arrive at this position isn't really an accurate indication of aircraft attitude at the moment of initial impact with the ground.

I appreciate that you have put a great deal of time into your research and you have made a good case that the aircraft might have been at a shallower bank angle based on your interpretation of the photographs of the scene and ground witness marks. I simply can't agree with your well presented conclusions.

Unfortunately the original investigators notes and measurements are no longer available, but almost certainly the severed high tension cable lengths would have been measured to give an estimate (and rough confirmation) of the angle at which they were severed. Detailed measurements would have been taken to order replacement cables to splice in repairs no matter what. The artificial horizon had witness marks indicating a bank angle between 90 and 100 degrees. Just two bits of physical evidence in addition to what the investigators on the scene where able to establish, such as the impact point on the rails in relation to the high tension cable breaks.

Clearly the crew had some initial measure of control over the bank angle and roll rate, probably using the rudder, but eye witness accounts and physical evidence indicates that the aircraft progessively rolled further and further until contact with the ground. There is simply no practical way that the crew could have levelled the wings or reduced the bank angle at impact given complete lack of aileron control.

First of all, thanks for your thoughts. This is what I came here for.

The key evidence at the final wreckage is the position of the wings. They are inverted with the leading edge pointing back along the path. So either the plane slid inverted, which the remaining rudder rules out, or it arrived upright. That, plus the ditch, tells us a lot about that final site and how the plane got there.

I didn't mean to say (in my document) that the final position was simply maintaining a position it had been in at the moment of initial impact. Many things happened in between. My point was that to arrive upright at the final site with as much energy as it had means that the plane cannot have been dissipating that energy in a cartwheel. It's the final site's energy, as much as position, that rules out the tumble.

I'm following various paths to try to locate more documentation. Something may turn up.

A previous post mentioned that the cables would be measured, but there's no need to do so from the power company's point of view. If they trusted the remainder of the snapped span, they could splice new line on one of the ground-level pieces, pull it to the opposite tower by pulley, and splice it in up there. If they didn't trust the snapped span, they would pull new line up to one tower using a pulley, over and on to the next, pull taut and splice it in.

None of that demands that they know exactly where the breaks were, and determining the break point would slow them down. I suspect they would measure only if asked by the investigating authority. I'm confident that such measurements would be routine today, but have no reason to think it would have been routine then.

I also don't have a description of the power lines. The measurement would be useful only if the lines had significant vertical separation. So in the absence of any explicit statement, I don't see any reason to say that some hypothetical measurement should be presumed to exist and therefore admitted as evidence. We just don't know.

The power lines are quoted as being two sets of three wires carrying 38,000 volts. These lines would be erected at a minimum distance from the ground and away from any horizontal obstructions to avoid the risk of arc over. The power lines would have complied with electrical standards imposed at the time and are unlikely to have been "over engineered".

So it should be possible to establish from the old standards, how thick the cables were, the typical breaking strain, at what height the cables were strung above the ground and the horizontal separation from the railway tracks.

This information may help to indicate the vertical path of the aircraft as it sliced through the power lines and the wing tip contacted the railway embankment. It should at least verify the estimates of a ten degree nose down flight path.

Standards for modern high voltage power lines are probably not too dissimilar to those as the time of the accident since the same laws of physics still apply to power handling and flash over voltages.

For example, in the UK, the minimum height above ground would be in the region of twenty feet. The cable thickness would be at least two inches, or more, depending on the current carrying capability.

Ok, thanks for seeing the power lines. The Chicago Trib says the power poles were 60 feet high and 300 feet east of the railroad embankment. This agrees very well with the map images in my document, using the scale on the left of the image.

That means the descent was very gradual, which agrees with witness reports. It also means anything steeper than 63% must have been in a stall and is not a feasible angle given the horizontal distance it had to cover to the tracks.

Once again we have to decide how much must be discarded for the remainder to make sense. The artificial horizon was treated with skepticism in the official reports. If we rule out the witness statements of the vertical bank, everything else fits.

ETA: The RR embankment was said to be the highest landform in the area. That means the power lines would have been somewhat less than 60 feet above the tracks, possibly considerably less.