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Help researching 1961 Electra crash

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Help researching 1961 Electra crash

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Old 10th Feb 2018, 22:47
  #401 (permalink)  
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Originally Posted by Concours77 View Post
You will have noticed I make the case for the aircraft rolling left at embankment Impact?
Yes, I've been following your ideas with interest.

I also feel comfortable to state they knew of the problem before they broke ground. The “turn” was way too early, the climb was almost flat, and they were committed to take off before a decision could be made to abort. The right turn was “noticed” by witnesses at eight thousand feet along, and 100 feet AGL.
It goes a long way toward explaining the very low gain in altitude.

Any mention of aileron trim set at impact?
From the CAB report: "Actual position of the aileron trim tab could not be determined but the aileron trim cockpit control was set at zero degrees."
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Old 11th Feb 2018, 03:13
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Which leads back to the obvious question, why was the rudder ineffective in resisting the roll induced by the ailerons?

Initially at least, the rudder would have been held in a position that matched the roll input to provide a balanced turn. As the bank angle increased beyond what was expected, one must assume that the control yokes were turned to reduce the angle of bank and a corresponding reversal of rudder input should have been instinctive.

Were the pilots so confused by the sudden complete lack of aileron control that they forgot to use the rudder? Was there concern that a full deflection of the rudder might lead to loss of control or induce a spin at relatively low speed and altitude?

The Electra was a pretty complex aircraft for the era so I am led to wonder if there may have been an element of "what is it doing now?", in the pilot's minds. Basically getting behind in flying the aircraft during the emergency because of all of the possible things that could have gone wrong. This seems to be just as much, if not more of a problem in today's fly by wire aircraft, with totally serviceable aircraft being flown into the ground (or sea) because a relative minor incident caused the crew to lose focus and situational awareness.
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Old 11th Feb 2018, 12:23
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Originally Posted by G0ULI View Post
The Electra was a pretty complex aircraft for the era so I am led to wonder if there may have been an element of "what is it doing now?", in the pilot's minds. Basically getting behind in flying the aircraft during the emergency because of all of the possible things that could have gone wrong.
My chapter on flight station resources is an attempt to get into their minds. I have yet to get any feedback on it from a pilot. I published it standalone, and it will be in the next release.

https://we.tl/x0L59Bpfmj
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Old 11th Feb 2018, 21:10
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The Electra was a pretty complex aircraft for the era so I am led to wonder if there may have been an element of "what is it doing now?", in the pilot's minds. Basically getting behind in flying the aircraft during the emergency because of all of the possible things that could have gone wrong. This seems to be just as much, if not more of a problem in today's fly by wire aircraft, with totally serviceable aircraft being flown into the ground (or sea) because a relative minor incident caused the crew to lose focus and situational awareness.

Questions. When was run up? Was it eliminated from the checks? Was the runway in good condition? Taxing along a bumpy surface and adding full power was perhaps enough to cause whirl? It is not enough to claim “standard power reduction” and then guess, and claim “nothing to see here”. Really? On take off? Or was it noticed in flight?

Evidence points to pre-occupation with a problem early in the run, leading to flat climb. Or, they were contemplating an abort, and wanted to stay low, in case. Power was not an issue. Or was it?

Were the pilots so confused by the sudden complete lack of aileron control that they forgot to use the rudder? Was there concern that a full deflection of the rudder might lead to loss of control or induce a spin at relatively low speed and altitude?

No, not confused, who wants crossed controls except in last resort territory?

Thank you megan.
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Old 12th Feb 2018, 01:03
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Originally Posted by megan View Post
such cross controlling would not be something in the fore front of a professional airline pilots mind, more a test pilots arena.
That's a good point. A couple pilots told me this is not something anyone trains for in airline flying.
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Old 12th Feb 2018, 02:26
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Reading through Craig's assessment of the cockpit environment, (which is excellent), it would seem that the crew had at best about 15 seconds to figure out a solution to the problem after they realised the aircraft bank was increasing and uncontrollable. Taking into account the startle factor and the compexity of the various systems, they never really had a chance of levelling the aircraft.

I completely agree with Megan's comments. From my limited experience of flying with crossed controls in light aircraft, it can be a somewhat uncomfortable experience with a lot of shaking and juddering accompanied by a dramatic loss of altitude. Not something anyone other than a test pilot would attempt in a commercial airliner.

The crossed controls technique can be applied to try and recover an approach which is too high and too fast, but going around the circuit for another approach is by far the safer option.
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Old 15th Feb 2018, 14:14
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megan

If that is the air show prang I am remembering, that was the third attempt at a loop by that pilot. He had high velocity, pulled all the way back, failing both Horizontal stabilizers. The instant they failed, after imparting extreme positive load to the wings, the aircraft, without its tail, “fell” into negative load, creating a “whiplash” reversal which tore the wings off. It is not at all surprising that given the extreme loads in reversal, the wings failed at similar stations. Shock load exceeds any required performance standard, so I would take exception to your analogy....

Your vehement defense of vertical requires the aircraft hit the berm at exactly ninety degrees on. Did it?

Dihedral?
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Old 15th Feb 2018, 15:25
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I didn't presume any given speed for knife edge flying. If the plane were in stable knife edge flight, we can treat the CG as a point load and the CP as the fulcrum. Since the rudder is the opposition to that, we can tell the mechanical advantage. These are all estimates, but the idea should be clear enough.

If you are at less than a vertical bank the load on the rudder is less. So if you know the maximum force the rudder can exert at any given speed, the gross weight lets you calc the maximum bank angle that the rudder can counter at that speed. That is, if the rudder force is X, (3.74*X)/GW = sin(maxBank). But for any speed fast enough to achieve knife edge flight, the load on the rudder will be the same (within the accuracy limits of this guesstimation) though as the speed gets higher the deflection decreases.

Your graphic is a stripped down version of what I show on page 36. I understand what you're saying, and that's what it takes to make prop four leave the marks on the tracks. But we don't have a smoking gun that makes the case. We have a picture that can be interpreted as you say, but it's not a slam-dunk. And we have a wealth of thin evidence suggesting the vertical bank was impossible. I'm not ideologically set against the vertical bank, but it doesn't seem to be the best explanation of what we find. I wouldn't have questioned it at all if the CAB had correctly reported which side was up, because that's what made me look again.

As for the wings both breaking at the same station, I take your point. The coincidence is an attention-getter, but I don't take it as proof of anything. The manuals don't give any clue that there would be a weak point there. The spars are continuous, the planks are continuous. So it's enough to make one look more closely at those numbers.
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Old 16th Feb 2018, 16:11
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Originally Posted by megan View Post
Concours, the horizontal stabiliser did not fail in the initial sequence. The aircraft was 27 knots in excess of VNE, the pilot pitched up 8° and the wings failed at the design limit load of +8.3G. No negative G is involved as the aircraft only pitches in a positive direction.For what it's worth I take exception to the lack of observation and deduction evident in your post.What about it?

BRDuBois, by my calculations using the VMC as a starting point, the maximum load the fin/rudder can generate is just a smidgen under 24,000, which occurs at VA. Full rudder beyond VA invites failure. Being back of the envelope stuff we are in agreement. A reminder though that in a balanced turn very little rudder is required.
Sorry, you’re wrong. Slow the video down, and look at the HS(s). They failed upward, just as the wings did. Without tail downforce, the aircraft instantly lost positive g. Now it is possible that pitch change is not discernible, but given the failure of both elements upward, it follows there is loss of alpha stability, so it is intuitive that the wings were lost ultimately due to load reversal.

You’ll figure it out.

clue: what is the difference between “failed” and “separated”?

Last edited by Concours77; 16th Feb 2018 at 16:26.
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Old 17th Feb 2018, 15:06
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Originally Posted by megan View Post
Question for you Ace. What aerodynamic phenomena caused the aircraft to go from your stated negative "g" with your failure of the tailplane to 8.3 positive?

Also what aerodynamic phenomena would cause the tailplane to fail upwards?
The aircraft entered a climb, at a velocity higher than allowed.
The aerodynamic surfaces were overloaded.
The tail in climb pitches the tail Down, to provide nose up.
Overloaded as it was, the tail at fuselage snapped.
The tail, In failing to provide consistent nose up, caused the aircraft to react nose down.
In addition to the already extreme positive load on the wings, the aircraft fuselage increased its moment down, and away from the wings. This unsustainable additional load failed the wings, which then separated in the chaotic drag induced by the flapping tail assembly and the loss of aerodynamic flight.....

The failure was in the tail; had the tail remained sound, it is arguable the flight may have survived.

An overloaded tailplane in climb fails “up”, but you knew that, right? It doesn’t look like “up”, but the tail lifts in opposite direction to the wings.

addendum. Notice, megan, the left HS fails first, the aircraft quits the climb, and the pitch down is evident. Our pilot “preloaded” the left side elevator with NU Trim, then trimmed out the NU trim with forward stick. Level, with NU Trim, when he released ND and pulled NU, the tail broke. The left wing also failed, just milliseconds post Max NU. Note yaw right after loss of left wing. The wings did not fail “at exactly the same moment”.....

Don’t try this at home, skipper.

Last edited by Concours77; 27th Feb 2018 at 14:32. Reason: Acro trick
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Old 5th Mar 2018, 14:43
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I've been working on my next report version, and want to use my virtual landscape for illustrations. I wasn't satisfied with the level of accuracy in tree placement. I had located trees and shrubs using aerial photos paired with perspective shots of the topo map, but the process seemed too loose.

I have ten usable photos of the scene, five aerial and five on the ground. Over the last several weeks I've positioned each one over my virtual terrain, paired with a virtual camera to recreate the viewpoint of the photographer. The positioning of the aerial shots comes from matching topo landmarks to the photos. This was an iterative process where I'd place ground objects and use them to place other photos and work out inconsistencies.

The ground shots can confirm object placement, but their highest value is in showing the height of trees and bushes. I might color-code those to make it clearer on the virtual terrain.

Once I have the images in place, I place trees initially in their approximate position and then adjust more finely as I flick photo visibility on and off. This is the same method astronomers use to detect celestial movement. I should have it done in another week or so.

I've put up a Youtube video showing the process.

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Old 6th Mar 2018, 01:47
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That is some very cool visualisation work Craig. It really emphasises how flat the surrounding area is. The railroad embankment appears to be the highest point around for quite some distance. It also seems to highlight that the trees do not appear to have attained any substantial height, so poor soil conditions prevail or extensive land clearance took place some time previously.

The drainage ditch also suggests soft, boggy soil conditions.

Not directly relevant to the accident, but it indicates the difficulties that may have been experienced by investigators in finding and recovering buried items from the ground.
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