More than a week on I am still unsure about this dig. The basic area of the planes was known, it was basically known what happened. Does the excavation of these sites (I would add TT's othetr WW2 digs to this) add anything?
It's a difficult question so I'm happy to be challenged.
Just to throw down a wee gauntlet as per your request The "basic reason for the accident was known". Not so. Many posters to this thread, including an eye-witness, do not know the cause. The theory proposed by the AAID bod has been justly demolished by many posters here. Unless/until the engines of the second a/c are brought to light, the 'air collision' theory cannot stand up to scrutiny.
So two aircraft just happened to crash out of the same formation at the same time.
The guy from the AAIB would confirm that eye-witnesses often report aircraft coming down in flames when no such thing happened. You'd also be surprised at the number of "eye witness" reports that start with the words "I heard a crash...".
Well said, Fil2. With all due respect to the gentleman who actually witnessed the event, it was a long time ago and he was very young. There were a number of witnesses from the other aircraft in the formation who saw the collision and don't talk about engine fires!
Nick Wotherspoon is quite right that we didn't do enough uncovering to arrive at such a firm conclusion as the programme suggests - I had to go with what I had. Can Nick confirm how much of Zuber's aircraft was at the second site? Even if it is not possible to recognise intact wings, tails etc, we look for evidence of the '4 corners' of the aircraft, that is to say that if we see evidence of any extremity such as a tip being there, then we assume the whole wing was present. See the Spitfire dig at Wierre-Effroy, where there was no sign of the tail surfaces but discovery of the rudder mass balance showed that the fin and rudder must have crashed with the aircraft.
With the wing damage we do know suffered by Hubbard's aircraft, it would have rolled violently left. In practice, this on its own can cause the tail to twist off. The loss of the tail will cause the aircraft to violently pitch down (not up). I recall that one of the Dambuster TV documentaries shows rare footage of a USAF A26 (I think) dropping a Highball mine at very low height. Either the bomb bounces too high or the splash removed the tailplane. The aircraft immediately noses over and is gone in about 1 second. Hubbards aircraft would have gone ballistic rather than aerodynamic very rapidly. Since Zuber crashed so close, I think we have to assume that he suffered major break-up as well, otherwise the aircraft would have continued to fly (rather than fall)and, even if not under control, would have been further away.
If I remember correctly there was mention of Zuber's plane coming down in a flat spin. If true it would've lost lift and fallen almost vertically. The height was stated as being 1,000 feet which is quite low so I wouldn't expect the wrecks to be very far apart, especially as they were originally flying in the same direction at about the same speed.
quote:Originally posted by Steve Moss: Can Nick confirm how much of Zuber's aircraft was at the second site?
Hi Steve - Zuber's aicraft was as predicted, little more than a mass of components - the post impact fire had consumed much of the airframe. We did however record by means of a sketch diagram where various components were found and most parts did seem to still be in their correct positions relevant to each other. The aircraft seemed to have impacted at a much steeper angle - the only major section of airframe surviving being the cockpit floor and nose wheel area which had embedded in the sand and was recovered at a depth of about 12 feet - there was no trace of the nose gunbay area or the guns. The cockpit itself had dissapeared save for the duralumin "armour" cladding, though internal fittings such as switch panels, radios, rudder pedals, control column and the intact pilot's seat were found. The centre sections of the wing spars, bomb bays and upper turret were all in their anticipated positions, though with very little airframe around them. The aircraft appeared to have broken at the gunners position, with the scant remains of the tail being at 90 degrees to the fuselage - however nothing remained of the vertical fin or tail planes, though at least the former is shown in the photos taken at the time. Finally the wings were reduced to the main spars only, with the port in approximately the correct position, including the U/C, but the starboard seemingly swept back at about 60 degrees, having broken at the main fuselage mountings - no sign was found of the starboard main U/C! & both sets of spars seemed incomplete.
quote:Originally posted by Alan Clark: Finally see the following link which shows a midair between two Beauforts with one aircraft slicing off the others tail from behind. Note also the very close final positions of the two aircraft. http://www.divetheworld.com/Diving/warbirds/Beafort-Crash/index.htm A.L.C.
Thanks for posting this Alan. I have this very clip on my HDD somewhere but I'd long since forgotten the source. ISTR a link on that site about the submerged Sunderland (Lake District).
The tragedy of this Beaufort incident is that they were performing a PLANNED aerobatic maneuvre - the 'Prince of Wales split', or some such. (As in Prince of Wales' three feathers). The contact looks to be surprisingly gentle and just goes to show how brittle aircraft components are, once subject to in-flight loading.
See this for yourself by standing (as opposed to stamping) on an upright, empty drinks can, on one leg! (I weigh about 90kg and they easily take my weight) then use a stick or a ruler to reach down and gently tap the side of the can. (At your own risk. No responsibilites accepted for ankles twisted, ornaments knocked over etc.)
Minus its tail, this particular aircraft pitches violently upward but note that it had already pitched up slightly, into its intended climb, by about 10deg, at the point when it is struck. The subsequent upward flip is reminiscent of what happened to Malcolm Campbell's Bluebird, just push of air from underneath.
The right hand plane loses its left wingtip and rolls violently to the left (asymmetric lift but much more than I would have imagined), striking the water first, inverted and at full speed but within 2-3 seconds. The middle aircraft goes to the vertical, yaws over, to face nose down, spirals a bit and hits second, closer to the camera position but not that far away from the other plane because it had gone in so soon.
<ExsistoFelicis>
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quote:Originally posted by manoamica: As I see it what happened was that one of the two that crashed, I do not know which, was in trouble before the collision, with one engine, I think the port one, on fire.
There is a phenomonon known as 'torching', which would look very much like a fire but is relatively harmless. Just over-rich mixture continuing to burn as it is spat out of the exhaust stub. This would certainly have caught your eye, even from 2 miles away.
I imagine that a genuine engine fire would involve larger flames and a considerable smoke trail, from burning oil and so forth, though no guarantee that you would have seen this smoke at the time.
quote:I do not recall seeing the actual collision. and assume that this was hidden by the trees at the southern end of the rec.
Bit of a long shot but, if you could make reasonable guesses as to the height of those trees, at the time, your position relative to the trees and project the angle of your line of sight to where the aircraft likely were, then it might be possible to extract some altitude information. At the very least limiting the upper value. The height of the cloud base may have gone into contemporary accident reports, so you can check your result for reasonableness.
quote: The tide was out atb the time, and I have made an enquiry with UKHO to see if times and heights that day are available.
Tide tables might not be of help, beyond saying in, out or 'on the turn'. Published heights relate to places where ships go, estuary mud flats not being one of those. Even geographically close places see tides rise out of synchrony, thanks to combined effects of tidal zone contours, river outflow rates and so on. London's high tide could be hours out of step with Liverpool's, for instance. Compare Blackpool tables with Liverpool and see what you find.
Unfortunately, I missed most of this prog. I caught the bit at the end about the attempted rescue of the crews and thought I heard mention of a boat being involved in getting out to the site but the water was not so deep as to make a rescue attempt appear futile, i.e. not submerged by any means. Knee-deep, say.
Whether the planes hit the ground with remaining forward momentum and skidded on mud (or shallow water) by different amounts, just _happening_ to end up close together can only be speculated about. Any potential skid marks were rapidly covered up by tide.
EF
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quote:Originally posted by Fil2: If I remember correctly there was mention of Zuber's plane coming down in a flat spin. If true it would've lost lift and fallen almost vertically. The height was stated as being 1,000 feet which is quite low so I wouldn't expect the wrecks to be very far apart, especially as they were originally flying in the same direction at about the same speed.
A flat spin does not totally proclude a component of forward motion, so it doesn't necessarily have to be a vertical drop. In fact you would be left having to explain how the a/c suddenly went from 150 mph forward speed to zero, first.
If you've seen those films of planes (particularly jet fighters) being stall tested, this generally involves starting at very high altitude and scrubbing off forward speed by climbing vertically vertically upward. The plane then, indeed, plummets vertically, tail first to begin with and may go into a spin at the point when its nose comes down towards level.
The only way to recover a stall is to point the nose down, restore airflow over the wings and gain sufficient forward speed. Rudder input is required at this point, to counteract any spin component. When it is in a flat spin, there is no control authority (airflow in all the wrong directions) and the pilot may be unable to get the nose down for a long while, not until they get into the denser part of the atmosphere, sub 10,000 ft.
Needless to say, stall/spin recovery in a WWII bomber of that size would need substanially more than the altitude these planes had available to them - and that's with all their parts attached.
EF
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quote:Originally posted by Nick_Wotherspoon: In the thoeretical TT scenario Hubbard has formed up so would be at cruising speed of say 160mph and Zuber is catching up so speeds up to say 200mph - the increased momentum of his plane would surely carry it further following the collision?
What about conservation of momentum though?
For the faster plane to have retained much of its excess speed, it would have had to slice cleanly through the other plane, with little or no kinetic energy transfer. However, the slower plane was not made of paper and the deformation of a wing spar is referred to, which is testament to the energy of the collision.
So, identical planes, identical fuel load but different speeds. Simple application of the maths would suggest that the collision causes the slower aircraft to gain some speed and the faster one to lose speed, with their two speeds coming out near identical, at the average value. Make allowances for the energy required to deform structures in the impact and shave off some speed to account for that. Thus they should end up reasonably close together on the ground. The difference of 80 feet would then come down to differences in air resistance on the two airframe remnants, one more damaged than the other, or changes in frontal area as they span in various axis's (axes?).
Something of which motorway tailgaters must be unaware is that kinetic energy goes with the square of the speed. If you're doing 80mph, the person in front brakes to 75mph and you collide with them, it is not like a 5mph impact into a stationary object, it's more like a 28 mph impact, in kinetic energy terms. For 200mph versus 160mph (for the sake of argument), it would be like a 120mph smash into something stationary. Somewhat excessive for this scenario but I'm just trying to get across how small a speed difference is capable of causing significant damage. See that Beaufort video clip for a graphic demonstration.
quote: A recent investigation I did into two hurricanes that collided whilst in formation at the same speed, still came down nearly half a mile apart and two P-38s which did the same impacted well over half a mile apart.
Were your comparson impacts at precisely the same altitude though? The higher up the impact occurred, the more opportunity there is for tumbling effects (and changing frontal area versus airflow) to divert (and this diverge) the paths of descent - 'falling leaf' analogy. The higher up you start, the larger the likely spread but a very random and unpredictable process altogether.
EF
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quote:Originally posted by Steve Moss: Even if it is not possible to recognise intact wings, tails etc, we look for evidence of the '4 corners' of the aircraft, that is to say that if we see evidence of any extremity such as a tip being there, then we assume the whole wing was present. See the Spitfire dig at Wierre-Effroy, where there was no sign of the tail surfaces but discovery of the rudder mass balance showed that the fin and rudder must have crashed with the aircraft.
Indeed so. I gather it was not uncommon for unexploded bombs to leave their tailfins behind on the surface. Presumably much the same happens to the lightwieght, deformable parts of the a/c, peeled off, left on the surface and doubtless cleared away from the site by locals, soon after the original crash. The mass balance of the tail (made of lead??) would have penetrated deeply enough into the ground not to be found intil a dig.
quote: With the wing damage we do know suffered by Hubbard's aircraft, it would have rolled violently left. In practice, this on its own can cause the tail to twist off. The loss of the tail will cause the aircraft to violently pitch _down_ (not up).
This is somewhat counter intuitive, especially if you consider that the lift component of the main wing actually points slightly rearward, rather then vertically upward (assuming a positive angle of attack whilst in level flight). However, the CofG is often designed to be slightly forward of the centre of lift (the imbalance controlled using elevator trim, mounted on the tail). The weight of the engines is almost certainly ahead of the overall CofG and counteracted by the tail surfaces which, once lost, causes the pitching down.
To me, this implies that the fixed horizontal tail surfaces are producing downforce on their side of the CofG (ie tendency to raise the nose).
The loss of the tail would move the centre of gravity forward no matter where the designer had put it. By the look of it the A26 had a weak point in the fuselage just at gunner's compartment, both aircraft failed in this area, so quite a lot of the aircraft's after fuselage would've been lost which would've made it very nose heavy.
In 1971 a BEA Vanguard (G-APEC) crashed in Belgium after the tail fell away (corrosion from a leaky toilet). It went into a near vertical dive.
For the faster plane to have retained much of its excess speed, it would have had to slice cleanly through the other plane, with little or no kinetic energy transfer.
Hello ExsistoFelicis, I have followed your posts with interest - Some very interesting points made - thank you for sharing them - I have to confess I had not considered the above & IMO it was a very "messy" rather than "clean" impact - which as you point out could well leave both aircraft falling at a similar trajectory.
The two examples I quoted (P-38s & Hurricanes) were both at around 7000 feet but over high ground - still they would have had at least double the distance to fall - I take your point.
However the thing that still really puzzles me is the apparent impact attitude of Hubbard's plane - my limited knowledge + all the comments made would seem to indicate that with the damage it had sustained, it should have dived straight in - nose down - yet it literally "belly-flopped".
Zuber's aircraft on the other hand, certainly appeared to have been a more "conventional" impact - high energy - nose down - though it had lost both engines before hitting the gound.
However I confess my interest in determining how an aircraft impacted is usually more to do with working out which direction to ask the digger operator to concentrate on than how the aircraft fell out of the sky!
Yes, 7000' feet up gives plenty of room for aerodynamic effects to make two planes diverge after a mid-air, or at least not just go vertically downwards. Shipwreck investigators sometimes find missing sections of hull a mile or more away from a main site for similar reasons.
quote:Originally posted by Nick_Wotherspoon: However I confess my interest in determining how an aircraft impacted is usually more to do with working out which direction to ask the digger operator to concentrate on than how the aircraft fell out of the sky!
To my mind, the mechanics of 'how' these things happen very much leads you to the 'where' the various pieces end up. If you can visualise a whole range of possible causes and outcomes then you only have to weigh up the probabilities of each and then go with your instincts. Chances are you shouldn't have to dig down more than twice to score a 'hit'. Furthermore, for every 'miss' you can then say, "if this, this and this had happened, we would expect to find something here and it's not there", which is a step closer to solving the mystery. Negative results do have a value of their own, in that regard.
On the other hand, if your stated goal was "get bits of aircraft to put on display", negative results can be just plain annoying...
It's plausible that neither aircraft lost entire tail sections or control surfaces whilst in the air, in spite of the damage from prop strikes; the tail pieces got flung off only after they impacted.
The aircraft which was faster and did the shunting, from behind (and below? - I missed crucial parts of the prog) loses both props. Assuming the pilot was not concussed by the mid-air impact, a controllable glide to a high-speed belly landing might have been achievable but a stall/spin into the ground ('pancake' as opposed to nose-first) seems to be more likely. In the event it was so hard that the engines came off their mountings and got left behind as the rest slid to a halt.
The "shuntee"'s plane may have lost just one engine. In theory this is a survivable situation - the whole point of twin engines is that failure of one, on take off, does not prevent the plane climbing to safe altitude, abeit at a crawl with heavy loading. The problem is that it yaws the aircraft to one side and can only be corrected if the rudder (and rudder trim) are present, functional and the cables/hydraulics are still connected. If that was specifically where the damage had occurred, the uncontrolled yaw would have developed into a skid, followed by one wing stalling ahead of the other, making the plane dip a wing.
The second plane goes in nose-down but, if one wing was low, struck the ground first and augered into the mud, it would have swung the rest of the plane around, thus leaving you with the noses of the two planes pointing, unexpectedly, towards one another.
The "basic reason for the accident was known". Not so. Many posters to this thread, including an eye-witness, do not know the cause. The theory proposed by the AAID bod has been justly demolished by many posters here. Unless/until the engines of the second a/c are brought to light, the 'air collision' theory cannot stand up to scrutiny.
