BobKatNew Wreckage Location Plan with probable paths of falling wreckage
With the help of members of this forum, we have now identified over 160 of the more than 200 items of wreckage found. This has enabled us to obtain a good picture of where the various parts of the aircraft fell.
Recent contact with some new eye-witnesses to the crash of ED908 (now in their eighties) has caused us to re-visit the probable flight path of the falling aircraft shown on the wreckage location plan. It seems that no one individual’s recollection is completely correct, almost certainly because of the ‘cork-screw’ gyrations of the stricken aircraft which were described, causing different impressions of the direction from which it had come. It could neither have come from the north-west, as described by one witness, or turned back on itself, as described by another. This is what gave rise to the question of what was the likely position of the aircraft when the explosion caused the port wing to detach, as discussed in the last few posts.
In consultation with a retired RAF navigator, we have now worked out the probable path of the falling aircraft and the detached wing. It seems that the loss of the port wing would have caused a short-lived deviation to the left of the forward momentum of ED908’s original flight path as the aircraft turned onto its back and then commenced an uncontrolled gyrating and tumbling descent rotating around an axis running approximately parallel to the original course. The detached port wing would have spiralled down following approximately the original course of the aircraft but would now be expected to fall to the right (not the left) of the rest of the fuselage. This is exactly what we see in the pattern of the pieces found. In particular we now find that the pieces of tail fin which broke away are directly under the probable flight path of the falling fuselage, which makes much more sense. The wind direction (derived from the formation’s heading in relation to the angle of the Oboe beam) would have tended to cause all the falling wreckage to drift slightly to the left of its original path.
As was pointed out by Planehunters in April 2014 (post #673), the pattern of the wreckage indicated that there must have been an explosion shortly before the aircraft hit the ground. The latest wreckage location plan now shows the probable flight paths of the falling fuselage and detached wing, and the approximate position of a presumed explosion in the port wing which led to this part of the wreckage being scattered over a wide area. This helps to explain the location of some of the smaller engine pieces found high up on the forest slopes.
For those interested in the forensic aspects of the crash, an aerial view of the likely scenario and a diagram illustrating the probable aerodynamics of the stricken aircraft are attached below, together with the amended wreckage location plan. Higher resolution copies are included in the photo-gallery.
Photo-gallery:
https://onedrive.live.com/redir?resid=BCF75E8AD40ADF0D!164&authkey=!AJrxfdmdr6MXSdw&ithint=folder%2cjpg
Index to parts found and annotated illustrations:
https://onedrive.live.com/redir?resid=bcf75e8ad40adf0d!1426&authkey=!AAJOZyTYrN-x0CQ&ithint=folder%2cjpg
BobKatBomb trajectory
Yes, I found it strange that there was no altitude mentioned in the table, Peter. However, I have now discovered that Terminal Velocity is defined as: the constant speed that a freely falling object eventually reaches when the resistance of the medium through which it is falling prevents further acceleration (not the velocity as the object hits the ground, as I had assumed). So, height is not relevant to the calculation!
Many thanks for the link to your earlier thread, Terry. I have to say having looked at the Wikipedia link, it is becoming apparent how skilled the WW2 navigators and bomb-aimers needed to be. The example quoted deals with a 500 lb bomb released at an altitude of 20,000 feet at a speed of 200 mph (presumably Indicated Air Speed) with a 25-mph wind. Assuming this was a head wind, then the ground speed would be 175 mph. The calculations apparently produced an answer that the bomb would travel approximately 6,500 feet before impact, with a trail of about 1,000 feet from the theoretical (vacuum) range of 7,500 feet. The effect of a 25-mph wind was said to be 300 feet and the time to fall was 37 seconds. The impact velocity was 1,150 ft/sec at an angle of 77 degrees from horizontal.
I have input the relevant details into my simple graph model for the theoretical trajectory. This calculates the time to impact as just over 35 seconds and the total distance as 9,050 feet. I can understand that the time taken in the quoted example would be increased from the theoretical figure because of the slowing caused by air resistance. But, I can’t understand the calculation of a shorter distance. Perhaps there are a large number of variables built in to the full equation – weight and dimensions of the bomb, drag on the aircraft, wind drift etc.
However, what is interesting, and most helpful, is the ‘trail’ of 1,000 feet shown for a total distance of 7,500 feet. This is extremely close to the total distance calculated for ED908. Using a simplistic calculation for the ‘drag’ factors in the example quoted, I have produced a graph which shows a ‘throw’ of 6,410 feet and a ‘trail’ of 1,042 feet for the total distance of 7,452 feet (not dissimilar to the one in my earlier post). If this is reasonably accurate, ED908 would have been 6,410 feet from the target at the release point on a bearing of about 95 degrees on the Oboe beam. So, its fall to earth would have commenced about 1.2 miles from the target, which is the question I was asked to try to solve. How accurate this is, I do not know, but it is the best estimate I can presently produce!!
Many thanks for your help, Terry. If anyone can add anything more to this topic, I would be glad to hear.
BobKatMany thanks, Terry. I’m not sure what to make of all that!! There seems to be no reference to the height from which the bombs were dropped in order to reach the terminal velocities shown. Am I missing something?
BobKatBomb trajectory
I have calculated the theoretical trajectory of the falling bombs using the formula (time=√(2 x height)/g) where g = 32.174 ft/sec2. This produces the result that with a starting height of 16,000 feet and a speed of 140 knots, the bombs reach the ground after 31 seconds (first graph). Using the formula, distance =velocity x time, this gives a range from the target of 7,452 feet, or approximately 1.4 miles, assuming no air resistance (second graph). The weight of the bombs is irrelevant to this part of the calculation.
As the aircraft’s wing detached immediately after bomb release, this would enable us to calculate the point at which the aircraft started its fall to earth. Or it would, if air resistance was not a factor in the calculations.
All the necessary calculations, allowing for wind drift etc, would presumably have been built in to the bomb-aimer’s computor, and in our case, the Oboe ground station transmissions.
The third graph shows the effect of air resistance on the bomb trajectory, but the ‘actual’ trajectory is simply an illustration, not based on any proper calculation. This is where I was hoping for some help. I fully appreciate the complexity of the calculation involving the weight of the bomb (500 lbs), but it may be that someone could give me an approximation of the reduction (in percentage terms) in the distance from bomb release to target which could occur in such a case. For example, might the theoretical 1.4-mile range reduce to 1 mile?
Any thoughts would be much appreciated, please.
BobKatResearch is continuing regarding the demise of ED908. I have been asked to ascertain at what range from the target the aircraft would have been at bomb release.
I understand that the information required for a calculation to be performed is as follows:
Type of aircraft: Avro Lancaster Mk.III
Weight of bombs: 18 x 500lb = 9,000 lbs
Height: 16,000 feet
Airspeed: 140 knots
I am told that the range is usually described as “Forward Throw”.
Can anyone help please?
BobKatNobody has yet mentioned Little Staughton airfield near St Neots. I last visited it about five years ago. At that time, it was still being used for light aircraft – so not falling into the category of disused airfields. Many old buildings survived in what was then a small industrial estate, including the Control Tower. Maybe somebody can confirm whether part of the runway is still being used?
There are some pictures on https://forum.keypublishing.com/showthread.php?96130-Little-Staughton-Airfield-2009-Thread-Revived&highlight=little+staughton
BobKatThanks again for all your trouble, Peter. The flexible pipe and valve fitting are now visible! It would seem that pieces 108B and 86 must have come from the port and starboard sides of the same engine.
BobKatMany thanks, Peter. The valve fitting looks a little different from our piece, presumably a modification to the original, or maybe a modern variant? I can’t see any diagrams or illustrations of the fitting in the Merlin engine manuals I have – only one for the cooling system and the radiator shutter ram which is not sufficiently detailed.
I guess we were lucky to find the picture from Ailes Anciennes of the starboard side of a wartime engine with its original fittings still in place. It seems that the only way we will ever be sure about the port side fitting is to find an intact wartime engine pictured from that side! If anyone knows of the whereabouts of such a picture, it would be good to hear.
BobKatPeter, I have now found a description of the operation of the pneumatic rams in The Lancaster Manual. I see that the Heywood Compressor operates a pneumatic system controlling the wheel brakes, radiator shutters, supercharger rams and idle cut-off rams. So my only remaining question is whether there is a similar valve to the one(s) found attached to each of the rams in the engine nacelle? I would assume the answer to be, yes, but if anyone has a close-up picture of the supercharger ram in situ which would confirm this, this would be much appreciated. The Ailes Anciennes photograph confirms the connection to the idle cut-off ram.
BobKatMany thanks, Peter. After some research yesterday, by a process of elimination, I had come to the same conclusion. I have been unable to find any pictures of the idle cut-off ram on the starboard side with a close-up of its fittings in place. The piece we have seems to fit into the side of the ram, with the flexible tube leading towards the bulkhead or carburettor, but it is difficult to tell. Am I right in saying that the supercharger ram on the port side would have had a similar fitting?
Without any knowledge of the engine mechanisms, I am struggling to understand the function of our piece. Am I right in saying both rams were operated pneumatically, and so our valve was controlling air-flow pressure?
Interestingly, the piece discovered at location 74 was found with what was identified as either a supercharger or idle cut-off ram. You kindly posted some photographs (post #774) showing the two rams in situ, but partially obscured by other fittings, so it is difficult to see the detail. If you have another photograph (or a diagram) showing more detail, that would be great.
Curiously, item 86 was found close to item 108B, so is it possible that we might have pieces from both rams from one engine?
BobKatLaurent has been working hard to identify item 108B, and I think he has solved it!
I attach a picture of the recovered engine of Lancaster ND689 which was undertaken by those working on Lancaster NX664. The picture below was found on the Ailes Anciennes website. Laurent’s eagle eyes have spotted what appears to be our piece No.86 (circled in the enlarged centre picture and shown at the top right below) and what is presumably also our piece 108B (shown at the bottom right below) which has fractured beneath the extension.
It may be that the pipework is out of position in the photograph as the engine is damaged, but I am unable to identify our piece from any of the illustrations of Merlin engines which I have. Can someone please help to confirm what is shown in the picture?
Photo-gallery:
https://onedrive.live.com/redir?resid=BCF75E8AD40ADF0D!164&authkey=!AJrxfdmdr6MXSdw&ithint=folder%2cjpg
Index to parts found and annotated illustrations:
https://onedrive.live.com/redir?resid=bcf75e8ad40adf0d!1426&authkey=!AAJOZyTYrN-x0CQ&ithint=folder%2cjpg
BobKatItem 108A
I think I may have solved the mystery of piece 108A. Flexible fuel pipe is also used forward of the bulkhead for the fuel feed to the engine, as pictured below (with thanks to those working on FM212 and NX611). Our piece has traces of some olive-green paint on the connection which would be consistent with it being fixed to the bulkhead. This could also explain the trace of red paint on the sleeve.
It would therefore seem possible that item 108B is also engine-connected and to be found forward of the bulkhead. This may narrow down the possibilities. Any ideas anyone?
Photo-gallery:
https://onedrive.live.com/redir?resid=BCF75E8AD40ADF0D!164&authkey=!AJrxfdmdr6MXSdw&ithint=folder%2cjpg
Index to parts found and annotated illustrations:
https://onedrive.live.com/redir?resid=bcf75e8ad40adf0d!1426&authkey=!AAJOZyTYrN-x0CQ&ithint=folder%2cjpg
BobKatLocation 108
A Happy New Year to all followers of this thread, and a New Year puzzle to welcome 2018!
Two of the three pieces found at location 108 have characteristics which should enable them to be identified. The third is a fragment of metal which could be part of a wing rib, or maybe part of a fuel tank.
The first picture shows all three items to give a comparison of relative size.
Item 108A has a central fixing ring with four nuts. Its right-hand part is almost identical to a part found nearly four years ago at location 49, except that that the letters ‘..UEL HOS..’ (presumably FUEL HOSE ?) and a number (2538171 ?) are visible on the end of the pipe as seen in the enlarged detail. There are traces of red and olive-green paint on the fitting which may provide a clue. The earlier piece – identified as an AGS711H sleeve – was made of brass cadmium. This fitting was replaced by AGS904H made of anodised aluminium alloy. AP2062A&C shows parts numbered AGS904H were used for 1-inch BSP pipework on the return part of the hydraulic system: the sleeve measured 1.67 inches across its flat sides. The delivery pipes of the hydraulic system measured ¾-inch BSP. There is no mention of this part being used for the fuel system which seems to have been modified a number of times.
AP2062A&C also shows that the fuel system in the outer wing used ‘Superflexit’ tubing. The bore is not shown, but later modifications used ‘Flylite No.4’ 1-inch bore tubing in the outer wing and along the spar. The two hexagonal sleeves on our piece measure 1.48 inches across the flat sides – the size of the mild steel cadmium AGS954H sleeve. All these are fittings for a 1-inch BSP pipe, which is the size of the protruding pipe at each end of our piece.
So, what is our piece? There is a fragment of thin metal (about 1mm thick and seeming not to be aluminium) trapped between the ring fitting and one of the washers which can be seen at the lower right of the second picture. Could this be part of a fuel tank or part of a wing rib to which it was attached? An illustration in the Parts List for the Mk.X Lancaster shows a fitting with four bolts inserted into the No.2 fuel tank with a flexible vent pipe attached. Could this be what Laurent has found? Can anybody provide further help to identify this, please?
Item 108B, which is pictured resting on the separate fragment of metal, is similar to two items previously found which are also pictured. It was suggested that the one found in 2015 may have been a high-pressure valve, but it was not positively identified. Both these parts have attachments for what appears to be a flexible pipe on their left. Laurent has measured the width of the hexagonal nut on the right of the latest piece as approximately 5/8 inches which corresponds to size B of the AGS fittings, with a ¼-inch BSP pipe. AP2062A&C shows fittings of this size in the flotation pipe and jettison pipe systems, both with ¼-inch flexible pipe attachments. We have three similar items. Any further help to identify these pieces would be much appreciated, please.
Photo-gallery:
https://onedrive.live.com/redir?resid=BCF75E8AD40ADF0D!164&authkey=!AJrxfdmdr6MXSdw&ithint=folder%2cjpg
Index to parts found and annotated illustrations:
https://onedrive.live.com/redir?resid=bcf75e8ad40adf0d!1426&authkey=!AAJOZyTYrN-x0CQ&ithint=folder%2cjpg
BobKatLocation 107
Attached is the first of Laurent’s new finds. It is an AGS 904F ¾“ BSP sleeve (pictured from two angles) and was mostly used in the hydraulic system in different parts of the aircraft. It cannot be identified to a particular location, but probably came from the port wing. It bears the Avro inspection mark R330A. Details of other new finds will follow when more information is to hand.
Photo-gallery:
https://onedrive.live.com/redir?resid=BCF75E8AD40ADF0D!164&authkey=!AJrxfdmdr6MXSdw&ithint=folder%2cjpg
Index to parts found and annotated illustrations:
https://onedrive.live.com/redir?resid=bcf75e8ad40adf0d!1426&authkey=!AAJOZyTYrN-x0CQ&ithint=folder%2cjpg
BobKatMany thanks, Peter. The only colour obviously visible is black so, if it is a piece of the engine cowling, then the assumption must be that it could not have come from the upper part of the cowling (panels 3 or 10 in the diagram in my post #1138), but that it must be from the lower part of the cowling. If there are Dzus fasteners attached, then it would seem that it must have come from either the upper corner of the rear of panels 1 or 2, or the upper corner of the front of panels 8 or 9, and not as I showed it in the diagram at the forward end.
Laurent has been busy over the festive break and he has found a few more pieces. I am waiting for confirmation of some measurements, after which I will post details.
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