jonwrightk7 wrote:drawing on k w mitchells post earlier, in steve holters transcript of the cockpit tape; thirteen seconds from impact donald remarks "and shes lost........ getting a lot of bloody row in here. could this relate to the compressor blades stalling? also quoting a report issued by bristol siddeley, direct to the project: "At the proposed maximum speed of 325 knots the intake will be approximately matched. (that is AO/AI=1) therefore care should be taken in throtteling back to avoid "bucketing" associated with intake spilling and pre-entry separation at the intake ramp". thats a tad over my head but what i think it means is that at the speeds donald reached on the final run, any throttlling back could cause the engine to "choke" on the sheer volume of air it was ingesting ------
I would be very much interested to read that Bristol Siddeley Report - could you give me a reference to it please?
As to the 'technical bit' it is possible to explain it reasonably simply if we examine the diagram below. Gas turbine physics is explained by a universal convention which uses 'stations' i.e. positions in the turbine duct. These are numbered '0' through '9' (see diagram). As the duct is closed i.e. it has an inlet and an outlet, it is possible to work out the velocities, temp's and pressures at each station and calculate factors such as mass flow, nozzle velocity and overall efficiency of each stage and the engine as a whole.
Now it is also important to know some critical cross-sectional areas, inlet area and nozzle area being two examples. 'A0' in your example above is the area at station '0' which is just in front of the engine and is taken to be that where the air is undisturbed and flows smoothly into the inlet area 'A1' at station '1'.
Now I do know after examining BB's inlet ducts - and with confirmation from Bill - that those ducts have constant area up to the face of the compressor. I think then that we can assume that 'A1' is also the same as 'A2' (a fact which I would like to confirm from your ref.).
This leads to the term ' --------- approximately matched ---------' but only at the quoted speed because everything changes when the airspeed changes. If the throttling back is too rapid there will be a huge build-up of air in the inlet duct which will cause 'bucketing' and 'overspill' - not too difficult to understand, I think. There will inevitably be a breakdown in streamline flow i.e. turbulence in the inlet with associated problems inputting the compressor and the possibility of local stalling and 'surging' (the phenomonen I described in the original note).
However, I do not think it is the reason for ' ---------- the bloody row ------------'
referred to by DC as that was the phase at approx. 300mph and BB still accelerating. Throttling back - or whatever caused the reduction in power - occurred later in the episode. Also when a jet engine surges it's deafening; it would have come through the RT and would have been heard by observers on the lakeside.
However, the explanation of that 'bloody row' is still intriguing ------------. Was it because BB was getting such a pummeling or was it the results of spray droplets hitting the compressor blades (DC also reports that he ' ------- can't see anything ------' so any spray that was obscuring the canopy would inevitably ended in the inlets)?
Or what about that front engine tie-bar having let go during this episode and not during the crash - a theory well argued by Bill but rejected at the analysis at the inquest. I've seen that adjustable rod on the replacement engine and despite it's high tensile rating looks awfy flimsy -------. If that had failed then there would have been a right racket and some nasty thrustline oscillations!
In conclusion, a personal comment; the more that I dig into the history of K7, it's development, operation and subsequent modifications - and - the interactions with the main players surrounding it and the situation(s) associated with it's final demise, I become less comfortable with conventional theories as to what happened. It's not that I reject them - certainly not - but there is enough there to sustain further examination and comment. This is only an attempt to get at the truth, and many I'm sure, share that goal.
And there's enough in this mystery to sustain us.
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