Technical Talk

[Engine 711]

Two things Mr 'Canopener'.

Why are some people so aggressive on Discusion Forum's? There is absolutely no need to be rude, and my reply certainly did not give you cause to be so.

The second thing is this.

Keith Mitchell and I (Neil Sheppard) did literally hundreds of hours of analysis with the full co-operation of Prof John Stollery (Consultant aero dynamicist retained by the Norris bros and DC) from Imperial College and latterly Cranfield and Mr AE James (managing director of Norris Bros and project manager for the 1966 rebuild). Tony carried out the post crash analysis in 1967. The conclusions we came to are on a basis of that work and are fully endorsed by Mr James and the late Prof Stollery. I suggest again that you take time to read our analysis before repeating the conclusion that Campbell hit his own wash when Bluebird left the water. Its a little bit more complicated than that.

Well said @sheppane - on both counts.

First thing - Because they can. Simple.

Second thing - I find the analysis & arguments presented in Ch10 of your book, quite convincing - as a professional engineer (*). Its a lot easier to simplify what happened - he hit a log, he hit a wave, he hit his own wake - all been offered over the years. But - to 'do the math(s)' - and show K7 was (always) potentially unstable at higher speeds - is more tricky and perhaps difficult for people to understand and to accept.

Similar 3 pointer racing hydroplanes to this day, quite often flip - much as K7 did. And probably for basically the same reasons - going too fast for the craft and/or conditions, on the day. On another day, could be fine - but today, they flip. On previous days, K7 has been fine - but not on 4Jan67 - not really on either run, tbh.

Run One was fast, very fast (297mph average, confirmed by timing) - K7 was 'floating' but DMC got her through. On Run Two was he trying for just a bit more speed - to push his average over 300 - probably. Did he have an Engine Flame Out at just the wrong time - yes - and then lost the very useful downward force on the bows, due to Engine Thrust - yes. What else could he have then done...? Probably nothing.

Its a lot easier to say he hit his own wake - or a log - or was foolhardy.

(* - Gas Turbines - Marine & Aero - for over 35 years)

IM

[rich1608]

Did he have an Engine Flame Out at just the wrong time - yes - and then lost the very useful downward force on the bows, due to Engine Thrust - yes. What else could he have then done...? Probably nothing.

Could that and previous flameouts have been caused by a missing clamp screw in the battery connection panel? See under 'Rebuilding K7’s Wiring Loom and Electrical Systems – Part 1' in the Diary http://www.bluebirdproject.com/index.php?id=63

[Engine 711]

Did he have an Engine Flame Out at just the wrong time - yes - and then lost the very useful downward force on the bows, due to Engine Thrust - yes. What else could he have then done...? Probably nothing.

Could that flameout have been caused by a missing clamp screw in the battery connection panel? See under 'Rebuilding K7’s Wiring Loom and Electrical Systems – Part 1' in the Diary http://www.bluebirdproject.com/index.php?id=63

Ok, have found the Diary bit you refer to. Hmm. A possible intermittent problem with 24V DC power - which runs the LP Boost Pump(s)....? I am not sure that's very likely. 24V DC also runs the Ignition Units, so 24V must be 'on' to start up - to light the flame, as it were. But after that, 24V is only running the LP Pump(s) and any Panel Indications - Air Pressure Warning and Low Pressure Fuel Warning are mentioned (as being 'on' - during Run 1 4Jan67), by DMC, I think...?

I really do not understand how K7's LP Fuel System was supposed to work, after the extra Tank & LP Pump were installed. Before then, I think the single LP Pump in the extra Tank under the Engine (the smaller L- shaped one - not the big Doughnut shaped on, around the Intake) sucked from its tank and fed fuel to the Engine Pump LP inlet....? So, the L-shaped tank got its Fuel from the Doughnut, via gravity or siphon....? Am unclear were the 2nd Aux Tank and 2nd LP Boost Pump were fitted, system wise.

Killing either of the LP Pumps would not be a problem immediately - the Engine Pump could still suck fuel. But the stopped LP Pump would prevent fuel getting through - so the tank it was in would run dry. Which would severely drop the Fuel Flow - and likely cause a Flame out.

Its possible - but to what degree would a not fully secure Battery Connection cause a loss of 24V DC....? Very difficult to say - and I think its unlikely. Very good spot though - and must remain a possible.

A Flame Out, btw, is literally that - the flame goes out (which is normally continuous). Usually due to lack of or shortage of fuel (strictly its Weak Extinction) - or additionally for K7, water in the front. Typically happens on a fast decel, from power. Another possibility (which is unlikely for the Orpheus) is a Compressor Surge - where air flow reverses and the flame is sucked/blown out of the front. Can melt your Compressor....


IM

[Engine 711]

But the stopped LP Pump would prevent fuel getting through - so the tank it was in would run dry. Which would severely drop the Fuel Flow - and likely cause a Flame out.

Nope- the second LP pump was in place on Bute, unplugged and not running for most of the time, and still allows fuel to flow through. Any benefit it may have imparted in Donald's final days still seems to be a mystery.

Ah, OK. So the 2nd LP Pump is in series with the 1st /main one, then....? Sorry, I cannot fathom how its supposed to help. The original LP Pump is down in the bilges, inside what I call the L-Shaped Tank. I believe the Aux Tank with the 2nd LP Pump is mounted higher up, above the engine centre line. Is that one first in line - so then feeds the original LP pump..?

The only LP Pumps I know are the LP stage of the Trent Main Fuel Pump - and are basically just an centrifugal impeller. I have no idea how Tank mounted Electric ones are designed.

IM

[Renegadenemo]

Killing either of the LP Pumps would not be a problem immediately - the Engine Pump could still suck fuel. But the stopped LP Pump would prevent fuel getting through - so the tank it was in would run dry. Which would severely drop the Fuel Flow - and likely cause a Flame out.

The LP pumps are of the centrifugal, submerged variety from the Gnat, manufactured by SPE and identical to those later used on the Harrier. In the event of a failure they have a door that lifts to ensure that fuel still flows. The Lucas piston pump would have to pull a little, something it's not really designed for, but it'll keep on trucking with a little cavitation going on long enough to get the aircraft on the ground. LP failure shouldn't have caused a flameout. We had no unexplained flameouts during operations on Loch Fad. The most likely explanation in Donald's day was the inclusion of a primitive anti-surge control unit, one of only two ever built and described by the engineers who built it, by modifying a bellows system designed with a totally different purpose in mind, as a 'lash up'. Coming out of the throttle quickly would flame out the engine because of this and, as he had only enough gas for a couple of starts at best, having to relight the engine then left him no option but to turn around and come straight back up the lake before the fuel ran out. We now know these things with absolute certainty.
How's that for illuminating...

[Engine 711]

The LP pumps are of the centrifugal, submerged variety from the Gnat, manufactured by SPE and identical to those later used on the Harrier. In the event of a failure they have a door that lifts to ensure that fuel still flows. The Lucas piston pump would have to pull a little, something it's not really designed for, but it'll keep on trucking with a little cavitation going on long enough to get the aircraft on the ground. LP failure shouldn't have caused a flameout. We had no unexplained flameouts during operations on Loch Fad. The most likely explanation in Donald's day was the inclusion of a primitive anti-surge control unit, one of only two ever built and described by the engineers who built it, by modifying a bellows system designed with a totally different purpose in mind, as a 'lash up'. Coming out of the throttle quickly would flame out the engine because of this and, as he had only enough gas for a couple of starts at best, having to relight the engine then left him no option but to turn around and come straight back up the lake before the fuel ran out. We now know these things with absolute certainty.
How's that for illuminating...

That's extremely informative. Thanks, Bill..

A quick 'Google' on Aircraft LP Boost Pumps suggested they could be CF types, with a built in bypass - but I simply was not sure, to say so.

A Lucas Pump, albeit a latter one, was tested for sucking, in Marine/Naval applications and was found to do just fine - which potentially allowed to removal of gravity feed back up tanks mounted high in the ship, designed to provide a positive pressure if the Ships LP pumps failed (due to loss of electrical power). Fuel high up in a Naval ship = Not Good .

Ok, so that leaves the Decel Control or Anti-Surge Unit. Hmm. Looks like a Smoking Gun to me - have spent many hours with such things, flaming out and/or surging engines for work. What is needed is something to support fuel pressure and flow as the engine decels. One option (from Marine Olympus) was what was called a Min Flow Servo Valve - which stopped Pump Servo dropping below a set level.

So we could conclude that the 700 series Orpheus (as used in K7) was a bit marginal on decels, if not handled very carefully. Easier to do in a Prototype Gnat with lots of sky, less so in K7 with a hard shoreline racing towards you. Also, that the quick turn round was perhaps forced, following the flame out an the end of Run 1. And that the flame out during Run 2 was perhaps similar to that in Run 1...?

All most illuminising. Thank you.

IM

[sheppane]

The LP pumps are of the centrifugal, submerged variety from the Gnat, manufactured by SPE and identical to those later used on the Harrier. In the event of a failure they have a door that lifts to ensure that fuel still flows. The Lucas piston pump would have to pull a little, something it's not really designed for, but it'll keep on trucking with a little cavitation going on long enough to get the aircraft on the ground. LP failure shouldn't have caused a flameout. We had no unexplained flameouts during operations on Loch Fad. The most likely explanation in Donald's day was the inclusion of a primitive anti-surge control unit, one of only two ever built and described by the engineers who built it, by modifying a bellows system designed with a totally different purpose in mind, as a 'lash up'. Coming out of the throttle quickly would flame out the engine because of this and, as he had only enough gas for a couple of starts at best, having to relight the engine then left him no option but to turn around and come straight back up the lake before the fuel ran out. We now know these things with absolute certainty.
How's that for illuminating...

That's extremely informative. Thanks, Bill..

A quick 'Google' on Aircraft LP Boost Pumps suggested they could be CF types, with a built in bypass - but I simply was not sure, to say so.

A Lucas Pump, albeit a latter one, was tested for sucking, in Marine/Naval applications and was found to do just fine - which potentially allowed to removal of gravity feed back up tanks mounted high in the ship, designed to provide a positive pressure if the Ships LP pumps failed (due to loss of electrical power). Fuel high up in a Naval ship = Not Good .

Ok, so that leaves the Decel Control or Anti-Surge Unit. Hmm. Looks like a Smoking Gun to me - have spent many hours with such things, flaming out and/or surging engines for work. What is needed is something to support fuel pressure and flow as the engine decels. One option (from Marine Olympus) was what was called a Min Flow Servo Valve - which stopped Pump Servo dropping below a set level.

So we could conclude that the 700 series Orpheus (as used in K7) was a bit marginal on decels, if not handled very carefully. Easier to do in a Prototype Gnat with lots of sky, less so in K7 with a hard shoreline racing towards you. Also, that the quick turn round was perhaps forced, following the flame out an the end of Run 1. And that the flame out during Run 2 was perhaps similar to that in Run 1...?

All most illuminising. Thank you.

IM

Many thanks for this stuff Bill and IM. I think it may go a long way to answering why quick turnaround only runs were deployed in 66 / 67. At no stage during those trial runs on the 10th, 12th, 13th and 14th December did K7 stop to refuel. There is only evidence that he came back straight away. My reading of this is he didn't stop because he had no certainty of getting the Orpheus started again. No start, no return, no Record. He was safe coming back straight away, but this situation removed an option not to.

[Engine 711]

Many thanks for this stuff Bill and IM. I think it may go a long way to answering why quick turnaround only runs were deployed in 66 / 67. At no stage during those trial runs on the 10th, 12th, 13th and 14th December did K7 stop to refuel. There is only evidence that he came back straight away. My reading of this is he didn't stop because he had no certainty of getting the Orpheus started again. No start, no return, no Record. He was safe coming back straight away, but this situation removed an option not to.

Neil - You are most welcome. Thank You, also - for writing what (IMHO) is the best book, on K7.

The other bit of supporting evidence, again from @renegadenemo, is that the On-Board Air Start system was/is not as capable as its spec suggests (it was claimed to do 6 starts - but didn't even at Norris Bros, unless recharged repeatedly). During the start of Run 1, DMC comments that Air Pressure Low is on - in other words he knew that any attempt at a full re-start was at best dodgy, at worst could fail - and then he could be stuck at the bottom of the lake - with (potentially) a record breaking 1st Run in the bag. Bugger. No wonder he relit the Orph ASAP, on the fly (before it ran down), then spun K7 around and lined up for a quick return. As he had done, before. Quite logical.

IanM

[rich1608]

Excuse my ignorance but I take it the Orph' had to be shut down for refuelling for obvious safety reasons?

[Renegadenemo]

Excuse my ignorance but I take it the Orph' had to be shut down for refuelling for obvious safety reasons?

Yes, it would be tricky to refuel with the engine running to say the least! The achilles heel was undoubtedly the on board air start. From what we know of spooling up the Orph', even with our converted HP starter, which reduces gas consumption, the air start on the boat will manage two starts at best and I'd say the second one would be marginal.
With 100litres of gas at 3200psi a good start will consume 1100psi with the engine heat soaked already and first start of the day will take about 1400psi. With the engine hot we can sneak a start with only about 700psi so our system will deliver maybe four decent starts if we don't allow too much heat to dissipate. The onboard system has only 32 litres of gas at 3200psi and factor in the January temps. It really was rubbish and my understanding of it is that it was basically an emergency measure in case the aircraft had to land away at a field with no capacity to start a turbine aircraft. It did, however, evolve into the V-Bomber rapid start system so we were able to perfectly reproduce its effect using Vulcan parts and offboard gas. Next job is to see if we can get a new pair of properly safe and tested start bottles to go on board so we can really see what it can/can't do.