richw_82If those aircraft are the only ones not ‘hot’ I’m surprised they even let people in the building.
richw_82Some folk have decided to visit the Vulcan all tickets soldout!!
Crikey… the only thing I can think of is that its either hard core Vulcan enthusiasts that want to add one more serial as ‘done’ on their list of cockpit visits, or people that get nosebleeds if they travel further North than Duxford!!
On a more serious note, I’m glad it has sold out, more funding gathered for RAFM. But can you imagine if the crew door of R5868 was open for one night for a limited number of tickets?
Regards,
Rich
richw_82I think there’s some confusion creeping in here.
The priming pumps have a pressure sensor/switch which activates a light on the priming switch on the engineers panel. It doesn’t cut off the power to the pump, it just lets you know that the pressure is there in the priming system. The only control of the pump is by rotating the switch on the engineers panel left or right to select the port or starboard pump.
With the priming switch rotated to select an engine, with the pressure light lit, you push the button in to activate the solenoid to allow priming fuel to each engine. This lets raw fuel into a rail on the top of the inlet manifold of each bank of the engine. It doesn’t go anywhere near a carb (Griffon 58 on the Shackleton doesn’t have a carburettor as such, just a rotary throttle body and a BIG injector.)
Regards,
Rich
richw_82Here’s the fuel system schematic for those that are interested. [ATTACH=CONFIG]225161[/ATTACH]
mjr –
I’ve not confirmed we’ve had more than the one strip gears. I’ll know better when I dismantle one of the pumps myself on my next visit to Coventry. I know one of them suffered a partial seizure when we were having water ingress, but we were pretty sure we had got past that point, as the latest checks of the tanks are coming up as good fuel, with no water. I haven’t been rebuilding the pumps so I don’t know what has been cross referenced and what hasn’t. Hence the need to look at it all in detail.
I still have the priming solenoids to check, the ones on the MR2 are slightly easier to get at on the outboards as we don’t have all the Viper kit squeezed into the nacelle!
I don’t think the fuel is an issue as it is all new, and from a single traceable source. We let things get down low then had WR963 refuelled from the airport bowser, with the date of the recent samples being on the fuel receipt. We’ve not used de-fuel for a couple of years now, due to contamination issues.
Bruce – Many thanks. Let me know what you find and I’ll sort something by way of our treasurer.
Regards,
Rich
richw_82Hi chaps,
Sorry for the delay in answering, my other half has been ill so my planned visit to Coventry didn’t happen and I had to rely on the rest of the team to get me the information.
The pumps the Shackleton uses for priming are the type with the fibre gears in a gearbox, they are the vane type pump. The same pumps are fitted both sides, so we have one working away merrily on the starboard side, and one that fails regularly on the port. I am prepared to cut the pumps some slack… it appears two pumps failed in different ways than to the water issues found in the past.
One has a stripped thread in the pump body which caused it to dump fuel. Another has a sealing issue between motor and gearbox. There also has been some mixing and matching of components during the rebuilds over the years that has resulted in less than perfect tolerances in the gearbox. We have started setting aside some parts to build a bench rig for these, to measure flow, pressure, and current draw. Combining this with a close attention to tolerances will allow us to rebuild our pumps and test them under the conditions found in the aircraft – hopefully resulting in failures being found before the part gets installed.
We are still looking at the replacement gears idea, following sending a pump away to some friends in MOD they suggest brass would be harder wearing over a longer period but remove the fire risk as it is soft enough to strip under load. Again, a test bench would prove its worth and we would be able to be quite violent with a test specimen if we had to write it up for those that need the justification.
Cypherus – thanks for the great description from your notes. What were they written for? Air Engineers course notes, or for instruction?
paul1867 – I’ll have the fuel system schematic uploaded tonight.
Kind regards,
Rich
richw_82Given the jewels that reside at Hendon, that is a distinctly mediocre list.
I can think of at least two museums off the top of my head you can get Vulcan access, and similar viewing most of the rest of the list at numerous locations (excluding the Spitfire.. which is only a close up look?? May as well visit the BBMF.).
But £24 extra to look inside a Vulcan? And there we were worrying about upping things to £2 instead of £1 to have a look in our Shackleton.
Regards,
Rich
richw_82The banjo fitting on the left is where the pressure switch sits to trigger the indicator lights on the priming switch. The large fitment on the right is a filter, fitted on the inlet.
WR963’s pumps are electric. We have a setup to test them (off aircraft) electrically and that they pump fuel through.
Regards,
Rich
richw_82We have the vane pump with the step down gearing, fitted on the port side of the aircraft. I’ve not checked or touched the starboard side as its been behaving perfectly. I need to get my head in the parts manual and find out what’s going on, I think given the differences!
Thanks for taking the time to dismantle things and post pictures Bruce.
Regards,
Rich
richw_82Bruce,
That’s definitely odd… all the ones I’ve had apart so far have two sets of step down gears from the motor. A small steel one, and a larger fibre one held on the shafts by a small steel pin. This is in the centre section, when you undo the four nuts and can sparate it into motor, gearbox and pump sections respectively. Everything I’ve found in the pump end is steel though?
Regards,
Rich
richw_82Based on Richard’s post about no load if the outlet is blocked I think I need to check the pump I took off to establish if it has definitely stripped its gears. If it hasn’t and still operates, then I need to check the pump that ‘failed’ last which is still fitted to WR963… if that shows the same then it points to the solenoid valves for priming at the back of each engine.
What was my assumption that the motor was at no load may have been correct – but the stripped gears may not be. Its possible the pump was behaving exactly as it should… and thats a tad annoying!
Regards,
Rich
richw_82The system is designed to build some pressure up, there is a pressure switch in the outlet line from the pump that lights up the indicators on the priming switch.
We are going to check the operation of the solenoids, but its just a strange failure, and not at all like the seizing we had through water. Thinking about it though, if the pump overpressures, it wouldn’t take much to slow the impeller down and with the motor fighting away at the other end of things, the gearbox is going to let go. I’m expecting to find a relief mechanism of some sort in the pump housing – its the only way I can think it would allow the pump to build and maintain pressure.
Regards,
Rich
richw_82As far as I know the Lancaster has a manual priming system, rather than electric pumps, so won’t suffer the problem we’re having. Its not a blocked tank vent as there’s definitely a good supply of fuel, and it would have to be blocked vents on all the tanks in the wing to cause starvation. A starvation issue would have shown up with poor running of No 1 and 2 before now; and with them using roughly a gallon a minute at idle, fairly quickly. We had them up to 2,400rpm at the back end of last year with no issues once running.
All the pumps are of a similar age, the newest one we have has a date from the 1970’s on the manufacturers plate. I’ll post pictures of what we find when we get them stripped down.
Regards,
Rich
richw_82Been trying to locate a detailed schematic of the fuel system since this problem was first mentioned, not found one yet sadly, Your comment stating that the Starboard pump was performing well for the most part and it was only the Port side that currently keeps stripping it’s gears begs two questions,
What if any are the differences between Port and Starboard fuel priming layouts.
Is the system fitted with any pressure relief method returning excess pressure to the tanks, if so I might tend to look at that aspect given you state that they only strip once they get up to pressure.
In terms of the priming system there is little to no difference between the port and the starboard system. Fuel is available from a manifold as soon as any tank **** is opened, and fed into the priming pump. From there it passes throught the pump and splits into two lines (one to each engine on that wing), with a solenoid allowing fuel into the priming rails on the top of the engine.
The switch inside the aircraft activates the pumps either side when turned to the left for 1 & 2, and the right for 3 & 4 respectively. The pump build pressure, and a yellow light comes on at the switch to signify this. Depressing the switch activates the solenoid for the engine selected allowing fuel into the priming rails, and into the inlet manifold of the engine.
I have not seen any pressure relief system built into the lines going back to the tank, so I would hazard a guess that the pumps feature this internally. With the thunder and hail moving in just after we shut down, we didn’t have time to strip the pumps for inspection and check the failed gears. I’ll report back when I’ve had a better look at them.
Regards,
Rich
richw_82I don’t believe so, water checks done on Saturday morning showed nothing from the fuel drains but good 100LL Avgas, and WR963 has been that way for a few weeks now. We also left the priming pump on the port side off aircraft, and drained the line from the fuel manifold that feeds it. As I said further up this thread – the worked fine when fitted, then when they got fuel pressure they stripped the gears. You could hear the motors screaming at no load rpms..!
richw_82We get it happen both sides, but the port side tends to cause the most issues. The pump on the starboard side is a very good one, and is doing well… we’re leaving it right where it is.
We’re going to rebuild a couple of pumps for the port side, and be very critical of which components we use. Any significant wear in the gears of stiffness in the gearbox seems to be instant death for them.
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