Spitfire engine start

[fenderplayer946]

Hello,

 

Just for interest's sake I pulled up the original issue pilots notes, because hey, why not? probably hoping they would shed some light on operating this magnificent machine.

 

I started to run through the check list and quickly noticed its different to both the training mission and the excellent video Wags have previously put up, undeterred I carried on only to find the "old" process doesn't get you anywhere. Needless to say this could be for a variety of reasons leading to a few questions....

 

1. Are the original pilots note inaccurate or did aircrew disregard them?

 

2. Has the aircraft the simulation based on (presumably) been modernised in anyway?

 

3. Due to modern safety reasons was the start-up process modified?

 

4. Is this specific mark different to the Mk IX Merlin 66 engine covered in the pilots notes?

 

5. Where the checklists used in Wags video/tutorial taken from? The Fighter Collection's pilots? Royal Air Force BBMF pilots?

 

After some research on Youtube, various Spitfire cockpit start up videos and many don't differentiate between marks, doesn't shed any light.

 

Link: http://zenoswarbirdvideos.com/Images/spit/SPIT9MANUAL.pdf

 

I understand that it is the beta and things are subject to change but due to the nature of the subject I thought it would already by nailed down. If anyone can shed some light it would be appreciated.

 

Thanks

 

Fend'

[Sokol1_br]

Linked PN - pag 19, right side (Merlin 66).

 

Supercharger switch.. AUTO. NORMAL

 

The only basic difference is set Supercharger switch, but in game always start in this position.

Other is if need pilot should continue pump the Fuel Primmer injector after press start+coil buttons.

Edited December 22, 2016 by Sokol1_br

[fenderplayer946]

That and when you utilise the idle cut-off, according to the linked doc you should get it fully forward after operating the wobble pump/booster pump but before priming. if i do this in DCS the engine won't start, even if I try operating the priming pump as I try to start.

[Kozmyk]

Idle Cut Off is pushed forward After the engine starts, otherwise you'll flood the blower and may start a fire.

 

The sequence of operations described on Page 19 36. (iii)

appears to contradict Page 14 25. Note

The idle cut-off control must be in the fully aft position,

or cut-off position, at all times when a booster pump is

on and the engine is not running; otherwise, fuel will

be injected into the supercharger at high pressure and

there will be, in consequence, a serious risk of fire.

Edited December 22, 2016 by Kozmyk

[fenderplayer946]

On the first pass it looks like it does but in para 36 (II) on page 19 is tells you to set the cut-off in the fully aft position thus removing the possibility of a fire in the supercharger, before operating the booster pump in III. Its this sequence that doesn't work in DCS, unless the notes are incorrect.

[Sokol1_br]

That and when you utilise the idle cut-off, according to the linked doc you should get it fully forward...

 

This guy set in this way (MH434 in ~80's).

 

Edited December 22, 2016 by Sokol1_br

[Kozmyk]

I would go with the DCS sequence, which works, rather than that pdf. which doesn't.

Open the idle cut-off after the engine starts.

Edited December 22, 2016 by Kozmyk

[fenderplayer946]

This guy set in this way (MH434 in ~80's).

 

 

As in the way mentioned in the pilots notes? at 2:40 you can see the idle cut-off fully forward.....

 

Kozmyk, yeah that's the only way that works in DCS, just wondering which is the most accurate more than anything else..... It's nothing game breaking.

[Sokol1_br]

I do my way - for fast start, and works. ;)

 

Is more like this guy: :D

 

[Kozmyk]

It's of course possible that something might have changed by 1946, the date on that pdf.

[blue_six]

That and when you utilise the idle cut-off, according to the linked doc you should get it fully forward after operating the wobble pump/booster pump but before priming. if i do this in DCS the engine won't start, even if I try operating the priming pump as I try to start.

Hi fenderplayer, I see what you mean. In the sim, pushing the idle cut-off lever forward before priming seems to deplete the fuel pressure you've built up with the boost or wobble pump - the low fuel pressure warning light comes back on 1-2 seconds after to lever goes forward. I think this explains the subsequent no start. Whether or not this modeling is representative of the RW remains open to discussion. Not a biggie to most of us, but the purists likely would disagree.

[fenderplayer946]

@Kozmyk, aye, only tried it out of interest, it would be interesting to see what had changed and why over the years.

 

@blue_six it would make sense if the fuel cock was off like and its not like you need the booster pump on to run the engine either. I also found that using the priming pump doesn't make a difference either.

[Sokol1_br]

Other thing curious is that you can start engine, taxi and take off without touch in Propeller Pitch lever... that SPAWN in back position (Coarse/Feathered).

[Reflected]

I have that Pilot's notes, and it distinctly says the idle cutoff should be moved forward right after the tank is pressurized. THEN prime, then magnetos on, and then start the engine while priming.

 

In DCS, however, the tank is depressurized as soon as the idle cutoff is moved forward. I don't think it's correct. This document matches the video linked above:

 

[Mark XVI]

Real, modern day Spitfires are started the same way like the original pilot's notes say, the only exception is (with some operators) to switch magnetos ON only after two prop turns (but the engine would start anyway even with the mags ON before the start, of course). I don't quite understand why DCS Spit requires different procedure (simulator limits?). I think that a real Spit would start even if using the DCS's procedure (but I have never tried, just in case), I mean Idle cut-off control forward when the engine starts to pick-up on a priming charge, like on Allisons. But what I don't understand at all is the reverse sequence of booster pump and priming. In all planes I have flown so far you pressurize the fuel system first, then prime. It saves a lot of unnecessary pumping of primer before it sucks some fuel from empty or unpressurized fuel pipes.

 

Just a technical side note, booster/wobble pump does not pressurize the fuel tank, it pressurizes the fuel line between the fuel tank and carburator and helps to keep the fuel pressure when an engine driven fuel pressure pump is not working (engine is shut down). It is not absolutely neccessary for engine operations, keep in mind that Merlin 61/63 equipped Spitfires F Mk.IXc (and olders Marks) had neither booster or wobble pumps. The tank pressurization is performed the different way (air pressure) and is not required for low-level operations

[blue_six]

But what I don't understand at all is the reverse sequence of booster pump and priming. In all planes I have flown so far you pressurize the fuel system first, then prime. It saves a lot of unnecessary pumping of primer before it sucks some fuel from empty or unpressurized fuel pipes.

The impression I get from examining the fuel system schematic in the RAF Pilot's Notes for the Spitfire IX, XI and XVI is that the priming pump has its own "plumbing" to the engine, independent of the primary fuel line which runs from the lower main tank, through the fuel cock, fuel filter and engine-driven fuel pump to the carburetor. As such the primer pump circuitry is not pressurized by the wobble pump and/or electric boost pump. The Pilot's Notes for the Mk IIA and B show this more clearly, with fuel for the priming pump being tapped from the side of the lower main tank, and pushed by the priming pump along a line terminating in the words "to cylinders." In contrast, the main fuel line in this older schematic is marked "to carburetor" just as we see in the Mk IX Notes.

[Mark XVI]

I'm not 100% sure. Mark II is not a good example as it has no boost/wobble pump at all. If you look at Mark IX fuel schematics then you can see the primer line goes through the booster pump. But of course I may be wrong as this schematics is not very clear and it is hard to say if the line goes "through" or "around" the pump

 

http://www.spitfireperformance.com/spitfire9-fuelsystem-lr.jpg

[Moafuleum]

In this documentary, some steps of a startup are shown, however, it is not clear of which version of spitfire. (start at ~ 22:00 mm:ss)

 

https://youtu.be/onnF2QSrEUc?t=22m

 

Anyway, one can see that after the pilot removes the covers of both the starter and the booster coil, he only presses the boost coil switch and not both as stated in Wags' video and in the pilot's notes. Of course the shown scenes do not claim to be complete and also fulfill some kind of entertainment purposes but nevertheless an interesting detail i noticed the other day. ;)

[blue_six]

I'm not 100% sure. Mark II is not a good example as it has no boost/wobble pump at all. If you look at Mark IX fuel schematics then you can see the primer line goes through the booster pump. But of course I may be wrong as this schematics is not very clear and it is hard to say if the line goes "through" or "around" the pump

 

http://www.spitfireperformance.com/spitfire9-fuelsystem-lr.jpg

 

Agree, not a good example, nor is the schematic you've linked us to entirely clear. My money is on the priming line running around not through the boost pump, given the way the two segments line up perfectly on either side of the pump. This isn't a biggie, either way. What we still don't know for certain is why we can't obtain a good engine start in the sim when we move the idle cut-off control forward prior to priming and hitting the start and booster coil buttons, per the sequence set out in the RAF Pilot's Notes. Is it an inherent limitation of the sim, or a bug that can be squashed?

[Friedrich-4B]

Agree, not a good example, nor is the schematic you've linked us to entirely clear. My money is on the priming line running around not through the boost pump, given the way the two segments line up perfectly on either side of the pump. This isn't a biggie, either way. What we still don't know for certain is why we can't obtain a good engine start in the sim when we move the idle cut-off control forward prior to priming and hitting the start and booster coil buttons, per the sequence set out in the RAF Pilot's Notes. Is it an inherent limitation of the sim, or a bug that can be squashed?

 

There seems to be some confusion here, probably because the language in the 1946 IX/XI/XVI Pilot's Notes is confusing: I would suggest ignoring those notes

 

Put simply:If the cut off control is opened(ie: pushed forward) before the engine fires, all you're doing is flooding the engine!

 

These pages are from the Spitfire VII/VIII PN's, dated December 1943: these state quite clearly that the idle cut out control is opened (pushed forward) after the engine fires, and certainly not before priming the engine!

 

 

Here are the pages from the Merlin 60-85 series Maintenance manual, January/July 1944: idle cut-off control open (pushed forward) after the engine has started.

 

 

There's nothing complicated or buggy about ED's starting sequence.

[blue_six]

Good finds, Friedrich-4/B; thanks for sharing this info and putting my mind at ease. I'll treat those 1946 Pilot's Notes with just a bit less respect from now on, and get on with exploring other features of this outstanding module.

[Sokol1_br]

This guy make their own rule, leave the lever ahead but move back and forth when press starter. :)

 

Edited December 29, 2016 by Sokol1_br

[IvanK]

A little more to add the discussion on Starting and the Idle cut off lever position. An excerpt from the RAF Air Transport Command Ferry notes handbook (a veritable goldmine).

 

[LeCuvier]

Just a minor note: I use the built-in cut-off switch in my TM Warthog throttle. Thus my throttle is closed when I push the Start & Boost Coil buttons, and it only opens when I push the throttle lever forward from the "Idle" position. That process differs from the instructions that require the throttle to be slightly open; but works fine for me.