As close to a real Spit as it gets

Then why does the fuel tank pressure warning lamp extinguish when I turn the fuel pump on?

And why does the engine even run, when I never turn the fuel pump on, because I though it was simply the fuel tank pressure pump?

:cry:

At altitudes below ~15,000ft the combination of gravity and air pressure is enough to supply the engine with fuel without the need for fuel pump. As altitude increase the drop in air pressure reaches the point at which these factors are not sufficiently powerful to feed the engine and ergo the pump is required.

As referenced here: https://forums.eagle.ru/showpost.php?p=3557839&postcount=4

For some reason we have a conglomeration of two separate system types, with both wobble & booster pump, maybe something to do with the DCS Spitty being modelled on a restored airframe, MH434, she may have collected some ahistorical modifications across the 75 years since her birth.

The cock on the lower right hand side of the front dash is for pressurising the drop tank system.

Pilot notes say that the fuel booster pump (under the elevator trim wheel) should only be used for max. 30 seconds prior to engine start, and then switched on thereafter.

Personally I prime with the wobble and then switch on booster pump after engine is running.

If operating with drop tanks, at 2000ft (or after 2 mins after takeoff, whichever comes first) I switch on the drop tank cock (lower right adjacent seat) and the drop tank pressure cock (lower right hand side of the front dash) and then switch off the main fuel tank booster pump and switch the main fuel tank cock off (just under starter and boost coil buttons).

It does mean that when bounced with a drop tank you have 5 separate things to do to get in fighting trim -

1. Switch on main fuel tank cock

2. Switch on main tank fuel booster pump

3. Switch off drop tank pressurisation cock

4. Switch off drop tank cock

5. Pull drop tank jettison handle

By which time your attacker, if he hasn't already shot you down has probably zoomed back into the sun whilst you're faffing about trying to get to fighting speed and power and reacquire him...!

Art, I start the Spitfire with the mixture lever forward all the time. Sometimes I need to pump the wobble pump a few times to get it to catch. But I think that's what happens with the real one, too. Maybe I'm misunderstanding what you're saying and I should have stayed out of the conversation. Feel free to tell me to mind my own buisiness.

You're very much welcomed to stay in the conversation, as long as you don't tell me the quoted document says X while it clearly says Y, as Rob did :D. That rubs me the wrong way and If I sounded like a d..ck, I'm sorry.

If you start the plane with lever forward, using wobble pump to help with pressure, good for you. What I'm saying is you shouldn't even have to touch it and neither did real pilots - one hand on starter and booster buttons, second hand on Ki-pump to help smooth-out the engine once it fires and... third hand on wobble pump ;) ?

Could you please post a short track of your preferred way of starting the engine with lever forward? I'm unable to do it unless I combine cranking with priming as mentioned previously (which apparently would be a correct method, but for Merlin 61 and 63 engines by the way). Timing is important here it seems.

Between the Supermarine Brits and the Eagle Dynamics Russians, it's a wonder anyone can understand anything on this aircraft :mad:

This is not specifically aimed at you Fenrir, other than when specifically quoted.

Before going on, let's agree on some basics.

Physics: Hydraulic pressure: it is not possible to compress a liquid.

Fuel pumps do not cause the fuel itself to be compressed (impossible), but exert a physical pressure through a membrane or other physical implementation pressing against the fuel in a chamber with one-way valves--one allowing fuel to ONLY enter the chamber, and one allowing fuel to ONLY exit the chamber. The fuel pressure depends on the amount of force of this physical object pressing against the fuel constricted inside the chamber.

The Pilot's Notes for Spitfire IX, XI, & XVI Merlin 61, 63, 66, 70 or 266 Engine "promulgated" by order of the Air Council, A.P. 15651, P & L--P.N. states that the Fuel Pressure warning light is asserted if fuel pressure falls below normal.

The ED Spitfire manual states on page 117 under "Fuel Pressure Warning Light" "To the left of the gasoline gauge is a lamp switch(1) that triggers upon a drop in pressure (below 10lb/in²) from the gasoline pump".

- "To the left of the gasoline gauge" WFT the Fuel Pressure Warning Light is to the RIGHT of the Main Fuel Tank Gauge. There is no switch nor light directly to the left of the Main Fuel Gauge!

- "a lamp switch"? a switch for turning a lamp on/off?!?!

Also in the Pilot's Notes in Section 5 Fuel contents gauges and pressure warning light:

"The fuel pressure warning light (18) is operative when the

switch (34) on the throttle quadrant is on and comes on at any

time when fuel pressure at the carburettor falls appreciably

below normal".

- Section 25 Idle cut-off control it states:

NOTE.—

- Section 33. Management of the fuel system

(iii) Use of the booster pump(s)

Elsewhere it states that during taxiing before take off and after landing, the Fuel Booster Pump should be turned off.

ED Spitfire manual, page 81:

"In order to prevent fuel boiling at high altitudes in warm weather conditions, the fuel system is equipped with a fuel tank pressurizer system that switches on automatically at altitudes above 20000 feet. An aneroid valve feeds air, pressurized by a vacuum pump, into the fuel tanks. Pressurizing, however, impairs the self-sealing of the tanks and should be turned on only when the fuel pressure warning lamp lights up."

So, this is the Fuel Tank Pressure butterfly/key switch on the front dash below the Main Fuel Tank Gauge?

"In very warm weather at very high altitudes a rich cut may occur with the tanks pressurized, and pressure must then be turned off. The pressurizing cock is on the starboard side of the cockpit immediately below the instrument panel.

The default position of the pressurizer system is OFF, and must be turned ON only when a red warning light signalizes that the fuel pressure has dropped below 10lb/in²."

So, the Fuel Pressure Warning Light, bc I don't know of any other it might be. Anybody?

"The control unit for the fuel pressurizer system is located under the right side of the instrument dashboard."

And further:

"The valve for disabling fuel tank pressurization installed in the ventilation line of the fuel tanks allows for immediate disabling of fuel tank pressure in case of damage to the pipelines or fuel tanks, as the defensive properties of the lower tank suffer in case of excess pressure. The valve is located in the right wing fairing, and the control unit is located to the right and below the pilot’s seat."

WHAT?!?! Where?!?! I can't find this.

So there are two controls for Fuel Pressure, the Wobble Pump, the Fuel Booster Pump, while the Fuel Pump itself apparently works automatically.

There are also two controls for fuel tank pressure, the Fuel Tank Pressure On/Off switch, and an hither to unknown and unlocatable control, unless the Fuel Tank Pressure On/Off switch is meant. Thanks ED :mad:

So, if I understand this correctly, the Fuel Pressure Warning Light actually indicates two different things at different times. Before take off, it indicates low fuel pressure (not fuel tank pressure), when the Undercarriage Indicator Master Switch has been switched on, and before the Fuel Booster Pump or Wobble Pump have been activated.

Right before take off, the Fuel Booster Pump must be turned on, after which time the Fuel Pressure Warning Light indicates low fuel tank pressure as well, indicating that the Fuel Tank Pressure On/Off Switch should be turned to On. This will also happen if the fuel tank currently being used runs empty.

At altitudes below ~15,000ft the combination of gravity and air pressure is enough to supply the engine with fuel without the need for fuel pump. As altitude increase the drop in air pressure reaches the point at which these factors are not sufficiently powerful to feed the engine and ergo the pump is required.

No, see above.

As referenced here: https://forums.eagle.ru/showpost.php?p=3557839&postcount=4

 

For some reason we have a conglomeration of two separate system types, with both wobble & booster pump, maybe something to do with the DCS Spitty being modelled on a restored airframe, MH434, she may have collected some ahistorical modifications across the 75 years since her birth.

No, the Spitfire originally only had a Wobble Pump to be use as above. Later the Fuel Booster Pump was added, so the Wooble Pump is almost redundant--it's a kind of back-up, which you may elect to use, depending on the situation.

The cock on the lower right hand side of the front dash is for pressurising the drop tank system.

No, nowhere does it say anything about this. In fact the Pilot's Notes says that each internal tank has it's own Fuel Booster Pump, but in our Mk IX there is no rear fuel tank behind the seat as in the P-51.

Pilot notes say that the fuel booster pump (under the elevator trim wheel) should only be used for max. 30 seconds prior to engine start, and then switched on thereafter.

... and only with the throttle completely off/all the way back.

Personally I prime with the wobble and then switch on booster pump after engine is running.

That is not priming. Priming is only done with the Priming Pump. Turning on the Fuel Booster Pump, or operating the Wobble Pump pressurizes the fuel lines AFTER the fuel tank.

Interestingly, the ED manual says about priming:

[TABLE]Outside air temperature, °C | +30° | +20° | +10° | 0° | -10° ~ -20°

Number of complete movements | 2 - 3 | 4 | 5 | 5 - 6 | Up to 15[/TABLE]

while the Pilot's Notes says:

An external priming connection is fitted and high volatility fuel

(Stores Ref. 34A/111) should be used for priming at

temperatures below freezing. Operate the priming pump until fuel reaches the priming nozzles (this may be judged by a sudden increase in resistance to the plunger) then prime the engine (if it is cold) with the following number of strokes

[TABLE]Airtemperature °C | +30° | +20° | +10° | 0° | -10° | -20°

Normal fuel | 3 | 4 | 7 | 12 | -- | --

High volatility fuel | -- | -- | -- | 4 | 8 | 18 [/TABLE]

If operating with drop tanks, at 2000ft (or after 2 mins after takeoff, whichever comes first) I switch on the drop tank cock (lower right adjacent seat)

Yes

and the drop tank pressure cock (lower right hand side of the front dash)

No, does not exist.

and then switch off the main fuel tank booster pump and switch the main fuel tank cock off (just under starter and boost coil buttons).

Yes

It does mean that when bounced with a drop tank you have 5 separate things to do to get in fighting trim -

 

1. Switch on main fuel tank cock

2. Switch on main tank fuel booster pump

Yes so far

3. Switch off drop tank pressurisation cock

No, as above, the Drop Tank does not have a Fuel Booster Pump. Maybe it is already under pressure. IDK.

4. Switch off drop tank cock

5. Pull drop tank jettison handle

Yes, but only steps 1, 2, 4, and 5.

By which time your attacker, if he hasn't already shot you down has probably zoomed back into the sun whilst you're faffing about trying to get to fighting speed and power and reacquire him...!

ummm ..... maybe? :joystick:

For some reason we have a conglomeration of two separate system types, with both wobble & booster pump, maybe something to do with the DCS Spitty being modelled on a restored airframe, MH434, she may have collected some ahistorical modifications across the 75 years since her birth.

According to the book «Spitfire Mk. IX & XVI Engineered» by Paul H. Monforton, some early Mk. IX Spits retained the wobble pump even after the electrical pump was installed. The wobble pump was removed on later production aircraft. So, some had both.