Recently a few of us have suffered ‘unexplained‘ engine cut-outs and not being able to restart mid-air. Red directed us to DCS forums where people have been talking about excessive oil pressures requiring fuel dilution and fuel tank pressure procedures as being possible causes.
At the base of these new problems in DCS Spitfire engine management are almost certainly modifications made by the developers with the arrival of the CW version to be closer to the real thing and the fact that we now have to play with drop tank fuel management. So I felt it would be useful to share with you instructions from the official Pilot’s Notes which if followed should stop the problems, although I have yet to test these in DCS.
I will first show some relevant extracts about systems and later talk about procedures, with my notes in italics. I have also put some important points in bold.
Fuel Cocks :
The cock control for the main tanks is a lever fitted below the engine starting pushbuttons and the pressurising control is below the right-hand side of the instrument panel. The cock control and jettison lever for the auxiliary drop tank are mounted together on the right hand side of the cockpit, below the undercarriage control unit. The jettison lever is pulled up to jettison the drop tank, but cannot be operated until the cock control is moved forward to the OFF position.
Fuel Pumps :
On Bendix-Stromberg carburettor installations (M66, M70 & M266) an electric booster pump, operated by a switch on the left-hand side of the cockpit, is fitted in the lower main tank. On early aircraft this pump is not fitted, but a hand wobble pump is provided instead. (In fact the DCS Spitfire has both, and we can dispense with the wobble pump operation).
Fuel Pressure Warning Light :
The fuel pressure warning light is operative when the switch on the throttle quadrant is on (automatically turned on when the the throttle lever is advanced) and comes on any time when fuel pressure at the carburettor falls appreciably below normal.
Idle Cut-Off Control (Merlin 66, 70 and 266) :
The idle cut-off valve on Bendix-Stromberg carburettors is operated by moving the short lever on the throttle quadrant through the gate to the fully aft position.
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.
Carburettor Air Intake Filter Control :
On tropicalised aircraft (as is the DCS model) the carburettor air intake filter control on the left-hand side of the cockpit has two positions OPEN and CLOSED (NORMAL INTAKE and FILTER IN OPERATION on later aircraft). The CLOSED position must be used for all ground running, take-off and landing and when flying in sandy or dust-laden conditions.
Note (i) In the air it may be necessary to reduce speed to 200 mph IAS or less before the filter control lever can be operated.`
(ii) The filter control lever must always be moved slowly.
After take-off : Unless operating in sandy or dust-laden conditions set the air intake filter control to OPEN at 1,000 ft.
Use of the air intake filter reduces the full throttle height considerably.
Management of the Fuel System,
b When fitted with a drop tank : [/b]
Start the engine , warm up, taxy and take off on the main tanks; then at 2,000 ft. turn ON the drop tank and turn OFF the main tanks cock. When the fuel pressure warning light comes on, or the engine cuts, turn OFF the drop tank cock and reselect the main tanks.
Note (i) When it is essential to use all the fuel from the drop tank its cock must be turned OFF and throttle closed immediately the engine cuts; a fresh tank should then be selected without delay. The booster pump in the newly selected tank, should be switched ON, or the hand wobble pump operated, to assist the engine to pick up but in addition to this it may be necessary to windmill the engine at high r.p.m. to ensure an adequate fuel supply.
(ii) Drop tanks should only be jettisoned if this is necessary operationally. [b]If a drop tank is jettisoned before it is empty a fresh tank should be turned ON before the drop tank cock is turned OFF.[/b]
(iv) The drop tank cock must always be off when the tank has been jettisoned or is empty, otherwise air may be drawn into the main fuel system thus causing engine cutting. [i][b](ie don’t play with this control in-flight !)[/b][/i]
b Use of the booster pump(s)[/b]
The main tanks booster pump should be switched ON for take-off and landing and at all times when these tanks are in use in flight.
Oil Dilution :
On the DCS forum there was a lot of debate about high oil pressure during flight, caused by high oil viscosity due low air temperatures, leading to engine damage and failure. One solution advanced was to dilute the oil with fuel to reduce its viscosity and pressure. The oil dilution button is located on the right-hand side of the cockpit under the rudder trim wheel, the higher of three buttons. A cover needs to be opened before the switch can be operated. However nothing about using this procedure in flight is mentioned in the Pilot’s Notes and no-one seemed to know how many pushes of the button were required.
The notes below appear in the After Landing section.
The correct dilution periods are
At air temperatures above -10°C . . 1 minute
At air temperatures below -10°C . . 2 minutes
The starting procedure we have been using in DCS is quite different from the Pilot’s Notes, but if the developers now program the aircraft to operate as in the real thing, the formal procedure is quoted below for reference.
Starting the Engine and Warming Up
Set the fuel cock ON
Ignition switches OFF
Throttle 1/2 in. to 1 in. open
Propeller speed control Fully forward
Idle cut-off control Fully aft
Supercharger switch AUTO. Normal Position
Carburettor air filter CLOSED Filter in Operation
Switch ON the main tanks booster pump for 30 seconds, then switch it OFF and set the idle cut-off control forward to the RUN position.
Operate the priming pump … to prime the engine (if it is cold) with the following number of strokes
Air Temperature °C +30 +20 +10 0 -10 -20
Normal Fuel 3 4 7 12 - -
High Volatility Fuel - - - 4 8 18
Switch ON the ignition (magnetos) and press the starter and booster-coil buttons
When the engine fires release the starter button; keep the booster-coil button depressed and operate the priming pump (if required) until the engine is running smoothly.
Screw down the priming pump then open up gradually the throttle to 1,000- 1,200 r.p.m. and warm up at this speed.
Note : Nothing is mentioned in the procedures about the operation of the fuel tank pressure control, nor does it appear in the start up or pre-flight check lists. I have been flying in DCS for months without touching this control and when you do turn it on it doesn’t seem to make any difference !
Check List before Take-off
T- Trimming tabs At training load At normal full load
(full main tanks, no ammo (full main tanks, ammo + 1
or external stores) 45-gallon drop tank)
7,150 lb. 7,800 lb.
Elevator 1 div nose down Neutral
Rudder(*) Fully right Fully right
P- Propeller control Speed control fully forward
F- Fuel Main tanks cock - ON
Drop tank cock - OFF
Main tanks booster pump - ON
F- Flaps UP
Supercharger Switch AUTO normal position. Red light out
Carburettor air filter control CLOSED filter in operation
* Rudder trim - if you follow this instruction in DCS it’s a sure way to finish careering off the runway ! . Setting the U of RUDDER vertical on the trim wheel seems to give the correct input.
