Background: the 6.0 Hornet F.I, Hornet F.III, and 4.7 Welkin F Mk.I all have a weird “Fuel Starvation” issue that immediately cuts the engines after surpassing -1.0G in WEP, or a few seconds at 100% throttle.
I have re-created the report for the Hornets with additional information containing fuel diagrams and fuel tank behavior in relation to the fuel pumps for the fuel injection system they possess. It is also worth noting that the Hornet F.I fuel system is modelled entirely wrong, almost like the pilot’s notes were not referenced during its creation. I find this incredibly strange for a number of reasons.
Another novel behavior by these aircraft is that (when using the extended info menu) I can see that for the first few seconds in WEP, they use extra fuel. For the Hornet F.III it is 24.62 kg/min and drops to 17.87 kg/min after a few seconds. After the consumption drops is when Negative-G maneuvers are no longer safe to perform. I can not even begin to explain this behavior, as it is only present on the Hornet F.I, F.III, and Welkin F.I. It is NOT related to 150 octane fuel or the Merlin engine series; I cannot reproduce this behavior on ANY other airframe in-game.
There are no other aircraft with the issue in-game to my knowledge and I feel like it is a bug rather than correct airframe behavior. It is NOT the same issue as early Spitfires, as that is carburetor flooding that makes the engine fail. I cannot find a reasonable explanation for this to be modelled in-game they way it is; would there be a technical aspect of engines and fuel feeding I do not know perhaps? Anyone with additional info would be a welcome voice on this issue to help me understand this better!
Provisional Pilot’s Notes for the Hornet F.I; AP 2864A, Provisional Pilot’s Notes for the Hornet F.III; AP 2864C, Provisional Pilot’s Notes for the Sea Hornet F.XX; AP 4037A, and the Rolls-Royce Two-stage, Two-speed Engine Maintenance Manual, Publication No. T.S.D. 94.
Per the Provisional Pilot’s Notes for the Hornet F.III; AP 2864C; on page 27, Part II, section 45: Aerobatics; “(ii) No attempt must be made to maintain inverted flight as oil pressure very quickly drops to zero.”. The same statement verbatim can also be found in the Provisional Pilot’s Notes for the Sea Hornet F.XX; AP 4037A; page 40, Part II, section 57: Aerobatics.
Ok so its sounds more like tips for pilots rather than a comprehensive systems manual. Theres no reason to mention how the fuel system behaves in negative g if the drop in oil pressure would kill the engine first. All the pilot needs to know is “don’t do negative g maneuvers”
Yes, it’s the pilot’s notes. Each RAF aircraft has one put together. I think the Merlin 130/131 did not have a proper way to combat oil flow in negative-g, but it was not problematic enough to warrant a full solution other than “dont stay upside-down for too long”.
This still doesn’t explain Gaijin’s reasoning for the engines not feeding fuel despite measures for that being in place.
Because its a simple system they applied to all aircraft. The engine would die either way due to the oil pressure but in game it says fuel starvation. For all practical purposes, it acts as it should
I don’t think so. The very unusual way the fuel is handled tells me there is a problem. I’m starting to think that the fuel consumption is outpacing the fuel accumulator.
It actually is. Using Gszabi’s datamines, I uncovered a fuel consumption that does indeed exceed the flow rate of the fuel accumulator. That is likely the issue.
The notes are written by pilots, for pilots. If the engine shuts down in inverted flight due to a drop in oil pressure, then you wouldnt even notice the fuel starvation thus theres no reason to mention it in the notes. Unnecessary information like that makes pilots consider more than they need to when it really isnt applicable. All the pilot needs to know is oil drop, engine stop
Would most likely be the engine seizing and stopping. It could possibly be restarted but only if youre lucky and it would likely have some damage to the bearings or pistons
That is not entirely true. The Provisional Pilot’s Notes (PPN) are prepared for pilots using info from the test pilots, engineers, and other system administrators that have something of note to provide. They are a shorthand for preparation, flight, maintenance, and emergencies prepared collectively by the RAF. They are also amended when new information surfaces, such as how the Hornet F.III’s 1st edition manual does not contain fuel economy info.
To my knowledge, losing oil pressure would lead to metal-on-metal contact and potentially degrade or damage the engines. As soon as gravity returns they should function again (assuming they even turned off in the first place).
10 seconds or so is probably the safe limit. The notes state “no attempt” to discourage any chance of damage, despite negative G definitely being possible.