Mixture: All Brit fighters tested

[IvanK]

Doing the Blenheim and its problematical to say the least. ... might need Klems script.

1. I cannot run smooth operation with Mixture levers back (normal) at any altitudes above 6000ft with +4/COARSE
2. Had to perform tests at 5000ft to be able to achieve smooth Engine operation in both NORMAL (BACK) and LEAN (FWD) positions.
3. Tests inconclusive.

METHOD
Stable Flight CHT 200C, BOOST +4, 5000Ft Coarse Pitch Rads 3 clicks open, CHT Stable at 200 C, QNH 1013

LEVER FORWARD in LEAN POSITION
Achieved RPM 1920, Achieved IAS 210
Fuel Used after 10 mins 12Gall (Total)
Fuel Flow 1.2gpm (Total)

Placed Mixture Lever to REAR (NORMAL) position RPM Reduced to 1820 RPM IAS reduced to 200.

LEVER IN REAR NORMAL POSITION
Achieved RPM 1820, Achieved IAS 200
Fuel Used after 10mins 12 Gall (Total)
Fuel used after 20mins 22 Gall (Total)
Fuel Flow 1.1gpm Total in 20min test .... too close to call.

CONCLUSION
Inconclusive with respect Fuel Flow. Almost the same FF achieved in both mixture lever positions ! Though the 20min test might imply that with the lever back fuel flow is less ... though 1.2gpm v 1.1gpm is too close to call imo.
Given Stable engine operation above 6000ft cannot be achieved in Rear (Normal) position then AUTO function is not operating.
Given at 5000ft selecting Mixture to REAR (Normal) results in reduced RPM and IAS I think it implies that actual Mixture orientation is operating in reverse. Maybe supported by 20min Fuel flow tests as well.

RECOMMENDED FIXES (work in progress)
Mixture control needs to be AUTO RICH or AUTO LEAN in that automatic altitude compensation is provide in both.
Stable operation at all altitudes in NORMAL (AUTO RICH) should be possible without boost restrictions
Stable operation at all altitudes in WEAK (AUTO LEAN) should be possible WITH boost limitations
Boost limits in WEAK (AUTO LEAN) +1.5lbs

[phoenix1963]

IvanK - I think you need carb heat above 5000k ft.
56RAF_phoenix

[IvanK]

Originally Posted by phoenix1963

IvanK - I think you need carb heat above 5000k ft.
56RAF_phoenix

I tried it and still get rough running.

[Torian]

Definitely need carb heat above 5000ft and mixture all the way forward (which is wrong). No problems for me when I do this but also run in full coarse pitch. May need to throttle back to 2.5 boost but smooth flight is no problem.

[Torian]

I posted this link over at ATAG but will put it in here. It's worth a careful read but here is a paragraph that I think is very relevent if u haven't got the mixture orientation correct in CloD

http://flighttraining.aopa.org/stude...l/mixture.html

"Excessive leaning at cruise power above 75-percent power will invite engine damage from overheated valves and incur the possibility of detonation. The probability of damage from over-leaning decreases rapidly as cruise power is reduced from 75 percent. For example, there is considerably less, if even any, possibility of engine damage from over-lean mixtures at 50-percent power. However, an over-lean mixture can foul spark plugs and combustion chambers because of cylinder misfiring.

Many older engines are equipped with non-alloy steel exhaust valves. During normal cruise power (approximately 50 percent to 75 percent) the exhaust valve will become glowing hot during the period that it is open and exposed to the hot gases leaving the cylinder. If the mixture is lean enough to create an oxidizing atmosphere, the exhaust valves usually will be damaged. (An oxidizing atmosphere is always present in lean mixtures.)"

This may be why u are getting rough performance Ivank if your mix levers are all the way back and u are using more than 75% power and/or climbing.

[IvanK]

I see where you are coming from Torian but given these things were meant to be AUTO RICH and AUTO LEAN with documented Boost limits for the AUTO LEAN setting rough running (assuming limits are observed) should not be an issue.

[Torian]

Agreed but "meant to be" and what what we have been lumbered with in CloD are very different. Unfortunately we have to learn to manage the engines in this sim in ways that weren't necessary in real life.
And in the case of Brit fighters, with less performance than they actually had.

[klem]

Originally Posted by IvanK

Doing the Blenheim and its problematical to say the least. ... might need Klems script.........................

It's here
http://forum.1cpublishing.eu/showthread.php?t=33661
in the first post, see the attachment.

I have added decimal places for fuel reserves.

It won't affect your fuel flow tests (I think) but I am probably going to amend it for level speed tests as the charted TAS is currently calculated from the IAS gauge Air Speed which some people are questioning as to its accuracy. I do include internal 'system' parameter Z_TAS in the output but I chart the TAS calculated from IAS.

I am beginning to think the IAS may be ok though as the Z_TAS is fairly close to TAS calculated from IAS (304mph vs 292mph for IAS 250mph or 4%). The modelled atmosphere could easily do that. Part of The confusion comes from the Z_IAS figure which appears to be way off what it should be, e.g. at a IAS of 250mph at 10,000 ft Z_IAS is only 6mph below Z_TAS because the Z_IAS of 132.46 m/s calculates as 298mph. But I need time to look more closely at it. Hopefully 1C will release more info on the C# parameters so we know what we are working with.