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