Quote:
Originally Posted by cheesehawk
109 supercharger isn't working properly, boost levels drop too dramatically after 5k. I believe this is why the AutoPP in the E-4 is failing after 6k, as it adjusts the PP according to the throttle setting (I believe the devs are using ATA instead) and assumes the drop in pressure is the result of decreasing the throttle to almost closed. The 109 had a gearing for the supercharger to keep the pressure up at altitude, probably why we can't reach 11k?
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I think the Supercharger is working just fine. DB601A Full throttle height is around 5000m according to most sources. Propeller Pitch in AUTO is a function of throttle lever position. As to RPM and ATA the 2 are effectively the same below Full throttle height as in general terms Throttle position determines or is directly linked to ATA and therefore RPM . Above Full throttle height that is obviously no longer the case as ATA reduces since the supercharger has reached its max output.
Here is a burst from "Schwarzeman" who has restored a number of DB engines and knows these things inside out He is a pilot as well. Its DB605 specific but the principal is the same:
"High altitude- above rated altitude(5.7km/605A) the ATA will reduce in relation to further climb, the U/min will stay the same (until the throttle is moved) and the prop clock will stay the same (until the TAS is changed)"
So what happens in COD at the moment ?
Start at 4800m Max ATA Prop AUTO 1.34ATA at say 250KMH then climb. I see ATA start to reduce at 4800m indicating Full throttle height (Supercharger at max output). As I continue to climb ATA is reducing but RPM remains 2300RPM. I continued the climb to 6000m ATA reduces to 1.1 but RPM is still steady at 2300RPM. As I climb at constant IAS (increasing TAS) I see the Prop clock fining (slight clockwise movement) to maintain the 2300RPM. So that to me indicates Throttle position is determining RPM in COD. This behaviour looks correct to me and replicates what Schwarzeman states pretty well, though I haven't documented the relationship of ATA drop off with Altitude above Full Throttle Height. (I will test this though
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EDIT:
ATA DROP OFF ABOVE FTH
1.34 ATA 4800m
1.2 ATA 5400m
1.1 ATA 5950m
1.0 ATA 6550m
0.9 ATA 7100m
So ATA reduction above FTH is around 0.1ATA per 500m
That agrees reasonably well with the RAE test data from AVIA 6/9352 "Performance tests on a Me 110 and a Me 109E (DB601 engines)
