If you experience the "prop pitch bug" in the 109E4

[CaptainDoggles]

I posted this in the bug thread but figured I might as well repost it here so it's more visible.

The bug I'm describing is the bug where if you take off in the E4, the Kommandogerat gradually decreases your prop pitch down to full coarse where it stays, keeping your RPMs down at 1500 or thereabouts and robbing you of any horsepower you might have, even at full throttle.

What I've found is that if you put it into manual mode and play around with the manual controls for a few seconds (i.e. give it a few clicks of Fine, and then a few clicks of Coarse) and then put it back into automatic mode it functions normally.

Hope this helps,

Doggles

[skouras]

thanks mate
i didn't saw this --- i've always take off in manual

[ATAG_Doc]

Toggle automatic prop pitch and as soon as you do catch your pitch from running away. EZ

[IvanK]

First up terminolgy Kommand Gerate is not fitted to the BF109 . It was a Mechanical engine control unit fiitted in the BMW801 that controlled a number of engine variables including Auto prop pitch on the FW190. The system on the 109 is a much more straight forward affair that concerns itself with Governed RPM only.

Auto prop pitch in the 109 installation was only "active" above a certain RPM (2000in the DB605 ...not 100% sure what is was on the DB601). A typical way to handle the Start Taxi Take off scenario is as follows. Start with prop pitch Full fine 12:00. Select Full throttle as RPM passes 2000 select AUTO. Personally I just take off in Manual get airborne and when the RPM gets to 2300 just select AUTO, since this is the Full throttle governed value. Coming in to land once I go back to manual and set 12:00 so max RPM in a hurry is available if required.

In general terms if you are using Max throttle then AUTO is the go imo. If you are using an intermediate setting like say a climb at 1.25ATA and dont want the commanded RPM (about 2000 in this case) then select manual and set 2300RPM for example. In combat with large TAS changes etc AUTO frees you up from sweating on the RPM.

In the end I think intelligent use of both AUTO and Manual is required to get the best out the engine.

In addition the way it seems to be mechanised in Sin is when you close the the Throttle and RPM goes below 1500 then prop fines up eventually to the 12:00 position. I guess it figures its ready for a max power application ... like in a Go Around situation etc.

[CaptainDoggles]

Okay, well you might not be experiencing the bug but some of us are.

The prop pitch never comes up if you take off in auto.

[AKA_Tenn]

just keep auto pitch off till u get ur rpms to 2300, if u decelerate or accelerate too quickly the auto pitch can't keep up and its stops workin

Thanks, IvanK, for the explanation. So this behaviour is historically correct?

[Insuber]

Did as suggested above, it works! Thank you.

[IvanK]

Originally Posted by 41Sqn_Stormcrow

Thanks, IvanK, for the explanation. So this behaviour is historically correct?

Historically I think the method was as follows.... The data below is valid for he DB605. So the 601 may differ. The source of this data Schwarzeman who is both a pilot and DB605 engine restorer/experten... so it seems reasonably Historically correct. Maybe some of our German speakers with access to the "E" or DB601 manuals could verify and or correct this. In general I think it is historically correct operation based on the data available.

THE SEQUENCE
Engine is shut down with Prop pitch Full fine 12:00
On Engine start You are below the governed range so RPM is directly proportional to ATA. (with prop on the full fine stop)
Prior to Take Off Pilot checks Prop Pitch 12:00 (Fully Fine) Verifies AUTO selected.
On Take off Pilot advances the throttle. Until 2000RPM is reached the RPM increases without Governing, just trying to achieve MAX RPM ASAP.
Once 2000RPM is exceeded the RPM is governed to the RPM demanded by Throttle position
In CLOD Full throttle selects 2300RPM as the Governed value. As TAS increases you eventually get to the point where 2300RPM is achieved. Any further TAS increaes gets the Governor in operation to hold the demanded RPM (2300 with Full throttle). The clock slowly starts winding back as the prop coarseens to hold the demanded 2300RPM. So inside the Governed range its essentially a constant Speed prop with the RPM being set by the Throttle position.

I am not sure on how it worked for real if throttle is selected to Idle and RPM goes below the governed value. In CLOD the min governed value seems to be 1500RPM (Not 2000 as in the DB605). Again CLOD with Idle selected and RPM below 1500 the Prop fines up to 12:00... so Max acceleration and RPM is available if Full throttle is selected in one continuous movement .... like in a Go Around.

Personally in game once I have the gear down I go manual and just set full fine (12:00) then just use ATA as required.

If I am cruising or climbing at lower than full throttle but still want say 2300RPM (Like in a 12.5ATA climb). Then I select manual and just treat like the E3. In Auto below FTH with 1.25 ATA you would probably only get around 2000RPM. As soon as combat is imminent I select AUTO and let it do its thing. .... Reduces the workload wrt to prop overspeed etc. Though you do need to be mindful of Low RPM if the throttle is closed and the time taken to get the RPM up. The high speed descent to beat up Hawkinge with subsequent climb needs a bit of thought. Its better to descent at High ATA (Throttle up) so as to keep the RPM up. Then if you need to climb RPM is already there.... either way dont get caught short with Low RPM and agonising wait for the RPM to build

TAKING OFF IN AUTO IN CLOD
What I see is this:
AUTO with Prop Full fine 12:00
Select Full throttle. RPM rapidly increases to 2000RPM
As IAS increases RPM increases at 100KMH I see 2100RPM, I get the full 2300RPM at around 180Kmh ...(lift off) as the acceleration continues the governor starts coarsening the prop. So You don't initially at very low forward speeds get the full 2300 RPM. This I am not sure if its correct. Schwarzeman states clearly for the DB605 that you can achieve rated RPM at full ATA stationary .. i.e. in a static run up. I wuld presume that a similar thing would happen with 601.

Most documentation I have read indicates that the optimum DB601A RPM ... or the upper governed value should be 2400 rather than the 2300 we see in game.... more research required here.... or a "virtual technical tap on the tacho" is required.

So far I think the E4 Auto prop is working as advertised. I am yet to see anything bugged. Its never locked in any position for me.

[IvanK]

Update.
If I slowly open the throttle on Take off in AUTO I get the prop coarsening as I go through 1500RPM. I then only get around 2000-2100rpm at lift off. Is this the bug you are referring too ?

Solution (Interim) Take off in manual select AUTO when above 2000RPM.