Bug 174 on 12lbs boost. Review please.

[CaptainDoggles]

Kwiatek, are you just really good at keeping the stick level or is there a trick? I want to test at FTH but I have trouble keeping the aircraft steady.

Maybe I need to decrease sensitivity on my trim controls.

[Osprey]

Try not to move your hand so much. I realise that it's so used to vigorous movements that it's tough for you, but I reckon you can manage it if you concentrate enough.

[Kurfürst]

Originally Posted by 41Sqn_Banks

There was no WEP for DB601 A1/Aa, only a special take-off boost. There is nothing that indicates that 1' Minute 1.4/1.45 was used for anything else than take-off or above 1-1.5 km altitude.

http://www.il2bugtracker.com/issues/40#note-10
http://www.il2bugtracker.com/issues/40#note-11

On the other hand there is nothing to suggest that 1,40/1,45 ata was not possible use at any altitude. So far I have not found any evidence that this was mechanically restricted to the 1st supercharger speed, and it quite likely that it was not.

OTOH I agree that the manuals insist that is to be used for special take off conditions. Which is kinda parallel to the Spitfire II limitations (which limit +12 to take off conditions only), so it just might be good idea to include a code that this 'WEP' on both planes should be only usable when the wheels are on the ground.?

[41Sqn_Banks]

Originally Posted by Kurfürst

On the other hand there is nothing to suggest that 1,40/1,45 ata was not possible use at any altitude. So far I have not found any evidence that this was mechanically restricted to the 1st supercharger speed, and it quite likely that it was not.

OTOH I agree that the manuals insist that is to be used for special take off conditions. Which is kinda parallel to the Spitfire II limitations (which limit +12 to take off conditions only), so it just might be good idea to include a code that this 'WEP' on both planes should be only usable when the wheels are on the ground.?

The take-off boost in Spitfire II was provided by a "gate control" which caused a fixed throttle valve setting, thus boost would fall off quickly with altitude (the throttle valve didn't open progressively to maintain the take-off boost)*.
The boost control cut-out on the other hand opened the throttle valve progressively to kept the +12 boost until it was completely opened, thus emergency boost was maintained up to FTH.

The DB601 manual indicated that for the take-off power the throttle valve is opened slightly more than under normal condition. This would theoretically allow to use 1' Minute boost up to FTH.

* with increasing altitude the throttle valve would again open progressively to keep +9 boost as the throttle lever is logically in the most forward position, but as we know it should only be used up to 1,000 feet this would normally not occur.

[ATAG_Snapper]

Originally Posted by Kwiatek

I checked 109 sea level speeds and nothing change comparing to pre beta patch version.

So i think there is no changes in FM of 109 ( also there is no info about it in beta patch notes). So still 109 is to slow ab. 20 km/h at 1.3 Ata power and ab. 20 km/h at 1.4 Ata - so generally 40 km/h slowier at the deck.

Moreover i checked british fighters in beta patch and i got:

Hurricane MK 1 Rotol

238 mph /383 kph at the deck at +6 1/2 boost ------ should be 262-265 mph /420-426 kph !!!!

So it is 24-27mph/ 38-43 kph too slow at + 6 1/2 boost power !!!!

There is no WEP - so no 100 octan fuel performacne - which should give ab. 25 mph/ 40 kph extra speed at low alts

Spitfire MK1a

255 mph at the deck at 6 1/2 boost ---------should be 283 mph !!!!

So it is 28 mph/45 kph too slow at 6 1/2 boost.

No 100 Octan fuel performance at all - boost cut out doesnt rise power at all.

Spitfire MK II

268 mph at deck at 6 1/2 lbs
285 mph at deck at 9 lbs ------ should be 286-290 mph so it is very accurate result!!!!

Still no 100 octan fuel performance - so no emergency +12 lbs.

Hi Kwiatek,

I did some trials both online (ATAG Server) and offline with the Spitfire Mark Ia and IIa. The online flight model does not match the offline flight model for the Spit IIa at altitudes of 5,000 and 10,000 feet.

For the Spit IIa, going into full overboost at 2800 rpms I recorded the following IAS (mph) at the different altitudes:

Sea level: online 292 ; offline 288
5,000 feet: online 270 ; offline 288
10,000 feet: online 262 ; offline 290

The methodology was simple: fuel 100%, radiator 50%, trim for level flight at designated altitude, then fly level and record direct off airspeed indicator.

Bizarrely, the Spitfire Ia showed a slight dip in IAS at 5,000 feet, then a small increase at 10,000 feet (online), offline it simply showed a significant decrease in IAS at 10,000 feet.

When adjusting prop pitch to 3,000 rpms at full overboost the Spitfire Ia showed a slight increase in speed at all altitudes tested, but the Spitfire IIa consistently blew its engine at the higher altitudes, although the same online difference in speed vs the offline speed was likewise reflected prior to engine failure.

The majority of combat online (ATAG Server) currently occurs at 10,000 feet or less, even with bomber streams at 11K - 14.5K. Airfield suppression (vulching) is permitted on ATAG which drags the action down to sea level, but steps are being taken with mission design & scoring to strongly encourage both sides to take the fight realistically higher -- much higher.

I was skeptical when I first heard of differences between the online and offline flight models until I actually tried them myself. I certainly encourage anyone to try this themselves, especially with other RAF and LW aircraft.

I've included the data I recorded (attached).