Aircraft Limitations

[CFC_Conky]

I'll need an extra pair of eyes, arms and legs!

[=CfC=BlueDog]

Aircraft Limitations (see Dropbox) now revised to include BF 109E3 and E3B information.

[=CfC=BlueDog]

Disappointing for the purists, but joy for the boy flyers - 'twould appear the engine/prop and airframe limitations are not "seriously" moddled in COD.

The boost and rpm are not time limited, nor are they value limited as per the Pilot's Notes.   Only exceedence of the the engine temperature limits will cause an engine failure.    I ran the Hurri Rotol at max rpm for 45 mins without any form of failure; also for 15 mins with high boost low RPM, again without problem.   But exceed about 115 deg C coolant temp and you will get a failure.

The bottom line is;with CRM and ET effects you can do whatever you like with your throttle and pitch control so long as you select rad fully open.    In that config you are unlikely to get any form of engine failure.   So the only thing you really need to sweat on is the coolant temp if you reduce your rad setting.   Puts a big question mark about fidelity of the sim.

Likewise with airframe limits:   I could select gear extend for the Spit at 310 mph; way above the limit of 160.   The gear will not actually extend until speed reduces to somewhere around 200 mph.    Flaps can be selected at 250 mph, but will not extend 'til speed is lower.   However, in both cases, actual extend speed is well in excess of the book limit without incurring failure.

Personally, I think the developers should have done better.

Only did spot checks on 3 types, so would appreciate any feedback from anybody's 'testing' - be it extensive or spot checking.   

[Badgerton Smedly]

Excellent form Bluey!  I have to admit that I haven't tried deliberately breaking anyhting yet and have been conforming to the known limits of the AC.

Well, if structural failures are not being represented then I think that the Nana Forums need telling!    Have you posted there yet?

I'll have a go myself later!

Badger

PS. I trust you have a 'chute attached whilst being 'Crash Test BD'! 

[=CfC=BlueDog]

Hello Badger, old bean.   I think it's way too early to input into the public forums - my info is based on spot checks only and I don't really have a clear understanding of what failures should occur and when.   For example, perhaps you could actually select gear down in the Spit at high speed and the high dynamic pressure might stall the actuators until a lower airspeed is reached - and even though the gear might come down at a higher speed than the limit according to the Pilot's Notes, it still might be within the design or ultimate limit for the equipment.   I just don't have any information at hand to tell me one way or another.

Regards the engine handling issues, again I plead ignorance - I just don't know what is (or is not) possible to model in a flight sim of this nature.   And again I don't have information about what happens in the real aircraft if the RPM is left at the upper limit for periods in excess of those specified - perhaps failure will not occur for some considerable time but engine life might be significantly reduced.

[=CfC=BlueDog]

Further information, this time for the BF109E3B:

Engine:

RPM/ATA:  Book figures give Max for takeoff as 2468/1.45 (5 mins); Climb 2368/1.35 (30 mins); Cruise 2326/1.2.   I flew around for 35 mins with RPM 2800 to 3000 ATA 1.35 to 1.45 without apparent detriment.   Go above 3000 and you will get a failure.   Collant temp is auto controlled but oil temp must be monitored carefully.   Ensure engine oil is warmed sufficiently before takeoff.  

Airframe:

Gear can be selected at high speed but will not extend until airspeed permits.  I selected at 400kph, book limit is 220 with gear in transit.   Flaps will travel at speed well above book operating limit (250kph).   I selected at 400 and they extended to full without failure.

Draw your own conclusions.

 

[=CfC=BlueDog]

Further to the above detail on the BF109:  higher RPM doesn't automatically mean more thrust.   Best thrust is obtained by altering prop pitch to maintain 2300 RPM with full throttle.   This will give about 1.35 ATA at sea level and 1.45 ATA with "Afterburner ON".   (Note, the extra boost turns off automatically after 1 minute.)  

So, at sea level, with full throttle and various RPMs you'll get something like:

1800 RPM:  380 kph
2300 RPM:  440 kph
2800 RPM:  400 kph

These are rough figures only but you can see the performance peaks around 2300 RPM.

Lovely stuff.
     

[CFC_Conky]

Hi Bluey,

Something else for the purists to ponder, operating the landing gear or flaps at their limit airspeeds won't break them...right away. One should operate them at a somewhat slower speed  than limit (10mph or so) to reduce strain on the works. Excessive stress loads will cause cracks to form in the various hinges, bell-cranks and other assorted  paraphernalia known only to Wilkins and 'is erks.

It's too bad that the RPM/manifold pressure relationship and/or limits appear to be under-modelled. Back in the day when I flew round engines, it was very important to think about RPM when operating the throttle.

As for the lack of thrust at higher RPM's on the 109, perhaps it's because there is more drag generated when the prop is in fine pitch. Fine pitch will take a bigger 'bite' out of the air at low speeds, which is a good thing, i.e. when you want to T/O or perform a go-around. On a constant speed prop the pitch will coarsen as speed increases to maintain constant RPM, but not when you are 'hand bombing' it.

Pip, pip,
Conky

[=CfC=BlueDog]

Excellent post, Conky, and right in all respects.   The drag at fine pitch and higher airspeed could be demonstrated in IL2 1946, but it was nowhere near as evident as in COD.   So COD is more realistic in that regard.

BTW I'm not suggesting that the gear should 'fly off' if thrown out above limiting airspeed; but it would be sweet if the gear failed to extend properly (fully) and the pilot had to make some decisions about landing following his imprudent actions.   The flaps are no doubt somewhat less robust than the gear and could well dislodge or jam.   Happens in 1946, so why not in COD!

So I'm just a grumpy old geezer that was expecting more from this sim.   It would have been cool if players had to look after their charges and fly within the published limits to get the most out of their beasts and avoid costly failures.   However, I need to remind myself that this is a combat flight sim where, for the fanboys, the most important thing is kicking butt; and if you break your jet it doesn't really matter.   'Esc E' and 'I' keys are pretty easy to press.   

[CFC_Conky]

They should put in a feature where if you break too many kites you have to buy the game again.