Blenheim operating limits and checklists

[Redroach]

Originally Posted by whoarmongar

Please answer me this question honestly guys. Has ANYONE taken off from England fully loaded arrived over target and bombed on target in the face off flak and enemy aircraft and got back home landed safe with full real settings CEM ?

I did, once, on syndicate. However, I didn't run into enemy aircraft - an escort or a formation is required for fighter defense anyways, even if all works properly. It's just bomber vs. fighter, that's never fair.
One additional drawback, though: On syndicate, you take off from Littlestone and your parking position is fairly close to the runway. So I didn't bother taxiing and pushed the throttle forward from the parking position, ending up on the runway at 40-50mph.
If I had taxied, I'd look at an additional wait time of 3 minutes plus just to cool the engines again in order to avoid blowing them on subsequent takeoff.
So yeah, the temperature models on the blenheim are pretty much crap. But this is CoD

P.S.: Oh, and I bombed an empty airfield...

[Blackdog_kt]

Originally Posted by JG53Frankyboy

AFAIK it has only auto rich and auto lean mixture setting...

Correct. In the Blenheim the levers move all the way (like a gradual, fully manual mix system) but they only have two functions: anything forward of the middle of the lever's movement range is auto lean and anything from the middle and back is auto rich.

This is not a glitch with CoD, the Mk.IV pilot's operating handbook describes how the real aircraft uses such a system.

[phoenix1963]

Well, I've just about tried every combination of mixture, carb heating, pitch, gills (radiator flaps), throttle... and I always get engine failures as I climb out.

I eventually discovered that the lean/rich setting seems to be exactly as labelled next to the lever, fully back seems to be auto rich.

I warm the engine with gills open (as per Klem's excellent pdf posted above), but takeoff with them open, or temps get too high (contrary to Klem's info). I use the 100 octane outer tanks (contrary to Klem's info).

I allow the engine oil temp to get above 40C before revving a little.

I cycle the prop pitch before taking off to circulate oil.

When I take off, I DON'T engage boost override and limit to about 4 lbs boost - that seems to get rid of most of the failures on takeoff - keeping revs below about 2500 and VERY gently increasing throttle.

As soon as I'm wheels-up I reduce throttle to about 0 boost and it seems to run sweetly on about 2200 rpm.

So I get off the ground OK with this recipe, but then I always get gasket failures, governor failures etc at around 2000ft - this is despite closing gills to keep temps up and adding some carb heat.

What am I doing wrong?!

56RAF_phoenix

[JG53Frankyboy]

my only advice would be, try lower rpms and always keep the engine temperaturebetween 200° and 250°.
i personaly never swith to course pitch, i always stay in fine and control the rpm with throttle.

and yes, in the british planes (Tiger Moth i dont know) full rich mixture is 3D cockpit lever full back, with whatevercontrol setting you get this. Digital info mixture reading is 0% (or mixture bar down) than !

[phoenix1963]

My thinking is: governor failures are because oil at the right temperature is not getting to the pitch mechanism; gasket failures are because oil or cylinder pressure or temperature is too high (maybe because I'm running at too low revs for the throttle setting); carburetta failures because it needs heat.

But maybe that's too simplistic?

I did notice, when incorrectly running too lean, that it was impossible to have oil temps and cylinder temps both correct.

56RAF_phoenix

[JG53Frankyboy]

there is no governor (at least that is my understanding how propellers are working......), the Blenheim IV has no CSP, only a two speed propeller.

[phoenix1963]

Originally Posted by JG53Frankyboy

my only advice would be, try lower rpms and always keep the engine temperature between 200° and 250°.

Yes Franky, I've just spent a very frustrating hour trying inner and outer tanks because of the conflicting information.

I never got off the ground once (mainly because I have a single throttle and struggle to steer, then overheat one of the engines)! But I can confirm that engine temperature between 200°C and 250°C. Over 250°C and you blow the cylinder head.

Certainly, after taxiing, it often pays to sit and let the engines cool to a little above 200°C to give plenty of margin for takeoff.

I struggle to believe the heat capacity was so low that the temps would vary that much. If it were that important and variable, the gauges would be in front of the pilot!

I also think Mechanist is onto something:

Originally Posted by Mechanist

Tailwheel is fixed about 30° to the right when you strat on the ground, making taxiing and straight takeoffs almost inpossible.

Looking at the behaviour in external views, I think the tailwheel is spring loaded somehow. That would be an easy programming error - forgetting -90° and +90° have the same magnitude restoring force but different signs.

56RAF_phoenix

[JG53Frankyboy]

actually, the Blenheims CEM is of that kind i wish EVERY developer would have to fly it for ,lets say, 10 missions (with a groundstart and at least one change from fine to coarse pitch every mission ) and for every mission he blews his engines he would get 10% less salary in that month !

perhaps that would let them think again......................

With this being the only british bombcarrier - i dont see good things for any comming online "war" with the BoB scenario .

The whole radial's CEM have to be looked in again IMHO.