Blenheim operating limits and checklists

[klem]

Thanks BlackDog.

I tried the Blenheim the other night and it was just a pain to get off the ground, especially not knowing why (like using the outer 100 octane fuel tanks). Also need to know those max boosts for each. Some of our guys want to try it although I'm not mad on the idea

Look forward to more of your info.

[Blackdog_kt]

Well, just to get you started:

Takeoff at full fine pitch. I don't know if the sim models the different fuel in the outboard tanks. The real life drill is to select outboard tanks, set the boost cut-out to on and give it +9 lbs boost while doing what is by now common knowledge to keep it from veering to the right (brake and left rudder to force left wheel braking, more throttle on the starboard engine and less on the port one), until you get sufficient speed that your rudder becomes effective.

In one of Freycinet's videos you can also see a different method. He only gives it about 60% throttle which lessens the drifting to the right, until the airspeed rises and the rudder is again effective.

Then you can advance both throttles to full, lay off the brakes and keep it going straight with the rudder.

Lift off at about 80-100mph but don't climb. Retract gear and disable the boost cut out (which lowers your maximum boost to +5 lbs) to keep your engines healthy.
Once you reach 120mph go to coarse pitch (pull the pitch levers all the way back, anything above that qualifies as fine pitch so if you just set it to 50% of the way you're still running full fine and high RPM).

Once you reach 150mph you can start climbing. Max climb is +5 lbs and about 2600-2700 RPM (going from memory here) but i don't know how the in-game CEM agrees with that. In any case, even the manual recommends climbing at lower settings for economy reasons so it should be perfectly possible.

Max continuous is +1.5 lbs for lean mixture and +3.5 (if i'm not mistaken) for rich mixture. Once again, mixture is either auto lean or auto rich, there are no in-betweens. In this case however the full-range motion of the levers is historically correct, you just set them according to the demarcation labels on the throttle quadrant. Lean is with the levers forward and rich is with the levers back.

To cut a long story short, as soon as you lift off raise your gear, level out, go to coarse pitch once you hit 120mph, disable the boost cut-out and throttle back to +3.5 lbs boost. When you hit 150 mph trim it for climb, start monitoring your engine temps (you might need to close the cowl flaps a bit, this will also give you some more speed and a better climb) and give yourself a pat on the back.

You might also want to switch to the inboard tanks once you're established in the climb, just to start learning good habits for when the different fuel is modeled (if it's not already). Another reason for this is that only the outboard tanks have the ability to jettison fuel (again, i haven't tested if this is modeled in the sim), so it makes sense to first burn the fuel you can't dump in an emergency during cruise to maximize on saving weight in such a case.

Once you reach your chosen cruising altitude and trim for level flight, throttle back to +1.5 lbs boost and set mixture to auto lean (levers full forward) to maximize your fuel economy.

[klem]

Don't know if this will help or not but I'm attaching some info I got from reading the Blenheim MkV pilot's notes. Ours is the MkIV but the engine is the same (Mercury XV)

[JG53Frankyboy]

in my experience so far, i dont use coarse pitch at all. I dont get enough rpm to keep the engine at needed temperature with coarse
I fly only fine pitch, and reduce throttle to keep rpm and temperature in the games desired limits...

[klem]

In case you were still wondering I got a reply from the Blenheim Society on the two fuels in the Blenheim:

...... has passed me your query re fuel of different octane ratings used in the Blenheim IVs. Yes they did have two different fuels in the same aircraft!
100 octane in one pair of tanks used for take-off and emergencies with a 'Plus 9 lbs boost' lever, and a lower octane fuel for far less boost pressure, used for cruising, in another pair, and of course this did lead to many accidents, often fatal.
How this came about is explained in detail in my book "The Bristol Blenheim - a complete history" published by Crecy. You can buy one at the discounted price of under £30 for Blenheim Society members from Ron Scot the Society Hon. Treasurer on 01 992 442 608 or borrow one from a public library.
Seems to me one or more of your group could join the Society at £15pa as they publish an excellent Journal, and have an annual Blenheim Day and lunch at Duxford with access to the actual aircraft and opportunity to meet the few remaining wartime crew and the present day engineers.
Regards Graham Warner

Enthusiasts may like to buy his book and even join their society

[335th_GRAthos]

Excellent information, impressive detail.

Now, coming back to reality, why can I not start the frigging engine?

fuel cocks (the round things on the right) on
magnetos on
throttle @20%
carb heater on (off did not make a difference either)
mixture middle
select engine #0
press I to start
It turns and dies


~S~

[JG53Frankyboy]

Try 10% throttle and FULL rich mixture ( digital infowondow reading is 0% !!)

[Mechanist]

Originally Posted by 335th_GRAthos

Excellent information, impressive detail.

Now, coming back to reality, why can I not start the frigging engine?

fuel cocks (the round things on the right) on
magnetos on
throttle @20%
carb heater on (off did not make a difference either)
mixture middle
select engine #0
press I to start
It turns and dies


~S~

If you have 60% or less fuel make sure you turn the fuel cocks twice, to the inner position. You can always check your fuelon the upper left panel over your head, also you can switch it in inner or outer position (outer in default)

20% throttle is a bit much, try it on 10%