Blenheim take off

[Seeker]

Now before I start, I know the fanbois will come crawling in droves to defend their religion, but none the less:

How does one take off in a Blenheim? I've just wasted 2 hours trying.

Yes, the rad is open.

Yes, the engines are warmed up.

However, I've yet to get as far as wheels up without blowing an engine.

What's the magic formula, with respect to manifold pressure and RPM?

I tell you what, this may be a sim, but it's sure as hell no game (<- obligatory hook for the really real realism fascists that are killing flight sims)

[baronWastelan]

Couple weeks ago I posted a track in the thread in "Gameplay" forum. Try doing a search on "Blenheim" in the title.

[JG53Frankyboy]

the cylinder temperature has to be minimum 200° !!!
gauges are over the fuelcock levers, look over your right shoulder.
That take a lot of time.....in singleplay you can use the speed up function.

If the engines are at that temperature, all works like a charm . But dont forget to check the ruder trimm, its 'off' by default

as you have only two propeller settings (0-4% is coarse, from 5% to 100% its fine pitch) dont give too much power during start to avoid overrev. And disable the carburetor heating, you need it to start the engines, but it reduces the power.

during flight, i always stay at fine pitch. rpm 2000to 2200. And if your engines begins to stutter, try if to enable the carb heating helps (it does in most cases)

The game lacks of documentation, true. As you are wondering very often "has this to be this way or is it a bug" ..........

[Blackdog_kt]

I can understand being irritated by the lack of documentation, but there's no need to project that to the same people you're asking for help. Even being an unintentional side-effect of being frustrated, someone will take offence and respond in an agressive manner, then the whole thread will go down the tubes and you won't have the answers you need.

We're all experiencing frustration at certain issues, but there's a lot of community knowledge accumulated already, all you have to do is ask and use the forum search function

Fear not, for there have been numerous threads on the Blenheim. I've started keeping a log of my posts regarding to frequently asked stuff, so i'll just copy-paste some of it that's relevant.

I think the Blenheim's mixture also behaves in a similar fashion to the Hurri and Spit, rich is back and forward is lean.

This is part of the confusion in the cross country quick mission if you stick with the default choice of the Blenheim, definitely one of the most challenging stock missions.

1) You have a definite crosswind pulling you to the right. I tested it with the Moth and it's weightless enough to swing around to the right with the engine stopped, weather-vaning into the wind.

2) You have the Blenheim's engine torque pulling the same way and if you try to run about half-throttle on the port engine and full throttle on the starboard engine to keep it straight, you end up with a longer take-off roll while one engine is running flat out and get some kind of failure on the starboard one, either a governor failure (if the oil is not sufficiently hot) or a blown oil gasket (if you keep running it at full).

3) All the while, you wonder why the damn thing won't get off the ground and when you restart the mission and accidentally look at the animated throttle quadrant you see the little letters telling you your mixture is set to full lean --> less power, more heat and failures.

I managed to take-off fine (if still not managing to completely maintain runway alignment) after setting it to rich. Now my next challenge is taking off with four 250lb bombs loaded, which i still haven't managed. I think i'll follow the advice of someone over at the 1c forums, taxi to the other end of the runway, turn 180 and take off in that direction so the crosswind will be pulling opposite the props.

Another thing to note, it might be beneficial to exercise the props between high and low RPM to "recycle" the cold oil in the governor with warmed up oil...maybe this will help with the prop governor failures and RPMs jolting around.

Finally, turn on your carb heaters for the start up but turn them off before take-off. Heated air = rarified air, it means running with the wrong mixture all over again but this time too rich.

The Blenheim:
The Blenheim is another tricky one, because it seems way sensitive to temp effects and especially having the correct oil temps. If your oil is cold, the oil pressure in the prop governor gets high and you get a governor failure.

Engine run-up:
Make sure to cycle the props between low and high RPM before applying power for take-off, as this will cycle the oil inside the governor and get warmed up oil from the engine into the system. This is called exercising the prop and is done during the engine run-up, prior to take-off.

Just keep the props at fine pitch, step on the brakes, full back stick, apply throttle until you get 1000-1500 RPM or so (arbitrary numbers, just something that won't break the engine from overheating while sitting on the ground and there's no airflow to cool it...in reality all aircraft have a specified RPM for the run-up) and move the pitch controls all the way back and forth a couple of times.

How the props work and how the game interface displays it:
As for the actual props now, it only has two-stage props but to put it in coarse pitch (the low RPM position) you have to pull the pitch slider all the way to the back. Anything higher than that puts it into fine pitch/high RPM. Effectively, this means that it has a prop similar to the one found on the in-game Spit Mk.I, but it doesn't "snap" between the two extreme positions (top and bottom) on its own. The bottom of the slider is the coarse pitch position, the rest of the slider all the way to the top is the fine pitch position.

Carburetor heating:
It does have carb heat but i haven't found any instruments displaying carb temps, so you need to read up a bit more to be able to set it.
You can't just set it to max either as it will reduce power, running too much heating lessens the air density in the carbs, so it's like running with too rich a mixture and choking the engine.

I've had some success setting it by ear, i just increase carb heat until the engines sound like they are losing power (this means i found the critical spot), then i decrease it a notch or two to get it back into the proper operating range and the engines sound healthy again. Had no problems up at 8000ft with this method last time i tried it in the free flight mission.

This is similar to leaning in an aircraft with manual mixture controls, which brings us to...


Setting the mixture:
First of all, there are two correct mixture settings for each altitude. The economy mixture is the leanest you can go without losing engine power, but it won't allow you to run high boost settings because of detonation and overheating. The best power mixture setting is a bit richer, burns a bit more fuel, but lets you run higher boost.

In modern and even not so modern general aviation aircraft, there are easy ways to set this: exhaust gas temperature and/or fuel flow gauges let you judge where is the correct mixture for each altitude.

In the Blenheim however we don't have those toys and we can't see the exhausts either, so we can't lean based on the colour of the exhaust flames.

Fear not, because there is a way. If you have a fixed pitch or two stage prop (which essentially is like having a fixed pitch prop that you can change mid-flight for another one with a different pitch) you can easily judge the changes in power.

This happens because for a given prop angle of attack, the power delivered by the engine has a direct effect on RPM. If your prop pitch remains constant, any change of throttle will change the RPMs too. In a similar fashion, every change of mixture that makes the engine run better or worse will also have an effect on RPMs.

This can be observed in aircraft with fixed props like the Tiger Moth (just lean until you get the highest RPM without touching your throttle), two-stage props and it would also work in aircraft that use the luftwaffe propellers, because they too are manually set to a specific angle by the pilot. It wouldn't work in an aircraft with a constant speed prop, because the resulting RPM change would be mitigated and cancelled out by the propeller governor, giving no useful indication to the pilot.

So, how does that help us with the Blenheim?
First, lean the mixture until you hear the RPMs increase. To know if you can lean further, keep at it until you hear the RPMs drop. This marks the point where further leaning doesn't yield any benefits, in fact leaning too much causes the engine to overheat.

So, as soon as you find that spot you've discovered the bottom of the useful mixture range for your altitude.

Go ahead and bump up the mixture towards rich a notch or two until the RPMs rise again. This is the economy mixture setting we mentioned earlier.

If you add a couple more notches of rich mixture (but not so much that it chokes and starts decreasing the RPM again), you will be at the best power mixture setting. This one is the best power mixture setting and it's the top of the useful mixture range for your current altitude.

In short, the scale looks something like this:
too lean---economy---best power---too rich.

Going too lean or too rich will cause your RPMs to drop, so just move the mixture controls until you find the range of highest RPM: the bottom of the range is economy mixture and the top of the range is best power mixture.

All this is presuming that the Blenheim has a completely manual system.

I don't know how exactly it works (is it semi-automatic between rich and lean like the Spit, or is it completely manual?), but if you try out the above method you can nail it down: if you don't see it working like i described, then it has a different system.

Also, just like in the Hurri, Spit and Tiger Moth, rich is backwards and lean is forward in regards to not only the animated cockpit controls, but also the info window sliders (the interface "HUD") and your actual, physical game controllers: you will need to press your "reduce mixture" key or pull your slider backwards to move towards richer mixture.

I've also found that the engines don't start easily if i set it to full rich, so i set it about halfway (if you look at the throttle quadrant, left-hand side in the cockpit, you will see a line marked as "normal" for the mixture controls, set it there). I guess full rich is only used when setting emergency and/or take-off/climb power to prevent the engines from overheating and cruising is done with mixture between "normal" and "weak".

It might also be a good idea to download a user made mission with Blenheims in it as a means to get rid of the crosswind in the stock cross country mission. I'm searching for the link but i can't find it now, it was posted here on the forums, it's a battle of France scenario with a flight of Blens taking off from France and going to back over the channel to Lympne airbase amidst a dogfight.

Alternatively, select the luftwaffe airfield attack mission from the quick mission builder. The first two groups of RAF aircraft spawn on the ground in that mission to simulate a scramble. Change the aircraft type for one of these groups to a Blenheim, click on the pilot icon to set it as the group you spawn into and set all other groups to zero amount of aircraft. This way you will be undisturbed in practicing start-up, take off and landing.

I hope this gets you started and eases your worries somewhat, cheers

[meplay]

Hi Seeker, the only thing i do is basically have my right engine throttle at 100% and left at around 50% and as my back wheel starts to come up i set the left engine to 100% also. The main thing that stops me from overheating though is when ive started to roll quit fast, i start to drop the prop pitch slowly till its about half way or lower and thats seem to be the only thing that stop my CHT from sky rocketing through the roof.

[Trumper]

Watch the use of the throttles, happens in real life
http://www.fightercontrol.co.uk/foru...p?f=18&t=20608

[JG53Frankyboy]

Originally Posted by meplay

Hi Seeker, the only thing i do is basically have my right engine throttle at 100% and left at around 50% and as my back wheel starts to come up i set the left engine to 100% also. The main thing that stops me from overheating though is when ive started to roll quit fast, i start to drop the prop pitch slowly till its about half way or lower and thats seem to be the only thing that stop my CHT from sky rocketing through the roof.

i just repeat myself, WHEN you warm up the engines to 200°C (NO joke!) , the engines work simultan when opening the throttles. No need to make on 50% and the other 100% than. It just take time to reach this temperature without speeding up the game...

CoD need a "warm engines" setting, RoF players know what i am talking about

[meplay]

Originally Posted by JG53Frankyboy

i just repeat myself, WHEN you warm up the engines to 200°C (NO joke!) , the engines work simultan when opening the throttles. No need to make on 50% and the other 100% than. It just take time to reach this temperature without speeding up the game...

CoD need a "warm engines" setting, RoF players know what i am talking about

yup i only put the left 1 at 50% throttle to stop it pulling off the runway to the right. then when i get rudder authority il (ie when tail is off ground) il set the left engine to full, i use prop pitch to stop CHT going above 250

I shoulda really said that ive already got my oil temp to 40 and my CHT to 200 by the time im ready for takeoff

[JG53Frankyboy]

you checked the ruddertrim ?
because as default it is full right IIRC.....

[meplay]

Originally Posted by JG53Frankyboy

you checked the ruddertrim ?
because as default it is full right IIRC.....

yeah i put it full left rudder at start of mission, still pulls over :/ i cant stop it unless i have my left engine to 50% and right to 100% throttle, even when i turn the cross wind to zero. on one of my own missions on the channel map.