Level bombing in the Blenheim

[jimbop]

I forgot to mention in the notes that I also adjust the altimeter. I think we discussed this above (or perhaps in the ATAG thread) - the altimeter is often set 200-300 feet too high. I click it left three times so am ~300 feet lower on instruments than default settings. I have edited above to include this.

[ATAG_Dutch]

I flew my own mission three times today, and got absolutely bloody nowhere.

Lots of practice and experimentation required methinks. Hmmmm........

[jimbop]

I'd set it up as an airstart just a few miles out from the target. Then you can rinse and repeat the drop. I must have done about 30 bomb drops before I started getting the hang of it.

[jimbop]

Originally Posted by ElAurens

You guys are flying a very different Blenheim than I am then.

And do you really think it was that hard to keep the engines alive in the real thing?

Poppycock!!!

The model is broken, plain and simple.

It's even worse than the G.50 and I won't try to sugar coat it and say well yes you can fly it, sort of.

It's garbage. I sort of have the feeling that the devs never intended it to be flyable, then thought better of not letting the RAF have any bombers at all, and patched it together for release.

ElAurens, I've been flying the Blenheim exclusively for a few days now and have become quite used to it. I am finding it quite forgiving! If you control the temps with the radiator to keep them at 190-240 you can pretty much do what you want with the boost. All the recommendations about only using 1.0 boost are rubbish - they just aren't using pitch and rads correctly. Keeping the temps under control means not too hot OR too cold. A lot if my early troubles were due to not having enough engine temp since you can't increase boost without adequate temperature.

I routinely climb at over 1000 feet per minute with 4.0lbs and 1800 RPM with the cylinder head temps at 210. I can easily firewall when need be and have no trouble taking off. Does this sound more like the sort of thing you would expect?

[ElAurens]

So you can take off 100% of the time without blowing an engine?

Amazing.

[jimbop]

Originally Posted by ElAurens

So you can take off 100% of the time without blowing an engine?

For sure. Warm up with rads closed, no carb heater until ~160 degrees. Open rads, full left trim and throttle up to slow taxi for runway alignment (probably need a spot of brakes now and then). Temps 190. Open throttles to about 70%, build speed, wheels up. Throttle down and cut prop back to coarse.

You will be doing 120 mph max so stay level until 150. Close rads to 60% when temps fall to 210 (about 30 sec at this speed if that) then start climbing.

The risky bit is fine pitch (high rpm) without good airflow. This will cook your cylinder head very fast (I think faster than realistic) so move to coarse as soon as you can after takeoff. After you have cooled down you can fiddle the coarse prop pitch to increase from 1600 to 2000 between coarse and fine and climb all day.

What threw me for a while was the awful engine sounds when increasing boost. I thought it was too hot but turns out it was too cold! Curse the designer who thought that was a good spot for cylinder head gauges...

Certainly not a perfect model and should not be that sensitive to temp but it is still flyable. And if I can do it I'm damn sure you can. I had some fun with the HE111 and tank targets on ATAG #2 last night! Well, until the flak had fun with me...

[Hooters2]

Agree with jimbop, his routine sounds the same as mine. It was a struggle to start off with but now no problem at all, you can scream in pretty quick for a skip bombing attack and the temps stay quite stable. As with many things it's when you change configuration, take off to climb, climb to cruise etc that you have to be careful. I like the Blenheim a lot.

[ElAurens]

Well, at least we finally have radials that can get too cold, unlike IL2 where you had to have the cowl flaps open all the time at any speed.

[ATAG_Dutch]

Originally Posted by ElAurens

So you can take off 100% of the time without blowing an engine?

No. But that's only because I keep forgetting to open my bloody cowl flaps!

But Jimbop is correct. The +1 boost guide in my vid is only really there so that when you select coarse pitch after take-off, the boost goes to +3, which helps establish temperature control habits - oil temp, head temp, cowl flaps, oil temp, head temp, cowl flaps etc..

It's actually much steadier on the temperatures when running at +4 or +5.

The only other thing to watch is that as IRL, the faster you go, the cooler your engines. So again when accelerating, watch the temps and adjust cowl flaps accordingly.

Once you're up and flying straight and level, +5 boost and coarse pitch can pull you along at 240-250mph quite easily at 300ft, without any temperature fluctuations to speak of. That's a pretty good speed compared to the Spits and Hurris in the game.

[Blackdog_kt]

There are problems with the model (actually, there's one main problem and it's got to do with how the temps fluctuate at given ranges), but it's not unflyable.

I don't have the sim currently installed due to a hard disk failure, but i was probably among the first 20 people to get a Blen off the ground in the stock cross country mission (that many people claim is bugged), bombload and all. That mission has a notoriously short runway and a crosswind and to be honest, it was an exercise in masochism, but i fancied the challenge and it was doable once in every 2-3 attempts.

In other scenarios (longer runways, taking off into the wind, managing your bomb and fuel load to get a lighter aircraft), things were much easier even some patches ago.

So, there are some problems and some workarounds which make the aircraft flyable despite its issues.

The problems:
1) Lack of intermediate flap positions: It's true the real aircraft had a two way switch similar to the Spit (full up or full down), but the lever could be "jammed" by the pilot into an in-between position to give partial flaps (at least i remember reading something like this in a manual). This would be excellent for those take-offs, as no flaps deprives us of lift but full flaps deprives us of speed, which deprives us of airflow to cool the engines and prolongs the take off run (which equals more time at rising temps, you get the idea).

2) "Funky" temperature modeling in the sim: It seems that temps rise slowly and drop fast at low power settings, while they climb really fast at higher ones. Now i'm not a real life pilot, so take this with a grain of salt, but from reading various accounts and flying a few expensive piston-engined add-ons on a friend's FSX installation, it seems there needs to be some revision here.

First of all, ambient temperature is a factor but that's got to do mostly with how difficult it is to get the engine started in the first place (especially for radials). Once it starts however, temps should rise sooner or later to the appropriate levels. Sooner or later in this context means within a minute or so.

The only time i've had a hard time starting pistons in a sim and having to deviate from checklists in those FSX add-ons was in two occasions. Both were when flying with real weather downloaded from the internet and selecting my home town during a winter night.

In the first such case, local weather was about -10 celsius at 6am simualtor time with a lot of humidity in the air (hence, high danger of carburetor icing). I tried to start up a Catalina and i had to give it 4-5 tries just for the first engine. After that, i had to apply carb heat and keep the cowl flaps closed, contrary to what the checklists specified.

Bear in mind that the add-on i was using is modeled after data gathered from a restored Dutch Catalina and used by its real-world pilots when they want to brush up on their technique without stressing out the real one, so it's got to be somewhat accurate.

The second case was with the A2A simulations Boeing 377 Stratocruiser (essentially a transport/airliner version of a B29 with improved engines). In that case, starting proved difficult too because the ambient temperature was below zero and i had to apply carb heat while actually turning the engine over during starting, just to thaw the ice in the carbs and get them to start. That add-on is also highly spoken off in terms of engine management.

Actually, everything i learned about CEM before CoD was even released, i learned it from flying these things on my friend's FSX installation.

Anyway in both cases, using a bit of extra power and carb heat, or closing the cowl flaps a bit enabled me to raise the temps to their appropriate range without problems.

Second, during daytime having the ground radiate heat back onto the aircraft could result in Spits overheating on idle just sitting on the tarmac. That's why they were periodically started by their ground crews when on alert: they should be warm enough to be able to start easily, but not so warm as though to overheat during taxi.

All in all, the temp model seems in need of a slight revision of its "response curves" so to speak.
The foundation is solid, it just needs a bit (and it really is not much) of fine tuning: temps should probably be easier to change during low power settings, the cooling effect of airflow should maybe be a bit more pronounced and finally, the "window" of permissible temps should be a bit wider. As it stands now anything below 180 degrees makes the engines sputter and cough on high boost, plus the expected temps for specific power settings are a bit off when compared to the manual (that last part about the manual is me going by memory, i might be wrong).

After all, the Blenheim manual states that taxi should be done with cowl flaps open and take off with cowl flaps closed! This tells us two things:

a) overheating is possible even on idle/low power if the flaps are closed (in the sim, it's almost impossible to even warm up unless the cowl flaps are closed)

b) once the aircraft gets moving, you have enough of a time window thanks to the cooling effect of airflow before you overheat (in the sim, it's impossible to attain the expected boost values for take off if you don't open them)

So, maybe what really happened is that the engines were a bit harder to start on a cold day, but after that it was easy to get 150-180 degrees within a couple of minutes or so and get rolling almost right away, then idle with the cowl flaps open to drop it down to let's say 150 so you have a bit of a "buffer" (and since the engines wouldn't sputter that easily at lower temps), before finally going full throttle with the cowl flaps closed for the take-off and opening them up again after taking off and throttling back to cruise.

These temp issues are apparent in all aircraft in the sim, but the radials are the ones mostly affected.

3) The outboard fuel tanks in the real one were mostly used for 100 octane fuel, while the inboard tanks were filled with 87 octane fuel: The outboard tanks were a modification (they were not even present on Mk.Is i think, but introduced on Mk.IVs for long range raids) and since they added weight, they thought they'd fill them up with 100 oct fuel, because the overweight aircraft couldn't get off the ground without using higher boost values (and high boost needs higher octane ratings, etc).

That's why enabling boost cut-out in the sim is a sure way to cook your engines. Our Blenheims come tanked up with 87 octane fuel, so they can't take the extra boost. Due to the temp funkiness described above, they can't even take the normal +5 boost that the real ones specified as WEP and take-off power. However, in our map we don't need that much fuel anyway.

Arguments to the tune of "but i bet they would use +9 when in danger, so they would have to keep at least a bit of 100 oct in the outer tanks" probably don't hold much weight, because that kind of fuel was reserved for the fighters mostly. I bet they wished they could engage WEP over Calais, but i highly doubt they were given priority for 100 oct fuel. The bombers were only using it because they couldn't get off the ground at lower boost values in the first place, in the event they were loaded for long range.

Long story short, for cross-channel raids just load up 50-60% fuel to keep the outer tanks empty, save yourself the weight and don't go above +4 boost and you're historically accurate for the most part. Long range raids where they needed to fill the outer tanks would probably be something like the raid on the Cologne power station, but we don't have anything to bomb that far in the sim due to the map size.

The workarounds in the case of the Blenheim:
1) Anticipate power and airflow changes: If it's one thing i learned flying FSX it's this. Don't wait to see the needle creep into the dangerous zone of the dial, expect it and preempt it.

You want to pull the power back and dive? Give it a few notches of cowl flaps less in advance, just as you pull the throttle back. Then, check the dials after 30 seconds to see if it needs further fine tuning. You want to exit that dive and climb at high power settings? Open the cowl flaps a few seconds after you start the climb and throttle up. It gets really easy with a bit of experience and after a while you'll have your own pre-set scenarios in your mind and thinking like this: "i'm doing about 250mph, i should keep cowl flaps below 50% open", or "i'm pulling up from a skip bombing attack at high power, once my IAS drops below 200mph i know i have to open cowl flaps 100%". Etc, etc, it just takes practice, so just do it offline, pause frequently at key points during your flight and look to your gauges to identify the notable patterns and trends.


2) Use an accelerated warm-up: Once your engines are running, keep the cowl flaps closed, step on the breaks and advance throttles until you hear the engines sputter, then back off a bit until they stop sputtering. Essentially, you are throttling up to the top of the engine's "comfort zone" for your given temps. However, throttling up raises the temps too, so every few seconds you can repeat this and increase throttle a bit more. Before you know it, you'll be pushing +1 to +2 boost while on the brakes, have a temp of 180 degrees and be ready to roll out.

At that point, open cowl flaps (maybe not 100% but open them), give it +1 boost or so to get it rolling and taxi to the runway. If you do a straight-in run that lets you use part of your taxi run for extra acceleration (like in some videos i've seen) all the better, just remember to open cowl flaps when you go to higher boost.

Otherwise, wait your turn at the runway and use that time to cool the engines down to 170-180 degrees, so that you have a sufficient "time window" available for high power during the take-off run.
DON'T start the run unless the engines can get to +2 boost or thereabouts without sputtering (step on the brakes and test this). If they are couching, they are not delivering enough power. If they throttle up nicely, then just let go of the brakes and after 3-4 seconds the temps will have risen sufficiently to enable you to push higher boost for the rest of the take-off roll.

Hope it helps. Jeez, you guys will get me reinstalling on my system partition and i really have to study these coming days