Blenheim operating limits and checklists

[JG53Frankyboy]

Originally Posted by Redroach

real manuals do help, in general, but in this case the blen's FM is quite a bit off in terms of engine temps....................

from Blackdocks posted manual , ok, i admit its from a Mk.V with CSP:


Maximum takeoff power to 1000ft, 3 minutes limit:
with 87 octane fuel:
+5 boost
2650 RPM

<- i dont tested these rpms, but my wild guess would be, in CoD you would coke the engines very fast.........

in general the given rpms in the manual are much higher than i ever fly (or can reach in coarse) in the game.
But again, true, they are numbers for a CPS Mercury - not the twospeed one of the M.IV.

[Redroach]

you even quoted the part which counts...

[Blackdog_kt]

I always end up postponing this, but i see a lot of people have many questions.
I finally decided to bite the bullet and do it, these are the most important bits as a quick and dirty reference

So, without further ado, here are the Blenheim MK.IV operating limits and abbreviated checklists, according to the proper Mk.IV pilot's operating handbook:

Take-off:

• Mixture auto-rich (levers back)
• Prop Pitch fine
• Cowl flaps 1/3 open when on long range load (long range load = all fuel tanks loaded), closed when on normal load (normal load = inboard tanks only)
• Flaps at 15 degrees when on long range load (can't be done in the sim yet, it has two-position flaps but they should be more like the Hurricane's with up/down/neutral settings to enable the pilot to set them partially open)
• Boost cut out on for long range load, off for normal load. With the cut-out enabled you can get +9 psi boost BUT it needs 100 octane fuel. In the real one, the outboard tanks were 100 octane and the inboard ones 87 octane. I don't know if this is reflected in the sim, so i don't use the boost cut-out just in case it's modeled with 87 octane across the board for all fuel tanks. Normal max boost with the cut-out disabled is +5 psi.
• Let the tail rise and the aircraft to lift off. Then, gear up and keep it mostly level to accelerate. Once you hit 120mph switch to coarse pitch, then climb only mildly to let it accelerate to 150 mph which is the best climb speed.
• Disengage boost cut-out before throttling back if you had it engaged.

Climb:

• Keep within the engine limits by adjusting cowl flaps position. Oil temps up to 80 degrees, cylinder head temperatures (CHT) up to 200 degrees.
  In the sim you can push the CHT up to 250 and the engines feel mushy below 180, so i keep it between 180 and 230.
• Best climb speed at full throttle is 150 mph up to 10000ft. For every 5000ft extra, reduce climb speed by 10 mph:
  • 150mph IAS up to 10000ft
  • 140mph IAS up to 15000ft
  • 130mph IAS up to 20000ft

Cruise:

• It's possible to fly at very low throttle settings, resulting in less than 1600 RPM.
• Absolute 5-minute limit for level flight is 2750 RPM at +5 psi boost. It shouldn't be exceeded unless in an emergency.
• Engine power limits for cruise
  • for auto-rich/normal mixture (mixture levers fully back): 2400RPM at +3.5 psi boost
  • for auto-lean/weak mixture (mixture lever fully forward): 2400RPM at +1.5 psi boost
• Lowest fuel consumption cruise: mixture auto-lean/weak and throttles back as far as it's possible to maintain level flight.
• Maximum range (most miles per gallon) cruise: Slightly higher speed than the one for lowest fuel consumption.
• Maximum range at 15000ft is obtained at 110mph IAS. In lower altitudes it's impractical to fly that slow (due to disturbed air), so 130 mph is used for extended range when flying low.
• Cowl flaps should be closed for economy cruise. I don't know if this is reflected in the sim, but running on rich and between +0 to +1 psi boost i can certainly close them more than halfway (i keep them about 1/3rd of the way open).

Diving:

• Maximum permitted speed: 285 mph IAS
• Engine RPM: up to 2750 if throttle is less than a third of the way open, at more than 1/3rd throttle up to 3100 RPM is permitted for a very short time (manual says momentarily).
• Prop pitch should be coarse (prop pitch controls fully back, everything above that in the sim corresponds to the fine pitch position).

Landing:

• Throttle back to bleed off speed, close cowl flaps if necessary to maintain CHT.
  
  This is very important, because if you just idle it and keep it there on a steep, long descent for an immediate flare and touchdown afterwords, your engines will cool way down and not develop any power when you need it for the flare and touchdown and you'll pancake onto the runway.
  
  It's also very important to remember to open the cowl flaps again once you apply throttle, in order not to damage the engines. Try to make it a habbit of adjusting them together: Throttle up- open cowl flaps some, throttle back- close cowl flaps a bit
• Once below 150 mph IAS, lower gear and set fine prop pitch.
• Enter the airfield circuit at 120 mph IAS.
• Drop full flaps when nearing the end of the circuit. The manual doesn't state more but full flaps sure is draggy in the sim, so i would say fly a normal rectangular pattern with gear down and drop flaps when turning from base leg to finals.
  
  Turning with both gear and flaps extended presents a ton of drag and shaves off quite a bit of altitude, leaving you to execute a fairly flat approach instead of a normal glide. And to keep it flat (ie, level) at such high drag you need a lot of power while you're at a low airspeed-->overheat danger.
  
  So, it's better to wait until you are aligned with the runway before lowering flaps.

Missed Approach and Go-around:

• Raise the gear immediately after leaving the ground to minimize drag.
• Don't raise the flaps until you reach a safe altitude of 500 feet. First, nose down a bit to accelerate to 100mph IAS, then raise the flaps.
• If one engine fails during the go-around, there is not sufficient power to complete the take-off at this high drag configuration. In such a case, closing throttles and landing at whatever cost is the only option.

After landing:

• Open cowl flaps while taxiing if the temperatures are high.
• If the aircraft is going to storage, change to coarse pitch before shutting down. If the props don't change over to coarse while taxiing, step on the brakes and throttle up a bit until the pitch changes (throttling up builds the necessary oil pressure for the prop governors).
• Close throttles for about a minute to allow the oil to settle in the sump.
• Stop engines by pulling the carburetor cut-outs. In the sim they are called slow running cut-outs and they are obscured, behind and to the left of the pilot's seat.
  Just map a key to it, select engine one and hold, not press, hold it down the slow running cut-out key until it stops. Select engine two and repeat to turn it off as well.
• Turn off ignition by switching off the row of magneto switches on the lower part of the instrument panel.
• Switch off the fuel supply by setting the wheel-shaped fuel selectors on your right-hand side cockpit wall to off.

Engine Limits:

• Power settings:
  
  • Take-off on 100 octane fuel (long range load - up to 14500lbs - select outer fuel tanks), up to 800-1000ft or for two minutes using max RPM at max boost (boost cut-out on): +9 psi boost, 2750RPM
  • Take-off on 87 octane fuel (normal load - up to 12500lbs - select inboard fuel tanks, outboard tanks empty), up to 1000ft or for three minutes: +5 psi boost, 2050-2650 RPM
  • Climb: +5 psi boost, 2650 RPM
  • Maximum cruise on rich mixture: +3.5 psi boost, 2400 RPM
  • Economy cruise on lean mixture: +1.5 psi boost, 2400 RPM
  • Maximum level flight power (5 minute limit): +5 psi boost, 2750 RPM
  • Maximum Dive (20 seconds limit): +5psi boost, 3100 RPM

• Oil Pressure:
  • Normal: 80 psi
  • Emergency minimum (5 minute limit): 65 psi
• Temperatures:
  
  • Oil Inlet Temperature:
    • Minimum for opening up throttle: 5 degrees
    • Maximum for continuous cruising: 70 degrees
    • Maximum for climbing: 80 degrees
    • Emergency maximum (5 minute limit): 85 degrees
  • Cylinder Head Temperature:
    • Maximum climb: 200 degrees
    • Maximum cruise: 180 degrees
    • Maximum level (5 minute limit): 240 degrees

[Blackdog_kt]

The above post is now also supplied on the initial page of the thread for ease of reference.

@ 2GFlea: If you want to incorporate this into your PDF checklists you are welcome to do so.

[Vengeanze]

Originally Posted by Blackdog_kt

I always end up postponing this, but i see a lot of people have many questions.
I finally decided to bite the bullet and do it, these are the most important bits as a quick and dirty reference

So, without further ado, here are the Blenheim MK.IV operating limits and abbreviated checklists, according to the proper Mk.IV pilot's operating handbook:

Take-off:

• Mixture auto-rich (levers back)
• Prop Pitch fine
• Cowl flaps 1/3 open when on long range load (long range load = all fuel tanks loaded), closed when on normal load (normal load = inboard tanks only)
• Flaps at 15 degrees when on long range load (can't be done in the sim yet, it has two-position flaps but they should be more like the Hurricane's with up/down/neutral settings to enable the pilot to set them partially open)
• Boost cut out on for long range load, off for normal load. With the cut-out enabled you can get +9 psi boost BUT it needs 100 octane fuel. In the real one, the outboard tanks were 100 octane and the inboard ones 87 octane. I don't know if this is reflected in the sim, so i don't use the boost cut-out just in case it's modeled with 87 octane across the board for all fuel tanks. Normal max boost with the cut-out disabled is +5 psi.
• Let the tail rise and the aircraft to lift off. Then, gear up and keep it mostly level to accelerate. Once you hit 120mph switch to coarse pitch, then climb only mildly to let it accelerate to 150 mph which is the best climb speed.
• Disengage boost cut-out before throttling back if you had it engaged.

Climb:

• Keep within the engine limits by adjusting cowl flaps position. Oil temps up to 80 degrees, cylinder head temperatures (CHT) up to 200 degrees.
  In the sim you can push the CHT up to 250 and the engines feel mushy below 180, so i keep it between 180 and 230.
• Best climb speed at full throttle is 150 mph up to 10000ft. For every 5000ft extra, reduce climb speed by 10 mph:
  • 150mph IAS up to 10000ft
  • 140mph IAS up to 15000ft
  • 130mph IAS up to 20000ft

Cruise:

• It's possible to fly at very low throttle settings, resulting in less than 1600 RPM.
• Absolute 5-minute limit for level flight is 2750 RPM at +5 psi boost. It shouldn't be exceeded unless in an emergency.
• Engine power limits for cruise
  • for auto-rich/normal mixture (mixture levers fully back): 2400RPM at +3.5 psi boost
  • for auto-lean/weak mixture (mixture lever fully forward): 2400RPM at +1.5 psi boost
• Lowest fuel consumption cruise: mixture auto-lean/weak and throttles back as far as it's possible to maintain level flight.
• Maximum range (most miles per gallon) cruise: Slightly higher speed than the one for lowest fuel consumption.
• Maximum range at 15000ft is obtained at 110mph IAS. In lower altitudes it's impractical to fly that slow (due to disturbed air), so 130 mph is used for extended range when flying low.
• Cowl flaps should be closed for economy cruise. I don't know if this is reflected in the sim, but running on rich and between +0 to +1 psi boost i can certainly close them more than halfway (i keep them about 1/3rd of the way open).

Diving:

• Maximum permitted speed: 285 mph IAS
• Engine RPM: up to 2750 if throttle is less than a third of the way open, at more than 1/3rd throttle up to 3100 RPM is permitted for a very short time (manual says momentarily).
• Prop pitch should be coarse (prop pitch controls fully back, everything above that in the sim corresponds to the fine pitch position).

Landing:

• Throttle back to bleed off speed, close cowl flaps if necessary to maintain CHT.
  
  This is very important, because if you just idle it and keep it there on a steep, long descent for an immediate flare and touchdown afterwords, your engines will cool way down and not develop any power when you need it for the flare and touchdown and you'll pancake onto the runway.
  
  It's also very important to remember to open the cowl flaps again once you apply throttle, in order not to damage the engines. Try to make it a habbit of adjusting them together: Throttle up- open cowl flaps some, throttle back- close cowl flaps a bit
• Once below 150 mph IAS, lower gear and set fine prop pitch.
• Enter the airfield circuit at 120 mph IAS.
• Drop full flaps when nearing the end of the circuit. The manual doesn't state more but full flaps sure is draggy in the sim, so i would say fly a normal rectangular pattern with gear down and drop flaps when turning from base leg to finals.
  
  Turning with both gear and flaps extended presents a ton of drag and shaves off quite a bit of altitude, leaving you to execute a fairly flat approach instead of a normal glide. And to keep it flat (ie, level) at such high drag you need a lot of power while you're at a low airspeed-->overheat danger.
  
  So, it's better to wait until you are aligned with the runway before lowering flaps.

Missed Approach and Go-around:

• Raise the gear immediately after leaving the ground to minimize drag.
• Don't raise the flaps until you reach a safe altitude of 500 feet. First, nose down a bit to accelerate to 100mph IAS, then raise the flaps.
• If one engine fails during the go-around, there is not sufficient power to complete the take-off at this high drag configuration. In such a case, closing throttles and landing at whatever cost is the only option.

After landing:

• Open cowl flaps while taxiing if the temperatures are high.
• If the aircraft is going to storage, change to coarse pitch before shutting down. If the props don't change over to coarse while taxiing, step on the brakes and throttle up a bit until the pitch changes (throttling up builds the necessary oil pressure for the prop governors).
• Close throttles for about a minute to allow the oil to settle in the sump.
• Stop engines by pulling the carburetor cut-outs. In the sim they are called slow running cut-outs and they are obscured, behind and to the left of the pilot's seat.
  Just map a key to it, select engine one and hold, not press, hold it down the slow running cut-out key until it stops. Select engine two and repeat to turn it off as well.
• Turn off ignition by switching off the row of magneto switches on the lower part of the instrument panel.
• Switch off the fuel supply by setting the wheel-shaped fuel selectors on your right-hand side cockpit wall to off.

Engine Limits:

• Power settings:
  
  • Take-off on 100 octane fuel (long range load - up to 14500lbs - select outer fuel tanks), up to 800-1000ft or for two minutes using max RPM at max boost (boost cut-out on): +9 psi boost, 2750RPM
  • Take-off on 87 octane fuel (normal load - up to 12500lbs - select inboard fuel tanks, outboard tanks empty), up to 1000ft or for three minutes: +5 psi boost, 2050-2650 RPM
  • Climb: +5 psi boost, 2650 RPM
  • Maximum cruise on rich mixture: +3.5 psi boost, 2400 RPM
  • Economy cruise on lean mixture: +1.5 psi boost, 2400 RPM
  • Maximum level flight power (5 minute limit): +5 psi boost, 2750 RPM
  • Maximum Dive (20 seconds limit): +5psi boost, 3100 RPM

• Oil Pressure:
  • Normal: 80 psi
  • Emergency minimum (5 minute limit): 65 psi
• Temperatures:
  
  • Oil Inlet Temperature:
    • Minimum for opening up throttle: 5 degrees
    • Maximum for continuous cruising: 70 degrees
    • Maximum for climbing: 80 degrees
    • Emergency maximum (5 minute limit): 85 degrees
  • Cylinder Head Temperature:
    • Maximum climb: 200 degrees
    • Maximum cruise: 180 degrees
    • Maximum level (5 minute limit): 240 degrees

I don't get it.

[JG53Frankyboy]

It just showes that a historical manual is not always helpfull to fly the CoD Blenheim.

Thx for the summary Blackdog !!

[Vengeanze]

Ok, I can take off and cruise no problem. But I'm concerned about the small margins when I take off.
I've read here that some of you take off when CHT is around 200. If I do that I'll overheat so I let CHT drop to 180 and then decidedly push throttle to max for +5 psi. At 80mph I quickly rotate and retract gear and ease down throttle to 60%ish and dip nose to gain speed to cool engine.
If I pause there and check CHT it's very very close to 240.

I run the cross-country mission so no bombs but full tank.

Any tip on how I can keep CHT down at take off?


Edit:
Btw, is the only way to load bombs to use FMB or online?


Edit 2:
One thing that struck me that I gonna try right now is to slowly increase throttle so I keep temprise minimal while gaining speed. Brb.

[xpupx]

I can honestly say that the Blenheim is the most rewarding aircraft to fly, It is not very forgiving but can take massive amounts of damage and still make it home on one engine as long as you have 10000 feet under your wings ant treat her well.
We frequently do 2 hour round trips in to La Have or the Rouen Boss from Sandown and make it home.
The following is how we do it!
Spawn Aircraft with 85% fuel.
Switch on magnetos 1&2.
Switch on wing tanks 1 & 2.
Switch on Boost cut off (just in case).
Drop your throttle to 11%.
Select and Start engine 1.
Select and Start engine 2.
Synchronize both engines.
Adjust your course setter to the north position.
Adjust your directional gyro to the heading you have just obtained from your course setter.
Trim your rudder to the neutral position.
Trim you elevators to just under the neutral position.
Open up radiators to the fully open position.
Increase throttle to 35% and you will start rolling out, once moving drop you pitch down to 90% and taxi to the run way (use you pitch controls to keep you water temp on or just above 200, the 12 o clock position on your dials).
Stop at the start of the runway and let your water temp drop to 200 (12 o clock position on your dials). Then increase throttle to 50% reset pitch to 100% and keep a straight line by using your brakes until your tail lifts.
As soon as you are airborne retract undercarriage and reset you elevator trim.
Reset elevator trim to make the aircraft climb at about a 25 degree angle and drop pitch to 90% and switch off boost.
The Blenheim should fly all day like this but keep this in mind:
Keep the water temp just over 200 degrees just past the 12 o clock position on your dials, use your pitch and radiator controls to do this as you get higher it gets colder you need less radiator and as your climb rate decreases you need less pitch.
You can push her up to around 70% throttle but damage will occur sooner or later.
When you get to 6000 feet turn on your carburetted heaters and this will settle your RPM down.
The thing to keep in mind is that every time you adjust a control there is a consequence for it, heat for water or oil, speed, height whatever. So when you move something you have to change something else.
By the time you get to your cruising altitude and trim the aircraft to fly level you should find that the radiator is almost closed the pitch is around 40% and the fuel mix can be dropped down to about 75% too, and you can get around 140 to 170 MPH if you get it right.
The bottom line is never take your eyes off dials it only take seconds to stuff an engine.
Hope this helps

[Blackdog_kt]

Due to the small disparities between sim and the manual for the real aircraft, that's what i usually do:

1) Set mixture to rich, prop to fine, open cowl flaps and start up. Sometimes carb heat might be needed, but remember to turn it off after starting as it can rob you of power at low altitudes. Also trim full left rudder.

2) Close cowl flaps to accelerate warm-up, step on the brakes and throttle up in steps: as soon as the gauges start bouncing around due to engine vibration (which indicates engines running rough) i stop advancing throttles and let the temps catch up, once it's warmed up a bit more and the shaking stops rinse and repeat.

3) When you reach 180-200 degrees CHT open cowl flaps, advance the throttle to obtain between 0 and +1 psi boost (about 60%) and start rolling down the runway.

4) As soon as you start picking up some speed your rudder will be effective in controlling the yawing motion caused by the props, so either adjust trim or use manual rudder inputs while advancing throttle the rest of the way.


I think we don't need that much fuel for the current map. One famous wartime raid involved an attack on the Cologne powerplants, that's the kind of distances these tanks were used for but we don't have that big a map yet.

Better to fly only on the inboard tanks and save up some weight, especially since it will translate to a shorter take-off roll and a faster transition into actual flight, where the overheating dangers are mitigated due to the increased airflow at higher speeds.

The inboard tanks are 140 gallons each (280 in total), the outboard ones are 94 gallons each (188 total). The full fuel load is thus 280+188=468 gallons.

To get the fuel percentage we need we can simply divide the gallons in the inboard tanks to the total: 280/468=0.598

So, setting fuel to about 60% should do it. I don't know if the sim will split it evenly across all tanks though but it's a small issue if it does: we might need to change over from one set of tanks to the other but other than that we'll be still flying with the correct fuel load.

I think that adding a more detailed interface for fuel in place of that slider (similar to the one we got for bombs and guns) at some point would be awesome: imagine having complete control over the contents of individual tanks, both in terms of quantity and in terms of octanes. Well, that's one for a future patch, for now just set fuel to 60% and fly

[Phazon]

Thanks for the tips Blackdog. So far I've managed one successful mission with the Blenheim on the Syndicate server but sometimes I still get caught out when starting up either waiting too long for the engines to get warm or not waiting enough.

Taking the fuel down to 60% might help get it moving a bit quicker on the ground for a take-off.