Blenheim operating limits and checklists

[Vengeanze]

I'm having a rough time keeping the temps within limits.
Either the oil gets too cool or the engine temp too hot.
There's no margins for error.
Any tip would be appreciated.

I found the tip of quickly turn on/off autopilot to lock tailwheel a tremendous help while warming up.

According to Blackdog and Fleas manual I should take off with rads closed but that doesn't work for me. Overheat before tailwheel lifts.

[JG53Frankyboy]

Originally Posted by Vengeanze

I'm having a rough time keeping the temps within limits.
Either the oil gets too cool or the engine temp too hot.
There's no margins for error.
Any tip would be appreciated.

I found the tip of quickly turn on/off autopilot to lock tailwheel a tremendous help while warming up.

According to Blackdog and Fleas manual I should take off with rads closed but that doesn't work for me. Overheat before tailwheel lifts.

Real pilotmanuals dont help much in game , and in the Blenheim even less!
You have to start with open cowlingflaps. I personally start with flaps down (unfortunatly you can set them only between full out and in ) and tray to keep the engine rpm between 2200&2300......not much, i know, but so i am at 90% of my starts on the save side.

Sa alread said, this plane needs a second look from 1C, even more important as it is the only RAF bombcarrier in game.

[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. Leave the coolers open until safely in the air and your engine temps start to drop.
And, in my experience, there is no such thing as "the oil gets too cold". Shortly after T/O, I set prop pitch to coarse, engage carb heaters at 5500 ft - with these actions, my oil temps were fine all the time.

My "engage AP for a second" referred to the wheel brakes, btw. Are you sure that the tailwheel gets locked, too?

[Vengeanze]

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. Leave the coolers open until safely in the air and your engine temps start to drop.
And, in my experience, there is no such thing as "the oil gets too cold". Shortly after T/O, I set prop pitch to coarse, engage carb heaters at 5500 ft - with these actions, my oil temps were fine all the time.

Ok. I thought I saw some connection between engine failure and low oil temp but if I understand you correct then the crucial thing is the engine temp which I should try to keep between 200 and 250?

Could you confirm this...
- Open rads lowers engine temps (and vice versa)?
- Activated carb heaters raise engine temps (and vice versa)?
- Throttling up i.e. higher rpm raise engine temps (and vice versa)?

How does coarse pitch affect the temps? I mean, lower rpm gives lower temp but coarse pitch give higher load on engine.

Originally Posted by Redroach

My "engage AP for a second" referred to the wheel brakes, btw. Are you sure that the tailwheel gets locked, too?

I ment wheel brakes. Sorry.

Thanks!

[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 !!