Post by volkerboehme on Aug 24, 2010 11:49:23 GMT -5
Concerning shock cooling of Merlin engines in the Canadair Argonaut the relevant warnings and required procedures are not surprisingly provided in the usual detailed on screen handling notes.
************************************
Canadair C-4 Argonaut Handling Notes
**********************************************
SUMMARY.
The Argonaut has four 1420hp Rolls Royce Merlin 724 engines which are carbureted and highly supercharged to give rated power up to 18,750 feet. They can each deliver 1760hp for take off from any runway below 13000 feet. The constant speed propellers can be feathered. Automixture control is standard.
WARNING - HIGH RISK OF SHOCK COOLING - observe all (minimum) boost and rpm restrictions at all times. Use GEAR and FLAP to decelerate aircraft.
Maximum fuel is 25,000lbs of high density AVGAS. Fuel must be offloaded to carry maximum payload. See aircraft.cfg and use FS9 menu.
>>>>>>>>>>>>>>>>>>>>>>>>>>>
Descent and Holding:
ABOVE FL200 <= 200 KIAS
NEVER EXCEED 223 KIAS
DO NOT SHOCK COOL ENGINES
BOOST => ZERO
RPM => 2200 whilst => FL130
Passing (below) FL130
BOOST => ZERO
RPM = 2000
...........
*****************************
From the Merlin XX onwards, deployed in the Hurricane II during the battle of Britain in 1940, the operation of radiator shutters and mixture was progressively automated in Rolls Royce engines, even in aeroplanes like the Lancaster and its derivatives which had a dedicated Flight Engineer. He prevented shock cooling mostly by sustaining adequate minimum boost. Different operators ordered different crews to observe different maxima and minima at different times for various reasons. FE or PNF exerted finer control over engine temperatures by variation of RPM subject to avoiding unwanted torque combinations. the setting cited in the provided handling notes meet that requirement.
The correct descent planning and execution technique for all propliners has only just been revisited in this forum. It does not relate to engine cooling type. It relates to ATC compliance and profit maximisation. PF constrains IAS (profile drag) to conserve fuel and moderates VSI to minus 700. Profit is maximised by descending at cruise IAS, (performing a cruise descent), else prior cruise would have been at a different profile drag. Consequently if zero boost does not cause prior cruise profile drag to be sustained more is applied, but if IAS builds beyond prior cruise IAS while descending at minus 700 VSI the crew are forbidden to reduce boost and they allow profile drag to rise above prior cruise IAS
Rapid reduction from cruise boost to minimum safe boost (zero boost <> 30 MAP) was no problem in what was essentially a Rolls Royce combat engine. Further reduction was a problem. This may have been mainly due to shock cooling risk, or mainly due to plug fouling risk, or both. It makes no difference to the detailed procedures provided in the on screen handling notes. As usual the cruise boost settings and all the other procedures are also 'hiding' in the supplied and detailed on screen handling notes.
They explain that there was also a risk of shock cooling engines, else plug fouling, during the approach and detailed procedures are again supplied in my usual operating target, by operating target, format.
*****************************
Approach and Landing:
DO NOT SHOCK COOL ENGINES
RPM = 2000
BOOST => ZERO
WHEN < 170 KIAS
FLAP = STAGE 1
GEAR = DOWN (now or later)
WHEN < 160 KIAS
FLAP = STAGE 2
REDUCE <= 140 KIAS
RPM = 2350
FINAL DESCENT
To achieve Vref at 50 AGL
GEAR = DOWN
FLAP = FULL
BOOST = SLOW reduction below zero
Cross airfield boundary 98 KIAS (Vref @ 72000 lbs)
****************************
Thus reduction below zero BOOST is forbidden until the final descent to land and until profile drag also < 140 KIAS and GEAR is DOWN and FULL FLAP has been deployed. Reduction below zero BOOST is the last thing we do to reduce profile drag in an Argonaut.
There is no mystery to solve concerning Canadair Argonaut operating procedures. Just the usual requirement to study the supplied detailed handling notes before flight if we have an interest in realistic propliner operation.
FSAviator.
************************************
Canadair C-4 Argonaut Handling Notes
**********************************************
SUMMARY.
The Argonaut has four 1420hp Rolls Royce Merlin 724 engines which are carbureted and highly supercharged to give rated power up to 18,750 feet. They can each deliver 1760hp for take off from any runway below 13000 feet. The constant speed propellers can be feathered. Automixture control is standard.
WARNING - HIGH RISK OF SHOCK COOLING - observe all (minimum) boost and rpm restrictions at all times. Use GEAR and FLAP to decelerate aircraft.
Maximum fuel is 25,000lbs of high density AVGAS. Fuel must be offloaded to carry maximum payload. See aircraft.cfg and use FS9 menu.
>>>>>>>>>>>>>>>>>>>>>>>>>>>
Descent and Holding:
ABOVE FL200 <= 200 KIAS
NEVER EXCEED 223 KIAS
DO NOT SHOCK COOL ENGINES
BOOST => ZERO
RPM => 2200 whilst => FL130
Passing (below) FL130
BOOST => ZERO
RPM = 2000
...........
*****************************
From the Merlin XX onwards, deployed in the Hurricane II during the battle of Britain in 1940, the operation of radiator shutters and mixture was progressively automated in Rolls Royce engines, even in aeroplanes like the Lancaster and its derivatives which had a dedicated Flight Engineer. He prevented shock cooling mostly by sustaining adequate minimum boost. Different operators ordered different crews to observe different maxima and minima at different times for various reasons. FE or PNF exerted finer control over engine temperatures by variation of RPM subject to avoiding unwanted torque combinations. the setting cited in the provided handling notes meet that requirement.
The correct descent planning and execution technique for all propliners has only just been revisited in this forum. It does not relate to engine cooling type. It relates to ATC compliance and profit maximisation. PF constrains IAS (profile drag) to conserve fuel and moderates VSI to minus 700. Profit is maximised by descending at cruise IAS, (performing a cruise descent), else prior cruise would have been at a different profile drag. Consequently if zero boost does not cause prior cruise profile drag to be sustained more is applied, but if IAS builds beyond prior cruise IAS while descending at minus 700 VSI the crew are forbidden to reduce boost and they allow profile drag to rise above prior cruise IAS
Rapid reduction from cruise boost to minimum safe boost (zero boost <> 30 MAP) was no problem in what was essentially a Rolls Royce combat engine. Further reduction was a problem. This may have been mainly due to shock cooling risk, or mainly due to plug fouling risk, or both. It makes no difference to the detailed procedures provided in the on screen handling notes. As usual the cruise boost settings and all the other procedures are also 'hiding' in the supplied and detailed on screen handling notes.
They explain that there was also a risk of shock cooling engines, else plug fouling, during the approach and detailed procedures are again supplied in my usual operating target, by operating target, format.
*****************************
Approach and Landing:
DO NOT SHOCK COOL ENGINES
RPM = 2000
BOOST => ZERO
WHEN < 170 KIAS
FLAP = STAGE 1
GEAR = DOWN (now or later)
WHEN < 160 KIAS
FLAP = STAGE 2
REDUCE <= 140 KIAS
RPM = 2350
FINAL DESCENT
To achieve Vref at 50 AGL
GEAR = DOWN
FLAP = FULL
BOOST = SLOW reduction below zero
Cross airfield boundary 98 KIAS (Vref @ 72000 lbs)
****************************
Thus reduction below zero BOOST is forbidden until the final descent to land and until profile drag also < 140 KIAS and GEAR is DOWN and FULL FLAP has been deployed. Reduction below zero BOOST is the last thing we do to reduce profile drag in an Argonaut.
There is no mystery to solve concerning Canadair Argonaut operating procedures. Just the usual requirement to study the supplied detailed handling notes before flight if we have an interest in realistic propliner operation.
FSAviator.