Post by volkerboehme on Aug 10, 2008 12:02:00 GMT -5
<< I have .....yet to see the issue of the rated power on the DC6B discussed.>>
The concepts have been discussed here in relation to other propliners every so often, but it is probably time to go over it again in detail using the DC-6B as the worked example this time around. There are two varieties of DC-6B available from calclassic.com. The kind with R-2800-CB16 engines and the kind with -CB17 engines. They have different power envelopes and different operating procedures.
<< According to the reference file, it has rated power up to 14,500 feet>>
Yes that is true for the variety with CB16 engines. The handling notes begin by explaining;
<<<<This version of the DC-6B has four 1700hp Pratt & Whitney R-2800-CB16 Double Wasp engines which are carburetted and highly supercharged to give rated power up to 14500 feet. 2400hp is available for take off (at sea level) and for two minutes in case of emergency using water/methanol injection. METO power is 1800hp to 8,500 feet.........>>>>
So we see that the CB16 is rated at only 1700hp but can nevertheless deliver 2400hp only very briefly and at low altitude for TOGA. We see that even the much lower METO power (1800hp) is only available up to 8500 feet. In any event to simulate operation of a DC-6B with CB16 engines we need all of the rest of the handling notes whose first sentence you cited. They explain both our operating limits and our operating targets step by step. Those values drive our decision making cycle.
Far from being denied the power that should be available for climb, it appears you have been applying emergency power instead of only climb power. You must have that emergency power available, on only three engines, for just two minutes, after an engine failure. The FD author must not deny you that emergency power for that circumstance, but all users must develop enough understanding and skill to avoid applying emergency power when you should apply climb power.
The same handling notes go on to explain that after we rotate we must restrict climb <= 500 VSI, accelerate to 140 KIAS, retract flap and then throttle back to METO MAP (45 inches). Then as soon as we are above all the obstacles in the published departure we must retard to climb MAP selecting only 39 inches and targeting only 1600hp which is less than rated power (1700hp). Our operating goal is always to throttle the engines to only 1600hp as soon as the obstacles ahead permit. That is set out step by step in the CB16 handling notes as follows.
*************************************
.........
ROTATE at 117 KIAS (@ 103800lbs)
Establish positive rate of climb
GEAR UP
ACCELERATE > 130 KIAS @ <= 500 ft/min
CLIMB 300 feet AGL
FLAP - STAGE 1
ACCELERATE 140 KIAS @ <= 500 ft/min
FLAP - UP
Establish 500 VSI
CALL for METO Power (1800hp)
**********************************
First climb segment:
METO Power (1800hp)
COWL FLAPS - MID
45 inches MAP
2600 RPM
160 KIAS
Check CHT < 260C
Plan 600 USG per hour
ABOVE all obstacles
CALL for climb power
***********************************
Second Climb segment:
Climb Power: (1600hp)
COWL FLAPS - MID
39 inches MAP
2400 RPM
160 KIAS
<<but I was just flying it and as always, the power begins to drop off immediately. It was already falling off between 4 and 5,000 feet, and I had dropped 5 inches of MAP by 7,500 feet.>>
You can expect that based on the content of the first few sentences of the handling notes, and the trigger values in the CB16 engine decision making cycle require you to reduce MAP much faster than the turbines reduce it anyway if you demand emergency power as altitude increases. We are not allowed to use full throttle to climb at low altitude. We are only allowed to use full throttle to accelerate to 140 KIAS at less than 500 VSI or to stagger along on three engines at low IAS after engine failure.
Part 8 of the 2008 Propliner Tutorial explains why we must use the RPM levers to control RPM as we accelerate. All classic era piston propliners have manual shift gear boxes and we must select the correct gear (to reduce RPM) as we accelerate and throttle down to establish climb at only 39 inches and only 2400 RPM. Using first gear to maximise RPM is only efficient at low speed. At the target IAS for climbing a hill we need a higher gear and lower RPM. If you are not following the handling notes you will be trying to climb (hills) in the wrong gear. You may be applying full throttle, but if you select the wrong gear poor performance results, just like a car with a manual shift gearbox trying to climb a hill at full throttle in the wrong gear.
The R-2800-CB16 engines are performing to the published numbers, but you may have ignored all the values in the handling notes because you have the misconception that it is both possible and beneficial to apply TOGA power settings for more than two minutes or at significant altitude or after IAS exceeds 140 KIAS. The handling notes explain that low altitude (hill) climbing is not conducted using full throttle and requires correct gear (RPM) selection.
Only very simple and low powered aeroplanes like the Cessna 172 have power systems that allow full throttle to be used for climb at low altitudes. Its fixed pitch airscrew slows the engine down without pilot interaction to reduce power output and prevent failure. In classic era propliners we are instead responsible for selecting the correct gear ratio (RPM) and the correct throttle setting all of the time. Not randomly, but very precisely to maximise acceleration, or as we try to climb (a hill). Each propliner has specific MAP, RPM, VSI and IAS targets set out in its handling notes and learning to progress the aeroplane from real configuration to real configuration, and real energy state to real energy state, using the real world MAP and RPM inputs is what makes them so interesting and different to fly. If you use the wrong values they fly badly.
If we wish to learn how to use a Grand Prix racing car simulation we need to learn the correct entry speed for each corner and what gear to be in; not just how to apply full throttle. Simply applying full throttle is rarely the solution to the problem that needs to solved in a racing car simulation or a flight simulator. Propliner simulation is even more demanding than racing car simulation. The speed targeting and matching RPM selection often need to be even more precise.
When we fly a DC-6B with more powerful CB17 engines we have quite different targets to achieve one by one and a different decision making cycle. Flight simulation would be very boring if the way we operated each aircraft was the same. It needs to be very different, even if we are flying the same aeroplane with only slightly different engines.
***********************************
............
ROTATE at 120 KIAS (@ 107000lbs)
Establish positive rate of climb
GEAR UP
ACCELERATE > 130 KIAS <= 500 ft/min
CLIMB 300 feet AGL
FLAP - STAGE 1
ACCELERATE 140 KIAS <= 500 ft/min
FLAP - UP
Establish 500 VSI
CALL for METO Power
**********************************
First climb segment:
METO Power (1900hp)
COWL FLAPS - MID
51 inches MAP
2600 RPM
500 VSI
Check CHT < 260C
Plan 620 USG per hour
CLEAR OF ALL OBSTACLES
WHEN IAS sustains > 170 KIAS
CALL for climb power
***********************************
Second Climb segment:
Climb Power: (1450hp)
COWL FLAPS - MID
41 inches MAP
2400 RPM
500 VSI
When we fly a DC-6B with CB17 engines our thermodynamic (input) targets are different and our aerodynamic (output) targets are different. For instance we see that we must not throttle the engines to 41 MAP until (*unless*) we have achieved our different target of 170 KIAS at 500 VSI. When we fly with CB16 engines our target is only 160 KIAS and we will always achieve it. When we fly with CB17 engines our target becomes 170 KIAS and we may not. This matters much more then may at first be apparent.
At high weights, or in hot weather, we may never achieve 170 KIAS, and so we will retain CB17 METO for a prolonged period on those days. Thus with the CB16 engine (which requires only 130 Octane AVGAS) we are always very quickly throttled back to 39 inches and 2400 RPM, but with the superior 145 Octane AVGAS that we must load to use CB17 engines we can use up to 51 MAP at 2600 RPM for an extended period. Having 145 Octane fuel and CB17 engines in a DC-6B makes a huge difference. It is not the maxima that are very different, it is how long we may apply them. The way it all works may be obscure to many, but the better fuel allows a higher IAS target and we can apply more MAP and more RPM for much longer whilst striving for it.
Failure to implement the mandated decision making cycle, causes us to have an unrealistic simulation. Failure to implement the handling notes can exaggerate the performance available greatly (using more MAP than allowed in real life for that engine), or it can cause a crash because we fail to select the correct gear ratio (RPM) for that particular engine at the target IAS, or because we use the wrong target IAS in our decision making cycle.
Applying the values in CB17 handling notes flying an aeroplane with CB16 engines does not work of course. The handling notes explain how to use the supplied flight dynamics. Simply guessing how to operate different engines and what their related VSI and IAS targets are in a given airframe is hopeless. They were coded to deliver realism, but realism is not scripted by the FD author. It has to be extracted by the user via his decision making cycle. This seems to be very hard for downloaders to grasp. Propliners are more complex than racing cars. What the user achieves with the racing car or the aeroplane depends on their skill, not FD author replication of its straight line velocity at full throttle in the highest gear.
It is the downloader who has to make the effort to study all the available documentation for the aircraft and engines to understand what his operating targets are. He must learn what values drive his decision making cycle. He must study what MAP and RPM to input under what circumstance, what value of which variable triggers selection of a different mix and match of power, and what pitch or VSI or IAS he must target using those inputs as they change. After we download an aeroplane it may take very lengthy study of the handling notes to understand its decision making cycle and how to operate it.
If we study the handling notes until we understand them and then follow them step by step we can understand why we need 145 Octane fuel and CB17 engines to depart La Paz in the Andes (with any useful payload) in a DC-6B for instance. Each propliner and each engine has very precise step by step operating rules that drive our decision making cycle and we need handling notes to explain what they are. No downloader can guess what they are. Most aircraft operating criteria are of the DO_UNTIL variety. The trigger value in the decision making cycle that requires a change of configuration, or power, or IAS, or VSI, or pitch, is critical to self delivery of realism. Without knowing the nature of the real world DO_UNTIL loops and the exit values from those real world loops we cannot enjoy realistic simulation. We must learn what they all are, aeroplane by aeroplane and engine by engine. They are in the handling notes.
Our decision making cycle revolves around the exit condition for our current DO_UNTIL loop. We must exit TOGA on reaching 140 KIAS. We must exit METO in a CB16 powered DC6B once above all obstacles, but only upon reaching 170 KIAS whilst also maintaining 500 VSI with CB17 engines, else we squander the advantage of 145 Octane AVGAS. Flight simulation is a series of decision making cycles with very specific and potentially multiple concurrent exit triggers. We must study what they are and we must vary our input accordingly to experience realism. Anyone can apply full throttle in a straight line in the highest gear, but that is not all that is involved in winning either a race, or an endurance test, or a hill climb contest. There is no simple link between throttle position and performance. Maximum performance has to be extracted using acquired skill.
Flight simulation is not about watching scripted events created by an FD author any more than a Grand Prix Racing game could be, or should be. It is all about learning the nature of the decision making cycle in that vehicle with that engine. What throttle setting, what gear, what speed, and to make things much more difficult during flight simulation, what altitude, what flap setting, what climb rate, and what pitch are needed to maximise whatever we are trying to maximise.
It thus becomes obvious that realistic aircraft and engine performance cannot result from random user inputs, in random user wing configurations, chasing random user pitch, VSI and IAS targets, yet many FS users still wish to believe that realism might emerge from that randomness anyway if FD authors would only write the code differently. The truth is that flight simulation realism is a goal downloaders must spend years learning to achieve. It is grasping that concept that matters more than actually having the decision making skills needed in the decision making cycle. They can only begin to be acquired once the requirement to learn them is grasped.
In passing, critical altitude (which was not asked about) is a whole different ball game. Its usage within MSFS flight dynamics is very complicated. It must be carefully encoded to have a false value to limit engine performance in ways that relate to known deficiencies within the Microsoft Flight Model.
<<The other issue I have with the 6B is the pronounced nose down attitude it has in the cruise, but this has already been addressed in this forum.>>
You will have noticed that all those threads explain that aeroplanes do not have a mind of their own and only ever do what good and bad pilots force them to do. By studying and eventually understanding both the aircraft specific handling notes and the 2008 Propliner Tutorial sim pilots can learn how to stop abusing aero engines and aeroplanes and how to achieve operating realism via a realistic decision making cycle using realistic trigger values in that cycle, for each and every phase of the flight.
You are far from alone in believing that FD authors, rather than sim pilots, decide and control cruise pitch etc, etc, but tuition is readily available and you have come to the right place to find it. However you must expect the learning curve to be steep and prolonged. Learning to fly propliners realistically is not a simple goal. It is however an very interesting challenge. It must begin with study of the 2008 Propliner Tutorial from www.calclassic.com/tutorials
FSAviator
The concepts have been discussed here in relation to other propliners every so often, but it is probably time to go over it again in detail using the DC-6B as the worked example this time around. There are two varieties of DC-6B available from calclassic.com. The kind with R-2800-CB16 engines and the kind with -CB17 engines. They have different power envelopes and different operating procedures.
<< According to the reference file, it has rated power up to 14,500 feet>>
Yes that is true for the variety with CB16 engines. The handling notes begin by explaining;
<<<<This version of the DC-6B has four 1700hp Pratt & Whitney R-2800-CB16 Double Wasp engines which are carburetted and highly supercharged to give rated power up to 14500 feet. 2400hp is available for take off (at sea level) and for two minutes in case of emergency using water/methanol injection. METO power is 1800hp to 8,500 feet.........>>>>
So we see that the CB16 is rated at only 1700hp but can nevertheless deliver 2400hp only very briefly and at low altitude for TOGA. We see that even the much lower METO power (1800hp) is only available up to 8500 feet. In any event to simulate operation of a DC-6B with CB16 engines we need all of the rest of the handling notes whose first sentence you cited. They explain both our operating limits and our operating targets step by step. Those values drive our decision making cycle.
Far from being denied the power that should be available for climb, it appears you have been applying emergency power instead of only climb power. You must have that emergency power available, on only three engines, for just two minutes, after an engine failure. The FD author must not deny you that emergency power for that circumstance, but all users must develop enough understanding and skill to avoid applying emergency power when you should apply climb power.
The same handling notes go on to explain that after we rotate we must restrict climb <= 500 VSI, accelerate to 140 KIAS, retract flap and then throttle back to METO MAP (45 inches). Then as soon as we are above all the obstacles in the published departure we must retard to climb MAP selecting only 39 inches and targeting only 1600hp which is less than rated power (1700hp). Our operating goal is always to throttle the engines to only 1600hp as soon as the obstacles ahead permit. That is set out step by step in the CB16 handling notes as follows.
*************************************
.........
ROTATE at 117 KIAS (@ 103800lbs)
Establish positive rate of climb
GEAR UP
ACCELERATE > 130 KIAS @ <= 500 ft/min
CLIMB 300 feet AGL
FLAP - STAGE 1
ACCELERATE 140 KIAS @ <= 500 ft/min
FLAP - UP
Establish 500 VSI
CALL for METO Power (1800hp)
**********************************
First climb segment:
METO Power (1800hp)
COWL FLAPS - MID
45 inches MAP
2600 RPM
160 KIAS
Check CHT < 260C
Plan 600 USG per hour
ABOVE all obstacles
CALL for climb power
***********************************
Second Climb segment:
Climb Power: (1600hp)
COWL FLAPS - MID
39 inches MAP
2400 RPM
160 KIAS
<<but I was just flying it and as always, the power begins to drop off immediately. It was already falling off between 4 and 5,000 feet, and I had dropped 5 inches of MAP by 7,500 feet.>>
You can expect that based on the content of the first few sentences of the handling notes, and the trigger values in the CB16 engine decision making cycle require you to reduce MAP much faster than the turbines reduce it anyway if you demand emergency power as altitude increases. We are not allowed to use full throttle to climb at low altitude. We are only allowed to use full throttle to accelerate to 140 KIAS at less than 500 VSI or to stagger along on three engines at low IAS after engine failure.
Part 8 of the 2008 Propliner Tutorial explains why we must use the RPM levers to control RPM as we accelerate. All classic era piston propliners have manual shift gear boxes and we must select the correct gear (to reduce RPM) as we accelerate and throttle down to establish climb at only 39 inches and only 2400 RPM. Using first gear to maximise RPM is only efficient at low speed. At the target IAS for climbing a hill we need a higher gear and lower RPM. If you are not following the handling notes you will be trying to climb (hills) in the wrong gear. You may be applying full throttle, but if you select the wrong gear poor performance results, just like a car with a manual shift gearbox trying to climb a hill at full throttle in the wrong gear.
The R-2800-CB16 engines are performing to the published numbers, but you may have ignored all the values in the handling notes because you have the misconception that it is both possible and beneficial to apply TOGA power settings for more than two minutes or at significant altitude or after IAS exceeds 140 KIAS. The handling notes explain that low altitude (hill) climbing is not conducted using full throttle and requires correct gear (RPM) selection.
Only very simple and low powered aeroplanes like the Cessna 172 have power systems that allow full throttle to be used for climb at low altitudes. Its fixed pitch airscrew slows the engine down without pilot interaction to reduce power output and prevent failure. In classic era propliners we are instead responsible for selecting the correct gear ratio (RPM) and the correct throttle setting all of the time. Not randomly, but very precisely to maximise acceleration, or as we try to climb (a hill). Each propliner has specific MAP, RPM, VSI and IAS targets set out in its handling notes and learning to progress the aeroplane from real configuration to real configuration, and real energy state to real energy state, using the real world MAP and RPM inputs is what makes them so interesting and different to fly. If you use the wrong values they fly badly.
If we wish to learn how to use a Grand Prix racing car simulation we need to learn the correct entry speed for each corner and what gear to be in; not just how to apply full throttle. Simply applying full throttle is rarely the solution to the problem that needs to solved in a racing car simulation or a flight simulator. Propliner simulation is even more demanding than racing car simulation. The speed targeting and matching RPM selection often need to be even more precise.
When we fly a DC-6B with more powerful CB17 engines we have quite different targets to achieve one by one and a different decision making cycle. Flight simulation would be very boring if the way we operated each aircraft was the same. It needs to be very different, even if we are flying the same aeroplane with only slightly different engines.
***********************************
............
ROTATE at 120 KIAS (@ 107000lbs)
Establish positive rate of climb
GEAR UP
ACCELERATE > 130 KIAS <= 500 ft/min
CLIMB 300 feet AGL
FLAP - STAGE 1
ACCELERATE 140 KIAS <= 500 ft/min
FLAP - UP
Establish 500 VSI
CALL for METO Power
**********************************
First climb segment:
METO Power (1900hp)
COWL FLAPS - MID
51 inches MAP
2600 RPM
500 VSI
Check CHT < 260C
Plan 620 USG per hour
CLEAR OF ALL OBSTACLES
WHEN IAS sustains > 170 KIAS
CALL for climb power
***********************************
Second Climb segment:
Climb Power: (1450hp)
COWL FLAPS - MID
41 inches MAP
2400 RPM
500 VSI
When we fly a DC-6B with CB17 engines our thermodynamic (input) targets are different and our aerodynamic (output) targets are different. For instance we see that we must not throttle the engines to 41 MAP until (*unless*) we have achieved our different target of 170 KIAS at 500 VSI. When we fly with CB16 engines our target is only 160 KIAS and we will always achieve it. When we fly with CB17 engines our target becomes 170 KIAS and we may not. This matters much more then may at first be apparent.
At high weights, or in hot weather, we may never achieve 170 KIAS, and so we will retain CB17 METO for a prolonged period on those days. Thus with the CB16 engine (which requires only 130 Octane AVGAS) we are always very quickly throttled back to 39 inches and 2400 RPM, but with the superior 145 Octane AVGAS that we must load to use CB17 engines we can use up to 51 MAP at 2600 RPM for an extended period. Having 145 Octane fuel and CB17 engines in a DC-6B makes a huge difference. It is not the maxima that are very different, it is how long we may apply them. The way it all works may be obscure to many, but the better fuel allows a higher IAS target and we can apply more MAP and more RPM for much longer whilst striving for it.
Failure to implement the mandated decision making cycle, causes us to have an unrealistic simulation. Failure to implement the handling notes can exaggerate the performance available greatly (using more MAP than allowed in real life for that engine), or it can cause a crash because we fail to select the correct gear ratio (RPM) for that particular engine at the target IAS, or because we use the wrong target IAS in our decision making cycle.
Applying the values in CB17 handling notes flying an aeroplane with CB16 engines does not work of course. The handling notes explain how to use the supplied flight dynamics. Simply guessing how to operate different engines and what their related VSI and IAS targets are in a given airframe is hopeless. They were coded to deliver realism, but realism is not scripted by the FD author. It has to be extracted by the user via his decision making cycle. This seems to be very hard for downloaders to grasp. Propliners are more complex than racing cars. What the user achieves with the racing car or the aeroplane depends on their skill, not FD author replication of its straight line velocity at full throttle in the highest gear.
It is the downloader who has to make the effort to study all the available documentation for the aircraft and engines to understand what his operating targets are. He must learn what values drive his decision making cycle. He must study what MAP and RPM to input under what circumstance, what value of which variable triggers selection of a different mix and match of power, and what pitch or VSI or IAS he must target using those inputs as they change. After we download an aeroplane it may take very lengthy study of the handling notes to understand its decision making cycle and how to operate it.
If we study the handling notes until we understand them and then follow them step by step we can understand why we need 145 Octane fuel and CB17 engines to depart La Paz in the Andes (with any useful payload) in a DC-6B for instance. Each propliner and each engine has very precise step by step operating rules that drive our decision making cycle and we need handling notes to explain what they are. No downloader can guess what they are. Most aircraft operating criteria are of the DO_UNTIL variety. The trigger value in the decision making cycle that requires a change of configuration, or power, or IAS, or VSI, or pitch, is critical to self delivery of realism. Without knowing the nature of the real world DO_UNTIL loops and the exit values from those real world loops we cannot enjoy realistic simulation. We must learn what they all are, aeroplane by aeroplane and engine by engine. They are in the handling notes.
Our decision making cycle revolves around the exit condition for our current DO_UNTIL loop. We must exit TOGA on reaching 140 KIAS. We must exit METO in a CB16 powered DC6B once above all obstacles, but only upon reaching 170 KIAS whilst also maintaining 500 VSI with CB17 engines, else we squander the advantage of 145 Octane AVGAS. Flight simulation is a series of decision making cycles with very specific and potentially multiple concurrent exit triggers. We must study what they are and we must vary our input accordingly to experience realism. Anyone can apply full throttle in a straight line in the highest gear, but that is not all that is involved in winning either a race, or an endurance test, or a hill climb contest. There is no simple link between throttle position and performance. Maximum performance has to be extracted using acquired skill.
Flight simulation is not about watching scripted events created by an FD author any more than a Grand Prix Racing game could be, or should be. It is all about learning the nature of the decision making cycle in that vehicle with that engine. What throttle setting, what gear, what speed, and to make things much more difficult during flight simulation, what altitude, what flap setting, what climb rate, and what pitch are needed to maximise whatever we are trying to maximise.
It thus becomes obvious that realistic aircraft and engine performance cannot result from random user inputs, in random user wing configurations, chasing random user pitch, VSI and IAS targets, yet many FS users still wish to believe that realism might emerge from that randomness anyway if FD authors would only write the code differently. The truth is that flight simulation realism is a goal downloaders must spend years learning to achieve. It is grasping that concept that matters more than actually having the decision making skills needed in the decision making cycle. They can only begin to be acquired once the requirement to learn them is grasped.
In passing, critical altitude (which was not asked about) is a whole different ball game. Its usage within MSFS flight dynamics is very complicated. It must be carefully encoded to have a false value to limit engine performance in ways that relate to known deficiencies within the Microsoft Flight Model.
<<The other issue I have with the 6B is the pronounced nose down attitude it has in the cruise, but this has already been addressed in this forum.>>
You will have noticed that all those threads explain that aeroplanes do not have a mind of their own and only ever do what good and bad pilots force them to do. By studying and eventually understanding both the aircraft specific handling notes and the 2008 Propliner Tutorial sim pilots can learn how to stop abusing aero engines and aeroplanes and how to achieve operating realism via a realistic decision making cycle using realistic trigger values in that cycle, for each and every phase of the flight.
You are far from alone in believing that FD authors, rather than sim pilots, decide and control cruise pitch etc, etc, but tuition is readily available and you have come to the right place to find it. However you must expect the learning curve to be steep and prolonged. Learning to fly propliners realistically is not a simple goal. It is however an very interesting challenge. It must begin with study of the 2008 Propliner Tutorial from www.calclassic.com/tutorials
FSAviator