Max perf. take off and Steep landings...
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Topendtorque:
One minor point - the speed for maximum range in a turbine helicopter cannot be determined in the manner you describe due to improved specific fuel consumption at higher power settings. For a turbine, fuel flow vs. airspeed is needed. To be really accurate in determining best range airspeed for both piston and turbine machines, you should use a graph of fuel flow vs. Airspeed.
Several textbooks make this mistake (but not mine!)
One minor point - the speed for maximum range in a turbine helicopter cannot be determined in the manner you describe due to improved specific fuel consumption at higher power settings. For a turbine, fuel flow vs. airspeed is needed. To be really accurate in determining best range airspeed for both piston and turbine machines, you should use a graph of fuel flow vs. Airspeed.
Several textbooks make this mistake (but not mine!)
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I appreciate that Shawn, and there were some excellent discussions by yourself and Nick re max range speed with turbines fairly recently somewhere close by.
of course the '47 speed will depend on the state of the blades and whether or not the main power port in the carburettor is opening or not. Just under that setting the max range speed must be the best, just over it and fuel disappears like there was no tomorrow, at about 22.5 inches or maybe a bit more. no two carbies are the same.
The reason I pursue the subject is because of the mass emergence of the R44 onto the airwork scene. Although i have not experimented with them in the same way as I have with '47's i suspect that the numbers would be similar.
I accept that there may be some useful difference between the carburetted and the later fuel injected models with the better blades.
Another useful guide on the pre landing power checks was to see what the margins were between IGE hover and full throttle. Five inches usually meant straight up and 3 to 4 inches would be acceptable for a 'max perf' T/O.
OGE hover power checks of course are simple, provided one is smart enough to remember to do them, many are not. one inch spare for climbing at that same weight and one more if one is to be operating close to trees etc where the airflow will be disturbed. don't forget that the air close to the ground may be quite a bit hotter than where the power check is done, meaning that a bit more will be required.
Another tip is one inch in the six cylinder machine usually represents, 10 hp and 100 pounds of weight that can be picked up, vertically, so calculate the power check according to the load to be dropped or picked up.
very simple really, just never pull more than is there.
of course the '47 speed will depend on the state of the blades and whether or not the main power port in the carburettor is opening or not. Just under that setting the max range speed must be the best, just over it and fuel disappears like there was no tomorrow, at about 22.5 inches or maybe a bit more. no two carbies are the same.
The reason I pursue the subject is because of the mass emergence of the R44 onto the airwork scene. Although i have not experimented with them in the same way as I have with '47's i suspect that the numbers would be similar.
I accept that there may be some useful difference between the carburetted and the later fuel injected models with the better blades.
Another useful guide on the pre landing power checks was to see what the margins were between IGE hover and full throttle. Five inches usually meant straight up and 3 to 4 inches would be acceptable for a 'max perf' T/O.
OGE hover power checks of course are simple, provided one is smart enough to remember to do them, many are not. one inch spare for climbing at that same weight and one more if one is to be operating close to trees etc where the airflow will be disturbed. don't forget that the air close to the ground may be quite a bit hotter than where the power check is done, meaning that a bit more will be required.
Another tip is one inch in the six cylinder machine usually represents, 10 hp and 100 pounds of weight that can be picked up, vertically, so calculate the power check according to the load to be dropped or picked up.
very simple really, just never pull more than is there.
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Max performance take off
Topendtorque
Some results from the desktop world:
Simulation of power curve of a R44-I near MTOW at ISA conditions
Calculated output MR HP. To convert this in Engine HP, one needs to add all mechanical losses plus the TR power. At low speeds where the TR needs to produce approx 500N in this scenario torque I think that the max engine HP of 205 allows for approx 165 MR HP (=red horizontal line).
As Shawn pointed out this graph also does not convert to fuel flow so that for optimal economic speeds it is only approximative.
The results are :
Possible interpretations:
Between IGE and OGE there is 23 MR HP difference, what translates to 30 engine HP so 3 inches. To be added to that is a required acceleration which probably adds 1 inch. This leads to 4 inches. I took 3 ft as IGE instead of 0ft this could explain the difference of 1 inch.
With respect to MP take off the max setting allows for 300 ft/min from 10-15 knts onwards, but again probably one inch margin is needed which translates to a 15-20 knts range.
Does that make any sense ?
d3
Some results from the desktop world:
Simulation of power curve of a R44-I near MTOW at ISA conditions
Calculated output MR HP. To convert this in Engine HP, one needs to add all mechanical losses plus the TR power. At low speeds where the TR needs to produce approx 500N in this scenario torque I think that the max engine HP of 205 allows for approx 165 MR HP (=red horizontal line).
As Shawn pointed out this graph also does not convert to fuel flow so that for optimal economic speeds it is only approximative.
The results are :
Possible interpretations:
Between IGE and OGE there is 23 MR HP difference, what translates to 30 engine HP so 3 inches. To be added to that is a required acceleration which probably adds 1 inch. This leads to 4 inches. I took 3 ft as IGE instead of 0ft this could explain the difference of 1 inch.
With respect to MP take off the max setting allows for 300 ft/min from 10-15 knts onwards, but again probably one inch margin is needed which translates to a 15-20 knts range.
Does that make any sense ?
d3
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MD900 - I need some help with your terminology. By "max performance" do you mean max all up mass? Or do you mean lower than max all up mass and using all excess power available for better acceleration/climb?
If you mean the former, then it should be included in all helicopter training courses within JAA Member States and it should be tested on all JAA Helicopter Licence Skills Tests for PPL(H) and CPL(H).
I believe the same requirement exists for FAA tests and I would expect it to be an ICAO requirement.
The graph that topend describes is simply the power curve and its significant values are also an ICAO requirement that ALL helicopter pilots should know.
Incidentally, topend - you might like to look at your 3rd conclusion. I would say that the speed is the "best angle of climb at low speed". This speed would normally be used to clear the closest obstacles after transition to forward flight. Maximum angle of climb is 90 degrees without a power limit. You are quite right, however, judgement of the space required to get it right can be tricky.
tam
If you mean the former, then it should be included in all helicopter training courses within JAA Member States and it should be tested on all JAA Helicopter Licence Skills Tests for PPL(H) and CPL(H).
I believe the same requirement exists for FAA tests and I would expect it to be an ICAO requirement.
The graph that topend describes is simply the power curve and its significant values are also an ICAO requirement that ALL helicopter pilots should know.
Incidentally, topend - you might like to look at your 3rd conclusion. I would say that the speed is the "best angle of climb at low speed". This speed would normally be used to clear the closest obstacles after transition to forward flight. Maximum angle of climb is 90 degrees without a power limit. You are quite right, however, judgement of the space required to get it right can be tricky.
tam
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Max power take off
Maximum slope
By rearranging the data of the previous graph for different speed/climb rates at a given load and power setting the following graph shows up:
Assumptions are (using data from previous plot) : 165 HP MR power available, loaded near MTOW, which means just enough for a high hover, but not enough for a vertical climb.
The curve shows a S-shape. Drawing a tangent shows that in this configuration 15 kts gives the steepest slope.
In order to start from IGE building up of speed towards 15 knts a lower initial climb rate would be used and hence a flatter initial path. In order to compute the detailed acceleration strategy and resulting distance some more calculations would be necessary.
As a pilot I would of course also take aborting options into consideration when determining the acceleration.
d3
By rearranging the data of the previous graph for different speed/climb rates at a given load and power setting the following graph shows up:
Assumptions are (using data from previous plot) : 165 HP MR power available, loaded near MTOW, which means just enough for a high hover, but not enough for a vertical climb.
The curve shows a S-shape. Drawing a tangent shows that in this configuration 15 kts gives the steepest slope.
In order to start from IGE building up of speed towards 15 knts a lower initial climb rate would be used and hence a flatter initial path. In order to compute the detailed acceleration strategy and resulting distance some more calculations would be necessary.
As a pilot I would of course also take aborting options into consideration when determining the acceleration.
d3
