Hello everyone,I've read some threads that touch on this, but I'm hoping some guys like Herve or one of the other gurus can shed some light on this question.We can start by saying that jets are much more straight-forward than turboprops to model. Throttle position sets CN2 in TBL1503 and 1504; TBL1502 sets the relationship between CN2 and CN1; TBL1506 sets thrust; TBL1507 sets Ram Drag; TBL1505 sets the spooling of the engine. And I think we can say the .cfg entries are straight forward.We can now say that the relationships between the tables for a turboprop, at least for me, don't really follow the straight-forwardness of the jet. Here's an example:I'm modelling a PW124B for the ATR72-200F. The TCDS' for the aircraft and engines give the N-speeds as well as the actual RPMs of the engines. When I set up TBL1503 relate a 100% throttle position to produce a CN1 (usually CN2, but in turboprops this is CN1 as you guys know) of 102.7% engine RPM with a static aircraft at Sea Level, AFSD reports, under the engine parameters, reads 101.5. When I look at TBL1503 in AFSD, it reads: 100% throttle, 1.000 IAP and 105% CN1. This is confusing the heck out of me. I'm under the assumption that, in turboprops, throttle position in TBL1503 would set the gas turbine (CN1 in AFSD) engine speed accurately with a static aircraft at sea level. Why would this read erratically for me?Then I'm assuming, after reading the notes for TBL1508 in AFSD, that this will set the relationship between the high and low speed turbines, and in turn, torque.After that, I'm guessing that TBL509 can be used to fine-tune the torque by changing the Friction?Any help would be greatly appreciated because, after 3 years of tinkering, I can't get these relationships to coalesce into a linear process to be able to properly set up a turboprop. Trial-and-error takes a long time and produces much frustration.Thanks in advance.Scott

When I set up TBL1503 relate a 100% throttle position to produce a CN1 (usually CN2, but in turboprops this is CN1 as you guys know) of 102.7% engine RPM with a static aircraft at Sea Level, AFSD reports, under the engine parameters, reads 101.5. When I look at TBL1503 in AFSD, it reads: 100% throttle, 1.000 IAP and 105% CN1. This is confusing the heck out of me.

Yes I understand it is confusing indeed..Engine parameters AFSD displays are based on what FS reports as N1/CN1 and N2/CN2 with comments regarding the meaning of those on turboprops. On the contrary, AFSD table output display is a raw reading of the tables according to the "published inputs" (that are throttle, IAP and CN2 for 1503)..Now, in line with your observation and based on a preliminary test I did, it seems table 1503 indeed outputs a CN1 value in turboprops. However, changing AFSD raw table output may add to the confusion. I'm afraid I'm not able at this time to tell you how MS coded the different steps. Others here will surely comment

Thank you Herve for the comment. it seems that no matter which table I change, the output stays at CN1: 101.5% and CN2: 100%. If I change TBL1503 to give, at 100% throttle, 117.7% at IAP 1.00 and Mach 0.00; I still only get CN1 of 101.5% and CN2 of 100.0%.If I lower the value in TBL1508, I can change the relationship between CN1 and CN2. CN1 stays the same, but CN2 will change up to a certain point. But after that point, torque will increase but CN2 will not.One other issue that has confused me for a year or two:At cruise and 100% throttle, I set the condition levers to the appropriate torque settings that I see in airliners.net photos. These are the references that I use to model the engines. However, after cruising for an hour or so, I pull the power levers back to start a descent and the engines stay spooled up for minutes. This usually ends up in an overspeed condition which is bad for users using FsP or wanting realism. Any thoughts? I compare my tables to the default king air and they are very similar with the exception of TBL1504. The king air numbers are much lower than what I've calculated these values should be.Thanks again, Herve

If I change TBL1503 to give, at 100% throttle, 117.7% at IAP 1.00 and Mach 0.00; I still only get CN1 of 101.5% and CN2 of 100.0%

Same here, at 100% throttle lever (with a modified 1503 table) as well as at idle power..I suspect tables 1503/1504 do not work the same as for turbojets. As far as for turboprops, N2 is %max RPM, output may also be limited to 100% whatever the high table values are, at least if tables 1503/1504 are used for that (?). Also you will notice N2/CN2 readings do not only depend on throttle lever but also on prop lever, so AFSD table reading is misleading here.

Very true Herve on the N2/prop lever point.I'm one of those sticklers for trying to set things up according to the specs. But what I find that is important with these elusive turboprops is to get the torque output correct as well as Tables 511 and 512. Adjusting 509 and 1508 will set up the proper torque while 511 and 512 will give you proper propeller thrust. So I'm willing to settle for that in order to produce results that come close to reference videos and photos. I would just love to solve this TP mystery. :)I also have figured out the issue with the engines remaining spooled up. I touched on it in another thread, but I'll summarise it here again: I use the published data that I can find to set up the first line of tbl1503, which is static at sea level as you know (CN=N). For all the other lines, I use the formula CN=N/SQRT(Theta Total). This usually gives me pretty close N readings throughout the operating range for jets. However, for TPs, using this method, where the lines that assign CN2 at higher altitudes are higher than the first line in 1503, I will encounter this "hung" engine issue. Whenever I arbitrarilly lower the higher IAP lines, the problem goes away. I've looked at the default TPs as well as some payware and see that the numbers are lower as well in these lines. It's very curious.

I've been doing some poking around on Microsoft's ESP Developer's center and found this: http://msdn.microsoft.com/en-us/library/cc707070.aspxIf you scroll down, you'll see some explanations to Tables 509, 1503, 1504, and 1508. The explanations for 1503 and 1504 are what we all already know. But for 509 and 1508, the explanations, to me, are a bit more interresting. This sample file doesn't exactly name the tables by name, but the descriptions closely compare to those in Aired.For 1508, it explains that this as a "N1 to shaft torque table" and the output (y-axis) is "percent maximum torque (corrected)". So could this be some correction for altitude, speed, to define the relationship in free turbine engines between the gas turbine and the turbine that turns the prop? Which would explain this tables' effect between N1 and N2?For 509, the ASP file explains this is RPM vs. Friction torque as explained in Aired. However, it further explains that the output from this table (y-axis) is Torque due to Friction expressed as a percentage of max torque. In tests, increasing this factor decreases torque so, thinking logically, this means this table introduces a loss of torque due to friction from the bearings in the engine itself as well as the friction in the gear box that drives the prop. One of the things that I find interresting is that, keeping in mind the definition above, the output from this table is in % of max torque that is defined in the .cfg and the default aircraft, as well as some of the payware I've peeked at (never copied but just looked at for comparrison) all have the same factors. At 100% RPM (another factor I find interresting that I'll explain in a bit) the torque due to friction is .80... or 80%?? According to the FAA's Airplane Flying Handbook, "The energy of the hot, high velocity gasses is converted to torque on the main shaft by the turbine rotors (TBL1508??). The reduction gear converts the high RPM-low torque of the main shaft to low RPM-high torque to drive the accessories and the propeller (TBL509??)The question comes back to: "OK, now how do we figure out how to set each of these tables?" It seems that, confirming Aired's description, that TBL1508 sets N2 by defining the low amount of torque produced by the process of the exhaust gasses producing a turning force on the prop turbine. It would then seem that we need to find some reference that can define appromixametly how much torque is produced by the gearbox and the process of the gas turbine turning the prop shaft in order to determine starting points for setting up a turboprop.The propblem reverts back to how to set the Gas Generator in Table 1503 to read accurately given throttle inputs. I can't seem to understand why I can't get any higher CN1 speeds than 101.5%.But in the end, I think it all comes down to the fact that, as long as you set up TBL1508 to give approximate N1/N2 relationships, you can adjust TBL509 to give proper torque at 100% prop RPM (which is what I think this table is referencing along the x-axis) as well as proper torque/HP at cruising prop RPM.I may go to the library and see if I can find some texts on turboprops.

The propblem reverts back to how to set the Gas Generator in Table 1503 to read accurately given throttle inputs. I can't seem to understand why I can't get any higher CN1 speeds than 101.5%.

Unfortunately, there is no way that I know of. I've found that tables 1503 and 1504 don't have any effect on turboprops, and seem to be hard coded in the executable. I tried placing all Y values to 0 and CN1 behaved as usual without reacting to the changes. I was interested on CN1 idle value, that is fixed at near 62%; I needed to bring it down to 52 % but wasn't able to do so. Also in turboprops CN2 is mapped to propeller RMP, expressed in percentage.Tom

This sample file doesn't exactly name the tables by name, but the descriptions closely compare to those in Aired.

I found this airfiletokens.h list some time agoUNUSED_AIR_TITLE EQU 000000001hOBSOLETE_AIR_DESCRIPTION EQU 000000002hOBSOLETE_AIR_PERFORMANCE EQU 000000003hUNUSED_AIR_TAIL_NUMBER EQU 000000004hUNUSED_AIR_SIM_NAME EQU 000000100hUNUSED_AIR_NORMAL_MDL_NAME EQU 000000101hUNUSED_AIR_SIMPLE_MDL_NAME EQU 000000102hUNUSED_AIR_CRASH_MDL_NAME EQU 000000103hUNUSED_AIR_PANEL_NAME EQU 000000104hOBSOLETE_AIR_AC_CATEGORY EQU 000000105hOBSOLETE_AIR_CONTROL_RESPONSE EQU 000000300hOBSOLETE_AIR_CG_TO_EYEPOINT EQU 000000301hOBSOLETE_AIR_FUEL_CAPS EQU 000000302hOBSOLETE_AIR_ENGINE_TYPE EQU 000000310hOBSOLETE_AIR_NUMBER_ENGINES EQU 000000311hOBSOLETE_AIR_FUEL_WEIGHT EQU 000000312hOBSOLETE_AIR_THROTTLE_LIMIT EQU 000000313hOBSOLETE_AIR_LANDME_AVAIL EQU 000000314hOBSOLETE_AIR_FLAPS_DETENTS EQU 000000315hOBSOLETE_AIR_MAX_OPERATING_MACH EQU 000000316hOBSOLETE_MAX_OPERATING_MACH EQU 000000316hOBSOLETE_AIR_AUTOPILOT_AVAIL EQU 000000317hOBSOLETE_AIR_FLAPS_AVAIL EQU 000000318hOBSOLETE_AIR_STALL_HORN_AVAIL EQU 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000001543hAIR_80_YAW_PARAMS EQU 000001544hAIR_80_CL_ALPHA_TABLE EQU 000001545hAIR_80_CM_ALPHA_TABLE EQU 000001546hOBSOLETE_AIR_80_AERODYNAMIC_CENTER EQU 000001547hAIR_80_DENSITY_ON_TP_TORQUE EQU 000001548hAIR_10XPACK_N1_MACH_ON_NOZZLE EQU 000001549hAIR_10XPACK_CD0_MACH EQU 00000154ah