Hi everyone. I'm trying to model a B1900D and I'm running into a common problem that I have. I'd like to figure this one out so it isn't as time consuming in the future. I have the TCDS info for the PT6A-67D as well as the prop data/weight. I set the .cfg entries the best I can as well as records 510, 511, 512, 1501-1507. They don't have any real great departure from the default King Air 350 besides using the data for the different engine: i.e.: max torque, prop diameter, beta angles and such. I'm not too familiar with the 509 and 1508 tables but I tweak to get the proper torque and HP.The problem is that as I'm cruising along at 25000', I need full power and set the condition levers to the proper RPM, just like I saw in a Airliners.net photo. However what happens is as I pull the power back to begin a descent, the engines keep spooled up for minutes even with the throttles pulled back to idle. It isn't bad if I don't use 100% throttle, the engines remain rather responsive.I've pulled up the .cfg and .air for the 1900 to the default king Air and there isn't anything that really stands out as being out of the ballpark. I'm using a Prop MOI of 57.461 which I calculated from the following equation: MOI=2/3 * prop weight (slugs) * prop radius^2. The prop weight (including HUB) acording to the TCDS (P10NE) is 132 lbs (or 4.10269 slugs).I'm not sure if it is a prop MOI mix-up on my part. Is the MOI .cfg entry fo the propeller section as a whole or just a blade (where it would multiply by the number of blades??)Could it also be in either the 509 TBL or 1508 TBL? It could be a friction problem, I suppose. But again, comparing my tbls with the King Air, it isn't too off. in the King Ait TBL509, @ x=100.0, y=.80. In mine, it is .685. And TBL 1508 are very similar.Any help would be greatly appreciated.Scott B.

Thought I'd add this:.cfg[GeneralEngineData]engine_type = 5 Engine.0 = -15.809, -8.600, 0.570Engine.1 = -15.809, 8.600, 0.570fuel_flow_scalar= 0.75min_throttle_limit = -0.25[propeller]thrust_scalar = 1.00 propeller_type = 0 propeller_diameter = 9.167propeller_blades = 4propeller_moi = 57.461beta_max = 50.00beta_min = 4.90min_gov_rpm = 25520prop_tc = 0.004gear_reduction_ratio = 19.349fixed_pitch_beta = 0low_speed_theory_limit = 80prop_sync_available = 1prop_deice_available = 1prop_feathering_available= 1prop_auto_feathering_available= 1min_rpm_for_feather = 700beta_feather = 79.0power_absorbed_cf = 0.92defeathering_accumulators_available= 0 prop_reverse_available = 1minimum_on_ground_beta = 1.0minimum_reverse_beta = -14.5[TurbineEngineData]fuel_flow_gain = 0.017inlet_area = 1.0 rated_N2_rpm = 32894.00 static_thrust = 178[turboprop_engine]power_scalar = 1.0maximum_torque = 3950Also could anyone explain what the prop_tc is and what it does? I have no idea. LOL.Thanks again,Scott B.

FIXED!!! Yea!!! I don't like to do this but I took the default King Air air file, renamed it, and put it in my B1900 folder and used it. The engines performed well. So I started to replace the engine sections in the .air file with mine until the engines started to screw up. The problem was TBL1504.The formula I found on one of the BBs someplace along the journey of learning was: CN = N / SQRT ( Theta Total). Where N = uncorrected Engine N rotation percent and Theta Total = Theta * (1 +.2 * M^2 ). Where Theta is the the standard temperature ratio between cruising altitude (I use max published altitude for the aircraft per TCDS) and Sea Level. This is in degrees Kelvin. M = Mach number. (for the tables I use max operating number or Mmo per TCDS). The formula to attain Theta Total is from Herve's AFSD.This generally led to having the high mach (TBL 1504) higher than the Low Mach TBL1503. Perhaps I was using the wrong formula for CN. Perhaps it is CN = N * SQRT. I'll give that a go and see what results I get. In comparrison, the origional tbl1503 that I calculated read the following at 100% throttle: IAP 1.000000 = 104.000000 IAP 2.700000 = 114.295777And TBL 1504 read the following at 100% throttle at .480000 Mach: IAP 1.000000 = 101.683594 IAP 2.700000 = 111.750052The King Air TBL 1504 read much less than mine. @ MACH .900000 IAP 1.000000 = 83.830000 IAP 4.237000 = 95.000000I am not familiar with the properties of a turbine engine's characteristics at altitude and high MACH numbers so I don't know if the engine would be capable of higher N percentages or not. I may have to see if I can ask some guys at Purdue for some insight or one of my friends who flies ERJs for American Eagle if he'd know.But at any rate, the question I had about tthe Propeller section still stands:What is prop_tc and what does it affect?Any help would be appreciated!