Determining torque limits?...

[ESzczesniak 128]

Hello all,I'm wondering if any one has a good way of determing appropriate torque limits to set for engine parameters? I ask mainly as a method of controlling EGT on takeoff. At most sea level airports, full throttle/100% torque works fine and does not exceed max EGT. However, at some airports higher in elevation using 100% torque would quickly exceed maximum EGT. Considering that some of my favorite routes are around Denver, Aspen, Colorado Springs and Telluride, this is particularly true.Of course why this happens is quite logical in the thinner air, but it still is something to be dealt with. The main reason I ask now is for the interaction with FS2Crew that is now available. Previously, I simply advanced the throttles until EGT reach the max line manually and left it sitting there until power reduction after takeoff. It was a bit tricky to fine tune this while rolling down the runway, but it worked. It also has given me an idea as to approximately where to set the torque limits, but this changes with temperature (should also change with humidity and altimeter setting, but not sure if this is modeled in FSX).However, FS2Crew has the FO set "full power" for you on the takeoff roll now bringing this whole issue up again (my understanding is that this, and all other parts of the FS2Crew flows are modeled realistically on a real world operator). If I let the FO do this without a torque limit, then at these higher elevation airports he's going to exceed the max EGT and fry my engines. I am aware of the "cheat" method of determining reduced torque takeoff by setting EGT to the white line, however it's not really reduced torque I'm after nor does this help me limit the FO setting the throttle. Additionally, I am aware that the TTL is supposed to be able to cut fuel flow to the engine to limit torque and/or EGT. However, at these high elevation airports I find that if I firewall the throttles that I would over run the max EGT (at lesat it trends that way very quickly, I've never done this just to see what happens). Is this simply because the TTL can only cut so much fuel flow (I think it was 15%) or because there's something wrong with my setup?I have to say that I'm a little protective of my JS4100 engines. I managed to make it all the way through the learning curve without a single blown engine or engine fire (yes, I do have that option on in the configuration manager). So, as meaningless as sim stats are, I'd like to continue safe engine practices. So back to the original questtion: are there any charts/tables/etc. anywhere that I can use to come up with a reasonably accurate torque limit to avoid this?Thanks in advance for any help.Sincerely,Eric Szczesniak

[rsrandazzo 6,353]

Erik-On the line, we had a big book that included all of the airports to which we operated. On each page there was a massive table covering one runway, and all possible temperature/weight variations. From these tables we would predict the reduced torque for takeoff...These books were compiled by a third party company that was paid thousands of dollars a month to provide us with predictive data that took into account first, second and third stage climb performance, obstacle clearance and terrain avoidance in areas of rising terrain.Unfortunately it simply isn't possible for anyone to provide this to the sim community, especially given the number of airports available.I had the privilege of flying a number of "company movements" into some places that we never operated line or charter flights- and for these airports we used the Torque-or-Temp-Out Technique...The process for a MAX POWER takeoff was: Advance the thrust levers to about 80% and let the temp stabilize, then slowly adjust the thrust levers forward until you hit EITHER the Torque or Temp limit on either engine.... The process for a REDUCED TORQUE takeoff was: Advance the thrust levers to about 80% and let the temp stabilize, then slowly adjust the thrust levers forward until the temp hits the lower white index line. Incidentally- this was almost ALWAYS the temp that would result from a reduced torque setting provided to us by the big book....

[MrGreen 0]

I guess this isn't the answer you are searching for, but can't you cheat? What i mean is that you check what torque % will hit the lower white mark and then give that to the FO? I don't own FS2C for js4100 but if i understood you correctly and you can set a torque limit that could solve your problem (although maybe a bit unrealistic)

[ESzczesniak 128]

I guess this isn't the answer you are searching for, but can't you cheat? What i mean is that you check what torque % will hit the lower white mark and then give that to the FO? I don't own FS2C for js4100 but if i understood you correctly and you can set a torque limit that could solve your problem (although maybe a bit unrealistic)

Yes, that would work, but that would require doing a runup to full takeoff power at some point prior to the runway for each and every flight (assuming density altitude changing). It's a thought, but hard to argue for that instead of just setting the power myself. Of course, maybe if I keep track of data, I can come up with a quick and dirty formula for setting the torque limit based on this...obviously nothing like the thousand dollar airplane charts, but I'd be happy to get in the ball park.