takeoff TIT

[topboltsto400]

On a -15 the takeoff is 1067-83...normally 1077. What is the +/- range for...I thought I heard it had some significance at one point?

[Lkuest]

I'm sure it's for a few things, including throttle alignment. The one thing that I CAN say that's not assumption is that the TIT indicator is required to read +-6 degrees of actual, which explains 1083 being 6 degrees above 1077. This would leave 1071 on the bottom end though. I think I read somewhere that the TD valve has to correct to within 4 degrees of desired. I can't remember where, so for all I know I just made it up. If that's right though, than that brings 1071 gauge inaccuracy down to 1067 with TD inaccuracy. Without spending lots of time researching it, that's the best I can do. 1067 + 4 (TD valve error) = 1071 + 6 (Gauge error-) = 1077 + 6 (Gauge error+) = 1083--1067-1083 range. The reason there might not be a 4 degree TD valve error on the high side might be explained by the redundant Temp Limiting setting on the amp that kicks in just above takeoff temp, so you should have 2 separate settings keeping things at 1077 or below instead of just 1 setting at 1071.

If I'm off base, someone else please chime in.

[Steve1300]

Lkuest, your guesses work as well as mine. I have often considered the gauge error to be the root cause of the temp limit for takeoff. In the civilian Herk world, our books call for us to set our slope at 1071 and not at 1077. I guess that to be to allow a TIT indicator error if 6 degrees. We should never see 1083 without a TD system malfunction.

As for TD system corrections, my failing memory reminds me that our corrections must be within 3 degrees. People with round steam gauges would have to guess if they fell within those kinds of limits.