SF340 A, B & WT Av tech tips
 

SAAB Manual AMM 76-10 CTOT torque fault finding

Sheet 1 - FIGURE 76-10-00-990-827-1 Fig. 101 CTOT System - Fault Isolation Page 1 of 2

the SAAB manual has an error on here stating the base voltage is 5.042 VDC +/- 10%....this 10% is incorrect and should read +/- 10mv...

yes a correction was submitted to SAAB but they are as interested in correcting their documentation as the Australian government is in building a real NBN.:D

Fault finding Torque Errors institute CTOT
 

The below table gives you the individual voltages per torque setting
for CTOT PN: 7239060-503 and can be measured on pins 1-6 and 3-5
SAAB does not have this information in its manual. The CTOT is only calibrated on the 100% and 60% settings, but if you want to save fuel and engine runs once at Ground idle pop the CTOT up, but don't disconnect plug in the Multi meter in pins 1 & 2 ( DECU voltage, 3 & 4 (DECU) voltage 5.042 +/- 10mv then if the pilots have reported a particular torque error select the CTOT to that Toque error and measure the output voltage on pins 3 to5 and 1 to 6 compare to values below. remember these values are the ideal, each percentage value is for the selector and the mv is the mode APR higher value and ON lower value.
100% 4.532 4.244 98% 4.447 4.159 96% 4.362 4.074 94% 4.277 3.989 92% 4.192 3.904 90% 4.108 3.820 88% 4.023 3.735 86% 3.938 3.650 84% 3.853 3.565 82% 3.768 3.480 80% 3.683 3.395 78% 3.598 3.310 76% 3.513 3.225 74% 3.428 3.140 72% 3.343 3.055 70% 3.259 2.971 68% 3.174 2.886 66% 3.089 2.801 64% 3.004 2.716 62% 2.919 2.631 60% 2.834 2.546

CTOT quick verification table
 

formula for working out the individual values

CTOT fomula

(100%-60%) / 20 steps= 2% torque



100% -60% /20 =2% 4.532 2.834
84.9mv

100% 4.532 4.244 90% 4.108 3.820 80% 3.683 3.395 70% 3.259 2.971 60% 2.834 2.546
TP 3-5 TP 1-6