Diego From Italy, joined Apr 2001, 135 posts, RR: 0 Posted (14 years 4 months 1 week 5 days ago) and read 2765 times:
Hi folks got a question I'd love to have your expert advice about.
In the Cheyenne you have two torque red lines, as matter of fact during the takeoff you set the power referring to the first red line while once you bring the prop back during the climb, the torque skyrockets to the second red line.
Does anybody have any clue why that happens?
Latechpilot From United States of America, joined Jun 2005, 0 posts, RR: 0
Reply 1, posted (14 years 4 months 1 week 3 days 18 hours ago) and read 2713 times:
Torque always increases as RPM decreases. As is the case with the PT-6 engine, you have a constant N1 while decreasing the prop RPM. When you decrease the prop RPM it (the prop) becomes harder for the engine to turn and that is why the torque rises. Keep in mind torque is measured in ft/lbs applied to the prop shaft. I'm not familiar with the Cheyanne in particular, but I assume the two red lines on the torque indication would be for max torque with props at max RPM and max torque for props at climb RPM. Or maybe it has to do with the initial power setting and the max allowable "ram rise." My experience with PT-6s come from BE-1900s. I am assuming that the prop systems are simular.