Yves77 2 Posted March 13, 2018 Share Posted March 13, 2018 Hi everyone I noticed that in V1.0.5 and 1.0.6 at every takeoff of the CRJ700 or 900 the stabilizer trim automatically moves down (or up) by a fixed amount exactly at lift off. This requires some manual counteracting of elevator and/or stab trim to correct the pitch in this critical phase which is not the real behaviour. So I did some investigation and I'm sure the problem relates to the AUTO trim function of the horizontal stabilizer. AUTO trim adjusts the stab trim by a fixed amount when the flaps are retracted or extended between 0 and 20° (autopilot off). This is a real world feature and works correctly in the sim when already in flight. On the ground, a flap setting change does not move the stab trim, at least not in the sim (the FCOM doesn't specify if this is an in-flight function only). When I set flaps from 0° to 8° or 20° before takeoff by pressing F7 2 or 3 times (or a joystick button), the CRJ seems to memorize the very last key press (e.g. from 8° to 20°). As soon as the main gear leaves the runway, the AUTO trim moves the stab by the programmed amount during 5 to 10 seconds. In other words, the AUTO trim is inhibited on the ground in the sim, but will execute the flaps related trim command with a delay when the CRJ leaves the runway. I'm not sure aymore if this also happened in V1.0.3. To give some numbers: Setting flaps from 0 to 20° before takeoff will give a stab trim nose DOWN input of 0.7 units after lift-off (e.g. vom 7.5 to 6.8 as shown on the Flight Control DIsplay). This is the same amount one gets if the flaps are extended from 8° to 20° during approach. A nose UP trim of the same dimension can also be observed when the flaps are moved from 20° to 8° before takeoff. It's also consistent with other flap settings change (from 0° to 1°, from 1° to 8° or vice versa). Do you see the same thing happening? - P3D v4.2 - FSUIPC 5.124 (also happens without FSUIPC) Best regards, Yves G. Link to comment Share on other sites More sharing options...
CRJ900 335 Posted March 13, 2018 Share Posted March 13, 2018 Can confirm this very behaviour on my end as well. The logic needs to be fixed. Shouldn't be too hard. Link to comment Share on other sites More sharing options...
Developer Hans Hartmann 3694 Posted March 20, 2018 Developer Share Posted March 20, 2018 There is no actual auto trim, but a trim correction when flaps are extended or retracted. This caused the trim input after leaving the ground. It's now fixed. Link to comment Share on other sites More sharing options...
Yves77 2 Posted March 22, 2018 Author Share Posted March 22, 2018 Thank you for fixing it! The CRJ FCOM calls it AUTO Trim, but it is of course not the same as a real auto trim such as in an Airbus. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.