I saw a video demonstrating the SU-30's thrust vectoring nozzles and noticed that the horizontal stabilizers begin moving up/down before the nozzles do. It seems that the F-22 also has this delay.

Then, after it's in an upright/downright position, if the pilot brings the stick back to center, both the nozzles and the stabilizers move at the same time. This leads me to believe that this is probably not some mechanical lag that causes it. So, why is there that initial delay?



Photo demonstrating this delay (note how the nozzles only begin moving some milliseconds after the stabilizer starts moving):

enter image description here

  • $\begingroup$ I don't think you can/should rule out mechanical reasons. If the system is hydraulic then it makes sense. The aircraft can not "anticipate" when the pilot will move the stick away from the neutral position, so this delay may be the time it takes to build the required hydraulic pressure to actuate the nuzzle $\endgroup$
    – DeepSpace
    Feb 15, 2021 at 20:18
  • 1
    $\begingroup$ On the other hand, another possible reason is that the designers did not want the aircraft to be too sensitive and/or "finicky" to control. Just because there is a delay on the ground/low altitude does not mean there is a delay at all altitudes/flight regimes. $\endgroup$
    – DeepSpace
    Feb 15, 2021 at 20:20
  • $\begingroup$ I have read that such thrust systems can be non-minimum phase control problems, meaning they have to get further from the goal before getting closer. What you are seeing might be a side effect of that. Here's a paper describing one control system which has a non-minimum phase transfer function for a ducted fan, which is pretty close to a vectored thrust jet engine. $\endgroup$
    – Cort Ammon
    Feb 16, 2021 at 3:46


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