From: niklas.holsti@tidorum.invalid   
      
   On 2021-10-10 9:38, JF Mezei wrote:   
   > On 2021-10-09 09:30, Otto J. Makela wrote:   
   >   
   >> I believe the strong ground effect created by the large flat bottom of   
   >> the shuttle had a part in these initial difficulties?   
   >   
   > That makes sense I guess. i was just very surprised to see that shuttle   
   > actually gain a few feet and stay up for an eternety (a few seconds).   
   >   
   > My "image" of the shuttle is that there was no way for it to do this and   
   > the main gear HAD to fall to the ground, abd the only control they had   
   > was keeping nose up to bleed speed before lowering it.   
   >   
   > Perhaps they changed the approach to ensure the shuttle had lower   
   > airspeed at the runway which would explain the "main gear must fall to   
   > the ground" while in early tests, a higher speed allowed that ground   
   > effect "flight".   
      
      
   In the video, Scott Manley clearly explains that the bouncy landing was   
   due to pilot-induced oscillation (PIO) through the fly-by-wire system,   
   and that it was fixed by correcting the fly-by-wire control algorithms.   
      
   PIO is usually caused by too long delays in responses to manual control   
   inputs. For the Shuttle there was (also?) another problem that the same   
   control surfaces were used for both roll and pitch, instead of having   
   separate controls, as Manley explains. It seems likely that the ground   
   effect also played a role by increasing lift at low altitude.   
      
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