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Civilian jet airliners don't need to push their yokes down to follow the curvature of the Earth because within the atmosphere the curvature is accounted for by automatical systems, right? I wonder whether there are jet aircraft (from the military, obviously) that actually have to push their yokes down for instance. The SR-71 Blackbird flew very fast (more than Mach 3) at very high altitudes (above 80,000 ft). Did Blackbird pilots have to be careful not to fly too much up due to the Earth's curvature, respectively not to cause a stall? Did Blackbird or other jet's pilots need to take other astrodynamics into account, such as rotational forces or other pitch concerns?

Giovanni
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It's the same question as for the ISS in orbit, gravity is pushing the yoke down for you. When you fly level you're actually keeping your distance from the earth center constant.

MaximEck
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  • But the nose pitch remains the same relative to the stars while not remaining the same relative to the surface. Therefore, it goes more and more up, till the threat of a stall. – Giovanni Sep 20 '20 at 18:13
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    No you adapt your nose pitch to remain at constant density altitude. – MaximEck Sep 20 '20 at 18:29
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    The ISS is moving at orbital velocity - crazy fast. Even the fastest aircraft is moving, even with Earth's rotation, far slower. Apples to Oranges comparison here. – Ralph J Sep 20 '20 at 19:04
  • The SR-71 went to 3500km/h; low Earth orbit is at 28000km/h. Indeed apples to oranges. – Sanchises Sep 20 '20 at 19:35
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    He is asking if an airplane will pitch up if flying level, thinking that the airplane will go on a straight line and at some point leave earth atmosphere by doing so, which to me is similar to leaving earth gravitational field. I'm answering that even the ISS at 400km and orbital velocity around our planet is not capable of doing and then explain what flying level actually means... – MaximEck Sep 20 '20 at 21:59
  • @RalphJ The fastest jet aircraft was the Blackbird. The fastest rocketplane is the SpaceShipTwo which actually flies into space and doesn't adapt its nose pitch automatically up there anymore. – Giovanni Sep 21 '20 at 05:24
  • @MaximEck So there's enough density up there for the Blackbird to remain a leveled orientation automatically, even when flying at Mach 3 and above 80k ft? – Giovanni Sep 21 '20 at 05:25
  • For the back bird definitely, the space limite is actually defined as the limit at which air density is so low that an airplane will have to will at orbital velocity to generate enough lift to fly level. Below that airplanes fly normally. The spaceship burn all its fuel during ckim with a nose up attitude, then it coast using its velocity to counteract gravity during some time which will bring it back down at on point and then in fall pretty much like a feather at first and then start to fly once low enough. But they don't really control the trajectory in space as they don't fly. – MaximEck Sep 21 '20 at 05:49
  • @MaximEck Wouldn't a too high speed become difficult at a certain point, even deep within the atmosphere and with the necessary heat protection? Perhaps I should ask that as a separate question. – Giovanni Sep 22 '20 at 05:50
  • @Giovanni look, this is very simple. Gravity and air density turns the flight path down. Then, because of the plane's aerodynamics, it prefers to turn "into the wind", like a wind vane or shuttlecock, so it naturally pitches down. – Abdullah is not an Amalekite Sep 23 '20 at 15:10
  • @Abdullah Why didn't you say that immediately? And unfortunately I can't upvote comments but I would yours. Still, a part of the question remains, namely at what speed would navigation become not good, but that's in a different question anyway. – Giovanni Sep 23 '20 at 15:26