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Do airline pilots increase thrust when ordered to increase altitude by traffic controllers? Do they simply use flaps, the yoke (or joystick in the case of airbus) and the stabilizers without any increase in thrust. What is the altitude increase sequence or procedure . Do they simply rely on auto pilot and if so does it increase thrust too?

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  • $\begingroup$ well, ATC hardly ever ‘orders’ pilots to do something, but if they did: how would expect to climb without adding thrust? trading speed for altitude would be a method, but it won’t get you very high. altitude, like speed, is energy and that energy has to come from somewhere $\endgroup$ – Radu094 Jan 11 '18 at 13:47
  • $\begingroup$ @Radu094 ' it won’t get you very high' It would actually. If you (temporarily) reduce speed, you have energy to spare for climbing. Drag goes up quadratically with speed, so if you reduce speed by 30%, you can use half the energy of your engines for climbing. $\endgroup$ – Orbit Jan 11 '18 at 13:57
  • $\begingroup$ well, it depends on what side of the drag curve you are, mind you, (as reducing speed will increase induced drag) but I see your (valid) point. I was only talking about trading kinetic vs potential energy (eg like a glider) which is not giving you much altitude $\endgroup$ – Radu094 Jan 11 '18 at 19:37
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Do airline pilots increase thrust when ordered to increase altitude by traffic controllers

Yes, without increasing thrust the act of ascending would reduce speed.

Do they simply use flaps

No, flaps are not used to climb. They are used to increase the surface area of the wing in order to allow the aircraft to fly at slower speeds (for example, during approach & landing).

What is the altitude increase sequence or procedure

Generally, and put simply, it is increase thrust then raise the nose.

Do they simply rely on auto pilot and if so does it increase thrust too?

They may well use the autopilot to do it all, but some autopilots do not control the throttle so that would be done manually by the pilot while the autopilot controls the rate of climb.

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    $\begingroup$ Almost all (or all) commercial airliners have an auto-throttle system, which is pretty much a part of the auto-pilot. If the pilot dials in a new altitude, the autopilot will pitch up and the auto-throttle will increase thrust to maintain speed. $\endgroup$ – Ron Beyer Jan 11 '18 at 15:35
  • $\begingroup$ @RonBeyer yeah, I guess my wording was bad there. I adjusted it. $\endgroup$ – Jamiec Jan 11 '18 at 15:36
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I’ll try my hand at a more ‘scholastic’-aviation approach:

The normal procedure taught in flight school for initiating a climb is P-A-T. That is Power-Attitude-Trim.

  1. You increase power on the engine(s) first.If left alone, the plane will settle (very slowly, google phugoid) into a climb eventually

  2. Because we do not want to wait the few mins or so it takes for the plane to settle into the climb, we use the elevator (via yoke or sidestick) to settle the attitude of the plane directly into a climb position (ie. point the nose higher up). A good pilot will do this without letting the speed climb or drop. ‘Call it pitch-for-speed.

  3. Now the plane is in a different power/attitude and even though the plane is (or should be) at the same speed, a little bit of trimming is required to null the forces on the yoke.

now you can sit back and enjoy the climb.

Leveling off after the climb is a A-P-T.... you guessed: Attitude-Power-Trim. The reasoning for the change of order is that you want to prevent the plane from a nose-up, low-power situation, with speed decaying quickly.

Mind you, in a modern airliner most of these things can be automated via an autopilot/autothrust as described in the other answers.

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Most airliners today use auto pilot and auto thrust when flying in level flight or climbing and descending.

The normal sequence for a climb is to enter a new altitude in the flight computer and then engage a climb mode on the autopilot. In any aircraft thrust is usually increased for a climb and decreased for a descent. The Auto-thrust will adjust automatically in most modes to maintain a desired speed and rate of climb. The autopilot adjusts the elevator or stabilizer to climb or descend to the set altitude.

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    $\begingroup$ Hmm, sounds like you're having to work too hard. Why not just say, "Alexa, flight level 350" or whatever. LOL $\endgroup$ – Terry Jan 11 '18 at 22:25
  • $\begingroup$ @Terry "Now purchasing 350 flight levels to be sent to your home address" $\endgroup$ – Zach Lipton Jan 11 '18 at 23:38
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    $\begingroup$ @Terry: Why do you think voice input would be easier than just entering a new desired altitude? Even apart from the problems posed by a noisy cockpit. $\endgroup$ – jamesqf Jan 12 '18 at 5:15
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    $\begingroup$ @jamesqf voice input is reserved for captains only. $\endgroup$ – kevin Jan 12 '18 at 6:30
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    $\begingroup$ @jamesqf I was just joking. I retired in 1999, and from my old fart standpoint, they've taken all the fun out of the job of being an airline pilot. My last 10 years was spent on 747-100/200s with a 3-man crew and no so-called glass cockpits. When assigned a higher altitude, we dialed (actually turned a physical dial) the new altitude into a little window of rotating digits for reference. Then the flying pilot would disengage the autopilot and ask the f.e. to set climb power. Reaching the new altitude, he'd engage the autopilot with altitude hold and ask the f.e. for cruise power. $\endgroup$ – Terry Jan 12 '18 at 7:41

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