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What pitch attitudes are common during an emergency descent? I assume it would be a fairly nose-down attitude, but I can't imagine how steep would feel to the passengers.

Suppose a gradual decompression takes place and no structural damage is present nor suspected. What would be the pitch attitude for common airliners like the Airbus A320 or the Boeing 737?

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    $\begingroup$ fun video on this youtube.com/watch?v=yHawjB2PzK0 $\endgroup$ – Cloud Aug 20 at 11:53
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    $\begingroup$ @Cloud Nice video! If you look carefully at around 2:40 they start descending. You can just about see the vertical speed on the PFD going down. Note how smooth it is :) $\endgroup$ – Bianfable Aug 20 at 11:58
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It is not as nose down as you may think. First, let us have a look at normal pitch attitudes during a normal descent (without speedbrake). These can be found in the QRH Performance Inflight Tables:

Normal Descent Table
(Boeing 737 NG QRH - 30.1 Performance Inflight - Flight With Unreliable Airspeed)

As you can see, normal descent attitudes are varying between -2.5° and 2.0° depending on aircraft weight and altitude.

For an emergency descent you would extend the speedbrakes which allows a steeper descent. The FCTM has some details on the procedure (see also this answer for more details):

To manually fly the maneuver, disconnect the autothrottles and retard thrust levers to idle. Smoothly extend the speedbrakes, disengage the autopilot and smoothly lower the nose to initial descent attitude (approximately 10° nose down).

About 10 knots before reaching target speed, slowly raise the pitch attitude to maintain target speed. Keep the airplane in trim at all times. If MMO/VMO is inadvertently exceeded, change pitch smoothly to decrease speed.

(Boeing 737 NG FCTM - 7.7 Maneuvers - Rapid Descent, emphasis mine)

Note that the 10° nose down attitude is only the initial pitch to start the descent and increase airspeed to MMO/VMO. Afterwards, the nose is raised to maintain the speed limit. This means the pitch will be between -10° and -2.5° during most of the emergency descent. Enough to notice it, but hardly the nose dive some Hollywood movies show.

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  • $\begingroup$ I disagree. I think you'd experience zero G in an emergency descent $\endgroup$ – Cloud Aug 20 at 11:52
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    $\begingroup$ @Cloud For sure not. Note words like "smoothly lower the nose" are chosen in the Boeing documents. Basically, you should not rapidly start the descent. The Zero G flights (the intentional ones) get zero G by flying on a parabola to achieve this (meaning you get zero G long before they actually descend). $\endgroup$ – Bianfable Aug 20 at 11:55
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    $\begingroup$ By all means, @Cloud, please write up an answer of your own referencing documentation of a procedure for a major commercial airliner that would produce a zero-G emergency descent. $\endgroup$ – FreeMan Aug 20 at 11:56
  • $\begingroup$ @Cloud you may experience a low load factor when putting the aircraft in a dive but then you rapidly reach max speed and continue on a straight path at constant speed (no acceleration and thus you experience 1G), but zero-G seems to be an extremely low load factor. $\endgroup$ – Manu H Aug 20 at 11:57
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    $\begingroup$ "the nose dive some Hollywood movies show" is often made even worse by many movies adding the Stuka siren sound effects (which in real life was a device deliberately added to make that sound, in order to frighten the enemy), so many people associate any aircraft which is rapidly descending with that loud wailing. $\endgroup$ – vsz Aug 21 at 6:10
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My experience was on the Regional Jets but from sim training I recall that the pitch down once at Vmo with flight spoilers extended was somewhere around 10-15 deg. The standard procedure for the CRJ was to declare "emergency descent", slam the thrust levers to idle, flight spoilers fully out, dial the Autopilot altitude preselect to 10000 ft, select the Autopilot to Speed Mode, and dial the speed select to Vmo, and just let the airplane do its thing while the two of you went through the QRH.

You will get a small G reduction during the pushover, but the AP would pushover gently enough to avoid making people in the back float around. If you push over manually, there is a risk of pushing too hard in the stress of the situation and banging heads against the ceiling in the back (it doesn't take much when you're going fast like that).

Any G reduction that occurs is only momentarily during the pushover. Once up to speed you are back to 1 G more or less. The pitch attitude in the descent would be noticeable to a passenger looking out the window from the slanting horizon, but I don't think it would look like they were diving straight at the ground. The scarier part would be the rumble from the spoilers being out, and the roar in the cabin from flying at Vmo.

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