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The obvious answer to this is... don't go into clouds.

But if you are flying among scattered or broken clouds and you go up above them, then when you reach your destination it's overcast and there is no way down - what is the safest way to descend through them?

I asked this at my club and someone suggested side slipping would be the best approach as you get through quickly and are less likely to experience unusual attitudes due to not pitching as much.

Please also assume there are no IMC instruments on board, i.e. no artificial horizon etc.

For reference, this happens a lot, like here.

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    $\begingroup$ If you are flying towards your destination and can see the ground below and out in the distance you can see an overcast layer below you, why would you ever continue the flight? Proper ADM is to land short of the destination where you can descend in VMC conditions. If you don't have proper instruments or training to fly in IMC you will kill yourself. $\endgroup$
    – wbeard52
    Commented Aug 22, 2023 at 13:28
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    $\begingroup$ Please don't ever do this dude! $\endgroup$
    – Jamiec
    Commented Aug 22, 2023 at 14:00
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    $\begingroup$ A closer example is this one, where an IFR-rated pilot flying IFR over the top found themselves stuck above an overcast but with a vacuum failure that knocked out some of their IMC instruments. This illustrates well exactly how dangerous this situation is- even an IFR-qualified pilot who is current and proficient can fail to control a plane in IMC even with some IMC instruments. Trying to do the same with no training and even fewer instruments is foolhardy if there is any alternative. If he had declared an emergency and flown straight for the closest $\endgroup$
    – Chris
    Commented Aug 22, 2023 at 17:09
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    $\begingroup$ weather that would permit a VFR descent, he'd probably still be alive today. $\endgroup$
    – Chris
    Commented Aug 22, 2023 at 17:10
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    $\begingroup$ I'm depressed by the number of very bad answers. No one is actually answering the question, everyone repeats something along the line of "don't be an idiot!" Which, yes, don't be. But if you have been, what aerodynamically is the thing to do? We teach accidental spin and stall recovery, which (generally) only happens to people being idiots, so there's value to understanding what to do if ever caught in this circumstance. IMC can arrive for a number of reasons, and they're not always clearcut flying into an overcast layer. I had near-IMC happen when I got sudden clear-air icing in a 7ECA. $\endgroup$ Commented Aug 29, 2023 at 13:28

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It depends a lot on the type of cloud. And the airplane.

Stratus clouds occur in calm air whereas cumulus clouds are caused by convection. In the calm air of stratus clouds it is rather unlikely that a well-trimmed airplane will go into a spiral dive all by its own. Exceptions will apply: I have flown gliders which not only will start a phygoid motion right after letting go of the stick, but also will invariably slowly but surely enter into a spiral dive.

Therefore: Know your airplane AND the type of cloud you encounter. Try descending in calm, cloudless air to learn how your airplane will react. If you still fly straight with a constant rate of descent after a minute, you can risk repeating that in clouds that lack any convection. Trim the airplane at a moderate speed and let go of the controls until you see the ground again.

However, if you have reason to suspect that the cloud contains turbulence, turn around and avoid entering the cloud. Gusts will upset even the most stable airplane and a spiral dive will become very likely. Humans have a tendency to continue on the same path when under stress. Discipline yourself and recognize when you are under stress and widen your options. Turning around is the much better choice over continuing into the clouds. And always turn around, irrespective of the type of cloud, when you know that your airplane will not fly straight for an extended time when left to itself.

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  • $\begingroup$ How come does turbulence push an a/c into a spiral dive? Is it because every airplane has a tipping point for bank where a spiral dive is inevitable, and the turbulence gives the energy needed to go past that point? $\endgroup$ Commented Aug 30, 2023 at 12:04
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    $\begingroup$ @KennSebesta Yes, while small pertubations can be tolerated, violent gusts cannot. I have heard enough stories of glider pilots who left a cloud inverted or in a spiral dive, being completely disoriented. My cloud flying experience is outlined above - I never flew through cumulus clouds, only through the haze at the fringe when climbing too high under the center of the cloud. $\endgroup$ Commented Aug 31, 2023 at 10:07
  • $\begingroup$ @PeterKämpf There are situations where there are no other options. Intended destination, 145 mi; fuel avail. ~120 mi; nearby airport w/fuel, 85 mi. Conditions, stratus 3000 ovrcast, stratocum, 5000 broken, stratocum 8000 broken, cumulus at 12000. Banking thru potential turbulence not readily an option, n factor concern, light aircrft. Just saying... $\endgroup$ Commented Aug 31, 2023 at 15:46
  • $\begingroup$ @ThomasPerry If you find yourself in that situation you have already made a series of mistakes. The consequences might not be felt immediately, but will come due eventually. Sometimes it will be better to land in a field than to try to penetrate clouds. Widen your opportunities and don't think it is only on airports where airplanes can be landed. Better to be able to walk away from the plane than arriving at the ground with assorted plane parts in free fall. $\endgroup$ Commented Aug 31, 2023 at 23:16
  • $\begingroup$ @PeterKämpf No argument there! Generally speaking, pilots make choices (not necessarily mine). In the United States, one of the leading causes of fatalities is fuel exhaustion. Pilots are sometimes at the will of unintended consequences & forced to make difficult risk-averse choices. My comment regarded your previous text; was purely intended in the third person & choices one makes given situational risks. Perhaps there isn't a field nearby & given weather conditions, no clear path to return. The pilot is left with these concerns; now what? I think you've addressed all that very well. $\endgroup$ Commented Sep 1, 2023 at 0:39
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Step -2: There is nowhere in the world you need to be badly enough to go VFR into IMC. If you're under enough pressure to get somewhere on time that you'd even consider going VFR into IMC, don't fly GA to get there!

Step -1: Exercise good Aeronautical Decision-Making (ADM) and do thorough preflight planning. Short of an unforecast overcast cloud deck appearing out of nowhere beneath you, you shouldn't ever find yourself in this position.

Step 0: The moment you think you might be forced to go VFR into IMC, you are in an emergency situation. Don't delay- declare an emergency to ATC and ask for help finding your way to a break in the clouds.

But suppose you are out of options and you need to descend through clouds. There are some major risks here:

  • Mid-air collision
  • Controlled Flight Into Terrain (CFIT)
  • Stall/spin
  • Spiral
  • Other Loss of Control In-flight (LOC-I)

Note: the next few steps are general advice. As usual, this may differ based on type, and you should follow your POH's instructions for an emergency descent through clouds if they differ.

Step 1: Plan your descent.

There's not much you can do about a midair collision. Declare an emergency to ATC (if you ignored the previous step and you haven't declared already) and have them clear the space for you. If you can't get a hold of ATC, do your best to avoid areas with heavy IFR traffic.

Avoiding CFIT mainly means picking a course through the clouds that has the most space between the cloud ceilings and the ground. ATC can help with this, and you may have some cockpit technology to help as well. If at all possible, you don't want to turn at all in the clouds, so try to find a straight course that will let you descend all the way through the cloud deck without turning.

If you will be relying on a compass to keep on course, an easterly or westerly heading is better to reduce compass errors. Of course, terrain considerations take precedence.

Step 2: set up the plane to fly itself as much as possible.

Point the plane on the course you want to descend through the clouds. Turn on full carb heat, if applicable. Set trim and power so the plane will fly at a moderate airspeed and descent rate with hands off the controls. Lock the throttle in place. The Cessna 152 POH recommends 70 knots and 500 to 800 fpm, but this will depend on the type. You don't want to be in slow flight, but any excess airspeed over that isn't doing you any good.

Once you have set up for this hands-off descent, put the ailerons in a neutral position and don't touch the stick again! If you don't touch the elevator, you can't stall or spin. It is much easier to avoid overcontrolling the plane if you avoid touching the ailerons. If you have an autopilot or wing leveler, use it!

In an ideal world, you would completely stop manipulating the controls entirely. Most planes will continue to fly themselves with no pilot input, and it is common for a disoriented pilot to fly themselves into a spiral dive. Unfortunately, most planes will eventually fly themselves into a spiral dive even with hands off. Which leads us to Step 3.

Step 3: Don't turn!

If you're not turning, you're not in a spiral dive. Watch the turn coordinator (if equipped) and the HI/HSI/compass. The most important thing in the world for you right now is that you are not turning. Make small, cautious adjustments to the rudder pedals as necessary to show wings level on the turn coordinator. Stop any trends that you see on the HI/HSI/compass. If you are using the compass, remember that there may be significant errors, especially on a northerly or southerly heading.

As long as you are not turning, you are not spiraling. As long as you don't touch the stick, you won't stall or spin. As long as you don't make abrupt or large inputs to the rudder, you hopefully should maintain control.

Coordination is not a concern. It's much better to be in a slight sideslip and not turning than it is to be perfectly coordinated and turning.

It's very important not to overcorrect. With incorrect or too aggressive inputs, you can induce a spiral dive within seconds. Most airplanes will take much longer to enter a spiral on their own accord.

You may enter a spiral dive despite your best efforts. Be ready to recover when you break out. Remember that pulling back is the one sure-fire way to die.

Step 4: When you break out, recover from the spiral dive if necessary. Don't pull the stick. Cut the throttle and level the wings. The nose will come up of its own accord as it seeks the trimmed airspeed. Don't pull. If the dive has developed and you are at high airspeeds, you may need to push to unload the wings.

Once you are in a usual attitude, resume normal VFR flight. Land as soon as possible. If the ceilings are low, you should seriously consider an off-airport landing rather than scud running in search of an airport.

Step 5: Learn from the experience.

If you've made it this far, congratulations! You've survived a VFR into IMC event and avoided becoming a statistic. Debrief. Figure out what went wrong and how to keep it from happening again. Fill out a NASA ASRS report, which will hopefully help other pilots from being in a similar situation and can protect you from certificate action if the FAA decides to go after you.

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    $\begingroup$ He said "no IMC instruments on board", which would mean no turn coordinator. $\endgroup$ Commented Aug 22, 2023 at 16:41
  • $\begingroup$ @quietflyer Just noticed that and made the edit. Anyway the TC isn't absolutely essential. It's just another tool to determine if you're turning. The lack of IMC instruments makes it even more essential that they not touch the ailerons. $\endgroup$
    – Chris
    Commented Aug 22, 2023 at 16:43
  • $\begingroup$ I would say the TC is absolutely essential unless certain very specific techniques are used to maximize the usefulness of the wet compass. See my answer for more... $\endgroup$ Commented Aug 22, 2023 at 17:14
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    $\begingroup$ I generally agree, but would strongly disagree that a mid-air collision is a major risk. It is a risk with severe consequences, but the odds of it happening at random in IMC are the least of any concerns with a flight. $\endgroup$ Commented Aug 29, 2023 at 13:22
  • $\begingroup$ Although I would disagree that planes are naturally stable without touching the ailerons. Certain planes are, and certain planes aren't. This conversation has come up about gliders, which can get more easily into this kind of IMC situation than many realize, and it's important to know if your glider is the kind where it will gently descend in a bank, or will increasingly fall over into a spiral. From my tests, the AC-5M will spiral down, so it's really important I never get caught above a cloud layer! $\endgroup$ Commented Aug 29, 2023 at 13:24
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Honestly, this is not a serious question. Long before you end up here you should have done something to prevent it in the first place. Didn't you notice the weather changing under you? When that happened you should have taken action to prevent ending up in this situation. But three options suggest themselves.

  1. If you are in contact, or can make contact, with an ARTCC controller, get him to give you a heading to the nearest place where the weather is not IMC, or where there is a hole you can let down through.

  2. If you have formation flying experience and are competent and proficient at it, another very risky, but possible alternative is to make contact with a nearby aircraft, join on their wing and fly formation on them as they penetrate the undercast and bring you down.

  3. Finally, in smooth air, if you at least have a turn & slip indicator and/or a mag compass, and know that the base of the undercast under you is sufficiently high enough above the ground, you could establish your aircraft in a stable, trimmed, wings level, constant airspeed glide with a small descent rate, and just let the plane take you down until you break out underneath. You would need to carefully monitor the turn and slip indicator as you descended through the clouds, and keep it neutral, also monitoring your heading for changes and applying small, very small, roll inputs to keep the turn & slip and compass stable as you descended. Even if you have practiced this, it will be very difficult. If you haven't practiced it, it will be near impossible. @quiet flyers more detailed answer below describes some considerations you should fully understand to attempt this.

Finally, I would not, I repeat, NOT, recommend slipping in the clouds, as the main risk in this scenario is spatial disorientation and any sideslip screws up your inner ear and creates a sense of tilting and turning that will make controlling the aircraft and keeping it stable much much more difficult.

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  • $\begingroup$ If you have WX information to know that the cloud base is of adequate height, you ought to be able to locate a safe place to descend in clear air. Now, if you let yourself run bingo fuel in this situation, you may be about to win a Darwin award... $\endgroup$
    – Zeiss Ikon
    Commented Aug 22, 2023 at 13:42
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    $\begingroup$ Not a serious question? It happens all the time. youtu.be/bLmzy8ZPgtc $\endgroup$
    – Cloud
    Commented Aug 22, 2023 at 15:06
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    $\begingroup$ @Cloud And the fact they generally end VERY badly for all involved should be the key takeaway. At all costs, you do NOT descend through cloud unless IFR rated in an IFR capable plane. Fly anywhere, bust airspace, call anybody, declare a MayDay, but do not penetrate the cloud. The takeaway isn't that there is a technique - the takeaway is that it's a fatal decision. airspace $\endgroup$
    – Dan
    Commented Aug 22, 2023 at 17:25
  • $\begingroup$ Re "also monitoring your heading indicator for changes and applying small, very small, roll inputs to keep the turn & slip and heading indicators stable as you descended. If you haven't practiced this, it will be difficult." -- the question appears to be phrased such that there are no gyro instruments. $\endgroup$ Commented Aug 22, 2023 at 20:33
  • $\begingroup$ @quietFlyer, I read that comment as just meaning no artificial horizon (attitude indicator), but I will edit answer to eliminate confusion. $\endgroup$ Commented Aug 23, 2023 at 12:52
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The second safest way would be to call for weather information and navigate to a landing site that has VFR conditions to descend and land, or look for a large enough opening in the cloud deck to descend through without requiring instruments (and yes, a forward slip plus flaps, if available, can help descend quickly without building excessive airspeed -- but you need to have practiced this first, because entering a slip incorrectly can also be unsafe). Flying into cloud without instruments like artificial horizon and the training to use them can lead to a "death spiral" because your inner ear can't reliably detect a descending turn until it has tightened enough to be in danger of breaking Vne (or the airplane). Not to mention that if you can't see, you can't avoid obstacles.

The safest way out of this condition is not to ever get into it. Call ahead for weather; choose not to fly when conditions are marginal or are forecast to become marginal; have alternative destinations planned in case conditions deteriorate while aloft, and descend below cloud deck before it closes in (and if that's too low to continue, land).

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What's the best way to get through clouds when not instrument rated?

...

Please also assume there are no IMC instruments on board, i.e. no artificial horizon etc.

...

I asked this at my club and someone suggested side slipping would be the best approach as you get through quickly and are less likely to experience unusual attitudes due to not pitching as much.

I would absolutely not sideslip, as it is not compatible with keeping your hands off the control yoke. You would have absolutely no idea whatsoever if you are continuing to maintain the "correct" amount of aileron input needed to exactly counter the roll torque caused (via slip-roll coupling) by your rudder input, or not. If you get it wrong, your bank angle starts to change-- perhaps toward more vertical.

As to what you might do instead--

I'm assuming by "no IMC instruments" you mean no gyro instruments of any kind, including gyroscopic heading indicator, and including turn rate indicator / turn coordinator. If you have either of those, I'd give a somewhat different answer.

I'm also assuming that you don't have a GPS.1

Is it turbulent, or is the air fairly smooth?

I've seen video of a Cessna 120 with no visible gyro instruments (the turn rate indicator was the only gyro instrument installed, and was intentionally covered up) and no GPS being kept wings-level in cloud in smooth air by using the wet compass to hold a southbound course, in the northern hemisphere. The aircraft was descended through about a thousand feet of cloud.

This would not likely work in too much turbulence, but works well when the air is fairly smooth.

It is critical to establish a southbound magnetic course (if flying in northern hemisphere) before entering cloud. On a southbound course, compass errors work in your favor-- the compass reacts in the same direction to banking as to turning, so it essentially anticipates the heading change that will soon result from a slight bank. On a northbound course, the compass gives hopelessly misleading indications to any significant bank. In the real word, if your heading deviates to have even a slight northerly component, you will probably lose control of the aircraft2, so stack the odds in your favor by selecting a due south magnetic course as your target.

Steering with rudder alone (so steering corrections are via a mixture of skidding plus mild roll rate due to slip-roll coupling) works best by far in a typical light plane, especially for a pilot who does not have a great deal of practice flying under the hood with this particular method, i.e. with no gyro instruments or GPS. Trim for a steady descent before entering cloud and then keep your hands off yoke, so that you do not accidentally over-control the aircraft either in pitch or in roll.

Incidentally, I've also seen a wet compass used, again by attempting to hold a southerly course in the northern hemisphere, to help a hang glider pilot hold course in cloud and successfully exit the cloud. In this case, the glider pilot was able to maintain a semblance of a controlled thermal circle in the cloud to gain several thousand feet of altitude by watching a rudimentary home-made piezoelectric-based turn rate indicator, but when he was ready to exit the cloud (goggles were starting to ice up), the GPS instrument he had available had far too much lag to allow a straight course to be maintained. (Consider that in any significant wind, the glider's ground speed may be near zero at times-- even with zero lag, a GPS is useless in such a case.) By using the turn rate indicator to maintain a very low turn rate until the compass was settled on a southerly course, and then transitioning to rely mainly or solely on the compass, the pilot was able to keep the glider on course and exit the cloud. These were obviously thermic conditions, considering the altitude gained-- which show that a wet compass still has some value even in conditions that are not glassy smooth. But entering more than the mildest of turbulence without some sort of actual turn rate indicator as a fallback, hoping to rely on the compass alone, would be an invitation to bad outcome. (As an aside: unlike paragliders, modern hang gliders, including the one involved here, are not inherently stable in roll. In the absence of corrective roll inputs, they inevitably slowly roll into a turn, which will eventually lead to a rather steep bank angle and high airspeed. Their characteristics in this area are much less "friendly" than those of a typical light airplane.)

In the magnetic "tropics", i.e. near the magnetic equator, the helpful characteristics of the compass that we see when flying on a southerly course in the northern magnetic hemisphere, or when flying on a northerly course in the southern magnetic hemisphere, vanish. (As do the unfavorable characteristics that we see when flying on a northerly course in the northerly magnetic hemisphere, etc.) An aircraft with a great deal of inherent roll stability might still be controllable by reference to the wet compass alone in such a situation, but an aircraft with milder positive roll stability, or any amount of inherent roll instability, would probably not be.3 The techniques described above rely heavily on the fact that given the proper choice of heading, the compass "errors" actually work to give a faster, stronger indication of any developing bank away from the intended course. In any event, all successful tests and demonstrations of such techniques that the author has knowledge of, were carried out at around 55 degrees of northerly magnetic latitude.

Then we have the "benign spiral maneuver" (see the related ASE question Would the benign spiral maneuver be one alternative to dealing with being "stuck above" or inside a cloud?) -- advocated as a way to descend through cloud in an emergency in some sailplanes-- with their long wingspans, gliders tend to be more spirally unstable, or less spirally stable, than most light airplanes, so perhaps the technique should be explored in light airplanes as well. I wouldn't rely on it in any aircraft that I hadn't personally confirmed it to work, including exploring the aircraft's response to intentional perturbations.

Disclaimer: don't try any of this at home.

Footnotes:

  1. If you do have a GPS, that opens up a whole can of worms-- what kind of GPS, and how best to use it? Some portable GPS's designed actually feature a aviation-style turn-rate-indicator display, based on ground-track-derived information, that makes a very functional substitute for a turn rate indicator as long as the wind speed is not so high that your ground speed drops near zero. On the other hand, if your GPS only has a heading-indicator-style display, how usable this will be for maintaining heading depends in large part on the update rate. My experience is that on a southerly heading at mid-latitude in the northern hemisphere, a wet compass is superior to a handheld GPS designed for general use (e.g. Garmin Etrex) for holding heading in a light airplane. And in any situation where the ground speed may approach zero (e.g. soaring in ridge or wave lift), there's no comparison. The discussion of whether and how to attempt to use a hand-held GPS to fly in cloud in an emergency situation really deserves its own specific question; this answer will focus on using the wet compass. But whatever you do, don't enable any magnetic-based heading function that your GPS may have. It suffers from most of the same errors as the wet compass, and will make the GPS essentially unusable in flight.

  2. This statement may sound a bit extreme. But consider that we'd like our method to have some resilience against not only the effects of any turbulence that may be present, but against any temporary inputs in the "wrong" direction on the pilot's part, due to either disorientation/ vertigo/ inability to rely solely on the instrument, or due to the simple awkwardness of having to always step away from the heading on the compass card that that represents the direction that you are trying to steer the aircraft toward. (Vertical card compasses avoid this problem.) In my experience it is very advantageous to choose a target course very near magnetic south, and it is challenging to keep the aircraft under control if the compass is allowed to show even a slight northerly component.

  3. This is a bit of a blanket statement-- obviously the amount of turbulence present, if any, is also a factor. Conventional "wet" compasses are also prone to errors other than the "northerly turning error" that we're focusing on here, such is those due to the inertia of the card. In smooth air, most aircraft could probably be controlled by reference to the wet compass alone even near the magnetic equator, but the more turbulent the air, the more the pilot is going to want some "help", either from strong inherent roll stability characteristics of the aircraft, or from the helpful "leading" effect that we see during any accidental deviations as we try to hold a course aimed toward the magnetic equator, at mid-magnetic-latitudes.

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  • $\begingroup$ Cessna recommends an easterly or westerly course, and that makes more sense to me. Certainly southerly is much better than northerly, but reacting to compass errors in a southerly direction seems more likely to lead to successive overcorrecting than a stable descent. It's not urgent to keep the plane from banking at all- you just want to avoid allowing a full-blown spiral to develop. Though this does rely on having some degree of stability typical of a light airplane, and your advice may very well be better for a hang glider. $\endgroup$
    – Chris
    Commented Aug 22, 2023 at 17:32
  • $\begingroup$ @Chris -- I've seen the Cessna manual, but I don't agree with it. I've played around with this a lot "under the hood" etc, and I would strongly recommend a southerly mag course, for the reasons described here. Experimental subjects include Ces 152, Ces 120, and a high-winged mid-engined pusher lightsport plane. $\endgroup$ Commented Aug 22, 2023 at 17:35
  • $\begingroup$ @Chris -- of course, in most aircraft, the compass is above the top of the glare shield, so there's no way to go "under the hood" and still see the compass. So the only way to legally do a hands-on exploration of this would seem to be in actual cloud under this sort of IFR clearance aviation.stackexchange.com/q/56680/34686 , perhaps with a safety pilot, and some sort of "reverse hood" blocking everything below the glare shield from the view of the experimenting pilot. So it's safe to say that there are few people who have hands-on experience exploring these techniques. $\endgroup$ Commented Aug 22, 2023 at 17:51
  • $\begingroup$ Re my earlier comment-- ""under the hood" etc"-- emphasis on the "etc". Use your imagination-- $\endgroup$ Commented Aug 22, 2023 at 17:52
  • $\begingroup$ Typos to fix-- "But entering cloud in more than the mildest of turbulence without some sort of actual turn rate indicator as a fallback..." Also "an aviation-style turn-rate-indicator" $\endgroup$ Commented Aug 29, 2023 at 15:30

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