How do pilots handle aircraft whenever it enters turbulence?

Primarily, the goal is to mitigate excessive force to the airframe. First and foremost, do not hurt the plane. And secondly, do not hurt the contents of the plane.

Way oversimplified, but that's all I could fit into a nutshell.

The long answer is far more varied. In a piston GA type plane, its pretty simple. In smooth air, you can fly up to the red line on the air speed indicator. In less than smooth air, the operating range is contained within the green arc on the ASI.

In the other extreme, jets operate in much tighter margins in order to get the best performance with the best efficiency. I'll let the more qualified folks here expound more on that, but with regard to turbulence, in addition to speed, weight and altitude really enter into the equation. It's been twenty years since my FE training days, but I think I recall factoring in a 1.5 G buffet when calculating speed and altitude.

Again, I'd rather the experts expand on that.

On jet airliners turbulance penetration includes a series of procedures. First you make sure the seat belt signs are on. Then it´s time to get the plane turbulance ready. The Thoughest part is speed control. Too fast and the plane goes into mach buffetting , too slow and it stalls. The higher the cruising altitude, the narrower the available speed band. In some cases the available speedband is a 20 - 30 kts indicated. The jet ignition is switched to continous ignition.The auto thrust is disconnected and thrust is adjusted manually to avoid the throttles being moved back and forth. The thrust limits of the fadec system is switched from cruise limit to maximum continous thrust. Keep the wings level and monitor the autopilot. If it cannot handle it take over. Rather loose or gain altitude instead of letting the speed out of control.... and try to get a different cruising altitude.

Isn't that what many call the "coffin corner?"

(Most (commercial)) aircraft have a turbulence penetration speed specified in the flight manual. At this speed, a certification level gust will not cause structural damage. You also have a margin to either stall speed (and yes, when these limits start coming together at high altitude is indeed what we call the coffin corner). You also try to fly smoothly, i e let the aircraft change altitude rather than to try to fight the draughts and stay at the same altitude, and to avoid power changes as stated previously.

Here's a rough outline from a handy AFM:

1) Avoid. Self-explanatory.

2) Secure aircraft (get yourself, everything and everyone strapped in).

3) Do not chase airspeed, but try to keep it in the vicinity of the penetration airspeed.

4) Avoid large power changes.

5) Use autopilot to the extent possible (but not IAS or ALT mode, VS/HDG mode recommended). Be prepared for A/P disconnects.
If hand-flying, use yaw damper and do not chase altitude. Avoid adjusting trim and fly on the AI, as altimeter, ASI etc may be misleading.

Close. As a big airplane climbs two things come into play. One is the low speed stall speed. Most of us are familiar with this. If you get the airplane too slow, it stalls and bad things happen. The second is just as serious and not nearly as well understood. It's called the high speed or mach buffet speed. I'm not very good at the really technical explanations. AirRabbit is da man if you want that. Any time that too great a lift demand is made on the wing, whether from too fast an airspeed (mach buffet) or from too high an angle of attack (stall) near the MMO, the "high-speed" buffet will occur. Simply put, you're outflying the capability of the wing. As you get higher in altituide the two speeds get closer together. Thus the term coffin corner.

Mach stall shares the separation of the smooth airflow from the surface of the wings with the "normal" stall. The reason for the separation differs though. In a mach stall, separation is caused by a shock wave forming on the wing due to supersonic airflow over the wing. Supersonic airflow over the wing occurs before the aircraft as a whole reaches supersonic speeds. In fact, airliners routinely cruise with local supersonic flow, but a mach stall is defined by the separation of airflow, not by the shock waves themselves.

As opposed to the normal stall, I wouldn't say it goes together with demanding too much lift from the wing, as it is really a speed related phenomenon. That being said, increasing the AoA and the lift generated does increase the speed of the local airflow over the top of the wing and thus will lower the airspeed at which a mach stall occurs. I'd like to call that an accelerated mach stall.

Again, the FAA choses an interesting way of describing an aerodynamical phenomenon and creates ample opportunities for misunderstanding...

I disagree. By exceeding the capability of the wing in a high speed environment you are indeed demanding too much lift from it. Or maybe a better way of putting it would be to say that you're asking it to do something that, given the conditions, it is not capable of doing. But in both the high speed and low speed environments it's a loss or a lack of lift and the result is a stall. Does it matter if the loss of lift is from a high AoA or boundary separation? Both result in not enough lift and the wing won't fly.

I've never been in a full blown high speed upset. I can remember two times in DC-8s that I could feel it coming on. The airplane was shuddering and there was an audible rumbling sound. We were too high, too heavy and too fast. The fastest fix is pretty simple. SLOW DOWN! I have talked to pilots who claim that they actually experienced a full blown mach buffet upset. They describe the events generally starting with only one wing stalling and then the airplane basically does an uncommanded descent. And it can take thousands of feet to recover the airplane. Another aspect is that it can sneak up on you if you aren't paying attention. You can be pushing the mach buffet speed in smooth air and getting away with it until you get into some turbulence. The wing loads up and mach buffet can spank you. That's what effte describes as an accelerated mach stall.

I've always thought more about the drag divergence and mach tuck if I get too close to Mach Crit...more than an accelerated mach stall. That nose goes over and you're out in the Q corner...you may very well bend the ship...which is a nice way of saying "get ripped into a thousand pieces"...

It's those "Mach Effects" that really rear their heads as that high speed margin comes down...the buffeting, the nose starting to dip...indications that you are pushing the center of lift too far back on the wings and starting to delve into the realm of test pilot...seeing how far you can push your craft in that flight envelope. Ranger said it...slow it down, Mario Andretti. You're a wake bump away from an elevator ride to h*ll...

At the lower levels and in a light aircraft, turb is bumpy and sometimes sudden as in a punch and can sometimes make you bang your head on the ceiling (rare unless the turb is from local mountains - even small mountains). Generally it feels worse than it actually is as the aircraft is simply moving with the `rude` airflow and excursions are short and . . . bumpy. With a little practice, it is easy to maintain Straight and Level but you are mega-tuned in and on the ball (scuse pun) If landing in turb (and yes, you have to land sooner or later. . . ) - if it is bad it is "almost" a wrestle - not with the controls but with keeping it straight and putting the aircraft exactly where you want it, i.e., on the centreline - it can be great fun if you do it all the time - or most alarming if you are not used to it. A fabulous way of getting to grips with the low level stuff (<1,000 ft agl) is to go up with your seasoned instructor while you are flying it and then you can grow into it. Best to avoid if possible especially if you are barely maintaining control of the aircraft. Also, your girlfriend sitting next to you may well cross you off her Christmas card list - as to a pax, it will be boring, scary and make them want to puke. Not recommend for taking the family for a "jolly" and a definate no-no for young children, for whom it would be cruel and most unfair and +ively terrifying. Not good. (and could put them off flying forever. . )

Is not the buffet caused by the inner wing root nearer the fuselage reaching mach crit - first?

Also, someone once said - If there is excursion on alt making alt hold difficult then knock of auto-throttle.
If there is excursion or rapid excursions making cabin service impossible and moving around the aircraft impossible then knock of A/P. Which sounds right, as the engines will be playing the Sword Dance trying to keep up and the A/P will probably go off in a huff anyway.

I'd say that depends on the airfoil. Usually you should be right though as the inner part of the wing has a thicker airfoil than the outer part. Therefore the laminar flow tends to rip off a bit sooner.
There are two different kinds of buffeting though. Low speed buffet and high speed buffet.

Low speed buffets are often a result of a relative high angle of attack. Somewhat like a stationary stall on the wing. If you pull the stick even harder the result will be a complete stall over the entire wing. These stationary stalls cause a high frequent shift of the center of lift relative to the wing. This can happen at any station of the wing though, depending on airfoil, angle of attack and the position of the ailerons, flaps or canards. This effect and the fact that most horizontal stabilizers are lying within the area of turbulence caused by the wing are noticed as concussions.

The high speed buffet is caused by airspeeds exceeding Mach crit. Mach crit (~M0.8) is the highest figure within transsonic flight not causing supersonic flow in ideal conditions though. It does happen stationary though but thats another matter. A wee bit above Mach crit. causes supersonic flow on top of the wing which then results in a shockwave building up from the trailing edge and causing static pressure jumps. The result is loss of laminar flow behind the shockwave. The interaction of various pressure values behind the wave and the trailing edge result in a loss of energie and higher drag. The shockwave also interacts heavily with the boundary layer and pulsates along the airfoil generating high tension/torsion forces on the wings structure again resulting in noticeable concussions. It is also likely that shockwaves happen to appear underneith the wing if airflow exceeds Mach>1. Putting all this together again adds up to a shift of the center of lift along the wing causing the buffet.


Hmm, now that I wrote all this and found some nice pics I can't even remember the question and why Istarted typing... Guess my bed is calling

Climb above the clouds.

Not necessarily. Turbulences or thermal air movement does not only occur within the zone of clouds. There are various forms of turbulence that can occur - even in clear and good weather.
The usual procedure is indeed to fly around bad weather zones and cruise alt is usually higher than most clouds. That was not the original question though...

Ranger is right, naturally, and chillspiller has got a cool post going there with the moving diagrams.

A little word on coffin-corner. dive in anytime, anyone, to refine the follwing but - coffin corner was more in the days of DC8 and 707s and at a very high altitude 41, 45 thou etc. this area wa interesting as the aircraft had climbed up to its operational ceiling probably heavy, where the air is very thin and travelling very fast near mach crit.
The coffin corner problem was: As you were so high and the air was so thin - you were not only near mach crit speedwise but you were also near the stall warner. So, if you approached Mach Crit and got either the buffet or other signs (what are the signs? well just look at the other posts here. . ) then the obvious answer would be to slow down.

Good game.
Good game.

The problem was, that to slow down meant that you also had to increase alpha (nose pitch up slightly) to maintain altitude - as - if you slow down then the aircraft will descend, a bit, more on that later. so, if you increase angle of attack (alpha) then you hit the stall warner [which can be 5 knots prior to an actual stall]. So, if you let it go down gently you then have the risk of hitting mach crit as anything that goes downhill, travels faster than anything climbing - nature. I KNOW we can descend without an inherent increase in airspeed but strange things occur at very high alt sometimes - like you raise the nose - stall warner. You lower the nose - stall warner. You raise the nose a tad and let it go and you get stall warner one and stall warner two. . . as it bounces from high nose att - to pitch down and back - all based on a changing, angle of attack. the `bounce` being a slight and gentle occilation of slight nz up to slight nz dn. L1011, leave it alone and it will fly fine = as for other aicraft - dunno.

Assuming you had got yourself boxed into a little corner where, you were so close to mach crit and so close to the stall condition as to render the `natural` descent impossible due to . . .excessive speed - then you were in theory, stuck.

Ranger is right and I will remember to slow down, but if we do that then we MUST accept a descent or, we are demanding an increase in alpha as we have just commanded a lower airspeed - and what happens to lift when you reduce the speed . . . ? see?

Yes, if there were turbulence clouds at the lower levels that may indeed ease the turb. If you attempt to avoid turb by climbing above the highest clouds, like, at the Tropopause - then you can still get Clear Air Turbulence - which compared to the low level stuff (SFC to 4,000` say,) is generally more severe and more violent - and has little if any visual clues. It can definately be found on the upper part of the core of a Jet-Stream on the polar side of the core - and, if you can find that then you can avoid it - it is difficult to establish where that is hence the term Clear Air Turbulence.

Also, not often mentioned but often experienced - is moderate to severe turb at high levels that comes from no-where - this is CAT too all it takes is a ribbon/river of air at quarter angles (from your 4 o`clock to your 10 o`clock) doing about 90 kts and fun you shall have. Happily though Met men and pilots DO keep one another posted by Pireps or Sigmets which are reports from pilots and relayed to the other pilots so a fair old picture can be established as to where the turb lies or rather at what levels they (the tibrs) are expected to be at - that way all the pilots avoid it/them, that is why you don`t spill your Dr. Pepper at FL330 when you are coming to London from the States, say. they also have deicated Met People rigging up all their electronic gear to pre-determine where the turb level are likely to be - like - consolidated technology.