TimePilot
Topic Author
Posts: 290
Joined: Sat Sep 03, 2005 10:40 pm

### Turbulence - Various Questions

I have read that turbulence is like a car driving over a bumpy road. If a car drives over bumps fast, then bumps are felt less than if that car were driving slow. Is this also true with aircraft? Is this why landing is such a critical phase of flight?

What does the altimeter do during light to moderate turbulence? Does is register anything?

It's been said that turbulence is for the most part harmless, but even if an aircraft is shaken from side to side? The autopilot still has no trouble with that? There is no danger?

How do people who are afraid to fly deal with bumpiness? I found on my recent flight, that it eventually either puts me to sleep if it's repetitive and uniform (that surprised me) or if I concentrated on something else like the movie playing, it didn't bother me as much.

Starlionblue
Posts: 17639
Joined: Fri Feb 27, 2004 9:54 pm

### RE: Turbulence - Various Questions

 Quoting TimePilot (Thread starter):I have read that turbulence is like a car driving over a bumpy road. If a car drives over bumps fast, then bumps are felt less than if that car were driving slow. Is this also true with aircraft?

I think that description is more about the sensation. Typically aircraft do not drive "full speed" through moderate turbulence. Airliners have what is known as a "turbulence penetration speed" which reduces stresses on the airframe.

 Quoting TimePilot (Thread starter):Is this why landing is such a critical phase of flight?

Nope. Landing is critical because it tends to be the part of flight that puts the most stress on the flight crew.

 Quoting TimePilot (Thread starter):What does the altimeter do during light to moderate turbulence? Does is register anything?

That depends on the sensitivity of the altimeter and how much turbulence there is. In theory the altimeter registers any change in altitude. Since a pressure altimeter derives altitude from pressure, there may be other factors.

 Quoting TimePilot (Thread starter):It's been said that turbulence is for the most part harmless, but even if an aircraft is shaken from side to side? The autopilot still has no trouble with that? There is no danger?

Side to side, up and down. Aircraft are built to take it.

Autopilots typically can take a certain deviation from their course. If turbulence is severe the deviation becomes too much and the autopilot shuts off (with all sorts of warnings). As for danger, it depends on how much turbulence. Like any atmospheric phenomenon turbulence should not be dismissed as always harmless. However it takes severe turbulence (as in, without your seatbelt you would be thrown out of your seat) to pose a practical threat to the integrity of the airframe (unless the pilots are screwing up by the numbers).

The best thing to do about severe turbulence is to avoid it if possible. Modern reporting helps.

I once heard a pilot say: "Don't worry about turbulence. Worry about windshear".

 Quoting TimePilot (Thread starter):How do people who are afraid to fly deal with bumpiness?

We try to distract ourselves with books and movies and alcohol.   I used to be scared of turbulence. Not so much anymore. I guess habit helps.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

mjlhou
Posts: 149
Joined: Mon Sep 04, 2006 7:23 am

### RE: Turbulence - Various Questions

Actually......turbulence is the opposite. The faster the aircraft is going, the worse the turbulence will be. Often times when we are flying through heavy turbulence especially on approach....the captain will request ATC to slow if ATC doesn't already give the direction before the request is made.

[Edited 2006-09-05 04:40:22]
Don't worry about things you can't change or control

flymatt2bermud
Posts: 551
Joined: Tue Jan 31, 2006 11:58 am

### RE: Turbulence - Various Questions

There are many types of turbulence.
Turbulence Reporting Criteria Table

Intensity
Aircraft Reaction
Reaction Inside Aircraft
Reporting Term-Definition

Light
Turbulence that momentarily causes slight, erratic changes in altitude and/or attitude (pitch, roll, yaw). Report as Light Turbulence; 1
or
Turbulence that causes slight, rapid and somewhat rhythmic bumpiness without appreciable changes in altitude or attitude. Report as Light Chop.
Occupants may feel a slight strain against seat belts or shoulder straps. Unsecured objects may be displaced slightly. Food service may be conducted and little or no difficulty is encountered in walking.
Occasional-Less than 1/3 of the time.

Intermittent-1/3 to 2/3.

Continuous-More than 2/3.

Moderate
Turbulence that is similar to Light Turbulence but of greater intensity. Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times. It usually causes variations in indicated airspeed. Report as Moderate Turbulence; 1
or
Turbulence that is similar to Light Chop but of greater intensity. It causes rapid bumps or jolts without appreciable changes in aircraft altitude or attitude. Report as Moderate Chop.1
Occupants feel definite strains against seat belts or shoulder straps. Unsecured objects are dislodged. Food service and walking are difficult.

 Quoting TimePilot (Thread starter):I have read that turbulence is like a car driving over a bumpy road. If a car drives over bumps fast, then bumps are felt less than if that car were driving slow. Is this also true with aircraft?

It all depends upon the type of turbulence you encounter. Turbulence is caused by unstable air, it can be created from several factors from light winds, to frontal systems, to mountain waves and extreme thunderstorms which can contain more force than an atomic bomb. On most small aircraft the airspeed indicator has a white (flaps extended) arc, a green (normal flight) arc, a yellow (smooth air, minimal control forces) arc and at the top the red line. Speeds on turbine aircraft are typically placarded. There are no yellow arcs but a turbulent air penetration speed which typically varies with the total aircraft weight. Glass cockpits have varying identifiers depending upon the manufacturer to provide airspeed references and limitations.
Once an aircraft enters turbulence it is standard procedure to not to exceed the applicable turbulent air penetration speed.

 Quoting TimePilot (Thread starter):Is this why landing is such a critical phase of flight?

Landing is a critical phase because the pilot or crew have many things to be aware of turbulence is only one item. Airspeed and altitude control, traffic separation, proper navigation and interpreting and following instructions are some others. Turbulence, cross wind components but even more important wind gusts can have very dramatic effect on the stability of an aircrafts approach. Pilots must be aware of all clues to maintain awareness and react appropriately such as increasing your approach speed at a factor to compensate for the wind gusts.

 Quoting TimePilot (Thread starter):What does the altimeter do during light to moderate turbulence? Does is register anything?

The altimeter should give you a reading of your altitude. If the static ports are affected by unstable air it can make the altimeter look like a high speed windshield wiper. It is always showing something, question is can your eyes keep up with it. Basically your just taking into considerations averages. It maybe that you pay more attention to your radar altimeter (which shows height above ground up to 2,500').

 Quoting TimePilot (Thread starter):It's been said that turbulence is for the most part harmless, but even if an aircraft is shaken from side to side? The autopilot still has no trouble with that? There is no danger?

Again, this depends upon the turbulence. We read accident reports about aircraft (from single engine, to turbo props to corporate jets) breaking up inflight, to say turbulence is 'harmless' is inaccurate. However, most light turbulence should not cause structural failure by itself. The autopilot, may or may not keep up with the turbulence. Depends on the level of turbulence and the type of autopilot.

 Quoting TimePilot (Thread starter):How do people who are afraid to fly deal with bumpiness?

To each his own, I think alot of it depends upon your orientation and understanding of what turbulence is and what is creating the turbulence you are in. If it's a big thunderstorm perhaps you should be afraid.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci

HAWK21M
Posts: 30002
Joined: Fri Jan 05, 2001 10:05 pm

### RE: Turbulence - Various Questions

 Quoting TimePilot (Thread starter):Is this why landing is such a critical phase of flight?

Probably because thats when the Aircraft is moving from Air to Ground which makes it all the more Important.

 Quoting TimePilot (Thread starter):How do people who are afraid to fly deal with bumpiness

I guess its a habit.one has to get used to.

 Quoting TimePilot (Thread starter):What does the altimeter do during light to moderate turbulence? Does is register anything?

Not unless the Variation is large.You would not notice it as you would probably be watching the Weather radar more closely at that trime
regds
MEL
I may not win often, but I damn well never lose!!!

YYZYYT
Posts: 918
Joined: Tue Apr 05, 2005 12:41 am

### RE: Turbulence - Various Questions

 Quoting HAWK21M (Reply 4):Quoting TimePilot (Thread starter): Is this why landing is such a critical phase of flight? Probably because thats when the Aircraft is moving from Air to Ground which makes it all the more Important.

He beat me to it!
In addition to all of those things that FlyMatt2Bermud mentioned, it all comes down to a simple equation:

airplane + ground = bad news

unless you get it exactly right.

AirWillie6475
Posts: 2372
Joined: Thu Jan 27, 2005 1:45 pm

### RE: Turbulence - Various Questions

I have read that turbulence is like a car driving over a bumpy road. If a car drives over bumps fast, then bumps are felt less than if that car were driving slow. Is this also true with aircraft? Is this why landing is such a critical phase of flight?
No, when there is turbulence you slow down, maybe not much in jet aircraft but in small planes such as Cessna 172s as soon as you encounter turbulence you have to lower the engine rpm to minimum cruise. 2 reasons for this, you feel the turbulence less and it's easier on the airplane. As far as the last question, landing is the hardest part of flying, it may not seem like it to the passengers in the back enjoying the view, but it is. I guarantee you if you ask an ordinary person what is the hardest part of flying they will say takeoff but to the pilots that's the easy part, landing takes a lot of planing and concentration.

[Edited 2006-09-07 04:36:07]

wilco737
Posts: 7275
Joined: Sun Jun 20, 2004 12:21 am

### RE: Turbulence - Various Questions

 Quoting TimePilot (Thread starter):Is this why landing is such a critical phase of flight?

Every landing is just a controlled collision with a planet

Sometimes smooth, sometimes less smooth and sometimes hard :S

The altimiter doesnt move a lot during light or moderate turbulence...

I was once stucked between two thunderstorm clouds (CB's) and this was REALLY bad! We had already slowed down to the desired speed for turbulence, but then it hit us hard... The Autopilot disengaged and we took over manual control! The altitude gain and loss was +/- 300 feet from our cleared level and even bank angles up to 30°... so it was not really comfortable! Thank god everybody was on their seat, as well then F/A... Otherwise it would've been pretty bad...
For the aircraft? No Problem at all! didnt get too high G loads or anything... After 30 seconds flight was smooth again...

The more difficult part for us pilots is to hit the buttons in the cockpit when it is shaking so much   Ever tried to change the channel on the radio on a bumpy road at 100mph? not so easy...

WILCO737

Starlionblue
Posts: 17639
Joined: Fri Feb 27, 2004 9:54 pm

### RE: Turbulence - Various Questions

 Quoting WILCO737 (Reply 7):For the aircraft? No Problem at all! didnt get too high G loads or anything... After 30 seconds flight was smooth again...

As I understand it, airliner wings will tend to unload if high g loads are becoming dangerous. But I may be misunderstanding.

 Quoting WILCO737 (Reply 7):The more difficult part for us pilots is to hit the buttons in the cockpit when it is shaking so much Wink Ever tried to change the channel on the radio on a bumpy road at 100mph? not so easy.

Pilot flying: "Oops..."
Pilot not flying: "'Oops'? What do you mean, 'oops'?"
PF: "I wanted to change the radio channel, but I think I accidentally vented the atmosphere from the cabin."
PNF: "Ah well... At least they won't be complaining about service being suspended..."
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

ThrottleHold
Posts: 547
Joined: Tue Jul 18, 2006 11:00 pm

### RE: Turbulence - Various Questions

 Quoting WILCO737 (Reply 7):The more difficult part for us pilots is to hit the buttons in the cockpit when it is shaking so much

Not as difficult as trying to hold onto your cup of coffee........especially when the caffeine is the only thing keeping you awake because of dreadful rosters!!

TimePilot
Topic Author
Posts: 290
Joined: Sat Sep 03, 2005 10:40 pm

### RE: Turbulence - Various Questions

 Quoting Starlionblue (Reply 1):I guess habit helps.

That's what I'm starting to think. I usually fly once a year (the route in my sig.) At most I fly 3 times a year.

Perhaps if I flew once a month I wouldn't be so nervous. Alas I don't have the ¥¥¥ ... and no place to go, really.

Starlionblue
Posts: 17639
Joined: Fri Feb 27, 2004 9:54 pm

### RE: Turbulence - Various Questions

 Quoting TimePilot (Reply 10):Quoting Starlionblue (Reply 1): I guess habit helps. That's what I'm starting to think. I usually fly once a year (the route in my sig.) At most I fly 3 times a year. Perhaps if I flew once a month I wouldn't be so nervous. Alas I don't have the ¥¥¥ ... and no place to go, really.

I think it takes more than once a month. Anyway I don't pay for all my trips. I get someone else to do it for me. Unfortunately I am expected to work and such when I'm away. Bummer.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

TimePilot
Topic Author
Posts: 290
Joined: Sat Sep 03, 2005 10:40 pm

### RE: Turbulence - Various Questions

Once a month isn't enough? How often do people here suggest I fly then?

FlyboySMF2GFK
Posts: 193
Joined: Sat Mar 20, 2004 6:13 am

### RE: Turbulence - Various Questions

 Quoting TimePilot (Thread starter):What does the altimeter do during light to moderate turbulence? Does is register anything?

A lot of the jet-jockeys here can probably reflect back to their piston-powered days and remember how much the "steam-gauge" needles bounce around during moderate and severe turbulence. I think someone mentioned a windshield wiper...

Don't know if it's the same with ADCs running glass cockpits.

Starlionblue
Posts: 17639
Joined: Fri Feb 27, 2004 9:54 pm

### RE: Turbulence - Various Questions

 Quoting Timepilot (Reply 12):Once a month isn't enough? How often do people here suggest I fly then?

Quite honestly, it took 5-8 flights a month for half a year to really "cure" my anxiety during turbulence. Your results may vary.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

allstarflyer
Posts: 3264
Joined: Mon Jan 10, 2005 7:32 am

### RE: Turbulence - Various Questions

 Quoting Starlionblue (Reply 1):The best thing to do about severe turbulence is to avoid it if possible. Modern reporting helps.

Agreed. The Pireps reported on the ADDS page of NOAA's website is the one I mainly use.

 Quoting FlyMatt2Bermud (Reply 3):To each his own, I think alot of it depends upon your orientation and understanding of what turbulence is and what is creating the turbulence you are in. If it's a big thunderstorm perhaps you should be afraid.

Yeah, definitely. But, then, if it's a big thunderstorm (and you're on a commercial flight), either it's a pop-up t-storm (which can happen) or else the person who dispatched your flight and/or the PIC and/or the controller is a real idiot for not checking the radar, reading the pireps, SIGMETS and forecasts and for not checking current flow of traffic. In a nutshell, it obviously pays to plan ahead.

 Quoting YYZYYT (Reply 5):airplane + ground = bad news unless you get it exactly right.

No truer words said about this. It's particularly troubling when coming upon landing and a cross-wind is buffeting the a/c. Fun to watch the looks of relief after landing (safely   ), though.

-R
Living the American Dream

flymatt2bermud
Posts: 551
Joined: Tue Jan 31, 2006 11:58 am

### RE: Turbulence - Various Questions

 Quoting WILCO737 (Reply 7): Every landing is just a controlled collision with a planet

I'll have to remember that next time I brief the cabin prior to landing:
"Folks, we're number 1, the tower has cleared to us to collide with ah.... Earth, yes! So, please check the security of your seat belts!"

[Edited 2006-09-19 18:33:12]
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci

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