Danger while turning during turbulence?

[claydice]

Turbulence by itself doesn't really worry me that much anymore. Turning by itself worries me a little more. However, turning during turbulence, when the plane is shaking, is what really worries me.

I was in a flight yesterday where the pilot was turning in turbulent conditions. I was looking out the window as the plane shook during the turn and in one occasion the plane jerked to the side it was turning. This actually happened both after the takeoff and during the final approach. It was very scary to say the least.

Is it possible for the plane to jerk too much to the side it is turning during turbulence, lose control and fall out of the sky? Can the turbulent conditions push the plane out of control on a turn? Did something like this happen in a crash in 1994 in Pittsburgh?

I fly a lot because of my job and it is a very stressful experience every time.

Thank you for your help.

[Captain Hutch]

Dear Claydice,

Thank you for you good questions. First, "Is it possible for the plane to jerk too much to the side it is turning during turbulence, lose control and fall out of the sky?" Theoretically, if the aircraft was well below normal flying speed, the angle of bank was steep enough, and the turbulence was severe enough, the wing on the inside of the turn could possibly stall and cause an out of control situation. However, let me put things into perpective. To my knowledge, and in my 40 years of aviation experience, I have not heard nor read of this particular situation happening. To give you a couple of numbers, the maximum degree of bank that airliners use is 30 degrees. At 30 degrees in a level turn 86% of the lift generated by the wings is used to maintain a level altitude. At 15 degrees of bank, 96% of the lift generated by the wings is used to maintain level flight. Normal airspeeds leave a wide margin above these levels to prevent a wing stall under these conditions. To anyone looking out the window at the wing as it dips to bank for the turn, even at a small bank the wing tip drops a noticeable amount below the horizon: for instance, for a 737 with the length of the wing being about 60' as measured from the center of the fuselage, the wing tip drops about 15 feet below the horizon in a 15 degree bank and about 30 feet in a 30 degree bank. So what I am saying is that even in a small banked turn you might think "wow, that wing is really dropping a lot". And even in the maximum bank of 30 degrees the flying speeds are so high as to be well above what detrimental effect any turbulence would cause.

The crash in 1994 near Pittsburgh involved a design flaw in the rudder hydraulics of the B737 that has since been corrected in all of the 737's flying today (I'm fairly certain of this, as it has long been corrected at my own airline). It so happened that at the extreme rudder pressure that the pilot was applying to change the direction of turn of the 737, the rudder actually moved in a direction opposite to that which the pilot was applying pressure. As I mentioned in another thread somewhere, it took several years of detective work to figure this one out, and for quite a while the murmuring was that the pilots had made a mistake. They were vindicated by a discovery by a very inquisitive engineer who tested the characteristics of the hydraulic fluid in the rudder chamber under conditions of extreme temperature and pressure.

Well, I hope this helps to put your mind at ease.

Hutch :tiphat:

[Barb-SAN]

To anyone looking out the window at the wing as it dips to bank for the turn, even at a small bank the wing tip drops a noticeable amount below the horizon: for instance, for a 737 with the length of the wing being about 60' as measured from the center of the fuselage, the wing tip drops about 15 feet below the horizon in a 15 degree bank and about 30 feet in a 30 degree bank. So what I am saying is that even in a small banked turn you might think "wow, that wing is really dropping a lot". And even in the maximum bank of 30 degrees the flying speeds are so high as to be well above what detrimental effect any turbulence would cause.

I flew back to San Diego from Portland yesterday, and had the good fortune to have a window seat in front of the wing ;) (yep, hovering over SWA online check-in precisely 24 hrs. before the flight, so got the A pass...:D ...and my favorite seat for photos, and even a clear day!!). You can see PDX about half-way between the winglet and Mt. Hood (white mountain on left side of photo). We were in the midst of a left banking turn to the south after taking off to the west. It SURE did seem like that wing dropped A LOT.

Capt. Hutch, can you tell from the photo what degree bank this is?

One reason I like the window seat is because I can get a visual confirmation of what my body is feeling while we are in the turns.

[Captain Hutch]

Barb-SAN,

That looks like a fairly shallow bank to me, maybe only 10 or 15 degrees or so. Hey, nice pic!

Hutch :)

[Barb-SAN]

Barb-SAN,
That looks like a fairly shallow bank to me, maybe only 10 or 15 degrees or so. Hey, nice pic!
Hutch :)
Thanks! I'll be looking forward to experiencing the 30 degree bank some day then...;) Looking down that long wing as it points toward the earth perhaps exaggerates the feeling of tipping.

Taking photos is one way of becoming slightly detached from the experience, and it's interesting to analyse them afterwards, look for identifying landmarks, etc. Everything happens so fast when you are actually flying...the turn is completed so quickly. Having a photo to study later is evidence of how much the plane really did tilt.

[CAflyer]

so pretty!

[tusphotog]

Barb,

That's not Portland. The Portland I know has rain, clouds and requires a jacket 300 days a year.

;)

I know that turn well. I experience it monthly. You must have flown down to San Jose or Oakland first, then went onward to SAN. As for steep bank angles, the only place I regularly experience one that's probably more than 10 degrees is out of SFO and OAK.

Here's a bit of a steeper climbing turn out of SAN heading eastbound after takeoff.

http://farm4.static.flickr.com/3111/3152477186_5d19b6d47d.jpg

[Barb-SAN]

Barb,
That's not Portland. The Portland I know has rain, clouds and requires a jacket 300 days a year.;)
Eh...see attached photo of ARRIVAL at PDX. Yes, there were clouds, rain, drizzle, spritzle, wind, cold etc. for most of the 10 days I was there, and I ALWAYS had on a jacket. It was such a relief to get away from the relentless sunshine and heat of San Diego. :tongue:
I know that turn well. I experience it monthly. You must have flown down to San Jose or Oakland first, then went onward to SAN.
Correct...we stopped at Oakland, didn't change planes, but did get new pilots for ours. Flying up from SAN, we stopped in Sacramento, but did not change planes or pilots.

I do like the new boarding system on SWA...much more civilized! Well, it's over a year old now, but it's the first time I've flown SWA since it was implemented.

I was wondering what happens to your boarding priority if you have to switch planes, e.g. on a route like I just did. Do you get two boarding passes when you check in online, one for each leg?

Tusphotog...love your photo...that's great lighting on the engine! Early morning?

[MathFox]

Yes, you get one boarding pass per leg. And because you can check in 24 hours before the first flight, you'll be pretty front of the line for the later flights if you check in early.

BTW, I got a reboarding pass on my last trip to the US (changed planes but kept the same flight number.)

[tusphotog]

Eh...see attached photo of ARRIVAL at PDX.

I was wondering what happens to your boarding priority if you have to switch planes, e.g. on a route like I just did. Do you get two boarding passes when you check in online, one for each leg?

Tusphotog...love your photo...that's great lighting on the engine! Early morning?

Ok, that's the Portland I know!

If you fly SAN-SMF-PDX and change planes in Sacramento, when you check in online you get checked in for both legs. You get BPs for both legs, and usually the second leg will generate a BP number that's lower since you're able to check in before the majority of people do. It's a pain if you're on a late morning or evening flight from a west coast hub (i.e. LAS or PHX) since everyone who is on connecting tickets from the east coast gets checked in before you.

Photo was shot in the late afternoon in December. I think around 3 or 4 pm, so about an hour before sunset.

[Barb-SAN]

Sorry to take the thread off the topic of turning and turbulence...I've started a SWA thread in the general discussion forum for this boarding pass issue. :) http://www.takingflight.us/forums/showthread.php?p=82907#post82907