dtwpilot225
Topic Author
Posts: 194
Joined: Tue Dec 13, 2011 1:31 am

737 tail shaking on power up

Mon Apr 03, 2017 8:39 pm

Hello, I was just wondering, I was watching a 737 takeoff yesterday and when they advanced the power I noticed the tail especially the leading edge of it shakes from the thrust of the engines. Obviously the 737 is a very safe aircraft but does this cause any long term damage or fatigue? Also second question, ehat did they actually change in the rudder system that prevents another disaster like the ones they had in the older models? Thanks!
 
User avatar
TWA772LR
Posts: 5282
Joined: Thu Nov 17, 2011 6:12 am

Re: 737 tail shaking on power up

Mon Apr 03, 2017 9:54 pm

I know they say the 737 is a dog, but this is ridiculous. ;)

Maybe it had to do with the air movement around the tail during take off and not the aircraft itself? Manufacturers do design the extremities of their aircraft to wobble as they move through the air. That actually makes it easier on the airframe itself; similar to how a skyscraper is designed to sway in high winds. I know stress tests for the wings are required and once they reach failure it is a very dramatic episode. It wouldn't surprise me if they have a similar test for horizontal stabilizer failure in the same fashion they do wing bend tests.
"It's not getting to the land of the nonrev that's the problem, it's getting back." ~~Captain Hector Barbossa
The thoughts and opinions shared under this username are mine and don't necessarily reflect those of my employer.
 
User avatar
77west
Posts: 871
Joined: Sat Jun 13, 2009 11:52 am

Re: 737 tail shaking on power up

Tue Apr 04, 2017 6:31 am

The 777 does this as well, in fact most airplanes will. The components are designed to be flexible precisely in order to prevent damage - so you will probably find that a fully rigid tail would fatigue at a greater rate than one with some "give"

They changed the rudder PCU valves - google 737 rudder to find more info.
77West - AW109S - BE90 - JS31 - B1900 - Q300 - ATR72 - DC9-30 - MD80 - B733 - A320 - B738 - A300-B4 - B773 - B77W
 
spudsmac
Posts: 260
Joined: Tue Feb 19, 2008 10:36 pm

Re: 737 tail shaking on power up

Wed Apr 05, 2017 5:48 pm

Didn't they also increase the approach speed so that if there is a rudder hardover the pilots will have enough control authority to keep the plane from continuing the roll?
 
User avatar
litz
Posts: 2036
Joined: Wed Dec 24, 2003 6:01 am

Re: 737 tail shaking on power up

Wed Apr 05, 2017 7:26 pm

Not sure about the approach speed, but pilots were trained once the hardover situation was understood (before the cause was found) in how to safely recover the airplane if it happened (by applying opposite aileron), and it was this training that helped the Eastwinds flight safely recover from the event. Even at the speed they were going, they could very easily have gotten into an unrecoverable situation w/out the training.
 
User avatar
CALTECH
Posts: 2967
Joined: Thu May 17, 2007 4:21 am

Re: 737 tail shaking on power up

Thu Apr 06, 2017 6:09 am

dtwpilot225 wrote:
Hello, I was just wondering, I was watching a 737 takeoff yesterday and when they advanced the power I noticed the tail especially the leading edge of it shakes from the thrust of the engines. Obviously the 737 is a very safe aircraft but does this cause any long term damage or fatigue? Also second question, ehat did they actually change in the rudder system that prevents another disaster like the ones they had in the older models? Thanks!


If the tail didn't shake, it would lead to more fatigue cracking. During High Power engine runs, the whole airplane is bouncing so much, it's hard to read the instruments.

https://www.youtube.com/watch?v=ZqM0HXtlSAE

https://www.youtube.com/watch?v=cEgiqCZLJqQ

https://www.youtube.com/watch?v=ChS3p3G44NQ

Quick pic of rudder system changes

Image
The gun is a precious Symbol of Freedom
Criminals are the deadly cancer on American society
Those who believe otherwise are consumed by an ideology
That is impervious to evidence of tyrants who disarm their citizens
 
User avatar
Faro
Posts: 1620
Joined: Sun Aug 12, 2007 1:08 am

Re: 737 tail shaking on power up

Thu Apr 06, 2017 9:59 am

Phenomenon is more acute with application of reverse on landing...quite striking sometimes how much the tail will shudder...


Faro
The chalice not my son
 
BHM
Posts: 9
Joined: Sun Aug 28, 2016 2:03 am

Re: 737 tail shaking on power up

Thu Apr 13, 2017 2:55 pm

Caltech, that second video was amazing. Thanks for sharing!
 
User avatar
DFWflightpath
Posts: 52
Joined: Sun Dec 21, 2014 4:55 pm

Re: 737 tail shaking on power up

Thu Apr 13, 2017 5:31 pm

question related to the high power test runs in the videos: how are brakes and chocks able to keep aircraft from moving when the engines are at TOGA thrust levels?
 
User avatar
7BOEING7
Posts: 2612
Joined: Fri Oct 12, 2012 5:28 pm

Re: 737 tail shaking on power up

Thu Apr 13, 2017 6:07 pm

DFWflightpath wrote:
question related to the high power test runs in the videos: how are brakes and chocks able to keep aircraft from moving when the engines are at TOGA thrust levels?


One could just say --because they are but....

In normal production Boeing airplanes with high thrust engines 747,767,777 & 787 are not taken to full thrust in the chocks to prevent possible damage. The first time the engines see full thrust "on wing" is during a taxi run up to about 80+/- kts prior to the initial B-1 takeoff.

By far the most spectacular horizontal tail movement at high power was a 757.
 
mcdu
Posts: 1083
Joined: Thu Apr 28, 2005 5:23 am

Re: 737 tail shaking on power up

Fri Apr 14, 2017 1:43 pm

spudsmac wrote:
Didn't they also increase the approach speed so that if there is a rudder hardover the pilots will have enough control authority to keep the plane from continuing the roll?


No the speeds were not increased for rudder hard over The speeds were increased because the airplane has geometric limits with flare and to reduce the risk of tail strikes.
 
trnswrld
Posts: 1146
Joined: Sat May 22, 1999 2:19 am

Re: 737 tail shaking on power up

Sat Apr 15, 2017 11:57 am

DFWflightpath wrote:
question related to the high power test runs in the videos: how are brakes and chocks able to keep aircraft from moving when the engines are at TOGA thrust levels?


Not only might they not be at full power, but I believe it's only one engine at a time. I could be wrong though.



This has always been my favorite engine run up video. You don't see the entire aircraft, and it's not even an HD video, but good god this engine screams!! The condensation and little tornados inside the engine look like some sort of black hole or time warp lol. The engine shakes like crazy. I don't know how they can make engine mounts that can handle this kind of power. Watch at 2:20, it's pretty cool they reduce power then push it back up to what seems like very high thrust settings and you just get a real sense of the amount of power.

https://youtu.be/waDeveWle54
 
User avatar
CorpCareer
Posts: 12
Joined: Mon Apr 10, 2017 7:05 am

Re: 737 tail shaking on power up

Mon Apr 17, 2017 11:34 am

spudsmac wrote:
Didn't they also increase the approach speed so that if there is a rudder hardover the pilots will have enough control authority to keep the plane from continuing the roll?


Yes, good memory....Reference https://en.wikipedia.org/wiki/USAir_Flight_427
New to Aviation or is your career in a holding pattern?
PM me for a free consultation.
 
User avatar
CorpCareer
Posts: 12
Joined: Mon Apr 10, 2017 7:05 am

Re: 737 tail shaking on power up

Mon Apr 17, 2017 11:36 am

trnswrld wrote:
DFWflightpath wrote:
question related to the high power test runs in the videos: how are brakes and chocks able to keep aircraft from moving when the engines are at TOGA thrust levels?


Not only might they not be at full power, but I believe it's only one engine at a time. I could be wrong though.



This has always been my favorite engine run up video. You don't see the entire aircraft, and it's not even an HD video, but good god this engine screams!! The condensation and little tornados inside the engine look like some sort of black hole or time warp lol. The engine shakes like crazy. I don't know how they can make engine mounts that can handle this kind of power. Watch at 2:20, it's pretty cool they reduce power then push it back up to what seems like very high thrust settings and you just get a real sense of the amount of power.

https://youtu.be/waDeveWle54


Bad ass video!!!!!
New to Aviation or is your career in a holding pattern?
PM me for a free consultation.
 
User avatar
CorpCareer
Posts: 12
Joined: Mon Apr 10, 2017 7:05 am

Re: 737 tail shaking on power up

Mon Apr 17, 2017 11:58 am

mcdu wrote:
spudsmac wrote:
Didn't they also increase the approach speed so that if there is a rudder hardover the pilots will have enough control authority to keep the plane from continuing the roll?


No the speeds were not increased for rudder hard over The speeds were increased because the airplane has geometric limits with flare and to reduce the risk of tail strikes.


Correct me if I am wrong but I believe Spudsmac is referring to the Approach flap setting of 1-10 on the B737 due to the rudder hardover incident on USAir flt 427. In that case they did increase the block speeds for flaps 1-10 in March of 1999.

However I believe MCDU you are referencing (Vref) which is the speed in which you would cross the threshold at on approach....That's the only speed that makes sense with your point. I don't believe that is the speed that Spudsmac was referring to.
New to Aviation or is your career in a holding pattern?
PM me for a free consultation.
 
mcdu
Posts: 1083
Joined: Thu Apr 28, 2005 5:23 am

Re: 737 tail shaking on power up

Mon Apr 17, 2017 12:46 pm

CorpCareer wrote:
mcdu wrote:
spudsmac wrote:
Didn't they also increase the approach speed so that if there is a rudder hardover the pilots will have enough control authority to keep the plane from continuing the roll?


No the speeds were not increased for rudder hard over The speeds were increased because the airplane has geometric limits with flare and to reduce the risk of tail strikes.


Correct me if I am wrong but I believe Spudsmac is referring to the Approach flap setting of 1-10 on the B737 due to the rudder hardover incident on USAir flt 427. In that case they did increase the block speeds for flaps 1-10 in March of 1999.

However I believe MCDU you are referencing (Vref) which is the speed in which you would cross the threshold at on approach....That's the only speed that makes sense with your point. I don't believe that is the speed that Spudsmac was referring to.



He said approach speeds, which is Vref. Maneuvering speeds are what you are talking with anything less than landing flaps. And in that case the answer is no. In the classics they manipulated the maneuvering speeds. In the NG they didn't, new wing and new rudder PCU.
 
User avatar
CorpCareer
Posts: 12
Joined: Mon Apr 10, 2017 7:05 am

Re: 737 tail shaking on power up

Mon Apr 17, 2017 1:15 pm

yes that's true MCDU, but sometimes people don't always say what they mean....Given the nature of the crash and the configuration of the aircraft at the time of the crash which wasn't in the landing configuration I assumed he meant the flap block speeds for 1-10 and wasn't referring to Vref..My fault if that's what he was referring to
New to Aviation or is your career in a holding pattern?
PM me for a free consultation.
 
User avatar
a36001
Posts: 276
Joined: Sun Sep 09, 2012 2:47 am

Re: 737 tail shaking on power up

Tue Apr 18, 2017 9:36 am

If you YouTube KPAE you will see just how much movement the vertical and horizontal tail moves when takeoff power is applied especially on the 777's! Every plane nut must watch these videos they are amazing!:-)
 
dtwpilot225
Topic Author
Posts: 194
Joined: Tue Dec 13, 2011 1:31 am

Re: 737 tail shaking on power up

Wed Apr 19, 2017 12:31 pm

Thanks for all the responses
 
User avatar
CALTECH
Posts: 2967
Joined: Thu May 17, 2007 4:21 am

Re: 737 tail shaking on power up

Sun Apr 30, 2017 9:57 pm

DFWflightpath wrote:
question related to the high power test runs in the videos: how are brakes and chocks able to keep aircraft from moving when the engines are at TOGA thrust levels?


For high power engine runs, the aircraft is loaded with A LOT of fuel, and if one engine is taken to Takeoff Power, the other engine engine is usually brought up with power, to flight idle, 70 % N1 or what ever the manufacturer states, to balance out the loads on the airplane.

Usually just brakes, no chocks, as the aircraft had to taxi to the approved engine run area.

At Denver Stapleton, running engines at high power in Fort Apache, was fun in the winter when ice and snow covered the ground...........

The shaking is scary for some the first time..........

http://www.youtube.com/watch?v=Du_TUbdWWcY
The gun is a precious Symbol of Freedom
Criminals are the deadly cancer on American society
Those who believe otherwise are consumed by an ideology
That is impervious to evidence of tyrants who disarm their citizens

Who is online

Users browsing this forum: Overthecascades, phugoid1982 and 26 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos