727-200 problem

[urpi]

Hi guys, I work for a cargo airline in SE Asia and I`ve had a problem a couple of days ago that I will like to share and maybe get some feedback from experience pilots and mechanics as well. I fly a 727-200 with -7 engines and after take off passing 3000 to FL180 we heard something like a compressor stall and after that we were entering a dashroll, we were able to control the aircraft, and we landed, after that during the inspection we found that the tail pipe of No 2 engine blowout in flight and the thrust came out asymetrically thats why the dashroll due to the irregular thrust and the yaw damper fighting that force, we disconnect upper yaw damper and reduced speed, and reduced pwr on no2 eng, therefore we flew at about 200kts IAS,
we have never seen such a thing like that and and thought that probably could be the result of metal fatigue but not sure. I like to hear your comments and may be able to send some pictures if want to see that.

Thanks,

urpi

 

[Thedude]

First off, what is a dachroll? I assume oyu meant dutch roll. If you did blow out the tail pipe of the #2 engine, very unusual, that engine is centerline thrust and if by some strange reason the thrust came out assymeteric the simple fix would be to reduce the power form #2. By turning off both yaw dampers, you put yourself in a situation to actually create a dutch roll is you were at a higher speed. Why would you disconect the upper vs the lower damper? As far as the unbalanced thrust goes when you actually loose #1 or #3 very little rudder is needed since all those egines are so close together. Either you have very low experience and did really know what was happeneing or this story is very fishy. I would like to see the pictures.
By the way I have about 4000hrs on the 727, -17 power

 

[urpi]

727

According to our maint department, the failure occured due to a very small crack on the tail pipe, which as a result we had part of the right side separated, and the engine blast had a more effect over the right side of the tal pipe, inducing a dutch roll at slow speed, The Cap. has over 22k flying hours and over 7k on 727, we disconnect the Yaw Damper because because it had a report on the last flight, and when we did that we came off the dutch roll and maintained no more than 210 IAS until the appch. Send me your email I will send you the pics.

urpi

 

[LR25]

Dude! I hate to do this, and I stay away from comments like yours, but I cant hold back.

I remember when FI was a pretty good place for info and help etc;, but ego's like yours that are rampant on here now have really degredated the community.

The guy was just trying to share and gain knowledge. I dont think he did it to let on he was a 727 king.

URPI, I hope this does not hijack your thread.

 

[urpi]

sorry don't mean to be an a...hole, is just that the people that is working here, has experience and never seen such a thing like that, well we found some cracks around the root of #2 eng tail pipe, off course maint here is not like in the us, I tried to put the pictures here but It didn't work, I will send you the pictures by mail.

 

[AirCobra]

I have a comment for the dude too or anyone else out there with more 727 experience than me. Does turning off the yaw dampers at low altitude affect the dutch roll characteristics that much? Thedude stated "By turning off both yaw dampers, you put yourself in a situation to actually create a dutch roll is you were at a higher speed. Why would you disconect the upper vs the lower damper?".

The reason I am asking is the limitation on the 727 requires the yaw dampers be operative above flight at 30,000 feet. Urpi said they were only at 3000 ft. The second reason is the first yaw damper speed restriction is at 25,000 where the limit is 350 knots. Since netiher of these limits came into play, how much of a factor would turning off the yaw dampers be when it came to compensating for dutch roll, since I don't normally associate dutch roll with low altitude flight?

I think this was not really dutch roll which I associate with aerodynamic factors, this seems more like asymmetric thrust which may have felt like dutch roll but was not dutch roll in true terms.

I think turning off the upper damper was the right move since the upper rudder only operates off low power (around 800 psi) from the B system. At low airspeeds the lower rudder operates off high power (around 2600 psi) from the A system, so this would give the captain full contol authority and not have a second yaw damper fighting the control inputs.

Any thoughts on this or am I offbase?

 

[urpi]

the problem is that the assymetric thrust because the exaust pipe is broken in pieces, therefore will try to push you towards one side and with the yaw dampers connected they will try to correct the problem, creating two forces pushing inducing the dutch roll, that's why disconnecting them and reducing pwr in # 2 eng helps controlling the aircraft. remember we were accelerating at the time we had the incident. thanks for your comment

 

[bubbers44]

urpi, I have had two yaw problems with the 727, one right after take off where I turned off the yaw damper that was showing the movement and causing considerable yaw problems. The second was at altitude cruising and an occasional yaw would happen so turned off the yaw damper that showed the movement and it continued so switched off the yaw damper that showed no movement and it fixed the problem. We observed the altitude and speed restrictions and had no more problems.

 

[bubbers44]

I don't think my reply helped your question any so just want to throw in what happened to my friend who had his copilot struggling with rotating and the airplane started going sideways so he took it and struggled around to land in his 727 with minimal climb capability. Half of the thrust reverser of the number 3 engine deployed deflecting exhaust to the right. He was able to decrease power on number three engine and return for landing. Boeing had never heard of that ever happening. I loved that airplane. It never let me down. Same with the 757.

 

[urpi]

I don't think my reply helped your question any so just want to throw in what happened to my friend who had his copilot struggling with rotating and the airplane started going sideways so he took it and struggled around to land in his 727 with minimal climb capability. Half of the thrust reverser of the number 3 engine deployed deflecting exhaust to the right. He was able to decrease power on number three engine and return for landing. Boeing had never heard of that ever happening. I loved that airplane. It never let me down. Same with the 757.

thank you for your comments. If you want I can send you the pictures of the exhaust tail pipe.