L1011-500 oscillating question
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Lot of talk of pod nod. Agree that its caused by VIGV's or fuel flow reg and should be reported but not sure I would call pod nod vibration! Rolls say pod nod has a frquency of 1-4 Hz and having had it a lot in the passed I wouldn't call it vib. I've had engine vibe that didn't show on the guages our boffins said it was too low a frequency but don't discount an airfame reason, gear door, cargodoor(aircraft doesn't have much diff on) or a wheel thats got a good flat spot vibrates like hell as its spinning down( you can feel the nosewheel realy well on the flightdeck or front gally).
Top marks for brining to the flightdecks attention. Free beer for you I think.
Kenny your buying but don't leave before she brings the tab.
Top marks for brining to the flightdecks attention. Free beer for you I think.
Kenny your buying but don't leave before she brings the tab.
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Well thanks for all your replies. Still, nothing has been resolved. I'm in the process of writing the safety director for some answers. <img src="wink.gif" border="0">
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Keep up the pressure as "news from the back" is always welcome.
Recall years ago at the old RUH airport I was taxiing out to runway 01 when the L4 F/A called on the intercom and mentioned that the floor was VERY hot. Back to the parking bay and had maintenance take a look...turned out to be a bleed air leak which burned thru a wire bundle.
Ah...not good.
Recall years ago at the old RUH airport I was taxiing out to runway 01 when the L4 F/A called on the intercom and mentioned that the floor was VERY hot. Back to the parking bay and had maintenance take a look...turned out to be a bleed air leak which burned thru a wire bundle.
Ah...not good.
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I had a F/A point out a fuel leak on number 3 engine just after take off.She wouldn't take no for an answer and insisted I come and take a look right away. Would have taken a long time to show on the guages. But from the rear galley(-500) it was clear as day.
It's nice when you know your flying with pros in the cabin.
It's nice when you know your flying with pros in the cabin.
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Thanks for the vote of confidence, I think I will need it come time to deliver this letter. I take safety VERY seriously and I agree that the cabin crew are helpful when alert and diligent.
As a side note though, there are the odd front end crew who humph and groan at some requests. We are only looking out for the safety of everyone.. and my motto is when in doubt "get your butt outta that seat and take a walk to the back!" Orrrr no coffee for you!
<img src="wink.gif" border="0"> <img src="tongue.gif" border="0">
As a side note though, there are the odd front end crew who humph and groan at some requests. We are only looking out for the safety of everyone.. and my motto is when in doubt "get your butt outta that seat and take a walk to the back!" Orrrr no coffee for you!
<img src="wink.gif" border="0"> <img src="tongue.gif" border="0">
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From my dim and distant past, POD NOD was a problem with the RB211-524 series, wing mounted engines, not -22B as Cathay Pacific flew. We would regularly replace the VIGV CONTROLLER for this problem.
[ 16 January 2002: Message edited by: All That Glitters ]</p>
[ 16 January 2002: Message edited by: All That Glitters ]</p>
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I asked a couple of our pilots if they had ever heard of "pod nod".. they all looked like I had spoken in tounges!
gesshhhhhhh. CAN A REAL PILOT PLEASE STAND UP? At my company anyways! Hahahaha <img src="wink.gif" border="0">
gesshhhhhhh. CAN A REAL PILOT PLEASE STAND UP? At my company anyways! Hahahaha <img src="wink.gif" border="0">
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FE Hopey............Had some ice go thru number 2 once at rotation. It was so noisy in the tail that people had to yell at each other . No indication on the vib meter. Pulled the throttle back a little , noise went away , flew the trip and replaced 5 fan blades. I was amazed that it didnt show on the vibs. Was told that it senses sideways movement but not forward and back. There was no vibration in the flight deck and we would not known we had a problem if a flight attendant had not called us.
Do a Hover - it avoids G
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locky
Nobody has mentioned your original comment that it only happens on second sectors. Sounds like a clue. If this IS invariably the case, then the trick will be to decide what component might be working under different circumstances from the first sector - temperature most likely, but not necessarily. Are you always operating from the same few airfields? Could it be related to a specially long or short taxy distance or is it not airfield related. Even negative answers help to eliminate possibilities.
Anyhow, you stick at it. Aeroplanes are only machines and there will always be a logical answer to a persistent characteristic. Aeroplanes fail only because somebody has not done something right. In this case you are not the weakest link.
Nobody has mentioned your original comment that it only happens on second sectors. Sounds like a clue. If this IS invariably the case, then the trick will be to decide what component might be working under different circumstances from the first sector - temperature most likely, but not necessarily. Are you always operating from the same few airfields? Could it be related to a specially long or short taxy distance or is it not airfield related. Even negative answers help to eliminate possibilities.
Anyhow, you stick at it. Aeroplanes are only machines and there will always be a logical answer to a persistent characteristic. Aeroplanes fail only because somebody has not done something right. In this case you are not the weakest link.
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Gentlemen,
I have in front of me an Operating Information Memo issued by Lockheed in May 20th 1980 called "Wing Engine Pod Motion" and a Notice To Operators issued by Rolls Royce on the 22nd of May 1981 called "Engine Thrust Oscillations". Looks to me like it will answer your questions.
A fairly long one to type, unfortunately no time doing it today, but I could have it posted in next couple of days. Interested or not???. .Cheers!!!
I have in front of me an Operating Information Memo issued by Lockheed in May 20th 1980 called "Wing Engine Pod Motion" and a Notice To Operators issued by Rolls Royce on the 22nd of May 1981 called "Engine Thrust Oscillations". Looks to me like it will answer your questions.
A fairly long one to type, unfortunately no time doing it today, but I could have it posted in next couple of days. Interested or not???. .Cheers!!!
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May 20, 1981. .L1011 Tristar - Operating Information Memo. .Subject: Wing Engine Pod Motion
Recently there have been a few pilot reports of small lateral and/or vertical airframe motion felt in the cockpit and/or cabin of 524 powered aircraft. Observation of the wing engine pods appeared to be moving in a somewhat elliptical path with the major axis in a lateral direction and at a frequency of 2 hz. The amplitude of the motion was reported at about 2 inches at the cowl inlet with 80% of the motion in the lateral direction and 20% vertically.
Testing and analysis has determined that this phenomenon is the result of thrust oscillations attributable primarily to the variable inlet guide vane system and possibly the engine fuel system (FFR, PAC). The oscillations, although felt through the airframe may not be detected by reference to engine instruments because of intrument damping characteristics.
The pod movement does not affect structural integrity or flight safety as it is a non-divergent limit cycle oscillation and the loads are very low - less than those normally associated with very light turbulence. Thrust oscillations of one engine usually results in observed motion of both wing pods.
If this phenomenon occurs in flight, and it has only been encountered in extremely smooth air, the offending engine can easily be found by individually retarding each power lever to flight idle and then restoring power. The oscillations will disappear when the power lever of the affected engine is moved to flight idle - and when restoring power, if the power is reset either slightly higher or lower than the earlier setting, the oscillation will not recur. The wing/pylon response to thrust oscillations is dependent somewhat on airspeed and fuel loading, thus wing pod motion has been reported for a range of power settings ranging from hold conditions to lightweight climbs usually around 250 knots indicated airspeed.
A Lockheed Information letter and a Rolls-Royce Notice to Operators Number 198, are being issued to advise Engineering and Maintenance personnel or recommended corrective actions in the event the phenomenon be encountered.. .End.
Rolls-Royce Notice to Operators. .Engine Thrust Oscillation:
......Rolls-Royce are informed by LCC (???) that the natural frequency of the L1011 wing/pylon suspension is in the order of 2.0 to 2.5 Hz, varying with wing tank loading. The coincidence of the frequency of engine control systems instability with the natural frequency of suspension, results in the amplitude of movement that has been observed. The resultant pod movement has on occasions also been referred to as a pod nod, rocking, circular, or figure of eight movement.
LCC confirms that such movement is not a safety item.
Reports to date show that the problem:. .a) Occurs in the power range 1.2 to 1.4 EPR and can be eliminated by moving the throttle to a setting above or below the power range.. .b) May, but not always, be accompanied by noticeable cyclic fluctuations of engine flight deck parameters.. .c) Is not always repeatable on ground run.. .d) Has occured with engines incorporating the P4/PF and P4/PS1 (not clearly readable) variable inlet guide vane (VIGV) control system.. .e) Has not been encountered with the B747 aircraft installation.
Rolls-Royce has recently taken full advantage of the opportunity to investigate this problem in flight with a L1011 aircraft at Palmdale and also with a service engine on a Derby test bed. Testing involved comprehensive instrumentation, particularly so on the test bed, to monitor the stability of the engine control system. In each investigation, instability of the VIGV control system was detected and was thereupon identified as originating from the VIGV controller.
From the initial experience gained to date in investigating this problem, Rolls-Royce consider the following order of approach to be appropriate when trouble shooting:. .a) Check air signal lines for leaks (VIGV and FF? loops).. .b) Change VIGV controller.. .c) Change separate bleed valve control unit (SBVCU).. .d) Change fuel flow regulator (FFR).. .END.
That's it folks. I skipped a few notes to make it shorter a bit, in the hope that it still makes sense.. .Cheers!!!
Recently there have been a few pilot reports of small lateral and/or vertical airframe motion felt in the cockpit and/or cabin of 524 powered aircraft. Observation of the wing engine pods appeared to be moving in a somewhat elliptical path with the major axis in a lateral direction and at a frequency of 2 hz. The amplitude of the motion was reported at about 2 inches at the cowl inlet with 80% of the motion in the lateral direction and 20% vertically.
Testing and analysis has determined that this phenomenon is the result of thrust oscillations attributable primarily to the variable inlet guide vane system and possibly the engine fuel system (FFR, PAC). The oscillations, although felt through the airframe may not be detected by reference to engine instruments because of intrument damping characteristics.
The pod movement does not affect structural integrity or flight safety as it is a non-divergent limit cycle oscillation and the loads are very low - less than those normally associated with very light turbulence. Thrust oscillations of one engine usually results in observed motion of both wing pods.
If this phenomenon occurs in flight, and it has only been encountered in extremely smooth air, the offending engine can easily be found by individually retarding each power lever to flight idle and then restoring power. The oscillations will disappear when the power lever of the affected engine is moved to flight idle - and when restoring power, if the power is reset either slightly higher or lower than the earlier setting, the oscillation will not recur. The wing/pylon response to thrust oscillations is dependent somewhat on airspeed and fuel loading, thus wing pod motion has been reported for a range of power settings ranging from hold conditions to lightweight climbs usually around 250 knots indicated airspeed.
A Lockheed Information letter and a Rolls-Royce Notice to Operators Number 198, are being issued to advise Engineering and Maintenance personnel or recommended corrective actions in the event the phenomenon be encountered.. .End.
Rolls-Royce Notice to Operators. .Engine Thrust Oscillation:
......Rolls-Royce are informed by LCC (???) that the natural frequency of the L1011 wing/pylon suspension is in the order of 2.0 to 2.5 Hz, varying with wing tank loading. The coincidence of the frequency of engine control systems instability with the natural frequency of suspension, results in the amplitude of movement that has been observed. The resultant pod movement has on occasions also been referred to as a pod nod, rocking, circular, or figure of eight movement.
LCC confirms that such movement is not a safety item.
Reports to date show that the problem:. .a) Occurs in the power range 1.2 to 1.4 EPR and can be eliminated by moving the throttle to a setting above or below the power range.. .b) May, but not always, be accompanied by noticeable cyclic fluctuations of engine flight deck parameters.. .c) Is not always repeatable on ground run.. .d) Has occured with engines incorporating the P4/PF and P4/PS1 (not clearly readable) variable inlet guide vane (VIGV) control system.. .e) Has not been encountered with the B747 aircraft installation.
Rolls-Royce has recently taken full advantage of the opportunity to investigate this problem in flight with a L1011 aircraft at Palmdale and also with a service engine on a Derby test bed. Testing involved comprehensive instrumentation, particularly so on the test bed, to monitor the stability of the engine control system. In each investigation, instability of the VIGV control system was detected and was thereupon identified as originating from the VIGV controller.
From the initial experience gained to date in investigating this problem, Rolls-Royce consider the following order of approach to be appropriate when trouble shooting:. .a) Check air signal lines for leaks (VIGV and FF? loops).. .b) Change VIGV controller.. .c) Change separate bleed valve control unit (SBVCU).. .d) Change fuel flow regulator (FFR).. .END.
That's it folks. I skipped a few notes to make it shorter a bit, in the hope that it still makes sense.. .Cheers!!!
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READY;. .thank you thank you thank you!. .John.. thank you as well. .I think I will forward this to our company.I haven't flown on this peticular jet in about a month.. .As for second sector flights, they are usually from down south so I assume the runways are much shorter.. .Thanks for the input fellas <img src="smile.gif" border="0"> it is very much appreciated
[ 30 January 2002: Message edited by: locky ]</p>
[ 30 January 2002: Message edited by: locky ]</p>
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I don't have to tell you Locky, but report it, report it, report it, and then keep reporting it, be a real pain in the butt over it, and something will get done. Recurring vibration or oscilation, in a part which really shouldn't be doing it, needs to be looked at.
I once grounded a BA 737 as SLF, when I noticed, on a climb out from Hamburg, a strangely coloured (QED essential) fluid, which appeared on the port wing leading edge. I told the FA, who got the Captain to come look. His response "Oh that's nothing to worry about" My response "I am a Pilot" His response "Ah" lol
Net result aircraft grounded at Birmingham, and my reward? A very waspish male flight attendant, on my depature from the aircraft hissed at me "Thanks to you, I won't get home tonight"
My response..... "Bite me"
So the moral is, maybe ask one of the SLF's if they notice something too, get the Captain, and the SLF will more than happily break the good news, something might get done quickly then
Tony. .(Happily grounding BA's fleet)
I once grounded a BA 737 as SLF, when I noticed, on a climb out from Hamburg, a strangely coloured (QED essential) fluid, which appeared on the port wing leading edge. I told the FA, who got the Captain to come look. His response "Oh that's nothing to worry about" My response "I am a Pilot" His response "Ah" lol
Net result aircraft grounded at Birmingham, and my reward? A very waspish male flight attendant, on my depature from the aircraft hissed at me "Thanks to you, I won't get home tonight"
My response..... "Bite me"
So the moral is, maybe ask one of the SLF's if they notice something too, get the Captain, and the SLF will more than happily break the good news, something might get done quickly then
Tony. .(Happily grounding BA's fleet)
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If what you heard/felt was a vibration it was not the common "pod nod", which is more like the a subdued version of the lurches you get on the underground.. .In hot climates, probably your "second sector",. .the F/E has a tendency to send the ram air doors a little too wide open, and depending on how open the ram air doors are, you can get a rumble, rattle, or chugging. At some openings it does feel like vibration, and is usually reported by F/As at L1 door.
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The "Louvers" can be manipulated when the respective Packs are in "MAN" position and when "Cool" (Turbine Bypass) or "Warm" (Ram Air) buttons are pushed. <img src="rolleyes.gif" border="0">