sammyb
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A Few Questions About The A32X Aircraft

Sun May 20, 2007 2:50 am

Hi all,

I have two questions

1. On all A32X aircraft that I have been on, while cruising the aircraft rocks ever so slightly from side to side even if it is smooth and calm. I have noticed this mostly on the A321 and just wanted to know what caused this very very slight rocking.

2. On some A32X aircraft the Hydraulic PTU seems to go on a lot longer than others of the same sort, why is this?

Thanks
 
Arniepie
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RE: A Few Questions About The A32X Aircraft

Sun May 20, 2007 4:19 am

Been on all of them except the 318 multiple times and I never noticed it, maybe a drunk pilot???  Silly
[edit post]
 
bio15
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RE: A Few Questions About The A32X Aircraft

Sun May 20, 2007 4:29 am

My guess is that you're probably witnessing this at a COP (Change Over Point) in flight when the next navaid is selected either by the autopilot or the pilots themselves, and the aircraft is simply re-tracking the desired radial. It could also happen when close to a navaid since tracking is much more sensitive. This happens normally, but it is hard to be noticed.

Alfredo
 
sammyb
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RE: A Few Questions About The A32X Aircraft

Sun May 20, 2007 4:41 am

Quoting Bio15 (Reply 2):
My guess is that you're probably witnessing this at a COP (Change Over Point) in flight when the next navaid is selected either by the autopilot or the pilots themselves, and the aircraft is simply re-tracking the desired radial. It could also happen when close to a navaid since tracking is much more sensitive. This happens normally, but it is hard to be noticed.

Thanks, I thought it was probably something to do with navigation but as you said it is very hard to notice unless you watch the wings and the horizon.
 
SB
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RE: A Few Questions About The A32X Aircraft

Sun May 20, 2007 11:11 am

It could also not be as smooth and calm as it seems ... tiny changes in wind direction could cause this as the autopilot alters heading by half a degree to stay on track.

S.
"Confirm leave the hold and maintain 320kts?!"
 
CaptOveur
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RE: A Few Questions About The A32X Aircraft

Sun May 20, 2007 4:36 pm

I think I remember reading in a thread a long time ago about worn autopilot components or something causing a pitch or roll osilation in older aircraft. I am thinking it isn't an issue if it is within certain limits.
Things were better when it was two guys in a dorm room.
 
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HAWK21M
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RE: A Few Questions About The A32X Aircraft

Sun May 20, 2007 5:58 pm

Quoting Sammyb (Thread starter):
On all A32X aircraft that I have been on, while cruising the aircraft rocks ever so slightly from side to side even if it is smooth and calm. I have noticed this mostly on the A321 and just wanted to know what caused this very very slight rocking.

What age were these Aircraft approx.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
sammyb
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RE: A Few Questions About The A32X Aircraft

Sun May 20, 2007 7:33 pm

Quoting HAWK21M (Reply 6):
What age were these Aircraft approx.

well,
the A321's that I have been on that I noticed it on are:

G-OJEG Monarch First Reg. Date: 14/05/1999
G-DHJH Mytravel First Reg. Date: 07/06/2000
G-SMTJ Mytravel First Reg. Date: 15/05/2003
G-OOAJ Air 2000 First Reg. Date: 12/05/1999
G-BXAW AirWorld First Reg. Date: 07/04/1997
 
Pihero
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RE: A Few Questions About The A32X Aircraft

Mon May 21, 2007 4:10 am

Quoting Bio15 (Reply 2):
My guess is that you're probably witnessing this at a COP (Change Over Point) in flight when the next navaid is selected either by the autopilot or the pilots themselves, and the aircraft is simply re-tracking the desired radial. It could also happen when close to a navaid since tracking is much more sensitive. This happens normally, but it is hard to be noticed.

Alfredo,
What you are describing could have applied for a 1960 or so airplane and airspace.
Nowadays, we don't navigate from VOR to VOR anymore, so what you called a cop (never heard of that word, btw) doesn'tr exist anymore as the airplane's track is computed and the route / direction changes are very smooth.

Sammyb,.
What you are describing could be put into some sort of very light dutch roll. Never experienced it in some 5000 hrs on the baby bus.

Regards
Contrail designer
 
DH106
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RE: A Few Questions About The A32X Aircraft

Mon May 21, 2007 6:43 am

I've noticed a similar tendency with many aircraft - i.e. the L1011
If you're looking out at the wingtip it's possible to perceive very small movements - fractions of a degree in roll.
On an aircraft of the A320's size, 1 deg of roll causes the wing tip to move up/down about a foot
In calm conditions you may just be seeing a tiny oscillations below the damping threshold of the autopilot.
...I watched c-beams glitter in the dark near the Tanhauser Gate....
 
9VSIO
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RE: A Few Questions About The A32X Aircraft

Mon May 21, 2007 3:55 pm

Quoting CaptOveur (Reply 5):
I think I remember reading in a thread a long time ago about worn autopilot components or something causing a pitch or roll osilation in older aircraft. I am thinking it isn't an issue if it is within certain limits.

I encountered constant roll oscillation in an A340 transatlantic - after asking on here, most people bet that it was turbulence and not the AP going mad.
Me: (Lining up on final) I shall now select an aiming point. || Instructor: Well, I hope it's the runway...
 
lro
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RE: A Few Questions About The A32X Aircraft

Wed May 23, 2007 1:45 am

To the PTU: Are you shure that you were taxiing with both engines on. Normally the PTU does also a self test after the first enginge was started. But i think thata there are also electric hydraulic pumps wihich might sound like the PTU.

best regards
 
bio15
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RE: A Few Questions About The A32X Aircraft

Wed May 23, 2007 7:08 am

Quoting Pihero (Reply 8):
Alfredo,
What you are describing could have applied for a 1960 or so airplane and airspace.
Nowadays, we don't navigate from VOR to VOR anymore, so what you called a cop (never heard of that word, btw) doesn'tr exist anymore as the airplane's track is computed and the route / direction changes are very smooth.

You're right. It makes a lot of sense that an Airbus aircraft, which I assume uses FMC RNAV/VNAV flies altitude and direction changes in a very smooth manner. I understand you are an airline captain, but the COP exists, and it is not 1960's airspace terminology.

    COP as defined in the ICAO Annex 2, Rules of the Air, tenth edition:

    Changeover point. The point at which an aircraft navigating on an ATS route segment defined by reference to very high frequency omnidirectional radio ranges is expected to transfer its primary navigational reference from the facility behind the aircraft to the next facility ahead of the aircraft.

    Note.— Changeover points are established to provide the optimum balance in respect of signal strength and quality between facilities at all levels to be used and to ensure a common source of azimuth guidance for all aircraft operating along the same portion of a route segment.


Current Jeppesen charts use a COP symbol on top of some airways that indicates where a frequency change is necessary by showing the distance to each navaid.

----
In my training I do fly VOR to VOR. When changing frequency between navaids there may be a minimal discrepancy between the selected radial and the desired radial due to VOR signal error and instrument error. In this case tracking may be required. An aircraft flying on autopilot mode tracking a VOR radial could rock side to side when changing between navaids to re-track the radial. I now understand that could not be the case with an A320 for many reasons, but it is not unlikely to occur on modern GA aircraft.


Alfredo
 
David L
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RE: A Few Questions About The A32X Aircraft

Wed May 23, 2007 7:54 am

Quoting DH106 (Reply 9):
On an aircraft of the A320's size, 1 deg of roll causes the wing tip to move up/down about a foot

I've certainly never experienced anything like that but...

Quoting Pihero (Reply 8):
What you are describing could be put into some sort of very light dutch roll.

... I did notice something less pronounced, barely perceptible, on two flights in Fokker 28s during the whole of the cruise... so I may have associated it with Dutch Roll for the wrong reasons.  Smile
 
Pihero
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RE: A Few Questions About The A32X Aircraft

Fri May 25, 2007 8:12 am

Quoting Bio15 (Reply 12):
the COP exists, and it is not 1960's airspace terminology.

Sorry. Alfredo.
I couldnm't find the word or an equivalent in the French Rules of the Air. I now remenber that , yes, the Jepps had it.
Comes from flying in smaller countries where two VORs on the same route were not that far apart.
Nowadays, I only use a VOR + radial as a preset back-up for a SID or a STAR.
How is flying going along ?
Contrail designer
 
DH106
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RE: A Few Questions About The A32X Aircraft

Fri May 25, 2007 3:52 pm

Quoting David L (Reply 13):
Quoting DH106 (Reply 9):
On an aircraft of the A320's size, 1 deg of roll causes the wing tip to move up/down about a foot

I've certainly never experienced anything like that but...

To clarify, I wasn't suggesting an oscillation of one foot up/down - just illustrating that a passenger with a good reference point for comparison i.e. a clear horizon beyond - could detect a small wing tip up/down movement much smaller than a foot which would translate to a fraction of one degree - a very small angle.
...I watched c-beams glitter in the dark near the Tanhauser Gate....
 
David L
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RE: A Few Questions About The A32X Aircraft

Fri May 25, 2007 7:49 pm

Quoting DH106 (Reply 15):
To clarify, I wasn't suggesting an oscillation of one foot up/down - just illustrating that a passenger with a good reference point for comparison i.e. a clear horizon beyond - could detect a small wing tip up/down movement much smaller than a foot which would translate to a fraction of one degree - a very small angle.

Fair enough.  Smile

My reference point was the bottom of the window tracing a slightly uneven zig-zag along the ground, as if the nose was tracing a small circle round the longitudinal axis.
 
DH106
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RE: A Few Questions About The A32X Aircraft

Fri May 25, 2007 8:29 pm

Quoting David L (Reply 16):
as if the nose was tracing a small circle round the longitudinal axis.

Definitely sounds like a small Dutch Roll - a sort of out of phase mix of yaw and roll.
The yaw damper's supposed to damp this down to a minimum - but I guess it's effectiveness can vary with a/c type, installation and other factors such as CG position, trim variable etc.
...I watched c-beams glitter in the dark near the Tanhauser Gate....
 
bio15
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RE: A Few Questions About The A32X Aircraft

Sat May 26, 2007 4:20 am

Quoting Pihero (Reply 14):
Comes from flying in smaller countries where two VORs on the same route were not that far apart.
Nowadays, I only use a VOR radial as a preset back-up for a SID or a STAR.
How is flying going along ?

That's correct. Most Flying in Colombia takes part around the Andean mountain chain, which goes westward up to the pacific coasts, and in the Atlantic coasts. VORs are not far apart in these areas. One large portion of Colombian territory is the oriental plains, which are significantly unpopulated, but you must fly through them to get to Leticia in the Amazonas (SKLT/LET), on the southmost boundary with Brazil. VORs on Upper Level airways for those flights are very far apart.

I'm 3 months away from getting my license, 5 to get the multiengine rating. I'm currently flying the last crosscountry flights to the Atlantic coastline and the Magdalena valley. Setting my eyes on AV,  Smile hopefully by the end this year a Fokker 50 F/O fellow captain.

regards
Alfredo
 
PGNCS
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RE: A Few Questions About The A32X Aircraft

Sun May 27, 2007 8:59 am

Quoting Pihero (Reply 8):
Never experienced it in some 5000 hrs on the baby bus.



Quoting DH106 (Reply 9):
I've noticed a similar tendency with many aircraft - i.e. the L1011

I've flown both and have never noticed a tendency for this behavior in either aircraft, and have noted much more yawing tendency in longer Boeing aircraft, especially in turbulence, and especially in the back. The 757-300 can be positively nauseating as far as I'm concerned.

I think the problem here with all of these opinions is that of perception. One person may be much more sensitive than another to motion in any axis. In my experience, yaw is definitely more noticeable the further aft in the aircraft you are.

I have found the L-1011 to be a veritable rock in cruise both in the cockpit and in the cabin. I have also had no complaints about the A-320 series.
 
David L
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RE: A Few Questions About The A32X Aircraft

Sun May 27, 2007 9:12 am

Quoting PGNCS (Reply 19):
I think the problem here with all of these opinions is that of perception. One person may be much more sensitive than another to motion in any axis.

I certainly didn't feel it. If I hadn't accidentally seen it, I'd never have known.

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