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gulfstream650
Topic Author
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The ERJ - Why Does It Constantly Rock?

Sat Jul 10, 2010 10:18 pm

I like the aeroplane but I was wondering why it constantly rocks from side to side (wing roll) in cruise compared to other aircraft?

Many thanks,

Gulfstream650
I don't proclaim to be the best pilot in the world but I'm safe
 
pilotpip
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RE: The ERJ - Why Does It Constantly Rock?

Sun Jul 11, 2010 3:41 am

Probably a combination of being at it's max designed limits (it's really noticable at FL370) and a crappy yaw damper. I'm sure somebody else will know the exact reason.

That wing doesn't have a ton of sweep and while there is a different wing and turbofans, you're dealing with a 30 passenger turboprop that was stretched into something it really wasn't desingned to do.
DMI
 
DC8FriendShip
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RE: The ERJ - Why Does It Constantly Rock?

Sun Jul 11, 2010 4:48 pm

Dutch Roll, a common occurance in swept wing aircraft. The yaw damper is supposed to help counteract this, but I guess that the Embraer design has trouble keeping up. It's not dangerous though, just uncomfortable for pax.
Come fly the Friendly Skies of United
 
tdscanuck
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RE: The ERJ - Why Does It Constantly Rock?

Sun Jul 11, 2010 6:15 pm

Quoting DC8FriendShip (Reply 2):
It's not dangerous though, just uncomfortable for pax.

It's not dangerous if properly damped (either by aero-damping or by a yaw damper). Undamped, it's bad news...several B-47's, and at least one 707, were lost due to Dutch roll getting out of control.

Tom.
 
AA737-823
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RE: The ERJ - Why Does It Constantly Rock?

Sun Jul 11, 2010 10:04 pm

Quoting tdscanuck (Reply 3):
It's not dangerous if properly damped (either by aero-damping or by a yaw damper). Undamped, it's bad news...several B-47's, and at least one 707, were lost due to Dutch roll getting out of control.

Ha, I was just about to say, "Yes, dutch roll can be incredibly dangerous!" but you beat me to it.

Anyhow, I've noticed this sometimes on ERJ's as well, all flying on the same route, but not the same aircraft. In other words, on multiple flights between A and B airports, I will sometimes notice it, and other times not.
 
Fly2HMO
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RE: The ERJ - Why Does It Constantly Rock?

Mon Jul 12, 2010 1:23 am

I've noticed it a lot too. The ERJs seem very prone to dutch roll. I remember as a pax that the 722s where pretty bad at it as well.
 
UAL747
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RE: The ERJ - Why Does It Constantly Rock?

Mon Jul 12, 2010 4:21 am

Yeah, now that you mention it, I have noticed that quite a bit on the ERJ. Also, it may have just been coincidence, but I noticed the A340-600 I took this winter to FRA do it quite a bit as well.

UAL
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way
 
DC8FriendShip
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RE: The ERJ - Why Does It Constantly Rock?

Mon Jul 12, 2010 2:40 pm

Quoting tdscanuck (Reply 3):
It's not dangerous if properly damped (either by aero-damping or by a yaw damper).

Yeah, should have been more clear. My mistake!
Come fly the Friendly Skies of United
 
747fan
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RE: The ERJ - Why Does It Constantly Rock?

Tue Jul 13, 2010 1:53 am

I've noticed it on flights I've had on the ERJ, although the movement was quite slight; I really only noticed it when looking out the windows. On the other hand the aircraft seemed to ride turbulence fairly well (my most recent flight on the type last month from DTW-SDF even when descending thru "puffy" summertime clouds was glass smooth!)
 
DashTrash
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RE: The ERJ - Why Does It Constantly Rock?

Tue Jul 13, 2010 3:23 am

It's a Honeywellism. Some of the older Citation X's I've flown do it as well. Same autopilot, but a different rudder set up that counteracts most of the oscillations.
 
ThePinnacleKid
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RE: The ERJ - Why Does It Constantly Rock?

Tue Jul 13, 2010 3:51 am

Most of us call it the "Honeywell Shuffle"... it also generally does a pretty poor job of intercepting the LOC... usually results in a lot... A LOT... of hand flown approaches.
"Sonny, did we land? or were we shot down?"
 
Fly2HMO
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RE: The ERJ - Why Does It Constantly Rock?

Tue Jul 13, 2010 6:42 am

Quoting DashTrash (Reply 9):
It's a Honeywellism.
Quoting ThePinnacleKid (Reply 10):
Most of us call it the "Honeywell Shuffle"...

Ah yes I do recall some conversations with pilots and others in the know complaining about sloppy Honeywell APs and other systems. Primus 1000-based systems seem to be the worse at it, which the cockpit from most Citations including the X and ERJs are based on IIRC.
 
DashTrash
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RE: The ERJ - Why Does It Constantly Rock?

Tue Jul 13, 2010 1:45 pm

Quoting Fly2HMO (Reply 11):
Ah yes I do recall some conversations with pilots and others in the know complaining about sloppy Honeywell APs and other systems. Primus 1000-based systems seem to be the worse at it, which the cockpit from most Citations including the X and ERJs are based on IIRC.

Yep. The X has the FMZ-2000. With later models equipped with IRS, they do pretty well. Earlier AHRS equipped models rock a bit but not as bad as the ERJs, probably due to mach trim and the upper rudder. As long as you're not hauling ass turning on to final, it intercepts the LOC and glideslope just fine. VNAV with the system isn't very good. Most of the time it misses crossing restrictions by a few hundred feet. It's great for advisory though.
 
access-air
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RE: The ERJ - Why Does It Constantly Rock?

Wed Jul 14, 2010 4:06 pm

I dont think all the responses understand what the original poster is trying to ask....
Ive been on a few EMB-145 flights and I too noticed this as well...
Its not the side to side yawing or pitching up or down, He is referring to the very slight but constant rocking or banking of the wings back and fourth...
I too wondered about that.....

Access-AIr
Remember, Wherever you go, there you are!!!!
 
bri2k1
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RE: The ERJ - Why Does It Constantly Rock?

Wed Jul 14, 2010 4:26 pm

Quoting Access-Air (Reply 13):

I think they get it. Especially on a swept-wing jet at cruise speeds, rudder input induces more of a roll than a yaw.
Position and hold
 
Fly2HMO
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RE: The ERJ - Why Does It Constantly Rock?

Wed Jul 14, 2010 6:11 pm

Quoting bri2k1 (Reply 14):
I think they get it. Especially on a swept-wing jet at cruise speeds, rudder input induces more of a roll than a yaw.

  

At least on initial rudder deflection.
 
ThePinnacleKid
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RE: The ERJ - Why Does It Constantly Rock?

Wed Jul 14, 2010 8:41 pm

Quoting Access-Air (Reply 13):
I dont think all the responses understand what the original poster is trying to ask....
Ive been on a few EMB-145 flights and I too noticed this as well...
Its not the side to side yawing or pitching up or down, He is referring to the very slight but constant rocking or banking of the wings back and fourth...
I too wondered about that.....

as stated... the ERJ does not have a "dutch roll" oscillation as some have suggested... it has a gentle and constant wing rocking like you and the OP identified... and, as previously discussed... is a function of the Honeywell avionics of the aircraft... as we call it at my carrier at least... "The Honeywell Shuffle"

To also be clear, while the ERJ was indeed generally an adaptation from the Brasilia, it was not just a simple stretch and slap some engines on and new wing... it really was designed from the outset as a true jet airliner... the only thing from the Brasilia days that really really held over and causes "issue" is the fusealge/front office windows.. the soundproofing is less than adequate for a jet/high speed regime and really is loud up front compared to most other jets... Aerodynamics however, is not an area that is lacking with the ERJ. It actually can go much much faster than certified and not even encounter Mach tuck... If I remember correctly, the initial onset of mach tuck didn't develop until close to M0.96... the ERJ is also super responsive to flight control inputs.. a function of Embraer's extensive experience with military aircraft prior to the ERJ series....
"Sonny, did we land? or were we shot down?"
 
tdscanuck
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RE: The ERJ - Why Does It Constantly Rock?

Thu Jul 15, 2010 2:17 am

Quoting Access-Air (Reply 13):
Its not the side to side yawing or pitching up or down, He is referring to the very slight but constant rocking or banking of the wings back and fourth...

Dutch roll is a coupled yawing and rolling, there's no pitch involved. Most aircraft do have a natural pitch oscillation too (phugoid), but that's a different cause and, normally, a different frequency.

Quoting ThePinnacleKid (Reply 16):
the ERJ does not have a "dutch roll" oscillation as some have suggested

It's certainly got a native dutch roll (essentially all swept wing aircraft do to some degree), but they're killing it off via flight controls or good aero damping.

Quoting ThePinnacleKid (Reply 16):
it has a gentle and constant wing rocking like you and the OP identified.

That's part of Dutch roll. It could also be a side-effect of the yaw damper. Even if the yaw damper is completely killing Dutch roll, it will cause roll oscillation unless you've also got FBW roll controls cancelling the roll-from-rudder (C_l_beta). It could also be that it's got slightly positive and lightly damped spiral stability, which will cause a roll oscillation.

Tom.

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