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747 Upper Deck:is This True?  
User currently offlineLY777 From France, joined Nov 2005, 2611 posts, RR: 2
Posted (7 years 7 months 2 days 4 hours ago) and read 25603 times:

A friend of mine who travels a lot on 744s on the upper deck(biz class) told me that on the upper deck of 747s, we don't feel any vibration, the turbulences are far less important than on the lower deck.
Is this true?


אמא, אני מתגעגע לך
37 replies: All unread, showing first 25:
 
User currently offlineKiwiandrew From New Zealand, joined Jun 2005, 8489 posts, RR: 14
Reply 1, posted (7 years 7 months 2 days 4 hours ago) and read 25576 times:
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the upper deck has always seemed noisier to me than the lower deck because of the way the air flows around the fuselage - but that is only my subjective opinion - I have only done 3 or 4 trips upstairs and 3 or 4 downstairs so I guess I don't have as much experience as your friend to base my opinion on


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User currently offlineHUYguy From United Kingdom, joined Apr 2006, 274 posts, RR: 0
Reply 2, posted (7 years 7 months 2 days 4 hours ago) and read 25537 times:

Surely it would be the same on both decks beings as the whole plane shakes in turbulence?

User currently offlineZvezda From Lithuania, joined Aug 2004, 10511 posts, RR: 64
Reply 3, posted (7 years 7 months 2 days 4 hours ago) and read 25512 times:

There is less turbulence forward than aft, so there would be less at the average point on the upper deck than the average point on the lower deck. The nose on the lower deck would have the least turbulence which is one of the reasons why most airlines locate their F cabins there.

User currently offlineDeaphen From India, joined Jul 2005, 1424 posts, RR: 1
Reply 4, posted (7 years 7 months 2 days 3 hours ago) and read 25422 times:

Quoting Zvezda (Reply 3):
There is less turbulence forward than aft, so there would be less at the average point on the upper deck than the average point on the lower deck. The nose on the lower deck would have the least turbulence which is one of the reasons why most airlines locate their F cabins there

correct me if i am wrong but i thought the least turbulence is in the centre of the place.. because the plane will be most turbulent at the front and the back. That was the conclusion i got once wheni asked this same question.

regards
nitin



I want every single airport and airplane in India to be on A.net!
User currently offlineAndz From South Africa, joined Feb 2004, 8414 posts, RR: 11
Reply 5, posted (7 years 7 months 2 days 3 hours ago) and read 25379 times:
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The upper deck is the place to be on a 747, in my experience it is quieter, it certainly rattles less than the main deck cabin and in SAA's case has better legroom too (Y class).


After Monday and Tuesday even the calendar says WTF...
User currently offlineTrekster From , joined Dec 1969, posts, RR:
Reply 6, posted (7 years 7 months 2 days 3 hours ago) and read 25358 times:

Upper deck still gets turbulance. I had to grab hold of a glass of wine flying LHR-YYZ when we hit some rough stuff.

Back of the plane indeed is the shaky part. SFO-LHR I was RIGHT at the back and my knees were moving while seated it was that bumpy. I was so tired i did not care and was asleep for 3 hours till the crew woke me


User currently offlineGr8Circle From Canada, joined Dec 2005, 3069 posts, RR: 4
Reply 7, posted (7 years 7 months 2 days ago) and read 24917 times:

I've travelled on the upper deck of 742's, 743's and 744's.....did not really feel it is any better than the main deck in terms of turbulence or vibrations....

What I don't like about the UD is the slant in the windows and the gap between the seat and the window.....on the other hand, due to the position, the wing does not significantly block your view..... smile 


User currently offlineEK413 From Australia, joined Nov 2003, 4681 posts, RR: 4
Reply 8, posted (7 years 7 months 1 day 23 hours ago) and read 24560 times:

In my opinion which comes with experience from alot of trips.....I believe you experience less and probably NO turbulence in the centre of the aircraft as opposed to the aft of the aircraft....

EK413



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User currently offlineTod From Denmark, joined Aug 2004, 1721 posts, RR: 3
Reply 9, posted (7 years 7 months 1 day 23 hours ago) and read 24488 times:

Quoting LY777 (Thread starter):
on the upper deck of 747s, we don't feel any vibration,

I haven't noticed the difference.

Quoting Gr8Circle (Reply 7):
What I don't like about the UD is the slant in the windows and the gap between the seat and the window

I like the gap and the sidewall stow box to put my stuff in. When trapped in a window seat long haul it is nice not to need to get into the overhead bin during the flight.

Quoting Andz (Reply 5):
it certainly rattles less than the main deck cabin

That can be caused by the age and manufacturer of the interior components too.

Tod


User currently offlineHotelbravo From United States of America, joined Sep 2005, 57 posts, RR: 0
Reply 10, posted (7 years 7 months 1 day 22 hours ago) and read 24091 times:

Quoting Zvezda (Reply 3):

It is actually not as simple as "quiet in front and noisy in the back". The 747 is known to have a particularly noisy flight deck due to the airflow around the cockpit. So it doesn't surprise me that the top passenger cabin is said to be noisier than the main deck.


User currently offlineSevenforeseven From France, joined Nov 2005, 164 posts, RR: 0
Reply 11, posted (7 years 7 months 1 day 22 hours ago) and read 23239 times:

Aircraft are always more "turbulent" at the rear 3/4 section. This is due to the fact that an aircraft fusealage actually flexes. B757 and A340-600 are very prone to this phenomina. It is known as fish tailing effect.
As for upper deck, well it probably feels less turbulant here because of its forward position.


User currently offlineTonyban From United States of America, joined Jun 2006, 336 posts, RR: 0
Reply 12, posted (7 years 7 months 1 day 22 hours ago) and read 23076 times:

I have only flown once in the upper deck. A Virgin Atlantic flight from SFO to LHR. Still felt plenty of turbulance but what stood out more was the sheer wind noise up there. The 'hump' definatelt causes the air flow to generate a lot of noise. Very noisy indeed.

User currently offlineFlyBoy84 From United States of America, joined May 2005, 370 posts, RR: 4
Reply 13, posted (7 years 7 months 1 day 21 hours ago) and read 22443 times:

Overall the 747 is a very stable plane anyway, to me. I've flown on one and there was some turbulence during the flight. But I can imagine that a 737 would have had more  bouncy  to the ounce that that 747!

User currently offlineAviateur From United States of America, joined Apr 2004, 1350 posts, RR: 12
Reply 14, posted (7 years 7 months 1 day 20 hours ago) and read 20242 times:

It doesn't make a whole lot of difference, but the smoothest place to sit is that portion of the cabin closest to the plane's centers of lift and gravity. Basically, that means the middle.

With many aircraft, the tail section is further from CL and CG than the nose -- with the yaw damper correcting for displacement and knocking the tail back and forth. This means the very front tends to be smoother than the very back. Thus it's possible you'll find a slightly nicer ride on the 747's upper deck than in row 63.

Noise is another matter. The upper deck does tend to be loud due to its thin diameter combined with airflow over and around its surface.

I wrote an article about this, which Airliners will not allow me to link to, but trust me...

PS

[Edited 2006-09-20 19:11:29]


Patrick Smith is an airline pilot, air travel columnist and author
User currently offlineAviateur From United States of America, joined Apr 2004, 1350 posts, RR: 12
Reply 15, posted (7 years 7 months 1 day 20 hours ago) and read 20242 times:

Accidental double post... sorry.

[Edited 2006-09-20 19:07:18]


Patrick Smith is an airline pilot, air travel columnist and author
User currently offlineSkyvanMan From United States of America, joined Aug 2004, 224 posts, RR: 0
Reply 16, posted (7 years 7 months 1 day 19 hours ago) and read 20083 times:

I don't remember the specifics about whether I felt turbulence or not but I vividly remember flying upper deck on UA from LAX to SYD and it was awesome. I loved the small cabin and it felt really more personalized and special, especially when we were on the gorund or I looked and could see parts of the plane below me.


The 3 best planes of all time: Shorts Skyvan, 330 and 360
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9375 posts, RR: 52
Reply 17, posted (7 years 7 months 1 day 19 hours ago) and read 19504 times:

Quoting Zvezda (Reply 3):
The nose on the lower deck would have the least turbulence which is one of the reasons why most airlines locate their F cabins there.

From an engineering stand point I can't think of a single reason why the center of gravity of the plane shouldn't be the part that experiences the least turbulence. I won't go technical, since I can't say I fully understand turbulence's effect. Honestly I kind of doubt anyone ever had gone in to the research that would be required to make such a calculation. The reason is that when you get something complicated like an airplane, you go so far beyond the models and fundamental equations that are central to the understanding of mechanical systems. Everything turns theoretical. There is no equation or way to exactly model the airflow around a wing or an airframe. Everything is based on empircal evidence and is just a guess. You can't even exactly model airflow around a tennis ball. Doesn't that make you feel good about the engineering that goes in to designing something like the 747?

With that said, the center of gravity should experience the least turbulence. The reason is that there is little damping in the fuselage since it is close to being modeled as a rigid structure (the wing is definitely the opposite, which is why you will see it move and for lack of a better term, flap). Since the fuselage is a rigid structure, the axis of rotation for turbulence when it is rotational and not translational should be around that point. Therefore rotational turbulence such as any turbulence through one of the three axes will go through that point and it will not move. You only have translational turbulence left which will be felt equally throught the plane. There are four ways to feel motion. Rotate up and down (pitch). Rotate left and right (yaw). Rotate axially (roll). Translate in any direction. So with this explanation, the upper deck should feel more turbulence than say the business class cabin on the lower deck or front part of economy.

With regards to noise, the nose of the 747 is the quietest place on an airplane in flight at cruising speed due to reduced wind noise and low engine noise. The wind noise is due to airflow along the nose being different since from what I have heard, it is more laminar or at least in a transition phase from laminar to turbulent flow at the nose since the airstream has not fully developed in to being turbulent as the nose slices through the air and is not a constant diameter. It may be laminar instead of being turbulent as it is along the side of the plane, and thus will make less noise since the air in contact with the fuselage is moving at a comparatively lower speed than it is along the concentric lenght that is experiencing turbulent airflow at a full 400+mph. I can explain further if people want, but I'm not completely certain about that. However, I do know that the 747 is a bit louder since it uses a louder environmental control system, so you hear a lot of air blowing around inside the cabin when compared to an A330 or A340. This has little to do with A versus B, but rather the separate contractors that designed the systems. Airbus and Boeing don't design the cabin pressurization system, but they do decide the specifications for it.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineMCOflyer From United States of America, joined Jun 2006, 8625 posts, RR: 15
Reply 18, posted (7 years 7 months 1 day 19 hours ago) and read 19242 times:

Quoting Sevenforeseven (Reply 11):
B757 and A340-600 are very prone to this phenomina.

That is defintely true. Its worse for the 753.

MCOflyer



Never be afraid to stand up for who you are.
User currently offlineKlkla From United States of America, joined Jul 2004, 903 posts, RR: 0
Reply 19, posted (7 years 7 months 1 day 19 hours ago) and read 19182 times:

It's amazing how so many people can have a different experience from the same thing.

I have flown United 744s many times in business and first and I definitely prefer the upper deck. IMO it's much quieter (can't say whether there is more or less turbulence, though). First class in 744 is very noisy for some reason, much more so than any other aircraft I have flown.


User currently offlineSpacecadet From United States of America, joined Sep 2001, 3517 posts, RR: 12
Reply 20, posted (7 years 7 months 1 day 18 hours ago) and read 18803 times:

Quoting RoseFlyer (Reply 17):
From an engineering stand point I can't think of a single reason why the center of gravity of the plane shouldn't be the part that experiences the least turbulence.

There is more than one kind of turbulence, and several other phenomena that feel like turbulence but aren't. These factors and others make the rear of any plane bumpier than anywhere else.

Quoting RoseFlyer (Reply 17):
With that said, the center of gravity should experience the least turbulence. The reason is that there is little damping in the fuselage since it is close to being modeled as a rigid structure (the wing is definitely the opposite, which is why you will see it move and for lack of a better term, flap).

Airplane fuselages are hardly rigid structures! They are in fact designed to flex/expand/contract in a number of different ways. Otherwise, modern flight would not even be possible - to operate at temperatures from 120F to -60F, speeds through turbulent air at 320 knots, and altitudes from below sea level to 47,000 feet, a fuselage *must* flex.

That's ignoring the fact that the "center of gravity" in any airliner is almost always towards the back of the plane and is rarely the center of the wing (that's what stabilizers and trim settings are for). So even if you meant what you actually said there, you'd be agreeing with me. But I know you're not saying what you mean up there.

The 747 in particular is known for having a pretty aggressive yaw damper system that actually made passengers in the rear of the plane sick on some of its early flights. (It was calmed down a bit over the years, but is still more aggressive than on other airliners.) The movement from the yaw dampers is, well, damped by the time it reaches the front of the plane - the nose still moves opposite to the tail, but not nearly as abruptly as the tail.

There are obvious control and aerodynamic surfaces at the rear of the plane that do not exist at the front. An eddie that passes over one of the stabilizers will have a direct effect on the rear of the plane. That effect will also be damped before it reaches the nose. Depending on the type of wind gust, it might not be felt at all in the front of the plane (a gust that hits the tail directly, for example, would not rotate the plane on its "gravitational" axis - it would rotate it around its nose).

There is of course vibration caused by engine exhaust also, which create eddies near the fuselage behind them. This is the worst on takeoff and landing, but in my experience can be felt pretty much all the time throughout the flight. The noise of the engines also creates vibration through the floor, which is not experienced as "turbulence" but does make the rear of the plane less comfortable and serene than the front.

Taken all together, yeah, the front of a 747 is a lot smoother than the rear. I can't really speak to the upper deck as I've never ridden up there, but I would think it would be just as smooth, though possibly noisier due to wind noise from above (which is not present on the lower deck).



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User currently offlineNewark777 From United States of America, joined Dec 2004, 9348 posts, RR: 30
Reply 21, posted (7 years 7 months 1 day 18 hours ago) and read 18744 times:

Quoting Sevenforeseven (Reply 11):
Aircraft are always more "turbulent" at the rear 3/4 section. This is due to the fact that an aircraft fusealage actually flexes. B757 and A340-600 are very prone to this phenomina. It is known as fish tailing effect.

I sat in the back of a CO 753 through some (relatively) heavy turbulence, and you can almost see the fuselage flexing and torquing. Pretty neat.

Harry



Why grab a Heine when you can grab a Busch?
User currently offlineVir744 From United Kingdom, joined Mar 2006, 55 posts, RR: 0
Reply 22, posted (7 years 7 months 1 day 18 hours ago) and read 17866 times:

Quoting Spacecadet (Reply 20):
That's ignoring the fact that the "center of gravity" in any airliner is almost always towards the back of the plane and is rarely the center of the wing (that's what stabilizers and trim settings are for). So even if you meant what you actually said there, you'd be agreeing with me. But I know you're not saying what you mean up there.

The centre of gravity is always within the wings Mean Aerodynamic Chord (MAC = average chord line over the span of the wing) and the C of G moves during flight, primarily as fuel is burned. The stab trim settings are required due to the difference between the centre of pressure and the C of G. As the weight of the aircraft acts through the C of G and the lift acts through the C of P a lever arm is formed causing the aircraft to have a pitch up or pitch down tendency. This is overcome by the stabiliser trim and where installed fuel transfer trimming.

Sorry if its teaching people to 'suck eggs'


User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9375 posts, RR: 52
Reply 23, posted (7 years 7 months 1 day 17 hours ago) and read 16912 times:

Quoting Spacecadet (Reply 20):
That's ignoring the fact that the "center of gravity" in any airliner is almost always towards the back of the plane and is rarely the center of the wing (that's what stabilizers and trim settings are for). So even if you meant what you actually said there, you'd be agreeing with me. But I know you're not saying what you mean up there.

From what I know (and I've never taken any advanced aerodynamics classes that related to airplane design, so my knowledge is limited to general fluid dynamics) the horizontal stabalizor does not produce lift for the purpose of supporting the weight of the airplane. It is used for control only. Therefore the center of gravity will be over the wing. I know for sure that it is on every jet that I have ever heard of.

What I said I guess doesn't make sense since I just assumed that the effect of damping would be less than that of the central axis of the plane. I'm still not conviced that it isn't. If the tail moves one way, I would assume that the nose to some degree would move the other way based on the center of gravity if the force causes the plane to rotate. An airplane is far more complicated than something that I've studied, but if you push one end of a beam at an end, it rotates about its central axis. I think the nose would move. But yes more forces would be generated around the vertical and horizontal stabalizors. Damping I know will have an effect, but the sheer mass of the system would also cause there to be the least motion at the center of gravity. All the parts of the airplane damp forces out before they get to the CG. So it would have to be a significant difference in forces at the front and back to make up for this effect. I can't say how much for sure since I decided not to study virbration systems and thinking about those higher order differential equations is something that I'd prefer not to do.

Quoting Spacecadet (Reply 20):
The 747 in particular is known for having a pretty aggressive yaw damper system that actually made passengers in the rear of the plane sick on some of its early flights.

Wow I did not know that. I've never worked on anything structural for airplanes. I work on aviation power systems, so something like damping by the fuselage is out of my area of knowledge other than what I have learned in college.

Quoting Spacecadet (Reply 20):
Airplane fuselages are hardly rigid structures! They are in fact designed to flex/expand/contract in a number of different ways. Otherwise, modern flight would not even be possible - to operate at temperatures from 120F to -60F, speeds through turbulent air at 320 knots, and altitudes from below sea level to 47,000 feet, a fuselage *must* flex.

I know a plane has to flex, but there is a difference between flexing and damping. The stress caused by temperature and pressure differences does cause strain, but that strain isn't the same that will damp a force caused by turbulence. Axial strain wouldn't have much if any effect on what happens to a plane as it undergoes turbulence. Also since a plane is essentially a tube, the axial forces, which cause the greatest stress on the airplane are where the aluminum is strongest. The longitudinal loads that would make a difference in the effect of turbulence are significantly less. Where is the line between damping effects of the fuselage and transmitting the forces? The wing for sure is far less rigid than a fuselage, but naturally a tube is going to be far more rigid than something like a wing, which has a load supporting structure that is made of long beams.

Quoting Spacecadet (Reply 20):
(a gust that hits the tail directly, for example, would not rotate the plane on its "gravitational" axis - it would rotate it around its nose).

No it will not. If the gust just hits the tail perpindicularly, then it will absolutely rotate about its center of gravity. However it isn't that simple. This goes back to this being an insanely difficult thing to model, but a gust is likely to hit the entire plane, but effect localized parts such as the tail more. The whole plane may move laterally, but also will rotate about its center of gravity. It can rotate in all three dimensions. Basic dynamics has proved that systems always rotate about their center of mass. Unless you anchor the nose to a fixed point, or add additional forces, there is no possible way that a plane would rotate about its nose as a whole. The plane may roll along its line of center of gravity which passes throught he nose and fuselage to the tail, but it will also rotate about the vertical axis too if there is a force on the tail and yaw left or right. To simplify, if you push the tail of a plane, it will move in three ways, and only one way is a rotation about the nose. The other way is a lateral motion and finally it will yaw. Only one point will not move based on that force, and that point may or may not even be on the plane, but the center of gravity will only be affected by one of the three motions whereas the nose will be affected by two.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineIkramerica From United States of America, joined May 2005, 21415 posts, RR: 60
Reply 24, posted (7 years 7 months 1 day 15 hours ago) and read 15477 times:

Quoting SkyvanMan (Reply 16):
I loved the small cabin and it felt really more personalized and special, especially when we were on the gorund or I looked and could see parts of the plane below me.

I always love how people say the "small cabin" of the upper deck is great, yet so many say that they wouldn't want to be 'cramped' into a 757 on a long haul flight, even in J or F. Not saying you say this, just an observation.



Of all the things to worry about... the Wookie has no pants.
25 Zvezda : I had once assumed the same thing. However, a couple of professionals have explained it to me and I more or less grasped a semblence of understanding
26 Post contains images Lemurs : Thanks for saying what I was thinking but didn't feel like typing. I sometimes think that the loudest narrowbody complainers would be perfectly happy
27 Lehpron : No, first class is there because it is most forward convinience for those passengers, like any F class seatmaps. Besides, the moment arm of being far
28 Satx : I'm no expert on aerodynamics, but I have flown both decks of a 747 before. My personal opinion is that the upper deck is generally quieter than most
29 Comorin : I've found that the upper deck is quieter and much less bumpy than other parts. One observation for all you finite element types is that a bump felt a
30 Vimanav : you can add the DC8-61/63/71/73 to that list rgds//Vimanav
31 Speedracer1407 : I'm not sure what you mean by "towards the back of the plane," but the center of gravity, in any commercial airliner, is forward of the center of lif
32 Luxair : I traveled many times on the upper Deck and can only confirm & agree with ur friends statement that there are less would even dare to say much less vi
33 Post contains images Keysman73 : Just back from flying Lufthansa upper deck and I have to say that I thought the "wind noise" was much louder than down stairs. It still seemed to be a
34 RoseFlyer : Out of curiousity, where downstairs are you comparing it to. I've flown on the upper deck many times and do notice a significant increase in wind noi
35 Keysman73 : Well I flew out to Hong Kong with Thai in normal economy before coming back with LH. I was in row 52 going out, so probably two-thirds of the way back
36 RoseFlyer : Well someone talked about accelerometers measuring the different effects, and that could measure it in different parts of the plane. Overall though,
37 Pygmalion : The CG of any commercial jet is always forward of the center of lift for stability reasons. It is a certification criteria. The center of lift is for
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