LH526
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Please Help Me Understand This Boeing Drawing

Tue Aug 18, 2009 11:59 am

Hi,

can anybody please help me understand this Boeing drawing?
The table on the right shows values for the B707 fuselage section diameters. R is the radius of the upper contour, I would need assistance on the values of WLA, WLB, WLC and WLD .... obviosuly they show heights or widths of the floor or fuselage shape changes. Is it the width from the CL? or the height above ground .. or height from fuselage bottom?

To fully understand the values and their meanings and respective location and application, I highly appreciate any help!

http://www.lx97.com/FUSELAGE339582.jpg

Thanks a lot & best regards

Mario
LH526

[Edited 2009-08-18 05:02:31]
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oly720man
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RE: Please Help Me Understand This Boeing Drawing

Tue Aug 18, 2009 1:01 pm

All distances seem to be inches. The widths would give a fuselage width of around 12ft (just under 4m) which makes sense.

The heights seem to have some ground reference that's about 8ft underground. WLC at 220 ins, (18ft or 5.5m) would put the bottom of the fuselage at around 160ins or 13ft (assuming symmetry referenced to WLA) which is rather high.

Looking at photos the ground clearance under the aircraft is around 1/3 the fuselage height that's around 180" or 15ft, so 5ft.
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LH526
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RE: Please Help Me Understand This Boeing Drawing

Tue Aug 18, 2009 1:24 pm



Quoting Oly720man (Reply 1):
WLC at 220 ins, (18ft or 5.5m) would put the bottom of the fuselage at around 160ins or 13ft (assuming symmetry referenced to WLA) which is rather high.

Yes, that's my thoguht exactly ... WLC and WLD stay the same throughout the length of the aircraft ... Each row in the table gives data of the respective STA fuselage section. WLA and WLB vary slightly .... now what are all these WLA - WLD values? lengths, heights, circumference .. I have no Idea.
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Tristarsteve
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RE: Please Help Me Understand This Boeing Drawing

Tue Aug 18, 2009 2:10 pm

WL stands for Water Line.
BL stands for Buttock Line.

Boeing always use fictitious points to start measuring.
i.e. the first Station STA is 294. The measuring starts 294 in front of the nose.
Same with Water Line, its on the floor.
I always thought this was to ensure that all measurements are positive, so that even when measuring to the bottom of the wheels when on jacks, it is a positive WL measure.
 
roseflyer
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RE: Please Help Me Understand This Boeing Drawing

Tue Aug 18, 2009 3:57 pm



Quoting Lh526 (Reply 2):
WLA and WLB vary slightly .... now what are all these WLA - WLD values? lengths, heights, circumference .. I have no Idea.

The WL stands for height above the "ground". If you look at the drawing, it does show where WLA, WLB, WLC and WLD are. WLC and WLD are at a consistent height throughout the plane because you would not want a sloped floor (or at least Boeing does not make sloped floors unlike Airbus).
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aeroweanie
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RE: Please Help Me Understand This Boeing Drawing

Tue Aug 18, 2009 8:19 pm

The drawing you have shows the fuselage cross-section of the 707 (not the KC-135, 727, 737 or 757 - I checked). Sta is the distance horizontally in inches from a fixed reference point is space. On the 707, the tip of the nose radome is at Sta 130. WL is the waterline, measured vertically from a fixed reference point is space (usually not the ground). WLA is the height in inches of the crown above this reference point. WLB is the height of the upper radius center point. I'm not sure what WLC is, but WLD is the height of top of the floor beams and where the upper lobe meets the lower lobe. BLE is the lateral distance from the centerline to the maximum width point on the fuselage. R is the radius of the upper lobe. Note that BLE does not equal R, which is kinda odd. BLF is where the upper lobe meets the lower lobe. For some reason, the details of the lower lobe aren't given here. A spot check confirms that WLB plus R equals WLA, as it should.

Sta 294.5 is right behind the cockpit. Note that WLA is constant from Sta 480 to Sta 1220. This is the constant section of the fuselage. Sta 1420 is right in front of the aft pressure bulkhead. Note that the Sta numbers are for the unstretched 707 fuselage. No 707s were built with this fuselage - all had stretches, done with plugs in the Sta 620 and Sta 960 areas.
 
tdscanuck
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RE: Please Help Me Understand This Boeing Drawing

Wed Aug 19, 2009 6:04 am



Quoting AeroWeanie (Reply 5):
I'm not sure what WLC is,

WLC is the height at which the upper "bubble" ends for certain portions of the fuselage.

Per note B, from STA 249.5-480 and STA 1270-1440, the segment defined by arrow B is a straight line. So, between the listed stations, the fuselage is round with a radius centered on WLB down until WLC, where it makes a straight line to WLD and then picks up the lower fuselage contour.

Outside the stations listed in note B, the fuselage is round with a radius centered on WLB all the way down to WLD, where it picks up the lower fuselage contour.

Tom.
 
KELPkid
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RE: Please Help Me Understand This Boeing Drawing

Wed Aug 19, 2009 6:10 am



Quoting TristarSteve (Reply 3):
Boeing always use fictitious points to start measuring.
i.e. the first Station STA is 294. The measuring starts 294 in front of the nose.
Same with Water Line, its on the floor.
I always thought this was to ensure that all measurements are positive, so that even when measuring to the bottom of the wheels when on jacks, it is a positive WL measure.

I've encountered GA planes whose POH writers do the same thing, the stations for computing weight and balance moments start at a ficticious place way out ahead of the nose...probably taken directly from the designer's calculations  Wink
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jetmech
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RE: Please Help Me Understand This Boeing Drawing

Wed Aug 19, 2009 7:04 am



Quoting TristarSteve (Reply 3):
i.e. the first Station STA is 294. The measuring starts 294 in front of the nose.



Quoting KELPkid (Reply 7):
the stations for computing weight and balance moments start at a ficticious place way out ahead of the nose

I think the reason for this is to allow for the future possibility of stretching the fuselage. This system allows for a longer forward fuselage whilst keeping station numbers positive.

Regards, JetMech
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Tristarsteve
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RE: Please Help Me Understand This Boeing Drawing

Wed Aug 19, 2009 9:06 am



Quoting JetMech (Reply 8):
I think the reason for this is to allow for the future possibility of stretching the fuselage. This system allows for a longer forward fuselage whilst keeping station numbers positive.

Good theory, but Boeing don't do that.
Don't know the 707, but on the B737 look at STN 500 and 727. This is where the plugs are, and the extra frames are numbered A B C etc, so each STN now consists of many frames.
 
Tod
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RE: Please Help Me Understand This Boeing Drawing

Wed Aug 19, 2009 5:05 pm

Stretched Boeing aircraft STA locations are identified with the STA of the start of the plug section and plus numbers.

Example: 767-300 STA 654+0 thru STA 654+121

Tod

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