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Please Help Me Understand This Boeing Drawing  
User currently offlineLH526 From Germany, joined Aug 2000, 2360 posts, RR: 14
Posted (5 years 2 weeks 1 day 13 hours ago) and read 11214 times:
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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]


Trittst im Morgenrot daher, seh ich dich im Strahlenmeer ...
10 replies: All unread, jump to last
 
User currently offlineOly720man From United Kingdom, joined May 2004, 6704 posts, RR: 11
Reply 1, posted (5 years 2 weeks 1 day 12 hours ago) and read 11172 times:

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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User currently offlineLh526 From Germany, joined Aug 2000, 2360 posts, RR: 14
Reply 2, posted (5 years 2 weeks 1 day 11 hours ago) and read 11162 times:
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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.



Trittst im Morgenrot daher, seh ich dich im Strahlenmeer ...
User currently offlineTristarSteve From Sweden, joined Nov 2005, 4001 posts, RR: 34
Reply 3, posted (5 years 2 weeks 1 day 10 hours ago) and read 11138 times:

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.


User currently offlineRoseflyer From United States of America, joined Feb 2004, 9612 posts, RR: 52
Reply 4, posted (5 years 2 weeks 1 day 9 hours ago) and read 11090 times:



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).



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineAeroWeanie From United States of America, joined Dec 2004, 1608 posts, RR: 52
Reply 5, posted (5 years 2 weeks 1 day 4 hours ago) and read 10940 times:
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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.


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 6, posted (5 years 2 weeks 18 hours ago) and read 10785 times:



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.


User currently offlineKELPkid From United States of America, joined Nov 2005, 6372 posts, RR: 3
Reply 7, posted (5 years 2 weeks 18 hours ago) and read 10779 times:



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



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineJetMech From Australia, joined Mar 2006, 2692 posts, RR: 53
Reply 8, posted (5 years 2 weeks 18 hours ago) and read 10757 times:



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



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineTristarSteve From Sweden, joined Nov 2005, 4001 posts, RR: 34
Reply 9, posted (5 years 2 weeks 15 hours ago) and read 10714 times:



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.


User currently offlineTod From Denmark, joined Aug 2004, 1725 posts, RR: 3
Reply 10, posted (5 years 2 weeks 7 hours ago) and read 10607 times:

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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