risingsunfitnes From Australia, joined Sep 2011, 32 posts, RR: 0 Posted (3 months 3 weeks 17 hours ago) and read 2864 times:
Hi all,
Did a search, but had no luck. I flew on Jetstar today (A320).... It got me wondering, why do their engine pilons look like patchwork quilts ? Its not only on A320... A300, 310, 330, 340 etc.
soon7x7 From United States of America, joined May 2006, 2527 posts, RR: 16 Reply 1, posted (3 months 3 weeks 5 hours ago) and read 2651 times:
In all pylons, there is much going on and much to access on a regular basis...Composite panels are used in many areas for streamlining, obviously, but as they must be removed often they are subject to damage so various types of fasteners and countersunk washers are used (big/ ugly). In the remaining areas you will see metallic surfaces, stainless steel, titanium, aluminum lithium, etc. All have varying degrees of grey/ silver, some represent super structure while others represent aerodynamic panels. To look inside a pylon, you would be surprised to see how much actual space exists in one. Below is pictured the innards of a 757 pylon. TRUMPS pylon to be exact. You can see much going on, electrical connections, pneumatic connections, thrust links, wing attach points (big ugly forgings),etc. With all that going on pylons assume tremendous loads of several types so by design they perform many functions other than just a place to hang an engine in the sense that they are designed to house many internal systems the engine requires.
jetmech From Australia, joined Mar 2006, 2446 posts, RR: 54 Reply 2, posted (3 months 2 weeks 4 days 18 hours ago) and read 2055 times:
Here's a good photo of a B744 / RR outboard pylon.
You can see the critical structural components of the pylon, which are the pylon torque-box itself, the diagonal brace in green, and an upper link which is not visible. The 747 outboard pylons (RR only?) also have a pair of spring-beams for additional flexibility, which are also not visible in the photo.
You can see the numerous cut-outs provided for internal access to the strut. The large, diagonally orientated rectangular cut-out is the housing for the pneumatic bleed air pre-cooler. The smaller cut-outs allow access to various pneumatic components within the strut and the rear engine mount bolts. On the 747, the area above the diagonal brace usually has quite a number of hydraulic system components, such as reservoirs and auxiliary pumps.
IIRC, the 747 struts were made of aluminium, with the cut-out panels of the same material, which resulted in a more homogenous external appearance. The various Airbus struts may derive their patchwork look from the use of a variety of materials such as titanium, steel and aluminium.
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From Australia, joined Sep 2011, 32 posts, 
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