QANTAS747-438
Topic Author
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757 Gears/747 Engines

Wed Feb 21, 2001 2:14 pm

Hey! 2 questions:

1) On the nose gear of the 757, what is that box above the tires? I see it had headlamps above it and the tires below it. In a book, I saw a picture of a pilot standing in front of it, and it appeared as if he was typing someting into it! I have NO idea what it is though.

2) How is it that the outboard engines of a 747 stay on the wing?! To me, it looks like they'd fall right off, but of course, there is a reason behind it. Also, how does it not snap the wing in half with full fuel? Dont the engines weigh a few tons?

Thanks!
---QANTAS747-438
My posts/replies are strictly my opinion and not that of any company, organization, or Southwest Airlines.
 
QANTAS747-438
Topic Author
Posts: 1660
Joined: Mon Jan 22, 2001 7:01 am

RE: 757 Gears/747 Engines

Thu Feb 22, 2001 5:37 am

Nobody knows the answer??!
My posts/replies are strictly my opinion and not that of any company, organization, or Southwest Airlines.
 
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sammyk
Posts: 1560
Joined: Mon Oct 25, 1999 11:31 am

RE: 757 Gears/747 Engines

Thu Feb 22, 2001 6:37 am

I don't know the answer to the first, but the answer to the second seems to show common logic. If you hold something in your hand, why doesn't your arm break? In the same manner, the wing is designed to be strong enough to hold two engines, fuel, and all other related equipment. It may not "look" strong enough, but obviously it is.

Sammy
 
Mason
Posts: 636
Joined: Sat Jun 12, 1999 12:01 am

RE: 757 Gears/747 Engines

Thu Feb 22, 2001 7:00 am

Actually, a wing with more weight doesn't need to be as strong as a wing with less weight. Let me explain. When in flight, gravity is acting on the fusalage, pulling it down (obviously). The wings create lift, and as a result, the wings appear to 'bend' upward, as you may have seen during a heavy takeoff. The fusalage is actually sagging between the wings. The 777 and 747 are famous for this effect, although just not as visible on other aircraft. Now then, when in flight, the wings want to bend upward (as explained above), so the engines, fuel, and weight of the wing itself 'push' it down. Therefore the more weight (in the form of engines) helps keep the wing down, whereas a wing with two engines doesn't have as much weight, so it needs to be stronger to keep the wings from ripping right off. If you have the chance, look at a 747 center section when being assembled. It is the strongest part of the aircraft, and can handle the weight of the engines and fuel with no problem. Also, the wings have braces that run parallel to the fusalage, to facilitate the 'bending' by making the wing more flexable. Seeing that this is not my area of speciality, I did the best I could to explain it. I hope this helps. Perhaps someone who is more articulate and educated on this topic could fill in the gaps. As for the 757 question, I have no clue. Sorry.
 
cfalk
Posts: 10221
Joined: Mon Dec 04, 2000 6:38 pm

RE: 757 Gears/747 Engines

Thu Feb 22, 2001 7:30 am

Mason,

Here's a good sample:

Click for large version
Click here for full size photo!

Photo © Andrew Hunt



Cheers,

Charles
The only thing you should feel when shooting a terrorist: Recoil.
 
VC-10
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Joined: Tue Oct 26, 1999 11:34 am

RE: 757 Gears/747 Engines

Thu Feb 22, 2001 7:38 am

The "box" on the 757 NLG is the cover over the steering metering valve. The valve ports hyd fluid to the steering jacks.