Questions tagged [aircraft-structures]

For structural engineering questions about airframes and the mechanical structures aboard aircraft

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1answer
52 views

How should I decide on the type of stringer to be used in an Aircraft's wing and fuselage?

I am trying to add stringers on the skins of an aircraft's wing as well as fuselage, for the same reason why they are present in most of the aircrafts i.e. to resist bending (and a possible buckling ...
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2answers
193 views

How is it possible that the design criteria for turbulence intensity has nearly doubled, but the manoeuvring load factor is the same?

https://www.law.cornell.edu/cfr/text/14/25.341 Here it says the turbulence intensity used for certification is 90 feet per second. Before, it was 50 feet per second, that section was added in 1981. So ...
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1answer
282 views

Is all the extra lift from flaps added upstream where the spars sit?

Flaps can significantly increase the lift for a wing, is all that extra lift added upstream where the spars sit? I ask this question because the flaps in airliners seem to be only connected by a few ...
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1answer
120 views

Can buckling of wing skin panels occur without external compressive loads?

State whether True or False: In general, the buckling of thin and slender structures occurs under applied axial compressive stresses. In the case of wing skin panels, they can fail in buckling even if ...
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2answers
204 views

What is the structural impact on the wing if no fuel is stored in the wings and just in the fuselage?

What is the structural impact on the wing if no fuel is stored in the wings and just in the fuselage and how to counter possible advantages/disadvantages? Has this topic already been researched?
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1answer
205 views

In wing design, how is factor of safety related to G-limits?

What does factor of safety mean with regard to the maximum G force an aircraft is rated for? Does a rating of 3Gs mean the same as a safety factor of 3? Or is there some extra margin?
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1answer
126 views

How do I find the shear center of an unsymmetrical airfoil?

I'm quite a newbie of these systems and I am designing the wing box of a drone. I know where I want my shear centre. However, I have been trying to determine the shear centre of my idealized airfoil. ...
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0answers
57 views

Texts on aero-engine structures

I have been scouring the web for resources on aero-engine structures and structural design (preferably civil turbofans) but unfortunately it seems like they are hard to come by. I would like dedicated ...
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1answer
2k views

Why are Stratolaunch's engines so far forward?

Stratolaunch's engines hang from pylons, not under the wing, but entirely forward of the wing's leading edge. (Even farther forward than, say, the 747's.) What benefit does this have, to compensate ...
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1answer
218 views

Is there any advantage to having both wings integrated into a single wing unit, rather than being attached separately to the fuselage?

if I have a wing, which is split in the middle of it and attached at each side of the aircraft (like in any commercial aircraft today), I get a bending moment at the root of the wing. What if I have ...
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2answers
536 views

How does an outflow valve work mechanically?

Under Environmental control and oxygen systems chapter of Aircraft Maintenance and Repair book by M. Kroes, there's an topic of working of the outflow valve The diagram is of a valve that also works ...
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0answers
40 views

Why is the assumed Lift-to-Weight-Ratio for the limit drop test for heavy aircraft (FAR-25) higher than for small aircraft (FAR-23)?

The FAR-25.725 assumes a Lift-to-Weight-Ratio L/W = 1 for the landing gear drop test while the FAR-23.725 assumes only L/W=0.667. This factor affects the load inertia factor n which is also needed for ...
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1answer
839 views

What's the difference between multiple disc brake and segmented rotor brakes?

Going through FAA's aircraft maintenance manual I came across a topic under braking systems, which had two different types of brakes: multiple discs and segmented rotor disc brakes Looking at the ...
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2answers
260 views

What is dual mode adaptive landing gear system?

Referring to the NASA document Design and Development of the Blackbird: Challenges and Lessons Learned. On page 31, there's a mention of dual-mode adaptive landing gear, which is quoted below. ...
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2answers
771 views

What are different components of an engine pylon?

What are the different structural components that are inside the fairing of engine pylon and what are the functions of each part? The pylons for each aircraft are made of Ti-64 alloys, can they be ...
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3answers
14k views

Why are commercial aircraft windows typically oval instead of circular?

Pretty much what the title says. Surely a circular window would allow more window area while not compromising on strength? Some planes(Gulfstream jets) do have circular windows. Is there a reason for ...
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1answer
321 views

How does the B777 Side brace locking mechanism work?

The B767 has jury strut actuators and their working is pretty straight forward. They oppose the collapsible geometry of jury strut and lock them in the over centre locking position. But for B777 this ...
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1answer
368 views

What materials form the structural elements of the Boeing 737?

What materials form the structural elements (leaving the spars, ribs etc) of the B737? It was tough to get any information on the kind of composites used on the 737 structure. Hoping to get some ...
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4answers
1k views

Why landing gears still need bungee springs?

While studying landing gear, I came across this term 'bungee spring' to which there was no definitive explanation in text with regards to its usage. So in the image, you can see for the jury strut/ ...
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0answers
52 views

Are the firewall and forward pressure bulkhead different components? [duplicate]

Suppose in a single engine aircraft, where the engine is located near the nose of the aircraft. If the cabin is pressurized, I know there will be a requirement of pressure bulkheads, both in the rear ...
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2answers
215 views

Could abrupt flight controls input cause damage in these circumstances?

I went flying yesterday with a friend in my 1972 Grumman AA-5. She's a good copilot for someone who doesn't know much about flying. I showed her how you can pitch up and down, cause 0G, and float, ...
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1answer
146 views

When does an UAV need an internal structure?

I´ve seen some UAV models without internal structure (stringers, longerons and frame). I guess the drone´s shell is the frame itself. So what is the best approach to calculate the shell thickness to ...
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3answers
12k views

Why does the second floor of the Boeing 747 occupy only part of the plane?

Why does the second floor of the Boeing 747 occupy only part of the plane, while the second floor of the Airbus a380 occupies the entire space of the plane?
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0answers
113 views

How do I reinforce a tubular spar that has been drilled vertically for an attachment bolt?

Previously posted a question about lift strut attachment to tubular wing spar with a bolt vertically through the spars. See drawing below. I tried using Bruhn's analysis book to formulate a a ...
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1answer
275 views

What's the wisdom of attaching an aircraft lift strut to a wing spar utilizing a single eye bolt vs the common two plate or strap method?

in the enclosed picture are three examples of types I'm speaking of. In the top picture, the lift struts are attached via a single eye bolt. The eye bolt is obviously vertical through the wingspar I ...
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3answers
5k views

What is the piece that covers the top part of tires?

I would like to know the name and the usefulness of this piece that covers the top of the tire of some planes, such as some Cessnas.
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2answers
2k views

How to calculate bending moments and shear forces on a wing?

I am trying to create a MATLAB script to plot the Bending Moment Diagram (BMD) and Shear Force Diagram (SFD) as a function of spanwise distance, x, along a wing from the wing root (x=0) to the wingtip ...
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6answers
7k views

Do aircraft have accelerometers?

Do modern aircraft employ accelerometers or other similar equipment to measure g-forces on the aircraft? I could imagine this being used as an inspection/service indicator, particularly after hard ...
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1answer
386 views

Stress on wing/fuselage-joint of aerial water tanker aircraft - and possible mitigating measures

Following the unfortunate crash of a C-130 aerial water tanker aircraft in Australia, a friend brought to my attention a 2002 C-130 tanker crash in the US. As can also be seen in this video, the wings ...
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1answer
569 views

How do the wings connect to the centre wing box?

First of all does the centre wing box form part of the fuselage as it's in the centre of the fuselage? Secondly how does the wing spars connect to this centre wing box to hold everything together?
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1answer
1k views

On a large transport aircraft where exactly is the Forward pressure bulkhead?

Is the Forward pressure bulkhead in front of the pilots.. I.e when you lift the Radome for maintenance is that the Forward pressure bulkhead you can see? Some images or a diagram would be great.
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1answer
2k views

What is the difference between a wing station and wing buttock line?

Can someone explain (with images) what the difference between a Wing Station and Wing Buttock Line is, in terms of aircraft structures location identification? The text I'm reading states: W. STA ...
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1answer
98 views

What is pressurization influence (if any) on maximum G load an airliner can withstand?

Reading here about skin thickness of airliners I was wondering if, considering some pressurized airliner at cruise altitude, there are differences in maximum operational acceleration loading the ...
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1answer
593 views

What exactly are the "sealed" leading-edge slats in B737 short field performance aircraft?

"The 737 design enhancements allow operators to fly increased payload in and out of airports with runways less than 5,000 feet long. The design enhancements include a two-position tail skid that ...
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2answers
879 views

What could cause the Boeing "Pickle Fork" issues?

The Boeing 737-NG has been in the news recently regarding cracks discovered in the "pickle fork" assembly which transfers loads from the wings to the body of the aircraft. The "pickle fork" was ...
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0answers
78 views

Wing fuselage joint in small aeroplanes [duplicate]

I know that there are bolts to connect the centre wing boxes of the fuselage and wings in large aircraft, but what are the methods of connecting the wings and fuselage of small aeroplanes? I’m mostly ...
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1answer
2k views

How do weapon pylons attach to a fighter's wings?

How do weapon pylons attach to a fighter's wings? I'm particularly interested in the inner structure.
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1answer
547 views

Why does taxiing produce large lateral loads on the 747's engine pylons?

While reading through a bunch of old AARs recently, I found (in the context of a 1993 747 in-flight engine separation) this interesting tidbit: [...] Boeing engineers report that the modifications ...
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2answers
3k views

Why does the Pilatus PC-24 have such a large "Airplane Support"?

The PC-24 has, under the fuselage, a kind of huge support to hold the wings. If we compare with the Citation CJ4 or the Phenom 300, this difference is quite significant. Why??
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2answers
3k views

How strong is aircraft-grade spruce?

I have been trying to find some real numbers on how strong a single solid piece of aircraft graded spruce wood timber is, but haven't had much luck and the numbers that I have found so far were either ...
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1answer
219 views

What adds more weight to a twinjet? Tail-engines or wing-engines?

Let's say we have a large commercial jet, with exactly 2 engines, capable of holding at least 200 passengers. It could be a traditional jet like the Boeing 777, where both engines are in the wing. Or ...
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1answer
152 views

What are the effects of dihedral on net lift of a wing? [duplicate]

I read somewhere on the internet that dihedral decreases wing lift,so my question is will dihedral decrease the lift of an airplane wing since the wings are attached to the fuselage at an angle ? If ...
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4answers
277 views

Where is the compression on a compression strut in a tube and fabric airplane coming from?

I understand the functions of every part of a tube and fabric (two spar) ultralight wings and the loads they carry but what keeps puzzling me is the compression strut of a two spar wing as seen above. ...
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2answers
313 views

What is the function of cross bracing of interplane strut?

Pic 1 is the top and lower wing of a biplane called Bloop Ultralight,what is the function of the cross bracing between the interplane struts as seen in pic 1(I'm not talking about landing and flying ...
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2answers
233 views

How does fuel efficiency depend on wing configuration?

Which of the following wing configurations is the most fuel-efficient?
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1answer
133 views

Structural rating of aircraft to withstand storm induced structural stresses

I was watching an accident report where an aircraft crashes when a storm destroys a wing spar. I'm curious is this only a danger for small aircraft or are there ...
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2answers
901 views

What is the function of interplane strut of a Biplane?

What kind of load does the interplane strut(s) carry,is it compression, tension or shear? In order words,what's their function and how do you calculate the force that the interplane strut carries?
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2answers
323 views

Compression and tension members of a biplane wing

I get why the upper wing of a biplane is a compression member (because the flying wire is attached to it at an angle) but what I fail to understand is why the lower wing is the tension member of a ...
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1answer
350 views

What is this loose object above the flap fairing? [duplicate]

During my flight, I noticed a loose object above one of the flap fairings. You can see it in this video: https://imgur.com/wCPSEem. Is it normal or should I notify the airline? People pointed out to ...
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2answers
689 views

How much lift does the wing attach fitting actually carry?

How do I calculate the lift force that the the bolt that join the wings to the fuselage of a strutted or braced airplane carry? I know in a cantilever airplane,the bolts have to carry all of the lift ...