MolaKule Q&A on Aircraft Structures III

MolaKule

MolaKule

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On most commercial aircraft, the engine is external and attached to the wing or fuselage.

What is the name of the structure that attaches the engine to the wing or fuselage?
 
I wanted to say nacelle but that's the outer shell. Our engines were internal so I learned the name in school but I'm old and forgot!
 
The reason for the engine change on our Gulfstream G550 was compressor stall during start. Once running, it was fine. A known problem due to Metco coating failure (sprayed on foamed aluminum abradeable coating) causing excessive compressor blade tip clearance.

The engine mount links are visible by the tech's left hand and one above. The yoke on the fuselage is less visible unless you are able to zoom in, but it's one healthy metal part. The thrust strut goes aft from the yoke and attaches to a frame and stringer assy.
CHXI2662.webp

IMG_3216.webp
IMG_3126.webp
 
UncleDave said:
A Pylon?
Click to expand...
(y)

The Pylon, also called an engine mount, is a structure positioned between the engine and the wing or fuselage.

It is designed to not only carry the dead weight of the engine, but also torque and engine thrust, both forward and reverse.

The pylon attaches to the engine "case" via two or more attachment points. The pylon attaches to the wing or fuselage via two or more attachment points as well.

The pylon not only has to resist various loads, but also acts as a conduit for systems such as hydraulics, electrical, and engine bleed. Below are diagrams for a pylon, the first being a general description and the second being a more detailed diagram.

Items called Fuse pins and hollow "Fuse" bolts are also incorporated into the pylon structure.

The second part of this question is: What is the purpose of Fuse pins and hollow "Fuse" bolts?

Pylon DC10.webp


Engine Pylon.webp
 
Last edited:
MolaKule said:
(y)

The Pylon, also called an engine mount, is a structure positioned between the engine and the wing or fuselage.

It is designed to not only carry the dead weight of the engine, but also torque and engine thrust, both forward and reverse.

The pylon attaches to the engine "case" via two attachment points. The pylon attaches to the wing or fuselage via two attachment points as well.

The pylon not only has to resist various loads, but also acts as a conduit for systems such as hydraulics, electrical, and engine bleed. Below are diagrams for a pylon, the first being a general description and the second being a more detailed diagram.

Items called Fuse pins and hollow "Fuse" bolts are also incorporated into the pylon structure.

The second part of this question is: What is the purpose of Fuse pins and hollow "Fuse" bolts?

View attachment 280277

View attachment 280276
Click to expand...

Is that drawing a DC 10 Pylon?
 
MolaKule said:
The first diagram, the general one, is that of a DC-10 wing-mounted pylon.

The second one below it is a generic pylon showing some internal structures.
Click to expand...

That upper drawing hits home, thats when I first learned it was called a Pylon.

Then I learned why holding the assembly with a forklift vs removing the entire assembly was a shortcut not worth the cost.
 
MolaKule said:
The first diagram, the general one, is that of a DC-10.
Click to expand...

UncleDave said:
That upper drawing hits home, thats when I first learned it was called a Pylon.

Then I learned why holding the assembly with a forklift vs removing the entire assembly was a shortcut not worth the cost.
Click to expand...
Yes, American Airlines Flight 191, a McDonnell-Douglas DC-10-10, crashed on takeoff from Chicago-O'Hare International Airport, Illinois, USA.

This was due to improper mounting of engines with a forklift.

"On the accident flight, during the takeoff rotation, the number-one engine and its pylon assembly separated from the left wing, ripping away a 3-foot (1 m) section of the leading edge with it. The combined unit flipped over the top of the wing and landed on the runway..."

https://en.wikipedia.org/wiki/American_Airlines_Flight_191

NTSB Report:

https://web.archive.org/web/2019042...tigations/AccidentReports/Reports/AAR7917.pdf
 
Last edited:
MolaKule said:
Yes, American Airlines Flight 191, a McDonnell-Douglas DC-10-10, crashed on takeoff from Chicago-O'Hare International Airport, Illinois, USA.

This was due to improper mounting of engines with a forklift.
Click to expand...
Douglas Aircraft did tell the airline that they could not give an NTO for this method. The forklift bled down during a break and put an improper stress on the pylon structure, causing hidden damage. The aircraft flew for several weeks after this but eventually the pylon separated from the wing structure taking the engine and hydraulic lines with it. Additional aircraft were found with cracks from this method both at American and another carrier.
 
MolaKule said:
Yes, American Airlines Flight 191, a McDonnell-Douglas DC-10-10, crashed on takeoff from Chicago-O'Hare International Airport, Illinois, USA.

This was due to improper mounting of engines with a forklift.

"On the accident flight, during the takeoff rotation, the number-one engine and its pylon assembly separated from the left wing, ripping away a 3-foot (1 m) section of the leading edge with it. The combined unit flipped over the top of the wing and landed on the runway..."

https://en.wikipedia.org/wiki/American_Airlines_Flight_191

NTSB Report:

https://web.archive.org/web/2019042...tigations/AccidentReports/Reports/AAR7917.pdf
Click to expand...
The sad thing was the newly installed camera system that allowed the passengers a “cockpit view” during operation. The passengers saw the impact coming from the pilots point of view.
 
burbguy82 said:
oh, I would say to break or distort, as a gauge? I know nothing of aviation tech. sorry
Click to expand...
@Skippy722 "They’re designed to fail after a certain amount of force has been applied to them to prevent greater damage."

Yes, break or fail; and thanks for keeping on topic.

If the engine were to run out of oil, the spinning components would seize, and a large torque component would result. We would then want it to make a clean break from the wing.

If the engine nacelle were to contact the ground, the resulting tilting force would damage the wing spewing combustible fuel. We want it to break clean from the wing.

If on takeoff or landing the engine were to make contact with a ground obstruction, we would then want it to break clean as above.
 
MolaKule said:
@Skippy722 "They’re designed to fail after a certain amount of force has been applied to them to prevent greater damage."

Yes, break or fail; and thanks for keeping on topic.

If the engine were to run out of oil, the spinning components would seize, and a large torque component would result. We would then want it to make a clean break from the wing.

If the engine nacelle were to contact the ground, the resulting tilting force would damage the wing spewing combustible fuel. We want it to break clean from the wing.

If on takeoff or landing the engine were to make contact with a ground obstruction, we would then want it to break clean as above.
Click to expand...
Okay I cheated a little…. I’ve machined them before! Albeit for a steel mill out in Illinois.

burbguy82 said:
so to make the engine fall on some unsuspecting fellow, and damage the plane less.
Click to expand...
A plane can fly missing an engine, potentially saving hundreds of lives both on the ground and in the air.

I did instantly think of that one episode of Shameless though 😂
 
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