Comment by KennyBlanken | Hacker News Reader

Comment by KennyBlanken | Hacker News Reader

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> A failure in these blades would be catastrophic, resulting in the destruction of the engine, likely followed by the plane itself.

Aaaaand the author just lost any credibility with me whatsoever. This is someone who knows big words, maybe did some research and ChatGPTing, and doesn't actually know shit about aircraft or their engines.

On passenger aircraft because passengers sit directly inline with the path a blade with insane levels of kinetic energy will probably go, the nacelle is designed to contain it.

The engine must be able to contain a "blade off" event where a blade snaps during full rated thrust. Two videos:

https://www.youtube.com/watch?v=j973645y5AA

https://www.youtube.com/watch?v=wcALjMJbAvU

The aircraft will not be "destroyed."

The blade could fail during takeoff climb and the plane would still be able to climb because all twin engine passenger jet aircraft must be able to conduct all phases of flight on one engine.

SWA 1380 had a passenger fatality not because of the blade hitting them, but because part of the cowling disintegrated, broke the window, and she was partially sucked out of the aircraft, which killed her.

If she'd been wearing her seatbelt, she would likely be alive today. As would several other passengers who, over the years, have been killed by debris breaking the window and them being sucked out.

The blade itself did not leave the engine.

https://en.wikipedia.org/wiki/Southwest_Airlines_Flight_1380

That article lists a number of incidents, in roughly half of which the blade was contained. All the flights made it back to an airport...

> If she'd been wearing her seatbelt, she would likely be alive today.

The passenger's seatbelt was buckled.

https://libraryonline.erau.edu/online-full-text/ntsb/aircraf...

"When flight attendant C reached row 14, she saw that the head, upper torso, and arms of the passenger seated in 14A had been pulled outside the airplane through the window. The passenger’s seat belt was buckled. Flight attendant C grabbed onto the passenger and, with assistance from flight attendant A, tried to bring the passenger back into the airplane, but flight attendant A reported that they could not get the passenger back into the airplane by themselves because of the pressure and the altitude. Two male passengers (in seats 8D and 13D) offered to help; they were able to pull the passenger back into the airplane and laid the injured passenger across seats 14ABC."

RIP Jennifer Riordan.

As with all design on aircraft, weight is a key part of the specification. A nacelle that could contain all possible failure modes would be too heavy to fly.

Losing a fan blade, as demonstrated in your two youtube links, is both a more likely event to occur and low enough energy to be able to contain with a reasonable structure.

However consider the situation in [0] where a turbine disk became detached from its shaft. The disk is still taking power from the exhaust gas, but rather using the energy to power the compressor or rotate the fan it is now just increasing its own kinetic energy. This continues until the incredibly strong turbine disk rotates itself apart. From the linked article:

> For engineering purposes, disk fragments are assumed to have infinite energy at the moment of release; they will cut through any reasonable material and cannot be contained

You can see from photographs of the aftermath, the nacelle is missing where this happened

[0] https://admiralcloudberg.medium.com/a-matter-of-millimeters-...

This is not my understanding by reading the article. The blade failure will destroy the plane if developed independently of the rest. So modern nacelles will contain the blast as you say but they have decades of integration testing together with the blades in all kind of conditions.

if you develop everything anew there will be mismatches in tolerances and thousands of potential individual failure risks that can be combined in interesting, unexpected and fatal ways.

Shrapnel is an issue, and depends what it takes out.

Take this incident for example:

https://admiralcloudberg.medium.com/a-matter-of-millimeters-...

Nacelle is designed to contain blades, but a failed blade can break downstream parts and nothing can stop high-pressure turbine disk parts from flying where they want

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