@Shalvenay Huh, I know I'd be curious to hear about it. I know incorrectly repaired rear pressure bulkheads have caused some very serious accidents (for example: en.wikipedia.org/wiki/Japan_Airlines_Flight_123)
I'd be curious to know what they do to prevent further damage if there is a blow out, if anything.
Yeah, I know that one was incorrectly repaired, but it's feasible that the same thing could happen on a correctly installed bulkhead. I wonder if it's considered enough of a risk that they do anything to guard against that particular failure... No idea. I guess that's why I'd be interesting in seeing you post a question on it :)
@JayCarr Jay, one of the ways you mitigate against such a failure is in the inspection program for critical structural areas. The major body damage agent is fatigue cycles, rather than all of a sudden impact loads. What that means is that with the right inspection regime, the airframe starts to "tell you" when it's beginning to degrade/fail. (In theory anyway).
@DanHulme Nope, I went to the announcement on Meta and asked the mod what the status was. He said they are still producing them, and he'd give us some sort of notice when the start shipping.
@DanHulme Christmas or Xmas are the common terms (though Christmas is by far the most popular.) Though I'm personally a fan of Christmahanakwanzadon.
@KorvinStarmast So...when something can be easily detected through routine inspection would you say that are less likely to build internal structures to prevent against failure? As opposed to something that may be more likely to spontaneously destroy itself, which they may design precautions and redundancies against?
@TomMcW Where you at these days? Feels like it's been...a day or two! Okay, maybe that's not that long...
Facts
The recurrent debate of whether simple questions are allowed or not is back. The questions are simple in the sense that answers are very easy to get online. Such recent questions:
Why does the Ka-50 (Hokum) have two main rotors, one on top of another?
What is the lump under the English E...
No. I have engaged with the question to try to understand what's behind it. The designs take into account X number of cycles, but you inspect to see if it is failing earlier than the fatigue life was designed for. I have since understood that the question is about "the AFB failed in flight, how is it that the rest doesn't fail? " That's a different question.
@KorvinStarmast Yeah, I wonder if anything is actually done. JAL123 kind of makes me think otherwise... I mean, the reality is they can't engineer against every possible problem or the planes would weigh so much they can't even get off the ground.
@JayCarr A factor of safety is applied to each design, and the load paths are analyzed in extraordinary detail to see where the plane needs beefy structure, and where weight can be saved. It's a trade off between weight and strength, and optimization as an art ...
@JayCarr I've been around. Just eavesdropping. You guys were talking DnD yesterday and, although pretty much every one of my friends was a purple Crown Royal bag full of dice guy, I only played a couple of times. Always borrowed somebody else character
@TomMcW I still keep my dice in purple crown royal bags. (You can also fit a few airline sized bottles in there with the dice ... :-)
@JayCarr It's about trade offs, as all design work is.
@JayCarr It is mostly data driven, but when you make decisions, there isn't always one "perfect" choice. There is "this is good for that, but hurts me here" and "that is good for this, and it hurts me there." It usually takes a number of iterations to arrive at which compromise is the best overall ... and sometimes cost rears its ugly head in ways that bite people later. (Classic example is the S-92 main gear box lube filter Titanium bolts ... and the crash in Canada a few years ago).
@JayCarr A lil busy. Doesn't hours hunting down a couple of answers last weekend.
@KorvinStarmast JAL obviously didn't do too great of a job inspecting that bulkhead. The bad repair was there, slowly cracking away for 7 years before it finally gave out
@JayCarr OK, that payoff was in chasing the weight bogey above the transmission deck, choosing Ti versus steel to avoid corrosion and be lighter. Steel is cheaper, but takes more effort to fight corrosion in service. A "supportability" (life cycle) cost savings that ended up not being one.
@KorvinStarmast They do mention in the report that there was no known history of titanium studs breaking in other Sikorsky craft (like the CH-53, though it used 6 studs instead of 3 for the...oil filter bowl in the MGB?)
Is that just kind of an excuse?
Like saying, "well, it's never been a problem before! Sure Ti may seem like an iffy material, but it's never failed us before now!"
Or is the a good way to go about designing an aircraft?
@kevin lol, "Finally", it took me 2 years to do that. Congrats though ;). It's what you get for being one of them folks who can actually answer questions instead of just asking them :).
@JayCarr The issue was galling of the threads in service, which means that over time they don't hold the nut on as well. There had been an incident in Australia previous to that mistake where someone had landed due to oil leaking, and galling of the threads had been a part of that incident's findings. That didn't translate very well into "everyone needs to keep an eye on this" so an unfortunate bit of timing, and the apprehension about ditching in a rough and very cold sea
@JayCarr combined tragically. yes, using Ti is a "good way" to design an aircraft, as the lighter material and corrosion resistance for a helicopter sure to be operating in a maritime environment are valid design choice considerations.
@JayCarr I highly recommend taking a look at the discussions on PPRuNe to get a variety of insights onto that accident. Some people in the industry make some very solid points.
@voretaq7 I did that once on r/flying, everyone insisted on just answering the question on reddit instead of taking the time to write up the answer here... facepalm
@KorvinStarmast Yeah, I somehow managed to find it. Apparently it starts with the actually original announcement of the crash. I imagine this will be some grim reading but...well, that's the nature of aircraft accidents unfortunately.
@voretaq7 See, I've been debating that on a few occassions lately...
@KorvinStarmast It sounds like a lot of the people on this forum knew the pilots and passengers personally?
@KorvinStarmast That was some pretty interesting reading. Parts of it were about pilotage, parts of it were about mechanical failure, and a lot of it was about trying to balance cost v. safety. Lots of opinions on that last one....
Just to make sure I'm clear. The cost savings would have been on the side of the operator, correct? Because the Ti is non-corrosive, so it would have (ostenisbly) required less maintenance than Steel as a result. Despite the fact that steel studs threads will last longer... Something that apparently wasn't entirely accounted for when the craft was built.
@JayCarr The issue is that all design is a trade off; chasing the weight reduction goal goes to extreme lengths; life cycle/supportability features in an aircraft are part of what goes into "why you should buy ours"
@JayCarr Maintenance man hours per flight hour projection, and spares requirement over the life of an airframe are frequent selling points when the people you sell to are commercial (profit driven) entities, not military organizations. S-92 was mostly built for the commercial market, though it hoped to see some mil market as well ... which hasn't happened as much ...
Why does a Q&A search for "circled r" show only reirab’s answer about private airports and not PMoubed’s question about the Communications section in the Chart Supplement? Both contain the phrase in question.
Facts
The recurrent debate of whether simple questions are allowed or not is back. The questions are simple in the sense that answers are very easy to get online. Such recent questions:
Why does the Ka-50 (Hokum) have two main rotors, one on top of another?
What is the lump under the English E...
How do you put a link to another question, I have seen them, but I don't know how to do it.
Why does a Q&A search for "circled r" show only reirab’s answer about private airports and not PMoubed’s question about the Communications section in the Chart Supplement? Both contain the phrase in question.
The Hangar
The Hangar