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  #41  
Old 20 April 2018, 12:17 AM
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The galleys definitely aren't designed to be turned upside down.
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  #42  
Old 20 April 2018, 12:26 AM
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I thought of the toilets due to what's probably an urban legend I once heard about a pair of pilots who were doing a ferry flight (that is, no passengers on board) and thought it would be fun to attempt a barrel roll, figuring no one would ever find out. According to the story they were caught when after they landed the ground grew found the lavatories covered with the blue fluid that had spilled out of the toilets.

ETA: And also the "poop train" thread probably made me think of toilets.

Last edited by WildaBeast; 20 April 2018 at 12:42 AM.
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  #43  
Old 20 April 2018, 12:45 AM
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Quote:
Originally Posted by jimmy101_again View Post
...The fuel systems and hydraulic fluid systems are almost certainly designed to be at least partly gravity fed...
Yup, covered that.
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  #44  
Old 20 April 2018, 01:36 AM
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I would think (WAG alert) that power would be the main problem even if the engines could fly inverted and all that other stuff were also fixed somehow. Some planes designed to fly upright only can also fly upside down but it takes a lot more power.
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  #45  
Old 20 April 2018, 07:12 AM
jimmy101_again jimmy101_again is offline
 
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Quote:
Originally Posted by ganzfeld View Post
I would think (WAG alert) that power would be the main problem even if the engines could fly inverted and all that other stuff were also fixed somehow. Some planes designed to fly upright only can also fly upside down but it takes a lot more power.
True, it might take considerably more power to fly upside down. But a plane in level flight isn't using all that much of its power capacity. If level flight took a very large percentage of the engines power capability then taking off or climbing would be an extremely slow process.

Planes are no doubt different, but for most cars cruising at 60 MPH takes 30ish horsepower. Even a pretty small modern car engine can generate 100 horsepower. You don't need 100+ horsepower to cruise at 60 (or 90), but you do need that much power to go from zero to 60 in a reasonable amount of time.
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  #46  
Old 20 April 2018, 03:01 PM
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Quote:
Originally Posted by erwins View Post

On the other hand, the number of people in pictures wearing the oxygen masks only over their mouths is a little disheartening. I mean, even if you missed the safety demo, it seems pretty obvious to me that you'd want to breathe normally, you know, through your nose. Obviously it didn't cause any major problems -- as I understand it, the plane descended rapidly after the decompression, so I'm not sure how long the oxygen was needed for.
You aren't alone in expressing concern over use of the oxygen masks:

Photos from damaged Southwest flight show passengers not heeding safety directives

Quote:
After the engine failure, pictures show a number of passengers incorrectly using their oxygen masks, which are deployed after a rapid drop in cabin pressure, reports CBS News' Kris Van Cleave. The masks are meant to be worn over both your mouth and nose.
https://www.cbsnews.com/news/southwe...-safety-demos/

~Psihala
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  #47  
Old 20 April 2018, 04:31 PM
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Here's a link to the video (https://youtu.be/EL5eMVGz5gk), but I'll summarize yesterday's press conference for those who understandably might not want to sit through it. On day two and above, the NTSB will release certain factual information, but they don't attempt to place those pieces into an overall puzzle. It's just a summary of what they know at the time.

The highlights:

-The failure took place as the flight was climbing out of 31,000 ft.

- Radar picked up pieces of the cowling falling through the atmosphere. The pieces were found based on estimates based on prevailing winds and from tips provided the public and/or law enforcement.

-At the moment of failure, there was an uncommanded left roll of 41 degrees, which the pilots recovered from. (Chairman Sumwalt, who flew for USAir, commented that normal bank angles are closer to 35 degrees.)

-The plane landed at 165 knots (190 mph - usual speed is around 130-135 knots) with five degrees of flaps (15 is normal) due to pilot concerns over potential controllability issues.

- Chairman Sumwalt then described the damage to the leading edge of the left wing. Based on paint transfers, the NTSB is determining which parts of the cowling struck the wing.

- On the issue of the window, the window is located at row 14, which is also where the deceased passenger was sitting.

- The NTSB has not found any significant amount of window glazing within the airplane or between the panel and the airplane's skin.

- There is a dent in the fuselage near the missing window.

- Pilot interviews were conducted on the day of the day 2 press conference.

- The NTSB recorders group will convene next week to listen to the Cockpit Voice Recorder. There was a brief explanation of the process of creating the transcript.

- Engine components are being assembled for transport to the NTSB Materials Lab in Washington D.C.

- Press questions.

~Psihala

Last edited by Psihala; 20 April 2018 at 04:44 PM.
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  #48  
Old 20 April 2018, 04:32 PM
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Quote:
Originally Posted by Psihala View Post
You aren't alone in expressing concern over use of the oxygen masks:

Photos from damaged Southwest flight show passengers not heeding safety directives

https://www.cbsnews.com/news/southwe...-safety-demos/

~Psihala
Yeah, the picture in that article is the only one I can find. It shows 3 people clearly wearing their masks wrong. I had been looking for something else, and thought I'd seen another pic with more people wearing them wrong, but when I looked again, I could not find any other picture of it. So I withdrew my comment, because the only evidence is 3 people did it this way. Should those 3 have paid better attention? Yes. But some reports made it sound like a large number of passengers got it wrong. I haven't seen evidence of that.

(I, like many regular flyers, can hear the instructions in my head at the mere mention of oxygen masks. And now that I travel with my kids, the flight attendants make a point of speaking to me directly to confirm that I know to secure my mask first before helping the kids. For the record, I'm still not sure that I would actually do that in an emergency. I know the reason, but I can't be sure that I would have the kind of rational thought required to override my impulse to help them.)

ETA: I just saw the second post. It sounds like it's possible that something hit the fuselage in a place and manner that caused the window to essentially pop out, rather than that a projectile came through the window.

Last edited by erwins; 20 April 2018 at 04:38 PM.
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  #49  
Old 20 April 2018, 04:36 PM
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Quote:
Originally Posted by jimmy101_again View Post
...a plane in level flight isn't using all that much of its power capacity...
You are correct that most airplanes have more power than required for cruise in order to takeoff and climb. Multi-engine airplanes generally have more margin besides, since the point of having more than one engine is (usually) so that you can remain in the air if one of the engines quits.

I don't know about jets, but the small airplanes I'm familiar with typically cruise at about 75% of rated power. Though I have taken cross-country flights in tired old airplanes where you push the throttle all the way in on takeoff and don't pull it back until you start descending at the destination.

Most small airplanes can stay in the air on surprisingly little power. The math for figuring out how much is pretty simple. Suppose you test a small airplane and find that it weighs 1000 lbs and that with the engine stopped it has a best glide rate of 8:1; that is, 8 feet forward for foot of altitude lost, at a speed of 70 mph--pretty typical performance. What you now know is that its drag at 70 MPH is 1000/8 lbs, or 125 lbs. That tells you that it takes 125 lbs of thrust to maintain level flight at 70 MPH.

The hard part is converting that thrust into horsepower. A rough approximation is:

HP ~ Thrust * Velocity (ft/sec)/550

70 MPH is 103 ft/sec, so:

HP ~ 125 * 103 / 550

HP ~ 23.4

You might look at that and be tempted to try building an airplane using a lawnmower engine (been done). But it bears remembering that that is just enough power to barely stay in the air at some certain speed, and going either faster or slower it descends. It also bears remembering that the parasitic drag that dominates the power requirements scales with the square of the speed. So if you want to go twice that 70 MPH, you need four times that 23.4 HP.

--Bob K.
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  #50  
Old 20 April 2018, 05:35 PM
jimmy101_again jimmy101_again is offline
 
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Quote:
Originally Posted by BoKu View Post
I don't know about jets, but the small airplanes I'm familiar with typically cruise at about 75% of rated power. Though I have taken cross-country flights in tired old airplanes where you push the throttle all the way in on takeoff and don't pull it back until you start descending at the destination.
Kind of like driving a 1960's era VW bug on a freeway. To throttle settings, idle and 100%.
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  #51  
Old 03 May 2018, 09:08 PM
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Sometime between 10 days and two weeks of the start of a major investigation, the NTSB releases a preliminary report of that investigation. Unless there are intervening, urgent, safety recommendations the agency determines are absolutely necessary, the preliminary report is often the last public update until a) the public docket is opened, and/or b) the Board meets to consider the final report.

Today, the NTSB did not issue a preliminary report, but rather an "investigative update" on what they've learned so far.

For those interested in reading it, it can be found here: https://www.ntsb.gov/investigations/...ntent=aviation

~Psihala
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  #52  
Old 03 May 2018, 11:25 PM
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Airplane

Thank you for posting that link Psihala.
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  #53  
Old 04 May 2018, 01:11 AM
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I know there are others who are following the story.



~Psihala
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  #54  
Old 04 May 2018, 01:55 PM
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Is it common for only one fan blade to exhibit signs of metal fatigue?

Seaboe
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  #55  
Old 04 May 2018, 06:13 PM
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It's plausible that that one particular fan blade had a manufacturing defect that made it weaker than all the others. Maybe GE or whoever makes the fan blades for them got a bad batch of titanium at some point that only affected one blade on that particular engine, or something like that.
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  #56  
Old 04 May 2018, 06:14 PM
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Assuming all the blades have no defects and there are no other mechanical issues, I think it would be uncommon for any one blade to fail. Any defects, though, in any blade will increase the chances of it.

Just weeks ago, the NTSB had a board meeting on an American Airlines uncontained failure from last year due to metal fatigue. There was a video summary during the meeting on how the ingots that form the blades are made and how the process can leave undetectable flaws in the material.

The answer will come out eventually, but I can't help wondering if this is going to be found to be of a similar origin. There hasn't been much time to act on the recommendations from that incident, even if the problem was discovered months before the report was prepared.

~Psihala

ETA: Quickly reviewing the docket information --- probably not similar. That was a failure of an entire disc and a different manufacturer.

Last edited by Psihala; 04 May 2018 at 06:39 PM. Reason: Get the Airline right, Psihala
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