Good A-380 Engine Failure Article: Systems Failures Galore

Re: Good A-380 Engine Failure Article: Systems Failures Galo

Pépé le Pilot said:
Just remember what happened to UA232...
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Well, hang on a second. Fly-by-wire aircraft still have to actuate the actual control surface. They still do that hydraulically. The United 232 accident was caused by a flaw in the DC-10, which was later remedied by hydraulic fuses. Not really a valid comparison.
 
Re: Good A-380 Engine Failure Article: Systems Failures Galo

dasleben said:
Well, hang on a second. Fly-by-wire aircraft still have to actuate the actual control surface. They still do that hydraulically. The United 232 accident was caused by a flaw in the DC-10, which was later remedied by hydraulic fuses. Not really a valid comparison.
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Well, in a way, it is valid. Neither aircraft was designed to withstand a burst of the magnitude which they experienced (fan burst on the DC-10, turbine on the 'Bus). The 380, possibly thanks to lessons learned from UA232, was non AS unprepared as the DC10.
 
Re: Good A-380 Engine Failure Article: Systems Failures Galo

jtrain609 said:
I think you're in for a high level of disappointment once you hit any aircraft with a high level of automation, be it Boeing, Embraer or Airbus.
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Reason 9,347 not to fly big airplanes.
 
Re: Good A-380 Engine Failure Article: Systems Failures Galo

Roger said:
Well, in a way, it is valid. Neither aircraft was designed to withstand a burst of the magnitude which they experienced (fan burst on the DC-10, turbine on the 'Bus). The 380, possibly thanks to lessons learned from UA232, was non AS unprepared as the DC10.
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You're right, but that doesn't have anything to do with fly-by-wire. That's the point I was trying to make.
 
Re: Good A-380 Engine Failure Article: Systems Failures Galo

dasleben said:
You're right, but that doesn't have anything to do with fly-by-wire. That's the point I was trying to make.
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Oh, I see. I thought we were both trying to make the point that FBW or no, if something sends shrapnel through your entire hydraulic and a few other systems you just might be boned. Unless your in the mighty Nine-Teen Hundo.
 
Re: Good A-380 Engine Failure Article: Systems Failures Galo

Roger said:
Oh, I see. I thought we were both trying to make the point that FBW or no, if something sends shrapnel through your entire hydraulic and a few other systems you just might be boned. Unless your in the mighty Nine-Teen Hundo.
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The mighty 1900 had so many other flying surfaces, and stability surfaces attached, you could probably lose an entire wing and be ok.
 
Re: Good A-380 Engine Failure Article: Systems Failures Galo

trafficinsight said:
Do they? I would think it's the opposite.
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I wrote that last post pretty late at night so sorry if it wasn't clear. I meant to articulate high pressure compressor/turbine (N2) vs. fan speed/low pressure turbine (N1). Kinetic Energy = 1/2 * mass * velocity ^2 (written as 1/2*I*w^2 for rotating things). I was digging around online looking for what the actual maximum N1 and N2 RPMs are and I ran across them in the TCDS for a GE CFM-56 engine (typical 737/A320 not A380) as being N1=4800 RPM and N2~15,200 RPM. Clearly the fan blades have the most mass, but the high pressure compressor/turbine blades are going three times as fast, and velocity gets squared in the Kinetic Energy equation so my guess was that ultimately the compressor/turbine blades will have more energy.

If they do, then couldn't they penetrate way further through the cowl/wing/cabin then a fan blade could if they spontaneously failed? That was my guess but I could be way off... :dunno:
 
Re: Good A-380 Engine Failure Article: Systems Failures Galo

I got the TCDS data from another forum and they were talking about how the tips of the fan blades were breaking supersonic, so just for fun I was wondering how fast the tips of the high pressure turbine were going. I assumed the diameter of the compressor/turbine section is ~2.5 ft (could be way off just cut the fan diameter of 5 ft in half), radius is then 1.25 ft and related it to angular velocity 15,200 RPM (converted to radians/sec -> 1591.7 rad/s) and you get Linear Velocity = Angular Velocity * Radius = ~2000 ft/sec. Mach 1 on a standard day is 1100 ft/s, so the tips of the high pressure turbine blades are going Mach 1.8. This is still for the GE, which is a lot smaller than the Trent 900.

Am I the only one that thinks that's INSANE? :insane:

Edit: The purpose of this post isn't to be all sensationalist "OMG we're gonna die!" on you guys, I just never fully appreciated how fast the HPT is actually going. That's some amazing engineering.
 
Re: Good A-380 Engine Failure Article: Systems Failures Galo

inigo88 said:
I got the TCDS data from another forum and they were talking about how the tips of the fan blades were breaking supersonic, so just for fun I was wondering how fast the tips of the high pressure turbine were going. I assumed the diameter of the compressor/turbine section is ~2.5 ft (could be way off just cut the fan diameter of 5 ft in half), radius is then 1.25 ft and related it to angular velocity 15,200 RPM (converted to radians/sec -> 1591.7 rad/s) and you get Linear Velocity = Angular Velocity * Radius = ~2000 ft/sec. Mach 1 on a standard day is 1100 ft/s, so the tips of the high pressure turbine blades are going Mach 1.8. This is still for the GE, which is a lot smaller than the Trent 900.

Am I the only one that thinks that's INSANE? :insane:
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Well, keep in mind that the air temperature at the turbine is really frakking hot so the speed of sound is significantly higher than standard.
 
Re: Good A-380 Engine Failure Article: Systems Failures Galo

I definitely see your point. Although in this case I just meant it for comparison against a more recognizable unit of speed (rather than calculating the actual mach number inside the hot section). We can all appreciate the speed of sound (and tend to associate it with standard atmospheric conditions at sea level), but feet/second or meters/second has very little tangible meaning unless you use those units all the time... and I personally tend to look at airspeed from the pilot's perspective in knots/mach number. :)
 
Re: Good A-380 Engine Failure Article: Systems Failures Galo

Autothrust Blue said:
Not to defend the pointy-heads in Toulouse (far from it most of the time, actually), but that's 150m remaining with:
* Slats up ("add such and such knots to Vref Conf 3")
* unknown CG
* Engine inoperative ("For landing, use conf 3, add such and such knots to Vref Conf 3")
* Inboard T/R consequently inoperative
* Brake/steering control unit fault/antiskid faults
* Unknown weight (I'm willing to wager that the aircraft was overweight)
* Aircraft structural condition unknown
* One hydraulic system inoperative ("...for landing use Conf 3 and add such and such knots...")
* Reduced aileron and spoiler effectiveness (I'd carry a few extra knots...)

That said, I don't like the decision to delete the outboard T/Rs to make weight, but I can understand the technical reasoning behind it. The pilot side of my personality disagrees with the engineering/technical half.

This, though, I'll buy:

Retrofit outboard T/Rs... :)
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I believe that the lack of outboard thrust reversers is not to save weight, but because the engines are so far from centerline that they are off the pavement and therefore putting reversers on them would just throw up a ton of fod.
 
Re: Good A-380 Engine Failure Article: Systems Failures Galo

Just a couple things:

1) The 747 has thrust reversers on the outboards. However, most of you need to realize how much footprint is put down by us and the A380. The brakes work really, really, really well. In aircraft this size, almost everything is operating near design limits, so if you reject a TO or have an abnormal landing where you are at a higher speed you expect to pop tires.

2) Especially for mshunter Boeings are far from perfect.
 
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