Why Flight 93?

[Reheat]

The Concorde used analog FBW computers, and the A320 was introduced with digital FBW in 1984. I think all the modern Airbus planes are FBW, as is the Boeing 777. As Apathoid points out in this excellent paper, the 757/767 engines are essentially FBW.

Gravy, you have amassed a profound amount and variety of knowledge. I am truly impressed! Good show!

 

[apathoid]

I see no need for measuring vane angle. What purpose would that serve when the differential data is already recorded on the FDR?

In case the vane itself wasn't working properly. Say it seizes up - it wouldn't necessarily be self-evident in the FDR pitch limit data. The planes Stall Warning Computer would simply think AoA vane was wherever it froze, and the PLI would be computed accordingly.

 

[Reheat]

In case the vane itself wasn't working properly. Say it seizes up - it wouldn't necessarily be self-evident in the FDR pitch limit data. The planes Stall Warning Computer would simply think AoA vane was wherever it froze, and the PLI would be computed accordingly.

Yes, I understand redundancy, but this is not that important or as critical in an Airliner to justify the cost. They don't press the envelope enough to justify it, IMHO. I suspect that's why there aren't two probes.

Perhaps I'm a bit biased as I flew an aircraft which was an engineer's dream, but a pilot's nightmare. There is such as thing as too much.....

 

[apathoid]

Yes, I understand redundancy, but this is not that important or as critical in an Airliner to justify the cost. They don't press the envelope enough to justify it, IMHO. I suspect that's why there aren't two probes.

Actually, there are two AoA vanes and if I recall, they are independent(the left would control the Captains, and the right would control Junior's stick shaker), but I agree. That's all I'd think was necessary is a parameter looking for an active stall warning for both sides. But, as I look at the AA77 and UA93 FDR parameter list - I can't help but think there are many, many parameters which have no bearing on safety of flight(EFIS map range, HSI display mode, etc...), but I guess if there was a parameter for every part that could fail and jeopardize flight safety - there would be literally thousands of possible parameters!

Perhaps I'm a bit biased as I flew an aircraft which was an engineer's dream, but a pilot's nightmare. There is such as thing as too much.....

Boeing isn't hip to the whole "less is more" or "keep it simple stupid" ideology. Airliners today are unbelievably complex, and the easier they become to operate for the pilots, the bigger the pain in the butt they are to maintain.....except the 777, there is a computer that comes pretty close to the capability of HAL9000 on board .

 

[Corsair 115]

...except the 777, there is a computer that comes pretty close to the capability of HAL9000 on board .

Oh great, now we're at the mercy of the software programmers.

"Hello, Boeing? Yeah, I found a little bug in the code. The jet's computer refuses to allow the jet to take off. It keeps spitting out the 'I'm sorry, Captain, but I can't do that' error message."

 

[Reheat]

I can't help but think there are many, many parameters which have no bearing on safety of flight(EFIS map range, HSI display mode, etc...), but I guess if there was a parameter for every part that could fail and jeopardize flight safety - there would be literally thousands of possible parameters!

Absolutely! I was shocked to note all of the recorded parameters.
Seems to me virtually every aircraft system is recorded.....

 

[R.Mackey]

I guess the military paves the way as fly-by-wire has been a viable concept since the 60's, 70's at the latest. I did not realize Commercial Airline design was so far behind the technology curve.

The military does pave the way in some respects, since it's willing to pay much more for performance.

It also bears keeping in mind that military aircraft, fighters in particular, tend to be troublesome fliers -- at or beyond the point of dynamic stability, rapidly changing aspect, dwelling in the transsonic region way more than they should... all of this makes fly-by-wire darn near essential. By comparison, the 757 and 767 are smooth and stable as an easy chair. Hence the slower adoption of FBW in commercial aircraft.

Boeing isn't hip to the whole "less is more" or "keep it simple stupid" ideology. Airliners today are unbelievably complex, and the easier they become to operate for the pilots, the bigger the pain in the butt they are to maintain.....except the 777, there is a computer that comes pretty close to the capability of HAL9000 on board .

Ah, yes, the DMC and the diagnostic reasoner... now you're actually talking about my field. (Some years ago, I learned the on-board reasoner is sometimes called the "RRR," in a parody of "777," named after the initials of its inventor.) You think that's bad, wait until you see the stuff on the drawing board. Going to be a while, though.

 

[Gravy]

Oh great, now we're at the mercy of the software programmers.

"Hello, Boeing? Yeah, I found a little bug in the code. The jet's computer refuses to allow the jet to take off. It keeps spitting out the 'I'm sorry, Captain, but I can't do that' error message."

Hey, if there's a computer glitch, I want it to happen on the ground! These guys weren't so lucky:

F-22 Squadron Shot Down By the International Date Line.

I don't know if this one was a hardware or software problem, but I'm including it because it comes with amusing photos. http://www.spaceref.com/news/viewsr.html?pid=20396

 

[R.Mackey]

Happens.

Last time it was on the ground: (I can't do that, Dave)

We've also all heard the story of the autopilot inverting the plane when it crossed the equator, but I believe this is apocryphal, referring instead to some quirk in a simulator...

 

[Reheat]

Those computer glitches with the F-22 will be fixed and are not likely to reoccur, BUT..... It is truly scary to me just how much our entire military system has become dependent on computers. In the AF (at least) computers are used for everything from preparing meals, communications, obtaining supplies, maintenance, flight planning....on and on.....

I know and understand that this is somewhat true in the civilian world, as well, but I know for a fact that many in the AF can not do their job without a computer. It's frightening to me that the crews can't flight plan without a darn computer to do it....

The firewalls are massive and thought to be impenetrable, but hackers are always getting better and better. The results of 911 were the result of a similar attitude, but how soon we forget. There is just too much at stake to be this dependent on computer technology. In addition, it's as if no one has ever heard of EMP. (I'd prefer a puking smiley right now)

 

[PhantomWolf]

except the 777, there is a computer that comes pretty close to the capability of HAL9000 on board .

It goes crazy and ejects the passagers into space?

 

[Gravy]

Happens.

Last time it was on the ground: (I can't do that, Dave)

That was my second example. I would have ejected.

We've also all heard the story of the autopilot inverting the plane when it crossed the equator, but I believe this is apocryphal, referring instead to some quirk in a simulator...

Actually, I've never heard that one. But the one where the seaplane can only make left turns after crossing the equator, that's gotta be true....

 

[R.Mackey]

That was my second example. I would have ejected.

No, you probably wouldn'a. That option was considered, but there was no assurance that the canopy would release on ejection. The canopy is supposed to be rigged with charges to fracture it, but with balky software confirmed there was no expectation they would function either. The seat also has blades aside the pilot's head to cut through, but that's really getting risky.

Needless to say, ejecting while your canopy remains intact and locked can lead to severe back problems, dizziness, headaches, and instant death.

Also firing the seat would do much more damage to the aircraft. A fully-fueled aircraft, at that. And possibly destroy the record of what caused the problem in the first place. The pilot made the right call, no doubt directed heavily by his support team.

 

[Gravy]

I was joking about ejecting by the way, although I didn't know they had looked into the option! I can picture the huddle:

"Okay, let's brainstorm. There are no bad ideas here."
"Well, he could eject...."
"Okay, when I said there are no bad ideas, I meant there are no bad good ideas."

 

[beachnut]

No, you probably wouldn'a. That option was considered, but there was no assurance that the canopy would release on ejection. The canopy is supposed to be rigged with charges to fracture it, but with balky software confirmed there was no expectation they would function either. The seat also has blades aside the pilot's head to cut through, but that's really getting risky.

Needless to say, ejecting while your canopy remains intact and locked can lead to severe back problems, dizziness, headaches, and instant death.

Also firing the seat would do much more damage to the aircraft. A fully-fueled aircraft, at that. And possibly destroy the record of what caused the problem in the first place. The pilot made the right call, no doubt directed heavily by his support team.

Did the canopy emergency release fail, or did they decide to not arm it and have it stay, and then the fire department may get hit during a cut out?

 

[R.Mackey]

I'm going by third-hand reports from a friend who joined the T&E squadron at Edwards, but to my knowledge they decided not to try the emergency release -- once the major software SNAFU was confirmed, they simply pulled all the breakers and let the fire department chop through the canopy.

Like you say, it would be bad if they armed the emergency release, it didn't go, and left them with a potentially ticking time bomb. I believe the plan was to leave a few unknowns as possible, even if it took hours to resolve (which it did).

It's a new plane, after all.

 

[beachnut]

I'm going by third-hand reports from a friend who joined the T&E squadron at Edwards, but to my knowledge they decided not to try the emergency release -- once the major software SNAFU was confirmed, they simply pulled all the breakers and let the fire department chop through the canopy.

Like you say, it would be bad if they armed the emergency release, it didn't go, and left them with a potentially ticking time bomb. I believe the plan was to leave a few unknowns as possible, even if it took hours to resolve (which it did).

It's a new plane, after all.

Thanks. It sounds like they did good.

 

[wtcconspiracy]

Well this is my first post as a member on this forum. And just wanted to say I think this thread brought up an excellent post. I do believe 9/11 is total staged event. But why flight 93. It made no sense to have a plane just crash into a field. I never understood this one. I have not had chance to read this whole thread but just wanted to say I thought this was excellend thread. I will continue to read through it.

Ben

 

[slyjoe]

Well this is my first post as a member on this forum. And just wanted to say I think this thread brought up an excellent post. I do believe 9/11 is total staged event. But why flight 93. It made no sense to have a plane just crash into a field. I never understood this one. I have not had chance to read this whole thread but just wanted to say I thought this was excellend thread. I will continue to read through it.

Ben

Welcome to the forum Ben.

You are commended for wondering why things don't make sense. As you will find out if you search the forum, there are generally more rational explanations for things than "staged events". Members of this forum have a wealth of knowledge regarding 9/11, so be prepared to have your pre-conceived beliefs challenged (if you are brave enough).

 

[CptColumbo]

Welcome to the forum Ben.

Since you have a problem with 93 fitting into your version of what occured on 9/11/01, I assume that you have a version of what you believed happened on that day.