keesje
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Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 8:24 am

Unusual incident, scary story, seemed to have been a software glitch :


PILOTS on a Boeing 777 from Perth to Kuala Lumpur battled to gain control of the plane last month after an unknown computer error caused the aircraft to pitch violently and brought it close to stalling.

A flight attendant dropped a tray of drinks and another began praying as the Malaysian Airlines pilots fought to counter false information being fed into the aircraft's autopilot system and primary flight display.

The glitch prompted plane manufacturer Boeing to issue a global notice to all 777 operators alerting them to the problem.


http://www.thecouriermail.news.com.a...ge/0,5936,16626627%255E421,00.html
"Never mistake motion for action." Ernest Hemingway
 
797
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 8:28 am

Wow! that's scary!

Hopefully nothing else happened and all the passengers are ok.

That's something new for me, I've never heard of something like it.

Greetz.!
Flying isn't dangerous. Crashing is what's dangerous!
 
Bohlman
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 8:34 am

An Australian Transport Safety Bureau report released yesterday reveals the pilot in command disconnected the autopilot and lowered the plane's nose to prevent the stall but the aircrafts automatic throttle responded by increasing the power.

The pilot countered by pushing the thrust levers to the idle position but the aircraft pitched up again and climbed 2000ft.


That is NOT the correct procedure to recover from a stall. Throttles to the wall. Always. Maybe I'm not reading that correctly, but even if you're climbing and you want to descend back down again. If you have a software/AP glitch where you may not have full authority over the control surfaces or engines, altitude is life and you regain a stabilized cruise before changing yet another thing and going back down to altitude.

Regardless, this sounds like a pretty serious problem, if it ends up not being pilot error:

"There is a very simple test to do before you take off and that will tell you if your system has that problem or not," he said.

"To this point we haven't had any people coming back saying they've had faults."

Mr Morton said there were 525 777s in service and they had accumulated more than 10 million flight hours and 2million landings.


While it's certainly possible that the computer got the glitch in the air, I think it's also equally likely that the problem was not caught on the ground during preflight. It'll be interesting to see what comes from this.
I'm not pro-Boeing or pro-Airbus, I'm pro-crew all the way.
 
N908AW
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 9:03 am

One of the defining problems on FBW these days. Why does a computer's false thinking get to override a pilot's thinking?
'Cause you're on ATA again, and on ATA, you're on vacation!
 
Btriple7
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 9:13 am

I read that the 777 has three separate computers, and all three computers must agree on the specifics of a command (whether issued by autopilot or the pilot himself) before the command is executed. It seems odd that Boeing did catch this problem in their extensive testing of these computer systems back when the aircraft was released.

Has Boeing traced the problem and figured out a solution for it? They can't just issue an alert about a problem to the airlines without a reasonable solution for it.

Regards,
Btriple7

BTW: This my 100th post on A.net!!!

[Edited 2005-09-17 02:15:32]
Just...fly.
 
Pihero
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 9:17 am

Apparently, this was caused by an ADIRU fault,compounded with a software glitch.
Problem is, if you revert to a former software, you're likely to have a heading/route offset situation.

very interesting.
Contrail designer
 
QFA380
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 9:34 am

Hasn't this topic been discussed before MH B772 Involved In Freak Fall Over Australia.

QFA380
 
lnglive1011yyz
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 9:34 am

Quoting N908AW (Reply 4):
One of the defining problems on FBW these days. Why does a computer's false thinking get to override a pilot's thinking?

DEFINITELY a major cause for concern.

At least the pilots were able to overcome.

Question though to anyone who would know: Could the pilots have cut the fuse in the cockpit for the autothrottes, or is that something that cannot be done from the cockpit?

1011yyz
Pack your bags, we're going on a sympathy trip!
 
SATL382G
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 9:37 am

Old news...
777 - Emergency Airwothiness Directive Issued (by Zeke Aug 31 2005 in Tech Ops)
"There’s nothing quite as exhilarating as being shot at and missed" --Winston Churchill
 
Btriple7
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:20 am

If Microsoft made computer software for Boeing:
Captain: My atitude indicater has frozen up!
Copilot: Maybe if we use a lower frame-rate it will go faster.
Captain: A lower frame rate! (Pause) Is there anyway to turn off these flying tips? You would think I already knew how to fly this plane.
Copilot: You know, I heard about this patch you can download to fix these problems.
Captain: Is it made by Microsoft?
Copilot: No, it's made by Apple.
Captain: Then it won't work. Microsoft doesn't like competition. I guess that's what Boeing gets for taking the cheap alternative.


Joking aside, this is a serious problem that Boeing must fix.

Regards,
Btriple7

[Edited 2005-09-17 03:29:29]

[Edited 2005-09-17 03:31:13]

[Edited 2005-09-17 03:31:51]
Just...fly.
 
DLKAPA
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:24 am

Quoting Lnglive1011yyz (Reply 8):
Question though to anyone who would know: Could the pilots have cut the fuse in the cockpit for the autothrottes, or is that something that cannot be done from the cockpit?

The article doesn't mention anything about the pilots switching off the autothrottle, just the autopilot, so from this I gather they left the autothrottle armed the entire time...why didn't they just pull it?
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
N62NA
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:29 am

Quoting Btriple7 (Reply 11):
this is a serious problem that Boeing must fix.

I wonder if this is a Boeing issue or a Honeywell issue, as the article states:


Investigations are focusing on faulty acceleration figures supplied by a device called the air data inertial reference unit.

The device, which was sent to manufacturer Honeywell...


Do all B777s have the Honeywell system, or is it like engines where the airline gets to choose among different manufacturers?
 
lnglive1011yyz
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:30 am

Quoting DLKAPA (Reply 10):
The article doesn't mention anything about the pilots switching off the autothrottle, just the autopilot, so from this I gather they left the autothrottle armed the entire time...why didn't they just pull it?

Minor technicality, but doesn't this imply the auto-throttle was not shutting off:

(taken from the article)

The pilot reported no difficulties flying the plane but noted that the automatic throttles remained armed.

1011yyz
Pack your bags, we're going on a sympathy trip!
 
DLKAPA
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:33 am

Quoting Lnglive1011yyz (Reply 12):

The pilot reported no difficulties flying the plane but noted that the automatic throttles remained armed.

Right but there is a separate switch for the autothrottle, so he could be noting that they remained armed because he left them that way...that's all I'm saying the article isn't very specific.
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
lnglive1011yyz
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:35 am

Quoting DLKAPA (Reply 13):
Right but there is a separate switch for the autothrottle, so he could be noting that they remained armed because he left them that way...that's all I'm saying the article isn't very specific.

Gotcha --

However, assuming they WANTED to disarm them, and they wouldn't, is the pilot able to from a fuse panel on the flight deck?

1011yyz
Pack your bags, we're going on a sympathy trip!
 
777ER
Crew
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:36 am

Quoting QFA380 (Reply 6):
Hasn't this topic been discussed before

Here a link to the topic that I started http://www.airliners.net/discussions...general_aviation/read.main/2252629
 
soylentgreen
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:46 am

Quoting Btriple7 (Reply 4):
Btriple7

Concerning the topic at hand, it's interesting to hear recent talk by Lockheed and others that the future of fighter planes, and possibly commercial aviation, will be in "pilotless" form. Yikes!

[Edited 2005-09-17 03:47:42]

[Edited 2005-09-17 03:48:09]
 
Btriple7
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:47 am

Quoting N62NA (Reply 11):
Do all B777s have the Honeywell system

As far as I know, yes. In fact, I do not know of any other manufacturer of cockpit systems (except for maybe Raytheon). But does Honeywell design the actual software?

Maybe someone else can shed some light.
Just...fly.
 
soylentgreen
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:48 am

It's interesting to hear recent talk by Lockheed and others that the future of fighter planes, and possibly commercial aviation, will be in "pilotless" form. Yikes!
 
Derik737
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 11:24 am

Quoting Btriple7 (Reply 17):
As far as I know, yes. In fact, I do not know of any other manufacturer of cockpit systems (except for maybe Raytheon). But does Honeywell design the actual software?

There are many other avionics companies like Rockwell Collins, Smiths, Thales, etc. that make "cockpit systems". The Honeywell ADIRU (Air Data Inertial Reference Unit) are standard on the 737NG and the 777 (and most likely every other current production Boeing commercial airplane).

Litton is another long-time IRU manufacturer (used on the DC-10's).

More info on 777 systems:

The aircraft has a triple redundant digital autopilot and flight director designed by Rockwell Collins. The BAE Systems (formerly Marconi Avionics) triple digital primary flight computers provide the control limits and flight envelope protection commands. Each of the three primary flight computers contains three different and separately programmed 32 bit microprocessors, a Motorola, Intel and AMD, to manage the fly-by-wire functions.

The Boeing 777 was the first aircraft with an ARINC 629 digital data bus linked to the main and standby navigation systems. The navigation system includes a Honeywell ADIRS air data and inertial reference system with a six-ring laser gyroscope, a Honeywell terrain collision avoidance system (TCAS) and a Honeywell and BAE Systems twelve-channel global positioning system. The aircraft is equipped with a Honeywell all color weather radar.
 
Btriple7
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 11:26 am

Quoting Derik737 (Reply 19):
Derik737

I think you summed it up better than any of us.
Just...fly.
 
YYZatcboy
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 11:36 am

Quoting Derik737 (Reply 19):
a Honeywell terrain collision avoidance system (TCAS)

?? I think they might mean GPWS or Traffic Collision Avoidance System?
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cfcuq
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 1:07 pm

Brings me to what I dislike about fly-by-wire ( or drive-by-wire for that matter ) where you have an artificial intelligence making what may be life and death decisions for you. Now I'm a DC-3 and DC-6 jockey, pulleys and cables were basically extensions of my hands and feet. (Granted, pee poor maint/ inspect could still get you in a prob, but the bird basically did what you told it, control boost systems still followed pilot commands). When I saw that first fly-by-wire bird flop into the trees at Paris because the computer decided that damn it, we are landing despite what the pilot was commanding, it made me shudder to think that my ( and maybe our ) destiny is controlled by a static spark.
Oh, flame me if you like, I'm a big boy and can take it.  Wow!
 
PhilSquares
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 1:12 pm

Quoting CFCUQ (Reply 23):
When I saw that first fly-by-wire bird flop into the trees at Paris because the computer decided that damn it, we are landing despite what the pilot was commanding, it made me shudder to think that my ( and maybe our ) destiny is controlled by a static spark.

Suggest you go back and re-read the accident report. The aircraft did everything it was commanded to do. If anything blame CFM for the slow spool up!
Fly fast, live slow
 
Boeing747_600
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 2:27 pm

Quoting Bohlman (Reply 2):
The pilot countered by pushing the thrust levers to the idle position but the aircraft pitched up again and climbed 2000ft.

Its safe to assume that the autothrottles were armed all the time since the captain is reported as having stated this. So the A/T would have over-rode his pushing the thrust levers to the idle position. The A/T will do this because it was most probably engaged in the SPD (speed) mode and therefore would increase thrust to maintain the commanded airspeed. The most probable reason for the pitch up was because of the nose-up thrust moment that most transport aircraft with wing-mounted engines experience when the engines are spooled up. The Autopilot couldnt have commanded this since it was reportedly disengaged at the time and couldnt have commanded pitch to maintain altitude (which appears to have been screwed up anyway!)

I find it odd that

(a) the A/T wasnt disengaged along with the A/P,

(b) the Captain pushed the thrust levers to the idle position when the airspeed was down to freaking 158 knots at FL410!!!!!! (How stupid is that when faced with a stall?!?!?!?) I cant beleive that he actually did that!

and

(c) He let the aircraft let the aircraft climb 2000 ft after observing the first anomaly
 
ikramerica
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 2:45 pm

Quoting 777ER (Reply 15):
Here a link to the topic that I started http://www.airliners.net/discussions...52629

Yeah, but why should that stop Keesje from reposting anything negative to B or positive to A?  Wink
Of all the things to worry about... the Wookie has no pants.
 
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glideslope
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 9:03 pm

Quoting N62NA (Reply 11):
I wonder if this is a Boeing issue or a Honeywell issue, as the article states:

Unlike most companies theses day, my understanding is Honewell keeps it's software design in-house.
To know your Enemy, you must become your Enemy.” Sun Tzu
 
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Starlionblue
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:06 pm

Quoting N908AW (Reply 3):
One of the defining problems on FBW these days. Why does a computer's false thinking get to override a pilot's thinking?

But that doesn't happen, not even on Airbi. You can ALWAYS turn off the autopilot. Even Airbi have manual reversion. It's an urban legend that pilots aren't in charge of FBW aircraft. Ask and Airbus pilot.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Morvious
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:15 pm

Quoting Ikramerica (Reply 26):
Yeah, but why should that stop Keesje from reposting anything negative to B or positive to A?

Not at all negative to Boeing, but like others said, Honywell.

Software glitches are there for life, there isn't just one piece of software that is 100% perfect.
have a good day, Stefan van Hierden
 
MarcoT
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 10:32 pm

There's a very interesting and detailed article about this incident and its implications by Peter Ladkin in the comp.risk newsgroup.
Apart from the Usenet newsgroup it can be retrieved at:

http://catless.ncl.ac.uk/Risks/24.03.html

where comp.risk issues are archived. One can also google (group) for it...

Since it is quite long I'll just quote a couple of hilights:

Quote:

Date: Wed, 31 Aug 2005 11:19:04 +0200
From: "Peter B. Ladkin"
Subject: Flight Control System Software Anomalies

In this era of fly-by-wire, I am fond of saying that, as far as I know, there has never been a commercial aircraft accident caused by anomalies in flight control software. And it has been 17 years (the first A320 was introduced into service in 1988).

It is thus well to remember that designing and writing critical software-based systems for such applications is not a routine task that we now know how to perform. In fact, there are plenty of anomalies that crop up that the public doesn't hear about. Here is one that made it out, and a pointer to another.

[..]

Emergency AD 2005-18-51 was issued on August 29, 2005. An unsafe condition had been identified through analysis of an incident, and Boeing had issued an Alert Service Bulletin on August 26 addressing the problem with workarounds. The Emergency AD makes these actions mandatory. The FAA explains as follows:

Since [AD 2005-10-03] was issued, we received a recent report of a significant nose-up pitch event on a Boeing Model 777-200 series airplane while climbing through 36,000 feet altitude. The flight crew disconnected the autopilot and stabilized the airplane, during which time the airplane climbed above 41,000 feet, decelerated to a minimum speed of 158 knots, and activated the stick shaker. A review of the flight data recorder shows there were abrupt and persistent errors in the outputs of the ADIRU. These errors were caused by the OPS using data from faulted (failed) sensors.
This problem exists in all software versions after P/N 3470-HNC-100-03, beginning with P/N 3477-HNC-100-04 approved in 1998 and including the versions mandated by AD 2005-10-03. While these versions have been installed on many airplanes before we issued AD 2005-10-03, they had not caused an incident until recently, and the problem was therefore unknown until then. OPS using data from faulted sensors, if not corrected, could result in anomalies of the fly-by-wire primary flight control, autopilot, auto-throttle, pilot display, and auto-brake systems, which could result in high pilot workload, deviation from the intended flight path, and possible loss of control of the airplane. ................

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other Boeing Model 777 airplanes of this same type design. Therefore, we are issuing this AD to prevent the OPS from using data from faulted (failed) sensors, which could result in anomalies of the fly-by-wire primary flight control, autopilot, auto-throttle, pilot display, and auto-brake systems. These anomalies could result in high pilot workload, deviation from the intended flight path, and possible loss of control of the airplane. This new AD supersedes AD 2005-10-03.

Note that the consequences list has been extended by "possible loss of control of the airplane". According to John Sampson, the incident to which
the AD refers occurred to a Malaysian Airlines B777-200 on 3 August 2005, on Flight MH 124 from Perth to Kuala Lumpur [3]. The aircraft returned to Perth after 51 minutes flight for an emergency landing after an ADIRU malfunction
which caused a "flight control outage".

This is the first public statement of which I know which addresses classes of Byzantine faults. Byzantine faults have occurred, seriously, in avionics before but the details are not public (see the quote from [6] below).
Byzantine faults are faults in which agents (sensors, computers) in a distributed system "lie" to their interlocutors: they do not fail silently but distribute erroneous data, or data which is read differently by different receivers. The name arose from a whimsical analogy by Lamport, Shostak and Pease to a group of Byzantine generals trying to reach agreement in a situation in which no one trusts anyone else to speak the truth.

[..]

Dealing with Byzantine faults became an extremely active area of distributed computing theory, but practitioners did not take them so seriously at first, perhaps partially due to the very high resource consumption of the solutions: Lamport, Shostak and Pease showed that any correct algorithm to achieve consensus required a large number of processors (roughly speaking,
at least 3n+1, where n is the number of "liars") and a lot of processor cycles. It follows that solutions judged to be practical are unlikely to be
complete solutions, and therefore one must analyse the actual problem space more closely to find out where one can most profitably handle possible problems, and which areas one can ignore.

Too short space for my favorite hopelessly long winded one liner
 
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Starlionblue
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RE: Scary Incident, Pilots Battling Autopilot B777

Sat Sep 17, 2005 11:00 pm

Quoting Morvious (Reply 29):
Software glitches are there for life, there isn't just one piece of software that is 100% perfect.

That is true, and if you look at accident stats in the last few decades pilots are "even less perfect" than software.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Derik737
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RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 12:39 am

Quoting YYZatcboy (Reply 22):
Quoting Derik737 (Reply 19):
a Honeywell terrain collision avoidance system (TCAS)

?? I think they might mean GPWS or Traffic Collision Avoidance System?

Good catch! I didn't notice that error when I copied the info.

The Enhanced Ground Proximity Warning System (EGPWS) computer is manufactured by Honeywell on all current production Boeing Commercial Airplanes. The airline may choose either Honeywell, ACSS or Rockwell Collins for the 777 Traffic Alert and Collision Avoidance System (TCAS) computer.

What's interesting is that the current Honeywell TCAS is actually the old Allied Signal TCAS and the current ACSS TCAS is the old Honeywell TCAS. When Honeywell merged with Allied Signal, they had to shed their TCAS product for the merger to be approved. L3 Communications purchased the old Honeywell TCAS product line (including Mode S Transponders) and formed ACSS with Thales.

Quoting Starlionblue (Reply 30):
Quoting Morvious (Reply 29):
Software glitches are there for life, there isn't just one piece of software that is 100% perfect.

That is true, and if you look at accident stats in the last few decades pilots are "even less perfect" than software.

I recently saw a flight data playback of a flight where the aircraft went into multiple high-rate climbs and stalls over an airport due to full nose-up trim. I was shocked beyond belief watching the 3D replay of this incident. I don't know what incident it was as I was not allowed to have the pertinent data. I even had to question the presenter a few times if it indeed was real. However, I do know that it was not a FBW aircraft.
 
neilking
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RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 12:52 am

Quoting PhilSquares (Reply 23):
Quoting CFCUQ (Reply 23):
When I saw that first fly-by-wire bird flop into the trees at Paris because the computer decided that damn it, we are landing despite what the pilot was commanding, it made me shudder to think that my ( and maybe our ) destiny is controlled by a static spark.

Suggest you go back and re-read the accident report. The aircraft did everything it was commanded to do.

I once read a quotation about the Habsheim accident which was something like "The A320 cannot exceed its envelope but that doesn't mean the envelope doesn't exist" which summed it up well for me. I'm not a pilot but I imagine flying that slow and that low put you right at the edge of the envelope!
 
PHXinterrupted
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RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 1:06 am

Quoting Ikramerica (Reply 25):
Quoting 777ER (Reply 15):
Here a link to the topic that I started http://www.airliners.net/discussions...52629

Yeah, but why should that stop Keesje from reposting anything negative to B or positive to A?

Exactly. Keesje will only post negative things about Boeing...nothing ever goes wrong at his beloved Airbus. lol
Keepin' it real.
 
Wiggidy
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RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 1:35 am

Quoting PHXinterrupted (Reply 33):
Exactly. Keesje will only post negative things about Boeing...nothing ever goes wrong at his beloved Airbus. lol

And nothing ever goes wrong at your beloved Boeing PHX, oh wait, what are we talking about here?

A quick question, who makes the FMS on the 777? Could this problem be attributed to faulty coupling between the FMS, INS, and autopilot?
-Wes
 
ikramerica
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RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 2:12 am

Quoting Morvious (Reply 28):
Not at all negative to Boeing, but like others said, Honywell.

If it were an A aircraft, K wouldn't have posted it. All I'm saying.

Not saying nothing goes wrong with B or A or E or C or any other plane. Just K seems to like to post only about B "failures" and A "triumphs" whenever possible.
Of all the things to worry about... the Wookie has no pants.
 
patrickj
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RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 2:36 am

Quoting Bohlman (Reply 2):
That is NOT the correct procedure to recover from a stall. Throttles to the wall. Always. Maybe I'm not reading that correctly, but even if you're climbing and you want to descend back down again. If you have a software/AP glitch where you may not have full authority over the control surfaces or engines, altitude is life and you regain a stabilized cruise before changing yet another thing and going back down to altitude.

In this instance the correct way to cause the nose to pitch down would be the removal of thrust thus causing a nose down pitching moment, rote recovery techniques can not be substituted for situational awareness. Since the aircraft recovered it sounds like the pilot did the right thing.
 
irelayer
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RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 2:58 am

I have a simple question:

Couldn't they have turned the autopilot off? Isn't there an emergency "red button" somewhere that just turns the damn thing off no matter what?

-IR
 
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glideslope
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RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 4:05 am

Quoting Ikramerica (Reply 35):
Not saying nothing goes wrong with B or A or E or C or any other plane. Just K seems to like to post only about B "failures" and A "triumphs" whenever possible

Hey, cut they guy a little slack. He needs all the strokes he can get these days. Between the 380 Re-Design and the 350 "what's it going to be, and when?" We must try and understand the frustration.  Smile
To know your Enemy, you must become your Enemy.” Sun Tzu
 
LCH
Posts: 47
Joined: Fri Sep 17, 2004 1:19 am

RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 4:19 am

Quoting IRelayer (Reply 37):
Isn't there an emergency "red button" somewhere that just turns the damn thing off no matter what?

Like the A/P disconnect bar? (Which is actually white...) =)
 
flyboy36y
Posts: 2897
Joined: Sun Mar 19, 2000 1:45 pm

RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 4:29 am

I think the reasl problem that caused these computer problems is that someone forgot to turn off their cell phone.
 
tundra767
Posts: 400
Joined: Fri Jan 14, 2005 9:33 am

RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 4:47 am

Sounds like Hal from 2001 A Space Oddessy paid them a visit.
 
backfire
Posts: 3467
Joined: Fri Oct 06, 2006 8:01 am

RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 5:10 am

Quoting Bohlman (Reply 2):
That is NOT the correct procedure to recover from a stall. Throttles to the wall. Always.

Sorry - I disagree. As any flight instructor will tell you, the first thing you do is to unstall the wing, almost always by applying nose-down pitch control. Increasing the throttle, particularly the thrust from under-wing engines, can increase the angle of attack, contributing further to the stall condition - it therefore becomes necessary to reduce the thrust as part of the recovery process. Only once the wing is unstalled should thrust be applied as part of the recovery.
 
Bohlman
Posts: 263
Joined: Mon Jun 06, 2005 11:52 pm

RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 5:26 am

Quoting Patrickj (Reply 36):
In this instance the correct way to cause the nose to pitch down would be the removal of thrust thus causing a nose down pitching moment, rote recovery techniques can not be substituted for situational awareness. Since the aircraft recovered it sounds like the pilot did the right thing.

Unfortunately, this is just not the case. Pitch due to thrust usually results in around 3 degrees of pitch, up or down. When you're at 158 KIAS, zero flaps, at FL410, and getting the stickshaker, you don't remove power. You pitch with the yoke, not with the engines especially in a stall situation. Also, contrary to popular belief, correct procedure in transport category aircraft is not a duplicate of GA airplanes, but to maintain pitch, increase power. Stick shakers come on before the onset of a stall (actual stalls in swept wing aircraft are pretty near unrecoverable), and because of the shear amount of power transport category aircraft have, they're designed to power out of it. You can't fool around with pitch or power settings when you're 400 feet off the ground and descending at around 800 FPM. It takes a while to stop the descent, and if you fool around for 5 seconds, and it takes the engines 15 seconds to spool up, you're getting pretty close to the ground.

Just because an aircraft recovers doesn't mean the pilot did the right thing, it means he may have gotten lucky. You can talk about situational awareness all you want, and criticize what I'm saying as preaching "rote recovery techniques", but even in hindsight, based on what that article said, there's no way he should have reduced the throttles.

Quoting Boeing747_600 (Reply 24):
the A/T wasn't disengaged along with the A/P,

I find it less surprising in the short term, seeing as they're separate switches. I do wonder why it wasn't/couldn't be disabled after that.

Quoting Starlionblue (Reply 30):
That is true, and if you look at accident stats in the last few decades pilots are "even less perfect" than software.

Yeah, and if you look at most of those statistics, it's because of multiple software failures that many of the accidents happened. Pilots are designed to deal with as many failures as humanly imaginable, but for everybody, there's a breaking point. However, because pilots have been trained to deal with, say, 8 failures at once, if a pilot crashes the plane with 7 failures, that's deemed pilot error, because he was trained to deal with 8, and should have been proficient enough to deal with 8. Also, when you say something like that, how many accident statistics don't exist because of pilots dealing with computer failures successfully? Without a pilot on board with an FMC failure, the plane would likely crash, but because that pilot is on board, that midflight FMC amounted to little more than an inconvenience to the pilots.
I'm not pro-Boeing or pro-Airbus, I'm pro-crew all the way.
 
Bohlman
Posts: 263
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RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 5:29 am

Quoting Backfire (Reply 42):

As I said in my post, this is the case for GA aircraft with tapered/hershey bar wings, but it is not the correct procedure in transport category aircraft with swept wings.
I'm not pro-Boeing or pro-Airbus, I'm pro-crew all the way.
 
User avatar
Starlionblue
Posts: 17053
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RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 5:41 am

Quoting Bohlman (Reply 43):
Quoting Starlionblue (Reply 30):
That is true, and if you look at accident stats in the last few decades pilots are "even less perfect" than software.

Yeah, and if you look at most of those statistics, it's because of multiple software failures that many of the accidents happened. Pilots are designed to deal with as many failures as humanly imaginable, but for everybody, there's a breaking point. However, because pilots have been trained to deal with, say, 8 failures at once, if a pilot crashes the plane with 7 failures, that's deemed pilot error, because he was trained to deal with 8, and should have been proficient enough to deal with 8. Also, when you say something like that, how many accident statistics don't exist because of pilots dealing with computer failures successfully? Without a pilot on board with an FMC failure, the plane would likely crash, but because that pilot is on board, that midflight FMC amounted to little more than an inconvenience to the pilots.

I don't know if we're agreeing or not  Wink Pilots may be imperfect, but I'd rather have them on board than not. Also, can you name one occasion where the cause of a commercial airliner crash was software?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
neilking
Posts: 98
Joined: Sun Aug 14, 2005 11:18 pm

RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 5:49 am

Quoting Backfire (Reply 42):
Sorry - I disagree. As any flight instructor will tell you, the first thing you do is to unstall the wing, almost always by applying nose-down pitch control. Increasing the throttle, particularly the thrust from under-wing engines, can increase the angle of attack, contributing further to the stall condition - it therefore becomes necessary to reduce the thrust as part of the recovery process. Only once the wing is unstalled should thrust be applied as part of the recovery.

I am not a pilot (just an enthusiast who frequently messes up landings on MS Flight Sim) but I can understand Backfire's point here - "Firewalling" the engines on a 777 (or any aircraft with engines slung under the wings) in a stall situation would just pitch the nose up even further, wouldn't it? From 1st principles, I would hazard the comment would it not be better to get the nose down and let gravity take its course and then sort the thrust out once we were in recovery, not descending like a runaway elevator.

But I accept that nobody but a true 777 pilot is qualified to pontificate on this so maybe I should keep my opinions to myself.

May I also say I am quite new to posting on A.net and my reactions so far are:-

1. I'm beginning to think there are some people who think they are very authoritative but actually don't really know what they are talking about. This is v confusing for people like me who are interested but get confused with possibly "bogus" replies.

2. The webmasters may wish to to consider giving true commercial pilots some sort of recognisable A.net accreditation (icon) so people like me can decide which posts to believe (especially on Tech/Ops - not so important in other forums).

3. I can't understand why some posters get so hostile!!!!

Just my thoughts - don't mean to cause any offence.

Rgds to all,

Neil
 
backfire
Posts: 3467
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RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 5:59 am

Quoting Bohlman (Reply 44):
As I said in my post, this is the case for GA aircraft with tapered/hershey bar wings, but it is not the correct procedure in transport category aircraft with swept wings.

I'm sorry to keep disagreeing dear fellow, but the information I gave is based on a 1998 bulletin compiled jointly by Boeing, Airbus and (then) Douglas chief test pilots specifically regarding stall recovery (not approach-to-stall manoeuvres) on large transport-category aircraft. In fact, the joint bulletin aimed to highlight just how similar the recovery processes were across the large-jet fleet of all the manufacturers. Nothing to do with GA.

Could you elaborate on why you appear to disagree with those credentials, as well as two trained and experienced Malaysia Airlines 777 pilots?

[Edited 2005-09-17 23:02:09]
 
Gasman
Posts: 1387
Joined: Mon Mar 01, 2004 10:06 am

RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 6:10 am

Quoting Neilking (Reply 46):
. I'm beginning to think there are some people who think they are very authoritative but actually don't really know what they are talking about.

You have wisdom beyond your years!  Smile

Over time you'll get an appreciation of who to take notice of on A-net. Occasionally you'll be reading what appears, by the tone of the author, to be an authorotative piece only to suddenly read something like "and this is just not the way the B777 flies on Microsoft Flight Simulator 2002!". Other times it's not so easy. If suspicious, click on the author. If the age says "13-18".........
 
Derik737
Posts: 262
Joined: Sat Dec 11, 2004 5:53 am

RE: Scary Incident, Pilots Battling Autopilot B777

Sun Sep 18, 2005 6:50 am

An approach to a stall is a controlled flight maneuver; a stall is an out-of-control, but recoverable, condition. These situations are handled differently. I will use the 737NG here for a baseline since that's the plane I have familiarity with.

During the initial stages of a stall, local airflow separation results in initial buffet giving natural warning of an approach to stall. A stall warning is considered to be any warning readily identifiable by the pilot, either artificial (stick shaker) or initial buffet. Recovery from an approach to stall is initiated at the earliest recognizable stall warning, initial buffet or stick shaker.

Approach To Stall - Stickshaker or Buffet

If ground contact is not a factor:

At the first indication of stall (buffet or stick shaker) smoothly apply maximum thrust, smoothly decrease the pitch attitude to approximately 5 degrees above the horizon and level the wings. As the engines accelerate, counteract the nose up pitch tendency with positive forward control column pressure and nose down trim. (At altitudes above 20,000 feet, pitch attitudes of less than 5 degrees may be necessary to achieve acceptable acceleration.) Accelerate to maneuvering speed and stop the rate of descent. Correct back to the target altitude.

If ground contact is a factor:

At the first indication of stall (buffet or stick-shaker) smoothly advance the thrust levers to maximum thrust and adjust the pitch attitude as necessary to avoid the ground. Simultaneously level the wings. Control pitch as smoothly as possible. As the engines accelerate the airplane nose will pitch up. To assist in pitch control, add more nose down trim as the thrust increases. Avoid abrupt control inputs that may induce a secondary stall. Use intermittent stick shaker as the upper limit for pitch attitude for recovery when ground contact is a factor.

When ground contact is no longer a factor, continue to adjust pitch as required to maintain level flight or a slight climb while accelerating to maneuvering speed for the existing flap position.

Autopilot Engaged

If an approach to a stall is encountered with the autopilot engaged, apply limit thrust and allow the airplane to return to the normal speed. At high altitude, it may be necessary to initiate a descent to regain maneuvering speed. If autopilot response is not acceptable, it should be disengaged.


Recovery from a Fully Developed Stall

An airplane may be stalled in any attitude (nose high, nose low, high angle of bank) or any airspeed (turning, accelerated stall). It is not always intuitively obvious that the airplane is stalled.

An airplane stall is characterized by any one (or a combination) of the following conditions:

• buffeting, which could be heavy
• lack of pitch authority
• lack of roll control
• inability to arrest descent rate.

These conditions are usually accompanied by a continuous stall warning. A stall must not be confused with the stall warning that alerts the pilot to an approaching stall. Recovery from an approach to a stall is not the same as recovery from an actual stall. An approach to a stall is a controlled flight maneuver; a stall is an out-of-control, but recoverable, condition.

Note: Anytime the airplane enters a fully developed stall, the autopilot and autothrottle should be disconnected.

To recover from a stall, angle of attack must be reduced below the stalling angle. Nose down pitch control must be applied and maintained until the wings are unstalled. Application of forward control column (as much as full forward may be required) and the use of some nose-down stabilizer should provide sufficient elevator control to produce a nose-down pitch rate. It may be difficult to know how much stabilizer trim to use, and care must be taken to avoid using too much trim. Pilots should not fly the airplane using stabilizer trim, and should stop trimming nose down when they feel the g force on the airplane lessen or the required elevator force lessen. Under certain conditions, on airplanes with underwing-mounted engines, it may be necessary to reduce thrust in order to prevent the angle of attack from continuing to increase. Once the wing is unstalled, upset recovery actions may be taken and thrust reapplied as necessary.

If normal pitch control inputs do not stop an increasing pitch rate in a nose high situation, rolling the airplane to a bank angle that starts the nose down may be effective. Bank angles of about 45°, up to a maximum of 60°, could be needed. Normal roll controls - up to full deflection of ailerons and spoilers - may be used. Unloading the wing by maintaining continuous nose-down elevator pressure keeps the wing angle of attack as low as possible, making the normal roll controls as effective as possible.

Finally, if normal pitch control then roll control is ineffective, careful rudder input in the direction of the desired roll may be required to initiate a rolling maneuver recovery.

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