Air France 447 - On topic only!

[3WE]

...Frozen pitot's generally result in an increase in the airspeed indication with altitude...

Why exactly?

The ASI actually measures the differential pressure between the pitot tube where air is being crammed in from the forward movement of the plane, and the approximate ambient pressure (that is represented by the pressure from the static port.)

If the pitot freezes (and seals like Gabriel says), and then you climb, the climb causes the ambient/static pressure to fall (you are climbing to thinner air), causing a greater differential which would show as a higher airspeed indication. (Generally, the static port is less likely to ice over).

Dudes have stalled out while trying to slow down from what they thought was increasing airspeed.

With respect to Air France, Gabriel largely dismisses this as the AF airspeed indications were low and not high (and yeah, maybe lowering the nose a little might be a good way to get some more speed....no, never mind)

[Evan]

So you pull up some to slow down, but then your speed increases more, so you pull up more.

To slow down from what? If your pitots are blocked, your airspeed indication is very low to begin with. Pulling up would seem a bit insane. Nice try though.

[Deadstick]

Whoops....why has no one said this (at least not recently)?:

If you freeze your pitot tube and climb, the indicated airspeed increases.

So you pull up some to slow down, but then your indicated speed increases more, so you pull up more.

Fixed, for Evan.

[3WE]

To slow down from what? If your pitots are blocked, your airspeed indication is very low to begin with. Pulling up would seem a bit insane. Nice try though.

Sorry Young Jedi...your lack of a pilots license and drivers license and lack of time on MSFS and in certain books has betrayed you.

Ready to face ITS and Flyboy, are not you. Your training complete is not.

[Evan]

Sorry Young Jedi...your lack of a pilots license and drivers license and lack of time on MSFS and in certain books has betrayed you.

How... (sorry, I had to cancel my geek warning)... How so?

Tell me, Jedi Master, how pitots blocked by ice crystals are going to result in an airspeed indication approaching overspeed?

(and no Jedi mind suggestion)

[Evan]

Hey, I just found this on Skybrary:

Autopilot, auto thrust, and flight directors can all contribute to loss of control in the event of unreliable speed.

Now how do we get line pilots to read Skybrary?

[3WE]

How... (sorry, I had to cancel my geek warning)... How so?

Tell me, Jedi Master, how pitots blocked by ice crystals are going to result in an airspeed indication approaching overspeed?

(and no Jedi mind suggestion)

In some ways, we have one of those collisions of knowing fundamentals versus "the aircraft-specific memory checklist from the QRH".

Someone else on this forum and this thread asked how the increase in airspeed indications worked...very recently.

I explained.

Gabriel and Deadstick also contributed information.

For further reading, I would suggest a generic instrument training book, check the index for instrument failures, and icing.

Do not check the Airbus QRH and memory item checklists. It has nothing to do with programming the computer.

Repeating, planes (note that I used plural) have been stalled out and crashed because of this phenominon. Additionally, a number of planes (again plural) have been stalled out or almost stalled, but fortunately the pilots recovered, again because of the blocked pitot increasing airspeed indications with climb phenomenon. I did not make these incidents up!

By the way- the words "approaching overspeed" speak not did I. Your ability to discern fundamental airmanship from the procedural side of the force weak still it is.

[Evan]

By the way- the words "approaching overspeed" speak not did I. Your ability to discern fundamental airmanship from the procedural side of the force weak still it is.

No. You didn't speak those words. You spoke these words:

So you pull up some to slow down, but then your speed increases more, so you pull up more.

Using the Force, I translated this to mean they would have a reason to slow down, aka overspeed.

Normally I'd just let you off the hook 3WE, but since you made this into a personal attack on my supposed ignorance...

...explain to me why they would want to pull up to slow down from an indicated airspeed already far below the normal one.

[Black Ram]

my gather from the report is that the investigators were NOT convinced the crew were in agreement over UAS. while they both mentioned "speeds" they never actually stated "UAS" or anything like this.

"The impression of an accumulation of failures created as a result probably did not incite the crew to link the anomaly with a particular procedure, in this case the “Vol avec IAS douteuse” procedure"

"The symptoms perceived may therefore have been considered by the crew as anomalies to add to the anomaly of the airspeed indication, and thus indicative of a much more complex overall problem than simply the loss of airspeed information."

"The PNF detected the climb based on observation and reasoning (“according to all three you’re climbing”), which indicates the beginning of a loss of confidence in the instrument readings."

I could go on quoting for a day or so, but the idea is that these guys were lost. Scared shitless and lost. The captain returned in the midst of absolute mayhem and he too became lost.

I agree they were lost. However, the other crews who experienced UAS didn't link it to the proper procedure either. But once again - and I think this is very important - none of them did what the pilots of AF 447 did. Also, they clearly knew they were in Alternate Law, so except if they were complete amateurs, they must have known the implications, namely the loss of flight envelope protections.

It is true the report sometimes seems to be trying to give the pilots the benefit of the doubt. However, this for me is a major let down, because it can be (and is sometimes) interpreted as exonerating AF and their training program, the real culprit here. Personally for me this is unacceptable and very dangerous. Just look at AF's history - they first crashed the A320, the A340 and the A330 (non-test flights), and the pilots' actions played a crucial role in all of those. I honestly get scared when I think what could be next... But, the good news is the recommendations and the summary of the causes of the tragedy in the end of the report talk over 90% about pilot training, interaction, overseeing, human factors. The only mention of the Bus is about the lack of a clear indication of UAS (no guarantee it would have had any effect) and a possible improvement of the cockpit ergonomics.

So I don't think Airbus failed big time. But since nothing can be perfect, I'm all for finding a way to make improvements (though it's not in the recommendations). I even thought, why can't the AP and AT carry out the UAS procedure on their own, instead of disengaging? Maybe more automation is the answer.

[Black Ram]

That said, I think the fault handling of the glass cockpit could be improved, but it is in no wise a "ten minute" upgrade! There is a lot of complex logic in there, and the ramifications of even the smallest change are big. There'll be testing and review and regulatory approval and and and and before it reaches a 'plane that one of us will ever board.

Yeah, but the first thing would be to announce plans for changes to the cockpit. I don't think I have heard even rumors.

[kris]

Repeating, planes (note that I used plural) have been stalled out and crashed because of this phenominon. Additionally, a number of planes (again plural) have been stalled out or almost stalled, but fortunately the pilots recovered, again because of the blocked pitot increasing airspeed indications with climb phenomenon. I did not make these incidents up!

Which ones?
AF447 is not one of them.

[Peter Kesternich]

Which ones?
AF447 is not one of them.

Northwest Flight 6231

http://en.wikipedia.org/wiki/Northwest_Airlines_Flight_6231

[Evan]

Ecam confusion theory

Ok, here's another bit o grasping speculation: It seems very obvious from the CVR that the crew never undertook the proper ECAM actions, which require verbal requests and confirmations between the two pilots as each item is processed and cleared. If not processed and cleared, the messages would present themselves as follows:

2:10:05 - The first ECAM item would have been: AUTO FLT AP OFF (loss of autoflight). This is a level 3 message, meaning it is displayed in red and remains at the top of the list because ECAM messages are displayed according to priority. It remains there throughout the crash sequence. Ok, fine.

2:10:08 - The next item would be an amber advisory message: F/CTL ALT LAW (PROT LOST) followed by a blue action message: MAX SPEED.......330/.82

I wonder if the PF, in a confused state of mind in IMC, was monitoring these messages and misinterpreted MAX SPEED.......330/.82 as an overspeed warning message... and initially pulled up to slow the aircraft.

Here's the thing: the ECAM only has so many lines and therefore displays the most important messages at the top based on priority, so other messages do not appear intil these messages are cleared by the crew (a green arrow indicates that more messages are waiting to be displayed). So, as a result...

2:10:10 - The amber message AUTO FLT A/THR OFF appears, along eith the blue action message THR LEVERS.......MOVE moving the existing message F/CTL ALT LAW (PROT LOST) down. The message MAX SPEED.......330/.82 is also pushed down the list BUT REMAINS DISPLAYED.

2:10:15 - The message ENG THRUST LOCKED appears along with a second crew action message THR LEVERS.......MOVE. Only now does the message MAX SPEED.......330/.82 momentarily scroll down off the display.

2:10:23 - the THR LK mode is deactivated

2:10:24 - As a result, the ENG THRUST LOCKED and both THR LEVERS......MOVE messages disappear, allowing room for the message MAX SPEED.......330/.82 to reappear!

2:10:24 - 2:12:?? - MAX SPEED.......330/.82 then likely remained on the ECAM until after 2:12:00 when the message NAV ADR DISAGREE and the related procedure for this replaced it on the ECAM.

Now look at the CVR. Pitch attitude begins to increase at 2:10:08, when the message MAX SPEED.......330/.82 first appears, and continues until reaching 12° at about 2:10:28 when the the PNF instructs the PF to watch his speed, and the PF replies that he is going back down.

The initial pull up and sustained pitch application almost exactly mirror the time that the message MAX SPEED.......330/.82 is initially displayed.

Ok, so it's just another food-for-thought theory, but the we have established that A) the crew was sufficiently disoriented, and B) the crew did not follow proper ECAM procedures or anything resembling CRM, so I don't find it that far-fetched to think they were this poorly acquainted with the meaning of the ECAM messages. And it would possibly explain both the initial pull and the duration of that pull. And C) the FD's (when available) might have been corroborating this action.

=========

Even if this is the reason for the pitch command, fault still lies with Air France for not training them on correct ECAM actions, and not with the ECAM itself. Yes, the messages can be—and hopefully will be—made clearer, but lets not forget that a dozen other A330 crews did not make this mistake and 767 pilots do just fine without any ECAM assistance. And, of course, Flight Directors need to be turned off (or at least disregarded) no matter what you are flying.

[3WE]

an indicated airspeed already far below the normal one.

Where did I say that?

[3WE]

If your pitots are blocked, your airspeed indication is very low to begin with.

This would conflict with general aeronautical knowledge.

I don't belive you will find this in generic training manuals, nor aircraft-specific manuals and memory checklists.