Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

Air France A330 accident

Tech Log The very best in practical technical discussion on the web

Air France A330 accident

Old 11th Jun 2009, 14:05
  #81 (permalink)  
 
Join Date: Dec 2002
Location: UK
Posts: 1,867
Re; “ Why must we assume that it was ice that did provoque an unreliable Airpseed situation ”

Supporting Blacksheep’s answer (#73, #79), see the presentation Instrument External Probes.
For ref, the certification Appx C for icing is on page 126 of CS 25 Large Aircraft, also see Fig 5 (page 182) and compare the events (outside the cert envelope) with the information on The Ice Particle Threat to Engines in Flight and other similar references to engine problems which involved TAT anomalies.

The relevance of TAT freezing is as an indicator of the ambient conditions (temp/ice/water near large Cbs), also that the displayed temperature will always change (increasing temp).
Whereas with pitot icing the indications may not change unless altitude is changed (trapped pressure) or there could be fluctuating indications as shown in the first link. Thus there could have been many more pitot icing events which went unnoticed – and involve a range of aircraft types depending on the type of pitot probe and how the data is ‘managed’ before being displayed.

Also see The Ice Crystal Weather Threat to Engines slides 7 & 19 - TAT anomalies & Appx C.
safetypee is online now  
Old 11th Jun 2009, 18:43
  #82 (permalink)  
 
Join Date: Jun 2009
Location: east of 10° west
Age: 58
Posts: 115
safetypee - ice crystals..

well aware of the ice crystal - engine compressor icing debate..

would like to throw the following into the debate..

the weather has not changed that much in the last 50 years..

let's assume the atmospheric conditions described in these phenomena have been around for a long while..

Question: Could it be that we all are too cozy with all the new technology nowadays and fly closer to storms more often than in earlier times..???!!!
falconer1 is offline  
Old 11th Jun 2009, 19:30
  #83 (permalink)  
 
Join Date: Dec 2002
Location: UK
Posts: 1,867
falconer1 – “…we all are too cozy with all the new technology nowadays and fly closer to storms more often than in earlier times…”

Absolutely, Yes !
Investigations of several of the engine incidents (pre 2000) indicated that the fight crews, who had moved up from commuter / older aircraft, were using the ‘new’ digital radars without appropriate conversion training. Thus they flew in the ‘green areas’ closer to storm centres than they would have done previously.
Other crews, brought up on the new equipment showed some complacency. Avoiding a clearly defined storm edge on the WXR could be finessed; crews did not question if they had generated the picture correctly, nor that some storms are much more severe than others – ‘they forgot to be afraid’ (James Reason).
More recently the trend is reversing with the focus on turbulence, but even this is challenged with the economics of operation and airspace constraints.
IMHO crews lack deep knowledge of systems operation and limitations, particularly in relationship to the threat of weather – we all lack time for additional learning, and suffer to some extent from commercial pressure.

The atmosphere hasn’t change, except that perhaps we are flying higher and thus experiencing a different set of conditions (a little bit colder, a little thinner air, ‘just small changes’, etc).
Also, other aspects of technology have changed. Many of the ‘supercritical’ technologies have been applied to engine components and possibly probes; modern systems use smaller, fine tolerance parts, which proportionately might suffer ice (or other particle) contamination more readily. They may require higher standards of maintenance.

Like many aspects of safety, hazards originate from change, particularly when we don’t notice the changes.
What is disappointing in this accident is that it appears that many of the probe problems were known and the hazard severity identified even by the regulator, but the safety activities were not applied proportionately or in time.
No blame, just seeking an understanding from which we might learn.
safetypee is online now  
Old 11th Jun 2009, 20:26
  #84 (permalink)  
 
Join Date: Jun 2009
Location: east of 10° west
Age: 58
Posts: 115
agree - safetypee, BUT

lest somebody thinks I get carried away with a very subjective view of the subject ( aren't we all??) let's not forget for our statistics guys...

we also fly A LOT MORE.. more planes more flights..

and all in all we are tons safer now..

maybe just a lot more critical if something happens..

so let's stay real..

a lot of superb guys & gals out there flying superb airplanes..

with a safety record, nobody would have believed possible a couple of decades ago...
falconer1 is offline  
Old 11th Jun 2009, 21:57
  #85 (permalink)  
 
Join Date: Mar 2002
Location: Florida
Posts: 5,150
It's A Man Machine Interface Issue

More and more our accident causal chains are containing man and machine interface issues.

We have less and less all machine or all crew issues as the primary cause (in spite of some folks that use probable cause in reports)

Yes the overall accident rate is decreasing since the paper I presented in 1992 but we still have a lot to learn about to how to live with the systems that we create.

As always we need to not only identify the causal factors but decide as an industry where and how to address those that are most common today

Do we improve the machine or the man since neither will achieve perfection?
lomapaseo is offline  
Old 11th Jun 2009, 23:46
  #86 (permalink)  
 
Join Date: May 2007
Location: Florence,AZ
Age: 76
Posts: 15
Man machine Interface

Lomapaseo
Now you're talking. We will continue to improve the machines...but the interface to a human is THE critical component in the total performance picture.
I had this discussion with Al Smith at MDC years ago (around the time of the DC-9-50). The man/machine interface has to be intuitive!! And, here is the crux, it has to be intuitive to the pilot...not the engineer who designed it!!
When I was at Bendix, the RDR 1E and 1F Pilot's Guides were written by engineers. Most pilots didn't read them.
I rode a lot of jumpseat with CO, WA, FR, MX. AW, HA, AN, AV, and Air Mic, talking with crew about the use of WXR. A colleague did the same with other airlines. We agreed that most pilots are non technical!! WXR is also subjective. That drove the development of color and Doppler, both attempts to make the radar less subjective. It's better but not perfect.
I have always been concerned with the automation in the aircraft failing and handing the aircraft off to the pilot at the worst possible moment. Not sure how we prevent that scenario, but if I were flying the airplane I'd want to have some hands on, in a sim or benign conditions, practice, to prepare for that contingency. I think that training is most important.
Putt is offline  
Old 12th Jun 2009, 02:14
  #87 (permalink)  
 
Join Date: Aug 2007
Location: Canada
Posts: 62
Falconer 1
let's assume the atmospheric conditions described in these phenomena have been around for a long while..
Actually I recall reading a study that was trying to quantify why the size of super-cooled water droplets was increasing. Speculation was that it was due to several things, one of them being the decrease in particulate matter in the atmosphere due to lower levels of certain types of pollution. The end result from our perspective was that the icing models that had been used to certify a/c deicing systems were no longer valid and would have to be reevaluated. A link to the study when I can locate it again.
jurassicjockey is offline  
Old 12th Jun 2009, 02:41
  #88 (permalink)  
 
Join Date: Mar 2002
Location: Florida
Posts: 5,150
Pilot's Guides were written by engineers. Most pilots didn't read them
Or didn't understand what they meant.

Yes indeed, the line rides were good for both sides. The trouble is we don't always think with the same side of our brains, but we have to get over this hurdle!!

It's good to knock heads even if it's only in forum words with guys like PJ2 and Safety Pee etc. etc. We're going to get there if only because we care.
lomapaseo is offline  
Old 12th Jun 2009, 03:30
  #89 (permalink)  
 
Join Date: Nov 2006
Location: SoCalif
Posts: 898
OT

I must know you, Putt, and you can't be Stan Lipnicki. I knew Al Smith at DAC also.

The avionics manufacturers wrote Pilots' Guides, and few of them reached the pilots. They were too expensive to just hand out, after all. Besides, how many pilots would have read them?

Today, it's so easy to put a PG on a site, with unlimited access.

I did get to provide limited pilot training during re-currents. One Capt. said, "Don't use it in Wx; it attracts lightning." I was caught flatfooted by that, but recovered, saying, "Your old radar transmitter was 60,000 watts peak. This new radar transmitter is only 100 watts; it won't attract lightning.

GB
Graybeard is offline  
Old 24th Jun 2009, 14:03
  #90 (permalink)  
 
Join Date: Jun 2009
Location: Tewksbury Mass USA
Age: 76
Posts: 42
Structural Failure Hardly

For Gerunf at Post 59, and all in this thread

Okay so structural failure of the vertical stabilizer is hardly likely.

Has anyone any thoughts on engine structural failures ?

Would not engine vibes tell the tale ?

Does the ACARS on this specific accident broadcast vibes data ?

Does the ACARS transmit in intervals ? One pilot forum commented it may be 10 minutes ?
Data Guy is offline  
Old 27th Jun 2009, 08:55
  #91 (permalink)  
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 18,584
I'd like to bring this thread BTTT with a question generated by comments on the R&N thread. I am surprised to discover that there is not just 'Alternate Law', but AL2 as well. Can someone explain SIMPLY what this does? I THOUGHT I understood the AB philosophy (a bit!) and that unless in 'Direct Law' you could not stall the a/c - in other words, despite bungling the hand flying, the FCC 'took care' of you and limited/adjusted your pitch. I read now on R&N (takata #2440) that this is not so and that AL2 has no such protection.

Q2: Is it correct that while (handflying) in AL(1) the FCC would adjust pitch (nose-down) if it sensed a large drop in airspeed towards the stall, or is AoA the over-riding trigger?

I suspect I'm going to get different answers to these questions from different folk - which would put me straight back on my 'bandwagon' about training not keeping up with systems.
BOAC is offline  
Old 27th Jun 2009, 10:08
  #92 (permalink)  
 
Join Date: Mar 2009
Location: Middle East
Age: 47
Posts: 217
Alternate Law

BOAC

Acc. to AMM:

-
The control law level which is:

No. 1: normal laws,

No. 2: alternate laws,

No. 3: direct laws, from the highest to the lowest level.


The law is such that:
-
each computer establishes the highest level of law (normal, alternate or direct) it can engage, taking into account the results of the internal monitorings and the availability:

. of the ADIRUs,

. of the control components,

. of the control surfaces, THS and slats and flaps.


-
among the computers which can engage the highest level of law , the computer having top priority is chosen (if only one computer is capable of the highest level of law , this computer is selected, whatever its priority level).



In FCOM is mentioned that ALTN LAW has 2 categories. ALT 2 would happen when U have an ADR DISAGREE>

With 2 ADR lost U have no HIGH AOA prot. anymore
with 3 ADR lost U have no HIGH SPEED prot. anymore

hope this helps







h3dxb is offline  
Old 27th Jun 2009, 10:13
  #93 (permalink)  
 
Join Date: Mar 2009
Location: Middle East
Age: 47
Posts: 217
AOA Protection

BOAC
Q2: Is it correct that while (handflying) in AL(1) the FCC would adjust pitch (nose-down) if it sensed a large drop in airspeed towards the stall, or is AoA the over-riding trigger?
In ALT 1:

PITCH ATT is lost, HIGH AOA on ALT, but lost at loss of weight or slat/flap pos. failure.


Hope this helps as well
h3dxb is offline  
Old 27th Jun 2009, 11:32
  #94 (permalink)  
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 18,584
I don't think it has answered the questions? Let me try another way.

Does the FCC still have 'over-ride' on the control DEMANDS in Alt 1 and 2, and would either 1 or 2 command a pitch down if an impending stall was sensed, or, conversely, a pitch up with high speed?

Tyro - where are you?
BOAC is offline  
Old 27th Jun 2009, 11:55
  #95 (permalink)  
 
Join Date: Mar 2009
Location: Middle East
Age: 47
Posts: 217
Airbus Philosophy

BOAC

The answer is YES/NO. like written before:

in ALTN1 the AOA protection is there (till you lost weight or slat flap pos informations) and the EFCS protects and takes over.
in ALTN2 AOA PROT is gone when U have 2 ADR's faulty, HIGH SPEED at 3 ADR's faulty and the direct stick to surface so called direct LAW is working.

Old Boeing champ with yr FCC's
h3dxb is offline  
Old 27th Jun 2009, 11:59
  #96 (permalink)  
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 18,584
That's clearer, thanks. So in the AF crash, as we understand it, they would have been at Alt2 with no high speed prot? What, then, is the difference between THAT Alt2 and DL? EG Are there still pitch and bank or some other limits?
BOAC is offline  
Old 27th Jun 2009, 12:06
  #97 (permalink)  
 
Join Date: Mar 2009
Location: Middle East
Age: 47
Posts: 217
I knew this question would come

Before U lost the AOA/HIGH SPEED etc. due to this ADR failure U have still the LOAD FACTOR LIMITATION to +2.5g and -1.0g which is also lost in direct law.
h3dxb is offline  
Old 27th Jun 2009, 12:08
  #98 (permalink)  
 
Join Date: Mar 2009
Location: Middle East
Age: 47
Posts: 217
FCOM

SmartCockpit - Airline training guides, Aviation, Operations, Safety


Check 1.27.30 pg1

rgds
h3dxb is offline  
Old 27th Jun 2009, 12:26
  #99 (permalink)  
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 18,584
Great link - thanks.
BOAC is offline  
Old 27th Jun 2009, 12:28
  #100 (permalink)  
 
Join Date: Aug 2002
Location: Switzerland, Singapore
Posts: 1,305
Well, in fact, there are two different AL's. But alternate in the correct sense doesn't exist at all! Funny to here that after so much squak?

AL is just a transitionary phase from normal to direct law. Actually, when you are in AL, you are direct law in roll and some (un)protected condition in pitch. To make it easier, AI called this mode AL. But generally speaking, there are only 2 laws, normal and direct. Which is completly logical: Eighter the computer does it, or you!

To make it even more complicated, there are two different AL! If you are still with me, continue to read: There is AL with protections and AL without. Pretty simple, when your computers still can deliver protections, they do, if they cannot, they don't. So it goes back again to the "AL doesn't exist" from above.

So, your question is: Do you have over- and underspeed protection in alternate law? Well, it depends. If you are in AL with reduced protection (that's what you mean by AL1 I guess), you still have low and high speed stability, and you have load factor stability. So in other words, you have it all (pitch-wise). In AL without proctection, you only have only load factor stability.

Or, in other words: In AL1 you still have all. Well, nearly all. In fact, you don't have anything. The trap is in the word "reduced" protection. As soon as you are in AL, the nice little green double bars at the speed tapes disappear, and amber X's are painted. This is a clear sign that you are not protected against high or low speed conditions. So you have to live with it.

If someone is still able to follow me, you are an Airbus pilot

Dani
Dani is offline  

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.