lomapaseo:

I get the jest! However, perhaps I worded my question inaccurately. I know the occupants of AF447 can tell us nothing. What I was trying to get at: if the passengers and, most importantly, the flight crew "felt" this rapid descent would it not make sense that the PF was applying stick up as he felt this rapid descent?

PS: don't need a bike to launch off a cliff. I'm fully cognizant of the feeling of rapid descents, having spent so many years jumping out of perfectly sound air craft!!!!!!

What do you feel when you're descending in an elevator?

Hi,

I feel something when the elevator go in motion (and I feel I go down or up)
It's just a very short feeling as the most of the travel (up or down) is made at constant speed (no acceleration or deceleration)
I have also a short feeling (of go up or down) when the elevator stop

Greybeard:

When I'm in an elevator which is going downwards I feel exactly that: descent.
Conversely, when I'm in an elevator which is going up I feel exactly that: ascent.

But a descending elevator does not normally descend at 10,000 ft/minute.

I just can't get my mind around an aircraft descending at 10,000ft/minute and no one
felt that. I'm not doing so out of any morbid or macabre reasoning. It just seems to me that at such a rate of descent that the PF might have felt the same and applied back pressure on the stick.

Then again, perhaps I don't fully understand the aerodynamics involved here.

One thing that has bugged me is that the flight control system very quickly gave up control when it lost airspeed information. In these degraded modes, I can understand dropping off the autopilot, but going to a degraded mode just because you lost two airspeed sensors is silly.

Others have theorized that using GPS/INS inputs could have been substutited for the missing pitot information, but actually there was, most likely a more simple solution and it is/was actually there all the time.

In every FADEC engine I have seen, the engine control requires total pressure at the engine inlet (so called PT2 sensors). I don't know what PT2 sensors are on the GE engines on the A330, but I'd pretty much bet that EACH engine has at least two of them. PT2 sensors are measuring the same thing as a the pilots pitot probe and the information could be readily suppled over the data bus to the aircraft. If the engine PT2 probes would have lost data in this event there would have been engine fault codes and a loss of engine control (engine FADEC failure), and that didn't happen. Since it didn't it is pretty safe to say they didn't have a loss of PT2 data in the FADECs.

It very likely that there were at least 4 or more total pressure probes that could have supplied sufficient information to keep the flight control system happy while the primary system sorted itself out.

Yes I know full well there are going to be certification issues with this kind of system. Probe life, reliability, and high angle of attack calibration are all issues, as well as issues related to continuing airworthiness if probes are changed from one type to another.

But all of that is paperwork. If they really wanted or needed that information, it was/is there all the time.

This goes back to what level of redundency do you need to be safe, but really, the extra data was most likely there all the time, all it would have taken is a programming change and the issue would never have arisen.

Maybe somebody with intimate knowledge of the CF6 in this installation can chime in on how the engine gets it PT2 information, but my guess, based on the dozen or two engines that I am most familiar with is that the data is out there.

In the first instance, you should be made aware of a Flight Global report attributed to the BEA.

Secondly, the FCOM provides the following statement on ABNORMAL ATTITUDE LAW -First reading of the above leads one to believe that each of the conditions is mutually exclusive, but if the Flight Global report is to be believed, that is not the case. The new interpretation is that the conditions are mutually exclusive PROVIDED all the ADRs haven't been rejected, but should all the ADRs be rejected, then an inertial upset involving either of the first two items will revert the aircraft to ABNORMAL ATTITUDE LAW.

If this was the case, the MANUAL PITCH TRIM ONLY was not displayed, as auto trim was still available.

Don't take it all as "gospel", as that is not what the FCOM currently says.

EDIT :: See post #1571 by A33Zab for details.

I suppose no one does to the full extent. See e.g. http://www.faa.gov/pilots/safety/pil...a/SpatialD.pdf

To me it seems there are two aspects to Auto Trim.
One is the normal behaviour of 1g Trim.

So the system tries to trim for 1g vertical acceleration.
This can theoretically only happen if the stick is neutral, because any Nose Up Stick Input means commanding > 1g.
Only when commandig 1g (i.e. Stick neutral) the system can know what the target FPV is where it is supposed to maintain 1g.

But that doesn't explain the 13° NU.

Somehow I've got a feeling it is a side effect due to the fact that after continuous NU the Aircraft started to stall and actually fell below 1g which the system tried to compensate by applying NU THS trim.

Somewhere there was a statement that the Autorim tries to support the elevator in case the latter alone is not able to achieve the requested attitude by the PF. I rather tend to think that the latter is a somewhat awkward description of what I mentioned in the preceding paragraph.

Air France Salvage Mission Ends - BBC
 

ADIRU
 

Went into the ADIRU today:

ADIRU computes AOAi from sensor resolver cos. and sin. and calculates
AOAc as function of AOAi, FLAPSLAT CONFIG and Sensor position(LH/RH)

If CAS < 60 Kts AOAi & AOAc are set to 0° and SSM (System Status Matrix) is set to NCD (No Computed Data),
this is also valid for TAS 0 Kts if CAS < 60

If CAS < 30 Kts it declares itself invalid and outputs 0 Kts and NCD.

These parameters are send to 8 similar ARINC output busses.
Bus 5-8 are reserved for the engines only. (Bus 7-8 are not used on A33).
Note: GE engine provides its own Air Data, A/C ADR is only used as backup.

PRIM 2 & 3 receives data by ADR's bus 2, PRIM 1 by ADR’s bus 3.

Note: In Back-Up Speed Scale (BUSS) equipped A/C AOA is send via IR bus
Note: Couldn't find if a SSM NCD is taken in account by PRIM but most probably it will.

In the 1st BEA report the unreliable speed logic is explained.

The PRIMs trigger a monitoring process when one of the speeds decreases more than 30 Kts (in 1 sec.) compared to the median value.
The PRIM opens a monitoring window during which it operate in ALT 2 Law, the rudder deflection limit is frozen but associated message is inhibited.
At the end of the monitoring window, if the diff. is less than 50 Kts the PRIM returns to normal law.
If not it remain in ALT 2 LAW and at that time the F/CTL RUD TRV LIM FAULTmessage is shown.
Outlier ADR is rejected and remaining control is on median value of the other 2 ADR’s
(Stall warning is generated by highest AOA and not the median value)
This means actual AOA could be indeed 40° while not triggering ABNORMAL ATTITUDE LAW due to a median AOA value below <30° as already mentioned in the BEA ‘leak’.

If 2 ADR outputs are erroneous, but different, and the remaining ADR is correct OR all 3 are erroneous but different:

The AP and A/THR disconnects and if disagree last for more than 10s, the PRIMs trigger the NAV ADR DISAGREEmessage.
ALTERNATE 2 LAW become active and latched for remainder of the flight.
(AP and A/THR can be re-engaged if ADR output was only transient.)

Active PRIM could in this case reject the correct ADR data.
That's why crew need to perform the unreliable speed Indic/ADR check QRH procedure and isolate the ADR in error. (Thus it will not be used for faulty PRIM input & indication).

The PF slight but consistent nose up command is a +G request to the PRIMs, the A/C feedback by means of accelerometers however results in a -G.
PRIM deflects elevator and due to negative result drives the THS all the way ANU.

Unfortunate left unnoticed because any hand on the trim wheel had cancelled the PRIM THS orders.

What do you feel when you're descending in an elevator?

This question is not fit for purpose unless a time frame is defined.

In a true equilibrium state you will feel nothing.

Rate of change of descent is quite another matter.

And as Dozy has commented, it's more hardware to fail. And failures, without very clever mechanical design, could be very bad failures.

In my sour moods I start asking, "Why does the A330 have any pilots at all?" Then two things come to mind. That would require more computer than was available in '386 days and pilots really have saved the A300 from bad conditions in the past. I still get the impression that some means to better integrate the pilots with the plane itself rather than via an automation condom might be worthwhile. Alas, nobody seems to agree on a way to do this which will not actually reduce the aircraft's reliability.

Has anyone ever done this in an airbus? :eek:

It seems to me that it is entirely possible that as they were in the convection that caused the assumed pitot icing, that they would be subjected to a significant level of turbulance and so detecting the overall trend of the aircraft by feel could be unlikely.

engineer-eer: is your point "PT2" a variation on the 5 measuring points of a gast turbine engine? IIRC, when we solved for various values in ideal engines, P1 = P2 was valid assumption, but doesn't that assume a few things about where one measures P2?

IIRC, IIRC, P1 is "outside" the system and P2 is "at the point of intake" and P3 is compressor discharge pressure P4 combustor out pressure and P5 exhaust pressure (afte it's been through the turbine wheels and made them spin) ... but it's been a few years since my turbojet engine class.

Something about using P2 to substitute for pitot air strikes me as very wrong, but I can't put my finger on it.

*My brain hurts, Mister Gumby!* :{

Engine sensors.
 

@ engine-eer.

Wouldn't do it for GE.

P0 is static port on ECU.
Sensor in inlet is Temp sensor T12
PS1.2 is static pressure ports just IFO fan.
The only probe measuring dynamic pressure is P2.5 just after the booster, but this is only used for conditioning monitoring and that's an option.

How and where? I was hoping somebody would have this sort of information.
Any links, or is this AMM or CMM type doc?
Makes lots of sense to this ancient.

Thank you for the excellent post A33Zab

Is there a threshold of displacement for the sidestick before inputs are valid? How slight is slight? In the a/c I drive, stick neutral and elevator neutral are not the same thing. This lends the stick a "loose" feel in its neutral position. As CONF iture mentioned:

PS: Can we infer the NU displacement from the info in the report:

10 degrees in 1 minute. Are we talking about a displacement so small that, let alone the PNF, even the PF might not have noticed the input?

mm43 - regarding feedback to the control stick I note that other forms of haptic feedback exist. I wonder if a vibration feedback to the pilot's back or some other convenient place could give a feel for control stick position without distracting the visual scan. If it was little vibrators in the seat back and one failed it would not be fatal such as an active stick force feedback might be. (Gus seems to hint that this can be done reliably enough military pilots will fly with it. But, as Dozy indicates it COULD be problematic if it went awry.)

A very enlightening post.

Manual inputs to the trim wheel override PRIM THS orders and the actuals are recalculated. That is how I understand it, and by implication, the PF could have braced himself using the trim wheel?

ADR
 

@ ChristiaanJ:

AMM - ADIRS 34-12-00 & ADR Operation 34-13-00.

Where as the English report shows only the following:

The French report seems to agree:
So BEA quotes nothing at all for 2:11:45 in either report. Here are their links, English and French. I choose to discount news reports that include information not in the BEA reports. It may be accurate as a leak. It is not official. And I prefer to go with the actual BEA reports as official data.

Comment to my own lengthy posting with BEA quotes. Here is a link that contains the French that was quoted in the article alex brin quoted.

It bears at best a superficial resemblance to the BEA reports with different times and some data being entirely different.

I choose to trust BEA and not get worked up over spurious reports.

rgbrock1

One feels acceleration. One does not feel velocity.

Howdy rg

What was felt inside by humans has a great deal to do with aspect, and rate, both of entry and exit. BEA claim roll excursions of 40 degrees. I assume they mean each way, so remember that in ALT 2, this a/c is "Twitchy on Aileron", and no one knows if these rollies were co-ordinated (with Rudder). Expect a fair amount of Yaw blended in, and Pitch is by no means nailed. Tail low, descent of 200 knots, with large g value trends. Not a walk in the park. Initially, the Brasilians made note of "flail injuries", those trauma that see extreme accelerations both positve and negative. This was noted of course on those recovered on the surface in the weeks following impact. I doubt there is a Seven Flags e-ticket ride that would come close to the accelerations in the fuselage. CAT can cause broken bones, necks, and serious Skull fractures. And that is simply the bottom falling out and back up.

Those unrestrained were thrown quite violently about. The picture thus far is presented as calm, measured, and conversational (Pilot to Pilot). I hope to God it was like that, but I truly doubt it was. In roll entry and recovery, those situate furthest from the cg (roughly) get the most shaking about. If your pilot is a known goofy foot, don't sit in back.

rgbrock,

I think if it´s a constant rate of descent you will not feel it (you might feel it at first when you go from level to a descent). In normal flight you are flying forward at 900 or more km/h, but you don´t feel it (except initial acceleration). Same thing , but vertical motion instead of horizontal.

Forget AoA, worry about speed
 

Thanks, A33Z.

So if we have the confusers not believing speed, or if they sense low speed, they forget about AoA protection? Does this work if the speed is zero or 1000 kts due to iced up pitots?

I can understand a WoW switch and 60 knots on the ground, but inflight???

Guess the engineers designed the system according to spec.

JD-EE: That's a creative idea, but I won't touch it with a 3.06 Meter pole.:)

Yeah, you aren't the only one who doesn't understand this bit of logic. Not sure if the fault is in the ADIRU logic or the stall-warning though - or maybe (I think the stall warning is not from ADIRU but higher level) both are "correct" for their inputs and outputs (eg. if the vanes don't work below 60kts maybe the ADIRU is "right" to send out no AOA value), but the overall result makes no sense.

It seems to be:That last one seems all wrong - if iAS is valid and <60kts in a big jet then surely you are stalled whatever the AOA vane says ? If iAS is invalid <60kts, then a warning might be spurious - but we run that risk if the speed is invalid but over 60kts, so why change at 60kts ?

It does look like a hole in the design (with the limited info we have at this point) - whether or not it is significant in the outcome in this case remains to be seen. Possibly it was irrecoverable anyway by the time this issue confused them.

POB Fall sensation
 

During the near 11,000 fpm from perigee to sea level the cabin pressure was kept quite constant during the few minutes fall? How typically varied?

What kind of "barometric" sensation the POB felt?

And during this fall, the ride was smooth? No bumps? No turbulence?

Just speed (constant)? Or some accelerations, (high AOA buffeting, together the recorded roll oscillations?

Most passengers realized the imminent crash? Felt the fall after perigee?

Or the few minutes "ride" was like a turbulent, same level typical one?

And both engines varying from TO/GA to idle (after the unusual 7,000 fpm climb while "en route") certainly put most POB alert.

And what about the aerodynamic noise (at the recorded AoA)?

Lonewolf,

Quote:

---

Something about using P2 to substitute for pitot air strikes me as very wrong, but I can't put my finger on it.

---

Station 1 is the free stream, PT2 is total pressure at the engine inlet. Total pressure is total pressure, whether you measure it at the engine inlet face or with a pitot tube, so long as it is properly derived and calibrated it’s the same.

A33Zab
That’s actually enough. If you have inlet temp, static pressure at the inlet, fan rpm and total pressure after the booster you have to use a fan map model and look up the pressure, but it can be calculated, and probably already is being calculated by the FADEC already and compared with the ideal map for condition monitoring. What you would do is, using the inlet temperature and rpm, you know how much pressure is being made by the fan and that allows you back calculate the free stream total pressure. Can be done pretty accurately (within a couple of knots) if you know the altitude.

Deep stall demo
 

Deep stall demo, described as bring "like falling onto a cushion", and "like falling onto a feather bed". (Maybe over-stated?)

Videos System > Viewing Video > SpaceShip Two Re-Entry Test - PestGaming

PJ2, thanks for your answer, very informative as always.
Do you think the QAR would have recorded the data for the #2 IAS ?
Would you know if all data available from the ACMS are automatically recorded in the FDR and/or QAR ?


I’m afraid the only option would be to link both sidesticks.
I think the sidestick as it is, is a great tool for a single crew operation, but for a multi crew … it is a sure way for wasting very valuable information.
For now I think some fighters have adopted a similar sidestick philosophy, also a Dassault Falcon, but I still don’t know what kind of sidestick the Bombardier CSerie will adopt … ?


Absolutely share your view.
The article you mention is not even signed ...
Flightglobal - Comment : AF447's new puzzles
Which 'detailed picture' ... !?
And apparently the problem is already solved !

What about this one :
Aviation Week - Air France Crash Suggests Inadequate Training
Full of inexactitudes and extrapolations.

Those aeronautical specialized media use their notoriety to misinform.

I'm not a jet pilot or engineer but..

Has the possibility of a fault with the PF stick been ruled out? Suppose that fault added a constant nose up. Presumably that would cause the THS trim to exagerate the problem? A stuck bit fault in a digital system can appear to add a constant to an otherwise correct value (eg it adds 1,2,4,8,16 etc) but you would hope error detection catches such faults.

Anyway Google finds..

Chapter 5. Flight controls

Hi,

OT about the feeling of the passenger
I jumped in the future and makes me in the court at the trial of the AF447
The potential feeling that had passenger and their knowledge of their fatal destiny can make a big difference in terms of money compensation to the families.
I'm sure it will be part of discussions among lawyers for the families of victims to demonstrate with the data of the flight that the victims had the knowledge of their fate.

And could that explain the initial disconnection of the autopilot? But what about the Auto Throttle? Could this be a case of extremely bad luck, with both the pitot probes and sidestick failing at the same time?

And there are a couple of other ways of cross-checking the pitot based airspeed. Inertial reference has already been mentioned, how about force required to deflect control surfaces, relationship between pitch/power/vertical speed (static/gps based)? The problem I think lies not in coming up with new ways to calculate airspeed, but how do we design and certify the software to work out which is valid? Simple voting between the various systems would probably not do - the system would need to cross-check the values and trends from the individual sources and estimate the probability of particular airspeeds being reliable. But how do we then present all this information to the pilot? Does any further advancement of the automation imply we need to take the humans out of the loop?


The BEA report did not mention anything about GPWS messages. Were the final seconds of what went on in the cockpit simply omitted from the report, or does this suggest that the ADIRU faults also led altitude measurements to be automatically deemed invalid?

Have read most of the technical discussion in these threads but one thing that seems strange is that there are no VS inputs recorded by the FDR ,if it records them at all,yet looking at the BEA released final track and 3 D graphic there was a reasonably tight turn to starboard presumably needing the rudder inputs -unless Bearfoil's suspicion re the VS is correct. I'm not aircrew but interested and impressed by the amount of expertise and the arguments between the experts.

Alternate with Manual Trim Law
 

Hi Golf-Sierra,

There may be lots of "very clever technical ways" of measuring airspeed. The aircraft has it's own natural way of flying a constant airspeed - simply don't change the power or stab trim.

I think it's a great pity that the stab trim didn't remain where it was once the system recognised spurious airspeed.
Do you think they will add another Law "Alternate with Manual Trim"?

Speed indication lower limit.
 

AOA / Speed lwr limits.

In the digital world they need to set a upper and lower limit.
You have only limited bits in a binary word and have to deal with accuracy, resolution, standarisation and......odds.

E.g. the odds to get into ALTERNATE LAW = 10^-5 per Flighthour (10^-3 under MMEL) as advertised.

The Speed indicating limits of ISIS (directly connected to Pt/Ps) are 5 - 600Kts, so backup is available.

AIB did develop the Back-Up Speed Scale. (Article dated Dec. 2007 - sorry can't get direct link working.)

5 Back UP Speed Scale (BUSS)
In order to decrease the crew workload in case of unreliable speed, Airbus has developed the Back-UP Speed Scale (BUSS) that replaces the pitch and thrust table. The BUSS is optional on A320/A330/A340. It is basic on A380, being part of the ADR Monitoring functions.
This indication is based on angle of atack (AOA) sensor information, and is therefore not affected by erroneous pressure measumements.
The BUSS comes with a new ADIUR standard (among other new system standards), where the AOA information is provided through the IRs and nor through the ADRs. This enables selecting all ADRs off without loosing the STALL WARNING PROTECTION.
The AOA information provides a guidance area in place of the speed scale. When the crew selects all ADRs OFF, then:
- The Back-Up Speed Scale replaces the PFD speed scale on both PFDs,
- GPS Altitude replaces the Altitude Scale on both PFDs.

The Back-Up Speed Scale then enables to fly at a safe speed, i. e. above stall speeds, by adjusting thrust and pitch.

http://i474.photobucket.com/albums/r...ab999/BUSS.jpg

The BUSS will be displayed once all ADRs are switched OFF. Therefore, on aircraft that have the BUSS, when the flight crew cannot identify the faulty ADR(s) when performing the troubleshooting, or when all ADRs are affected, the flight crew will switch OFF ADRs, and will fly the green area of the BUSS.

However, if the safe conduct of the flight is affected, the memory items must still be applied before troubleshooting.
As the BUSS is associated to the ADR monitoring funcitions, some unreliable speed situations can be automatically detected (e. g. new ECAM warning "NAV ADR 1+2+3 FAULT"), and some ECAM procedures will lead to the BUSS activation by requesting to switch OFF all ADRs.

****************************************************

But all of that wouldn't make any difference to this SWISS CHEESE case.

BTW ADIRS are also common in modern B brand airliners.