AF 447 Search to resume

[BOAC]

All this techno-babble about GPS/INS etc. All we need are:

1) Multiple (3?) probes with adequate heating

2) Instruments which provide basic attitude and engine settings WITH NO COMPUTER INTERFACE for use in any failure of 1)

3) Crews trained to use 2) if 1) happens.

So simple.

[auv-ee]

Originally Posted by JD-EE

auv-ee
I was concerned with that towing scenario and potentially snagging the ROV to cage tether on rocks given the mountainous terrain.

It's all about situational awareness. With lights, cameras and maybe an altimeter (acoustic range to bottom) on the cage/depressor, this can be done. Remember that 1knt is only 0.5m/sec horizontally, and the winch rate is typically 1-1.5m/sec; it's manageable. Doing this depends on the tools available to the operator (tether management between depressor and ROV, adequate visibility, ...), the operator's skill, and the severity of the terrain/currents. Certainly there are times and places where the ship can move with the ROV deployed, and others where it cannot.

[gums]

Salute!

Thank you, BOAC. Well said, IMHO.

The current crop of "Playstation" pilots and crew are beginning to scare me.

Fer chrissakes, point the plane best you can using the ADI or stby gyro and keep power where it would normally be. NO AUTOPILOT in turbulence. Let the jet fly as it was designed to and she'll prolly do just fine.

Seems we had a "bus" Delta crew with a loss of IAS and such and they did just fine holding attitude and normal power setting ( inbd to Tokyo?). Sheesh

Gums sends ...

[bearfoil]

Can't fly pitch and power w/o AH and throttles, though. The AH is an option, only luddites would want one.

bear

[FlexibleResponse]

engine P1
Quote:
Originally Posted by ettore
Would air speed measurments at the engine intake, compared against the tremendous engine's thrust, be reliable ?
Not a bad idea at all. Very likely each engine has its own probes for measuring intake total pressure P1 and intake total temperature T1, which are used by the engine electronic control system (FADEC). The difference between Pitot pressure and P1 is engine intake total pressure loss, which is quite small in cruise. I don't know if the engine's P1 probes have ever experienced similar icing problems as the airplane's pitots.

HN39

Yes the engine probes in the A330 fitted with Roller engines did suffer this problem. RR engines have a P1 probe to measure pressure ratio as the thrust is measured as EPR.

Quite a few years back I had a pax visit to the fight deck of my A330 and who was an engineer from RR Derby. I (actually the a/c) was able to demonstrate this problem as we negotiated TS's over the Philippines and each engine was affected in turn by icing as the supercooled water at cruise altitude exceeded the heating capability of the probes. The effect of the icing of the P1 probes was to reduce maximum allowable EPR (blue triangle in the EPR gauge) in each engine as it was affected by icing. The RR man was excited to access the data from the MCDU (under supervision of course).

I subsequently learned that RR first knew of this problem from experience on the B747-400 but they were reasonably unconcerned as the consequential P1 error from icing was temporary in time and reduced the max allowable EPR and therefore was considered to be safe.

[auv-ee]

BEA Phase 3 Update

BEA has updated their Phase 3 Search page to briefly describe the results of the search. I don't see any new information, other than an updated search coverage map.

Sea Search Operations

[MurphyWasRight]

Quote:
engine P1
Quote:
Originally Posted by ettore
Would air speed measurments at the engine intake, compared against the tremendous engine's thrust, be reliable ?
Not a bad idea at all. Very likely each engine has its own probes for measuring intake total pressure P1 and intake total temperature T1, which are used by the engine electronic control system (FADEC). The difference between Pitot pressure and P1 is engine intake total pressure loss, which is quite small in cruise. I don't know if the engine's P1 probes have ever experienced similar icing problems as the airplane's pitots.

HN39

Given that the need for true backup airspeed is rare here is another possible option:

Deploy the RAT (ram air turbine) emergency generator and use the RPM and generated power to compute air speed.

This would also require air temperature and static pressure for decent accuracy, although even without those a usable estimate might be possible.

I don't know if this is at all practical (max speed etc) but it would certainly be an alternate method.

(I created a similar message yesterday but appear to have not actually submitted it, so pardon in advance if this shows up as a dupe.)

[HazelNuts39]

AoA in gust encounter

For whom it may interest - How AoA changes when encountering an upward gust:
25 fps gust
35 fps gust

HN39

[Smilin_Ed]

Murphy Sez

Deploy the RAT (ram air turbine) emergency generator and use the RPM and generated power to compute air speed.

The rat will also accrete ice and given that it (probably) isn't heated will ice up pretty quickly.

As an old f@&t, I have to say that if you really get into icing and turbulence (which you should avoid anyway), the way to survive it is to keep the power at cruise settings and fly attitude. Ignore altitude fluctuations. Turn the autopilot OFF or you'll be fighting it constantly. You will move up and down with the air mass but as long as you are stabilized within the air mass, you will get through it.

[mm43]

HazelNuts39;

Very interesting.

Looking at the graphs in post #1467, I sense that the relationships between AoA, vertical gust velocity and "g" are fairly linear, and riding a 50fps gust is going to give an AoA of 5.6 degrees and 1.72g. Does using a fixed mixing zone figure, e.g. 300 feet, produce a higher "g"?

It follows that loss of an effective CL is a given.

mm43

[HazelNuts39]

Originally Posted by mm43

Does using a fixed mixing zone figure, e.g. 300 feet, produce a higher "g"?

mm43;
thanks for your reply. The 35 fps gust with 300 ft mixing zone will result in a peak AoA of 5,0 degrees and 1,55 g. At higher AoA's the cL-alpha will become non-linear and "g" will be limited by cLmax (stall).

35 fps 300 ft

regards,
HN39

[UNCTUOUS]

DECONSTRUCTING the BBC Treatment in the Search for alternative explanations

To assist an author looking at the entire vista of AF447 plausible scenarios, I've deconstructed the BBC transcript to as much as possible offer one alternative explanation.
.
The first file is the unexpurgated BBC transcript and the second is a commentary on certain aspects of that (with the line numbers in the 2nd file relating directly to the BBC transcript's line numbers).
.
RIGHT-CLICK save as ......
.
Please feel free to comment upon either/both (seeking validation/verification).
.
a. BBC Transcript
..................link one
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b. Comments upon the BBC program's treatment of the AF447 mystery
..................link two
.
..................

[auv-ee]

Originally Posted by UNCTUOUS

From linked comments, regarding control of pitot heat:
This could be done via an altitude switch or via an outside air temperature (OAT) threshold. This recourse assumes that the OAT

If the underlying problem is that there can be both too little and too much pitot heat, then it seems that the logical approach is the direct one: to embed a thermistor in the pitot head and regulate the heat (for example, by duty cycle) to maintain a safe temperature at any speed/altitude. Someone likely knows a good temperature to use for the core of the probe that would keep the whole probe ice-free, possibly 40-60C?

[sensor_validation]

@UNCTUOUS

What is your mechanism for a pitot to slightly under-read?

If the ram-port blocked the the indicated flow will fall to zero if the drain open - guess you are looking for partial blockage of ram with drain open? If the drain also blocked the total pressure locked and indicated flow will vary with static pressure (known danger during take-off climb). I fear drain holes blocking at similar rate on more than one pitot could lead to small over-read before all 3 disagree, but as Takata has already pointed out still unlikely.

What are the real speed margins before or after a reduction in speed for turbulence entry?, and what is magnitude of drain hole blockage effect? If ice detected/suspected how much engine power will be used on wing anti-icing measures?

@auv-ee

Its going to be very difficult to maintain the temperature of pitot tube in 500 mph wind at much above the ambient air temperature - monitoring the power needed would turn it into a "hot-wire anemometer". If melting out ice the surface in contact with the ice will be at the freezing point of the water - a principle you could use to detect ice! You do need temperature control when on the ground to avoid turning the probes into soldering irons.

[jcjeant]

Hi,

UNCTUOUS
Thank you .. good job.

[GreatBear]

@UNCTUOUS

In your section 173: "An ACARS message from the airplane recorded the sudden onset of critical Mach and the autopilot disconnecting due to the high aerodynamic trim loads it was holding (and no longer could)."

There were no ACARS messages recording "the sudden onset of critical Mach." The AUTO FLT AP OFF message arrived at 02:10:10 quickly followed by AUTO FLT REAC W/S DET FAULT (unavailability of the reaction to wind shear detection function), then F/CTL ALTN LAW (PROT LOST) and the others.

Overspeed/underspeed/stall as part of the upset sequence has been discussed at length on this and the prior thread, and remain still in the realm of whatIfs. MachCrit is but one of the possibles. Need the black boxes to work out the sequence.

I'd be interested in your expert opinion and description of the politics that might be influencing the science of the "researches" so far. Who are the interested parties and national and international stakeholders; what are the lawers looking for (and why); what are the truths that would be favorable or unfavorable to these groups and why. Can the truth be bent in such investigations? How? That description would in many human ways define our times...

GB

[UNCTUOUS]

GreatBear asked:
I'd be interested in your expert opinion and description of the politics that might be influencing the science of the "researchs" so far. Who are the interested parties and national and international stakeholders; what are the lawyers looking for (and why); what are the truths that would be favorable or unfavorable to these groups and why. Can the truth be bent in such investigations? How? That description would in many human ways define our times...

The following linked input (for the same author) may answer that:
.................link

GreatBear also said:
In your section 173: "An ACARS message from the airplane recorded the sudden onset of critical Mach and the autopilot disconnecting due to the high aerodynamic trim loads it was holding (and no longer could)."

There were no ACARS messages recording "the sudden onset of critical Mach." The AUTO FLT AP OFF message arrived at 02:10:10 quickly followed by AUTO FLT REAC W/S DET FAULT (unavailability of the reaction to wind shear detection function), then F/CTL ALTN LAW (PROT LOST) and the others.

Overspeed/underspeed/stall as part of the upset sequence has been discussed at length on this and the prior thread, and remain still in the realm of whatIfs. MachCrit is but one of the possibles. Need the black boxes to work out the sequence.

.
One of three likely events precipitated the upset:
a. BBC Scenario - Pilots neglected to add power (i.e. left throttles in CLB) after dial-selecting a slowdown to turbulence penetration speed and this led to an autopilot kick-out and stall/LoC following the airspeed indicators winding back to zero (the pure precipitation instant pitot freeze-over theory). Considered an unlikely confluence of events in comparison to (b. below) - a more insidious development during a relatively smooth cruise in the dense CirroStratus cloud to be found in the ITCZ areas (i.e. crew ennui/lethargy/surprise more likely to be a player than when alert and roughing it in the grip of a storm).
.
b. Favoured Scenario - Autothrust quietly adds power incrementally as supercooled ice crystals overcome the limited pitot-heating abilities and gradually accumulate as a granular filter inside each pitot (clogging drain and tube equally). Pilots fail to notice power adds or fuel flow increases as it's common to monitor the fuel management synoptic in long-haul (vice the engines page). In fact it's probably SOP to do so - as any engine fault will be separately annunciated, whereas fuel transfer discrepancies or leaks will only show up latterly). Aircraft hits Mach crit and mach tucks (autopilot disconnects and a/c pitches down violently).
.
c. Possible Scenario - As per b., however autopilot kicks out prior to Mach crit, due to one of:
(i) Holding too much pitch force due to THS being incorrectly trimmed by invalid airspeed data (...and a/c pitches them down into Mach Crit)
(ii) Airspeed splits becoming large enough to trigger a system-detected discrepancy..... and A/P kick-out occurs
.
In any of these three cases, particularly if the THS was in an out-of-trim state at A/P disconnect, the crew would be without airspeed info and therefore prone to hitting either an aerodynamic stall or Mach Crit. This would quickly lead to an "upset" as the Airbus Flight Control system protections in Normal or a degraded Law (ALT 1/2) would not be able to prevent an unusual attitude developing. Any misinterpretation of their predicament would put them in a world of greater hurt.
.
e.g. Max power and stick forward as a result of an assumed stall would embed them in Mach tuck. Rolling the wrong way in an attempted roll-out from an autorotative flick-roll would be an entry into an unrecoverable unusual attitude. Large bank angles always involve steep nose-drops - which lead to rapid acceleration of a heavy jet at height.
.
Finally, GreatBear said: "There were no ACARS messages recording "the sudden onset of critical Mach." Well think it through. Why would there be in any airspeed pitot compromised scenario? It's not a missing message, it's a disabled capability. That's one of the issues that I have with the cascade failures typical of (and endemic to) interdependent and integrated automation.
.

[BOAC]

Pilots neglected to add power (i.e. left throttles in CLB) after dial-selecting a slowdown to turbulence penetration speed

- excuse a dumb q from a non-AB chap - isn't the A/T supposed to do that?

Unctious- I am now totally confused as to what you are presenting regarding BBC/ACARS. First you 'present' "An ACARS message from the airplane recorded the sudden onset of critical Mach" with no comment and then you tell GB "Well think it through. Why would there be in any airspeed pitot compromised scenario? It's not a missing message, it's a disabled capability."

[GreatBear]

Thanks, BOAC, my point exactly.

UNCTUOUS. I'm still having trouble picturing the auto throttle creep necessary to your "favoured" Mach tuck scenario when, by measuring ground speed until the upset (A/P disconnect, ten seconds after the last position report), the A/C seemed to be traveling at a constant cruise speed... see diagram. Perhaps creep towards the upper right of the coffin corner (+20kts? +40knts? +more? to a flick-roll) occurred in a very short timespan? Short enough not to influence the 0200 to 0210 distance traveled segment?

GB

[henra]

/Quote GreatBear

occurred in a very short timespan? Short enough not to influence the 0200 to 0210 distance traveled segment?

Hmm, without change in attitude this seems technically not feasible to me given the SEP of an A330 @210t at FL350.
That will take 'ages' to get it to Mcrit given a constant level attitude (>10min).
Had it left that level attitude before than something was pear shaped anyway.
Or they pushed the nose down due to a perceived risk of a stall.
Either way you see it a subtle Mcrit encounter without preceding event seems not very likely (at least to me).
However, an Mcrit encounter after an initial LoC seems absolutely possible.