Air India AI 171 Crash in Ahmedabad (3 Viewers)

[Anants]

If genuine, some useful info from other aviation forum:

Noshow wrote:
They can release just the data and leave any in depth analysis to their experts for later on. There is a public global interest in knowing what went wrong.

Which is a pretty inane ask. Why Indian investigators should go out of the way to release information they collected to public when they themselves are still investigating and analyzing? Indian are also investigating Sabotage angle.. if there is sabotage angle you are saying without completing criminal investigations - India should release evidences and data collected for the possible offending party to wipe off any possible clues left?

Is it that you agree with this sentiment as you like NoShow cant hide the frustrations that these incompetent brown people should be allowed to do anything independent?

 

[Spitfire IX]

Which is a pretty inane ask. Why Indian investigators should go out of the way to release information they collected to public when they themselves are still investigating and analyzing? Indian are also investigating Sabotage angle.. if there is sabotage angle you are saying without completing criminal investigations - India should release evidences and data collected for the possible offending party to wipe off any possible clues left?

Is it that you agree with this sentiment as you like NoShow cant hide the frustrations that these incompetent brown people should be allowed to do anything independent?

No. I referred to what the investigator/analyst wrote as useful info. Do you find it so? Does it matter if he/she is Indian, Peruvian, Chinese, English, black, brown, white, purple or whatever? It looks like an expert view to me.

 

[Anants]

No. I referred to what the investigator/analyst wrote as useful info. Do you find it so? Does it matter if he/she is Indian, Peruvian, Chinese, English, black, brown, white, purple or whatever? It looks like an expert view to me.

An expert who is talking through his hat. That is a stupid statement you quoted of noshow which hardly shows his expertise.

 

[Spitfire IX]

An expert who is talking through his hat. That is a stupid statement you quoted of noshow which hardly shows his expertise.

Sorry, checking out of this conversation. Tried to make a useful contribution. It seems you could not see that.

 

[Anants]

Sorry, checking out of this conversation. Tried to make a useful contribution. It seems you could not see that.

What useful you wrote you got my "reaction" what Quoted inane part deservedly got my disdain. Thank you for bowing out.

 

[Bhartiya Sainik]

These veteran defence journalists talking about fuel switches pointed to the engine fire handles on international level news.

These people are part of top big media houses, with good salary.
The media houses gave big fee for their ride in jet fighters.
Still they can't do simple google & YT search also. In schools there is Internet search competition.
This is the quality of reporting we have.


View: https://www.youtube.com/watch?v=O0eHzRg98T4

 

[Bhartiya Sainik]

Possibility of maintenance issues are there, but it spans numerous things.

But if considering FUEL CONTAMINATION then
Our expectation is that when initial contamination builds up,
at an international busy airport where continous refuelling take place,
it should cause engine sputter/stuter/shudder,
that too in multiple jets,
on multiple days & time,
forcing for maintenance,
not a sudden crash only for 1 jet,
that too late at 1:38 pm local time,
It is analogous to us sneezing, coughing & not straight away dropping dead on floor unless we inhaled nerve gas, cyanide, etc.

Common enthusiasts like us consider contamination as water, paste like dirt, some solid particles but not to the limit of 100% blocking valves, filters, etc, so rapidly in short time, causing complete loss of thrust & crash a vehicle.

In a default scenario, there are S.O.P.s & ISO standards to follow, multiple quality checks, quick checks & elaborated checks.
+ we would expect many filters & quality checks at every step used while transfering fuel from beginning till end -
- refinery to transport tanker
- transport tanker to airport storage
- airport storage to fuelling tanker
- fuelling tanker to aircraft

Captain Steve in his videos & statements said the fuelling trucks have contamination detection mechanism.

BUT, i realized that depending upon contaminant, catastrophic faults can be fast in 1st flight or span multiple flights.
So if those fuel giants are so careless then it would be a scam of unprecedented scale.
Citizens might stop taking fuel from them, their shares in stock market will collapse, the company or subsidiary might go bankrupt.

Each GenX-1B engine has -
- Fule Metering Unit
- LP & HP pumps
- LP & HP filters

View attachment 40090
View attachment 40091


So contamination should cause pressure & flow irregularities recorded by FMU (Fuel Metering Unit), forcing for maintenance.

IDK the Black Box contains data of how many flights.
The data can be recorded in redundant bit level for max data.
If it has last few flights data then irregulaties will be recorded there.

While discussing on other forum, I came across 2 examples of contamination on different jet models & different bludner mistakes of adding 38x fuel-additive biocide & bad construction practices of fuel storage area. it is worth to have a lookat them:







Cathay Pacific Flight 780, 13 April 2010,
Airbus A-330,
Surabaya, Indonesia, to Hong Kong International Airport
(https://en.wikipedia.org/wiki/Cathay_Pacific_Flight_780)


View: https://www.youtube.com/watch?v=lPeZr9uSfTg

RAT was manually, proactively deployed.
In flight they had chance to use APU also.
Left engine N1 ran at 74% & right engine N1 at 17%.

The root cause was bad construction practice during rain leading to salt water getting into fuel pipe, reacting with filter & releasing SAP particles.
View attachment 40185
View attachment 40186
View attachment 40187
View attachment 40188
===============================================================




Titan Airways, Airbus A321,
24 Feb 2020, Cyprus - London, no errors !!!!!!.
25 Feb 2020, London - Gatwick, On ground for left engine -

HP Fuel valve warning, ​

engine took 2 attempts to start.​

25 Feb 2020, Gatwick - Balice (Poland), no errors !!!!!!
26 Febl 2020, Balice (Poland) - Gatwick, On ground for left engine -

2 times HP Fuel valve warning, ​

engine stall warning once,​

left engine took 3 attempts to start, ​

momentary errors in flight ​

& thumping sound after landing.​

26 Feb 2020, Gatwick - London, On ground for left engine -

ignitor fail alert, ​

engine fail alert 2 times, ​

engine took 4 attempts to start, ​

incident on take-off,​

Fortunately the engines didn't fail completely & the jet could turn around & land,

thumping sound after landing.​

View: https://www.youtube.com/watch?v=E4Qclymu2EA

This one happened due to multiple mistakes, that too on ground before 1st & 2nd flight & ultimately in 5th flight during takeoff -
- Language barrier in Cyprus, not understanding what is PPM (Parts Per Million).
- Wrong calculation & 38x quantity of Kathon biocide over-use & concentration in HMU, not due to algae.
- As per re-enacted animation it seems that biocide was added improperly from top access port, not mixed well with proper tools, leaving sludge on bottom & tank outlet, went into HMU & choked it. Hence right engine started but left engine took 4 attempts to start on ground.
- Before next flight the ground engineer referred to troubleshooting by fault code rather than engine model, hence of wrong engine.
- & no boroscope inspection was done.

View attachment 40206
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View attachment 40209

///////////////////////////////////////////////////////////////////////////////////////////////


> These incidents happened either mid-flight, means issues took time to manifest.
Or in 2nd example, many engine start faults happened on ground bcoz it is a unique series of blunder mistakes, but then ultimately in 5th flight during T/o.

> In these 2 cases both the engines did not cease but ran at low RPMs due choking of piston of FMU (Fuel Metering Unit) & valve of HMU (Hydro Mechanical Unit).
While in case of AI-171 the pilot's Mayday call reported something like "no thrust, no power, losing lift, going down", speculating 0% RPM.
So, for AI-171 we've to look at -

- maintenance records, ​

- maintenance areas ​

- historical warning messages also in Black Box apart from latest.​

Re-thinking on possible contamination -

Chemistry is such a tricky aspect of nature, it is difficult to proactively discover all chemical reactions.
The 2 examples we discussed were very educating -
- The excess biocide example, spanned across 5 flights, with errors in flight & on ground, yet the A/c survived.
- The salt water reacting with filter & releasing polymer particles jamming the FMU valve, within 1 flight itself, the flight surviving fortunately.

In a tropical country, during summer season, a possible contamination would have different reasons, most likey with poor maintenance.
But we don't know yet about historical maintenance records of AI-171 airframe, the H/w issues or the S/w alerts if any.

So on this angle we've to assume something similar to 2nd example of salt water causing full fuel contamination & rapid reaction within 1 flight, so much rapid that the problem didn't occur mid-flight but immediately after take-off.

What kind of chemical reaction can take place in fuelling chain -
- causing only 1 flight,
- impacting both engines same time,
- around mid-day noon,
- when local flights would depart in morning,
- probably taking fuel from same source?

Either it should be internal to airframe, or to the fuelling truck.

I checked some YT videos of fuel filter & pump in GenX-1B engine & found that there are multiple rings for sealing joints, just like in our kitchen pressure cooker.
I wonder if a reaction can take place here.




View: https://www.youtube.com/watch?v=NOTM93cjfGM




View: https://www.youtube.com/watch?v=BL2LRvtwp9o




I couldn't find pic/vid of 787 fuel tank fuel pump. Perhaps it might little bigger but identical to this one i found - of A320.

 

[Spitfire IX]

Suspected loss of thrust from engines.

I await confirmation from the FDR data

- this was the case
- this was not commanded by the crew

 

[Bhartiya Sainik]

So far we know that -
> There are 2 CDNs/networks.
> The 2 EECs are dual channel redundant with power from PMA & backup. So 4x links out from FMC.
> If 6x fuel pumps fail then engine can suction feed.
> 4x redundant generators.
> Just 1 engine is sufficient for safe emergency landing.
> Batteries & RAT would be enough for emergency controls & landing.

> Now, when we look at some key points below from the official video on 787's electrical system showcasing so much redundancy, then it becomes very difficult to believe that an electrical HARD fault can cause a crash, even if someone throws a bucket of water in equipment bay short circuiting everything.

>> On H/w aspect, just at least 1 control-link from FMC to 1 of the EECs should survive with batteries+RAT & PMA on the ends.

However, manufacturing mistakes, maintenance mistakes & S/w glitches remain a concern.


View: https://www.youtube.com/watch?v=aARt2RVJDbA


> List of electricity sources for various purposes -
- 4x engine driven main generators giving 235 VAC.
- 2 APU generators giving 235 VAC with battery.
- 3 PMGs (Permanent Magnet Generators)
- 2 PMAs (Permanent magnet Alternators) for EEC
- Main batteries in forward avionics bay.

> Power sources remain isolated throughout the generation & distribution channels (probably to avoid short circuit).
> During power transfers a brief power interruption may occur as buses are energised from new power source.
> APU is started electrically by main battery turning any 1 APU Starter/generator to turn APU.
> Engines are started electrically by main battery turning engine starter/generator to turn spool, not by bleed air from APU.



> Main battery gives power for -
- A/c start
- APU start
- Refuelling ops
- Towing ops
- Electric braking (as backup)
- Captain's flight instruments (till RAT deployed)

> APU on ground gives power for -
- APU start
- Navigation lights (during batter-only towing ops)

> Electricity for flight control electronics -
- primary - 3 PMGs fully independent.
- secondary - 28 VDC.
- Additional dedicated batteries during temporary power interruptions.

> Electricity for EEC -
- primary - fully independent PMA.
- secondary - 115 VAC bus.
- During engine start the 115 VAC bus gives initial power, then switching to PMA after minimum engine RPM.



> Power distribution methods -
- Primary for higher loads - 115 VAC, 28 VDC in forward bay & 135 VAC in aft bay.
- Remote for lower loads - 17 RPDUs (Remote Power Distribution Units)



> The 4 engine generators power the 4 AC buses in aft bay.
> If any generator & its bus fails, it is powered by remaining buses.



> There are multiple power modes -
- for ground ops, depending upon power sources available.
- For flight, obviously 4x generators should be working.
- With 1 engine loss, 2 generators would suffice for nearest safe landing.
- In-air RAT-only mode - powers Captain's flight instruments, flight controls, navigation, communication.
- In-air battery-only mode - powers all same things as in RAT-only mode except center pitot heat.

> RAT deploys automatically under 1 of the conditions -
- both engines failure.
- all 3 hydraulic system pressure low.
- loss of all electrical power to Captain's & FO's flight instruments.
- loss of all 4 EMPs (Electric Motor Pumps) & FCS fault on approach.
- loss of all 4 AMPs & 1 engine failure on take-off or landing.



> 2 redundant BPCUs (Bus Power Control Units) provides function -
- Flight deck control/indication.
- Power transfer.
- Overall load management.
- some loads are automatically prioritised or inhibited at predefined conditions.



> CBIC (Circuit Breaker Indication & Control) shows status of Thermal & Electronic circuit breakers & control the electronic ones.

 

[Bhartiya Sainik]

After looking at hydraulic system, there seems to be redundancy here also, may not cause a crash.


View: https://www.youtube.com/watch?v=pfZdOMbR7B8

Also found a detailed diagram in video for changing hydraulic filter.




OBSERVATIONS from CBT video -

> There are 3 hydraulic systems - center, left, right, with their reservoirs.
> The center one has control over highest # of control surfaces.
> The left & right systems seem to have very limited controls, but the CBT says it is adequate.

> Left system controls -
- some flight control surfaces - 1 flaperon pair, 1 spoiler pair.
- thrust reverser
- left tail-stab
- rudder

> Right system controls -
- some flight control surfaces - aeleron, 1 flaperon pair, 1 spoiler pair.
- thrust reverser
- right tail-stab
- rudder

> Center system controls -
- aelerons, flaps, most flaperons, 2 spoiler pairs.
- both tail stabs
- rudder

> Total 7 hydraulic pumps - 2 engine driven left/right, 2 electrical left/right, 2 electrical central, 1 RAT.
> Engine driven pumps are primary & mechanically driven by N2 spool.
> Demand pumps are secondary/supplementary & electrical & work under conditions -
- system pressure low.
- for 3 mins after both engines started on ground.
- from time the T/o thrust is set to flaps retraction or Radar Altitude >2000 ft.
- flaps or slats are in motion.
- from gear down or Radar Altimeter <1000 ft. to ground speed <40 knots.
- for thrust reverser.

> Secondary Demand electric pumps &/or central electric pumps will display fault when -
- low pressure
- excess fluid temperature
- switched OFF

> The 2 central electric pumps take primary/secondary role based on odd/even calendar days.



> RAT pump in emergency caters to flight controls of center hydraulic system.

> RAT will auto-deploy when -
- both engines have failed.
- all 3 hydraulic system pressure low.
- loss of electricity to Captain's & FO's flight instruments.
- loss of all 4 EMPs & FCS fault on approach.
- loss of all 4 EMPs & 1 engine fail on T/o or landing.



> Hydraulic isolation function gives safety during leaks by -
- Nose gear isolation valve.
- Reserve steering isolation valve.
- Alternate extended isolation valve.
- Reserve standpipe.
- All isolation valves are automatic FMC controlled, no manual operation available.

> When fire handle is pulled up, it shuts the EDP valve depressurising the EDP.

> If big electrical failure happens then load shed might disable 1 or more Demand electrical pumps, but RAT pump will backup central system.


DERIVATIONS from observations -
> During T/o, central EMPs, primary EDPs & secondary EMPs are operational.

> Hydraulic isolation function may not be for gear retraction.

> RAT pump may not retract the landing gears. I guess it would be last priority. Or may be the RAT electricity might do it if/when sufficient.

> The hydraulic & electrical videos don't say about secondary electricity to central EMPs or secondary Demand EMPs.
The 28 VDC system & additional battery are backups of 3x PMGs, they support fuel pumps, but may not be for hydraulic EMPs.
So perhaps EMPs don't have backup directly from generators or PMGs, but only indirect loop from central busses.

> We saw in Electrical video that central electrical bus fail should not affect basic flight due to battery+RAT for cockpit & FMC; 2x PMAs for their EECs, 3x PMGs for GCUs & hence generators should function.

> If electricals fine but some glitch in air data sensors &/or FMC &/or EEC pulling back the engine RPMs, then primary EDPs will be INOP but secondary Demand EMPs would function.

> If central electric busses fail then central EMPs & secondary Demand EMPs would be INOP but RAT pump will backup central hydraulics & the primary EDPs will still remain primary.

> If central busses fail & RPM glitch then central EMPs, primary EDPs & secondary Demand EMPs would be INOP, but RAT would backup central hydraulics enough for emergency flight & landing.