Lion Air 737 Missing

[Alisoncc]

Big difference Speedy, you knew how to fly the aeroplane. Nowadays all they do is press buttons, keep fingers crossed and hope the computer knows what it's doing. And when the computer gets confused all is lost.

[ExSp33db1rd]

So it would seem, sad.

[Cacophonix]

ADIRU, not ADR surely?

Data from the black box showed that the two flights before Denpasar-Jakarta also experienced the same problem,” he said.

“In the black box there were four flights that experienced problems with the airspeed indicator.”

But Nyoman Rai Pering, head of Lion Air’s largest engineering facility located in Batam, told the Guardian problems with the plane were not isolated to the airspeed indicators in the days leading up to the crash.

Asked why the plane had descended from 39,000 feet to 30,000 feet on a flight from Manado to Denpasar on 27 October, and contrary to its regular flying pattern was then grounded for 12 hours, Pering acknowledged the plane had been undergoing repairs during that period.

“Yes, we took time to fix the problem Manado to Denpasar to make sure everything was fixed. We replaced the part suspected by our engineer,” Nyoman said.

“I think the problem was with the angle of attack, which controls the stability of the aircraft.”

The “angle of attack” or AOA indicates whether a plane is going to stall.

Given the acknowledged issues with both the angle of attack and airspeed indicators, aviation analyst Gerry Soejatman said the problems the jet encountered may be wider that initially believed, and linked to the plane’s air data reference unit (ADR).

The ADR takes in several key indicators including airspeed, altitude, air temperature, and the angle of attack.

“With all of this happening within a few days we suspect the problem is not just limited to the airspeed indication. This might mean there was an issue with the ADR box as a whole,” he said.

“It might be the ADR itself that was a fault, not those sensors.”

https://www.theguardian.com/world/2018/ ... ur-flights


https://en.m.wikipedia.org/wiki/Qantas_Flight_72

The Australian Transport Safety Bureau (ATSB) identified in a preliminary report that a fault occurred within the Number 1 Air Data Inertial Reference Unit (ADIRU) and is the "likely origin of the event". The ADIRU (one of three such devices on the aircraft) began to supply incorrect data to the other aircraft systems.

The initial effects of the fault were:

false stall and overspeed warnings
loss of attitude information on the Captain's primary flight display
several Electronic Centralised Aircraft Monitor (ECAM) system warnings
About two minutes later, ADIRU No. 1, which was providing data to the captain's primary flight display, provided very high (and false) indications for the aircraft's angle of attack (AOA), leading to:

the flight control computers commanding a nose-down aircraft movement, which resulted in the aircraft pitching down to a maximum of about 8.5 degrees,
the triggering of a Flight Control Primary Computer (FCPC) pitch fault.

Caco

[Boac]

Alison - I do not have access to the NG Tech manual but this from the 6/7/800

"The pitot static system is comprised of three separate pitot probes and six flush
static ports. Two pitot probes and four static ports interface with the air data
modules. The remaining auxiliary pitot probe and alternate static ports provide
pitot and static pressure to the standby instruments. The auxiliary pitot probe is
located on the first officer’s side of the airplane."

[Slasher]

My unfamiliarity with the latest 737s makes it hard for me to make any informed comment, but from my posted graph earlier it looks to me like a flight control problem possibly associated with faulty AoA data. It would certainly look that way if it was a Scarybus and not one of Bill's machines.

QF72 was to turn 2 ADRs off which would put the flight controls in Alternate Law and one could then manually recover from the Airbus death dive. However since Boeing by philosophy is NOT to exclude the pilot, I can't see how it'll do a death dive if it was an ADR or AoA input fault. I just hope they didn't look at an Airbus and said "Hmm... we'll give that idea a try in our new li'l jettie!"

A descent becomes necessary to cruise below F300 to comply with RVSM* requirements. It indicates to me they had no A/P height-keeping function as well as other things and had to fly manually.

* Reduced Vertical Separation Minima - i.e. 1000 ft vertically between aircraft when flying above the RVSM entry flight level (typically FL285). It typically requires A/P and alt hold functions operative. Below 285 the 2000 ft separation is in force and no alt hold automatic function is required.

[Cacophonix]

ADIRU, not ADR surely?

From the 737 manual <<not MAX 8 though>>

Each ADIRU comprises an ADR and an inertial reference (IR) component.

The Air Data Reference part of the ADIRU receives digital inputs of pitot- and static pressure, and total air temperature to calculate air data parameters. Error corrections are accomplished by using analog inputs from the AOA vane.
The Air Data Reference processor calculates:
– Altitude
– Barometric corrected altitude
– Altitude rate
– Computed airspeed
– Maximum allowable airspeed
– Mach
– True airspeed
– Static air temperature
– Total air temperature
– Impact pressure
– Static pressure
– Total pressure

The Inertial Reference part needs latitude alignment and a position input to operate, where after it uses 3 accelerometers and 3 Laser gyros which sense motion and angular movements of the aircraft to determine attitude, heading, acceleration and position.
The Inertial Reference processor calculates:
– Pitch
– Roll
– Yaw
– Latitude
– Longitude
– True heading
– Magnetic heading
– Inertial velocity vectors
– Linear accelerations
– Angular rates
– Track angle
– Wind speed and direction
– Inertial altitude
– Vertical speed and acceleration
– Ground speed
– Drift angle
– Flight path angle and acceleration

13568787_1299614943400452_6697125301279681995_o.jpg (56.41 KiB) Viewed 430 times

Caco

[Boac]

A comment on Av Herald suggests that there is an imminent Boeing safety alert for the Max. It is very disturbing that a crew could not apparently overcome whatever went wrong in the flying conditions they had which were daylight and probably VMC. Shades of FBW madness?

[Boac]

Again thanks to Av Herald
"On Nov 7th 2018 Boeing issued an Operations Manual Bulletin (OMB) to all Boeing 737 MAX Operators stating that the investigation into the crash of PK-LQP found one of the Angle of Attack Sensors had provided incorrect readings, which could cause the aircraft's trim system to uncommandedly trim nose down in order to avoid a stall during manual flight. The OMB directs "operators to existing flight crew procedures to address circumstances where there is erroneous input from an AOA sensor." The OMB reiterates the Stabilizer Runaway non-normal checklist."

This is the checklist for the 6/7/800 ) NB NOT the MAX
"
1 Control column. . . . . . . . . . . . . . . . . Hold firmly
2 Autopilot (if engaged) . . . . . . . . . . . . .Disengage
Do not re-engage the autopilot.
Control airplane pitch attitude manually with control column and main electric trim as needed.
3 If the runaway stops:
■ ■ ■ ■ (see 5)
4 If the runaway continues:
STAB TRIM CUTOUT
switches (both) . . . . . . . . . . . . . . . . CUTOUT
If the runaway continues:
Stabilizer
trim wheel . . . . . . . . . . Grasp and hold
- - - - - - - - - - - - - - - - - - - - - - -
5 Stabilizer . . . . . . . . . . . . . . . . . . . Trim manually
6 Anticipate trim requirements.
7 Checklist Complete Except Deferred Items"

This suggest that the issue was NOT a speed discrepancy as at first thought, although both could have occurred together I guess if the ADR malfunctioned. With all that gong on I would not have gone within 3 miles of the autopilot!

Lawyers will have a field day........a tragic loss of life.

[Alisoncc]

Thanks for that Boac. Very illuminating.

[Boac]

FAA AD issued as well now, virtually repeating the Boeing, but interestingly adding that failure of an AoA sensor (there are two on the 737) can cause several of the symptoms reported by previous LionAir crews including:
IAS Disagree warning (NB not specifically an actual IAS disagree)
Feel Diff pressure warning
ALT disagree
Various instrument speed margin warnings erratic
Stick shaker (on the affected AoA side)
Inability to engage Autopilot (I have assumed that as they subsequently flew below RVSM airspace)

Quite how an AoA sensor fail can cause IAS and ALT disagree or a Feel Diff warning is beyond me, but I assume it will be to do with the mini wiggly amps in the ADR.

[Cacophonix]

Boac's excellent summation of the issues above got me to, as is my way, to review in detail how Boeing think about AoA, something that we as pilots of various types, levels of experience etc. understand perfectly of course, or perhaps not!

Boeing AoA

Caco

[Undried Plum]

Inability to engage Autopilot

Then they were ****.

[Sisemen]

It would appear that Lion Air has just had another incident where a 737 smacked into a lamp post whilst taxying. Not having a good run are they?

[Undried Plum]

engage Autopilot

[Cacophonix]

Autopilot Checklist - In case of ECAM alert check pilot main valve and if necessary administer executive relief!

Undried Plum you have made this fool laugh again.

Caco

[Slasher]

one of the Angle of Attack Sensors had provided incorrect readings, which could cause the aircraft's trim system to uncommandedly trim nose down in order to avoid a stall during manual flight.

The stabilizer FFS? The STABILIZER trim system of all things? You're kidding me right?

I would've assumed Boeing would install a stick pusher direct to the elevators which could be manageably overridden by the pilots in an event such as this. The Scarebus computery only pushes the elevator in a similar circumstance and NEVER the THS (stabilizer).

If this is true then IMO it's a serious design flaw and I'm bloody disappointed that Bill's mob had incorporated it.

[larsssnowpharter]

OK, I'm happy to admit that I am a dinosaur who has never flown commercial, who believes that instruments should be round and who doesn't understand half the acronyms being bandied about in this thread.

But I do remember one thing that was drummed into me over 50 years ago during training.

"Fly the picture."

That lesson, well learned, really helped on a number of occasions where I could have got myself in trouble.

As I understand it, this event occurred in decent VFR conditions. So. What is wrong with turning off the automatics and turning back and landing.

Or have we bred a generation of pilots who can only press buttons on a human computer interface to activate programs written by some spotty faced kid in his/her parent's basement. If so, Lord help us!

[Boac]

The stabilizer FFS?

- my (limited) understanding of the function is that by trimming nose down as the stall AoA is approached it makes the pull to increase AoA harder. Gone, it seems, are the days when we learnt not to stall aircraft and to recognise the symptoms of same. AF447 showed that.

I assume that a rogue AoA sensor, eg 'reading' 'max' AoA, would persuade the system to keep on trimming the stab nose down. This can only be stopped by using the Stab Trim cut-out switches as per the checklist, or temporarily interrupted by use of the pilots' electric trim.

I have long been a 'get those control system computers out of my life' fan. If I do not understand what something is doing I do not like it! As you can probably tell, I am not an AB fan.

[Cacophonix]

Sounds like the current crop of commercial automatons should be forced to fly a couple of hours in a light twin with a couple of emergencies thrown in every month just to remind them what flying an aircraft is really all about. Truth is flying a light twin single pilot IFR is as far away as we on earth are from Andromeda when it comes to poling around the airways multi-crew in one of the modern glass cockpit jets.

Caco

[Boac]

Indeed, and the common 'traditional' route to commercial airlines of air taxi type ops has bee replaced by MCC training with minimal hours.