1991 Thailand plane crash. Lauda Air Flight 004.

**Backspin** · 11-01-2021, 11:47 AM

A mini documentary was just released about it. It is a brutal sequence of events. As far as the cause goes , it looks like another Boeing cockup to me

**Neverna** · 11-01-2021, 01:24 PM

I'd say poor decision making by the pilot was a significant cause of the plane crashing.

**harrybarracuda** · 11-01-2021, 01:47 PM

Originally Posted by Neverna

I'd say poor decision making by the pilot was a significant cause of the plane crashing.

I don't think the pilot decided to deploy a single thrust reverser at cruising speed and cruising altitude.

**Edmond** · 11-01-2021, 01:49 PM

Would have been a bit of a rude awakening for the folks onboard. Suddenly flying nose down faster than the speed of sound.

**Neverna** · 11-01-2021, 01:49 PM

Originally Posted by Neverna

I'd say poor decision making by the pilot was a significant cause of the plane crashing.

Originally Posted by harrybarracuda

I don't think the pilot decided to deploy a single thrust reverser at cruising speed and cruising altitude.

I didn't say he did or suggest he did.

**Latindancer** · 11-01-2021, 02:13 PM

I remember when this accident happened. Thai locals went out to loot the bodies / body parts and luggage in the debris.

**cyrille** · 11-01-2021, 02:35 PM

Perhaps Eddie could give us some insight into how the relatives would have felt about that.

**Edmond** · 11-01-2021, 03:14 PM

Shocked and disgusted.

Absolutely shocked and disgusted.

And angry.

**Troy** · 11-01-2021, 03:51 PM

Originally Posted by Neverna

I'd say poor decision making by the pilot was a significant cause of the plane crashing.

I think that's a little harsh. Do you mean he should have aborted take-off on the first indication? Nothing in the procedures to indicate he should.

One it happened in flight they had 6-10 seconds to identify cause and carry out corrective actions. That was the conclusion I heard from testing at Gatwick, a colleague spent the night adding the malfunction for testing the following day.

Also several changes made to the throttle reverser system as a direct result of this accident.

**harrybarracuda** · 11-01-2021, 04:48 PM

Originally Posted by Neverna

I didn't say he did or suggest he did.

Then there is little decision making open to him once the deployment happened. They have checklists to go through and there isn't one (or at least there wasn't) for that particular failure.

**Backspin** · 11-01-2021, 08:06 PM

If it were Thai or any 3rd world pilots , half of the blame would go to them by default. Kinda like the 737 Max crashes. But these were seasoned European pilots. So that option wasn't available

**aging one** · 11-01-2021, 08:31 PM

Originally Posted by Backspin

If it were Thai or any 3rd world pilots , half of the blame would go to them by default.

WTF?? Where you gonna go next?

**cyrille** · 11-01-2021, 08:41 PM

If I had to guess, I'd say the boomer c^nts involved in all this.

**Edmond** · 11-01-2021, 08:48 PM

Originally Posted by cyrille

boomer

One day, I'm going to be bothered to read up the meaning of that word.

Other than a possible noun for the plane as it exploded.

**Neverna** · 11-01-2021, 08:56 PM

Originally Posted by Troy

Do you mean he should have aborted take-off on the first indication?

They got a warning alarm [REV ISLN] five minutes after take off - a warning of possible system failure that could cause the thrust reverser to deploy. The crew disussed it for five minutes but then decided to carry on their way. Five minutes later, an engine reversed thrust, leading to the plane's eventual crash. It's my view that being so close to Don Muang airport (only 5 minutes away), they should have turned back to get the plane checked out.

**Neverna** · 11-01-2021, 08:58 PM

Originally Posted by Backspin

But these were seasoned European pilots.

The Captain was American.

**harrybarracuda** · 12-01-2021, 01:21 AM

Originally Posted by Neverna

They got a warning alarm [REV ISLN] five minutes after take off - a warning of possible system failure that could cause the thrust reverser to deploy. The crew disussed it for five minutes but then decided to carry on their way. Five minutes later, an engine reversed thrust, leading to the plane's eventual crash. It's my view that being so close to Don Muang airport (only 5 minutes away), they should have turned back to get the plane checked out.

And yet the report says

"The Quick Reference Handbook (QRH) was consulted to determine appropriate crew actions in response to the alert. No actions were required, and none were identified as being taken."

Boeing initially insisted that the thrust reverser couldn't possibly deploy mid-flight.

Later they grudgingly released an advisory that more frequent checks should be carried out on the wiring, and an enhanced locking feature be installed:

Within 3 years after the effective date of this AD, install
an additional thrust reverser system locking feature (sync-lock) in
accordance with Boeing Service Bulletin 767-78-0062, Revision 2,
dated June 3, 1993, or Revision 3, dated February 24, 1994.

That should tell you all you need to know.

The pilots were blameless in this and the final report confirmed it.

The Accident Investigation Committee of the Government of Thailand determines the probable cause of this accident to be uncommanded in-flight deployment of the left engine thrust reverser, which resulted in loss of flight path control. The specific cause of the thrust reverser deployment has not been positively identified.

And the NSTB rapped Boeing on the knuckles (which is about all they are ever allowed to do):

The Safety Board is also concerned that Boeing 767 flightcrew emergency procedures may not provide appropriate and timely guidance to avoid loss of flight path control in the event that the reversers deploy in flight.

**Troy** · 12-01-2021, 01:40 AM

Originally Posted by Neverna

They got a warning alarm [REV ISLN] five minutes after take off - a warning of possible system failure that could cause the thrust reverser to deploy. The crew disussed it for five minutes but then decided to carry on their way. Five minutes later, an engine reversed thrust, leading to the plane's eventual crash. It's my view that being so close to Don Muang airport (only 5 minutes away), they should have turned back to get the plane checked out.

I can see how you might think this way from the information in the above mini doc, however, there is quite a lot of missing information that is quite important. I have had a quick read of the accident report to refresh my memory.

The REV ISLN is an amber advisory and there was no associated REV amber indicating the Thrust Reverser was actually unlocked. The warning means that if you were to select the Thrust Reverser in flight then it would actually deploy, rather than be inhibited by the in-air safety circuit. The FO read from the check list "additional system failures may cause in-flight deployment
expect normal reverse operation after landing" That is, NO ACTION required on seeing this advisory amber warning.

In fact, this aircraft had a history of problems on the Left Thrust Reverser with 10 reported false indications in the 5 months leading to the accident. Lauda maintenance had replaced many components in the system to remove these nuisance warnings. These will be in the aircraft log and speed read by both pilots during the briefing, I got the impression from the Captain's hesitancy during their chat that he vaguely recalled the fault. However, the conversation time was finding the fault indication in the checklist and discussing whether to talk to maintenance for further advice.

They has just reached transition height (referenced to 1013mb), which is 6000ft in Thailand, they are at maximum takeoff weight and max power setting for climb. It isn't so simple to turn around at this point and land. They would need authorisation to do this from the maintenance guys on the ground because there is no Emergency to declare from the checklist, with the history of the intermittent fault this would be unlikely. Even if they had been given permission, they would then need to dump fuel for a while to get down to Max Landing weight (they'd need to dump at height >6000ft for ~15-20mins).

The engine fit on this aircraft was P&W with FADEC, which is a FBW system with no mechanical linkage between the throttles and the engines. Normally, to deploy the Thrust Reverser, the throttle needs to be pulled back to IDLE and another, smaller, lever on the top of the throttle pulled up and over. With the older mechanical system the throttle will slam back to IDLE if the Reverser deploys. Not so on the FADEC engine where the throttle remains in position. All the Boeing aircraft I have known provide throttle feedback of engine setting (different to Airbus philosophy). This FADEC system with no throttle movement would have confused the pilots when the actual event happened, certainly long enough for the recovery to have been impossible at that speed and power setting.

Sorry if that's too much detail (or too little!). I tried to condense as much as I could.

The accident report:

Lauda Air B767 Accident Report

**Neverna** · 12-01-2021, 07:15 AM

^ Thanks for your detailed reply, Troy. Appreciated.

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