QANTAS A380 Uncontained failure.

[RichPa]

Sorry for asking this, it would be impossible for me to read this huge thread, could someone explain to me how it was possible that the engine can not be stopped by any method after landing? Is this an A380 issue or a general flaw regarding all modern FADEC jet engines?

[DozyWannabe]

It's specific to neither A380 nor FADEC. If the control connection to the engine is damaged or severed, then it cannot be shut down. For an older example, the Pan Am 747 at Tenerife in 1977 had its engines running even as it was consumed by fire. This was because the impact from the KLM 747 had ripped out all the engine control cables, which in the 747 run through the ceiling of the lower cabin.

[RichPa]

Thank you very much for your answer. I guess it is designed that it is better to run in case of malfunction in the air instead of inadvertently shutting off, right?

But even using the fire switch doesn't work, does this seem ok to you? What do you think?

[DozyWannabe]

It's not really a case of being OK or not, it's just a basic fact that if the control connection is broken, it's not going to work. Thankfully such occurrences are very rare.

[RichPa]

I just can't think what if the engine wasn't at idle, the outcome of not being able to shut it down it had been really serious.

[Turbine D]

Dozy,

Don't forget about the A-340 testing incident at Airbus that hit the wall on November 15, 2007...

From the BEA Report:

Engine #3 and #4 kept running after impact and did not stop immediately. It was not possible to shut them down, neither by activating the fire extinguisher handles nor by positioning the thrust levers on OFF. Water and foam spray on engine #4 managed to extinguish it at 18:48.

Due to the proximity of the wall this was not was not possible with engine #3 in a similar manner to engine #4. It shut down by itself only on November 16 at 01:25 after it had consumed all the fuel from its collector tank.

Again the electrical connections from the engines to the cockpit were severed.

[RichPa]

Were they jammed above idle?

[barit1]

At the risk of being redundant (again), let me point out that R-R has suffered a few turbine disc disconnects - with different engine models, different containment philosophies, and quite different results.

I give you QF74, 744, RB211 on 30 Aug 2010 (SFO local date): Qantas QF74 Uncontained Engine Failure - Video & Pics
IPT came disconnected from its shaft and drifted aft due to pneumatic forces in the engine. In this case, the IPT blades DID clash (i.e. first made contact) with LPT stator vanes, thus very rapidly destroying the driving torque to the loose IPT disc. Blade shrapnel penetrated the case and cowl, but the pieces were relatively small so the damage to the airframe was limited.

Contrast this with the QF32, A380, 04 Nov 2010 SIN: T972 suffers IPT disc rupture after shaft disconnect. No rotor/stator airfoil clash, instead the disc became axially restrained against relatively hard/smooth/low friction internal surfaces. Disc continued to accelerate, driven by relatively intact airfoils, until burst speed was reached.

Which, I ask you, was the more successful containment?

[lomapaseo]

Which, I ask you, was the more successful containment?

The requirement and design intent for containment is not a 100% requirement which of course is impossible to acheive so it's not even attempted.

Instead the regulations look at it as similar to many other requirements including birds, ice etc. The regulations set forth a minimun level that must be demonstrated by test and analysis.

For engine containment the demonstration requirement is for the more likely failure of a blade and its consequences at maximum running speed. Given that in the QF 32 event a disk separation occured t would have been impractical for any engine design currently existing to have contained the debris by verifieable design.

Instead the burden falls to the design intent to minimize the failure condition that caused the non-containment using best industry practices. This does include but is not limited to the presumption that some designs will permit the blades to be mangled in order to save the disk.

Indeed there was a lesson learned in all this for all manufacturers not just RR

[barit1]

Indeed there was a lesson learned in all this for all manufacturers not just RR

I submit that for some, this was a painful re-learning of an old lesson.

Turboshaft/turboprop designers learned long ago they must design for the loss-of-load case - shaft or gear failure, loss of a prop, etc. Turbine overspeed can occur very very rapidly in this case, and active overspeed protective systems are commonly employed to protect the aircraft.

[Joetom]

Containment can be achieved, but too heavy(£/fuel) at the moment.

I thought some APU's in the tail cone have it but only to avoid the tail/tail control devices being damaged by items/parts leaving the engine, however to save weight, items/parts can exit it other directions, I never walk below an operating APU.

[Turbine D]

I just can't think what if the engine wasn't at idle, the outcome of not being able to shut it down it had been really serious.

The engine on the QF32 was not at idle, it ran at the thrust setting at the time when the disc failure on the adjacent engine occurred during climb out. As I recall, the crew had to deal with this fact in calculating the landing distance required and maneuvering the aircraft to line up on the approach to the runway. They did not know the engine wouldn't shut down until the very end of the rollout when they attempted to shut it down.

[barit1]

Let us be clear about this:

DISC failure is unlikely to ever be contained because of the size/mass/velocity of the disc fragments. The mitigation for this is to make a disc failure very unlikely. The sacrifice of turbine blades by interference with stator parts is a small price to pay in protecting the aircraft, even if it results in a lesser-energy uncontained failure.

On the other hand, BLADE failure is generally containable, or at worse, a low-energy case penetration.

[Turbine D]

RichPa,

Were they jammed above idle?

From the BEA Final Report (I eliminated the sections pertaining to brake details):

Between 15:58:10 and 15:59:03 the thrust is increased gradually from idle to a steady value of 1.25 EPR. This engine thrust setting corresponds to a position of the thrust levers between MCT (Max Continuous Thrust) and MTO (Max Take Off Thrust).

At 16:02:06 the person in the right seat starts talking but is interrupted at 16:02:08 by the person in the left seat who announces :
“Euh ... cabin is ... aircraft is moving forward”

The first significant LONGITUDINAL ACCELERATION parameter values showing a forward acceleration of the aircraft are observed around 16:02:07. The recorded ground speed starts to increase at 16:02:09 (3)

Note (3): Ground Speed values are recorded in increments of 1 kt.

Between 16:02:08 and 16:02:13 the ground speed increases from 0 to 4 kt.

At 16:02:11 the person on the left seat again says :
“Aircraft is moving forward”

An action on the brake pedals is recorded from around 16:02:11

The parking brake is deactivated around 16:02:13
The person on the right seat announces :
“Parking brake off”

From the moment the park brake is released:
• the brake pedals are briefly released on two occasions
• the recorded ground speed increases rapidly from 4 to 31 kt in seven seconds

The angle of the nose gear reaches 77 degrees right at 16:02:19 and remains at that value until the end of the recording. From 16:02:18 we can hear on the CVR severe vibration noises followed by impact noises.

The thrust levers did not move until 16:02:20 when they are retarded to the IDLE detent. The EPR values of the 4 engines start to decrease immediately afterward.

The longitudinal acceleration becomes significantly positive, indicating an aircraft deceleration, around 16:02:20.5

FDR recording ends between 16:02:21 and 16:02:22

I would assume the engines that couldn't be shutdown were at idle or close to idle.

[Turbine D]

barit1,

The sacrifice of turbine blades by interference with stator parts is a small price to pay in protecting the aircraft, even if it results in a lesser-energy uncontained failure.

I absolutely agree with your statement. It is a best design practice. You may not be able to prevent a disk that fractures due to a defect, but you can prevent a run away disk reaching a burst speed condition by the design and interactions of the surrounding airfoils.

[kennr]

QF32 A380 incident

The ATSB report is now out... see Investigation: AO-2010-089 - In-flight uncontained engine failure Airbus A380-842, VH-OQA, overhead Batam Island, Indonesia, 4 November 2010

[IFixPlanes]

The final report is online.

[40KTSOFFOG]

Qantas A380

Report into the Qantas A380 Uncontained Engine Failure has now been published!


http://www.atsb.gov.au/media/4148371...-089_final.pdf

[IFixPlanes]

To lazy to search for the original thread?
http://www.pprune.org/tech-log/43797...ml#post7911846

[deptrai]

after a cursory skim through I was a bit surprised not to see recommendations regarding ECAM (irrelevant or even conflicting items), but at a second glance it seems some of this (trim tank availability) may already have been taken care of by Airbus. Seeing the extensive damage documented in detail still makes me shudder, yet simultaneously I'm thinking, chapeau to modern engineering (Airbus in this particular case, more than RR Trent):

The effect on the aircraft’s controllability in those configurations was rated as ‘minor’

and

Despite significant system and structural damage following the uncontained engine failure, the simulation identified that the aircraft had sufficient redundancy to continue safe operation