Posts about: "RAT (All)" [Posts: 683 Pages: 35]

What is the precise trigger for the RAT to deploy automatically on the 787? Full failure of both engines?

You are saying the RAT is deployed but we can rule out engine failure?

I thought this was meant to the *professional* pilot\x92s forum

Quality unlikely as only 1 aircraft affected (and further departures restarted promptly)

Fuel supply/management more likely and PERHAPS related to multiple electrical/electronic failures reported inbound, albeit to cabin systems.

Gear unable to be retracted and flaps retracted due to no hydraulic pressure? It would certainly explain the RAT being deployed and the loss of lift.

Of course the RAT will deploy if all three hydraulic systems have low pressure even with both engines running. This is the case on the 77/78.

Please all... let's get more facts and data before unwarranted speculation about cause or culpability.

That's especially pertinent about questionable aspects like flap extensions used for takeoff, temperature effects, limited runway distance, and other likely irrelevant circumstances.

The "bang", Mayday call, potential RAT deployment, and high alpha touchdown may prove significant, ....if and only if they are later verified by accident investigation.

It is most inappropriate to yet for any professional aviators be inferring any flight crew, airline, or OEM connections whatsoever. Only sympathy and aid for the crew, passengers, families, airline, and those impacted by this tragic crash, and support to the accident investigators, ....should be in our thoughts and prayers at this point.

Well, the certainly sound like they are working; failed engines sound different. No sign of smoke or damage either.

Conceivably, it could be a double engine failure but that's very unlikely.

Ok, so...

Some have said the RAT appears to have been deployed. This would suggest a hydraulic/electrical failure on the plane.

A hydraulic/electrical failure could well make it impossible to retract the gear immediately.

But, what do flaps do in the event of a major hydraulic/electrical failure? Is there a default that they revert back to? I was under the impression the RAT can't power the flaps?

We can, I think, rule out engine failure, at least single engine failure because the rudder is still straight on in the
Video. You can also hear the engines..

Suggests dual engine shutdown/rollback (VFGs offline) with auto RAT deployment.
Full length departure.
Aircraft flaps/slats extended.
Mayday broadcast.
This has a long way to go. I wouldn't be judging the Liveware until the data\x92s been analyzed in detail.

Symmetric is the key word.

The chances of both engines having simultaneous flame outs due to fuel contamination is almost not possible...too many variables to have them fail at the same time.

What we are seeing is a fairly stable flight path....in that the wings remain level throughout and a point in the flight where the vertical profile changes from a normal take off flight path into the high nose attitude descending one...albeit without any significant or abrupt maneuver.

Strange.

You have heard AC with the RAT deployed HUNDREDS of times? The RAT is a last resort, when all other power sources have failed. All engines, the APU and (possibly) batteries on AC as the 787. Yet you have heard hundreds of RAT deployments passing overhead? Yeah, sure.

The video from the NE end of the runway, beside the RVR sensor shows a liftoff occurs abeam the closed high speed taxiway between C and D. Thats at 1250m to run to the DER. The first 10 seconds of flight is steady, and then the aircraft stops climbing and starts a gentle descent, and 5 seconds later the pitch starts to increase in 2 stages with impact around 20 seconds after liftoff. This is not the ADSB data, it is the video at the boundary on F/B.

The video take from the south end of the airport appears to show the RAT deployed.

The flight VAAH-EGLL is not a particularly heavy departure, the takeoff distance is not unreasonable for a twin jet, at under 7,000' from brakes release. I have limited developmental time only on the 787 before EIS, and I cannot recall any surprising latent threat in the performance of the aircraft for a premature flap retraction, and that certainly would not result in a RAT deployment. An accidental ATR low level off capture might get exciting for a few seconds, but it would not result in a RAT either.

The seat 11A pax survivor is remarkable.

Primary trigger: Loss of all four AC power sources.

• These include:
  • Left Integrated Drive Generator (IDG)
    
  • Right IDG
    
  • Left Backup Generator
    
  • Right Backup Generator
    Engine failure alone does not trigger the RAT, must be all of above

What does a RAT deployment sound like inside the cabin? Could the mere deployment be perceived as the 'loud bang' in a high stress situation?

IME, admittedly going back a few years, a RAT being propelled into its deployed position does indeed make a humungous bang.

In flight, the RAT deploys automatically if any of the following occur:
• both engines have failed
• all three hydraulic system pressures are low
• loss of all electrical power to captain’s and first officer’s flight
instruments
• loss of all four EMPs and faults in the flight control system occur on
approach
• loss of all four EMPs and an engine fails on takeoff or landing

(EMP = electric motor pump, hydraulic)
FYI the RAT is an emergency source for electrical and/or hydraulic power.

Regarding that possibility some members here are posting a scenario where RAT are deployed, could this be possible (im no 787 driver at all)?

1) Near the moment of Rotation or a few seconds after it, an Engine failure occurred. (Bird, Fod, Mx, Tech, etc)
2) By destiny irony as in Kegworth or Taipei aviators cut the good one by mistake.
3) No running engines, RAT comes alive...

May all RIP, such a sad day for us all...

Is it anywhere near seat 11A on a 787 though?

No the RAT is behind the wing box, 11A at the very front of the A/C.

As far as I know the flaps will stay where they are if hydraulic power is lost. There is an electrical over ride function as a back up but I doubt the crew would have used that as it's a guarded switch.