Posts about: "FDR" [Posts: 113 Pages: 6]

That picture of the mostly intact tail section should indicate that the FDR and CVR should be eminently recoverable, most likely not even damaged, right?

Assuming we're not facing a repeat of the Boeing 737‑800 crash at Muan International Airport when loss of loss of both engines apparently also cut power to Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR)

787 gear and flaps/slats are both on the centre system, powered by 2x big electric pumps and no EDPs, so retraction should be minimally impacted by engine failure assuming electric power was still available and reconfiguration worked. Note the 787 has two generators per engine so generator failure is also unlikely to contribute, unless both engines failed taking out all four generators (and presumably no APU running).

From that thread, I believe it was discussed that on most/all other large transports, deploying the RAT re-powers the CVR/FDR. The 737 didn't have that happen because no RAT. You may still get a few second gap while the RAT deploys.

The 787 has 2x Enhanced Airborne Flight Recorders (EAFR), which each record both cockpit voice and flight data. I expect they are also fitted with the dedicated batteries that the Jeju was a year or two too early to require. Per the NTSB , the forward recorder has a 10-minute backup battery.

Hopefully flight data is not going to be an issue for this investigation.

The suggestion is that the buzzsaw/propeller sound is the RAT; it does sound a bit like an interference pattern, but you don't get the engine roar with it.

It's also maybe visible in a few stills (e.g. post 64).

From the airport CCTV video it looks to me like a normal takeoff and start of climb, until suddenly there's a loss of climb performance with no obvious upset at that point. From the picture of the wing post crash it looks like the flaps were still deployed (N.B. based on pre-accident photos that's the right wing so closest to the camera is aileron and flaps are further away, damage had me confused first time), so I'm going with loss of thrust rather than flap retraction.

From the videos from bystanders it looks like RAT deployment (both sound and zoomed in pictures) rather than thrust lever retard, and that would also explain failure to retract gear - if you are dealing with both engines out at that altitude then gear isn't your first thought. From the airport CCTV video I don't see anything that looks like bird strikes at that point in the climb i.e. no obvious flocks of birds, no smoke out of the engines, no slewing one way as one engine fails and then the other is cut by accident - plus you wouldn't cut the engine at that point, you'd climb on one engine and then sort it out.

Even fuel contamination or water build up in both tanks is likely to result in one engine failing a few seconds before the other. So I can't come up with anything other than both fuel cutoff switches that would result in loss of thrust and RAT deployment. Looking at a picture of the cutoff switches https://www.nycaviation.com/2013/08/...is-fired/30179 I don't see how they get hit by accident.

I'm confused, hope we get an FDR / CVR readout soon.

FDR, that particular failure mode was engineered out of the logic long ago - there is no exception to the A/T takeoff lockout logic unless one of the 'unlock' conditions is true (and overboost isn't one of them).

The latest hi res video does have audio and very clear. You can hear a RAT sound as it passes by or certainly a deep propeller sound, And a blob where the RAT would be. Only the FDR will help here, That would point to total power loss. But the sudden loss of lift apparent in the video doesn't look like power loss.

There isn't enough clarity on numerous issues, and without answers to the following, zero conclusions can be made as to a possible cause. This is definitely one that could go in numerous directions. Anyone claiming to have the definitive answers must have the FDR data, and I'm assuming that shouldn't take too long to be located and analysed.

1a. Were flaps deployed at start of take off roll?
1b. Were flaps retracted coinciding with climb rate reduction?
2. Did the RAT definitely deploy? The videos are grainy low quality. AI improvement surely isn't reliable.
3. If the RAT deployed, would that indicate complete power loss?
4. Was there any other audio indicating thrust loss or variations during departure?
5. Can we confirm the pilot Mayday indicating thrust loss? If so, that needs investigation as a first priority. The pilot was telling us the cause. Unless we have alternative information he should be believed.
6. Why was the gear not retracted? Distraction, hydraulic failure, flap instead of gear, intentionally, the possibilities are endless.
7. If complete thrust loss occurred, other than a severe fuel issue, what could cause simultaneous flameout? That would be almost unimaginable, yet this is what the pilot allergy said happened. It would have massive ramifications if that gets confirmed.

I don't think the video clips we have are clear enough to say anything at all at this stage. Flaps are hard to see on 787 imo for departure settings. All I can say is it appeared to climb well in the first seconds, then coinciding with the point that gear would usually be retracted, lift appears to very quickly be lost. That indicates sudden speed loss, or lift loss. Speed loss would be thrust, lift loss would be flap retraction if thrust was still available.

The pilot allegedly reported thrust loss, that should be highest on the list of causes imo. In the case of double engine failure without any apparent outside influence visible on videos, that would be quite something for investigators to fathom.

I don't know if anyone has data to show speed trend at the point the aircraft starts to descend, or a better audio for thrust variations at that point. I'm guessing that the update frequency on FR24 would be too slow to show that sudden change at the highest point achieved.

We'll have the answers soon enough, all I can say is there appears to be no clear answers here without the data recorders or clear improved information. Indeed no conclusions whatsoever can be made as to crew actions either.

RIP crew and passengers, condolences to the families.

The Dreamliner as two identical “Enhanced Airborne Flight Recorders”, one in the tail section and one beneath the flight deck. Each one contains the CVR + FDR in one module, both have 10 minutes of battery power backup. I see reports that the one in the tail section has been recovered. All to easy to surmise the contents will be tampered with at the request of politicians/investors

It's fine that the \x93Enhanced Airborne Flight Recorders\x94 have 10 minutes battery backup. If the bits of equipment/sensors sending data to be recorded don't have power, you will be recording 10 minutes of silence/blank data.

The concept of powering 'critical (sensor) equipment' has been floated - the problem being that it must be possible to power down malfunctioning equipment in case of fire - real or suspected. Having independent power supplies and battery back-ups all around the airframe, each with an ability to lose their magic smoke, is a poor idea.

Commercial passenger jet aircraft already have robust power supplies with multiple generators and emergency battery support. However, if one malfunctions, rather than fails completely, it can be difficult to decide which one to disable, as it can cause problems in all systems.

I understand that the FDR has been recovered from the crashed 787.
Could anyone tell me how many engine parameters are recorded and what is the sample rate.
Thank you.

What will that give you?

Most likely anything between 256 and 1024wps, individual parameters will vary with regards sample rate. Not au-fait with 787 but other Boeing aircraft may have dataframes relative to the original owner requirements (though this is unlikely to vary much given my experience with Boeing aircraft). I\x92m not sure if GE have a real time EHM feed like RR? Anyhow, and not wanting to speculate too much, if there was anything engine related it would certainly show up on the DFDR and GE could possibly even know that by now if they are equipped with real time health monitoring. In my opinion, for what it\x92s worth, the CCTV footage is consistent with flap retraction instead of gear, something that would also be easily identifiable upon review of the FDR which will be reported upon in due course.

Not yet seen a response to my question about which engine parameters are recommended by the FDR and what is the sample rate.
Hopefully you might be able to answer this.
Many thanks.
I am a retired gas turbine engineer who worked on safety systems and assessments and assisted on a number of accident investigations (military fast jets) and would be interested to know this.

I can't tell you off the top of my head. I was an engineer at final assembly (mostly final body join and functional testing) and then did support for airlines post delivery (working with their engineering teams on maintenance and operation) so I wasn't intimately involved in anything data wise on the FDR. My personal belief is that it should end up being glaringly obvious why the engines stopped working with the data they have, just to many coincidences happening at literally the exact same time for it to be some minuscule problem never envisioned before. Pretty sure FDR and CVR will tell all.

Bit surprising that we don't have confirmation of the 2nd FDR recovery by now, especially with the seemgly realtively intact tail section. The
DFDR was reportedly recovered from this rooftop:




The CVR can't far away and muss be a rather high priority search item.

Interdentally I have read some reports mentioning a DVR (Digital VIDEO recorder). Is AI fitting such devices in their aircrafts ?

Are the FDR and CVR not combined in the 787? (One in the front and one in the tail, but recording the same info??)

I'm really trying to resist engaging here, but anyone who states what pilots, 'would', do in a given situation, simply hasn't grasped the most elementary, 1.01, fundamentals of human behaviour.

Again and again, I've listened to CVRs, or looked at FDR plots, or sat next to people in a flight deck or crew room, or restaurant, or anywhere (but especially in the back of a simulator)... and pondered what on earth led competent individuals to do what I had just witnessed. Of course, if the individuals aren't competent to start with (and that is NOT directed at this crew, but embellishes my point) there may be less mystery.

Also worth remembering, for those of us who do, the ludicrous training delivered by Airbus on the A320 family at the start, when they told people that, (a) pulling the stick back and holding it there will save you, and, (b) you don't need unusual attitude training in an FBW aircraft. I think we know how that played out. I'll add an element of my briefing for a departure in a single-engined aircraft, if a forced landing was not an option (eg Rochester, Biggin Hill), which also covers what I have always thought I would do faced with total power loss in a bigger machine, 'I will manoeuvre the aircraft to hit the softest thing I can, as slowly as possible'. Very glad I never had to see that through.

OK, another hour spent going through all the posts since I was on last night...
I won't quote the relevant posts as they go back ~15 pages, but a few more comments:

TAT errors affecting N1 power set: The FADEC logic (BTW, this is pretty much common on all Boeing FADEC) will use aircraft TAT if it agrees with the dedicated engine inlet temp probe - but if they differ it will use the engine probe . The GE inlet temp probe is relatively simple and unheated, so (unlike a heated probe) a blocked or contaminated probe will still read accurately - just with greater 'lag' to actual temperature changes.

TCMA - first off, I have to admit that this does look rather like an improper TCMA activation, but that is very, very unlikely. For those who don't know, TCMA is a system to shutdown a runaway engine that's not responding to the thrust lever - basic logic is an engine at high power with the thrust lever at/near idle, and the engine not decelerating. However, TCMA is only active on the ground (unfamiliar with the 787/GEnx TCMA air/ground logic - on the 747-8 we used 5 sources of air/ground - three Radio Altimeters and two Weight on Wheels - at least one of each had to indicate ground to enable TCMA). TCMA will shutdown the engine via the N2 overspeed protection - nearly instantaneous. For this to be TCMA, it would require at least two major failures - improper air ground indication or logic, and improper TCMA activation logic (completely separate software paths in the FADEC). Like I said, very, very unlikely.

Fuel contamination/filter blockage: The fuel filters have a bypass - if the delta P across the filter becomes excessive, the filter bypasses and provides the contaminated fuel to the engine. Now this contaminated fuel could easy foul up the fuel metering unit causing a flameout, but to happen to two engines at virtually the same time would be tremendous unlikely.

Auto Thrust thrust lever retard - the TO lockup in the logic makes this very unlikely (it won't unlock below (IIRC) 400 ft., and even that requires a separate pilot action such as a mode select change or thrust lever movement). And if it did somehow happen, all the pilot needs to do is push the levers back up.

Engine parameters on the FDR: I don't know what exactly is on the 787 FDR with regards to engine parameters, but rest assured that there is plenty of engine data that gets recorded - most at one/second. Getting the FDR readout from a modern FDR is almost an embarrassment of riches. Assuming the data is intact, we'll soon have a very good idea of what the engines were doing

It's not surprising. The 787 was designed with a modern digital flight recorder (Enhanced Airborne Flight Recorder, EAFR). It does both - records data and voice. No more separation of CVR+FDR. Just one device.

But the 787 was equipped with two redundant recorders. One in the aft, one in the front compartment. Both record identical data. If one of them was found in usable condition, then they're good. It will already have all the data they need.

The speed at which there was a complete loss of thrust and electrical power degrading to the point of flickering lights and RAT deployment suggests to me an actual engine shutdown rather than anything linked to auto thrust or fuel contamination. There are not many things which can cause an engine to shut down: LP valves, FADEC incl TCMA, crew action\x85