Posts about: "RAT (All)" [Posts: 607 Pages: 31]

and people are saying this happened all at the same time within 30-45 seconds ?

Yep, total rubbish - 45 years airline flying - deployed it only once and never saw it anywhere else.

Forgive me if appear to be being a bit pedantic but the 787 does not have IDGs and BUGs.
Each engine has two identical Variable Frequency Starter Motor Generators.
They are a combined starter motor and generator.

More in this ancient thread here-
787 electrical system - variable frequency generators?

It's been postulated that pulling both fuel cutoffs would drop the RAT and cause the engines to spool down. To those with SIMs, at what point in the takeoff would this action create the flightpath shown in the videos?

Then, confoundingly, there's that swirl of dust in the port wingtip vortex on rotation. Is Ahmedabad unusually dusty? Do all takeoffs there create this, or only rotations close to or beyond the end?

Every 787 in service has had the RAT deployment tested during Boeing/Customer flights prior to delivery.

Many people living/working in the Everett or Charleston areas will have heard the RAT many times.

I am not a pilot so apologies if this is a basic question.

Under what conditions will the RAT deploy? Is this automated or does the PF / PM need to hit a switch? <-- [Edit] I see this was largely answered in post 369. Thanks!

Watching the CCTV from the airport, it doesn't look like there was much time to do anything. I'm surprised someone called a Mayday (if that's true). And even to me, it seems pretty clear that bird never had enough power to go much of anywhere except where it did.

All so very tragic.

I can confirm that this happens in the Blagnac area too!

Kind of, agreed.

Once already airborne and positively climbing, having 2 engines running and possible TOGA should yield as much as 250% of the required performance (100% - one engine out safe flight path 2,4% gradient).

The RAT (if true) is a massive smoking gun. I'd be happy to learn if anyone with a trained eye sees anything amiss with the ground roll and liftoff. I don't (but not an expert).

And it makes clear why it was filmed, it sounds very different to a normal take off, and most probably, it was a suddendly change of sound from 2 engines TOGA to a RAT.

There are people in the world who have a different, less limited lived experience from you.

As noted in my profile, I live in the Apple Maggot Quarantine area. Specifically, I live in Lynnwood, Washington directly under the approach path for Paine Field's runway 34 Left, and I've been there since 2007. I lived in Mukilteo from 2000-2007, which is more next to the runway than under it. I also own and operate a small aircraft based at Paine Field and am outside on the ramp at least every other day. Boeing manufactures the 777 and 787 at Paine field. Two thousand, nine hundred and fourty-six of them have been made since 2000, when I moved here. The RAT is deployed and tested during EVERY SINGLE first flight of every aircraft Boeing produces that has a RAT installed. And sometimes it requires a re-test on subsequent flights.

So yeah, I have heard a deployed RAT, from the ground, HUNDREDS of times. I've heard it while preflighting my airplane, I've heard it while mowing my lawn, I've heard while lying in bed. And this is exactly what they always sounds like. Another poster compared it to the sound of a T-6 Texan, which is really quite similar. You can find dozens and dozens of videos on YouTube of aircraft landing at Paine Field with the RAT out. It's not rare, it happens daily.

Would explain the lack of thrust, but not the RAT deployment.

Thanks for your input and a reminder to others manners cost nothing! You don't know who you're speaking to

There are no IDGs on a 787. There are 4 identical variable frequency starter-generators.

For those still under the impression that the takeoff or rotation was at the runway end... In the video of the CCTV camera you can see rotation happens basically behind the small structure in the foreground. Unless I am severely mistaken... Knowing the approximate rotation of the camera, one can simple draw a line until it intersects with both the structure and the runway:



Yes, it is just an approximation, but I'd say they still had a decent chunk of runway left, and not in any way close to taking out antennas on the opposite end.

So... likely not at MTOW, not using the full runway, normal rotation, followed by videos of it with RAT deployed which should only happen upon loss of all electrical/hydraulical sources, which should only really happen on loss of both engines without APU running, combined with barely (if any) sound produced by the engines in said videos... It leads me to form some sort of image of what happened. Could still be completely wrong.

I have done a RAT deployment test flight on a previous type, and even though I was prepared for it, it was still a bit of a shock to see the cockpit go mostly blank before reconfiguring itself. I don't know how quickly the 787 would reconfigure, if there is any downtime at all, but that would not have been a thing you'd expect at 100-200ft AGL. I do not know how many of us would quickly overcome the startle.

OK, I promised some informed speculation when I got back, so here goes:
Disclaimer: never worked the 787, so my detailed knowledge is a bit lacking.

First off, this is perplexing - especially if the RAT was deployed. There is no 'simple' explanation that I can come up with.

GEnx-1B engines have been exceptionally reliable, and the GE carbon composite fan blades are very robust and resistant to bird strike damage (about 15 years after the GE90 entry into service, I remember a GE boast that no GE90 (carbon composite) fan blades had needed to be scrapped due to damage (birdstrike, FOD, etc. - now that was roughly another 15 years ago, so is probably no longer true, but it shows just how robust the carbon composite blades are - far better than the more conventional titanium fan blades).

Not saying it wasn't somehow birdstrike related, just that is very unlikely (then again, all the other explanations I can come up with are also very unlikely ).

Using improper temp when calculating TO performance - after some near misses, Boeing added logic that cross-compares multiple total temp probes - aircraft TAT (I think the 787 uses a single, dual element probe for aircraft TAT, but stand to be corrected) and the temp measured by the engine inlet probes - and puts up a message if they disagree by more than a few degree tolerance - so very, very unlikely.

N1 power setting is somewhat less prone to measurement and power setting errors than EPR (N1 is a much simpler measurement than Rolls EPR) - although even with EPR, problems on both engines at the same time is almost unheard of.

The Auto Thrust (autothrottle) function 'falls asleep' at 60 knots - and doesn't unlock until one of several things happens - 250 knots, a set altitude AGL is exceeded (I'm thinking 3,000 ft. but the memory is fuzzy), thrust levers are moved more than a couple of degrees, or the mode select is changed (memory says that last one is inhibited below 400 ft. AGL). So an Auto Thrust malfunction is also extremely unlikely. Further, a premature thrust lever retard would not explain a RAT deployment.

TO does seem to be very late in the takeoff role - even with a big derate, you still must accelerate fast enough to reach V1 with enough runway to stop - so there is still considerable margin if both engines are operating normally. That makes me wonder if they had the correct TO power setting - but I'm at a loss to explain how they could have fouled that up with all the protections that the 787 puts on that.

If one engine did fail after V1, it's conceivable that they shut down the wrong engine - but since this happened literally seconds after takeoff, it begs the question why they would be in a big hurry to shut down the engine. Short of an engine fire, there is nothing about an engine failure that requires quick action to shut it down - no evidence of an engine fire, and even with an engine fire, you normally have minutes to take action - not seconds.

The one thing I keep thinking about is someone placing both fuel switches to cutoff immediately after TO. Yes, it's happened before (twice - 767s in the early 1980s), but the root causes of that mistake are understood and have been corrected. Hard to explain how it could happen (unless, God forbid, it was intentional).

And this just highlights the difficult decision faced by moderators when trying to reduce noise on a thread because, without this additional supporting information , I too raised an eyebrow over the claim of hearing hundreds of RAT deployments.

NOT especially getting at you slacktide , indeed thanks for the followup and presenting your experience/reasoning, however, to assist everyone, including *relevant* background/support detail with one's post is to be encouraged! If you don't have this, or are just speculating from a position of little experience or knowledge, maybe the best contribution would be to sit on your hands for a bit and learn from others?

FP.

So, looking around the interwebs it seems like the 787 RAT takes 8 seconds to deploy, and only provides full RAT power at 130 knots or better.

Does it seem like the RAT should already be deployed in the videos we have seen, given an 8 second deployment time, and adding in the time needed for the system or pilot to decide it should be deployed?

It must take a little time for the engines to spool down and the other power sources to fail after takeoff.

I'm reminded a little of Emirates EK321, back in 2021, where the pilots left the MCP altitude setting at 0ft. https://simpleflying.com/emirates-bo...-long-takeoff/

However, that would have nothing to do with the RAT deployment.

So, I'm in no way connected with Aviation, but I am a bit of a data geek and hope it's an appropriate thing to post. I was interested to see how this flight related to others, so did a bit of data wrangling with FlightRadar and Google Earth. This obviously comes with some caveats:

- The data may not be reliable, coverage could be patchy and FlightRadar probably do some data processing that they don't reveal.

That said, what I did was for the past 7 days of this flight - i.e. 787s travelling to Gatwick I downloaded the raw .CSV data for each flight. From that I took the first sample with an altitude of >0 i.e. the first point that the flight looked to be airborne. On my picture (which I've tried to show in 3D as far as possible), these are labelled as 1-1, 2-1, 3-1 etc and orange. As I don't have enough posts to include the visualisation, here it is:

postimg.cc/gLW8zXDg

The flight from today is in red with a larger marker. As you can see, it appears to be in the same position in space as every other flight this week at the same point in time (with all the caveats above). It did, however, have a ground speed approx. 10knts less than any other flight this week. Is that significant? I don't know. It certainly isn't airspeed anyway, so may not mean much.

I remember reading a quote from FlightRadar somewhere in this thread that this was the last valid sample from this flight. Obviously, given the course of events we wouldn't expect many samples, so the next thing I did was to take the second valid row of data from each flight and plot that (in green 2-1, 2-2, 2-3 etc) - what this showed that all of the other flights in the last week did manage to transmit a data point before they flew over the crash site so had todays flight transmitted anything there is a reasonable chance that it would have been picked up in a similar location to the others. That is wasn't seems to suggest there is a good chance that the data wasn't sent. One possibility could be a loss of power, but I'm sure there are many other factors that could result in missing a data point.

I don't want to draw too many conclusions from this because the data is probably not that reliable but it does seem to suggest a fairly normal take off that didn't get close to over running the runway.

Does it correspond to the reported bang, RAT deployment, etc? Maybe.

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.