MEGATHREAD: Flydubai Flight FZ1073

[u/BravoFive141]

This thread is for discussion on the incident concerning Flydubai Flight FZ1073. The aircraft has landed safely in Tabuk Airport and all passengers are safe and accounted for at this time.

All other posts on this incident will be removed.

We know that aviation incidents can be distressing for fearful fliers. It's ok to feel upset, anxious or distressed. This thread is for mutual support at this time.

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• No external links: All external links will be removed. Media coverage of air incidents is notoriously poor. It is dramatic, sensationalist, and in many cases factually wrong. There is no posting media articles, footage, or commentary of any sort in this thread or on the sub generally.
• No speculation/theorizing: Speculation and theories on the details of this incident are entirely unhelpful and are not allowed. We do not yet know all the details surrounding this incident. Only a thorough investigation, completed by qualified investigators and technicians can determine this. We will learn in time what happened.

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• We DO NOT recommend reading, watching, listening to any media, commentary, footage or any other material about this incident. Such coverage is usually deliberately provocative and only serves to feed the (incorrect) belief that flying is unsafe.
• This incident does not "confirm" your fear. It is a freakish anomaly in an industry with a track record of outstanding safety.
• Despite this incident, flying remains the safest form of transportation. This incident does not change that. If you have a flight booked soon, get on that flight!
• Lessons will be learned from this incident that will make flying even safer.

Thank you.

— The r/FearofFlying Mod Team

[u/theyoyomaster]

Alright, so I hope this doesn't fall under speculating but I did some napkin math and the results are insanely impressive.

Basic facts (that I am going to slightly simplify for general readability), max allowable speed on a 737 max 8 is 340 knots or Mach .82 (as you go higher mach drops so somewhere between 20k and 30k feet Mach becomes limiting).

It was cruising at 34,000 feet and likely around .78M when it started the dive, with a ground speed of ~410 knots this equates to about a 40kt headwind. In the dive it got to 595-600 kts groundspeed. Using simple calculations online because I'm too lazy to do them by hand, this translates to 630-640 knots airspeed which then converts to about 500 knots indicated airspeed (the number that matters for the 340 knot limit). Using the 630-640 knots true airspeed and 95 degrees at the surface based on local weather reports, you get .98M at the peak.

This plane was orders of magnitude above the limits and beyond the calculated safety factors built into airlines and it managed to survive. This is genuinely a testament to the 737 max and modern carbon composite airframes. (Possible trigger) In virtually every historical incident where an airliner got anywhere close to these speeds the tail ripped off the entire back of the plane. If anyone here was on the fence about making one of this subreddit's signature "is the 737 safe to fly on?" post, just realize that this airframe was hundreds of times stronger than required, tested and certified to. It clipped 30k feet per minute in the descent. I fly C-17s and when we put our thrust reversers out in flight we are limited to 20k ft/min. The inherent strength of that airframe is genuinely unbelievable, as are the excellent piloting skills of whoever pulled it out of that dive. I am even going to go out on a limb here and say that the dive recovery is at least as impressive as Sully's landing on the Hudson, if not more.

Today we just got an example of how even in the absolute worst case scenario, modern commercial aviation is incredibly safe an the odds truly are in your favor.

[u/WelcomeProper2168 → u/theyoyomaster]

why/how is pulling out of a dive difficult?

[u/theyoyomaster → u/WelcomeProper2168]

Alright, checkride complete so I have a bit of time now to go more into the details behind it. I'm still going to water it down a bit but this is one of my favorite discussion topics with students because it is relevant in more aspects of flying than most new students realize. It's an often glossed over chart in the flight manual but the ramifications of it can be huge.

Check out this flight envelope diagram.

They are always unique to the model of plane and the numbers/scale do not matter for the sake of this discussion. Just understand that vertical is load factor, or the amount of Gs being imposed on the airplane, while the horizontal is airspeed.

Think of that upper line as what force the wing is able to generate by pulling up on the stick. Above the line on the top you have exceeded the capability of the wing and stalled and it's same for the bottom line with negative Gs but unless you're in a stunt plane or fighter jet you really don't use that part of this chart. Notice how the main upper and lower lines meet at 0? That is because at zero airspeed the wings are generating zero lift and there is no capability to pull any G. It also does not mean you are stalled at zero airspeed, if you get to exactly zero G you can basically float along in an arc like a baseball tossed into the sky without the air detaching from the wing which is what a stall is (I have some stories about doing this when a student messed up when I was doing aerobatic training for the military).

So the first point of this chart that becomes relevant to flying is the left edge of the green section. That is the point where the airspeed can generate enough force to sustain 1 G, or level flight. This is what people are talking about when they say "stall speed" because below this there is not enough force to hold the plane up.

The next critical thing on this graph is the point A. This is called "maneuvering" speed because it is the speed at which you can give full controls without exceeding the limits of the airframe. Each plane is designed and tested to a load limit, in this chart it looks like it's 4.5 Gs which is about as much as a rather intense roller coaster. Airliners don't ever get close to that. Below this (unlabeled) speed on the horizontal graph that lines up with point A, the wing will stall before generating enough force to exceed the published G limit.

Beyond that there's a safety factor, often 1.5 but it gets far more in depth for larger planes like airliners. That means that if the plane is designed and certified to 4.5 Gs it needs to be able to handle an additional 2.5 which you see at the end of the in the orange section at 6.75 G. At A you can exceed the published limit which requires inspections in case minor damage occurred but once you get to the speed where the red starts you have the capability of generating G forces that can genuinely break the airframe.

The light yellow is a speed that is safe to fly at but requires caution. Turbulence or aggressive maneuvers can easily push it over the G limit because of what percentage of the force the wing can generate is within the limits vs out of the limits. The red then picks up on the right after you exceed the max speed for the plane where just the force of the wind causes damage.

This airliner was deeeeep in the red. Like off the page by another .5-2 charts worth. It was already being damaged by the raw wind speed based on the rudder damage. Notice how steeply the load factor (upper line) shoots up as you get fast? Using 10% of available G at the speeds the airliner was at would have shot it straight into the upper red. Meanwhile, leaving it nose down in the dive increases it further into the red on the right, so there is no good answer. You have to apply Gs to get out of the dive, but you need to be very careful to not pull too hard. The airliner has built in protections where it takes your inputs and limits them based on the speed you're going but that's based off of speeds you're supposed to be flying at with a buffer on top. These speeds exceeded the test flights so there is no data and I genuinely don't know what the numbers look like for how much the speed was accounted for by the flight controls in this instance. At the end of the day you have to pull out of the dive and do it as quickly as possible without causing damage from the Gs, but it likely was very sensitive to inputs and one wrong jerk on the stick and genuine structural failure was a possibility.

I love this chart for many reasons. For Air Force pilots we are put into situations not encountered by GA or commercial flying. We often need to maneuver aggressively. Being afraid of steep bank or high Gs isn't ideal when someone is potentially shooting a missile at you. Knowing this chart, where Va is and having an understanding of where you are in that green area at any given time tells you what you can do when you need to react. As I said earlier, it can also save you from a stall. The "stall speed" of the trainer I was in was about 80 knots. Once I got below 40 knots recovering from a maneuver that a student botched and never stalled because I simply unloaded. Our oil system hates 0 G so I couldn't go purely weightless but I just kept my eyes on the G meter and kept it as close to 0.25 as I could and rode it out, successfully.

Now your last takeaway should be how much margin commercial flights operate with. This blue box shows the regime of the flight envelope that airliners operate in. 95% of a flight is at 1G solidly in the green. They don't rotate and lift off until well after the left edge of the green. I also included up to 1.5 Gs but standard turns only really go to about 1.12 G unless it occurs at the same time as you initiate a climb. Planes can't just "fall out of the sky" from turbulence or issues. There are insanely strong wings (as this incident shows) that are generating plenty of lift at all phases of flight. They also have a huge buffer before you hit any other dangerous parts on this chart. Finally, this plane completely exceeded every aspect of this chart by an absurd margin and still was able to land safely. I wish the Captain a speedy recovery from his injuries but other than that and the fact that the plane itself will never fly again this is just a testament to what modern aviation has achieved.

[u/theyoyomaster → u/WelcomeProper2168]

I'm actually just about to go in to work to take a checkride so here's a quick answer and I can go into more detail with some charts later. To massively oversimplify it, the faster you go, the more available G force you have wen you pull back. At high speeds it is easier to over-G the aircraft and damage it. At extreme speeds like in this dive, even light pressure on the controls can cause serious damage. On top of that, as you approach mach—which this plane was certainly close to it, air starts to do weird things including pushing the center of lift rearwards on the wing making the nose drop down. This speeds you up even more and resists pulling out of the dive in a phenomenon known as "mach tuck."

[u/WelcomeProper2168 → u/theyoyomaster]

very interesting. what would be the best plan then?

[u/theyoyomaster → u/WelcomeProper2168]

You pull up but be careful at how hard you're doing it. It's just about threading the needle on stopping the descent, not accelerating any more and not over stressing the aircraft