Why AirAsia 8501 Disappeared From Radar

indonesia_asia_a320_pk-axc_java_sea_141228_1
Figure 1: ATC screen grab of QZ8501

One of the many baffling aspects of the QZ8501 story so far is why the plane disappeared from radar screens when it did. Did the plane suffer some kind of catastrophic event that caused the plane’s transponder to cease functioning? Or did something else occur?

I believe that we now have enough information to answer that question.

All we know about the plane’s final moments comes via two images that were apparently leaked from the official inquiry. The first (figure 1, above) is said to be a screen grab from an air traffic control (ATC) screen shortly before the plane disappeared. The second (figure 2, after the jump) is a screen grab taken very shortly afterward, this time from what looks to be some kind of analysis software, showing the plane’s speed, heading, rate of climb, and so forth.

According to Embry-Riddle Aeronautical University professor Martin Lauth, who helped me to understand the symbology of figure 1, the yellow arrow is pointing at the symbol for the plane in question, here designated “AWQ8501.” The number to the right, 353, is the ground speed of the plane in knots. The number below, 363, indicates that the plane was at 36,300 feet, and the white arrow to the right of it shows that the plane was climbing.

Next, let’s talk about the four white lines coming from the QZ8501 symbol, starting with the one heading more or less straight down and connecting it to “AWQ8501.” That line just indicates which symbol the tag corresponds to. Moving clockwise, we next find a much shorter line sticking to the left. This is a visual indicator of how far the plane will move in a certain amount of time — controllers typically set it for anywhere from one to three minutes, and in this case it seems to set for one minute. We already know the speed of the plane, but this line tells us its heading: a little south of due west, on a heading of 265 degrees true.

That, of course, is not the direction the plane was supposed to be heading. It was supposed to be going to RAFIS, marked by the next line, working clockwise. So what we see here apparently is a plane that’s either diverting to the west to avoid weather or is simply out of control.

Finally, we see a line that projects from the QZ8501 symbol almost directly to the north and continues past the edge of the image. This appears to indicate the radar station which is collecting the displayed information, in this case a facility at the town of Pontianak on the island of Borneo. The data on the screen either comes from the plane’s Mode S transponder via secondary surveillance radar, or is routed through the same transponder to a different systems called ADS-B.

Either way, the thing to understand is that these are line-of-sight systems. That means that if an aircraft gets too low, the transmission of information will be blocked by the curvature of the earth. How low? Well, of course, it depends on hour far apart the plane and the antenna are. In this case, the plane was about 200 nautical miles away. A back-of-the-envelope calculation suggests that the altitude below which the plane will be unable to transmit to the station is about 20,000 feet. (By the way, a tip of the hat to Mike Exner and Don Thompson for turning me on to all of this.)

In the final ATC screen grab we see that the plane was at 24,025 feet and descending at 11,518.75 ft/min, which is equivalent to 130 mph straight down.

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Figure 2: Final ATC location information

This is never something that a commercial jet wants to do, but we now understand that we have no reason to believe that the plane’s electronics were compromised: rather, we would expect the plane to vanish from ADS-B and radar screens around this time anyway, for the simple reason that it will henceforth be hidden by the curvature of the earth.

In other words, for all we know the plane’s avionics might well have been in perfect working order at this point.

Oh, and by the way, I’m also attaching a screen grab (figure 3) from Google Earth showing the locations of the things I talk about above, including the 200 nm range ring around Pontianak. I’m also including, for sheer curiosity value, the 0:11 and 0:19 ping rings from MH370. I am in no way advocating that this is the case, but I think it’s worth noting that there is a non-zero probability that QZ8501 (just by chance!) came to rest on top of the wreckage of MH370.

Or, to look at it another way, it’s possible that the searchers looking for 8501 could find 370 first.

QZ8501 Google Earth Screen Grab
Figure 3

UPDATE: Below, I’ve added the

 

QZ8501 final ATC positions

93 thoughts on “Why AirAsia 8501 Disappeared From Radar”

  1. This seems disturbingly similar to AF447 so far. The rapid climb, stall, and crash. It seems impossible to believe the pilots here made the same mistakes as the 447 pilots, but I guess we’ll have to wait and see.

    The mention of MH370 made me chuckle. Even if QZ8501 isn’t on top of MH370, there’s an ever so slight chance that the vessel on the bottom of the sea they think is QZ8501 is actually MH370.

  2. Jeff, this is astonishing.
    I’d like to ask:
    Firstly, Who leaked these docs and Why?
    What is their motive to do so before the official investigation?
    When did the airline become aware of pending storm?
    Was there a Pending storm?
    Is it true that Fernandez sold almost 1million shares in travel insurance arm of business a couple of days before the crash?
    If so, it implies he also had a prior warning of an Air Asia flight being targeted.
    The Chinese blogger seems to be legit, warning of another MAS or AirAsia.
    It’s also been suggested that HAARP warfare maybe in play here,
    So I did a little research and it’s frightening to say the least, just what this technology is capable of doing, especially if it’s in the hands of dangerous criminals, or if used in Geopolitical Warfare.
    For the sake of humanity, I really hope it was tragically and sadly a strait forward (for lack of another word) crash..
    Keep up your great work Jeff and IG group

  3. The “leaked radar data” became public thanks to @GerryS (Gerry Soejatman). We owe Gerry a lot for his contribution. He is a well-connected professional, so we can be reasonably confident it is accurate data.

    In addition to the two radar screen grabs, Gerry tells us that ATC personnel who supplied the radar data also reported to him that in the final few minutes, QZ8501 experienced very high ROC (+6000 to +9000 ft/min) and very high descent rates (>15,000 ft/min). The glide ratio at 24,025 feet, computed from the very low horizontal and vertical speeds at 23:19:46 is only 0.56, meaning QZ8501 must have hit the water within ~2 minutes and 2-3NM of this final radar fix.

    Given the radar data, ADS-B data, recovered debris & body locations down wind and down current 55 NM, the extreme up and down velocities at altitude, plus the crucial observation that most bodies discovered in the first few days had no clothing other than tight fitting undergarments…given all this, the aircraft must have suffered a major structural failure at high altitude. The bulk of the fuselage probably “floated down” in a flat spin or inverted flat spin like a heavy leaf falling at 120kts or so. The tail may be separated by a mile or more.

  4. @airlandseaman: re: MH370: in a prior post, I recall you mentioning that the Inmarsat employee who passed suddenly on March 17 was, in your opinion, not likely central to the MH370 investigation (I’m going by memory, because I’m struggling to locate the actual post). Would you be able to re-post your statement, and expand on what you feel supports that view? Many thanks.

    P.S. I should have thanked you last week for taking the time to review my impact distribution model – appreciated.

  5. http://www.heraldsun.com.au/news/the-latest-air-disaster-has-highlighted-safety-fears-and-questions-on-how-planes-in-the-modern-age-can-simply-disappear/story-fni0fiyv-1227173108479?sv=98ffa897978e5be97c1a1d53f5051f68

    “But Pacific Aviation Consulting director Oliver Lamb says if an aircraft is not in the air it can’t be tracked.

    As it turned out, sadly, that was the case with QZ8501.

    Its wreckage was found within 10km of its last radar position.

    Even then, the debris took three days to find, leading Bartsch to suggest the chances of finding MH370 were looking increasingly remote.

    “No one knows where its last position was. It’s all based on best estimates from a few satellite pings,” he says.

    “The reasons why they found QZ8501 were there was wreckage and oil slicks in the vicinity of its last known position. I suspect now the chances of ever finding MH370 are decreasing significantly.”

    What it amounts to is an enormous amount of grief for hundreds of families globally.

  6. Be somewhat cautious of the altitudes reported by the plane. They are not from GPS, but rather barometric (ie air pressure) altitudes. In stormy weather there can be abrupt changes at the same actual altitude. In other words a margin of error needs to be attached to them which can bring the conclusions from extreme climb/descent to reasonable values.

  7. While we ponder the 8501 & it’s path, 370 still haunts us. Separating the two is pertinent. The exacerbation & concern at times is cross-linked, at least for me. 8501 should be the only subject matter discussed or otherwise relevant to this subject matter, albeit 370 is dear to our hearts. 8501 is 8501.

  8. @airlandseaman

    Why is everything “leaked”. That side of the ocean seems to be ONLY “leaked”….whats up with that? The more we move on with these tragedies , it seems the more we’re asking ?????. Whats up with that??? Is it saving face? Cultural differences in the face of reason? Why do we have to fight and rely on “leaks” for basic info.?

  9. @Chris

    I really believe it is a cultural issue. In my experience dealing with Asian cultures, even the notion of a QC engineer was taboo. No one wants to be associated with failures and forensics. As I alluded earlier coordinated disaster response such as our ICS system in the US is not implemented in that region. It leads to a great deal of frustration for people accustomed to a much different interaction. I had the same feelings relative to the information flow from Fukushima. It is what it is.

  10. @airlandseaman: I’ve figured out why I couldn’t find your post – it was a tweet (Dec.20):

    “Sat Controller not likely involved in 370 analysis. Very sad for ISAT colleagues, but unrelated.”

    So my question is very simple: on what did you base this statement?

  11. W in T H

    WSJ: Air Asia didn’t have permission to fly route on day of crash, Indonesia says
    By I Made Sentana And Ben Otto
    Updated Jan. 3, 2015 12:55 a.m. ET

    “Tommy Soetomo, the head of state-owned airport operator PT Angkasa Pura I, said AirAsia had a slot to fly on Sundays. But Mr. Barata said that information was outdated and that AirAsia should have returned the slot to the government. Before October, AirAsia had permission to fly daily to Singapore from Surabaya, Indonesia’s second largest city, he said. He didn’t say why the number of flights was cut.”

    http://t.co/HXZ9JznRfg

  12. @airlandseaman:
    ” most bodies discovered in the first few days had no clothing other than tight fitting undergarments…given all this, the aircraft must have suffered a major structural failure at high altitude.”

    Would water rushing in at 100+ kts rip clothes off?

  13. @Nihonmama & Dennis W

    Looks like the world spins on an entirely different level in regards to latitude & longitude of real world thought & understanding.

    Can’t even imagine the RPM’s would be spinning @ the FAA & NTSB with non-authorized flights?!?! While the “Industry” has good things to say about Tony Hernandez. Unauthorized flights, during weather events hopefully lands him in jail.

  14. @ airlandseaman

    Do we have more on the air directive regarding this AC?

    Looks more & more like a break-up. While flying unauthorized sky’s, no telling what shape the AC was in. How many cycles..etc. Unbelievable!

  15. Regarding the questions of operating compliance now emerging from the Indonesian authorities, there is quite a ‘back-story’ in the recent history of air traffic management in Indonesia.

    Consider that the crew of QZ8501 made an enroute request to deviate from their filed flight plan. The response from ATC, to that request, took some minutes & was not acknowledged by the flight crew. The response was granted too late. The response would have required negotiation across the two Indonesian FIR control centres as QZ8501 was approaching the Jakarta FIR boundary.

    The “authorities” are now spinning against Indonesian-AirAsia calling into question its compliance with SKEP/195/IX/2008, route approval procedures, and with AOC 121, the airline operator certificate for passenger services. The Minister of Transport, has been reported to personally visit I-AA HQ, auditing their pre-flight procedures, and find an inconsistency in their attention to weather forecasting. The minister’s reason for preempting his own Directorate General for Civil Aviation was not questioned in the report nor why this should be the focus of public attention before the independent National Transportation Safety Committee even issues a Preliminary Report in its investigation of QZ8501’s loss.

    Air Traffic Management services in Indonesia are currently undergoing significant change as the service is re-constituted in a single ANSP body, AirNav Indonesia.
    The performance of the air traffic management service is every bit as important as the pilots’ to manage the safe flight of aircraft. The NTSC report must include a detailed timeline of the ATC communications to the aircraft & between the AirNav Indonesia area control centres.

    Just as Malaysia employed Ketchum-ICON of Singapore, an IATA recognised specialist in crisis management PR for the aviation industry, it’s to be expected that Indonesia had the same call.

    :Don

  16. Brock: A satellite controller is someone who “drives the bus”, not someone that “designs or engineers the bus”.

    gysbreght: I’m not an expert on the clothing subject, but I’ve heard several experts explain that the observation re missing (loose) clothing is common for bodies in free fall. I do have 210 jumps, and I can tell you from that experience that it would not be surprising for loose clothing to be blown off at free fall speeds. Terminal velocity at low altitude is about 120mph, but at FL35, it would be about double that…shredding clothing. I do not believe the same thing can happen when an aircraft, with people inside, impacts the ocean.

    Don: I agree with your analysis. We are starting to see some authorities circling the wagons and pointing fingers to divert attention from their own weaknesses and failures.

  17. @airlandseaman: You said, “Terminal velocity at low altitude is about 120mph, but at FL35, it would be about double that…shredding clothing.”

    Independent of the terminal velocity for a body, which will vary with altitude due to changing air density, the aerodynamic drag on the falling body should not exceed the weight. A higher fall would have the forces acting on the body for a longer period of time, but not necessarily with higher shear levels at the surface of the body. It’s similar to why the drag on a plane is relatively constant for a given indicated air speed, even if the true air speed varies with altitude, all other things (such as pitch and control surface position) being constant.

    In a nutshell, I am not sure that clothing will be more severely shredded due to a fall from a higher altitude.

  18. @airlandseaman:
    “Terminal velocity at low altitude is about 120mph, but at FL35, it would be about double that…shredding clothing. I do not believe the same thing can happen when an aircraft, with people inside, impacts the ocean.”

    If you correct for density, which determines the force exerted, the terminal velocity at FL350 (in terrms of CAS or EAS) is not different from that at sealevel. And then the density of water is about eight times greater than air at sealevel. I do not believe that it is certain that the fuselage broke in mid-air, but consider it more likely that it broke on impact.

  19. @gysbreght: You said, “And then the density of water is about eight times greater than air at sealevel.”

    More like 800 times the density, not 8 times. Air is about 1.2 kg/m3, vs 1000 kg/m3 for water.

  20. Hey guys. Seriously…do you think I am unaware of the gas laws? I’m just saying that accident investigation experts tell me missing (loose) clothing is more consistent with falling bodies, less so with water rushing in to a broken fuselage. That is all. It is guesswork intended to improve the odds of finding the aircraft sooner. The facts will come out once we have the boxes.

  21. @ChrisButler:

    If Tony Hernandez is going to jail, he should have company. How could Air Asia have been flying an international route, on an ‘outdated’ slot (since Oct) and the Indonesian government (at least the Ministry of Transport) not be culpable as well?

    There’s enough negligence lurking here to fill a Panamax tanker.

  22. @airlandseaman,

    I suppose you have asked these “accident investigation experts” how many incidents of falling bodies they have investigated?

  23. Note MH17, which broke up at altitude: a number of the bodies had no clothing (underwear only).

  24. @Nihonmama

    Really confounded….not a freaking taxi service on the streets of everyday life?!?! It’s an airline….speechless!!

  25. Lack of clothing is a standard sign of passengers being ejected into a very high velocity airflow due to airframe breakup – similarly breakages of limbs/joints. The initial airflow speed is due to the velocity of the aircraft at the point of breakup, the bodies will of course subsequently slow to terminal velocity.

  26. @ChrisButler:

    Speechless is an understatement…

    But on one level, not really shocked.

    As a airline brat, rode on airplanes like people take taxis. Then survived (USSR-era) Aeroflot and a prop plane (with the flight attendants praying in their seats) into the Amazon basin — in a massive storm. But on occasion, traveling in Asia took the cake. To wit: An Egypt Air flight from Bangkok to Cairo where we watched the runway (and us leave it) from our seats, because the cockpit door was wide open. And it stayed open for a while — as the flight attendants chatted each other up. Had I not been so exhausted (a 3:00am departure from a jam-packed, madhouse airport), I probably would have been slightly more aghast. Went to sleep instead.

    As Don aptly notes, there’s a “backstory” with respect to QZ8501 – and not just with respect to traffic management. It may prove to be as much of a story as the tragic crash itself.

  27. @Richard Cole: Thank you for correcting me. A body ejected from the plane will either accelerate or decelerate until the terminal velocity is reached. Most likely, the body will decelerate since the plane is probably traveling faster than the terminal velocity when breakup occurs, so the highest aerodynamic forces on the body occur just after breakup, as you say.

  28. Gysbreght,

    At speed >100 kts rheological laws for water change. In brief, it behaves similar to asphalt. So, you question becomes equivalent to the question “what asphalt can do at 100 kts?”. I guess the answer is clear.

  29. @airlandseaman, brock

    “Brock: A satellite controller is someone who “drives the bus”, not someone that “designs or engineers the bus”.

    In my view, “Not being part of the analysis” is not a strong basis for classifying the controller’s sudden death as unrelated.

    If the controller (surely a highly qualified engineer in his own right?) was “driving the bus” during MH370’s flight time, he may have asked questions as to what effects his manoeuvering would have had on the log records, if any. Or he may have known, what effects it should have had, but failed to see them in the published log, then asked the wrong person why it is so…

    Cheers
    Will

  30. Gysbreght,

    Suggested keywords: cavitation, compressibility of water, elastic properties of water, fracture of fluids.

  31. Unless the airasia aircraft had a defect seems likely a bomb or it might have been shot down??

  32. Oleksandr:

    Let’s return to the issue under discussion:

    Two esteemed posters on this blog believe that discovery of a floating body that “had no clothing other than tight fitting undergarments” is evidence of inflight breakup. I am arguing that it is not because, if the fuselage broke up at impact, massive influx of water into sections of the fuselage could have ripped off the clothing on that body. The airplane was cruising at 300 kt CAS. The equivalent water speed that produces the same forces is 10.5 kts.

    Also the body of a stewardess was recovered fully clothed with her name tag attached to her uniform. Maybe her sitting position at impact explains the different condition.

    If it is assumed that QZ8501 was not destroyed by a missile or bomb, what forces would break a fuselage in mid-air?

  33. @ALSM – I agree with your theory. I thought it was long settled that missing clothes indicated a mid-air breakup or free fall. Based on early reports, it sounded like the first bodies were located behind the flight path. It looked to me a lot like AA 591 – where parts of the rear of the aircraft came apart. Look also at MH17 or even Asiana, where the tail assemblies came off as a unit. Such a breakup would obviously lead to wild altitude swings.

    I’m also still 100% behind Victor’s calculations, understanding that they are back-of-the-envelop. No unusual weather patterns are needed, yet.

    A simple structural failure in the rear of the plane fits the events just fine. My only question is whether the transponder in the front or middle if the aircraft could survive a structural failure in the back of the aircraft.

  34. @Neils: re: “NW point”: just re-requesting sourcing details on the paragraph you posted here in mid-December.

    You later clarified that this response came from the “SearchWG” – was this the MH370 “Search Strategy Working Group”? Was this an e-mail from them to you? I’d like you attribute this key data as accurately as possible.

    Please feel free to contact me via Twitter, if you’d rather not post specifics in this forum.

    Thanks in advance, and sorry to pester!

  35. The breakup of the plane at altitude could have been caused by weather, an excessive high-g maneuver, an onboard explosion, or a high speed projectile. (At this point, I don’t see how any of these scenarios can be definitively dismissed.) A breach of the skin of the plane could have led to explosive decompression and complete structural failure, such as what is predicted to have occurred to MH17. The recovery of the fuselage as well as the black box will be critical to understanding what happened.

    My guess is the cover provided by thick, moisture-laden clouds will make it difficult to use satellite imagery to gain additional insight.

  36. Gysbreght,

    A structural mid-air failure of the fuselage due to external natural forcing is an extremely unlikely event. I would prefer to refrain of further speculations, as the autopsy can provide definite answers…

    There is, however, another incident involving today’s (or already yesterday’s) AirAsia flight 7633 – reportedly engines stalled just before take off, again in Surabaya. I guess it might be right time for the investigators to check kerosene and the way engines are serviced in AirAsia.

    Q re MH370. If the aircraft is left in auto-throttle constant thrust mode during climb/descent without further human’s input, how does it deal with altitude and airspeed?

  37. I am not going to argue if the terminal velocity would strip the cloths off, but diving from FL35 there are part of the flight where the drag would exceed the gravitational pull. As the terminal velocity is high when the air density is low at higher altitude, when the air gets denser and denser, the falling body gets slower and slower to reach the respective terminal velocity. If the drag force never exceed the gravitational force, the falling body will never slow down.

  38. Oleksandr:

    RE YR Q: ” If the aircraft is left in auto-throttle constant thrust mode during climb/descent without further human’s input, how does it deal with altitude and airspeed?”

    If you mean with the autopilot off, the autothrottle maintaining rated CLB thrust, the FBW flight control system will maintain approximately constant pitch attitude. As thrust reduces with altitude, the speed will decrease and angle of attach will increase. When the AoA reaches alphaprot, the FCS will change to alpha protection mode and maintain alphaprot, until the sidestick is pushed forward.

  39. Oleksandr,

    Please ignore my response to your question. I was thinking of AirAsia 8501 not MH370. My description is for the A320, the B777 is different and I have to think about it.

  40. Oleksandr,

    Returning to your question, I should first say that I am less familiar with the B777 systems. However, the basic flight control law of the B777 (known as C*U) is speed-stable, so I think the B777 would maintain constant CAS. The variation of altitude then depends the thrust set.

  41. @Rand:

    Re MH370:

    @rahmatomar(ex RMAF): “Malaysia conducts inquiries as well as criminal investigation into the disappearance”

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