Category: Aviation

[Editor’s note: IG kingpin Michael Exner has delved into the recent crash of TransAsia Flight 235 with characteristic vigor, and recently sent around some images he generated from ADS-B data that go a long way toward establishing what happened. I asked him if I could reprint the material here and he agreed. — JW]

I reviewed the flight paths for flight GE235 for the previous week. In every case, the path was nearly the same. The plane makes a departure to the east and turns to the right about 160 degrees shortly after takeoff. [See image above.] This is what happened on the day of the crash too. However, in the case of the crash day, the airspeed and altitude just seconds into the flight, at the start of the first right turn, was already low and slow. For all flights in the previous week, the plane was between 2000-3000 feet at the first turn (point furthest east), and the speed was between 130 and 170 kts. For the day of the crash, the plane was at 1250 feet and 83 kts, which is below stall speed for 15 degrees flap setting. [See image below, after the jump; click to enlarge.] This suggests that the left engine was not producing full power from a point very early in the flight. Indeed, the ADS-B data indicates that the airspeed at liftoff was normal (136 knots at 100 feet), but began falling immediately after liftoff. This suggests that the left engine flameout occurred immediately after liftoff, near the east end of the runway.

Continue reading Guest Post: TransAsia 235 Crash Timeline

My thanks to @socalmike_SD, who has been researching airplane crashes that closely resemble AirAsia Flight 8501. Particularly striking is the case of Pulkovo Aviation Enterprise Flight 612, a Tupolev Tu-154 which crashed in 2006 near Donetsk, Ukraine. The plane was flying at 37,000 feet when it entered an area of thunderstorms and experienced severe turbulence. The flight crew asked for (and was granted) permission to climb 2000 feet to avoid the worst of the storm, but soon after doing so entered into manual flight mode, stalled, and entered a flat spin. Here is an excerpt from the cockpit voice recorder transcript:

Continue reading Airliner Stalls, Crashes After Trying to Climb Over Thunderstorm

Independent Group member Bill Holland appears to have sorted out the head-scratcher concerning the location of the QZ8501 tail section. His explanation jibes with where we’d expect the plane’s fuselage to wind up, given the fact that just before it disappeared from radar it was descending with alarming speed. I’m pasting here Bill’s recent email in toto:

I think I have the tail GPS coordinates figured out…

I kept finding references to the tail being found that translate as:
The mapping experts who are in MGS Ship Geo Survey finds it precisely in the coordinate 03.3839S (South latitude) and 109.4343E (East Longitude).

But, I searched and found a version that seems to make more sense:
Aga pun menyampaikan titik koordinatnya, yakni: Latitude 3;38;39S, Longitude 109;43;43 E.
…in English:
Aga also convey the point coordinates, namely: Latitude 3; 38; 39s, Longitude 109; 43; 43 E.

The numbers being quoted are correct, … Only the punctuation was wrong!

-03° 38′ 39″ 109° 43′ 43″ (degrees minutes seconds)
This is about 2.5nm South East of the last SSR/ADS-B location (Google Maps measures 3.03 statute miles = 2.63nm)

In my screen grab [above]:
– the lower yellow start marke the tail section (and the blue annotation is the distance from the purple star)
– the purple circle is the last lat/lon from the SSR (ADS-B),
– the purple star is the approx location from the primary radar image.
– The red box is supposed to be “Most Probable Area 2”,
– the black tilted rectangular outline is the left (Western) section of the “Underwater Search Area”.
– The yellow diagonal line is Route M635 between TAVIP to RAFIS.
– The black diagonal line is the FR24 estimated flight path (the inverted teardrops are individual extrapolations from FR24 after the last valid ADS-B data data they received)

[ignore the white square, the blue square, the Northern yellow star, and the green diagonal line]

-Bill

Really, it’s remarkable that searchers didn’t scour this location right away, and instead spent a week searching far down-current. There appears to have been some confusion between the nature of floating debris, which disperses as it’s carried by currents, and debris on the seabed, which will tend to remain where it falls, more or less directly under the point where it impacts the water.

The latest news is that preparations are underway to raise the tail section and hoist it onto a ship. Hopefully, the black boxes will be found within, and the cause of the accident one step closer to being revealed.

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.

Continue reading Why AirAsia 8501 Disappeared From Radar

One of the things that’s being talked about a lot in the coverage of AirAsia 8501 is the idea that under certain circumstances a commercial airliner might start to go too slow, stall, and fall out of the sky. But does that happen? I scoured by brain, did some Google searches, and asked Twitter, but I haven’t found a single case of a classic power-off stall by a commercial jet at altitude. Then again I did find some accident and incident reports that seemed germane to the case. I’m listing them below; if anyone wants to alert me to others I’d be grateful.

 ANA (flight number unknown), September 6, 2011. “Two flight attendants were slightly hurt and four passengers got airsick when the All Nippon Airways Boeing 737-700 with 117 people aboard descended sharply, veered off course and went belly up over the Pacific on its way from southern Japan to Tokyo on Sept 6. ANA said Thursday that the co-pilot is believed to have mistakenly hit the rudder controls instead of the door lock to allow the pilot back in the cockpit. It said the crew managed to stabilize the plane after the co-pilot’s error and land it safely.”

Air France 447, June 1, 2009. The only true case I’ve been able to find of a commercial jet experiencing a stall at altitude and fatally crashing. The kicker is that the plane was held in the stall by a disoriented pilot.

Qantas flight 72, October 7, 2008.  “While the aircraft [Airbus A330-303] was in cruise at 37,000 ft, one of the aircraft’s three air data inertial reference units (ADIRUs) started outputting intermittent, incorrect values (spikes) on all flight parameters to other aircraft systems. Two minutes later, in response to spikes in angle of attack (AOA) data, the aircraft’s flight control primary computers (FCPCs) commanded the aircraft to pitch down. At least 110 of the 303 passengers and nine of the 12 crew members were injured; 12 of the occupants were seriously injured and another 39 received hospital medical treatment.

Continue reading Airliners in Unusual Attitudes

As I write this, AirAsia flight 8501 has been missing for less than 24 hours, and in the absence of wreckage its too early to speculate on what happened. But the flight, which took off from Surabaya bound for Singapore, appears to have been traveling through an area of intense thunderstorm activity, so it may be instructive to look at the kind of danger this sort of weather can present to aircraft.

The region around the equator is known to meteorologists as the Intertropical Convergence Zone, or ITC. Here, the heat and moisture of warm ocean waters provides the energy to power tremendous updrafts that produce clusters of thunderstorms called a Mesoscale Convenction Complex. These storms can punch up through the stratosphere up to 50,000 feet, far above the crusing altitude of commercial airliners. From Smartcockpit.com:

A thunderstorm brings together in one place just about every known weather hazard to aviation. A single thunderstorm cell can hold 500 000 tons of water in the form of liquid droplets and ice
crystals. The total amount of heat energy released when that much water is condensed amounts to approximately 3 x 1014 calories. Equated with known energy sources, this falls just below an entrylevel hydrogen bomb. Even a small thunderstorm would have the caloric equivalent of a Hiroshimatypeatomic weapon… The thunderstorm occupies a unique place in the pantheon of aviation meteorology because it is the one weather event that should always be avoided. Why always? Because thunderstorms are killers.

Some of the deadly forces include lighning, airframe icing, large hailstones, extreme turbulence, and downdrafts that can reach speeds in excess of 100 mph. Perhaps the greatest hazard facing a modern airliner, however, is the sheer volume of precipitation that a thunderstorm can put out.

On May 24, 1988, a TACA 737 en route from Belize to New Orleans was descending towards its destination when it blundered through a thunderstorm. At an altitude of just 2000 feet, a deluge of rain and hail doused the flames of its twin turbofans. Unable to regain power, the captain managed through superb airmanship to put the stricken plane down undamaged atop a mile-long levee. Notes superb aviation writer Peter Garrison:

The event was not unique. Nine months earlier, an Air Europe 737 descending through rain and hail over Thessaloniki, Greece, had suffered a double flameout. In that case, the crew managed to restart the engines and land without trouble. In 2002, a Garuda Indonesia 737, also descending among thunderstorms, suffered a double flameout over Java. Its crew ditched the airplane in a river; one person died, and there were a dozen serious injuries.

According to preliminary reports, the pilot of QZ8501 had asked air traffic control for permission to ascend from 32,000 to 38,000 feet in order to evade the weather. Historically, however, attempting to fly over a thunderstorm has proven a dangerous strategy. In 2009, Air France 447 was flying through the upper reaches of a thunderstorm when it hit turbulence and its pitot tubes froze, leading to loss of airspeed indication; in the ensuing confusion the pilot flying lost situational awareness and flew the plane into the ocean.