Wake Turbulence Epilogue

In the news today, Communication and Transportation Secretary Luis Téllez again discussed possible discrepancies with the certification of the pilot of the doomed flight two weeks ago in Mexico city.  (The first instance is mentioned in this past post on the cockpit voice tapes.)

To this point, I’ve tried to refrain from giving my own personal opinion on what the cause was, though I have strictly maintained that wake turbulence could have been a major factor.  That said, the significance of Téllez’s comments are hard to misinterpret: he is finding fault with both the pilot and the mechanism by which pilots gain and maintain their certification.  Recall the strange comments (see this past post on Mexican unions) made by the ASPA and SNCTA spokesmen just days after the accident… I wonder what ASPA has to say about wake turbulence and the possibility of pilot error now?  (You can draw your own conclusions!)

For more on my opinion regarding the possibility of wake turbulence, read through some of the past posts on the accident, many of which discuss it (especially the one on the unions).


I was not in Mexico City when Téllez was making today’s comments, having just hopped a flight home to San Francisco for the Thanksgiving holiday.  However, in a strange and bizarre coincidence, as we came in to land at SFO, on final approach and perhaps 1000 feet above the ground, the plane was shaken by two jarring and turbulent shocks…. and which immediately brought to mind the recent accident.  In our case, we were flying an Airbus 320, and the result of the shocks was, for the most part, lateral motion and a slight drop in altitude.  Of course, the pilots quickly recovered and we landed without further incident.  But, as we pulled up the the gate, the pursor (main flight attendant) came on the PA and announced:

“For those of you wondering what that large bump was right before landing, the pilot called to notify us that it was caused by the [Boeing] 747 in front of us.”

Some things you can’t make up.


San Francisco, CA

Turbulence & a Learjet

Earlier today, the Secretary of Communication and Transportation Luis Téllez held a press conference to discuss the analysis of the cockpit voice recorder from the first of the black boxes. 

The results of the analysis seem to indicate that turbulence, likely caused by the preceding Boeing 767, was the cause of the accident.  In particular, the transcription shows the pilot referring to turbulence in the seconds before the disaster.

Piloto: Órale la turbulencia de éste
Copiloto: Ay guey
Piloto: Ay cabrón

Pilot: Hey, there’s some turbulence
Copilot: Oh boy
Pilot: Uh-oh

Of course, that’s not the full story… in his statement, the Secretary states that the pilots may not have been qualified to fly the plane and that the audio tape indicates that the pilot was unfamiliar with both the terrain of the flight path as well as the aircraft’s electronic flight instruments.  At the time of the accident, the Learjet was only 4.15 miles behind the Boeing… as the pilots had taken more than a minute to heed air traffic control’s request to slow down.  And to put you conspiracy theorists to rest: there is no sign of an explosion — ASA Director, Gilberto López Meyer.

Could turbulence be to blame?  Wake turbulence creates a highly localized but very severe vortex (see post on the unions) that, in theory, could have trailed the 767 by several miles.  The Learjet, which was on approach to the airport, only 1000 meters (or so) off the ground, and was already at or near minimum airspeed could have had trouble had it hit such a vortex.   And to quote a friend of mine: “These planes aren’t meant to fly upside-down.”


México, D.F.

The Mexican Government Reacts to the Crash

The black boxes from the Learjet arrived back in Mexico this morning.  El Universal reports that Communication and Transportation Secretary Luis Téllez will examine the contents sometime tomorrow (Friday), so I assume that we’ll have an announcement shortly thereafter.  In the mean time, I wanted to continue my running commentary on the reaction to the crash, this time looking at the Mexican government and the Calderón administration. 

Initially, President Felipe Calderón seemed quite shaken by the events of the disaster.  Of course, it’s important to consider the gravity of the event; Calderón lost one of his strongest allies in government to what, at the time, seemed like a likely assassination.  The drug cartels that were hypothesized to be a possible cause have been the cause of significant violence in Mexico over the past few years and a major focus of Calderón’s administration, affecting both domestic and foreign policy.  Mouriño’s death likely caused Calderón to examine thoughts of how the presidency and his actions have affected his own mortality… frankly, I’d be quite shaken, too.

Following the disaster, Calderón and his administration took several steps to show both strength and control.  Initially after the accident, Calderón appealed for calm and patience, and expressed the need to not jump to conclusions about the cause of the crash.  Many in the public deeply suspected foul play, a hypothesis given credence by a plethora of articles in the local media.

Following this claim, Calderón made good on his promise by:

In my opinion, the actions taken by Calderón indicate several key ideas.  First, he wanted to take control and ensure order of the investigation; thereby stemming the possibility of rampant rumors of the assassinations and corruption that have been plaguing the country.  Second, he brought in many experts, both local and foreign; not only does this help ensure that officials identify the correct cause of the accident, but it provides support to whatever conclusion is reached in both the eyes of the media and the general public.  And, as if on cue, U.S. Ambassador Garza recently reiterated that there is no sign of sabotage… I can’t believe that Garza would make these comments without Calderón’s ok.

The need for such support seems clear following the controversy that erupted during the week regarding leadership of the PAN political party.  As I understand, Mexican political parties, even more than those in the U.S., are themselves conglomerates and factionalized.  On Monday, Calderon plead for an end to the “pettiness” within the party and said that the replacement for Mouriño would be chosen based on his party loyalty.  I was originally confused by much of this (I guess this is what happens when you get your news from the papers!)… but on Tuesday allegations surfaced that elements within the party had previously sought to remove Mouriño.  This “shadow” group even had a name… “El Yunque” (the anvil).  It’s not clear to me whether Manuel Espino (former PAN leader) was the origin of these rumors or was merely grabbed by the media for his reaction, but suffice it to say, politics being what they are, I’m sure that Espino didn’t hide from the spotlight.  And, today, Espino made public comments denying that he was behind any of the strife.  Does it really matter (to Espino)?

I’ll try to talk to a few experts on Mexican politics to gain additional perspective.


México, D.F.


Update: following the comments made by Garza, a number of Senators (in each of the 3 main political parties in México) spoke out against him.

Mexican Unions Reacts to the Crash

The pilots and controllers unions here in México have been quite active in their refutation that wake turbulence could have caused the Lear jet to crash last Tuesday.  I wanted to take the time to respond to some of their statements.  While I respect their expertise, I am quite confused by their responses… and I wanted to present this discussion as a complement to earlier discussions of the reaction to the public.


On Wednesday, the day after the crash, ASPA (Asociación Sindical de Pilotos Aviadores), which is the Union for Mexican Pilots, discounted the possibility that wake turbulence could have been an issue:

“Se pudo haber movido un poco, pero eso no es ninguno motivo de peligro o de riesgo o de intuir que eso pudo haber tirado al avión”

Basically: “(The plane) could have moved a little (due to wake vortices), but there’s no reason to believe this could have caused a risk or danger to the plane.” 

— ASPA spokesperson Leonardo Sánchez Herrera — El Universal, 5 Nov. 2008

True, wake vortices (which are caused by all aircraft, all the time!) often do not result in any harm, ASPA’s conclusion is completely incorrect.  First, as I originally posted (“Why things fly…”), wake vortices have caused accidents before, such as American Airlines flight 587… but there are others, too.  While I am not a pilot (nor an expert on flying), I’ve had personal experience with wake turbulence as a passenger and can assert that “move a little” is a vast understatement (we rolled 40° in a Boeing 757).  In both my experience and in that of AA 587, these were large aircraft, which means that they were much more able to handle turbulence than a smaller Learjet.  Perhaps the best analog to this Lear jet in the wikipedia list is the accident which killed Rich Snyder (of In-N-Out fame), or this article about a Cessna that was flipped as if it was made of “balsa wood”: small jet + wake turbulence = uncontrolled roll + crash.  I’m not sure where ASPA is coming from when they say that the wake turbulence of a big jet could not have had an effect.


Then, on Saturday, SNCTA (Sindicato Nacional de Controladores de Tránsito Aéreo), the union of air traffic controllers, asks:

“¿Cómo es que no afectó al helicóptero que venía volando cerca de él?”

Or: “How is it that the wake vortices didn’t affect a nearby helicopter?”

— SNCTA spokesperson Leonardo Sánchez Herrera — El Universal, 9 Nov. 2008

I am absolutely baffled by this comment.  To understand why, requires a little background on wake vortices.  Simply put, as aircraft fly through the air, they create very turbulent, but highly localized, vortices in their wake.  It’s not as if the dangerous wake vortices affect everything — the helicopter simply did not fly through them.  Frankly, air traffic controllers know this.


Furthermore, SNCTA also reported on Saturday that radar says the plane was 4-5 miles away from the aircraft in front and not 2.8 miles as previously reported.  First, I can’t verify whether or not this is true, though I do wonder 1) why did aircraft controllers initially report a distance of 2.8 miles and 2) why did aircraft controllers ask the Learjet to reduce to the minimum speed possible (which would increase this aircraft separation)?  Second, how do they know that 4 miles is sufficient?  El Universal cites:

“…el manual de Jeppesen indica que un Learjet 45 debe estar a cuatro millas de un Boeing 767.”  

Basically: “The Jeppesen manual says that a Learjet 45 should trail a Boeing 767 by 4 miles”

— Miguel Ángel Valero, president of the Mexican Pilots College — El Universal, 8 Nov. 2008

However, the ICAO standard miles-in-trail would be 6 nautical miles.  (I mention ICAO because the nice folk at the airport threw the ICAO books at us when we pointed out that the design of terminal 2 could have been better… a story for another time!)  And I can attest that, in my own personal experience (read above!), we were five miles behind the plane in front of us… at least according to the air traffic controller who I was listening to at the time.  

So that’s the story today.  I maintain that wake vortices could have been a factor in the crash of the plane.  And, for now, I’ll refrain from drawing any conclusions as to the unions’ comments.


México, D.F.


Sunday update: EL Universal, 9 Nov 2008: The distance between the jets was 3.9 miles; El Universal’s experts disagree about whether this was sufficient to avoid problems with wake turbulence.  They also discuss the possibility of failure of the Learjet’s air brakes (a mechanical part of the plane) that the pilots could have tried to deploy to slow the plane just before the accident.

Mouriño and the cartels

Nina, fellow Fulbrighter and researcher on Mexican government policy, has posted her take on the plane crash, with a great summary of the recent (and violent) history between Mouriño, the Mexican Government, and the drug cartels.

With each passing day, I grow more confident that this was just a terrible tragedy.  But as Nina’s discussion shows, the history here is a story in itself…. it’s no wonder that the public has reacted with such skepticism and fear.


México, D.F.


Rather than a new post, I’d thought I’d add on this link: BBC: Mexican authorities rule out a bomb (in English)

More on the local reaction….

I’ve got nothing new to say, but these interviews (from El Universal / in Spanish) do a good job of capturing the opinions and fears of many other people that I’ve talked to.

Mexico City media coverage of Mouriño/the crash

I am continuing to follow the news on the crash on Tuesday that killed Mouriño.  While I don’t expect an answer to the crash for quite a while, possibly many weeks, I find both the investigation and the continuing public reaction to be of great interest.  

The initial reaction of the public is that the crash was the result of sabotage.  In my conversations yesterday with a number of people, they expressed the belief that Learjets are very sound and completely safe.  And, of course, relative to travel by car, they are.  However, the idea that anything is infallible or, ahem, unsinkable would only leave room in an explanation for sabotage.  Part of my intention with yesterday’s post was to point out that aircraft or their pilots can and do fail.

So where do things stand?  First, the investigation has been placed under the auspices of the Federal Government (PGR), as opposed to the military or other/local agencies.  Second, they have recovered the black boxes, which are being examined by experts from the U.S.  A particular quote in this second article stood out to me:

“Cualquier hipótesis puede ser eventualmente válida y a medida que la investigación va avanzando y que se va reuniendo más evidencia se van descartando hipótesis”

Loosely translated as: “We’re looking at every possibility and continuing to collect evidence.” (If I read this correctly!)

— Gilberto López Meyer, Director of ASA (Aeropuertos y Servicios Auxiliares), regarding the possibility that wake turbulence could be the cause.  (Also: although I think that vortices might be to blame, the pilot’s union disagrees.)

I think this statement and article are important for several reasons; first, they indicate that the investigation is being undertaken in a methodical, rational manner; second, that by bringing in outside experts, the officials not only help to ensure that a proper (i.e. correct) conclusion is reached, but they also make lend credence to the investigation.  Whatever confidence the public here has in Mexico, it seems to me that they don’t have such confidence in the government!

The media, as well, seems to be picking up on the possibility that the crash was, indeed, an accident.  Articles from El Universal are above; here are some from other papers:

So we’ll see where things go from here.


México, D.F.

Why things fly, why they don’t

I’ve been talking to a lot of different people today, mostly chilangos here in el D.F., about yesterday’s air crash and their views.  I need to do a bit more thinking and a lot more listening, but I hope to have something meaningful to say as a commentary on local public opinion, although this may not be for quite a while.  For right now, though, I think I can safely summarize the general mood as one of deep suspicion that the “accident” was an assassination.

I’m certainly not an expert on aviation accidents.  However, I’m struck by the heady coincidences of the crash… the timing just as the US presidential returns came in, the location in the affluent center of Mexico City… coincidences that certainly magnified the impact of the tragedy on Mexicans and on their president, Felipe Calderon.  These coincidences certainly point many to suspecting foul play (and with the recent heavy fighting with the drug cartels, it’s no wonder!).  I mean, if I wanted to cause fear and intimidation, causing the crash of a plane carrying a senior government official into the center of the capital would be a way to do it.

But why do aircraft crash?  (With a little help from wikipedia)

So what happened in this case — could it have been an assassination?  Missiles and bombs tend to be easy to identify as they result in mid-air explosions which often cause the wreckage to be spread over larger areas.  In this case, eye witness reports don’t seem to indicate either.  Another possibility is mechanical sabotage…. though this would mean that the location of the crash was purely coincidental.  And wouldn’t that eliminate the #1 reason why foul play is suspected?  Furthermore, I’d think that if I wanted to assassinate a government official, I’d favor other methods that would guarantee success; after all, the plane was only a few minutes from landing safely.

On the other hand, there does exist evidence that the crash might have been an accident.  Initial reports suggest that wake turbulence (the Learjet was following too close behind a Boeing 767) could have played a role.  Furthermore, it has been reported that the pilot reported an emergency before contact was lost, which suggests that there was at least enough time for the pilot to realize that something was wrong, perhaps a mechanical problem.  Time will tell.

Additional note: this link, which has a video/audio report of the local air traffic control, suggests that no such emergency request was made.  (That said, from what I can tell, the Learjet was asked to change frequencies just before the accident, so I can’t be sure.) 

Thoughts?  Comments?


México, D.F.

From fire, destruction

I must admit, the whole course of events from last night still make me dizzy.  For those not in Mexico: the equivalent of the Mexican VP, a man with many enemies, died last night in a plane crash in the center of the city.



The timing of the crash, at almost the exact time at which the initial results showed that Barack would, indeed, become the U.S. president, makes for a strange, bizarre comparison.  And that the accident was perhaps a mile and a half from where I live; and merely a stone’s throw from the balcony on which I was later standing at the U.S. embassy election reception; and, of course, that I study aviation.  In my opinion, I don’t see any way that these could be anything but twisted coincidences… but who knows?  My head spins.


México, D.F.