Friday, February 1, 2019

A unique take on AF 447 by Flying Magazine

The January 2019 issue of Flying magazine has a unique take on the June 2012 AF 447 accident. It is one that I don't think I've ever seen taken on an accident before. It is how it should have turned out. It is a reminder that despite all the "magic" in our cockpits today, sometimes you still have to be a pilot, an aviator, stick and rudder guy, what the passengers think they're getting when they climb on board, a person of the sky who understands the air and the machine. One who uses his superior knowledge to avoid having to use his superior skill, but also one with that skill to keep everyone alive.

Inside the Saving of Air France 447 | Flying Magazine
air france 447

Sunday, December 2, 2018

Response to AeroTime New Hub article

The following is my response to an AeorTime New Hub interview between two Air France pilots; a B777 captain and an A320 captain.

Interview: Would Air France F447 have happened with Boeing?

Here:
https://www.aerotime.aero/aerotime.team/21361-interview-would-air-france-f447-have-happened-with-boeing

Of course, I covered this subject in Understanding Air France 447, (Could this have happened in a Boeing? - my conclusion was: it already has!)

Most of the comments  I agree with. Especially the emphasis on being able to fly the airplane, and not just rely on computers. Those pilot skills must be there and be able to be called upon at the most inopportune moments. Maintenance of pilot skills, like any skill, requires practice. That means hand flying the airplane when practical. Otherwise, it's like being called upon to give a surprise concert for a large audience and you haven't practiced for a year.

The comment section on the page could not contain my full remarks, which are below:


Air France 777 captain appears to misunderstand how the Airbus works. His statement "how Airbus auto trim works. As the co-pilot pulled back on the stick, the pitch trim helped him going backward to trim the aircraft because the computer acts as if Bonin* wanted the speed as low as possible... The pilots were not aware of the fact that the pitch trim was trimming all the way back, because on an Airbus you don’t have an artificial feeling, no stick shakers."

Autotrim only serves to align the elevators with the stabilizer. In Normal and Alternate laws it has NO EFFECT on how the airplane feels or behaves. In the flight control law where AF447 found itself (ALT2) and the sidestick demands g-load. As a result, it's basically a point and PROT) the stick changes from g-load demand to full back law the hard protection is replaced (due to various failures) with a "stability", which is the airplane's natural aerodynamic stability to pitch down when very slow.

However, the transition from g-load to stability mode is based on indicated airspeed. In the case of AF447, the airspeeds were rejected by the flight control computers because it had become unreliable due to the pitot tube issues. This left the airplane in full-time g-load demand.

When at least 2 of 3 airspeed sources were deemed unreliable, the autopilot disconnected. This dropped the job of hand flying the airplane into the laps of the unsuspecting and very-soon-to-by confused pilots, when they least expected it, and probably least prepared to handle it. "Startle factor" is the term used here that describes their diminished mental capacity to perform.

He said "They should have read the pitch trim indicator, which is something you forget to do on an Airbus, because it’s always in trim! They also should have had a visual warning telling them to use the pitch trim manually (Man pitch trim)."  This is not correct. At least not for the fist full minute with the stall warning going off.  All they had to do initially was to point the airplane down. It did not require any trim action. Now later on, when the angle of attack was extremely high (>45°) and the trim was full nose up, my own tests indicate that manually reducing the nose-up trim may have been required for a successful recovery from the 20,000 ft/min descent they put themselves in.

But instead of nose-down input, which would have worked, they instituted the only stall recovery action they apparently remembered: full power. Except at cruise altitude, they were pretty much already af full power and the extremely minor amount of power still left would produce no results.

Unfortunately, Bonin's initial actions on the stick (be then intentional or as a consequence of something else) were to pitch the airplane up. But the airplane's neutral stability allowed the nose to just stay there.
 It did not require trim to hold it there. That was its job. If he had pulled it back and then just let go completely, the result would have been much the same. The lack of the low-speed stability meant that as the airplane approached the stall AOA, there was nothing to pitch it down except the pilot - who was probably trying to follow the ever-reliable flight director which was telling him to continue the climb.

As the airplane began to stall and lose lift, the airplane started to sink, and thus the actual g-load was reduced. The airplane responded to this less-than-demanded g load with all it had at its disposal to increase the g load: Up Elevator. This obviously just made things worse and within a few seconds, the angle of attack increased to 45° and more (though the pitch attitude remained at 15° or less).
What this required from the start was for the pilot flying to FLY THE AIRPLANE. That is, command a pitch and power setting commensurate with level flight (2.5° & 83% N1). Any pitch and power setting remotely close would have kept the crew out of trouble for a long time. It only took about 40 seconds for all of the pitot tube issues to resolve themselves, and they could have been on their merry way like the dozens of other crews that employed that strategy in similar circumstances. However, by the time the pitot tubes were clear, the flight was in a far worse position, having climbed 3000 feet and lost over 100 knots of indicated airspeed. A recovery at this point required far greater skill than the minimal skill required to fly straight and level just 60 seconds earlier that they failed to exhibit.

All this and more, including what recovery steps were required at each step of the way are detailed in my book "Understanding Air France 447".

It is further interesting to note that Airbus seems to have taken this accident to heart in the design of the A350. It has extremely robust airspeed backups (even if all pitot tubes become unusable), and Alternate law maintains all of the same hard protections as Normal law (assuming the physical flight control surfaces are not damaged beyond carrying them out). Further, the autopilot remains engaged in an extended envelope (right up to the abnormal attitude parameters (120° bank, 50° pitch, etc) So, in this case, the AP/FD would not have disengaged at all.


A320/330/350 Captain/instructor/check airman, also B777 type rated

Friday, October 26, 2018

Soaring: Gold Distance Flight


The following article appears in the members-only section on the Soaring Society of America blog page. In Soaring badges are awarded for certain milestones. The Gold badge requires a 5 hour flight, an altitude gain of 3000 meters (9843 ft), and a 300 km (186 statute mile) cross-country flight. This is the story of my Gold badge distance flight.
———

The path to the Gold badge was a long time coming. The five-hour duration, common with the Silver badge was accomplished in 1994 in Minnesota. The altitude gain was accomplished at Minden Wave Camp in 2017 and also qualified for the Diamond altitude gain. It was the solo wave flight at the end of the camp and achieved over 27,000 feet with about a 19,000 foot altitude gain.

Photo #14947 | Wave flight at Minden Wave Camp 2017
The distance leg has been the most challenging. It wasn't until a few years ago that I even realized that the local pilots were regularly doing regular cross country flights at all. The 2017 Wave Camp experience really help to light my fire on this.
Back at Warner Springs started working on small local goals, extending the limits of local soaring and small tasks to practice with the flight recorder. A 2017 Silver badge attempt was foiled by a change in the rules the previous fall that measured the 50km required distance from release, instead of a designated start point. This put me short by only about 2 miles. It would be another year before conditions would be good enough to make the attempt again. In the meantime I purchased my own glider, a 1978 LS3, which provided better performance than the rental ships. I updated it with an S80 moving map vario, transponder, FLARM, and ADS-B in/out.

Preparing for the Gold distance, I spent quite a bit of time with the Badge and Record guide trying to determine just what would qualify for the 300 km gold distance. I’d had a few email exchanges with Rollin Hasness, the SSA Badge and Record guy who helped to clarify some task and declaration questions. However, sometimes you don’t know what you don’t know.
I had some gold tasks set up and made a few attempts over the summer months but the combination of the conditions and my chosen flight path prevented me from getting very far. I programmed a couple of routes that used a turnpoint twice and a 161nm triangle task to have options to pick from on the flight day. Along came a Saturday forecast with excellent conditions. This was to be the day! I shared my task file via email with my soaring buddy Dave, who would fly with me in his Discus.

We consulted that morning with Garret Willat, my official observer and trusted instructor. Should we fly to the North or South first and double back or the triangle. He suggested using the triangle but moving the southern turnpoint (Jacumba) 10 miles west due to the forecast location of the convergence line. I modified the task in my Oudie IGC, but then the whole task was also short by nearly that many miles. That meant we’d have to modify other turn points as well. Modifying the task on the recorder is not quite as easy as on my desktop computer, and we didn’t want to be last in line to launch. The gliders were lined up for takeoff and I decided to keep the original task after all and not risk messing it up. We decided a good approach might be to get as close as possible and make an out-and-back dash to Jacumba from as close as I could be within the lift line.

Photo #14942 | Overlooking the desert
Dave had trouble loading the task into his nav system so I lent him my Nano3 flight recorder with the task installed. I would act as his official observer, and off we went.

We soared to our start point ( or so I thought) over Mt Palomar. We climbed high then dived down through the start gate to have more leeway on the finish altitude.

As they often do, the forecast wasn't quite as wonderful as predicted. Once underway, I could hear some of the regular X-C pilots were having a little trouble, but I had been lucky and able to stay near the 11,000 foot cloud bases (about 8000 above the field), taking every opportunity to stay high. I wasn't going to win any speed records, but I mostly didn't want to land out. Dave took a different path and lost altitude after leaving Mt Palomar and headed back towards the airport. He as working hard to stay up, so I pressed on. So much for team flying.

I worked my way south, making a few retreats to the previous thermal to try a new path when one didn't work out. I joined up with a cross country veteran, who as it turned out would not be going as far south as I was. “How far south are you going?” he asked. “It depends on how scared I am” I answered. “Hoping for Jacumba.”

Finally, I could see Jacumba airport. It sits right on the Mexican border. As predicted, it was  out under the blue sky. I explored the edge of the lift and stepped out from under it but it didn’t look like I was going to be able to execute the out-and-back dash and arrive back in the lift as high as I wanted to be. “oh, well, maybe another day” I thought and started to head back North. Looking back I saw a cloud form to the East of the line, closer to Jacumba. This could work! I headed to the new cloud and climbed as high as I could, made the dash out to Jacumba and rounded the point, making sure my trace was inside the turn sector on the flight recorder’s path. I flew back under the cloud line and headed back north.

Shortly after another pilot reported good lift to the east of the cloud line near Mt Laguna, about 10 miles from my position. This was right along the line where the mountains descend into the desert below. In that desert was my alternate airport for this leg: Agua Caliente.Photo #14944 | Hanging out at cloud base
As I flew northward I was having marginal success with maintaining altitude which eventually dwindled down to about 8,000 feet (2000 feet above the peak of Mt Laguna). A thermal any time now would be great. I had Agua Caliente in sight and was looking at the path I would take around the intervening hills to reach it.  As I reached the peak, my luck improved and I worked a thermal back up to 11,000 feet and continued to work my way north.

Photo #14945 | Beautiful flat botto
In the meantime, and unbeknownst to me, Dave had made it to Mt Laguna and was just a little north of me. As I reached his postion, he was down at 6,000 feet below the edge of the mountains. I caught up to him and circled above, keeping an eye on him. He was within gliding distance of Agua Caliente, but it didn’t look like it from my vantage point above. I was hoping I wasn’t going to have to watch him land out. I circled above at the cloud base and eventually Dave was able to work himself back up (which qualifyied him for his Silver badge altitude gain). Stopping to thermal a few times and staying high, we flew towards the northern turn point of Mt. St. Jacinto, a 10,800’ peak just west of Palm Springs. There was another glider going in that direction who reported where he had found lift as well. We made it about 1500 feet above the peak. Turning southward again, Dave elected to take a detour to Mt Toro to the southeast, while I headed to my finish point on My Palomar.

I arrived at Mt Palomar with plenty of altitude and circled my finish point, just to be sure, then made a high speed run to home, with some 360’s south of the airport to loose energy. About five hours since takeoff I landed happy to have completed my Gold distance.  Another pilot informed me that that 300km triangle would also qualify for the Diamond Goal flight. That was an exciting prospect, a second diamond and gold badge in one!

Post flight, Garret and I finished the paperwork for the badge application.  While Dave had not made the Gold distance task as planned, his reaching Mt Laguna, along with his climb back from his low point plus more than five hour duration since release allowed him to complete all three legs of the Silver Badge in one flight!
Photo #14943 | View of Warner Springs from over Julian
Upon returning home and going over the flight again, I discovered that in constructing the 300km task (converted to 161 nautical miles) that the correct conversion was 161.9nm. The task was short by less than a mile. I let Garret know that we’ll chalk this one up to lessons learned and try again. The next day I realized that the Badge and Record guide had provided another option: the post-flight declared finish point. The task was a loss for the Diamond Goal but for the Gold Badge we were back in business and sent in the files.

Rollin informed us that the application was unsuccessful as I hadn’t crossed the start line and the distance was too short. I had programmed a turnpoint segment as a start geometry as  the Badge and Record Guide had allowed, but that part was out of date. I flew past the start point, but I was not within ½ km of the start waypoint to be within the required 1km start line. Ouch, another unexpected lesson.  But how could the distance be short, even with the post-flight declared finish? There was even extra distance now. Rollin discovered that when we transcribed the task to the application in order to reflect the post-flight finish point, we were off by exactly 1 degree of latitude on the Jacumba turn point (33N instead of 32N), which made the task look like it was about 120 miles too short! Garret confirmed that indeed the intended point was as stored in the task in the IGC file. While the declared start point wasn’t valid, I could use the release point along with the post-flight declared finish point and have the task flight meet the requirements. Good enough for the Gold distance, but that won’t work for the Diamond Goal. The task was accepted, and I’m the proud holder of Gold Badge number 2765.

Photo #14946 | Gold badge with an altitude diamond
I sent Rollin some suggested corrections for the Badge and Record guide from my lessons, and he appreciated the feedback. Now, I’ve got the Diamond Goal task set up. I wonder what additional lessons that will bring.

Saturday, July 8, 2017

New ebook out on Airbus Fly-by-Wire


My latest ebook on the workings of the Airbus fly-by-wire flight control laws is now available.
Book Cover

In the previous publication A330 Normal Law: Putting Fly-by-wire into Perspective, I gave a brief history of fly by wire technology (older than you think) and the details of Airbus’ implementation of fly-by-wire to make a safe, intuitive, and well behaved flight control system a reality: Normal law. Included are the handling characteristics and how they differ from a conventional airplane, the protections provided by the system, even an example of the unexpected effects of the protections. 

This newest release, Airbus Flight Control Laws: The Reconfiguration Laws explains what happens when Normal law can no longer function with a review on aircraft handling, stability, and how each of these different operating laws operate. Covered are Alternate, Direct, and Abnormal Attitude laws, and a condition when there are no laws at all: backup control. Also introduced in this edition are differences between the different Airbus families (A320, 330/340, and 350) for each of these situations. While there are many similarities, the capabilities of the protections and autopilot functions for the various models have expanded over time as each new model was introduced.

The focus is from the pilot’s perspective, with emphasis on handling characteristics and their implications and not on the mechanical and computer architecture that each model uses to carry them out.  It is written so that even seasoned Airbus veterans will gain new insights something about their airplane, yet it remains accessible to any aviation enthusiast.

You’ve read the Airbus vs. Boeing discussions, but can you spot the errors in their arguments? If you want to know what all the fuss is about, this will get you well on your way to being literate on the subject.

Airbus Flight Control Laws: The Reconfiguration Laws is available virtually anywhere ebooks are sold: Amazon, iBooks, BN.com, googleplay, smashwords.com, and other ebook sellers.

Wednesday, May 31, 2017

Air France 447: Eight Years Later


Eight years ago on the night of May 31st, 2009, Air France flight 447 from Rio de Janeiro, Brazil was lost in the Atlantic Ocean north of Brazil.
Virtually every aviator today knows the number 4-4-7 and the unnecessary tragedy it represents. The initial reaction of many was “how could this happen?” How could three airline pilots possibly lose control of their aircraft in under a minute and kill everyone on board within 4 ½ minutes of the autopilot disconnecting—essentially because the autopilot disconnected?
But the world of aviation has not sat idly by in its aftermath. The NTSB has a saying: “From tragedy we draw knowledge to improve the safety of us all.”
Much like the June 1975 crash of Eastern flight 66 at JFK due to a microburst, and the follow-on windshear crashes of Pan American 759 in New Orleans (1982) and Delta 191 in Dallas-Fort Worth (1985), these accidents lead to increased research and education on the weather phenomena and the development of windshear warning systems, both on the ground and as airborne equipment.
Also like the December 1974 crash of TWA 514 into the mountains outside of Washington, DC, which lead to the increased awareness of minimum safe altitudes, the installation of the basic Ground Proximity Warning Systems (GPWS) on all transport aircraft and the subsequent development of the modern look-ahead GPWS systems.
In each of these cases, the development that resulted in the aftermath of these accidents significantly reduced or virtually eliminated those causal factors in the years since.
Loss of control in flight (LOC-I) now remains as the leading accident factor in the few accidents and incidents we see in recent times.The loss of Air France 447 and another LOC-Iaccident earlier that same year, Colgan 3407 on February 12, 2009, spurned:
  • Increased awareness of the need for manual flying practice and more concentration on hand flying skills.
  • The need to be aware of normal pitch attitudes and power settings for all flight regimes.
  • The roll of the startle factor in pilots being able to cope with unexpected unusual conditions.
  • The roll of automation dependency in this increasingly automatic industry.
  • Increased training, now mandated, in upset recovery, high altitude stalls, with a revised emphasis on correction of a stall by reducing angle of attack, not just power application.
  • Increased minimum flight times for new airline pilots.
And while most of the emphasis is focused on human flying skill (and rightly so), technological advancements have also been taken, almost surely with this accident in mind. The new Airbus A350’s autopilot now can remain engaged in all but the most extreme situations, thus far reducing the instances where pilots are unexpectedly handling a causal factor (e.g., weather), system malfunction, and autopilot disconnection all at the same time. The system allows the airplane to recover back to within the normal flight envelope from extremes of speed, bank, and pitch and reduces the other recovery maneuvers that must be hand flown by providing for the capability of the autopilot to fly windshear and TCAS traffic resolution advisory maneuvers automatically, and allow the pilots to take over when they are ready. Enhancements to the weather radar allow for better analysis of a storm and provide an aural warning should one several minutes ahead go unnoticed.
Yet, still, the problem of LOC-I has not been eliminated, even though the lessons of AF447 seem loud and clear. Air Asia 8501 in December 2014, stands as a stark reminder that continued diligence is required.
Commercial aviation is very safe, it is in fact amazingly safe, but it is not inherently so. It is safe because a lot of people work hard every day to make it that way, and to keep it that way.



Sunday, December 11, 2016

Repeat after me: "Declaring an Emergency, Proceeding Direct"

LaMia Flight 2933 (LMI2933) was a charter flight of an Avro RJ85, operated by LaMia, that crashed near Medellin, Colombia shortly after 22:00 local time on November 28, 2016, killing 71 of the 77 people on board. The flight had run out of fuel.

While it was supposed to be flight planned to fly to its destination of Medellin, then its alternate Bogota, and then for an additional 30 minutes, upon arrival in the Medellin area it was only minutes from total fuel exhaustion.
Avro RJ 85

The aircraft had been flight planned to (or beyond) its maximum range. According to the Wikipedia article, this operator had repeatedly flown to or beyond the legal limits of the airplane. In all likelihood, the PIC was blatantly reckless. Arrests have been made and government officials suspended, but that's not the point of this entry.

Approaching its destination of Medellin, the flight was issued holding instructions due to another aircraft that had, ironically, a fuel situation. That would later be determined to be caused by a malfunctioning fuel gauge. That flight was making a precautionary landing and had been given priority. LMI2933 was third in line for landing and had been issued a holding pattern. At the point they entered the holding pattern, they had six minutes of fuel on board.
this doesn't mean that you wait to declare an emergency until you have less than 30 minutes of fuel on board, but as soon as it looks like you'll land with less than that

LMI2933 mentioned to ATC an “issue with fuel”, but that is a long way from declaring an emergency, which they eventually did, but not before they had apparently already run out of fuel, saying "Lamia 933 is experiencing a total failure, total electrical failure, out of fuel." The electrical failure, was of course due to the fact that the engines had stopped working due to fuel starvation. The airplane was already in a descent due to engine failure at the time they asked for radar vectors to the airport.

ICAO (International Civil Aviation Organization) requires "If the PIC calculates that the flight will arrive with less than reserve fuel (30 minutes minimum), then it is required to declare a Mayday-fuel." Note that this doesn't mean that you wait to declare an emergency until you have less than 30 minutes of fuel on board, but as soon as it looks like you'll land with less than that on board, even though you may have much more on board at the time.

It should have been clear to this crew that this had been the situation for a while. Other than proper flight planning and landing at an airport short of the stretched limit of Medellin, the crew should have declared and emergency due to fuel as soon as they contacted the Medellin controller (as well as with each previous controller).

When told of "an issue with fuel" the controller was apparently preparing to bring them in next, which was kind of the controller—but not required. When issued the holding instructions the crew accepted them and took two turns in the holding pattern.

The captain, who as also an owner of the airline, may not have  wanted to admit that his planning was that bad, and he had gotten them into a terrible situation. Had he landed "safely" he may well have had legal action taken against him for violating multiple safety regulations, instead they did not admit their situation and not only the pilots, but most of the passengers paid the ultimate price.

There are many lessons in this accident. No doubt among them will be safety culture, fuel planning, and CRM. More will probably be revealed when the final accident report is issued. But clearly one clear lesson to put into play when all of the unexpected events pile up and you're short on fuel is that saying "an issue with fuel", "minimum fuel" or other similar terms does not get you the immediate priority handling that you need. The words "mayday" or "emergency" must be used. If still, you do not get what you need to land safely, then you must violate any clearance or other regulation to maintain the safety of the flight. In this you are not only allowed, you are required!
Repeat after me "Declaring an emergency, Proceeding Direct...."



Other reading on the subject
https://fearoflanding.com/accidents/not-enough-fuel-the-disgusting-truth-about-lamia-flight-2933/
https://airwaysmag.com/industry/lamia-bolivia-2933-lesson-to-be-learned/
http://nsnbc.me/2016/12/02/its-official-colombias-caa-confirms/

Monday, May 9, 2016

Flying Around Turbulence

In response to an article in the Washington Post on an in-flight severe turbulence event, one commenter (who also wrote to me) questioned:

Is it possible to fly around bad weather or just too costly in terms of time and fuel to do so?

I'm just an armchair captain, but what I have seen on flights I've been on recently is a willingness to fly straight through the weather instead of flying around it. Southwest flight from Minneapolis to Phoenix flew over thunderstorms in the Colorado area. Turbulence was moderate to significant, though not as severe as this article records. The pilots tried FL360, FL380, and FL400. Eventually FL380 gave us the smoothest ride but it was still really bumpy. So maybe more consideration should be given to flying around the weather rather than straight through it. I know that means additional fuel costs and possibly delays, but isn't that better than very uncomfortable passengers, or in this case, passengers fearing for their lives? I'm more than willing to accept a 15 minute or 30 minute longer flight in order to be comfortable, rather than a roller-coaster ride that gets me in 10 minutes early. The airline has to factor in that passengers may not fly that airline again if the in-flight experience is too severe. And yes, you should ALWAYS have your seatbelt fastened when you are seated. No argument there.

First, the premise “Why don’t pilots try to fly around bad weather?” presumes to know what the pilots have tried to do to detect and avoid the “weather.” Unless you have interviewed the crew or done other specific research on the specifics of that flight, you don’t know what the crew has “tried” to do.  In fact, in your own statement you say that “The pilots tried FL360, FL380, and FL400. Eventually FL380 gave us the smoothest ride but it was still really bumpy.” Of course, this indicates that the pilots tried at least other vertical options. It’s not likely you were informed of the lateral options that were considered.

Quoting the article about the Allegiant Air incident: "Initial reports from our crew indicate that it was unreported moderate clear air turbulence that caused the injuries and subsequent diversion.” It becomes much more difficult to avoid turbulence that you don't know is there.
Turbulence is caused by numerous factors, including, but not limited to, thunderstorms, tropopause and jetstream interactions, wave action (e.g., mountain wave), trough lines and their associated areas of convergence and divergence, and wake turbulence from other aircraft, among others. Several of which are referred to collectively as Clear Air Turbulence (CAT).

Correctly predicting CAT is a combination of art, science, and luck. Causal factors include jet stream/tropopause shear zones (which typically have the most significant turbulence in the area above the jet and at a lower altitude where the accompanying tropopause slops below the jet core known as the upper front). The temperature lapse rates in each air mass (either side of the Jet & Trop) will produce a variability in the thickness of the turbulent area either side of the tropopause (which can often be a 6,000 ft thick band of potential turbulence). Of course the height of the tropopause is often right in the operational altitudes of most airliners, and that height changes—sometimes up to 15,000 feet at the jet stream boundary, limiting options of vertical avoidance. Horizontal avoidance is also tricky, and it's often just not possible to "fly around" the continuous line of a jetstream.

Wake turbulence, usually manifests itself as a short jolt of turbulence as the aircraft crosses behind the path of another, often out of sight, aircraft. It can be quite violent. You can often visualize this turbulence as a tornado like vortex in the contrail of a passing aircraft. The vortex spreads and settles with time, leaving its location hidden—if not accompanied by a tell-tail contrail.

Trough lines, while defined as a line of low pressure, also indicate areas of a shift in wind direction, often many hundreds of miles long, through a wide range of altitudes. The sift is often accompanied by a decrease in wind speed along the line resulting in areas of convergence ahead and divergence behind the trough line which result in vertical air movement generating turbulence. But not all trough lines generate turbulence. Predicting it requires an analysis of such factors as the speed of the trough’s movement and the degree with which the temperature and wind gradients are out of phase. These factors are usually not within the pilot’s toolbox, both in terms of the raw data and in terms of the ability to conduct the necessary analysis, since very few pilots are also meteorologists.

Thunderstorms are the more obvious hazard and are generally easier to see and avoid. However, even with thunderstorms there is a lot of variability as the turbulence is not limited to the confines of the cloud. The cumulonimbus disturbs the air around it, often throws hail out the top and is a dynamic beast capable of climbing at > 6000 feet per minute. Turbulence can exist for many miles downwind, even well clear of the cloud. Weather radar certainly helps, but it only indicates water, and not turbulence directly and requires a certain degree of skill and interpretation. If there were only one plane in the sky and the airplane had unlimited performance capability things would certainly be easier. However, any deviation requests must be coordinated with ATC which as to balance separation from other traffic restricted airspace and other constraints. The flight you were on was lucky that it had the capability to climb to FL380 or FL400, which is often not the case.

That said, different human and company attitudes are sure to apply in the aggressiveness with which different levels of turbulence are avoided. Operations on often-busy oceanic routes out of radar contact have even less flexibility available to crews for lateral or vertical deviations. Sometimes the best you can do is have everyone seated while passing through an area of turbulence that could not be flight planned arount. My own airline  is one of the few (if not the only?) airlines with a meteorology department which puts a lot of time, money, and effort into predicting and helping crews avoid turbulence, as well as educating pilots on its causes and avoidance. Its weather products are used by several other airlines as well. However, it is not a foolproof system. I can't speak for Allegiant Air, nor do I know what the upper-air charts looked like for that day. Sometimes you can be smart and avoid it, and sometimes no matter what you try, you can't.

Keep those seat belts fastened!

Sunday, August 2, 2015

MH 370 Floating Part Found - So Where is it?

A B-777 flaperon, almost certainly to be determined to be from the missing flight MH370 turned up on Reunion Island, located off the east coast of Madagascar.
As  of today, it's been over 509 days that's  about 12,400 hours. I give the figure in hours, because when applied to a  drift rate that will easily reveal how many miles this part may have traveled before showing up on the Reunion Island beach, 600 miles east of Madagascar.

Some Indian Ocean-current charts look fairly simple. Like this one. But even there. a plane crashing just about anywhere in the entire Indian Ocean could have parts end up near the shores of Madagascar eventually.


This chart, from the Kenya Meteorological Department, shows that the currents may be a bit more complex than the simplified illustration above. In fact, the Indian Ocean currents are full of meanders and eddies that slow and complicate the drift journey.
The current velocities range from near zero, to 130 cm/sec (0-2.5 knots/2.9 mph) The average speed appears to be somewhere between 1/2 and 1 mph, or 6000—12,000 miles traveled. Of course a floating object is also affected by the winds, not just the current.
.

The effect of the wind on any floating object will depend on the profile of the object and how much of it sticks up out of the water. Some areas are know for their 40 knot or greater winds!

Looking at the tracking data for drift buoys released after the  Air France 447 crash on June 1, 2009  it becomes clear that performing a backwards drift calculation is a difficult proposition. This illustration covers two weeks. Working backwards over 17 months with only a few specimens (one or two so far) places the possible origins virtually anywhere in the entire ocean.
Let's look at a couple of 12,000 mile possibilities based on the simplified current chart above. :

Some maps have been drawn and drift plotted to show that debris from the theoretical crash sight off of southwestern Australia could have ended up on the Reunion Island beach. But, what other locations in the Indian Ocean would also land parts in the target area? It's not a stretch for the part to have circled parts of the Indian Ocean several times, depending on which chart of ocean currents you refer to. 

At this point, nearly 17 months after the loss of the aircraft, determining where it started out is kind of like trying to figure out the address a car started from based on the off ramp it took from the interstate, when it's been gone long enough to cross the country three times!

Perhaps what this find will do mostly is to show that the airplane did in fact crash somewhere in the water, and  that it was not hijacked to Kazakhstan, or even shot down as MH17 over the Ukraine.

I find that many people simply underestimate the situation of 20,000+ square miles of ocean, much of it 3 miles deep. Cases in point:

  • Searchers knew very closely where AF447 must have been, yet it took two years to find it. 
  • A Northwest Airlines DC-4 crashed in lake Michigan in 1950 (flight 2501) has still never been found. 
  • When Steve Fossett's aircraft crashed in September 2007, it took a year of extensive searching by up to two dozen aircraft, and while search crews had found eight previously uncharted crash sites, Fossett's aircraft remained elusive. Only with clues from a hiker was the wreckage finally found near a California mountain top only 65 miles from his takeoff position. 


I believe the mystery of MH370 will continue for a long time.