April 26, 2011

Thunderstorms are Beautiful - From a Distance

Every year I receive a reminder from my employer that thunderstorm season is on its way.  Frankly, I don't need to be reminded, as thunderstorms are generally hard to miss, but someone making a lot more money than me thinks I need to be reminded.  Spring brings with it an increase in turbulence related injuries for our cabin crews, concerns over lightning strikes for our ground workers and a plethora of added concerns for our pilots and dispatchers...but it's high altitude transitions across lines of thunderstorms like the one described below that I dread the most.


It was the first week in April this year before my first encounter with a line of severe thunderstorms.  The day started in Dallas with an early morning flight to Las Vegas where I was scheduled to sit for about an hour then turn around and fly back to where I had started.  The weather was absolutely gorgeous in both cities, although the Dallas area was forecasting a possibility of storms in the afternoon...not particularly unusual for a Spring day in Texas.  The flight to Las Vegas was uneventful with clear skies and a smooth ride all the way to touchdown.

The flight back to Dallas was equally uneventful until the descent, where we encountered a small, but building line of storms.  I wouldn't even classify this line of rain showers as a thunderstorm at this point, just rain clouds with some vertical development.  Ft. Worth Center, the Air Traffic Control facility handling our flight, allowed us to delay our descent which allowed us to fly over the top of the relatively short storm.  We were forced to make a few small deviations late in the descent but never encountered any turbulence. 

After a short time on the ground in Dallas, we continued on to Birmingham, Alabama for a long layover in preparation for an afternoon flight back to Dallas the next day.  Over night, the small area of rain showers that we easily topped on our way into Dallas the day before had grown quite mature, stretching from Louisiana to Pennsylvania, and was literally on our doorstep by the time we were scheduled to depart.  The picture below shows what the storm looked like when we left Birmingham.  The green line depicts our track through the weather. 


The next picture is a closer look at our track.  Take a look and see if you think you would have taken the same path before you continue reading.


We took off from Birmingham, headed west and were granted an unrestricted climb to a requested cruise altitude of 34,000 feet.  We experience light to moderate turbulence during the first few minutes of our climb and asked the Flight Attendants to remain seated until we were above the rough air.  The departure controller instructed us to climb on a westerly heading directly toward the approaching weather, but after a quick glance at the weather radar we could see that this was not going to work.

Atlanta Center was working several flights through the area that were having some success with a path through a small break in the storm just to the west of Birmingham.  If you look at the map above, you can probably see the hole he wanted us to fly through.  The problem was that the aircraft making their way through this hole were already at their cruise altitude and above much of the weather you see on the map.  We, on the other hand, would not be able to fly through the same hole without first making it to 34,000.

As we climbed, it quickly became clear that we needed another plan, so we requested a left turn to parallel the storm until we had gained enough altitude to make our way through another hole.  As we reached our planned cruise altitude of 34,000 feet, a break in the storm became apparent and we made our move.  We widened out to the left initially then made a gradual turn to the west and picked our way through the hole. 

Hole? You say you don't see a hole? As bad as it looks in the pictures above, we were able to find a safe path around the worst of the storm and managed a pretty smooth ride.  One thing you must remember is that the weather maps you see online or on the evening news are top-down views of the storms and do not depict the height of a thunderstorm.  Air Traffic Controllers see this same 2D view of weather and will often warn pilots that they are about to fly through heavy rain showers that they are actually thousands of feet above.  A thunderstorm is a three dimensional beast and the 2D nature of most maps just doesn't paint the full picture.

I took the picture below just after we made our turn to the west.  On the right side of the screen you see "WX+T" over "+0.5".  This indicates that my NAV screen was set to display weather radar and turbulence information and that the radar beam was directed .5 degrees nose up...basically level.



It's at about this point that I usually get a tingling sensation in my toes that's my body's way of telling me to pay attention. I had already checked the aircraft performance charts and found that we were capable of climbing another 2,000 feet if needed...but I had no intention of climbing.  That extra 2,000 feet was the extra performance that I needed to feel comfortable as we crossed the storm ahead.  The thunderstorms were "embedded" which meant the storm cells you see on the radar screen above were hidden from view by cloud cover.  As we entered the clouds, we would have to engage the wing and engine anti-ice systems to keep the engines, wings and tail clear of ice.

The anti-ice systems on most jet aircraft use air from the engines to heat the leading edges of the engines, wing and tail and the air used to keep these areas clear of ice is a direct draw on the engine.  Any power draw on the engine will affect the aircraft's ability to maintain altitude.  As an example, an MD80 that weighs 133,700 pounds is capable of maintaining 34,000 feet with the engine and wing anti-ice systems turned off.  With those systems turned on, the aircraft would have to weigh less than 130,300 pounds to maintain the same altitude...a 3,400 pound reduction in the lift capability of the aircraft.  For these reasons, I wanted to stay at 34,000.

One nice thing about the average line of thunderstorms is that they're usually only about 10 to 20 miles wide.  So that uncomfortable feeling I get from flying around a thunderstorm so close to the maximum capability of the aircraft only lasts for a few minutes...then it's gone.  It also brings to mind an old saying.  "There are old pilots and there are bold pilots, but there are no old, bold pilots."  I'm not ashamed of the uncomfortable feeling I get when operating near the edge of the envelope.  I intend to be an old pilot...not a bold one.

We encountered light to moderate turbulence and at one point as we flew through a significant downdraft, the auto throttles advanced the engines to full power in an attempt to maintain the speed I had selected on the flight guidance panel.  Since we had elected to stay at a lower altitude, there was ample power to maintain our speed and altitude.  With the engines sitting steady at max cruise power, I was pleased with the decision not to climb to a higher altitude.

The ride through weather such as this always seems to be the worst just before you break out the back side of the storm and into clear air.  As we broke out into blue sky with my concern and tingly toes in the rear view mirror, I took a moment to look back and appreciate the storm we would leave behind.  Thunderstorms are beautiful...from a distance.

April 3, 2011

Grounded Jets at American and Southwest - History Worth Remembering

View of the hole taken from the cabin

I’ve been sitting around this morning perusing stories about Southwest Airlines and their third explosive depressurization in as many years.  This all got me thinking about the FAA’s $7.2 million dollar fine against Southwest in 2008 followed quickly by a $24.2 million dollar fine against cross town rival American Airlines for a separate but related offense.  This past Friday, a 15 year old Southwest Boeing 737-300 lost pressurization while cruising at 36,000 feet after developing a large hole in the fuselage. 

The picture below illustrates how bad things could have been.  On April 28, 1988 a huge section of metal peeled away from the fuselage of another Boeing 737,  Aloha flight 243, exposing passengers to the elements as if the aircraft had been equipped with a convertible top.  They lost a crew member on that flight when Flight Attendant C.B. Lansing was sucked from the aircraft and fell to her death.  In addition to FA Lansing’s death, another 65 passengers and crew were injured. 
Aloha 243. April 28, 1988
As a result of the Aloha accident, the FAA ordered mandatory inspections of all Boeing 737 series aircraft.  Almost twenty years later in March of 2007, Southwest Airlines representatives notified the FAA that it had inadvertently missed these inspections on some of its aircraft. Some were nine months overdue.  It was revealed during the investigation that Southwest flew 46 Boeing 737s on 59,791 flights without the required maintenance inspections.


The aircraft in question were supposed to be grounded immediately, but the Southwest planes were not. For another nine days, the jets in question made more than 1,400 additional flights.  The airline was initially fined $10.2 million in March of 2008 for their lapse in procedures.  Southwest appealed the fine and eventually settled the case after agreeing to pay $7.5 million.  The largest fine ever levied against an airline.  The record wouldn't last.

As the record setting fine at Southwest rippled through the airline industry, it became apparent that many of the issues with Southwest's planes held true for other types of aircraft as well.  After the FAA found that Southwest had failed to comply with inspections of its 737s, the agency announced that it would conduct unscheduled inspections of aircraft owned by other airlines including American Airlines. As a result, many airlines began canceling flights in order to check or double-check their planes and maintenance records.

It was at this point that maintenance repair discrepancies surfaced at American Airlines and its fleet of MD80s.  At issue with the MD80 was the wiring that electrifies the planes' auxiliary hydraulic system.  But the problem wasn't with the functionality of the wiring. It was determined years ago that the wiring harness for the auxiliary hydraulic pump on the MD80 series aircraft was susceptible to rubbing and chafing as a result of its proximity to the landing gear doors.  


MD80 Auxiliary Hydraulic Pump - The wire bundle from center screen to right (white).  Closed gear door in the foreground.


The FAA, aircraft manufacturers and airlines became very concerned about wire bundles and the possibility of electrical sparks after the loss of TWA 800 in 1996 off Long Island which resulted in the deaths of all 230 passengers.  But the TWA 800 accident involved a Boeing aircraft, not McDonnell Douglas, the maker of the MD80, and the explosion on TWA 800 initiated inside a fuel tank after fuel vapors were ignited by an electrical short circuit.  The wire bundle in question on the MD80 is not in or even near the fuel tank.

The FAA issued an Airworthiness Directive (AD), an order to complete an inspection or work on an aircraft.  It should be noted that, as the largest operator of MD80s in the world, American Airlines was often called upon by the FAA to help write such directives and they did in fact write the initial version of this AD.  The initial version called for a protective sheath to be installed around the auxiliary hydraulic wire bundle and called for the sheath to be held in place by a series of ties that were to be placed one inch apart for the entire length of the wire bundle(This can all be seen in the picture above).  While American’s initial version of the procedure called for the ties to be one inch apart, it also allowed for slight variations of up to 1/8th of an inch.  The final FAA version came in the form of a 38-page handbook and omitted the 1/8th inch allowance.  American Airlines admitted that its engineers may have had some trouble deciphering the procedure.   



What occurred behind closed doors between American and the FAA at this point is unclear.  But it appears that an agreement could not be reached on a number of issues.  Were the aircraft in compliance?  If they were not, how much time, if any, would the airline have to correct the issue?  In the case against Southwest, the FAA allowed the airline to continue flying their jets while the required inspections were completed.  It was during this time that another 1400 flights took place with uninspected aircraft.

It is a misconception that the FAA grounded American’s MD80s…that decision was made in house.  But the massive and recent fine against Southwest was weighing heavily on the decision makers at American.  Grounding the fleet probably resulted in a smaller fine, but when you consider the lost revenue and massive inconveniences to the flying public, an argument could be made that it was a “cut your nose off to spite your face” move. 

th of an inch.  The airline has long disputed the agency’s findings, claiming that the violations were minor and never endangered passengers.  The FAA fined American Airlines $24.2 million for failing to properly follow the agency's Airworthiness Directive.  The fine reflected a more aggressive stance by the F.A.A., which has been criticized for being lax on some maintenance issues, particularly surrounding American Airlines and in the case involving Southwest.

The transportation secretary, Ray LaHood, said in a statement, “We expect operators to perform inspections and conduct regular and required maintenance.” 

The previous highest fine was set at $9.5 million in 1987 against Eastern Airlines. But the company paid only about $1 million before going out of business.