It’s In the Small Details

A few years ago, I wouldn’t have believed that I’d spend 1-3 hours a night watching YouTube videos. But this has evolved quite a bit from the early days of shaky cams, airplane noise in the background, and questionable advice. The questionable advice is still out there but is swamped by so much good advice and programming.

Although I haven’t flown as a pilot in command of my mighty 100 hp Beechcraft since the late 80s, flying and aviation safety videos have held my interest. Specifically, aviation accidents and their causes.

The causes range all over the spectrum, from (mainly) general aviation pilots blundering willingly into bad weather and visibility conditions, to the usual weight and balance problems, to a passenger who wanted the door open for photography, and the pilot willingly tying it to the wing strut, not realizing how much drag that would create on takeoff.

A Canadian production company has made hundreds of videos, now on YouTube, that profile mainly airliner accidents. I have found these videos to be excellent in their quality. They use not only archival videos from the accident scene, but interview many of the surviving pilots and passengers and accident investigators.

Then they have actors reenacting the accident. And go through the thought process (and elimination) of various hypotheses until the true cause is discovered.

Last night I watched their episode on the British Air 777 that had no engine power on final approach to Heathrow. With the heroic flying by the crew to avoid a far worse catastrophe in taking this now huge glider over buildings and motorways to a “landing” right before the runway threshold.

It took Boeing about a year to find the cause of this elusive problem, but they finally determined that ice crystals formed on the fuel/oil heat exchanger of each Rolls Royce engine, starving it of fuel. And believe it or not it was a simple change of the design that prevented the crystals from clogging the fuel line.

Accident investigators want to find the causes to see if the potential is inherent in other planes of the same model. Or learn from the situation and prevent it from happening again.

There was a landmark case in rural Ontario, Canada involving ice on the wings of a Fokker F-28 regional jet which prevented the plane from gaining altitude at liftoff.  From that investigation airports around the world changed the way planes are deiced – from the terminals to closer to the runways on the taxiways. And longer lasting deicing fluid was developed, as it was determined that even if that plane was deiced, enough time had elapsed to takeoff that more ice probably would have formed on the wings.

Icing is deadly because it disturbs the airflow over the wings and impedes lift.

But I wanted to mention a few cases here where a lapse in proper maintenance protocol had such catastrophic consequences. Errors that were tiny but had devastating consequences.

The first involved the crash of an Emery Air DC-8 at my hometown.  In Sacramento we had 2 major air force bases, Mather and McClellan. Mather used to be where for generations they taught navigators. With modern avionics, that isn’t needed anymore. Mather eventually evolved to a hub for UPS and formerly Emery Air Freight.

An Emery Air DC-8 took off at night and immediately had pitch problems. The First Officer (right seat) was flying, and initially the captain thought that he had pulled back too hard on the yoke. To do so risks both stalling, when the wings can no longer provide lift, and a tail strike.

But almost as soon as they became airborne, it became obvious that it was another problem. The plane was virtually uncontrollable. They eventually maneuvered the plane 180 degrees and had the runway in sight when they lost all control, and plummeted into an auto salvage yard a short distance from the runway.

If you watch the linked video, one of the NTSB investigators said that the scene was “like a war zone”, with bits of plane mixed with the wrecked cars.

Amazingly, they traced the problem to a missing cotter pin. A part that costs far less than $1, even for aviation-certified parts. It is simply a pin that goes through a bolt shaft and nut that ensures that the bolt cannot work its way loose.

Your car’s front wheel bearings might use a cotter pin.

Anyway this pin was used to secure the elevator dampers, and a young unsupervised mechanic had failed to secure the nut with a cotter pin. In the subsequent 12 weeks, the nut worked its way loose until that fateful night at Mather when on takeoff the bolt fell loose with the elevator jammed in the up position.

If you’d like to jump to the pertinent part where they explain the problem, it is here.

The second case involves 2 separate incidents both involving a Boeing 757.  Both involved the pitot-static system. In the first case, an Aero Peru 757 was flying blind at night over the ocean – without critical instruments –  all because a maintenance worker while washing the plane put tape over the pitot-static ports and failed to remove it. While the worker should have removed it, the First Officer in doing the walk around inspection missed it too, being nighttime.  As complex and computerized as modern airliners are today, their computers depend on that simple system used for 100 years that feeds them the airflow information. If it isn’t working, the computers don’t work.

The second case involved a 757 leaving the Dominican Republic for Germany.  The cause was a wasp nest built inside one of the pitot tubes. Most aircraft operators use a cover over the tubes when the plane is inactive and this apparently wasn’t done.

As an aside, this cause is also what downed Air France Flight 447, although ice had built up in the tube. Technically I suppose the direct cause was the First Officer’s mishandling of the situation, with his trying to pitch the airplane up by pulling back on the stick (?), resulting in its stalling and pancaking into the ocean from 30,000 feet at 250 mph. Ironically there had been an upgrade to the tubes that would have prevented this, but it had not been installed in that aircraft yet.

While I acknowledge that it is easy for me to second guess a man whose actions led to the deaths of all aboard, but it reminds me of this book I reviewed some years ago about wilderness survival, and who survives and who doesn’t. One of the things the author emphasized is when faced with a difficult situation, stop for a moment, and think it through. In the Air France example, the plane was flying straight and level into the storm when the ice in the pitot tube forced the autopilot to give up and disengage.

The last example shows why among licensed A & P mechanics (FAA licensed for Airframe and Powerplant) there should be a strict division of labor between the Inspectors/managers and the mechanics doing the work.

A team was working on a regional airliner, an Embraer, replacing the rubber deicing boots on the horizontal stabilizer. The manager thought he would help them and started removing screws on the leading edge.

Later a second team came in and did not know about the missing screws. They were supposed to document every step taken in the repair in a logbook, and the manager did not do this. And to compound this, the morning was coming and the maintenance team decided to do that side at a later time.

The plane rolled out and started its day’s flight. When the pilots were descending the extra speed was enough to blow that leading edge off, making the plane pitch into a violent and uncontrollable dive.

So much of life is in the small details.