Aircraft Accidents and Lessons Unlearned VII: Continental Express 2574

The most frustrating part of accident investigation is when findings and fixes are short-lived.  It’s even worse when the findings and fixes are non-existent.  Aircraft accidents are fickle things; when JFK Jr. died, the world was on edge, yet a cargo aircraft can be destroyed and no one pays notice.  Attention to an aircraft tragedy is dependent on many factors, e.g. how many were lost; that there are no other accidents at the same time; what celebrity may have been on the aircraft; or how it happened.

We live in a 24/7 media society; we are quickly distracted by other events.  But we are distracted at our own peril; the life we save could be our own.

On September 11, 1991, a Britt Airways’ EMB-120RT, operating as Continental Express flight 2574, crashed near Eagle Lake, Texas.  The National Transportation Safety Board (NTSB) describes the accident as a result of an inflight breakup.  The aircraft did break up before impact, yet that isn’t why it crashed.  Simply put: a piece of the aircraft fell off resulting in an aerodynamic upset followed by the inflight breakup.

This is not a trivial point; the part falling off was not due to structural failings or hydraulic system shortsightedness; if the part stayed on, the aircraft could probably be flying to this day.  The reason the part – a horizontal stabilizer forward spar cap – fell off was due to factors that keep plaguing the aviation industry today, twenty-six years later.

The night before the accident, maintenance was performed on the horizontal stabilizer, where the right spar cap was removed.  The horizontal stabilizer, which, on the EMB-120RT, sits high on the vertical stabilizer forming the T-tail, required replacement of the de-ice boots that cover the spar cap’s leading edge; these de-ice boots break away ice buildup that disturbs the flow of air.

During shift turnover, a miscommunication occurred between two work-shifts, resulting in the spar cap not being secured to the Horizontal Stabilizer.  While in flight, the spar cap departed the aircraft; aerodynamic differences between the right and left stabilizer then caused the aircraft to roll and plunge, structure peeling off during the uncontrolled descent.

In aviation, maintenance on certain areas of the airplane dictate that a second set of eyes check the work on, e.g. flight controls, landing gear, doors and certain engine components.  In the air carrier world, this is required per Title 14 of the Code of Federal Regulations (CFR) Part 121.371 (c) No person may perform a required inspection if he performed the item of work required to be inspected.  In the air carrier world, these types of inspections are called Required Inspection Items (RII); they are performed by Required Inspection Inspectors.

In the regular world, a homeowner cannot build a deck without it being inspected by an engineer/inspector for the town or village; house wiring cannot be installed without a similar inspection by a licensed electrician.  These inspections are important to guarantee the house doesn’t catch fire or the homeowner’s safety isn’t threatened by a poorly designed/built deck structure.  It provides peace of mind.

RII inspectors provide similar peace of mind.  The inspector receives extra training on inspection techniques, tools and equipment, that are used to conduct more intricate inspections; this type of training is more than the average mechanic receives.  The inspector provides a ‘second set of eyes’ to assure the job is done completely and within limits.

The caveat is, that according to Title 14 CFR 121.371 (c), the inspector must divorce himself from the job; they cannot lend a hand, because then the separation of maintenance and inspection is broken.  Only by standing outside the maintenance performed can the inspector remain impartial and provide an uncorrupted inspection.

During the maintenance on the EMB-120RT, the inspector joined in the replacement of the right hand de-icing boot, i.e. he broke the separation of inspection and maintenance.  The 2nd shift inspector removed the fasteners on the top edge of the horizontal stabilizer’s spar cap.  As the work progressed, the 2nd shift (the mechanics that began the job, yet did not know that the fasteners on the top edge were removed), turned over the work to 3rd shift.  There was no documentation to this fact and the 3rd shift inspector did not receive turnover information from the 2nd shift inspector about the missing fasteners.

NOTE: There is one unfortunate truth behind accident investigation: important changes to training occur faster in the Flight department of an airline than the Maintenance department.  This is because Flight communicates better and can implement changes easier than Maintenance can, e.g. after Delta 191, an L1011 crashed in Dallas in 1985, wind shear avoidance training became mandatory, almost immediately.  Furthermore, airline pilots talk directly with each other, allowing the safety items to flow unobstructed throughout the industry; Maintenance departments don’t enjoy this type of seamless communication.  One reason was that up until 2001, the NTSB never gave Maintenance much thought beyond the accident aircraft’s records; the Maintenance phases of investigations were accomplished by engineers, not certificated mechanics.

How Continental Express 2574 hurt the future of aviation was that two accidents occurred over ten years later, under similar circumstances.  Air Midwest flight 5481, January 8, 2003; and Colgan flight 9446, August 26, 2003; two aircraft accidents separated by eight months and nine hundred miles.

One common denominator that joins them to Continental Express 2574 is the violation of Title 14 CFR 121.371 (c); the inspectors corrupted the inspector-mechanic separation.  As a result, a combined fatality count between the three accidents stands at thirty-seven, all because persons involved ignored the same Federal Regulation; a simple rule designed to enhance safety; a rule that was proved to be necessary.  And what of the many times since, where the same rule, or others like it, were ignored for the expediting of maintenance.

The most frustrating part of accident investigation is when findings and fixes are short-lived.  It’s even worse when the findings and fixes are non-existent … or ignored.