Aircraft Accidents and Lessons Unlearned XXXV: Executive Air Charter, Inc Flight 5452

According to National Transportation Safety Board (NTSB) report, AAR-88/07, on May 8, 1987, an Executive Air Charter, Inc. doing business as an American Eagle commuter flight, a CASA C-212-CC aircraft, flight 5452, departed San Juan, Puerto Rico, on a flight to Mayaguez, PR. Unfortunately, that is the last clear account in the report’s History of the Flight section. The narrative of how the aircraft crashed then reverted to hearsay, quoting multiple witnesses. A statement by one witness said the aircraft turned right on final into Mayaguez, nosed over and struck the ground. Multiple witness reports were always unreliable; they contradict each other, or recollections are often exaggerated.

American Eagle (Executive Air Charter) 5452, accident number DCA87MA030, is one of the most important accidents to yet be analyzed; the NTSB Archive information was not available. The fatalities in American Eagle 5452 were minimal, yet this accident report represents the Achilles heel in the NTSB’s investigatory process: the absence of experience, particularly in Aircraft Maintenance and aircraft-specific issues. Report AAR-88/07 failed to provide quality safety recommendations or findings.

Reading through report AAR-88/07, there is confusion on what was actually discovered that pointed to Aircraft Maintenance actions as the most prominent probable cause, aka probable guess. Was the right hand propeller out of adjustment? Was the right governor bad from the repair station? Did the flight crew make a mistake?

On May 1 through 5, the right hand (#2) Honeywell-Aerospace TPE331 turboprop engine was swapped due to previous discrepancies. During run tests, the right propeller was replaced because of extensive propeller vibrations. The propeller governor was also adjusted. The plane test flew successfully before flying four consecutive revenue flights on May 5th. On the first revenue flight, the captain reported problems with the right propeller; Maintenance adjusted the propeller’s governor. On the day’s last flight, Maintenance adjusted propeller blade angles to address another problem.

On May 6th, the airliner flew eight scheduled revenue flights without any discrepancy. On May 7th, the aircraft flew two flights and the captain reported a problem; Maintenance readjusted the propeller blades, then eight revenue flights with no issues. The aircraft crashed on the first flight on May 8th.

Each time the pilots wrote up a discrepancy, the mechanics addressed the problem. This is important; it not only demonstrated that Maintenance was addressing pilot discrepancies immediately, but that several legs had been flown without incident. The NTSB engineer did not realize that repeat write-ups can happen, that a problem can resurface because conditions at altitude are different than conditions on the ground; cables can tighten in colder air or engine vibrations at flight idle can offset settings that were perfect during ground operational checks. Adding to the technical confusion, were numerous trouble-free consecutive flights that were flown … without incident. Which brings us back to the baffling History of the Flight section and its confusing description of the crash. What this points to is the fundamental inexperience of NTSB investigators to understand the mechanics’ actions.

Per section 1.12.1, General Information, “The right wingtip first struck the ground 643 feet short of the runway threshold and 67 feet to the right of the extended runway centerline.” The aircraft traveled about 100 feet, presumably in an upright position. The fuselage remained intact, except for the cockpit. All passengers survived with minor injuries.

It is uncertain why this information was not relayed in the History of the Flight section. It could have been easily established by observing ground scrapes, wreckage distribution (found in Appendix D), fuel spatter, localized fuselage damage, techniques that were taught at the NTSB Academy investigator classes. Instead, AAR-88/07 dedicated twice as much report space to conflicting witness descriptions, amounting to some speculation in the recording of facts. The impact evidence was not corrupted; ground impacts are evidence intensive, as opposed to water impacts, because the evidence is preserved. More importantly, evidence found at the impact site did not support Aircraft Maintenance being to blame.

The NTSB employs only engineers to conduct aircraft-specific investigations, e.g. Powerplants, Structures, Aircraft Maintenance and Systems. This is a major problem for the investigatory process. An aircraft engineer, who designs airliners, has experience that is limited to designing a single system of an aircraft’s dozens of systems. Furthermore, they were never exposed to airliners operating in the airline environment. Since they never did, they did not know what to look for as cause for an accident. This calls for an analogy.

In the 1981 movie, Raiders of the Lost Ark, in a rush to capture the map to the Ark of the Covenant – which was engraved on a medallion – the Nazi interrogator, Toht, accidentally burns the map into his palm. Using this imprint, the Nazis forge a new map and begin digging … in the wrong place. Why? Because the rest of the map’s instructions were on the backside of the medallion.

For over five decades, the NTSB has used engineers to investigate aircraft-specific issues. This is akin to digging for answers in the wrong place. It is true engineers have access to aircraft blueprints, but maintenance investigations have little to do with blueprints; they are about people, work hours, maintenance manuals, inspection programs, training, etc. The Federal Aviation Administration (FAA) places such a high importance on Aircraft Maintenance, that half the FAA workforce is dedicated strictly to overseeing that specialty. An engineer who investigated aircraft maintenance issues would be just as ineffective if he investigated pilot issues just because the engineer designed the aircraft the pilot flies.

From the maintenance that took place on May 5th through May 6th, the NTSB engineer concluded that the “evidence indicates[ed] that the carrier’s maintenance personnel were inclined to take the most expedient means to correct an engine rigging problem …” There was no evidence to support this assertion, no interviews. The NTSB engineer came to this conclusion without factual proof as a basis.

The 1.6.2 Maintenance History section of AAR-88/07, the pilot discrepancy reports stated the various mechanical problems found by previous pilots logged in the maintenance logbook; the pilot write-ups were documented. However, even though mechanics addressed the pilots’ concerns each time, the report did not say what the mechanics’ actions were. This raises questions: What did the mechanics do to fix the problems? What did the mechanics document in the logbook? What did the maintenance manual instruct the mechanics to do? Did the maintenance manual give proper steps to adjust the propeller?

This is where the NTSB engineer did not dig in the right place. Many maintenance manuals were written with poor instructions. As an aircraft sees time, the manuals are revised to correct the manual instruction errors. As to the quality of maintenance, larger airlines have the benefit of more experienced mechanics, those who base their work practices on ‘tribal knowledge’; the tricks of the trade that the manuals cannot demonstrate, e.g. blocking cables. Especially these days where major airlines can afford to draft the most experience, like sucking oxygen out of the room, there is no one to pass on the tribal knowledge to the mechanics at the smaller airlines, such as regional airlines.

This is key to understanding how despite a newly replaced engine and propeller being installed, major problems had surfaced. What was important was to find out why they repeated and fix the problems, e.g. manuals or training, that led to the repeat discrepancies. That did not happen.

This is why the safety benefits of this accident were non-existent, too much guesswork, just like the reliance on witnesses for the accident description. The NTSB engineer who investigated Aircraft Maintenance issues did not cover the bases; he allowed speculation to replace facts; he shrugged off researching the maintenance program or maintenance manual quality. The NTSB engineer did not have the fundamental experience to pursue the answers. He did not know where to dig.

This accident was a lost opportunity to improve safety. The accident came at a time when regional airlines were still growing into what they are today, where numerous regional airlines fly in contract to the major airlines. Instead, it became a lost opportunity to capture and fix problems with the young regional airline industry. This problem has now grown and possibly spread to more airlines.

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