Aviation Accidents and Lessons Unlearned LXXXI: CommutAir Flight 4821

On January 3, 1992, while executing an Instrument Landing System (ILS) approach, a CommutAir Beech 1900C, flight 4821 (CA4821), registration number N55000, crashed outside Gabriel, NY, as it completed its flight from Plattsburgh to Adirondack Regional Airport in Saranac Lake, NY. The aircraft, which was operated under Title 14 code of federal regulations (CFR) Part 135, impacted terrain on a wooded hillside. The registered airliner’s owner was Champlain Enterprises, flown as a regional carrier for US Airways. National Transportation Safety Board (NTSB) investigation number DCA92MA016 was assigned to this accident; there was no accident report number. No accident information was researchable from the NTSB Archives.

The NTSB probable cause: “Failure of the captain to establish a stabilized approach, his inadequate cross-check of instruments, his descent below specified minimum altitude at the final approach fix, and failure of the copilot to monitor the approach. Factors related to the accident were: weather conditions and possible precipitation static interference caused by inadequate grounding between the radome and fuselage that could have resulted in unreliable glide slope indications.”

CA4821 Accident Report

Possible precipitation static interference? What? The CA4821 accident report was empty of any related information. The NTSB investigated a transport category aircraft accident – a revenue flight, not Part 91 – with fatalities, but didn’t even assign the CA4821 accident a blue cover report.

The significance of this accident, namely the flight, was that a revenue air operator contracting with a major airline, should’ve given the investigation and resulting accident report a major accident status. Why did the NTSB disregard this accident from major status when the findings should’ve contributed to the industry’s safety in a high traffic environment? As it were, the six-page – four of them half-pages – final CA4821 report, which took 26 months – two years and two months – to investigate and write, was ambiguous and lacked any serious information that was technically accurate or factual. The report presented little to communicate that was not theory.

NTSB letter to the FAA Administrator about CA4821

A safety recommendation paper was later generated by Carl Vogt, NTSB Chairman (eleven days after the CA4821 accident report was published) titled simply: A-94-74 through -76; it was addressed to the Administrator for the Federal Aviation Administration (FAA) – at the time – David Hinson. The document contained the recommendations for DCA92MA016; it also included a collection of investigatory information left out of what the NTSB considered: the ‘Final’ report.

The document wording begins with a review of the accident followed by excuses for the incomplete investigation, namely the flight data recorder (FDR) was not required in the airliner and the cockpit voice recorder – CVR – was ‘so severely burned’; the data was destroyed. The document goes on to say, “… the Safety Board’s analyses of the circumstances leading to the accident were derived from survivor interviews, aircraft position data recorded by air traffic control radar, weather information, and the examination of the airplane’s wreckage.” NTSB investigators explained there would be little factual information to work with.

A lack of factual information would allow for the free flow of opinion and personal interpretation.

NOTE: The following report details were edited for this article. It’s always recommended the reader review the original document for themselves.

The CA4821 narrative explained the analyses of the aircraft’s path; it showed interception of the localizer from below seventeen nautical miles (nm) from the airport but re-intercepted the localizer thirteen nm out, where the descent was initiated.

Beech 1900-C Instrument Panel

The captain said, “… could recall no mechanical problems and stated his [the captain’s] belief the airplane was on the glideslope needles nearly centered throughout the descent.” NTSB investigators examined the cockpit instruments finding, “… witness marks of the glideslope deviation needles near the on-glideslope position,” which agreed with the captain. “Other flight instruments provided altitude and course indications that were consistent with the approach path.” This agreed with radar findings.

In the next paragraph, the NTSB investigators waffled on the captain’s testimony, saying, “… the captain’s premature descent below the FAF [final approach fix] minimum altitude and his failure to establish a stabilized approach.” The accident report, by contrast, stated, “Although post-accident tests were not conclusive, the Safety Board believes that the glide slope indications might have [bold added intentionally] been unreliable due to precipitation static interference.”

These contradictory statements between the Recommendations to Hinson and the CA4821 accident report are troubling. For one, why wasn’t the ‘precipitation static interference’ issue raised more prominently in the CA4821 accident report instead of as an ambiguous note. What was ‘precipitation static (P-static) interference’? How did it affect the glide slope? Was the captain correct all along or did the captain’s testimony not fit the NTSB’s interpretation of the facts?

Furthermore, what’s factual about ‘believes’ or ‘might have’ when assigning cause to an accident?

In the Recommendation letter – not in the CA4821 accident report – NTSB investigators defined ‘P-static interference’ as, “… caused by the electrostatic charge built up on an airplane as it passes through particulate matter suspended in the air. The particulate matter usually is in the form of rain, snow, or ice. The weather conditions during the descent were conducive to fog or freezing rain.” This clarified P-static interference, except on page four of the CA4821 accident report, NTSB investigators stated for Precipitation and Obscuration: N/A [not applicable] – None – Fog. No precipitation or obscuration at the time of the accident. There was fog, but at what altitude did it rise to?

Was there particulate matter or wasn’t there? Meteorological conditions at Saranac Lake – per the CA4821 report – were -2°C (below freezing) on … the … field. Was it ground fog? The lowest cloud – not fog – condition was 500 feet above ground level. Did the fog extend to 6,000 feet of altitude where CA4821 captured the glide slope? No one knows because this information isn’t in the CA4821 accident report.

Was this razzle-dazzle? Did NTSB investigators arbitrarily throw out numbers and terms? Why did they place weather information in two separate reports, independent of each other? Why were any facts of consequence left out of the CA4821 accident report? Why is there no archive information? Why was it so difficult to discover the Hinson recommendation letter, that it was not aligned with the CA4821 accident report?

NTSB investigators stated that during P-static testing (??) “… evidence was found of an inadequate electrical ground path between the radome and the fuselage on five (of eight) other Beechcraft 1900C airplanes in the CommutAir fleet,” that, “After testing, it was noted that pin-hole sized burn marks created during P-static testing appeared to be identical to those observed before the tests …”

“Tests conducted after the accident indicated that sufficient electrical charge could have [bold added intentionally] built in the existing weather conditions …” Could have? The NTSB went on to say, “While these holes showed possible [bold added intentionally] evidence of an inadequate ground path existed …” Possible? After a two-year investigation, the best the NTSB offers is … could have? Possible? Arcing could affect? Where are the facts? How did the NTSB research this evidence? Did they use the experience of knowledgeable avionics technicians? Who researched the P-static issue: the NTSB or Beech?

The NTSB stated, “Instrument flight training manuals and the FAA Airman Information annual discuss static noise only in the context of interrupting communications and some low frequency navigation aids. The FAA Instrument Flying Handbook, [Advisory Circular] AC 61-27C, similarly stated, ‘Signals in the higher frequency bands are static free’.”

To be clear, NTSB investigators, during a 26-month investigation where all evidence was at hand, based its investigation and probable cause on two general training manuals and an advisory circular that were not specific to the model aircraft. NTSB investigators recognized no one with actual knowledge or avionics experience who could’ve helped. Only NTSB pilot investigators, with no technological experience beyond flying airplanes with instruments, used their lack of knowledge by failing to properly investigate the P-static issue, while also neglecting to put any of this information in the actual CA4821 accident report.

Had NTSB investigators used Beech technicians to discover possible contributing factors? If so, how did they maintain bias-free data? NTSB investigators also prevented operators of the Beech 1900-C access to their findings by not putting the information in an accident report and only placing the information in a letter to the FAA Administrator. They blamed the captain and deceased first officer for not doing their job correctly, allegations the NTSB couldn’t prove factually.

To add further confusion, NTSB recommendation A-94-76 advised the FAA to, “Revise the Airman’s Information Manual and Instrument Flying Manual Handbook to address the characteristics of and hazards posed by precipitation static.” Recommendations were made to conduct inspections, but NTSB investigators didn’t ask experienced professionals for help in verifying the need. NTSB investigators then called for manuals that weren’t technically accurate to any specific aircraft model to be revised … to what? How was safety served?

This is the 81st aviation accident investigation report this author has researched for issues contrary to safety. Of the NTSB accident reports researched, not one report has led to quality safety improvements; provided a root cause; or even proved a theory. This begs the question: Does anyone actually read these reports? If they do, no one has pointed out that safety hasn’t been improved. This type of investigative malpractice has gone on for over 57 years and no one is concerned or even asking what the traveling public is getting for its tax dollars.