'Red marks' confound accident investigators

 - July 24, 2007, 8:12 AM

Twenty-two months after the crash of a Cessna 208B Caravan Cargomaster following its night takeoff from Mobile, Ala., NTSB investigators still appear no closer to discovering the cause of the accident, although theories abound.

Cargomaster N76U departed the Mobile Downtown Airport at 7:40 p.m. on Oct. 23, 2002, on an IFR flight plan to Montgomery, Ala. Five minutes later, after a routine exchange of communications with ATC, the aircraft descended rapidly from its assigned altitude of 3,000 feet and hit the ground 7.7 nm from the airport in a right-banked, nose-down attitude at a speed estimated to have been more than 200 knots. The 56-year-old ATP instrument-rated pilot had about 4,000 hours experience, including a period as a Cessna 208 instructor, and he had flown the route many times before. His last words to ATC were, “I needed to deviate. I needed to deviate. I needed to deviate. I needed…”

Weather was not considered to be a contributing factor, and neither was icing, with the freezing level reported at 11,500 feet. Only one other aircraft was flying in the vicinity: a FedEx DC-10 inbound to Mobile, which ATC radar tracked passing two miles away from the Cargomaster at 4,000 feet. The radar tracks of the two aircraft did not cross, although when advised by ATC of the DC-10’s position, the Cargomaster pilot responded, “Roger. I got him above me right now.” Sixteen seconds later, he made his last transmission about needing to deviate before dropping below radar coverage.

A post mortem on the pilot performed by the Alabama State Medical Examiner described the cause of death as “multiple blunt force injuries,” with no evidence of drugs or similar substances or physical incapacitation. The pilot was the sole occupant, and the aircraft was carrying approximately 420 pounds of cargo. An in-flight airframe breakup of the three-year-old aircraft also seemed improbable, since the wreckage was all contained within a radius of 200 yards. The Cargomaster’s PT6A turboprop engine was assessed as operating normally before impact, although when recovered it was found to have broken into two separate parts.

Mysterious Red Marks
While the aircraft suffered severe structural damage consistent with a high-speed impact with the ground, there was one curious aspect that has continued to puzzle investigators. “As the wreckage was being recovered,” stated the NTSB preliminary report, “various parts were observed with localized red transfer marks. The marks were small and had a definitive direction of transfer: however, the direction varied. During wreckage review, a concentrated effort was made to determine the location on the airframe of pieces of wreckage with transfer marks.”

In all, 34 separate red marks were counted, occurring mainly along the forward lower left fuselage but also at more distant points, including the upper surface of the right wing, the tailplane and, strangely, inside the nosewheel tire. The marks were also described as being smear-like, and not linked with impact indentations. The aircraft’s maintenance staff in Mobile testified that its blue-and-gray-on-white exterior bore no such marks when it departed that night.

Samples of the red substance were sent to the U.S. Air Force’s Wright Patterson AFB for infrared spectroscopy analysis, and the result was compared with other red objects known to be aboard the aircraft. These included samples of the aircraft’s paint, a cargo bag, a tow bar, a fire extinguisher, a pitot-head cover and a baseball cap. A red paint sample from a USAF pilotless drone was also provided by the military test center at Tyndall AFB, Fla., since collision with such an aircraft was suggested by some as a possible cause of the accident.

However, USAF officials said there were no launches that night and, in any event, the crash site was beyond their drones’ range. Samples of red paint from the barge used to take the wreckage ashore were also compared, as were samples from a nearby lighthouse. No matches were made with any of the objects tested. Samples of the red substance were also given to the aircraft’s insurers, whose independent analysis agreed with that of the Wright Patterson investigators. After post-accident storage at an aircraft salvage facility, the wreckage was released to the insurance company in February last year.

NTSB Preliminary: A Midair Collision
Numerous theories were subsequently proposed concerning the cause of the accident, mostly suggesting a midair collision. The FedEx DC-10, which was still at Mobile, was visually inspected for damage, but none was found. Similarly, no components from another aircraft were found in the area, and a piece of black material embedded in the wing, and thought at first not to be part of the aircraft, turned out to be from its cockpit light dimmer assembly. Nevertheless, the apparently frequent overflights of the swamp region by drug smugglers were cited locally as a possible collision factor, as were other aircraft “flying under the radar,” terrorist rocket attacks, onboard explosives, errant USAF drones, meteorites and falling space junk. And inevitably, after it became known that the aircraft’s callsign was “Night Ship 282,” one Internet conspiracy site conjured up an encounter with a UFO, and suspiciously described the Cargomaster’s callsign as a “code name.”

In the end, having no tangible evidence of what actually caused the accident, Atlanta-based NTSB investigator Butch Wilson could only conclude in his preliminary accident report that the Cargomaster “collided in flight with an unknown object.”

Midair Now Questioned by NTSB
On June 11 last year, and possibly in response to continued public interest, the NTSB issued an update on its investigation of the accident. The brief statement offered little more than the preliminary report, except to note that the wreckage was now at the laboratory facilities of the NTSB Academy for a “two-dimensional layout and detailed examinations.” An NTSB spokesman confirmed to AIN that the wreckage had been repossessed from the insurers, to whom it had been released in February.

But absent from the June update was Wilson’s reference to a midair collision. The agency spokesman told AIN that this was “a conclusion,” and inappropriate in a preliminary report when other (unspecified) accident causes were still being investigated. However, the update did state that a cockpit visibility study was under way, which would appear to suggest that investigators have not entirely ruled out the possibility that the pilot might have seen something before whatever happened, happened. And the spokesman said that no explanation for the red substance had yet been revealed, but that laboratory analysis was continuing.

Finally, an unusual and perhaps slightly disturbing aspect of the crash investigation: the NTSB update noted, “A third propeller blade was recently discovered at the accident site” and “the major components of the propeller assembly have now been accounted for.” But it turns out that while most of the aircraft wreckage was initially declared to have been recovered from the crash site by the NTSB, it was by no means all, and some critical parts remained behind in the swamp.

The third blade–bent and with the now familiar red mark on it–was actually recovered in early June by the dead pilot’s sister, herself a 727 pilot, who has made frequent visits to the swamp in a search for more clues. During previous visits, and long after NTSB investigators had left the site, she was reported to have recovered more than 700 pounds of aircraft debris, including the other two propeller blades. Discussing this aspect, a former military accident investigator remarked that “it didn’t speak well for the NTSB’s post-accident procedures.”