It’s a scenario no pilot enjoys contemplating: The aircraft is flying perfectly when a loud bang is heard, followed by indications of an impact and unknown damage. The June 1 "IFR Fix: Unknown problem, imperfect solution" posed that scenario, spotlighting decisions a pilot would have to make—and defer—to conclude the event.
Two examples reported by pilots of pressurized twin turboprops to the Aviation Safety Reporting System capture the demands of such occurrences. Both pilots heard a loud noise. Both aircraft experienced the failure of a window, and other damage, when components separated.
One stricken aircraft was in cruise; the other, near landing. Were these emergencies? Dramatic to ponder, but secondary to problem solving.
A Mitsubishi MU-2B-60 was cruising at Flight Level 220 northwest of Albuquerque, New Mexico, when the pilot "heard a loud bang from the right side of the plane behind the cockpit. All cockpit indications were normal, all flight instruments were normal, and there was no shudder or movement of the aircraft." A passenger reported a broken window.
The outer of three panes had failed, causing cabin altitude to climb from 5,000 feet msl to 10,000 feet msl. The right engine was functioning normally, and "as we were literally over the middle of nothing, I notified ATC of the situation but told them I was not declaring an emergency but wanted to descend to a lower altitude."
Prepared to divert, the pilot continued to the destination, Scottsdale, Arizona. Later, damage was found including dents and impact marks on the right prop, and damage to the horizontal stabilizer.
"As Pilot in Command (with my family the passengers on board) my focus was on maintaining aircraft control, determining what had happened, following the checklist and then making an informed, deliberate decision on what further actions should be taken," the pilot wrote.
A Beech King Air 300 pilot heard a loud pop. "Two seconds later I realized that a portion of the right side engine cowling (door) had departed the aircraft and struck the window causing the blowout."
Disconnecting the autopilot, the pilot found "all systems functioning normally, I proceeded with the IFR approach to an uneventful landing at our intended destination eight minutes later."
The report noted that the pilot or a mechanic had neglected to reinstall fail-safe screws in the cowling during hurried maintenance the previous day, and it credited the aircraft’s T-tail design with avoiding damage to the King Air’s horizontal tail.