Plane Crash in Philly
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I was reviewing the ADSB data a few hours ago about this. Seems like a stall or weight issue. The data is incomplete which seems like an electrical issue but either way after take off it gain altitude “too” quickly and then without any deceleration it descends just as quickly, maybe it was inverted after it hit apex? They’re lucky sort of that it landed in a mall parking lot and not the neighborhood.
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Cockpit voice recorders are amazingly hardened bits of tech. They are often kept in the back of the plane, so as to better survive a crash, but their audio comes from a microphone usually found on the instrument panel above and between the two pilot stations. The utility of this recording does not come just from what the pilots might say; the sound of a stall warning indicator or landing gear retraction or engine noise could each allow investigators to infer things about the flight's last moments.
The NTSB eventually found the cockpit voice recorder of the Learjet 55, which was inside the impact crater and buried "under 8 ft of soil and debris." The unit was pretty beat up—or, as the government puts it, displayed "significant impact-related damage as well as liquid ingress." So NTSB sent the device to its Vehicle Recorders Laboratory in Washington, DC, hoping to salvage some of the audio.
After "extensive repair and cleaning," technicians were able to listen to the tape... and they found to their chagrin that it contained nothing related to the accident. In a preliminary report on the plane crash, released last week, NTSB investigators said that "the CVR did not record the accident flight and during the audition it was determined that the CVR had likely not been recording audio for several years." Even the most hardened, comically over-specced devices can fail—and sometimes it's not even the fire, the impact, or the "liquid ingress" that brings them down.
Still, NTSB is not out of options. The Learjet contained another important piece of tech: an Enhanced Ground Proximity Warning System (EGPWS) computer. The device may contain crash data in nonvolatile memory, and it has been shipped off to its manufacturer to see what, if anything, can be recovered.
