A Gulfstream G-IV was on a positioning flight for a maintenance input. The aircraft had departed Caracas (Venezuela) late in the afternoon and was heading for Fort Lauderdale (Florida, USA) on an IFR (Instrument Flight Rules) flight plan.
The incident aircraft as found by inspectors from Gulfstream (Source & © Gulfstream)
Shortly before reaching the Top of Descent (~2 hours and 15 minutes after take-off) while cruising at flight level 430 (~43.000 feet / 13.100 meters) at a speed of 0.8M, the crew was alerted by a "CABIN DFRN 9.8" warning and a "DOOR MAIN" warning. (The crew did not report if they received a "CABIN DFRN 9.6" message. although the DFDR data shows this was presented) The first warning indicated that the cabin differential pressure was at 9.8 psi (Max 9.55 psi), while the second indicated that the main (passenger) door was snot closed and locked.
The crew donned their oxygen masks and referred to the applicable checklist in the aircraft Quick Reference Handbook. During this time a loud 'BANG' was heard from the cabin after which the crew initiated an emergency descent while manually opening the cabin pressure outflow valve. The crew did not declare an emergency and descended to 12.000 feet above sea level (MSL). The flight continued without further issues to fort Lauderdale and an uneventful landing followed.
DFDR (Digital Flight Data Recorder) data as obtained by Gulfstream (Source & © Gulfstream)
After shutting down the aircraft the crew performed a walk around but did not find any obvious discrepancies.
A day later the aircraft was ferried to Boca Raton Airport for the scheduled maintenance, a short 20-minute flight. During the maintenance check extensive damage to the aircraft was found;
Damaged floor beams
Damaged fuselage frame under the right galley
Cracked floor beam
Damaged (dimpled) floorboards
Damages between ribs
Damaged wing links
Damaged aircraft structure, see the report at the bottom of the blog for more details on the structural damage. (Source and © Gulfstream)
A thorough inspection of the aircraft exterior found a blocked static port for the CPRV (Cabin Pressurisation Relief/Safety Valve). According to the OEM (Gulfstream), this effectively resulted in an inoperative CPRV. (This valve is operative should have prevented an overpressurised cabin)
The aircraft was considered damaged beyond economic repair and was written off. The file below is the complete inspection report of the aircraft damage made by Gulfstream and part of the NTSB docket ERA15la328 which is available by clicking here.