Summary
We propose to supersede Airworthiness Directive (AD) 2009-17- 01, which applies to certain Gulfstream Model G-IV, GIV-X, GV-SP airplanes and Model GV airplanes. AD 2009-17-01 currently requires, an inspection for sealant applied to the exterior of the auxiliary power unit (APU) enclosure (firewall), and a revision of the airplane flight manual (AFM), as applicable. Since we issued AD 2009-17-01, we received a report indicating that the type design sealant applied to the APU enclosure is flammable and failed certain tests. This proposed AD would require revising the AFM, and revising the applicability to include additional airplanes. We are proposing this AD to address the unsafe condition on these products.