Antonomous Environmental Definition of C-130 Flap Well Skin Panel

Abstract

Air Force C-130 aircraft require numerous aluminum doubler repairs on the wing flap skin aft of the right-hand outboard engine. These repairs are costly and require riveting. Rivets often provide new areas of stress concentration, which causes new cracks to develop elsewhere. Boeing and the Air Force Research Laboratory (AFRL) are measuring the thermal and strain environment behind the right-hand outboard engine of a North Carolina Air National Guard (NCANG) operational C-130 aircraft (TN 93-1456) for use in design of a damped repair patch to prevent the growth of cracks in skin under the wing flap panel. During June 2003. AFRL engineers and technicians acquired data using an autonomous damage dosimeter during five operational C-130 flights. The damage dosimeter measures structural strains and temperatures on in-service aircraft to diagnose structural conditions that are difficult to analyze, such as acoustics and high cycle fatigue (HCF). The first flight was from Charlotte, North Carolina to Warner Robins Air Force Base (AFB), Georgia and returned to Charlotte. The last four flights were assault flights where the C-130 simulated cargo drops. Pilots logged the altitude and indicated airspeed, engine speed, and flap positions for the first four flights. Flap position settings were compared with dosimeter temperature and root mean square (rms) strain measurements. This paper presents typical third octave plots showing engine speed vibratory frequencies, rms time histories (TH), and correlation data for a flight. This paper also presents typical limited data in TH, probability density function (PDF), power spectral density (PSD), and rain flow formats.