50-52-01\tHAMILTON STANDARD: Applies to All Convair Model 240 Series, Douglas DC-6 and Martin Models 202 and 202A Aircraft Equipped With Hamilton Standard 2H17 Series Blades.\n \n\tCompliance required daily until further notice.\n \n\tThere have been several cases in which a crack has been detected in Hamilton Standard 2H17 blades during routine ground inspections and recently there was a case in which a section of the blade tip shell was lost in flight requiring an unscheduled landing. In order to eliminate the possibility of other blade failures, the following precautionary measures must be taken:\n \n\t(1)\tThoroughly clean the entire surface of each blade to remove oil, grease, dirt, etc., so that an adequate inspection of the entire blade surface can be made.\n \n\t(2)\tCarefully examine visually at close range (12 inches-14 inches) and in detail, the entire surface of each blade for cracks and surface defects in accordance with Hamilton Standard Service Bulletins Nos. 177 and 193. Any suspected areas should then be more closely examined by using a suitable magnifying glass, permanent magnet or any other suitable means as required.\n \n\t(3)\tIf any cracks are found in the blade surface, it must be retired immediately from service. All doubtful cases should be referred to the propeller manufacturer.\n \n\tThis directive supplements previous Hamilton Standard information on the same subject to all affected operators.