Raytheon Model Raytheon Model DH.125, HS.125, and BH.125 Series Airplanes; Model BAe.125 Series 800A (C-29A and U-125), 800B, 1000A, and 1000B Airplanes; and Model Hawker 800 (including variant U-125A), and 1000 Airplanes

Comment on 2005-NM-017-AD This proposed airworthiness directive addresses problems with certain Raytheon aircraft equipped with Honeywell fan venturi. The problem has apparently been brought to the attention of the FAA by Raytheon's identification of the problem resulting in issuance of AD 94-11-03 and further experience evidenced by later bulletins. A cursory investigation of the part numbers mentioned in the current proposed action indicates that the problem may be more wide spread than presently identified. The corrective action requires that a certain part number venturi be replaced by a "new and improved" venturi. The "new and improved" venturi, P/N 132322-3-1, is known to exist on certain Israel Aircraft Industries aircraft. If therefore follows logically that the possibility exists that the older P/N 132322-2-1 may also be installed on these aircraft. For reference see the attached PDF scan showing the existence of the "new and improved" part. Aircraft manufactures, particularly those not in the United States, seem blissfully unaware of 14 CFR 21.303 (PMA) and appear to assume that all their products are forever configured just as they leave the factory or are modified only in accordance with manufacturer instructions. The real world doesn't operate this way as the use of alternative PMA parts is becoming increasingly common. The FAA needs to take note of this fact. Instead of the seemingly knee-jerk reaction of issuing an AD requiring compliance with a service bulletin, we would suggest the FAA view the service bulletin as a starting point for further research into the problem. There is a real danger that the manufacturers' myopic viewpoint could result in severe safety compromises if simply adopted by the FAA into regulatory actions without due consideration given to the broader aspects of an identified problem. This commenter, Modification and Replacement Parts Association (MARPA) therefore requests the following: 1. That a determination be made whether the defective parts are installed on other aircraft, in particular those manufactured by Israel Aircraft Industries. If so, then consideration should be given to making the airworthiness directive applicable to the Honeywell part rather than the airframe upon which it is installed or, alternatively, to the Honeywell part and the identified airframes. 2. Because there exists at least one know PMA part for a modified fan venturi there also exists the possibility that other PMA parts for the older, unmodified venturi may also exist. In the instant case the PMA holder is also the OEM manufacturer so the parts are numbered identically. This is, however, usually not the case as PMA manufacturers are encouraged, and in some cases required, to identify PMA parts by alternative designations. The applicability language should be modified to also cover possible PMA alternatives rather than just a single part number lest the possibility that a defective PMA part escape the regulatory requirement. 3. The mandated installation of a certain part number is at variance with FAR 21.303 that permits the installation of other (PMA) parts. The language that requires the installation of a certain part number to the exclusion of all other part numbers should be modified to permit installation of PMA equivalent parts. Jack Buster - AD Committee