§3.396 and the changes to & 3,383 are intended to cover pressurized cabins from the standpoint of design.

basic loads, fatigue evaluation, and testing. These criteria were developed by using the principles which are applicable to pressurized cabins on transport category airplanes and, therefore, in mary respects the aforementioned provisions are substantially the same as those which apply to transport category airplanes, The record of past powerplant fires on amall airplanes indicates the need for certain inprovenents in the fire protection provisions for such airplanes, particularly with respect to fnel esysten lines and fittings. In this regard, § 3.550 is being amended to require that provisions for flexibility in fuel lines which are subject to internal pressure and axial loading be made by flexible hose assemblies rather than by hose and hose-clamp assemblies which are subject to loosening. In addition, there is being incorporated in & 3,550 a provision which prohibits the use of flexible hose assemblies which might be adversely affected by temperature in locations where high temperatures will exist, With these changes, the provisions of § 3.550 will be consistent with those governing transport category airplanes, The currently effective provisions of 8 3.637 require stutoff means for lines carrying flammable fluids into the engine compartment on multiengine airplanes having a stall speed greater than 70 mph or a weight greater than 6,000 pounds. These provisions are being amplified to set forth specific design criteria, In addition, a new § 3.636 is being added which requires lines and fittings carrying flammable fluids or geses in the engine compartment to be fire resistant, Among other substantive changes being made, there 1a a revision of § 3.122 which reduces the prescribed minimm control speed Vn) applicable to multiengine airplanes with one engine inoperative fron 1,3 Yay to 1.2 Vay. In view of the relatively low all-engines-operating olimb speeds associated with small multiengine airplanes, this change is intended to assure that the all~engines-operating climb speed will be sufficiently above Vo to minimize the probability of Ylight speeds below Vag in the event of an engine failure, Changes are being made to the provisions of & 3.667 to incorporate more up-to-date safety standards with respect to the design and performance of auto-pllot systens, There are included also a few other changes which are leas substantive, or which are editorial or clarifying in nature. . -_ Interested persons have been afforded an opportunity to participate in the making of this anendment (21 _F.R. 9217), and due consideration has been given to all relevant matter presented. In consideration of the foregoing, the Civil Aeronautics Board hereby amends Part 3 of the Civil Air Regulations (1 CFR Part 3, as amended) effective August 12, 1957. - 1. By amending 8 3.75 by deleting paragraphs (c) and (d) and by inserting a new paragraph (c) to read as follows: