Tuesday, 15 November 2011

Aft Pylon - Structural Differences

Aft Pylon

Structurally, the aft pylon on both types was identical with all other variants until about 1968 when United States Marine Corps CH-46s were fitted with beefed up tail sections to better withstand hard landings when under fire in combat zones.  In and of itself the new tail is not spectacular, however the aerodynamic shape of the tail changed from that associated with the Labrador, Voyageur and KV-107s to a more symmetrical shape.  This feature, the original asymmetrical tail is illustrated below.  This is important to know when you go to select a model kit. In the meantime, the picture below will give the reader an idea as to the original shape of the CH-46 tail and that of Labs and Voyageurs.  Once you have selected which variant you will model, careful attention to the details of each aircraft will be necessary...In the Aft Pylon Pages you will note that I have kept the Labradors and Voyageurs separate and that I have tried to put them in chronologically.!

asymetrical   pylon    of    early 46 variants

Screen opening found in a variety of locations on Lab pylons varies widely through the evolution of the Labrador, until they eventually were nearly identical to Voyageurs as a result of several modifications, although the pictures will show some features were always distinctly Labrador...so study the pictures of the individual pages carefully if accuracy is your aim. A Flight Engineer (FE) friend of mine seems to recall that the extra screens on the Labrador, which are on both sides in the same location, were for additional cooling and venting. He speculates that with the extra intake of air, the need to vent that air prevented unwanted pressurization necessitating the large rectangular opening on the aft left side of the Labrador tail. The only problem with this theory is that Swedish helicopters have the same small screens on either side, but the Canadian Labrador is the only variant that has the rectangular opening. He recalls that as our helicopters operated in the hover for long periods and more frequently than most other operators of the H-46 variants it was determined that the extra cooling and venting would mitigate the risk of fumes accumulating in an overheated location that could lead to overheating or possibly fires? All discussion of the tail mounted auxiliary power will be covered in a later blog._

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