Date: 19 Feb 98 01:34:02 From: "Rich Duncan" <firstname.lastname@example.org> Organization: gte.net References: 1
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One of the reasons for mounting the engines under the wings is to minimize the possibility of high energy turbine/compressor blade damage occurring to the passenger cabin - and hence the passengers themselves. If you look at passenger airplanes with engines in the plane of the cabin - you will normally not have any passenger seats in the plane of the high energy compressor or turbine sections - this area is relegated to the lavatories and the galleys. On smaller commuter type airplanes the limitations are less stringent although still in place to some extent. As an example there are normally no seats in the plane of the propeller. Another reason to mount engines below and forward of the wing is to allow for gravity flow of fuel to the engines in the unlikely event that all the fuel pumps (electric and engine driven) fail. In the case of all Boeing aircraft (except on the 727-100/200 and recently acquired DC-9/MD-80/MD-90//717-200 and engine #2 on the DC-10/MD-11) the engines will continue to run in this exact situation - although not at full takeoff power. If the engines were mounted above the wings the fuel pumps would be necessary at all times. Also the upper wing mounted engines on the YC-14 were placed not because of noise but to provide additional lift during takeoff and landing - via "coanda effect" (blown flaps). They were a pain to work on due to the placement and a problem due to the hot exhaust blowing on the upper wing skins and upper surface of the flaps. Also in exact opposite to your reasoning, regarding noise, it is quieter in the cabin with the engines under the wing. By the way I had a chance to ride on a VFW Fokker VFW-614 once and I remembered that it had a very noisy cabin and I always worried about the engines in the event of a failure. They also blocked the view from the cabin even more so than a normal low wing design.