Read this:
http://uk.news.yahoo.com/5/20090423/...d-870a197.html
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The nosecone can be a sensitive part of the plane protecting the radome. It is streamlined (hence the cone) so it's not a problem as air flows by however when a larger object hits the cone head one. It can crumple slightly or at worst what's happened here the metal has broken and the radome is exposed.
As far as i know though the plane is still airtight and there is no decompression at all. It is just a small cell at the front containing the signal receiver for the radar.