webViewDidFinishLoad not called for non http:// url schemes

Question

I am trying to load a url scheme for Facebook and place that within a UIWebView as follows:

let fb:NSURL! =  NSURL(string:"fb://feed");
webView.loadRequest(NSURLRequest(URL:fb));

I have set the webView delegate appropriately and have the following functions defined:

func webViewDidFinishLoad(webView: UIWebView) {
    print("hellO");
}
func webViewDidStartLoad(webView: UIWebView) {
    print("hello");
}

These aren't called currently. However, when i change the url to something like "www.google.com" or something of the like the statements are printed.

NOTE: The Facebook feed is successfully loading, it just isn't triggering the didStart or didFinish methods.

Is what I'm trying to do even possible for non http:// url schemes?