For a landing light you definitely want a "spot" beam, but you need to check the beam angle. This site --
http://www.knots2u.com/HID%20Light.htm -- offers STC landing light kits for dozens of general aviation models and notes, "Bulbs are available in a 16 degree (landing) or a 34 degree (taxi) configuration." So there's your answer--approximate those beam angles and you should be fine. Here's one from a site that I like that ought to work fine --
http://www.superbrightleds.com/morei...ght/1407/3301/ -- but there are lots more as well.