Oleo's are the shock absorbing struts you find on full size aircraft, they make oleo's for model aircraft as well, here's a link to a setfor the TF AT-6 with oleo's, and a set of robart addon oleo's.
[link]http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXES71&P=0[/link]

http://www3.towerhobbies.com/cgi-bin...?&I=LXES33&P=0

The only problem with the TF AT-6, is the gear is so short, that oleo's are almost impossible to fit on it. But robart does make the gear for it.