Charge (heraldry) others, but the most frequently occurring of these are various forms of dragons. The "dragon", thus termed, is a large monstrous reptile with, often, a forked or barbed tongue, membraned wings like a bat's, and four legs. The "wyvern" and "lindworm" are dragons with only two legs. The salamander is typically shown as a simple lizard surrounded by flames. Also notably occurring (undoubtedly owing much of its fame to Napoleon, though it also appears in much earlier heraldry) is the bee. Animals' heads are also very frequent charges, as are the paw or leg ("gamb") of the lion, the wing
Westland Wyvern (and equally troubled) Blackburn Firebrand. Several second-line squadrons also received Wyverns around this time. Total production was 127 airframes with 124 aircraft completed, as the last three Eagle piston-engined airframes, VR138, -139, and -140, were never completed. The first carrier trials were carried out by the first pre-production Wyvern TF.2 aboard on 21 June 1950. Despite this, when the Wyvern S.4 entered service with 813 Naval Air Squadron in May 1953, it had not obtained clearance for carrier operations, this being obtained only in April 1954. The Wyvern was in service with the Fleet Air Arm from 1954 to 1958.