Improved ASW version of Wessex HAS.1 with more powerful 1,600 shp NGa.18 Mk.165 Napier Gazelle turboshatft engine. Three prototypes built and 42 conversions from HAS.1. 
During 1965, Rolls Royce bought out the Napier engine company (manufacturers of the Gazelle), which resulted in a shortage of engine spares and subsequent problems with Wessex operations on HMS Bulwark and HMS Kent.
Specifications | |
List of Operators of Westland Wessex HAS.3 | |
| From | Organisation with model Wessex HAS.3 | ||
| 1956 |
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| 1958 |
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| 1961 |
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| Construction Numbers on database of Wessex HAS.3 | ||||||
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Construction Numbers | Help Us | |
| C/N | Year | History | |
wa 8  | 1959 |  XM327 | |
 | wa 9 | 1959 | XM328 |
| wa 14 | 1960 | XM833 | |
wa 15  | 1960 | XM834 | |
| wa 17 | 1961 | XM836 | |
| wa 18 | 1961 | XM837 |
| wa 19 | 1961 | XM838 |
| wa 25 | 1961 | XM844 | |
| wa 30 | 1961 | XM871 | |
| wa 31 | 1961 | XM872 | |
| wa 40 | 1961 | XM919 | |
| wa 41 | 1961 | XM920 | |
| wa 44 | 1961 | XM923 |
| wa 48 | 1962 | XM927 |
| wa 54 | 1962 | XP103 | |
| wa 55 | 1962 | XP104 | |
| wa 56 | 1962 | XP105 | |
| wa 61 | 1962 | XP110 | |
| wa 70 | 1962 | XP137 |
| wa 75 | 1962 | XP142 | |
| wa 83 | 1962 | XP150 |
| wa 86 | 1962 | XP153 | |
| wa 89 | 1962 | XP156 | |
| wa 98 | 1963 | XS119 | |
| wa100 | 1963 | XS121 |
| wa101 | 1963 | XS122 | |
| wa105 | 1963 | XS126 | |
| wa108 | 1963 | XS149 |
| wa112 | 1963 | XS153 | |
| wa239 | 1964 | XT255 | |
| wa240 | 1965 | XT256 |
| wa241 | 1965 | XT257 | |
| wa242 | 1965 | XS862 |