An account from a naval architect who worked on the Type 23 links flight-deck reinforcement to the change from Sea King to Merlin. The frigate had been designed around the Sea King, but the two helicopters placed their heavy wheel loads at opposite ends despite occupying a similar weight class. Steel reinforcement beneath some flight decks addressed the different load pattern. That experience makes additional flight-deck space for the Type 052DL's larger Z-20 a credible explanation for lengthening the ship. Helicopter compatibility depends on where landing loads enter the hull as well as on overall dimensions and mass.
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Helicopter undercarriage geometry shapes flight decks
The Type 23's move from Sea King to Merlin shows why adapting the Type 052DL for the larger Z-20 involves load geometry as well as helicopter weight.