Memory Beta, the wiki for licensed Star Trek content.

STARSHIP
USS Yaan
Class:	Constitution (Achernar subclass)
Registry:	NCC-1762
Affiliation:	Federation Starfleet
Status:	authorized (stardate 5930)

The USS Yaan (NCC-1762) was a Constitution-class Federation heavy cruiser starship of the Achernar-subclass, ordered for construction in the 23rd century, named for the star Yaan.

Construction of Yaan was authorized by the Starfleet appropriation of stardate 5930. (Reference book: Star Fleet Technical Manual)

The stardate given would seem to suggest this ship was ordered during the TAS era. It is not positively known if this vessel was built, only that it was authorized.

Achernar-subclass (Constitution-class mk III class I/class XI cruiser/heavy cruiser starships)
Refit with mk III engines	Bismark • Bonhomme Richard • Challenger • Constellation • Constitution • Defiant • Eagle • El Dorado • Endeavour • Enterprise • Essex • Excalibur • Exeter • Farragut • Hood • Hornet • Intrepid • Kent • Kongo • Lexington • Potemkin • Republic • Saratoga • Valiant • Yamato • Yorktown
Built to mk III specifications	Akagi • Ark Royal • Caspan • Chikuma • Discovery • Forrestal • Kaga • Kitty Hawk • Langley • Littorio • Marseille • Radetsky • Richelieu • Rivoli • Santissima Trinidad • Sirius • Ticonderoga • Victory
Authorized for construction	Achernar • Ahzdar • Alam'ak • Alferaz • Alfr • Androcus • Annobon • Astrad • Behr'ak • Czar'ak • Ekinus • Elohim • Esabl • Eskiis • Galina • Ghar • Ghondr • Hajj • Hiemdal • Horok • Jassan • Jenshahn • Jupiter • Kars • Kasimar • Kep Salu • Kestral • Ketoi • Maat • Mazda • Mengen • Mirazh • Mondoloy • Mongo • Ndele • Oblik • Oomaru • Paegan • Pari • Pelione • Phardos • Pilar • Procyon • Proxima • Qizan • Qual'at • Quindar • Rigil Kentaurus • Salayna • Samaara • Shaandra • Shahr • Sinuiji • Sol • Tajarhi • Tali • Temir • Thelonii • Tholus • Tulan • Tutakai • Xanthii • Yaan • Za'faran • Zaahm • Zindar