Edit your aircarft.cfg like this:

[fltsim.X+1];//<----------------- X is your last [fltsim...] entry, eg.: whwn 1 --> enter: 2 as X+1
title=Yak38 Blue
sim=ht_yak38
model=
panel=
sound=
texture=52
kb_checklists=Yak-38_Check
kb_reference=Yak-38_Ref
atc_id=52
atc_airline=Marine
atc_flight_number=52
ui_manufacturer="Yakovlev"
ui_type="Yak-38"
ui_variation="- 52"
ui_typerole="SVTOL Jet"
ui_createdby="Harri Thaha"
description=The Yakovlev Yak-38 (NATO reporting name: "Forger") was the Soviet Naval Aviation's only operational VTOL strike fighter aircraft in addition to being its first operational carrier-based fixed-wing aircraft. It was developed specifically for, and served almost exclusively on, the heavy Kiev-class aircraft carriers.