1.
To talk down someone who is flying an aircraft in an emergency means to give them instructions so that they can land safely.
The pilot began to talk him down by giving instructions over the radio.
PHRASAL VERB : V n P
2.
If someone talks down a particular thing, they make it less interesting, valuable, or likely than it originally seemed.
They even blame the government for talking down the nation’s fourth biggest industry...
Businessmen are tired of politicians talking the economy down.
≠ talk up
PHRASAL VERB : V P n (not pron) , V n P