Salaam
In Ramadan when imam leads witr, he stays silent in 3rd rakat (reads fatiha and surah quietly) and calls taqbeer for qunoot and goes into ruku thereafter. ....is sajda sawh necessary or not?
Your Duas on these blessed nights.
Wa Alaykum Al-Salam
It is Waajib to recite loudly in all three units of the witr of Ramadan and therefore if the Imam by mistake recited quietly in the third unit of the witr of Ramadan then Sijdah of Sahw became necessary and if he forgot to perform the Sijdah of Sahw then it is necessary to repeat the Salah.
It is mentioned in Bahare Shariat with reference to Al-Durr Al-Mukhtaar,
'To recite loudly in the first two units of Fajr, Maghrib and Isha and every unit of the Jumu'ah, Eidayn, Taraweeh and Witr of Ramadan is Waajib upon the Imam.'
It is also mentioned in the same reference,
'If a Waajib is missed by mistake and the Sijdah of Sahw is not performed then it is Waajib to repeat the Salah.'
If the Imam recited quietly on purpose then it is necessary to repeat the Salah and the Sijdah of Sahw will not be enough to compensate for it,
'If the Waajib is missed on purpose then the Sijdah of Sahw will not resolve the fault, rather it is Waajib to repeat the Salah.'
It is a sin to miss a Waajib on purpose and thus in such case repentance is also necessary and Allah knows best.
Faqeer Zahid Hussain Al-Qadiri
20th Ramadan Al-Kareem 1438AH