"The penalty save was a good moment for me," said Darlow, Newcastle's third-choice goalkeeper standing in for the injured Tim Krul and Rob Elliot.
"You never know in football when your chance will come. Krul and Elliot did an excellent job and now it is my turn to carry on the baton till the end of the season.
"We have to keep going and make sure we avoid relegation."
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Palace had the upper hand in a drab first half, with Darlow keeping out Yannick Bolasie's ferocious volley shortly before the break.
Newcastle looked a different team after the interval with Georginio Wijnaldum pulling the strings and Townsend making darting runs on the right flank.
One such raid produced a free kick in the 58th minute and the former Tottenham midfielder curled an unstoppable shot from 25 metres into the top right corner past visiting goalkeeper Wayne Hennessey.
Newcastle's hard work looked set to be cancelled out after midfielder Moussa Sissoko gifted Palace a penalty in the 70th minute when he handled a Yohan Cabaye corner kick.
The home fans held their breath as Cabaye stepped up and then erupted in joy as Darlow parried the former Newcastle playmaker's tame spot-kick.
"It could be a massive three points and I am glad I played may part," said Townsend.
"It is a huge relief. I was going to shoot the other side of the wall but they had such tall players. I decided to wrong-foot the keeper and it worked out perfectly."
(Writing by Zoran Milosavljevic, editing by Pritha Sarkar)
