\usetypescript[postscript]
\definetypeface[postscript][rm][serif][times][default]
\mainlanguage[de]

\setupbodyfont[postscript,10pt]%\setupinterlinespace[line=9pt]

\setupbodyfontenvironment [postscript] [10pt] [interlinespace=9pt] % text
\setupbodyfontenvironment [postscript] [13pt] [interlinespace=27pt] % chapter

\setuplayout[grid=both]

\def\MyChapter{%
 \switchtobodyfont[rm,13pt]\bf
 \setupinterlinespace % without \setupinterlinespace you get different struts for number and text
% \setuplocalinterlinespace[line=16pt]% <- spurious space between 1. and 2. line (caused by different struts)
% \setupinterlinespace[line=16pt]% <- bodytext interlinespace disturbed
 }

\setuphead[chapter]
[grid=both,style=\MyChapter]



\starttext
\showframe
\showgrid
\showstruts

\chapter{����\par ����\par ����\par ����}

����\par ����\par ����\par ����

\startgridcorrection%[top] % no argument possible!
\switchtobodyfont[rm,13pt] % also wrong interlineskip without grid correction
\snaptogrid\hbox{����\par} % needed to snap in; maybe obsolete, if grid correction argument works
 ����\par ����\par ����
\stopgridcorrection

\stoptext