Answer
$New\space length\space of\space the\space aircraft = 41.036 m$
Work Step by Step
$Previous\space length\space of\space the\space aircraft = 41 m$
$New\space length\space of\space the\space aircraft = 41 m + 3.6 cm \space (length\space of\space the\space antenna)$
When we are adding two physical quantities both of them should have the same units. Therefore we can convert centimeters into meters and solve the problem as follows.
$3.6 cm = 3.6\times10^{-2} m$
$\space\space\space\space\space\space\space\space\space\space = 0.036 m$
So we can calculate the new length by using the above value,
$New\space length\space of\space the\space aircraft = 41 m + 0.036 m = 41.036 m$
