diff --git a/schema/cpacs_schema.xsd b/schema/cpacs_schema.xsd
index 972c516..f99a938 100644
--- a/schema/cpacs_schema.xsd
+++ b/schema/cpacs_schema.xsd
@@ -1051,10 +1051,11 @@ cpacs@dlr.de
is defined in a so-called <path>, which is componsed of a list of <step> elements.
The control parameter values for each step are arbitrary floating point values. However, it is strongly recommended to use
- values between -1. and +1., or between 0. and +1. (depending on the type of control surface). The smallest and the largest value implicitly
- define the maximum deflection limits. It is mandatory, that the value “0.” is within the specified range, as this value is treated as
- undeflected and used to specify a “clean” aircraft configuration (e.g. used in the clean aero performance map). It is recommended, but not
- mandatory to specify a <step> with a <controlParameter> of 0. Consequently, no <controlParameter> must be used twice within
+ values between -1 and +1, or between 0 and +1 (depending on the type of control surface). The smallest and the largest value implicitly
+ define the maximum deflection limits. It is mandatory, that the value “0” is within the specified range, as this value is treated as
+ undeflected and used to specify a “clean” aircraft configuration (e.g. used in the clean aero performance map).
+ Furthermore, it it is mandatory for the <step> elements to be sorted in ascending order of the control parameters.
+ It is recommended, but not mandatory to specify a <step> with a <controlParameter> of 0. Consequently, no <controlParameter> must be used twice within
a single <path> definition. Deflection values between two specified steps are handled by linear interpolation.
The following example shows the usage of control parameters within a control surface deflection path definition: