diff --git a/sw/simulator/flightModel.ml b/sw/simulator/flightModel.ml
index 279a5f13f9..72de7e5f70 100644
--- a/sw/simulator/flightModel.ml
+++ b/sw/simulator/flightModel.ml
@@ -87,18 +87,50 @@ module Make(A:Data.MISSION) = struct
       Not_found ->
 	failwith (Printf.sprintf "Child 'section' with 'name=%s' expected in '%s'\n" name (Xml.to_string A.ac.airframe))
 
+  let tag_define = fun sect name ->
+    try
+      (ExtXml.child sect ~select:(fun x -> ExtXml.attrib x "name" = name) "define")
+    with
+        Not_found ->
+	      failwith (Printf.sprintf "Child 'define' with 'name=%s' expected in '%s'\n" name (Xml.to_string sect))
+
   let defined_value = fun sect name ->
     try
-      (Xml.attrib (ExtXml.child sect ~select:(fun x -> ExtXml.attrib x "name" = name) "define") "value")
+      (Xml.attrib (tag_define sect name) "value")
     with
-      Not_found ->
-	failwith (Printf.sprintf "Child 'define' with 'name=%s' expected in '%s'\n" name (Xml.to_string sect))
+        Not_found ->
+	      failwith (Printf.sprintf "Child 'define' with 'name=%s' in '%s' has no value\n" name (Xml.to_string sect))
 
   let float_value = fun section s ->
     let x = (defined_value section s) in
     try float_of_string x with Failure "float_of_string" ->
       failwith (sprintf "float_of_string: %s" x)
 
+  (* FIXME: refactor code_unit_scale of tag to pprz.ml *)
+  let code_unit_scale_of_tag = function t ->
+    (* if unit attribute is not specified don't even attempt to convert the units *)
+    let u = try ExtXml.attrib t "unit" with _ -> failwith "Unit conversion error" in
+    let cu = try ExtXml.attrib t "code_unit" with _ -> "" in
+    (* default value for code_unit is rad[/s] when unit is deg[/s] *)
+    try match (u, cu) with
+        ("deg", "") -> Pprz.scale_of_units u "rad" (* implicit conversion to rad *)
+      | ("deg/s", "") -> Pprz.scale_of_units u "rad/s" (* implicit conversion to rad/s *)
+      | (_, "") -> failwith "Unit conversion error" (* code unit is not defined and no implicit conversion *)
+      | (_,_) -> Pprz.scale_of_units u cu (* try to convert *)
+    with
+        Pprz.Unit_conversion_error s -> prerr_endline (sprintf "Unit conversion error: %s" s); flush stderr; exit 1
+      | Pprz.Unknown_conversion (su, scu) -> prerr_endline (sprintf "Warning: unknown unit conversion: from %s to %s" su scu); flush stderr; failwith "Unknown unit conversion"
+      | _ -> failwith "Unit conversion error"
+
+  let code_value = fun section s ->
+    let t = (tag_define section s) in
+    try
+      let coef = try (code_unit_scale_of_tag t) with _ -> 1. in
+      (ExtXml.float_attrib t "value") *. coef
+    with
+        _ ->
+          failwith (Printf.sprintf "Can't convert 'define' with 'name=%s' in '%s' to floating point value\n" s (Xml.to_string section))
+
   let simu_section =
     try section "SIMU" with _ -> Xml.Element("", [], [])
 
@@ -139,12 +171,12 @@ module Make(A:Data.MISSION) = struct
 
   let infrared_section = try section "INFRARED" with _ -> Xml.Element("",[],[])
 
-  let nominal_airspeed = float_of_string (defined_value misc_section "NOMINAL_AIRSPEED")
-  let maximum_airspeed = try float_value misc_section "MAXIMUM_AIRSPEED" with _ -> nominal_airspeed *. 1.5
-  let max_power = try float_value misc_section "MAXIMUM_POWER" with _ -> 5. *. maximum_airspeed *. weight
+  let nominal_airspeed = code_value misc_section "NOMINAL_AIRSPEED"
+  let maximum_airspeed = try code_value misc_section "MAXIMUM_AIRSPEED" with _ -> nominal_airspeed *. 1.5
+  let max_power = try code_value misc_section "MAXIMUM_POWER" with _ -> 5. *. maximum_airspeed *. weight
 
-  let roll_neutral_default = try float_value infrared_section "ROLL_NEUTRAL_DEFAULT" with _ -> 0.
-  let pitch_neutral_default = try float_value infrared_section "PITCH_NEUTRAL_DEFAULT" with _ -> 0.
+  let roll_neutral_default = try code_value infrared_section "ROLL_NEUTRAL_DEFAULT" with _ -> 0.
+  let pitch_neutral_default = try code_value infrared_section "PITCH_NEUTRAL_DEFAULT" with _ -> 0.
 
 
   let vert_ctrl_section = try section "VERTICAL CONTROL" with _ -> Xml.Element("",[],[])