diff --git a/libraries/AP_HAL_SITL/SITL_State.cpp b/libraries/AP_HAL_SITL/SITL_State.cpp
index 4850e40b02..06fe08506f 100644
--- a/libraries/AP_HAL_SITL/SITL_State.cpp
+++ b/libraries/AP_HAL_SITL/SITL_State.cpp
@@ -400,17 +400,18 @@ void SITL_State::_simulator_servos(struct sitl_input &input)
     }
 
     float engine_mul = _sitl?_sitl->engine_mul.get():1;
-    uint8_t engine_fail = _sitl?_sitl->engine_fail.get():0;
+    uint32_t engine_fail = _sitl?_sitl->engine_fail.get():0;
     float throttle = 0.0f;
     
-    if (engine_fail >= ARRAY_SIZE(input.servos)) {
-        engine_fail = 0;
-    }
     // apply engine multiplier to motor defined by the SIM_ENGINE_FAIL parameter
-    if (_vehicle != Rover) {
-        input.servos[engine_fail] = ((input.servos[engine_fail]-1000) * engine_mul) + 1000;
-    } else {
-        input.servos[engine_fail] = static_cast<uint16_t>(((input.servos[engine_fail] - 1500) * engine_mul) + 1500);
+    for (uint8_t i=0; i<ARRAY_SIZE(input.servos); i++) {
+        if (engine_fail & (1<<i)) {
+            if (_vehicle != Rover) {
+                input.servos[i] = ((input.servos[i]-1000) * engine_mul) + 1000;
+            } else {
+                input.servos[i] = static_cast<uint16_t>(((input.servos[i] - 1500) * engine_mul) + 1500);
+            }
+        }
     }
 
     if (_vehicle == ArduPlane) {
diff --git a/libraries/SITL/SITL.cpp b/libraries/SITL/SITL.cpp
index 03ba5f1771..b4541b822d 100644
--- a/libraries/SITL/SITL.cpp
+++ b/libraries/SITL/SITL.cpp
@@ -246,7 +246,7 @@ const AP_Param::GroupInfo SIM::var_info[] = {
     // @Param: ENGINE_FAIL
     // @DisplayName: Engine Fail Mask
     // @Description: mask of motors which SIM_ENGINE_MUL will be applied to
-    // @Bitmask: 0: Servo 1, 1: Servo 2, 2: Servo 3, 3: Servo 4, 4: Servo 5, 5: Servo 6, 6: Servo 7, 7: Servo 8
+    // @Bitmask: 0: Servo 1, 1: Servo 2, 2: Servo 3, 3: Servo 4, 4: Servo 5, 5: Servo 6, 6: Servo 7, 7: Servo 8, 8: Servo 9, 9: Servo 10, 10: Servo 11, 11: Servo 12, 12: Servo 13, 13: Servo 14, 14: Servo 15, 15: Servo 16, 16: Servo 17, 17: Servo 18, 18: Servo 19, 19: Servo 20, 20: Servo 21, 21: Servo 22, 22: Servo 23, 23: Servo 24, 24: Servo 25, 25: Servo 26, 26: Servo 27, 27: Servo 28, 28: Servo 29, 29: Servo 30, 30: Servo 31, 31: Servo 32
     AP_GROUPINFO("ENGINE_FAIL",   58, SIM,  engine_fail,  0),
     AP_SUBGROUPINFO(models, "",   59, SIM, SIM::ModelParm),
     AP_SUBGROUPEXTENSION("",      60, SIM,  var_mag),
diff --git a/libraries/SITL/SITL.h b/libraries/SITL/SITL.h
index 54d9350437..d80f641c5f 100644
--- a/libraries/SITL/SITL.h
+++ b/libraries/SITL/SITL.h
@@ -197,7 +197,7 @@ public:
     AP_Float drift_speed; // degrees/second/minute
     AP_Float drift_time;  // period in minutes
     AP_Float engine_mul;  // engine multiplier
-    AP_Int8  engine_fail; // engine servo to fail (0-7)
+    AP_Int32 engine_fail; // mask of engine/motor servo outputs to fail
 
     // initial offset on GPS lat/lon, used to shift origin
     AP_Float gps_init_lat_ofs;