diff --git a/ArduCopter/Copter.h b/ArduCopter/Copter.h
index a19395b6f2..cfaef9245c 100644
--- a/ArduCopter/Copter.h
+++ b/ArduCopter/Copter.h
@@ -915,6 +915,7 @@ private:
     uint32_t perf_info_get_max_time();
     uint32_t perf_info_get_min_time();
     uint16_t perf_info_get_num_long_running();
+    uint32_t perf_info_get_num_dropped();
     Vector3f pv_location_to_vector(const Location& loc);
     Vector3f pv_location_to_vector_with_default(const Location& loc, const Vector3f& default_posvec);
     float pv_alt_above_origin(float alt_above_home_cm);
diff --git a/ArduCopter/Log.cpp b/ArduCopter/Log.cpp
index b8d7fdaebb..06920824c3 100644
--- a/ArduCopter/Log.cpp
+++ b/ArduCopter/Log.cpp
@@ -339,6 +339,7 @@ struct PACKED log_Performance {
     int16_t  pm_test;
     uint8_t i2c_lockup_count;
     uint16_t ins_error_count;
+    uint32_t log_dropped;
 };
 
 // Write a performance monitoring packet
@@ -352,9 +353,10 @@ void Copter::Log_Write_Performance()
         max_time         : perf_info_get_max_time(),
         pm_test          : pmTest1,
         i2c_lockup_count : hal.i2c->lockup_count(),
-        ins_error_count  : ins.error_count()
+        ins_error_count  : ins.error_count(),
+        log_dropped      : DataFlash.num_dropped() - perf_info_get_num_dropped(),
     };
-    DataFlash.WriteBlock(&pkt, sizeof(pkt));
+    DataFlash.WriteCriticalBlock(&pkt, sizeof(pkt));
 }
 
 // Write an attitude packet
@@ -731,7 +733,7 @@ const struct LogStructure Copter::log_structure[] = {
     { LOG_CONTROL_TUNING_MSG, sizeof(log_Control_Tuning),
       "CTUN", "Qfffffecchh", "TimeUS,ThrIn,AngBst,ThrOut,DAlt,Alt,BarAlt,DSAlt,SAlt,DCRt,CRt" },
     { LOG_PERFORMANCE_MSG, sizeof(log_Performance), 
-      "PM",  "QHHIhBH",    "TimeUS,NLon,NLoop,MaxT,PMT,I2CErr,INSErr" },
+      "PM",  "QHHIhBHI",    "TimeUS,NLon,NLoop,MaxT,PMT,I2CErr,INSErr,LogDrop" },
     { LOG_MOTBATT_MSG, sizeof(log_MotBatt),
       "MOTB", "Qffff",  "TimeUS,LiftMax,BatVolt,BatRes,ThLimit" },
     { LOG_STARTUP_MSG, sizeof(log_Startup),         
diff --git a/ArduCopter/perf_info.cpp b/ArduCopter/perf_info.cpp
index 7da62c69f3..e6d499c999 100644
--- a/ArduCopter/perf_info.cpp
+++ b/ArduCopter/perf_info.cpp
@@ -15,6 +15,7 @@ static uint16_t perf_info_loop_count;
 static uint32_t perf_info_max_time;
 static uint32_t perf_info_min_time;
 static uint16_t perf_info_long_running;
+static uint32_t perf_info_log_dropped;
 static bool perf_ignore_loop = false;
 
 // perf_info_reset - reset all records of loop time to zero
@@ -24,6 +25,7 @@ void Copter::perf_info_reset()
     perf_info_max_time = 0;
     perf_info_min_time = 0;
     perf_info_long_running = 0;
+    perf_info_log_dropped = DataFlash.num_dropped();
 }
 
 // perf_ignore_loop - ignore this loop from performance measurements (used to reduce false positive when arming)
@@ -77,3 +79,9 @@ uint16_t Copter::perf_info_get_num_long_running()
 {
     return perf_info_long_running;
 }
+
+// perf_info_get_num_dropped - get number of dropped log messages
+uint32_t Copter::perf_info_get_num_dropped()
+{
+    return perf_info_log_dropped;
+}