diff --git a/ArduPlane/ArduPlane.cpp b/ArduPlane/ArduPlane.cpp
index b1328674a3..2b7a6f60b2 100644
--- a/ArduPlane/ArduPlane.cpp
+++ b/ArduPlane/ArduPlane.cpp
@@ -340,11 +340,12 @@ void Plane::one_second_loop()
 void Plane::log_perf_info()
 {
     if (scheduler.debug() != 0) {
-        gcs_send_text_fmt(MAV_SEVERITY_INFO, "PERF: %u/%u %lu %lu\n",
+        gcs_send_text_fmt(MAV_SEVERITY_INFO, "PERF: %u/%u Dt=%u/%u Log=%u\n",
                           (unsigned)perf.num_long,
                           (unsigned)perf.mainLoop_count,
-                          (unsigned long)perf.G_Dt_max,
-                          (unsigned long)perf.G_Dt_min);
+                          (unsigned)perf.G_Dt_max,
+                          (unsigned)perf.G_Dt_min,
+                          (unsigned)(DataFlash.num_dropped() - perf.last_log_dropped));
     }
 
     if (should_log(MASK_LOG_PM)) {
diff --git a/ArduPlane/Log.cpp b/ArduPlane/Log.cpp
index e53b403e4b..b96f1b54db 100644
--- a/ArduPlane/Log.cpp
+++ b/ArduPlane/Log.cpp
@@ -198,6 +198,7 @@ struct PACKED log_Performance {
     uint16_t main_loop_count;
     uint32_t g_dt_max;
     uint32_t g_dt_min;
+    uint32_t log_dropped;
 };
 
 // Write a performance monitoring packet. Total length : 19 bytes
@@ -209,9 +210,10 @@ void Plane::Log_Write_Performance()
         num_long        : perf.num_long,
         main_loop_count : perf.mainLoop_count,
         g_dt_max        : perf.G_Dt_max,
-        g_dt_min        : perf.G_Dt_min
+        g_dt_min        : perf.G_Dt_min,
+        log_dropped     : DataFlash.num_dropped() - perf.last_log_dropped
     };
-    DataFlash.WriteBlock(&pkt, sizeof(pkt));
+    DataFlash.WriteCriticalBlock(&pkt, sizeof(pkt));
 }
 
 struct PACKED log_Startup {
@@ -229,7 +231,7 @@ void Plane::Log_Write_Startup(uint8_t type)
         startup_type    : type,
         command_total   : mission.num_commands()
     };
-    DataFlash.WriteBlock(&pkt, sizeof(pkt));
+    DataFlash.WriteCriticalBlock(&pkt, sizeof(pkt));
 }
 
 struct PACKED log_Control_Tuning {
@@ -424,7 +426,7 @@ void Plane::Log_Arm_Disarm() {
         arm_state               : arming.is_armed(),
         arm_checks              : arming.get_enabled_checks()      
     };
-    DataFlash.WriteBlock(&pkt, sizeof(pkt));
+    DataFlash.WriteCriticalBlock(&pkt, sizeof(pkt));
 }
 
 void Plane::Log_Write_GPS(uint8_t instance)
@@ -477,7 +479,7 @@ void Plane::Log_Write_Home_And_Origin()
 const struct LogStructure Plane::log_structure[] = {
     LOG_COMMON_STRUCTURES,
     { LOG_PERFORMANCE_MSG, sizeof(log_Performance), 
-      "PM",  "QHHII",    "TimeUS,NLon,NLoop,MaxT,MinT" },
+      "PM",  "QHHIII",  "TimeUS,NLon,NLoop,MaxT,MinT,LogDrop" },
     { LOG_STARTUP_MSG, sizeof(log_Startup),         
       "STRT", "QBH",         "TimeUS,SType,CTot" },
     { LOG_CTUN_MSG, sizeof(log_Control_Tuning),     
diff --git a/ArduPlane/Plane.h b/ArduPlane/Plane.h
index a52a734944..55af69d48e 100644
--- a/ArduPlane/Plane.h
+++ b/ArduPlane/Plane.h
@@ -706,6 +706,9 @@ private:
 
         // number of long loops
         uint16_t num_long;
+
+        // accumulated lost log messages
+        uint32_t last_log_dropped;
     } perf;
 
     // Camera/Antenna mount tracking and stabilisation stuff
diff --git a/ArduPlane/system.cpp b/ArduPlane/system.cpp
index 9c7d9d1424..6afe0f6266 100644
--- a/ArduPlane/system.cpp
+++ b/ArduPlane/system.cpp
@@ -637,6 +637,7 @@ void Plane::resetPerfData(void)
     perf.G_Dt_min       = 0;
     perf.num_long       = 0;
     perf.start_ms       = millis();
+    perf.last_log_dropped = DataFlash.num_dropped();
 }