Category Archives: Aviation Safety

MH370: Chinese ship detects pulse signal in Indian Ocean. How to never lose a black box again?

FDR detector

A Chinese ship involved in the hunt for the missing Malaysia Airlines MH370 in the Indian Ocean reportedly detected an underwater ping like those emitted by the aircraft black boxes.

On Apr. 5, the sonar detector-equipped Haixun 01 picked up an acoustical signal on 37.5 kHz frequency, the same as emitted by the Underwater Locator Beacon of flight recorders.

According to Xinhua news agency, the “ping” was detected at about 25 degrees south latitude and 101 degrees east longitude, within the search area of 88,000 sq. miles in the Indian Ocean to the west of Australia, where aircraft, ships and submarines from 26 nations, are currently searching for any debris from the missing Malaysia Airlines Boeing 777 mysteriously disappeared since Mar. 8.

On the same day the signal consistent with the aircraft black box was picked up, a Chinese patrol plane (most probably an Il-76 deployed to Perth), spotted some floating debris (see image below).

possible debris

At the moment, there is no confirmation that the signal and the pieces are related to the missing MH370.

Lessons Learned

Is there a way to prevent a plane from disappearing from the skies as happened to the Malaysian B777?


Current airplanes make several different kind of services available to passengers: interactive media, movie, games, music, but also Internet and telephone. The latter use satellite channels. This links could be used to stream CVR (Cockpit Voice Recorder) and FDR (Flight Data Recorder) data (or just a subset of flight parameters) or, to reduce transmissions and save much money, simply report the black boxes position (coordinates) to ground stations in real time.

Another option is to make Underwater Locator Beacons more powerful and capable to operate for longer periods (they are currently limited to 30 days).

Then there’s another problem to be addressed: the capability of pilots to switch off all communication and navigation systems to make the plane (almost) invisible to radars. Since we can’t be completely dependent on aircrews to track airplanes wherever they fly, any “new” system should be designed in such a way pilots can’t switch it off.

Top image credit: Reuters


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[Video] Egyptian DHC-5 Buffalo utility aircraft performs belly landing


Quite unusual: an Egyptian Air Force plane is forced to perform a belly landing with extended nose gear.

You don’t see this kind of maneuver every day.

Reportedly filmed on Mar. 24, at an undisclosed airport, the following footage shows a textbook landing of an Egyptian Air Force DHC-5 Buffalo plane.

The transport plane suffered a failure that prevented its main landing gear from extending, forcing the Buffalo to attempt a belly landing.

The emergency ended with minor damage to the fuselage.

Recently we published another video showing an emergency landing on Dry Lake of a B-1B Lancer whose nose gear failed to extend.


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Doppler effect analysis on Satellite pings disclosed MH370′s final route


Even if the aircraft’s crash position could not be determined, Doppler effect analysis on SATCOM pings enabled INMARSAT to determine MH370′s final route over South Indian Ocean until a final, “partial ping,” received 8 minutes after the last known one.

Whereas search for debris from the missing Malaysia Airlines MH370′s Boeing 777 continues in a wide area located about 2,300 kilometers to the southwest of Perth, Australia, INMARSAT released new details to explain how the British satellite telecommunications company was able to exclude the so-called “north route” and focus on the southern one, pointing towards the South Pole.

As already explained on a previous post, hourly SATCOM system pings continued for more than 7 hours since the Loss Of Contact with MH370, until 08.11 AM LT.

Based on the round-trip times of such pings, two arcs made of all the possible positions  located at the same distance from the INMARSAT satellite were drawn.

But it was further analysis, on Doppler Effect, as well as correlation between the “signature” of other B777s, that clearly indicated the aircraft southbound route.

Doppler Effect

The Doppler effect is something we are familiar without even knowing it. The sound of the ambulance’s siren or the train whistle are among the most common examples of how Doppler Effect works: the high pitch of the siren of an approaching ambulance suddenly drops as the vehicle passes you. Even if the source wavelength and speed do not change, movement of the source alters the wavelength and frequency of the sound.

You can use several online tools to calculate the frequency change induced by motion.

Since satellite pings are carried on a radio wave, the sensed wavelength, frequency increase or decrease depending on the fact the aircraft is moving towards or away from the satellite.

The difference between the expected received frequency and the actual measured one due to Doppler Effect is known as Burst Frequency Offset.

By comparing the Burst Frequency Offset due to Doppler on MH370 against the predicted one based on six B777s flying on the same day, INMARSAT could determine close correlation for the southern route and eliminate the northern one.


Here’s an excerpt from UK Air Accidents Investigation Branch (AAIB) release that explains how INMARSAT calculated the route.

As you have heard, an aircraft is able to communicate with ground stations via satellite.
If the ground station has not heard from an aircraft for an hour it will transmit a ‘log on / log off’ message, sometimes referred to as a ‘ping’, using the aircraft’s unique identifier. If the aircraft receives its unique identifier it returns a short message indicating that it is still logged on. This process has been described as a “handshake” and takes place automatically.
From the ground station log it was established that after ACARS stopped sending messages, 6 complete handshakes took place.
The position of the satellite is known, and the time that it takes the signal to be sent and received, via the satellite, to the ground station can be used to establish the range of the aircraft from the satellite. This information was used to generate arcs of possible positions from which the Northern and Southern corridors were established.

In recent days Inmarsat developed a second innovative technique which considers the velocity of the aircraft relative to the satellite. Depending on this relative movement, the frequency received and transmitted will differ from its normal value, in much the same way that the sound of a passing car changes as it approaches and passes by. This is called the Doppler effect. The Inmarsat technique analyses the difference between the frequency that the ground station expects to receive and that actually measured. This difference is the result of the Doppler effect and is known as the Burst Frequency Offset.
The Burst Frequency Offset changes depending on the location of the aircraft on an arc of possible positions, its direction of travel, and its speed. In order to establish confidence in its theory, Inmarsat checked its predictions using information obtained from six other B777 aircraft flying on the same day in various directions. There was good agreement.
While on the ground at Kuala Lumpur airport, and during the early stage of the flight, MH370 transmitted several messages. At this stage the location of the aircraft and the satellite were known, so it was possible to calculate system characteristics for the aircraft, satellite, and ground station.
During the flight the ground station logged the transmitted and received pulse frequencies at each handshake. Knowing the system characteristics and position of the satellite it was possible, considering aircraft performance, to determine where on each arc the calculated burst frequency offset fit best.
The analysis showed poor correlation with the Northern corridor, but good correlation with the Southern corridor, and depending on the ground speed of the aircraft it was then possible to estimate positions at 0011 UTC, at which the last complete handshake took place. I must emphasise that this is not the final position of the aircraft.


Here below is an INMARSAT image which shows the southern tracks for a ground speed of 400 and 450 knots ground speed.


MH370 tracks


Last “Partial” Ping

Noteworthy, INMARSAT collected  evidence of a partial handshake between the aircraft and ground station at 00:19 UTC, 8 minutes since the last acknowledged response. This partial ping is currently being investigated: there are several different theories, including the one that the final handshake was attempted outside of the hourly window, possibly at fuel starvation because of power fluctuations.

At 0115 UTC, when the ground earth station sent the next log on / log off message, no response was sent by the plane, indicating that the MH370 was no longer logged on to the network (because already crashed).

Lessons Learned

1) Pilots have the power to make aircraft almost invisible to radars. This will have to be addressed in some way, with some system capable to track the plane regardless of the aircrew’s willingness.

2) Black Box data have to be streamed via satellite and stored for the shortest time possible (until the next flight, then automatically erased) somewhere (for instance, in a Cloud Network architecture, to save money and have it immediately available, should the need arise).

Image credit: INMARSAT via AAIB

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MH370 contrails possibly spotted by Satellite over Indian Ocean before crash


On Mar. 24, Malaysian PM officially announced that Malaysia Airlines MH370 crashed in southern Indian Ocean, where a satellite might have spotted its contrails.

A large and difficult operation involving both patrol aircraft and ships has been in progress for days in southern Indian Ocean, more than 2,300 kilometers to the southwest of Perth, Australia.

Which “sensor”, antenna or intel provided the hint to determine that the aircraft headed towards the South Pole, instead of following the northern route, is unclear. Anyway, Malaysia’s PM has officially confirmed that the area currently being patrolled is where the aircraft crashed after more than 7 flight hours.

Did the investigator have a look at satellite imagery, looking for some contrails? Maybe. For sure imagery of the visible and infrared channel were used to look for a sign of the “zombie” MH370 flight, as done by a meteorologist, by Tim Vasquez, meteorologist.

Since Mar. 17, in an attempt to find contrails of the missing Boeing 777, Vasquez has published some interesting images of the Indian Ocean on his website Weather Graphics.
Such images, “enhanced to compensate for the dim early morning conditions” were also posted to the Professional Pilots Rumour Network community. PPRUNE users found a signature of what resembled a contrail (barely visible in the top image: left, the feature without annotations, right with measurements and coordinates).

“Analysis of the METEOSAT7 imagery showed that this signature does bear a close resemblance to a typical early morning cloud shadow from a contrail onto the top of a stratified lower middle cloud layer, which given the appearance of double layers and a slightly cold signature on the IR channels appears to be a low overcast altostratus or altocumulus later at about 5 to 10 thousand feet beneath an mid-level inversion. This is in a region with virtually no air traffic, and no published air routes within several hundred miles,” Vasquez explains.

However, considering the limited resolution of the imagery, the signature could also be something else, including noise in the satellite data or the back edge of a cirrus bands type of cloud.

Interestingly, the suspected contrail falls precisely within the search area where satellites and patrol aircraft are concentrating.

Provided this is really a contrail, it would be generated by an aircraft flying a heading of 210° magnetic (track 196°): assuming that the MH370 flew the last few hours with autopilot in heading hold mode of 210°, Vasquez backtracked the contrail in time, back to the western Strait of Malacca, where a turn southbound was started for unknown reason past 2.15 AM LT.

Here’s the track of the MH370 reverse engineered by Vasquez:


Image credit:

Obviously, regardless to whether the one in the satellite is really an MH370′s contrail, the reason for a turn towards the South Indian Ocean remains a mystery. Especially if we consider that the aircraft, until 2:15AM LT, had followed a northern route.

By the way, at the time MH370 was last seen on radar (on radial 295 at 200 nautical miles from Butterworth airbase, Malaysia), the “zombie” Boeing 777 was more or less on the very same position as Emirates 343, a B777-300 from Kuala Lumpur, flying at FL340, 490 KIAS.

An interesting detail to fuel theories that MH370 was using another wide body to escape radar detection. Maybe, until something went wrong.


Image credit: screenshot from

H/T to Guido Olimpio for the heads-up


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New satellite images of possible MH370 debris show object possibly thousand miles away from eventual crash site

Chinese satellite

Search efforts are currently focusing in an area several thousand kilometers to the southwest of Australia and possibly well beyond MH370 endurance.

Fifteen days after MH370 vanished while enroute from Kuala Lumpur to Beijing, no new clues surfaced about the route the aircraft flew past the last known position on radial 295, 200 NM (Nautical Miles) to the northwest of Butterworth airbase.

However, search and rescue forces from 26 countries seem to be focusing on the southern route, rather than the northern one, as if there are details, still unknown to the general public, besides the last SATCOM ping at 08.11AM LT, that may have suggested the investigators to concentrate in the South Indian Ocean.

That part of the world is probably one of the most challenging for a search operation, an area characterized by strong winds and currents, were the ocean bed is between 3,000 and 5,000 meters deep.

On Mar. 18, Chinese satellites spotted possible debris within the 10,500 square nautical miles currently being investigated but the object 22.5 meters long and 13 meters wide was not found by the aircraft dispatched from Australian bases to patrol the area: it could have drifted some hundred miles away or may no longer being floating.

Still, what’s worth a note is the area where the various satellites and maritime patrol aircraft (including a P-8 Poseidon of the U.S. Navy) have been operating in the last few days. Based on the coordinates on China’s satellite imagery (44° 57′ 29” S 90° 13′ 43” E) the slice of Ocean being patrolled is located some 3,130 Nautical Miles from the last known point.


MH370 route

Image credit: Scott Henderson (



The aircraft was last seen on radars at 02:15AM LT near IGREX point. Let’s assume that it immediately turned southbound (something we should rule out since the aircraft would have overflown Indonesia).

When it disappeared from radars, it was flying at 475 Kts. At that cruise speed, it would cover between 2,850 and 3.087 nautical miles (6 hrs and 6,5 hrs) before running out of fuel.

The area where satellites are looking is some hundred miles farther. The aircraft alone could not cover about 5,800 km in 6 – 6.5 hours (that is considered the residual endurance of the Boeing 777 from the last radar contact position) because it would have to fly at a speed exceeding its maximum speed (thus reducing its range, that was calculated basing on the typical cruise speed).

Do investigators believe the pilot set autopilot/speed and altitude hold in such a way to cover a longer distance? Or do they believe the aircraft has crashed northern but pieces drifted towards the Southern Pole?

As said, ocean currents and wind can transport objects many miles away in a direction that may be difficult to predict. According to this interesting piece, by Accuweather, there’s a broad northward current that, theoretically, could bring some pieces closer to Western Australia.

All the articles about MH370 can be read here (scroll down).

MH370 southbound route


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