Transavia Boeing 737 Suffers Unreliable Altitude Indicator

On April 24th, a Transavia Boeing 737-700 took off from Rotterdam (Netherlands) for Alicante (Spain). As the aircraft was climbing out of Rotterdam, the crew quickly discovered that the aircraft’s transponder was not properly transmitting altitude information. The crew, estimating that they were flying at 6,500 feet, were told by air traffic control that the military’s three-dimensional radar put them closer to FL110 (roughly equivalent to 11,000 feet.) The aircraft safely diverted to Amsterdam’s Schiphol airport.

Transavia Boeing 737 Suffers Unreliable Altitude Indicator
The aircraft involved was a Boeing 737-700 registered as PH-XRX. Photo: Eric Salard via Wikimedia Commons 

Problems encountered after take-off

On April 24th, an 18-year-old Transavia Boeing 737-700, registered as PH-XRX, was intending to fly from Rotterdam to Alicante as HV-6051 when it encountered problems during its climb from Rotterdam airport’s runway 06.

According to the Aviation Herald, the aircraft’s Mode-S transponder was not transmitting any plausible altitude information. The crew requested to level off and was cleared to maintain 5,000 feet. Rotterdam ATC informed the flight crew that no altitude information was being communicated from the aircraft, despite switching the transponder source.

When asked by ATC about their altitude, the crew reported that they “believed” to be at 6,500 feet. This was based on their stand-by instruments, which they deemed reliable.

However, Rotterdam ATC inquired with the Dutch military, who had three-dimensional radar. The military reported that the aircraft was at FL110- about 4,500 feet higher than the crew’s estimate.

Transavia Boeing 737 Suffers Unreliable Altitude Indicator
The aircraft eventually diverted to Amsterdam from Rotterdam. Photo: RadarBox.com

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Altitude errors and unreliable airspeed

The crew made the decision to divert to Amsterdam, requesting runway 06 at Schiphol Airport. As the aircraft approached Amsterdam, the crew explained that a normal takeoff was performed at Rotterdam, but during the climb, they received indications of unreliable airspeed and altitude errors on both the captain’s and first officer’s instruments (both left and right pitot systems).

As the aircraft continued its approach to Amsterdam, it was also confirmed by the ATC there that no altitude information was being communicated. Another aircraft, operating in the vicinity and maintaining an altitude of FL070, was used to verify that the Transavia 737’s Traffic Alert and Collision Avoidance System (TCAS) indications were working correctly.

Using the aircraft’s standby altimeter set to the local QNH (pressure setting), the crew reported descending through 4,400 feet. The military radar at this time was reporting an altitude of 3,200 feet.

Ultimately, despite the challenges encountered, the aircraft landed safely at Amsterdam Schiphol on runway 06. The entire ordeal, from take-off at Rotterdam to landing at Schiphol, took about 35 minutes.

A replacement aircraft, Boeing 737-800, registered as PH-HXC, was deployed to continue the journey. It reached Alicante with a delay of two and a half hours.

Transavia Boeing 737 Suffers Unreliable Altitude Indicator
The aircraft has been primarily based in Rotterdam, flying most often to Faro (Portugal) and Alicante in Spain. Photo: RadarBox.com

Two months of inactivity

Before the incident, the 737-700 had been inactive for some time. According to RadarBox.com, PH-XRX’s most recent flight before the incident was back in late February. The jet had flown from Tangier (Morocco) to Rotterdam on February 19th before its lengthy two-month stay on the ground.

Transavia Boeing 737 Suffers Unreliable Altitude Indicator
The activity graph for PH-XRX over the past year. Photo: RadarBox.com

With so much time spent inactive, this may have been a contributing factor in getting the aircraft back into service. Indeed, some commenting on the incident have suggested time in storage as a factor. It will be interesting to see what results from a full investigation will produce.

Let us know your thoughts on this incident by leaving a comment.

Simple Flying contacted Transavia for more information. However, no response was received at the time of publication.

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