Transavia B737 at Rotterdam on Apr 24th 2021, we think we are 6500 feet, military radar tells FL110, unreliable speed and altitude on both left and right pitot systems

Last Update: June 3, 2021 / 17:57:56 GMT/Zulu time

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Incident Facts

Date of incident
Apr 24, 2021

Classification
Incident

Flight number
HV-6051

Destination
Alicante, Spain

Aircraft Registration
PH-XRX

Aircraft Type
Boeing 737-700

ICAO Type Designator
B737

A Transavia Boeing 737-700, registration PH-XRX performing flight HV-6051 from Rotterdam (Netherlands) to Alicante,SP (Spain), departed Rotterdam's runway 06 normally, however, on climb out the Mode-S transponder did not transmit any plausible altitude information. The crew soon after takeoff requested to level off, was cleared to maintain 5000 feet. Rotterdam ATC advised they did not receive any altitude information from the aircraft, the crew apparently switched source of the transponder and asked "and now", but ATC again advised still no altitude reading was available. ATC queried about their altitude, the crew reported they "believed" to be at 6500 feet, they were flying on their stand by instruments which they deemed reliable. ATC inquired with military three dimensional radar who informed the aircraft was actually at FL110. The crew decided to divert to Amsterdam and requested runway 06 at Schiphol Airport. On approach to Amsterdam the crew explained they had a normal takeoff from Rotterdam, in the climb they received indications of unreliable airspeed and altitude errors on both captain's and first officer's instruments, they believed their stand by instruments were reliable however. Amsterdam approach also confirmed receiving no altitude readout whatsoever. ATC and crew used another aircraft operating in the vicinity and maintaining FL070 to verify that the aircraft's TCAS indications were still working correctly, the crew reported they were descending through 4400 feet according to their stand by altimeter set to the local QNH, at the time the military radar reported they were at 3200 feet. The crew advised no assistance was needed after landing with the current situation on board. The aircraft landed safely on Amsterdam's runway 06 about 35 minutes after departure from Rotterdam.

A replacement Boeing 737-800 registration PH-HXC reached Alicante with a delay of 2.5 hours.

The occurrence aircraft is still on the ground in Amsterdam about 24 hours after landing. Prior to the occurrence it had last flown on Feb 19th 2021.

On May 11th 2021 the Dutch Safety Board (Onderzoeksraad, DSB) announced, they have opened a short/brief investigation on Apr 29th 2021 stating: "Shortly after takeoff, erroneous altitude and airspeed values were displayed on the captain’s and first officer’s instruments. The crew was able to reach adequate airspeed and altitude by use of standby instruments and decided to divert to Amsterdam Airport Schiphol, where the aircraft made a safe landing."

On Jun 3rd 2021 the DSB reported they are investigating two occurrences, this one as well as Incident: TUI Belgium B738 near Amsterdam on Oct 3rd 2020, unreliable airspeed, where unreliable airspeeds following storage due to the Corona Pandemic had occurred. As result of the investigations so far the DSB stated, that in one case the pitot covers had not been removed, in the other case the pitot pipes had not been properly reconnected, in both cases the crew were able to use visual references outside the aircraft in favourable weather conditions. The DSB stated that EASA well as Boeing had issued warning identifying safety risks of returning aircraft to service after long term storage. The DSB further stated that there is no possibility for flight crews to test the pitot systems prior to departure. The DSB subsequently argues, that the safety risk was known in both occurrences, yet, they did happen. The DSB anticipates that an increasing number of aircraft will be returned to service in the days and months ahead leading to an increase of numbers of non-standard maintenance. The incidents show, that extra attention is needed to address this risk. This is why the DSB issues an interim warning to airlines and maintenance companies of this safety risk.
Aircraft Registration Data
Registration mark
PH-XRX
Country of Registration
Netherlands
Date of Registration
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Airworthyness Category
Legal Basis
Manufacturer
The Boeing Company
Aircraft Model / Type
737-700
ICAO Aircraft Type
B737
Year of Manufacture
Serial Number
Aircraft Address / Mode S Code (HEX)
Maximum Take off Mass (MTOM) [kg]
Engine Count
Engine
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Engine Type
Incident Facts

Date of incident
Apr 24, 2021

Classification
Incident

Flight number
HV-6051

Destination
Alicante, Spain

Aircraft Registration
PH-XRX

Aircraft Type
Boeing 737-700

ICAO Type Designator
B737

This article is published under license from Avherald.com. © of text by Avherald.com.
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