Major safety issues with grounded aircraft

Picture ANP

Under recent flight bans, airlines have parked their planes galore at airports. For example, KLM transferred a number of Boeing 737s to Groningen Airport Eelde. It also happened during the first flylockdown last year. At the time, planes were even parked on the Aalsmeerbaan near Schiphol.

Now it turns out that big mistakes are made when bringing planes back into the air, which could have led to disaster. One case concerned a Transavia aircraft on 24 April this year after take-off from Rotterdam Airport, the other a TUIfly aircraft on 3 October 2020 at Schiphol. According to the board, both cases are about “serious incidents”.

On one device, the cover for the altimeter tubes on the nose of the device was not removed. This cover is usually applied after a unit has been grounded for some time to prevent the ingress of dirt or insects that interfere with the operation of one of the crucial systems that measure height and speed.


In the second plane, pipes that had been interrupted during parking were not properly secured when the plane was made ready for flight again. The errors first appeared when the planes were in the air; the crew cannot see on the ground whether it is working or not.

In both cases, after take-off, the pilots were given incorrect information about flight altitude and speed, and the captain and co-pilot were shown different data. In the past, similar failures in other circumstances have led to air disasters. Both the Transavia and TUIfly aircraft had to return to the airport immediately. This was successful because the weather was good and the pilots could fly back into sight. The situation would have been different in bad weather or in the dark.

Both the manufacturer Boeing and the European Aviation Authority Easa have in recent months warned that the correct actions must be taken when the aircraft is to be prepared for flight again, following a similar incident with a Boeing 777.

According to Minister Cora van Nieuwenhuizen (Aviation), the Civil Aviation Authority ILT has also previously pointed out to the airlines European guidelines for restarting aircraft that have been on the ground for a long time. “The ILT has recognized the risks posed by this situation and has drawn explicit attention to it in its oversight of maintenance companies and airlines,” the minister wrote to Parliament.

Check again

The Dutch Security Council is now concerned that, despite all these warnings, such errors are more common now that airlines have ‘unpacked’ almost all aircraft again. “Due to the expected increase in the number of flights as a result of the relaxation of corona measures at home and abroad, many aircraft will be made ready to fly again in the coming months. This will lead to an increasing number of non-standard maintenance activities. ”

Therefore, on Thursday evening – before the investigation of both incidents is completed – the Council warned that airlines and maintenance companies will once again inspect aircraft that have run aground in recent months. Normally, no notification is made during the investigation period.

The ‘convincing recommendation’ applies in any case to the Dutch airlines KLM, Transavia, TUIfly and Corendon Dutch Airlines. “We started our own investigation immediately after the incident,” said a spokesman for Transavia, “and measures have been taken to prevent this. The processes have been adjusted and an additional inspection has been carried out on all aircraft that have been parked for a long time. We are also studying the recommendations of the OVV. ”


Clogged altimeters and speedometers have previously led to air disasters. In 1996, two planes crashed because the so-called pitot tubes, which measure the air pressure of one of the systems that measure altitude and speed, were still covered.

In February of the same year, a plane belonging to the German holiday pilot Birgenair crashed with 189 people on board the sea near the Dominican Republic. The pilots lost control of the aircraft in the dark because the security systems provided conflicting misinformation.

The plane had been grounded for 25 days, after which a nest of wasps had ridden in the altimeter. In October 1996, 70 people were killed when an Aeroperu plane crashed into the sea after takeoff. After a wash, I forgot to remove the cover from the altimeter tubes.

Clogged altimeters probably also caused the air disaster with an Air France Airbus in 2009. That unit disappeared across the Atlantic after the altimeters had to be frozen to, possibly after a wrong de-icing operation.

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