Serious incident to the Cessna - 310 registered N443LT on 20/12/2017 at Toussus-le-Noble (Yvelines)

Investigation progression Closed
Progress: 100%

Cat. 3 investigation report: report concerning an occurrence with limited consequences, based on one or more statements not independently validated by the BEA.

This is a courtesy translation by the BEA of the Final Report on the Safety Investigation published in July 2021. As accurate as the translation may be, the original text in French is the work of reference.

Note: The following information is principally based on statements made by the pilot. This information has not been independently validated by the BEA.


The pilot in training, accompanied by an instructor, took off at 07:57 from runway 25R of Toussus-le-Noble aerodrome for an IFR flight to Tarbes.
The instructor indicated that, during the initial climb in instrument flight conditions and shortly after the transfer to the Paris-Orly frequency, he noted that the alternators were not operating. The instructor announced the electrical failure to the controller, asked to be radar vectored and took back the controls in order to return and land at Toussus-le-Noble aerodrome.

Around 08:05, as the aeroplane was being vectored towards the east in order to return and intercept the localizer path, the pilots noted a total electrical failure: radio contact was lost and the navigation instruments ceased operating.
Using the standby horizon and the compass, the instructor initiated a right turn to approximately align on the final for runway 25 of Toussus-le-Noble aerodrome without getting closer to Paris-Orly airport. Then the instructor started a descent to pass under the cloud layer and find visual flight conditions. The instructor indicated that he had sight of the ground again at an altitude of about 1,900 ft and that he corrected by sight the final approach path to Toussus-le-Noble aerodrome. After manually extending the landing gear, he landed on runway 25R at 08:16.

2.1 Context of the flight

As he wished to go to Tarbes for a professional meeting, the pilot, also owner of the aeroplane, asked his usual instructor to accompany him so he could carry out that flight according to the instrument flight rules (IFR). It was agreed that, during this flight, in order to become familiar with IFR flight, the owner would be the pilot flying in the left seat, guided by the instructor in charge of radio communication and navigation in the right seat.

2.2 Meteorological information

The weather conditions reported by Toussus-le-Noble aerodrome were as follows:  visibility 7 km, FEW at 1,400 ft, OVC at 2,400 ft. Sunrise at Versailles on the day of the serious incident was at 08:42.

2.3 Flight crew
2.3.1 Pilot in training

The owner of the aeroplane, aged 55, held a PPL(A) with a multi-engine piston rating (MEP). He was qualified to fly the Cessna 310 under visual flight rules (VFR) by day only. He did not hold the instrument flight rating.
At the time of the serious incident, he had logged 220 flight hours, of which 60 hours were on type and 3 hours and 40 minutes in the last 3 months, all on type.

He was in the front left seat during this flight.

2.3.2 Instructor

The instructor, aged 54, held a CPL(A) with the following ratings: instrument rating-multi-engine (IR-ME), single engine piston (SEP), MEP, class rating instructor (CRI) and flight instructor (FI) with an IR extension.
He had logged 7,256 flight hours of which 812 hours on MEP class aeroplanes. Within the 12 months preceding the occurrence, he had performed instruction flights on the C310 N443LT for the owner of the aeroplane on 29 March and 28 October 2017.
He was pilot-in-command during the serious incident flight and was in the front right seat.

2.4 Statements
2.4.1 Instructor

He explained that, during the initial climb, he saw that the “Low voltage” light situated above the left wheel was illuminated. He then asked the pilot in the left seat to check the alternator breakers situated on the left side panel and to set the alternator control switches to OFF then ON.
He had good knowledge of the area and the altitudes at which it was possible to descend safely in the Toussus-le-Noble final approach sector.

2.4.2 Aeroplane’s owner

The owner of the aeroplane explained that, on that morning, he had started up the aeroplane’s engines normally and that all the procedures were executed with the alternators correctly positioned on ON and connected to the onboard electrical system.
He had felt significant stress from the moment the electrical failure occurred in instrument flight conditions until he recovered sight of the ground, once they had descended below the cloud layer. Nevertheless, it did not prevent him from performing the appropriate procedures.