French to English Tech/Engineering Aerospace / Aviation / Space inversion of oil hoses in helicoptor engine

The owner of a helicopter is seeking the liability of the company who carried out the servicing of the helicopter. The servicing company had inverted the "in" "out" oil hose connections and the owner claims that this caused overheating of the oil causing damage to the engine. The Judge has appointed an expert to carry out an appraisal, giving him the following instructions:

-Examiner à cette occasion les photo prises contradictoirement de l’inversion des deux tuyauteries souples "in" et "out" reliées au moteur et au niveau des raccords d’huile de la cloison pare-feu arrière moteur vers le radiateur et la *bêche* à huile et établir qu’elles ont pu générer une surchauffe induisant la révision prescrite par le constructeur

This is my translation of the paragraph:

-To examine, on this occasion, the photos taken in the presence of both parties of the inversion of the two “in” and “out” hoses connected to the engine and the oil connections of the firewall at rear of engine going to the radiator and the oil reservoir and establish that they could have generated overheating making necessary the maintenance prescribed by the constructor.

I have translated "bêche" by "reservoir" since "spade" appears unlikely and I cannot find any suitable translation for "bêche" in any dictionaries, technical or other.

I would be most grateful for suggestions for this term and remarks concerning my translation of the paragraph. I am a complete novice in this field and have only just realised that oil plays a role in cooling an engine - not just air or water.