BEA Note 43.027: Paul Magès warns about hydraulic safety (19 December 1961)

In this document

This typewritten note is addressed by Paul Magès to Mr. Duclos, with copies to Messrs. Clément, Guystant and Louis p. 15. It bears the number BEA 43.027 and was typed on 19 December 1961 by "Etab. MEIGNAN" p. 15.

Objective of the note

Magès wishes to "definitively eliminate all risks, even infrequent ones, of sudden breakdown on the road due to a hydraulic failure" and asks his correspondents to report any "actual cases observed" of which they are aware p. 15.

Origin of the envisaged failures

Two mechanisms are mentioned:

• a sudden rupture of a component, tube or seal, for which it would be necessary to "find a solution to increase their safety factor" p. 15;
• a progressive leak that empties the reservoir, leading to air intake by the pump, the draining of the main accumulator, the breakdown of the vehicle and a risk of destroying the pump p. 15.

Suggested solutions

To prevent this second case, Magès proposes a float switch in the reservoir — comparable to the one used "for truck brake reservoirs" — which would turn on the red brake reserve accumulator lamp in the event of an abnormal drop in level p. 15. He also mentions the usefulness of "a spare can" to allow reaching a garage p. 15. He concludes by asking: "Is this solution not applied in Switzerland on the DS?" p. 15.

The document bears several handwritten annotations: a number "19-12-61" in red, the mention "RH16", an arrow pointing to the title, and above all a large red brace framing the paragraph on the float switch — a likely sign that a reader wanted to highlight this proposal.

Context

The DS, launched by Citroën in 1955, relies on a suspension and hydropneumatic circuit designed by Paul Magès, powering the suspension, brakes, power steering and gear shifting simultaneously. A failure of this single circuit could therefore, in theory, affect several vital functions of the vehicle simultaneously — which explains the attention paid by Citroën engineers to the reliability of this system in the years following its launch.

Archivist's perspective

This note illustrates Magès' constant concern to improve the safety of his invention based on real usage feedback rather than theoretical assumptions — he explicitly asks for "actual cases observed" p. 15. It is likely part of a continuous monitoring process of the hydraulic system, in the same vein as the survey on hydraulic leaks of January 1962, which seems to be a direct echo of this request made a few weeks earlier.

The reference to a practice already "applied in Switzerland" also suggests that some export markets had anticipated this type of warning device, information that Magès is clearly seeking to bring up within Citroën.