French investigators are probing an incident in which a Cessna CitationJet passed over a Hop Embraer 170 after suffering an in-flight altitude deviation.

The CitationJet – a 1995 airframe operated by VallJet and registered F-HGPG – was operating a non-scheduled service from Paris Le Bourget to Geneva on 12 January.

It had been climbing through 23,000ft with its autopilot engaged when it suddenly experienced a change in aerodynamic load and an increase in nose-up pitch.

Although the executive jet had been cleared to a cruise altitude of 27,000ft, it reached 28,000ft and “passed over” the Embraer 170 which was en route from Lyon to Caen, says French investigation authority BEA.

CitationJet F-HGPG-c-Valljet

Source: Valljet

BEA states that the CitationJet pitched nose-up and exceeded its assigned altitude

It states that the CitationJet crew reported a failure of altitude and speed indicator, and an erroneous altitude transmission by the transponder of 27,000ft.

Neither of the aircraft received an airborne collision-avoidance system warning.

BEA indicates that the incident occurred in the vicinity of Auxerre but states that no injuries resulted. It identifies the Hop aircraft involved as F-HBXG.