Parmi les accidents d’avions légers pour lesquels le BEA a ouvert une enquête entre 2019 et 2025, près d’une vingtaine sont attribués, de manière probable ou avérée, aux conséquences d’une évolution prolongée au second régime de vol. Cela représente 4 % des accidents d’avion de masse maximale au décollage inférieure à 2,25 t, en France, sur cette période. Ces accidents constituent toutefois 15 % des accidents mortels et contribuent à 21 % des victimes pour cette catégorie d’aéronef.
Ces accidents surviennent principalement dans deux contextes de vol :

• dans une phase normalement transitoire partant d’une faible vitesse (décollage ou interruption de l’approche ou de l’atterrissage) ;
• lors d’évolutions en région montagneuse.

Contrairement au décrochage, dont les manifestations sont généralement bien identifiées, le passage au second régime peut se faire de manière progressive. Le pilote conserve alors l’impression de maitriser son avion alors même que celui-ci évolue à une incidence élevée, avec un excédent de puissance devenu insuffisant pour accélérer et monter, avec parfois une faible réserve d’énergie.

Le second régime de vol est une notion abordée lors de la formation initiale des pilotes d’avion. Pourtant, les récentes enquêtes ont souvent mis en évidence des situations au cours desquelles les pilotes évoluaient au second régime sans en avoir conscience. Les témoignages recueillis auprès des pilotes montrent que plusieurs d’entre eux n’ont pas identifié qu’ils évoluaient au second régime de vol. Les difficultés rencontrées ont souvent été interprétées comme un manque de puissance moteur et une incapacité de l’avion à monter, sans que le lien avec l’évolution à forte incidence au second régime de vol ait été établi.

La présente étude a pour objectif de :

• rappeler les principales notions théoriques associées aux régimes de vol, les symptômes du second régime de vol et les actions nécessaires pour en sortir ;
• présenter les principaux contextes d’entrée au second régime de vol, les menaces et risques associés, ainsi que les facteurs contributifs les plus courants ;
• proposer des pistes de réflexion sur la formation des pilotes, en présentant les limites des méthodes pédagogiques actuelles au regard des situations réelles d’entrée au second régime de vol.

Certain aircraft are equipped with ballistic parachutes attached to the airframe, allowing them to reach the ground safely in an emergency situation. While some certified aeroplanes are equipped with these systems, they are mostly installed on fixed-wing microlights. Recent investigations have revealed occurrences in which all the circumstances for the parachute to be used seemed to be present, without it being activated by the pilot or a passenger.  

The aim of this study is to gain a better understanding of the (cognitive, emotional and physical) mechanisms involved in the activation or non-activation of a ballistic airframe parachute. 

In the event of depressurisation or smoke, the members of the crew and the passengers may need to use oxygen. For this eventuality, pilots have quick-donning masks at their disposal, stowed in storage boxes on both sides of the cockpit.

The study carried out by the BEA focused on the following subjects:

- the possible mechanisms leading to a fire and a pressurised oxygen leak in or near the oxygen mask storage box;
- the spread of a fire in the presence of a pressurised oxygen leak;
- the possibilities for extinguishing this type of fire;
- the acoustic characterisation of these phenomena.

The fire breakout mechanisms studied included external sources of heat (lithium batteries in electronic devices or glowing cigarettes), internal ignition in the hoses or the ignition of grease and dust in the oxygen-enriched environment.
 

YouTube videos:

• Vidéo Oxygen Fire in cockpit 1/4 Battery tests
• Vidéo Oxygen Fire in cockpit 2/4 Cigarette tests
• Vidéo Oxygen Fire in cockpit 3/4 Extinguisher tests
• Vidéo Oxygen Fire in cockpit 4/4 Propagation tests

The phenomenon of icing of the piston engine induction system is sometimes mentioned in safety investigation conclusions as either a proven or possible cause for a decrease in engine power. This is particularly the case when no other hypothesis is envisaged.

The nature of the phenomenon means that investigators rarely observe it or identify its physical evidence on the wreckage. To justify the use of this hypothesis, when engine data is not recorded and accidents are fatal, the estimated meteorological conditions at the time of the event are generally compared with a "Temperature/Dew Point" graph showing zones corresponding to different levels of icing probability/severity (see Figure 4). Several models of these graphs exist and are widely available.

The BEA's reflections on the legitimacy of this approach in the scope of a safety investigation prompted it to conduct this study. This work naturally led to the industry and the authorities being questioned about their knowledge of this phenomenon and how to take it into account. 

The study focuses on three main areas:
-  bibliographic research focusing on the information available from the various authorities, manufacturers and scientific sites;
-  a test campaign on a powerplant equipped with a Lycoming engine;
-  a measurement campaign on aircraft equipped with Rotax engines, supplemented by measurements on an engine of the same type installed on a test stand.
 

Reduction in engine power at take-off 

Between 2015 and 2019, in France, more than one in ten fatal accident involving small aeroplanes or fixed-wing microlights is due to a reduction in engine power at take-off. This study sets out the main characteristics of these accidents, as observed during the investigations carried out by the BEA.  It describes the probable or proven causes of the power losses as well as the reactions most frequently observed in these circumstances, and the resulting consequences. 

• Scope of the study  
  • Period: 2015 to 2019 
  • Aircraft category: light single-engine aeroplane, fixed-wing microlight 
  • Investigation authority: BEA 

• For more detailed information:  
  • Accident to the ROBIN DR400-180 registered F-GFXE on 28 July 2018 at Charleville-Mézières (investigation report, available in French only) 
  • Accident to the Tecnam P2002 registered F-HOAB on 16 July 2018 at Les Mureaux (investigation report, available in French only) 
  • Accident to the DR400-140B registered F-GBUP on 21 May 2015 at Saint-Laurent-Blangy (investigation report, available in French only) 
  • "Perte partielle de puissance au décollage” (Partial power loss during take-off)
    (FFA basic rule) 
  • Bulletin de sécurité des vols  (Flight safety bulletin)
    (FFPLUM, February 2020) 
  • Avoidable Accidents No. 3 - Managing partial power loss after takeoff in single-engine aircraft
    (ATSB  study) 

Towards the end of the 2000’s, the BEA observed that a number of public

air transport accidents or serious incidents were caused by a problem

relating to “aeroplane state awareness during go-around” (ASAGA). Other

events revealed inadequate management by the flight crew of the

relationship between pitch attitude and thrust, with go-around mode not

engaged, but with the aeroplane close to the ground and with the crew

attempting to climb.

Study concerning glider accidents over French territory between 1999 and 2001. A translation in German is also available.

The Robinson R 22 is a two-blade helicopter well-liked by flying clubs and individuals who find its performance good value for money. This has favoured the rise in the number of R 22s in France since its entry into service. The upsurge of R 22 accidents that occurred in 2000 highlighted the need to update the 1991 study. This new study concerns Robinson R 22 accidents that occurred between 1988 and 2001.

Study concerning the collisions that occurred over French territory between 1989 and 1999 and that involved at least one civil airplane.

1992-1999. Study concerning accidents that occurred during agricultural spraying flights on French territory between 1992 and 1999.

Many pilots use their aircraft in visual flight conditions for their personal and professional trips. The question must be asked, however, as to whether visual flying is best adapted for trips arranged on a long-standing basis for which the pressures and stakes are sometimes determining factors. This study analyses accidents where pilots were trying to reach their destination at all costs.