Flight from Texas to the Bahamas
The Learjet 60 took off this morning in Austin-Bergstrom and was scheduled to fly to North Eleuthera in the Bahamas. The operator was Aurora Aviation, which operates under the name Upper Jet. There were two crew members and seven passengers on board.
During the flight, the conditions deteriorated. The crew reported moderate turbulence at FL350, altitude deviations of several hundred feet, and ice accretion. Shortly thereafter, precipitation began to fall. The pilots requested a climb to FL370, which the air traffic control approved. However, less than 30 seconds later, the crew reported an uncontrolled descent and initiated a Mayday call.
Tracking data show how quickly the situation developed. Within about a minute, the Learjet lost around 27,000 feet of altitude. At the same time, the speed increased sharply, with the crew even reporting an overspeed condition. Video footage from the ground finally shows the aircraft in an extremely steep descent just before impact.
High-altitude rudder parts found far away
The discovery of large parts of the left vertical stabilizer is particularly important for the investigators. These were discovered in several fragments about two to six kilometers from the actual crash site. This means that at least parts of the aircraft had already detached in the air.
It remains completely unclear whether this loss of structure caused the loss of control or was merely a consequence of it. An aircraft that loses control at very high speed can be subjected to loads that are significantly above the design limits. Turbulence can further increase these loads. It is also conceivable that a technical or structural problem had already occurred beforehand and caused the unusual flight situation.
This exact sequence is now one of the most important questions in the investigation.
Weather and frost at the focus
Weather is a central component of the investigations. There was heavy rainfall and convective activity in the region; other aircraft also reported deviations from weather patterns. The Learjet crew reported ice accretion, turbulence, and precipitation immediately before the accident.
However, the fact that icing was reported does not automatically mean that it was the cause. The Learjet 60 is approved for flights under known icing conditions and has corresponding de-icing systems. However, combinations of icing, turbulence, high altitude, and low aerodynamic reserve can be problematic.
At high altitudes, the usable speed range between low speed and the maximum allowable Mach number is narrower than at lower altitudes. If severe turbulence or significant changes in speed occur there, the situation can quickly become critical.
Overspeed could play an important role
The overspeed reported during the descent flight is particularly noticeable. With a strong nose-down pitch, a jet can accelerate very quickly. If the allowable Mach number or speed is significantly exceeded during this process, the aerodynamic loads increase sharply.
In conjunction with turbulence, this can lead to extreme forces on the elevator and control surfaces. The discovery of the elevator pitch far from the point of impact generally fits such a scenario, but it does not prove it.
The NTSB will therefore, among other things, investigate what speed and flight position existed immediately before the components were torn off and whether there are any indications of overload, material failure, or other damage at the points of rupture.
Difficult salvage of the wreck
The jet struck almost vertically near a heavily trafficked road and residential areas. The aircraft was completely destroyed. Despite the location in a populated area, no people were killed on the ground; one person was injured.
The recovery is proving difficult. The impact left a deep crater that was partially filled with water after heavy rain. Additionally, debris was found on houses’ roofs and far outside the main crash site.
According to maintenance records, a cockpit voice recorder was installed. It was initially unclear whether it could be recovered. A working recorder could provide important clues about warnings, sounds, system conditions, and the crew's communication in the final minutes.
No reliable cause of the accident yet
Despite the striking circumstances, it would be premature at present to definitively attribute the accident to icing, turbulence, or a structural problem. Interactions between several factors are also possible, such as a loss of control with subsequent overspeed and resulting structural overload.
Possible problems with flight control, autopilot, or other systems must also be investigated. In addition, weather data, radar and ADS-B recordings, as well as maintenance records for the aircraft, must be included.
Significance for general aviation
Even though the Learjet 60 is a powerful business jet, several aspects of the accident are relevant to all IFR aviation. This includes, in particular, handling convective weather and icing at high altitude.
Approval for Known Icing does not mean that every form of icing or every weather condition can be flown safely. Likewise, the accident shows how quickly a situation that initially appeared to be under control can deteriorate. There was only a few seconds between the crew’s desire for a different altitude and the complete loss of control.
Conclusion
The crash of the Learjet 60 in Florida currently raises two questions in particular: What caused the extreme loss of control – and when exactly did the structural failure occur?
The combination of icing, turbulence, precipitation, subsequent overspeed, and parts of the altitude rudder that were found far away provide important clues, but no definitive explanation yet.
What will be decisive is whether the rudder failure occurred as a result of an already existing loss of control and high aerodynamic loads, or whether a structural or technical problem triggered the loss of control in the first place.
Until this order is clarified, any definitive attribution of the cause of the accident remains premature.
Source references:
Aviation magazine
