More information is emerging about the weekend helicopter crash that killed NBA star Kobe Bryant and eight other people in California. The crash was originally attributed to poor weather and mountainous terrain, but new information indicates that there may be more to the story.
The accident aircraft was a Sikorsky S-76 Spirit helicopter. The S-76 is an executive helicopter designed in the 1970s. The accident aircraft was built in 1991 and originally operated by the State of Illinois until the current owner bought it in 2015 per Aviation-Safety.net. Fans of the old “Airwolf” television show will recognize the S-76.
We know that there were widespread areas of fog and low ceilings along the California coast that morning as the helicopter flew from Santa Ana to Camarillo. The aircraft was on a “special VFR (visual flight rules) flight plan, which requires the pilot to remain clear of clouds and have at least one-mile visibility. Weather reports at nearby Van Nuys airport from around the time of the crash show visibility at about two miles and ceilings as low as 400 feet.
ATC recordings indicate that the pilot was flying low and following roads when the accident occurred. This technique, called pilotage, is rarely used in jet airplanes but is common in helicopters and small airplanes that fly lower and slower. When this technique is combined with low ceilings, it is often termed “scud-running.”
Initially, the assumption was that the helicopter became lost in the fog and low ceilings and inadvertently flew into a mountain. The crash site was in an area of high terrain northeast of Malibu. The technical term for this sort of accident is “controlled flight into terrain” (CFIT).
The assumption that the accident was CFIT was bolstered by the revelation that the accident aircraft was not equipped with TAWS (terrain awareness warning system). TAWS is a generic industry term for devices that were formerly called GPWS (ground proximity warning systems). Modern TAWS uses a database of obstacles and terrain paired with the aircraft’s GPS location as well as radar altimeters to warn pilots about dangerous terrain near their altitude. Back in 2006, the NTSB recommended that helicopters with more than six seats be retrofitted with TAWS.
Despite the possibility of CFIT, radar data indicates that there may be another cause for the crash. FlightRadar24 posted an analysis of the accident aircraft’s radar track and what it shows is not consistent with CFIT.
Rather than flying a consistent speed and altitude up until impact, the radar returns show that the helicopter’s speed and altitude were erratic in its last moments. The aircraft’s downward vertical speed (speed of climb or descent) increased dramatically with two spikes upward where the descent rate slowed at about five seconds before radar contact was lost. When the helicopter disappeared from radar, it was descending at about 5,000 feet per minute.
At the same time, the helicopter’s ground speed (the speed of the aircraft over the ground) increased from about 110 knots (125 mph) to 160 knots (184 mph). The ground speed slowed the same time that the vertical speed spiked. This data is consistent with the ground speed and vertical speed increasing together as the helicopter entered a dive.
While the crash investigators at the NTSB have not reached a formal conclusion, it seems likely that the pilot, who was supposed to keep clear of clouds, inadvertently entered the clouds and became disoriented. With low ceilings and visibility, this would be easy to do. The radar data looks as though the helicopter entered an uncontrolled dive just before it crashed. The technical term for such an accident is “continued flight into IMC (instrument meteorological conditions).”
With local ceilings at about 500 feet, the helicopter would have had to fly very low to keep clear of the clouds. If the pilot entered the clouds or fog and then lost control, he would have had only a few seconds to recover before crashing. If the accident was the result of pilot disorientation rather than CFIT, retrofitting the helicopter with TAWS would have not prevented the crash.
The pilot of the helicopter was Ara Zobayan, per the Daily Beast. Zobayan was a flight instructor and had earned both his commercial helicopter license and instrument rating in 2007. While Zobayan was licensed to fly in the clouds and low visibility, there was was no information on whether he had met currency requirements for recent experience. On a special VFR flight plan, he still would have been required to remain clear of clouds and could have become disoriented as he tried to do so.
The NTSB is still investigating the crash and they will look at many other things in addition to the radar data. The helicopter may have included a cockpit voice recorder (CVR) that will hold clues to the last seconds of the flight. The wreckage will be examined for evidence of mechanical failures that could have caused the accident. Witnesses on the ground will be interviewed and any pictures or videos that might shed light on the crash will be examined.
At the moment, however, it looks likely that the crash was the result of weather and continued flight into IMC that led to pilot disorientation. Flying high-performance aircraft only a few hundred feet above the ground can be very unforgiving. When bad weather is thrown into the mix, the results are all-too-often fatal.
[Updated 1/29/2020 8:49pm to include information on the pilot]