Three separate fatal accidents in the past six weeks have involved catastrophic in-flight break-ups of Robinson R44 helicopters — the latest in a series of similar crashes that have plagued the industry for decades.
The first of these recent accidents occurred on June 19 near Bluestem, Washington, killing pilot Ryan Sandvig and passenger Mark Manteuffel. According to a preliminary report from the U.S. National Transportation Safety Board (NTSB), the R44 was being ferried from Seattle to Coeur d’Alene, Idaho, when it crashed in open, hilly terrain in clear weather. The tail rotor assembly and approximately two feet of the tail cone were separated from the helicopter and found about 340 feet (a little over 100 meters) away from the fuselage.
The second accident took place on July 11 off the Hawaiian island of Kaua‘i, claiming the lives of pilot Guy Croydon and passengers James Quintua and Amy Nichole Ruark Quintua. The helicopter was being operated as a doors-off sightseeing flight by Aloha Helicopter Tours, doing business as Ali’i Air Tours, when it broke apart in flight and fell into the ocean off Kauai’s Na Pali Coast.
According to the NTSB’s preliminary report on the accident, released last week, witnesses hiking on the Kalalua Trail along the coast reported that strong, gusty wind conditions prevailed at the time of the crash, around 1:05 p.m. local time. The witnesses told investigators that they were hit by a “huge” and sudden gust of wind, which was followed by a very loud “bang” noise.
“As their attention was drawn to the source of the loud noise, they saw the helicopter wreckage freefalling into the ocean in two sections, a main fuselage section, and the tail boom section,” the report states. “The witnesses said that the helicopter wreckage sank moments after striking the water, about one quarter of a mile offshore.”
A comprehensive underwater search by the U.S. Coast Guard using side scan sonar technology was not able to find the main fuselage, but ultimately located the severed tail boom section in about 77 feet of water.
The third accident, on July 28, involved an R44 operated by SGC Saga Aviation, which crashed into a rice field in Yanagawa City, Fukuoka Prefecture, Japan. According to local news reports, a pilot and mechanic were killed in the crash, but their identities were not immediately released.
Few official details are available at this time regarding the accident, which is under investigation by the Japan Transport Safety Board.
Helicopter tail strikes can happen for multiple reasons, including low rotor RPM and inappropriate control inputs. In Robinson helicopters — which are among the most popular and widespread helicopters thanks to their relative affordability — tail strikes are often associated with low G mast bumping, something that Vertical has covered extensively in the past.
Low G mast bumping is a phenomenon that afflicts two-bladed main rotor systems like those on Robinson helicopters, which are designed in such a way that when one blade flaps up, the other flaps down. In low G conditions — which can occur in turbulence or if a pilot abruptly noses the aircraft over after a climb — the weight of the fuselage can become momentarily unloaded from the rotor disc, and the fuselage may experience a rapid roll to the right due to aerodynamic phenomena.
If the pilot responds with a left control input while the rotor system is still unloaded, the rotor disc may tilt excessively relative to the fuselage. This can result in the hub of the rotor system “bumping” the mast, and the blades flapping down enough to slice through the tail boom or cabin — almost always with fatal results.
Last year, Robinson introduced a new horizontal stabilizer design intended to reduce the rolling moment in low G conditions and make pilot-induced mast bumping events less likely (as Vertical explained in detail here). As of May 2024, the new design has been certified for all models of Robinson helicopters — R22, R44, and R66 — and is now standard on all newly manufactured aircraft. It is also available as a retrofit kit at a discounted price, but the modification is not mandatory. While all three R44 helicopters involved in the recent in-flight break-ups had the legacy empennage design, it is too soon to know whether that had any bearing on the accidents. The NTSB aims to complete most accident investigations within 12 to 24 months, but can sometimes take longer to issue its final reports.
