History of Flight
On December 29, 2014, at 1025 eastern standard time, a Robinson R22 Beta, N771MM, was substantially damaged when it impacted terrain while performing an autorotation near Palm Beach County Park Airport (LNA), Lake Worth, Florida. The flight instructor (CFI) was fatally injured, and the student pilot sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which departed about 0940. The flight was operated by Palm Beach Helicopters, Inc., and was conducted under 14 CFR Part 91.
A witness, a CFI who was taxiing an airplane, reported hearing the accident helicopter announce its position on a right base leg with the intent to conduct an autorotation to taxiway Bravo. The witness offered to hold to allow more room. Shortly after, he observed the helicopter enter a rapid descent from between 800 and 1,000 feet above ground level (agl). About 500 feet agl, the helicopter seemed to level off, then pitched abruptly nose-down and descended to ground contact. Just prior to impact, he heard a panicked, mostly unintelligible radio transmission from the helicopter. He believed the CFI onboard was conducting all radio transmissions.
Another CFI, taxiing a helicopter with a student, heard the accident helicopter transmit, "we're going in the grass" over the airport's common traffic advisory frequency. An airplane then reported a helicopter down, and the CFI flew to the accident site to assist.
In a statement two days after the accident, the student pilot recounted that he and the CFI were practicing autorotations following a simulated engine failure. He could not recall who initiated the autorotation. About 100 feet agl, the CFI said, "We're going down, we're going down," and at that time the CFI was controlling the helicopter. The student added, "I don't know if the engine cut off, or the engine didn't turn back on."
In a subsequent interview two weeks later, the student stated the flight was Lesson 2 in Stage 3 of the school's private pilot training course. He recalled that he and the CFI had been flying for about 40 minutes and had conducted two or three steep approaches and a maximum-performance takeoff. The accident autorotation was the first of the flight. He remembered that the CFI was controlling the helicopter as it descended through about 100 feet agl, and as the CFI rolled on the throttle to recover, there was no response from the engine. The CFI then said, "We're going down, we're going down." He also observed the CFI using his cell phone on the downwind leg, appearing to be conducting a video call, and turning the phone to show the outside view. He could not recall when the CFI discontinued using the phone.
In a written statement after the interview, the student recalled that the CFI asked for the controls on the downwind leg prior to entering the autorotation. He handed over the controls and looked south out his door. He then saw the CFI "fighting with the cyclic and collective."
Surveillance video from a nearby building captured approximately the last 2 seconds of the flight before impact, showing the helicopter descending rapidly at a steep angle.
Personnel Information
The CFI held commercial pilot and flight instructor certificates with ratings for rotorcraft-helicopter and instrument helicopter, as well as an airframe and powerplant mechanic certificate. His most recent FAA first-class medical certificate was issued in March 2014. He had about 397 total flight hours, with about 280 hours in the accident helicopter make and model, and about 121 hours of flight instruction given.
The student held an FAA second-class medical and student pilot certificate issued in December 2012. He reported about 37 total flight hours, all in the accident helicopter make and model.
Aircraft Information
The helicopter, manufactured in 1996, was equipped with one Lycoming O-360 series, 145 hp reciprocating engine. The most recent 100-hour inspection was completed on December 1, 2014, at which time the airframe had 4,162.9 hours total time and the engine had 1,978.7 hours since overhaul. The 2,200-hour inspection was completed on February 13, 2013 at a total airframe time of 2,184.2 hours.
Meteorological Information
The 0953 automated weather observation at PBI reported wind from 180 degrees at 7 knots, visibility 10 miles, scattered clouds at 2,100 ft, temperature 26°C, dew point 22°C, and an altimeter setting of 30.13 inches of mercury. A carburetor icing probability chart indicated the potential for serious carburetor icing at glide power.
Wreckage and Impact Information
The helicopter came to rest on its left side in a grassy area about 700 feet northwest of the runway 15 threshold at LNA. The wreckage path was oriented approximately 140 degrees magnetic and extended about 75 feet from the initial impact point. The initial impact was a large metal stake about 3 feet high. The second impact point was a small crater about 4 feet long and 1 foot deep, about 15 feet past the initial point, containing a portion of the forward skid crosstube. The vertical stabilizer, horizontal stabilizer, and part of the tail rotor were next to the crater. The tail boom separated from the fuselage and fractured into several pieces, some with main rotor blade contact signatures. The skids separated and fractured. The fuselage exhibited downward crushing, and the cabin was fractured aft of the seat structures. Both fuel tanks were intact and contained fuel; fuel caps were secure. Fuel vent tubes were separated from the auxiliary tank by impact. The main rotor remained attached; one blade was bent up with chordwise creases, the other bent up about 45 degrees near its root. Neither blade had significant leading edge damage. The tail rotor drive shaft separated, with a 5-foot portion found about 500 feet west of the main wreckage; the aft portion was not recovered.
Flight control continuity was confirmed from the cockpit to the main rotor system. Tail rotor control continuity was established from the cockpit to the intermediate flex coupling. The main rotor gearbox rotated smoothly, with no anomalies. V-belts, sheaves, overrunning clutch, and tail rotor gearbox showed no anomalies. The engine remained attached; the mixture control wire was impact-separated. The carburetor heat control was bent and in the off position. The carburetor air box was partially crushed, and the heat slider valve was in a mid-travel, partially open position. The carburetor remained attached; the throttle control arm was about 1/8 inch from full throttle. The exhaust system was partially crushed. Spark plugs showed normal wear. The engine was rotated by hand, thumb compression obtained on all cylinders, crankshaft continuity established. Oil was added, and the engine started, accelerated, and ran continuously for several minutes using onboard fuel. A magneto check showed no anomalies. The carburetor fuel bowl contained blue liquid consistent with 100LL aviation fuel, no contamination, internal components undamaged, and the fuel inlet screen was free of debris.
Additional Information
Cell Phone Information
The CFI's cell phone was retained for examination but was passcode-protected and could not be unlocked. Usage records from the cellular service provider could not conclusively determine whether the phone was in use at the time of the accident.
Practice Autorotations
According to the flight school's pilot training syllabus, Stage 3, Lesson 2 objectives included advanced maneuvers such as autorotation to a power recovery. The student's training record indicated he completed Stage 2 on December 23, 2014. Instructor notes from December 22, 2014, stated, "gap in training is evident in proficiency, basic straight [and] level unsatisfactory, [aeronautical decision making] needs work, approaches need work."
The flight school specified that all 180-degree and straight-in autorotations be terminated with a power recovery throughout private pilot training. All landings and practice autorotations were to be performed to a hard-surfaced runway or taxiway.
The school's written procedures for a straight-in autorotation with power recovery described initiating the maneuver at 700 feet agl, applying carburetor heat, lowering the collective fully, and rolling the throttle to full idle, holding it firmly against the stop. About 40 feet agl, recovery was initiated by applying aft cyclic to a skids-level attitude held for 3 seconds before entering a flare, then cracking the throttle open, applying forward cyclic, and raising the collective to a hover about 5 feet agl. The guide stated, "Make an IMMEDIATE power recovery if the following conditions do not exist through 100' AGL: Aircraft aligned with touchdown point; Rotor RPM in the green; Airspeed within +/- 5 [knots] of 65 [knots]; Rate of descent <1,500 fpm."
The manufacturer's Pilots Operating Handbook outlined a procedure for practice autorotation with power recovery, including adjusting carb heat, lowering collective to down stop, adjusting throttle for small needle separation, keeping rotor RPM in green arc, airspeed 60-70 KIAS, beginning cyclic flare at about 40 feet AGL, and at about 8 feet AGL applying forward cyclic and raising collective.
Robinson Helicopter Company Safety Notice SN-38, "Practice Autorotations Cause Many Training Accidents," stated: "There have been instances when the engine has quit during practice autorotation. To avoid inadvertent engine stoppage, do not roll throttle to full idle. Reduce throttle smoothly for a small visible needle split, then hold throttle firmly to override governor. Recover immediately if engine is rough or engine RPM continues to drop."
Safety Notice SN-24, "Low RPM Rotor Stall Can Be Fatal," described rotor stall as similar to airplane wing stall, occurring due to low rotor RPM, and stated that recovery becomes virtually impossible even with full down collective.
FAA publication P-8740-71, "Planning Autorotations," concluded that the number one error in practice autorotations is the flight instructor's failure to take control and terminate the maneuver before it becomes unrecoverable.
Medical and Pathological Information
An autopsy of the CFI performed by the Office of the District Medical Examiner, District 15, Palm Beach County, Florida, identified the cause of death as blunt force injuries. Toxicological testing by the FAA Bioaeronautical Sciences Research Laboratory was negative for carbon monoxide, ethanol, and all tested-for drugs and their metabolites.