20180724014579A

Accident · Substantial damage

FAA accident report · Bell - Hagglund UH-1H · Oakdale, CA · July 24, 2018

Date
July 24, 2018 · 17:30 local
Place
Oakdale, CA
Airport
Oakdale Municipal
Phase of flight
Landing: Touchdown
Operating rules
General operating rules (Part 91)
Operator
X66L
Damage
Substantial damage
Aircraft
N107CH
NTSB investigation
NTSBWPR18LA206
Reported as
Bell - Hagglund UH-1H
Reported engine
Lycoming T53-L-703
People aboard
2
Fatal injuries
0
Other injuries
1
Pilot’s certificate
Commercial pilot
Pilot’s flight hours
11,000 total

From the FAA’s Accident/Incident Data System (AIDS), through its Aviation Safety Information Portal, as reported. The NTSB investigates accidents separately, and its record of an accident is the fuller one. The aircraft is matched to the registry by N-number and event date, checked against the reported make and model; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

What happened

The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.

The accident occurred while repositioning to a new aerial fire fighting assignment for the state fire agency under a cwn contract order. In cruise flight at approximately 500 AGL, the pilot and his passenger reportedly suddenly heard an unusual noise, which grew louder. However, no unusual or increase in normal vibration was reported. The pilot initially diverted to the nearest airport O27, but due to the increase in noise, elected to make an immediate off airport precautionary power on landing into the wind on a grassy hilltop near a ranch house & highway. An EMT passing on the highway, who witnessed and immediately responded to the sceene, stated that the aircraft circled the lz once then touched down and suddenly popped back up in the air 50 ft, spun at least a 360 degree clockwise rotation out of control and then came down hard on its nose, raising a debris / dust cloud. The next day, the pilot was overheard stating to a fire agency investigator, that on approach, when he initially came to a height of aprox 5 ft, the aircraft made an uncommanded climb and then nosed over, and fighting the cyclic, then contacting the ground hard.

The pilot was seated in the left pilots seat, an STC approved PIC seat, and suffered a superficial laceration to his chin.

A non esential passenger, seated in the right pilots seat, was seriously injured, and airlifted from the scene, with fractured T12 cervical vertebrae.

The evidence at the accident site showed that the nose first, and then tail skid, had contacted the ground hard. The cross tubes of the landing gear were spread and collapsed aftward from the skid tubes. The rotor blades had contacted the ground, chopping the battery hatch in half and the upper wsps was completely knocked off. One blade showed the drag brace pulled from the trailing edge and the blade mostly disintegrated, and the other blade showed the pitch horn pulled from its grip, with the blade mostly intact except for damage to the tip section. The transmission was torn from its mounting and tilted to the right front corner of the aircraft at a 45 degree angle.

Detailed examination of the wreckage revealed that the swash plate support had broken free from the gimbal ring, thus disconnecting the main rotor flight controls. The fracture surfaces showed polishing, and the collective sleeve showed significant battering by the gymbal ring bolt heads, at 4 equally spaced abraded areas where they had been contacting the collective sleeve in flight for some time proir to the blade tudden stoppage impact at the accident scene.

As the FAA filed it

THE ACCIDENT OCCURRED WHILE REPOSITIONING TO A NEW AERIAL FIRE FIGHTING ASSIGNMENT FOR THE STATE FIRE AGENCY UNDER A CWN CONTRACT ORDER. IN CRUISE FLIGHT AT APPROXIMATELY 500 AGL, THE PILOT AND HIS PASSENGER REPORTEDLY SUDDENLY HEARD AN UNUSUAL NOISE, WHICH GREW LOUDER. HOWEVER, NO UNUSUAL OR INCREASE IN NORMAL VIBRATION WAS REPORTED. THE PILOT INITIALLY DIVERTED TO THE NEAREST AIRPORT O27, BUT DUE TO THE INCREASE IN NOISE, ELECTED TO MAKE AN IMMEDIATE OFF AIRPORT PRECAUTIONARY POWER ON LANDING INTO THE WIND ON A GRASSY HILLTOP NEAR A RANCH HOUSE & HIGHWAY. AN EMT PASSING ON THE HIGHWAY, WHO WITNESSED AND IMMEDIATELY RESPONDED TO THE SCEENE, STATED THAT THE AIRCRAFT CIRCLED THE LZ ONCE THEN TOUCHED DOWN AND SUDDENLY POPPED BACK UP IN THE AIR 50 FT, SPUN AT LEAST A 360 DEGREE CLOCKWISE ROTATION OUT OF CONTROL AND THEN CAME DOWN HARD ON ITS NOSE, RAISING A DEBRIS / DUST CLOUD. THE NEXT DAY, THE PILOT WAS OVERHEARD STATING TO A FIRE AGENCY INVESTIGATOR, THAT ON APPROACH, WHEN HE INITIALLY CAME TO A HEIGHT OF APROX 5 FT, THE AIRCRAFT MADE AN UNCOMMANDED CLIMB AND THEN NOSED OVER, AND FIGHTING THE CYCLIC, THEN CONTACTING THE GROUND HARD.

THE PILOT WAS SEATED IN THE LEFT PILOTS SEAT, AN STC APPROVED PIC SEAT, AND SUFFERED A SUPERFICIAL LACERATION TO HIS CHIN.

A NON ESENTIAL PASSENGER, SEATED IN THE RIGHT PILOTS SEAT, WAS SERIOUSLY INJURED, AND AIRLIFTED FROM THE SCENE, WITH FRACTURED T12 CERVICAL VERTEBRAE.

THE EVIDENCE AT THE ACCIDENT SITE SHOWED THAT THE NOSE FIRST, AND THEN TAIL SKID, HAD CONTACTED THE GROUND HARD. THE CROSS TUBES OF THE LANDING GEAR WERE SPREAD AND COLLAPSED AFTWARD FROM THE SKID TUBES. THE ROTOR BLADES HAD CONTACTED THE GROUND, CHOPPING THE BATTERY HATCH IN HALF AND THE UPPER WSPS WAS COMPLETELY KNOCKED OFF. ONE BLADE SHOWED THE DRAG BRACE PULLED FROM THE TRAILING EDGE AND THE BLADE MOSTLY DISINTEGRATED, AND THE OTHER BLADE SHOWED THE PITCH HORN PULLED FROM ITS GRIP, WITH THE BLADE MOSTLY INTACT EXCEPT FOR DAMAGE TO THE TIP SECTION. THE TRANSMISSION WAS TORN FROM ITS MOUNTING AND TILTED TO THE RIGHT FRONT CORNER OF THE AIRCRAFT AT A 45 DEGREE ANGLE.

DETAILED EXAMINATION OF THE WRECKAGE REVEALED THAT THE SWASH PLATE SUPPORT HAD BROKEN FREE FROM THE GIMBAL RING, THUS DISCONNECTING THE MAIN ROTOR FLIGHT CONTROLS. THE FRACTURE SURFACES SHOWED POLISHING, AND THE COLLECTIVE SLEEVE SHOWED SIGNIFICANT BATTERING BY THE GYMBAL RING BOLT HEADS, AT 4 EQUALLY SPACED ABRADED AREAS WHERE THEY HAD BEEN CONTACTING THE COLLECTIVE SLEEVE IN FLIGHT FOR SOME TIME PROIR TO THE BLADE TUDDEN STOPPAGE IMPACT AT THE ACCIDENT SCENE.

NTSB investigation

The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.