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ASN Wikibase Occurrence # 59494
Last updated: 21 November 2019
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Date:04-JAN-1991
Time:12:33 LT
Type:Silhouette image of generic R22 model; specific model in this crash may look slightly different
Robinson R22 Beta
Owner/operator:Private
Registration: ZK-HDC
C/n / msn: 1535
Fatalities:Fatalities: 2 / Occupants: 2
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Location:near Hukerenui, Northland -   New Zealand
Phase: En route
Nature:Private
Departure airport:
Destination airport:
Narrative:
On January 4, 1991, at about 1233 local time, a Robinson R22 Beta helicopter, registered in New Zealand as ZK-HDC, broke up in flight during a personal flight near Hukerenui , New Zealand.

Witnesses about 150 meters from the accident site observed the helicopter flying normally between 50 and 100 feet above the ground when they heard a loud noise. Immediately afterward, several items, including the main rotor, separated from the helicopter, and the helicopter descended to the ground and caught fire. The private helicopter pilot and passenger were killed, and the helicopter was destroyed. The pilot had accumulated a total of 213 flight hours, 153 of which were in helicopters and 47 in the R22 helicopter.

The weather at the accident site was determined to be a variable scattered cloud base of 2,500 to 3,000 feet, with visibility in excess of 30 km, and winds from the southwest at 20 to 25 knots. Light or moderate turbulence in the area was considered likely.

The investigation by the New Zealand TAIC found the accident site to the windward side of a row of tall pine trees and downwind of an unobstructed expanse of rolling pasture land. The wreckage of ZK-HDC was located in a flat paddock. The TAIC reported that the left door, pieces of the canopy, the magnetic compass, the passenger's handbag, landing light fragments, and a metal clip (used to retain the rubber boot of the main rotor blade) were among the debris found some 150 meters before to the helicopter's ground impact location. The main rotor blades remained attached to the main rotor head assembly and were located 50 meters north of the burned fuselage. The upper section of the main rotor driveshaft was fractured and exhibited a torsional overload failure. The TAIC reported that it found no significant damage to the leading edge of either main rotor blade, and the blade damage was characteristic of low rotational energy at the time of ground impact.

One blade exhibited evidence of striking the cockpit canopy along a line between a point immediately above the forward upper corner of the right door to a midpoint on the forward edge of the left door's "transparency." The other main rotor blade had rotated about 180 in pitch before it also struck the canopy with its trailing edge. Mast bumping was evident on the pitch stops. The right door was found about 1 meter to the north of the rear end of the tail boom.

The examination of the helicopter's tail rotor driveshaft revealed that it had failed in overload with the tail rotor operating normally when impact occurred. The tail rotor blades had been bent symmetrically at right angles, close to their hubs with no significant damage to their leading edges.

The TAIC found most of the helicopter's instruments and cockpit area damaged by post impact fire; however, examination of the rotor and engine tachometer revealed an impact-captured main rotor speed of 100%, and an airspeed indication of 52 knots. The positions of the collective and throttle could not be established because they were destroyed by fire. The TAIC's examination of the engine and transmission were impeded by fire damage. The examinations revealed no defects that would have led to an in-flight power loss.

The TAIC report discussed the possibility and consequences of abrupt pull-ups and pushovers and low-G maneuvering, citing the R22 Pilot Operating Handbook and RHC Safety Notice "SN-11." However, the report contained no information that suggested that low-G maneuvering was observed by anyone before the accident. The TAIC analysis speculated that the pilot may have been flying low to avoid crosswinds and to look for friends who were driving the same route. As the terrain rose and fell along the flight path, the TAIC suggested that the pilot may have followed the terrain and thus encountered a low-G condition, precipitating the accident.

Sources:

1. https://taic.org.nz/inquiries?SkinSrc=[G]skins/taicAviation/skin_aviation
2. http://www.griffin-helicopters.co.uk/accidentdetails.aspx?accidentkey=42886
3. http://www.rotorshop.com/sir9603.pdf
4. http://www.libertyhelicopters.co.uk/NTSB_Special%20Report/NTSB_R22Reports/Hukerenui_NZ.htm


Revision history:

Date/timeContributorUpdates
10-Apr-2009 23:35 XLerate Added
22-Dec-2011 17:19 Dr. John Smith Updated [Time, Cn, Operator, Phase, Nature, Source, Damage, Narrative]
01-Mar-2015 19:11 Dr. John Smith Updated [Location, Source, Narrative]
18-May-2018 04:22 Ron Averes Updated [Location]

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