ASN Wikibase Occurrence # 145275
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| Date: | Saturday 21 April 2012 |
| Time: | 11:00 |
| Type: |  Robinson R22 Alpha |
| Owner/operator: | Castor Aviation |
| Registration: | N121MR |
| MSN: | 0496 |
| Year of manufacture: | 1985 |
| Total airframe hrs: | 2451 hours |
| Engine model: | Lycoming O-320 A2B |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Destroyed |
| Location: | 12 miles North of Palmer, Matanuska-Susitna Borough, Alaska -
 United States of America
|
| Phase: | Landing |
| Nature: | Training |
| Departure airport: | Wolf Lake Airport, Palmer, Alaska (4AK6) |
| Wolf Lake Airport, Palmer, Alaska (4AK6) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On December 18, 2016, about 11:00 AST (Alaska Standard Time), a Robinson R-22 Alpha helicopter, N121MR, sustained substantial damage during a collision with mountainous, snow-covered terrain about 12 miles north of Palmer, Alaska. The two occupants aboard, the certificated flight instructor seated in the left seat, and the private helicopter pilot seated in the right seat, sustained minor injuries. The helicopter was registered to, and operated by, Castor Aviation Ltd. of Wasilla, Alaska, as a visual flight rules (VFR) instructional flight under the provision of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The flight originated from the Wolf Lake Airport, Palmer, at 10:02 AST.
During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on December 18, the flight instructor stated that he was providing flight instruction to the private pilot who was working towards a commercial helicopter pilot certificate. He added that at the time of the accident, they were practicing pinnacle landings to an area of remote, snow-covered mountainous terrain in the Hatcher Pass Management Area.
The flight instructor said that just before the accident, the private pilot accomplished two successful pinnacle landings to sites situated about 4,200 and 4,600 feet mean sea level (msl). After a third pinnacle landing site was selected, a gravel-covered site on a mountain ridgeline situated about 4,300 feet msl, the private pilot circled the site several times for reconnaissance. He said that while circling, the pair discussed the maneuver, which included a preplanned escape route that was just to the right of the landing site.
The flight instructor said that during the accident approach, while the private pilot was manipulating the flight controls, he confirmed that all cockpit indications were "in the green," no warning lights were illuminated, the manifold pressure was between 20 to 21 inches, and the descent rate was at 150 feet per minute. He reported that as the helicopter neared the site, about 10 to 20 feet above the surface, he realized that it had a steep uphill grade making the site unsuitable for landing. He explained that, as he was getting ready to tell the private pilot to initiate a go-around, the low rotor revolutions per minute (RPM) warning light and horn activated. The private pilot reported that when the low rotor RPM warning light and horn activated, he observed the gauge indicated about 90 percent RPM.
The flight instructor then took control of the helicopter, attempting to maneuver it to the right and towards the predetermined escape route, but it descended and the skids subsequently struck the uneven terrain. He said that after the initial collision, he increased collective pitch and applied right cyclic, but it began to spin to the right, while descending. The helicopter continued to spin, while descending, and it subsequently struck an area of steep, snow-covered terrain. The helicopter then rolled downhill multiple times before coming to rest in an area of steep, snow-covered terrain. Both occupants egressed from the wreckage, a cellular phone was utilized to request rescue assets, and the occupants were extracted from the accident site via a helicopter from a separate operating company.
The helicopter sustained substantial damage to the main rotor system, fuselage, tail boom, and tail rotor system.
The flight instructor reported that there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.
In the recommendation section of the NTSB Accident/Incident Reporting Form 6120.1, the flight instructor reported that to never execute a practice approach to an area you are not 100 percent sure you could land the helicopter to in the event of something happening in the last 25 to 50 feet. He further reported that if the landing surface would have been a bit more suitable, the helicopter might have been able to touch down and then come back up to take the planned escape route.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to maintain main rotor revolutions per minute (RPM) during a pinnacle landing, which resulted in a main rotor stall condition, a loss of control, and a subsequent impact with terrain. A contributing factor was the flight instructor's failure to monitor the main rotor RPM during the pinnacle landing.
Aircraft presumably written off as "damaged beyond economic repair", although the registration N121MR was not cancelled by the FAA until April 4 2018, almost six years later.
Accident investigation:
 |
|
Sources:
1. Accident Number: ANC17LA013 at https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20161219X44123&AKey=1&RType=HTML&IType=LA
2. FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?omni=Home-N-Number&nNumberTxt=121MR
3. http://helihub.com/2012/04/21/21-apr-12-n121mr-robinson-r22a-palmer-us-alaska/
4. http://helicoptersafety.blogspot.com/2012/04/21-apr-12-n121mr-robinson-r22-palmer-ak.html
5. https://en.wikipedia.org/wiki/Wolf_Lake_Airport,_Alaska
History of this aircraft
Other occurrences involving this aircraft
| 18 December 2016 | N121MR | Castor Aviation Ltd | 0 | Hatcher Pass area, 12 miles north of Palmer, Matanuska-Susitna Borough | |
sub |
| Loss of control | ||||||
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 24-Apr-2012 12:34 | gerard57 | Added |
| 24-Apr-2012 17:13 | Geno | Updated [Cn, Operator, Phase, Source, Damage, Narrative] |
| 24-Apr-2012 18:28 | RobertMB | Updated [Time, Aircraft type, Location, Source, Narrative] |
| 10-Oct-2016 16:30 | Dr.John Smith | Updated [Operator, Location, Departure airport, Destination airport, Source, Narrative] |
| 21-Dec-2016 19:28 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 27-Nov-2017 20:35 | ASN Update Bot | Updated [Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative] |
| 03-Sep-2018 21:36 | Dr.John Smith | Updated [Time, Aircraft type, Operator, Other fatalities, Location, Nature, Departure airport, Destination airport, Source, Damage, Narrative] |
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