Robinson Helicopter R44 accident near East Troy, Wisconsin, May 4, 2018
On May 4, 2018 at about 4:55 pm local time, a 1999 Robinson Helicopter R44, registered N444VH, was substantially damaged in an accident during maneuvering (hover) near East Troy, Wisconsin (East Troy Muni airport). It was an instructional flight under general aviation rules (Part 91). No one was hurt; 2 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A partial loss of engine power for reasons that could not be determined based on the available information, which resulted in impact with terrain and dynamic rollover during the subsequent attempted landing.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 4, 2018 · about 4:55 pm local time
- Place
- East Troy, Wisconsin · East Troy Muni · map
- Type
- Accident
- Injuries
- No one was hurt; 2 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Robinson Helicopter R44 UNDESIGNAT, built 1999 · all R44s on the register
- Registration
- N444VH · registry record · serial 0571
- Damage
- Substantial damage
- Flight
- Instructional flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The flight instructor and pilot receiving instruction were maneuvering to begin practice hovering when the helicopter experienced a lateral vibration. The instructor assumed control of the helicopter and attempted to land; however, the helicopter yawed to the left and both the instructor and pilot applied full right pedal to align the helicopter's nose with its ground track. Shortly thereafter, they heard the low rotor rpm horn and saw the associated warning light illuminate. The helicopter continued to the left, and as they lowered to the ground, the right skid caught on the grass and the helicopter experienced a dynamic rollover, resulting in substantial damage to the main rotor blades and fuselage. Examination of the airframe and engine revealed no preimpact mechanical malfunctions or failures that would have precluded normal operation, and the helicopter had adequate fuel onboard for the flight. Although the weather conditions at the time of the accident were conducive to the formation of carburetor icing at glide and cruise power, the helicopter was equipped with a carburetor heat assist device, which automatically applied or reduced carburetor heat with changes in collective input. The reason for the partial loss of engine power could not be determined based on the available information.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Loss of engine power (partial) during maneuvering (hover) defining event
The NTSB's findings
- Aircraft › Aircraft power plant › (general) › (general) › Unknown/Not determined
Flight instructor
- Certificate: flight instructor, commercial pilot
- Ratings: instructor: helicopter; rotorcraft: helicopter
- Flight time: 1,804.4 hours in all; 1,102.2 in this make and model; 66.3 in the last 90 days; 37.1 in the last 30 days; 1,755.6 as pilot in command; 648.1 on instruments
- Last flight review: August 3, 2016
- Medical certificate: Class 2 (with waivers/limitations)
- Seat: left
- Injury: no injuries
Pilot
- Certificate: commercial pilot
- Ratings: instrument: helicopter; rotorcraft: helicopter
- Flight time: 328 hours in all; 0 in this make and model; 43.5 in the last 90 days; 16.9 in the last 30 days; 2,727 as pilot in command
- Last flight review: November 22, 2017
- Medical certificate: Class 2 (without waivers/limitations)
- Seat: rgt
- Injury: no injuries
The aircraft
- Last inspection: 100-hour inspection
- Maximum gross weight: 2,400 lb
- Seats: 4
- Landing gear: fixed
- Engine: Lycoming O-540 SERIES (piston); 0 hours total
- Operator: Mf Helicopters LLC
The flight
- Flight plan: none
- Runway 18, 2,446 ft by 75 ft
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 280° at 9 knots, gusting 14
- Visibility: 10 statute miles
- Sky: scat at 1,800 ft
- Temperature: 61°F (16°C), dew point 52°F (11°C)
- Altimeter: 29.88 inHg
- Observation at 11:55 am from KBUU, 7 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 2 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
5 documents, released by the NTSB on February 22, 2021. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 (Instructor Pilot) | PDF, 10 pages | View Download |
| 2 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 (Pilot Receiving Instruction) | PDF, 10 pages | View Download |
| 3 | Accident Site Photographs | PDF, 2 pages | View Download |
| 4 | Engine Logs | PDF, 5 pages | View Download |
| 5 | Memorandum of Record for FAA Exam | PDF, 1 page | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.