Rhoads AUTOGYRO MTO SPORT N574BR

Summary

On 21 May 2018 at about 15:45 local time, a Rhoads AUTOGYRO MTO SPORT registered N574BR, operated by Blue Sky Gyros LLC, was involved in an accident near San Manuel, Arizona, United States. 2 people were on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

21 May 2018 at 15:45

Classification

Accident

Location

San Manuel, Arizona, United States

Nearest airport

San Manuel Airport (E77)

Coordinates

32.6353, -110.6417

Aircraft

Rhoads AUTOGYRO MTO SPORT

Registration

N574BR

Category

Gyrocraft

Year built

2015

Engines

1

Operator

Blue Sky Gyros LLC

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Route

San Manuel → San Manuel

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR18LA158

Nobody was injured.

The fracture of the propeller hub due to corrosion pitting along the propeller blade root seat, which led to cracking that was propagated due to high-cycle fatigue.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The flight instructor reported that he and the student pilot were conducting a familiarization flight. After an uneventful takeoff and when the gyroplane was about 400 ft above ground level, she heard a “loud bang,” followed by severe vibrations and a total loss of engine power. She chose to initiate an emergency landing and turned right back toward the runway and landed uneventfully. During the landing roll, she saw that the gyroplane was on fire. The gyroplane came to a stop, and the fire was extinguished. Examination of the gyroplane revealed that the muffler, coolant line, and both carburetors were either fracture separated or shaken loose. One of the propeller blades and part of the propeller hub were missing, which likely resulted in an imbalance and subsequent severe vibrations and extensive vibration-related damage. One of the propeller blades had impacted a rotor blade. A fuel line was found damaged and open, which likely started the in-flight fire, and the fuselage and horizontal stabilizer exhibited substantial damage. Examination of the propeller and propeller hub components revealed no evidence that the propeller blade fractured before the hub failed. The propeller hub fractured due to fatigue cracking that initiated at a network of corrosion pits along the surface of the propeller blade root seat. The internal tube exhibited a rough surface texture and an approximate 45° slant orientation. Tube material adjacent to the tube fracture had thinned and exhibited deformation in multiple locations. The periphery of the angled root seat exhibited chatter marks on the root of the propeller blade. Based on the characteristics of the fracture surfaces and the chatter marks, it is likely that the fatigue cracks propagated due to high-cycle rotational and vibrational loads from normal propeller operation. Due to the nature of the high-cycle fatigue and the inability to determine the loads and rpms of the propeller during the accident flight, the investigation could not determine exactly when the fatigue cracking initiated. Examination of the corrosion pits found elements in them consistent with common salts. The tight fit of the blade roots against the hub seats could have led to crevice corrosion if moisture and salt had penetrated the area. In addition, contact with some composite components (such as carbon fiber) can create galvanic couples with aluminum, which will become susceptible to preferential corrosion. Based on the evidence, it is likely that the corrosion pitting along the propeller blade root seats led to the initial cracking, which was propagated by high-cycle fatigue. Further, it is likely that the propeller hub design was not adequate because it did account for the repetitive stresses that occur during normal operation.

Quoted verbatim from the NTSB record.