| Tail Number / N-Number | N4121D |
| Manufacturer | HELIO |
| Model | H-391B |
| Year Built | 1957 |
| Manufacturer's Serial Number | 041 |
| Aircraft Type | Fixed wing single engine |
| Category | Land |
| Builder Certification | Type Certificated |
| Number of Seats | 4 seats |
| Weight Class | CLASS 1 (Up to 12,499 pounds gross take off weight) |
| Engine Manufacturer | LYCOMING |
| Engine Model | GO-435C&D SER |
| Engine Type | Reciprocating |
| Number of Engines | 1 engine |
| Horsepower | 260 hp (194 kW) |
| Average Cruising Speed | 117 miles per hour |
| Type of Registrant | Individual |
| Owner Name | SESSIONS JOHN L |
| Street | 1609 S MARGARET AVE |
| City | KIRBYVILLE |
| State | TX |
| Zip Code | 75956-2632 |
| Region | Southwestern |
| County | Jasper County |
| Country | US |
| Fractional Ownership | No |
| Airworthiness Classification | Standard |
| Airworthiness Date | 1957-01-04 |
| Certificate Issue Date | 2012-03-22 |
| Last Action Date | 2020-10-13 |
| Expiration Date | 2028-03-31 |
| Status | Valid Registration |
| Mode S Code | 51157015 |
| Mode S Code Hex | A4DE0D |