# N9991F: Helio HST-550A, registration cancelled 1988-08-26

- Type: Cancelled registration (FAA registry, deregistered aircraft)
- Cancelled: August 26, 1988
- Status when cancelled: N-number assigned, not yet registered
- Airframe: [Helio HST-550A](https://openairdocs.org/model/helio-hst-550a) (registry code 4301006)
- Data sheets: [TCDS A4EA](https://openairdocs.org/tcds/A4EA) (OpenAirDocs)
- Serial number: 004
- Type of aircraft: Fixed wing single engine
- Mode S code: ADF693
- The mark today: https://openairdocs.org/aircraft/N9991F
- FAA registry: https://registry.faa.gov/AircraftInquiry/Search/NNumberResult?nNumberTxt=9991F
- Page: https://openairdocs.org/deregistered/N9991F-1988-08-26

From the FAA registry file of November 5, 2026, cancelled registrations. Owners' street addresses are left out. The Mode S code belongs to the N-number, not the airframe.

ADs and bulletins for the Helio HST-550A: https://openairdocs.org/model/helio-hst-550a.md

## NTSB investigations (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB LAX88FA241](https://openairdocs.org/ntsb/LAX88FA241), Jun 30, 1988: Helio HST-550A (N9991F), Perris, CA, destroyed, 1 fatal. Probable cause: FAILURE OF THE ELECTRICAL STABILIZER TRIM CONTROL THAT RESULTED IN AN UNCOMMANDED FULL NOSE DOWN ELEVATOR TRIM COMMAND.

## FAA accident and incident reports (2)

From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [Accident 19880630027299A](https://openairdocs.org/incident/19880630027299A), Jun 30, 1988: Helio HST550A (N9991F), Perris, CA, Destroyed, 1 fatal. Pitch trim in full down position after dropping skydivers. No time to parachute.
- [Incident 19870821062539I](https://openairdocs.org/incident/19870821062539I), Aug 21, 1987: Helio HST550A (N9991F), Davis, CA, 1 fatal. Main chute failed to open after free fall. Reserve deployed too late. Chutist impacted the ground.

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