# NTSB LAX90LA187: Hughes 269C, N7441F, Rialto, CA, May 23, 1990

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: May 23, 1990, 11:10 local (18:10 UTC)
- Place: Rialto, CA
- Coordinates: 34.099674, -117.380584 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=34.0997&lon=-117.3806&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report November 23, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 26813
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX90LA187
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/26813/pdf
- Page: https://openairdocs.org/ntsb/LAX90LA187

## Probable cause

IMPROPER MAINTENANCE PROCEDURE BY MAINTENANCE PERSONNEL TO TROUBLESHOOT A REPORTED DEFICIENCY AND THE PILOT'S DECISION TO DEMONSTRATE THE VIBRATION, EXCEEDING THE DESIGN LIMITS OF THE HELICOPTER AND INDUCING GROUND RESONANCE. CONTRIBUTING TO THE ACCIDENT WAS THE LOW NITROGEN CHARGE OF THE LANDING GEAR DAMPERS.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, landing - flare/touchdown
  - landing gear,skid assembly - pressure too low
  - maintenance,pressurizing - improper, company maintenance personnel (cause)
  - aircraft performance,landing capability - other (contributing factor)
- Miscellaneous/other, landing - flare/touchdown
  - design stress limits of aircraft - exceeded, pilot in command
  - in-flight planning/decision - improper, pilot in command (cause)
- Roll over, landing - flare/touchdown

## Analysis

THE HELICOPTER ENCOUNTERED GROUND RESONANCE DURING A MAINTENANCE TEST FLIGHT. THE CFI NOTICED AN UNUSUAL VIBRATION DURING STUDENT TRAINING. THE PILOT SUSPENDED THE TRAINING AND INFORMED MAINTENANCE. THE PILOT THEN ATTEMPTED TO DUPLICATE THE VIBRATION FOR ONE OF THE MAINTENANCE MECHANICS. AFTER TWO UNSUCCESSFUL ATTEMPTS, THE PILOT LANDED THE HELICOPTER ON A SLIGHT SLOPE. AFTER ONE SKID TOUCHED DOWN, THE HELICOPTER BEGAN TO VIBRATE. THE PILOT REDUCED THE THROTTLE AND THE VIBRATION BECAME MORE SEVERE. ACCORDING TO THE PILOT, THE HELICOPTER BEGAN TO DISINTEGRATE.

## Aircraft

- Registration: [N7441F](https://openairdocs.org/deregistered/N7441F-2018-06-08), registration cancelled 2018-06-08, S/N 460487, built 1978 (OpenAirDocs)
- Reported make and model: HUGHES 269C
- Registry model: [Hughes 269C](https://openairdocs.org/model/hughes-269c) (registry code 4470504) (OpenAirDocs)
- Registry engine: [Lycoming HO-360 series](https://openairdocs.org/engine/lycoming-ho-360-series) (registry code 41513, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 460487
- Airframe hours: 2366
- Engines: LYCOMING HIO-360-D1A 190 horsepower reciprocating
- Damage: Substantial damage
- Flight: Part 91
- Registered owner: California Aviation Research
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, April 22, 1990, 87 hours before
- Flight plan: Unknown
- Airport: L67, Rialto

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 42; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--no waivers/lim.; seat: right; flight hours: 6,200 total, 184 in this make and model, 5,873 as pilot in command, 120 in the last 90 days, 100 in the last 30 days, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 270° at 5 knots
- Visibility: 20 statute miles
- Lowest ceiling: none

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19900523017159A](https://openairdocs.org/incident/19900523017159A), May 23, 1990: Hughes 269C, Rialto, CA, Substantial damage. Landing gear dampers were undercharged. Pilot landed one skid first. Shock set off ground resonance. Disintegrated.

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.

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