# Incident 20010725019489I: Hughes 500N, Los Angeles, CA, July 25, 2001

- Type: FAA incident report (Accident/Incident Data System), as reported
- Date: July 25, 2001, 02:00 local time
- Place: Los Angeles, CA
- Airport: Los Angeles International
- Phase of flight: Forced/Precautionary Landing
- Operating rules: General operating rules (Part 91)
- Location: 33.9500° N, 118.4111° W: From the FAA
- Nearby events: https://openairdocs.org/map.md?lat=33.9500&lon=-118.4111&mi=10
- Aircraft: N953SD, a cancelled registration (https://openairdocs.org/deregistered/N953SD-2005-03-02) (OpenAirDocs)
- Registry model: Mcdonnell Douglas Helicopter 500N (registry code 3027374, https://openairdocs.org/model/mcdonnell-douglas-helicopter-500n) (OpenAirDocs)
- Registry engine: Allison 250-C20 series (registry code 03020, https://openairdocs.org/engine/allison-250-c20-series) (OpenAirDocs)
- Reported make and model: HUGHES 500N
- Pilot flight hours: 1,700 total, 1,000 in this make and model, 240 in the last 90 days
- NTSB investigation: [NTSB LAX01IA262](https://openairdocs.org/ntsb/LAX01IA262) (OpenAirDocs)
- FAA source: FAA Aviation Safety Information Portal (https://asip.faa.gov/)
- Page: https://openairdocs.org/incident/20010725019489I

## Narrative

As the FAA filed it, in capitals; the FAA replaces private details with ^PRIVACY DATA OMITTED^.

(-23) SEE ATTACHED PILOT STATEMENT FROM DEPUTY SINCLAIR, THE PIC FOR THIS FLIGHT. THIS INVESTIGATION CONTINUES AS OF THIS DATE.  HOWEVER A SDR WAS SUBMITTED. PILOT'S STATEMENT: SHORTLY AFTER TAKEOFF FROM THE LAX WEST HELIPADS, AND EXTREMELY LOUD SQUEAL AND SEVERE HIGH-PITCHED VIBRATION WAS HEARD/FELT IN THE AIRFRAME.  A "BUZZ" WAS FELT IN THE ANTI-TORQUE PEDALS.  ALTITUDE WAS APPROXIMATELY 300' AND AIRSPEED WAS 60 KIAS.  THE PITCH OF THE VIBRATION VARIED WITH PEDAL POSITION.  ENGINE SYSTEMS INSTRUMENTS, N2 AND ROTOR RPM WERE ALL IN THE GREEN. A PRECAUTIONARY LANDING WAS MADE AT THE LAX WEST HELIPADS.  WHEN THE VIBRATION BEGAN, THE AIRCRAFT WAS FLYING EASTBOUND PAST THE LAX CONTROL TOWER. THE TOWER OPERATOR ADVISED THAT HE COULD HEAR THE SQUEALING SOUND FROM INSIDE THE TOWER.  DESPITE THE VIBRATION, THE AIRCRAFT RESPONDED TO FLIGHT CONTROL INPUTS AS NORMAL ALTHOUGH A STIFFNESS OR BINDING WAS NOTED IN THE ANTI-TORQUE PEDALS.  SEVERAL HOURS EARLIER DURING THE FIRST FLIGHT OF THE EVENING, THE BINDING IN THE PEDALS WAS FIRST NOTED.  THE STIFFNESS OR BINDING WAS FELT WHEN THE PEDALS WERE POSITIONED AT APPROXIMATELY 2" OF RIGHT PEDAL BEYOND THE NEUTRAL POSITION.  IT WAS MOST NOTICEABLE D URING OUT OF TRIM RIGHT ORBITS AND LANDING APPROACHES. THE PEDALS WOULD BIND AT THAT SPOT THEN BECOME LOOSE AGAIN BEYOND THAT POINT CAUSING UNDESIRABLE EXCESSIVE YAW.  THIS PEDAL STIFFNESS HAS BEEN ENCOUNTERED IN THE PAST WITH THE 520N AIRCRAFT.  SUBSEQUENT INSPECTION BY MAINTENANCE PERSONNEL REVEALED DAMAGE TO SEVERAL FAN DRIVELINE COMPONENTS.

## The NTSB's investigation of this event (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 LAX01IA262](https://openairdocs.org/ntsb/LAX01IA262), Jul 25, 2001: Mdhi 520N (N953SD), Los Angeles, CA, incident, minor damage. Probable cause: the excitation of the first bending mode natural frequency of the aft tube assembly that is installed through the rotating NOTAR fan drive system. Contributing factors to the incident included the…

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. For accidents, the NTSB's own investigation is the fuller record.

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