Sikorsky S-76B N76UT

Summary

On 30 June 1994 at about 23:40 local time, a Sikorsky S-76B registered N76UT was involved in an accident near Newport, Rhode Island, United States. 3 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

30 June 1994 at 23:40

Classification

Accident

Location

Newport, Rhode Island, United States

Coordinates

Not recorded

Aircraft

Sikorsky S-76B

Registration

N76UT

Category

Helicopter

Engines

2

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Executive/Corporate

Phase of flight

Not recorded

Route

Goat Island → East Hartford

Aircraft damage

Substantial

Weather

VMC

Light

Dusk

NTSB number

NYC94FA106

Nobody was injured.

the failure of the left hand helical gear in the main gear box (MGB), due to undertorqued attaching bolts installed by the manufacturer, which resulted in a partial MGB failure. This failure resulted in the loss of the number one engine, illumination of the MGB chip light and a ditching to salt water on emergency floats.

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

Read the full NTSB narrative

AFTER DISCHARGING PASSENGERS ON AN ISLAND, THE S-76 HELICOPTER DEPARTED FOR A RETURN FLIGHT TO THE MAINLAND. ONE MINUTE AFTER TAKEOFF, AT 500 FEET ABOVE THE WATER, A VIBRATION FOLLOWED BY A LOUD BANG OCCURRED. THE MAIN GEAR BOX (MGB) CHIP LIGHT ILLUMINATED AND THE NUMBER ONE ENG DROPPED OFF LINE. A FORCED LANDING WAS INITIATED, THE EMERGENCY FLOATS WERE INFLATED AND A DITCHING TO WATER WAS ACCOMPLISHED. THE NUMBER ONE ENG WAS SHUT DOWN, AND THE ACFT WAS WATER TAXIED ON THE SECOND ENG. AFTER A SECOND BANG WAS HEARD THE NUMBER TWO ENG WAS SHUT DOWN. EXAMINATION REVEALED THAT THE LEFT HAND (NUMBER ONE ENG) HELICAL GEAR IN THE MGB, FAILED FROM FATIGUE CRACKS ACROSS THE 12 ATTACHING BOLT HOLES. THE TORQUE REQUIRED ON THE 12 NUTS WAS 4OO INCH POUNDS. THREE NUTS HAD LESS THEN 60 INCH LBS, THE REMAINING NINE HAD NO TORQUE. BOTH MGB OIL PUMPS WERE SEIZED FROM FOD THAT ENTERED THE PUMPS THROUGH AN ALTERNATE OIL PATH, THAT BY-PASSED THE OIL SCREENS. THE NUMBER TWO ENG PINION GEAR IN THE MGB, FAILED DUE TO OVERHEATING FROM THE LACK OF LUBRICATION. ELAPSED TIME WAS LESS THAN 6 MINUTES FROM INITIAL FORCED LANDING TO SECOND ENGINE SHUT DOWN.

Quoted verbatim from the NTSB record.