Mark Huber is an aviation industry veteran who has worked in the flight training, aircraft sales, aircraft component, and airport development businesses. He has flight time in more than 50 different and diverse aircraft, including helicopters, aerobatic aircraft, vintage warbirds, jet fighters, business jets and turboprops, and transport-category aircraft. He has jumped out of several of these—on purpose—with a parachute. His defense and aviation journalism has been published in a variety of national and international periodicals.

Contributor

Mark Huber

The sudden loss of main gearbox (MGB) oil pressure in a Sikorsky S-92A, registration LN-ONH, last year has been tied to a worn vespel spline adapter driving one of two oil pumps, according to a recent report from the Accident Investigation Board of Norway (AIBN).&nbsp;

 


Operated by Bristow Norway, the helicopter was conducting search and rescue training on Sept.&nbsp;25, 2021, when the flight crew noted a drop in MGB oil pressure from 58 to 6 psi in 30 seconds. The crew immediately executed a successful landing at Ekofisk's Lima&nbsp;platform&nbsp;(ENLE) 1.9 nm away.&nbsp;Data from the flight data recorder showed that the oil pressure dropped from 59 to 32 psi in three seconds. It stabilized at around 5 to 6 psi after 33 seconds.

 


One minute 50 seconds after the low oil pressure alert, LN-ONH landed at ENLE. The S-92A MGB holds 10 gallons of oil. It is pumped from the sump via the separate, external oil cooler and into the MGB.&nbsp;

 


The AIBN found that excessive wear on the adapter was caused by a combination of factors, including&nbsp;“a higher service life on the component than logged, natural variation in production and materials of the vespel spline adapter, and the individual torque load on the pump.”&nbsp;Following the incident, Sikorsky reduced the service life of the vespel spline adapter to prevent reoccurrence.

 


This is not the first report of problems with the vespel spline adapter on the S-92A.&nbsp;In 2005, the MGB oil pressure of a S-92A suddenly dropped to 5 to 6 psi due to a worn vespel spline adapter. After that incident, Sikorsky readjusted the replacement interval of the adapter to 50 flight hours, changed the surface finish of the pump driveshaft, and added a check valve to stop oil flowing back into the pump in the wrong direction.

 


In another incident in 2008, a vespel spline adapter had moved on the drive shaft, such that only half the adapter was engaged, leading to MGB oil pressure dropping to 15 to&nbsp;17 psi. No further incidents were officially reported and Sikorsky eventually extended the life limit of the vespel spline adapter to 750 flight hours. However, in July 2021 Bristow noted excessive wear on a vespel spline adapter when changed out at 750 hours and sent both the adapter and the pump to Sikorsky for analysis.

News and issues regarding all manner of civil and military rotorcraft and their powerplants, including helicopters, tilt rotors and unmanned air vehicles.

Accident Board Takes Fresh Issue with S-92 Main Gearbox

Issues with Vespel spline adapters continue to overhang S-92 main gearboxes. 

2024 Corporate Aviation Leadership Summit

Charlotte Bailey

News about bills, laws, regulations and other governmental decisions affecting aviation and aerospace. Topics include FAA re-authorizations, taxes on fuel and aviation activities, environmental legislation, ICAO decisions, governmental mediation of labor conflicts and World Trade Organization disputes and decisions.

Essential news and analysis on the defense aerospace business. Your trusted source for new and ongoing programs and requirements in military aircraft (manned and unmanned), engines, avionics, weapons and associated systems, including ground-based air defense.

Pentagon permission facilitates sale of Bell 412EXP and 407M

U.S. Approves $800M Bell 407/412 Sale to Iraq Military

News and information on safety procedures and concerns.

News and issues relating to the aerospace industry that are related to the science, engineering and business of flight in space involving civil, industrial and military applications, and similar topics related to flight in the atmosphere of the Earth that are not covered more directly by other AINonline subject channels. In other words, both astronautical and aeronautical subjects, except for those aeronautical topics that are specifically covered elsewhere on this website.

Fire and disaster management agency to use aircraft in aerial reconnaissance role

Japan Orders Its First H160 for Emergency Response

Flights with two scaled technology demonstrators will inform potential future iterations 

Singaporean eVTOL Conducts Test Campaign In Germany 

Matt Thurber

New developments and products in avionics, specifically about aircraft electronics in the cockpit.

News and issues relating to business, corporate and private aviation, primarily regarding turbine-engine-powered airplanes and helicopters. Subjects include aircraft, engines, maintenance, operations, personnel, acquisitions, accidents, safety, security, and training.

More In Rotorcraft

U.S. Approves $800M Bell 407/412 Sale to Iraq Military

Pentagon permission facilitates sale of Bell 412EXP and 407M

Japan Orders Its First H160 for Emergency Response

Fire and disaster management agency to use aircraft in aerial reconnaissance role

Singaporean eVTOL Conducts Test Campaign In Germany

Flights with two scaled technology demonstrators will inform potential future iterations

FAA Approves TSO for ASU Panoramic Night-vision Goggles

Lightweight white-phosphor NVG have a 94-degree field of view

FAA Floats Special Conditions for Skyryse Fly-by-wire R66

Proposed rule addresses pilot awareness of control limits

Vertical Lift Groups Extend Trade Show Partnership

European Helicopter Association and Vertical Aviation International extended their alliance

Sikorsky Is Upgrading the Black Hawk Helicopter for Evolving Military Needs

Armed forces will be able to outfit Black Hawks with new armament and equipment.

Sikorsky’s S-97 Raider Points to a New Level of Performance for Future Helicopters

Originally developed for the U.S. military, X2 technology is in search of a new customer.

AIN Products

SUBSCRIPTIONS

RESOURCES

ABOUT AIN