Flight crew of B777 heading out over the atlantic experiences a sudden hard jolt during climb. Decis...

Attributes
ACN	422788
Time
Date	199812
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : hfd
State Reference	CT
Altitude	msl bound lower : 24500 msl bound upper : 24500
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Navigation In Use	Other
Route In Use	enroute : atlantic
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : flight engineer
Experience	flight time last 90 days : 240 flight time total : 20000 flight time type : 750
ASRS Report	422788
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

We experienced a routine flight departing ewr to lhr and the 3 of us had flown together already on 3 previous flts this month. The night sky was clear as we climbed to our cruising altitude of FL350. Passing through FL245 just east of hfd VOR, we experienced a sudden jolt of the aircraft. It was like hitting a hidden pothole at 60 mph. Just 1 jolt, very sudden and then gone. My first thought was a glancing midair with another aircraft although none were nearby. That also ruled out wake turbulence. Facing 6 hours at night over open ocean, we reluctantly decided to return to ewr for an inspection. This was made with the knowledge of a recent security threat to east coast airlines regarding middle east terrorists. About 35000 pounds of fuel was jettisoned during descent on our direct route to ewr. Although we didn't declare an emergency, by asking for rescue equipment to stand by, ATC declared it for us. A routine approach and smooth overweight landing was made at ewr. Maintenance thoroughly inspected the aircraft while all cargo was offloaded. When nothing unusual was found, the flight was reloaded and continued on to lhr 4 hours late.

Original NASA ASRS Text

Title: FLC OF B777 HDG OUT OVER THE ATLANTIC EXPERIENCES A SUDDEN HARD JOLT DURING CLB. DECISION IS MADE TO JETTISON FUEL AND RETURN FOR A MAINT CHK.

Narrative: WE EXPERIENCED A ROUTINE FLT DEPARTING EWR TO LHR AND THE 3 OF US HAD FLOWN TOGETHER ALREADY ON 3 PREVIOUS FLTS THIS MONTH. THE NIGHT SKY WAS CLR AS WE CLBED TO OUR CRUISING ALT OF FL350. PASSING THROUGH FL245 JUST E OF HFD VOR, WE EXPERIENCED A SUDDEN JOLT OF THE ACFT. IT WAS LIKE HITTING A HIDDEN POTHOLE AT 60 MPH. JUST 1 JOLT, VERY SUDDEN AND THEN GONE. MY FIRST THOUGHT WAS A GLANCING MIDAIR WITH ANOTHER ACFT ALTHOUGH NONE WERE NEARBY. THAT ALSO RULED OUT WAKE TURB. FACING 6 HRS AT NIGHT OVER OPEN OCEAN, WE RELUCTANTLY DECIDED TO RETURN TO EWR FOR AN INSPECTION. THIS WAS MADE WITH THE KNOWLEDGE OF A RECENT SECURITY THREAT TO EAST COAST AIRLINES REGARDING MIDDLE EAST TERRORISTS. ABOUT 35000 LBS OF FUEL WAS JETTISONED DURING DSCNT ON OUR DIRECT RTE TO EWR. ALTHOUGH WE DIDN'T DECLARE AN EMER, BY ASKING FOR RESCUE EQUIP TO STAND BY, ATC DECLARED IT FOR US. A ROUTINE APCH AND SMOOTH OVERWT LNDG WAS MADE AT EWR. MAINT THOROUGHLY INSPECTED THE ACFT WHILE ALL CARGO WAS OFFLOADED. WHEN NOTHING UNUSUAL WAS FOUND, THE FLT WAS RELOADED AND CONTINUED ON TO LHR 4 HRS LATE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Flight crew of B777 heading out over the atlantic experiences a sudden hard jolt during climb. Decision is made to jettison fuel and return for a maintenance check.