A learjet 35 descending through FL250 experienced a loud bang with deceleration and slight brief pit...

Attributes
ACN	588378
Time
Date	200307
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl bound lower : 25000 msl bound upper : 26000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	common carrier : air taxi
Make Model Name	Learjet 35
Operating Under FAR Part	Part 135
Flight Phase	descent : vacating altitude descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : atp
Experience	flight time last 90 days : 150 flight time total : 3700 flight time type : 1200
ASRS Report	588378
Person 2
Affiliation	company : air taxi
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 6000 flight time type : 4000
ASRS Report	588239
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist flight crew : overcame equipment problem flight crew : returned to intended or assigned course
Consequence	faa : investigated other other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

I was PF on jul/tue/03 direct to ZZZ descending out of FL250 and experienced a loud bang associated with a deceleration and a nose down pitching for a brief second. After the occurrence, I spoke with the captain I was flying with and we went over all system to evaluate what had happened. I slowed down to 250 KIAS and all engine/hydraulic/electrical instruments were all normal. Also, all flight controls were operating normally. After landing and requesting emergency services the fire truck told us that our right engine cover was missing, so we shut down that engine and taxied to maintenance. Nobody was injured to our knowledge. No flight control loss occurred. A proper preflight action was conducted by myself that morning and all appeared normal. Callback conversation with reporter revealed the following information: the reporter stated he was flying the aircraft and descending from FL260 to FL250 when a yaw to the right was felt with slight nose down pitch. The reporter said the airplane was slowed to 250 KTS and all engine, hydraulic and electrical instruments were checked and found normal. The reporter stated that on the ground it was discovered the right engine upper cowling had departed the aircraft and the right lower cowling was folded inboard against the aft fuselage. The reporter said when the upper cowling left the airplane it struck the dorsal fin damaging the VHF antenna. It then damaged the right lower elevator surface. The reporter stated only 1 of 6 latches were holding the lower cowling. The reporter said the airplane was given a thorough walkaround preflight check and the cowling was unlatched only to check and service the oil on both engines. The reporter stated the cowling was latched and checked prior to departure. The reporter said the airplane was 3 hours into the flight when the cowling departed the aircraft. The reporter stated he believes the FAA preliminary finding was cowling latch failure.

Original NASA ASRS Text

Title: A LEARJET 35 DSNDING THROUGH FL250 EXPERIENCED A LOUD BANG WITH DECELERATION AND SLIGHT BRIEF PITCH NOSE DOWN. R ENG UPPER COWLING DEPARTED ACFT.

Narrative: I WAS PF ON JUL/TUE/03 DIRECT TO ZZZ DSNDING OUT OF FL250 AND EXPERIENCED A LOUD BANG ASSOCIATED WITH A DECELERATION AND A NOSE DOWN PITCHING FOR A BRIEF SECOND. AFTER THE OCCURRENCE, I SPOKE WITH THE CAPT I WAS FLYING WITH AND WE WENT OVER ALL SYS TO EVALUATE WHAT HAD HAPPENED. I SLOWED DOWN TO 250 KIAS AND ALL ENG/HYD/ELECTRICAL INSTS WERE ALL NORMAL. ALSO, ALL FLT CTLS WERE OPERATING NORMALLY. AFTER LNDG AND REQUESTING EMER SVCS THE FIRE TRUCK TOLD US THAT OUR R ENG COVER WAS MISSING, SO WE SHUT DOWN THAT ENG AND TAXIED TO MAINT. NOBODY WAS INJURED TO OUR KNOWLEDGE. NO FLT CTL LOSS OCCURRED. A PROPER PREFLT ACTION WAS CONDUCTED BY MYSELF THAT MORNING AND ALL APPEARED NORMAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED HE WAS FLYING THE ACFT AND DSNDING FROM FL260 TO FL250 WHEN A YAW TO THE R WAS FELT WITH SLIGHT NOSE DOWN PITCH. THE RPTR SAID THE AIRPLANE WAS SLOWED TO 250 KTS AND ALL ENG, HYD AND ELECTRICAL INSTS WERE CHKED AND FOUND NORMAL. THE RPTR STATED THAT ON THE GND IT WAS DISCOVERED THE R ENG UPPER COWLING HAD DEPARTED THE ACFT AND THE R LOWER COWLING WAS FOLDED INBOARD AGAINST THE AFT FUSELAGE. THE RPTR SAID WHEN THE UPPER COWLING LEFT THE AIRPLANE IT STRUCK THE DORSAL FIN DAMAGING THE VHF ANTENNA. IT THEN DAMAGED THE R LOWER ELEVATOR SURFACE. THE RPTR STATED ONLY 1 OF 6 LATCHES WERE HOLDING THE LOWER COWLING. THE RPTR SAID THE AIRPLANE WAS GIVEN A THOROUGH WALKAROUND PREFLT CHK AND THE COWLING WAS UNLATCHED ONLY TO CHK AND SVC THE OIL ON BOTH ENGS. THE RPTR STATED THE COWLING WAS LATCHED AND CHKED PRIOR TO DEP. THE RPTR SAID THE AIRPLANE WAS 3 HRS INTO THE FLT WHEN THE COWLING DEPARTED THE ACFT. THE RPTR STATED HE BELIEVES THE FAA PRELIMINARY FINDING WAS COWLING LATCH FAILURE.

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.

A learjet 35 descending through FL250 experienced a loud bang with deceleration and slight brief pitch nose down. Right engine upper cowling departed aircraft.