Narrative:

During climb from lax en route to mry on vector to and just intercepting V-23 approximately 5 NM north of lax, captain and I felt a thump which was different than the turbulence we were encountering (light). We didn't know what it was and both looked out our windows at the engines and wings. I was PF so captain talked to the flight attendant on the intercom. She felt it also and thought it came from the left, side of the aircraft and said she thought it might have been a bird strike (ingestion). She said (later) passenger looked up at the time but that no one said anything during the flight. Captain and I noted that both engines were running fine (all indications normal) and that the aircraft was still flying normally with no other indications of anything amiss. Therefore, captain decided to continue to mry and said we would make a postflt inspection for a possible bird strike. Flight continued normally and without incident to mry. Postflt inspection by me revealed a 2 ft by 2 ft hydraulic bay access panel located on the bottom, aft portion of the right engine nacelle had separated from the aircraft. Airflow and propeller wash apparently blew the aluminum door up and inward where it struck the bottom of the inboard flap, then flew into the fuselage striking the emergency exit door and just aft. The flap (made of composite material) had a 1 ft by 1 ft by 2 inch shaped tear on the underside and an 8 inch jagged tear on the top. The fuselage was scraped and dented. The aircraft's pressure vessel remained intact and no other damage was apparent (ie, to the tail, etc). Company mechanics (2) subsequently repaired the aircraft in mry (replaced inboard flap and access door and repaired fuselage skin) and signed aircraft off for flight. This incident raised 2 issues in my mind. 1) could it have been prevented? We had flown the aircraft all day and no one had opened the hydraulic access door. Particularly before this flight I had remained with the aircraft on the ground in lax and know that no mechanic had opened the door (therefore, it was not left open). Both the captain and I made a preflight walk around and neither of us noticed any of the doors' latches opened. Subsequent discussions with company mechanics revealed: a) original embraer design was poor and additional 'cam' lock fasteners were located next to each original fastener. B) another door had come open (although didn't separate) just 3 weeks prior on another aircraft. C) another airline had so many door failures that they put 2 additional cam lock fasteners next to each original fastener. Furthermore, design of door puts hinge parallel to aircraft longitudinal axis so that if door becomes unfastened, it will open so as to be wrenched by the aerodynamic forces (poor). The mechanics that repaired the damage said they believe the door was properly latched at the time of the separation and that one or more fasteners probably failed. Therefore I conclude neither the captain nor I could have prevented the incident as the door appeared to be latched properly. In light of the poor original design and the obviously inadequate redesign, an airworthiness directive should be issued to develop a better redesign. 2) could we have returned to lax as soon as the thump was felt? I feel we were prudent in continuing in that all engine indications remained constant and normal. All aircraft performance and handling remained constant and normal. Both flight deck crew members saw nothing abnormal from the cockpit, looking at the wing leading edges and engines. The flight attendant, who also looked at the wing leading edges, saw nothing abnormal. No passenger said anything about any abnormal sound, sight, or sensation. In short, there was a brief, relatively mild thump followed by nothing abnormal. Since we thought we might have hit a bird (at worse) and nothing was indicating abnormally, there appeared to be no reason to return to lax. Callback conversation with reporter revealed the following information: reporter states that he filed an irregularity report but has heard nothing further to date. He intends to follow up with maintenance. The mechanic who worked on the panel replacement said that this same thing had happened recently. Another mechanic stated he too had worked on similar problem. These are hartwell latches (push type) and originally there were 4 on the panel, now there are 8. One other commuter company has gone to using 12 latches to avoid such problems. Reporter has heard that his company may change to using zeuss fasteners to avoid repeat. Reporter feels this is poor design as the panel opens in a way to fly off toward the fuselage instead of away from it due to propeller wash. The panel came off over land but has not been retrieved and reporter is grateful it did not impact someone on the ground. Reporter gave a follow-up call to say that his company safety officer put out a message that the company is planning to change all latches to screws to help alleviate the problem.

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Original NASA ASRS Text

Title: EMB 120 HAS HYD BAY ACCESS PANEL COME OFF INFLT.

Narrative: DURING CLB FROM LAX ENRTE TO MRY ON VECTOR TO AND JUST INTERCEPTING V-23 APPROX 5 NM N OF LAX, CAPT AND I FELT A THUMP WHICH WAS DIFFERENT THAN THE TURB WE WERE ENCOUNTERING (LIGHT). WE DIDN'T KNOW WHAT IT WAS AND BOTH LOOKED OUT OUR WINDOWS AT THE ENGS AND WINGS. I WAS PF SO CAPT TALKED TO THE FLT ATTENDANT ON THE INTERCOM. SHE FELT IT ALSO AND THOUGHT IT CAME FROM THE L, SIDE OF THE ACFT AND SAID SHE THOUGHT IT MIGHT HAVE BEEN A BIRD STRIKE (INGESTION). SHE SAID (LATER) PAX LOOKED UP AT THE TIME BUT THAT NO ONE SAID ANYTHING DURING THE FLT. CAPT AND I NOTED THAT BOTH ENGS WERE RUNNING FINE (ALL INDICATIONS NORMAL) AND THAT THE ACFT WAS STILL FLYING NORMALLY WITH NO OTHER INDICATIONS OF ANYTHING AMISS. THEREFORE, CAPT DECIDED TO CONTINUE TO MRY AND SAID WE WOULD MAKE A POSTFLT INSPECTION FOR A POSSIBLE BIRD STRIKE. FLT CONTINUED NORMALLY AND WITHOUT INCIDENT TO MRY. POSTFLT INSPECTION BY ME REVEALED A 2 FT BY 2 FT HYD BAY ACCESS PANEL LOCATED ON THE BOTTOM, AFT PORTION OF THE R ENG NACELLE HAD SEPARATED FROM THE ACFT. AIRFLOW AND PROP WASH APPARENTLY BLEW THE ALUMINUM DOOR UP AND INWARD WHERE IT STRUCK THE BOTTOM OF THE INBOARD FLAP, THEN FLEW INTO THE FUSELAGE STRIKING THE EMER EXIT DOOR AND JUST AFT. THE FLAP (MADE OF COMPOSITE MATERIAL) HAD A 1 FT BY 1 FT BY 2 INCH SHAPED TEAR ON THE UNDERSIDE AND AN 8 INCH JAGGED TEAR ON THE TOP. THE FUSELAGE WAS SCRAPED AND DENTED. THE ACFT'S PRESSURE VESSEL REMAINED INTACT AND NO OTHER DAMAGE WAS APPARENT (IE, TO THE TAIL, ETC). COMPANY MECHS (2) SUBSEQUENTLY REPAIRED THE ACFT IN MRY (REPLACED INBOARD FLAP AND ACCESS DOOR AND REPAIRED FUSELAGE SKIN) AND SIGNED ACFT OFF FOR FLT. THIS INCIDENT RAISED 2 ISSUES IN MY MIND. 1) COULD IT HAVE BEEN PREVENTED? WE HAD FLOWN THE ACFT ALL DAY AND NO ONE HAD OPENED THE HYD ACCESS DOOR. PARTICULARLY BEFORE THIS FLT I HAD REMAINED WITH THE ACFT ON THE GND IN LAX AND KNOW THAT NO MECH HAD OPENED THE DOOR (THEREFORE, IT WAS NOT LEFT OPEN). BOTH THE CAPT AND I MADE A PREFLT WALK AROUND AND NEITHER OF US NOTICED ANY OF THE DOORS' LATCHES OPENED. SUBSEQUENT DISCUSSIONS WITH COMPANY MECHS REVEALED: A) ORIGINAL EMBRAER DESIGN WAS POOR AND ADDITIONAL 'CAM' LOCK FASTENERS WERE LOCATED NEXT TO EACH ORIGINAL FASTENER. B) ANOTHER DOOR HAD COME OPEN (ALTHOUGH DIDN'T SEPARATE) JUST 3 WKS PRIOR ON ANOTHER ACFT. C) ANOTHER AIRLINE HAD SO MANY DOOR FAILURES THAT THEY PUT 2 ADDITIONAL CAM LOCK FASTENERS NEXT TO EACH ORIGINAL FASTENER. FURTHERMORE, DESIGN OF DOOR PUTS HINGE PARALLEL TO ACFT LONGITUDINAL AXIS SO THAT IF DOOR BECOMES UNFASTENED, IT WILL OPEN SO AS TO BE WRENCHED BY THE AERODYNAMIC FORCES (POOR). THE MECHS THAT REPAIRED THE DAMAGE SAID THEY BELIEVE THE DOOR WAS PROPERLY LATCHED AT THE TIME OF THE SEPARATION AND THAT ONE OR MORE FASTENERS PROBABLY FAILED. THEREFORE I CONCLUDE NEITHER THE CAPT NOR I COULD HAVE PREVENTED THE INCIDENT AS THE DOOR APPEARED TO BE LATCHED PROPERLY. IN LIGHT OF THE POOR ORIGINAL DESIGN AND THE OBVIOUSLY INADEQUATE REDESIGN, AN AIRWORTHINESS DIRECTIVE SHOULD BE ISSUED TO DEVELOP A BETTER REDESIGN. 2) COULD WE HAVE RETURNED TO LAX AS SOON AS THE THUMP WAS FELT? I FEEL WE WERE PRUDENT IN CONTINUING IN THAT ALL ENG INDICATIONS REMAINED CONSTANT AND NORMAL. ALL ACFT PERFORMANCE AND HANDLING REMAINED CONSTANT AND NORMAL. BOTH FLT DECK CREW MEMBERS SAW NOTHING ABNORMAL FROM THE COCKPIT, LOOKING AT THE WING LEADING EDGES AND ENGS. THE FLT ATTENDANT, WHO ALSO LOOKED AT THE WING LEADING EDGES, SAW NOTHING ABNORMAL. NO PAX SAID ANYTHING ABOUT ANY ABNORMAL SOUND, SIGHT, OR SENSATION. IN SHORT, THERE WAS A BRIEF, RELATIVELY MILD THUMP FOLLOWED BY NOTHING ABNORMAL. SINCE WE THOUGHT WE MIGHT HAVE HIT A BIRD (AT WORSE) AND NOTHING WAS INDICATING ABNORMALLY, THERE APPEARED TO BE NO REASON TO RETURN TO LAX. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT HE FILED AN IRREGULARITY RPT BUT HAS HEARD NOTHING FURTHER TO DATE. HE INTENDS TO FOLLOW UP WITH MAINT. THE MECH WHO WORKED ON THE PANEL REPLACEMENT SAID THAT THIS SAME THING HAD HAPPENED RECENTLY. ANOTHER MECH STATED HE TOO HAD WORKED ON SIMILAR PROB. THESE ARE HARTWELL LATCHES (PUSH TYPE) AND ORIGINALLY THERE WERE 4 ON THE PANEL, NOW THERE ARE 8. ONE OTHER COMMUTER COMPANY HAS GONE TO USING 12 LATCHES TO AVOID SUCH PROBS. RPTR HAS HEARD THAT HIS COMPANY MAY CHANGE TO USING ZEUSS FASTENERS TO AVOID REPEAT. RPTR FEELS THIS IS POOR DESIGN AS THE PANEL OPENS IN A WAY TO FLY OFF TOWARD THE FUSELAGE INSTEAD OF AWAY FROM IT DUE TO PROP WASH. THE PANEL CAME OFF OVER LAND BUT HAS NOT BEEN RETRIEVED AND RPTR IS GRATEFUL IT DID NOT IMPACT SOMEONE ON THE GND. RPTR GAVE A FOLLOW-UP CALL TO SAY THAT HIS COMPANY SAFETY OFFICER PUT OUT A MESSAGE THAT THE COMPANY IS PLANNING TO CHANGE ALL LATCHES TO SCREWS TO HELP ALLEVIATE THE PROB.

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.