Narrative:

While preflting, I found a problem with the nose stout. I called maintenance and continued my preflight. A thorough preflight was accomplished until the left nacelle (started with nose of aircraft and went clockwise). While checking exhaust stack (left side), and propeller I was sidetracked into going back to the nose where the mechanic was working on the problem previously mentioned. After checking to see what I should be looking for, on the nose stout, through the day (ie, possible problems), I went back to the l-hand nacelle to complete the preflight. I don't recall going back to the left (outboard nacelle) side like I should have. Instead, I went to the inboard left nacelle - all appeared normal. The locks for the upper cowling are a 90 degree turn hexagonal stem about 3/4 inch long (when viewed from the side of the cowling). There was very little in the way of markings on the locks to confirm their locking position. Normally, there is a horizontal line on the face - or an arrow to match up with a reference line on the cowl. However, on this aircraft, it was very difficult to see any of the markings. A much better test would to have been to strike the cowl with an upward blow of my palm to jar the cowling and see if is was secure, I did not. We took of (no passenger), and later noticed the cowl missing. Returned for landing, and found none of the (4) blocks had been secured. The aircraft flew normally and we did not notice any differences in performance, lndgs, etc. The director of operations, FAA FSDO (albany), and direct of maintenance were notified. The outcome was as follows: me, incident report with albany FSDO regarding situation. Letter on file of employer, stating I received remedial training on fastening cowl locks. Mechanic - possible violation for failure to lock down cowling. After maintenance was performed. Letter on file by employer stating situation. Regarding human factors, etc, I believe there were 2 major factors involved. 1) there was no visual indicator that notified a potential problem. Ie, zeus (not sure of spelling) fasteners stick out when they are not secured. The same applies to normal latches - it is obvious when they are not secured. In this case, it is easy to overlook a fastener with little or no marking on it. The only true test is to strike the cowl to check for security. This appears to be a poor design. 2) I let myself get sidetracked midway through preflight. I should have returned to a point well before where I knew I left off.

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Original NASA ASRS Text

Title: L ENG COWLING FELL OFF AFTER TKOF.

Narrative: WHILE PREFLTING, I FOUND A PROB WITH THE NOSE STOUT. I CALLED MAINT AND CONTINUED MY PREFLT. A THOROUGH PREFLT WAS ACCOMPLISHED UNTIL THE L NACELLE (STARTED WITH NOSE OF ACFT AND WENT CLOCKWISE). WHILE CHKING EXHAUST STACK (L SIDE), AND PROP I WAS SIDETRACKED INTO GOING BACK TO THE NOSE WHERE THE MECH WAS WORKING ON THE PROB PREVIOUSLY MENTIONED. AFTER CHKING TO SEE WHAT I SHOULD BE LOOKING FOR, ON THE NOSE STOUT, THROUGH THE DAY (IE, POSSIBLE PROBS), I WENT BACK TO THE L-HAND NACELLE TO COMPLETE THE PREFLT. I DON'T RECALL GOING BACK TO THE L (OUTBOARD NACELLE) SIDE LIKE I SHOULD HAVE. INSTEAD, I WENT TO THE INBOARD L NACELLE - ALL APPEARED NORMAL. THE LOCKS FOR THE UPPER COWLING ARE A 90 DEG TURN HEXAGONAL STEM ABOUT 3/4 INCH LONG (WHEN VIEWED FROM THE SIDE OF THE COWLING). THERE WAS VERY LITTLE IN THE WAY OF MARKINGS ON THE LOCKS TO CONFIRM THEIR LOCKING POS. NORMALLY, THERE IS A HORIZ LINE ON THE FACE - OR AN ARROW TO MATCH UP WITH A REF LINE ON THE COWL. HOWEVER, ON THIS ACFT, IT WAS VERY DIFFICULT TO SEE ANY OF THE MARKINGS. A MUCH BETTER TEST WOULD TO HAVE BEEN TO STRIKE THE COWL WITH AN UPWARD BLOW OF MY PALM TO JAR THE COWLING AND SEE IF IS WAS SECURE, I DID NOT. WE TOOK OF (NO PAX), AND LATER NOTICED THE COWL MISSING. RETURNED FOR LNDG, AND FOUND NONE OF THE (4) BLOCKS HAD BEEN SECURED. THE ACFT FLEW NORMALLY AND WE DID NOT NOTICE ANY DIFFERENCES IN PERFORMANCE, LNDGS, ETC. THE DIRECTOR OF OPS, FAA FSDO (ALBANY), AND DIRECT OF MAINT WERE NOTIFIED. THE OUTCOME WAS AS FOLLOWS: ME, INCIDENT RPT WITH ALBANY FSDO REGARDING SIT. LETTER ON FILE OF EMPLOYER, STATING I RECEIVED REMEDIAL TRAINING ON FASTENING COWL LOCKS. MECH - POSSIBLE VIOLATION FOR FAILURE TO LOCK DOWN COWLING. AFTER MAINT WAS PERFORMED. LETTER ON FILE BY EMPLOYER STATING SIT. REGARDING HUMAN FACTORS, ETC, I BELIEVE THERE WERE 2 MAJOR FACTORS INVOLVED. 1) THERE WAS NO VISUAL INDICATOR THAT NOTIFIED A POTENTIAL PROB. IE, ZEUS (NOT SURE OF SPELLING) FASTENERS STICK OUT WHEN THEY ARE NOT SECURED. THE SAME APPLIES TO NORMAL LATCHES - IT IS OBVIOUS WHEN THEY ARE NOT SECURED. IN THIS CASE, IT IS EASY TO OVERLOOK A FASTENER WITH LITTLE OR NO MARKING ON IT. THE ONLY TRUE TEST IS TO STRIKE THE COWL TO CHK FOR SECURITY. THIS APPEARS TO BE A POOR DESIGN. 2) I LET MYSELF GET SIDETRACKED MIDWAY THROUGH PREFLT. I SHOULD HAVE RETURNED TO A POINT WELL BEFORE WHERE I KNEW I LEFT OFF.

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.