Piper PA-31B-310 N7407L

Summary

On 1 May 1991 at about 12:53 local time, a Piper PA-31B-310 registered N7407L, operated by John Westbrook, was involved in an accident near Bennett, Colorado, United States. One person was on board and one died. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

1 May 1991 at 12:53

Classification

Accident

Location

Bennett, Colorado, United States

Coordinates

39.7398, -104.7807

Aircraft

Piper PA-31B-310

Registration

N7407L

Category

Airplane

Engines

2

Operator

John Westbrook

Operating rule

Part 91: General Aviation

Purpose of flight

Business

Phase of flight

Not recorded

Route

Englewood → Des Moines

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

DEN91FA065

1 person died.

IN-FLIGHT SEPARATION OF THE LEFT ENGINE COWL ASSEMBLY THAT WAS NOT PROPERLY LATCHED, AND FAILURE OF THE PILOT TO MAINTAIN MINIMUM CONTROL SPEED, WHICH RESULTED IN HIS LOSS OF AIRCRAFT CONTROL. FACTORS RELATED TO THE ACCIDENT WERE: AN INADEQUATE PREFLIGHT INSPECTION, INADEQUATE MARKINGS/ALIGNMENT INDICATIONS TO ASSURE THAT THE COWL FASTENERS WERE LOCKED, AND AN INSUFFICIENTLY DEFINED PROCEDURE IN THE FLIGHT MANUAL FOR CHECKING THE COWL FASTENERS.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

SHORTLY AFTER TAKEOFF, WHILE CLIMBING TO CRUISE ALTITUDE, THE PILOT REPORTED THE LEFT ENGINE COWL ASSEMBLY HAD COME OFF. WITNESSES OBSERVED THE AIRPLANE AT LOW ALTITUDE & NOTED THAT IT WAS 'YAWING, SPUTTERING, AND ROCKING BACK AND FORTH.' THEY INDICATED THE LEFT ENGINE WAS NOT RUNNING & THAT THE AIRPLANE BANKED SHARPLY TO THE RIGHT & DISAPPEARED BEHIND TREES BEFORE CRASHING. AN INVESTIGATION REVEALED THE LEFT PROPELLER HAD NOT BEEN FEATHERED. THE LEFT ENGINE COWLING WAS FOUND 1.8 MILES FROM THE ACCIDENT SITE. THE THREE PRIMARY (EYEBOLT) COWL FASTERERS ON THE OUTBOARD SIDE OF THE LEFT UPPER COWL WERE FOUND UNLOCKED & SEVEN OTHER COWL ATTACHING STUDS (SCREWS) WERE MISSING. THE COWLING HAD BEEN REMOVED 16 DAYS BEFORE THE ACCIDENT TO INSTALL AN OIL/AIR SEPARATOR. THIS WAS THE FIRST FLIGHT SINCE THAT WORK WAS PERFORMED. THE MECHANIC, WHO DID THE WORK, SAID HE NOTED SEVERAL COWL STUD FASTENERS WERE MISSING & THAT HE HAD NOTIFIED THE PILOT. THE PILOT WAS REPORTED TO HAVE REPLIED THAT HE HAD SOME FASTENERS & WOULD TAKE CARE OF THE PROBLEM.

Quoted verbatim from the NTSB record.