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HISTORY OF FLIGHT
On March 9, 2004, about 1410 Pacific standard time,
an Ercoupe 415-C, N93707, experienced an in-flight separation of both wings and
impacted hilly terrain 7 nautical miles southeast of Oakdale, California. The
pilot was operating the airplane under the provisions of 14 CFR Part 91. The
commercial pilot, who also held a certified flight instructor certificate, and
one passenger, sustained fatal injuries. The airplane was destroyed. The flight
departed the Oakdale Airport at 1400, for the local area personal flight. Visual
meteorological conditions prevailed, and no flight plan had been
filed.
According to an aviation maintenance technician (AMT) that worked
on the airplane, the owner was receiving flight instruction to obtain her
private pilot certificate. She had flown earlier that day. A relative of the
owner, the passenger on the accident flight, departed with the CFI about 1400.
The owner reported to the AMT that during her flight, the CFI was performing
aileron rolls and fuel was pouring over the windscreen.
PERSONNEL
INFORMATION
A review of Federal Aviation Administration (FAA) airman
records revealed that the pilot held a commercial pilot certificate with ratings
for airplane single and multiengine land, and instrument airplane. The pilot
held a certified flight instructor (CFI) certificate with ratings for airplane
single and multiengine land, and instrument airplane.
The pilot held a
first-class medical certificate that was issued on November 29, 2002. It had no
limitations or waivers.
An examination of the pilot's logbook indicated
an estimated total flight time of 1,133 hours. He had en estimated 4 hours in
this make and model. His last flight review was completed during his certified
flight instructor multiengine checkride on December 19, 2002.
The pilot
was employed as a CFI at the Sierra Academy of Aeronautics. His resume indicated
that prior to that he taught aerobatics to students in Modesto, California, from
July 2002 until October 2002. A school name was not listed.
The airplane
owner was interviewed. She reported that she had flown with the CFI on the
flight just prior to the accident flight. The flight consisted of climbs and
descents. When she was asked if she went upside down in the airplane during that
flight she responded affirmatively. She also reported that during a previous
lesson on March 6, she and the CFI completed loop maneuvers.
A pilot that
had flown formation with the accident pilot about a month prior to the accident
said that he performed an aileron roll about 2,500 feet above ground level (agl)
in a PT-22. He looked over and saw the accident pilot perform the same maneuver
in the Ercoupe at 1,500 feet above ground level (agl). Following the flight, he
did not speak to the accident pilot about the maneuver.
A former
instrument student of the accident pilot reported that the accident pilot was
his mentor and friend. While flying a hold, the accident pilot calmed the
student and assisted him in flying the appropriate altitude. The student felt
that the accident pilot was an excellent teacher.
A family member
reported that the accident pilot attended 2 hours of aerobatic training to
improve his skills as a pilot. The accident pilot was frustrated with flight
schools that taught by rote learning and always wanted students to attain a
certain level of proficiency. The family member also stated that the accident
pilot was cautious with people that had not flown often.
AIRCRAFT
INFORMATION
The airplane was an Ercoupe 415-C, serial number 1030. A
review of the airplane's logbooks revealed a total airframe time of 1,600.9
hours at the last annual inspection. The logbooks had an entry for an annual
inspection dated December 6, 2003. The tachometer read 396.9 at the last
inspection. The current owner purchased the airplane in November
2003.
According to the previous owner, prior to his purchase, the owner
had a hard landing. The airplane was ferried for repairs to Oakdale, but the
owner passed away while the repairs were being made. The previous owner then
purchased the airplane "as-is" and began researching the maintenance
requirements for the airplane. It was noted that three ADs had been issued over
the years since the nosegear was damaged. While determining how the inspections
were to be performed, the previous owner and the aviation maintenance technician
decided to remove the wings in order to gain better access to the center
section.
They removed the wings and washed out the center section. It was
then inspected using a high-power light and mirror. He noted finding nothing but
"minor surface corrosion." Before reinstalling the wings, they sprayed the
inside with a corrosion inhibitor.
Following the inspection, the previous
owner decided to sell the airplane to a friend of the family that was just
beginning flight training.
The entry in the airframe logbook for December
6, 2003, stated the following: "Performed annual inspection. Removed L & R
(left and right) wings for compliance of AD 2002-26-02 center section. AD
2003-21-01 outer wing panels, AD 2002-26-02 c/w [complied with] IAW [in
accordance with] action (1) (3) next due December, 2004. AD 2002-16-04 c/w IAW
action (i), (4), (1), by installation of part number 48076 s/w AD 59-05-04, c/w
59-35-05, AD 59-05-04, AD 59-25-05, due every 100 hours or annual." The airplane
was signed off as airworthy.
Ercoupe Service Bulletin (SB) No. 18 was
issued for the reinforcement of the center section belly skin. This was a direct
result of cracks occurring in the center section belly skin at the rearmost
rivet attachment in the center section belly skin outer stiffeners.
On
July 24, 2000, SB 31, Wing Center Section Inspection, was issued. The service
bulletin required inspection within the next 5 hours of operation or at the next
100-hour or annual inspection, whichever occurred first. The SB was intended to
detect corrosion and prescribed methods of inspection.
AD 2002-26-02 was
intended to detect and correct corrosion in the wing center section, which could
result in failure of the wing center section structure during flight. The AD
contained three methods of accomplishing the inspection: install inspection
openings; use a scope and a light source; or remove outer wing panels to gain
visual access to the wing walkway box structure. It was noted that if any
corrosion or corrosion damage was found, the components were to be fixed prior
to further flight. The AD also required submitting a Malfunction and Defect
Report, FAA Form 8010-4 within 10 days, if corrosion or damage was
found.
AD 2003-21-01 was issued in response to additional reports of
corrosion on airplanes found during compliance with AD 94-18-04 R1. The actions
of the AD were intended to prevent wing damage caused by a corroded wing outer
panel structural component. The AD called for installation of inspection
openings in the outer wing panels and inspection of the area for corrosion and
corrosion damage. It also called for repetitive inspections every 12
months.
All of the current inspection methods are done visually and there
is no requirement for nondestructive inspection (NDI) or nondestructive testing
(NDT).
The airplane was fueled in a private hangar prior to the accident.
No fueling records were available.
METEOROLOGICAL CONDITIONS
The
closest official weather observation station was Modesto, California (MOD),
which was located 11 nautical miles (nm) southwest of the accident site. The
elevation of the weather observation station was 97 feet mean sea level (msl).
An aviation routine weather report (METAR) for Modesto was issued at 1353. It
stated: winds from 310 degrees at 13 knots; visibility 10 miles; skies clear;
temperature 25 degrees Celsius; dew point 14 degrees Celsius; altimeter 30.07
inches mercury.
WRECKAGE AND IMPACT INFORMATION
Inspectors from
the Federal Aviation Administration (FAA) responded to the accident scene. The
airplane came to rest in open, hilly pasture. The wings detached from the
fuselage and were about 252 feet apart, and approximately 400 feet from the main
wreckage. The empennage was approximately 200 feet from the fuselage. There was
no fire. The primary wreckage was at 37 degrees 44.726 minutes north latitude by
120 degrees 37.886 minutes west longitude. The debris path of about 1,051 feet
was on a magnetic heading of 315 degrees.
The engine came to rest
inverted. The propeller remained attached to the engine. One tip blade was
curled aft; the other blade was not curled. The spinner was
crushed.
MEDICAL AND PATHOLOGICAL INFORMATION
The Stanislaus
County Coroner completed an autopsy. The FAA Toxicology and Accident Research
Laboratory performed toxicological testing of specimens of the pilot. The
results of analysis of the specimens were negative for carbon monoxide, cyanide,
volatiles, and tested drugs.
TESTS AND RESEARCH
Investigators
examined the wreckage at Plain Parts, Sacramento, California, on March 17,
2004.
The fuselage had separated from the engine and was twisted and
crushed. The front spar separated at its center section, which coincided with
the location of two 6/32-inch screw holes. The upper spar on the left wing was
bent upward and the webbing was buckled. The upper spar on the right wing was
not bent. The fracture surface on the right lower spar was diagonal.
The
wing walk box section was examined. The wing skin surface and hat sections
displayed surface corrosion. The angle brace stiffners were flaking and the
corrosion had the appearance of intergranular or exfoliation type
corrosion.
A National Transportation Safety Board senior metallurgist
examined the two fractured portions of the front spar from the center section of
the wing. The spar fractured approximately along the centerline of
the fuselage. The fracture extended through the upper and lower
caps and the web portion. The total length of the two fractured spar
pieces measured 51 inches.
Visual examination of the front
spar revealed the upper and lower spar caps and webs contained mating fractures.
The mating fractures for the upper spar cap were placed next to each other and
visually examined. The upper spar cap portion adjacent to the fracture exhibited
bending deformation consistent with the outboard ends of the spar cap bending
upward relative to the spar. The upper spar cap was deformed slightly forward
relative to the position of the lower spar cap and the upper portion of the web
also was bent forward. Further to the left of the fracture location, the upper
spar cap contained bending deformation that was in the opposite direction to
that associated with the fracture. The web portion in the center section between
the upper and lower spar cap contained buckling deformation from excessive
loading in the vertical direction. The web portion contained fractures on a
plane of 45 degrees relative to the length of the web that is typical of an
overstress separation.
The web of the wing spar is riveted to vertical
flanges on the upper and lower spar caps. Twenty rivets between the web and
upper cap flanges were found fractured, allowing this portion of the web to
separate from the upper cap. Remnants of the fractured rivets remained attached
to the upper spar cap, but the head portions of these rivets were missing. The
20 rivets fractured at the shank portion near the transition between the shank
and head. The fractured rivets were firmly in place and the exposed
portions of the rivet heads and tails showed no evidence of degradation from
corrosion. One of the rivet faces was examined using a
scanning electron microscope and showed intergranular features consistent with
stress corrosion cracking in aluminum alloy. An ultrasonic
inspection of several of the intact and fractured rivets did not indicate that
any of the intact rivets were cracked.
The aft side of the wing spar
contains vertical stiffeners that are attached by rivets to the web, lower
flange of the upper cap, and upper flange of the lower cap. The wing spar
contained 5 of these stiffeners within the region of the 20 rivets with
fractures near the rivet head. At these five stiffener locations, the rivets
through the upper spar cap flange also fractured at the transition between the
bucked tail and shank. The fractured shank portion adjacent to the tails
contained elongation deformation, and the fracture faces in this area showed a
matter appearance typical of a ductile fracture. The ductile
fractures were not covered with aluminum oxide.
The majority
of the wing spar was covered with green primer, with the exception of the
outboard ends that were covered with tan paint. The front face of the
cap on the left piece contained two corrosion damage areas. The
corrosion in these two areas extended between
the layers of the extruded material of the upper cap, typical of exfoliation
corrosion.
ADDITIONAL INFORMATION
The Safety Board
investigator released the wreckage to the owner's representative on June 23,
2005.
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