History of Flight
On April 5, 2021, about 0950 central daylight time, a Piper PA-23-250, N5018Y, was destroyed when it was involved in an accident near Springfield, Tennessee. The flight instructor and the commercial-rated pilot receiving instruction were seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The purpose of the flight was to conduct multi-engine training.
The instructor stated that during taxi, he briefed the student on a simulated engine failure during the takeoff roll. The student responded appropriately, then initiated a takeoff with about 4,400 ft of runway remaining. Shortly after becoming airborne, the left engine started losing power and the airplane began yawing. The instructor attempted to feather the left engine propeller, but it would not feather. He described a descent he could not arrest and his attempts to maintain control during the forced landing.
Witnesses reported an unusual sound from the airplane during the takeoff roll, inconsistent with takeoff power. One witness, an airline transport pilot and mechanic, stated the airplane climbed to about 100 ft above ground level while on runway heading with landing gear extended. It then entered a shallow left turn and disappeared behind a tree line. Another witness described popping, sputtering, and crackling noises, and said the airplane was clearly struggling to climb.
The company mechanic reported that the airplane was normally airborne by the time it reached the company hangar, but during the accident takeoff, it did not lift off until past the windsock, about 1,400 ft into the takeoff roll. ADS-B and radar data showed the airplane departed from runway 22, reached 86 knots groundspeed about midfield, then slowed and did not exceed 80 knots. It climbed shallowly for about 1 mile, then entered a descending, decelerating left turn until the last target near ground level at 59 knots.
Personnel Information
The flight instructor held a commercial pilot certificate with ratings for airplane single-engine land, multiengine land, and instrument airplane, and a flight instructor certificate with ratings for airplane single and multiengine. His multiengine rating was added September 20, 2020. He reported 1,618 total flight hours, with 13 hours in the accident airplane make and model.
The pilot receiving instruction held a commercial pilot certificate with ratings for rotorcraft-helicopter and instrument helicopter, and private privileges for airplane single-engine land. He had accrued 1,200 total flight hours. His multiengine training began 3 days before the accident, with 1.5 hours of multiengine experience, all in the accident airplane.
Aircraft Information
The airplane was manufactured in 1963 and powered by two Lycoming O-540-A1D5, 250-horsepower engines. Its most recent annual inspection was completed March 5, 2021, at 6,866.16 total aircraft hours.
Pilots who flew the accident airplane during the week before the accident reported that the left engine either stopped or ran roughly on the ground and in the air when the fuel selector was in the left inboard tank position. When moved to the left outboard tank position, the engine could be restarted or smooth operation restored. These power-loss events were reported to maintenance. On April 2, 2021, a flight instructor could not start or sustain power on the left engine with the inboard tank selected but ran it continuously on the outboard tank. He demonstrated the discrepancy to maintenance before rejecting the airplane.
According to the Owner's Handbook, the airplane's takeoff run was 750 ft and 1,100 ft over a 50-ft barrier. The landing roll was 900 ft.
Wreckage and Impact Examination
The airplane was examined by two FAA aviation safety inspectors. The cockpit and cabin areas were destroyed and came to rest inverted. The wings were mostly separated. The left engine propeller blades appeared undamaged and in what approximated a feathered position. The right engine propeller blades showed twisting, bending, leading edge gouging, chordwise scratching, and tip curling.
Control continuity was confirmed through several breaks, with overstress features. The right wing fuel tank contained about 15 to 20 gallons of fuel, with a clear fuel pickup and intact filter screen. The right side gascolator contained debris, and its filter screen was obstructed with rust. No fuel was noted in the left gascolator, its filter screen was not installed, and the gascolator securement was not safety wired. The aluminum gascolator bowl had deep corrosive pitting with fresh scribe marks consistent with recent cleaning.
The left wing inboard fuel tank was breached, contained trace fuel, and the fuel cap had a loose fit. A 12-inch length of white adhesive duct tape was found loose inside the tank; the adhesive residue matched the fuel cap gasket. The fuel pickup was clear but its filter screen was not installed.
Fuel system continuity was confirmed visually and with compressed air.
The right engine exhibited continuity, compression, and suction on all cylinders. Both magnetos produced spark. The carburetor had impact damage but internal components were intact. The fuel pump operated by hand.
A cursory examination of the left engine was performed prior to shipment for a test run. Continuity, compression, and suction were observed from all cylinders. The oil suction screen had no debris; the oil pressure screen contained about ¼ teaspoon of particulate matter, some magnetic. Due to metal contamination, disassembly was performed instead of a test run. Removal of cylinders revealed spalled intake tappets on Nos. 1 and 2, and spalled exhaust tappet on No. 3. The corresponding camshaft lobes (Nos. 1 and 2 intake, No. 3 exhaust) were severely spalled. Both magnetos produced spark. The carburetor and fuel pump appeared similar to the right.
Additional Information
The most recent engine field overhauls were completed December 9, 1997, more than 23 years before the accident. Lycoming Service Instruction No. 1009BE stated that engine models should be overhauled within 12 calendar years to mitigate deterioration. The left propeller damage and impact signatures were consistent with a feathered position, with no power at impact. The propeller governor bench-tested within specifications except for the low rpm setting, which did not prevent normal operation. The most recent propeller overhauls were December 13, 1999; Hartzell Propeller Service Letter HC-SL-61-61Y specified overhaul periods of 2000 flight hours or 60 calendar months.
Airframe examination showed the landing gear handle and actuators in the down position, consistent with gear extended.
The Airplane Flying Handbook noted that prior to takeoff, pilots should identify a point at which the airplane should be airborne; if not, takeoff should be discontinued.
Vmc (minimum control speed) is defined as the calibrated airspeed at which, with the critical engine suddenly inoperative, directional control can be maintained with not more than 5 degrees bank. There is no requirement for climb capability at Vmc.
Flying Light Twins Safely indicated that loss of directional control may occur at speeds nearly 20 knots above published Vmc when wings are held level. Vmc is solely concerned with directional control under specific conditions, not climb performance.