Pilot Debrief

METCALFE ROBERT B VANS RV 6 near Selma, CA — 2017-10-30

Final reportWPR18LA021
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Date
2017-10-30
Location
Selma, CA, USA
Aircraft
METCALFE ROBERT B VANS RV 6
Registration
N88MV
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Descent

Probable cause

The pilot’s failure to properly secure an alternator ground cable swage that led to problems with the electrical system and/or electronic engine controls, which resulted in a total loss of engine power.

NTSB narrative

The pilot reported that about 25 minutes into the local personal flight in the experimental amateur-built airplane, with all systems appearing to operate normally, he noticed that the batteries (located near his right foot) were getting hot and that the system voltage indicated about 15.5V, which was above the normal value of about 13V. Almost immediately thereafter, the engine lost total power. The pilot activated the bus manager emergency power switch and independently selected each of the two engine control units but was unable to restore engine power. He chose a rural road for a forced landing but changed his path to clear a truck on the road; the airplane impacted a vineyard on the side of the road, nosed over, and came to rest inverted. The pilot had recently decided to change the carburetor and conventional magneto ignition systems to electronic versions for "performance and efficiency improvements." He purchased a kit that included an electronic fuel injection system and replaced the magnetos himself with a fully electronic ignition system. After completing the installations, the pilot began testing the systems and engine operation. Two days before the accident flight, he conducted two flights of the airplane with the new systems; both flights were brief and uneventful. Postaccident examination revealed no anomalies with the airplane fuel system or the engine itself. Because the engine was completely reliant on electricity for operation and control of the ignition and fuel injection, the cause of the engine power loss was likely due to a problem with the electrical system or supply. The only nonimpact-related anomaly discovered during the engine and airframe examination was that the swage/crimp of the terminal to the conductor of the primary alternator ground cable was loose, and the conductor and terminal bore evidence (black residue) of electrical arcing. The appearance was consistent with that residue having been caused by the looseness of the swage/crimp and as having been loose for an extended period before the accident. This looseness and arcing indicated that there were transient power interruptions. Such interruptions also create the potential for spurious electrical power variations, which could potentially interfere with the operation of the airplane's electrical or electronic systems, including the alternator, batteries, bus manager, and both the fuel injection and ignition systems.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have switched to backup battery or emergency power sooner.

NTSB coding

Evidence available

  • Photos
  • 11 docket documents
View NTSB final reportView NTSB docket

Docket documents11

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