Piper PA46 N301DM

Summary

On 2 June 2016 at about 09:20 local time, a Piper PA46 registered N301DM was involved in an accident near Seattle, Washington, United States. 2 people were on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

2 June 2016 at 09:20

Classification

Accident

Location

Seattle, Washington, United States

Nearest airport

Boeing Field/King County Intl (BFI)

Coordinates

47.5300, -122.3019

Aircraft

Piper PA46

Registration

N301DM

Category

Airplane

Year built

1999

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Reno → Seattle

Aircraft damage

Substantial

Weather

VMC

Light

Night/Dark

NTSB number

WPR16LA127

Nobody was injured.

The pilot’s failure to use the emergency procedures checklist for generator failures or for gear extension following a loss of electrical power due to the separated flag terminal of a diode in overstress, which resulted in a gear-up landing.

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

Read the full NTSB narrative

The pilot departed in dark night conditions for the cross-country flight. While air traffic control vectored the accident airplane for the instrument approach to the destination airport, both of the airplane’s generator circuit breakers popped out, but the pilot did not observe a generator failure light. He subsequently pushed both circuit breakers in and they remained in. Shortly thereafter, when given the final vector to join the localizer, the instrument panel went dark, and all post lights, backlit gauges, and engine instrument gauges went dark and failed. The failure also affected the three green landing gear down-and-locked lights and the landing gear warning horn. According to the pilot, it was too dark to see the position of all the circuit breakers; rather than troubleshooting the problem in the air, he elected to proceed with the instrument approach. The pilot subsequently landed with the landing gear retracted, which resulted in substantial damage to the undercarriage and the left wing. A postaccident examination revealed that a diode located between the left main electrical bus circuit breaker and the main bus was found to have a separated flag terminal, which caused an open circuit. As a result, it is likely that before the accident, the left tie bus and main bus circuit was not providing a conductive electrical path, which required the right tie bus and main bus circuit to carry the full load. When the right main electrical bus circuit breaker tripped due to an excessive electrical load, the electrical path from the tie bus to the main bus no longer provided power. Subsequent testing of the subject diode revealed that the solder joint had failed in overstress though the diode itself was functional. The pilot reported that he did not refer to or use the airplane's emergency procedures checklist for a generator failure, which directs the pilot to reduce electrical loads in the event of such a failure. Depending on how much the electrical load was reduced, the pilot may have prevented the right main circuit breaker failure and retained the ability to lower the landing gear. Additionally, the pilot failed to use the emergency landing gear extension procedure. The generator failure emergency procedures checklist contains a CAUTION that states, "Without electrical power, the landing gear must be lowered with the emergency extension procedure. The gear position lights, and the flaps will be inoperative." Had the pilot used the checklists for a generator failure and, subsequently, for gear extension, this accident would have likely been prevented.

Quoted verbatim from the NTSB record.