Pilot Debrief

Cirrus SR22 near Tyler, TX — 2019-11-22

Final reportCEN20LA020
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Date
2019-11-22
Location
Tyler, TX, USA
Aircraft
Cirrus SR22
Registration
N969JM
Category
Airplane
Highest injury
Serious
Fatalities
0
Phase of flight
Cruise

Probable cause

A total loss of engine power as a result of detonation due to a combination of improper magneto to engine timing and a rich fuel mixture.

NTSB narrative

According to the pilot, about 2 minutes after leveling off at a cruise altitude of 3,000 ft above mean sea level (msl), the engine shook and vibrated. He switched his multifunction display (MFD) to the engine parameter page and all engine indications appeared normal. About 2 minutes later, the indication of the No. 5 engine cylinder turned from green to red. He then reported the engine problem to air traffic control and announced his intentions to divert to an alternate airport. Unable to maintain altitude he began a descent. Shortly thereafter, the engine appeared to operate normally, and he was able to climb about 200 ft per minute before the shaking returned. The airplane descended out of the clouds about 1,200 ft msl, and the pilot deployed the airplane’s parachute system. The airplane impacted the ground and was substantially damaged. A postaccident examination of the engine revealed that the No. 5 piston head exhibited cleaning and damage consistent with detonation, while the No. 1 cylinder exhibited signatures consistent with the initial phase of detonation. The magneto timing on the engine measured at 27° before top center (BTC) rather than the factory specification of 24° BTC. According to the engine manufacturer, coupled with a rich mixture, this could result in detonation. When asked to describe the engine leaning procedure used, the pilot stated that he would lean the mixture to the blue line on the MFD. According to the airframe manufacturer, the Lean Assist blue line does not take into account engine timing. It is likely that the incorrect engine timing, when combined with a mixture setting that was too rich for the engine condition, resulted in detonation. Investigators did not establish the last time the engine timing was adjusted.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have leaned the mixture correctly to prevent detonation.

NTSB coding

Evidence available

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

Docket documents11

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