Maule M7-235B near Sunriver, OR — 2019-06-22

Probable cause

A partial loss of engine power due to the separation of baffling in both mufflers. Contributing to the accident was the pilot's failure to retract the landing gear on the float-equipped airplane before performing a forced landing to the river.

Contributing factors

Contributing to the accident was the pilot's failure to retract the landing gear on the float-equipped airplane before performing a forced landing to the river.

NTSB narrative

The pilot and passenger departed on a local flight in the amphibious airplane from a paved runway. The passenger described the airplane's rate of climb after takeoff as "slow" and stated that it was apparent that the airplane would not clear the 50-ft-tall trees ahead. A witness described the airplane as "struggling to gain altitude" and noticed a "definite power loss." The pilot performed a forced landing to a river, where the airplane immediately nosed over and began filling with water. The landing gear was found in the extended position and the water rudders were retracted. The landing gear position indicators were operational and also indicated that the landing gear was extended. The position of the landing gear likely resulted in the airplane nosing over upon impact with the water. Examination of the engine revealed that the muffler baffles had broken at the weld point. The left muffler baffling moved freely inside of the muffler. The right muffler baffling was turned 180° and was obstructing the exhaust outlet. A test run of the engine with the mufflers installed was unsuccessful; however, upon removal of the mufflers, the engine performed with no anomalies. There is no requirement to check the inside of a muffler during annual or 100-hour inspections to ensure that the baffling is intact. It could not be determined as to how long these mufflers had been in this condition. It is likely that the airflow restriction of the separated baffling resulted in a partial loss of engine power and the airplane's subsequent inability to climb after takeoff.

Analysis

Primary failure mode

Engine power loss

First missed decision gate

Pilot could have aborted takeoff when slow climb was evident.

NTSB coding

• Landing gear not configured · Emergency descent

Evidence available

• Photos
• 10 docket documents

Docket documents10

• Release of Aircraft Wreckage, NTSB Form 6120.15form
• FAA Inspector's Statementinterview
• Passenger's Statementinterview
• Witness' Statementsinterview
• Certification of Party Representativeother
• Engine Examinationother
• Letter from Viper Aviationother
• Maule AFM Supplement 2other
• Accident Report Photographsphotos
• Toxicology Reportreport