Mooney M20J N4570H

Summary

On 29 July 2013 at about 23:35 local time, a Mooney M20J registered N4570H, operated by Stable Air LLC, was involved in an accident near Leonardtown, Maryland, United States. 2 people were on board and 2 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

29 July 2013 at 23:35

Classification

Accident

Location

Leonardtown, Maryland, United States

Coordinates

38.2878, -76.6011

Aircraft

Mooney M20J

Registration

N4570H

Category

Airplane

Year built

1979

Engines

1

Operator

Stable Air LLC

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Route

Leonardtown → Leonardtown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ERA13LA342

2 people had minor injuries.

The improper installation and inspection of the throttle linkage by maintenance personnel, which resulted in the throttle linkage coming loose and a subsequent partial loss of engine power.

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

Read the full NTSB narrative

The flight instructor and certificated pilot, who was the pilot flying, were practicing instrument maneuvers about 1,500 feet mean sea level when the engine stopped responding to throttle control inputs and producing enough power to maintain level flight. The flight instructor unsuccessfully attempted to restore engine power, and the pilots chose to conduct an off-airport landing to a field, which resulted in substantial damage to the fuselage and wings. Following the accident, one of the airplane's owners inspected the airplane before the wreckage recovery. He removed the engine cowling and found a bolt and nut resting on the bottom of the cowling. He also noted that the throttle arm linkage was not connected to the throttle body arm. He reported that the throttle linkage was found in the full-forward position and that the throttle body arm was found in the low-power setting. He asked an individual to move the throttle control in the cockpit and noted that the throttle linkage moved but that the throttle body arm did not move. A postaccident test run of the engine was performed following the replacement of the bolt that connected the throttle cable to the throttle control arm, and no anomalies were noted that would have precluded normal operation. Review of maintenance logbook records revealed that the most recent annual inspection was completed on April 15, 2013, at a recorded tachometer reading of 5,276.8 hours. The mechanic who performed the inspection reported that all engine control cables were "checked" and lubricated and that the throttle linkage bolt, nut, and cotter key were in place. The most recent engine maintenance was performed 6 days and 1 flight hour before the accident by the same mechanic. During the maintenance, the starter was removed, overhauled, and reinstalled on the engine, and no maintenance was conducted in the area of the throttle linkage and throttle body arm. It is likely that, during maintenance at a previous undetermined time, the cotter pin was removed from the throttle linkage bolt and nut and not reinstalled. The nut then gradually loosened and fell off, which allowed the bolt to become loose. The missing cotter pin should have been detected during the most recent annual inspection or engine maintenance.

Quoted verbatim from the NTSB record.