NTSB Final Report: Focke-Wulf FWP-149D | Aero-News Network
Aero-News Network
RSS icon RSS feed
podcast icon MP3 podcast
Subscribe Aero-News e-mail Newsletter Subscribe

Airborne Unlimited -- Most Recent Daily Episodes

Episode Date



Airborne-Wednesday Airborne-Thursday


Airborne On YouTube



Airborne-Unlimited-05.15.24 Airborne-AffordableFlyers-05.16.24


Thu, Sep 14, 2023

NTSB Final Report: Focke-Wulf FWP-149D

The Mechanic Told The Pilot Not To Fly The Airplane Until The Laboratory Results Were Returned

Location: Killeen, Texas Accident Number: CEN21FA304
Date & Time: July 4, 2021, 17:22 Local Registration: N9145
Aircraft: Focke-Wulf FWP-149D Aircraft Damage: Destroyed
Defining Event: Loss of engine power (total) Injuries: 1 Fatal
Flight Conducted Under: Part 91: General aviation - Personal

Analysis: The pilot was conducting a cross-country flight when the airplane had a total loss of engine power while it approached the intended destination airport.

Based on witness accounts, the pilot was unable to glide the airplane to the intended destination airport and entered an inadvertent aerodynamic stall at a low altitude. One witness reported that the airplane’s wings rolled left-and-right 2 to 3 times before the airplane “stalled” with the left wing down. The airplane impacted the ground in a left-wing down roll attitude and was destroyed during a postimpact fire.

Postaccident examination of the engine determined that the loss of engine power was due to a fatigue failure of a crankshaft counterweight mounting lobe, which resulted in the separation of a counterweight and catastrophic secondary damage to the engine drivetrain. A couple days before the accident, an aviation mechanic found metal contamination in the engine oil filtration system after an associated warning light illuminated during a postmaintenance engine run. The mechanic and pilot discussed the metal contamination and agreed to have it submitted to a laboratory for identification.

The oil filtration system was equipped with a ball-and-spring “bypass” switch, which when wired to a cockpit warning light offered a visual indication of when the filtration system was bypassing engine oil instead of flowing through the filter screen. A separate magnetic chip detector was offered as an optional feature for the oil filtration system; however, postaccident examination of the oil filtration system confirmed that the optional chip detector was not installed. As such, the warning light installed in the instrument panel was mislabeled “chip detector” instead of a label that conveyed the oil filtration system was in a bypass condition.

When the mechanic saw the warning light illuminated during his post-maintenance engine run, it was a visual indication that the engine had produced enough metal contamination to restrict oil flow in the filtration system, resulting in a bypass condition. The mechanic cleaned the filtration housing, filter screen, and bypass switch. He then added new oil to the engine and performed another engine run, during which the “chip light” did not illuminate. The mechanic told the pilot not to fly the airplane until the laboratory results were returned, but he did not ground the airplane to prevent additional flights.

The pilot conducted three flights, totaling at least 1.8 hours, following the maintenance. As such, it is likely he erroneously believed the airplane was safe to fly if the “chip detector” warning light was not illuminated, when, in fact, the engine was not in an airworthy condition due to the progressive failure of the crankshaft counterweight mounting lobe that likely produced the metal contamination found during the last maintenance.

A review of automatic dependent surveillance-broadcast track data revealed that the pilot did not maintain the airplane’s best glide airspeed during the final minutes of the flight. Based on the published glide performance, the airplane did not have sufficient altitude to reach the runway at any point during the approach. However, had the pilot maintained best glide airspeed the airplane would have retained a safe margin above the aerodynamic stall speed and, as such, might have resulted in a less severe off-field landing.

Probable Cause and Findings: The National Transportation Safety Board determines the probable cause(s) of this accident to be -- The total loss of engine power due to a fatigue failure of a crankshaft counterweight mounting lobe, which resulted in a counterweight separation and catastrophic secondary damage to the engine drivetrain. Contributing to the accident was the mislabeled warning light, the pilot’s erroneous belief that the airplane was safe to operate after the metal contamination was observed in the oil filtration system, and his failure to maintain best glide airspeed during the forced landing, which resulted in the airplane exceeding its critical angle-of-attack and an inadvertent aerodynamic stall at a low altitude.

FMI: www.ntsb.gov


More News

Samson Sky Hits the Wind Tunnel

Improvements Stack as Brand Readies for Mass Production Samson Sky updated followers on its flying car progress, describing some of the travails of the wind tunnel as they get clos>[...]

ANN's Daily Aero-Term (05.22.24): LAHSO

LAHSO An acronym for “Land and Hold Short Operation.” These operations include landing and holding short of an intersecting runway, a taxiway, a predetermined point, or>[...]

Aero-FAQ: Dave Juwel's Aviation Marketing Stories -- ITBOA BNITBOB

Dave Juwel's Aviation Marketing Stories ITBOA BNITBOB ... what does that mean? It's not gibberish, it's a lengthy acronym for "In The Business Of Aviation ... But Not In The Busine>[...]

ANN's Daily Aero-Linx (05.19.24)

Aero Linx: Space Medicine Association (SMA) The Space Medicine Branch was founded in 1951 as the first constituent organization of the Aerospace Medical Association (AsMA). In 2006>[...]

ANN's Daily Aero-Term (05.19.24): Back-Taxi

Back-Taxi A term used by air traffic controllers to taxi an aircraft on the runway opposite to the traffic flow. The aircraft may be instructed to back-taxi to the beginning of the>[...]

blog comments powered by Disqus





© 2007 - 2024 Web Development & Design by Pauli Systems, LC