WPR21LA208 · Boeing A75N1(PT17)
One Slim Rabbit Boeing A75N1(PT17) · Accident: loss of engine power (partial) during initial climb
Event
- NTSB case
- WPR21LA208
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- Event fatalities
- Unknown
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Boeing A75N1(PT17)
- Aircraft type
- Boeing A75
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N75016
- Operator
- One Slim Rabbit
- Onboard fatalities
- Unknown
- Route
- From not recordedTo not recorded
- Aircraft age
- About 79 years (built 1942)
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Initial climb
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Loss of engine power (partial)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Aircraft › Aircraft propeller/rotor
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The airplane was climbing out shortly after takeoff when the pilot noticed that the engine rpm was decreasing, and that the airplane was not gaining altitude. The pilot added that, even with the decrease in engine rpm, the engine was still producing some engine power. The pilot-rated passenger stated that the airplane was not gaining or losing altitude and that he verified that the propeller, throttle, and mixture control levers were in the correct settings. The pilot decided to maneuver away from power lines and make a forced landing onto a field. Subsequently, the lower part of both wings impacted the ground and sustained substantial damage.
A postaccident examined revealed that the propeller governor had a relief valve spring that was shorter in length than a standard relief valve spring. The shorter relief valve spring resulted in an internal governor pressure of 125 psi, which was less than the manufacturer’s setting of 180 to 200 psi. The lower internal pressure setting slowed the governor’s ability to make the immediate corrections in propeller blade pitch necessary to maintain the engine rpm during the climb out, which caused the engine to lose partial power.
Probable cause
The improper installation of a relief valve spring that was shorter than the standard spring length, which slowed the response of the propeller governor to change the pitch of the blades during climbout, resulting in a partial loss of power.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR21LA208
- Event ID
- 20210527103156
- Case number
- WPR21LA208
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, cause areas. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: cd16b1087a45b24a7211fa6162d1d6367b223f893ded3cf5d0a19df0efbdda96; retrieved 2026-09-16T14:05:36.785Z.