Amateur-built CX4 accident near Upland, California, June 24, 2020
On June 24, 2020 at about 6:45 pm local time, a 2017 amateur-built CX4, registered N274DR, was substantially damaged in an accident during enroute (descent) near Upland, California (Cable airport). It was a personal flight under general aviation rules (Part 91). 1 person was seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The inflight separation of the propeller assembly due to a fatigue fracture of the crankshaft. Contributing to the accident was the pilot’s restricted visibility during landing, which resulted in an excessive approach speed, a long landing, and subsequent impact with terrain.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 24, 2020 · about 6:45 pm local time
- Place
- Upland, California · Cable · map
- Type
- Accident
- Injuries
- 1 person was seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built CX4 No Series, built 2017
- Registration
- N274DR · no longer on the register · serial 122
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot reported that while returning to the airport after an uneventful flight, the propeller separated from the engine, which resulted in the windscreen and canopy being covered with oil and restricting forward visibility. The pilot continued toward the airport; however, as the airplane crossed the threshold of the runway, he noted that he was going way too fast as he was attempting to keep the airplane aligned with the runway. Subsequently, the airplane touched down near the departure end of the runway, bounced, and impacted the ground. Postaccident examination of the airplane revealed substantial damage to the fuselage and both wings. The propeller assembly and a portion of the engine crankshaft was separated and not located. Examination of the remaining portion of the crankshaft revealed that two fractures initiated at the termination of a square keyway slot in the crankshaft. The presence of ratchet marks at the fracture origins and the presence of progressions marks along the fracture path were indicative of fatigue fracture initiation and growth.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Powerplant sys/comp malf/fail during enroute (descent) defining event
The NTSB's findings
- Aircraft › Aircraft power plant › Engine (reciprocating) › Recip engine power section › Fatigue/wear/corrosion
- Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Airspeed › Not attained/maintained
- Personnel issues › Psychological › Attention/monitoring › Monitoring equip/instruments › Pilot
Pilot
- Certificate: private
- Ratings: single-engine land
- Flight time: 1,130 hours in all; 32 in this make and model; 12.7 in the last 90 days; 11.2 in the last 30 days; 1,130 as pilot in command
- Last flight review: September 21, 2019
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: ctr
The aircraft
- Last inspection: condition inspection, July 2, 2021
- Maximum gross weight: 910 lb
- Seats: 1
- Landing gear: fixed
- Engine: Hummel VW 2400CC (piston); 32 hours total
The flight
- Departed from: CCB Upland CA at 6:00 pm
- Flight plan: none
- Runway 24, 3,863 ft by 75 ft
Weather at the time
- Light: daylight
- Wind: from 220° at 5 knots
- Visibility: 8 statute miles
- Sky: clear
- Temperature: 81°F (27°C), dew point 59°F (15°C)
- Altimeter: 29.86 inHg
- Observation at 6:55 pm from KCCB
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
4 documents, released by the NTSB on June 22, 2022. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | NTSB Materials Laboratory Report | PDF, 6 pages | View Download |
| 2 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 7 pages | View Download |
| 3 | Evidence Control Form | PDF, 1 page | View Download |
| 4 | Photo Array | PDF, 2 pages | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.