De Havilland DH112 VENOM N747J

Summary

On 20 July 2018 at about 21:04 local time, a De Havilland DH112 VENOM registered N747J, operated by World Heritage Air Museum, was involved in an accident near Sheboygan, Wisconsin, United States. 3 people were on board and one died. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

20 July 2018 at 21:04

Classification

Accident

Location

Sheboygan, Wisconsin, United States

Nearest airport

Sheboygan County Memorial (SBM)

Coordinates

43.7608, -87.8350

Aircraft

De Havilland DH112 VENOM

Registration

N747J

Category

Airplane

Year built

1957

Engines

1

Operator

World Heritage Air Museum

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Sheboygan → Sheboygan

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

WPR18FA200

1 person died.

The airplane's encounter with wake turbulence from the lead airplane in the formation flight, which resulted in a compressor stall and the airplane's subsequent inability to climb.

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

Read the full NTSB narrative

The pilot was conducting a formation training flight consisting of two airplanes; the accident airplane was in the No. 2 position. The airplane took off about 8 seconds behind the lead (No. 1 position) airplane. Witnesses described the airplane's takeoff as sluggish and indicated that the airplane's wings rocked back and forth shortly after lifting off. The witnesses' testimony was consistent with one witness' video recording, which showed the airplane climbing away from the runway and making a shallow left turn. As the airplane passed the witness' position, the engine sound decreased and rapidly increased. The airplane reached an altitude of about 200 ft above the ground before descending and impacting a farm structure. Another video captured the airplane descending in a slightly nose-up and wings-level attitude before impact. The flaps and landing gear both appeared retracted in that video. No preimpact anomalies with the airframe and engine were found that would have precluded normal operation of the airplane. Signatures consistent with circumferential rub marks within the turbine were identified. Although the rate of rotation at the time of impact could not be determined, the retraction of the landing gear at a normal rate showed that the engine was likely producing some power at that time. One of the witnesses to the accident was a pilot with experience in the accident make and model. He described the engine powering the airplane as "high airflow and thrust" and indicated that the engine could experience a compressor stall when operating at a high angle of attack and a high-power setting. He also stated that the airplane could get into a low energy state if an engine failure occurred and that the airplane would normally accelerate "very quickly" if it leveled off at 200 ft. The witness accounts of the accident airplane's wings rocking back and forth were consistent with the airplane encountering the wake turbulence of the lead airplane. Wake turbulence can disrupt airflow to the engine of a trailing airplane. The final seconds of the witness' video showed the pilot controlling the airplane during the climb to 200 ft, after which the airplane began descending. Thus, the wake turbulence from the lead airplane likely disrupted airflow to the engine and caused a compressor stall and a partial loss of engine power, which resulted in the airplane's inability to continue to climb. Toxicology testing identified sedating medications in the pilot's specimens, but the levels of the medications at the time of the crash were well below the levels that would have caused significant effects. Therefore, it is unlikely that impairing effects of these medications contributed to this accident.

Quoted verbatim from the NTSB record.