Pilot Debrief

CESSNA 172N near Big Bear, CA — 2017-07-29

Final reportWPR17FA171
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Date
2017-07-29
Location
Big Bear, CA, USA
Airport
L35
Aircraft
CESSNA 172N
Registration
N5381J
Category
Airplane
Highest injury
Fatal
Fatalities
2
Phase of flight
Initial climb

Probable cause

The pilot's exceedance of the airplane's critical angle of attack during takeoff in high density altitude conditions, which resulted in an aerodynamic stall, loss of control, and subsequent impact with terrain.

NTSB narrative

The commercial pilot and passenger departed in the airplane from the airport, which was located at an elevation of 6,752 ft mean sea level (msl). Airport surveillance video showed that the airplane became increasingly slow during the initial climb after takeoff. A witness reported that, as the airplane approached the end of the runway, it stopped climbing and entered a nose-high pitch attitude that the witness described as "hanging by the prop." The airplane then turned 90° to the downwind leg of the airport traffic pattern and sank as the wings rocked back and forth before it disappeared behind trees. The wreckage orientation indicated that the airplane maintained a southerly heading before it descended into the tree line. The airplane impacted the ground in a nose-down attitude with partial forward bending of the tail, consistent with an aerodynamic stall. Postaccident examination of the airplane did not reveal any preimpact anomalies. The density altitude about the time of the accident exceeded 9,100 ft msl. The effects of high density altitude conditions on takeoff performance include increased takeoff roll distance and reduced rate of climb. Review of performance charts indicated that the airplane should have been able to climb at a rate around 440 ft per minute; however, the video indicated that the airplane was climbing at a rate of 340 ft per minute. It is likely that, experiencing degraded airplane performance due to the density altitude, the pilot responded by increasing the airplane's pitch attitude in an attempt to improve its rate of climb. The pilot subsequently exceeded the airplane's critical angle of attack, which resulted in an aerodynamic stall and impact with terrain. The pilot's primary flight experience was in turbine engine-equipped rotorcraft, and he had recently received a checkout in the accident airplane make and model that included high density altitude operation and mixture leaning procedures. The airplane's mixture control was found in the full rich position after the accident; however, the position of the control before and during the takeoff could not be determined. If the pilot departed in the high density altitude environment without leaning the fuel/air mixture control or subsequently enrichened the fuel/air mixture control to troubleshoot the airplane's reduced takeoff performance, this would have further reduced the available engine power and the airplane's climb rate.

Analysis

Primary failure mode
Controlled flight into terrain
First missed decision gate
Pilot could have aborted takeoff when unable to maintain altitude.

NTSB coding

Evidence available

  • Video
  • Photos
  • 16 docket documents
View NTSB final reportView NTSB docket

Docket documents16

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