ANC15LA034

NTSB accident investigation · Piper PA 22 · Skwentna, AK · June 1, 2015

Accident · Minor injuriesLimited investigationFinal report
Date
May 31, 2015, 20:00 local (Jun 1, 2015, 04:00 UTC)
Place
Skwentna, AK
Injuries
1 minor
Damage
Substantial damage
Phase of flight
Maneuvering
Aircraft
N2828PPiper PA 22
Defining event
Maneuvering-low-alt flying: Loss of engine power (total)
Weather
Visual (VMC) · Day
Status
Completed · report September 8, 2015
Report
Approved by Office Director
NTSB office
Alaska Regional Office
Parties
FAA
FAA report
20150531013389A
Case key
91283

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

On this page

Probable cause

The NTSB’s determination of the probable cause, and any contributing factors.

The pilot's failure to follow the airplane's operating limitations by rapidly opening the throttle, which resulted in a loss of engine power. Contributing to the accident was the pilot's decision to maneuver the airplane at low altitude even though he was not taking off or landing.

Findings · 4

NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings.

Analysis

The pilot stated that he was maneuvering the airplane at low altitude to practice approaches at an unimproved airstrip. After passing over some trees in a northerly direction, the airplane began a rapid descent. The pilot applied full power in an effort to correct for the descent, but the engine power decreased. When the airplane was about 25 ft above ground level, the left wing struck a tree, and the airplane then impacted terrain in a slight left bank. The airplane slid along the ground for about 18 ft before impacting a berm, which caused the airplane to become airborne and rotate counterclockwise 180 degrees before coming to rest in a near-level pitch attitude. A Federal Aviation Administration airworthiness directive (AD) applicable to the airplane required that a placard with the following operating limitation be placed near the throttle: "DO NOT OPEN THROTTLE RAPIDLY – (IDLE TO FULL THROTTLE, 2 SECONDS MINIMUM.)" The AD was issued to prevent power interruption and acceleration hangup that could result from abrupt throttle movement. The airplane was in compliance with the AD. The pilot stated that, when he opened the throttle, he did so rapidly, faster than the 2-second requirement. It is likely that the pilot's rapid opening of the throttle interrupted the fuel supply to the engine, which resulted in a loss of engine power.

Factual narrative

The factual narrative454 words

On May 31, 2015, about 2000 Alaska daylight time, a tailwheel-equipped Piper PA-22 airplane, N2828P, sustained substantial damage after impacting terrain while maneuvering at low level about 17 miles southeast of Skwentna, Alaska. The student pilot and sole occupant received minor injuries. The airplane was registered to, and operated by, the pilot under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 as a personal cross-country flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan had been filed. During an interview with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on June 01, 2015, the pilot stated that he was maneuvering the airplane to "drag the runway" of an unimproved airstrip. After passing over some trees in a northerly direction, the airplane began a rapid descent. The pilot applied full power in an effort to correct for the descent, but the engine power decreased. About 25 feet above ground level (agl), the left wing struck a tree, and the airplane impacted terrain in a slight left bank. The airplane slid along the surface for about 18 feet before impacting a berm, which caused the airplane to become airborne and rotate counter clockwise 180 degrees before coming to rest in a near level pitch attitude. During a post-accident examination of the airplane, including maintenance records, it was discovered that Federal Aviation Administration (FAA) Airworthiness Directive (AD) 73-09-06 was applicable to Piper PA-22-150 airplanes with Lycoming O-320 series engines and Marvel Schebler Carburetors Model MA-4-SPA, part numbers 10-3678-11, 10-3678-12, and 10-3678-32. The accident airplane was equipped with a Lycoming O-320 engine and a Marvel Schebler Carburetor, model number MA-4SPA, P/N 10-3678-32, and the airplane was in compliance with the AD by having the required placard in place at the time of the accident. The AD states, in part: "To prevent power interruption and acceleration hangup resulting from abrupt throttle movement, accomplish the following: Attach the following operating limitation placard to the instrument panel near the throttle in full view of the pilot. Use 1/8 inch min. size lettering. 'DO NOT OPEN THROTTLE RAPIDLY – (IDLE TO FULL THROTTLE, 2 SECONDS MINIMUM)' The placard may be fabricated by the owner or operator." The pilot stated that when he advanced the throttle, he did so in a rapid motion, faster than the 2-second requirement. The closest weather reporting facility is Skwentna Airport, about 17 miles northwest of the accident site. At 1850, an aviation routine weather report (METAR) from the Skwentna Airport was reporting in part: winds from 290 degrees at 7 knots; visibility, 30 statute miles; sky condition, few clouds at 3500 feet, scattered at 20000 feet; temperature 77 degrees F; dewpoint 37 degrees F; barometric pressure 29.74inHG.

Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident.

Aircraft

Registration
N2828P
Reported as
Piper PA 22
Category
Airplane
Serial number
22-3121
Built
1955
Airframe hours
4,082
Engine
Lycoming O-320 SERIES, 150 horsepower, reciprocating
Damage
Substantial damage
Flight
Personal · Part 91
Operator
Levi S. Wood
Registered owner
Levi S. Wood
Airworthiness certificate
Standard, Normal
Last inspection
Annual · June 9, 2014
Departed
SKW · Skwentna, AK
Destination
MRI · Anchorage, AK
Equipment
Electronic flight bag or handheld device, Angle of attack indicator, ADS-B, Handheld GPS

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Student pilot
Age
43
Injuries
Minor
Certificate
Student
Medical
Class 3, With waivers/limitations
Seat
Left
Restraint
3-point
Flight hours
55 total · 55 in this make and model · 14 as pilot in command

Weather

Conditions
Visual (VMC) · Day
Wind
290° at 7 knots
Visibility
30 statute miles
Lowest ceiling
None
Temperature
77 °F, dew point 37 °F
Altimeter
29.73 inHg
Observed at
PASW, 18 nm away

Docket · 3

The files NTSB released with the investigation on July 30, 2015, on NTSB’s docket system: statements, records, photos and specialists’ reports. 3.6 MB in all.

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.

Other investigations on N2828P · 2

Matched to the same aircraft by N-number and date.