ASN Wikibase Occurrence # 236881
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| Date: | Monday 8 June 2020 |
| Time: | 08:45 LT |
| Type: |  Piper PA-12 Super Cruiser |
| Owner/operator: | Private |
| Registration: | N3188M |
| MSN: | 12-1867 |
| Year of manufacture: | 1947 |
| Engine model: | Lycoming O-235 SERIES |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Lake Hood Airport (PALH/LHD), Anchorage, AK -
 United States of America
|
| Phase: | Landing |
| Nature: | Training |
| Departure airport: | Anchorage, AK |
| Anchorage, AK | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The flight instructor reported that after conducting a landing and departure at a remote lake in the float-equipped airplane, they climbed to about 500 ft above ground level (agl) before turning to a left crosswind traffic pattern leg. While on the left crosswind leg, the airplane yawed abruptly to the right and the pilot receiving instruction indicated that the controls felt strange. The flight instructor assumed control of the airplane and noticed drastically diminished control about the vertical axis. In addition, significant downward elevator pressure (forward control yoke) was required. The flight instructor decided to return to their destination airport, where emergency services were available, and conducted an uneventful landing.
An examination of the rudder revealed that the vertical rudder post fractured above the upper hinge point and the top portion of the rudder folded over the horizontal stabilizer tail brace wires. As part of the NTSB's investigation, examination of four other similarly fractured rudder posts revealed that they had all fractured above the upper hinge. Each of the rudder posts exhibited evidence of a progressive fracture mechanism. Although the fracture surfaces of the accident rudder post were obliterated by post-fracture contact, fatigue fracture features were observed on three of the other rudder posts.
Analysis of the material composition of all of the posts found it to be consistent with Piper part number 40622 posts made of American Iron and Steel Institute (AISI) 1025 carbon steel. According to engineering drawings, rudder posts were originally manufactured from AISI 1025 carbon steel. A Piper engineering change order specified a change to AISI 4130 low-alloy steel that was incorporated into the part number 40622 engineering drawing in June 1974. According to Advisory Circular 23-27, Parts and Materials Substitution for Vintage Aircraft, AISI 4130 low
Accident investigation:
 |
|
Sources:
NTSB ANC20LA059
FAA register: https://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=N3188M
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 10-Jun-2020 08:51 | Captain Adam | Added |
| 01-Jul-2022 09:09 | ASN Update Bot | Updated [Time, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative, Category, Accident report] |
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