Tuesday, November 7, 2017

Cirrus SR-22, N999VX, registered to PHD Ventures Inc: Incident occurred November 07, 2015 at Paso Robles Municipal Airport (KPRB), San Luis Obispo County, California

The National Transportation Safety Board did not travel to the scene of this incident. 

Additional Participating Entities:  
Federal Aviation Administration / Flight Standards District Office; San Jose, California
Cirrus Aircraft; Duluth, Minnesota 

Aviation Incident Factual Report - National Transportation Safety Board:  https://app.ntsb.gov/pdf

Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms

http://registry.faa.gov/N999VX



NTSB Identification: WPR16IA025
14 CFR Part 91: General Aviation
Incident occurred Saturday, November 07, 2015 in Paso Robles, CA
Aircraft: CIRRUS DESIGN CORP SR22T, registration: N999VX
Injuries: 5 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

On November 7, 2015, at 1234 Pacific standard time, a Cirrus SR22T, N999VX, sustained minor damage during the landing roll at Paso Robles Airport, Paso Robles, California. The airplane was registered to PHD Ventures Inc., and operated under the provisions of 14 Code of Federal Regulations Part 91. The flight instructor, student pilot, and three passengers were not injured. Visual meteorological conditions prevailed and no flight plan was filed.

According to the flight instructor, the student pilot was flying the airplane and the airplane touched down normally on the main gear. The student pilot then lowered the nose of the airplane and the nose landing gear collapsed.

Post incident examination revealed that the nose landing gear had separated. The nose landing gear consists of a main strut tube and two gusset tubes near the top portion of the main strut tube. The separation involved a crack beginning at the edge of the side gusset tubes weld to the main strut tube. Prior to the incident, a similar event had occurred, NTSB Incident WPR15IA252, and following this event, additional incidents occurred, including one in Japan. 

The NTSB Materials Laboratory examined the nose landing gear strut and determined that the failure of the landing gear was the result of high stress fatigue cracking due to sideways bending from one side. No mechanical or metallurgical anomalies were noted with the landing gear. 

On March 7, 2016, Cirrus Design Corporation issued Service Advisory Letter SA 16-03, which denoted the following:

• Cracks have been discovered on the nose landing gear strut assembly at the welds between the strut tube and the LH and RH gusset tubes.

• A visual inspection of the welds between the strut tube and the LH and RH gusset tubes for cracks must be performed every time the engine cowling is removed.

• If cracks are found, the aircraft is prohibited from flight until the nose landing gear strut assembly is replaced. (Refer to AMM-32-20).

Additionally, Cirrus Design Corporation performed structural testing of the nose landing gear. 

Based on the data provided by the NTSB metallurgy lab, and a video of the Japan incident airplane experiencing nose landing gear shimmy 6 months before the nose gear collapsed, Cirrus explored two different methods of producing side loads in the nose landing gear. The first was through taxi and towing, the second through shimmy. Flight testing showed that significant side loads on the nose landing gear would develop during a shimmy event.

As a result of the testing, Cirrus did the following:

In April 2016, Service Bulletin SB2X-32-22 was released to inspect all the nose landing gear in the field for cracks in the welds between the strut tube and the LH and RH gusset tubes. In addition to the one-time inspection required by Service Bulletin SB2X-32-22, Cirrus added a post-shimmy inspection to Chapter 5-50 Unscheduled Maintenance Checks of the Aircraft Maintenance Manual (AMM). Similar to the hard/overweight landing inspection, this post-shimmy inspection would look specifically for cracks at the gusset welds exactly as noted in the Service Bulletin.

Based on the potential for damage to the nose landing gear due to loading from non-standard and abusive tug operation, Service Advisory SA16-05 was released offering aircraft towing guidance. This guidance includes the following;

• When towing aircraft, do not stop/start abruptly, especially when the tow bar is at an angle greater than 45° either side of center.

• When positioning the aircraft with a towing vehicle, the angle of the tow bar must be less than 45° either side of center for both pulling and pushing. Hand towing must be used if angles greater than 45° either side of center are needed for positioning.

• Do not tow aircraft at speeds higher than 15 mph.

Cirrus Aircraft also incorporated specific emphasis and recommendations on how to further discourage shimmying on landing and actions to be taken if the situation occurs on landing in their pilot training program. These incorporations are included in the Landing Standardization Course. Maintenance guidance is also available to mechanics following a shimmy event.

To increase the strength of the weld in the critical area on the nose landing gear, the thickness of the main strut tube was analyzed with an increased wall thickness from 0.125-inch to the full thickness of 0.156-inch. The result of the analysis was an increase (3-5%) in the local stress levels in the static analysis. This design change has been made for all new and replacement gear.

NTSB Identification: WPR16IA025
14 CFR Part 91: General Aviation
Incident occurred Saturday, November 07, 2015 in Paso Robles, CA
Aircraft: CIRRUS DESIGN CORP SR22T, registration: N999VX
Injuries: 4 Uninjured.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

On November 7, 2015, at 1234 Pacific standard time, a Cirrus SR22T, N999VX, sustained minor damage during the landing roll at Paso Robles Airport, Paso Robles, California. The flight was being operated under the provisions of 14 Code of Federal Regulations Part 91. The flight instructor, student pilot, and two passengers were not injured. Visual meteorological conditions prevailed and no flight plan was filed.

According to the flight instructor, the student pilot was flying the airplane and the airplane touched down normally on the main gear. The student pilot then lowered the nose of the airplane and the nose landing gear collapsed.

1 comment:

D Naumann said...

OK, which one is it, four or five passengers? The two NTSB reports report two different things.

If it's five, I hope one was a babe-in-arms.