The commercial pilot and his passenger were returning to the airport near Tucson, Arizona, after a 30-minute personal flight. The pilot reported he configured the Cessna 310J for landing, but that the landing gear down indication did not illuminate.
He cycled the landing gear several times, but the landing gear down indication still did not illuminate.
After an air traffic controller confirmed that the landing gear was down, he initiated the landing.
The airplane touched down uneventfully, but, about three seconds later, the right main landing gear (MLG) collapsed.
The airplane subsequently veered right and departed the right side of the runway, which resulted in substantial damage to the right aileron and elevator.
A post-accident examination of the landing gear system revealed that the right MLG down-lock tension was about 30 pounds less than the tension prescribed by the airplane’s service manual.
The fork bolt normally used to adjust the down-lock tension was covered in dirt and oil.
Examination also revealed that the MLG nonadjustable drive tube had separated outboard a few inches from a clevis fitting. The signatures on the tube indicated that it failed in compression on the forward/aft plane.
A review of maintenance records revealed that the airplane’s last annual inspection occurred about four months before the accident. The condition of the fork bolt indicates that it had not been adjusted during this inspection.
The pilot also reported that the rigging procedure in the service manual, which included an item to verify the landing gear down-lock brace tension, was not used during any recent inspections.
Maintenance personnel’s failure to perform the rigging procedure during the airplane’s most recent annual inspection likely led to the insufficient down-lock tension and the drive tube’s failure and the subsequent collapse of the right MLG due to the compression forces experienced upon touchdown.
Probable cause: The insufficient right main landing gear (MLG) down-lock tension due to maintenance personnel’s failure to perform a rigging procedure during the airplane’s most recent inspection, which resulted in the right MLG collapsing during landing.
NTSB Identification: WPR16LA015
This October 2015 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
A quote from the article bothers me: “A review of maintenance records revealed that the airplane’s last annual inspection occurred about four months before the accident. The condition of the fork bolt indicates that it had not been adjusted during this inspection.”
So what? Is there a reason to molest any aircraft rigging during an annual/100 hr, or for that matter, to do a gear swing if there are no squawks and all parts pass a visual inspection? With or without such a functional check, does fiddling with rigging automatically come with an inspection? There’s a lot of assumin’ going on here, and I don’t think much of it is right. But I’m willing to learn.
An annual/100 hr inspection is just that and nothing more. It does not include maintenance. Admittedly, some items such as oil screen inspections are often interpreted as part of an oil change, but it’s wrong.
Does it include a gear swing? It doesn’t seem so:
https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=&r=PART&n=14y1.0.1.3.21#ap14.1.43_117.d
(c) Annual and 100-hour inspections. (1) Each person performing an annual or 100-hour inspection shall use a checklist while performing the inspection. The checklist may be of the person’s own design, one provided by the manufacturer of the equipment being inspected or one obtained from another source. This checklist must include the scope and detail of the items contained in appendix D to this part and paragraph (b) of this section.
Looking at Appendix D to Part 43—Scope and Detail of Items (as Applicable to the Particular Aircraft) To Be Included in Annual and 100-Hour Inspections,
(e) Each person performing an annual or 100-hour inspection shall inspect (where applicable) the following components of the landing gear group:
(1) All units—for poor condition and insecurity of attachment.
(2) Shock absorbing devices—for improper oleo fluid level.
(3) Linkages, trusses, and members—for undue or excessive wear fatigue, and distortion.
(4) Retracting and locking mechanism—for improper operation.
(5) Hydraulic lines—for leakage.
(6) Electrical system—for chafing and improper operation of switches.
(7) Wheels—for cracks, defects, and condition of bearings.
(8) Tires—for wear and cuts.
(9) Brakes—for improper adjustment.
(10) Floats and skis—for insecure attachment and obvious or apparent defects.
I see nothing about gear swings or re-rigging. Do you? Is it in the manufacturer’s maintenance manual? Perhaps, but it isn’t mandatory to use the MM unless the inspection indicates maintenance is required.
Is there an item in the OM or MM limitations section that requires it? TCDS? An airworthiness directive? A mandatory service bulletin (which aren’t ‘mandatory’ for part 91operators)? If so, it isn’t identified in the article.
If it isn’t required, what is the point of the article?
Here’s a similar discussion by Mike Busch, an expert in the field of shall/should/will/mandatory and regulatory clarity of the ‘how to’ vs ‘when to’ variety:
https://www.avweb.com/news/savvyaviator/savvy_aviator_63_recommended_or_required-199001-1.html
One of the well-known failings of GA is maintenance based on time, not condition. Replacing perfectly good stuff because the calendar or hour meter says so causes MIFs – maintenance induced failures and high infant mortality of new parts. Condition maintenance works great if a component or system can be inspected because it saves a lot of time and money.
A reading of the expanded NTSB report is comical, with the owner claiming a back-seat passenger damaged the floor, which damaged the right gear tubes, which the owner replaced with assistance. The owner did other things too that are germane to the problem but not mentioned in the original story. So we’ve been misled. Also missing are the successful landings made before the failure, and that the gear had been swung with ‘no discrepancies noted.’
Why is the ntsb involved in a gear collapse with no injuries?
A simple gear swing on a 310 at Annual is not enough and regular rerigging a necessity. Surprised there was no mention of right engine/prop damage.
It’s the owner’s fault. The mechanic is not required to do everything in the Maintenance Manual on a part 91 Annual Inspection. If the owner knew anything at all about his airplane he would know that following the gear rigging procedure in the MM is critical. 310 gear has been failing due to this type of neglect for decades. The information is widely available from the various type clubs and owners groups.
Disagree.. The mechanic signed of the annual and released the aircraft as “airworthy”. However, by failing to follow the maintenance manual he did not, in fact, verify the aircraft was indeed airworthy. Bottom line? Let’s hope, for his sake, the mechanic and shop have insurance. There is no way the pilot owner is at fault, unless he was aware of the fine print in the maintenance instruction and in full knowledge instructed the mechanic to cut corners.
FAR Part 91.403 (a): The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with part 39 of this chapter.
Robert, I concur that the owner/operator is “primarily responsible”, however this does not mean the mechanic can shirk a fundamental responsibility to exercise ‘due diligence’ when hired to inspect OR maintain an aircraft. I expect the mechanic and shop may own the repairs because the mechanic failed in his duty to follow the checklists. Clearly, a pilot/owner is not required to be an expert in aircraft maintenance. By hiring a shop licensed and advertising their competency to accomplish maintenance IAW FAA regulations and manufacturer instructions the pilot/owner fully complied with 14 CFR 91.403 (a). That clause does not create a free ride for either the IA who signed off on the annual, nor the mechanic who failed to exercise ‘due diligence’ by following manufacturer maintenance requirements.
The pilot joined the “20% club”… that is, pilots who experienced a maintenance induced failure caused by maintenance error. IMHO, not nearly enough attention is given to reducing maintenance error problems that then become events where “the pilot is the first person to arrive at the scene of THE accident”.