The FAA has turned a previous service bulletin requiring inspections of Cessna 210 spar caps into an Airworthiness Directive that goes into effect March 9, with compliance due within 60 days or 20 hours’ time in service.
The mandatory service bulletin was released last November after the inflight breakup of a Cessna 210 in Australia was traced to fatigue cracking emanating from a “corrosion pit.”
The AD is for all Cessna Models 210G, T210G, 210H, T210H, 210J, T210J, 210K, T210K, 210L, T210L, 210M, and T210M airplanes. The FAA estimates the AD affects 1,520 airplanes registered in the U.S.
The AD requires visual and eddy current inspections of the carry-thru spar lower cap, corrective action if necessary, application of a protective coating and corrosion inhibiting compound (CIC), and reporting the inspection results to the FAA.
After the May 26, 2019, in-flight breakup of the T210 in Australia, the FAA issued an airworthiness concern sheet (ACS), advising owners of the accident and requesting relevant information about the fleet.
Following the ACS, the FAA received reports of widespread and severe corrosion of the carry-thru spar on Models 210G, T210G, 210H, T210H, 210J, T210J, 210K, T210K, 210L, T210L, 210M, and T210M airplanes. Further investigation identified that these early model airplanes were manufactured without corrosion protection or primer, increasing their susceptibility to corrosion, according to the AD.
Additionally, the design of these early model airplanes, where the upper surface of the spar is exposed to the environment, allows a pathway for moisture intrusion. Model 210-series airplanes were also delivered with foam installed along the carry-thru spar lower cap. The foam traps moisture against the lower surface of the carry-thru spar cap, which can increase the development of corrosion.
Corrosion of the carry-thru spar lower cap can lead to fatigue cracking or reduced structural strength of the carry-thru spar, which could result in separation of the wing and loss of airplane control.
The AD requires compliance no later than 60 days after March 9, stating “an unsafe condition exists that requires the immediate adoption of this AD without providing an opportunity for public comments prior to adoption. The FAA has found that the risk to the flying public justifies waiving notice and comment prior to adoption of this rule because of a severe and widespread corrosion issue affecting the carry-thru spar lower cap on some Textron Model 210-series airplanes.”
As of Jan. 29, 2020, Textron has received 194 inspection reports on Models 210G, T210G, 210H, T210H, 210J, T210J, 210K, T210K, 210L, T210L, 210M, and T210M airplanes. Of these 194 reports, 96 airplanes have reported corrosion (49%) with 18 of those reports (9%) resulting in removing the carry-thru spar from service.
The corrosion observed included several instances of exfoliation corrosion and stress corrosion cracking.
The FAA has determined that the large number of corrosion reports and the severity of the corrosion identified on a critical single load path part necessitate issuance of an immediately adopted rule. If the corrosion initiates a fatigue crack or affects the carry-thru spar’s ability to support the required structural loads, the airplane may suffer a catastrophic failure, according to FAA officials.
Estimated costs to comply with the AD is around $2,500. If corrosion is found, the FAA estimates it will cost about $43,000 to remove the corrosion and replace the spar.
“The FAA has no way of determining the number of airplanes that might need these repairs,” the AD notes.
The AD also notes that replacement spars are not currently available from Textron.
“Textron no longer produces the current spar design, and they are working to develop a new spar design,” it reads. “The FAA does not have data to determine the availability of replacement spars from other sources.”
Read the full AD here.