Australia Urges More Action On Cessna Wing Carry-Through Structures

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Australia’s Air Transportation Board says a fatal crash involving a Cessna P210 in 2019 likely would have been prevented if Cessna hadn’t relaxed inspection requirements for the wing spar carry-through structure on the aircraft eight years previously. The aircraft in question was being flown daily by a geophysical survey company when the beam broke, a wing separated and the pilot and passenger were killed. The plane was flown a lot and racked up an average of more than 1,000 hours a year in the previous six years and that was a factor in the crash according to the ATSB.

In 1992, Cessna began requiring regular eddy current and visual inspections of the spar based on hours flown, but in 2011 it determined that historical data justified changing the requirement to inspections every three years. “Had the previous flight-hour based eddy current inspection schedule remained in place, it is almost certain that the fatigue crack within the wing spar carry-through would have been detected before this accident occurred,” ATSB Chief Commissioner Angus Mitchell said. After the Australia crash, Textron, which owns Cessna, issued service bulletins requiring immediate inspections of the carry through structure and the FAA followed up with an AD, but the three-year schedule for subsequent inspections remained.

“The ATSB acknowledges the significant safety actions taken to date by the manufacturer and regulators as a result of this accident and the ATSB’s investigation, and notes that these measures have addressed the short-term risk of further similar failures,” said Mitchell. “Further, the ATSB welcomes Textron’s ongoing efforts to address the risk of cracking in wing spar carry-through structure of Cessna 210 aircraft used for low-level geophysical survey operations. However, the ATSB remains concerned by the indefinite nature of the manufacturer’s proposed analysis and certification program and recommends that further action be taken to address this safety issue.”

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15 COMMENTS

  1. If the issue is concern over corrosion, then a calendar limit for inspections is appropriate. If the issue is concern over metal fatigue, then a usage-based limit (either hours or cycles) is appropriate. Normally, the inspection interval is set at half of the expected life between the time a minimum-detectable defect could exist and an outright failure. That way there should always be two chances to see the defect before a failure would occur. If this airplane was operating 1000 hours per year, then maybe a good inspection interval for the fleet would be 5 years or 1000 hours, whichever comes first. That should give everyone two chances to detect an issue before it becomes a problem.

    • Technically speaking, metal fatique is one big parts of the types of corrosion.
      In aviation and maintenance terms it is often called as ‘stress corrosion’.
      With regard to the 210s carry thru spar, you will have a perfect example of stress corrosion.
      Thousands of repeating cycles of cyclic bending forces, and an badly protected metal in a environment that is basically a moisture, dirt and dust trap (electrolytes) that is prone to largley changing temperatures as well (parked sun, hangared, sudden cool down in flight).

      In the french licence build REIMS-Cessnas you wont see a lot of the environmental and stress corrosion issues that you see in other Cessnas, because they used way higher manifacturing standards and quality (deburring everything) and primed every single metal part with Zinc-Chromate, or later Epoxy prime – whereas most US produced Cessnas are bare unprotected metal.
      But as far as I know, REIMS never build 210s – that would have been an interesting technical case study.

      • Coatings are good – you’d have to prove to me that Cessna US did not use any coating, I thought something basic like ‘zinc chromate’ was standard practice in aviation except on fully exposed surfaces.

        Stress corrosion tends to occur in certain alloys processed certain ways, such as rolling bar into sheet, then machining – L188 Electra for example, integral stringers in upper wing skin.

          • During the late 1970s and first half of the 1980s at least, bare aluminum was the standard unless the airplane was agricultural (188 series and the Ag 185), had the optional seaplane kit installed (on the models that had the seaplane kit as an option) or the buyer specified zinc chromate, which was, as I recall, an option.

  2. Sad all around.

    Use of airplane should be included.
    Long ago a colleague asked me about the spar on his Cessna 337, which shop found cracked.
    I checked Cessna’s bulletins and found the subject, including recommendation for more frequent inspection if used for low level flying such as pipeline patrol.
    I asked the pilot owner what his airplane was being used for. ‘Bird dog’ flying in forest fire fighting – flying over fires, directing tankers (often leading them over the drop zone).
    Oh! that’s worse than pipeline patrol, much turbulence around forest fires.

    An expensive lesson for him in checking what the airplane will be used for before you lease it out.

    • Sure, proper planning required but completely within reason. However, now that I think about it, even cruising at 12,500′ you’re still planning on where to put the thing if you have to. (Or you should be). Maybe things have changed but we used to teach students to be able to explain their options before they pushed in the throttle and then explain where they were going to land at any point in the flight.

      • Yes, consider options for sure.

        But they are much greater from altitude.

        Maybe can belly into farm field in some areas, such as some pipeline flying is over, but much of it and resource sensing is over uncleared ground.

        (I assume the small airplane was only carrying a cheap magnetometer or just making visual observations, with video recording, of type of vegetation and rock outcrops as clues to potential areas to survey better from air or ground. (Sensing equipment can get wild, one Dash7 has cables strung around it, literally, arranged to clear propellers in front.)

  3. I may be totally off base, but do the Aussies seem to have a disproportionate number of structural type failure incidents?

    Regardless, I am sure all of us who fly aging airframes get that ‘sure hope all is well in there’ mental popup when encountering exceptionally heavy turbulence, or even if we pull a couple of G’s in a hard turn. In addition to the mandated periodic dye penetrant inspections my 12,000+ hour Bonanza’s web spars get a very close visual look-see any time the area is opened up.

    • Old Kingair came apart in southwest US last summer, enroute to a forest fire area.

      Known wing structure problem.

      (News reports I saw did not say if it was just transporting people to a base or was observing/directing fire fighting operations.)

      (The latter called ‘bird dog’ in Canada, I forget term US uses.
      I suppose the ‘bird dog’ term comes from dogs that point hunters to location of game birds.
      The fire fighting ‘bird dog’ airplanes reconnoiter the fire area then direct tankers to a good drop location, taking note of terrain and proper escape path.
      A CV580 and an L188 tanker were lost in BC several years ago because tanker pilots did not follow ‘bird dog’ instructions on route to take. Tanker pilots did not recognize that judging height of terrain is very difficult with variation of it and vegetation.)

  4. Know your plane and the stress you, or someone else is putting on it. If you fly doing surveys there are likely high stress loads being put on your aircrafts wing spars. I would check them every annual. If you fly your aircraft like an airliner on IFR flight plans rarely places stress on the wings, I would check them tri-annual.
    Why do people need regulations to keep them from do stupid things?… I guess I just answered myself… from doing stupid things.

    • Airfield roughness or waviness and landing technique is also a factor.

      Assault landings by C-130s for example.
      Civilian Hercs fared better, even though landing on temporary gravel runways in the Arctic and elsewhere.
      But ignorance of wing fatigue risk cost a Saturn L382 in SE US.

      Manufacturing variation is substantial risk – outer wings built by Lockheed-California had short edge margin in skin-spar fastening. Touring factory in Lockheed-Georgia where outer wing fabrication had been transferred to I showed personnel there how entire row of fasteners could be wrong. (They were using an SS template and a drill attachment that indexed on the template, but template was located manually by measuring at ends of it – so if that was not done accurately many fastener locations would be wrong.)

  5. It ought to be standard practice to specify both an hourly and a calendar based requirement for all inspections of flight safety critical parts. A lot of flight schools fly their airplanes almost 1,000 hours per year…