Emergency AD Issued For Otter Elevator Spars


The FAA has issued an emergency AD mandating the immediate inspection of the left-hand elevator auxiliary spar on De Havilland DHC-3 Otters a month after an Otter floatplane crashed in Washington State, killing all 10 people onboard. The AD was issued Oct. 4 after “multiple recent reports of cracks” in the spar, the FAA said. “The unsafe condition, if not addressed, could result in elevator flutter leading to elevator failure, with consequent loss of control of the airplane,” the AD says. Although there’s no suggestion in the AD that it was prompted by the accident, witnesses reported the aircraft suddenly dove into the water in Mutiny Bay, just off Whidbey Island, last Sept. 4.

The emergency AD requires “repetitive detailed visual inspections of the entire left-hand elevator auxiliary spar for cracks, corrosion, and previous repairs, and depending on the findings, replacement of the left-hand elevator auxiliary spar. This AD also requires sending the inspection results to the FAA.” The type certificate for the Otter is held by Canadian manufacturer Viking Air and Transport Canada, which has been consulted about the AD.

Russ Niles
Russ Niles is Editor-in-Chief of AVweb. He has been a pilot for 30 years and joined AVweb 22 years ago. He and his wife Marni live in southern British Columbia where they also operate a small winery.

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  1. Such a tough question if you sit from my perspective, which is that I have no knowledge of this aircraft. Did the FAA have to wait for dead bodies to issue AD? Did operators and FAA know this issue with the elevator was possible, such that this accident isn’t really a surprise to those who know? Or was this really an eye opener for FAA and operators?

    Frankly, aging aircraft scares the crap out of me. Flying is risky as it is, and I don’t think many of us (especially renters) can actually assess with confidence that the aircraft we fly are in good shape. I know Paul Bertorelli has videos on what will kill you and how rare in flight breakups are, but as aircraft age is the trend going up? Will this type of accident be more frequent occurrence?

    I’m prolly getting skittish in my older age

    • I share your sentiments. Complete, data-plate-out restorations aside (maybe), the fact is that time will eventually get to all of them. And with so many aircraft in the GA fleet are now (sometimes much) older than the pilots flying them, I have to wonder when we will reach the knee in the curve where bad things start happening more regularly.

      But, then there’s the rub. The older planes are still flying because those are what people that actually need budgets can “afford” to keep flying. (Ask me how I know!) However, they all do so by prioritizing repairs, inspections, and upgrades according to budgets and (perceived) urgency. And, the reality is that invasive, expensive, potentially-damaging, precautionary disassembly and inspection will naturally fall far down that list.

      So, does that mean the choice for a lot of GA pilots (and their unwitting passengers) is between accepting the risk with older planes or giving up entirely? And, if so, does that mean the graveyard spiral that GA seems to be entering (due to prices, regulations, and public sentiment) is going to accelerate?

  2. On the other hand there have been several AD’s issued in the past that cost owners a lot of money for no reason ( Piper Cherokee wing pull) and probably did more damage taking wings apart than was needed. The C208 main gear pull is another. I have seen many horizontal stabilizer spar cracks on Cessna 172’s, usually caused by owners/pilots sitting on or pushing down on the stabilizer, yet no AD that I know of has been issued. How does the FAA make that balance?

  3. RE: “…usually caused by owners/pilots sitting on or pushing down on the stabilizer…” I’ve seen pilots from the same large organization I mention below do the same thing to a C172 as it’s manhandled (sans tow bar) into a parking space. In that case a person was still at the controls filling out the flight log… and also likely to add a little challenge to the maneuver.

    A few years ago on a post maintenance pre-flight I found the horizontal stabilizers on one of a large organization’s C182R aircraft. The play (“oil canning”) created about 3″+ of up and down movement in response to light pressure on the tip of the air foil. In a second instance
    (same plane, same large organization) oil canning was less extreme, as was the up and down movement movement of the left horizontal stabilizer… but still not something Cessna Corp included in the C182R TCDS!… Fwiw, “oil canning” means (for pilots old enough to recall metal oil cans) loud sheet metal clunks as the formed aluminum is deformed and released. Long and short of it was 12 rivets were pulled through the spar on the left horizontal stab in the first instance, and I expect the second instance likely had at least a couple unseated rivets in the spar. If you wonder how it could be… yes, this aircraft was also jockeyed into a tight tiedown by lifting the nose and wheeling the aircraft on its main wheels.

  4. The question of how old is too old is a difficult one to answer because it depends so heavily on the service life of the airframe and how it has been used and, more importantly, how it is stored when not in use. The problem with most rental aircraft is that they are heavily used by pilots with less than perfect skills and they spend their lives parked outside in the weather. On the one hand, the high number of hours flown is good for the engines, but the airframes take a beating. A privately owned plane that is housed in a hangar has a better life protected from the elements, but are often flown much fewer hours, which accelerates internal wear on the engines.

    To me, the biggest danger to an aging airplane is corrosion, especially when they live near a coastline or in high humidity climates that see frequent rainstorms and damp overnight conditions. And, each model seems to have its own problem areas (Bonanza magnesium tail feathers, C-210 carry through spars, etc.) that require special attention and sometimes expensive and invasive inspections or repairs. The FAA has a tough job monitoring accidents and service difficulty reports to decide when a problem warrants a fleet-wide AD. Sometimes they do overreact, but it’s their job to be more conservative when public safety is at stake. Are more frequent or more aggressive inspections the answer? Mike Busch and others say no, it isn’t. As several posters have said, the answer to the issue is more affordable replacement aircraft, but that ship seems to have sailed. So take good care of the planes we have now, because they are all we have unless you manage to win the lottery.