Accident Probe: Deferred Maintenance

When owners neglect basic inspections and maintenance, the risk of "something" happening greatly increases.


Owning an aircraft is an empowering experience. Winged assets in your hip pocket can open up all kinds of opportunities and adventures free of many concerns associated with traditional clubs and aircraft rental operations. It’s also an awesome responsibility, often isn’t kind to your wallet and can bring many new and unanticipated challenges.

For one obvious example, owners become responsible for ensuring that all maintenance and inspection requirements are met and the aircraft is airworthy. While it often can be tempting to postpone or refuse to buy expensive parts and services, it’s a “pay me now or pay me later” situation where deferring inspections or repairs may seem economical at first blush, such actions have a way of catching up to us in the end. Then there’s the ethical issue of carrying innocent passengers who place their faith and trust in the owner/pilot that the aircraft is safe and airworthy, and meets current, accepted standards.

As both the pilot and aircraft age, it’s easy for complacency to creep in, manifesting itself in dangerous ways. We might cut corners on basic training or responsibilities other pilots readily accept, for example, or place more faith in our experience with the aircraft than is warranted. Just as we should ride with an instructor more often than every two years to establish and retain proficiency, we also should be getting an unbiased, professional (read “expensive”) mechanical assessment of the aircraft from time to time.

Failing to embrace these responsibilities can lead to all sorts of mayhem, ranging from simple paperwork issues to the catastrophic. Here’s an example of how a complacent owner can lead to the latter.


On January 6, 2020, at 1423 Eastern time, a 1966 Cessna 172H Skyhawk was destroyed when it collided with terrain while maneuvering near Newborn, Georgia. The solo private pilot (male, 72) was fatally injured. Visual conditions prevailed.

The owner/pilot departed Toccoa, Georgia, at about 1230, destined for Cairo, Georgia, some 240 NM away. The pilot’s daughter later stated he likely wanted to look at property in the Cairo area. The pilot’s daughter was not aware of a reason the pilot would be looking at property near the accident site. Newborn is approximately 70 NM from Toccoa.

According to FAA data, about an hour into the flight, the airplane began flying “a meandering track” for about 10 miles, and then made a right turn to the north and completed several left 360-degree turns before completing two additional right 360-degree turns. After briefly turning north, it completed several more 360-degree turns before continuing into 13 360-degree right turns progressing in an easterly direction until radar contact was lost near the accident site. 

Two witnesses observed the airplane flying low just before the accident, and another witness stated that the airplane was circling and then descended below the tree line. The airplane impacted terrain and a post-accident fire ensued.


The airplane impacted dense woods and terrain on a magnetic heading of about 215 degrees and left a debris path about 180 feet long, coming to rest inverted. Both wings had separated and the fuselage was consumed by a post-impact fire. All major components were located at the scene and in the debris path.

The left and right flaps were found in the retracted position. The propeller was sheared off the engine; it displayed gradual aft bending and diagonal chordwise scrapes on the blades. Flight control continuity was confirmed through multiple overload breaks and failures.

The left muffler was sound with no evidence of cracks or through-thickness metal wastage. The right muffler and shroud were substantially damaged and exhibited cracks and through-thickness metal wastage. Holes and wall thickness loss were also noted around the muffler body. Other than the condition of the right muffler, examination of the airframe and engine revealed no pre-impact anomalies that would have precluded normal operation.

The pilot reported 344 hours total flight time for his most recent aviation medical exam on November 15, 2013. The pilot’s last logbook entry was on July 16, 2019; his total flight time was 358.65, of which 15 minutes were flown during the previous six months.

The airplane’s most recent annual inspection was completed on September 17, 2018. Only three other records of maintenance were found for the 10 years before the accident: two annual inspections on May 27, 2013, and November 18, 2010, and replacement of the left muffler on April 1, 2010. The airplane had been operated about 93 hours over that period.

The mechanic who conducted the 2013 annual inspection and almost all of the airplane’s maintenance from 2008 to 2013 knew the airplane well and was a friend of the pilot. He considered the airplane in “rough shape.” Within the last few years, the mechanic told the pilot he didn’t want to “touch” the airplane unless he agreed to a comprehensive annual inspection. 

Probable Cause

The NTSB determined the probable cause(s) of this accident to include: “The pilot’s impairment/incapacitation from carbon monoxide poisoning due to a degraded muffler. Contributing to the accident was the pilot’s failure to properly maintain the airplane.”

According to the NTSB, the right muffler’s condition likely led to an escape of exhaust gases and allowed carbon monoxide (CO) to enter the cabin during the flight. Toxicology testing performed identified 48 to 61 percent carboxyhemoglobin in the pilot’s blood. Levels of CO of 40 percent and above lead to confusion, seizures, loss of consciousness and death.

Although toxicological testing detected potentially impairing medications, it is most likely the pilot experienced CO poisoning during the flight, leading to his impairment/incapacitation, as demonstrated in the airplane’s erratic flightpath. The pilot’s underlying cardiac disease would have increased his susceptibility to CO poisoning. The NTSB said, “Had the pilot had the airplane inspected, it is possible that the deteriorated condition of the right muffler might have been detected and corrected.”

CO Symptoms

We’ve run a number of articles over the years about carbon monoxide (CO) poisoning aboard personal airplanes. The basics remain the same: good maintenance of the exhaust and ventilation systems, some kind of modern detector and awareness of related symptoms, capped off by deciding that there’s a problem and doing something about it.

Early CO-poisoning signs can be mistaken for everyday symptoms of something else. So it’s important to know that the combination of these conditions should be a flashing red light. According to the Mayo Clinic, those symptoms include:

  • Dull headache
  • Weakness
  • Dizziness
  • Nausea or vomiting
  • Shortness of breath
  • Confusion
  • Blurred vision
  • Loss of consciousness

Aircraft Profile: 1966 Cessna 172H Skyhawk

Not accident aircraft.

OEM Engine: Continental O-300-D

Empty Weight: 1330 lbs.

Maximum Gross Takeoff Weight: 2300 lbs.

Typical Cruise Speed: 114 KTAS

Standard Fuel Capacity: 42 gal.

Service Ceiling: 13,100 ft.

Range: 515 NM

VS0: 43 KCAS

This article originally appeared in the January 2023 issue of Aviation Safety magazine.

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Joseph E. (Jeb) Burnside
Jeb Burnside is the editor-in-chief of Aviation Safety magazine. He’s an airline transport pilot who owns a Beechcraft Debonair, plus the expensive half of an Aeronca 7CCM Champ.


  1. We have turned away customers based on the poor condition of their aircraft. The risk and liability for GA shops has greatly increased, along with insurance costs. Unfortunately, this was a fatal accident, there will be a law suit guaranteed to whom ever did the last annual.

  2. There’s deferred maintenance…and there’s DEFERRED maintenance. Cracks in the royalite instrument panel cover? deferred is probably not a safety of flight issue (unless they’re so bad pieces are obstructing instruments)…cracks in the muffler, loose cover plates, missing structural hardware, frayed wiring, hoses past their ‘sell-by’ date…corrosion…Nah.

    But inspections, IRAN’ing of marginal appliances, and all the other ‘nickle and dime’ stuff you think needs attention…just do it. We have a legal obligation, as well as moral, to maintain our ships in an airworthy condition. That’s the obligation we assumed when we signed the title application. Besides…there is that ‘pride of ownership’ thing. No plane is perfect…and ‘good enough’ is the lowest we should accept. In 30+ years of ownership…I’ve had annuals where the owner-assisted inspection and maintenance took a few days with minor squawks…and others where the dreaded phone call “you’re making metal” arrived to a sharp intake of breath (and an object lesson in why aircraft overhauls cost what they do…).

    I hear/read stories like this and just shake my head.

  3. I will always remember two pieces of sage advice of the A&P at my local airport.
    Some years back I was looking at a Cessna 152 that, despite having been kept in an open-to-the-North T-Hangar for many years, still looked pretty good. He said “Remember when you were learning to fly in a 150, you were 16 and weighed about 155. What do you and your wife weigh now?” I told him, and he said “You could probably put enough gas in it to go around the pattern twice.” Ouch. Point made. Then, after I told him the tail number of the plane, he said “Run, do not walk, away from that aircraft. It has so much wing spar corrosion that it’s not been safe to fly for a long time. It belongs in a salvage yard. I’ve refused to annual it before.” I thanked him and did so.

  4. Flown 93 hours in ten years. That is 9.3 hours per year! The per hour cost for hanger or tie down alone would be too much.

  5. So, a pilot looking at buying property first flies a little erratically (looking out the window for it) and then persistently flies both left and right 360’s and got too low?

    And the conclusion is hypoxia and not simple distraction while looking at the ground?

    • “Toxicology testing performed identified 48 to 61 percent carboxyhemoglobin in the pilot’s blood. Levels of CO of 40 percent and above lead to confusion, seizures, loss of consciousness and death.”

      • You’re correct. Sorry I saw 40% (30–40% severe headache, dizziness, nausea, vomitting) but did not read that he had way above that! My mistake. Sorry about that.

  6. It is the perfect storm. As airplanes age they need more maintenance but the supply chain is withering as suppliers consolidate or simply close with no other enterprise providing the part.

    Parts costs are rising at an almost exponential rate exacerbated by the regulatory administrative burden to certify low demand parts and the cost of insuring the vendor against a potential huge liability.

    The GA maintenance infrastructure is in also decline. There is a shortage of mechanics and GA maintenance shops are finding it hard to compete with large corporate and airline shops which can offer more attractive wage and working conditions.

    Finally the worst thing you can do to an airplane is not fly it. It is hard to justify spending a lot on maintenance when an airplane is flying less than 10 hours a year. Sadly I think we are going to see more and more light aircraft that are deteriorating past the point of no return.

    Ultimately however as was pointed out in the article, it is up to the owner to maintain his or her aircraft. Failure to do so has consequences that can’t be ignored.