The 1965 Cessna 172 “Fox” model was 2,000 feet above the ground after lifting off from Oakland/Troy Airport (KVLL) on the north side of Detroit, Michigan, when it happened. First, the engine shuddered. Then it started to run rough. Airspeed dropped as the RPM rolled back.
About equidistant from his home base and the next nearest airport, the pilot turns back for home. He fiddles with throttle and mixture controls, does an in-flight mag check, then changes tanks. Nothing helps.
When he increases throttle “trying to get a little more thrust” to keep altitude, the engine gets worse. He later told the NTSB, “I knew I was going to have to land off-field.”
He spies a “perfect,” arrow-straight, “less-used road” right as the engine seizes. He makes for it, but he’s too high and overshoots his planned touchdown, landing long and hot — and finds himself fast approaching an intersection with a second road. A road which, charmingly, features a crab apple tree-lined median. As he zips through the intersection of the two roads, the left wing clips the trees and the off-field landing becomes an accident.
The plane veers sharply left, flips on its back, and skids to a stop in a sad little crumble in the median amongst the crab apples, its tail overhanging the road.
The pilot releases his seat belt, falls to the ceiling of the plane, and crawls out the door. As he stands up he sees the exposed belly of the airplane. It is covered in oil.
The Pilot
The pilot was the owner of the 172, and had been for about eight years. At the time of the accident he was 63 years old. He held Commercial-Multi, CFI, and ATP certificates. He had a 737 type rating but was flying under the third class privileges of a two-year-old Class 2 medical. Despite his certificates, he did not list himself as a working professional pilot.
His logbook showed 3,929 hours total time, which is not that many hours for an ATP of his age, suggesting either a late career start, or that he was a victim of industry headwinds during his career.
The latter strikes me as more probable, when thinking about his age at the time of the accident.
He (like me) is a member of the generation of pilots who suffered the “Black Swans” of the Gulf War, the 1990s recession, 911, and COVID. Our generation got hit by so many industry-numbing setbacks that I’m not sure we can really call them Black Swans anymore, but if someone wants to create some sort of Commercial Pilot Black Swan Squadron patch, I’ll proudly wear one.
But back to our hero.
More than 70% of his flight time is single-engine land, with 421 hours in make and model. He only flew two hours in the previous month, but clocked 29 hours within the last 90 days.
The NTSB
When investigators inspected the wreck they noted damage to both wings, the horizontal and vertical stabs, and the top of the fuselage. The windshield was knocked out, the prop was damaged, and the motor mount bent, which is the least of the motor’s issues.
Investigators found a gaping pair of holes in the top of the engine case above the two left-rear cylinders. Consistent, investigators say, with “catastrophic failure due to a lack of lubrication.”
A huge puddle of oil is discovered on the ground outside his hangar and a trail of oil leads down the taxiway, too. Oh, right, and the trail extends down the first part of the runway. You wouldn’t think seven quarts could make such a mess, but it will.
The oil leak is traced to an externally-mounted oil cooler, which had been installed under a field approval. But the cooler isn’t blamed for the oil system failure. Instead, the pilot is.
The Flight
Rewinding to before the accident, it’s early in the afternoon shortly before Christmas, and the battle plan for the day was described by the pilot as “basic proficiency.”
He was headed for the local practice area where he planned to practice steep turns and stalls, then get in a pair of landings on return to home base.
The pilot estimated the outdoor temperature was around 35℉, while weather data gathered by the NTSB at the time of the pilot’s departure put it at 28℉. Chilly, we can all agree, perhaps even freezing, but not crazy cold.
Before pulling the airplane out of its hangar, he rotated the prop 10 times to get the oil moving and lubricate the engine. He told authorities that he did not preheat the engine.
Nor did he, apparently, wait for the engine to warm up, but headed straight for the runway — the departure end of which was right by his hangar — where he did a quick run-up and took off.
He told the NTSB that during the engine run-up and takeoff roll, the engine oil temperature gauge was “not registering.” He didn’t recall what the oil pressure gauge showed.
More NTSB
In its report, the NTSB made a big deal out of the pilot’s cold weather starting technique, which I, too, find fault with.
But in fairness, most of the documents quoted by the NTSB — including a Continental Motors Service Information Letter — dealt with starts of cold-soaked engines below 20℉. And regardless if we believe the pilot or the NTSB investigators about the temperature that afternoon, it was nowhere near that cold.
And while I’m sure many of you are clamoring for the pilot’s head for taking off with no oil temperature indication, if you look at the airplane’s POH for cold weather starts, it does say that you may not get an indication on the oil temp gauge, and that this is perfectly OK.
The POH reads: “During cold weather operations, no indication will be apparent on the oil temperature gauge prior to takeoff if outside air temperatures are very cold. After a suitable warmup period (2-5 minutes at 1,000 rpm), accelerate the engine several times to higher engine RPM. If the engine accelerates smoothly and the oil pressure remains normal and steady, the airplane is ready for takeoff.”
But, of course, he didn’t do that two- to five-minute warm up, so I guess you can go ahead and take his head. Oh, and if you bother to read the whole section, the POH isn’t using “around freezing” for this cold weather ops advice, or even Continental’s 20°. The POH is giving operational advice for temperatures 0℉ and colder!
Additionally, the NTSB report says for outside temps below 40℉, for this airplane, the recommended oil is SAE 20. For temps above 40℉ the proper oil is SAE 40. The airplane had neither.
Instead, the airplane was filled up with SAE 50, which was rated for an operating temperature range of 60℉ to 80℉. Apparently this thicker oil was put in the engine by the pilot that autumn, when the airplane was based in Las Vegas, which might be a perfectly reasonable choice for that environment at that time of year, although maybe not, if not approved.
But wait. There’s more.
The pilot-owner reported that the plane had seven quarts of oil in the sump, and that he had added a half-quart of Marvel Mystery Oil — an oil additive product — to “try and thin it a bit.”
Analysis
So let’s talk about that oil additive, often called MMO. It was invented by Burt Pierce in the 1920s.
You may never have heard of Pierce, but you have heard of his other great invention. He was the inventor of the Marvel Carburetor, which by the time of MMO, was used on an astonishing 80% of vehicles, and a great number of airplanes, as well. But many of his carbs were suffering problems with clogged carburetor jets due the high lead content of gasoline at the time. Pierce’s Mystery Oil was designed as an internal cleaning product to prevent clogged jets.
But as an unintended side effect, it apparently helped with piston setting, resulting in higher compressions and reduced blow-by, making it popular with racers, which in turn led it to become a legendary success as a product.
That, plus the fact that, at the time, no one knew what it was made of (mainly mineral oil as it turns out), fueled more speculation than clean jets, and — as befits a legend — over time, MMO would take on other mystic and mythical powers.
While not “approved” for certificated aircraft engines, MMO has a following in some sectors of GA. I put “approved” in quotes as the FAA doesn’t really approve oil additives, but it does sometimes “accept” them. Acceptance is basically the FAA saying that it can’t see any harm in using it. A good example of an accepted additive is CamGuard.
Now in fairness, MMO perhaps could be accepted, it might simply be that no one has asked the FAA to accept it.
But either way, the view of the engine manufacturer is another kettle of fish all together. Continental, for instance, says use of any additives, FAA accepted or not, is verboten and voids your engine’s warranty.
I’m not sure what the pilot’s logic was in using the MMO additive to thin his oil. But there’s a lot of hangar talk, and hangar experts, when it comes to legendary products like MMO.
Mike Busch, of Savvy Aviation, had this to say about MMO on his website: “Pitchmen have long been promoting oil additives that eliminate friction and wear, increase fuel economy, improve your landings, raise your IQ, and rescue your marriage.”
So why not use it to change the viscosity?
But why not just change the damn oil to the right stuff instead of playing hangar chemist?
Perhaps it was because his plane would be out of annual in a few days. The previous annual, back in Nevada, was signed off on the first of December the previous year. Maybe he knew the new guy would change the oil as part of the inspection.
Busch, by the way, goes on to say that when it comes to MMO, “folks have been pouring this stuff into aircraft engines for more than 80 years.”
Based on his experience, his feeling is that, used in moderation, it “doesn’t do any harm,” but from what he’s seen, “it doesn’t seem to do much good either.”
Needless to say, I didn’t write to ask him what he thought about using it as an engine oil viscosity adjuster.
And to be clear, the NTSB wasn’t laying the blame on the Marvel Mystery Oil, but it basically used the pilot’s use of it as one nail in the lid of his metaphorical coffin, as part of a chain of disregard for the proper manufacturer’s guidance for cold weather operations.
Discussion
The pilot didn’t preheat the engine prior to start, nor did he warm it at low RPM to operating temperature prior to takeoff. He just jumped in, fired up, and blasted off into the wild blue yonder. Well, blasted off into the first 2,000 feet of the wild blue yonder, anyway.
Did he believe the Marvel Mystery Oil would work its mythical magic? Or is this a case of SSOP (Sucky Standard Operating Procedure)? Or did he simply fall back on old habits that worked fine for him in a warmer part of the country? Did time in the airlines somehow affect his GA sense?
And, hey, did his poor oil grade choice, cold start, and lack of warm-up even cause the oil leak, or did the oil cooler fail in some way that had nothing to do with pilot abuse of the recognized and recommended cool weather start-up procedures?
The Takeaway
Just because we may never know the true cause of the oil leak that killed the engine and wrecked this airplane doesn’t mean that there aren’t any takeaways.
The obvious premium takeaway here is to make sure to match your oil to the operating environment. Well, more than your oil really — your standard operating procedures, too. It might be fine in a warm climate to fire and fly, but that doesn’t work in colder climates. If you’ve moved, please adjust your SOPs to your new environment.
Another key takeaway is not to simply read the checklists in the POH, but read the supporting material that is provided with them. Don’t just flip to the “cold weather ops” checklist without knowing how that is defined in the book.”
It really wasn’t cold enough for the oil temperature gauge not to work. It wasn’t registering because there was no oil to measure. Maybe with heightened awareness as to what temperature to expect that acceptable mode of failure, he would have been better alerted to the real problem.
And lastly, while we spend a lot of energy on aeronautical decision making, perhaps we need to revisit critical thinking as a pilot skill. I’m not dissing Marvel Mystery Oil (I like a good mystery as well as the next person) but buying seven quarts of the right oil for the climate strikes me as better critical thinking than trying to make my own home-brew oil.
The Numbers
Want to read more? Download the NTSB’s final report here or view the items on docket here.
