The two shattered links of the accident chain were not adjacent, as they so often are.
In fact, they occurred well over an hour apart, but together conspired to bring the PA-28 Cherokee out of the sky.
The first link came before the prop even spun, sometime during an otherwise diligent preflight. The second was a skipped memory item from the emergency checklist that, otherwise, would have saved the day.
From Preflight to the Final Moments
The pilot, whom NTSB documents identify as a doctor, was planning a cross-country flight early in the evening of a Thursday in May 2023, launching out of KPLR, St. Clair County Airport, in Pell City, Alabama, bound southwest for KMVC, Monroe County Aeroplex Airport — a pleasant hop of 138 nautical miles.
He had refueled the airplane two days before, and started the flight with 48 gallons of fuel in the wings, which he verified visually during his preflight.
He launched drawing from the right fuel tank of the 180-horse Cherokee. A half hour into the flight he switched tanks.
Then, 25 minutes later, north of Selma, Alabama, the engine spools back to idle. He springs into action. Fuel pump on. Mixture full rich. Carb heat on.
No joy.
He’s using Flight Following, and declares an emergency. ATC advises he’s six miles from the nearest airport. He doubts he can make it, picks a pasture, and establishes best glide. He cracks the door open and gets ready to put her down.
He’s kept his head and done everything he should. Well…everything but one thing. Which, ironically, is the very first step on the airplane’s Engine Power Loss In-Flight Checklist.
The Accident
He almost makes the pasture. Almost, but not quite, and he descends into a grove of pine trees. He tries to line up between rows and get the airplane as slow as possible, but he gets a bit too slow, the plane buffets, then nose dives into the ground, rolling onto its left side, snapping both wings off, and mangling the tail.
The pilot is not injured, escaping with only a few minor scrapes and bruises.
As the metaphorical dust settles, he shuts off all the switches, kills the ignition, takes the keys, grabs his belongings, and makes his way to the pasture.
The Pilot
We don’t know too much about the pilot from the official records. He was a 66-year-old male. His only FAA certificate was a private pilot certificate. He did not have an instrument rating. He held a 3rd class medical.
His total flight time was 390 hours, of which 360 were in make and model, respectable numbers and experience for a GA flyer.
The NTSB
So what caused the engine to lose power?
I’m sure, by now with the clues I’ve given you, that you’ve already figured out he ran out of fuel in one of his two tanks. But the reason that happened may surprise you.
During the NTSB’s post-accident examination, investigators found the left wing fuel sump drain was in the open and locked position. Link One.
The largely intact left tank was empty, and the fuel selector was positioned to that tank.
A photo of the airplane taken several minutes after the accident showed fuel staining on the left flap, aft of the fuel drain, consistent with fuel leakage during the flight.
The NTSB Final Report summarizes the smoking gun: “It is likely that when sampling the fuel from the left wing before the flight, the pilot inadvertently twisted the sump drain into the up and locked open position, allowing fuel to drain during the entire flight, resulting in fuel starvation.”
And the NTSB also provided an alternate ending to the story, writing, “Had the pilot followed the emergency checklist procedures, and switched to the right wing fuel tank, he would have likely been able to restore power to the engine.” Link Two.
Analysis & Discussion
Sump drains come in two broad types: Push-type drain valves and lock-open valves.
With the push-type, which are often flush-mounted, you use a wide sump cup with a thin rod mounted in the center. You place the rod in a hole in the center of the drain, push up, and fuel squirts down into the cup.
With the lock-style you typically use a strainer that looks more like a large test tube. The sump valve has a cross bar that seats in a pair of notches at the top of the tube. Pushing up on the bar lets fuel escape.
But here’s the thing: If you push up and twist, the valve “locks” open. The intent is for maintenance folks to have a way to drain fuel, which actually takes a while as the drain tube is narrow.
When tanks need to be drained, a mechanic will usually place a large bucket under the wing, open the valve, and go away and do something else for a while. I once dropped a fuel level “straw” into my tank and the maintenance folks at Great Bend, Kansas, had to drain the fuel to get it out again, which took long enough for my son Rio to have a bonus preflight breakfast.
It’s worth noting here that many locking sumps also have the push-feature for sampling, letting you use either a cup or a tube-style tester.
The Takeaway
Having a sump accidentally lock in the open position during preflight, I think, is pretty common for those of us who deal with airplanes that use that style of valve.
Usually it’s unambiguous. The tester quickly overflows — especially if it’s the more slender tube type — and our hands get a good fuel soaking. What follows is language as blue as the fuel, and some frantic action to unlock the @&%$#! sump to shut it off. How the pilot missed the fact his sump was locked open is hard to say.
My guess would be that it was a combination of age (we older aviators are not as flexible when it comes to getting under a Cherokee’s low wings than younger pilots) and perhaps he was using one of those fancy larger fuel testers that re-filters the fuel as you pour it back in the wing.
For historical perspective, we used to just flick the small amount of sample fuel onto the tarmac to evaporate quickly — now a no-no as we have a better understanding of the risks of lead — so there was no need to re-filter.
Now that the easiest thing to do with the sampled fuel is to return it to the tank (and the fact that some modern airplanes have a lot of sumps), there’s been a trend toward larger-volume fuel testers with filtering features.
My point here is that a larger fuel strainer — some of these things can hold 12 ounces or more — might not have overflowed to alert the pilot, particularly if he was stooped over, reaching under the wing.
Whether you’d notice a growing pool of fuel under your wing would really depend on the surface you were parked on and where the fuel sumping comes in your preflight sequence.
That was a long-winded way of saying that the takeaway from the first link in the accident chain is that if you fly more than one airplane, there’s a good chance you might deal with both styles of sumps, so you want to be aware that one type can lock open and — especially if you use larger sampling devices — you should be sure to get an eyeball on the sump drain after sampling to ensure it’s not gushing fuel. The locking type extend down out of the wing about three-quarters of an inch or so, making them easy to see.
As for the second link, the one that broke the chain in the air and truly caused the accident, the takeaway is what I’ve been saying for years: When the engine stops, your first action should not be pitch for best glide.
Instead, it should be switch tanks.
The Numbers
Want to read more? Download the NTSB’s final report here or view the items on docket here.
