NTSB: Rain, a Missing Gasket, and a Rushed Preflight

The plan was simple enough. A pilot would fly a recently restored Grumman American GA-7 from Pennsylvania to its new owner down in Tennessee. The airplane only had a handful of flight hours since its most recent annual inspection, and at first-glance looked ready to make the trip.

But the aircraft had also been sitting outdoors through weeks of winter weather. Between mid-December and the day of the early February flight, the airport recorded more than 10 inches of precipitation, the sort of accumulation that might not attract much attention in the moment, but that has a way of working its way into places it doesn’t belong.

On Feb. 1, 2024, a pilot arrived at Chester County G.O. Carlson Airport shortly after midday. People at the airport later told investigators he made it clear he was watching the clock, mentioning he was “in a hurry” because he had a commercial return flight to catch later that evening.

For someone with roughly 1,800 hours of flight experience and a reputation locally as both a community figure and an active pilot, the trip ahead probably felt routine.

A Preflight That Didn’t Go Far Enough

The airplane’s 116-gallon fuel system was topped to the tabs with about 80 gallons of 100LL aviation gasoline before departure.

Witnesses later described a brief walk-around preflight inspection. The pilot checked the oil and circled the airplane once, but according to statements in the NTSB’s final report, no checklist made a discernible appearance during the preflight and the pilot was not seen drawing fuel samples from either tank.

After jumping in and starting up, the pilot taxied to the runway. Witnesses later said they did not see a pre-takeoff run-up, though it was possible it could have been done out of view.

Whatever the case may be, the GA-7 took the runway and lifted off into the winter afternoon skies.

A Departure Cut Short

At first, nothing appeared unusual. Observers said the engines sounded smooth during the takeoff roll and the initial climb, but things changed moments later.

Witnesses told investigators that they could hear a loud “pop,” followed shortly after by sputtering sounds as the aircraft attempted its climb away from the airport.

The plane then aggressively banked to the right. Witnesses said they saw the GA-7 briefly correct left before continuing more-or-less along runway heading. It descended out of view behind a line of trees towards a residential area past the airport.

ADS-B data showed the climb rate and groundspeed drop quickly as the aircraft entered a tight, descending right turn consistent with a Vmc roll. The track ended near the crash site.

The airplane struck the ground minutes after departure.

What Investigators Eventually Found

The engines themselves were found to have been in good shape, showing normal mechanical continuity with no pre-impact failures discovered that would have prevented safe operation.

The problem was to be found in the fuel system.

Samples from the sump tank, the engine-driven fuel pump and the right engine carburetor bowl all contained water and debris.

Investigators also discovered another small but incredibly significant detail. The right fuel cap was missing its rubber gasket, the seal designed to keep rainwater from entering the tank. The gasket should have been detected during the airplane’s most recent annual inspection, and indeed, could have been discovered with a thorough preflight inspection.

With the airplane parked outdoors through weeks of rainfall, the missing seal was the likely culprit that allowed water to enter the fuel system.

The NTSB concluded that the accident resulted from a loss of engine power caused by water-contaminated fuel that went undetected during the preflight inspection. It also pointed to the earlier maintenance inspection’s failure to identify the missing fuel-cap gasket as a contributing factor.

Flying Begins Before The Engine Starts

Accident investigations certainly do at times uncover complicated mechanical failures or rare technical circumstances, but far more often than not, tragedies begin with simple stuff like this. We talk about the “swiss cheese” of aviation safety. No flight is without risk; there will always be some “holes” in the cheese, but we need to recognize them, mitigate them, and make sure they don’t line up to our peril.

In this case, the holes in the cheese were elements that should have been recognized: an airplane parked outside during a prolonged rainy period, a maintenance detail that slipped past both formal and informal inspection and a rushed preflight that did not include checking the fuel.

Fuel contamination is one of the most well known and simplest-to-check risks in general aviation, but it’s also one of the easiest to skip in a pinch.

Flight begins before the engine starts. Just as we can’t make our planes fly faster than they’re capable of going to save time, so we also can’t compensate for a time crunch by rushing or skipping a preflight. That preflight inspection step is as much part of the flight as a takeoff roll or a stabilized approach. If a thorough preflight will make us late, we can either accept that we’ll be late, or we can choose not to conduct the flight in the first place.

A thorough walk around, confirmed by both our good sense as pilots and our checklists, remains by far the simplest defense against a departure that ends far sooner than planned.