Get the latest news on coronavirus impacts on general aviation, including what AOPA is doing to protect GA, event cancellations, advice for pilots to protect themselves, and more. Read More
Already a member? Please login below for an enhanced experience. Not a member? Join today
Menu

What went wrong? Faulty assumptionsWhat went wrong? Faulty assumptions

Small errors add up to tragedy

The ATP-rated pilot summoned all his experience to redirect fate in a battle he was losing. Heavy weight, with center of gravity aft of limits, and eyeing his fuel gauges, he was descending on the GPS approach, in instrument meteorological conditions, when he lost power on both engines 13 miles from the field.
What went wrong
Illustration by Brett Affrunti

Amid the confusion and a daunting workload, he restored one engine, but didn’t feather the propeller on the dead engine and left the flaps extended. According to the NTSB investigation, that was the last in a series of mistakes and misjudgments that would cost the pilot and five passengers their lives.

The aircraft was a Beechcraft Baron 58. According to the NTSB, the tragic sequence began when the 5,600-hour pilot (with 2,400 hours Baron time) believed he had refueled to full capacity several days before the mishap flight. In actuality, investigators believe, he was approximately 12 gallons short of his expectation. Tip tanks on a Beech 58 can be partially refueled through the main wing filler port, but a full top-off requires pumping the last six gallons directly through the fueling port of each tip tank. Left and right fuel gauges on a Beech Baron 58 register full once the tanks are above 75 gallons and stay at that full reading until fuel falls below that level. The engine data monitoring system the pilot used accurately tracked fuel consumption, but it required manual inputs after each refueling to update total fuel.

The only way to confirm a full top-off in a Beech 58 is to open each main wing and tip tank fuel cap and visually check the fuel status. There was no cockpit indication to the pilot that his actual fuel state was 12 gallons less than full. The aberration lay dormant for five uneventful flights.

At maximum gross weight, he knew his fuel state was tight, leaving little margin for contingencies. It’s likely he believed the risk of adding more weight was greater than the risk of fuel exhaustion.Video surveillance confirmed the pilot visually checked the left-wing tank quantity before the mishap flight; however, the Baron wing tanks only have tabs that indicate 40 and 60 gallons. Unless the tanks are at either of those quantities, actual fuel quantity can only be roughly estimated by visual inspection. The pilot was planning a departure with what he believed was 54 total usable gallons. Fuel levels would have been well below the 40-gallon tab on each wing, so a visual inspection provided no insight. He seemed to accept this by not bothering to check the right fuel tank.

The pilot’s manual fuel and flight time log indicated he thought his fuel state to be 54 usable gallons at engine start of the mishap flight. According to his ForeFlight flight plan, he believed his trip from West Houston Airport (IWS) to Kerrville Municipal Airport/Louis Schreiner Field (ERV) legally required 58 gallons, including reserves, but would only require 38 gallons to fly. Based on NTSB reports, the pilot knew he was fudging his reserve requirement by four gallons but thought he would have sufficient fuel to fly the trip. What difference is four gallons when you’re burning 28 gallons per hour?

The pilot was managing a dilemma almost all GA pilots have faced. He likely would have preferred more fuel, but taking on more fuel would exacerbate his gross weight problem. He was already at, perhaps slightly above, the Baron’s limitations. At maximum gross weight, he knew his fuel state was tight, leaving little margin for contingencies. It’s likely that he believed the risk of adding more weight was greater than the risk of fuel exhaustion. That risk-management calculation would have succeeded except for the hidden problem, still beyond his recognition, that he didn’t have enough usable fuel to fly the trip.

The actual usable fuel state at departure was close to 42 gallons and the Baron consumed it all. Weather worse than forecast precluded vectors to a visual approach, which the pilot likely expected. Instead, he was forced to fly beyond the airport and shoot an approach back into Kerrville, using more fuel than he planned, but less than what he thought was on board.

Pilots who have pushed fuel limits can attest to the sinking feeling as seconds grind by. The fuel gauges become a dominant part of the instrument scan; watching, willing them to stop dropping. It’s difficult to stay in the moment and not second guess the decision. Your present self is agitated with what it must now contend with, because of the flawed logic of your past self—and your future self butting in, asking how you will ever explain such a poor decision.

In those last few minutes, the pilot understood his issue was fuel exhaustion, but he would have been confused. He used an engine data monitor to track fuel consumption, which aligned with his manual log, both of which led him to infer he was low but had fuel to make it. His fuel gauges also indicated fuel remaining. He didn’t know he’d been carrying 12 gallons less fuel for the last five flights. And he didn’t know his fuel gauges were lying to him in the worst possible way, indicating more fuel than there actually was. The NTSB would discover that excessive resistance in the fuel tank transmitters caused a surplus fuel reading of approximately five gallons in each wing tank.

In dense weather, 13 miles from his destination at about 2,000 feet agl, both engines sputtered and quit within 10 seconds of each other. The pilot dead-sticked the Baron for 40 seconds, sinking rapidly before somehow routing fuel to restart the left engine. Continuing inbound on the approach, he broke out below the overcast at 500 feet agl, near course guidance, but well below approach profile altitudes and in a descent he couldn’t arrest. Using full power on the left engine he raised the nose further, still further in a futile attempt to stop the descent.

A single-engine Baron near maximum gross weight will not hold level flight with flaps extended and an unfeathered propeller. Sinking to 300 feet agl, the airspeed fell below 83 knots, VMC in a Beech 58 Baron—an ominous threshold for all twin aircraft. The airplane began rolling to the right, which no amount of rudder or aileron could avert. The aircraft crashed flat, wings almost level, indicating the pilot flew the Baron through the VMC roll, fighting to the end to minimize the force of impact.

The accident sequence started with a misunderstanding of the actual fuel state, eight days before the accident. The ultimate irony is that the decision on the mishap flight to operate just four gallons shy of legal requirements proved catastrophic.

Four gallons wouldn’t normally matter, but on this flight, four gallons would have been enough to keep both engines operating for 13 more miles, thus precluding the final sequence of events and mortal configuration errors—the same four gallons the pilot seemed to believe was just a technical requirement and not a practical one. Fate has a morbid sense of irony.

Email [email protected]
airsafetyinstitute.org

Richard McSpadden

Senior Vice President - AOPA Air Safety Institute
Richard McSpadden lead’s AOPA’s ASI, committed to reducing General Aviation mishaps by providing free educational resources and supporting initiatives that improve General Aviation safety and grow the pilot population.

Related Articles