N1953YMooney M20E · 1964

On October 26, 2023, at 1430 eastern daylight time, a Mooney M20E, N1953Y, was substantially damaged when it was involved in an accident in Pembroke Pines, Florida. The pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to the pilot, before the flight he requested that 20 gallons of fuel be added to each wing (40 gallons total) even though he was only planning to fly about 1.5 hours. Before the flight, he conducted a preflight inspection according to his checklist, which included sumping “both main tanks after fueling.” Once he was inside the airplane, he completed his interior checks, and “sumped both [fuel] lines from [the] interior valve.”

When he started the engine, with the fuel selector on the right fuel tank, all indications were normal, including the oil pressure, oil temperature, fuel flow, amperage, and voltage. He then taxied to the southwest run-up area and performed his run-up checklist, verifying that the flight controls were free and the magnetos were operating. He then cycled the propeller, and checked the vacuum gauge, ammeter, voltmeter, and conducted an idle check. All were in the green. He then performed his pre-flight checklist, requested clearance for takeoff, and lined up on the runway.

After leaving the traffic pattern at HWO, the pilot flew to Dade-Collier Training and Transition Airport (TNT), Miami, Florida, for touch-and-go landings; however, the pilot only performed one landing, as TNT was closing for maintenance. The pilot then flew back to HWO and radioed the control tower for the option (which gave the pilot the discretion to conduct a touch-and-go, low approach, stop-and-go, or full-stop landing).

The pilot then began his descent to runway 10L and performed his pre-landing checklist, making sure that the ram air handle was closed, the cowl flaps were closed, the wing flaps were set, and the electric boost pump was on. He then made sure the fuel selector valve handle was set, the landing gear was down and locked, the mixture was full rich, the propeller control was full forward, and his seat belts were latched. He then realized that he had been flying on the right fuel tank for about an hour and had never switched fuel tanks, so he switched to the left fuel tank to balance the fuel load as he was close to the final approach to the runway.

Upon touchdown, the pilot retracted the wing flaps, visually checked the runway length remaining, and decided to perform a touch-and-go. He then applied full throttle and confirmed the airplane had a positive rate of climb. During the climb, at approximately 150 feet, the propeller rpm started to slow drastically and the pilot realized he was low. The pilot then banked the airplane to the left to return to the airport and the propeller completely stopped turning. He then declared an emergency, checked that the landing gear was still down and locked, then saw that there was traffic on the roadway in front of him. He saw a grassy area next to a sidewalk that looked clear and braced for landing.

A witness who observed the pilot preparing his airplane for the flight reported that he did not witness the pilot sump either wing fuel tank for water being despite the airplane “being parked for at least a month or two.” He then observed the airplane taxi out of its parking spot shortly after. Later, he saw the airplane performing a low pass on runway 10L. As the airplane was going into a nose-up attitude, he heard the engine back firing as it was making a shallow left turn. He then lost sight of the airplane.

The mechanic who conducted the airplane’s most recent annual inspection stated that he had called the pilot while he was in the hospital after the accident and asking him what happened and the pilot recounted the accident flight to him. The mechanic asked the pilot if he had checked the fuel tanks during his preflight inspection; he reported that the pilot said he had sumped the tanks after refueling 20 gallons in each tank. He asked if the pilot had drained the fuel filter and the pilot could not recall. The pilot stated that he had performed a run-up, and that it was good.

The airplane struck a fence during the forced landing and all three landing gear collapsed. After the airplane was recovered from the accident site, FAA inspectors and the mechanic opened the drain valve on the fuel filter with the fuel valve still in the closed position and found no fuel in the filter (first responders reported moving the fuel selector during the accident response). After switching the fuel selector valve to the left tank, they immediately got fuel to the filter, a sample of which showed the presence of water in the fuel. Then they switched the fuel selector valve to the right tank, which produced a clean fuel sample.

Examination of the wreckage by the NTSB revealed that both wings and the fuselage displayed multiple areas of wrinkling and deformation. The right wing displayed tearing and heavy creasing about 4 feet inboard of the wingtip, and buckling was observed behind the firewall mounting location on both sides of the fuselage. The firewall had been torn and crushed, and the engine was canted approximately 10° downward. No evidence of any preimpact failures or malfunctions of the airframe or engine that would have precluded normal operation was discovered.

Further examination of the wreckage revealed that the airplane’s fuel system was not standard. Monroy long-range fuel tanks had been installed, which could carry a total of 86 gallons:17 gallons in each wing’s outboard tank and 26 gallons in each wing’s inboard tank. Each wing’s outboard tank was plumbed to its respective inboard tank, which it would feed via gravity. The inboard tanks would then feed the fuel selector, which had “LEFT,” “RIGHT,” and “OFF” positions.

Additional examination also revealed the presence of water throughout the fuel system, including both left and right fuel tanks, the fuel selector valve sump drain/strainer, the fuel distribution manifold, and the fuel servo. Examination of a sample of fuel from the fuel truck used by the fuel provider did not show evidence of water or contamination.

The pilot reported that the airplane had 40 gallons of fuel on board at takeoff.

The airplane’s owner’s manual indicated that each of the 26-gallon inboard fuel tanks had a sump drain under the wing from which fuel could be sampled to check for water or sediment contamination. According to the manual’s “FLIGHT PROCEDURES” section, during pre-flight inspection the pilot should, “Check the left tank for fuel level and drain sump,” “Check the right fuel tank for fuel level and drain sump,” and after entering the cabin, “Drain the fuel selector valve on the floorboard and turn the selector to the proper tank. Be sure the drain returns to the ‘OFF’ position and that the pull ring is properly positioned in the cavity provided.”

FAA Advisory Circular 20-125, Water in Aviation Fuels, says in part:

Water can enter an aircraft fuel system through leaks in the vents, seals, or poorly fitting fuel caps on filler openings during rain or snow storms or when the aircraft is washed, from refueling system equipment, by condensation and precipitation (especially when an aircraft has partially filled tanks), and when refueling during rain or snow storms.

Water occurs in aviation fuels in two forms:

Dissolved Water: All aviation fuels dissolve water in varying amounts depending upon the fuel composition and temperature. Dissolved water in fuel is similar to humidity in air.

o Lowering fuel temperatures will cause dissolved water to come out of solution as free water somewhat like fog comes out of air. The creation of free water occurs at a rate of about one part per million per degree Fahrenheit (1 ppm/deg. F).

o Dissolved water is not a problem for aircraft operation as long as it remains in solution. Dissolved water cannot be removed by filtration but can become free water with temperature change. Once free, it can cause operating problems.

Free Water: Any water in excess of that which will dissolve is called free water. Free water can appear either as water slugs (in bulk quantities) or as entrained water.

o Water slugs are, as the name implies, a relatively large amount of water appearing in one body or layer. A water slug may be a pint or less or may be measured in gallons depending on the capacity of a fuel tank.

o Entrained water is suspended in tiny droplets in the fuel. Individual droplets may or may not be visible to the naked eye, but they can give the fuel a cloudy or hazy appearance depending upon their size and quantity.

o When a water slug and fuel are violently agitated (for instance when passing through a pump), entrained water results. Entrained water will settle out in time depending upon the droplet size, specific gravity and viscosity of the fuel and currents within the tank. For this reason, a water haze may be seen in turbine fuel, but the haze is seldom seen in aviation gasoline. Entrained water may also be formed by the lowering of the temperature of a fuel saturated with dissolved water. Furthermore, entrained water droplets can join together to form large drops or slugs of free water.

FAA Advisory Circular 20-105C, Reciprocating Engine Power-Loss Accident Prevention and Trend Monitoring, says in part:

o Many engine power-loss accidents can be avoided if pilots take the time to plan the flight and perform a thorough preflight inspection.

o Check each fuel tank drain for operation. Check for water or debris in the fuel. Also check the color of the fuel to ensure that jet fuel has not been mixed with Aviation Gasoline (AVGAS).

It goes on to say that water contamination continues to be a major cause of fuel-related accidents. There are three ways water can enter a fuel system:

o Condensation: This phenomenon is exactly what causes windows in a warm house to “sweat” during the winter months. Condensation can happen inside a less-than-full fuel tank. When a temperature difference occurs between the walls of the fuel tank and the air in the tank (tank walls are colder than the air in the tank), water droplets will form on the inside top part of the fuel tank walls and drain down into the fuel. The effects of condensation can be reduced by keeping the fuel tanks full while the aircraft is parked.

o Through the Fuel Filler Caps: The entry of rainwater or melting snow into the fuel system is made easier if the fuel filler caps have cracked or nicked “O” rings or scored and deformed filler necks. Many high-performance General Aviation (GA) aircraft have flush-mounted fuel caps that have at least two “O” rings. The most visible “O” ring is the one on the circumference of the fuel cap that provides the seal between the cap and the filler neck wall. The second “O” ring (one that is frequently overlooked by both mechanics and pilots) is the one located in the center of the fuel cap and seals the fuel cap lock assembly. Because of the design, the fuel cap lock sits in a well in the center of the fuel cap. The well provides a catch basin for water runoff. If the smaller “O” ring is defective, water will find a way into the tank. This potential hazard can be by an aggressive filler neck/cap inspection and “O” ring replacement schedule.

o During the Fueling Process: Careless fuel dispensing practices are generally the causal factors for water contamination of fuel. Fueling when it is raining; poor maintenance of the fuel truck or fuel farm, filters, water separators; or lack of adequate inspections or dispensing procedures contribute to the problem. To prevent dispensing contaminated fuel, Fixed-Base Operators (FBO) should ensure the following that fuel handling personnel are adequately trained, fuel dispensing equipment is functional and clean, the fuel, both in the storage tanks and fueling trucks are checked at least once a day for overall quality and indications of water or other contaminates, and each inspection should be documented.