N9471H

On September 30, 2018, about 0844 Pacific daylight time, a Howard Aircraft DGA-15P, N9471H, was destroyed when it was involved in an accident near Kernville, California. The airline transport pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot reported that he was returning home after attending a fly-in event. After waiting for the engine oil to warm up to 60°C, he performed the engine run-up. During this time, he checked the rpm drop between magnetos, verified that the carburetor heat functioned normally, and cycled the propeller. After completing the run-up checklist, the pilot selected the main fuel tank, which was about 3/8 full. The forward tank was about half full. He then waited about 10 minutes for the traffic pattern to clear before departing. The airplane lifted off the runway at about 70 mph and accelerated to about 85 mph in a 10° nose high attitude. The airplane reached about 50 ft above ground level (agl) before the engine lost total power and the airplane started to descend rapidly. After impacting the runway, both main landing gear separated, and the airplane slid about 300 ft before coming to rest upright. The airplane was destroyed by postcrash fire; however, the engine compartment survived the fire with minimal thermal damage. In a subsequent statement, the pilot reported that the main fuel tank may have been less than 3/8 full, as he had recently flown 1.5 hours.

According to FAA records, the airplane was manufactured in 1943 and registered to the pilot on January 6, 2016. The airplane was powered by a Pratt & Whitney R-985 AN-14B, air cooled, 450 horsepower radial engine. Maintenance records indicated that the airplane's most recent annual inspection was completed on April 26, 2018, at a total time of 2,208 flight hours. The engine had accrued a total of 5,683 total hours at the time of the inspection and 508 hours since its most recent overhaul, which was completed on January 8, 1996. A maintenance record from June 2018 showed that the pistons for cylinder Nos. 3 and 5 were removed and reinstalled to facilitate the installation of new piston rings.

The engine was test run for 10 minutes at 1,000 rpm and subsequently advanced 200 rpm every 10 minutes. During the 15-minute engine run at 1,800 rpm, the left and right magnetos were shut down individually, which revealed a drop of 60 rpm for the left magneto and 80 rpm for the right magneto. Engine power was then advanced to 1,900 rpm for 15 minutes, 2,000 rpm for 15 minutes and 2,100 rpm for 5 minutes. The engine ran smoothly and continuously for the duration of the engine run.

Examination of the fuel selector valve did not reveal any obstructions and the wobble fuel pump operated normally when actuated by hand. According to the Pilot's Operating Handbook (POH), the wobble pump is normally used during starting and emergency operations.

The POH, dated June 22, 1943, was intended for models of the accident airplane that belonged to the United States Navy and included procedures for the engine start, takeoff, and the climb. The "Starting Procedure" stated that the fuel selector should be moved to the "Main Tank" and subsequently primed using the wobble pump with the throttle control in the "IDLE-CUTOFF" position. There was no procedure to change fuel tanks until having reached the "CRUISING" stage of flight, which required the pilot to select the "FRONT TANK." Similar procedures were found in a the POH for a subsequent model, dated January 7, 1947.

The airplane was equipped with three fuel tanks beneath the cabin: a front tank, a main tank, and a rear tank, totaling 122 gallons. According to the POH, the main tank should be selected for takeoff and landing.

The November 2018 issue of The Howard Newsletter, a publication of the Howard Aircraft Foundation, the airplane’s type certificate holder, discussed the fuel system operation in relation to the accident circumstances. According to the issue, the accident airplane make and model should be operated using the forward tank during takeoff and landing. The article further stated that this was "factory direction" for most all Howard DGA-15s; however, the foundation was unable to produce any POHs, engineering data, or placards that required the forward tank be selected during takeoff. The author's opinion of the rationale behind this information is based on a theory that the main fuel tank can become un-ported during takeoff due to the location of the fuel sump, fuel tank quantity, pitch attitude, and acceleration rate.

Howard DGA-15 airplanes holding serial numbers 500 – 700 (the accident airplane was 813), directed the pilot to take off with the fuel selector on the main tank; however, some aircraft in this series were also equipped with a placard that stated, "TAKE-OFF PROHIBITED ON ANY TANK WITH FUEL BELOW YELLOW MARK." In its article, the Howard Foundation stated that the implication behind this placard was that a fuel level at or above the yellow mark was sufficient to preclude any un-porting of the fuel pickup. Additionally, with the main tank about one-third full, "the acceleration of the Howard, in concert with the pitch attitudes attainable when the aircraft is light, could lead to the un-porting of the fuel pickup of the main tank." According to a drawing issued by the company's engineering department on November 26, 1943, (see figure) a fuel selector for the accident airplane make and model required selection of the front tank during takeoff and landing.

Figure: Howard DGA 15P Fuel Selector Placard

The Howard Aircraft Foundation provided correspondence that took place between the Howard Aircraft Corporation and the Civil Aviation Authority from 1942 and 1943 and included discussions about a "fuel system failure." The records indicated that an engine failure during takeoff or climb may occur at low fuel quantities. This information did not cite the fuel level that could result in an engine failure. The discussions referenced a re-calibration of the fuel gauges and the installation of a placard that shows the minimal fuel required to take off and land on the main fuel tank.

The Howard Aircraft Corporation ceased operations in 1944. The accident airplane was manufactured in 1943 and was not equipped with a placard or any warning to use the front tank during takeoff or caution the pilot from attempting to takeoff below a specified fuel quantity. In addition, the pilot was unaware of the airplane's history of fuel system failures.

The article included prior incidents of pilots who experienced power interruptions or losses of engine power or discovered that their airplane would not draw fuel from the main tank below a certain fuel quantity. In one example, the pilot experienced an interruption in engine power about 50 feet agl with the fuel selector on the main tank and with a fuel quantity "significantly less than half full." In another example, a Howard Foundation member reported that the airplane will not draw fuel from the main fuel tank in a three-point attitude if the fuel quantity is less than about 20 gallons, which is just below 1/3 of a tank.

The 0856 recorded weather observation at China Lake Naval Air Weapons Station, China Lake, California, located about 37 nautical miles east of the accident site, included wind from 310° at 4 knots, 10 statute miles visibility, clear skies, temperature 17°C, dew point 03°C, and an altimeter setting of 29.90 inches of mercury.