OCEANA, VA, USA
N156XD
Saab-Scania AB (Saab) F-35 DRAKEN
The pilot was conducting the second of two support flights for a U.S. Navy ship. On each flight, he made three passes. Following the last pass of the second flight, the pilot made a 5g pull-up. Once 'on top', he noted that the airplane's fuel quantity was rapidly going down. The pilot declared an emergency, and climbed the airplane to 35,000 feet, where the engine flamed out. He established a 300-knot glide, and was vectored to a naval air station. He stated that the airplane either reached, or was above three 'key' positions, and on airspeed. However, after the third key, he realized the airplane would not reach a runway, so he successfully ejected less than 50 feet above the ground. The airplane impacted a plowed field, and remained upright until it skidded to a stop. There was no post-impact fire, and there was no evidence of fuel leakage, nor of the failure of any airframe component. The second flight was about 15 minutes longer than the first. With the airplane's capacitance fuel indicating system; high speed flight fuel quantity indications could be inaccurate. The 2,700-hour pilot had 43 hours of flight time in make and model.
On June 26, 1998, at 0945 eastern daylight time, an experimental Saab F-35 Draken, N156XD, was substantially damaged when it impacted the ground, short of the runway, during a forced landing at Naval Air Station Oceana (NTU), Oceana, Virginia. The certificated commercial pilot ejected from the airplane and was not injured. Visual meteorological conditions existed, and a instrument flight rules flight plan had been filed for the contract flight, which originated from Williamsburg International (PHF), Williamsburg, Virginia, at 0858. The flight was conducted under 14 CFR Part 91. The airplane, a former military jet, was owned and operated by Flight Test Dynamics of Inyokern, California. It was providing services to the U.S. Navy in warning areas off the Maryland and Virginia coasts. The pilot had flown it earlier that morning, and had conducted a flight profile similar to that of the accident flight, with three training runs/passes by a ship. He reported that during the last run, he had passed over the ship with a fuel indication of 1,600 pounds, and that later he landed at PHF with a fuel indication of 1,000 pounds. There were no significant discrepancies with the airplane. After refueling, the airplane departed on its second flight. The pilot reported that there were no abnormal indications during that flight until after completing the third pass over the ship. During "pull off," the pilot saw that there was between 1,400 and 1,500 pounds of fuel remaining, and established a 5g pull-up to a climb. He marked "on top" of the ship, switched frequency, and was ready to call the area controller when he noticed that "the fuel was now passing through 900 pounds (the rate was noticeable on the gauge.)" Climbing through 15,000 feet, the pilot declared an emergency, and requested vectors to the nearest airfield. The controller vectored the pilot towards NTU, and the pilot then attempted to troubleshoot the problem. He switched to the external fuel tanks, then switched back to the main tanks. When he received a call from the air traffic controller, he noted that he had 400 pounds of fuel remaining, "still dropping rapidly. I informed them that I now had 'very little' and was going to be a flameout soon unless my problem was a gauge error." The pilot also noted that "the rate that the fuel was leaving the aircraft had not diminished." Once in the 20,000 foot-plus altitude regime, the pilot informed the controller that he was going to continue to climb the airplane to enhance the glide. In addition: "I had already ascertained that I was not in afterburner (pulled the throttle to idle, and my performance did not indicate afterburner was lit.) I considered that the AB fuel pump could be pumping but with no ignition of the AB, but by now I had between 200 and 300 pounds, and I elected to select military power and continue my zoom for maximum altitude...I knew there was a switch to turn off the AB pump, but did not switch it off. (Partly because I was going to have to come inside the cockpit to find it and partly because I had such little fuel left I was concentrating on aviating/navigating at this point.) As the airplane zoomed to approximately 35,000 feet, "the engine surged and then flamed out." The pilot estimated that the distance to NTU was 45 nautical miles, and from the maximum range descent profile section of his pocket checklist, that he had a glide range of 50 to 60 nautical miles. Approaching the coastline, the pilot spotted the airfield, and after determining that the airplane could reach it, or at least its boundaries, he elected to continue towards it. The pilot reported that he arrived at the first key position (abeam the landing area at 8,000 feet and 300 knots) at 10,000 feet and 300 knots. He arrived at the second key position (6,000 feet at 300 knots) at 6,500 feet and 300 knots. He arrived at the third key position at his target of 4,000 feet and 270 knots. "Considering where I had started, I knew that I was losing altitude too quickly for the profile, and that I would likely be short on final." The pilot transmitted that the airplane would be landing short of the runway. He aligned it with the runway, over a plowed field. At an estimated 50 feet, and an airspeed of 150 knots, the pilot ejected. The airplane impacted the ground, and skidded to a stop in an upright attitude. No post-crash fire ensued. The pilot returned to the airplane to shut down the battery and fuel system to prevent fire. According to a Federal Aviation Administration (FAA) Inspector, during post-accident inspection, there was no evidence of fuel leakage on or about the airplane, nor was there any evidence of failure of any airframe component. The airplane was not disassembled for inspection. The president of Flight Test Dynamics provided a statement. In it, he noted that when the airplane was refueled after the first flight, it had 550 pounds of fuel remaining onboard, which was confirmed by both the fuel gauges and the amount of fuel then pumped into the airplane. He also noted that the second flight was "15-20 minutes shorter than the first," and that bingo fuel to NTU was 1,700 pounds. He stated that since the pilot had a concern that the airplane was "losing or using fuel at an abnormal rate, the first and foremost action the pilot should have taken [was] to get his head in the cockpit and check all those items which might prevent further loss of fuel, regardless of the small amount of fuel remaining...," and that "[The pilot's] entire attention at this time should have been in the cockpit and his concern should have been with a potentially very important switch...." An investigator for Sweden's Board of Accident Investigation (BAI) contacted Saab, the airplane's manufacturer. Saab informed him that when the afterburner is secured, there is a pressure guard (circuit breaker) that cuts the fuel flow. The BAI Investigator noted that with high speed flight, it might be difficult to determine actual fuel consumption, and that with a high speed climb, the capacitance fuel system might show more fuel remaining than is actually there. In addition, although the profiles of the two flights may have been similar, the airplane uses a lot of fuel, and even "small changes could affect the remaining fuel quickly." According to the pilots operating manual, the planned fuel margin should have been 15 percent, to allow for a safe go-around, if needed. The investigator also contacted a retired Saab investigator, who related to him about two accidents in the 1960's: one occurred from leaking fuel from "an uncontained AB-pump that led to empty tanks," and another was "caused by pilot error when the engine fuel crane was maneuvered instead of the AB fuel crane." According to the pilot, he had 2,470 hours of total flight time, with 43 hours in make and model.
The pilot-in-command's inadequate fuel management which led to fuel exhaustion and subsequent loss of engine power. A related factor was the pilot's unfamiliarity with the fuel system.
Source: NTSB Aviation Accident Database
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