The third Beechjet dual engine flameout in less than two years has left NTSB investigators, as well as aircraft manufacturer Raytheon and engine maker Pratt & Whitney Canada, scratching their heads. Meanwhile, without any answers or precise operating guidance, Beechjet pilots, owners and passengers are left to ponder a disturbing trend.
Business aviation safety consultant Robert Breiling of Robert E. Breiling & Associates said it is unprecedented for the same business-jet type to suffer three dual flameouts. He asserted that the flameouts are no longer just a coincidence and likely point to a problem with the Beechjet itself or its operating procedures.
After the first incident in July 2004, the problem was initially perceived to center around an ultra-low concentration of fuel anti-icing additive. (The Beechjet is not equipped with fuel heaters and thus relies on the fuel additive to prevent ice crystals from forming and clogging the fuel filters. An oil cooler is installed in the jet’s fuel tanks, though its heating effectiveness is unknown.) But this theory might prove to be a wild goose chase, given the circumstances surrounding the two latest Beechjet flameouts–one on Nov. 28, 2005, and another this past June 14.
According to the NTSB, on June 14 Beechjet 400A N440DS lost power from both P&WC JT15D-5 engines while the airplane was in cruise flight at FL380 near Norfolk, Va. The pilots reported that they were in cruise flight in VMC at Mach 0.76 about 70 miles south of Norfolk when ATC issued a heading that steered the twinjet toward an upsloping cloud deck.
Unsure if they would remain clear of the clouds, the pilots decided to turn on
the engine anti-ice. They then turned on the engines’ igniters and reduced the power from 101.5 percent to 89.5 percent N1, but before they could turn on the engine anti-ice both engines flamed out simultaneously. (Raytheon does not recommend activation of engine anti-ice above 90 percent N1 to “prevent transient exceedence of ITT limits.”) The pilots declared an emergency and turned toward Norfolk.
The left engine restarted on its own at about FL300 and the right engine restarted on its own at about FL240, and the pilots continued to Norfolk, where they landed without further incident. Post-incident tests confirmed that “the fuel system icing inhibitor was present and in the correct concentration and that the fuel met the requirements for jet-A.”
In the November incident, the crew of Beechjet 400A N691TA experienced a double engine flameout at FL380 on a positioning flight from Indianapolis International Airport to Marco Island Airport, Fla. An NTSB preliminary report said the Beechjet crewmembers subsequently made two restart attempts and an air-start attempt before deadsticking the twinjet to a safe landing at Jacksonville International Airport, Fla. According to information obtained recently by AIN, the fuel system icing inhibitor was found to be “slightly low” in this aircraft.
In the July 12, 2004, incident, both engines of Beechjet 400A N455CW flamed out at FL390 while the airplane was descending from FL410 over the Gulf of Mexico. The pilots were able to restart the right engine at 17,000 feet and safely divert to Sarasota, Fla.
On April 17, two months before the most recent event, Raytheon Aircraft issued Safety Communiqué No. 269, which gives details of the Jacksonville event and reminds operators about engine anti-ice procedures. The document notes that engine anti-ice should be activated “when flying in or near visible moisture in possible icing conditions.” It later adds, “No lower temperature limit exists for the operation of anti-ice systems. Operators should be aware that air moving through the engine experiences a significant temperature increase as it passes through the compressor section…[which] could bring the air temperature to a range where internal engine ice formation might occur if engine anti-ice were not operating.”
According to the NTSB investigator in charge, the common link among the Beechjet dual flameouts is that “all three airplanes were at high altitude near convective activity and the power had just been retarded.” He further told AIN, “We are still looking at everything, including mechanical and operational factors in these incidents.”
Marc Fruchter, president of Aviation Consultants and a type-rated Beechjet pilot with 2,000 hours in type, offered some insight into these incidents. He recommends using a fuel anti-icing additive in all turbine aircraft, especially for the Beechjet since he claims that the airplane’s tanks like to collect water and sediment. In fact, he emphasized that the Beechjet must sit perfectly still for at least three hours before the tanks are drained to allow water to settle fully–otherwise the water will remain in the tanks even after draining.
Additionally, Fruchter believes that recurrent training should emphasize the smooth reduction of power. Aggressive power reductions can cause flameouts, he said, adding that this is especially true for P&WC turbofans.
“The Beechjet is a wonderful airplane, and I would be very comfortable flying
it again,” Fruchter noted. “It just requires pilots to be properly trained in power management, as well as precise fuel-draining procedures.”
Neither Raytheon nor P&WC would comment for this story, citing the ongoing NTSB investigations. The NBAA Beechjet subcommittee, a liaison between Beechjet operators and Raytheon, also declined AIN’s request for an interview about the recurring dual flameouts.