The National Transportation Safety Board issued a list of safety recommendations Monday affecting operators of Bombardier CL600-series regional jets and corporate aircraft.

In its letter to the FAA, the NTSB recommends the agency require manufacturers of airplanes equipped with General Electric CF34-1 or CF34-3 engines to adopt a standard procedure to handle high-power, high-altitude sudden engine shutdowns... as well as a procedure to restart those engines after such an event.

The Board also recommends manufacturers of other turbofan engines review their designs, to see if their powerplants are susceptible to similar cases of "core lock" the NTSB says contributed to the loss of a Pinnacle Airlines regional jet in 2004.

In that accident, two pilots ferrying a CRJ200 were killed after they flew the plane on a "joyride" up to 41,000 feet, and experienced an aerodynamic stall. The disturbed airflow caused the engines to flame out... and the pilots were unable to get them restarted.

Below are the recommendations sent to the FAA:

• For airplanes equipped with CF34-1 or CF34-3 engines, require manufacturers to perform high power, high altitude sudden engine shutdowns; determine the minimum airspeed required to maintain sufficient core rotation; and demonstrate that all methods of in-flight restart can be accomplished when this airspeed is maintained. (A-06-70)
• Ensure that airplane flight manuals of airplanes equipped with CF34-1 or CF34-3 engines clearly state the minimum airspeed required for engine core rotation and that, if this airspeed is not maintained after a high power, high altitude sudden engine shutdown, a loss of in-flight restart capability as a result of core lock may occur. (A-06-71)
• Require that operators of CRJ-100, -200, and -440 airplanes include in airplane flight manuals the significant performance penalties, such as loss of glide distance and increased descent rate, that can be incurred from maintaining the minimum airspeed required for core rotation and windmill restart attempts. (A-06-72)
• Review the design of turbine-powered engines (other than the CF34-1 and CF34-3, which are addressed in Safety Recommendation A-06-70) to determine whether they are susceptible to core lock and, for those engines so identified, require manufacturers of airplanes equipped with these engines to perform high power, high altitude sudden engine shutdowns and determine the minimum airspeed to maintain sufficient core rotation so that all methods of in-flight restart can be accomplished. (A-06-73)

  

• For those airplanes with engines that are found to be susceptible to core lock (other than the CF34-1 and CF34-3, which are addressed in Safety Recommendation A-06-71), require airplane manufacturers to incorporate information into airplane flight manuals that clearly states the potential for core lock; the procedures, including the minimum airspeed required, to prevent this condition from occurring after a sudden engine shutdown; and the resulting loss of in-flight restart capability if this condition were to occur. (A-06-74)
• Require manufacturers to determine, as part of 14 Code of Federal Regulations Part 25 certification tests, if restart capability exists from a core rotation speed of 0 indicated rpm after high power, high altitude sudden engine shutdowns. For those airplanes determined to be susceptible to core lock, mitigate the hazard by providing design or operational means to ensure restart capability. (A-06-75)
• Establish certification requirements that would place upper limits on the value of the minimum airspeed required and the amount of altitude loss permitted for windmill restarts. (A-06-76)

FMI: www.ntsb.gov