FAA Flags Fuel Risk in Rotorcraft Sideward Maneuvers

The FAA has issued a bulletin warning that current cockpit fuel indications in some rotorcraft may not accurately reflect the safe minimum fuel needed during sideward-pulling external-load operations, posing a risk of fuel starvation at higher-than-expected fuel levels. The concern is based on NTSB findings from five MD Helicopters 369-series accidents.

Issued June 10, the Special Airworthiness Information Bulletin (SAIB) follows an NTSB investigation of five MD 369-series accidents during Class C RLC (rotorcraft-load combination) missions. In each case, the helicopters were dragging loads laterally while in high bank attitudes. The NTSB determined that fuel unporting—when fuel shifts away from the tank pickup point—occurred even though fuel levels appeared sufficient by cockpit indication.

“In four of the accidents, the helicopters experienced fuel starvation at fuel loads between 94-146 pounds,” the FAA noted, “which is above the minimum level of 78 pounds used to meet the requirements of §91.151.”

Because certification standards did not anticipate prolonged high bank angles during these missions, and guidance in AC 27-1B and AC 29-2C is outdated, the FAA advises operators to confirm whether their flight manual supplements account for this risk. Specifically, it recommends that manuals include the maximum demonstrated bank angle held for extended durations, minimum useful fuel required at that angle with an added 20% safety margin, and operating procedures tailored to these conditions.

This is not an airworthiness directive but a safety recommendation targeted at design approval holders, operators, and inspectors. While not mandating changes, the SAIB warns that current fuel quantity indications may not accurately reflect the amount needed for safe operations at sustained bank angles.