The US Marine Corps test team is finalising a set of solutions to deficiencies found during flight tests of the upgraded Bell UH-1Y at NAS Patuxent River, Maryland. The problems are similar to those found on the AH-1Z last year.

The UH-1Y's main problems were inadequate longitudinal flying qualities, high rotor yoke loads, insufficient longitudinal and lateral cyclic margin and poor directional stability in forward flight.

"We have lots of power left and were running out of forward stick, and lateral interference with the crew's legs and seats," say the USMC test team, adding that flying quality issues have been cured by changing the horizontal elevator and developing the stability and control augmentation system (SCAS).

The same changes to the elevator, which was redesigned with a resized metal elevator without endplates, also helped cure the control margin problem. The cyclic envelope issue was solved by increasing cyclic control authority in both axes from 100% to 120% and, although increasing control sensitivity, "it did not cause any unacceptable SCAS- off handling characteristics and actually improved low-airspeed handling qualities reducing the tendency to pilot induced oscillation [PIO]," says the team. The second UH-1Y flew last month.

The firstUH-1Y has a fully functional integrated avionics suite and testing has revealed some deficiencies, including over-sensitive pitot static instruments and reverse sensing of the balance ball, which will be corrected by new software. The latest load is expected to help the test team "fine tune" the sensitivity of the engine, drive train and flight instruments for later production versions.


Source: Flight International