US Army: CH-47F Block II comes with less power than planned

WASHINGRON — The US Army intends to refrain from using the Advanced Chinook Rotor Blades [ACRB] when upgrading its Chinook helicopter fleet to the CH-47F Block II version, according to Brigadier General Robert Barrie, program officer for the US Army Aviation Corps, learned, citing Soldat&Technik.

US Army: CH-47F Block II comes with less power than planned
Photo credit: Rotor & Wing International

Problems during flight testing, which the Army had classified as a potential safety risk, are given as the reason for not using the new rotor blades. “When we started development flight testing of the rotor blades, we had two problems. On the one hand, there was a vibration problem and on the other hand, there was a stall on the rear rotor,” Barrie is quoted as saying in the US trade press. According to consistent reports, the combination of these two problems, coupled with the lack of a cost-effective solution, led the Army to halt this part of the Block II development program.

Block II is a product improvement of the Boeing CH-47F. This should include new rotor blades, improved gears, non-segmented tanks, and an increase in payload [approx. 1.8 t] and range.

The innovative ACRB rotor blades made of composite materials were originally developed for the RH-66 Comanche reconnaissance helicopter, which never went into series production. The new rotor blades should give the Chinook helicopter an additional lift of 771 kg. Abandoning the new rotor blades could now mean that the modernization program will only offer about one-ton additional load capacity for the future Block II Chinooks – five of which were contracted in autumn 2021.

US Army: CH-47F Block II comes with less power than planned
Photo credit: FlightGlobal

A new drive system remains in the Block II program, which improves the power transmission to the rotor blades and should generate up to nine percent more torque. Also a single cell fuel tank on each side [the previous three fuel cells in each landing gear nacelle are merged into one large cell; eliminating the equipment to transfer fuel between cells saves about 90kg of weight and slightly increases fuel capacity], electrical system upgrades as well further, previously unspecified modifications to the airframe should contribute to the increase in performance of the Chinook.


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