Page 46 - HeliOps Frontline Issue 26

46 HELIOPS FRONTLINE / ISSUE 26 / 2019

resistance to Improvised Explosive Devices. The increased weight
of the Chinook, coupled with the heavier JLTV, results in less
mission flexibility as fuel or payload needs to be traded – either
the JLTV isn’t carried as far underslung or the vehicle is de-‘roled’
to an extent.
The Army anticipated such a problem and initiated the CH-47F
“Block II” program to ‘buy back’ some of the performance loss. The
Block II enhancements included a new rotor design, the Advanced
Chinook Rotor Blade (ACRB), which features swept back tips for
the first time, and promises to increase payload by some 1500lbs;
a very ‘convenient’ figure. There are also improvements to the
transmission drivetrains, which, Boeing claim’s increases available
torque by 9% by reducing losses between the engines and the
rotors. Finally, the current fuel system (for ‘thin-tank’ aircraft) has
6 separate tanks, one main and two auxiliary tanks per side, with
associated piping, transfer and booster pumps. The Block II reverts
to a simpler design, with one tank per side, the same as the ‘fat
tank’ aircraft have. This configuration provides a handy weight
reduction and reduces the complexity, and therefore the likelihood
of malfunction in the system. From a personal perspective, having
flown the UK’s version of the CH-47D for 2000hrs, I’m a little
sceptical of the new tank design, particularly from a survivability
and crash-worthiness perspective. The old 6-tank design enabled
the crew to isolate a tank in case of battle damage and for the
tanks to separate and seal independently in the event of a heavy
landing. The UK aircraft, at least, also had a dry-bay inert gas fire
suppression system.