 Ishthe47guy wrote: |
| The B models had fiberglass blades with a slightly larger chord (32 inch). The early C models had these blades also. Later C's & all D & subsequent models (E,F,G) have the current wide chord (36 inch) fiberglass blades. The blades have never been considered retractable, but more so they have the ablity to be folded. I've done shipboard ops, but since we had the aft deck all to ourselves, we never had to fold the blades. Chris Ish |
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Chris is right. I also crewed CH-47s for a considerable amount of time, I began working and crewing A models, then C models and finally they dragged me kicking and screaming to crew D models. This time included 3 years with 2/160th SOAR and more than my share of CH-47 load outs.
As Chris mentions, A models had a narrow chord blade consisting of a titanium spar with a series of aluminum skinned "pockets" attached. This technology was fairly standard and was widely used. B and C models had improved blades, but still a fairly narrow chord.
To add some insight as to FRBs, they came into service in the mid 80s at about the same time the "D" model was being fielded. The blades were retrofitted to C models (and I believe some of the existing B models) The advantage of wider chord on the FRBs was increased lift and as a side benefit, the rotor system was operated at lower RPMs, which meant less wear on the drive train and airframes.
Chris is also correct in stating that there has never been any provisions for an "automated" blade fold as exists on CH-46s. While the concept of folding blades on Chinooks is an simple one, and there are balde fold kits made for the aircraft, folding the blades is time consuming and manpower extensive.
When I was stationed at Hunter Army Airfield, we sometimes had to pack the hangar in preparations for hurricanes...It took less time to completely pull the blades (all that had to be removed was one bolt on the blade damper and the vertical hinge pin) than to fold them, plus, there weren't enough blade fold kits for all the aircraft we wanted to put in the hangar.
Now on the face of it, it would seem like less work to simply pull the #9 synch shaft and the damper bolts and fold the blades, but when the aircraft is put back together, the rotor system has to be "phased" to ensure that there is no blade to blade contact between the forward and aft rotor systems which can be time consuming.
When prepping a CH-47 for a C-5 load out, common practice was to pull all the blades, pull both rotor heads, pull the forward transmission, and the aft pylon. The blades and rotor heads were then put inside the helicopter and the forward transmission and aft pylon were tied down seperately. It sounds like a lot of work...and it is, but a crew that has done it often enough can complete the process in a matter of hours.
My thoughts? Screw all the blade fold crap and just pull the damn things, and when you get where you're going, hang the blades back on.
Jonathan Primm