I couldn't open the link, but could this be a case of a proposal to transport 2 howitzers from Point A to Point B & it's been twisted into a gunship proposal story? I just can't see the attachments working for firing & regardless of weight, it couldn't be that much trouble to at least remove the howitzers' wheels/tires to save some weight. As the howitzers are intact & appear 'road ready' as opposed to creating a Chinook 'battleship', I just don't buy the structures at the very least, much less the simplistic theory. It's not dated April 1 anywhere, is it? Kinda like a pic of an AU-23, IIRC, with a Sparrow missile hanging under the wing, yeah, it CAN carry it, because it would attach to the rack, but that's all it could do with it. I think the caption even said something like the only damage it could do was 'if it dropped it on someone's head'.
Design arrangement and mounting approaches, weight estimates, balance
calculations, stress analyses, and helicopter performance predictions
of an aerial artillery system utilizing two externally-mounted 105mm
XM204 soft recoil howitzers on a CH-47C Chinook helicopter are presented.
This design provides for all the firing modes and operational
capabilities required by the Weapons Command, including the ability to
offload one howitzer when the helicopter is hovering. The study includes
an analysis of the structural integration of the weapons and
aircraft including muzzle blast effects and airframe dynamic responses.
A minimum adequate fire control system for air-to-ground firing and
typical ground artillery fire control equipment was included. Mission
capabilities of this system include delivery of 60 rounds of rapid
air-to-ground firing at the midpoint of a 100-nautical-mile radius
with 15 minutes loiter to acquire the target. Delivery of a howitzer
for detached firing and a mission using the aerial artillery for
attached firing were also considered. Model testing that demonstrated
the feasibility of modclLng the 105mm howitzer for muzzle blast effects
was also included.
This was a Boeing-Vertol study from October 1972 for the US Army Weapons Command, Rock Island Arsenal, Illinois (just about my home town).
Nope, just real basic test rigs with some reinforced Chinook skin and pressure gauges to prove the aircraft wouldn’t be torn apart. The study was done in 1972 just as the flood of Vietnam era funding that might well have gotten it prototyped dried up, and it didn’t help that the XM204 howitzer itself was ultimately rejected for land service. I love the proposed laser range finding sight for anti tank use though. Always been the best part of this concept.
Video of XM204 explaining its soft recoil method of operation and thus why its actually sane to fire two of them from a helicopter.
From what I saw, the principle it's based on is "firing out of battery" whereupon the barrel is resting in the recoil position, being released to move forward as it fires, the motion and the recoil mostly canceling each other out, resulting in low recoil.
Since this got bumped up, I found out why the XM204 didn’t work out. Basically the issue was with semi fixed ammo and variable bag charges the exact moment the powder charge would burn could not be predicted. In a normal howitzer that was fine, very short delays changed nothing. However in a soft recoil howitzer the moment you pulled the lanyard the barrel starts moving forward, so a delay in firing changes the length of the recoil stroke. This led to erratic performance and was impossible to resolve at the time. Soft recoil guns on armored vehicles all used fixed ammunition that did not have this problem. It might be solvable today with newer high power laser based ignition systems but 120mm mortars now have such great range the demand for a very small 105mm doesn't exist.