Boeing CH-47 Chinook (0708744)

What are the racks on the sides.

Antenna, Tony

(and shadow of antenna)

HF Antenna

How do those rotors NOT HIT?

Steve

Self preservation - Sorry couldn't resist.

STEPHEN FURTAK The rotors are connected by a shaft running along the dorsal fuselage (either that or the crews have become VERY adept at starting the engines precisely on time...smile).

just retired from Boeing Flight Test at Mesa AZ - Philadelphia sent us their CH47 block IIs for Flight test.
drive shaft between the two transmissions (fore and Aft) keeps the rotors egg-beater-ing properly. it's in the "crown" on the dorsal surface.
"rack" on the side I think was HF antenna.

Is there any way to trace what happened to a Chinook 815814 that I was an FE in Vietnam?

Joe Williams - Check out:
https://www.chinook-helicopter.com/history/Historical_Summary.html
...and in particular, under each model number check out the:
Click-N-Go Here to read more on the disposition of the CH-47(letter).
When I poked around, the airframe numbers don't match the format you show, but maybe you can figure it out.
There's a good chance it's been remanufactured into a newer model.

Matt Smith, it's really the combining transmission which is connected to the driveshaft between the forward and aft transmissions, that controls the synchronization of the rotor system. You can see the air intake on the rear pylon just above the number 1 engine intake cover.