Torque variation with speed
 

I’m thinking of tandem rotor aerodynamics here.

Does torque vary with increasing speed for a fixed collective setting? If so I’d be grateful for an explanation.

I managed to avoid tandem rotor P of F so I'll leave this one well alone :)

Chinook PofF:

“it just does, OK?”

I thought that was the same for all rotary POF. :)

Here's a guess from a non-tandem person:

As the speed increases, the relative airflow is less of the vertical and more of the horizontal. Induced flow decreases, the Total Reaction isn't bent backwards so far, so the torque required to overcome the horizontal (backwards) component of TR is less.

AC - but the front head affects the rear head in mysterious ways -

And he is talking about fixed collective vs torque as speed increases - in a single rotor you would mention the vertical stabiliser offloading the TR but that doesn't happen in a tandem (I think):)

I’m not surprised to have had so few replies - it’s not as simple as single rotor PoF. I suspect that there will be a small torque reduction as there is a small pedal input needed in the hover to maintain heading because of the unequal proportion of lift generated by each head (Chinook 45% front, 55% aft) at different heights thus creating a couple - the tandem rotor equivalent of tail rotor roll.