Why couldn't the co-pilot reach the rudder on Alaska Airlines 261?

Question

Alaska Airlines flight 261 was an MD-80 that suffered a catastrophic horizontal stabilizer failure. The CVR recorded the pilots some minutes after they first declared an emergency:

Completely inverted and still diving at a -9 degree pitch, the crew struggled to roll the plane, with the captain calling to "push push push...push the blue side up," "ok now lets kick rudder...left rudder left rudder", to which the copilot responded, "I can't reach it". The captain then replied "ok right rudder...right rudder," followed 18 seconds later by "gotta get it over again...at least upside down we're flying."

Granted that by then they were hanging upside down, but aren't the pilots strapped in with four-point harnesses? I'm wondering:

1. What might have prevented the copilot from reaching the left rudder (but possibly still able to reach the right rudder)?
2. Why would the captain ask the copilot to push the rudders instead of just doing it himself?

Answer 1

The MD-80 uses a mechanical linked flight control system according to this article. This means, that aerodynamic forces of the control surfaces are transmitted directly to the control column. This can lead to very high flight control forces acting on the flight controls. From your wikipedia article:

only by pulling with 130 to 140 lb (580 to 620 N) on the controls did the flight crew stop the 6,000 ft/min (1,800 m/min) descent of the aircraft

Concerning your 2. question: Given this, it is obvious that the captain did not ask the co-pilot to push the Rudder for him, but with him. He coordinated their efforts in flying the airplane by quite literally joining forces as the control forces were too high for one man.

Concerning your 1. question: I do not know exactly, however I speculate that the co-pilot could not reach the rudder pedals because his seat was not properly adjusted (for example because he was not flying actively when the incident took place), and the rudder was pressed such that the left rudder pedal was farther away. This would also explain why the captain then stated to push on the right side, as he assumed that the co-pilot might reach that pedal as it was closer to him. But again that is speculation.