Duke Freed will pull the lever above his head to begin the "Shoot in" sequence.  The cockpit module will come down and spin twice before locking into Grendizer's head.  This sequence takes 6 seconds.

Now that Duke Freed is in Grendizer's head, the Grendizer super robot is operational.  All Duke Freed has to do is pull another lever to his right and launch the "Dizer GO" command.

When Grendizer returns to Spazer, Duke Freed will make it jump and do a scrambler turn.  The exhuasts on the back of Spazer will raise up open.  Then Grendizer will launch to the back of Spazer, and Duke Freed will shout out the "Spazer Close" command.

Finally, the cockpit module will return from Grendizer's head back to the Spazer wing.  This sequence is called the "Shoot Out" sequence and it takes 7.5 seconds for it to happen.

From the story of Grendizer, we know that this machine was built by Vega.  It is interesting to look at the inside of Grendizer and the inside of Commander Blacki's Mother Burn flagship.  I couldn't help but to notice the similarity.

Below are pictures from episode #13 when Duke Freed went down to do some repairs during his battle.

And below here you see the inside of the Mother Burn flagship, similar wouldn't you say?