The timing of the collision is pretty hard to say using the AIS track.
Around 1630 UTC give or take a minute, Or as you say between 1630 UTC and 1633.
I think other people have concluded, Based on Impact damage and the AIS track the Fitz approximate heading at time of impact was around SE. 135. This appears to be consistent.
Here is the speed and heading info from the ACX AIS track starting approximately 10 minutes prior to the collision.
1619 UTC 18.1 Kn Co 069
1621 UTC 18.4 Kn co 070
1624 UTC 18.4 Kn Co 070
1627 UTC 18.5 Kn Co 070
1630 UTC 17.3 Kn Co 088
1633 UTC 11.2 Kn Co 135
The speed and heading at 1633 the ACX is approximately 90 degrees from her heading of 070. her speed reduced to 11.2 knots.
My guesstimation of the Manoeuvering characteristics of a Container ship of the ACX Crystals size with a single screw direct reversible slow revving diesel.
At 18.5 knots, Rudder Hard to starboard, No engine Movement, approximately 4 minutes later. Heading Changed by about 90 Degrees, Advance approximately 0.5 miles. Speed reduced to 10 or 11 knots. Give or take a Knot, Minute or a Cable.
My guess the ACX version of events so far. Is roughly consistent with the AIS track. Working back from 1633, My guess the Hard to starboard was applied around 1628 UTC or 1629 UTC. Pure speculation of course.
I don't see any apparent indication from the AIS of telegraph or throttle movement until some time after 1633 UTC
The ACX Applied Hard to starboard, After signaling with the flashing light (probably at least 1 set of 5 short flashes) waiting for a reaction and seeing none.
The ACX Decided to signal the vessel approaching on her port bow. After having become concerned the Vessel she perceived as give way was not taking appropriate action.
The ACX has a vessel approaching on her port bow. Less than 3 miles away, The ACX perceives it is a crossing situation and she is the stand on vessel.
The ACX reports the Fitz as a Crossing Vessel. (Masthead and sidelights visible) approx. 40 deg x 3 miles to Port 10 minutes prior to the collision. Its unlikely this timing is accurate its based on the OOW recollection. Its Unlikely it was logged.
The VDR data from the ACX will show the Radar Picture. If tracked by the ARPA the Data will show the relative and true motion of the Fitz and the timing of any alterations of course and or speed. It will be possible to calculate from raw target data even if the Fitz was not tracked as an acquired target.
The ACX report having used a light to flash at the Fitz. When probably prior to ordering hard to starboard, How long before?
Using an ALDIS light to Flash 5 Short and rapids. I have done this.
Radio, Who was he going to Call, "Ship My Port Bow" He didn't its an omission. Would It have done any good? Not the point. Wasn't done.
The ACX identifies the Fitz as a crossing vessel. Presumably The ACX could see Masthead and side lights. There is no mention of stern light by the ACX. This does not mean it was always a crossing situation. Or not just the ACX considered it a crossing situation.
So the ACX stood on maintaining her course and speed. With a vessel approaching quickly from a distance of less than 3 miles away on her port side.
A container ship this size stopping distance? crash stop ball park 1.5 miles give or take a bit.
Turning circle 0.5 miles give or take a bit.
This is all happening pretty close to acceptable minimums.
The ACX reports 3 people on bridge in hand steering, Was this Capt., OOW and QM or OOW, QM and Lookout.
The ACX makes a routine course alteration which may have contributed to a close quarter situation developing.
After this alteration.
They see the ship to Port, They see it change course and speed, It takes them a while to figure out its now on a collision course, They wait around for it to react, It takes them a while to get concerned, Then their reaction going hard to starboard is very late and the approaching ship is very close.
To little to late.