Two questions:

1) When did the Beagle crash in the Valley of the Ancients?
2) Was this the crash that created the Valley?

Question 1:
DA3 postulates that the spaceship crashed in the year 1019 ("DA3 p. 3: “a little over five years before”"). David Ross (Zimriel) went with this in his Blackmoor fan gazetteer timeline. Although ZGG used much of Zimriel's work in their D20 Blackmoor line, they also presented ideas that really didnt mesh too well with this date.

The idea of such a recent crash also causes problems with the FFC since that is set in the years 995-1000 and we already have the City of the Gods in place at this time.

Question 2:
While there are some sources that seem to indicate that the Valley of the Ancients was created by the Spaceship Crash, this seems unlikely to me for several reasons. Not the least just the massive damage done to the terrain.

The D20 Blackmoor line presents the Fall of Hadeen, a religious event of the Peshwah, believing a dead god fell to the ground, seen as a falling star. While this could easily be mistaken for the falling spacecraft, it seems more likely that these are two separate events with the falling star creating the valley and the space ship crashing into the same area much later.

-Havard

In 1973 and early 1974 we were playing John Snider's "Star Empires" campaign at the same time that we were playing pre D&D in Blackmoor. The planet where Blackmoor was located was on John's star map near Scott Belfry's Avian empire, so his scout ships attempted to explore it. After losing some ships they quarantined the planet. Stephen Rocheford's minor humanoid empire might have been near it, too, since the aliens in the City of the Gods were humanoids. I think that Richard Snider's character had a cape, captured from the Avians, that allowed him to fly...

I have 650 as the year the Beagle crashed. This is a guesstimate based on the statement that the ship crashed "Many ages ago" in the Leron description from Riders of Hak (page 40) and the description of the Ash Goblins which states "generations" of mutated goblins have produced the "current" version. By these statements alone we are looking at a matter of at least a century or two before the late 900's for the date of the crash.

I'd guess the 5 years ago reference can be retconned as when Stephen escaped from stasis.

I'd never heard the idea that the VoA was somehow created by the crash and I find that basically impossible.

All plausible. There is no need to connect the crash of the Beagle with the Avian empire's exploration or that of the other nearby humanoid empires from the Star Empires campaign.