I would add that, at least, the US got better at coordinating CAS as the NW Europe campaign went on. Initially for example US L-4 Grasshoppers did not carry aircraft radios to communicate with fighter bombers they were later equipped with these allowing a more real time response. By Nov 44 it had become common place with at least 1st and 3rd US Armies to have figher bombers on station accompanying advancing columns and have those aircraft directed on targets by L-4s and ground controllers with the columns.
I would agree in large part with Zetterling's findings where ground attack aircraft were not being directed onto targets by either ground or air controllers. On their own, it is difficult for fast ground attack aircraft to locate targets and subsequently effectively attack them.
It is also obvious that where they can, like in the case of railroads, they were very effective.

Here is a link to Zetterlings article:

http://web.telia.com/~u18313395/norm...s/article.html

Its good but is effective outlining what Ian Gooderson argued in his book. While it is true not many tanks were destroyed allied aircraft, especially the typhoon, had a certain morale effect similar in away to what the Tiger tank had on allied tank men. This is someting significant missed int he historiography.

It is true that in the CAS role it was very hard to pinpoint a stationary target but a moving one was easier. The best use for the aircraft was in the Battlefield Interdiction Role i.e. stopping the reinforcements and supplies reacginh the frontline. by the time of normandy the allied TAF were effectivly able to cordon the area off and seriously hinder the movement of german forces into the battle zone. This was probably their most significant contribution to the campaign.

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Thoughts on Military History
Cornish Scale Modellers
Ross' Military Modelling and Art

Well, ran across this little bit of data from a book titled aircraft of ww2 by Jim Winchester.

The FW 190 could also carry a bomb called the sc1000, which weighed 3.968 lbs. " The " largest & most powerful bomb carried by any fighter of the war.