I remember reading that Macedonian phalanxes were fairly resistant to arrows and javelins since the upright pikes would deflect most missiles.
On the other hand, I've also read that the Scottish Schiltrons were vulnerable the English and Welsh longbowmen.
So how different were the phalanx and schiltron? Were other pike blocks, like the Swiss or the Spanish Tercio resistant to missiles? Though the prevalence of gunpowder might make the latter two a tough comparison to earlier pike formations.
"The Art of War in the Middle Ages" covers this specifically. Chapters IV and V describe how heavy cavalry eventually gave way to pike formations, perfected by the Swiss pike squares who dominated the field at their height. The subsequent chapter describes how 2 strategies eventually developed to overcome these types of formations. The first would be longbows or the equivalent of longbows to wear down the from extreme distance (this style would require at least some footmen and preferable cavalry not only to screen and protect the archers from charges but to deliver the knockout blow when the enemy ranks were sufficiently denuded) and a more hand to hand style using swords and bucklers to knock aside the pike points and get in close where the pikes were ineffective.
The former strategy was aptly demonstrated at the battle of Falkirk where the Scottish pike formations were a large target the English Longbows could pepper until the final cavalry charge on the bedraggled survivors. A quote from the above text: "Concentrating the rain of arrows on particular points in the columns, the king fairly riddled the Scotch ranks, and then sent in his cavalry with a sudden impetus. The plan succeeded, the shaken parts of the masses were pierced, and the knights, having once got within the pikes, made a fearful slaughter of the enemy. The moral of the fight was evident: cavalry could not beat the Scotch tactics, but archers supplemented by horsemen could easily accomplish the required task. Accordingly, for the next two centuries, the characteristics of the fight of Falkirk were continually repeated whenever the English and Scotch met. Halidon Hill, Neville’s Cross, Homildon, Flodden, were all variations on the same theme. The steady but slowly-moving masses of the Lowland infantry fell a sacrifice to their own persistent bravery, when they staggered on in a vain endeavour to reach the line of archers, flanked by men-at-arms, whom the English commander opposed to them. The bowman might boast with truth that he ‘carried twelve Scots’ lives at his girdle;’ he had but to launch his shaft into the easy target of the great surging mass of pikemen, and it was sure to do execution.".
An example of the latter strategy was demonstrated by the Spanish vs the Swiss at the battle of 1502 "under the walls of Barletta", again from the above text. "‘When they came to engage, the Swiss at first pressed so hard on their enemy with the pike, that they opened out their ranks; but the Spaniards, under the cover of their bucklers, nimbly rushed in upon them with their swords, and laid about them so furiously, that they made a great slaughter of the Swiss, and gained a complete victory.’ The vanquished, in fact, suffered at the hands of the Spaniard the treatment which they themselves had inflicted on the Austrians at Sempach. The bearer of the longer weapon becomes helpless when his opponent has closed with him, whether the arms concerned be lance and halberd or pike and sword. The moment a breach had been made in a Macedonian or Swiss phalanx the great length of their spears became their ruin. There was nothing to do but to drop them, and in the combat which then ensued troops using the sword alone, and without defensive armour, were at a hopeless disadvantage in attacking men furnished with the buckler as well as the sword, and protected by a more complete panoply. Whatever may be the result of a duel between sword and spear alone, it is certain that when a light shield is added to the swordsman’s equipment, he at once obtains the ascendancy. The buckler serves to turn aside the spear-point, and then the thrusting weapon is free to do its work. It was, therefore, natural that when Spanish and Swiss infantry met, the former should in almost every case obtain success." and shortly after "The Spaniards, however, turned at once and fell furiously on the Germans, ‘rushing at the pikes, or throwing themselves on the ground and slipping below the points, so that they darted in among the legs of the pikemen,’"
A schiltron appears to be a sort of circular formation with ranks "Wallace, having selected an excellent position behind a marsh, formed his spearmen in four great masses (or ‘schiltrons,’ as the Scotch called them) of circular form, ready to face outward in any direction."
It may not be the exact answer you were looking for but I think it might point you in the right direction the entire book is very interesting and full of accounts of battles and even some cool maps.
I remember reading that Macedonian phalanxes were fairly resistant to arrows and javelins since the upright pikes would deflect most missiles.
This idea stems from one comment by Polybius, as discussed by u/Iphikrates in https://www.reddit.com/r/AskHistorians/comments/ax2yb2/ive_heard_that_one_of_the_advantages_of_the/
For a 16 deep phalanx, with the first 5 ranks with sarissae levelled, there will only be 11 hafts held high per file. A pikeman's own sarissa won't protect against arrows or javelins coming down from above. Exactly how many hafts would help protect a particular pikeman would depend on how far back in the phalax they are, and what angle the missiles are coming down at (a little steeper than 45 degrees for javelins and slingstones at extreme range, steeper again for arrows which are more affected by drag, and less steep for everything at closer ranges). This could translate to the front half getting no effective protection against missiles from hafts through to the rear rank being protected by a maximum of 10 hafts. With minimal sideways overlap between the space covered by the hafts, our lucky rear-ranker might be protected by about 30cm/1 foot of wooden haft. Considering that there will be overlap in the protection from each haft, the rear ranks might hope that about half of arrows and javelins that might reach them will be stopped. A screen, but a leaky screen. The front half will gain little protection. Which could explain why nobody other than Polybius mentions this screening.
More generally, close-order infantry formations without armour or shields can be quite vulnerable to arrows (thus, the popularity of the shield wall). A two-handed spear/pike makes using shields more difficult; the Macedonian phalangite carried a shield of about 60cm/24" diameter (at least sometimes), but it would have been limited to providing passive protection due to both hands being needed for the sarissa, and thus would not have provided much, if any, protection for the head. The Macedonian phalangite shield would provide reasonable protection for the left arm and torso and, with a helmet, would perhaps provide better protection than the sarissa hafts.
Trokelowe, in his Annales, notes that the Scottish schiltron at Bannockburn used shields:
Ex parte eorum omnes pedites erant: viri quidem electi, animosi valde, securibus praeacutis caeterisque armis bellicis decenter communiti, conserta ante se scutorum spissitudine, cuneum impenetrabilem statuerunt.
quoted in translation in Brown (2008) as
They were all on foot; picked men they were, enthusiastic, armed with keen axes, and other weapons, and with their shields closely locked in front of them, they formed an impenetrable phalanx.
This might describe the formation as including men with axe and shield, who will provide useful protection with their shields, and also help protect the spearmen against enemy infantry who get in close (past the spear points).
At Flodden, the Scottish pikemen didn't use shields, but they (at least those in the front ranks) were armoured well enough to make the English archery relatively ineffective.
Without shields or armour, spearmen/pikemen (indeed, any infantry) could suffer terribly from archery. Active protection in the form of friendly archers or cavalry to keep enemy archers away was important. Failing that, the spearmen/pikemen could attack the enemy archers. However, if the threat of enemy cavalry attack forced them to keep a static formation, they could be left defenseless against archery. After guns largely displaced armour, or at least got to the point where they could reliably defeat armour, this was the situation for pikemen - defence against gunfire depended on one's own musketeers, or cavalry, or charging the musketeers. In the absence of friendly musketeers in sufficient number, and pinned down by cavalry, the pike unit could easily face destruction (as the Swiss found out).
References:
Brown, Chris (2008). Bannockburn 1314. Stroud: History Press.