In Lord of the Flies, Piggy's death comes at a time when he has finally decided he should make himself heard. He has always been afraid of Jack and has hidden behind the conch or Ralph. It takes a lot of courage to come forward now. A hero has to be courageous and be interested in the greater good. If Piggy was only interested in saving himself he would not have selflessly faced Jack or talked of "which is better-rules ... or to hunt and kill?"
Previously, in chapter 5, Piggy admits his fear of Jack and how the feeling he gets from Jack is comparable to having asthma when he can't breathe. He admits that Jack would be unlikely to hurt Ralph but "he'd hurt the next thing" which is Piggy. Piggy urges Ralph to keep up his position as chief because things are "going rotten" and only Ralph has some hope of reestablishing order. Piggy is always the person who can talk sense into Ralph and Piggy does not claim credit for himself, revealing his humility. Golding therefore uses characterization to develop Piggy's supportive role and reveal his true value. Just before his death when he bravely confronts Jack, Piggy grasps at "the talisman the fragile, shining beauty of the shell" (ch 11).
When he dies moments later, the conch is smashed on the rocks and the visual picture is vivid as the reader imagines "a thousand white fragments." The reader is brought down to earth with a jolt as the narrator states that the conch "ceased to exist." Then it is Piggy's turn and it is almost as if his death is happening in slow motion as he "traveled through the air sideways." However, the reader is again jolted into reality as the narrator describes the "stuff" coming out of Piggy's head. The language is blunt and shocking and real. Golding uses very descriptive language to complete the scene and reveal Piggy's hero status as, one moment he is standing up for himself and for all that is right and just and the next minute he is callously and almost incidentally removed from the picture.
Piggy's significant death whilst holding the conch leaves Jack ecstatic that the conch no longer stands in his way. The very fact that he seems unaware of the real implications and that Piggy has just died having" twitched a bit, like a pig after it has been killed" reveals his brutality and his apparent belief that a human life holds no value above that of a pig.
You will find several references in the eNotes pages to Piggy's hero status and also those things that reveal that it can be argued that he is not necessarily a hero.