Appropriately, this entire post is a flashback to something I wrote in the OWW discussion group a while ago. There we were discussing narrative tension.
One device which classically saps narrative tension out of a chapter is to begin with the happy end and then flash back. I think this is why so many people advise against flashbacks in a story.
Lord Theoddues Kelvin wiped his forehead. Zounds, that was close! He almost hadn't made it safely back to London.
When Dr. Devil had left him stranded in the lava pit, surrounded by hungry cyborg dinosaurs, he'd had to think quickly. First, he'd grabbed a nearby rock and thrown it at the control panel on top of the T-Rex's head. But the rock wasn't strong enough to break the plastic casing around the control mechanism. He leaped and rolled out of the way just as the tremendous jaws snapped at the spot where he had just stood...
No matter how exiting the scene in the flash back, it's boring because the writer just told you he'll make it back out alive. Plus, having a long scene in the past perfect tense is really annoying.
Not all flashbacks have to kill tension, however. Flashbacks can increase tension, if done right. Here's an example from my trendy steampunk romance:
Lord Theoddues Kelvin knew the moment he kissed the hand of the
Incomparable he had lost his heart. After a lifetime as a bachelor
explorer, he had finally found the Angel to lure him home to a
comfortable existence of brandy before the fireplace. He vowed he
would do anything to win her.
"Forgive me, we haven't been properly introduced. Miss...?"
"Viola Devil," she smiled. "Oh, here comes Father now."
Dr. Devil entered the room. He paused just a moment, a flash of shock
registering on his face, when he saw Theo.
(Four months earlier)
Dr. Devil shoved Theo into the lava pit filled with hungry cyborg
dinosaurs... [etc, ending on a hook other than the question of Theo's
survival, for instance, Theo discovers Dr. Devil has stolen the
Medallion of Time.]
"I believe we've met," Theo said with a tight smile.
"Why, how marvelous!" Viola exclaimed. Neither man moved. They watched
each other like two panthers. Her brow furrowed. She glanced between
the two men, sensing the tension between them, but not understanding it.
"Yes." Dr. Devil fondled the engraved bronze medallion he wore around
his neck, taunting Theo with it. "Lord Kelvin and I share an interest
In both examples, we know ahead of time that Theo survives the dinosaur pit. In the second example, there is still tension (hopefully) because the real question isn't whether he survived, but what is his relationship to Dr. Devil and how will this impact his relationship with Viola?
Some stories are more exciting if not told chronologically. In my sip [series in progress], just to make my life difficult, I use flashbacks in every single novel. They are not all flashbacks to the same character -- in a sense, they aren't flashbacks at all, but other strands of the story, told achronologically. They are told in the order the scenes need to be revealed, or peeled away.
For an example of this technique used to marvelous effect, see Ursula Le Guin's The Dispossesed.
Importantly, acrhonology fits the theme of my story, as it does in The Dispossessed, so it is not something I could simply cut or rearrange. One of the story's themes is the way the past, and the way different characters see the past, affects the present and how they see one another. So not only does the story include flashbacks, it includes flashbacks of the same scene told from a different PoV. Hopefully, this will not undermine narrative tension, but buttress it.