Management: The sudden death of its leader can be devastating, especially when void occurs at a smaller firm.

It’s one of the worst things that can happen to a company: The top person dies suddenly, leaving a void at the top.

It’s especially difficult for smaller businesses, where top managers may be family members and may not have planned who will succeed the owner or president.

And it can mean trying times even for the best-run companies.

“It can be absolutely devastating to have the rug pulled out from under people like this,” says management consultant Diana Ho.

“Yes, there’s the future of the firm to consider, but there are also the personal repercussions.”

The latest company to face tragedy at the top is the In-N-Out hamburger chain, whose president was killed Wednesday in a plane crash in Santa Ana.

Restaurant companies, say experts, are particularly vulnerable because they employ comparatively large numbers of people--which means leadership is that much more important.

Questions on how well a company has planned for change in its top management comes up every few years--every time a top officer suddenly dies.

In 1987, an airliner carrying four Chevron USA managers, including the oil company’s president, crashed in Southern California’s Santa Lucia Mountains. That caused companies around the nation to once again reassess their policies on how many top executives may fly on the same plane.

While the prospect of a plane crash is relatively remote, there are numerous ways to lose top executives, including physical ailments like heart attacks.

So one of the most important things to do in succession planning, experts say, is to keep a company from becoming a “one-man band,” especially a small company.

It’s not just sudden death for which companies must prepare. Many founders leave chaos behind when they retire, especially in family companies where it is psychologically difficult to choose a successor from among family members.

And sometimes greedy heirs squabble and overturn arrangements set in place by the founder, said Tiffany Haugen of the University of California’s Graduate School of Management.

“The people running a company are usually so incredibly busy growing it that they don’t have time to plan for their succession,” Haugen says.

“Or in some cases, psychologically they don’t want to face it--look at how many people put off writing their wills.”

It isn’t known what kind of arrangements In-N-Out had made to replace President Rich Snyder--the son of the company’s founder--in the event of his sudden death. The company wasn’t talking Thursday, but a source close to the hamburger chain said Snyder did in fact have a contingency plan in place.

Snyder is also said to have promoted from within, ensuring that decision-making was spread through the ranks.

“Rich delegated authority every day,” says Richard Terra, vice president of Shamrock Meat in Los Angeles, which supplies ground beef to the In-N-Out burger chain. “To me, that’s one of the company’s biggest success stories.”

Says Jeffrey Sonnenfeld of Atlanta’s Emory University: “That means the company has an internal pool, a reservoir of management talent to draw on.

“But,” says Sonnenfeld, “the comparison (to Snyder) is going to be inevitable. It’s going to be a tough job.”

It is becoming easier for companies to devise a succession plan. There is even computer software, like the SuccessPlan program, to help companies prepare for changes at the top.

Then there are so-called “key man” insurance policies for top executives or sometimes at big law firms for “rain-makers”--lawyers who bring well-paying clients.

When Perry Ellis, head of the fashion empire that still bears his name, died in 1986, his key man policy paid $5 million.

Public companies, since they’re usually larger and more closely-watched, tend to do better at orderly successions, says Elliot Gordon, an executive headhunter at Korn/Ferry International.

Consider the case of Eagle Computer Inc., whose chairman in 1983 flipped over his new red Ferrari a few hundred yards from Eagle’s Los Gatos headquarters and died a day after the company’s first offering of stock to the public.

Eagle had built itself a strong bench--it had a talented layer of vice presidents who kept the small computer concern running smoothly after the tragedy.

“Private companies, on the other hand, typically do the least planning, especially if no family member seems a likely successor,” says Gordon.