Dart Group Corp., the Landover holding company owned by Herbert H. Haft and his family, notified the Securities and Exchange Commission yesterday that it is considering buying Jack Eckerd Corp., the nation's second-largest drugstore chain.

The former owner of Dart Drug Stores -- the nation's 22nd largest chain -- Dart Group told the SEC that it already has purchased 5 percent of Eckerd stock, or 1.8 million shares, for $46.5 million.

Dart is studying "acquiring 100 percent of the capital stock," the company said, noting that it planned to buy more shares after a waiting period required by federal antitrust laws. Usually, that waiting period lasts about 20 days.

Herbert Haft and other Dart officials were unavailable for comment. So, too, were Eckerd officials. However, Eckerd officials have indicated to employes they would fight an unfriendly takeover.

According to Chain Drug Review, Eckerd stands just behind Walgreen Co. in the ranking of chain drugstores. Sales in 1,511 stores in 15 states totaled $2.6 billion and profits $85.4 million for Eckerd's fiscal year ended July 28, 1984.

Although one of the largest chains, it has had very difficult times over the past few years, drugstore industry experts say. "Five years ago it was one of the most successful chains around. Then it made an ill-advised acquisition," one expert said. That acquisition was American Home Video, which operates 207 specialty video stores. The chain has consistently lost money, because "Eckerd miscalculated where consumers would buy their video equipment -- not in specialty stores but in department and discount stores," said one industry expert who declined to be named.

The drugstore chain also has lost money, so much so that Eckerd just announced that its third-quarter earnings dropped by half from the previous year. Nonetheless, the company is still one of the best in the industry, having a dominant share of the market in about 15 of the 50 largest cities, an industry official noted.

"The company is a terrific acquisition in the right hands," said the expert.

Drugstore industry officials and financial analysts have been anxiously anticipating that the Hafts would make a move to buy another major retailing company after Dart sold off its 73 drugstores for $160 million in a surprise move last year. That left Dart Group Corp. as the holding company of the two specialty discount retail chains it created -- Crown Books and Trak Auto. Dart Group owns 34 percent of Crown and 67 percent of Trak. The sale also brought in $160 million to the Dart Group's coffers, which analysts have been expecting the Hafts to use for a major acquisition.

Earlier this year, there was speculation that the Hafts were about to bid for May Department Stores Co. -- the parent company of The Hecht Co. -- after Crown disclosed in SEC documents that it had bought about 1 percent of May's stock for $15 million. A month later, however, Crown told the SEC that it had sold its May shares for a $500,000 profit.