<PAGE>
 
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
 
                               ----------------
 
                                 SCHEDULE 14D-1
                               
                            (AMENDMENT NO. 10)     
 
                   TENDER OFFER STATEMENT PURSUANT TO SECTION
                14(D)(1) OF THE SECURITIES EXCHANGE ACT OF 1934
 
                              GRUMMAN CORPORATION
- --------------------------------------------------------------------------------
                           (NAME OF SUBJECT COMPANY)
 
                           NORTHROP ACQUISITION, INC.
- --------------------------------------------------------------------------------
                                    (BIDDER)
 
                    Common Stock, $1.00 par value per share
                       (Including the Associated Rights)
- --------------------------------------------------------------------------------
                         (TITLE OF CLASS OF SECURITIES)
 
                                    40018110
- --------------------------------------------------------------------------------
                     (CUSIP NUMBER OF CLASS OF SECURITIES)
 
                            Richard R. Molleur, Esq.
                              Northrop Corporation
                             1840 Century Park East
                             Los Angeles, CA 90067
                                 (310) 553-6262
 
                                    COPY TO:
 
                             Karen E. Bertero, Esq.
                            Gibson, Dunn & Crutcher
                             333 South Grand Avenue
                             Los Angeles, CA 90071
                                 (213) 229-7000
- --------------------------------------------------------------------------------
                 (NAME, ADDRESS AND TELEPHONE NUMBER OF PERSON
     AUTHORIZED TO RECEIVE NOTICES AND COMMUNICATIONS ON BEHALF OF BIDDER)
 
                           CALCULATION OF FILING FEE
- --------------------------------------------------------------------------------

<TABLE>
<CAPTION>
           TRANSACTION VALUATION*                       AMOUNT OF FILING FEE**
<S>                                                     <C>
              $2,174,165,160.00                              $434,833.03
</TABLE>

- --------------------------------------------------------------------------------
   
*  For purposes of calculating fee only. Assumes purchase of 35,067,180 shares
   of Common Stock, $1.00 par value per share, of Grumman Corporation at $62.00
   per share.     
   
** 1/50th of 1% of Transaction valuation.     
 
[_]CHECK BOX IF ANY PART OF THE FEE IS OFFSET AS PROVIDED BY RULE 0-11(A)(2)
   AND IDENTIFY THE FILING WITH WHICH THE OFFSETTING FEE WAS PREVIOUSLY PAID.
   IDENTIFY THE PREVIOUS FILING BY REGISTRATION STATEMENT NUMBER, OR THE FORM
   OR SCHEDULE AND THE DATE OF ITS FILING.
 
Amount previously paid: Not Applicable              Filing party: Not Applicable
                                                       
 
Form or registration no.: Not Applicable            Date filed: Not Applicable
                                                        
 
                               Page 1 of 4 Pages

<PAGE>
 
   
  This Amendment No. 10 amends and supplements the Tender Offer Statement on
Schedule 14D-1 dated March 14, 1994 (the "Schedule 14D-1"), of Northrop
Acquisition, Inc. (the "Purchaser") and Northrop Corporation ("Northrop"), as
amended, filed in connection with the Purchaser's offer to purchase all of the
outstanding shares of Common Stock, par value $1.00 per share, of Grumman
Corporation, a New York corporation (the "Company"), and the associated
preferred stock purchase rights, as set forth in the Schedule 14D-1, as amended
(the "Offer").     
       
ITEM 11. MATERIAL TO BE FILED AS EXHIBITS.
 

<TABLE>
   <C>     <S>
   (c)(17) Press release, dated April 17, 1994.
</TABLE>


                               Page 2 of 4 Pages

<PAGE>
 
                                   SIGNATURE
 
  After due inquiry and to the best of my knowledge and belief, I certify that
the information set forth in this statement is true, complete and correct.
   
Dated: April 18, 1994     
 
                                        NORTHROP CORPORATION
 
                                        /s/ Richard R. Molleur
                                        ----------------------------------------
                                        Name: Richard R. Molleur
                                        Title: Corporate Vice President
 
                                        NORTHROP ACQUISITION, INC.
 
                                        /s/ Richard R. Molleur
                                        ----------------------------------------
                                        Name: Richard R. Molleur
                                        Title: Vice President and Secretary
 
                               Page 3 of 4 Pages

<PAGE>
 
                                 EXHIBIT INDEX
 

<TABLE>
<CAPTION>
 EXHIBIT
   NO.                DESCRIPTION
 -------              -----------
 <C>     <S>                                    
 (c)(17) Press release, dated April 17, 1994.
</TABLE>

 
 
                               Page 4 of 4 Pages





<PAGE>
 
NEWS

                           [LETTERHEAD OF NORTHROP]

                                                           FOR IMMEDIATE RELEASE
                                                           ---------------------

NORTHROP RECEIVED 93.4 PERCENT OF
- ---------------------------------
GRUMMAN STOCK IN TENDER OFFER
- -----------------------------

      LOS ANGELES -- April 17, 1994 -- Northrop Corporation announced today that
the tender offer by its wholly owned Northrop Acquisition, Inc. subsidiary to 
purchase for cash all outstanding shares of Grumman Corporation's common stock 
(including the associated preferred stock purchase rights) at $62 per share 
expired at midnight E.D.T. on Friday, April 15, 1994.

      Northrop has been advised by the depository, Chemical Bank, that as of 
that time there had been tendered and not withdrawn 32,766,109 shares of Grumman
common stock, representing approximately 93.4 percent of their outstanding 
shares on a fully diluted basis.

      Having successfully received at least two thirds of the total number of 
outstanding shares, under New York law Northrop said it will move promptly to 
complete its acquisition of Grumman pursuant to the previously reported merger 
agreement of April 3, 1994.  Following the acquisition, those shares of Grumman 
not tendered under the tender offer and still outstanding will be converted into
the right to receive $62 per share in cash.

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