<PAGE>
                                                                     Exhibit 4.1


                           SALE OF MEMBERSHIP INTEREST

     This sale of Membership Interest is made effective as of the 26th day of
February 2002, by Cash Long and Jeff Patterson ("Sellers") unto Western Wind
Energy Corp. ("Buyer").

     WHEREAS, Buyer entered into an agreement with Sellers providing for the
sale by Sellers to Buyer of Sellers' Membership Interests in that certain
Limited Liability Company commonly known as AERO ENERGY, LLC.

     NOW, THEREFORE, KNOW ALL MEN BY THESE PRESENCE, for and in consideration of
the amount of Ten and 00/100 Dollars ($10.00) and other good and valuable
consideration, the receipt of which is hereby acknowledged, Sellers do hereby
grant, bargain, sell, convey, transfer, assign, set over and deliver unto Buyer,
its successors and assigns, the following: All Sellers' rights, titles, and
interests in the Membership Interest in AERO ENERGY, LLC.

     To have and to hold the Membership Interest unto Buyer, its successors and
assigns forever, and Sellers do for themselves, and their successors and
assigns, covenant and agree to and with Buyer to warrant and defend the title of
the Membership Interest hereby sold unto Buyer against all and every person and
persons whomsoever. Sellers shall deliver, and Buyer has accepted the Membership
Interest.

     IN WITNESS WHEREOF, Sellers have caused this sale of Membership Interest to
be executed and made effective February 26, 2002.


SELLERS:
                                                     /s/ Cash Long
                                                     ---------------------------
                                                     Cash Long

                                                     /s/ Jeff Patterson
                                                     ---------------------------
                                                     Jeff Patterson


STATE OF CALIFORNIA                )
                                   ) SS.
COUNTY OF KERN                     )

     On Aug. 2, 2002, before me, Terry A. Moore, a Notary Public, personally
appeared Cash Long, [ ] personally known to me or [ ] proved to me on the basis
of satisfactory evidence to be the person whose name is subscribed to the within
instrument and acknowledged to me that he executed the same in his authorized
capacity, and that by his signatures on the instrument the person, or the entity
upon behalf of which the person acted, executed the instrument.

    WITNESS my hand and official seal.


TERRY A. MOORE                                /s/ Terry A. Moore
COMM. #1335023                                ----------------------------------
Notary Public - California                    Notary Public
KERN County
My Comm. Exp. Dec 15, 2005
[OFFICIAL SEAL]

                                       1
<PAGE>


STATE OF CALIFORNIA                )
                                   ) SS.
COUNTY OF KERN                     )

     On Aug 2, 2002, before me, Terry A. Moore, a Notary Public, personally
appeared Jeff Patterson, [ ] personally known to me or [ ] proved to me on the
basis of satisfactory evidence to be the person whose name is subscribed to the
within instrument and acknowledged to me that he executed the same in his
authorized capacity, and that by his signatures on the instrument the person, or
the entity upon behalf of which the person acted, executed the instrument.

    WITNESS my hand and official seal.


TERRY A. MOORE                                /s/ Terry A. Moore
COMM. #1335023                                ----------------------------------
Notary Public - California                    Notary Public
KERN County
My Comm. Exp. Dec 15, 2005
[OFFICIAL SEAL]





                                       2