<PAGE>

                                                                    Exhibit 10.5

                           STOCK PURCHASE AGREEMENT

              THIS AGREEMENT is made and entered into as of the 11th day of
July, 1991, by and between Parker-Hannifin Corporation, an Ohio Corporation
having an address at 17325 Euclid Avenue, Cleveland, Ohio 44112 ("PARKER"), and
Innovative Solutions & Support, Inc., a Pennsylvania Corporation having an
address at 420 Lapp Road, Malvern, Pennsylvania 19355 ("IS&S").

              PARKER wishes to purchase and IS&S wishes to sell an ownership
interest in IS&S under the terms of this Agreement. PARKER and IS&S also wish to
enter into two (2) other Agreements executed of even date herewith pertaining to
aircraft instrumentation products ("Instrumentation Agreements").

         NOW, THEREFORE, the parties agree as follows:

                                    ARTICLE I
                  PURCHASE, SALE AND TERMS OF PREFERRED SHARES

         1.01. THE PREFERRED SHARES. IS&S has authorized the issuance and sale
to PARKER of IS&S Class B Convertible Preferred Stock, par value $.001 per share
("Class B Shares") to be authorized and unissued prior to Closing (as defined
below). The description, rights, preferences and other terms and conditions
relating to the Class B Shares of IS&S shall be as set forth in Exhibit 1.01
hereto. The shares of Class A and Class B Convertible Preferred Stock, and any
unrealized shares of Convertible Preferred Stock, are referred to collectively
herein as "Preferred Shares."

         1.02. THE CONVERSION SHARES. Prior to Closing IS&S shall have
authorized and reserved, and IS&S covenants thereafter to continue to reserve,
free of preemptive rights and other preferential rights, a sufficient number of
previously authorized but unissued shares of its Common Stock to satisfy the
rights of conversion of all holders (including Parker) of the Preferred Shares.
Any shares of IS&S Common Stock issuable upon conversion of the Preferred
Shares, and such shares when issued, are referred to as the "Conversion Shares."
The description, rights, preferences and other terms and conditions relating to
the Conversion Shares shall be as set forth in Exhibit 1.02 hereto.
<PAGE>

         1.03. SALE AND PURCHASE OF CLASS B SHARES. Subject to the conditions,
terms, representations and warranties of this Agreement, IS&S will issue and
sell, and PARKER will purchase at the Closing (as defined below), one hundred
thousand (100,000) Class B Shares, representing 16.7% of the issued outstanding
capital stock of IS&S, for an aggregate purchase price of three million dollars
($3,000,000) (the "Purchase Price").

         1.04. CLOSING. The sale and purchase of the Class B Shares (the
"Closing") shall take place on July 12, 1991 (the "Closing Date"), or at such
other place and date as may be agreed to by IS&S and PARKER.

         1.05. PAYMENT AT CLOSING. At the Closing, PARKER will pay the Purchase
Price by:

               (a) TRANSFER FUNDS. Wire transfer of the sum of two million five
hundred thousand dollars ($2,500,000) to an account designated by IS&S, as
payment for 83,333-1/3 Class B Shares; and

               (b) CONTRIBUTE NOTE. Contribute a January 24, 1991 note
receivable in the amount of $500,000 ("Note Receivable") to the capital of IS&S,
by signing the Capital Contribution Agreement attached as Exhibit 1.05(b), as
payment for 16,666-2/3 Class B Shares.

         1.06. USE OF FUNDS. The funds received by IS&S from PARKER, under
Article 1.05 above will be used by IS&S only to repay a certain loan to IS&S
from Geoffrey S.M. Hedrick (Article 4.10 below), to repay certain expenses of
Douglas Gemmell (Article 4.10 below), and to fund operating expenses in the
ordinary course of business and capital equipment purchases consistent with
current and proposed operations.

         1.07. CLASS B SHARES AT CLOSING. At the Closing, IS&S will deliver to
PARKER certificates for the one hundred thousand (100,000) Class B Shares to be
issued and sold to PARKER, duly registered in PARKER's name.

                                      -2-
<PAGE>

         1.08. CERTIFIED FINANCIAL INFORMATION AT CLOSING. At the Closing, IS&S
will deliver to PARKER Arthur Anderson certified financial results (including
footnotes) for IS&S fiscal year 1990, identical in substance and form to the
unsigned financial results for IS&S fiscal year 1990 attached hereto as Exhibit
4.09.

                                    ARTICLE 2
                 REPRESENTATIONS AND WARRANTIES OF PARKER

         PARKER represents and warrants to IS&S as follows:

         2.01. SECURITIES LAWS COMPLIANCE. It is Parker's present intention to
acquire the Class B Shares and Conversion Shares for its own account, and the
Class B Shares and Conversion Shares will be acquired by it for the purpose of
investment and not with a view to distribution or resale thereof. PARKER
acknowledges and agrees that the Class B Shares and Conversion Shares have not
been registered under the Securities Act of 1933, as amended ("Securities Act")
or the securities laws of certain states and that the certificates representing
the Class B Shares and Conversion Shares will be subject to the restriction
that, unless a registration statement under the Securities Act is in effect in
respect to PARKER's Class B Shares and Conversion Shares, PARKER may not sell or
otherwise transfer or dispose of its Class B Shares or Conversion Shares or any
interest therein unless it shall first furnish to IS&S an opinion of counsel
reasonably satisfactory to IS&S to the effect that registration thereof under
the Securities Act and applicable state securities laws is not required. PARKER
understands and agrees that unless registered under the Securities Act, the
certificates representing the Class B Shares and the Conversion Shares, whether
upon initial issuance or upon any transfer thereof, may bear a legend reading
substantially as follows:

         "The Shares represented by this certificate have not been
         registered under the Securities Act of 1933, as amended. The
         shares have been acquired for investment and not with a view
         to distribution or resale, and may not be sold, mortgaged,
         pledged, hypothecated or otherwise transferred without an
         effective registration statement for such shares under said
         Act, or an opinion of counsel for the Owner that registration
         is not required thereunder."

                                       -3-
<PAGE>

         2.02. CORPORATE STATUS AND AUTHORITY. PARKER is a corporation duly
organized, validly existing and in good standing under the laws of the State of
Ohio, and has the corporate power and authority to acquire the Class B Shares
and Conversion Shares hereunder. The execution, delivery and performance by
PARKER of this Agreement and the transactions contemplated hereby have been duly
authorized by all necessary corporate action on the part of PARKER, and this
Agreement constitutes the valid and binding obligation of PARKER, enforceable
against it in accordance with its terms.

         2.03. AGREEMENT NOT IN BREACH OF OTHER INSTRUMENTS. The execution and
delivery of this Agreement, the consummation of the transactions contemplated
hereby and the fulfillment by PARKER of the terms hereof, will not result in a
breach of any of the terms and provisions of, or constitute a default under, or
conflict with or cause any acceleration of any material obligation of PARKER
under any agreement, indenture or other instrument to which PARKER or its assets
is bound, PARKER's Articles of Incorporation or By-laws, any judgment, decree or
order, or any applicable law, rule or regulation.

                                    ARTICLE 3
                       CONDITIONS TO PARKER'S OBLIGATIONS

         3.01. CONDITIONS TO PARKER'S OBLIGATIONS AT THE CLOSING. The
obligations of PARKER on the Closing Date to purchase and pay for the Class B
Shares shall be subject to the satisfaction of each of the following conditions
precedent, each of which IS&S agrees to use its best efforts to cause to be
fulfilled and any one or more of which may be waived by PARKER:

               (a) REPRESENTATIONS, WARRANTIES AND PERFORMANCE. Each of the
representations and warranties of IS&S set forth in Article 4 shall be true and
correct on the Closing Date, and IS&S shall have performed all of its
obligations under this Agreement to be performed prior to or at the Closing;

               (b) AIRCRAFT INSTRUMENTATION AGREEMENTS. IS&S and PARKER shall
have entered into the Aircraft Instrumentation Agreements;

                                      -4-
<PAGE>

               (c) EMPLOYMENT AND NONCOMPETE AGREEMENTS. Geoffrey S.M. Hedrick
and Douglas Gemmell shall have each entered into employment and noncompete
agreements with IS&S in the form attached as Exhibit 3.01(c);

               (d) SHAREHOLDER AGREEMENT. Geoffrey S.M. Hedrick shall have
entered into the Shareholder Agreement attached as Exhibit 3.01(d), which
required Mr. Hedrick to vote his shares of IS&S Common Stock to elect a person
designated by PARKER to the Board of Directors of IS&S;

               (e) CORPORATE DOCUMENTS. IS&S shall have furnished PARKER true
and correct copies of all charter documents of IS&S; the resolutions of the
Board of Directors and, if required by law, the stockholders, of IS&S evidencing
approval of this Agreement, the issuance of the Class B Shares, and other
matters contemplated hereby; the By-Laws of IS&S; and all documents evidencing
other necessary corporate or other action and approvals, if any, with respect to
this Agreement, the Class B Shares and the Conversion Shares; and

               (f) OPINION OF COUNSEL. IS&S shall have delivered to PARKER a
favorable opinion of Wolf, Block, Schorr and Solis-Cohen, counsel for IS&S, in
the form set forth in Exhibit 3.01(f).


                                    ARTICLE 4
                         REPRESENTATIONS AND WARRANTIES

         Except as set forth in the Disclosure Schedule attached hereto as
Exhibit 4.00, IS&S represents and warrants to PARKER as follows:

         4.01. ORGANIZATION AND STANDING OF IS&S. IS&S is a duly organized and
validly existing corporation in good standing under the laws of the Commonwealth
of Pennsylvania and has all requisite corporate power and authority for the
ownership and operation of its properties and for the carrying on of its
business as now conducted and as now proposed to be conducted. IS&S is duly
licensed or qualified and in good standing as a foreign corporation authorized
to do business in all jurisdictions wherein the character

                                      -5-
<PAGE>

of the property owned or leased, or the nature of the activities conducted by
it, makes such licensing or qualification necessary, except where the failure to
be so licensed, qualified or in good standing would not have a material adverse
impact on IS&S. IS&S has no Subsidiaries.

         4.02. CORPORATE ACTION. All of the provisions of this Agreement, the
Preferred Shares, the Conversion Shares and any other agreements and instruments
executed in connection with this Agreement are the valid and binding obligations
of IS&S. The issuance and delivery of the Class B Shares and the execution,
delivery and performance of this Agreement and any other agreement and
instruments executed in connection with this Agreement have been duly authorized
by all necessary corporate or other action of IS&S. Sufficient shares of
authorized but unissued Class B Shares to be issued to PARKER hereunder and
sufficient shares of authorized but unissued Common Stock of IS&S to be issued
in connection with the prospective conversion of the Preferred Shares will have
been reserved by appropriate corporate action prior to Closing. Neither the
issuance of the Class B Shares nor the issuance of the Conversion Shares will
require any further corporate action other than as contemplated herein or by the
Articles of Incorporation, and will not be subject to preemptive or other
preferential rights or similar statutory or contractual rights either arising
pursuant to any agreement or instrument to which IS&S is a party or which are
otherwise binding upon IS&S.

         4.03. GOVERNMENTAL APPROVALS. No authorization, consent, approval,
license, exemption of or filing or registration with any court or governmental
department, commission, board, bureau, agency or instrumentality, domestic or
foreign, under any applicable laws, rules or regulations presently in effect, is
or will be necessary for, or in connection with, the offer, issuance, sale,
execution or delivery by IS&S of the Class B Shares or the Conversion Shares or
for the performance by it of its obligations under this Agreement, the Preferred
Shares or the Conversion Shares.

         4.04. LITIGATION. There is no litigation or governmental proceeding or
investigation pending or, to the best knowledge of IS&S, threatened against IS&S
affecting any of its properties or assets. To the best knowledge of IS&S, there
is no litigation or governmental

                                      -6-
<PAGE>

proceeding or investigation pending or threatened against any officer of IS&S or
against Douglas Gemmell. Neither IS&S, nor to the best knowledge of IS&S, or any
officer of IS&S or Douglas Gemmell, is in default with respect to any order,
writ, injunction, decree, ruling or decision of any court, commission, board or
other government agency. The foregoing sentences include, without limiting their
generality, actions pending, or to the best knowledge of IS&S threatened,
involving the prior employment of any IS&S officer or employee or their use in
connection with IS&S business of any information or techniques allegedly
proprietary to any of their former employers.

         4.05. REGISTRATION RIGHTS. Except as set forth in Article 7 hereof, no
person has demand or other rights to cause IS&S to file any registration
statement under the Securities Act relating to any securities of IS&S or any
right to participate in any such registration statement.

         4.06. CERTAIN AGREEMENTS OF OFFICERS AND EMPLOYEES.

               (a) To the best knowledge of IS&S, no employee of IS&S is in
violation of any term of any employment contract, patent disclosure agreement,
noncompetition agreement, or any other contract or agreement or any restrictive
covenant relating to the right of any such officer or employee to be employed by
IS&S, or relating to the use of trade secrets or proprietary information of
others; and

               (b) Each present or former officer and employee of IS&S who is or
was authorized to have access to proprietary information of IS&S has executed
IS&S's nondisclosure and inventions agreement attached as Exhibit 4.06(b). To
the best knowledge of IS&S, no officer or employee or former officer or employee
of IS&S is in violation of the terms of the aforesaid agreement or of any other
obligation relating to the use of confidential or proprietary information of
IS&S.

         4.07. COMPLIANCE WITH OTHER INSTRUMENTS. IS&S is in compliance in all
respects with the terms and provisions of this Agreement and of its Articles of
Incorporation and By-Laws and in all material respects with the terms and
provisions of the mortgages,

                                      -7-
<PAGE>

indentures, leases, agreements and other instruments to which IS&S is a party
and of all judgments, decrees, governmental orders, statutes, rules or
regulations by which it is bound or to which it or any of its properties or
assets are subject. There is no term or provision in any of the foregoing
documents and instruments which materially adversely affects the business,
assets or financial condition of IS&S. Neither the execution and delivery of
this Agreement, the Preferred Shares or the Conversion Shares, nor the
consummation of any transaction contemplated by this Agreement, has constituted
or resulted in or will constitute or result in a material default or violation
of any term or provision in any of the foregoing documents, instruments,
judgments, decrees, orders, statutes, rules and regulations.

         4.08. TITLE TO ASSETS, PATENTS.

               (a) IS&S has title to all of its assets now carried on its books
as owned by it including those reflected in the most recent balance sheet of
IS&S (Article 4.09 below) or acquired since the date of such balance sheet free
of any mortgages, pledges, charges, liens, security interests or other
encumbrances; and

               (b) IS&S owns, or to the best knowledge of IS&S, it has a valid
right to use, the patents, patent rights, licenses, permits, trade secrets,
trademarks, trade names, copyrights, inventions and intellectual property rights
being used to conduct its business as now operated and as now proposed to be
operated; and IS&S has not received any notice and does not have any reason to
believe that the conduct of its business as now operated and as now proposed to
be operated does or will conflict with valid patents, patent rights, licenses,
permits, trade secrets, trademarks, trade names, copyrights, inventions and
intellectual property rights of others. IS&S has no obligation to compensate any
person for the use of any such rights.

         4.09. FINANCIAL INFORMATION. The balance sheets and income statements
of IS&S attached hereto as Exhibit 4.09, (i) include the Arthur Anderson
unsigned financial results (including footnotes) for IS&S fiscal year 1990, and
(ii) present fairly the interim financial position of IS&S as of April 30, 1991.
IS&S has no liability, contingent or otherwise, not

                                      -8-
<PAGE>

adequately reflected in or reserved against in the aforesaid balance sheets that
could, together with all such other liabilities, materially affect the financial
condition of IS&S, nor does IS&S have any reasonable grounds to know of any such
liability. Since the date of the aforesaid interim balance sheet, (i) there has
been no material adverse change in the business, assets, financial condition,
operations or prospects of IS&S; (ii) the business, financial condition,
operations or prospects of IS&S or any of its properties or assets has not been
materially and adversely affected as the result of any legislative or regulatory
change, any revocation or change in any franchise, license or right to do
business, or any other event or occurrence, whether or not insured against; and
(iii) IS&S has not entered into any transaction or agreement outside the
ordinary course of business, and has not made any distribution of its capital
stock.

         4.10. LOANS AND GUARANTEES. IS&S has not made any loan or advance to
any person which is outstanding on the date of this Agreement, nor is IS&S
obligated or committed to make any such loan or advance, nor does IS&S own any
capital stock, assets comprising the business of, obligations of, or any
interest in, any person, except as set forth in Exhibit 4.10. IS&S has not
assured or guaranteed the indebtedness of any other person, except as set forth
in Exhibit 4.10. All contracts of IS&S which require the expenditure of or
anticipate the receipt of $50,000 or more by IS&S are as set forth in Exhibit
4.10.

         4.11. SECURITIES ACT. IS&S has complied and will comply with all
applicable federal or state securities laws. Neither IS&S, nor to the best
knowledge of IS&S anyone acting on its behalf, has offered to sell any capital
stock of IS&S (including without limitation Common Stock, the Preferred Shares
or Conversion Shares or similar securities), or solicited offers with respect
thereto from, or entered into any preliminary conversations or negotiations
relating thereto with, any person, so as to bring the issuance and sale of such
capital stock under the registration provisions of the Securities Act.

         4.12. DISCLOSURE. Neither this Agreement, the financial statements
incorporated herein as Exhibit 4.09, nor any other agreement, document,
certificate or written statement furnished to PARKER by IS&S or its authorized
representatives in connection with the transactions contemplated hereby contains
any untrue statement of a material fact or fails

                                      -9-
<PAGE>

to state a material fact necessary to make the statements contained herein or
therein, taken as a whole, not misleading. There is no fact within the special
knowledge of IS&S or any officer of IS&S or Douglas Gemmell which has not been
disclosed herein or in writing by them to PARKER which materially adversely
affects the business, properties, assets, financial condition, operations or
prospects of IS&S. Financial projections furnished by IS&S were prepared by IS&S
in good faith, based upon assumptions which, when made, were reasonable.

         4.13. CAPITALIZATION; STATUS OF CAPTIAL STOCK. IS&S has a total
authorized capitalization consisting of (a) 2,000,000 shares of Common Stock, of
which 350,000 shares are issued and outstanding, and (b) 500,000 shares of
Preferred Stock, consisting of 250,000 shares of Class A Convertible Preferred
Stock, of which 100,000 shares are issued and outstanding, 200,000 shares of
Class B Convertible Preferred Stock, of which 47,500 are issued and outstanding
immediately prior to the sale of Class B Shares to PARKER under this Agreement,
and 50,000 shares of undesignated Preferred Stock, of which none are issued and
outstanding. A complete list of the shares of Common Stock and Convertible
Preferred Stock presently issued and outstanding, and the names in which such
shares are registered, is set forth in Exhibit 4.13 hereto. IS&S has granted
options to purchase a cumulative total of 41,720 shares of Common Stock, and the
names of the persons who have received such options, the number of shares
subject to the option, the option price, and the exercise date are also set
forth in Exhibit 4.13. All the outstanding shares of capital stock of IS&S have
been duly authorized, are validly issued and are fully paid and nonassessable.
The Class B Shares when issued and delivered in accordance with the terms
hereof, and the Conversion Shares, when issued and delivered upon conversion of
the Preferred Shares in accordance with the Articles of Incorporation, when so
issued, will be authorized, validly issued and fully paid and nonassessable.
Other than as provided in this Agreement or as set forth on Exhibit 4.13, there
are no options, warrants or rights to purchase shares of capital stock or other
securities of IS&S which are authorized, issued or outstanding, nor is IS&S
obligated in any other manner to issue shares of its capital stock or other
securities. Except as otherwise contemplated by this Agreement, there are no
restrictions on the transfer of shares of capital stock of IS&S other than those
imposed

                                      -10-
<PAGE>

by relevant state and federal securities laws and the Shareholders Agreement to
which IS&S and certain of its shareholders are parties. The offer and sale of
all shares of capital stock or other securities of IS&S issues before the
Closing complied with or were exempt from all federal and state securities laws.

         4.14. BOOKS AND RECORDS. The books of account, ledgers, order books,
records and documents of IS&S accurately and completely reflect all material
information relating to the business of IS&S, the assets of IS&S, and the nature
of all transactions giving rise to the obligations or accounts receivable of
IS&S.

                                 ARTICLE 5
                             COVENANTS OF IS&S

         5.01. AFFIRMATIVE COVENANTS OF IS&S. The affirmative covenants of this
Article 5.01 will not apply after the earlier of (i) the consummation of the
first underwritten public offering by IS&S pursuant to a registration statement
filed with the Securities and Exchange Commission in which the aggregate net
proceeds to IS&S exceed $5,000,000 ("Qualified Public Offering"), or (ii) the
date PARKER owns less than ten percent (10%) of the then issued and outstanding
capital stock of IS&S. During the period prior to an event set forth above, IS&S
will:

               (a) ACCESS TO BOOKS AND RECORDS. At such times as are reasonably
acceptable to IS&S, permit PARKER to examine and make copies of and extracts
from the records and books of account of, and, at all times accompanied by a
duly authorized representative of IS&S, visit and inspect the properties of IS&S
and discuss the affairs, finances and accounts of IS&S with any of its officers,
employees, directors and independent accountants. PARKER agrees that, to the
extent set forth in Article 6.02 below, it shall keep confidential and not
disclose to third parties (except for professional advisers who shall be advised
of the confidential nature of such information and shall agree to maintain its
confidentiality, or as may be required by law) any confidential or proprietary
information received by it pursuant to this Article 5, so long as such
information is not generally available to the public;

                                      -11-
<PAGE>

               (b) QUARTERLY STATEMENTS. As soon as available and in any event
within forty five (45) days after the end of each fiscal quarter of IS&S,
furnish to the IS&S Board of Directors consolidated and consolidating balance
sheets of IS&S as of the end of such quarter and consolidated and consolidating
statements of income setting forth in each case in comparative form the
corresponding figures for the corresponding period of the preceding fiscal year,
all in reasonable detail and duly certified (subject to year-end audit
adjustments) by the chief financial officer of IS&S or in his or her absence by
a person designated as the acting chief financial officer, as having been
prepared in accordance with generally accepted accounting principals
consistently applied, subject to the exception that footnotes and related
schedules required by generally accepted accounting principles need not be
included;

               (c) YEAR END STATEMENTS. As soon as available and in any event
within one hundred twenty (120) days after the end of each fiscal year of IS&S,
furnish to the IS&S Board of Directors consolidated and consolidating balance
sheets of IS&S as of the end of such fiscal year and consolidated and
consolidating statements of income and retained earnings and of changes in
financial position of IS&S and reconciliations of sources and uses of working
capital for such fiscal year, setting forth in each case in comparative form the
corresponding figures for the preceding fiscal year, together with an opinion
thereon of independent public accountants approved by the IS&S Board of
Directors;

               (d) SIGNIFICANT TRANSACTIONS. Promptly, fully and in detail,
inform the IS&S Board of Directors of any discussions, offers or contracts
relating to significant capital restructuring (including issuance or purchase of
equity or debt securities), mergers, acquisitions or divestitures of any nature
involving IS&S, of which IS&S has knowledge, whether initiated by IS&S or by any
other person;

               (e) BOARD REPRESENTATION. Within thirty (30) days after the
Closing Date, take all steps necessary or appropriate to appoint a person
designated by PARKER to be a member of the IS&S Board of Directors, and
thereafter to nominate or appoint such person in accordance with PARKER's
written request to IS&S. Such designee shall be subject to

                                      -12-
<PAGE>

the approval of the IS&S Board of Directors, which approval will not be
unreasonably withheld. Such designee shall serve as a director until the
occurrence of an event eliminating the covenants in this Article 5 or until such
individual's earlier resignation, incapacity, death or the withdrawal of such
individual's designation by PARKER, subject to the right of the shareholders of
IS&S to remove such designee in accordance with the IS&S By-Laws and applicable
law. The parties acknowledge that Robert H. Rau shall initially serve on the
Board as PARKER's designee;

               (f) CONVERSION AND VOTING TRUST. Within thirty (30) days after
the Closing Date, convert all Preferred Shares to Conversion Shares; and
terminate all Voting Trust Agreements or other agreements that transfer or
require the transfer of any voting rights of such Conversion Shares from the
owner of the Conversion Shares to any officer or employee or director or other
shareholder of IS&S or to any person under the control of any of the aforesaid,
except that this termination provision will not apply to the transfer of voting
rights with respect to 50,000 shares of IS&S capital stock beneficially owned by
Stephanie H. Hedrick;

               (g) AGREEMENTS. Retain in effect and fulfill its obligations
under its employment and noncompete agreements with Geoffrey S.M. Hedrick and
Douglas Gemmell (see Article 3.01(c) above), and use its best efforts and take
all reasonably necessary actions to enforce substantially all of its rights
under each such Agreement; and

               (h) CHANGE OF CONTROL. Deliver to PARKER a good faith irrevocable
offer in the form attached as Exhibit 5.01(h) to repurchase the Series B Shares
or Conversion Shares transferred to PARKER under this Agreement and perform all
of its obligations under such offer if control of IS&S passes to a competitor of
PARKER in the aircraft fuel management business.

                                      -13-
<PAGE>

         5.02. FURTHER RIGHTS OF PARKER.

               (a) Upon the occurrence of an event set forth in the first
sentence of Article 5.01 above and until PARKER owns less than five percent (5%)
of the then issued and outstanding capital stock of IS&S:

                   (i) As soon as available and in any event within forty five
     (45) days after the end of each fiscal quarter of IS&S, IS&S shall furnish
     to PARKER consolidated and consolidating balance sheets of IS&S as of the
     end of such quarter, together with consolidated and consolidating
     statements of income, all in reasonable detail and prepared in accordance
     with generally accepted accounting principles consistently applied, subject
     to the exception that footnotes and related schedules required by generally
     accepted accounting principles need not be included; and

                   (ii) As soon as available and in any event within one hundred
     twenty (120) days after the end of each fiscal year of IS&S, IS&S shall
     furnish to PARKER consolidated and consolidating balance sheets of IS&S as
     of the end of such fiscal year, together with consolidated and
     consolidating statements of income and retained earnings and of changes in
     financial position and reconciliations of sources and uses of working
     capital, reviewed by the Company's independent public accountants and
     prepared in accordance with generally accepted accounting principles
     consistently applied, subject to the exception that footnotes and related
     schedules required by generally accepted accounting principles need not be
     included.

               (b) In the event Articles 5.01 and 5.02(a) are not in effect and
until PARKER no longer owns any shares of capital stock of IS&S, IS&S shall
furnish to PARKER within forty five (45) days from the end of each fiscal
quarter and within one hundred twenty (120) days from the end of each fiscal
year, condensed consolidated and consolidating balance sheets and statements of
income for the end of each fiscal quarter and fiscal year, respectively, in each
case prepared in accordance with generally accepted accounting principles
consistently applied.

                                      -14-
<PAGE>

               (c) In each case, the financial information provided to PARKER
pursuant to Article 5.02 shall be subject to the obligation of PARKER to
maintain the confidentiality of such information to the extent required by
Article 6.02. Notwithstanding anything in this Article 5.02 to the contrary,
IS&S shall not be obligated to comply with this Article 5.02 in the event IS&S
is required to file, and does file, reports with the Securities and Exchange
Commission pursuant to Section 13 or 15(d) of the Securities Exchange Act of
1934, as amended or any similar statute.

         5.03. PARKER EMPLOYEES. So long as PARKER is a shareholder of IS&S,
neither IS&S nor any officer or director or affiliate of IS&S will directly or
indirectly induce or attempt to influence any employee of PARKER to terminate
his or her employment with PARKER. This Article 5.03 will not prevent IS&S from
soliciting or employing any person who is a former employee of PARKER.


                                    ARTICLE 6
                               COVENANTS OF PARKER

         6.01. IS&S EMPLOYEES. So long as PARKER is a shareholder of IS&S,
neither PARKER nor any officer or director or affiliate of PARKER will directly
or indirectly induce or attempt to influence any employee of IS&S to terminate
his or her employment with IS&S. This Article 6.01 will not prevent PARKER from
soliciting or employing any person who is a former employee of IS&S.

         6.02. CONFIDENTIALITY. So long as either of the Instrumentation
Agreements is in effect, the confidentiality obligations of PARKER with respect
to information received by PARKER from IS&S will be according to the terms of
the Instrumentation Agreements. Effective upon termination of the
Instrumentation Agreements, (a) with respect to all information received by
PARKER from IS&S after such termination, PARKER will take at least the same
precautions to maintain such information in confidence as PARKER takes to
maintain in confidence its own confidential information, and (b) with respect to
all information received by PARKER from IS&S after such termination other than
condensed balance sheets and condensed statements of income, PARKER will not use
such information

                                      -15-
<PAGE>

to compete with IS&S with respect to any customer or with respect to any
product. PARKER may at any time refuse to receive information from IS&S or
designate a particular officer or employee of PARKER to be the recipient of all
information from IS&S. In no event will PARKER have any obligation with respect
to any information received from IS&S after termination of the Instrumentation
Agreements which (a) is already known to PARKER at the time it receives the
information from IS&S or is developed at any time by PARKER without use of
information from IS&S which is otherwise confidential under this Agreement, or
(b) is or becomes publicly known through no wrongful act of PARKER, or is or
becomes known to other persons or entities without written obligation of
confidentiality to IS&S, or (c) is rightfully received by PARKER from a third
party who did not receive it from IS&S, or (d) is approved for release by
written authorization of IS&S.


                                    ARTICLE 7
                       PREEMPTIVE AND REGISTRATION RIGHTS

         7.01. PREEMPTIVE RIGHTS. The rights of PARKER and obligations of IS&S
with respect to preemptive rights concerning the Preferred Shares and the
Conversion Shares are set forth in attached Exhibit 7.01.

         7.02. REGISTRATION RIGHTS. The rights of PARKER and obligations of IS&S
with respect to registration of the Preferred Shares and the Conversion Shares
are set forth in attached Exhibit 7.02.


                                    ARTICLE 8
                                  MISCELLANEOUS

         8.01. MODIFICATION AND WAIVER. No cancellation, modification,
amendment, deletion, addition or change in this Agreement or any provision
hereof or the waiver of any right or remedy herein provided shall be effective
for any purpose unless specifically set forth in writing and signed by an
officer of the party or by the individual to be bound thereby. No waiver of any
right or remedy in respect of any occurrence or event on one occasion shall be
deemed a waiver of such right or remedy in respect of such occurrence or event
on any other occasion.

                                      -16-
<PAGE>

         8.02. ENTIRE AGREEMENT. This Agreement includes the attached Exhibits
which are incorporated by reference and comprises the entire Agreement between
IS&S and PARKER with respect to the purchase and sale of IS&S stock.

         8.03. ASSIGNMENT AND RIGHT OF FIRST REFUSAL.

               (a) ASSIGNMENT. The disposition of PARKER's Class B Shares and
Conversion Shares shall at all times be within the control of PARKER. None of
PARKER's rights under this Agreement may be assigned by PARKER in connection
with such disposition by PARKER of its Class B Shares or Conversion Shares,
except that the transferee of at least 20,000 of such shares will at all times
prior to a Qualified Public Offering be entitled to (i) the same rights as
PARKER would have had under Article 7 of this Agreement if PARKER would have
retained ownership of such shares, and (ii) information of the type described in
Article 5.02(b) above, information provided to other shareholders of IS&S who do
not have a representative on the IS&S Board of Directors, and information
available to such transferee under applicable state law, provided such
transferee agrees in writing to the same confidentiality and nonuse obligations
as apply to PARKER under Article 6.02 of this Agreement.

               (b) RIGHT OF FIRST REFUSAL. Notwithstanding the foregoing, in the
event PARKER desires to transfer its Class B Shares or Conversion Shares other
than to an affiliate, it shall first obtain a bona fide offer in writing for
such shares which PARKER is willing to accept and then provide IS&S with a right
of first refusal to purchase such of the Class B Shares or Conversion Shares
subject to transfer on the same terms and conditions as being offered by the
potential transferee. Such right of first refusal shall be exercised by IS&S by
delivery of written notice thereof to PARKER within twenty (20) days of receipt
of the notice from PARKER of the bona fide offer. The consummation of such
purchase shall occur within twenty (20) days of IS&S's exercise of such right of
first refusal, using the closing procedure set forth in Exhibit 5.01(h) of this
Agreement.

                                      -17-
<PAGE>

         8.04. CONTROLLING LAW. This Agreement will be construed and performed
and governed by the laws of the Commonwealth of Pennsylvania.

         8.05. NOTICES. Any notice provided for herein shall be in writing and
shall be deemed to have been sufficiently given on the date of receipt by
recipient (as evidenced by the carrier's return receipt card) if sent by
registered mail or overnight carrier (such as Federal Express), postage prepaid,
and addressed to the other party at its address as set forth below, or
personally delivered thereto:

      If to IS&S:         INNOVATIVE SOLUTIONS & SUPPORT, INC.
                          420 Lapp Road
                          Malvern, Pennsylvania  19355
                          Attention:  Mr. Geoffrey S.M. Hedrick

      If to PARKER:       PARKER-HANNIFIN CORPORATION
                          17325 Euclid Avenue
                          Cleveland, Ohio 44112
                          Attention: Secretary

         8.06. AGENTS OR BROKERS. IS&S represents and warrants that it has
incurred no liabilities for any brokerage commission, finders' fees or the like
in connection with the transaction described in this Agreement. PARKER
represents and warrants that it has taken no action which would give rise to any
claim by any person for brokerage commissions, finders' fees or the like
relating to this Agreement or the transaction described in this Agreement.

         8.07. SURVIVAL OF REPRESENTATIONS AND WARRANTIES. All representations
and warranties made in this Agreement are given as of the Closing Date and shall
survive the execution and delivery hereof for a period of three (3) years from
the Closing Date.

         8.08. SEVERABILITY. The invalidity or unenforceability of any provision
of this Agreement shall not affect the validity or enforceability of any other
provision.

                                      -18-
<PAGE>

         8.09. COUNTERPARTS. This Agreement may be executed in any number of
counterparts, all of which taken together shall constitute one and the same
instrument, and either of the parties hereto may execute this Agreement by
signing any such counterpart.

         8.10. FURTHER ASSURANCES. From and after the date of this Agreement,
upon the request of either party, the other party will execute and deliver such
instruments, documents and other writing as may be reasonably necessary or
desirable to confirm and carry out and to effectuate fully the intent and
purposes of this Agreement.


         IN WITNESS WHEREOF, each of the parties hereto has executed this
Agreement on the date indicated below.

                               INNOVATIVE SOLUTIONS & SUPPORT, INC.


                               Signature: /s/ GEOFFREY S. M. HEDRICK
                                         ---------------------------------------
                               Name:  Geoffrey S.M. Hedrick
                                    --------------------------------------------
                               Title: Chief Executive Officer
                                    --------------------------------------------
                               Date:
                                    --------------------------------------------


                               PARKER-HANNIFIN CORPORATION


                               Signature: /s/ ROBERT H. RAU
                                         ---------------------------------------
                               Name: Robert H. Rau
                                    --------------------------------------------
                               Title:  PRESIDENT-PARKER  BERTEA AEROSPACE GROUP
                                    --------------------------------------------
                               Date:   JULY 11, 1991
                                    --------------------------------------------

                                      -19-
<PAGE>

                                LIST OF EXHIBITS

EXHIBIT NO.          DESCRIPTION

1.01                 Terms and Conditions of Series B Shares

1.02                 Terms and Conditions of Conversion Shares

1.05(b)              Capital Contribution Agreement

3.01(c)              Hedrick/Gemmell Employment/Noncompete Agreement

3.01(d)              Hedrick Shareholder Agreement

3.01(f)              Opinion of IS&S Counsel

4.00                 Disclosure Schedule for Exceptions

4.06(b)              IS&S Nondisclosure and Inventions Agreement

4.09                 IS&S Balance Sheet and Income Statement

4.10                 List of IS&S Loans, Guarantees and Material Contracts

4.13                 List of IS&S Shareholders and Stock Options

5.01(h)              Repurchase Offer

7.01                 Preemptive Rights

7.02                 Registration Rights
<PAGE>

                                  EXHIBIT 7.02
                               REGISTRATION RIGHTS
                               -------------------


     A. "Piggy Back" Registration. If at any time or times IS&S shall determine
        --------------------------
to register under the Securities Act (including pursuant to a demand of any
shareholder of IS&S exercising registration rights) any of its Preferred Stock
or its Common Stock of the type which has been or may be issued upon the
conversion of the Preferred Shares, other than on Form S-8 or Form S-4 or their
then equivalents, it shall send to PARKER written notice of such determination.
If within thirty (30) days after receipt of such notice, PARKER shall so request
in writing, IS&S shall use its best efforts to include in such registration
statement all of the shares PARKER requests to be registered. If, in connection
with any offering involving an underwriting of stock to be issued by IS&S, the
managing underwriter shall impose a reduction in the number of shares of such
stock which may be included in any such registration statement because, in its
judgment, such reduction is desirable to effect an orderly public distribution,
such reduction shall be imposed on PARKER on a pro rata basis in the proportion
that the total number of shares of PARKER to be included in the offering bears
to the total number of shares to be included in the offering, other than shares
included in the offering to be issued by IS&S for its own account. No incidental
right under this Section A shall be construed to limit any registration required
under Section B unless the registration of shares under this Section A is made
due to the demand of a shareholder who is an affiliate of PARKER.

     Notwithstanding anything in this Section A to the contrary, IS&S shall only
be required to include shares in a registration statement and send notices of
determination to register under the Securities Act, as described above, with
respect to the first Qualified Public Offering of IS&S, and each registration
occurring prior to such Qualified Public Offering.

     B. Required Registration. If one or more holders of at least 25% of the
        ----------------------
IS&S shares then outstanding shall notify IS&S in writing that it or they intend
to offer or cause to be offered for public sale at least ten percent (10%) of
the outstanding IS&S shares, IS&S will so notify all holders of IS&S shares,
including all holders who have a right to
<PAGE>

acquire shares. Upon written request of any holder given within thirty (30) days
after the receipt by such holder from IS&S of such notification, IS&S will use
its best efforts to cause a registration statement covering such of the shares
as may be requested by any holder thereof (including the holder or holders
giving the initial notice of intent to offer) to be filed with the Securities
and Exchange Commission as expeditiously as possible and to cause such
registration statement to become and remain effective. If IS&S determines to
include shares to be sold by it in any registration request pursuant to this
Section B, such registration shall be deemed to have been a registration under
Section A of this Exhibit 7.02. Notwithstanding the foregoing, IS&S shall not be
obligated to file a registration statement with the Securities and Exchange
Commission pursuant to this Section B, (1) prior to the consummation by IS&S of
its initial underwritten public offering, (2) within ninety (90) days following
the effective date of any registration of securities by IS&S in an underwritten
public offering, (3) on any more than one occasion unless a registration
statement covering all requested shares owned by PARKER is for whatever reason
not declared effective, in which case PARKER shall be entitled to exercise its
right to request registration hereunder until a registration statement with
respect to such requested shares is declared effective, or (4) if the number of
shares included in such registration shall have a fair market value (based upon
the probable offering price, as estimated in good faith by the Board of
Directors of IS&S or by the proposed underwriters) of less than $5,000,000.

     C. Registration on Form S-3. In addition to the rights provided the holder
        -------------------------
of Shares in Sections A and B above, if the registration of shares under the
Securities Act can, at any time or from time to time, be effected on Form S-3
(or any similar form promulgated by the Securities and Exchange Commission),
IS&S will promptly so notify each holder of shares, including each holder who
has a right to acquire shares, and then will at the request of holders of at
least 10% of the IS&S shares then outstanding at any time, and from time to time
thereafter, as expeditiously as possible, use its best efforts to effect
registration under the Securities Act on said Form S-3, of all or such portion
of the shares as such holder or holders of shares shall specify; provided,
however, that IS&S shall not be required to effect more than two such
registrations in any calendar year and further provided that the estimated
market value of the shares to be included in any such registration shall be at
least $1,000,000.
<PAGE>

     D. Effectiveness. IS&S will use its best efforts to maintain the
        --------------
effectiveness for up to six (6) months of any registration statement pursuant to
which any of the shares are being offered, and from time to time will amend or
supplement such registration statement and the prospectus contained therein if
and to the extent necessary to comply with the Securities Act and any applicable
state securities statute or regulation.

     E. Exchange Act Registration. If IS&S at any time shall list any of its
        --------------------------
shares on any national securities exchange and shall register such shares under
the Exchange Act, IS&S will, at its expense, simultaneously list on such
exchange and maintain such listing of, all of the IS&S shares. If IS&S becomes
subject to the reporting requirements of either Section 13 or Section 15(d) of
the Exchange Act, IS&S will use its best efforts to timely file with the
Securities and Exchange Commission such information as the Commission may
require under either of said Sections; and in such event, IS&S shall use its
best efforts to take all action as may be required as a condition to the
availability of Rule 144 under the Securities Act (or any successor exemptive
rule hereinafter in effect) with respect to such shares. IS&S shall furnish to
any holder of shares forthwith upon request (i) a written statement by IS&S as
to its compliance with the reporting requirements of Rule 144, (ii) a copy of
the most recent annual or quarterly report of IS&S as filed with the Securities
and Exchange Commission, and (iii) such other reports and documents as a holder
may reasonably request in availing itself of any rule or regulation of the
Securities and Exchange Commission allowing a holder to sell any such shares
without registration.

     F. Further Obligations of IS&S. Whenever under the preceding sections of
        ----------------------------
Exhibit 7.02, IS&S is required hereunder to register shares, it agrees that it
shall also do the following:

        (1) Furnish to PARKER such copies of each preliminary and final
prospectus and such other documents as PARKER may reasonably request to
facilitate the public offering of its shares;

        (2) Use its best efforts to register or qualify the shares covered by
said registration statement under the applicable securities or "blue sky" laws
of such
<PAGE>

jurisdictions as PARKER may reasonably request; provided, however, that IS&S
shall not be obligated to: (i) qualify to do business in any jurisdiction where
it is nor then so qualified; (ii) take any action which would subject it to the
service of process in suits other than those arising out of the offer or sale of
the securities covered by the registration statement in any jurisdiction where
it is not then so subject; (iii) subject itself to taxation in such
jurisdiction; (iv) register in a state requiring, as a condition to such
registration, escrow or surrender of any securities of a security holder; or (v)
incur expenses in excess of $10,000 in connection with registration in all
states so requested unless PARKER agrees to reimburse IS&S for expenses so
incurred in excess of such amount;

     (3) Furnish to PARKER a signed counterpart of

           (a) an opinion of counsel for IS&S dated included as an exhibit to
the registration statement pursuant to the requirements of the Securities Act,
and

           (b) "comfort" letters signed by IS&S independent public accountants
who have examined and reported on IS&S financial statements included in the
registration statement, to the extent permitted by the standards of the American
Institute of Certified Public Accountants,

covering substantially the same matters with respect to the registration
statement (and the prospectus included therein) and (in the case of the
accountants' "comfort" letters) with respect to events subsequent to the date of
the financial statements, as are customarily covered in opinions of issuer's
counsel and in accountants' "comfort" letters delivered to the underwriters in
underwritten public offerings of securities, to the extent that IS&S is required
to deliver or cause the delivery of such opinion or "comfort" letters to the
underwriters in an underwritten public offering of securities;

     (4) Permit PARKER or its counsel or other representatives to inspect and
copy such corporate documents and records as may reasonably be requested by
them;

     (5) Furnish to PARKER a copy of all documents filed and all correspondence
<PAGE>

dispatched from or to the Securiries and Exchange Commission in connection with
any such offers; and

        (6) Use its best efforts to insure the obtaining of all necessary
approval from the National Association of Securities Dealers, Inc.

     G. Obligations of PARKER. Whenever under the preceding sections of this
        ----------------------
Exhibit 7.02, IS&S is required hereunder to register Shares) PARKER agrees to do
the following:

        (1) To furnish IS&S with appropriate information as may be included in
the registration statement; and

        (2) To become a signatory to the underwriting agreement and such other
agreements as required by the underwriters, but only with respect to the shares
being offered by PARKER.

     H. Expenses. In the case of a registration under Sections A or B, IS&S
        ---------
shall bear all costs and expenses of each such registration, including, but not
limited to, printing, legal and accounting expenses, Securities and Exchange
Commission filing fees and "blue sky" fees and expenses; provided, however, (1)
that with respect to Section A, in the case of a registration in which IS&S is
not registering any shares for its own account, PARKER shall bear all such costs
and expenses (on a pro rata basis based on the number of shares being sold by
such holder or holders), and (2) that with respect to Section B, PARKER shall
bear all such costs and expenses (on a pro rata basis based on the number of
shares being sold by such holder or holders), exclusive, in each case, of the
cost of any year end audit of IS&S financial statements and exclusive of any
compensation of directors, officers or employees of IS&S, all of which shall be
borne entirely by IS&S. Notwithstanding the foregoing, whether or not IS&S is
registering shares for its own account in connection with a registration under
Sections A or B, IS&S shall have no obligation to pay or otherwise bear any
portion of the registration fees, transfer taxes or underwriters' commissions or
discounts attributable to the shares being offered and sold by PARKER or the
cost of fees
<PAGE>

for counsel not engaged by IS&S. PARKER shall bear all costs and expenses in
the case of registrations under Section C.

     I. Exception. IS&S shall nor be required to effect a registration under
        ----------
this Exhibit 7.02 if, in the written opinion of counsel for IS&S, which counsel
shall be reasonably acceptable to PARKER, PARKER may sell, without registration
under the Securities Act, all shares for which it had requested registration
under the provisions of the Securities Act in the manner and in the quantity in
which the shares were proposed to be sold.

     J. Transfer of Registration Rights. The registration rights of PARKER
        --------------------------------
herein granted may be transferred to any transferee of PARKER's shares of IS&S
(1) who is an affiliated person, as that term is defined in the Investment
Company Act of 1940, of PARKER (including a partner of PARKER) or (2) who
acquires at least 50,000 Preferred Shares or an equivalent amount of Conversion
Shares issued upon conversion thereof (as adjusted for stock splits, stock
dividends, reclassifications, recapitalizations or other similar events).

     K. Granting of Registration Rights. IS&S shall not, without PARKER's
        --------------------------------
consent, grant any rights to any Person to register any shares of capital stock
or other securities of IS&S if such rights could reasonably be expected to
conflict with the rights of PARKER granted pursuant to this Agreement.

     L. Sales Following Initial Public Offering. PARKER agrees that for a period
        ----------------------------------------
equal to the greater of: (i) ninety (90) days after IS&S initial public offering
of securities or (ii) such longer period as may be imposed by the underwriters
in the initial public offering of securities but in no event longer than
eighteen (18) months, it will not, without the consent of IS&S (or the
underwriters, as they may require), sell in the open market any IS&S shares held
by it, whether or not any IS&S shares held by it are included in such offering.