Subject: ACCEPTANCE AND USE OF

ELECTRONIC SIGNATURES, 

ELECTRONIC RECORDKEEPING 

SYSTEMS, AND ELECTRONIC MANUALS 

Date: 10/29/02 

Initiated by: AFS-300

AC No: 120-78 

Change:

1. What is the purpose of this advisory circular (AC)? 

a. This AC is not mandatory and does not constitute a regulation. This AC provides 

guidance on the acceptance and use of electronic signatures to satisfy certain operational and 

maintenance requirements. This AC also provides guidance on the acceptability of electronic 

recordkeeping systems and electronic maintenance manuals, including inspection procedures 

manuals, quality assurance, operations manuals, and training manuals required by Title 14 of the

Code of Federal Regulations (14 CFR). After the Federal Aviation Administration (FAA)

accepts an electronic system, that system may be used to generate aircraft records (such as load 

manifest, dispatch release, aircraft maintenance records, maintenance task cards, pilot training

records, flight release, airworthiness release, flight test reports, etc.) when these records can be 

properly authenticated. 

NOTE: In this AC, the term “electronic signature” refers to either electronic 

signatures or digital signatures. The specific electronic signature used

depends on the end user’s preference and the system application.

b. This AC describes an acceptable means, but not the only means, of complying with the 

FAA’s operational and maintenance requirements. Specifically, handwritten signatures, records 

and mechanic’s stamps continue to be acceptable. However, if you use the electronic means 

described in the AC, you must conform to it in all important respects. 

2. Who does this AC apply to? 

Air carriers under 14 CFR parts 121, 129, or 135 

Operators under 14 CFR parts 91, 125, 133, or 137 

Persons performing airmen certification under 14 CFR parts 61, 63, 65, 141, and 142 

Individuals performing maintenance or preventive maintenance under 14 CFR part 43 

Repair stations under 14 CFR part 145 

 
AC 120-78 10/29/02 

Aviation maintenance technical schools under 14 CFR part 147 

DEFINITIONS 

3. For purposes of this AC, what definitions apply? 

a. Authentication. The means by which a system validates an authorized user’s identity. 

These may include a password, a personal identification number (PIN), a cryptographic key or 

badge swipe. 

b. Computer Hardware. A computer and the associated physical equipment directly

involved in the performance of communications or data processing functions. 

c. Computer Software. Written or printed data, such as programs, routines, and symbolic

languages, essential to the operation of computers.

d. Digital Signature. Cryptographically generated data that identifies a document’s 

signatory (signer) and certifies that the document has not been altered. Digital signature 

technology is the foundation of a variety of security, electronic business, and electronic 

commerce products. This technology is based on public/private key cryptography, digital 

signature technology used in secure messaging, public key infrastructure (PKI), virtual private 

network (VPN), web standards for secure transactions, and electronic digital signatures.

e. Electronic Signature. The online equivalent of a handwritten signature. It is an

electronic sound, symbol, or process attached to or logically associated with a contract or other 

record and executed or adopted by an individual. It electronically identifies and authenticates an 

individual entering, verifying, or auditing computer-based records. An electronic signature

combines cryptographic functions of digital signatures with the image of an individual’s 

handwritten signature or some other visible mark considered acceptable in a traditional signing

process. It authenticates data with a hash algorithm and provides permanent, secure userauthentication. 

f. Electronic Recordkeeping System or Manual. A system of record processing in which 

records or manuals are entered, stored, and retrieved electronically by a computer system rather 

than in the traditional hard copy form. 

g. Signature. Any form of identification used to acknowledge completion of an act and 

authenticate a record entry. A signature must be traceable to the individual making the entry,

and it must be handwritten or part of an electronic signature system or other form acceptable to 

the FAA. 

4. Why is the FAA providing guidelines for electronic signatures, electronic recordkeeping 

systems and electronic manuals? 

a. The Government Paperwork Elimination Act (GPEA), Public Law 105-277, Title XVII, and 

the Electronic Signatures in Global and National Commerce Act (E-Sign), Public Law 106-229, 

encourage use of electronic signatures. When electronic signatures are used and accepted, 

electronic recordkeeping and document transfer will also be encouraged meeting the goals of the

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10/29/02 AC 120-78 

Small Business Paperwork Relief Act of 2002. This AC represents the FAA’s effort to implement 

these laws to meet certain FAA operational and maintenance requirements. 

b. Before the enactment of ESign on June 30, 2000, the regulations on signatures 

acknowledging satisfaction of maintenance and operational requirements did not reflect current 

advances in information storage and retrieval technology. These earlier rules were developed 

when use of electronic media for the storage and retrieval of data was neither available to, nor 

contemplated by, the aviation industry or the FAA. 

c. As the complexity of aircraft design, operations, and maintenance processes increased, the 

number of records and documents generated and required to be retained by aircraft owners, 

operators, manufacturers, and repair facilities expanded dramatically. Electronic information 

storage and retrieval systems have enhanced significantly the aviation industry’s ability not only

to meet FAA record-retention requirements, but also to manufacture, operate, and maintain 

today’s highly complex aircraft and aircraft systems in a demanding operational environment. 

d. The Office of Management and Budget (OMB), Executive Office of the President, has 

issued OMB Circular A-130, Management of Federal Information Resources. This document 

directs the FAA and other government agencies to recognize the limitations on electronic recordkeeping systems due to restrictions on the use of electronic signatures. With this AC, the FAA 

recognizes this limitation and will now permit the use of electronic signatures on certain 

maintenance and operational records. Owners, operators, and maintenance personnel may now 

use complete electronic recordkeeping systems because the requirement to authenticate 

documents with non-electronic signatures has been eliminated. Such systems may now be used 

to generate aircraft records (e.g., load manifests, dispatch releases, maintenance task cards, 

aircraft maintenance records, flight releases, airworthiness releases, and flight test reports) that

can be properly authenticated with an electronic signature. 

e. Acceptance of electronic signatures will encourage the use of electronic maintenance 

record retention and record entry requirements for maintenance, preventive maintenance,

inspection, rebuilding, and alteration records.

f. Using electronic signatures and various computer systems will also enhance

communication with local Flight Standards District Offices (FSDO) or Certificate-Holding

District Office (CHDO). Their use will provide for the online transmission of manual revisions 

and other routine written correspondence between operators and the FAA. 

g. Using electronic signatures will make it easier to identify a document signer (signatory). 

Their use will help eliminate the traceability difficulties associated with illegible handwritten 

entries and the deterioration of paper documents. 

DISCUSSION—ELECTRONIC SIGNATURE 

5. What is an acceptable electronic signature? 

a. General. Before recent changes to permit the use of electronic signatures, handwritten 

signatures were used on any required record, record entry, or document. The electronic 

signature’s purpose is identical to that of a handwritten signature or any other form of signature

currently accepted by the FAA. The handwritten signature is universally accepted because it has 

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AC 120-78 10/29/02 

certain qualities and attributes (e.g., subparagraph c(4)(d) below concerning employee 

termination) that should be preserved in any electronic signature. Therefore, an electronic 

signature should possess those qualities and attributes that guarantee a handwritten signature’s 

authenticity. 

b. Forms of Electronic Signatures. 

(1) An electronic signature may be in the following forms. 

A digital signature

A digitized image of a paper signature

A typed notation 

An electronic code 

Any other unique form of individual identification that can be used as a means of 

authenticating a record, record entry, or document

(2) Not all identifying information found in an electronic system may constitute a 

signature. For example, the entry of an individual’s name in an electronic system may not 

constitute an electronic signature. Other guarantees equal to those of a handwritten signature

should be provided. 

c. Attributes of an Acceptable Electronic Signature. First and foremost, an electronic 

signature must be part of a well-designed program. This program should, at a minimum, 

consider the following. 

(1) Uniqueness. An electronic signature should retain those qualities of a handwritten 

signature that guarantee its uniqueness. A signature should identify a specific individual and be 

difficult to duplicate. A unique signature provides evidence that an individual agrees with a 

statement. An electronic system cannot provide a unique identification with reasonable certainty

unless the identification is difficult for an unauthorized individual to duplicate. An acceptable 

method of proving the uniqueness of a signature is by using an identification and authentication 

procedure that validates the identity of the signatory. For example, an individual using an

electronic signature should be required to identify himself or herself, and the system that 

produces the electronic signature should then authenticate that identification. Acceptable means 

of identification and authentication include the use of separate and unrelated identification and 

authentication codes. These codes could be encoded onto badges, cards, cryptographic keys, or 

other objects. Systems using PINs or passwords also are an acceptable method of ensuring

uniqueness. Additionally, a system could use physical characteristics, such as a fingerprint,

handprint, or voice pattern, as a method of identification and authorization. 

(2) Significance. An individual using an electronic signature should take deliberate and 

recognizable action to affix his or her signature. Acceptable, deliberate actions for creating a 

digital electronic signature include, but are not limited to, the following: 

Badge swipes 

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10/29/02 AC 120-78 

Signing an electronic document with a stylus 

Typing specific keystrokes 

Using a digital signature

(3) Scope. The scope of information being affirmed with an electronic signature should 

be clear to the signatory and to subsequent readers of the record, record entry, or document. 

Handwritten documents place the signature close to the information to identify those items 

attested to by a signature. However, electronic documents may not position a signature in the 

same way. It is therefore important to clearly identify the specific sections of a record or 

document that are affirmed by a signature from those sections that are not. Acceptable methods 

of marking the affected areas include, but are not limited to, highlighting, contrast inversion, or 

the use of borders or flashing characters. Additionally, the system should notify the signatory

that the signature has been affixed. The user should be asked to ensure that the identified 

material is, in fact, what is being signed for after affixing the signature. The user also should be 

able to retrieve a report listing all places where his or her digital electronic signature has been 

applied. The FAA is not concerned with the computer technology used to accomplish the above 

tasks. Instead, the FAA concern is with the accuracy of the record and that the signatory is fully

aware of what he or she is signing.

(4) Signature Security. The security of an individual’s handwritten signature is 

maintained by ensuring that it is difficult for another individual to duplicate or alter it. An 

electronic signature should maintain an equivalent level of security. An electronic system that 

produces signatures should restrict other individuals from affixing another individual’s signature 

to a record, record entry, or document. Such a system enhances safety by preventing an 

unauthorized individual from certifying required documents, such as an airworthiness release. 

(a) A corresponding policy and management structure must support the computer 

hardware and software that delivers the information. 

(b) Signature authenticity/verification: Through control and archives, the computer 

software should determine if the signature is genuine and if the individual is authorized to 

participate. This can be accomplished by comparing the signature to a public key archive or 

some other means. This capability should be an integral part of the computer software. 

(c) Archiving electronically signed documents: Since no paper document with an ink 

signature exists, a means of safely archiving electronically signed documents should be part of 

any electronic signature computer software. This will provide for future authentication. 

(d) The system should contain restrictions and procedures to prohibit the use of an 

individual’s electronic signature when the individual leaves or terminates employment. This 

should be done immediately upon notification of the change in employment status. 

(e) Procedures should be established allowing the organization to correct documents 

that were electronically signed in error. The signature should be invalidated anytime a 

superseding entry is made on the same document. (The entry should be voided but remain in 

place. Reference to a new entry should be made and electronically signed and dated). 

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AC 120-78 10/29/02 

(5) Non-repudiation. An electronic signature should prevent a signatory from denying

that he or she affixed a signature to a specific record, record entry, or document. The more 

difficult it is to duplicate a signature, the likelier the signature was created by the signatory. The 

system’s security features that make it difficult for others to duplicate signatures or alter signed 

documents usually ensure that a signature was indeed made by the signatory. Many off-the-shelf

computer software packages, such as Adobe Acrobat, contain a self-sign utility. Although such 

computer software can provide an electronic signature for individuals or a group of individuals 

participating in an electronic signature program, a self-sign utility by itself cannot be used. 

However, it can become the basis of a digital signature program if the public and private keys are 

issued and controlled by a trusted third party.

(6) Traceability. An electronic signature should provide positive traceability to the 

individual who signed a record, record entry, or any other document. 

d. Other Acceptable Forms of Signature/Identification. Although this AC specifically

addresses electronic signatures, other types of signatures, such as a mechanic’s stamp, may also 

be acceptable to the FAA. If identification other than a handwritten signature is used, access to 

that identification should be limited to the named individual only. For example, the individual 

should secure a mechanic’s stamp when it is not in use. Similarly, a computer entry used as a 

signature should have restricted access that is limited by an authentication code that is changed 

periodically. Access to issued stamps or authentication codes should be limited to the user. 

Although a signature may take many forms, the FAA emphasizes that not all electronic entries 

may satisfy the criteria to qualify the entry as an acceptable signature. 

e. Compliance with Other Regulatory Requirements. Although the FAA now permits the 

use of electronic signatures to meet certain FAA operational and maintenance requirements, any

computer hardware used to generate the required documents and records must continue to meet 

current regulatory requirements. A proper signature affixed to an improperly created document 

still results in a document that does not meet regulatory requirements. Methods and procedures 

used to generate an electronic signature must therefore meet all regulatory requirements for a 

recordkeeping system to be used by owners, operators, or maintenance personnel. In addition, 

electronic signatures should only be used to satisfy the maintenance and operational 

requirements relating to this AC. Electronic signatures may not be considered acceptable in

other areas covered by 14 CFR having more specific applicability (i.e., legal depositions and 

various other applications). Although the acceptance of electronic signatures will foster the use 

of electronic recordkeeping systems, the FAA continues to accept paper documents to satisfy

current regulatory requirements. 

6. How does an operator or individual receive FAA approval to use an electronic 

signature? 

a. Announcing Intent to Use Electronic Signatures. Certificate holders and operators 

intending to use electronic signatures should consult with their local FSDO or CHDOs before 

implementing an electronic system. To obtain FAA approval, the certificate holder or operator 

must submit a letter to the appropriate FSDO or CHDO (see Appendix 1 for sample letter) 

describing the proposed system and include the proposed section or revision to the operator’s 

manual. 

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10/29/02 AC 120-78 

b. Description of Electronic System and Proposed Manual Changes. The electronic 

system description should explain how electronic signatures will be used in the operator’s 

maintenance and operational activities. The proposed manual section or revision should clearly

state who in the organization has authority and the overall responsibility for implementing,

modifying, revising, and monitoring the electronic signature computer software. In addition, the 

operator’s manual must explain how electronically signed documents required aboard an aircraft

will be transferred (in accordance with the appropriate regulations) prior to the aircraft’s 

operation. Required documents include aircraft maintenance releases, dispatch releases, etc. 

c. FAA Approval Process. The appropriate FAA Principal Inspector will review the

electronic signature proposal. If the proposed electronic hardware and computer software system 

meets the elements of this AC, the inspector will make the appropriate entry on the operator’s

operation specifications. For a part 91 operator, the FSDO will review the operator’s proposed 

procedures. If the procedures are acceptable, the FSDO will provide the operator with a letter of 

acceptance (see Appendix 2 for sample letter). 

DISCUSSION—ELECTRONIC RECORDKEEPING SYSTEMS 

7. What is an acceptable electronic recordkeeping system? 

When constructing an electronic recordkeeping system to meet the operational and maintenance 

requirements addressed in this AC, the following elements must be considered and addressed in 

the operator’s manual or in the directions for the system. This information must be made 

available to each individual responsible for using the system. 

a. Security. 

(1) The electronic system should protect confidential information. 

(2) The system should ensure that the information is not altered in an unauthorized way.

(3) A corresponding policy and management structure should support the computer 

hardware and computer software that delivers the information. 

b. Procedures. Before introducing an electronic recordkeeping system, computer 

procedures must be incorporated into the operator’s manual or in the directions for the system to 

include the following: 

(1) Procedures for making required records available to both the National Transportation 

Safety Board (NTSB) and FAA personnel. If the computer hardware and software system is not 

compatible with the FAA and the NTSB system, the organization will provide an employee or

representative to assist. This individual must be familiar with the computer system and assist in 

accessing the necessary computerized information. This procedure and computer system must 

be capable of producing paper copies of the viewed information at the request of the FAA or 

NTSB authorized representative. 

NOTE: The FAA and NTSB must be able to review the records and

information at their respective offices when necessary and on request. 

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AC 120-78 10/29/02 

Persons or entities can fulfill this request in many ways, i.e., floppy disk, 

paper copy, etc. 

(2) Procedures for reviewing the computerized personal identification codes system to 

ensure that the system will not permit password duplication. 

(3) Procedures for auditing the computer system every 60 days to ensure the integrity of

the system. A record of the audit should be completed and retained on file as part of the 

operator’s record retention requirements. This audit may be a computer program that 

automatically audits itself.

(4) Audit procedures to ensure the integrity of each computerized workstation. If the 

workstations are server-based and contain no inherent attributes that enable or disable access, 

there is no need for each workstation to be audited.

(5) Procedures describing how the operator will ensure that the computerized records are

transmitted in accordance with the appropriate regulatory requirements to customers or to 

another operator. The records may be either electronic or paper copies. 

(6) Procedures to ensure that records required to be transferred with an aircraft are in a 

format (either electronic or on paper) that is acceptable to the new owner/operator. 

(7) Guidelines for authorized representatives of the owner/operator to use electronic 

signatures and to have access to the appropriate records. 

(8) A description of the training procedure and requirements necessary to authorize 

access to the computer hardware and software system. (Recognizing that the details will vary

with the different individuals who need access, the training description may simply be part of the 

position description. Its location should be referenced in the manual.) 

8. How does an operator or individual receive FAA approval to use an electronic 

recordkeeping system? 

a. Announcing Intent to Use Electronic Recordkeeping. Certificate holders and operators 

intending to use electronic recordkeeping should consult with their local FSDO or CHDO before 

implementing an electronic system. To obtain FAA approval, the certificate holder or operator 

must submit a letter to the appropriate FSDO or CHDO (see Appendix 1 for sample letter) 

describing the proposed system and include the proposed section or revision to the operator’s 

manual. 

b. Description of Electronic System and Proposed Manual Changes. The electronic 

system description should explain how the electronic recordkeeping will be used in the 

operator’s maintenance and operational activities. The proposed manual section or revision 

should clearly state who in the organization has authority and the overall responsibility for 

implementing, modifying, revising, and monitoring the electronic recordkeeping computer 

software. 

c. FAA Approval Process. The appropriate FAA Principal Inspector will review the

electronic recordkeeping proposal. If the proposed electronic hardware and computer software 

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10/29/02 AC 120-78 

system meets the elements of this AC, the inspector will make the appropriate entry on the

operator’s operation specifications. For a part 91 operator, the regulations do not require FAA 

approval; however, if the part 91 operator wants to submit its electronic system to the local 

FSDO, the FSDO will review the operator’s proposed procedures. If the procedures are 

acceptable, the FSDO will provide the operator with a letter of acceptance (see Appendix 2 for 

sample letter).

DISCUSSION—ELECTRONIC MANUALS 

9. What is an acceptable electronic manual?

a. General. Assuming its contents have been FAA approved, manuals on CD-ROM, 

Internet-based systems, or other electronic media are acceptable. 

(1) These electronic formats offer improved data accessibility, quality control, and speed 

distribution over paper or microfilm-based information storage systems that result in enhanced

safety. In addition, the industry and government should experience a reduced economic burden 

because users will have rapid access to information at reduced cost as well as improving the 

presentation of technical data contained in a certificate holder’s or operator’s manual(s). 

Presentation is improved by using media formats incompatible with the use of paper or

microfilm-based manuals such as visual displays, video, graphic files, audio, animation, and 

computer data files. 

(2) Electronic manual computer hardware and software systems must deliver the same, 

or better, accuracy and integrity maintained by paper/microfilm-based systems. In addition, 

electronic manuals must still comply with requirements about the currency, completeness, use, or 

availability of the technical data. 

b. Electronic Manual Construction. When constructing an electronic manual to meet the 

operational and maintenance requirements addressed in this AC, the following elements must be

considered and addressed. 

(1) Storage and Retrieval. Computer hardware and software system must store and 

retrieve the manual’s technical data under conditions of normal operation and use. The system 

must not permit unauthorized modification of the data it contains. 

(2) Maintenance and Support. Maintenance and support for the system, including

provisions for outages and necessary alternative retrieval services, may be provided by sources 

independent of the certificate holder or operator. However, the certificate holder or operator is 

still responsible for compliance with all regulatory requirements and cannot be delegated.

(3) Access to Manual. Appropriate certificate holder or operator personnel must be able 

to access the manuals. Procedures for distributing the manuals/technical data may be similar to 

procedures distributing information contained in paper or microfilm manuals. Certificate holders

or operators may use their current manual distribution system to distribute electronic manuals.

(4) Revisions to Manual. Procedures will be established to verify that revisions (i.e., 

incremental, temporary or scheduled revisions) to the technical data contained in the 

maintenance portion of its manual are current and complete. In addition, revisions must be 

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AC 120-78 10/29/02 

approved by the appropriate authority before distribution. FAA approval may be accomplished 

in accordance with subparagraph d below, Revision Control Procedures.

(5) FAA/NTSB Access. Any FAA or NTSB authorized representative must be able to 

retrieve, print, or view the information in any electronic manual. If a certificate holder or 

operator is required to provide information to the FAA or NTSB, they should provide the record 

in a format usable by the requesting agency.

(6) User Instructions. Users will be provided information describing the electronic

system’s use and operation. Such information will include instructions for using publications, 

reference information, and system administration information. These instructions need not be in 

paper form. They will consist of the following: 

Electronic, context-sensitive help 

Online or system responses to specific operator queries 

Telephonic or electronic access to a designated assistance line 

Other information included in the electronic system

(7) Training. A training program will be provided to employees or contractors who use

the electronic manual. The subject matter and objectives of the training will vary depending on 

the employee or contractor job responsibilities and function level within the organization. 

Customer training will include security awareness and policy and procedures for the system. 

Acceptable methods of providing this training may include, but are not limited to, classroom 

instruction, online or system tutorials, user guides, and simulated problem-solving exercises. 

Any training program will define minimum competency criteria and the method for users to 

demonstrate competence. 

(8) Enhancements. Additional features (such as text searching, hypertext links, or other 

enhancements) that facilitate access to the information are generally not required for a system to 

be approved. 

c. Functional Considerations. 

(1) The electronic system should allow users to retrieve the technical data from any

electronic manual stored in the system. The electronic manual should be able to access, navigate, 

and retrieve applicable information at a computer workstation. Information stored in the 

electronic manual may occur in either a stand-alone or a shared environment.

(2) The content of an electronic manual must be clearly identifiable and vieweable by the 

user. This material must easily correlate to corresponding information in a printed version of the 

manual. Requested information must be displayed on a computer screen or comparable device. 

If connected to a paper printer, the system must be able to print any information contained in an 

electronic manual. 

d. Revision Control Procedures. These procedures apply to organizations operating under 

an FAA-issued certificate with a continuous aircraft maintenance program. Electronic or paper 

manual revision can be submitted to the appropriate FAA FSDO/CHDO and the appropriate 

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10/29/02 AC 120-78 

FAA Principal Inspector for approval via electronic data transfer, e-mail, or paper. This 

submission will normally contain a cover letter that requests approval and gives a brief

description of the revision. After reviewing the revision, the FAA Principal Inspector will send 

back to the certificate holder an e-mail or paper memorandum approving or rejecting. In most 

cases, the approval of manual revisions only require the principal inspector to initial and date the

list of affected pages. However, if the computer system uses a continuous flow of information 

process, a table of revisions should be used. The table of revisions must contain each chapter, 

section, task or sub-task number to be revised. With a table of revisions, the same process of 

initialing and dating the list of affected sections will apply. In either case, the copy of signed

revisions will become archive copies of the manual revisions for the operator and the FAA.

(1) Validation of Revision Control Procedures. Procedures must be established to 

audit the revision process to ensure contents of the electronic system are current and complete. 

The revision control procedures for electronic manual data may be similar to the revision control 

procedures used for other storage media.

(2) Revision Transmittal Letter/Release Notes. Many certificate holders and operators 

frequently use internal distribution documents that specify the current revision number and date 

for each revision. If this document is provided separately, it conveys the revision number and 

date with applicable instructions to the users. A user can inspect and review this documentation 

to determine data currency. 

(3) Data Currency Audit. Procedures must be established to ensure the currency of the 

technical data (regardless of the storage media). They must ensure that all electronic storage 

media contain the current revision and associated revision dates. With electronic media, page

level insertion audits of manuals may no longer be necessary for users to ensure information 

currency.

(4) User Responsibility. Users of information or printed data from electronic manuals 

systems must ensure the information or printed data is from the most current manual. 

e. Special Considerations in Displaying Information. 

(1) Data Content and Information Form. 

(a) Information retrieved from an electronic manual might be displayed in a different 

format than it appears on paper or microfilm pages. These formatting differences may be caused 

by advancements of electronic retrieval systems. The information should be identical in content 

regardless of its format. 

(b) Any computer-displayed information should be readily traceable to its original 

source. This information must be readily accessible to the user and should be able to obtain the 

following: 

The manual title

Applicable aircraft, airframe, engine, propeller, appliance, component, or part 

make and model 

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AC 120-78 10/29/02 

Effective date of the data

Revision simultaneously displayed with the technical data (e.g., on the 

computer screen) 

(2) Page Numbers and Revision Data.

(a) Complete display of traditional letter size (8.5” x 11”) documents may not be 

possible on certain computer displays. Frequently, the video monitor will display only one-third

to one-half of a paper page, and the user must scroll through the on-screen display to see the

complete page. In addition, some systems may print an entire page although the video monitor 

displays only a partial page. This situation may result in electronic systems assigning,

displaying, or printing page numbers not matching the approved copy of the manual. Therefore, 

certificate holders and operators must ensure information displayed or printed can be traced to

the correct revision level of the manual. 

(b) The contents of a chapter, section, or subject in a maintenance manual may be 

displayed as a continuous flow of information without displaying the actual page numbers of the 

approved manual. The user may elect to display only a portion of a manual page. If this occurs, 

the organizational format of the manual should be retained, and a means of referencing the 

section or page of the manual from which the data was obtained should be provided. Some 

electronic manuals systems may provide a page number as with paper manuals. Some systems 

will only provide the chapter, section, and a page block or task number. In these cases, the user 

must output such blocks of information after selecting them.

(3) References to specific chapters, sections, or paragraphs of the manual may be used to 

ensure information traceability to corresponding sections of a printed version. This permits the 

technical data to be easily referenced by the user and ensures traceability of the information to its 

source. 

(4) The most common method of updating a manual is to issue a revision with a list 

identifying the pages to which the revision applies. Each subsequently revised page contains the 

revision status. This same process may be applied when the manuals are in electronic format. 

The FAA recommends that certificate holders and operators prepare a table of revisions. That 

table should be included in the electronic manual to show when each page of the manual was 

revised. Some electronic manuals using a continuous flow of information process may not be 

capable of producing a list of effected pages. Therefore, a table of revisions needs to contain the 

revised manual, chapter, section, subject, task or sub-task numbers. 

f. Data Archive. A maintenance recordkeeping requirement often requires retention or 

access to previously used technical data to support or verify a method of repair or maintenance. 

To comply with those traceability requirements, a certificate holder or operator must archive 

earlier versions of manuals to provide for future needs to duplicate, regenerate, or reconstruct 

maintenance instructions. The archived materials should be obtained from the original source of 

the data. Regardless of the source, the certificate holder or operator is responsible for ensuring

the availability of any required record. 

(1) Preservation of Stored Data. Procedures will be established to ensure the integrity

of the stored technical data, regardless of the storage medium. These procedures should include: 

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10/29/02 AC 120-78 

Ensuring that no unauthorized changes can be made 

Selecting storage mediums that minimize regeneration of errors or deterioration 

Exercising, refreshing, or duplicating archived technical data at a frequency

compatible with the storage life of the medium (i.e., before the storage medium 

deteriorates)

Storing duplicate copies in physically separate archives to minimize the risk of

data loss in the event of a fire or natural disaster 

(2) Technological Advances. Certificate holders and operators should ensure all 

electronic systems components are maintained to enable retrievable archived manuals. Future 

changes in data storage media may result in a need to replace current computer hardware or a 

need to use another storage medium. Future systems must be able to retrieve archived technical

data. Otherwise, the certificate holder or operator will have to maintain the old system to ensure

data availability. 

10. How does a certificate holder or operator receive FAA approval to use an electronic 

manual? 

a. Announcing Intent to Use Electronic Manual. Certificate holders and operators 

intending to use an electronic manual should consult with their local FSDO or CHDO before 

implementing an electronic system. To obtain FAA approval, the certificate holder or operator 

must submit a letter to the appropriate FSDO or CHDO (see Appendix 1 for sample letter) 

describing the proposed system and include the proposed section or revision to the operator’s 

manual. 

b. Description of Electronic System. The electronic system description should explain how 

the electronic manual will be used in the operator’s maintenance and operational activities. The

proposed manual section or revision should clearly state who in the organization has authority

and the overall responsibility for implementing, modifying, revising, and monitoring the 

electronic manual computer software. 

c. FAA Approval Process. The appropriate FAA Principal Inspector will review the

electronic manual proposal. If the proposed electronic hardware and computer software system 

meets the elements of this AC, the inspector will make the appropriate entry on the operator’s

operation specifications. For a part 91 operator, the FSDO will review the operator’s proposed 

procedures. If the procedures are acceptable, the FSDO will provide the operator with a letter of 

acceptance (see Appendix 2 for sample letter).

11. Are there any related documents? 

a. Title 14 CFR: parts 43, 61, 65, 91, 119, 121, 125, 129, 133, 135, 137, 141, 145, and 147. 

b. FAA Orders. Copies of the following documents may be purchased from: New Orders, 

Superintendent of Documents, P.O. Box 371954, Pittsburgh, PA 15250-7954. 

Par 9 Page 13 
AC 120-78 10/29/02

(1) Order 8300.10, Airworthiness Inspector’s Handbook. 

(2) Order 8400.10, Air Transportation Operations Inspector’s Handbook. 

(3) Order 8700.1, General Aviation Operations Inspector’s Handbook. 

12. Does this AC cancel any prior ACs? 

This AC cancels AC 120-69, Use of CD-ROM System, dated August 14, 1997. 

13. How can one get this and other FAA publications? 

a. You can get the federal aviation regulations and those ACs for which there is a fee from 

the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402. 

You can view a list of all ACs at http://www.faa.gov/RegulatoryAdvisory/ac_index.htm. You 

can view the federal aviation regulations at

http://www.access.gpo.gov/nara/cfr/cfrhtml_00/Title_14/14tab_00.html. 

To request free ACs, contact: 

U.S. Department of Transportation 

Subsequent Distribution Office

Ardmore East Business Center 

3341 Q 75th Avenue 

Landover, MD 20785

b. To be placed on FAA’s mailing list for free ACs, contact:

U.S. Department of Transportation 

Distribution Requirements Section, 

SVC-121.21 

Washington, D.C. 20590 

/s/ Louis C. Cusimano for

James J. Ballough 

Director, Flight Standards Service 

Page 14 Par 11 
10/29/02 AC 120-78 

 Appendix 1 

APPENDIX 1. 

SAMPLE LETTER OF INTENT FOR NON-CERTIFICATE HOLDERS

[Requester Letterhead]

To: [FAA Flight Standards District Office with geographic jurisdiction over the 

requester’s operations] 

From: [Requester] 

Date: [Date] 

Subject: Use of Electronic System - Signatures/Recordkeeping/Manuals 

This letter is to inform you that [requester non-certificate holder] intends to use an electronic 

(signatures and/or recordkeeping and/or manual) system for [describe what the system will be

used for]. This system has been established using the guidelines outlined in FAA Advisory

Circular 120-78. 

This organization intends to implement the system on [date].

Company facilities, equipment, and personnel are available for your review and/or inspection at 

[address] on [date]. Please contact [name] at [telephone] to arrange a visit to review the system 

and to discuss any FAA concerns. 

Thank you in advance for your assistance in this matter.

Sincerely,

[Requester]

Page 1 (and 2) 

10/29/02 AC 120-78 

 Appendix 2 

APPENDIX 2. 

SAMPLE LETTER OF FAA ACCEPTANCE FOR 

NON-CERTIFICATE HOLDERS

Federal Aviation Administration 

San Antonio Flight Standards District Office 

1992 Barrett Avenue 

Travis, Texas 76321 

[Date] 

Mr. John Smith 

1234 South Airport Way

San Antonio, Texas 78910 

Dear Mr. Smith: 

This letter confirms acceptance of the electronic system used by the owner/operator of 

[registration number or attached list]. The electronic system for (signatures, and/or 

recordkeeping, and/or manuals) meets the requirements of Title 14 of the Code of Federal 

Regulations, part 91. The accepted procedures meet the intent of the AC 120-78, Acceptance and 

Use of Electronic Signatures, Electronic Recordkeeping Systems, and Electronic Manuals. 

FAA acceptance is limited to those individuals who are trained by the owner/operator in the use 

of electronic equipment in accordance with the owner’s/operator’s required procedures. 

This office should be notified of any significant changes in the design or operation of the system. 

The FAA should have access to the system at all times. Any changes to designated FAA user 

identification codes or passwords should be submitted to the FAA Flight Standards District 

Office as soon as practical after the change. 

Unless withdrawn, this letter is valid indefinitely, and should be transferred with the aircraft 

records as part of any aircraft ownership transfer. 

Sincerely,

[Name]

Aviation Safety Inspector [Operations and/or Maintenance] 

Page 1 (and 2)