Approved data can be: type certificate data sheets (TCDS), supplemental type certificates, (STC), airworthiness directives (AD), airframe/engine/propeller FAA-approved instructions, appliance manufacturer's manuals or instructions (even if they do not specifically state they are FAA approved), CAA Form 337 dated prior to 10/1/55, FAA Form 337 field approved for multiple installation in Block 3, technical standard order (TSO), DER-approved data, designated alteration station (DAS), designated option authorization-approved data, repair data performed under a SFAR 36 for the holder's facility only, parts manufacturer approval, and anything stamped "FAA Approved Data." If you cannot find the approved data to make the repair or alteration from the list above, the next step would be to apply for an STC or a field approval.
Not a field approval
Field approvals are not covered under a regulation. The field approval process is covered under FAA policy in FAA Order 8300.10 Volume 2 Chapter 1. Because the field approval is a procedure, dictated by policy and not a rule, the mechanic is not automatically entitled to a field approval - even if the mechanic submits a "perfect" FAA Form 337 to the FAA. And why not? Because the authority to grant a field approval and the great burden of responsibility that goes with signing Block 3 of the FAA Form 337 has been delegated only to the local FAA FSDO airworthiness inspectors.
FAA inspector's responsibility
Before granting a field approval, the FAA inspector must determine that the affected aircraft or component part can be expected to operate safely and conform to the regulatory requirements by which the aircraft or part was certificated under.
The responsibility for data approval is so monumental that no one, not even the FAA administrator, may force the inspector to approve or deny a field approval for major repair or major alteration against the inspector's better judgment. The inspector's judgment is based on his or her level of knowledge, skills, experience, and background in the aircraft or component in which the major repair or alteration is going to be performed.
For example, if the inspector has no experience with installing fuel tanks for rocket fuel in hot air balloons, then he or she should deny the request. This does not mean the mechanic is left out in the cold. He is welcome to find another inspector in the same office or another inspector in another FAA office with the experience and background to sign off Block 3.
Since it's the inspector who makes the final decision and is held accountable by the FAA for that decision, most inspectors are overly cautious when it comes to signing off a field approval. Wouldn't you be? Have you ever worked along side any mechanic during your aviation career that you would not sign off anything he did? Yet, mechanics routinely submit requests for field approval to FAA inspectors who barely know them let alone worked along side of. This makes inspectors a little nervous when their career is on the line.
When I taught FAA inspectors the major repairs and major alteration course at the FAA Academy, and when I wanted to emphasize the importance of this approval and the need to do it right, I said this to my students: "When you sign Block 3 of the FAA Form 337 you cease being a judge and become a partner in the major repair or alteration being performed."
Another thing mechanics should consider is that the FAA inspector does not get "points" for each Block 3 the inspector signs. Field approvals are listed as demand work in the inspectors work program. The inspector is graded on his or her performance on required items such as Part 145 inspections or surveillance of Part 121 or 135 operators.
So the next time the FAA inspector signs a Block 3 for you, don't forget to thank your partner who signed his life away, just like you did on the bottom of the Form 337.
What cannot be field approved?
Some major alterations are so complex that it would take a whole team of engineers to put their arms around it. So the policy folks in Washington put forth a list of major alterations that require engineering approval or even an application for an STC in FAA Order 8300.10. The following is a partial list of items that cannot be field approved.
1. Increases in gross weight or major changes to center of gravity range.
2. Installation or relocation of equipment that may adversely affect structural integrity or flight or ground handling characteristics of the aircraft.
3. Any alteration of the control surfaces' dimensions, travel, or balance.
4. Changes to the aircraft's basic dimensions or external configuration.
On May 21, 2003, seven months after the Federal Aviation Administration (FAA) made the first substantive revision to field approval policy in 20 years
The Question: To field approve or to STC? By Joe Hertzler R ecently I was studying the field approvals of FAA Form 337s, what I consider to be the hottest issue between the FAA and...
In Part 2 of my tome on field approvals, we will cover current field approval policy found in Change 16 to FAA Order 8300.10.
My father was a big man, straight from the old sod. He was a lot smarter than I and a card-carrying survivor of the depression years.