FAA Feedback: So You Say You Want a Field Approval?

June 20, 2014
A field approval is the granting, by an FAA airworthiness inspector, of FAA “approval” for a major repair or major alteration.

“Getting an FAA field approval is a lot like getting an elephant pregnant. 1. It’s harder work than anyone would imagine, 2. It’s accomplished by a lot of screaming and yelling, 3. Both parties are not sure of what the other is doing, and 4. It takes 19 months before you see any results.”

What is a field approval?

A field approval is the granting, by an FAA airworthiness inspector, of FAA “approval” for a major repair or major alteration. The approval is given only after conducting a physical inspection and/or after reviewing data.

There are three different kinds of field approvals for which the local FAA inspector can sign off:

Examination of data only: This is the most common form of field approval. The mechanic or repairman submits “acceptable” data to the local FAA office for approval. The “approved data” can be used to perform a major repair or major alteration.

Once the data has been approved under this procedure, it can be used only for that one aircraft (describe in Block 1 of FAA Form 337).

However, if you want to do the exact same repair or alteration to another like make or model aircraft you can use the original Form 337 as the basis for obtaining a new field approval for the second aircraft.

Physical inspection, demonstration or testing of the repair or alteration: This is rarely done except in cases where technicians find unapproved engine or components installed on aircraft, which apparently have been installed for some time. Since the aircraft has flown successfully for many hours, an FAA inspector can, if satisfied with the installation, approve the installation. He does so by signing a new Form 337.

Examination of data only for duplication on identical make and model aircraft by the original modifier: This is a procedure that saves the maintenance technician and the FAA a lot of time. For example, one technician wants to install duplicate avionics packages on as many Cessna 501s as possible; or maybe he wants to install duplicate installations of tundra tires on Beech 18s.

The technician can submit the data to be approved along with a request that the data approved be extended to other identical aircraft. The FAA inspector, if satisfied, signs Block 3 that grants duplication of the data from the original Form 337.

When the technician finishes a duplicate alteration on other aircraft, he sends the FAA a regular FAA Form 337 properly filled out listing the “approved data” on the back and making reference to the field approval. To avoid problems, attach a duplicate copy of the original Field Approval Form 337.

What a field approval is not

A field approval is not a regulation; it’s a policy.

Because it is a procedure and not a rule, a mechanic is not automatically entitled to a field approval – even if he submits a “perfect” FAA Form 337 to the FAA.

Why? Because the authority to grant a field approval and the great burden of responsibility that goes with signing Block 3 of the Form 337 has been delegated only to the local FAA district office airworthiness inspector.

The responsibility for data approval is so monumental that no one, not even the FAA Administrator, may force the inspector to approve a major alteration or major repair against his or her better judgment.

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.

Why do you need a field approval?

Four regulations, FAR 65.95, FAR 121.378, FAR 135.437 and FAR 145.51 all require “approved” data for major repairs and major alterations.

Approved data can be type certificates data sheets (TCDS), airworthiness directives (AD), Designated Engineering Representative (DER) data, Designated Alteration Station (DAS) data, FAA-Approved Manufacturer’s Data Supplemental Type Certificates (STC) and appliance manufacturers’ manuals.

If you can’t find approved data of this type, your only chance for getting data approved is to apply to the FAA for an STC, or to ask a local FAA inspector for a field approval.

What can’t be approved?

Some repairs and alterations are so complex they’re actually design changes and require an STC. The following alterations are examples of alterations that can’t be field approved.

  • Installations that increase gross weight and/or changes in center of gravity range.
  • Any installation that affects structural integrity, flight or ground handling.
  • Changes in movable control surfaces or travel.

Helpful hints for field approvals

• First do not cut metal, splice wire or install equipment until you receive the approval. The only thing worse than not getting a field approval is telling your customer the fancy equipment you installed in his aircraft has to be removed.

• Determine if the repair or alteration is major as defined by FAR 1. If it’s major, go to the next step.

• Don’t set unreasonable goals. Allow a reasonable time, at least 30 days for the field approval.

• Research all sources for “approved data” to make the repair or alteration. If you find approved data in the type certificate under optional equipment or under notes, sign off the repair or alteration in the logbook. No Form 337 is required because the repair or alteration has already been approved under the type design and is considered minor. For all other approved data, a Form 337 is required. If there’s no approved data, go to the next step.

• Call or visit the FAA inspector and describe your repair or alteration. Find out what kind of data the inspector wants to see. Then assemble it in a reasonable and understandable format. The data must be current, accurate and must support as well as describe the alteration or repair. Data can be in the form of drawings, sketches or photographs. References to AC 43.13-IA and 2A, manufacturer’s maintenance manuals, kits, bulletins and service letters may be helpful.

• A cover letter for the Form 337 describing in detail how you’re going to accomplish the repair or alteration is also helpful. Vague or useless technical references are unprofessional and should be avoided because it destroys your credibility.

• With your research done send the FAA inspector duplicate copies of the Form 337 along with the data you want approved.

If you did your homework carefully and followed these helpful hints, you’ll have a 75 percent chance of getting your repair or alteration approved on the first attempt. If you don’t, find out what’s wrong and try again.

This article first appeared in the January/February 1992 issue of Aircraft Technician.

About the Author

Bill O'Brien