FAA Form 337
This class is to provide you with a basic
understanding of the FAA Form 337.
You will learn the uses of this form and
information about completing some of
On the next few slides we will see the
front and back of the Form 337.
At the top of the form itself are
See FAR 43.9, FAR 43 Appendix
B, and AC 43.9-1 …for instructions…
It also states that:
“This report is required by law. Failure
to report can result in a civil penalty
for each such violation.”
The current version of FAA Advisory
Circular 43.9-1() provides instructions
for completing FAA Form 337, Major
Repair and Alteration (Airframe,
Powerplant, Propeller, or Appliance).
FAA Form 337 is used to document
two things, and only two things:
This means that you need to know how
to determine what is a major repair or
major alteration. That is outside the
scope of this class (actually, it is a
class all by itself!).
A comment about documenting major repairs.
Due to an exception in Part 43, Appendix
B(b)2, a Repair Station may document a
Major Repair using a signed copy of the
work order in lieu of the Form 337.
So there may be occasions when you
perform a major repair and don’t issue a
337. This is based on customer
preference. We will use either a 337 or the
work order to document a major repair,
depending on what the customer wants.
Appendix B TO PART 43 states:
“Execute FAA Form 337 at least in
“Give a signed copy of that form to the
“Forward a copy of that form to the FAA
Aircraft Registration Branch in Oklahoma
City, Oklahoma, within 48 hours after the
aircraft,….is approved for return to
The Duncan Aviation RSGOM states:
“An original signed FAA Form 337 is
provided to the aircraft owner or
operator. A copy shall be sent to the
FAA in Oklahoma City and a copy is
stored with the work order.”
Duncan Aviation minimum requirements:
One original, Two copies.
Item (Block) 1
A 337 can only be issued to an aircraft!
Not a component part. Doesn’t make any
difference if you worked on a cabinet,
engine, prop or other appliance. The 337
is for the aircraft the item is installed on.
This affects “send in” or spare
components in a big way. Here’s how….
When a major repair or major
alteration is made to a component
part, items (blocks) 1, 2, and in some
cases 5 will be left blank and the
original and duplicate copies of the
form (337) will remain with the part
until it is installed on an aircraft.
So let’s understand this.
We can perform a major repair or
alteration to a spare part. We can fill out
all of a 337 (including signing it) except
items 1 and 2. The part can sit in the
warehouse for weeks or months. The
person who installs the part onto an
aircraft fills out items 1 and 2 and then
has 48 hours to forward a copy of the
completed 337 to the FAA after approving
the aircraft for return to service.
Item (Block) 1
Nationality and registration mark:
The FAA only accepts 337s for US
registered (N) aircraft. If you are
providing a “courtesy” 337 for a
foreign registered aircraft, don’t bother
sending a copy to the FAA. They
won’t take it. The FAA only maintains
information for US registered aircraft.
Item (Block) 3
For FAA Use Only.
Block 3 is used by the FAA for field
Field approval refers to a method of
approving the data for a major repair
or major alteration. When this method
is used by the person completing the
337, all data is submitted to the FAA
for approval. Once the FAA has
approved the data, they will sign in
block 3 showing their approval. This
is commonly referred to as a field
If you need to use the field approval
method, here’s a tip:
Get your data approved before you do
There is nothing quite as discouraging as
fixing up an airplane in a way you think is
great, only to have the FAA disagree and
want it done another way! And that could
happen if they don’t agree with your data
on a field approval.
Item (Block) 6
When you sign this, you are taking full
responsibility that you know what was
done and that it conforms to the data
and Part 43 maintenance
At Duncan Aviation, the person signing
here must be an Inspector
Block 6 asks for the name and address of
the person (agency) who did the work, the
kind of agency (mechanic, repair station,
etc), their certificate number, the date they
finished the work and their signature.
Duncan inspectors sign as agents of
Duncan Aviation. When signing on behalf
of Duncan, we check the box next to
“Certificated Repair Station” and use the
repair station number, not your personal
Notice the statement in box “D”. This is
what you are certifying when you sign.
You are certifying that the repair or
alteration conforms to the description (or
data) shown on the back of the 337 along
with any attachments.
Thus, you are making the conformity
statement for the repair or alteration.
Item (Block) 7
Approval for Return to Service!
This is the block where the repair or
alteration is either Approved for return to
service, or Rejected for return to service.
If you’re involved with installing a part that
has a 337 with it, make sure that item 7 is
Where block 6 says the work conforms to
the data, block 7 says it has been
inspected and is approved for return to
service (also called RTS approval)
(RTS = Return To Service)
Conformity and RTS approval are two
Notice the first line. It says the unit was
inspected and then gives you the choice
to declare it “Approved” or “Rejected”
One of these boxes must be checked!
(Hopefully “Approved”) But you must
inspect the work before you know if it can
be approved. Does this mean you
personally must go and look at the repair
or alteration and verify every single
If you do not personally inspect every
detail, you absolutely have the
responsibility to ensure that properly
authorized Duncan Aviation inspectors
signed off on their respective portions of
As a repair station, our system allows an
inspector to review individual squawks stamped
by other qualified inspectors as a means to
Once a date is put in block 7, you
started a countdown!
You have 48 hours to get a copy in
the mail to the FAA.
for send in items (those 337s will be
mailed by the person installing the
item on the aircraft.)
Item (Block) 8
Description of Work Accomplished
Sounds self explanatory, right?
And to some degree, it is. Describe
the work in sufficient detail that a
person unfamiliar with the job can
understand what was done.
Other things that we want to include in the
Description of Work Accomplished:
The FAA Approved Data that was
Any change to the Weight and Balance
ICA (Instructions for Continued
Any Flight Manual Supplements.
Instructions for Continued
Generally these usually apply to
major alterations, but some major
repairs may affect the Inspection
Program the aircraft is following!
So, if you have performed a major
alteration, the FAA wants to ensure
the owner/operator has the necessary
knowledge to maintain the “altered
You must put in some type of
information that tells the operator how
to inspect and maintain this alteration
you just signed off.
* Thank You *
That completes the training on FAA
Form 337. You now have knowledge
of when this form is used, and how to
review one to ensure all information is
there, and what to do with the
If you have any other questions, feel
free to ask any Chief Inspector or
Quality Department Inspector.
1. Instructions for completion of FAA Form 337 are contained in
what FAA document?
2. What is a field approval?
3. What two types of work may be documented on the 337?
4. What type of data must be referenced in block 8?
5. What must be done with the original 337?
6. How many copies must be made of the 337?
7. What must be done with the copies?
8. Will the FAA accept a 337 issued for a foreign registered
9. What data is put in block 8?
10. Who signs block 3, and why?