Experimental Airworthiness: The certification process

The certification process

Joe Hertzler

Let’s take a look at the background, progress, and current situation surrounding the use of an Experimental Airworthiness Certificate to authorize flight following installations of equipment as a part of the certification process of a Supplemental Type Certificate.

On April 23, 2002, the FAA issued Order 8130.29 to supersede policy memorandum 2000-03 issued March 28, 2000. The title of the new order is "Issuance of a Special Airworthiness Certificate for Show Compliance Flight Testing." Although subtle, one change stands out between the previous policy memo and the new order and leaves the industry in an unfortunate situation. The new order includes the following statement under the procedures section of the order:

FAA Order 8130.29 paragraph 6(e)(3)(a): "(a) The applicant must ensure the aircraft is in compliance with all of the airworthiness regulations for its current standard airworthiness certificate."

Some may look at this statement and think that it is simple to show the aircraft is eligible for its current standard airworthiness certificate. But the fact is, the person who needs to be satisfied is the FAA Safety Inspector or designee in charge of the issuance of an experimental certificate. In most cases, such satisfaction is no different than a complete re-certification or issuance of a standard airworthiness certificate under the requirements of FAA Order 8130.2. With this new order, we now must meet those requirements before the experimental certificate is issued rather than when the standard certificate is to be reinstated. But the issue is deeper than that.

In addition to this significant change, there are a few terms, both in the regulation, and in this new FAA Order that, left without further explanation, lead FAA field engineers and inspectors to request more from STC applicants than is required. Let’s look at the impact and the need to request further action by the FAA on this issue.

There are really two issues:

1. The FAA, with little or no matrix or guideline on what type of change should require a Show Compliance Flight Test, determines the need for a show compliance flight test vs. adequate ground testing.

2. The use of an Experimental Airworthiness Certificate for required Show Compliance test flights is "not appropriate" according to Amendment 21-21.

What requires a Show Compliance Flight Test?

As an industry we are involved in modifications of business and commercial aircraft ranging from minor installations to major design changes that encompass many areas of an aircraft. The modifications that are performed are nearly always tested in the air following the installation even though the modifications do not always require such flights. The purpose of a flight can vary but in most cases significant ground testing has been performed to demonstrate compliance and the purpose of the flight test is only to make minor adjustments or identify minor programming changes.

Even though the intent of the regulation (21.191 (b)) exempts most modifications that are performed due to lack of need to flight test that aircraft, the misinterpretation by the FAA, at the field level, has created a great deal of costly and unnecessary work.

The issue really is that many FAA field engineers believe that because the aircraft has been subject to the Supplemental Type Certificate (STC) process that it is not possible to "show compliance" sufficient to "approve for return to service," (thereby reinstating the current standard airworthiness certificate) until the aircraft has been test flown. It is obvious that in some cases, an operational flight test must be conducted in order to "show compliance". But 14 CFR Part 21 provides some guidance as to what type of change should warrant such a flight.

21.93 Classification of changes in type design

Paragraph (a) reads: In addition to changes in type design specified in paragraph (b) of this section, changes in type design are classified as minor and major. A "minor change" is one that has no appreciable effect on the weight, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness of the product. All other changes are "major changes" (except as provided in paragraph (b) of this section).

Paragraph (b) is relative to the noise levels emitted from an aircraft and refers to a change in noise levels as "acoustical change".

CFR Part 1 defines a major alteration as an alteration not listed in the aircraft, aircraft engine, or propeller specifications that:

(1) Might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or

(2) Is not done according to accepted practices or cannot be done by elementary operations.

Next, let’s look at the similarity contained in 14 CFR Part 91 relative to the maintenance of the aircraft:

91.407 Operation after maintenance, preventive maintenance, rebuilding, or alteration

Paraphrasing, paragraph (a) of this regulation states that an aircraft that has undergone maintenance, preventive maintenance, rebuilding, or alteration may not be operated unless it has been approved for return to service by a person authorized under 43.7, and the maintenance record entry required by 43.9 or 43.11 has been made. In the certification world, what this means is that the standard airworthiness certificate for an aircraft that has undergone alteration is not effective until the aircraft is approved for return to service in accordance with Part 43.

Now, it is paragraph (b) that really stands out as a common theme with the other areas of the regulations. Paragraph (b) reads:

No person may carry any person (other than crewmembers) in an aircraft that has been maintained, rebuilt, or altered in a manner that may have appreciably changed its flight characteristics or substantially affected its operation in flight until an appropriately rated pilot with at least a private pilot certificate flies the aircraft, makes an operational check of the maintenance performed or alteration made, and logs the flight in the aircraft records.

Appreciably is defined by Webster as "to a noticeable degree."

Substantially is defined as "to a great extent or degree."

So, this rule could be read as: . . . in a manner that may have, to a noticeable degree, changed its flight characteristics or, to a great extent or degree, affected its operation in flight . . .

Finally let’s look at 14 CFR Part 21.191 which covers the use of Experimental Certificates:

21.191 Experimental Certificates

Experimental Certificates are issued for the following purposes:

(a) Research and development. Testing new aircraft design concepts, new aircraft equipment, new aircraft installations, new aircraft operating techniques, or new uses for aircraft.

(b) Showing compliance with regulations. Conducting flight tests and other operations to show compliance with airworthiness regulations including flights to show compliance for the issuance of type and supplemental type certificates, flights to substantiate major design changes, and flights to show compliance with the function and reliability requirements of the regulations.

(c) Crew training. Training of the applicant’s flight crews.

(d) Exhibition. Exhibiting the aircraft’s flight capabilities, performance, or unusual characteristics at air shows, motion picture, television, and similar productions, and the maintenance of exhibition flight proficiency, including (for persons exhibiting aircraft) flying to and from such air shows and productions.

(e) Air racing

(f) Market surveys

(g) Operating amateur-built aircraft

(h) Operating kit-build aircraft

Now, let’s go back to the new FAA Order, 8130.29:

FAA Order 8130.29, Paragraph 6(a) states: The applicant’s package should enable the ACO project engineer to determine whether flight testing to show compliance with airworthiness regulations is necessary or whether other means, such as analysis and/or ground testing, could be used instead.

So, what’s the point? The point is there are hundreds of changes to type design that take place even within the context of a single STC. Each package should be looked at individually and the major changes in type design differentiated from the minor. Once the major changes are clear, then a determination as to whether or not a Show Compliance Flight Test will be required should be made. If the major change that has taken place has nothing to do with the certification weight of the aircraft, the balance envelope as previously certificated, strength of the structure of the aircraft, or the operational and flight characteristics, for example, it probably really doesn’t need to be flown to "show compliance." But there is no matrix type guidance to the ACO project engineers that will help them make that decision.

Due to the technology explosion we have experienced over the past 15 years a large percentage of the STC’s applied for, many which are one-time STC’s, are for the installation of new navigation and flight management equipment. These new systems are installed as secondary to the primary means of navigation for the aircraft anyway, and could be turned off in flight without causing an incident. The drawings created and approved by the FAA provide a method by which the installation can be inspected and tested on the ground. The inspection is to conform to the drawings and to show proper form, fit, and function. The drawings will have been reviewed and approved, meaning they have been found to conform to the current regulatory requirements. In many cases, once installed, the new equipment can be activated on the ground and verified to operate properly. Following these successful ground tests for show compliance should have satisfied the FAA. A flight could then easily be conducted "not predicated on the use of the new equipment" and proper operation of the equipment verified. It is the norm, however, rather than the exception for the FAA to require a production flight test "Show Compliance Flight Test" even for avionics equipment upgrade-type of installations. The FAA’s reasoning for requiring an operational check flight is to check for electromechanical interference (EMI). Understanding that the equipment in question has been turned on and found to function properly on the ground, and can be turned off in the air without incident, it is amazing that this sort of test would require an Experimental Airworthiness Certificate. Consider this, when a Learjet Model 35 receives a 12-year inspection, the leading edge of the Learjet Model 35, (and many other Learjet models) is removed and the wing structure under the leading edge is inspected. The leading edge on the Learjet is so critical that just the removal and reinstallation can cause the aircraft to stall differently. For this reason, before that aircraft can be "approved for return to service," a flight test pilot from Learjet must perform a "stall flight" and verify that the aircraft will not stall erratically. This type flight test is accomplished in accordance with FAR 91.407 (b), without the need for an Experimental Certificate, probably every day of the week.

The new order (8130.29) even states, "It is important to emphasize that changes to the type design require flight testing only when other means cannot show full compliance with airworthiness regulations." The problem is the subjectivity involved. It seems that no one wants to take the responsibility to say, "we don’t need to fly the aircraft." So the question is "what type of change really requires a Show Compliance Flight Test?" The problem is the answer is always the same "All Changes." We believe that FAA headquarters must provide clear, detailed guidance to ACO project engineers on what type of change requires a Show Compliance Flight Test.

Supposedly, an effort was begun in mid to late 1998 by AIR-200 (which is the manager of the Production and Airworthiness Certification Division of the FAA) to clarify and standardize the process of requiring production flight tests and the use of Experimental Airworthiness Certificates for those flights. A portion of that effort was to outline what types of changes should require a Show Compliance Flight Test vs. the use of adequate ground testing to show compliance. To this point we have only seen the policy memorandums leading up to and the latest issuance of FAA Order 8130.29.

Experimental Airworthiness Certificate for required Show Compliance Test Flights

The significant change in the new FAA Order 8130.29 vs. the superceded policy memorandum is that the new order requires the "applicant" to ensure the aircraft is in compliance with all of the airworthiness regulations for its current standard airworthiness certificate. Failure to do so will "impact the standard airworthiness certificate reinstatement process." Ironically, the main purpose of this FAA order as it was being developed was to provide for the reinstatement of the standard airworthiness certificate without a complete recertification of the aircraft. After all, if the aircraft had a current standard airworthiness certificate prior to entering the "Certification" arena the only thing in question should be the modifications that took place as part of the STC certification process.

To ensure the aircraft is in compliance with all of the airworthiness regulations for its current standard airworthiness certificate an in-depth audit of all the aircraft’s records must be conducted. Such an audit can be fairly insignificant for newer aircraft, but aircraft receiving the upgrade-type modifications are the ones that will have accumulated lots of time and come with lots of records. Such an audit can be very expensive.

It is simple enough and justifiably necessary, during the STC certification process, to ensure that the modification to the aircraft is performed in a way that results in a properly altered configuration. It is, however, completely unnecessary to take the aircraft through a complete re-certification process simply because the owner has chosen to upgrade the flight management system.

The current STC process itself ensures that the modifications being performed on an aircraft are accomplished in compliance with all certification requirements. It is impossible to obtain an STC without having complete, unequivocal FAA concurrence and approval since the approval comes from the FAA. This process is modeled after the type certificate process and is even referred to right alongside the type certification process in FAA guidance material:

FAA Order 8110.4.02: a. General. The TIA is prepared by the ACO on FAA Form 8110-1 and is used to authorize official conformity, airworthiness inspections, and flight tests necessary to fulfill certain requirements for TC, STC, and amended TC certification. In addition the TIA may contain a section (Operational and Maintenance Requirements) that provides for certain other operational evaluations identified by the AEG.

An aircraft that requires a flight test to fulfill certain requirements for TC and/or amended TC certification is permitted to complete those operations using a special flight permit (see FAR 21.197, page 52). Yet aircraft that require flight tests to fulfill certain requirements for STC certification are actually required to be placed into experimental category.

FAR 21.197

(a) A special flight permit may be issued for an aircraft that may not currently meet applicable airworthiness requirements but is capable of safe flight, for the following purposes:

1. Flying the aircraft to a base where repairs, alterations, or maintenance are to be performed, or to a point of storage.

2. Delivering or exporting the aircraft.

3. Production flight testing new production aircraft.

4. Evacuating aircraft from areas of impending danger.

5. Conducting customer demonstration flights in new production aircraft that have satisfactorily completed production flight tests.

Another significant FAA statement was found in the amendments to FAR 21 which also applies to the STC process.

Amendment 21-21 dated 6/6/1968 contains the following statement from the FAA regarding the use of Experimental Airworth-

iness Certificates: "Various comments were received concerning this proposal, particularly with respect to the fact that as proposed, production flight testing would have been identified as an experimental operation. This, of course, is not appropriate. Therefore, in light of these comments and after further consideration, the FAA has determined that these changes are not necessary."

By issuing this statement the FAA indicates it has researched the issue and already acknowledged, during the rulemaking process that placing an aircraft into experimental for the purpose of production flight-testing is "not appropriate".

It doesn’t make sense that a special flight permit is good enough for "new production aircraft" but not for newly modified aircraft. The situation is the same. The aircraft has been modified, conformity inspections have been conducted to verify compliance with all approved drawings and a "Production Flight Test" is required to verify all systems are go.

The STC process is just another arm of the TC production process subject to the same regulations and requirements.

In closing, this experimental certificate issue is serious and should not be taken lightly. We have gone to great lengths to attempt to make sense of the decisions that have been made surrounding the STC process and the need for Show Compliance Test Flights and further, the authorization method for those flights.

Why can the manufacturer of an aircraft fly that aircraft without a standard airworthiness certificate under the authority of a special flight permit when the modification centers applying for the issuance of a Supplemental Type Certificate cannot? It does not make sense. Or as the FAA has put it, it is "not appropriate."

Why are we required to conduct a "Show Compliance Flight Test" for equipment that has been installed that is secondary equipment to primary operable equipment when that secondary equipment has had a complete functional test on the ground and can be turned off and taken out of the system if required?

As an industry, we should respectfully request a quick and in-depth review of FAA Order 8130.29 as well as the multiple policy memorandums that lead up to its issuance, for purpose, content, and applicability.

Additionally, we should request that FAA headquarters quickly issue a new policy that provides for the use of special flight permits for STC production flight testing and set in motion rulemaking action to revise FAR 21.197(a) 3 to include aircraft flown for STC production flight tests. Such action would allow the current standard airworthiness certificates to remain intact while aircraft requiring a test flight are flown using the special flight permit. AMT

Joe Hertzler is the president of AVTRAK, Inc., an Aurora, Colorado-based company. Joe is an A&P mechanic with Inspection Authorization and also a private pilot.

Additional ReSource

FAA Order 8130.29

FAA Policy Memorandum 2000-03

Title 14 CFR Parts 1, 21, 43, 91

FAA Order 8110.4.02

CFR Amendment 21-21