FINAL REGULATORY EVALUATION 

FUNCTION AND RELIABILITY FLIGHT TESTING FOR TURBINE-POWERED 

AIRPLANES WEIGHING 6,000 POUNDS OR LESS 

(14 CFR, Section 21.35) 

OFFICE OF AVIATION POLICY AND PLANS 

AIRCRAFT REGULATORY DIVISON (APO-300) 

Daniel F. Leach 

May 2, 2011 
I. INTRODUCTION

For Title 14, Code of Federal Regulations (14 CFR), part 23 aircraft certifications, function and 

reliability (F&R) flight testing is required by 14 CFR § 21.35(b)(2) for all airplanes weighing more than 

6,000 lbs. maximum certificated weight. F&R flight testing is not required for gliders or for part 23 

airplanes weighing 6,000 lbs. or less. This Final Regulatory Evaluation examines the impact of this 

Federal Aviation Administration (FAA) final rule, which will extend F&R flight testing to part 23 

turbine-powered airplanes weighing 6,000 lbs. or less. The exception for gliders and for reciprocatingengine-powered airplanes weighing 6,000 lbs. or less will be retained. 

The FAA has determined that this change is necessary to promote safety. This safety determination is 

based on the new light-weight turbine-powered airplanes having design features and performance 

characteristics similar to larger airplanes. We expect that adoption of this final rule will enhance safety 

and reduce costs by substantially reducing the number of service difficulties and airworthiness directives 

experienced post-certification. 

II. GUIDE TO ACRONYMS USED IN THIS DOCUMENT

AD—Airworthiness Directive 

CAB—Civil Aeronautics Board 

CAR—Civil Air Regulations 

CFR—Code of Federal Regulations 

FAA—Federal Aviation Administration 

F&R—Function and Reliability 

SCR—Special Certification Review 

SDR—Service Difficulty Report 

VLJ—Very Light Jets 

III. BACKGROUND

The requirement for F&R flight testing originates with the Civil Aeronautics Board (CAB) imposing 

a “service test” requirement for all U.S. aircraft in 1947 (12 FR 2086, March 29, 1947). The purpose of 

this test was to “ascertain whether there is reasonable assurance that the airplane, its components, and 

equipment are reliable and function properly.” A preceding rulemaking (12 FR 1028, February, 13, 1947) 

referred to a study showing extensive maintenance issues and a greater likelihood of accidents in the early 

life of new model aircraft. The conclusion was drawn that the accident rate would be significantly 

reduced if before type certification, the Civil Aeronautics Board (CAB) required aircraft to undergo tests 

specifically designed to ascertain their reliability and proper functioning. 

In 1950, the CAB amended the airworthiness standards to exclude “... smaller airplanes, specifically 

those of 6,000 pounds maximum weight or less” from the service test requirement (15 FR 8899, 

December 15, 1950). The introductory text of the revision explains that most of the significant changes in 

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the amendment “stem from the desire for simplification of the rules in this Part with respect to the smaller 

airplanes, specifically those of 6,000 pounds maximum weight or less, which would be expected to be 

used mainly as personal airplanes.” The introductory text explains that the service test requirement was 

removed for airplanes of 6,000 pounds or less maximum weight because “experience seems to indicate 

that this rule imposes a burden upon the manufacturers not commensurate with the safety gained.” 

The requirement for F&R flight testing, and the exception for part 23 airplanes of 6,000 pounds or 

less maximum weight, is now found in 14 CFR part 21 (§ 21.35(b)(2)). The decision to exclude part 23 

airplanes of 6,000 pounds or less maximum weight from F&R flight testing was based on the state of 

technology existing in 1950. These airplanes were also expected to be used mainly as personal airplanes. 

Civil aircraft produced in the period 1945-1955 were typically single piston-engine airplanes weighing 

less than 3,000 pounds with engine output less than 300 horsepower. 

IV. DISCUSSION OF COSTS AND BENEFITS

A. Total Costs and Benefits of this Final Rule

We expect that the typical certification project for an airplane subject to the final rule will be for a 

new airplane design with a turbine engine type previously used in a type certificated aircraft requiring 165 

hours1

 of F&R flight testing at a total cost of about $317,000. In the case of a new airplane design and an 

engine type not previously used on a type certificated airplane, we estimate that double the hours (330) 

will be required, so the total cost will double to $634,000. We expect that this final rule will enhance 

safety and reduce costs by substantially reducing the number of safety incidents and Airworthiness 

Directives experienced post-certification. A partial estimate of the expected costs that will be avoided for 

a single new airplane design amounts to $1.8 million, with a present value of $1.6 million. These avoided 

costs are approximately six times the costs of our 165-hour “typical” estimate and approximately triple 

the higher 330-hour estimate. Consequently, the expected benefits of this final rule greatly exceed its 

modest expected costs. For additional detail, see the separate sections on costs and benefits below. 

 

1

 See the separate cost section below for the reason we increased the number of hours from 150 (the minimum 

required by § 21.35(f)) to 165. 

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Response to Cessna Comment

In a comment on the NPRM Cessna stated 

that the proposed NPRM has the potential to impose “burden upon the manufacturer not 

commensurate with safety gained.” For example, if a simple, well-developed airplane were 

modified with a reliable, well-developed turbine engine, it is not likely that F&R testing 

would discover issues not encountered during properly conducted certification testing. In this 

case, the 150 hour F&R testing proposed by the NPRM would be an undue burden on the 

manufacturer .... 

The rule addresses applicability only and does not change the minimum number of hours required by 

§ 21.35(f) (that is, 150 or 300 hours, whichever appropriate). Some simultaneous flight testing performed 

as part of the certification process may also be counted toward F&R flight testing if the conditions of 

§ 21.35(a) are met at the time the testing was performed (for example, testing related to Type Inspection 

Authorization). Given the substantial cost-beneficial nature of the rule for our case of a newly type 

certificated airplane with an engine previously used on a type certificated airplane, we believe the rule 

will remain cost-beneficial. 

B. Who is Affected by this Rule?

Manufacturers of part 23 turbine-powered airplanes weighing 6,000 lbs or less are affected. 

C. Assumptions and Sources of Information

 We use a two-year period of analysis, as we find this period sufficient to show the cost-beneficial 

nature of this final rule. We use the period from the beginning of 2007 to the end of 2008, as the data 

used in the analysis are from this period. The short period of analysis reflects the inherent nature of 

F&R flight testing, designed as it is to uncover design or system reliability flaws that otherwise would 

reveal themselves in the very early life of an aircraft. 

 Discount rate is 7 percent (Office of Management & Budget, Circular A-94, “Guidelines and 

Discount Rates for Benefit-Cost Analysis of Federal Programs,” October 29, 1992, p. 8). 

 Data on costs of compliance with this proposal were obtained from a part 23 airplane manufacturer 

and FAA estimates. 

D. Costs of this Final Rule

We estimate the costs of this final rule based on the F&R costs incurred by a part 23 airplane 

manufacturer for a turbojet airplane with a maximum weight greater than 6,000 lbs. The turbine-powered 

Eclipse EA-500, with maximum weight less than 6,000 lbs, was recently type certified under a program in 

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which it voluntarily undertook a reduced 200-hour F&R program, 100 hours pre-certification and 100 

hours post-certification.2

 The F&R costs for the Eclipse EA-500 would be difficult, if not impossible, to 

obtain, however, as Eclipse Aircraft has been liquidated under Chapter 7 bankruptcy and a new firm, 

Eclipse Aerospace, has been formed to take over the Eclipse assets. We believe our use of more readily 

obtainable data for a part 23 turbojet weighing somewhat more than 6,000 lbs. is adequate. Moreover, as 

we will see below, the ad-hoc nature of Eclipse’s voluntary F&R program appears to have limited the 

appropriateness of the Eclipse F&R cost data even if available. We may overestimate the cost of F&R 

flight testing by our use of costs for an airplane weighing more than airplanes affected by the final rule. 

 We estimate F&R cost per hour in order to more easily incorporate different estimates of total F&R 

flight hours. Test pilot and flight test engineer costs are FAA estimates. All other cost estimates were 

provided by a part 23 airplane manufacturer. The estimates are shown in the Table 1 below: 

 

2

 Pratt & Whitney Canada developed a new PW610F engine for the Eclipse EA-500. 

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Table 1. Estimated Costs of F&R Flight Testing 

Cost Item F&R Cost/hr 

 Total Item 

Cost 

(150 hours) Hours 

 Cost to replace two 

engines 

 Cost to 

replace one 

engine 

Fuel ($4.10 per US gal) $ 377.20 $ 56,580 1100 $ 464,890.80 $ 232,445.40 

Labor (Mechanic) $ 51.50 $ 7,725 150 $ 63,394.20 

Parts $ - 1 $ 422.63 

Engine reserves $ 422.63 $ 63,394 

Total "direct" cost $ 127,699 Hours Test AP Refurbishment 

 Indirect factor1 0.35 $ 44,695 1100 $ 315,839.18 

 150 $ 43,068.98 

Refurbishment of test 

airplane2 $ 287.13 $ 43,069 

1 $ 287.13 

Discount allowance3 $ 240.00 $ 36,000 

Test pilot costs4 $ 168.27 $ 25,240 

Hours 2 Test Pilots 1 Pilot (year) 

Flight test engineer costs4 $ 76.92 $ 11,538 2080 $ 350,000.00 $ 175,000 

F&R Cost (150 hrs) $ 288,242 150 $ 25,240.38 

F&R Cost (165 hrs) $ 317,066 1 $ 168.27 

F&R Cost (330 hrs) $ 634,132 

Hours Flt Test Engineer 

2080 $ 160,000.00 

150 $ 11,538.46 

1 $ 76.92 

Table notes: (1) Pre & post flight, trip expenses and other administrative costs 

(2) Refurbishment of the test airplane after completion of all type certification prior to airplane sale 

(3) $240 is per hour estimated reduction in airplane resale value owing to used status. 

(4) Test pilot and flight test engineer costs are FAA estimates. All other cost estimates were provided by a part 23 airplane 

manufacturer. 

Cost Discussion

For aircraft subject to F&R flight testing under 14 CFR § 21.35(b)(2), § 21.35(f) requires at least 300 

hours of F&R flight testing “with a full complement of engines” for aircraft “incorporating turbine 

engines of a type not previously used in a type certificated aircraft,” and at least 150 hours for all other 

aircraft. As most proposed very light jet (VLJ) type certification projects appear to be based on the type 

certificated Williams FJ-33 engine or other previously type certificated engines, we expect this minimum 

requirement to hold for the typical project subject to this final rule. 

F&R flight testing for 150 hours was required for the airplane whose data we use here, so one of our 

cost estimates assumes 150 hours of F&R flight testing. Sometimes, to fulfill the requirements of F&R 

flight testing, more than the minimum number of flight hours are necessary. For the purposes of this cost 

analysis, we used an average extension of 10%, or 15 hours, so our “typical” estimate assumes 165 hours 

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of F&R flight testing. We double that estimate to also provide an estimate for a new airplane design with 

a new engine design. 

 We now discuss the detailed cost items in Table 1. We make no changes to the Fuel cost estimate 

provided to us, as the price of fuel assumed is close to the current price. The cost of Parts is minimal as 

parts are typically provided on consignment. Other major cost categories reflect user cost, or wear and 

tear, of the test airplane. After testing the test airplane may be sold. Buyers understandably will be 

reluctant to buy the airplane with its heavily tested engines of uncertain value, so the used engines are 

returned to the vendor and the cost of two new engines is allocated to the entire 1100 hours used in the 

sample certification testing program. (We were unable to ascertain whether the used engines had been 

provided on consignment, or whether the airplane manufacturer had received a discount on the new 

engines upon returning the used engines.) The engine cost of one hour of F&R flight testing is 1/1100 of 

the total cost so the cost of a 150 F&R flight testing program is 150 times that. These costs are labeled in 

the table as Engine reserves. The Total “direct” cost of $127,699 is the sum of fuel costs, mechanic costs, 

and engine reserves. Total “direct” cost is multiplied by an Indirect factor of 0.35 to account for pre- and 

post-flight costs, trip expenses, and other administrative costs. As the cost of engines has been accounted 

for, Refurbishment of test airplane essentially reflects user cost of the airframe. The Discount allowance

of $240 is the per hour estimated reduction in the resale value of the airplane owing to its used status. The 

cost estimates provided to us did not include crew costs, so these costs are FAA estimates. We estimate 

the hourly costs of two test pilots and one flight test engineer using fully-burdened annual salaries and an 

engineering labor year (2080 hours). 

Our final figures are $288,242 for a 150-hour F&R flight testing program, $317,066 for a 165-hour 

program, and $634,132 for a 330-hour program. 

E. Benefits of this Final Rule

We expect that adoption of this final rule will enhance safety and reduce costs by substantially 

reducing the number of service difficulties experienced post-certification. This expectation is supported 

by evidence from the service experience of the Eclipse EA-500. The Eclipse Special Certification 

Review3

 (SCR) team looked at 85 Eclipse Service Difficulty Reports (SDRs), submitted between July 29, 

2007, and May 13, 2008. The Eclipse SCR team "concluded the majority of the SDRs resulted from 

reliability issues separate from compliance with the minimum FAA standards" (Eclipse SCR, Executive 

Summary). There also were six Eclipse-related ADs issued in the one-year period between November 

2007 and November 2008, and the Eclipse SCR also reports several instances of undocumented problems. 

 

3

 Special Certification Review: Eclipse Aviation Corporation Model EA-500 Airplane. Prepared for the Federal 

Aviation Administration Associate Administrator for Aviation Safety, September 12, 2008.

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Eclipse voluntarily conducted its own limited F&R flight testing. However, the FAA team did not view 

F&R flight testing as a requirement for Eclipse to receive its type certificate (Eclipse SCR, p. 28). This 

deficiency in Eclipse’s volunteer F&R flight testing program provides direct empirical evidence for the 

benefits of F&R flight testing. The general evidence from SDRs and ADs has already been noted. More 

specifically, the number of SDRs and ADs experienced by the Eclipse EA-500 appears to have been high. 

Table 2 below compares the SDR/AD experience of the Eclipse EA-500 compared to the Cessna 510. 

These airplanes are highly comparable, both being twin-engine VLJs and close competitors. Moreover, 

both models were type certificated in the same month (September 2006) and began delivery within one 

month of each other (Cessna: November 2006, Eclipse: December 2006).4

 Table 2 shows that while there 

are 60% more Eclipse EA-500s, the number of SDRs issued against the Eclipse EA-500 is almost triple 

the number issued against the Cessna 510.5

 Of more concern, there have been six ADs issued against the 

Eclipse EA-500 and none against the Cessna 510. 

Table 2. Eclipse EA-500 vs. Cessna 510 

 

Eclipse 

EA-500 

Cessna 

510 

No. of US-Registered Airplanes 264 163

No. of SDRs (part 91 operations only)1 28 10

No. of ADs 6 0

Table note: (1) Excludes 85 Eclipse SDRs written by DayJet, under part 135 operations. 

General Note: Figures in table as of December 1, 2009. 

Listed in Table 3 below are the main specific problems encountered by the Eclipse EA-500, ranked by the 

estimated likelihood these problems would have been uncovered by a mandatory F&R flight testing 

program. The cost of the modification to solve the pitot/angle-of-attack (AOA) problem—and hence the 

avoidance of which would be a benefit of F&R flight testing--has been estimated in AD 2008-02-04. 

While there are costs associated with the other problems (and corresponding benefits from avoiding 

them), they are difficult, if not impossible, to estimate. For example, AD 2008-24-07 addresses the 

problem of engine surges by limiting the Eclipse EA-500 to a maximum operating altitude of 37,000 feet, 

 

4

 We should note, however, that (1) the Eclipse EA-500 was a new aircraft design, while the Cessna 510 was a 

derivate design and (2) Eclipse Aviation had no previous experience certifying an aircraft, while Cessna Aircraft is a 

well-established firm with decades of certification experience. 

5

 In order not to distort the comparison between the Eclipse EA-500 and the Cessna 510, 85 SDRs written by DayJet 

for its Eclipse fleet under part 135 operations were excluded, as SDRs are required for part 135 operations, but 

voluntary for part 91 operations (other than subpart K operations). 

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Table 3. Major Eclipse Problems 

Eclipse problem Reference 

Likelihood these problems will be revealed by 

a mandatory F&R flight testing program 

Trapping of moisture and freezing condensation in the 

pitot/angle-of-attack (AOA) system, causing erroneous 

AOA and airspeed information, with consequent 

possible loss of control. 

SCR, p. 25, 

AD 2008-02-04 Likely (70-75% chance) 

Engine surges caused by hard carbon buildup on the 

static vane, which could lead to loss of engine power. AD 2008-24-07 Probable (50-60% chance) 

Pitch & rudder trim problems. SCR, p. 17 Probable (50-60% chance) 

Brake problems. (Eclipse brakes are mechanical.) SCR, p. 26 Measurably increase likelihood (40-50% chance) 

Tire problems SCR, p. 26 Measurably increase likelihood (40-50% chance) 

Autopilot turbulence sensitivity, often disengaging and 

not easily reengaging. SCR, p. 26 Small (10% chance) 

Throttle position exceeding its maximum range, which 

could cause loss of control of both engines. AD 2008-16-15 Unlikely (1-2% chance) 

so the cost of this AD is the loss in benefits from not being able to operate at the maximum altitude for 

the airplane. As we show below, however, the benefit from avoiding just the pitot/AOA problem greatly 

exceeds our estimated cost of F&R flight testing, even for a full 330-hour testing program. 

Direct Costs Per Airplane of Pitot/AOA Problem

AD 2008-02-04 addresses the Eclipse pitot/AOA problem with a design modification. The AD 

estimates the parts cost of the modification to be $7,000 and that the modification will require 30 workhours at a billable wage rate of $80 an hour, for a total wage cost of $2,400 per airplane. So the total 

direct cost per airplane is estimated to be $9,400 per airplane. The AD does not estimate out-of-service 

cost, which we now estimate. 

Out-of-Service Cost Per Airplane of Pitot/AOA problem

We estimate out-of-service cost as the opportunity cost of capital, the capital in this case being the 

airplanes themselves. Conceptually, we measure the opportunity cost of capital as the cash flow forgone 

because the airplane is out of service. We measure that cash flow by lease rates. As a percentage of 

airplane value, lease rates for the Eclipse EA-500 range from 0.4% to 0.6% per month. During the period 

2007-2008 airplane value is approximated by new airplane selling price of approximately $1.6 million.6

Based on an estimated 30 hours of labor, we use a four-day out-of-service time and estimate out-ofservice cost per airplane as $1.6 million x .5% x 4/30 = $1,067. 

 

6

 Robert Zuskin, Jet Perspectives, Inc., Sterling, Va. Zuskin reports that the selling price of the Eclipse EA-500 was 

heavily discounted from its list price.
Total Costs of Pitot/AOA Problem

We present our total estimated costs of the Pitot/AOA problem in Table 4 below: 

Table 4. Cost of Design Modification to the Eclipse Pitot/AOA System 

[Estimated Avoided Costs Owing to F&R flight testing] 

Labor cost $ 2,400 30 work-hours x $80/hr 

Parts cost $ 7,000 

Total direct cost per airplane $ 9,400 

Total direct cost on U.S. operators (264 APs) $ 2,481,600 

Out-of-service costs per airplane $ 1,067 

Total out-of-service costs (64 airplanes) $ 68,267 

Total Cost on U.S. operators (264 airplanes) $ 2,549,867 

Expected Benefit (Total Cost [avoided] x 0.7 probability) $ 1,784,907 

Present Value Benefit (Expected Benefit discounted 1.5 

years) $ 1,612,649 

The design modification of the pitot/AOA system was required by AD 2008-02-04 for the existing fleet 

of 64 Eclipse EA-500 airplanes at the time of AD issuance, January 9, 2008 (Published in Federal 

Register, January 22, 2008 (73 FR 3618)). The effective date of the AD was February 26, 2008, with a 

compliance period of 60 days. For the remaining airplanes produced by Eclipse Aircraft, the modification 

was incorporated during production. Accordingly, the cost of the design modification applies to all 264 

U.S-registered model EA-500 airplanes (of 267) produced by Eclipse Aviation until it ceased production 

in October, 2008. Out-of-service costs, however, apply only for the 64 airplanes directly affected by the 

AD. 

As shown in the table we estimate the total cost of the design modification for the Eclipse fleet to be 

$2.5 million. As discussed above, however, we assess the probability of F&R flight testing uncovering the 

pitot/AOA problem to be approximately 0.7 to 0.75. Accordingly, using the lower figure, we calculate the 

Expected Benefit as the Total Cost (avoided) times 0.7, or $1.8 million. As the FAA issued a type 

certificate for the Eclipse EA-500 on September 30, 2006, approximately 1.5 years prior to the 

compliance date for this AD, we discount the Expected Benefit 1.5 years to find a Present Value Benefit 

of $1.6 million. 

V. SUMMARY

This Final Regulatory Evaluation examines the impact of this final rule, which will extend F&R flight 

testing to part 23 turbine-powered airplanes weighing 6,000 lbs. or less. The exception for gliders and for 

reciprocating-engine-powered airplanes weighing 6,000 lbs. or less will be retained. The FAA has 

determined that this rule change is necessary to promote safety. This determination is based on the new 

10
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light-weight turbine-powered airplanes having design features and performance characteristics similar to 

larger airplanes. We expect that this final rule will enhance safety and reduce costs by substantially 

reducing the number of service difficulties experienced post-certification. 

The evidence for this proposition is provided by the experience of the Eclipse EA-500, which appears 

to have had an unusually high number, per airplane, of post-certification SDRs and ADs. Eclipse did 

voluntarily conduct its own limited F&R flight testing. However, the FAA team did not view F&R flight 

testing as a requirement for Eclipse to receive its type certificate. Consequently, we find that there were a 

number of problems experienced by the EA-500 post-certification with significant likelihood of being 

uncovered by a mandatory F&R flight testing program. We deem one of these problems—the problem 

with the pitot/AOA system--as “likely” to have been uncovered by a mandatory F&R flight testing 

program. We estimate the expected total costs of fixing this one problem--and hence the avoidance of 

which would be a benefit of F&R flight testing—to be $1.8 million, almost six times our estimated 

$317,000 cost of F&R flight testing. The benefits of F&R flight testing greatly exceed its modest costs.