1

U.S. Department of Transportation

FEDERAL AVIATION ADMINISTRATION

Office of Aviation Policy and Plans

Washington, D.C. 20591

INITIAL REGULATORY EVALUATION

NOTICE OF PROPOSED RULEMAKING

Airplane and Engine Certification Requirements in Supercooled Large Droplet, Mixed 

Phase, and Ice Crystal Icing Conditions

14 CFR PART 25 & 33

OFFICE OF AVIATION POLICY AND PLANS

REGULATORY ANALYSIS DIVISION

Michael D. Lukacs

June 16, 2010
2
3

Executive Summary .....................................................................................................4

History...........................................................................................................................6

Regulatory Background...............................................................................................7

Assumptions .................................................................................................................8

Fleet .............................................................................................................................10

Smaller Part 25 Airplane Fleet...............................................................................10

Medium Airplane Fleet..........................................................................................12

Total Fleet – Medium and Smaller........................................................................16

Larger Airplane Fleet .............................................................................................17

Benefits ........................................................................................................................20

Averting Events on Smaller and Medium Airplanes ......................................20

Historical SLD Events ............................................................................................20

Estimated Cost Of An SLD Event .........................................................................22

Averting Injuries and Fatalities .........................................................................23

Averting Hull Loss and Accident Investigation Costs ....................................23

Annual Risk.............................................................................................................24

Quantified Benefits for Smaller & Medium Airplanes........................................25

Benefits from averting events involving larger airplanes ...............................28

Quantified Benefits-Larger Airplanes...................................................................29

Benefits from Engine Requirements..................................................................31

Benefit Summary ....................................................................................................34

Costs ............................................................................................................................35

Smaller Airplane Certification Costs ........................................................................36

System Design, Certification & Analysis..............................................................37

Aerodynamic Wind Tunnel Tests .........................................................................38

Analysis ...................................................................................................................39

Flight Testing ..........................................................................................................39

Airplane Certification Cost - International Impact..................................................42

New Larger Airplane Certification Cost ..................................................................43

Engine Certification Cost...........................................................................................44

Hardware Costs – Smaller & Medium Airplanes....................................................46

Fuel Costs – Smaller and Medium Airplanes ..........................................................47

Smaller Airplanes Fuel Cost ..................................................................................48

Medium Airplane Fuel Cost..................................................................................48

Other Airplane Operating Costs ...............................................................................49

Cost Summary ............................................................................................................50

Benefit Cost Summary ...............................................................................................51
4

Executive Summary 

This Notice of Proposed Rulemaking (NPRM) would amend the airworthiness standards 

applicable to certain transport category airplanes certificated for flight in icing conditions 

and the icing airworthiness standards applicable to certain airplane engines. The total 

estimated benefits are $405.6 million ($99.5 million present value), and exceed the total

estimated costs of $71.0 million ($54.0 million present value). On an annualized basis, 

for the time period 2012-2064, the benefits are $7.0 million, and the costs are $3.8 

million. The benefits and costs are summarized below.

Summary of Benefits and Costs

Nominal Benefits PV Benefits

Smaller & Medium Airplanes $249,580,915 $69,994,259 

Larger Airplanes $156,004,884 $29,498,469 

Total Benefits $405,585,799 $99,492,728 

($7.0 million annually)

Costs

Nominal Cost PV Cost

Engine Cert Cost $7,936,000 $6,931,610 

Engine Capital Cost $6,000,000 $5,240,632 

Total Engine $13,936,000 $12,172,242 

Smaller Airplane Certification Cost $24,999,039 $21,835,129 

New Larger Airplane Certification 

Cost

$3,154,600 $2,755,350 

Derivative Larger Airplane 

Certification Cost

$10,438,800 $9,117,652 

Hardware Costs $10,390,000 $5,842,024 

Fuel Burn All $8,046,676 $2,261,941 

Total Costs $70,965,115 $53,984,338 

($3.8 million annually)

First, we explain the accident history and background that led to this NPRM. Next, we 

provide the regulatory background of the requirements contained in the proposed rule. 

Third, we detail our assumptions and estimates of the fleet that would be affected by the 
5

proposed requirements. Finally, we examine the estimated benefits and costs associated 

with the proposed rule, and follow it with the benefit/cost summary. 

We have determined that this proposed rule: (1) has benefits that justify its cost; (2) is 

not an economically “significant regulatory action” as defined in section 3(f) of 

Executive Order 12866; (3) is “significant” as defined in DOT’s Regulatory Policies and 

Procedures; (4) would not have a significant economic impact on a substantial number of 

small entities; (5) would not create unnecessary obstacles to the foreign commerce of the 

United States; and (6) would not impose an unfunded mandate on state, local, or tribal 

governments. 
6

History 

On October 31, 1994, an Avions de Transport Regional ATR 72 series airplane crashed 

in Roselawn, Indiana, resulting in the deaths of 68 passengers and crew members. After 

extensive investigation, the National Transportation Safety Board (NTSB) concluded that 

freezing drizzle conditions created a ridge of ice on the wing’s upper surface aft of the 

deicing boots and forward of the ailerons, and that the ridge of ice contributed to an 

uncommanded roll of the airplane. The atmospheric condition that contributed to the 

Roselawn accident is currently outside the icing envelope for certification of transport 

category airplanes. The accident would not have occurred had the proposed requirements 

been in affect at the time of airplane design.

The certification requirements for transport category airplanes and engines do not address 

the safe operation of airplanes in supercooled large droplet (SLD), mixed phase, or ice 

crystal icing conditions, and the operating rules do not specifically prohibit operations in 

these conditions. The proposed requirements contained in this NPRM are based on

recommendations by both the NTSB1and Aviation Rulemaking Advisory Committee 

(ARAC).

2 We estimate the benefits and costs associated with certifying designs to these 

requirements in the following sections. 

 

1

 NTSB recommendations A-96-54, A-96-56, and A-96-58; available in the Docket and on the Internet at: 

http://www.ntsb.gov/Recs/letters/1996/A96_48_69.pdf.

2

Ice Protection Harmonization Working Group
7

Regulatory Background

Title 14, Code of Federal Regulations, part 25, appendix C, and part 33 specify the 

certification requirements for icing conditions. Icing conditions containing freezing 

drizzle and freezing rain are not currently considered during certification of an airplane’s 

ice protection systems. These two conditions constitute an icing environment known as 

SLD. Exposure to these conditions can result in ice accretion that impairs the safe 

operation of an airplane. This rule would require airplanes to either safely exit following 

the detection of any specifically identified appendix O icing conditions, or safely operate 

without restrictions. Specifically, the proposed § 25.1420 would allow three options: 

 § 25.1420(a)(1) - detect appendix O conditions, and then operate safely while 

exiting all icing conditions. 

 § 25.1420(a)(2) - safely operate in a selected portion of appendix O, detect 

when the airplane is operating in conditions that exceed the selected portion, 

and then operate safely while exiting all icing conditions. 

 § 25.1420(a)(3) - operate safely in all of the appendix O conditions.

Similarly, SLD conditions are not currently considered during engine certification. 

Exposing engines and externally mounted probes to these conditions can result in 

hazardous ice accumulations that may result in engine damage, power loss, and loss of or 

misleading airspeed indications.

The proposed regulations would reduce the risk of accidents by including certification 

requirements for (1) SLD icing conditions for transport category airplanes most affected 

by these icing conditions; (2) mixed phase and ice crystal conditions for all transport 
8

category airplanes; and (3) SLD, mixed phase, and ice crystal icing conditions for all 

turbine engines.

This regulatory evaluation estimates the total additional incremental benefits and costs of 

the proposed requirements contained in the rule. We obtained the basis of our cost 

estimates from the industry. The manufacturers based their estimates upon 

accompanying advisory circulars (AC), which describe acceptable means for showing 

compliance. The compliance costs are analyzed in context of the part 25 and part 33 

certification requirements. We have evaluated the operational costs based upon estimates 

and analysis of operators who routinely operate in SLD environments.

The FAA seeks comments on its determination of the costs and benefits and requests that 

all comments contain supporting data and additional documentation.

Assumptions 

The societal costs include the overhead costs that are allocated to labor as well as the 

direct cost. The basis for the labor rates are from the 2009 data on the mean burdened 

hourly labor rates of aeronautical engineers using data principally from the Department of 

Labor’s Bureau of Labor Statistics. On that basis, we use $77 per hour as the burdened 

wage rate for engineers used in this regulatory evaluation.

 

For purposes of this evaluation, we conservatively assume that all certifications are 

approved one year after the rule is codified (2011), and that production/deliveries begin 

to occur the following year (2012). The number of deliveries and the corresponding 
9

delivery years depend on the airplane type. We explain these numbers in the fleet section 

of this analysis. This production and delivery profile creates a slowly building fleet, until 

production stops. Once airplanes reach 25 years, they start to retire.3 Because the 

production cycles and deliveries are customized to the various (and different) airplane 

types, it is important for the reader to focus on present value benefits and costs.

 

The estimated benefits are larger than the estimated costs for the lifecycle of airplanes 

that are certificated, delivered, operated, and retired; and the rule will be cost-beneficial 

for all future certificated airplanes.

This analysis focuses on incremental benefits and costs that accrue to citizens and 

manufacturers in the United States. We acknowledge costs to foreign companies who 

might choose to comply with the requirements contained in this proposed rule.4 

The estimates in this evaluation contain both nominal and present values. For both the 

benefits and the costs, we use a discount rate of 7% as prescribed by OMB, as this 

discount rate reflects the time value of money. Focusing on present values, allows for a 

comparison of benefits and costs over time. 

 

3

 BACK Associates Fleet Database

4

 OMB Circular A-4, page 15. 
10

Fleet

This section outlines the fleet methodology to estimate the number of designs, production

rates, and delivery cycles of an airplane that would be affected by this proposal. Our 

reasoning, and the underlying assumptions used in this analysis, are described below. 

We group airplanes into three categories: smaller airplanes, medium airplanes, and larger 

transport airplanes, based primarily upon size. The categories approximate business 

airplanes, regional airplanes, and larger airplanes. The estimated number of certifications 

and deliveries depend on the airplane type. The number of production years depends on 

the airplane category. 

SMALLER PART 25 AIRPLANE FLEET 

To develop the estimated fleet for smaller part 25 airplanes, we analyzed historical data 

for the type certifications, production cycles, and deliveries of similar smaller part 25 

transport category airplanes. There are three U.S.-owned airplane manufacturers 

(Cessna, Raytheon, and Gulfstream) currently producing smaller part 25 airplanes. In 

addition, Learjet, a subsidiary of Bombardier, manufactures part 25 airplanes in this 

category within the United States. We analyzed these manufacturers’ type designs and 

their associated annual airplane deliveries resulting from new airplane certifications for 

U.S. manufacturers from 1966 through 2007. The data is summarized in table 1 below. 

TABLE 1 – SMALLER CERTIFICATION SUMMARY

Years (1964-2007)

Total Count of New Designs 11

Designs per Year 0.250

U.S. Deliveries 3122

U.S. Deliveries Per Period Per Type Certificate 

(TC) 33

Estimated Number of Designs in 10 years 3

Annual Deliveries To U.S. Per TC 99
11

From 1964 through 2007, there were approximately 3.0 new airplane type certificates per 

10-year period for smaller airplanes. As detailed in table 2, for each type design, on 

average, there are roughly 33 deliveries in the United States annually (3,118 deliveries to 

the U.S. / 95 TC years5). For the total number of type certificates (3), we estimate 99 

airplanes would be delivered annually. 

TABLE 2 – SMALLER PART 25 DELIVERIES

 

5

 Number of Years of deliveries per new type certificate data sheet (TCDS). The average number of years 

produced is 10 years. 
12

Shown below is the affected fleet for smaller airplanes. It is based on three type designs, 

33 annual deliveries per type design (which equates to 99 annual deliveries), 10 years of 

deliveries per type design, and an airplane retirement of 25 years on average. 

TABLE 3 - SMALLER AIRPLANE FLEET

Year Deliveries Retirements Net Fleet

2009

Effective Date of Rule 2010

3 Certifications Occur 2011

Deliveries Begin 2012 99 99

2013 99 198

2014 99 297

2015 99 396

2016 99 495

2017 99 594

2018 99 693

2019 99 792

2020 99 891

2021 99 990

2022 990

2023 990

2024 990

2025 990

2026 990

2027 990

2028 990

2029 990

2030 990

2031 990

2032 990

2033 990

2034 990

2035 990

2036 990

2037 99 891

2038 99 792

2039 99 693

2040 99 594

2041 99 495

2042 99 396

2043 99 297

2044 99 198

2045 99 99

2046 99 0

MEDIUM AIRPLANE FLEET

The delivery and production data for similar medium transport category airplane type 

certificates are summarized in table 4. To estimate the affected potential fleet of medium 
13

airplanes/regional airplanes, we use available historical data for similar airplanes as 

suggested by industry representatives. 

TABLE 4 - MEDIUM AIRPLANE PRODUCTION

Model Deliveries Production Years

Jetstream J41 100 6

ATR 42-72 808 23

EMB-120 352 17

EMB-135/EMB-145 875 12

Dornier 328 66 8

DHC-7 111 12

CL600 1641 11

DHC-8 507 22

 SAAB 340 430 14

SAAB 2000 63 5

Fokker 27/50 992 39

Fokker 28 241 20

BAE 146/AVRO RJ 391 19

Total 6577 208

The data summarized in table 5, represents similar designs for the 1965-1999 time 

period.

6

 Based on this history, roughly 0.4 medium transport airplanes are certificated 

annually. Accordingly, we estimate four medium transport certifications will occur over 

a ten year period, and we conservatively assume all certification approvals occur in 2011. 

 TABLE 5 - MEDIUM AIRPLANE CERTIFICATION SUMMARY

Years (1965-1999)

Total Count of New Designs 13

Designs Per Year 0.4

Total Deliveries 6577

Deliveries Per Period Per TC 32

Estimated Number of Designs in 10 years 4

Annual Deliveries To U.S. Per TC 17

The approximate annual number of worldwide deliveries of medium airplanes per type 

certificate is 32 (6,577 airplanes/208 years). Of these, roughly 32 affected airplanes

delivered annually on a worldwide basis, 52% (17 airplanes per type design) are expected 

 

6

 Industry gave the FAA input in the analysis of the time periods used for the different categories of 

aircraft. The categories and time periods analyzed depended on several factors in coordination with 

industry input such as the original type certifications, historical delivery and production schedules (for 

both in production and out of production airplanes) for each specific category of aircraft. 
14

to be delivered and operated in the United States annually. For a 16-year production

period (the medium airplane average), 68 medium airplanes will be delivered annually to 

the U.S. (4 certifications x 17 airplanes). We use the transport category airplane service 

life (25 years). Table 6 shows the estimated fleet over time with the corresponding 

airplane production, deliveries, and retirements for medium transport category airplanes.
15

 TABLE 6 – MEDIUM AIRPLANE FLEET

Year Deliveries Retirements Net Fleet

2009

Effective Date of Rule 2010

2 Certifications Occur 2011

Deliveries Begin 2012 68 68

2013 68 136

2014 68 204

2015 68 272

2016 68 340

2017 68 408

2018 68 476

2019 68 544

2020 68 612

2021 68 680

2022 68 748

2023 68 816

2024 68 884

2025 68 952

2026 68 1020

2027 68 1088

2028 1088

2029 1088

2030 1088

2031 1088

2032 1088

2033 1088

2034 1088

2035 1088

2036 0 1088

2037 68 1020

2038 68 952

2039 68 884

2040 68 816

2041 68 748

2042 68 680

2043 68 612

2044 68 544

2045 68 476

2046 68 408

2047 68 340

2048 68 272

2049 68 204

2050 68 136

2051 68 68

2052 68 0
16

TOTAL FLEET –SMALLER AND MEDIUM

Aggregating the airplane sizes accounts for various sizes of airplanes that would be 

affected by the proposed rule. For purposes of this evaluation, we conservatively assume 

that all certifications are approved one year after the rule is codified (2011), and that 

production/deliveries begin to occur the following year (2012). The estimated number of 

certifications, deliveries, and production years depend on airplane type. As detailed in 

our previous fleet discussion, the total annual affected fleet for smaller and medium 

airplanes equals the total annual net number of smaller affected airplanes plus the total

annual net number of medium airplanes. Table 7 shows the total affected fleet for 

smaller and medium airplanes. 

TABLE 7 – TOTAL SMALLER AND MEDIUM AIRPLANE FLEET

Smaller 

Deliveries

Smaller

Retirements

Net Fleet 

Smaller 

Airplanes

Medium 

Deliveries

Medium 

Retirements

Net Fleet 

Medium

Total Net (Net 

Smaller + Net 

Medium)

2012 99 0 99 68 0 68 167

2013 99 0 198 68 0 136 334

2014 99 0 297 68 0 204 501

2015 99 0 396 68 0 272 668

2016 99 0 495 68 0 340 835

2017 99 0 594 68 0 408 1002

2018 99 0 693 68 0 476 1169

2019 99 0 792 68 0 544 1336

2020 99 0 891 68 0 612 1503

2021 99 0 990 68 0 680 1670

2022 0 0 990 68 0 748 1738

2023 0 0 990 68 0 816 1806

2024 0 0 990 68 0 884 1874

2025 0 0 990 68 0 952 1942

2026 0 0 990 68 0 1020 2010

2027 0 0 990 68 0 1088 2078

2028 0 0 990 0 0 1088 2078

2029 0 0 990 0 0 1088 2078
17

Smaller 

Deliveries

Smaller

Retirements

Net Fleet 

Smaller 

Airplanes

Medium 

Deliveries

Medium 

Retirements

Net Fleet 

Medium

Total Net (Net 

Smaller + Net 

Medium)

2030 0 0 990 0 0 1088 2078

2031 0 0 990 0 0 1088 2078

2032 0 0 990 0 0 1088 2078

2033 0 0 990 0 0 1088 2078

2034 0 0 990 0 0 1088 2078

2035 0 0 990 0 0 1088 2078

2036 0 0 990 0 0 1088 2078

2037 0 99 891 0 68 1020 1911

2038 0 99 792 0 68 952 1744

2039 0 99 693 0 68 884 1577

2040 0 99 594 0 68 816 1410

2041 0 99 495 0 68 748 1243

2042 0 99 396 0 68 680 1076

2043 0 99 297 0 68 612 909

2044 0 99 198 0 68 544 742

2045 0 99 99 0 68 476 575

2046 0 99 0 0 68 408 408

2047 0 0 0 0 68 340 340

2048 0 0 0 0 68 272 272

2049 0 0 0 0 68 204 204

2050 0 0 0 0 68 136 136

2051 0 0 0 0 68 68 68

0 0 0 0 0 68 0 0

LARGER AIRPLANE FLEET

The proposed design requirements contained in §§ 25.773, 25.903, 25.929, 25.1093, 

25.1323, 25.1324 (angle of attack systems), 25.1325, 25.1521, and 25.1533 would extend

to all transport category airplanes. Table 8 summarizes the certifications for current U.S. 

manufacturers of larger airplanes. 
18

TABLE 8 – LARGER AIRPLANE CERTIFICATIONS

TC Model Total Production Years

1958 DC-8 310 14

1963 727 1287 22

1965 717, 1290 42

1967 737 2855 42

1967 G-1159 983 41

1970 747 296 40

1971 DC-10, 315 30

1982 757 730 23

1982 767 429 22

1995 777 229 14

Total 8,724 290

We use summarized data in table 9 to estimate the number of future certifications of 

larger airplanes. The historical evidence shows that, on average, larger airframe 

manufacturers in the United States receive approval for 0.2 new airplane type certificates 

per year, which equates to roughly 2 over a 10-year period. 

Table 9 - Summary Data for Larger Airplane Certifications

Years (1958-2006)

Total Count of New Designs 10

Designs Per Year 0.2

U.S. Deliveries 8,724

U.S. Deliveries Per Period Per TC 31

Estimated Number of Designs in 10 years 2

The approximate annual number of deliveries to the U.S. of larger airplanes per type 

certificate is 31 (8,724 airplanes/290 production years), and we estimate the approximate 

number of production years is 29. Table 10 shows the estimated fleet for larger airplanes. 

There are 2 type certificates, followed by 29 years of deliveries with 62 airplanes 

delivered annually. We use the same transport category airplane service life (25 years). 
19

TABLE 10 – LARGER AIRPLANE FLEET

Year Deliveries Retirements Net Fleet

2009

Effective Date of Rule 2010

2 Certifications Occur 2011

Deliveries Begin 2012 62 62

2013 62 124

2014 62 186

2015 62 248

2016 62 310

2017 62 372

2018 62 434

2019 62 496

2020 62 558

2021 62 620

2022 62 682

2023 62 744

2024 62 806

2025 62 868

2026 62 930

2027 62 992

2028 62 1054

2029 62 1116

2030 62 1178

2031 62 1240

2032 62 1302

2033 62 1364

2034 62 1426

2035 62 1488

2036 62 62 1488

2037 62 62 1488

2038 62 62 1488

2039 62 62 1488

2040 62 62 1488

2041 62 1426

2042 62 1364

2043 62 1302

2044 62 1240

2045 62 1178

2046 62 1116

2047 62 1054

2048 62 992

2049 62 930

2050 62 868

2051 62 806

2052 62 744

2053 62 682

2054 62 620

2055 62 558

2056 62 496

2057 62 434

2058 62 372

2059 62 310

2060 62 248

2061 62 186

2062 62 124

2063 62 62

2064 62 0
20

BENEFITS

As we will show, accidents in apparent SLD conditions tend to be associated with stalls, 

loss of control, and catastrophic outcomes. The purpose of this proposed rule is to 

prevent such outcomes in the future. The industry and the FAA analyzed the historical

SLD events for airplanes certificated under part 25 and part 33. We evaluated all the 

events for applicability and preventability in context of the requirements contained in this 

proposed rule. An event is defined as an accident or incident that might have been 

prevented had the requirements in this proposal been in effect during the certification

process. We describe the event, provide the basis for benefits, and estimate the risk for 

three categories of benefits that directly align with the proposed requirements. 

 Benefits from averting events involving smaller and medium airplanes

 Benefits from averting events involving larger airplanes

 Benefits from averting engine events 

Averting Events on Smaller and Medium Airplanes

HISTORICAL SLD EVENTS

Below, we examine the historical related SLD events for smaller and medium airplanes. 

We have included some basic information on each accident and the justification for 

applicability. 
21

1) 4/29/1993

An Embraer EMB-120 was substantially damaged when it collided with rough terrain 

during an overrun following a forced landing. The forced landing was executed

following a stall and loss of control at 17,412 feet during climb, which resulted in 

damage to the left engine and propeller. Of the 3 crewmembers and 27 passengers 

aboard, 13 individuals received minor injuries.

The NTSB found that, in combination with other factors, ice accretion led to an 

aerodynamic stall, loss of control, and a forced landing. 

Justification for applicability:

The meteorological report indicated the possibility of SLD icing in the area of this 

accident. Proposed 14 CFR 25.1420 would require a means of detecting appendix O

conditions for which the manufacturer has not certificated the airplane and would also 

require that the airplane be capable of operating safely within those conditions for the 

purpose of exiting those conditions.

2) 10/31/1994

An ATR-72 struck the ground after the flightcrew lost control of the airplane during an 

adverse roll event at 9,200 feet causing a total of 68 deaths.

The NTSB found that the probable cause of the accident was the loss of control, 

attributed to a sudden and unexpected aileron hinge moment reversal that occurred after a 

ridge of ice accreted beyond the deice boots while the airplane was in a holding pattern. 

It intermittently encountered supercooled cloud and drizzle/rain drops, the size and water 

content of which exceeded those described in the icing certification envelope. 

Justification for applicability:

After encountering large droplet icing conditions, the airplane stalled and lost control, 

which may have been consistent with appendix O. Proposed 14 CFR 25.1420 would 

require the airplane be able to safely operate in appendix O conditions or have a means of 

detecting appendix O conditions and be capable of operating safely within those 

conditions for the purpose of exiting those conditions.

3) 12/30/1995

Two fatalities occurred as a result of a Cessna 560 colliding with the terrain at the Eagle 

River Airport, Eagle River, Wisconsin. The NTSB determined the probable cause of the 

accident was the pilot’s failure to maintain airspeed while executing the circling 

approach. Factors were descent below minimum descent altitude, fog, low ceiling, and 

icing conditions.

Although the ice accretion was not described as consistent with large droplet icing, a 

sheriff’s deputy reported freezing rain and sleet were falling at the time of the accident. 
22

Justification for applicability:

Existing airplanes have not substantiated that they are capable of safely operating in 

appendix O (freezing drizzle and freezing rain) conditions. Proposed 14 CFR 25.1420 

would require the airplane be able to safely operate in appendix O conditions or have a 

means of detecting appendix O conditions and be capable of operating safely within those 

conditions for the purpose of exiting those conditions.

4) 01/09/1997

An Embraer EMB-120RT crashed while being vectored for approach to runway 3R at 

Detroit Metropolitan Wayne County Airport, which resulted in 29 deaths. 

The investigation revealed that it was likely that the airplane gradually accumulated a 

thin, rough glaze/mixed ice coverage on the leading edge deicing boot surfaces, possibly

with ice ridge formation on the leading edge upper surface. 

The NTSB determined one of the probable causes was the failure to establish adequate 

airplane certification standards for flight in icing conditions. 

Justification for applicability:

Existing airplanes have not substantiated that they are capable of safely operating in 

appendix O (freezing drizzle and freezing rain) conditions. Proposed 14 CFR 25.1420 

would require that newly certificated airplanes safely operate in appendix O conditions or 

have a means of detecting and exiting appendix O conditions.

5) 3/19/2001

There was an accident involving an Embraer 120, which resulted in neither deaths nor 

injuries. The NTSB determined the cause of the accident as the failure of the flightcrew 

to maintain airspeed during an encounter with severe icing conditions, which resulted in 

an inadvertent stall, loss of control, and structural damage to the airplane.

Justification for applicability:

The airplane encountered SLD icing. The flightcrew delayed exiting the conditions. 

Proposed 14 CFR would require a means of detecting appendix O conditions for which 

the manufacturer has not certificated the airplane. It would further require that the 

airplane be capable of operating safely within those conditions for the purpose of exiting 

those conditions.

ESTIMATED COST OF AN SLD EVENT

As shown in the above events, SLD accidents tend to be associated with stalls, loss of

control, and catastrophic outcomes. We examined these historical events (that could have 

been prevented had the requirements of this proposal been in effect), and use them as a 
23

basis for the benefit of averting future events.

Our “generic” SLD event is based on the “average” SLD event, and we find that the 

historical cost of an average SLD event is $126.9 million. 

Averting Injuries and Fatalities

The first category of benefits associated with an average SLD event is averting fatalities 

($6.0 million per fatality) and averting injuries ($18,000 per injury).

For each historical event, we multiply the average number of past fatalities by 

$6.0 million and the number of injuries by $18,000. As shown in the fourth column of 

table 11, for all SLD events, the average cost of averting injuries and fatalities is 

$118.9 million. 

Averting Hull Loss and Accident Investigation Costs 

In addition to the injuries and fatalities, averting an SLD event would also spare the 

accompanying hull loss and the cost of the accident investigation. The total estimate for 

averting hull loss and accident investigation costs is $20.0 million per fatal event. The 

FAA uses the replacement cost of an airplane operating in scheduled commercial service 

to approximate the value of a destroyed airplane. The replacement value for a single 

airplane is $11.46 million

7

 and the FAA conservatively assumes there would be no 

collateral damage. The estimated accident investigation costs are $8.6 million.

8

 

7

 “Economic Values for FAA Investment and Regulatory Decisions.” Table 5-1, column 3, calculates the 

weighted average estimated current market value for all airplanes. 

8

 Ibid
24

Table 11 summarizes the total estimated cost of an average SLD event at $126.9 million. 

This blended event accounts for both the medium airplanes (where there are more seats 

and passengers) and smaller airplanes (where there are less seats and passengers).9 

TABLE 11 - AVERAGE SLD EVENT FOR SMALLER AND 

MEDIUM AIRPLANES

Date of Event Deaths Injuries Averting 

Injuries & 

Fatalities

Accident 

Investigation & 

Airplane

Total

04/29/1993 0 13 $234,000 0 $234,000 

10/31/1994 68 0 $408,000,000 $20,006,900 $428,006,900 

12/30/1995 2 0 $12,000,000 0 $12,000,000 

01/09/1997 29 0 $174,000,000 $20,006,900 $194,006,900 

 3/19/2001 0 0 $0 0 $0 

Average $118,846,800 $8,002,760 $126,849,560 

Benefit from 

averting death $6,000,000 

Benefit from 

averting injury $18,000 

ANNUAL RISK 

We estimate annual risk using the projected fleet in combination with the historical rate 

of preventable events. As shown in the previous section, we have examined the recent 

history of SLD events for the years 1993 though 2007 and found that there were at least 

five preventable SLD events during this time period. Similarly, the total number of 

airplanes operating from 1993 through 2007 was 132,01810(see table 12). These Form 41 

numbers represent major, national, and regional carriers who report commercial service. 

 

9 Three of the events were catastrophic in nature. 

10 Form 41. There are no Form 41 business jet operations (primarily in the small category of aircraft. 
25

TABLE 12 – HISTORICAL FLEET 

Year Fleet

1993 6,139

1994 6,455

1995 6,787

1996 7,187

1997 7,380

1998 8,067

1999 8,730

2000 8,935

2001 9,052

2002 11,727

2003 90,30

2004 10,509

2005 10,551

2006 10,764

2007 10,705

Fleet Years 132,018

To develop the overall historical likelihood of an accident (from 1993-2007), we divide 

the minimum number of events (5) by the sum of the annual number of airplanes in the 

fleet (132,018). Assuming a uniform distribution over the analysis period, the annual risk 

equals the average annual number of accidents per airplane multiplied by the total net 

annual affected fleet. The result (0.0000378736233) is the historical average annual 

number of accidents per affected smaller and medium airplane in absence of this 

proposed rule.

QUANTIFIED BENEFITS FOR SMALLER AND MEDIUM 

AIRPLANES

Aggregating the airplane sizes accounts for various sizes airplanes that would be affected 

by the proposed rule. We calculate the annual estimated quantified benefits for newly

designed and produced smaller and medium airplanes by multiplying the risk of an 

accident per airplane by the expected value of averting an SLD accident and then by the 

annual affected fleet. As detailed in our fleet discussion, the total annual affected fleet is 
26

the total annual net number of smaller affected airplanes plus the total annual net number 

of medium airplanes. When summed over time, we arrive at the total quantified benefits.

 

Shown in table 13 are benefits for the period of analysis ending in 2051. We multiply the 

net affected fleet by the annual risk (0.0000378736233 per airplane) and by the average 

cost ($126.9 million) of averting an SLD event. Again, as the period of analysis is 

different from smaller and medium airplanes versus larger airplanes, the reader should 

focus their attention on present values. The total estimated benefits are $249.6 million

($70.0 million present value). 
27

TABLE 13 – QUANTIFIED BENEFITS SMALLER & MEDIUM AIRPLANES

Year Net Fleet

Smaller + 

Medium

Annual Risk Per Airplane Nominal Values

(risk x fleet 

x$126.9 mil)

Present Value

2012 167 0.0000378736233 $802,310 $654,924 

2013 334 0.0000378736233 $1,604,620 $1,224,157 

2014 501 0.0000378736233 $2,406,930 $1,716,108 

2015 668 0.0000378736233 $3,209,241 $2,138,453 

2016 835 0.0000378736233 $4,011,551 $2,498,192 

2017 1002 0.0000378736233 $4,813,861 $2,801,711 

2018 1169 0.0000378736233 $5,616,171 $3,054,825 

2019 1336 0.0000378736233 $6,418,481 $3,262,830 

2020 1503 0.0000378736233 $7,220,791 $3,430,546 

2021 1670 0.0000378736233 $8,023,102 $3,562,353 

2022 1738 0.0000378736233 $8,349,791 $3,464,866 

2023 1806 0.0000378736233 $8,676,480 $3,364,889 

2024 1874 0.0000378736233 $9,003,169 $3,263,163 

2025 1942 0.0000378736233 $9,329,858 $3,160,346 

2026 2010 0.0000378736233 $9,656,547 $3,057,016 

2027 2078 0.0000378736233 $9,983,237 $2,953,679 

2028 2078 0.0000378736233 $9,983,237 $2,760,448 

2029 2078 0.0000378736233 $9,983,237 $2,579,858 

2030 2078 0.0000378736233 $9,983,237 $2,411,082 

2031 2078 0.0000378736233 $9,983,237 $2,253,348 

2032 2078 0.0000378736233 $9,983,237 $2,105,933 

2033 2078 0.0000378736233 $9,983,237 $1,968,161 

2034 2078 0.0000378736233 $9,983,237 $1,839,403 

2035 2078 0.0000378736233 $9,983,237 $1,719,068 

2036 2078 0.0000378736233 $9,983,237 $1,606,606 

2037 1911 0.0000378736233 $9,180,926 $1,380,832 

2038 1744 0.0000378736233 $8,378,616 $1,177,722 

2039 1577 0.0000378736233 $7,576,306 $995,277 

2040 1410 0.0000378736233 $6,773,996 $831,664 

2041 1243 0.0000378736233 $5,971,686 $685,198 

2042 1076 0.0000378736233 $5,169,376 $554,336 

2043 909 0.0000378736233 $4,367,065 $437,664 

2044 742 0.0000378736233 $3,564,755 $333,885 

2045 575 0.0000378736233 $2,762,445 $241,812 

2046 408 0.0000378736233 $1,960,135 $160,356 

2047 340 0.0000378736233 $1,633,446 $124,888 

2048 272 0.0000378736233 $1,306,757 $93,374 

2049 204 0.0000378736233 $980,068 $65,449 

2050 136 0.0000378736233 $653,378 $40,778 

2051 68 0.0000378736233 $326,689 $19,055 

Total $249,580,915 $69,994,259 
28

Benefits from averting events involving larger airplanes

SLD also poses a risk for larger airplanes. Although the proposed § 25.1420 SLD 

requirements would not extend to larger airplanes, the other design requirements 

contained in this proposal do not distinguish based upon airplane weight and therefore 

extend to larger airplanes. French investigators indicate that a recent Air France A330 

accident where 228 people died could have been the result of airspeed indicators failing. 

Investigators are considering the possibility that the plane's pitot tubes may have iced 

over and given dangerously false readings to cockpit computers.

11 This rule would 

introduce new SLD, mixed phase, and ice crystal icing requirements for pitot tubes.12

For larger airplanes, we assign a 30%-40% range of uncertainty in order to assess the 

overall potential risk to this category of airplanes. We estimate 35% as the approximate 

proportional of the requirements contained in this rulemaking package that would be 

applicable to larger airplanes. Further, we estimate that 35% is the approximate risk that 

a larger airplane would be involved in an SLD event. When multiplied, we arrive at 

12.3% which represents the final overall SLD risk for larger airplanes. To quantify the 

individual risk per airplane (for larger airplanes), we multiply the estimated annual risk 

for smaller airplanes (0.0000378736233) which we developed earlier, by 12.3%, which 

equals 0.00000465845567. This resulting value is the estimated annual risk for a larger

airplane. We multiply the estimated annual risk per affected larger airplane by the net 

affected fleet to arrive at the total annual risk for the fleet of larger airplanes. 

 

11 The accompanying news story can be found at 

http://www.cbsnews.com/stories/2009/06/09/world/main5074662.shtml

12 The Air France A-330 accident was not used in the in the calculations of quantitative benefits that would 

occur as a result of this proposed rule.
29

QUANTIFIED BENEFITS-LARGER AIRPLANES

The annual expected value of a larger airplane accident equals the affected fleet 

multiplied by the cost of an accident then multiplied by the risk.13 The total estimated 

quantified benefits for larger airplanes equals the annual expected value of averting an 

annual catastrophic SLD accident summed over the analysis period.

The number of fatalities in a catastrophic accident for a larger airplane equals the load 

factor multiplied by the number of seats plus the crew (126).14 Multiplying 126 averted 

fatalities by $6.0 million (the estimated cost of averting a fatality) equals $756 million. 

When this total is added to the estimated cost of accident investigation ($8.6 million), and 

then added to the estimate of airplane damage ($11.5 million), the total cost of a larger

airplane accident equals $776.1 million.

Shown in table 14 are estimated annual and total larger airplane benefits for the period of

analysis. We multiply the net affected fleet by the annual risk (0.00000465845567 per 

airplane) and by the average cost ($776.1 million) of averting an SLD event on a larger

airplane. When summed over time, the total estimated benefits are $156.0 million 

($29.5 million present value). 

 

13 The affected fleet and methodology is shown earlier in the affected fleet discussion. 

14 For large airplanes we use tables 9 and 6 of the 2009 Aerospace Forecasts. The average number of seats 

times the average load factor gives the approximate number of passengers on a large airplane (122). 

When added to the pilot, copilot, and two crewmembers, the total number of individuals on board would 

be approximately 126. 
30

TABLE 14 – LARGER AIPLANE BENEFITS

Year Net Fleet Annual Risk Per Airplane Nominal Values

(risk x fleet x$776.1 mil)

Present Value

2012 626622 0.00000465845567 $ 224,145 $ 182,969 

2013 124 0.00000465845567 $ 448,290 $ 341,998 

2014 186 0.00000465845567 $ 672,435 $ 479,437 

2015 248 0.00000465845567 $ 896,580 $ 597,429 

2016 310 0.00000465845567 $ 1,120,725 $ 697,931 

2017 372 0.00000465845567 $ 1,344,870 $ 782,726 

2018 434 0.00000465845567 $ 1,569,015 $ 853,440 

2019 496 0.00000465845567 $ 1,793,160 $ 911,551 

2020 558 0.00000465845567 $ 2,017,305 $ 958,407 

2021 620 0.00000465845567 $ 2,241,449 $ 995,230 

2022 682 0.00000465845567 $ 2,465,594 $ 1,023,134 

2023 744 0.00000465845567 $ 2,689,739 $ 1,043,127 

2024 806 0.00000465845567 $ 2,913,884 $ 1,056,126 

2025 868 0.00000465845567 $ 3,138,029 $ 1,062,959 

2026 930 0.00000465845567 $ 3,362,174 $ 1,064,378 

2027 992 0.00000465845567 $ 3,586,319 $ 1,061,062 

2028 1054 0.00000465845567 $ 3,810,464 $ 1,053,625 

2029 1116 0.00000465845567 $ 4,034,609 $ 1,042,620 

2030 1178 0.00000465845567 $ 4,258,754 $ 1,028,545 

2031 1240 0.00000465845567 $ 4,482,899 $ 1,011,849 

2032 1302 0.00000465845567 $ 4,707,044 $ 992,936 

2033 1364 0.00000465845567 $ 4,931,189 $ 972,167 

2034 1426 0.00000465845567 $ 5,155,334 $ 949,866 

2035 1488 0.00000465845567 $ 5,379,479 $ 926,322 

2036 1488 0.00000465845567 $ 5,379,479 $ 865,721 

2037 1488 0.00000465845567 $ 5,379,479 $ 809,086 

2038 1488 0.00000465845567 $ 5,379,479 $ 756,155 

2039 1488 0.00000465845567 $ 5,379,479 $ 706,687 

2040 1488 0.00000465845567 $ 5,379,479 $ 660,455 

2041 1426 0.00000465845567 $ 5,155,334 $ 591,529 

2042 1364 0.00000465845567 $ 4,931,189 $ 528,795 

2043 1302 0.00000465845567 $ 4,707,044 $ 471,737 

2044 1240 0.00000465845567 $ 4,482,899 $ 419,881 

2045 1178 0.00000465845567 $ 4,258,754 $ 372,792 

2046 1116 0.00000465845567 $ 4,034,609 $ 330,067 

2047 1054 0.00000465845567 $ 3,810,464 $ 291,336 

2048 992 0.00000465845567 $ 3,586,319 $ 256,260 

2049 930 0.00000465845567 $ 3,362,174 $ 224,527 

2050 868 0.00000465845567 $ 3,138,029 $ 195,849 

2051 806 0.00000465845567 $ 2,913,884 $ 169,963 

2052 744 0.00000465845567 $ 2,689,739 $ 146,625

2053 682 0.00000465845567 $ 2,465,594 $ 125,613 

2054 620 0.00000465845567 $ 2,241,449 $ 106,723 

2055 558 0.00000465845567 $ 2,017,305 $ 89,767 

2056 496 0.00000465845567 $ 1,793,160 $ 74,573 

2057 434 0.00000465845567 $ 1,569,015 $ 60,983 

2058 372 0.00000465845567 $ 1,344,870 $ 48,851 

2059 310 0.00000465845567 $ 1,120,725 $ 38,046 

2060 248 0.00000465845567 $ 896,580 $ 28,446 

2061 186 0.00000465845567 $ 672,435 $ 19,939 

2062 124 0.00000465845567 $ 448,290 $ 12,423 

2063 62 0.00000465845567 $ 224,145 $ 5,805 

2064 0 0.00000465845567 $ - $ - 

Total $ 156,004,884 $ 29,498,469 
31

Benefits from Engine Requirements

From 1988-2003, there were over 100 documented cases of ice crystal and mixed phase 

engine power loss events. These events are directly related to the proposed engine 

requirements. Of these events, there were eleven total power loss events15 from

flameouts. One of the events occurred when a Beechjet 400 with PWC JT15D engines 

had a total power loss at top-of-descent and could not relight the engines. That event 

resulted in a dead-stick forced landing at Jacksonville airport. Clearly having to relight

engines during a flight is a serious event, which can result in an accident. The FAA has 

examined these historical events and has found that the historical events resulted in about 

a 12% diversion rate.16 

Similar to the other design requirements contained in the proposed rule, we have included 

five of the most significant recent events and include some basic information on each

accident and the justification for applicability. Each of these events could have been 

mitigated by the part 33 requirements contained in this rule.17 We also did not include 

engine damage events where power loss did not occur, but there was core damage. We 

believe these damage costs would also be averted once the rule is in place. 

1) Beechjet Incident

 

15 Total power loss events are events where all engines loose power at the same time

16 FAA Engine and Propeller Directorate- This 12% diversion rate comes from 17 known diversions out of 

141 known power loss events. The list includes the following engine models: JT8D, JT15D, Tay 

615/620, CF6-80C2, Trent, and ALF502

17 The proposed requirements contained in part 33 focus on mixed phase and ice crystals as the new feature, 

in addition to having a ground based icing test that includes SLD. In addition to the events listed, there are 

also unscheduled landings that are preventable with the proposed requirements. We conservatively do not 

estimate these additional benefits, but note that operators will realize cost savings whenever these events 

are averted. 
32

NTSB Identification: ENG04IA021

14 CFR 91: General Aviation

Incident occurred Monday, July 12, 2004, in Sarasota, FL

Probable Cause Approval Date: 12/20/2007Airplane: Raytheon Corporate Jets Beechjet 

400A, registration: N455CW

Note: CAAM 3 due to loss of >3k feet with both engines out.

see NTSB web site for narrative:

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20040804X01143&key=1

Event Description: The Hawker-Beech Beechjet 400A was descending through flight 

level 390 when both of the engines flamed out and lost all power while operating in 

instrument meteorological conditions with convective storms in the area. The pilots, after 

several attempts, were able to get one engine restarted as the airplane was descending 

through 10,000 feet and diverted to a nearby airport. High-altitude ice crystals had 

accreted on the compressor vanes and were ingested into the high pressure compressor 

when the pilots retarded the power levers causing compressor surges and flameouts of 

both engines.

Justification for Revised Rule Applicability: Proposed revisions to 14 CFR 33, § 33.68 

would require turbine engines to demonstrate acceptable and safe operation in the 

proposed mixed phase and ice crystal icing environment of part 33, appendix D.

2) Beechjet Incident

NTSB Identification: DCA06IA007. 

14 CFR 91: General Aviation

Incident occurred November 28, 2005, in Jacksonville, FL

Probable Cause Approval Date: 6/30/2008Airplane: Raytheon Corporate Jets Beechjet 

400A, registration: N691TA

Note: CAAM 4 due to forced landing with both engines out.

See NTSB web site for narrative:

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20060104X00004&key=1

Event Description: The Hawker-Beech Beechjet 400A was descending through flight 

level 380 in visual meteorological conditions in the vicinity of cumulonimbus buildups. 

Upon reducing power to initiate descent the crew heard a “popping” noise, and both 

engines rolled back. The crew declared an emergency, elected to divert to Jacksonville 

airport, and initiated emergency procedures. All attempts to restart the engines were 

unsuccessful. The crew executed a successful emergency dead-stick landing.

Justification for Revised Rule Applicability: Proposed revisions to 14 CFR 33, §33.68 

would require turbine engines to demonstrate acceptable and safe operation in the 

proposed mixed phase and ice crystal icing environment of part 33, appendix D.

3) Beechjet Incident

NTSB Identification: ENG06IA020. 

14 CFR 91: General Aviation

Incident occurred Wednesday, June 14, 2006, in Norfolk, VA

Probable Cause Approval Date: 1/31/2008Airplane: Raytheon Corporate Jets Beechjet 

400A, registration: N440DS

Note: CAAM 3 due to loss of >3k feet with both engines out.
33

See NTSB web site for narrative:

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20060712X00929&key=1

Event Description: The Raytheon Beechjet 400A was cruising at flight level 380 when 

both of the engines flamed out after the pilots had reduced power prior to turning on the 

engine anti-ice systems. The airplane was in visual meteorological conditions, but was 

approaching clouds that were known to be remnants of a tropical storm. The left and 

right engines restarted on their own as the airplane descended through flight levels 300 

and 240, respectively.

Justification for Revised Rule Applicability: Proposed revisions to 14 CFR 33, § 33.68 

would require turbine engines to demonstrate acceptable and safe operation in the 

proposed mixed phase and ice crystal icing environment of part 33, appendix D.

4) MD-82 Incident 

NTSB Identification: CHI02IA151. 

Scheduled 14 CFR 121: Air Carrier SPIRIT AIRLINES INC.

Incident occurred Tuesday, June 4, 2002, in Wichita, KS

Probable Cause Approval Date: 1/28/2005

Airplane: McDonnell Douglas MD-82, registration: N823NK

Note: CAAM 3 due to loss of >3k feet with both engines out.

See NTSB web site for narrative:

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20020612X00866&key=1

Event Description: The airplane experienced a roll back of engine power on both engines 

and subsequently stalled while in cruise flight at flight level 330. The weather conditions 

were consistent with the presence of ice crystals at the cruise altitude. The engine inlet 

probes became blocked due to the ice crystals, resulting in a false engine pressure ratio 

(EPR) indication and subsequent retarding of the throttles by the auto-throttle system. 

The NTSB stated that factors included the presence of ice crystals at altitude, and the 

icing of the engine inlet probes resulting in a false engine pressure ratio indication.

Justification for Revised Rule Applicability: Engine inlet probes and engine inlet 

systems are addressed in the proposed revisions to 14 CFR 33, § 33.68, which would 

require turbine engines to demonstrate acceptable and safe operation in the proposed 

mixed phase and ice crystal icing environment of part 33, appendix D.

5) Fokker 70 Accident

Date: January 5, 2004

Location: Near Munich Airport

Type of airplane: Transport Category Airplane

Manufacturer / Model: Fokker Aircraft B.V. / F28 MK0070 (Fokker 70)

Injuries to persons: Three minor injuries

Damage to airplane: Airplane severely damaged

Note: CAAM 4 due to forced landing off airport and damaged aircraft.

See German BFU accident report at BFU web site for narrative:

http://www.bfu-web.de/cln_007/nn_226462/EN/Publications

/Investigation_20Report/2004/Report__04__AX001-

0__MUC__Fokker,templateId=raw,property=publicationFile.pdf/Report_04_AX001-

0_MUC_Fokker.pdf
34

Event Description: A Fokker 70 with Rolls-Royce Tay 620 engines departed from 

Vienna for a scheduled flight to Munich. While in descent to Munich, at flight level 90, 

heavy engine vibrations were indicated. This occurred after a prolonged time under 

moderate mixed phase icing conditions (snow) and low engine thrust where ice accreted 

on the rotors of the low pressure compressors of both engines. The accreted ice then shed 

and impacted the ice-impact-panels thereby dislodging them and blocking the fan bypass 

duct that provides primary thrust. The crew declared an emergency due to engine 

problems and requested to be cleared for an immediate landing. The airplane was 

immediately cleared for a descent. Because the airplane could not maintain the glide 

slope it was forced to land approximately 2.5 NM short of the beginning of the runway 

on a snow covered field with the landing gear partially extended. The fuselage 

undercarriage was heavily damaged.

Justification for Revised Rule Applicability: This event occurred while operating in 

moderate snow conditions. Part 33 currently does not address snow (mixed phase) 

conditions. Proposed revisions to 14 CFR 33, § 33.68 would require turbine engines to 

demonstrate acceptable and safe operation in the proposed mixed phase and ice crystal 

icing environment of part 33, appendix D.

The continued incidents, accidents, diversions, and power losses demonstrate the need for 

these proposed engine requirements. The above events are precursor events that, if not 

addressed through rulemaking, could result in an unrecoverable power loss and 

consequent fatal accident. 

BENEFIT SUMMARY

As summarized in table 15, the total estimated benefits are $405.6 million ($99.5 million 

present value). Due to the period of analysis, the reader should focus on the present value 

benefit estimate of $99.5 million.

TABLE 15 - SUMMARY OF BENEFITS

Nominal Benefits PV Benefits

Smaller & Medium Airplanes $ 249,580,915 $ 69,994,259 

Larger Airplanes $ 156,004,884 $ 29,498,469 

Total $ 405,585,799 $ 99,492,728 
35

COSTS

This regulatory evaluation provides the estimated incremental societal costs and benefits

for the United States that would result from this proposed rule. Accordingly, we estimate 

costs to U.S. manufacturers and to U.S. operators. While we estimate costs to 

international manufacturers separately, we do not include these costs in the overall 

United States compliance costs.

 

First, we estimate the certification costs to smaller, medium, and larger airplanes. 

Second, we analyze the additional cost for engine certification and hardware. Lastly, we 

estimate additional fuel costs and other operating costs.

 

The total estimated costs of this proposed rule are $71.5 million ($54.1 million present 

value). This section discusses how these costs are developed. We incorporate 

manufacturer cost estimates detailing certification and testing costs. The estimates were

based upon the manufacturer’s assessment of the labor hours, equipment, and materials 

that would be required to comply with all the proposed requirements and are based upon 

the accompanying advisory circulars (ACs) describing an acceptable means for showing 

compliance. For this analysis, the manufacturer’s estimated costs were adjusted for

inflation, our assumptions, and specified labor rates.

 

The proposed rule would require evaluating the operation of newly certificated airplanes 

in the SLD, mixed phase, and ice crystal icing environment and developing a means to 
36

differentiate between different Supercooled Large Drop icing conditions, if necessary. 

Specifically parts 25 and 33 would be amended to address SLD, mixed phase, and ice 

crystal icing conditions. We propose to create a new:

 § 25.1324, Angle of attack systems

 § 25.1420, Supercooled large drop icing conditions

 part 25, appendix O (supercooled large drop icing conditions)

 part 33, appendix C (this will be intentionally left blank as a placeholder)

 part 33, appendix D (mixed phase and ice crystal icing conditions)

In addition, the requirements would:

 Expand the certification icing environment to include freezing rain and 

freezing drizzle.

 Require airplanes most affected by SLD icing conditions to meet certain 

safety standards in the expanded certification icing environment, including 

additional airplane performance and handling qualities requirements.

 Expand the engine certification regulations, and some airplane component 

certification regulations (for example angle of attack and airspeed indicating 

systems), to include freezing rain, freezing drizzle, ice crystal, and mixed 

phase icing conditions.

Smaller Airplane Certification Costs

Manufacturers provided the FAA with hourly estimates for the certification cost across 

the summary categories shown in table16. Based on their information, the estimated cost 
37

for each smaller airplane new design is $8.3 million. Multiplying this new certification 

cost by the number of smaller airplane certifications (3), the total new cost for smaller 

airplane certification is $25.0 million ($21.8 million present value). Following table 16, 

each of the categories is discussed. 

TABLE 16 - SMALLER AIRPLANE CERTIFCATION COST

Smaller Airplane Summary of Certification Cost Per Program

System Design $107,800

SLD Ice Det. System Qual / Certification $107,800

Supporting Analysis $1,162,971

 Total System Design, Certification & Analysis $1,378,571

Aerodynamic Wind Tunnel Tests $1,192,366 

Icing Tunnel Tests $438,868

Total Tunnel Testing $1,631,234

Analysis $1,200,000

Artificial Ice Shapes - Flight Test $725,570

Icing Tanker - Flight Test $1,676,778

Natural Ice - Flight Test $2,920,960

Total Flight Testing $5,323,208

Total: $8,334,113

SYSTEM DESIGN, CERTIFICATION AND ANALYSIS

Manufacturers expect to incur design, certification, and analysis costs totaling

$1.4 million per design. They provided detailed hourly estimates for design, certification,

and analysis to be in compliance with this proposed rule. Table 17 shows these detailed 

estimates with the system design and certification cost breakdown of what the 

manufacturer might do to show compliance with the requirements contained in this 

proposed rule. 
38

TABLE 17 – SMALLER AIRPLANE CERTIFICATION COSTS

 Hours $/hour18 Cost

System Design

System architecture / Integration 1,200 $77 92,400 

System Safety Assessment 200 $ 77 15,400 

Subtotal 107,800 

SLD Ice Det System Qual / Certification

SLD Ice detection qualification 300 $77 23,100 

SLD Ice detection system certification 1,100 $ 77 84,700 

Subtotal 107,800 

Supporting Analysis $1,162,971

Total $1,378,571

AERODYNAMIC WIND TUNNEL TESTS

Wind and icing tunnel test are frequently done to reduce the amount of flight tests in 

natural icing conditions because flight testing in general is costly. Wind and icing tunnel 

testing would be performed in order to demonstrate and certify to the proposed 

requirements and confirm the analysis results. The cost per design for wind tunnel tests 

is $1.2 million per design, and $0.5 million for icing tunnel tests. The details for both 

sets of tests are shown in Table 17. 

 

18 See earlier discussion on labor rates. 
39

TABLE 18 – SMALLER AIRPLANE TUNNEL TESTING

Aerodynamic Wind Tunnel Tests Hours US$/hour Cost

Model rework $20,000 

Wind tunnel rental $1,000,000 

Test Proposal - report 100 $77 $7,700 

Ice shapes fabrication – roughly 5 shapes to be 

tested

5 Units $2,326 $11,630 

Conduct ice testing 600 $77 $46,200 

Data analysis 150 $77 $11,550

Test Results - report 150 $77 $11,550

Travel expenses $83,736 

TOTAL Wind Tunnel Testing: $1,192,366

Icing Tunnel Tests

Model rework (assume available from other tests) $20,000

Icing tunnel rental $300,000

Test Proposal 100 $77 $7,700

Conduct ice testing 600 $77 $46,200

Data analysis 150 $77 $11,550

Test Results - report 150 $77 $11,550

Travel expenses (industry estimate of 6 people for 

2 weeks at a total of $3,489 per week)

 $41,868 

TOTAL Icing Tunnel: $438,868

Total Tunnel Testing $1,631,234

ANALYSIS

There is some variability in the various manufacturers’ methods for certification, and 

each manufacturer typically uses a variety of analysis and test methods to optimize the 

airplane and ice protection systems design. The additional analysis for compliance with

the proposed requirements is expected to cost an average of $1.2 million for each design. 

FLIGHT TESTING 

Manufacturers would perform flight testing to show compliance with the requirements 

contained in this proposed rule. The primary purpose of flight testing is to determine that 

the design is effective and performs its intended functions during flight as predicted by
40

analysis. The flight testing is also used to evaluate any degradation in performance and 

flying qualities, to verify the adequacy of the flightcrew procedures and limitations, and 

to confirm that the powerplant installation performs satisfactorily while in icing 

conditions. The costs are based upon industry estimates for the approximate number of 

hours required to demonstrate compliance with the proposed requirements. We use the 

hourly cost of labor as an estimate when appropriate. For hourly unit costs that differ 

from our standard labor rates, we have updated industry estimates to incorporate 

inflation. The details provided by the industry are shown below and comprise the largest 

estimated proportion of certification costs because they require several additional items 

that support the actual airplane testing (such as but not limited to icing tanker rental, 

renting a chase airplane, and flying the airplane to required location). Table 19 lists the 

estimated cost elements with the total estimated cost for the flight testing accompanying

each certification of roughly $5.3 million.
41

TABLE 19 - FLIGHT TESTING

Hours Hour Cost /Hr. Total

Artificial Ice Shapes - Flight Test Campaign

Test Proposal - report (ice shapes + perform.) 200 $77 $15,400

Ice shapes definition 320 $77 $24, 640 

Ice shapes fabrication 500 $77 $38,500

Ice shapes installation 250 $77 $19,250

Conduct artificial ice testing 30 $19,771 $593,130 

Data analysis 150 $77 $11,550

Test Results - report 300 $77 $23,100 

TOTAL: $725,570

Icing Tanker - Flight Test Campaign

Test Proposal - report 100 77 $7,700 

Icing tanker rental 20 27,617 $552,342 

Cost and time to fly the airplane to tanker place 15 18,780 $281,694 

"Chaser" rental (to document the tests) 20 4,419 $88,375 

Conduct icing tanker tests 20 18,780 $375,592 

Data analysis 150 77 $11,550

Cost and time to fly the airplane back 15 18,780 $281,694 

Test Results - report 150 77 $11,550

Flight crew (pilots / maintenance / eng) support $66,281 

TOTAL: $1,676,778

Natural Ice - Flight Test Campaign

Test Proposal - report 100 $77 $7,700 

Cost and time to fly the airplane to SLD area 15 $19,770 $296,550 

Icing meteorological support 40 $125 $5,000 

Specific icing instrumentation for SLD (rental) $160,000 

Airplane preparation (FTI, painting, cameras...) 200 $77 $15,400 

Conduct natural ice tests in SLD 100 $19,770 $1,977,000 

Data analysis 150 $77 $11,550

Cost and time to fly the airplane back 15 $19,770 $296,550 

Test Results - report 150 $77 $11,550

Flight crew (pilots / maintenance / eng) support $139,560 

TOTAL: $2,920,860

Total Flight Testing $5,323,208
42

Airplane Certification Cost - International Impact

While we estimate international compliance costs, we do not include these costs in the 

overall cost of compliance because regulatory evaluations assess the impact on the U.S. 

economy. As discussed in the fleet analysis, it was necessary to estimate the number of 

designs by foreign companies to determine the number airplane deliveries from foreign 

manufacturers to the United States.

 

Currently there are no United States manufacturers of airplanes who make airplanes in 

the medium airplane category (primarily commercial passenger regional jets). As 

analyzed in the certification costs, we estimate the total cost of each new airplane 

certification at $8.3 million. During a 10-year certification period, there would be 

roughly 3 foreign new medium airplane programs as identified by manufacturers. As 

such, the international cost to medium airplane foreign manufacturers would be roughly

$24.9 million.

Based on historical data provided to the FAA from foreign larger airplane manufacturers, 

over a period of 10 years, manufacturers identified 3 additional programs at $1.6 million, 

8 larger programs at $1.2 million and 17 less extensive programs with an average cost of 

$127,050. As such, the total estimated cost to larger airplane manufacturers is 

$16.6 million.

When we add the international cost of larger airplane manufacturers ($16.6 million) to 

the international cost of medium airplane manufacturers ($24.9 million), the total 

estimated cost to foreign firms is roughly $41.5 million.
43

New Larger Airplane Certification Cost

Some of the proposed certification requirements extend to larger airplanes. 

Manufacturers provided the additional amount of time required to show compliance with

the proposed rule. The additional cost per certification equals the additional compliance 

hours multiplied by the burdened hourly cost for engineers. For the larger airplanes costs 

are estimated at $1.6 million and the breakdown is shown in table 20.

19

TABLE 20 - LARGER AIRPLANE CERTIFICATION 

 Hours Cost Per hour Cost

25.773 Pilot compartment view 

System architecture / Integration 500 $77 $38,500

SSA 200 $77 $15,400 

25.903 & 25.1093 Engines/Engine Installation

Aero analysis 1800 $77 $138,600

System validation $1,200,000 

25.1323 Airspeed indicating system

Aero analysis 600 $77 $46,200 

System validation 600 $77 $46,200 

25.13xx 

Aero analysis 600 $77 $46,200 

System validation 600 $77 $46,200 

TOTAL: $1,577,300

These costs equal the cost per larger certification multiplied by the total number of 

certifications for larger airplanes (2 certifications). The total cost of these requirements is 

$3.2 million ($2.8 million present value). 

Industry representatives also provided estimated additional certification costs for 

additional programs. The derivatives certification costs are expected to be less complex 

overall than a new design. As such, manufacturers have provided a range based upon the 

complexity of the project. New programs identified by the manufacturer would be the 

 

19 This is a per design cost for each new TCDS. 
44

most expensive costing $1.6 million. For larger derivative certification projects that 

might include a new engine installation costs would be $1.2 million per program. Less 

extensive derivative programs could be handled through analysis only with average cost 

of $127,050.

Based on historical data, over a period of 10 years, manufacturers identified an additional

three programs (beyond the two new type certificates), four larger derivatives at 

$1.2 million and 15 less extensive derivates with an average cost of $127,050. As such, 

the total cost for derivatives is $10.4 million ($9.1 million present value).

When we add the total larger airplane derivative cost of $10.4 million ($9.1 million 

present value) to the new larger airplane cost of $3.2 million ($2.8 million present value), 

the total estimated cost for larger airplanes is $13.6 million ($11.9 million present value).

Engine Certification Cost

Proposed engine design and installation requirements would increase costs to engine 

manufacturers. As such, we analyze and evaluate the part 33 engine certification costs 

separately. Manufacturers provided data based upon revised AC 20-147, Turbojet, 

Turboprop, and Turbofan Engine Induction System Icing and Ice Ingestion, which shows 

acceptable compliance methods. As shown in table 21, total additional costs for part 33 

designs are roughly $14.0 million ($12.2 million present value). 
45

TABLE 21 - ENGINE COST SUMMARY

Nominal Cost PV Cost

Engine Cert Cost $7,936,000 $6,931,610 

Engine Capital Cost $6,000,000 $5,240,632 

Total Engine $13,936,000 $12,172,242

The proposed revisions for engine certification would change the environmental 

requirements to evaluate engine protection and operation in icing conditions. The effect 

of the change would be to require an evaluation of safe operation in the revised icing 

environment. The proposed rules would require engines and engine installations to 

operate safely throughout the SLD conditions defined in proposed new part 25, appendix 

O, and the newly defined mixed phase and ice crystal conditions defined in proposed new 

part 33, appendix D.

 

Industry has provided data for several different engine “sizes,” and we aggregate this data 

to determine an average cost per engine certification. The data is further sub-divided into 

certification and capital costs. Table 22 shows the estimated certification costs at 

$496,000 per program. These costs are expected to occur once for every new 

certification program. 
46

TABLE 22 – ENGINE COSTS PER CERTIFICATION

Average Cert. Costs

Engine Analysis (Mixed Phase Glaciated) $ 30,000 

Engine Analysis SLD $ 50,000 

Engine Icing Tests $ 300,000 

Ice Slab Testing (Saved) $ (100,000)

Soft Body Tolerance Analysis $ 116,000 

Test Facilities $ 100,000

 $ 496,000 

From 1996-2005, there were 16 new part 33 turbine engines, or 1.6 engines per year. For 

this analysis, we assume all 16 engine certifications would occur in 2011. With 

certification costs of $496,000 per certification, the total estimated engine certification 

costs are $7.9 million ($7.0 million present value).

 

In addition to these certification costs, there would be additional capital costs to modify

manufacturer facilities in order to provide an ice crystal cloud (as way of showing 

compliance with the proposed requirements). The estimated cost is $1 million per engine 

manufacturer. We expect all 6 manufacturers of part 33 engines to incur this cost in 

2011, for a total cost of $6.0 ($5.2 million present value).

 

The capital cost of $6.0 ($5.2 million present value) plus the certification cost of 

$7.9 million ($7.0 million present value) equals the total engine costs of $14.0 million 

($12.2 million present value). 

Hardware Costs – Smaller and Medium Airplanes

The industry estimates there would be additional SLD ice detectors costs at $10,000 for 

approximately 1⁄2 of the estimated affected deliveries of smaller and medium airplanes. 
47

Industry estimates that roughly 50% of airplanes might be certified using visual cues and 

the remaining might be certified with detectors. When the ice detector costs of $10,000 

are multiplied by the estimated fleet per year and summed cost over the period of 

analysis, the total estimated hardware costs are $10.4 million ($5.8 million present value). 

Fuel Costs – Smaller and Medium Airplanes

These proposed requirements would add operating costs from the additional hardware 

and accompanying weight changes on each smaller and medium airplane. In this 

analysis, we incorporate the recent cost of fuel forecast using data from the FAA 

Aerospace Forecast 2009-2025. We use this forecast along with the fuel consumption 

methodology as explained in FAA’s guidance, Economic Values for FAA Investment and 

Regulatory Decisions20, and the estimated average incremental fuel cost of 192 cents per 

gallon

21 in order to estimate the additional cost of fuel per affected airplane.

 

Again, we use the 50% factor to account for our fuel consumption cost estimates as only

1⁄2 of the fleet would incur the cost of carrying the additional SLD ice detectors. First, we 

estimate the additional fuel cost for smaller airplanes followed by the estimated costs for 

medium airplanes.

22

 

20 For the additional fuel consumption estimates, the FAA uses 0.005 gallons per flight hour per pound of 

additional weight. As shown in table 6-1 of Economic Values for FAA Investment and Regulatory 

Decisions, this is equivalent to a passenger Boeing Model 737-300 airplane with a median stage length of 

500 nm and an Embraer Model ERJ-135 airplane with a median stage length of 250 nm. 

21 Cents expressed in 2009 dollars. 

22 Industry has informed us that there are no estimated additional costs for large airplanes.
48

SMALLER AIRPLANES FUEL COST

The additional incremental weight impact is first multiplied by the fuel burn factor per 

airplane. The product multiplied by the flight hours and then by the cost of fuel equals 

the annual additional fuel consumption cost.

 

For smaller airplanes, we calculate the annual additional cost of fuel by multiplying the 

estimated additional hardware weight of approximately 19 pounds by the fuel burn factor 

of 0.005 gallons per hour per pound to arrive at 0.0935 gallons per hour per airplane. 

This product is then multiplied by the annual flight hours per airplane of 402 hours23 and 

finally by the cost of fuel ($1.92 /gallon) to arrive at the first year annual estimated 

additional cost of fuel for each smaller airplane of $73.

 

Once we calculated the estimated annual additional fuel cost per smaller airplane, we 

multiplied this additional cost by the affected fleet. The industry expects roughly one 

half of the estimated affected fleet would not incur such costs. When multiplied by the 

affected annual fleet of smaller airplanes that would incur cost because of this proposal, 

and summed over the period of analysis, the total smaller airplane fuel cost is $0.9

million ($0.3 million present value). 

MEDIUM AIRPLANE FUEL COST

Similarly, for the category of medium airplanes, we calculate the annual additional cost 

of fuel by multiplying the estimated additional hardware weight of 19.2 pounds by the 

fuel burn factor of 0.005 gallons per hour per pound to arrive at 0.0935 gallons per hour 

 

23 2007 GA Survey – Table 1.1 & 1.4 Turbojet Total (353,400 hours / 880 aircraft)
49

per airplane. We multiplied 0.0935 by the 2,878 annual flight hours per airplane24 and

finally by the cost of fuel ($1.92/gallon) to arrive at the total annual estimated additional

fuel cost of $525 for each medium airplane operating in commercial service. The total 

estimated additional fuel cost equals $525 per airplane multiplied by fifty percent of the

estimated affected fleet that would incur such costs. When summed over time, the

estimated additional fuel consumption costs for medium airplanes are $7.1 million 

($2.0 million present value). 

Other Airplane Operating Costs

The FAA originally asked ARAC to estimate other operational costs beyond the 

additional hardware and fuel consumption costs. Accordingly, ARAC provided this data 

to the FAA. However, as we neared completion of our cost analysis for these 

requirements, we queried individual operators and Chief Pilots informed us they were 

already in compliance and there were no additional operational costs beyond fuel and 

hardware. 

When asked about the existing operations in SLD, Chief Pilots referenced AC 91-51A, 

Effect of Icing on Aircraft Control and Airplane Deice and Anti-Ice Systems, where:

“...Pilots can minimize the chance of a roll upset by being sensitive to cues that 

identify severe icing conditions before control or handling characteristics of the 

airplane are degraded to a hazardous level.”

 

24 DOT, Form 41
50

In addition to the guidance documents and crew training, operators referenced airplane 

flight manuals that require the flightcrew to exit severe icing conditions (which might 

include SLD icing conditions). They recognize the dangers of operating in SLD 

conditions and avoid these conditions. Operators routinely, and on a regular basis, incur 

SLD operational costs from diversions by exiting SLD conditions, diverting to alternate 

airports, and cancelling flights. Operators acknowledge these as existing costs and agree 

there might be only minimal incremental costs as a result of the certification requirements 

contained in this proposal.25

Cost Summary 

The estimated total cost for the period of analysis is $71.0 million ($54.0 million present 

value). Table 22 details the costs by category. The present value costs will be compared 

to the present value benefits in the benefit/cost summary. 

 

25 Impacts on Dispatch - Manufacturers believe compliance with the proposed rule would result in a 

decrease in passenger payload (of 5 passengers) during SLD conditions due to a decrease in medium 

airplane performance. This performance limitation is expected to occur only in SLD conditions (not every 

flight or under normal operating conditions). When an operator takes off or plans to take off in SLD 

conditions, it is expected that it would offload 5 passengers (or equal weight) to offset performance 

limitations. This would equate to a revenue decrease of roughly $390 per flight. Data from the industry 

was used to estimate 0.09 as the performance limited flights taking off into SLD. When multiplied by the 

estimated decrease in revenue per flight ($390), total annual costs are approximately $35, which we believe 

is minimal. For the affected fleet of medium airplanes, the total estimated impact on dispatch is $15,960 

($3,878 present value). 
51

TABLE 23 - COST SUMMARY

Nominal Cost PV Cost

Engine Cert Cost $7,936,000 $6,931,610 

Engine Capital Cost $6,000,000 $5,240,632 

Total Engine $13,936,000 $12,172,242 

Smaller Airplane Certification 

Cost 

 $24,999,039 $21,835,129 

New Larger Airplane

Certification Cost

 $3,154,600 $2,755,350 

Derivative Larger Airplane 

Certification Cost

 $10,438,800 $9,117,652 

Hardware Costs $10,390,000 $5,842,024 

Fuel Burn All $8,046,676 $2,261,941

Total $70,965,115 $53,984,338

Benefit Cost Summary 

The affected fleet and categories of benefits and costs are analyzed over different time 

periods and are customized to the requirements of this proposal. It is important for the 

reader to focus on present value benefits and costs. As such, the total estimated benefits 

are $405.6 million ($99.5 million present value). The total estimated costs are 

$71.0 million ($54.0 million present value). On an annualized basis, for the time period 

2012-2064, the benefits are $7.0 million, and the costs are $3.8 million. Accordingly, the 

benefits of the rule justify the costs, and the rule is cost beneficial.