52382 Federal Register / Vol. 71, No. 171 / Tuesday, September 5, 2006 / Proposed Rules 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Parts 91, 121, and 125 

[Docket No.: FAA–1999–6482; Notice No. 

06–12] 

RIN 2120–AG87 

Revisions to Digital Flight Data 

Recorder Regulations for Boeing 737 

Airplanes and for Part 125 Operators 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Supplemental Notice of 

Proposed Rulemaking (SNPRM). 

SUMMARY: The FAA is revising a 

previous proposal to increase the 

number of digital flight data recorder 

(DFDR) parameters required for all 

Boeing 737 series airplanes. Based on 

safety recommendations from the 

National Transportation Safety Board 

(NTSB) following the investigations of 

two accidents and other incidents 

involving 737s, the FAA proposed the 

addition of flight recorder equipment to 

monitor the rudder system on 737s. 

Since that time, the FAA has mandated 

significant changes to the rudder system 

on these airplanes. Accordingly, this 

new proposed rule would apply to a 

different set of airplanes than originally 

anticipated. We are requesting comment 

on this change in applicability and are 

requesting updated economic 

information regarding installation of the 

proposed monitoring equipment. The 

original proposed rule also sought to 

amend the flight data recorder (FDR) 

requirements of part 125 that would 

affect all airplanes operated under that 

part or under deviation from that part; 

we have included that same proposal in 

this SNPRM. 

DATES: Send your comments on or 

before December 4, 2006. 

ADDRESSES: You may send comments 

identified by Docket Number FAA– 

1999–6482 using any of the following 

methods: 

• DOT Docket Web site: Go to http:// 

dms.dot.gov and follow the instructions 

for sending your comments 

electronically. 

• Government-wide rulemaking Web 

site: Go to http://www.regulations.gov 

and follow the instructions for sending 

your comments electronically. 

• Mail: Docket Management Facility; 

U.S. Department of Transportation, 400 

Seventh Street, SW., Nassif Building, 

Room PL–401, Washington, DC 20590– 

0001. 

• Fax: 1–202–493–2251. 

• Hand Delivery: Room PL–401 on 

the plaza level of the Nassif Building, 

400 Seventh Street, SW., Washington, 

DC, between 9 a.m. and 5 p.m., Monday 

through Friday, except Federal holidays. 

For more information on the 

rulemaking process, see the 

SUPPLEMENTARY INFORMATION section of 

this document. 

Privacy: We will post all comments 

we receive, without change, to http:// 

dms.dot.gov, including any personal 

information you provide. For more 

information, see the Privacy Act 

discussion in the SUPPLEMENTARY

INFORMATION section of this document. 

Docket: To read background 

documents or comments received, go to 

http://dms.dot.gov at any time or to 

Room PL–401 on the plaza level of the 

Nassif Building, 400 Seventh Street, 

SW., Washington, DC, between 9 a.m. 

and 5 p.m., Monday through Friday, 

except Federal holidays. 

FOR FURTHER INFORMATION CONTACT: For 

technical issues: Timothy W. Shaver, 

Avionics Systems Branch, Aircraft 

Certification Service, AIR–130, Federal 

Aviation Administration, 800 

Independence Avenue, SW., 

Washington, DC 20591; telephone (202) 

385–4686; facsimile (202) 385–4651; email tim.shaver@faa.gov. For legal 

issues: Karen L. Petronis, Senior 

Attorney, Regulations Division, AGC– 

200, Office of the Chief Counsel, Federal 

Aviation Administration, 800 

Independence Ave., SW., Washington, 

DC 20591; telephone (202) 267–3073; 

facsimile (202) 267–7971; e-mail: 

karen.petronis@faa.gov. 

SUPPLEMENTARY INFORMATION: 

Comments Invited 

The FAA invites interested persons to 

participate in this rulemaking by 

submitting written comments, data, or 

views. We also invite comments relating 

to the economic, environmental, energy, 

or federalism impacts that might result 

from adopting the proposals in this 

document. The most helpful comments 

reference a specific portion of the 

proposal, explain the reason for any 

recommended change, and include 

supporting data. We ask that you send 

us two copies of written comments. 

We will file in the docket all 

comments we receive, as well as a 

report summarizing each substantive 

public contact with FAA personnel 

concerning this proposed rulemaking. 

The docket is available for public 

inspection before and after the comment 

closing date. If you wish to review the 

docket in person, go to the address in 

the ADDRESSES section of this preamble 

between 9 a.m. and 5 p.m., Monday 

through Friday, except Federal holidays. 

You may also review the docket using 

the Internet at the Web address in the 

ADDRESSES section. 

Privacy Act: Using the search function 

of our docket Web site, anyone can find 

and read the comments received into 

any of our dockets, including the name 

of the individual sending the comment 

(or signing the comment on behalf of an 

association, business, labor union, etc.). 

You may review DOT’s complete 

Privacy Act Statement in the Federal 

Register published on April 11, 2000 

(65 FR 19477–78) or you may visit 

http://dms.dot.gov. 

Before acting on this proposal, we 

will consider all comments we receive 

on or before the closing date for 

comments. We will consider comments 

filed late if it is possible to do so 

without incurring expense or delay. We 

may change this proposal in light of the 

comments we receive. 

If you want the FAA to acknowledge 

receipt of your comments on this 

proposal, include with your comments 

a pre-addressed, stamped postcard on 

which the docket number appears. We 

will stamp the date on the postcard and 

mail it to you. 

Proprietary or Confidential Business 

Information 

Do not file in the docket information 

that you consider to be proprietary or 

confidential business information. Send 

or deliver this information directly to 

the person identified in the FOR FURTHER

INFORMATION CONTACT section of this 

document. You must mark the 

information that you consider 

proprietary or confidential. If you send 

the information on a disk or CD–ROM, 

mark the outside of the disk or CD–ROM 

and also identify electronically within 

the disk or CD–ROM the specific 

information that is proprietary or 

confidential. 

Under 14 CFR 11.35(b), when we are 

aware of proprietary information filed 

with a comment, we do not place it in 

the docket. We hold it in a separate file 

to which the public does not have 

access, and place a note in the docket 

that we have received it. If we receive 

a request to examine or copy this 

information, we treat it as any other 

request under the Freedom of 

Information Act (5 U.S.C. 552). We 

process such a request under the DOT 

procedures found in 49 CFR part 7. 

Availability of Rulemaking Documents 

You can get an electronic copy using 

the Internet by: 

(1) Searching the Department of 

Transportation’s electronic Docket 

Management System (DMS) Web page 

(http://dms.dot.gov/search); 


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(2) Visiting the FAA’s Regulations and 

Polices Web page at http://www.faa.gov/ 

regulations_policies/; or 

(3) Accessing the Government 

Printing Office’s Web page at http:// 

www.gpoaccess.gov/fr/index.html. 

You can also get a copy by sending a 

request to the Federal Aviation 

Administration, Office of Rulemaking, 

ARM–1, 800 Independence Avenue, 

SW., Washington, DC 20591, or by 

calling (202) 267–9680. Make sure to 

identify the docket number, notice 

number or amendment number of this 

rulemaking. 

Anyone is able to search the 

electronic form of all comments 

received into any of our dockets by the 

name of the individual submitting the 

comment (or signing the comment, if 

submitted on behalf of an association, 

business, labor union, etc.). You may 

review DOT’s complete Privacy Act 

statement in the Federal Register 

published on April 11, 2000 (Volume 

65, Number 70; Pages 19477–78) or you 

may visit http://dms.dot.gov. 

Small Business Regulatory Enforcement 

Fairness Act 

The Small Business Regulatory 

Enforcement Fairness Act (SBREFA) of 

1996 requires FAA to comply with 

small entity requests for information or 

advice about compliance with statutes 

and regulations within its jurisdiction. If 

you are a small entity and you have a 

question regarding this document, you 

may contact your local FAA official, or 

the person listed under FOR FURTHER

INFORMATION CONTACT. You can find out 

more about SBREFA on the Internet at 

http://www.faa.gov/avr/arm/sbrefa.htm, 

or by e-mailing us at -AWASBREFA@faa.gov. http://www.faa.gov/ 

regulations_policies/rulemaking/ 

sbre_act/. 

Authority for This Rulemaking 

The FAA’s authority to issue rules 

regarding aviation safety is found in 

Title 49 of the United States Code. 

Subtitle I, Section 106 describes the 

authority of the FAA Administrator. 

Subtitle VII, Aviation Programs, 

describes in more detail the scope of the 

agency’s authority. 

This rulemaking is promulgated 

under the authority described in 

Subtitle VII, Part A, Subpart III, Section 

44701. Under that section, the FAA is 

charged with prescribing regulations 

providing minimum standards for other 

practices, methods and procedures 

necessary for safety in air commerce. 

This regulation is within the scope of 

that authority since flight data recorders 

are the only means available to account 

for aircraft movement and flight crew 

actions critical to finding the probable 

cause of incidents or accidents, 

including data that could prevent future 

incidents or accidents. 

I. Background 

A. Statement of the Problem 

Two aviation accidents in the United 

States involving Boeing 737 series 

airplanes (737s) appear to have been 

caused by a rudder hardover with 

resultant roll and sudden descent: 

United Airlines flight 585, near 

Colorado Springs, Colorado, on March 

3, 1991, and USAir flight 427, near 

Aliquippa, Pennsylvania, on September 

8, 1994. Following lengthy 

investigations, the NTSB determined 

that the rudder on 737s may experience 

sudden uncommanded movement, or 

movement opposite the pilot’s input, 

which may cause the airplane to roll 

suddenly. Other incidents of suspected 

uncommanded rudder movement have 

been reported, including a 1996 

incident involving Eastwind Airlines 

(Eastwind) flight 517, a 737–2H5, and 

five incidents in 1999 involving U.S.- 

registered airplanes. 

The 737s involved in the United 

Airlines and USAir accidents, and those 

in the more recent incidents, were 

equipped with the flight data recorders 

required by the regulations then in 

effect. However, these airplanes were 

not required to record, nor were they 

equipped to provide, information about 

the airplane’s movement about its three 

axes or the position of flight control 

surfaces immediately preceding the 

accident or incident. While the FAA has 

undertaken a series of measures 

designed to address the suspected 

rudder problems, our efforts have been 

limited by a lack of data that focused on 

the control and movement of the 

components of the 737 rudder system. 

Without more data, neither the FAA nor 

the NTSB can definitively identify the 

causes of suspected uncommanded 

rudder events. 

B. FAA Actions 

Following piloted computer 

simulations of the USAir accident and 

reports of malfunctions in the yaw 

damper system of 737s, the FAA 

mandated design changes to the rudder 

system of 737s. First, the FAA issued 

Airworthiness Directive (AD) 97–14–03 

(62 FR 34623, June 27, 1997), which 

requires installation of a newly designed 

rudder-limiting device and a newly 

designed yaw damper system, in an 

effort to address possible rudder 

hardover situations and uncommanded 

yaw damper movements. Second, in 

response to the possibility of a 

secondary slide jam and rudder reversal, 

the FAA issued AD 97–14–04 (62 FR 

35068, June 30, 1997). That AD requires 

operators to install a new vernier 

control rod bolt and a new main rudder 

power control unit (PCU) servo valve in 

each airplane. 

C. Safety Recommendations: 1995–1997 

Between 1995 and 1997, while 

investigating the USAir accident, the 

NTSB issued 20 safety 

recommendations dealing with the 737; 

three of those (A–95–25, A–95–26, and 

A–95–27) dealt specifically with 

upgrades to the FDR for all 737s. The 

NTSB stated that if either the United 

Airlines or the USAir 737 had recorded 

data on the flight control surface 

positions, flight control inputs, and 

lateral acceleration, the NTSB would 

have been able to identify quickly any 

abnormal control surface movements 

and configuration changes or autopilot 

status changes that may have been 

involved in the loss of control. 

At the time it made its 

recommendations, the NTSB recognized 

that the 737 had flown over 92 million 

hours since its initial certification in 

December 1967, and that the airplane’s 

accident rate is comparable to that of 

other airplanes of a similar type. 

Nonetheless, the Board concluded that 

the design changes made to the rudder 

system in accordance with the issued 

ADs did not eliminate the possibility of 

other potential failure modes and 

malfunctions. 

D. FAA Response: 1997 Regulations 

In response to these safety 

recommendations, the FAA published 

revisions to the DFDR requirements for 

all airplanes (Revisions to Digital Flight 

Data Recorder Rules; Final Rule (62 FR 

38362, July 17, 1997)). The revised 

DFDR regulations prescribe the 88 

parameters that must be recorded on 

DFDRs, with the exact number of 

parameters required to be recorded 

determined by the date of airplane 

manufacture. The number of parameters 

that must be recorded range from 18 for 

a transport category airplane 

manufactured on or before October 11, 

1991, to 88 for airplanes manufactured 

after August 19, 2002. 

E. NTSB’s 1999 Findings and Safety 

Recommendations 

On March 24, 1999, the NTSB issued 

the final report of its investigation into 

the crash of USAir flight 427. The NTSB 

determined that the probable cause of 

the accident was a loss of control 

resulting from the movement of the 

rudder surface position to its blowdown 

limit. Further, the NTSB stated that 


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‘‘* * * the rudder surface most likely 

deflected in a direction opposite to that 

commanded by the pilots as a result of a jam 

of the main rudder PCU servo valve 

secondary slide to the servo valve housing 

offset from its neutral position and overtravel 

of the primary slide.’’

In its March 1999 report, the NTSB 

concluded that the 1997 regulations for 

upgrading DFDRs are inadequate for 

existing 737s, because they do not 

require specific flight control 

information to be recorded. Because 

several 737 rudder-related events have 

been associated with the yaw damper 

system (which moves the rudder 

independent of flightcrew input), the 

NTSB concluded that it is important 

that yaw damper status (parameter 89), 

yaw damper command (parameter 90), 

standby rudder status (parameter 91), 

and control wheel, control column, and 

rudder pedal forces (parameter 88) be 

recorded on all 737s. The NTSB also 

pointed out that, for optimal 

documentation, the indicated 

parameters need to be sampled more 

frequently than is required currently. 

The NTSB stated that by recording the 

yaw damper’s operation and the 

resultant rudder surface movements, a 

yaw damper event could be 

distinguished quickly from a flightcrew 

input or a rudder anomaly. The NTSB 

considers this information critical to 

investigating 737 incidents or accidents. 

The NTSB stated that if pilot flight 

control input forces had been recorded 

on the United Airlines, USAir, or 

Eastwind FDRs, the NTSB investigations 

would have been resolved more quickly 

and actions taken to prevent similar 

events would have been hastened. 

On April 16, 1999, the NTSB 

submitted the following 

recommendations to the FAA regarding 

recording additional parameters on 737 

DFDRs: 

Recommendation No. A–99–28. 

Require that all 737s operated under 

part 121 or part 125 that currently have 

a FDAU be equipped, by July 31, 2000, 

with a flight data recorder system that 

records, at a minimum, the parameters 

required by the 1997 DFDR regulations 

applicable to that airplane, plus the 

following parameters: Pitch trim, 

trailing edge flaps, leading edge flaps, 

thrust reverser position (each engine), 

yaw damper command, yaw damper 

status, standby rudder status, and 

control wheel, control column, and 

rudder pedal forces. Yaw damper 

command, yaw damper status, and 

control wheel, control column, and 

rudder pedal forces should be sampled 

at a minimum rate of twice per second. 

Recommendation No. A–99–29. 

Require that all 737s operated under 

part 121 or part 125 that are not 

equipped with a FDAU be equipped, at 

the earliest time practicable, but no later 

than August 1, 2001, with a flight data 

recorder system that records, at a 

minimum, the same parameters noted in 

safety recommendation No. A–99–28. 

The NTSB also noted in its final 

report on the USAir accident that 737 

flightcrews continue to report 

anomalous rudder behavior and that the 

NTSB considers it possible that another 

catastrophic event related to 737 rudder 

upset could occur. 

F. FAA Response: Notice No. 99–19 

The FAA agreed with the intent of 

NTSB Safety Recommendation Nos. A–

99–28 and A–99–29 and the NTSB’s 

concerns regarding continuing reports of 

rudder-related incidents on 737s. On 

November 9, 1999, the FAA issued 

Notice No. 99–19 (64 FR 63140, 

November 18, 1999), which proposed 

that all 737s be required to record the 

parameters listed in § 121.344(a)(1) 

through (a)(22), (a)(88), plus three new 

parameters, designated as (a)(89) 

through (a)(91). The new parameters are 

yaw damper status, yaw damper 

command, and standby rudder status. In 

addition, the FAA proposed increasing 

the required sampling rate for the 

control forces listed in current 

paragraph (a)(88) for 737s. The FAA 

proposed that all 737s equipped with a 

FDAU of any type as of July 16, 1996, 

or manufactured after July 16, 1996, 

comply by August 18, 2000. For all 737s 

not equipped with a FDAU of any type 

as of July 16, 1996, the FAA proposed 

a compliance date of August 20, 2001. 

The FAA noted that if it received 

sufficient data to support an extension, 

the compliance period for airplanes 

retrofitted to include FDAUs between 

July 16, 1996, and November 18, 1999, 

would be extended to August 19, 2002. 

The FAA proposed corresponding 

changes to part 125 for 737s operated 

under that part. In addition, the FAA 

proposed that no deviation authority 

from the FDR requirements of part 125 

would be granted for any model 

airplane, and that any previously issued 

deviation from the DFDR requirements 

of part 125 would no longer be valid. 

The FAA also proposed that § 91.609 be 

amended to reflect that all airplanes 

operating under part 91 under deviation 

authority from part 125 must comply 

with the DFDR requirements in part 

125, notwithstanding such deviation 

authority. 

II. Continuing Need for This 

Rulemaking 

The original NPRM, issued by the 

FAA in 1999, proposed that in addition 

to other applicable requirements, all 737 

model airplanes must record certain 

additional parameters of flight data, 

including those specifically designed to 

monitor rudder system components. 

The FAA added that it planned on 

issuing the final rule with an immediate 

effective date to address the unresolved 

issues with the airplane as soon as 

possible. 

In January 2001, Boeing submitted a 

letter to the docket requesting that the 

FAA delay the release of any final rule. 

The request was based on Boeing’s 737 

Rudder System Enhancement Program 

(RSEP), which itself was based on an 

NTSB recommendation to develop a 

‘‘reliably redundant rudder system’’ for 

the 737. Boeing stated that the RSEP 

changes will make the 737 rudder 

system functionally equivalent to the 3- 

actuator system found on its 757 and 

767 model airplanes. 

Boeing’s letter states that on January 

16, 2001, it presented a detailed 

description of its 737 RSEP changes to 

the NTSB. While noting that the 

proposed rule would be applicable to 

the original rudder system, not the one 

being developed under the RSEP, it 

attempted to minimize the value of a 

final rule that applied only to airplanes 

with the older system installed. Boeing 

also questioned whether it would still 

be appropriate to treat the 737 different 

than other airplanes once the rudder 

system was modified. 

While the redesigned rudder control 

system meets the latest FAA system 

requirements, it remains a system 

unique to the 737 model airplane. In 

Boeing 757/767/777 model airplanes, 

the rudder control system has three 

separate actuators in separate power 

control units (PCU) that are always 

powered. The original design of the 737 

rudder control system had a single input 

into a valve that controlled two installed 

actuators in the PCU. In the redesigned 

737 system, there are three actuators, 

but they are housed in two PCUs rather 

than the three present in the other 

Boeing model airplanes. The main PCU 

has two actuators, each with its own 

valve that accepts input. The third 

actuator is in a standby PCU that is not 

normally powered unless the main PCU 

fails. Thus, the 737 rudder control 

system effectively still has only two 

actuators during normal flight 

operations, and a single actuator when 

the main PCU is inoperative. 

Several events have occurred since 

the NPRM was issued in 1999, 

including Boeing’s RSEP. One of the 

recommendations issued by the NTSB 

included the formation of an 

engineering test and evaluation board 

(ETEB) to conduct a failure analysis of 


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the rudder actuation control system of 

the 737. The 737 ETEB was formed in 

May 1999 and issued its final report in 

July 2000. 

Among the key findings of the 737 

ETEB are the following: 

(1) The 737 rudder control system is 

susceptible to a number of failures and 

jams. These failures and jams can affect 

the operation of the rudder power 

control units and can result in 

uncommanded rudder motion. 

(2) A number of failures and jams of 

the 737 rudder control system were 

detected in configurations on which the 

FAA later issued corrective action under 

one or more Airworthiness Directives 

(ADs). More than two dozen of these 

failures and jams (alone or in 

combination) have what are considered 

catastrophic failure effects. 

(3) Even when 737s were in 

compliance with the ADs issued at the 

time, rudder control system failures and 

jams were still present. 

(4) Most of the failure modes were 

discernable on both the older (classic) 

models and the newer (next generation) 

models of the 737. 

(5) There were no catastrophic failure 

modes identified at cruise speed and 

altitude. One change to the hydraulic 

pressure system mandated by AD 

reduced the time an airplane was 

exposed to catastrophic failure modes, 

but exposure was not eliminated during 

takeoffs and landings. 

Among its recommended long-term 

actions, the ETEB recommended that 

the 737 rudder system be modified to 

ensure that no single failure or single 

jam of the rudder control system would 

cause an uncommanded rudder motion 

that has catastrophic results. 

The NTSB did not withdraw or 

change its recommendation regarding 

further monitoring of the rudder system 

on 737s, and indicated in a February 

2001 letter to the FAA that it had not 

changed its position regarding the need 

for installation of the new FDR 

equipment ‘‘at the earliest possible 

opportunity regardless of any rudder 

system modification.’’

In November 2001, the FAA 

published a proposed AD that would 

require the installation of a new rudder 

control system (and accompanying 

changes to nearby systems) (66 FR 

56783, November 13, 2001). The FAA 

determined that the inherent failure 

modes in the 737 rudder system, 

verified by the ETEB, result in a design 

system architecture that is unsafe. The 

FAA also determined that the rudder 

system design architecture led to a need 

for non-normal operational procedures, 

which had also been implemented by 

AD. The FAA concluded that the 

combination of the inherent failure 

modes and the non-normal operational 

procedures, considered together, present 

an unsafe condition that warranted the 

incorporation of a newly designed 

rudder control system. 

The final rule AD was published on 

October 7, 2002 (67 FR 62341), with an 

effective date of November 12, 2002, 

and gives all operators of 737 model 

airplanes 6 years to install a new rudder 

control system. 

Boeing has been installing the newly 

designed rudder control system on 737 

model airplanes manufactured since 

January 2003. Boeing is also installing 

the additional sensors that were 

proposed in the NPRM on these newly 

manufactured 737s, and those 

parameters are being recorded. 

When we began drafting a final rule, 

we realized that the 737 fleet that would 

be affected by the proposed rule—those 

airplanes with the original rudder 

system—had already begun to shrink in 

number. The promulgation of several 

Airworthiness Directives means that by 

the 2008 compliance date for those ADs, 

no 737 aircraft left in the U.S. fleet 

would have the old rudder system. 

Therefore, we no longer find it 

appropriate to require the installation of 

flight recorder equipment to monitor 

those parts of the aircraft which became 

life-limited by these ADs and will be 

eliminated by 2008. 

This SNPRM attempts to address the 

changes in circumstances introduced by 

the RSEP, the findings by the ETEB, and 

the ADs issued by the FAA by revising 

the fleet of airplanes affected by the 

proposed rule, and by changing the 

proposed compliance time to coincide 

with the modifications required by the 

ADs. 

The FAA does not have convincing 

evidence that the redesigned rudder 

control system obviates the need for the 

additional flight recorder parameters. 

The newly designed rudder system is 

unique in that the third actuator is only 

activated upon the failure of the main 

PCU, at which point the two main 

actuators are no longer performing. 

Thus, the FAA has tentatively 

concluded that the information that 

would be gathered by the addition of the 

proposed parameters could provide 

meaningful information in the event of 

a rudder control failure. While the ETEB 

conducted considerable testing of the 

737 aircraft and its rudder system, those 

tests cannot duplicate the actual flight 

experience of either the original or the 

new rudder system as it would be 

recorded using the parameters 

proposed. The only way to get this data 

is by installation of equipment that will 

record the movement of the rudder 

surface and the companion actions of 

the yaw dampers. The ETEB did not 

have this information because the 

equipment to record it was not 

mandatory. Since the additional 

parameters have yet to be installed, 

investigators of an accident or incident 

remain similarly limited today. 

Boeing has indicated that there have 

been no reports of rudder hardover 

incidents on 737s with the redesigned 

rudder system. However, since the 

system has only been installed as 

original equipment on airplanes since 

2003, and since compliance with the 

retrofit is not required until 2008, only 

limited historical data on the function 

and reliability of this redesigned system 

is available. 

Additionally, as discussed above, the 

redesigned rudder system does not 

actively power three actuators. Rather, 

the third actuator only powers up in the 

event of a power failure to the two 

primary actuators. Thus, while the new 

design incorporates three actuators, 

similar to the design of Boeing’s 757/ 

767/777 model airplanes, a functional 

difference remains between the new 737 

rudder system and that installed on 

other Boeing airplanes. 

We note that the rudder control 

system enhancement can be split into 

three separate tasks and are not 

normally accomplished at once. The 

first two changes can be accomplished 

with the old rudder control system still 

in place. As of August 2004, Boeing had 

shipped 2,957 kits needed for the first 

part of the installation, but only 728 kits 

for the third part. The FAA assumes 

these numbers have gone up; however, 

since there is no reporting requirement 

for compliance with the AD, we have no 

way of knowing how many new 

components or complete rudder control 

systems have been installed. However, 

the FAA understands that the wiring kit 

provided by Boeing for the first part of 

the redesigned rudder system includes 

the wiring required for the proposed 

additional sensors, making the 

installation of the parameters less 

burdensome than originally anticipated. 

Compliance with this rule, if adopted, 

would require the installation of the 

sensors and their connection to the 

DFDR system. These circumstances 

argue for either the issuance of this rule 

(to take advantage of the work yet to be 

accomplished on the majority of the 737 

fleet) or withdrawal, as soon as possible. 

We continue to believe that unless the 

proposed additional flight recorder 

sensors are installed and the function of 

the new system components are 

monitored, there will never be any 

means to eliminate the rudder system as 

a possible cause of any future incident 


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or accident, or to identify the particular 

component or action as a source of the 

problem if the rudder control system is 

involved. These are the circumstances 

that spurred the original NTSB 

recommendations on the 737, but we are 

cognizant of the significant changes in 

circumstances that have occurred in the 

last five years, including the mandated 

changes to the original rudder system, 

and the decline in reported incidence of 

rudder hardover events. 

We are also aware that we now need 

new information on the costs and 

benefits of requiring these 

enhancements on a fleet of aircraft that 

did not exist when we originally 

proposed the rule, those with the new 

rudder system installed. 

The FAA originally evaluated the cost 

data associated with this SNPRM nearly 

five years ago, shortly after the close of 

the comment period for the NPRM. 

Since then, some 737s may have been 

retrofitted with the new rudder, and 

may be partially equipped to record the 

additional flight data parameters. 

Further, with the introduction of the 

new Boeing 737 rudder, there is a new 

class of airplane that will incur 

retrofitting costs that may be different 

from those costs reported by the 

industry and used in the Supplemental 

Preliminary Regulatory Evaluation 

(Supplemental PRE) that accompanies 

this rulemaking document. Because the 

FAA does not have the data necessary 

to evaluate the impact of, and need for, 

a rule requiring the additional 

parameters for those 737s equipped 

with the new rudder control system, the 

agency requests more current 

information for the following specific 

questions as well as any additional data 

that the public believes needs to be 

incorporated into the economic 

analysis. 

1. How many 737s are in your fleet? 

2. How many 737s do not record the 

flight parameters that we are proposing 

be recorded? How many 737s currently 

record these parameters? 

3. How many 737s have been 

retrofitted with the new Boeing rudder? 

How many of those airplanes do not 

record the flight data parameters that we 

propose to be recorded? 

4. How many 737s are expected to be 

retrofitted with the new Boeing rudder 

in each of the years 2006, 2007, and 

2008? 

5. How many 737s are expected to be 

retired in each of the years 2006, 2007, 

and 2008? 

6. For those 737s that have already 

been retrofitted under the AD but do not 

record the additional flight data 

parameters, how much would it cost to 

install the equipment to record the 

additional flight data parameters? How 

many days would it take to install the 

equipment to record those additional 

flight data parameters on those airplanes 

if the work were done: during a major 

maintenance session; an overnight 

maintenance session? 

7. Are the assumptions and estimates 

made in Table 1 of this notice and the 

accompanying Supplemental PRE, and 

throughout that report, accurate? If you 

are able to provide more current data, 

please submit it. 

8. Please provide an update on the 

status of the various design changes that 

would still need to be accomplished to 

provide the information necessary to 

install the proposed flight recorder 

parameters on the fleet expected to be 

retrofitted with the new rudder design. 

We are issuing this SNPRM to gather 

information on the need for flight 

recorder parameters that monitor the 

new rudder system. This proposal 

represents a shift in the scope of the 

rule. When the DFDR enhancements 

were proposed, work was still in 

progress in diagnosing the functions and 

perceived weaknesses of the original 

rudder system. We have modified the 

original proposed regulatory text to 

require that the flight recorder 

parameters proposed in 1999 be 

installed concurrent with the new 

rudder system; we have redrafted the 

rule to state that compliance would be 

required no later than November 12, 

2008, the date that compliance is 

required with the Airworthiness 

Directives mandating the installation of 

the redesigned rudder system. We have 

made other changes to the proposed 

regulatory text based on comments to 

the NPRM. These changes, which are 

explained later in the document, will 

not be revisited. Accordingly, we 

request interested parties to direct their 

attention to our requests for data, the 

need for additional parameters for the 

redesigned 737 rudder control system, 

and the proposed November 2008 

compliance date. 

In summary, the FAA finds this 

supplemental proposal necessary in 

order to update the status of the number 

and configuration of 737s in the current 

fleet. Since we do not track operator 

compliance with ADs, the information 

requested here will tell us how many 

airplanes have been retrofitted with the 

new rudder system and the estimated 

costs for installing the DFDR parameters 

if the new rudder system has already 

been installed. We expect to receive 

information on the number of 

retirements expected, as well as the 

number of aircraft that are already in 

compliance because they are new or 

because the proposed DFDR rudder 

parameters may have been installed 

voluntarily. 

III. Summary of Comments 

The FAA received 17 comments on 

the proposed rule. Of the 17 comments, 

the Air Transport Association of 

America, Inc. (ATA), submitted three 

separate comments; one of the ATA 

submissions included seven comments 

from member airlines. Only one 

commenter, the Air Line Pilots 

Association (ALPA), supports the 

proposed rule as published. 

Specifically, ALPA agreed that a 

potentially unsafe condition has been 

identified and concurs with the 

proposed amendments. The other 

commenters generally supported the 

intent of the proposed rule; however, 

these commenters expressed concern 

about: 

(1) The time frame for compliance 

proposed in the Notice of Proposed 

Rulemaking (NPRM), 

(2) the availability of installation 

instructions, 

(3) the unavailability of parts, and 

(4) the probability of considerable 

airplane out-of-service time. 

The amount of time that has elapsed 

since comment was invited, and the 

events that have occurred since 

comment was invited, has caused most 

of the comments to become outdated. 

The proposed compliance times are no 

longer applicable, nor are the costs that 

were applied to them. Accordingly, we 

are not including a discussion of 

comments concerning compliance time, 

parts availability, or out of service time 

since these issues no longer exist under 

current circumstances. 

Comments on Specific Proposed 

Requirements 

The following disposition of 

comments addresses those comments 

that were not overtaken by intervening 

events and actions. Some of the 

questions and information submitted 

with them remain relevant to the actions 

contemplated under this modified 

proposal. 

Boeing stated that it typically does not 

develop or commit to design changes 

until the release of a final rule. 

However, because of the proposed short 

time frame for compliance, Boeing had 

already implemented production design 

changes in an attempt to accommodate 

the expected compliance schedule. 

Boeing noted that a typical design 

change of this magnitude would require 

a minimum of 18 months to allow time 

to develop the design and to work with 

parts suppliers, operators, and the FAA. 


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A. Compliance Issues for Rudder Pedal 

Forces 

Proposal: The FAA stated in Notice 

No. 99–19 that it had received inquiries 

from the NTSB and Boeing concerning 

an acceptable means of recording the 

rudder pedal control input forces 

required by paragraph (a)(88) of 

§ 121.344; the requirement was added in 

the 1997 amendment to the DFDR 

regulations. 

To meet the 1997 regulations, Boeing 

developed a rudder pedal force 

transducer that is placed ‘‘midstream’’

in the rudder control system. The 

transducer is designed to identify 

whether the input was coming from the 

cockpit or from the rudder assembly. 

The NTSB indicated informally that it 

would prefer a system that measures the 

rudder input force at the individual 

rudder pedals. This would require the 

addition of four transducers (one on 

each rudder pedal) rather than the 

single one designed by Boeing. The FAA 

noted that the NTSB believes that only 

the installation of four rudder pedal 

force sensors would meet the intent of 

its April 16, 1999 recommendation to 

record rudder input force. 

The FAA acknowledged the 

difference between the data acquired 

using Boeing’s already approved single 

transducer system and the NTSB’s 

suggested four-pedal sensor retrofit. The 

FAA requested comment on the 

necessity and feasibility of 

instrumenting all four rudder pedals on 

737s with force sensors as a means of 

complying with paragraph (a)(88). The 

FAA also requested comment on 

whether Boeing’s single force transducer 

should remain an accepted means of 

compliance with parameter 88 for all 

737s that do not have the transducer 

installed or had not yet otherwise 

complied with paragraph (a)(88). In 

addition, the FAA requested cost data 

for the four-pedal retrofit to determine 

whether the incremental increase in 

benefits that would be provided by that 

configuration would be offset by the 

additional time and costs involved if 

such a requirement were mandated. 

Comments: The FAA received two 

comments on recording rudder control 

inputs, one from the NTSB and one 

from Boeing. 

The NTSB stated that the rudder 

pedal force exerted by each 

crewmember is critical to its 

understanding the loss of control 

problems experienced in the 737. The 

NTSB added that in its investigation of 

a 1999 rudder incident involving 

Metrojet, not knowing the amount of 

rudder pedal force exerted has made it 

impossible to separate pilot actions from 

(possible) rudder system anomalies. The 

Board argued that a single sensor placed 

midstream in the rudder control system, 

as introduced by Boeing, would not 

identify whether the flightcrew inputs 

are in opposition to each other or 

whether the nose wheel steering (NWS) 

or some other system anomaly forward 

of the sensor causes the inputs. In 

addition, any jams in the controls 

between the pedals and the sensor may 

go undetected, because the amount of 

force exerted by the flightcrew would 

not be registered by the sensor. The 

NTSB stated that, if the upgrade 

required only a single force sensor in 

the rudder system, the possibility would 

remain that the information would not 

be sufficient to identify some future 

flight control problems even after the 

proposed retrofit. 

Boeing commented that neither the 

existing rule nor the proposed rule 

includes specific requirements that 

support a change to the current design 

to measure individual rudder pedal 

force. Boeing stated that the 1997 rule 

contained no requirement to measure 

any disagreement between pilot inputs. 

According to Boeing, the NTSB 

recommendations and the proposed rule 

suggested that the only issue is the 

ability to quickly distinguish a yaw 

damper event from a flightcrew input or 

a rudder anomaly. Boeing believed the 

current single transducer design meets 

this intent. 

Boeing claimed the current 737 NG 

airplane rudder pedal design satisfies 

the parameter 88 requirements defined 

in the existing rule. Boeing added that 

the rudder design on 737–100 through 

–500 series airplanes delivered since 

August 1998 is identical to that on the 

737 NG airplanes, and retrofit kits are 

available for this installation in 

airplanes delivered before then. Boeing 

noted that any change to the 

requirements to which this installation 

complies would require additional 

retrofit. 

Boeing further stated that the 

proposed addition of four individual 

rudder pedal force sensors would 

require a significant number of design 

changes in the rudder control 

mechanism and to the structure of the 

cockpit floor. The 737 has severely 

limited space in the area these would be 

placed, which limits design options. At 

the time the NPRM was issued, Boeing 

and its suppliers had not yet been able 

to identify a design solution that could 

be implemented without significant 

structural and system changes that 

would make retrofit complex, lengthy, 

and costly. Boeing added that it 

expected the design definition and 

implementation of four transducers 

would take much longer than the 

implementation dates proposed. 

Boeing also argued that four 

transducers would provide no major 

incremental gain in information. 

According to Boeing, a single transducer 

allows investigators to determine why 

the rudder moved, by pilot action or 

system input, but that a single 

transducer will not show whether a 

pedal jammed. The four transducers 

would enable Boeing to determine 

whether the rudder moved and may 

allow determination of which pedal was 

jammed or restricted. However, the four 

transducers, like the single transducer, 

would not permit determination of why 

a rudder pedal was jammed or 

restricted, because the jam or restriction 

is also ‘‘upstream’’ of the transducers. 

FAA reply: Although specifically 

requested, the FAA did not receive any 

cost data or time estimates for a fourrudder-pedal sensor retrofit as described 

in the NPRM. While the FAA 

understands the NTSB’s desire for the 

information that such rudder pedal 

sensors might provide, general 

comments from Boeing indicate that 

such a retrofit would be both timeconsuming and costly. The FAA is 

unaware of a sensor currently in 

production that could meet the design 

requirements that would be necessitated 

by the NTSB’s request. Even if such a 

sensor does exist, Boeing also indicated 

(in its comment and in discussions with 

the FAA) that major redesign of the 

aircraft might be necessary, including 

moving a floor beam, since there is so 

little space available under the rudder 

pedals of the 737. Such modifications 

would take several years to design and 

incorporate into the production line; the 

engineering for in-service airplanes 

would be more complicated, since 

changes to major structural components 

would mean a change to the airplane’s 

original type design and the 

airworthiness certification of every 

affected airplane. The time that such 

design and retrofit would take far 

exceeds any recommendation of the 

NTSB, and argues against the NTSB’s 

own characterization of the 

modification as time-sensitive. 

Further, the FAA is unable to say with 

any certainty that the information that 

might be gathered by the NTSB’s 

proposed pedal force sensors would 

lead to a solution to the rudder problem. 

The rudder pedal force sensors may 

well be able to identify the amount of 

force an individual pilot is placing on 

a pedal, but the amount of force does 

not seem to have been an issue in the 

noted accidents or incidents. If there is 

a problem in the rudder system, then 

the amount of force exerted in an 


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attempt to overcome it is less important 

than finding where the malfunction is 

occurring. If pilots are fighting each 

other for control using the rudder 

pedals, then the issue is not with the 

airplane itself. It is a suspected problem 

with the airplane itself that is the reason 

for proposing this rule, and the FAA has 

determined that continuing to allow 

compliance with parameter 88 using a 

single midstream transducer reflects the 

best balance of cost and information to 

be gained in an attempt to locate the 

source of the problem in a timely 

fashion. 

Accordingly, the FAA has decided 

against promulgating a four-pedal 

sensor requirement. The agency has no 

basis for concluding that a retrofit of 

individual rudder pedal sensors would 

be cost beneficial when the costs 

themselves cannot readily be estimated 

without a significant investment of time 

and energy. Moreover, since the FAA is 

unable to quantify the requirements 

either for the equipment or the 

recording rate and sensitivity, any 

information on estimated costs becomes 

that much less reliable and certainly 

falls short of the legal requirements for 

imposing the eventual cost on operators. 

B. Compliance Issues for the Control 

Column and Control Wheel 

Proposal: Parameter (a)(88) requires 

that control wheel and control column 

input forces be measured and recorded. 

The current rule requires that airplanes 

with breakaway capability record both 

left and right side control wheel forces. 

The FAA noted in the preamble to the 

NPRM that there also are issues of 

acceptable means of measuring control 

column and control wheel forces. The 

FAA specifically requested comment on 

the means and costs of measuring these 

control forces under the requirements 

proposed in this rulemaking. 

Comments: The FAA received 

comments from Boeing, Alaska, United 

Airlines, ATA, and the NTSB on the 

control column and control wheel 

systems. 

Boeing stated that to comply with the 

existing rule for parameter (a)(88), 

Boeing intended to modify the control 

column and control wheel force 

transducers for DFDR application to 

achieve the increased force range. 

Boeing would also install new flight 

control computer hardware and 

software to interface with the new 

transducers. 

Boeing stated that the retrofit for the 

737–100 through –500 series airplanes 

is basically the same as that for the 737 

NG airplanes. However, it noted the 

737–100 through –500 series airplanes 

include two control column force 

transducers in the same location as the 

737 NG airplanes, but that the force 

applied by individual pilots cannot be 

determined because the elevator control 

systems of the 737–100 through –500 

series airplanes do not have a jam 

override device between columns. 

Boeing also described the FAAapproved single-wheel force transducer 

design for parameter (a)(88), and stated 

that it meets the intent of the existing 

rule provided that the left and right 

control wheel positions also are 

recorded. Boeing stated that the aileron 

system measures both cockpit control 

positions, but only the left side’s force. 

Each pilot’s control inputs go through 

the left side force transducer, except in 

the event of a failure. Boeing added that 

because the FAA does not typically 

consider dual failures a likely event, the 

proposed configuration should be 

acceptable. 

Boeing noted that to comply with the 

existing requirements for parameter 

(a)(88), the control wheel force 

transducer would have to be modified 

specifically for DFDR application to 

achieve the increased force range. New 

flight control computer hardware and 

software would have to be installed to 

interface with the new transducer and 

the force transducer stops would have to 

be modified to allow the additional 

range. 

Boeing further stated the control 

wheel retrofit of the 737–100 through 

–500 series airplanes is basically the 

same as that of the 737 NG airplanes, 

except that Boeing would add a (new) 

second control wheel position 

transducer to the first officer’s control 

wheel to allow the 737–100 through 

–500 series airplanes’ configurations to 

be identical with that of the 737 NG 

airplanes. 

The NTSB stated that although it is 

concerned that the current control force 

sensors will not meet the range and 

accuracy requirements of the proposed 

rule, suitable control force sensors were 

likely to be available by the then 

proposed compliance dates. The NTSB 

contended that separate sensors to 

measure the pilot and copilot flight 

control input forces must be used when 

breakaway features are employed 

(breakaway capability allows either 

pilot to operate the airplane 

independently). 

Two operators of 737s and the ATA 

commented that as of the date of the 

NPRM, the required sensors had not yet 

been developed. 

FAA reply: The primary objection 

raised by the commenters was that the 

regulation would force early compliance 

with parameter (a)(88) for control wheel 

and control column forces, and that the 

sensors required to record to Appendix 

M specifications were not available and 

had not yet been designed. Sensor 

design and availability are no longer 

issues since all aircraft manufactured 

after August 19, 2002 have been 

required to meet Appendix M standards 

for parameter (a)(88). Nor is there any 

need to provide for more than one 

sensor type since a sensor that records 

to Appendix M standards now exists for 

use in a retrofit. Accordingly, the FAA 

intends to adopt the rule as originally 

proposed, with the Appendix M 

standards applicable to all 737s 

recording all functions required by 

parameter (a)(88) (±70 pounds control 

wheel force and ±85 pounds control 

column force). 

The FAA understands that the lateral 

control system on the 737 has an 

override device between the two control 

wheels that allows either pilot to 

operate the control wheel 

independently, but that the primary 

control path for both pilots is through 

the left cable control path. The right 

control is not usually connected and is 

used only in the event of a failure. A 

single control wheel force transducer in 

the left cable path records the inputs 

from both pilots. The FAA agrees that 

the single control wheel force 

transducer is acceptable, provided the 

left and right control wheel positions 

are also recorded. The use of a single 

force transducer with two position 

sensors is acceptable because 

comparison of the two position sensors 

allows detection of a breakout of the 

override between the control wheels; 

this breakout allows the right cable 

control path to become active. 

C. Compliance Issues; Other Parameters 

1. Standby Rudder Status 

Proposal: In the NPRM, the FAA 

proposed to add recording of the 

standby rudder status. The standby 

rudder system is an alternative source of 

hydraulic power to the rudder that is 

used when primary hydraulic power is 

lost. The intent of the proposed 

requirement was to record whether the 

standby rudder system switch is in the 

on or off position. 

Comment: Boeing believed the intent 

of recording the standby rudder status 

was to determine the actual status of the 

standby rudder system and not the 

position of any particular switch. 

Boeing indicated that the system should 

record the state of the standby hydraulic 

rudder shutoff valve, which also is 

controlled by both of the standby rudder 

system switches. Boeing maintained this 

would provide a clearer indication of 

the actual status of the standby rudder 


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system than recording whether the 

standby rudder switch is in the on or off 

position. The ATA stated that the 

sensors for the standby rudder status 

parameter have not been designed for 

any 737. 

FAA reply: The FAA agrees with the 

comments and we have revised the 

proposed language in paragraph (a)(91) 

to indicate that it is the valve position 

that needs to be recorded for standby 

rudder status, not the position of the 

switch, as initially proposed. 

2. Thrust Reverser 

Proposal: Under the 1997 DFDR 

regulations, instrumentation of the 

thrust reversers (§ 121.344(a)(22)) was 

not required until the year 2001 for 

some airplanes and is not required at all 

for older airplanes. The proposal would 

require all 737s regardless of age to 

record the thrust reverser position. 

Comment: Boeing stated that the 

requirement for recording thrust 

reverser positions would require 

modifications to the engine accessory 

unit (EAU) to monitor the thrust 

reverser. According to Boeing, 

approximately 937 737–100 and –200 

airplanes will require two new PC cards 

and associated connectors and wiring, 

and approximately 250 737–300 and 

–400 airplanes will require four new PC 

cards and associated connectors and 

wiring if the proposal is adopted. 

Boeing requested that the FAA not 

require instrumentation of the thrust 

reversers for the older 737–100 through 

–500 series airplanes. The 737 NG 

airplanes would be retrofitted to record 

thrust reverser position. Boeing 

suggested specific language that could 

be used to codify its request. 

FAA reply: The SNPRM does not 

incorporate Boeing’s suggested change. 

Under § 121.344(b)(1), adopted in 1997, 

the only airplanes not required to record 

thrust reverser position, parameter 

(a)(22), are airplanes manufactured on 

or before October 11, 1991, that were 

not equipped with a FDAU as of July 16, 

1996. All other airplanes must either be 

retrofitted to record, or record at 

manufacture, thrust reverser position. 

The distinction made in 

§ 121.344(b)(1) was introduced to 

prevent the oldest airplanes from having 

to be retrofitted with a FDAU to meet 

the 1997 rule, not because thrust 

reverser data is not important. Under 

this SNPRM, the other recording 

requirements for 737s necessitate the 

installation of a FDAU, eliminating the 

distinction made in the 1997 rule. 

Further, the FAA cannot accept Boeing’s 

suggested language because it is general 

and would relieve not only 737s but 

certain other airplanes from the 1997 

requirement to record parameter (a)(22). 

This proposal would require all 737s to 

record parameter (a)(22). 

3. Yaw Damper Status and Yaw Damper 

Command 

Proposal: Proposed paragraph (a)(89) 

would add the recordation of yaw 

damper status. The intent of the 

requirement is to determine whether the 

yaw damper is on or off. Proposed 

paragraph (a)(90) would add the 

recordation of yaw damper command. 

The intent of this requirement is to 

record the amount of voltage being 

received by the yaw damper system. 

This determines how much rudder 

movement is being commanded. 

Comment: For the 737–100 through 

–500 series airplanes, Boeing proposed 

to record the yaw damper linear variable 

displacement transducer (LVDT) 

position feedback from the new yaw 

damper coupler through an ARINC 429 

interface, and, if the DFDR capacity 

allows, the yaw damper command from 

the yaw damper coupler through an 

ARINC 429 interface. Boeing noted that 

the 737 NG airplanes record both the 

yaw damper command from the stall 

management yaw damper and the yaw 

damper LVDT position feedback 

through an ARINC 429 interface. The 

ATA stated that sensors for yaw damper 

status and yaw damper command 

parameters are not addressed in a 

retrofit service bulletin. 

FAA reply: Sensors for the yaw 

damper status and yaw damper 

command parameters have been 

developed and have been installed in 

737s manufactured since August 18, 

2000. The sensors exist and the FAA 

continues to believe that the parameters 

should be required. 

4. Other Issues 

Proposal: The current DFDR 

regulation allows single-source 

recording for control input and control 

surface positions, parameters (a)(12) 

through (a)(14) or (a)(12) through (a)(17), 

depending on the date of airplane 

manufacture. The proposed rule 

eliminated the allowance to record these 

from a single source. 

Comments: Boeing stated that 

§ 121.344(b) and (c), as proposed, 

removes the allowance to permit 

recording parameters (a)(12) through 

(a)(17) from a single source and applies 

the full requirement of appendix M to 

part 121 to recording these parameters. 

However, paragraph (d) still permits 

recording parameters (a)(12) through 

(a)(17) from a single source. 

FAA reply: Removing the allowance 

for recording control and surface 

positions from a single source was an 

error in the proposed rule. This SNPRM 

includes the single-source recording as 

provided in the 1997 rule. A sentence 

has been added in § 121.344(m) 

indicating that single-source recording 

would remain available to airplanes 

otherwise subject to § 121.344(b)(1), 

(c)(1), or (d)(1). 

Proposal: The proposal removes 737s 

from the requirements of § 121.344(b) 

and (c), adds specific 737 requirements 

to § 121.344(d), (e), and (f), and adds 

new § 121.344(m). 

Comments: Boeing indicated that 

§ 121.344(d), (e), and (f), as proposed, 

state that all 737s must comply with the 

requirements in paragraphs (m)(1) and 

(m)(2). Boeing contended this language 

overlooks the requirements of paragraph 

(m). Boeing also did not understand 

why paragraphs (d), (e), and (f) were not 

revised as paragraphs (b) and (c) to 

except the 737. Boeing stated that the 

addition of paragraph (m) makes it 

unclear as to what is required for 737s 

and that it would be much clearer to 

include the additional 737 requirements 

in the existing applicable paragraphs. 

Boeing further stated that § 121.344(m), 

as proposed, is inconsistent with 

paragraphs (b), (c), and (d) in that it 

requires recording parameters (a)(88) 

through (a)(91), while paragraphs (b), 

(c), and (d) do not. 

FAA reply: The modifications to the 

compliance schedule for installation of 

the additional parameters have removed 

the issue of compliance time; 

compliance time is no longer 

determined by the date of FDAU 

installation. 

For consistency, § 121.344(b), (c), (d), 

(e), and (f) are similarly revised to 

reference the 737 requirements in 

§ 121.344(m). The FAA has decided 

against putting the 737 requirements in 

each subparagraph because it would be 

cumbersome, unnecessarily repetitive, 

and introduce more possibilities for 

error. 

Proposal: The note to parameter 

(a)(88) in current Appendix M to part 

121 requires airplanes that have a flight 

control breakaway capability (which 

allows either pilot to operate controls 

independently) to record both control 

force inputs; the note also discusses 

sampling rates. 

Comments: Boeing pointed out that 

the note to parameter 88 in appendix M 

to part 121 and appendix E to part 125 

indicates that all the comments in the 

remarks column do not apply to the 737. 

Boeing believed that the note is meant 

to indicate that it is only the sampling 

interval remarks that do not apply to the 

737s. The NTSB also stated that the 

remarks section covers, in addition to 

the sampling rate requirements, a 


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requirement to record both control force 

inputs for those airplanes that have a 

flight control breakaway capability that 

allows either pilot to independently 

operate the airplane, which still would 

apply to 737s. 

FAA reply: The FAA agrees with 

Boeing, and has revised footnote 18 to 

clarify application of the parameter for 

737s. The requirement to record both 

control force inputs for systems with 

breakaway capabilities does apply to the 

737, but as discussed above, the FAA 

has approved the use of a single control 

wheel force transducer provided that 

both control wheel positions are 

recorded (although both pilot’s inputs 

go through the left side force transducer, 

except in the event of a failure). Because 

the FAA historically has not considered 

a dual failure a likely event, this 

configuration is acceptable. 

Proposal: The FAA proposed the 

same changes to the digital flight data 

recorder regulations in § 125.226 as 

those proposed in § 121.344. In 

addition, the FAA proposed the same 

changes to Appendix E to part 125 as 

those proposed to Appendix M to part 

121. The FAA also proposed that 

airplanes operating under deviation 

authority from part 125 must comply 

with the flight data recorder 

requirements of part 125 for the 

particular aircraft. The FAA specified 

that this deviation requirement would 

apply to all aircraft and not only the 

737. The FAA specifically sought 

comments on why the flight data 

recorder requirements of part 125 

should not be made applicable to 

aircraft operated under deviation 

authority. In addition, the FAA sought 

comments from affected persons 

operating aircraft under deviation 

authority from part 125 concerning the 

proposed compliance schedule. 

Comments: The FAA received no 

comments on the proposed changes to 

part 125. Accordingly, the changes to 

part 91, applicable to part 125 airplanes 

operated under deviation authority, and 

the changes to part 125 and Appendix 

E are proposed again here without 

change from the original proposal. 

IV. Changes Adopted in This SNPRM 

When the FAA proposed the 

recordation of new flight data recorder 

parameters in November 1999, the ETEB 

was still in the process of conducting its 

failure analysis, and other action by the 

agency was not yet contemplated. The 

ETEB’s finding and the FAA’s 

subsequent decision to issue the AD 

requiring replacement of the rudder 

system mandate that this rule be 

modified to account for those actions. 

This proposed rule, if adopted, would 

require the installation of the flight 

recorder parameters proposed in the 

NPRM with the following modifications. 

The installation would be accomplished 

simultaneously with the installation of 

the redesigned rudder system in order to 

minimize the costs and out-of-service 

time required. The regulatory evaluation 

for this proposed rule has been 

significantly revised to include this 

extended compliance time. This 

extension of the compliance time also 

addresses the majority of the comments 

received in response to the proposed 

rule. Specifically, this SNPRM 

incorporates the following changes: 

• Sections 121.344(b), (c), (d), (e), and 

(f) and § 125.226(b), (c), (d), (e), and (f) 

would be amended to indicate that all 

737 model airplanes also must comply 

with the requirements in § 121.344(m) 

or § 125.226(m), respectively. Sections 

121.344(m) and 125.226(m) would be 

added to indicate that in addition to 

other applicable requirements, all 737 

model airplanes must record the 

parameters listed in paragraphs (a)(1) 

through (a)(22) and (a)(88) through 

(a)(91) in accordance with the ranges, 

accuracies, resolutions, and recording 

intervals specified in Appendix M to 

part 121 or Appendix E to part 125, 

respectively. The proposed compliance 

times have been changed to state that 

the installation of the equipment 

required to record these parameters 

must be accomplished during the 

installation of the modified rudder 

system required by AD or no later than 

November 2008. These sections would 

also reinstate the language allowing 

single-source recording, as discussed in 

the disposition of comments. The 

parameters that may be recorded from a 

single source would be determined by 

the age of the airplane and its applicable 

regulations. 

• Footnote 18 would be added to 

parameter 88 in Appendix M to part 121 

and Appendix E to part 125 and would 

read ‘‘For all 737 model airplanes: The 

seconds per sampling interval is 0.5 per 

control input; the remarks regarding the 

sampling rate do not apply; a single 

control wheel force transducer installed 

on the left cable control is acceptable 

provided the left and right control 

wheel positions also are recorded.’’

Footnote 19 would be added to 

parameter 88 in Appendix M to part 121 

and Appendix E to part 125 and would 

read ‘‘For all 737 model airplanes 

manufactured on or before January 31, 

2001, Range values are: Full Range; 

Control wheel ± 15 lbs.; Control column 

± 40 lbs.; and Rudder pedal ± 165 lbs.’’

• Sections 121.344 (a)(91) and 

125.226(a)(91) would be revised to read 

‘‘standby rudder valve status’’ and in 

appendix M to part 121 and appendix 

E to part 125, the range for parameter 91 

would be revised to read ‘‘Discrete.’’

• The range for the rudder pedal in 

parameter 88 in appendix M to part 121 

would be corrected to read ‘‘Rudder 

pedal ± 165 lbs.’’

No 737s are exempt from this 

rulemaking. Airplanes that have been 

manufactured since January 2003 would 

already be incompliance with this rule 

because the rudder parameters proposed 

here would have been installed at 

manufacture. 

V. Chronology 

The following is a list of selected 

events relevant to 737 rudder control 

issues and FAA rulemaking actions: 

Date Event 

December, 1967 ................... The Boeing 737 is type certificated. 

March 3, 1991 ...................... United Airlines flight 585 crashes near Colorado Springs, CO; loss of rudder control implicated, but the flight recorder was rudimentary (5 parameters recorded as required by regulation). 

1993 ..................................... NTSB Recommendation on the 737 rudder system. 

September 8, 1994 .............. Crash of USAir flight 427 near Aliquippa, PA. 

June 9, 1996 ........................ Rudder hardover reported on Eastwind flight. 

1996 ..................................... FAA issues AD on flight crew procedures to overcome potential system failures. 

1995–1997 ........................... NTSB issues 20 safety recommendations on the 737, three in 1995 recommending upgrades to the DFDRs. 

June, 1997 ........................... FAA issues two ADs on 737 rudder system components. 

February 23, 1999 ................ USAir flight 2710 reports uncommanded rudder hardover at cruise. 

March 24, 1999 .................... NTSB final report on USAir 427 indicates loss of control from uncommended rudder hardover as probable cause; 

says 1997 DFDR rule changes by FAA not adequate for 737. 

May, 1999 ............................ ETEB formed to conduct failure analysis on rudder control actuation system of the 737. 


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Date Event 

November 18, 1999 ............. FAA NPRM proposing three new DFDR parameters for 737s, proposing compliance in 2000 or 2001 based on installed equipment. 

December 20, 1999 ............. Comment period for NPRM closes. 

1999 ..................................... Five rudder hardover incidents reported on 737s during the year. 

July, 2000 ............................. ETEB final report finds numerous failure modes on 737 rudders, recommends modification of the entire rudder 

system. 

September, 2000 .................. Boeing begins its Rudder System Enhancement Program (RSEP). 

January 16, 2001 ................. Boeing makes a presentation to the NTSB on its RSEP findings. 

January, 2001 ...................... Boeing submits letter to FAA rule docket requesting delay of any final rule in anticipation of final RSEP findings 

expected later that year. 

February, 2001 ..................... In a letter to the FAA, the NTSB maintains its position on installation of new DFDR parameters on 737s as soon 

as possible, and regardless of rudder system modification. 

February, 2001 ..................... Boeing applies for a change in type design based on its RSEP. 

November 13, 2001 ............. FAA publishes NPRM AD on modified rudder system. 

October 7, 2002 ................... FAA publishes final rule AD to install modified rudder system; compliance is due in 6 years (11/11/2008); special 

flight crew procedures in effect since 1996 are superseded as of installation. 

January, 2003 ...................... New Boeing 737s are delivered with the new rudder system and the three DFDR rudder parameters as original 

equipment. 

VI. Paperwork Reduction Act 

This SNPRM proposes to amend the 

regulations to add a requirement for all 

737s to record additional flight data 

parameters. These additional parameters 

are not required by the current 

regulations and would provide the only 

currently available means of gathering 

information that the FAA and the NTSB 

anticipate will help assess the cause of 

incidents that appear to be related to 

rudder anomalies on 737 airplanes. 

The respondents are all U.S. 

certificate holders operating 737 

airplanes under parts 91, 121, 125, and 

129. 

The required information would be 

electronically recorded on the DFDR 

each time the airplane begins its takeoff 

roll until it has completed its landing 

roll and kept until the airplane has been 

operated for 25 hours. The recorded 

data would be overwritten on a 

continuing basis and accessed only 

following an accident. This requirement 

would be a nominal addition to a 

passive information collection activity 

and therefore does not contain a 

measurable additional hour burden. 

As required by the Paperwork 

Reduction Act of 1995 (44 U.S.C. 

3507(d)), the U.S. Department of 

Transportation submitted the 

information collection requirements to 

the Office of Management and Budget 

(OMB) for its review and assignment of 

an OMB control number and one was 

assigned. However, when the control 

number came up for reauthorization, we 

decided not to renew it. If this proposed 

requirement is made final, we will 

reapply for the authorization. 

VII. International Compatibility 

In keeping with U.S. obligations 

under the Convention on International 

Civil Aviation, FAA policy is to comply 

with International Civil Aviation 

Organization (ICAO) Standards and 

Recommended Practices to the 

maximum extent practicable. The FAA 

has determined that there are no ICAO 

Standards and Recommended Practices 

that correspond to these regulations. 

VIII. Economic Evaluation, Regulatory 

Flexibility Determination, International 

Trade Impact Assessment, and 

Unfunded Mandates Assessment 

Changes to Federal regulations must 

undergo several economic analyses. 

First, Executive Order 12866 directs 

each Federal agency to propose or adopt 

a regulation only if the agency makes a 

reasoned determination that the benefits 

of the intended regulation justify its 

costs. Second, the Regulatory Flexibility 

Act of 1980 requires agencies to analyze 

the economic impact of regulatory 

changes on small entities. Third, the 

Trade Agreements Act (19 U.S.C. 2531–

2533) prohibits agencies from setting 

standards that create unnecessary 

obstacles to the foreign commerce of the 

United States. In developing U.S. 

standards, the Trade Act requires 

agencies to consider international 

standards. Where appropriate, agencies 

are directed to use those international 

standards as the basis of U.S. standards. 

Fourth, the Unfunded Mandates Reform 

Act of 1995 requires agencies to prepare 

a written assessment of the costs, 

benefits, and other effects of proposed 

or final rules. This requirement applies 

only to rules that include a Federal 

mandate on State, local, or tribal 

governments or on the private sector, 

likely to result in a total expenditure of 

$100 million or more in any one year 

(adjusted for inflation). 

Based on the available information, 

the FAA believes that this proposed 

rule: 

(1) Would have benefits that justify its 

costs and would be a ‘‘significant 

regulatory action’’ as defined in the 

Executive Order and as defined in 

DOT’s Regulatory Policies and 

Procedures; 

(2) Would have a significant impact 

on a substantial number of small 

entities; 

(3) Would have minimal effects on 

international trade; and 

(4) Would not impose an unfunded 

mandate on state, local or tribal 

governments or on the private sector. 

The FAA has placed these analyses in 

the docket and summarizes them as 

follows. 

Data Sources 

The principal data sources used are 

the public comments from the ATA and 

six airlines, as well as discussions with 

representatives from Boeing and several 

airlines that operate 737s, an ATA 

survey of its members, avionics vendors, 

and repair stations that will perform 

some of the FDR system retrofits. In this 

section, the FAA addresses the public 

comments concerning the Preliminary 

Regulatory Evaluation and the economic 

effects of the proposed rule. 

Affected Airplanes and Industries 

In the November 1999 NPRM, the 

FAA estimated the proposed rule would 

affect 1,306 737s projected to be in 

service in the year 2000, and 2,144 737s 

that will be manufactured between 2001 

and 2020. 

In the Supplemental PRE, the FAA 

estimates that this proposed rule would 

affect 1,171 current 737s projected to be 

active in 2008. The FAA believes this 

proposal would not affect 737s in 

production because Boeing voluntarily 

manufacturers these airplanes to the 

rule’s requirements. Currently, eight 

airlines (Southwest Airlines, 

Continental Airlines, United Airlines, 

Delta Airlines, U.S. Airways, American 


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Airlines, America West Airlines, and 

Alaska Airlines) operate 80 percent of 

the affected airplanes. One major airline 

(Southwest Airlines) and two national 

airlines (Aloha Airlines and Sun 

Country Airlines) operate 737s 

exclusively. 

Benefits 

The principal benefit from increasing 

the number of recorded flight data 

parameters is the increased probability 

that the information gathered can be 

used to determine more precisely the 

causes of future 737 rudder-related 

accidents. Once these causes are known, 

regulatory agencies and the aviation 

industry could effect corrective actions 

(e.g., an airplane design modification or 

changes in operating procedures) that 

could prevent such future accidents. 

In the NPRM, the FAA estimated the 

number of these future 737 accidents 

based on the assumption the historical 

accident rate would remain constant. 

The ATA and Continental Airlines 

disagreed by noting that the FAA issued 

several ADs on the 737 rudder system 

since 1995, and no rudder-associated 

accidents had happened since then. 

(These comments, made in 2000, do not 

include the 2002 AD (Number 2002–20–

07) that requires 737 rudders to be 

retrofitted to prevent an uncommanded 

rudder hardover event.) Continental 

Airlines believed that, to the extent that 

the ADs have mitigated this unknown 

problem, an accident rate based on the 

pre-AD 737 historical rate will 

overestimate the future accident rate. 

The FAA agrees the historical 737 

accident rate is not appropriate for this 

analysis. Given the recent ADs, there is 

insufficient information to specify the 

future 737 accident rate and how much 

this rulemaking will reduce it. As a 

result, the FAA has changed the 

approach used in the NPRM in 

analyzing benefits in this SNPRM 

analysis. Rather than predicting a 

number of future accidents, as was done 

for the NPRM, the Supplemental PRE 

estimates the potential quantified 

benefits that would occur if recording 

these flight data parameters would lead 

to the prevention of an accident. Should 

the FAA receive sufficient data in 

response to this rulemaking notice to 

permit it to predict a number of future 

accidents, it may revert to the 

methodology used in the preliminary 

regulatory evaluation supporting the 

NPRM. 

In the NPRM, the FAA used the 

following values to quantify the 

potential benefits from a prevented 737 

accident: $2.7 million for each 

prevented fatality, an average of 96 

passengers and crew on a 737, for a 

resulting total of $259.2 million an 

airplane; $20 million for a destroyed 

737; $5 million for ancillary damage to 

ground structures; and $31 million for 

the resultant government and industry 

accident investigation. Thus, the 

average potential benefit from 

preventing a 737 in-flight accident was 

estimated to be $315.2 million in 1999 

dollars. There were no comments on 

this estimate. 

In the Supplemental PRE, the FAA 

uses the following updated values and 

average 737 size to quantify the 

potential benefits from a prevented 737 

accident: $3 million for each prevented 

fatality; an average of 113 passengers 

and crew on a 737, for a resulting total 

of $339 million an airplane; $17 million 

for a destroyed 737; $6 million for 

ancillary damage to ground structures; 

and $33 million for the resultant 

government and industry accident 

investigation. These changes are the 

result of increased costs, as well as an 

increase in the average number of 

passengers aboard a 737. Thus, the 

average potential benefit from 

preventing a 737 in-flight accident is 

about $395 million in 2003 dollars. 

Significant Differences in the Economic 

Models Used in the Preliminary 

Regulatory Evaluation and the 

Supplemental Preliminary Regulatory 

Evaluation 

Table 1 lists the significant 

differences in assumptions and values 

between those used in the NPRM and 

those in this analysis. The specific 

impact that each value has on the 

revised compliance costs is discussed in 

the individual compliance cost sections. 

Although there are other differences that 

have changed the calculated costs, the 

differences listed in Table 1 are the most 

significant ones. 

TABLE 1.—SIGNIFICANT DIFFERENCES IN ASSUMPTIONS AND VALUES BETWEEN THE PRELIMINARY REGULATORY

EVALUATION AND THE SUPPLEMENTAL PRELIMINARY REGULATORY EVALUATION

Assumption or value Preliminary regulatory analysis Supplemental preliminary regulatory analysis 

Number of Airplanes .......................................... 1,306 (in Year 2000) ........................................ 1,567 (in Year 2004). 

Number of Retrofitted Airplanes ......................... 1,306 (by Year 2001) ....................................... 1,171 (by Year 2008). 

Annual Increase in Flight Hours & Fuel Burn .... 4.1 percent ....................................................... Varies depending on number of airplanes. 

Year of First Retrofits ......................................... 2000 ................................................................. 2005. 

Number of years to retrofit ................................. 18 months ........................................................ 4 years. 

How scheduled retirements are handled ........... All airplanes active on the final rule date are 

retrofitted.

No airplane scheduled for retirement before 

2008 is retrofitted. 

Who does initial engineering redesign ............... All individual STC holders ................................ Boeing. 

Hourly Labor Rates: Engineers; Mechanics ....... $100; $70 ......................................................... $125; $85. 

How recorders are affected ................................ Newer recorders in 737 ‘‘Classic’’ airplanes 

can be reprogrammed at a unit cost of 

$10,000..

All recorders in 737 ‘‘Classic’’ airplanes must 

be replaced at a unit cost of $20,000. 

How FDAUs are affected ................................... Existing FDAUs in 737 ‘‘Classic’’ airplanes 

can be reprogrammed at a unit cost of 

$20,000.

All FDAUs must be replaced in 737 ‘‘Classic’’

airplanes at a unit cost of $50,000. 

How FCCs are affected ...................................... No impact—no cost ......................................... Must be reprogrammed at a cost of $10,000 

per airplane. 

How many airplanes retrofitted during a ‘‘C’’ or 

‘‘D’’ maintenance check.

33 percent ........................................................ 100 percent. 

How many out-of-service days for a retrofit not 

done during a ‘‘C’’ or ‘‘D’’ maintenance check.

4–9 ................................................................... 2–8.1

How many out-of-service days for a retrofit 

done during a ‘‘C’’ maintenance check.

2–7 ................................................................... 0–6. 

Per gallon price of aviation fuel .......................... $0.61 ................................................................ $0.75. 


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TABLE 1.—SIGNIFICANT DIFFERENCES IN ASSUMPTIONS AND VALUES BETWEEN THE PRELIMINARY REGULATORY

EVALUATION AND THE SUPPLEMENTAL PRELIMINARY REGULATORY EVALUATION—Continued 

Assumption or value Preliminary regulatory analysis Supplemental preliminary regulatory analysis 

Future production 737s ...................................... All affected at a per airplane cost of $38,900 No cost because parameters 89–91 would 

have been installed in the absence of the 

final rule. 

1 In the event we receive information that some airplanes cannot be retrofitted during a ‘‘C’’ or ‘‘D’’ check, we will use an out of service time of 

2 to 8 days for FDR equipment installation. We specifically request that this estimate be verified by affected operators. 

Compliance Costs for the Supplemental 

Rule 

As summarized in Table 2, the FAA 

estimated in the NPRM that the cost to 

retrofit a 737 would vary between 

$41,800 and $221,950 per airplane, 

depending upon the 737 model, its FDR 

system equipment, and whether the 

retrofit would be completed during a 

‘‘D’’ check, a ‘‘C’’ check, or would 

require a separate dedicated scheduled 

maintenance session. See also the 

footnote to Table 1. 

TABLE 2.—PER AIRPLANE COMPLIANCE COST BY 737 SERIES AND FDR SYSTEM ESTIMATED IN THE PRELIMINARY

REGULATORY EVALUATION

[All values in 1999 $] 

737 Series Equipment and 

labor costs 

Out-ofservice days Out-of-service 

lost net revenue 

Total costs and 

lost net revenue 

200 ........................................................................................... $160,200–176,400 4–7 $250–800 $160,450–177,200 

200-Advanced (No FDAU) ....................................................... 160,200–176,400 4–7 4,900–8,600 160,690–185,000 

200-Advanced (FDAU) ............................................................ 68,800–90,000 2–4 2,450–4,900 71,250–94,900 

300 (No FDAU) ........................................................................ 175,200–191,400 6–9 20,375–30,550 195,575–221,950 

300 (FDAU) .............................................................................. 35,100–90,000 2–4 6,800–21,550 41,900–111,550 

400 (No FDAU) ........................................................................ 160,200–176,400 6–9 17,350–30,350 177,550–206,750 

400 (FDAU) .............................................................................. 35,100–90,000 2–4 8,675–25,250 43,775–107,350 

500 (No FDAU) ........................................................................ 175,200–191,400 6–9 20,150–30,200 195,350–221,600 

500 (FDAU) .............................................................................. 35,100–90,000 2–4 6,700–19,100 41,800–109,100 

600 ........................................................................................... 35,100 2–4 15,375–30,750 50,475–65,850 

700 ........................................................................................... 35,100 2–4 17,350–34,675 52,450–69,775 

800 ........................................................................................... 35,100 2–4 20,800–41,575 55,900–76,675 

900 ........................................................................................... 35,100 2–4 21,950–43,875 57,050–76,975 

The FAA estimated in the NPRM the 

total costs of compliance with the 

proposed rule between 2000 and 2020 

would be about $255 million, which 

had a present value of $205.4 million. 

Of the $255 million total costs, the onetime costs to retrofit the existing 737 

fleet (engineering plus retrofitting plus 

losses from out-of-service time) would 

have been $158.7 million. If the rule had 

been issued on January 1, 2000, the 

$158.7 million would have been spent 

within 20 months or the airplanes 

would have been grounded. The 

increased costs to manufacture future 

737s from 2000 through 2019 would 

have been $86 million. Finally, the 

increased annual costs of the additional 

fuel burn due to the increased weight of 

the airplane and the additional 

maintenance of the FDR system from 

2000 through 2019 would have been 

$10.3 million. 

In the Supplemental PRE, after 

incorporating data from the comments 

and updating the fleet and unit cost 

data, the FAA has determined that the 

cost per 737 will be between $189,320 

and $201,320 for a 737–200, between 

$189,320 and $209,320 for a 737–300/ 

400/500 that does not have a FDAU, 

between $142,120 and $167,120 for a 

737–300/400/500 that has a FDAU, 

between $49,410 and $63,410 for a 737 

NG that does not record parameters 89–

91, and $9,475 for a 737 NG that records 

parameters 89–91. 

The FAA has tentatively determined 

the total cost to comply with this 

SNPRM would be about $143 million 

between 2004 and 2014, which has a 

present value of about $126.5 million. 

Of the $143 million, about $140 million 

will be expended during the first 4 years 

for engineering costs, retrofitting costs, 

and out-of-service costs, $2 million will 

be for increased fuel consumption, and 

$0.7 million will be for additional FDR 

system maintenance. There will be 

minimal compliance costs for 

production 737s because Boeing has 

been voluntarily installing the 

capability to record the additional data 

required by the proposed rule since 

August 2000. 

Summary of Factors Creating the 

Significant Differences Between the 

Estimates 

There are 4 major factors that create 

the differences between the NPRM and 

SNPRM estimates. 

The first factor, which increases onetime retrofitting compliance costs, is the 

FAA’s assumption that some of the 

existing solid-state recorders and 

existing FDAUs could be 

reprogrammed. However, the ATA, 

Alaska, Aloha Airlines, Continental 

Airlines, Southwest Airlines, and 

United Airlines commented that 

retrofitting the FDR systems in the 737- 

‘‘Classic’’ series requires purchasing 

new recorders and new FDAUs; they 

cannot be reprogrammed. Boeing, 

American, and Aloha Airlines reported 

that their 737-‘‘NG’’ series recorders and 

FDAUs could be reprogrammed. The 

FAA accepts both these positions. As a 

new recorder costs between $10,000 and 

$15,000 more than a reprogrammed 

recorder, and a new FDAU costs 

$30,000 more than a reprogrammed 

FDAU, the impact on the total 

retrofitting cost is considerable. 


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A second factor, which lowers 

compliance costs, is that 135 fewer 737s 

will be retrofitted under the SNPRM 

than would have been retrofitted under 

the originally proposed rule. 

A third factor, which lowers 

compliance costs, is that the FAA 

significantly reduces its estimated 

number of labor hours to retrofit FDR 

systems to record flight data parameters 

(a)(19) through (a)(22) in 737s with 

FDAUs. In the NPRM, the FAA 

estimated it would take 400 hours while 

the FAA now estimates that it takes 100 

hours. 

A final factor that lowers compliance 

costs is that the Supplemental PRE 

analysis contemplates that the flight 

data parameter retrofit will be 

performed when a 737 is retrofitted with 

a new rudder rather than within the 20 

months originally proposed in the 

NPRM. Since the publication of the 

proposed rule, more 737s have been 

retired, reducing those estimated costs. 

Commenters’ Retrofit Cost Estimates 

In the NPRM, the FAA used 

retrofitting costs largely provided by the 

industry. In the comments to the NPRM 

estimates, Aloha Airlines estimated a 

cost of $165,100 to $185,000 to retrofit 

its 737–200 Advanced airplanes that did 

not have a FDAU, $71,250 to $94,900 to 

retrofit its 737–200 Advanced airplanes 

that have a FDAU, and $52,450 to 

$69,775 to retrofit its 737–700 airplanes. 

American Airlines estimated a cost of 

$47,250 plus lost revenue for 2+ days 

out-of-service for each of its 737–800 

airplanes. Continental Airlines did not 

report a total cost, but was in general 

agreement with the FAA estimates, if 

the FAA adjusted its costs to recognize 

that existing recorders and FDAUs in 

737-‘‘Classic’’ airplanes cannot be 

reprogrammed and must be replaced. 

United Airlines estimated a total 

retrofitting cost of $24,100,000 and for 

its fleet of 158 737-‘‘Classics’’, for an 

average airplane cost of $152,500. The 

FAA has tentatively determined the 

retrofitting cost of a 737-‘‘Classic’’

ranges from $142,000 to $189,000 while 

the retrofitting cost of a 737-‘‘NG’’

ranges from $9,475 to $49,410. 

Time to Engineer New Designs for the 

Retrofitted FDR Systems 

In the NPRM, the FAA assumed that 

each STC holder would independently 

do all the engineering redesign. Boeing, 

the ATA, Alaska, Continental Airlines, 

Southwest Airlines, and United Airlines 

commented that such an approach 

would be inefficient and lead to 

duplication of effort. Industry expects 

Boeing to do the initial engineering 

work, which the STC holders would 

then modify for their various FDR 

systems. The FAA accepts those 

comments and has adjusted its analysis 

accordingly. 

In the NPRM, the FAA estimated that 

airlines and repair stations would 

redesign 40 FDR systems and it would 

take 16 to 26 weeks and cost each FDR 

system holder $200,000 to complete the 

first FDR system redesign. As 

engineering data from one STC can be 

used in other STCs, the FAA assumed 

that after five such FAA approvals, an 

STC holder could use commonality 

demonstrations to reduce this cost from 

$200,000 to $25,000 per STC. Thus, the 

FAA estimated a total one-time cost of 

$2.95 million for the initial engineering 

redesign. 

Boeing indicated that the FAA 

significantly underestimated the 

engineering hours required for each 

individual engineering analysis. 

Although Boeing did not provide 

specific estimates in its comments, the 

FAA has assessed the engineering 

analyses for the 737 series as a one-time 

cost of $6.6 million, which consists of 

30 engineering years. 

In the NPRM, the FAA assumed that 

three engineers working full-time for 

four months (one engineer year) would 

be needed for an FDR system redesign 

STC approval, at a cost of $200,000 per 

STC application. The FAA further 

estimated that 32 applications would be 

made for a one-time engineering cost of 

$7.5 million. 

Aloha Airlines, Continental Airlines, 

Southwest Airlines, United, and U.S. 

Airways commented that it would take 

from six months to one year after Boeing 

completes the initial engineering 

analysis for them to complete their 

design modifications and obtain FAA 

approvals. They did not, however, 

provide an estimate of their engineering 

time or costs to complete these 

applications. In the Supplemental PRE, 

the FAA estimates that 15 STC 

applications will require one engineer 

year (at a cost of $250,000) to complete, 

while 25 of the STCs will require 250 

engineer hours (at a cost of $31,250) to 

complete. On that basis, the calculated 

total STC engineering cost is $4.6 

million. 

Aloha Airlines stated the FAA 

underestimated the number of 

engineering analyses because each 

airplane ‘‘configuration’’ within a 737 

series would need a separate 

engineering analysis. They commented 

that 13 of their 18 airplanes will need 

a $200,000 analysis. The FAA agrees 

that an adjustment in the cost 

calculations needs to be made for the 

different configurations. However, 

because much of the engineering is 

identical for each configuration within a 

737 series, the FAA has tentatively 

determined that it will take half of the 

engineering time for a commonality 

demonstration STC (125 hours) for a 

configuration STC. The FAA has 

calculated a per configuration cost of 

$16,125. Finally, the FAA has 

tentatively determined that 60 of these 

‘‘configuration’’ STCs will be performed 

because most airlines’ fleets have fewer 

configurations than the Aloha Airlines 

fleet. The FAA estimates a total cost of 

$967,500 for this engineering. 

Alaska also noted that two of the 

sensors had not been developed for any 

airplane and several other sensors had 

not been approved for use in many of 

the 737-‘‘Classic’’ airplanes. Thus, as 

well as the design STC approval, the 

FAA would also need to issue Parts 

Manufacturing Authorizations (PMAs) 

to the new sensors manufacturers. 

Alaska posited that although the 

vendors will incur most of these 

development costs, these costs should 

be included in Boeing’s initial 

engineering costs because Boeing will 

be the kit supplier. 

In the NPRM, the FAA estimated the 

total one-time engineering costs to 

modify the FDR system STCs and obtain 

FAA approval would have been $9.15 

million. The FAA now calculates the 

total costs to modify the FDR system 

STCs and obtain FAA approvals are $15 

million. 

Equipment and Labor Costs to Retrofit 

FDR Systems 

In the NPRM, the FAA estimated the 

equipment and labor costs to retrofit 

FDR systems for compliance with the 

proposed rule would be $124.3 million. 

Based on the comments and the revised 

fleet, the FAA has reduced the 

anticipated equipment and labor cost to 

comply with the final rule, if adopted, 

to $111.8 million. 

In the NPRM, the FAA estimated that 

156 737s would have their recorders 

replaced, while the remaining 1,150 

737s would have their recorders 

upgraded with additional memory. The 

FAA estimated that: a new recorder 

would cost $25,000; upgrading the 

memory of a recorder that records 18 

flight data parameters would cost 

$10,000; upgrading the memory of a 

recorder that records 22 flight data 

parameters would cost $5,000; and 

upgrading the memory of a recorder that 

records more than 22 parameters would 

cost $1,900. 

ATA, Aloha Airlines, Continental 

Airlines, Southwest Airlines, and 

United Airlines commented that all of 

their 737-‘‘Classics’’ would have their 


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recorders replaced because they cannot 

be reprogrammed. 

Accepting and incorporating industry 

comments, and with the increased 

numbers of retirements, the FAA has 

tentatively determined that 605 737s 

will need their recorders replaced and 

279 737s will need their recorders 

reprogrammed by 2008. 

Finally, Continental Airlines reported 

new recorder costs of $13,000 while 

Aloha Airlines reported a recorder cost 

of $25,000. In the Supplemental PRE, 

the FAA has assessed a cost of $20,000 

per recorder, the average of these two 

estimates and estimates provided by 

avionics manufacturers. 

In the NPRM, the FAA estimated that 

installing a new recorder would require 

32 labor hours to remove the old 

recorder and to install and test a new 

recorder. Upgrading an FDR would 

require 16 labor hours to remove, 

reprogram, reinstall, and test. The FAA 

received no comments on this estimate 

and uses it in the Supplemental PRE. 

In the NPRM, the FAA estimated the 

cost of replaced or upgraded recorders 

would be $17.2 million. Based on the 

increased recorder cost estimate and the 

fewer retrofitted 737s, the FAA now 

calculates that the total cost of replaced 

or upgraded recorders in this is $14.6 

million, which has a present value of 

$12.8 million. 

In the NPRM, the FAA estimated that 

a FDAU would be retrofitted into 496 

737s that did not have one, while the 

existing FDAUs in 810 737s would be 

reprogrammed. The same commenters 

who addressed the issue of the recorder 

all agreed that, whereas the FDAUs in 

their 737-‘‘NGs’’ can be reprogrammed, 

every FDAU in their 737-‘‘Classics’’

would have to be replaced—those units 

cannot be reprogrammed. The FAA 

agrees with these comments. In the 

Supplemental PRE, the FAA has 

tentatively determined that by 2004 

operators of 198 737–200s will have 

introduced FDAUs into their airplanes; 

that operators of 407 737–300/400/500s 

with a FDAU will have installed new 

FDAUs in their airplanes; and that 

operators of 279 737–700/800/900s will 

have reprogrammed their existing 

FDAUs. 

Continental Airlines and Aloha 

Airlines reported a $50,000 cost for a 

new FDAU and a cost to reprogram a 

FDAU of between $7,500 and $10,000. 

In the Supplemental PRE, the FAA uses 

a cost of $50,000 for a new FDAU and 

an average of the two estimates ($8,750) 

as the cost to reprogram a FDAU. 

In the NPRM, the FAA noted that 

retrofitting a 737 with a FDAU would 

require rerouting the FDR system wiring 

because the recorder (where the wires 

formerly terminated) is located aft, 

while the new FDAU would be in the 

front. Relying on estimates from 

Southwest Airlines and United, the 

FAA estimated that retrofitting a FDAU 

would take 200 labor hours, which 

includes the associated labor hours to 

rewire the existing FDR system. Aloha 

Airlines submitted the only specific 

comment on this issue and it agreed 

with the FAA estimate. Thus, the FAA 

continues to assume 200 labor hours to 

retrofit a FDAU. 

In the NPRM, the FAA estimated that 

it would take 48 hours for a FDAU on 

a 737-‘‘Classic’’ airplane and 40 hours 

for a FDAU on a 737-‘‘NG’’ airplane to 

be removed, shipped to the 

manufacturer, reprogrammed, 

reinstalled, and tested. Three airlines 

filed comments on these estimates. 

Aloha Airlines reported that it will take 

the same number of labor hours (200) to 

replace an existing FDAU as it will to 

retrofit a FDAU in an FDR system that 

did not previously have one. The FAA 

disagrees. The effort to retrofit a FDAU 

is greater than the effort to install one 

in an airplane that did not have it. 

Continental Airlines estimated a cost of 

$71,500 for the equipment and labor 

costs to replace a FDAU. However, that 

estimate also included the cost to record 

the additional flight data parameters 

and the increased sampling rate for 

flight data parameter (a)(88). United 

Airlines similarly estimated a total labor 

cost of $33,000 for the entire retrofit. 

The numbers submitted by Continental 

Airlines and United Airlines do not 

allow the FAA to distinguish the 

number of labor hours to replace a 

FDAU from the total labor hours for the 

retrofit. After reviewing the comments, 

the FAA has increased the estimated 

number of labor hours to replace a 737- 

‘‘Classic’s’’ FDAU from 48 hours to 80 

hours and reduced the number of labor 

hours from 40 hours to 20 hours for a 

737-‘‘NG’s’’ FDAU. 

Accordingly, the FAA calculates that 

the labor costs to install a FDAU in an 

FDR system that did not have one is 

$17,000; the labor costs to replace a 

FDAU is $6,800; and the labor costs to 

install a reprogrammed FDAU is $1,700. 

In the NPRM, the FAA estimated the 

total FDAU equipment and labor costs 

to retrofit FDAUs would be $37.6 

million. In the Supplemental PRE, the 

FAA calculates the total equipment and 

a labor cost to retrofit FDAUs at $40.9 

million, which has a present value of 

$35.8 million. 

In the NPRM, the FAA divided the 

equipment and labor costs for the 

additional wiring for adding the sensors 

into three components: (1) The costs to 

record flight data parameters (a)(19) 

through (a)(22); (2) the costs to record 

flight data parameters found in (a)(88) at 

the greater ranges and increased 

sampling rates; and (3) the costs to 

record flight data parameters (a)(89) 

through (a)(91). That division is 

continued in this analysis. 

In the NPRM, the FAA estimated the 

costs of the sensors and wiring for a 737 

FDR system to record parameters (a)(19) 

through (a)(22) were $20,000. The only 

specific comment received on this 

estimate was from Aloha Airlines, 

which agreed with the estimate. As a 

result, the FAA uses this value in the 

Supplemental PRE. 

In the NPRM, the FAA estimated that 

the installation of the sensors and 

wiring to record flight data parameters 

(a)(19) through (a)(22) would take 200 

labor hours for a 737–200, a 737–200 

Advanced, or a 737–400 airplane. It 

would take 400 labor hours for a 737–

300 or a 737–500 series airplane. 

Boeing commented that the FAA 

misclassified the labor costs for the 737–

400 because the avionics in that series 

are essentially the same as the avionics 

in the 737–300 and 737–500 series 

airplanes. These airplanes employ 

ARINC 700 systems, while the 737–200 

and 737–200 Advanced are, basically, 

‘‘all analog’’ airplanes. Boeing 

contended the labor time (and cost) to 

rewire a 737–400 airplane is similar to 

the labor hours (and costs) for a 737–300 

or a 737–500 airplane. The FAA accepts 

Boeing’s comment and has assigned the 

same number of labor hours for all the 

737–300/400/500 airplanes. 

As Aloha Airlines uses the same 200 

labor hour estimate for its 737–200 

retrofits, the FAA continues to use the 

200 labor hours in the NPRM to retrofit 

737–200s in the Supplemental PRE. 

Boeing noted that there are minor 

differences in the amount of wiring 

among all of its 737- ‘‘Classics’’. The 

FAA agrees and has revised its estimate 

for the 737–300/400/500 series retrofit 

to record flight data parameters from 

400 labor hours to 200 labor hours. 

Thus, the FAA calculates the sensor and 

labor cost to record flight data 

parameters (a)(19) through (a)(22) of 

$17,000 for a 737-‘‘Classic’’. The total 

anticipated cost to record flight data 

parameters (a)(19) through (a)(22) is 

$37,000. Boeing also commented that 

the FAA had not specifically estimated 

the costs for the individual sensors and 

other equipment required to record 

flight data parameters (a)(19) through 

(a)(22). The FAA agrees; however, the 

FAA notes that the airline cost estimates 

were not provided on an individual 

sensor basis. Consequently, the FAA 

could not establish individual sensor 

cost estimates. 


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In the NPRM, the FAA used 

preliminary industry estimates that it 

would cost $12,000 to add the necessary 

sensors and wiring to record flight data 

parameter (a)(88) in a 737 FDR system 

that does not currently record it or that 

does not record it at the proposed range. 

American Airlines commented that it 

will cost $8,000 for the sensors to record 

this flight data parameter at the 

proposed range. The FAA accepts the 

American Airlines estimate and has 

assumed a cost of $8,000. 

In the NPRM, the FAA assumed that 

it would cost $12,000 to replace all 

sensors currently recording flight data 

parameter (a)(88) in order to comply 

with the higher sampling rate 

requirement. Boeing, however, reported 

that the existing sensors can be 

reprogrammed to transmit information 

at the increased sampling rate. The FAA 

agrees with Boeing and has tentatively 

determined there will be no sensor costs 

to comply with the higher sampling 

rates for flight data parameter (a)(88). 

In the NPRM, the FAA estimated that 

it would take 160 labor hours to install 

the sensors in a 737-‘‘Classic’’ FDR 

system that was either not recording 

flight data parameter (a)(88) or not 

recording it at the proposed range. 

Aloha Airlines reported a total of 360 

labor hours to record flight data 

parameters (a)(88) through (a)(91). As 

three of the six flight data parameters to 

be recorded are found in (a)(88), the 

FAA has assumed that half of the labor 

hours reported by Aloha Airlines (180) 

hours will be used to install flight data 

parameter (a)(88) for a labor cost of 

$15,300 per airplane. 

In the NPRM, the FAA estimated that 

it would take 160 labor hours to replace 

the sensor in a 737–‘‘NG’’ that was 

recording flight data parameter (a)(88) at 

the lower sampling rate. The FAA 

believes that it takes fewer labor hours 

to reprogram the sensor to record flight 

data parameter (a)(88) than it will take 

to introduce new sensors and wiring 

into a FDR system that had not 

previously recorded it. In the 

Supplemental PRE, the FAA has 

tentatively determined that it will take 

80 labor hours (at a cost of $6,800) to 

install new sensors for flight data 

parameter (a)(88). 

Boeing did not provide a labor hour 

estimate to install reprogrammed 

sensors to record at the higher sampling 

rate. In the Supplemental PRE, the FAA 

estimates that it takes one-half (40) 

hours to reprogram the sensors than it 

does to install new sensors at a labor 

cost of $3,400 per airplane. 

The FAA also estimates that the 

retrofit costs to install new sensors to 

record flight data parameter (a)(88) are 

$23,300 for a 737-‘‘Classic’’ and $14,800 

in a 737-‘‘NG’’. The cost to install 

reprogrammed sensors in a 737-‘‘NG’’ is 

$3,400. 

Aloha Airlines and American Airlines 

provided sensor costs or the number of 

labor hours to retrofit FDR systems to 

record flight data parameters (a)(89), 

(a)(90), and (a)(91). The American 

Airlines comment provided aggregated 

data and the FAA could not disaggregate 

some of their costs. Aloha Airlines 

reported a total wiring and sensor cost 

of $12,000 to record flight data 

parameters (a)(88) through (a)(91). The 

FAA agrees with this estimate. As the 

FAA has also determined that the 

wiring and sensor cost to retrofit flight 

data parameter (a)(88) is approximately 

$8,000, the FAA concludes that the 

wiring and sensor costs to retrofit flight 

data parameters (a)(89) through (a)(91) 

should be approximately $4,000. 

As noted, the FAA has determined 

that half of the labor time reported by 

Aloha Airlines is to install flight data 

parameter (a)(88) and half the time is to 

install flight data parameters (a)(89), 

(a)(90), and (a)(91). Thus, the FAA 

calculates that 180 labor hours (at a cost 

of $15,300) will be required to install 

flight data parameters (a)(89), (a)(90), 

and (a)(91) in a 737-‘‘Classic’’. The FAA 

has also assumed that 80 labor hours (at 

a cost of $6,800) will be required to 

install flight data parameters (a)(89), 

(a)(90), and (a)(91) in a 737-‘‘NG’’. The 

FAA calculates that the retrofitting costs 

to record flight data parameters (a)(89), 

(a)(90), and (a)(91) is $27,300 for a 737- 

‘‘Classic’’ and $10,800 for a 737-‘‘NG’’. 

In the NPRM, the FAA estimated the 

total retrofitting sensor and wiring costs 

to have been: $84,000 for a 737–200 or 

a 737–400 airplane without a FDAU; 

$100,000 for a 737–300 or a 737–500 

airplane without a FDAU; $49,000 for 

an older 737 airplane with a FDAU; and 

$24,000 and for a newer 737 airplane 

with a FDAU. 

In the Supplemental PRE, the FAA 

estimates that the retrofitting sensor and 

wiring costs, per 737, are: $89,600 for a 

737-‘‘Classic’’ that records 18 flight data 

parameters; $52,600 for a 737-‘‘Classic’’

that records 22 flight data parameters; 

$25,600 for a 737-‘‘NG’’ manufactured 

before August 2000: and $10,800 for a 

737-‘‘NG’’ manufactured after August 

2000. 

In the NPRM, the FAA estimated that 

the total sensor and wiring costs to 

retrofit all 737 FDR systems by the 

compliance date would be $69 million. 

The FAA now calculates that the total 

sensor and wiring costs to retrofit all 

737 FDR systems by the compliance 

date is $48 million, which has a present 

value of $42 million. 

In the NPRM, the FAA did not 

consider (and did not estimate) any cost 

for reprogramming the flight control 

computers (FCCs). Boeing and American 

Airlines commented that recording the 

additional flight data parameters would 

require reprogramming the FCCs. 

Boeing provided no cost estimates for 

FCC reprogramming, but American 

Airlines reported that it will cost $5,000 

per FCC to reprogram the 2 FCCs (for a 

total cost of $10,000 per airplane). The 

FAA accepts the American Airlines 

estimate and applies it to all 737s. The 

FAA now calculates a total cost to 

reprogram the FCCs of $8.8 million, 

which has a present value of $7.7 

million. 

In the NPRM, the FAA estimated that 

the equipment and labor costs to retrofit 

the existing 737 fleet were $17.2 million 

for recorders, $37.7 million for FDAUs, 

and $69.4 million for wiring and 

sensors, for a total cost of $124.3 

million. In the Supplemental PRE, the 

FAA calculates that the equipment and 

labor costs to retrofit the existing 737 

fleet are $14.7 million for recorders, 

$40.9 million for FDAUs, $47.2 million 

for wiring and sensors, and $8.8 million 

for FCCs, for a total cost of $111.6 

million, which has a present value of 

$92.6 million. 

Total One-Time FDR System Retrofitting 

Costs 

In the NPRM, the FAA estimated the 

total one-time compliance costs and 

losses from out-of-service time would 

have been $149.6 million. Based on the 

comments and updated data, the FAA 

now calculates that the total one-time 

compliance costs and losses from out-ofservice time would be $125.2 million, 

which has a present value of $109.5 

million. 

Annual Costs Resulting From 

Retrofitting 737 FDR Systems 

The Supplemental PRE also 

contemplates annual compliance costs 

from: (1) Additional airplane weight due 

to retrofitted FDR system; and (2) 

additional maintenance costs to 

annually validate the FDAU. 

In the NPRM, the FAA estimated that 

the proposed rule would add 40 pounds 

to a 737 that does not have a FDAU and 

records 18 flight data parameters and 

add 10 pounds to a 737 that has a FDAU 

and records at least 22 flight data 

parameters. In calculating the estimated 

additional fuel cost, the FAA assumed 

a per-airplane average of 2,750 flight 

hours per year, a price of $0.61 per 

gallon of aviation fuel, and 0.23 

additional gallons consumed per 

additional pound per flight hour. These 

assumptions resulted in per-airplane 


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annual costs of $400 for a 737 that adds 

40 pounds and $100 for a 737 that adds 

10 pounds. On that basis, the FAA 

estimated the total cost from the 

increased fuel consumption during 2001 

and 2020 would have been $6.1 million, 

which has a present value of $3.6 

million. There were no comments on 

this estimate. 

In the Supplemental PRE, the 

underlying NPRM methodology is 

maintained but certain parameters are 

updated (from 2,750 to 3,360 flight 

hours per year and from $0.61 to $0.75 

per gallon cost of aviation fuel). 

However, the FAA has revised the 

weight added by the retrofitted sensors 

and wiring for 737–300/400/500s from 

10 pounds to 20 pounds. On that basis, 

the FAA now calculates that adding 40 

pounds to a 737 would increase its 

annual fuel costs by $584, adding 20 

pounds would increase its annual fuel 

costs by $292, and adding 10 pounds 

would increase its annual fuel costs by 

$146. These revised calculations result 

in a total fuel cost increase of $2 million 

between 2005–2014, which has a 

present value of $1.4 million. 

In the NPRM, the FAA estimated that 

the incremental annual inspection and 

validation of a FDAU would cost $750. 

On that basis, the FAA estimated the 

total cost from the increased 

maintenance during 2001 and 2020 

would have been $4.2 million, which 

has a present value of $2.7 million. As 

there were no comments on this 

estimate, the FAA has decided to retain 

it. Based on the number of 737s that 

would have had FDAUs introduced into 

the airplane and on the number that 

would have been retired between 2005 

to 2014, the FAA calculates a total 

maintenance cost increase of $700,000, 

which has a present value of $535,000. 

In the NPRM, the FAA estimated that 

the increased annual operational and 

maintenance costs between 2001 and 

2020 would have been $10.3 million, 

which has a present value of $6.3 

million. In the Supplemental PRE, the 

FAA calculates that the increased 

annual operational and maintenance 

costs between 2005 and 2014 are $2.7 

million, which has a present value of 

$1.9 million. 

Compliance Costs for Production 737s 

In the NPRM, the FAA estimated a 

total cost for 737s manufactured 

between 2000 and 2020 of $86 million, 

which has a present value of $40.4 

million, to install the equipment to 

record proposed flight data parameters 

(a)(89), (a)(90), and (a)(91). As 

previously discussed, the Supplemental 

PRE has taken into account Boeing’s 

voluntary installation of this equipment 

on all its 737s since August 2000, 

indicating that the SNPRM would 

impose no compliance costs on 

production 737s. 

Benefit-Cost Comments 

In the NPRM, the FAA estimated that 

the expected present value of the 

benefits ($156 million) would have been 

less than the present value of the 

quantifiable total compliance costs 

($214 million). However, the FAA noted 

there is considerable uncertainty about 

the potential number of future 

accidents. As a result, the FAA 

concluded that it was in general 

agreement with the NTSB 

recommendations that this information 

is needed. 

Boeing disagreed with an aggregated 

benefit-cost approach and commented 

that an appropriate analysis should be 

based on an individual provision-byprovision (or, in this case, flight data 

parameter by flight data parameter) 

evaluation. In principle, the FAA agrees 

with the Boeing comment. However, the 

FAA has no data that can support a 

parameter-by-parameter cost 

calculation. All of the submitted 

retrofitting cost data were block costs in 

which no individual flight data 

parameter costs were provided. In 

practice, such a detailed benefits 

analysis presupposes the existence of an 

objective probability function based on 

an engineering analysis for each flight 

data parameter of the potential for the 

additional information to lead accident 

investigators to the cause of an accident. 

It is precisely because engineering 

analyses have been unable to determine 

the causes of these accidents that such 

individual probabilities cannot be 

determined. At best, current engineering 

analyses have established that one of 

this group of several flight data 

parameters, if recorded, may help to 

determine the causes of future 

accidents. As a result, the FAA has 

decided against reevaluating its benefitcost analysis in the Supplemental PRE 

based on the individual flight data 

parameters. 

Finally, Boeing commented that the 

FAA should analyze the proposed rule 

for individual airplanes based on their 

expected remaining service life with a 

possible view of exempting older 737s. 

The justification is that the potential 

benefits to any individual 737 airplane 

would be lower the shorter its 

remaining service life while the costs 

would not be similarly reduced. 

Although the FAA agrees that, for an 

individual 737, the incremental benefits 

received from a dollar of cost are lower 

for older airplanes, the FAA disagrees 

that this is an appropriate framework to 

analyze the recording requirements. The 

primary benefits attributable to this 

proposed rule do not accrue to the 737 

that would have an accident, but, rather, 

to every other 737 that would not have 

a similar accident because engineering 

or operational changes that would 

prevent such future accidents would be 

developed from the flight data recorded 

from the accident or incident. The FAA 

is not able to correlate the potential 

probability of such an accident to the 

age of a 737. Accordingly, in any year, 

the FAA assumes that all 737s face an 

equal probability that an accident may 

occur to any one of them. If some 737s 

were exempted from the rule and if an 

uncontrolled rudder movement accident 

were to happen to one of those 

exempted airplanes, then no such future 

accident would be prevented for the 737 

fleet because the necessary flight data 

would not have been recorded and no 

appropriate engineering or operational 

changes could have been made. 

However, in recognition of the potential 

economic impact, the FAA agrees with 

Boeing’s suggestion that it is appropriate 

to limit the applicability of this rule to 

not include those 737s that have a 

limited remaining service life. Thus, 

this proposed rule would apply only to 

737s that would be in service 4 years 

after the promulgation of the final rule. 

Regulatory Flexibility Determination 

The Regulatory Flexibility Act of 

19805 U.S.C. 601–612, directs the FAA 

to fit regulatory requirements to the 

scale of the businesses, organizations, 

and governmental jurisdictions subject 

to the regulation. The FAA is required 

to determine whether a proposed or 

final action will have a ‘‘significant 

economic impact on a substantial 

number of small entities’’ as defined in 

the ACT. If the FAA finds that the 

action will have a significant impact, 

the FAA must perform a ‘‘regulatory 

flexibility analysis.’’ However, if an 

agency determines that a proposed or 

final rule is not expected to have a 

significant economic impact on a 

substantial number of small entities, 

section 605(b) of the Act provides that 

the head of the agency may so certify, 

and a regulatory flexibility analysis is 

not required. The certification must 

include a statement providing the 

factual basis for this determination, and 

the reasoning should be clear. 

In the NPRM, the FAA prepared a 

Preliminary Regulatory Flexibility 

Analysis because the proposed rule 

might have had a significant economic 

impact upon a substantial number of 

small entities. The FAA had concluded, 

after that preliminary analysis, that the 

proposed rule may not have met that 


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criterion, but it reported its analysis and 

requested public comments. The FAA 

received no comments about the 

Preliminary Regulatory Flexibility 

Analysis. 

However, subsequent to publication 

of the NPRM, the Office of Advocacy of 

the Small Business Administration 

published new guidelines that defined a 

small airline as one that has fewer than 

1,500 employees. In 2003, the FAA 

performed a new Regulatory Flexibility 

Analysis for this SNPRM. In that 

analysis, of the 20 airlines that would be 

affected by the SNPRM, 12 have fewer 

than 1,500 employees and are small 

entities. Of these 12 airlines, one had a 

positive net operating income, seven 

had negative net operating income, and 

net operating income data were not 

available for four airlines. Twelve 

airlines is a substantial number of 

airlines and the cost per airplane is 

significant—particularly when the 

airline has negative net operating 

income. 

Therefore, based on that information 

available at that time and the definition 

of a small business, the FAA 

Administrator has determined that the 

proposed rule could have a significant 

economic effect on a substantial number 

of small entities. Under the new 

definition, our preliminary conclusion 

is that it will have a significant 

economic impact. 

This determination is explained in 

more detail in the Regulatory Flexibility 

Section of the Supplemental PRE. 

However, since the results of that 

evaluation are based on data that are not 

current, we are requesting that affected 

operators provide us with more current 

data to be used to update the Regulatory 

Flexibility Evaluation before any final 

rule is issued. 

Trade Impact Assessment 

The Trade Agreement Act of 1979 

prohibits Federal agencies from 

establishing any standards or engaging 

in related activities that create 

unnecessary obstacles to the foreign 

commerce of the United States. 

Legitimate domestic objectives, such as 

safety, are not considered unnecessary 

obstacles. The statute also requires 

consideration of international standards 

and, where appropriate, that they be the 

basis for U.S. standards. The FAA has 

assessed the potential effect of this 

rulemaking and determined that it 

would have only a domestic impact and, 

therefore, no affect on any tradesensitive activity. 

Unfunded Mandates Assessment 

The Unfunded Mandates Reform Act 

of 1995 (the Act) is intended, among 

other things, to curb the practice of 

imposing unfunded Federal mandates 

on State, local, and tribal governments 

or on the private sector. 

Section 202(a) (2 U.S.C. 1532) of Title 

II of the Act requires that each Federal 

agency, to the extent permitted by law, 

prepare a written statement assessing 

the effects of any Federal mandate in a 

proposed or final agency rule that may 

result in the expenditure by State, local, 

and tribal governments, in the aggregate, 

or by the private sector, of $100 million 

or more (adjusted annually for inflation) 

in any one year; such a mandate is 

deemed to be a ‘‘significant regulatory 

action.’’ The FAA currently uses an 

inflation-adjusted value of $128.1 

million in lieu of $100 million. Section 

203(a) of the Act (2 U.S.C. 1533) 

provides that before establishing any 

regulatory requirements that might 

significantly or uniquely affect small 

governments, an agency shall have 

developed a plan under which the 

agency shall: 

(1) Provide notice of the requirements 

to potentially affected small 

governments, if any; 

(2) Enable officials of affected small 

governments to provide meaningful and 

timely input in the development of 

regulatory proposals containing 

significant Federal intergovernmental 

mandates; and, 

(3) Inform, educate, and advise small 

governments on compliance with the 

requirements. 

With respect to (2), Section 204(a) of 

the Act (2 U.S.C. 1534) requires the 

Federal agency to develop an effective 

process to permit elected officers of 

State, local, and tribal governments (or 

their designees) to provide the input 

described. 

This rulemaking does not contain a 

significant Federal intergovernmental or 

private sector mandate because the 

compliance costs to the private sector 

would be about $48 million in each of 

the years 2005, 2006, and 2007, and no 

more than $3 million in any following 

year. Therefore, the requirements of 

Title II do not apply. 

Executive Order 13132, Federalism 

The FAA has analyzed this 

rulemaking under the principles and 

criteria of Executive Order 13132, 

Federalism. We determined that this 

action will not have a substantial direct 

effect on the States, or the relationship 

between the national Government and 

the States, or on the distribution of 

power and responsibilities among the 

various levels of government, and 

therefore does not have federalism 

implications. 

IX. Environmental Analysis 

FAA Order 1050.1E identifies FAA 

actions that are categorically excluded 

from preparation of an environmental 

assessment or environmental impact 

statement under the National 

Environmental Policy Act in the 

absence of extraordinary circumstances. 

The FAA has determined this 

rulemaking action qualifies for the 

categorical exclusion identified in 

paragraph 312d and involves no 

extraordinary circumstances. 

X. Regulations That Significantly Affect 

Energy Supply, Distribution, or Use 

The FAA has analyzed this SNPRM 

under Executive Order 13211, Actions 

Concerning Regulations that 

Significantly Affect Energy Supply, 

Distribution, or Use (May 18, 2001). We 

have determined that it is not a 

‘‘significant energy action’’ under the 

executive order because it is not a 

‘‘significant regulatory action’’ under 

Executive Order 12866, and it is not 

likely to have a significant adverse effect 

on the supply, distribution, or use of 

energy. 

List of Subjects 

14 CFR Part 91 

Aircraft, Aviation safety, Reporting 

and recordkeeping requirements. 

14 CFR Part 121 

Air carriers, Aircraft, Aviation safety, 

Reporting and recordkeeping 

requirements, Safety, Transportation. 

14 CFR Part 125 

Aircraft, Aviation safety, Reporting 

and recordkeeping requirements. 

The Amendment 

In consideration of the foregoing, the 

Federal Aviation Administration 

proposes amending Chapter I of Title 

14, Code of Federal Regulations as 

follows: 

PART 91—GENERAL OPERATING AND 

FLIGHT RULES 

1. The authority citation for part 91 

continues to read as follows: 

Authority: 49 U.S.C. 106(g), 1155, 40103, 

40113, 40120, 44101, 44111, 44701, 44709, 

44711, 44712, 44715, 44716, 44717, 44722, 

46306, 46315, 46316, 46504, 46506–46507, 

47122, 47508, 47528–47531, articles 12 and 

29 of the Convention on International Civil 

Aviation (61 stat. 1180). 

2. Amend § 91.609 by adding a new 

paragraph (h) as follows: 

§ 91.609 Flight recorders and cockpit 

voice recorders. 

* * * * * 


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(h) An aircraft operated under this 

part under deviation authority from part 

125 of this chapter must comply with all 

of the applicable flight data recorder 

requirements of part 125 applicable to 

the aircraft, notwithstanding such 

deviation authority. 

PART 121—OPERATING 

REQUIREMENTS: DOMESTIC, FLAG, 

AND SUPPLEMENTAL OPERATIONS 

3. The authority citation for part 121 

continues to read as follows: 

Authority: 49 U.S.C. 106(g), 40113, 40119, 

41706, 44101, 44701–44702, 44705, 44709–

44711, 44713, 44716–44717, 44722, 44901, 

44903–44904, 44912, 45101–45105, 46105, 

46301. 

4. Amend § 121.344 by removing the 

word ‘‘and’’ after paragraph (a)(87); by 

removing the period after paragraph 

(a)(88) and adding a semicolon in its 

place; by adding new paragraphs (a)(89), 

(90) and (91), (b)(4), (c)(4), (d)(3), (e)(3) 

and (m); and by revising paragraph (f) to 

read as follows: 

§ 121.344 Digital flight data recorders for 

transport category airplanes. 

(a) * * * 

(89) Yaw damper status; 

(90) Yaw damper command; and 

(91) Standby rudder valve status. 

(b) * * * 

(4) In addition to the requirements of 

paragraphs (b)(1) through (b)(3) of this 

section, all Boeing 737 model airplanes 

must comply with the requirements of 

paragraph (m) of this section, as 

applicable. 

(c) * * * 

(4) In addition to the requirements of 

paragraphs (c)(1) through (c)(3) of this 

section, all Boeing 737 model airplanes 

must comply with the requirements of 

paragraph (m) of this section, as 

applicable. 

(d) * * * 

(3) In addition to the requirements of 

paragraphs (d)(1) and (d)(2) of this 

section, all Boeing 737 model airplanes 

also must comply with the requirements 

of paragraph (m) of this section, as 

applicable. 

(e) * * * 

(3) In addition to the requirements of 

paragraphs (e)(1) and (e)(2) of this 

section, all Boeing 737 model airplanes, 

also must comply with the requirements 

of paragraph (m) of this section, as 

applicable. 

(f) For all turbine-engine-powered 

transport category airplanes 

manufactured after August 19, 2002—

(1) The parameters listed in 

paragraphs (a)(1) through (a)(88) of this 

section must be recorded within the 

ranges, accuracies, resolutions, and 

recording intervals specified in 

appendix M to this part. 

(2) In addition to the requirements of 

paragraphs (f)(1) of this section, all 

Boeing 737 model airplanes must also 

comply with the requirements of 

paragraph (m) of this section. 

* * * * * 

(m) In addition to all other applicable 

requirements of this section, all Boeing 

737 model airplanes must record the 

parameters listed in paragraph (a)(1) 

through (a)(22) and (a)(88) through 

(a)(91) of this section within the ranges, 

accuracies, resolutions, and recording 

intervals specified in Appendix M to 

this part. The approved recorder and all 

equipment necessary to record the 

parameters required by this paragraph 

must be installed no later than the 

installation of the redesigned rudder 

system required by one or more 

Airworthiness Directives issued under 

part 39 of this chapter. The singlesource recording provisions of 

paragraphs (b)(1)(ii), (c)(1), and (d)(1) of 

this section may be used for airplanes 

otherwise subject to those paragraphs. 

5. Amend Appendix M to part 121 by 

revising item 88 and adding items 89 

through 91 to read as follows: 

Appendix M to Part 121—Airplane 

Flight Recorder Specifications— 

Continued 

* * * * * 

Parameter Range Accuracy 

(sensor input) 

Seconds per 

sampling 

interval 

Resolution Remarks 

88. All cockpit flight 

control input 

forces (control 

wheel, control 

column, rudder 

pedal).18 19

Full range ..............

Control wheel ±70 

lbs. 

Control column ±85 

lbs. 

Rudder pedal ±165 

lbs. 

±5% .................. 1 0.2% of full range ........ For fly-by-wire flight control systems, 

where flight control surface position 

is a function of the control input device only, it is not necessary to 

record this parameter. For airplanes 

that have a flight control break away 

capability that allows either pilot to 

operate the control independently, 

record both control force inputs. The 

control force inputs may be sampled 

alternately once per 2 seconds to 

produce the sampling interval of 1. 

89. Yaw damper 

status.

Discrete (on/off) ..... ........................... 0.5 

90. Yaw damper 

command.

Full range .............. As installed ....... 0.5 1% of full range.

91. Standby rudder 

valve status.

Discrete ................. ........................... 0.5 

18For all 737 model airplanes: the seconds per sampling interval is 0.5 per control input; the remarks regarding the sampling rate do not apply; 

a single control wheel force transducer installed on the left cable control is acceptable provided the left and right control wheel positions also are 

recorded. 19For all 737 model airplanes manufactured on or before January 31, 2001, Range values are: Full Range; Control wheel ±15 lbs.; Control column ±40 lbs.; and Rudder pedal ±165 lbs. 


jlentini on PROD1PC65 with PROPOSAL2
52400 Federal Register / Vol. 71, No. 171 / Tuesday, September 5, 2006 / Proposed Rules 

PART 125—CERTIFICATION AND 

OPERATIONS: AIRPLANES HAVING A 

SEATING CAPACITY OF 20 OR MORE 

PASSENGERS OR A MAXIMUM 

PAYLOAD CAPACITY OF 6,000 

POUNDS OR MORE 

6. The authority citation for part 125 

continues to read as follows: 

Authority: 49 U.S.C. 106(g), 40113, 44701–

44702, 44705, 44710–44711, 44713, 44716–

44717, 44722. 

7. Amend § 125.3 by adding a new 

paragraph (d) to read as follows: 

§ 125.3 Deviation authority. 

* * * * * 

(d) No deviation authority from the 

flight data recorder requirements of this 

part will be granted. Any previously 

issued deviation from the flight data 

recorder requirements of this part is no 

longer valid. 

8. Amend § 125.226 by removing the 

word ‘‘and’’ after paragraph (a)(87); by 

removing the period after paragraph 

(a)(88) and adding a semicolon in its 

place; by adding new paragraphs (a)(89), 

(90), and (91), (b)(4), (d)(3), (e)(3), and 

(m); and by revising paragraph (f) to 

read as follows: 

§ 125.226 Digital flight data recorders. 

(a) * * * 

(89) Yaw damper status; 

(90) Yaw damper command; and 

(91) Standby rudder valve status. 

(b) * * * 

(4) In addition to the requirements of 

paragraphs (b)(1) through (b)(3) of this 

section, all Boeing 737 model airplanes 

also must comply with the requirements 

of paragraph (m) of this section. 

(c) * * * 

(4) In addition to the requirements of 

paragraphs (c)(1) through (c)(3) of this 

section, all Boeing 737 model airplanes 

must comply with the requirements of 

paragraph (m) of this section, as 

applicable. 

(d) * * * 

(3) In addition to the requirements of 

paragraphs (d)(1) and (d)(2) of this 

section, all Boeing 737 model airplanes 

also must comply with the requirements 

of paragraph (m) of this section, as 

applicable. 

(e) * * * 

(3) In addition to the requirements of 

paragraphs (e)(1) and (e)(2) of this 

section, all Boeing 737 model airplanes, 

also must comply with the requirements 

of paragraph (m) of this section, as 

applicable. 

(f) For all turbine-engine-powered 

transport category airplanes 

manufactured after August 19, 2002—

(1) The parameters listed in 

paragraphs (a)(1) through (a)(88) of this 

section must be recorded within the 

ranges, accuracies, resolutions and 

recording intervals specified in 

appendix E to this part. 

(2) In addition to the requirements of 

paragraph (f)(1) of this section, all 

Boeing 737 model airplanes must also 

comply with the requirements of 

paragraph (m) of this section. 

* * * * * 

(m) In addition to all other applicable 

requirements of this section, all Boeing 

737 model airplanes must record the 

parameters listed in paragraph (a)(1) 

through (a)(22) and (a)(88) through 

(a)(91) of this section within the ranges, 

accuracies, resolutions, and recording 

intervals specified in Appendix E to this 

part. The approved recorder and all 

equipment necessary to record the 

parameters required by this paragraph 

must be installed no later than the 

installation of the redesigned rudder 

system required by one or more 

Airworthiness Directives issued under 

part 39 of this chapter. The singlesource recording provisions of 

paragraphs (b)(1)(ii), (c)(1), and (d)(1) of 

this section may be used for airplanes 

otherwise subject to those paragraphs. 

9. Amend Appendix E to part 125 by 

revising item 88, and adding items 89 

through 91 to read as follows: 

Appendix E to Part 125—Airplane 

Flight Recorder Specifications—

Continued 

* * * * * 

Parameter Range Accuracy 

(sensor input) 

Seconds per 

sampling 

interval 

Resolution Remarks 

88. All cockpit flight 

control input 

forces (control 

wheel, control 

column, rudder 

pedal).18 19

Full range ..............

Control wheel ±70 

lbs. 

Control column ±85 

lbs. 

Rudder pedal ±65 

lbs. 

±5% .................. 1 0.2% of full range ........ For fly-by-wire flight control systems, 

where flight control surface position 

is a function of the displacement of 

the control input device only, it is not 

necessary to record this parameter. 

For airplanes that have a flight control break away capability that allows 

either pilot to operate the control 

independently, record both control 

force inputs. The control force inputs 

may be sampled alternately once per 

2 seconds to produce the sampling 

interval of 1. 

89. Yaw damper 

status.

Discrete (on/off) ..... ........................... 0.5 

90. Yaw damper 

command.

Full range .............. As installed ....... 0.5 1% of full range. 

91. Standby rudder 

valve status.

Discrete ................. ........................... 0.5 

18For all 737 model airplanes: the seconds per sampling interval is 0.5 per control input; the remarks regarding the sampling rate do not apply; 

a single control wheel force transducer installed on the left cable control is acceptable provided the left and right control wheel positions also are 

recorded. 19For all 737 model airplanes manufactured on or before January 31, 2001, Range values are: Full Range; Control wheel ±15 lbs.; Control column ±40 lbs.; and Rudder pedal ±165 lbs. 


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* * * * * 

Issued in Washington, DC, on August 25, 

2006. 

John J. Hickey, 

Director, Aircraft Certification Service. 

[FR Doc. 06–7406 Filed 9–1–06 8:45 am] 

BILLING CODE 4910–13–P 


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