NTSB Aviation Investigation Report AIR-24-06 - Boeing 737 Rudder Rollout Actuator Safety Concerns

Aviation Investigation Report

AIR-24-06

Mitigate Safety Concerns Involving

Boeing 737 Airplanes with Collins Aerospace

SVO-730 Rudder Rollout Guidance Actuators

Introduction

The National Transportation Safety Board (NTSB) is providing the following

information to urge The Boeing Company and the Federal Aviation Administration

(FAA) to take immediate action on the safety recommendation s in this report

concerning the potential for a jammed or restricted rudder control system on certain

Boeing 737 airplanes . We identified th ese issue s during our ongoing investigation of

the rudder pedal anomaly involving a Boeing 737-8, N47280, while landing at

Newark Liberty International Airport (EWR), Newark, New Jersey, on

February 6, 2024.

On the basis of the results of postincident testing conducted in July 2024 and

information from Boeing and Collins Aerospace, the NTSB is concerned that Boeing’s

mitigation to overcome a jammed or restricted rudder control system during landing

could also result in a large input to the rudder pedals and a sudden, large and

undesired rudder deflection sufficient to cause loss of control or departure from the

runway. A jammed or restricted rudder scenario could be come even more

concerning if a high -crosswind or an engine -out condition were simultaneously

occu rring with a jammed or restricted rudder, not only because the amount of rudder

available to respond to these conditions might be insufficient to maintain control of

the airplane if the jam is not cleared —but also because excessive rudder input may

result if the jam is cleared by responding with Boeing’s mitigation . As a result, the

NTSB is issuing two urgent safety recommendation s to The Boeing Company and two

urgent safety recommendations to the FAA.

Background and Analysis

On February 6, 2024, about 1555 eastern standard time, the flight crew of

United Airlines flight 1539, a Boeing 737 -8, N47280, experienced a rudder pedal September 26, 2024 Aviation Investigation Report AIR-24-06

Aviation Investigation Report

AIR-24-06

2 anomaly while landing at EWR.1 In a postincident statement, the captain reported

that, during the landing rollout, the rudder pedals were “stuck” in their neutral

position and did not move in response to the “normal” application of foot pressure to

maintain alignment with the runway centerline.2 The flight was operating under the

provisions of Title 14 Code of Federal Regulations Part 121 as a scheduled

international passenger flight from Lynden Pindling International Airport,

Nassau, Bahamas, to EWR.3

According to data derived from the flight data recorder, the flight crew applied

approximately 32 pounds of force to the rudder pedals before touchdown which

yielded no discernible effect on the rudder position or heading.4 The flight crew

attempted to clear the jammed rudder controls immediately after touchdown,

applying approximately 75 pounds of force to the rudder pedals when the airspeed

was about 120 knots, again with no effect on the rudder position or heading.

With the airplane’s airspeed continuing to decrease during rollout, the flight

crew applied approximately 42 pounds of force to the pedals, but the jam persisted.

The captain elected instead to use the nosewheel steering tiller as the airplane

slowed to a safe taxi speed. The captain stated that, after the airplane entered the

assigned taxiway, he asked the first officer to check the rudder pedals on his side of

the flight deck, and the first officer indicated that the same anomaly was occurring.

Data derived from the flight data recorder indicate that shortly after, with the

airplane traveling at a groundspeed of less than 20 knots, the flight crew applied

approximately 59 pounds of force on the rudder pedals, and the rudder pedals and

rudder surface b egan to operate normally. The airplane taxied to the gate without

further incident, and all airplane occupants (2 flight crewmembers, 4 cabin

1 According to the captain, during preflight duties for the first flight leg of the day (the incident

flight was the second flight leg), he noticed a previous maintenance note regarding the rudder pedals.

The captain recalled that the writeup stated, “rudder pedals stuck at neutral position on short final and

had to push hard.” The captain wr ote in a postincident statement that he thought that the writeup

“appeared to be resolved. During our first leg, we didn’t notice anything unusual with the rudder

pedals during the after -start checklist, taxi out (during the rudder check), takeoff or landi ng.”

2 According to Boeing, rudder pedal force ranges from 15 to 75 pounds (the latter at full pedal

travel), with about 45 pounds as the average pedal force during rudder use.

3 Visit ntsb.gov to find additional information in the public docket for this ongoing NTSB

investigation (case number DCA24LA094 ). Use the CAROL Query to search safety recommendations

and investigations.

4 Values presented for amounts of force applied to the rudder pedals are approximations

based on the data available.

Aviation Investigation Report

AIR-24-06

3 crewmembers, and 155 passengers) deplaned without any injuries or damage to the

airplane.

United Airlines received the incident airplane from Boeing on

February 20, 2023. The airplane was equipped with a Collins Aerospace SVO -730

rudder rollout guidance actuator, which was electrically disabled based on the

operator’s delivery requirements for the autoflight system.5 Although the actuator was

disabled, it remained mechanically connected to the upper portion of the airplane’s

aft rudder input torque tube by the actuator’s output crank arm and a pushrod, as

shown in figure 1.6

Figure 1 . Rudder control system with rudder rollout guidance actuator

(Source: Boeing. Image copyright Boeing. Reproduced with permission).

5 The Collins SVO -730 rudder rollout guidance actuator is i nstalled only on Boeing 737 NG and

737MAX airplanes equipped for category IIIB operations . (The incident 737 -8 was a MAX variant. )

United Airlines does not require category IIIB capability for its Boeing 737 fleet. According to FAA

Advisory Circular 120 -28D, category IIIB operations involve a precision instrument approach and

landing with no decision height and a runway visual range less than 700 ft but not less than 150 ft.

6 Pilot control of the Boeing 737 -8 rudder is transmitted in a closed -loop system from the

pilots’ rudder pedals in the cockpit, through a single cable system, an aft rudder quadrant, and a pedal

force transducer, to the aft rudder input torque tube in the vertical stabilizer. Rotation of the torque

tube provides the command inputs to the main and standby rudder power control units to move the

rudder surface.

Aviation Investigation Report

AIR-24-06

4 Postincident examination and testing of the incident SVO -730 rudder rollout

guidance actuator found that the torque needed to rotate the actuator’s output crank

arm was 2.8 inch-pounds at room temperature ; this torque value was within specified

design limits. After the actuator was subjected to cold temperatures in a chamber for

1 hour, the output crank arm could not be rotated at the previous torque value.

Increases in torque were incrementally applied. The torque needed for the output

crank arm to start r otating was 520 inch -pounds, which significantly exceeded the

specified design limits . Once the output crank arm started rotating, a torque of about

100 inch -pounds was required to sustain the rotation; this torque value also

exceeded the specified design limits. Disassembly of the actuator revealed evidence

of moisture within the unit , as shown in figure 2, which would account for the

resistance observed in excess of specified design limits.

Figure 2. Incident actuator bearing with area of moisture (Source: Collins Aerospace).

Note: The image in the figure is magnified and not an accurate representation of its size.

Afterward, three additional SVO -730 rudder rollout guidance actuators were

examined and tested in the same manner (cold soaking) as the incident actuator . One

actuator was an in -service unit that United Airlines removed from another Boeing 737

airplane in its fleet as part of a removal service bulletin that the airline requested from

Aviation Investigation Report

AIR-24-06

5 Boeing regarding the actuator as a result of this incident .7 The other two actuators

were provided by Collins from its service center.

The test results were compared with those from the incident actuator. Results

for o ne of the three actuators w ere similar to the incident actuator : The unit failed the

cold chamber test, and the torque to move its output crank arm was substantially

beyond the specified design limits when subjected to cold temperatures.8

Disassembly of this actuator found evidence of moisture and corrosion in the area

adjacent to the pressure test port pinhole .9 Also, ev idence of pooled moisture

(staining/discoloration) was found inside this actuator on the bottom and sidewall of

the actuator gearbox, which was the same area in which moisture was observed

inside the incident actuator.10 The test results suggested the possibility that the

pressure test port pinhole provided a path for moisture ingress.

During a postincident internal review , Collins determined that a sealed bearing

in the incident actuator’s clutch assembly was not assembled according to drawing

requirements during the actuator ’s production. Specifically, Collins found that a

clutch bearing on the upper gearbox assembly was inadvertently assembled with the

seal facing toward the clutch teeth instead of the seal facing away from the clutch

teeth . On August 12, 2024, Collins notified Boeing that 353 SVO -730 rudder rollout

guidance actuators it had delivered to Boeing were affected.11 Collins provided its

7 Nine of United Airlines’ Boeing 737 airplanes had initially been configured for another

operator with SVO -730 rudder rollout guidance actuators (including the airplanes with the incident

actuator and the actuator referenced in this sentence). As with the i ncident actuator, the other eight

actuators were electrically disabled (according to a service bulletin dated November 10, 2022) based

on United’s delivery requirements for the autoflight system. These eight actuators also remained

mechanically connected t o the upper portion of the aft rudder input torque tube by the output crank

arm and pushrod. A service bulletin, dated May 6, 2024, provided instructions that allowed United to

permanently remove the SVO ‑730 rudder rollout guidance actuators from its 737 airplanes.

8 This actuator was from Collins’ service center . A second actuator also failed the test, but the

results did not significantly exceed the specified design limits. A third actuator (which was previously

installed on a United Airlines Boeing 737 airplane) passed the test.

9 According to Collins , the pressure test port is used to test production actuators before

delivery. The pressure test port is on the upper gearbox , and the area with pooling is inside the lower

gearbox.

10 Of the two actuators tested that did not fail, one was an actuator that United Airlines had

removed from its fleet; during post -testing disassembly, it was observed that the bearing had been

assembled incorrectly but showed no evidence of moisture ingress. The other actuator that did not fail

was also subsequently disassembled; its bearing had been assembled correctly and did not show

evidence of moisture ingress.

11 Collins delivered this notice in a letter to Boeing with the subject “SVO -730 Clutch Bearing

Installation.”

Aviation Investigation Report

AIR-24-06

6 safety assessment to Boeing that indicated the possibility of a hazard related to these

353 actuator units .

In response to this information, Boeing issued Multi Operator

Message MOM -MOM -24-0442 -01B on August 23, 2024, to both domestic and

foreign operators. The message explained the issue of the clutch bearing’s

misassembly and stated that 353 affected actuator units were delivered to Boeing

starting in February 2017 .12 The message also stated that the incorrect manufacture of

the bearing made the actuator assembly “more susceptible to moisture ingress.”

Boeing stated in the message that it had determined the issue posed no immediate

threat to safety. However, the multi -operator message stated that, to reduce “any

unnecessary risk ” in the 737 fleet, Boeing would develop a plan to remove the

affected actuator units from the fleet and replace them with conforming units, which

Collins would provide. Boeing indicated that its plan and the associated timeline

would be shared when available with 737 operat ors.

The NTSB’s investigation of this incident is ongoing. However, preliminary

findings suggest that the rudder control system was stuck (as discovered during the

landing rollout) as a result of moisture that previously entered the actuator through

the pressure test port pinhole, migrated to the incorrectly assembled sealed bearing,

and froze during flight. This scenario would explain why the incident captain had

difficulty using the rudder pedals for directional control immediately after

touchdown.

According to information from United Airlines’ Boeing 737 flight manual

(section 2.90.38, Non -Normals/Flight Controls), Boeing’s mitigation for a jammed or

restricted flight control in the yaw axis in flight or during landing is to “overpower the

jammed or restricted [rudder control] system.”13 As previously stated, Collins

determined that 520 inch -pounds of torque was required to move the actuator’s

output crank arm due to the restriction that resulted after the actuator was subjected

to cold temperatures and the moisture (via cold soaking) had frozen.

Boeing subsequently calculated that the 520 inch -pounds measured during

the testing would correlate to about 87 pounds of force applied to the rudder pedals.

However, this amount of force applied during landing or rollout could, in clearing a

12 Collins moved its manufacturing facility from Melbourne, Florida, to Mexicali, Mexico, in

February 2017. The 353 actuator units that Collins and Boeing identified were all manufactured in the

Mexicali facility.

13 The United Airlines’ Boeing 737 flight manual also stated to “ use maximum force, including a

combined effort of both pilots, if needed. A maximum two -pilot effort on the controls will not cause a

cable or system failure.” This section implied that pilots should apply as much force as they would be

capable of exerting .

Aviation Investigation Report

AIR-24-06

7 jam or restriction, also result in a large input to the rudder pedals and a sudden,

large, and undesired rudder deflection that could unintentionally cause loss of

control or departure from a runway. Accordingly, the NTSB is concerned that

Boeing’s mitigat ion for a j ammed or restricted rudder control system —to apply

maximum force to overcome the jam or restriction as indicated in the Boeing 737

Quick Reference Handbook —might not be appropriate during a landing or rollout for

the same reason.

The NTSB notes that, because the flight crew’s substantial applications of force

to the rudder pedals during landing and immediately after touchdown were

insufficient to clear the restriction, a large, sudden, and undesired rudder input and

its likely cons equences did not occur during these critical phases of flight.14,15

During the investigation of this incident, the NTSB learned that , in general,

United Airlines was unaware that the rudder rollout guidance actuator was installed

on nine of its Boeing 737 airplanes, each of which had an autoflight system that had

been reconfigured from category IIIB to category IIIA capability .16 The NTSB is

therefore concerned that Boeing 737 flight crews might not be aware that (1) some

737 airplanes are equipped with a rudder rollout guidance actuator that remains

mechanically engaged even when electrically disconnected, and (2) some of these

actuators might become restricted in flight or during landing due to a manufacturing

defect that allows moisture to accumulate inside it and freeze. The NTSB is also

concerned that Boeing 737 flight crews might not be aware of the appropriate

response if th is condition were encountered in flight or during landing.

The NTSB is unaware of any simulator training for Boeing 737 flight crews in

which a large force input is needed to overcome a restricted rudder control system.

In response to a 1999 NTSB safety recommendation, the FAA stated that its

inspectors were required to determine whether operators of Boeing 737 airplanes

were providing initial a nd recurrent training on the “ jammed or restricted rudder

14 The output crank arm of the Collins SVO -730 rudder rollout guidance actuator includes

shear pins that are designed to break with substantially greater pedal force than the flight crew

applied in this incident if a jam or restriction occurs within the actuator, which would allow normal

operat ion of the rudder control system to resume.

15 In a postincident statement, the captain explained, “I did not want to push too hard on the

rudder pedals in case it released suddenly.”

16 The rudder rollout guidance actuator is not required for United Airlines’ category IIIA

operations. FAA Advisory Circular 120 -28D defines category IIIA as a precision instrument approach

and landing with a decision height lower than 100 ft or no decision height and a runway visual range

not less than 700 ft.

Aviation Investigation Report

AIR-24-06

8 procedures ” in the Boeing 737 operations manual .17 However, only general

procedures for jammed or restricted flight controls are provided in the Boeing 737

Airplane Flight Manual and Flight Crew Operating Manual , and the rudder rollout

guidance actuator is not mentioned as a potential source for a jam or restriction in the

rudder control system. Among these procedures, flight at a warmer altitude —if the

flight crew suspects that frozen water has caused a jam —is recommended only after

the crew is advised to first attempt applying “maximum force, including a combined

effort of bot h pilots” to “overpower the jammed or restricted system.”

Although the incident flight crew was able to respond successfully to the

restricted rudder control system without knowledge about the failure mode related to

the rudder rollout guidance actuator, other flight crews would benefit from advance

notification about the possibility of encountering a restricted rudder control system in

flight or during landing . The NTSB concludes that informing Boeing 737 flight crews

of (1) the potential for a restricted rudder control system in airplanes equipped with

Collins Aerospace SVO -730 rudder rollout guidance actuators with incorrectly

assembled bearings and (2) the appropriate mitigations if such a situation were to

occur in flight or during landing would help prevent undesired rudder input and its

likely consequences during these critical phases of flight.

As a result, the NTSB recommends that Boeing instruct operators of 737NG

and 737MAX airplanes with Collins Aerospace SVO -730 rudder rollout guidance

actuators with incorrectly assembled bearings to notify flight crews that the rudder

control system might b ecome jammed or restricted in flight or during landing due to

moisture that could accumulate and freeze in the actuators.

The NTSB also recommends that Boeing determine, for 737NG and 737MAX

airplanes with Collins Aerospace SVO -730 rudder rollout guidance actuators with

incorrectly assembled bearings, appropriate flight crew responses, besides applying

maximum rudder pedal force, if the condition described in Safety

17 On April 16, 1999, the NTSB issued Safety Recommendation A -99-25, which asked the FAA

to “require all 14 Code of Federal Regulations part 121 air carrier operators of the Boeing 737 to

provide their flight crews with initial and recurrent flight simulator training in the ‘uncommanded yaw

or roll’ and ‘jammed or restricted rudder’ procedures in Boeing’s 737 operations manual.” On

October 1, 2001, the FAA stated that it issued (in December 2000) Joint Flight Standards Information

Bulletin for Air Transportati on 00 -16A, which directed flight standards district offices, certificate

management offices, and principal operations inspectors to ensure that all Part 121 air carriers that

operate Boeing 737 airplanes provide their flight crews with initial and recurren t flight simulator

training in the uncommanded yaw or roll and jammed or restricted rudder procedures contained in

the Boeing 737 operations manual. On January 3, 2002, the NTSB classified this recommendation

Closed —Acceptable Action. According to United A irlines, no simulator training is done for a jammed

rudder (or other flight control), but the United Airlines manager of flight standards stated that

simulator training is conducted for upset recovery, some of which could fulfill the requirement for

uncomm anded yaw or roll training.

Aviation Investigation Report

AIR-24-06

9 Recommendation A-24-27 were encountered in flight or during landing and then

notify operators to disseminate this information to flight crews of these airplanes.

In an August 28, 2024, email to the NTSB, Boeing provided preliminary

information indicating that 25 US -registered airplanes have or had an affected

SVO -730 rudder rollout guidance actuator installed. Boeing also indicated that, of the

25 airplanes, 9 airplanes were part of United Airlines’ Boeing 737 fleet and that , as

stated previously, the rudder rollout guidance actuators installed on those airplanes

had already been removed . Boeing added that the remaining 16 US-registered

airplanes were leased to fore ign operators. On the basis of th at information, Boeing

stated that no US operators appeared to be currently affected by the recently

discovered safety issue s involving SVO -730 rudder rollout guidance actuators.

The NTSB recognizes that the information Boeing provided was preliminary,

and while Boeing identified 25 affected actuators delivered on Boeing 737 airplanes,

there remains uncertainty about how many affected actuators sent directly to

operators and installed after delivery are currently on airplanes . As a result, there

could be additional Boeing 737 airplanes beyond those 25 delivered by Boeing that

have incorrectly assembled bearings in their SVO -730 rudder rollout guidance

actuators, and it is essential that this possibility is clearly addressed. Further , the NTSB

is concerned that foreign operat ors have Boeing 737 airplanes equipped with the

affected actuators. In addition, t he NTSB is concerned about the amount of time that

it would take for Boeing 737 operators to remove all affected rudder rollout guidance

actuator s, for Collins to provide conforming units, and for the operators install them

(if the operator wants to maintain the ability to perform Category IIIB landings).

A restricted rudder control system resulting from frozen moisture in an

incorrectly assembled actuator bearing could increase a flight crew’s workload during

a critical phase of flight . For example, a f light crew would not likely diagnose the

non-normal condition involving jammed or restricted rudder pedals until attempting

to make a rudder pedal input while on approach or during the landing rollout and

realizing that the pedals are jammed or restricted . This situation could be come even

more critical if a high -crosswind or an engine -out condition were simultaneously

occu rring with the jammed or restricted rudder because the amount of rudder

available to respond to these conditions might be insufficient to maintain control of

the airplane if the jam is not cleared. Furthermore, the force required to clear the jam

Aviation Investigation Report

AIR-24-06

10 may result in a large, sudden, and undesired input to the rudder.18 Without the

appropriate pilot response, a loss of airplane control could result.

Boeing has indicated that 737 airplanes can be safely flown without the rudder

rollout guidance actuator installed . The NTSB r ecognizes that Boeing 737 operators

would be precluded from performing category IIIB approaches without the actuators.

The NTSB concludes that the removal of Collins Aerospace SVO -730 rudder rollout

guidance actuators with incorrectly assembled bearings from Boeing 737 airplanes

would eliminate a potential cause of a restricted rudder control system on those

airplanes.

Thus, the NTSB recommends that the FAA determine whether Collins

Aerospace SVO -730 rudder rollout guidance actuators with incorrectly assembled

bearings should be removed from Boeing 737NG and 737MAX airplanes and, if so,

direct US operators to remove the actuators until acceptable replacement actuators

become available for installation. The NTSB also recommends that the FAA, if they

determine the affected Collins Aerospace SVO -730 rudder rollout guidance actuators

should be removed, notify international re gulators that oversee operators of

Boeing 737 airplanes about the safety issues involving the SVO -730 rudder rollout

guidance actuator and encourage them to require the removal of actuators with

incorrectly assembled bearings from 737NG and 737MAX airplane s until an

acceptable replacement actuator becomes available for installation.

Conclusions

Findings

Informing Boeing 737 flight crews of (1) the potential for a restricted rudder

control system in airplanes equipped with Collins Aerospace SVO -730 rudder

rollout guidance actuators with incorrectly assembled bearing s and (2) the

appropriate mitigations if such a situation were to occur in flight or during landing

would help prevent undesired rudder input and its likely consequences during

these critical phases of flight .

18 Unrelated to this incident, the FAA issued Airworthiness Directive (AD) 2024 -03-04 after

receiv ing a report of a missing nut and washer and a migrated bolt in the aft rudder quadrant of a

Boeing 737 airplane. The AD, which became effective on February 28, 2024, stated that, if a l oss of

rudder control via the rudder pedals were to occur, “r udder surface position would then be based only

on the rudder trim and yaw damper systems. ” Further, the AD stated that, “with the limited rudder trim

authority, there would not be enough rudder control to counter an engine -out scenario during

takeoff/climb out or to counter a high crosswind (above 20 kts) during landing. This condition, if not

addressed, could result in the loss of continued safe flight and landing.”

Aviation Investigation Report

AIR-24-06

11 The removal of Collins Aerospace SVO -730 rudder rollout guidance actuator s with

incorrectly assembled bearing s from Boeing 737 airplanes would eliminate a

potential cause of a restricted rudder control system on those airplanes.

Recommendations

To The Boeing Company :

Instruct operators of Boeing 737 NG and 737MAX airplanes with Collins

Aerospace SVO -730 rudder rollout guidance actuator s with incorrectly

assembled bearings to notify flight crews that the rudder control system

might become jammed or restricted in flight or during landing due to

moisture that could accumulate and freeze in the actuator s.

(A-24-27) (Urgent)

For 737 NG and 737MAX airplanes with Collins Aerospace SVO -730

rudder rollout guidance actuator s with incorrectly assembled bearings,

determine appropriate flight crew response s, besides applying

maximum rudder pedal force, if the condition described in Safety

Recommendation A-24-27 were encountered in flight or during landing

and then notify operators to disseminate this information to flight crews

of these airplanes. (A-24-28) (Urgent)

To the Federal Aviation Administration :

Determine whether Collins Aerospace SVO -730 rudder rollout guidance

actuators with incorrectly assembled bearings should be removed from

Boeing 737 NG and 737MAX airplanes and, if so, direct US operators to

remove the actuators until acceptable replacement actuators become

available for installation . (A-24-29) (Urgent)

If you determine the Collins Aerospace SVO -730 rudder rollout

guidance actuators with incorrectly assembled bearings should be

removed, notify international regulators that oversee operators of

Boeing 737 airplanes about the safety issues involving the SVO -730

rudder rollout guidance actuator and encourage them to require the

removal of actuators with incorrectly assembled bearings from 737 NG

and 737MAX airplanes until an acceptable replacement actuator

becomes available for installation . (A-24-30) (Urgent)

Aviation Investigation Report

AIR-24-06

BY THE NATIONAL TRANSPORTATION SAFETY BOARD

JENNIFER HOMENDY MICHAEL GRAHAM

Chair Member

THOMAS CHAPMAN

Member ALVIN BROWN

Member

J. TODD INMAN

Member

Report Date: September 26 , 2024

Aviation Investigation Report

AIR-24-06

13 The NTSB is an independent federal agency charged by Congress with investigating every

civil aviation accident in the United States and significant events in the other modes of transportation —

railroad, transit, highway, marine, pipeline, and commercial space. We determine the probable causes

of the accidents and events we investigate and issue safety recommendations aimed at preventing

future occurrences. In addition, we conduct transportation safety research studies and offer information

and other assistance to family members and survivors for each accident or event we investigate. We also

serve as the appellate authority for enforcement a ctions involving aviation and mariner certificates

issued by the Federal Aviation Administration (FAA) and US Coast Guard, and we adjudicate appeals of

civil penalty actions taken by the FAA.

The NTSB does not assign fault or blame for an accident or incident; rather, as specified by

NTSB regulation, “accident/incident investigations are fact -finding proceedings with no formal issues

and no adverse parties … and are not conducted for the purpos e of determining the rights or liabilities

of any person” (Title 49 Code of Federal Regulations section 831.4). Assignment of fault or legal liability

is not relevant to the NTSB’s statutory mission to improve transportation safety by investigating

accidents and incidents and issuing safety recommendations. In addition, statutory language prohibits

the admission into evidence or use of any part of an NTSB report related to an accident in a civil action

for damages resulting from a matter mentioned in the report (Title 49 United States Code section

1154(b)).

Recent publications are available in their entirety on the NTSB website . Other information about

available publications also may be obtained from the website or by contacting —

National Transportation Safety Board

Records Management Division, CIO -40

490 L’Enfant Plaza, SW

Washington, DC 20594

(800) 877 -6799 or (202) 314 -6551