AD 99-06-15 SUPERSEDED

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 99-06-15 which was sent previously to all known U.S. owners and operators of Bell Helicopter Textron Canada (BHTC) Model 407 helicopters by individual letters. This AD requires installing a tail rotor pitch-limiting left-pedal stop, installing an airspeed limitation placard, marking a never-exceed velocity (Vne) placard on all airspeed indicators, and revising the Limitations section of the Rotorcraft Flight Manual (RFM). This amendment is prompted by three accidents involving in-flight tail rotor blade strikes against the tailboom. The actions specified by this AD are intended to prevent the tail rotor blades from striking the tailboom, which could result in separation of the aft section of the tailboom with the tail rotor gearbox and vertical fin, and subsequent loss of control of the helicopter.

Final rule; request for comments

99-06-15 BELL HELICOPTER TEXTRON CANADA: Amendment 39-11111. Docket No. 99-SW-16-AD.

Applicability: Model 407 helicopters, certificated in any category.

NOTE 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For helicopters that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (i) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required before further flight, unless accomplished previously.To prevent the tail rotor blades from striking the tailboom, which could result in separation of the aft section of the tailboom with the tail rotor gearbox and vertical fin, and subsequent loss of control of the helicopter, accomplish the following:

(a) Install a stop that limits the maximum distance that the left pedal can travel in accordance with Part I of the Accomplishment Instructions in Bell Helicopter Textron Canada Technical Bulletin 407-98-13, dated December 12, 1998 (TB).

(b) Adjust the rigging of the directional controls in accordance with Part II of the Accomplishment Instructions in the TB.

(c) Install the airspeed limitation placard shown in Figure 1 of this AD so that it completely covers and obscures the airspeed limitation placard, P/N 407-070-201-103. Ensure that the replacement placard is at least 2 1/16-inches tall and 3 9/16-inches long.

407 AIRSPEED LIMITATIONS -KNOTS- IAS

AD 99-06-15
OAT

PRESSURE ALTITUDE FT X1000
C
0
2
4
6
8
10
12
14
16
18
20
52
98
93
88
-
-
-
-
-
-
-
-
40
10
0
95
91
86
81
76
-
-
-
-
-
20
10
0
10
0
95
90
85
80
76
71
66
61
-
0
10
0
10
0
10
0
95
90
85
80
75
70
65
60
-20
10
0
10
0
10
0
10
0
95
90
85
80
75
70
65
-40
97
93
88
83
79
74
70
65
61
-
-

MAXIMUM AUTOROTATION VNE 100 KIAS

FIGURE 1

(d) Install a redline at a Vne of 100 KIAS on all airspeed indicators. Remove or obscure any previously installed lines or arcs above 100 KIAS. If the redline is installed on the instrument glass, also install a slippage mark on the glass and on the instrument case.

(e) Add the following statement to the Limitations section of the Rotorcraft Flight Manual (RFM): When operating at an airspeed of 60 to 100 KIAS, maintain yaw trim within one ball diameter of the centered position of the turn and bank (slip) indicator, and avoid sudden or large directional control inputs in flight.

(f) Mark the airspeed limitations placard in Figure 1-3 in the RFM to indicate that it has been superseded by this AD, and insert a copy of this AD into the RFM. Also, mark the airspeed indicator in Figure 1-5 of the RFM to indicate a Vne of 100 KIAS.

(g) This AD revises the limitations section of BHTC Model 407 RFM by replacing sheet 1 of Figure 1-3 in the RFM with Figure 1 of this AD, revising sheet 3 of Figure 1-5 of the RFM, and adding an operational limitation for allowable yaw trim and directional control input.

(h) Report any uncommanded right yaw, uncommanded movement of the pedals during flight, or tail rotor blade contact with the tailboom within 24 hours of the occurrence to the Manager, Rotorcraft Certification Office, telephone (817) 222-5170. Reporting requirements have been approved by the Office of Management and Budget and assigned OMB control number 2120-0056.

(i) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Rotorcraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Rotorcraft Certification Office.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Rotorcraft Certification Office.

(j) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the helicopter to a location where the requirements of this AD can be accomplished, provided they are for a one-time ferry flight without passengers, and that airspeed during the flight does not exceed 60 KIAS. For helicopters with a left-pedal stop installed in accordance with the TB, the airspeed must not exceed 100 KIAS for a one-time ferry flight without passengers.

(k) The modifications shall be done in accordance with Parts I and II of the Accomplishment Instructions in Bell Helicopter Textron Canada Technical Bulletin 407-98-13, dated December 12, 1998. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Bell Helicopter Textron Canada, 12,800 Rue de l'Avenir, Mirabel, Quebec JON1LO, telephone (800) 463-3036, fax (514) 433-0272. Copies may be inspected at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

NOTE 3: The subject of this AD is addressed in Transport Canada (Canada) AD CF-98-36R3, dated March 5, 1999.

(l) This amendment becomes effective on April 22, 1999, to all persons except those persons to whomit was made immediately effective by Priority Letter AD 99-06-15, issued March 9, 1999, which contained the requirements of this amendment.

On September 25, 1998, the FAA issued Priority Letter AD 98-20-41, applicable to BHTC Model 407 helicopters, which restricted the airspeed to 25 knots indicated airspeed less than the Vne airspeeds indicated on the airspeed limitation placard. The priority letter also required installing an airspeed limitation placard, marking a redline at a Vne of 115 knots and applying a red arc from 115 to 140 knots on all airspeed indicators, and revising the Limitations section of the RFM that requires pilots to maintain yaw trim within one ball width of the centered position of the turn and bank (slip) indicator. That action was prompted by two accidents involving in-flight tail rotor blade strikes against the tailboom on Model 407 helicopters. Persons aboard both helicopters reported hearing a loud "bang" immediately prior to experiencing a loss of directional control of the helicopter. Subsequent inspection of the helicopters revealed that the aft section of the tailboom, including the tail rotor, the tail rotor gearbox, and the vertical fin, had separated from the helicopters in-flight. In both cases, inspection of the retrieved tailbooms confirmed that the tailbooms had been struck at least three times by the rotating tail rotor blades. The specific cause of these two in-flight tail rotor blade strikes against the tailboom has not been determined; however, flight test data indicated that tail rotor blade strikes were more likely to occur at higher airspeeds and altitudes. The data indicated that the cause of the tail rotor strikes is excessive tail rotor blade flapping. The reason for the excessive tail rotor blade flapping is unknown, but it may be aggravated by left pedal input. Excessive tail rotor flapping, if not corrected, could result in the tail rotor blades striking the tailboom, separation of the aft section of the tailboom with the tail rotor gearbox and vertical fin, and subsequent loss of control of the helicopter. Transport Canada, which is the airworthiness authority for Canada, issued AD CF-98-36, dated September 25, 1998, to require that the airspeed be reduced to minimize the risk of a tailboom strike during flight. After the issuance of Priority Letter AD 98-20-41, BHTC issued Technical Bulletin No. 407-98-13, dated December 12, 1998 (TB), which recommended a reduction in Vne of only 15 KIAS with the installation of a left pedal stop to limit maximum tail rotor blade pitch.

Transport Canada then further notified the FAA that an unsafe condition may continue to exist on BHTC Model 407 helicopters. Transport Canada advised that installing the tail rotor pitch-limiting left-pedal stop in accordance with the TB and further reducing the Vne is required to minimize the risk of a tailboom strike during flight. Transport Canada classified the TB as mandatory, and issued AD CF-98-36R3, dated March 5, 1999, in order to assure the continued airworthiness of these helicopters in Canada. That actionwas prompted by a third accident involving an in-flight tail rotor blade strike against the tailboom on BHTC Model 407 helicopters. The pilot in this latest accident reported that the helicopter was in straight and level cruise flight at 110 KIAS in non-turbulent conditions when the helicopter experienced an uncommanded left pedal hardover. The pilot reported that this uncommanded full left pedal movement was followed by a loud "bang" and then a loss of directional control of the helicopter. Subsequent inspection of the helicopter revealed that the aft section of the tailboom, including the tail rotor, the tail rotor gearbox, and the vertical fin, had separated from the helicopter in-flight. This helicopter did not have the tail rotor pitch-limiting left-pedal stop installed.

Since the unsafe condition described is likely to exist or develop on other BHTC Model 407 helicopters of the same type design, the FAA issued Priority Letter AD 99-06-15 to supersede Priority Letter AD98-20-41. Priority Letter AD 99-06-15 requires, before further flight, installing a tail rotor pitch-limiting left-pedal stop and adjusting the rigging of the directional controls, installing a new airspeed limitation placard, marking a new Vne limit of 100 knots indicated airspeed on all airspeed indicators, and revising the RFM to reduce the airspeed limitation further and to maintain the previously revised yaw-operational limitations. This priority letter AD is intended to prevent the tail rotor blades from striking the tailboom, which could result in separation of the aft section of the tailboom with the tail rotor gearbox and vertical fin, and subsequent loss of control of the helicopter. The actions specified by the superseding priority letter AD are required to be accomplished in accordance with the TB described previously. The short compliance time involved is required because the previously described critical unsafe condition can adversely affect the structural integrity of the helicopter. Therefore, installing a tail rotor pitch-limiting left-pedal stop, installing a new airspeed limitation placard, marking a new Vne limit on all airspeed indicators, and revising the RFM are required prior to further flight, and this AD must be issued immediately.

Since it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual letters issued on March 9, 1999 to all known U.S. owners and operators of BHTC Model 407 helicopters. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to make it effective to all persons.

The FAA estimates that 200 helicopters of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per helicopter to accomplish the required actions, and the average labor rate is $60 per work hour. Required parts will cost approximately $245 per helicopter. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $73,000.

Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 99-SW-16-AD." The postcard will be date stamped and returned to the commenter.

The regulations adopted herein will not have substantial direct effects on the States, on the relationship between thenational government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.

39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive to read as follows:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Office of the Regional
Counsel, Southwest Region, Attention: Rules Docket No. 99-SW-16-AD, 2601 Meacham Blvd., Room 663, Fort Worth,
Texas 76137.
The applicable service information may be obtained from Bell Helicopter Textron Canada, 12,800 Rue de l'Avenir, Mirabel, Quebec JON1LO, telephone (800) 463-3036, fax (514) 433-0272. This information may be examined at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Jurgen Priester, Aerospace Engineer, FAA, Rotorcraft Directorate,
Rotorcraft Certification Office, ASW-170, 2601 Meacham Blvd., Fort Worth, Texas, 76137, telephone (817) 222-5159,
fax (817) 222-5783.