Transport Transports 

Canada Canada

 TP 7245E

 

AIRWORTHINESS DIRECTIVE

The following airworthiness directive (AD) may be applicable to an aircraft which our records indicate is registered in your name. ADs are issued pursuant to Canadian 

Aviation Regulation (CAR) 593. Pursuant to CAR 605.84 and the further details of CAR Standard 625, Appendix H, the continuing airworthiness of a Canadian registered aircraft is contingent upon compliance with all applicable ADs. Failure to comply with the requirements of an AD may invalidate the flight authorization of the aircraft. Alternative means of compliance shall be applied for in accordance with CAR 605.84 and the above-referenced Standard. 

This AD has been issued by the Continuing Airworthiness Division (AARDG), Aircraft Certification Branch, Transport Canada, Ottawa, telephone 613 952-4357.

Pursuant to CAR 202.51 the registered owner of a Canadian aircraft shall, within seven days, notify the Minister in writing of any change of his or her name or address. 

To request a change of address, contact the Civil Aviation Communications Centre (AARC) at Place de Ville, Ottawa, Ontario K1A 0N8, or 1-800-305-2059, or www.tc.gc.ca/civilaviation/communications/centre/ address.asp 

24-0022 (01-2005)

1/3 No.

CF-2007-20R2

Issue Date 

6 February 2009 

Number: CF-2007-20R2 

Subject: Failure of Main Landing Gear Retract Actuator 

Effective: 9 March 2009 

Revision: Supersedes Airworthiness Directive CF-2007-20R1 issued on 11 October 2007.

Applicability: Bombardier Inc. DHC-8 aircraft, Models 400, 401 and 402, serial numbers 4001, 4003, 4004, 

4006, 4008 through 4208. 

Compliance: When indicated, unless already accomplished. 

Background: Two cases of main landing gear collapse had been reported. Main landing gear collapse may 

result in unsafe landing of the aircraft. 

Revision 1 of this directive amended the time compliance in paragraph C.2 (3 months in addition 

to 500 hours air time), to add new paragraph C.3 to cater for retract actuator which has 

accumulated less than 4,000 landings or 2 years since new and to add new paragraphs B.2 and 

C.4 to require that the respective inspections be repetitively performed until terminating action 

becomes available. 

Revision 2 of this directive amends the detailed visual inspection requirement in paragraph C.3 to 

include the main landinggear retract actuator, part number 46550-11, and to add new paragraph F 

to mandate the incorporation of main landing gear retract actuator part number, 46550-13 as the 

terminating action and to add new paragraph G for the maintenance requirement. 

Corrective 

Actions: 

A. General Visual Inspection of the Main Landing Gear System: - Applicable to DHC-8 

Aircraft, Models 400, 401, and 402, Serial Numbers 4001, 4003, 4004, 4006, 4008 

through 4182 

For all aircraft, before further flight after the effective date of the original issue of this directive 

(12 September 2007), perform a general visual inspection of the left hand and right hand 

main landing gear system in accordance with Bombardier DHC-8 Series 400 Maintenance 

Requirements Manual (PSM 1-84-7), Part 1 (Maintenance Review Board Report), tasks 

Z700-03E (left hand) and Z700-04E (right hand). Rectify any discrepancy found prior to 

further flight. 

B. General Visual Inspection of the Main Landing Gear Retract Actuator Jam Nut: 

- Applicable to DHC-8 Aircraft, Models 400, 401, and 402, Serial Numbers 4001, 4003, 

4004, 4006, 4008 through 4208 

1. For all aircraft, before further flight after the effective date of the original issue of this 

directive (12 September 2007), perform a general visual inspection of the left hand and 

right hand main landing gear retract actuator jam nut to ensure the wire lock is in place 

and the nut is secured. If the wire lock is not in place or the jam nut is not secured, prior 

to further flight, accomplish Bombardier Repair Drawing (RD) 8/4-32-059, Issue 5, or 

later approved revision. 

2. Subsequently, at intervals not to exceed 250 landings, or one month from the previous 

inspection, whichever occurs first, repeat the general visual inspection of the left hand 

and right hand main landing gear retract actuator jam nut to ensure the wire lock is in 

place and the nut is secured. If the wire lock is not in place or the jam nut is not 

secured, prior to further flight, re-torque the jam nut and safety lockwire in accordance 

with Bombardier RD 8/4-32-059, Issue 5, or later approved revision. 
No.

 N° CF-2007-20R2 2/3 

C. Detailed Visual Inspection of the Main Landing Gear Retract Actuator: - Applicable to 

DHC-8 Aircraft, Models 400, 401, and 402, Serial Numbers 4001, 4003, 4004, 4006, 4008 

through 4182 

1. For aircraft main landing gear retract actuator (p/n 46550-7 or 46550-9) that have 

accumulated 8,000 or more landings, or more than 4 years in service since new, at the 

effective date of the original issue of this directive (12 September 2007), perform a 

detailed visual inspection and any required action(s) in accordance with Bombardier RD 

8/4-32-059, Issue 5, or later approved revision, before further flight after the effective 

date of the original issue of this directive (12 September 2007). 

2. For aircraft main landing gear retract actuator (p/n 46550-7 or 46550-9) that have 

accumulated between 4,000 to 7,999 landings, or between 2 to 4 years in service since 

new, at the effective date of the original issue of this directive (12 September 2007), 

perform a detailed visual inspection and any required action(s) in accordance with 

Bombardier RD 8/4-32-059, Issue 5 or later approved revision within 500 hours air time, 

or 3 months, whichever occurs first, after the effective date of the original issue of this 

directive (12 September 2007). 

3. For aircraft main landing gear retract actuator (p/n 46550-7 or 46550-9) that have 

accumulated less than 4,000 landings, or less than 2 years in service since new, at the 

effective date of the original issue of this directive (12 September 2007), and for aircraft 

main landing gear retract actuator (p/n 46550-11), prior to retract actuator reaching 

4,500 landings or 27 months in service since new, whichever occurs first, perform a 

detailed visual inspection and any required action(s) in accordance with Bombardier RD 

8/4-32-059, Issue 5 or later approved revision. 

4. Subsequently, at intervals not to exceed 2,000 landings, or one calendar year from the 

previous inspection, whichever occurs first, repeat the detailed visual inspection and 

any required action(s) in accordance with Bombardier RD 8/4-32-059, Issue 5 or later 

approved revision. 

Note: 1) Respective inspections performed in accordance with earlier issues of 

Bombardier RD 8/4-32-059 satisfy the requirements of this directive, 

paragraphs B and C. 

2) If the visual inspection of the piston (p/n 46570-1/-3) threads and thread relief 

area for evidence of corrosion in accordance with Bombardier RD 8/4-32-059 

Rev. NC was performed without using borescope or 10X magnification mirror, 

a one time deferral for up to 500 landings is permissible to complete the 

inspection of the piston using borescope or 10X magnification mirror.

D. Reporting Requirement: - Applicable to DHC-8 Aircraft, Models 400, 401, and 402, 

Serial Numbers 4001, 4003, 4004, 4006, 4008 through 4208 

Within 7 days after each inspection, report any discrepancies found during any of the above 

inspections to Bombardier Technical Help Desk. 

E. Ferry Flight: - Applicable to DHC-8 Aircraft, Models 400, 401, and 402, Serial Numbers 

4001, 4003, 4004, 4006, 4008 through 4208 

 To permit the ferry of an aircraft to a location where the inspection requirements of this 

directive can be accomplished, adhere to the following procedures and limitations: 

Flight Crew Limitations and Procedures: 

1. Ferry Flight with gear extended and pinned. 

2. Landing to be conducted at a minimum descent rate. 

3. Minimize braking on landing. 

4. Flight to be conducted per Aircraft Operating Manual (AOM) Section 4.8. 

5. Essential crew only on board. 

6. Flight in known or forecast icing condition is prohibited. 

Maintenance Procedures: 

1. Inspect the left hand and right hand main landing gear retract actuator jam nut to ensure 

the wire lock is in place and the nut is secure. 

2. Perform the general visual inspections as defined in accordance with Bombardier All 

Operators Message No. 236 Rev A or later revisions. 

3. If items 1 and 2 results are satisfactory, insert main landing gear ground lock pins and 

lockwire in place. 

4. Ensure the nose landing gear ground lock is engaged. 
No.

 N° CF-2007-20R2 3/3 

F. Modification of Main Landing Gear Retract Actuator: - Applicable to DHC-8 Aircraft, 

Models 400, 401, and 402, Serial Numbers 4001, 4003, 4004, 4006, 4008 through 4182 

1. For aircraft main landing gear retract actuators (p/n 46550-7 or 46550-9 or 46550-11) 

that have accumulated 7,500 or more landings or more than 4 years in service since new 

at the effective date of this directive: 

Within 500 landings or 3 months from the effective date of this directive, whichever 

occurs first, incorporate Bombardier Modsum 4-901603 to replace the affected retract 

actuator with a new design retract actuator, p/n 46550-13. Bombardier Service Bulletin 

(SB) 84-32-55, Revision A, dated 10 March 2008, or later revisions approved by the 

Chief, Continuing Airworthiness, Transport Canada provides approved instructions for 

incorporating Modsum 4-901603. 

2. For aircraft main landing gear retract actuators (p/n 46550-7 or 46550-9 or 46550-11) 

that have accumulated less than 7,500 landings, and 4 years or less in service since new 

at the effective date of this directive: 

Prior to reaching 8,000 landings or 51 months in service since new, whichever occurs 

first, incorporate Bombardier Modsum 4-901603 to replace the affected retract actuator 

with a new design retract actuator, p/n 46550-13. Bombardier SB 84-32-55, Revision A, 

dated 10 March 2008, or later revisions approved by the Chief, Continuing Airworthiness, 

Transport Canada provides approved instructions for incorporating Modsum 4-901603. 

3. Incorporation of Modsum 4-901603 provides terminating action to the detailed visual 

inspection requirements of paragraph C of this directive.

Note: 1) Incorporation of Modsum 4-901603 in accordance with Revision NC of 

Bombardier SB 84-32-55, dated 14 January 2008, meets the requirements of 

paragraph F of this directive. 

2) Incorporation of Modsum 4-901610 to replace the affected retract actuator 

with a new design retract actuator, p/n 46550-15, also satisfies the 

requirements of paragraph F of this directive. 

G. Maintenance Requirement: - Applicable to DHC-8 Aircraft, Models 400, 401, and 402, 

Serial Numbers 4001, 4003, 4004, 4006, 4008 through 4208 

1. Within 30 days after the effective date of this directive, amend the Transport Canada 

approved maintenance schedule by incorporating task numbers 320100-211 (Detailed 

Inspection of the Retraction Actuator Rod End Jam Nut, Gland Nut and Actuator 

Attachment Pins for Condition, Security of Installation and Corrosion) and 320100-212 

(Restoration of the Retraction Actuator for Complete Overhaul) as introduced by the 

Temporary Revision (TR) MRB–35 of the DHC-8 Series 400 Maintenance Requirements 

Manual, PSM 1-84-7. 

2. Incorporation of maintenance task numbers 320100-211 and 320100-212 provides 

terminating action to the general visual inspection requirements of paragraph B of this 

directive. 

Authorization: For Minister of Transport, Infrastructure and Communities 

D. Ferguson 

A/Chief, Continuing Airworthiness 

Contact: Mr. Anthony Wan, Continuing Airworthiness, Ottawa, telephone 613-952-4410, facsimile 613-996-

9178 or e-mail wana@tc.gc.ca or any Transport Canada Centre.