AD 75-26-07
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Viking Air Limited | DHC-6-1 | Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft |
| aircraft | Viking Air Limited | DHC-6-100 | Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft |
| aircraft | Viking Air Limited | DHC-6-200 | Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft |
| aircraft | Viking Air Limited | DHC-6-300 | Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft |
Unsafe Condition
Contact welding of the reverse current relay(s), Hartman part number A700AP or A700AAP, may cause electrical fire hazards.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect reverse current relays for overheat, pitting, corrosion, or surface damage; replace unserviceable relays before further flight. Install a placard prohibiting cross generator engine starting except in emergencies. Conduct bench tests for relays with over 2400 hours time in service. Comply with specific timeframes based on relay usage.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Compliance required within specified timeframes: 25 hours time in service for certain relays, 100 hours for bench tests, and 10 flight hours for placard installation. If inspections are not done, flight under FAR 21.197 is allowed to reach a maintenance base.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
De Havilland Model DHC-6 Series Twin Otter aircraft certificated in all categories, including models DHC-6-1, DHC-6-100, DHC-6-200, DHC-6-300.
AI-generated summary from the source AD text. Verify against the official source before acting.
Federal Register Abstract
Electrical Fire Hazards
Applicability Source Text
Show captured applicability text from the source AD
AD Final Rules - DRS_75-26-07.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 75-26-07 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft Subject: Electrical Fire Hazards Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 12/17/1975 Make: Viking Air Limited Model: DHC-6-1 | DHC-6-100 | DHC-6-200 | DHC-6-300 Product Type: Aircraft Product Subtype: Small Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 75-26-07 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-2455 AD NUMBER: 75-26-07 SUBJECT HEADING: Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft ACTION: SUMMARY: DATES: Effective December 17, 1975. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 75-26-07 De Havilland: Amendment 39-2455. Applies to all DeHavilland Model DHC-6 Series Twin Otter aircraft certificated in all categories. Compliance required as indicated to preclude the hazards of an electrical fire due to contact welding of the reverse current relay(s), Hartman part number A700AP or A700AAP. 1. For aircraft containing reverse current relays which have between 1000 to 2400 hours time in service since new or overhauled, or aircraft having reverse current relays which have less than 1000 hours time in service which have been used for cross generator engine starts, accomplish the following: (A) Within the next 25 hours time in service, after the effective date of this AD, unless already accomplished, (i) Remove the reverse current relays from the aircraft. (ii) Examine relay for indications of overheat. (iii) Inspect relay contact points under ten-power glass for signs of pitting, corrosion or other surface damage. If any of the above conditions in 1(A) (ii) or 1(A) (iii) are present, replace relay with a serviceable unit before further flight. 2. This applies to aircraft containing reverse current relays with more than 2400 hours' time in service since new or overhauled. (A) Unless already accomplished, inspect relays in accordance with Paragraph 1(A) of this AD (B) Unless accomplished, within the previous 2400 hours' time in service after the effective date of this AD, conduct bench tests of reverse current relays within the next 100 hours' time in service after the effective date of this AD, in accordance with DeHavilland of Canada LTD. PSM 1-6-2 Part 7 or PSM 1-63-2 Chapter 24-30-00. 3. Within the next 10 flight hours, install the following placard in full view of the pilot: "CROSS GENERATOR ENGINE STARTING IS PROHIBITED, EXCEPT IN AN EMERGENCY." 4. Following a flight for which an emergency cross generator engine start was made, within the next 25 hours' time in service, accomplish the inspection required by paragraph 1(A) of this AD. 5. If any inspection required by this AD is not accomplished within specified time above, airplane may be flown in accordance with FAR 21.197 to a base where inspections can be made. This amendment is effective December 17, 1975. FOOTER:
Document Text
Show stored source text (verify against official source)
AD Final Rules - DRS_75-26-07.html Copy URL Print/Save as PDF Document Versions Feedback Details AD Number: 75-26-07 Document Type: AD Final Rules Docket Number: Unknown Subject Heading: Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft Subject: Electrical Fire Hazards Status: Current Citation: This information is not available. Citation Publish Date: Effective Date: 12/17/1975 Make: Viking Air Limited Model: DHC-6-1 | DHC-6-100 | DHC-6-200 | DHC-6-300 Product Type: Aircraft Product Subtype: Small Airplane Affected AD: Superseded AD: Affected By: Superseded By: Service/Office: Office of Primary Responsibility: CFR Part Reference: Part 39 Comments: AIRWORTHINESS DIRECTIVES FINAL RULES: 75-26-07 CITATION: This information is not available. PAGE NUMBER: DOCKET NUMBER: Unknown AMENDMENT: 39-2455 AD NUMBER: 75-26-07 SUBJECT HEADING: Airworthiness Directives; de Havilland Model DHC-6 Series Twin Otter Aircraft ACTION: SUMMARY: DATES: Effective December 17, 1975. ADDRESSES: FOR FURTHER INFORMATION CONTACT: SUPPLEMENTARY INFORMATION: REGULATORY TEXT: 75-26-07 De Havilland: Amendment 39-2455. Applies to all DeHavilland Model DHC-6 Series Twin Otter aircraft certificated in all categories. Compliance required as indicated to preclude the hazards of an electrical fire due to contact welding of the reverse current relay(s), Hartman part number A700AP or A700AAP. 1. For aircraft containing reverse current relays which have between 1000 to 2400 hours time in service since new or overhauled, or aircraft having reverse current relays which have less than 1000 hours time in service which have been used for cross generator engine starts, accomplish the following: (A) Within the next 25 hours time in service, after the effective date of this AD, unless already accomplished, (i) Remove the reverse current relays from the aircraft. (ii) Examine relay for indications of overheat. (iii) Inspect relay contact points under ten-power glass for signs of pitting, corrosion or other surface damage. If any of the above conditions in 1(A) (ii) or 1(A) (iii) are present, replace relay with a serviceable unit before further flight. 2. This applies to aircraft containing reverse current relays with more than 2400 hours' time in service since new or overhauled. (A) Unless already accomplished, inspect relays in accordance with Paragraph 1(A) of this AD (B) Unless accomplished, within the previous 2400 hours' time in service after the effective date of this AD, conduct bench tests of reverse current relays within the next 100 hours' time in service after the effective date of this AD, in accordance with DeHavilland of Canada LTD. PSM 1-6-2 Part 7 or PSM 1-63-2 Chapter 24-30-00. 3. Within the next 10 flight hours, install the following placard in full view of the pilot: "CROSS GENERATOR ENGINE STARTING IS PROHIBITED, EXCEPT IN AN EMERGENCY." 4. Following a flight for which an emergency cross generator engine start was made, within the next 25 hours' time in service, accomplish the inspection required by paragraph 1(A) of this AD. 5. If any inspection required by this AD is not accomplished within specified time above, airplane may be flown in accordance with FAR 21.197 to a base where inspections can be made. This amendment is effective December 17, 1975. FOOTER:
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
This site is not affiliated with or endorsed by the FAA. Always verify with official sources.
Related Airworthiness Directives
2023-10-02
final ruleAirworthiness Directives; Transport and Commuter Category Airplanes
Unsafe Condition: Radio altimeter anomalies that are undetected by the automation or pilot, particularly close to the ground (e.g., landing flare), could lead to loss of continued safe flight and landing. Additional...
2022-11-12
final ruleAirworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier, Inc. and de Havilland, Inc.) Airplanes
Unsafe Condition: binding of the rod end bearing connecting the lower fuel control unit (FCU) push rod assembly to the FCU power lever, which can occur after a period of non-utilization of the aeroplane, and may lea...
2022-11-09
final ruleAirworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier Inc. and de Havilland, Inc.) Airplanes
Unsafe Condition: Cracks and corrosion damage to the aileron internal structure, which could lead to progressive looseness of the aileron at the hinge support rib push-pull rod attachment, flutter condition, and deg...
2022-10-07 Recurring
final ruleAirworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier, Inc. and de Havilland, Inc.) Airplanes
Unsafe Condition: Damage to the flight control system of DHC-6 aeroplanes was found during inspection. The damage has been attributed to ground gusts. The damage included cracks in the base of the lower control colu...