AD/DHC-8/102 Amdt 1 - Pitot Static System Contamination

Several distinct concepts underpin this directive, each traceable to the source text.

Pitot static system contamination is the central hazard. The background describes incidents of airspeed mismatch believed to be caused by contamination within pitot lines or blockage within pitot static probes. Blockage of a probe’s pitot drain can allow moisture to enter and freeze at altitude, blocking the pitot line. The consequence is erroneous airspeed indications to the flight crew, which can lead to loss of control.

Repetitive maintenance is the initial interim response. The original issue required periodic cleaning of drain holes (every 70 hours TIS) and pitot lines (every 600 hours TIS). This imposes ongoing cost and operational disruption, as aircraft must be taken out of service at those intervals.

Terminating action is the concept that a modification ends the need for the repetitive task. The amendment mandates modifications that improve water drainage and freeze protection, rendering the cleaning cycles unnecessary. Requirement 3 terminates Requirement 2; Requirements 4, 5 and 6 terminate Requirement 1. This shifts the compliance burden from ongoing labour to a capital investment in redesign.

Applicability by serial number is a key concept. The directive applies to models DHC-8-400, DHC-8-401 and DHC-8-402, serial numbers 4003 through 4154. However, several sub-ranges are defined for different requirements. Note 1 excludes aircraft S/N 4147 to 4154 from Requirement 1 cleaning because they already have new design probes installed during production under Bombardier ModSum 4-113525. Requirement 6 applies only to S/N 4115 through 4145 for a one-time inspection. These distinctions mean operators must carefully identify which serial numbers they operate and cross reference each requirement.

Approved data is another concept. The directive does not contain step-by-step instructions; instead it references Bombardier Service Bulletins and Aircraft Maintenance Manual (AMM) tasks. For example, cleaning must be done per AMM PSM 1-84-2 Task 20-00-40-170-801. Modifications must follow Bombardier Service Bulletins SB 84-34-59 Revision D (or later approved revisions) for tubing modification, SB 84-34-90 Revision B for left probe replacement, SB 84-34-91 Revision B for right probe replacement, SB 84-34-93 Revision A for standby probe replacement, and SB 84-34-99 Initial Issue for the one-time inspection. The directive also allows that earlier revisions of these bulletins, if incorporated before the effective date of this amendment, satisfy the requirement. This provides flexibility but also creates a compliance history issue: operators must check which revision was used.

Compliance times expressed in hours time in service (TIS) is important. Hours TIS accumulate only when the aircraft is actually flown. This contrasts with calendar based intervals and can cause practical challenges for aircraft with low utilisation: the 6000 hour window might take years to reach, but the interim cleaning intervals still apply until modifications are done.

Delegation of authority is implicit: the directive is signed by James Coyne as Delegate of CASA. This indicates the legal basis under the Civil Aviation Act. The directive references Transport Canada AD CF-2005-15R1, showing international coordination.

The primary duty bearers are the registered operators of Bombardier DHC-8-400, DHC-8-401 and DHC-8-402 aeroplanes with serial numbers 4003 through 4154. These operators must ensure compliance with all requirements that apply to their specific serial numbers. The compliance burden falls directly on them: they must schedule maintenance, procure parts, contract modification services, record compliance, and bear the cost of down time and labour.

Maintenance organisations perform the actual work. They must be appropriately authorised and hold the relevant AMM and Service Bulletins. They need to be alert to the serial number exclusions and the differences between revisions of bulletins. The directive does not mandate who may carry out the work, but under normal regulatory arrangements only approved maintenance organisations can perform such airworthiness directive compliance.

Bombardier is affected indirectly. The directive mandates use of Bombardier’s own modifications and service bulletins. Bombardier must continue to support these products, supply kits, and ensure that later revisions of the bulletins are approved by the Chief, Continuing Airworthiness, Transport Canada. Bombardier faces potential liability if the modifications prove inadequate, but the directive does not address that.

Transport Canada and CASA are the regulators. The directive was originally issued by Transport Canada (CF-2005-15R1) and this amendment is adopted by CASA for Australian registered aircraft. The directive shows that the two authorities coordinate, with CASA referencing the Transport Canada approval of later revisions.

Aircraft owners who lease aircraft to operators are also affected indirectly because the obligation to comply usually falls on the operator, but the lease agreement will allocate responsibility. The directive itself does not distinguish between owner and operator.

The Australian travelling public and freight customers are affected in that the directive aims to maintain safety in the Q400 fleet. However, the direct cost impact may eventually be passed through to ticket prices or lease rates. Because the modifications are relatively expensive and require downtime, some operators may choose to retire or sell affected aircraft rather than comply, which could reduce capacity on certain routes.

Particularly affected are operators with the older serial numbers 4003, 4004, 4006, 4008 through 4114, which must undergo both the tubing modification (Requirement 3) and the probe replacements (Requirements 4 and 5) plus the interim cleaning cycles. Operators with later serial numbers 4115 through 4145 face an additional one-time inspection (Requirement 6) before the standby probe replacement. Operators with serial numbers 4147 to 4154 are exempt from the initial cleaning requirement (Requirement 1) but still must do the standby probe replacement (Requirement 5) and, if within the range, inspection Requirement 6. This creates a cascading set of obligations that require careful maintenance planning.

The directive imposes several distinct duties on the operator.

Duty to clean the pitot static probe drain hole (Requirement 1). This must be done initially within 30 days after 4 August 2005 (the original effective date) and thereafter at intervals not exceeding 70 hours TIS. The cleaning must follow AMM Task 20-00-40-170-801, specifically Procedure 2 sub paragraphs (1) to (3). After cleaning, the operator must examine the drain hole for blockage per Procedure 1 of that task. If blocked, the cleaning and examination must be repeated on the affected probe. This duty continues until Requirements 4, 5 and 6 are all accomplished. Note 1 excludes aircraft with new design probes (S/N 4147 4154) from this duty.

Duty to clean pitot lines (Requirement 2) applies only to aircraft serial numbers 4003, 4004, 4006, 4008 through 4114 that have not been modified per Requirement 3. The cleaning must be performed per AMM Task 34-11-00-170-801 initially within 30 days after 4 August 2005 and then at intervals not exceeding 600 hours TIS. This duty terminates once the aircraft is modified under Requirement 3.

Duty to modify the pitot static system tubing (Requirement 3) applies to the same serial number range as Requirement 2 (4003, 4004, 4006, 4008 through 4114). The operator must incorporate Bombardier ModSum 4-113488 using SB 84-34-59 Revision D (or later approved revision) within 6000 hours TIS after the effective date of this amendment (31 July 2008). Note 2 allows that incorporation of earlier revisions A, B or C before the effective date also satisfies this requirement.

Duty to replace pitot probes (Requirements 4 and 5). Requirement 4 applies to serial numbers 4003 through 4146 and requires replacement of left and right primary pitot probes with new design probes. The left probe replacement follows SB 84-34-90 Revision B (or later approved) per ModSum 4-113530. The right probe uses SB 84-34-91 Revision B per ModSum 4-113531. Note 3 and Note 4 allow earlier revisions if done before the effective date. Requirement 5 applies to all serial numbers 4003 through 4154 and requires replacement of the standby pitot probe per SB 84-34-93 Revision A (or later) per ModSum 4-113526. Note 5 allows the initial issue of SB 84-34-93 if incorporated before the effective date.

Duty to inspect standby pitot static system tube assemblies (Requirement 6) applies only to serial numbers 4115 through 4145. This one time inspection must be carried out before Requirement 5 (the standby probe replacement) and must follow the Accomplishment Instructions of the Initial Issue of SB 84-34-99 dated 4 April 2007 (or later approved revision). Any necessary rectification must be performed.

Rights retained by the operator. The operator may use later revisions of the service bulletins as approved by the Chief, Continuing Airworthiness, Transport Canada. The operator may also rely on modifications already incorporated before the effective date using earlier bulletin revisions, provided they were completed before 31 July 2008. The operator may choose to accomplish the modifications early, thereby terminating the repetitive cleaning duties sooner and reducing ongoing labour cost. The directive does not prohibit alternative means of compliance, but they would require separate CASA approval under normal rules.

No duty to report compliance is explicitly stated in this directive, but under general regulations compliance must be recorded in the aircraft logbook and the maintenance organisation must issue a release.

The source text of this airworthiness directive does not specify penalties for non compliance. However, under the regulatory framework, an airworthiness directive is a mandatory requirement made under the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations 1998 (CASR). Failure to comply with an AD is an offence that can attract civil penalties, including fines, and can lead to the grounding of the aircraft. The Australian Civil Aviation Safety Authority has enforcement powers that include issuing infringement notices, seeking court orders, suspending or cancelling certificates of registration or airworthiness, and prosecuting operators.

In practical terms, the most immediate consequence of non compliance is that the aircraft is not airworthy. The operator cannot lawfully operate the aircraft until the AD is complied with. If an operator attempts to operate while the AD is overdue, the flight operations are illegal and the pilot in command is also potentially liable. Insurance coverage may be voided.

The directive itself provides no grace period beyond the stated compliance times. The compliance times are based on hours time in service, not calendar date. Once the threshold is reached, the requirement falls due immediately. If an aircraft accumulates hours quickly, the window to plan the modification may be short. Operators who fail to schedule the modification within the 6000 hour TIS period face enforcement risk.

There is also a potential for cascading enforcement: if the interim cleaning requirements (Requirements 1 and 2) are not done at the prescribed intervals, the aircraft is non compliant even before the modification deadlines arrive. The directive provides no alternative means of compliance or extension mechanism within its text; any extensions would need to be sought from CASA on a case by case basis.

Given that this amendment became effective on 31 July 2008, operators have been subject to these requirements for many years. Practically, most operators of this fleet should have already complied. However, if an aircraft has been stored or has low utilisation, the 6000 hour TIS deadline might not yet have been reached, meaning the obligations could still be outstanding. CASA could prosecute for non compliance discovered during a ramp inspection or maintenance audit.

The source does not list any enforcement actions or penalties imposed. That is typical for an AD; penalties are set out in the parent legislation, not in the directive itself.

This airworthiness directive exists within a hierarchy of regulations. It is made under the Civil Aviation Act 1988 and the Civil Aviation Safety Regulations 1998, specifically Part 39 which governs airworthiness directives. Compliance with an AD is mandatory for the holder of an airworthiness certificate for the aircraft. It also interacts with the regulations on maintenance (Part 42 and Part 145) which require that maintenance be performed by approved organisations and recorded properly.

The directive explicitly cross references Transport Canada AD CF-2005-15R1. Australia and Canada have bilateral agreements for airworthiness that allow each authority to adopt the other’s ADs. This means that for aircraft imported from Canada, the Canadian AD applies, and CASA adopts it for the Australian register. The operator must use the Canadian approved service bulletins, with later revisions approved by Transport Canada. However, the directive also mentions the Chief, Continuing Airworthiness, Transport Canada as the approver, not CASA. This could cause confusion if an operator seeks to use a different method: CASA would need to approve any deviation.

The directive also references Bombardier Aircraft Maintenance Manual (AMM) tasks. These AMMs are themselves approved by Transport Canada under the type certificate data sheet. Operators must use the applicable revision of the AMM current at the time of maintenance. The directive does not specify which revision of the AMM is acceptable; presumably the latest approved revision is required.

The service bulletins referenced (SB 84-34-59, 84-34-90, 84-34-91, 84-34-93, 84-34-99) are Bombardier commercial documents. They are not legislation, but the directive incorporates them by reference. If Bombardier revises those bulletins after the effective date, the operator may use the later revisions provided they are approved by Transport Canada. This creates a dynamic compliance environment.

The directive also implicitly interacts with the regulations on continuing airworthiness records. Compliance must be recorded in the aircraft logbook and the maintenance organisation must issue a certificate of release to service under CASR Part 42 or Part 145. Failure to record compliance would be a separate regulatory breach.

Because this directive mandates modifications, it may also interact with the requirement to update the aircraft’s weight and balance data if the modifications change weight, and with any supplemental type certificates that cover the same probes.

For operators who also operate under a foreign air operator certificate, there may be additional scrutiny from the foreign regulator. The directive does not address cross border issues.

Notably, the directive does not expressly state that it supersedes any other directive. It amends AD/DHC-8/102, so the original issue remains partially in force. Operators must ensure they are on the latest amendment.

The source text provides the amendment history only implicitly. The directive is titled AD/DHC-8/102 Amdt 1, indicating that it is the first amendment to the original AD/DHC-8/102. The original issue became effective on 4 August 2005. The background states: “The Original issue of this Directive was an interim action to avoid the potential for erroneous airspeed information, by mandating the periodic cleaning of the pitot static probe drain hole and the pitot lines.” That original issue therefore consisted of Requirements 1 and 2 only, with no modifications required.

This Amendment 1, effective 31 July 2008, added Requirements 3 through 6, which mandate the modifications and the one-time inspection. The amendment also introduced the terminating action language: modifications end the repetitive cleaning cycles. The effective date of this amendment is 31 July 2008, as stated clearly: “This Amendment becomes effective on 31 July 2008.”

The notes in the amendment allow that modifications incorporated before the effective date using earlier revisions of the service bulletins also satisfy the requirement. This grandfathering provision is important: operators who had already performed the modifications based on earlier bulletins (e.g., Revision A of SB 84-34-59) do not need to redo them. However, compliance with the original repetitive cleaning requirements was still mandatory until the modifications were accomplished, even if done before the amendment.

There is no indication of any further amendments after this one. The directive as supplied appears to be the latest version. However, given the age of the document (2008) and the fleet age, it is likely that CASA has issued further amendments or superseding directives, but the source does not provide them. For purposes of this deep dive, we treat this as the current version as provided.

The amendment history is sparse, but it does illustrate a typical regulator escalation: an interim maintenance action followed by a permanent engineering modification once it was developed and certified. This pattern is common in airworthiness regulation.

The directive also notes that the original issue was based on Transport Canada AD CF-2005-15R1, and this amendment presumably updates that reference, though only the original Transport Canada AD number is cited.

The source text contains no mention of any litigation relating to this directive. The absence of litigation is not surprising for an airworthiness directive of this nature. Airworthiness directives are rarely challenged in court because they are justified by safety findings and operators typically comply rather than face grounding. Where litigation does occur, it usually concerns disputes over the scope of the directive, the adequacy of the approved data, or the reasonableness of compliance times, but no such case is cited.

The directive covers a known safety issue with a well documented hazard (airspeed mismatch leading to potential loss of control). The modifications were developed by the original equipment manufacturer (Bombardier) and mandated by the regulator. There is little incentive for an operator to litigate, as the cost and risk of non compliance outweigh the cost of compliance.

There is no indication of product liability litigation against Bombardier for the alleged pitot static system defects. The background says incidents were “reported to Transport Canada”, but does not quantify how many incidents or whether they caused accidents or injuries. If there were accidents, litigation would likely have involved Bombardier, but none is referenced here.

Similarly, there is no mention of any legal challenge to CASA’s decision to adopt the Transport Canada directive. The delegation of authority is clear.

Because this directive is from 2008, any litigation would have occurred years ago. A search of Australian court databases reveals no reported judgments citing this specific AD. That is consistent with the minimal litigation history for most ADs.

Thus, the litigation history for this instrument is effectively none. The deep dive should state this factually, without implying that the regulation is above scrutiny. It simply has not been the subject of reported legal proceedings.

Several features of this directive are easily overlooked and can lead to inadvertent non compliance.

Serial number nuance with Requirement 1. Note 1 states that aircraft S/N 4147 to 4154 have new design probes installed during production (Bombardier ModSum 4-113525), so cleaning of the pitot static probe drain hole is not required on those aircraft. But those aircraft still require the standby probe replacement (Requirement 5) and, if within the range, the one time inspection Requirement 6. An operator who applies Requirement 1 to those serial numbers would waste effort, but more importantly, if an operator fails to note this exclusion and skips Requirement 1, that would be fine because the aircraft is exempt. The real gotcha is that Requirement 1 is not a one time task; it is repetitive. Operators with aircraft in the affected range must continue cleaning every 70 hours TIS until all of Requirements 4, 5 and 6 are accomplished. That could be a long time if the modification is not done promptly. The cumulative labour cost can be significant.

Requirement 6 must be done before Requirement 5. The compliance section states explicitly: “For Requirement 6 - Prior to accomplishing Requirement 5.” This ordering is easy to miss if an operator plans to do all modifications at once. The standby probe replacement (Requirement 5) cannot be completed until the one time inspection of the standby pitot static system tube assemblies (Requirement 6) is finished and any necessary rectification is done. If the operator schedules the modifications in the wrong order, the standby probe replacement would be non compliant until the inspection is accomplished. This could cause a maintenance release issue.

Use of approved revisions. The directive allows operators to use later revisions of service bulletins approved by the Chief, Continuing Airworthiness, Transport Canada. But the directive does not define “later revisions” or how an operator can verify that Transport Canada has approved them. If Bombardier issues a Revision C to an SB after the directive effective date, the operator must confirm that Transport Canada has approved that revision. Using an unapproved revision could render the modification non compliant. The notes also allow earlier revisions if incorporated before the effective date. But if an operator accidentally uses an earlier revision after the effective date, the work does not satisfy the directive. There is a trap for operators who may have old copies of SBs in their maintenance libraries.

Compliance times in hours TIS, not calendar time. For a low utilisation aircraft, the 6000 hour TIS limit might not be reached for many years. However, the interim 70 hour and 600 hour cleaning intervals still apply. If an aircraft only flies 200 hours per year, the 70 hour drain hole cleaning would be required roughly three times per year, which is manageable. But if an operator does not track TIS accurately, they might exceed the interval. Also, the 6000 hour TIS clock started on 31 July 2008. Even for a low time aircraft, that is nearly 16 years ago as of 2024. Most aircraft would have far exceeded 6000 hours by now, so the modification deadlines are likely past. Any operator still flying these aircraft without the modifications is almost certainly non compliant. This is a trap for aircraft that have been in storage or have undergone a long term parking: the TIS clock does not run while parked, but the calendar date is irrelevant; TIS is the metric. The operator must calculate TIS accurately and ensure modifications were done before the threshold.

Note 6 references Transport Canada AD CF-2005-15R1. This is not just informational; it indicates the source directive. If Transport Canada issues further amendments to its AD, Australia may adopt them as separate amendments. An operator relying solely on this Australian directive may miss subsequent amendments that CASA has adopted but that are not yet reflected in the document provided. The gotcha is that the provided text might be outdated.

No allowance for alternative means of compliance. The directive does not mention the possibility of obtaining an alternative method of compliance (AMOC) from CASA. However, Part 39 regulations normally allow operators to request an AMOC. The absence of mention in the directive does not remove that right, but an operator who assumes an AMOC is available without approval is taking a risk.

Operators of affected DHC-8-400 series aircraft with serial numbers 4003 through 4154 must follow a structured process.

First, determine which serial numbers are in the operator’s fleet and map each aircraft to the applicable requirements. Create a matrix: for each aircraft, list whether it falls into the range for Requirements 1, 2, 3, 4, 5 and 6. Pay special attention to the sub ranges. For example, aircraft S/N 4115 to 4145 are subject to Requirement 6. Aircraft S/N 4003, 4004, 4006, 4008 through 4114 are subject to Requirements 2 and 3. Aircraft S/N 4003 through 4146 are subject to Requirement 4. All aircraft S/N 4003 through 4154 are subject to Requirement 5. Note that Requirement 1 does not apply to S/N 4147 to 4154.

Second, assess the current compliance status. Check maintenance records to determine whether any of the modifications (Requirements 3, 4, 5) have already been incorporated, and if so, which revision of the service bulletin was used and when. If the modification was done before 31 July 2008 using an earlier bulletin revision, it still counts. If done after that date, the required revision for that date applies (the newer Revision B or D as specified). Also check whether the one time inspection for Requirement 6 has been accomplished for aircraft S/N 4115 4145.

Third, calculate accumulated hours time in service for each aircraft as of 31 July 2008 and as of the current date. The compliance times for modifications are relative to the effective date of this amendment (31 July 2008). For aircraft that were already in service at that date, the 6000 hour TIS clock started then. For aircraft that entered service after that date, the clock starts at first flight? The directive does not address new production aircraft after the effective date, but since the applicability is by serial number, any aircraft in the range that were built after 2008 would still be subject to the same requirement. The operator must work out the TIS accumulation from the effective date or from delivery, using conservative interpretation.

Fourth, plan the modifications. Since the 6000 hour TIS limit is likely long since past, the modifications should already be complete. If not, they must be accomplished immediately. Obtain the correct revision of each service bulletin from Bombardier. For Requirement 3, use SB 84-34-59 Revision D (or later Transport Canada approved). For Requirement 4 left probe: SB 84-34-90 Revision B; right probe: SB 84-34-91 Revision B. For Requirement 5: SB 84-34-93 Revision A. For Requirement 6: SB 84-34-99 Initial Issue (or later approved). Ensure that the maintenance organisation has access to these documents.

Fifth, schedule the work with an approved maintenance organisation. Note that Requirement 6 must be done before Requirement 5, so plan accordingly. They can be done in the same maintenance visit if the inspection is performed first and then the standby probe is replaced. The other modifications (Requirements 3 and 4) can be done in any order and at any time within the 6000 hour window, but best practice is to do them together to minimise downtime.

Sixth, continue to perform the interim repetitive tasks (Requirements 1 and 2) until the modifications are completed. For Requirement 1, clean drain holes every 70 hours TIS. For Requirement 2 (if applicable), clean pitot lines every 600 hours TIS. Record these tasks in the aircraft logbook. Once the modifications are accomplished, the repetitive tasks are terminated and no further cleaning is required.

Seventh, document compliance. Each modification and each repetitive task must be recorded in the aircraft maintenance records with reference to the airworthiness directive, the service bulletin revision used, and the date and TIS at accomplishment. A certificate of release to service must be issued.

Eighth, consider the ongoing airworthiness management. Because the modifications are terminating actions, once completed, the aircraft no longer needs the repetitive cleaning. However, future maintenance must continue to comply with the AMM and any subsequent mandatory inspections for the new probes. The operator should update the airworthiness program to remove the repetitive cleaning tasks and add any new inspections required by the service bulletins.

If an operator finds that compliance cannot be met, for instance because spare parts are unavailable, they must contact CASA immediately to request an extension or alternative means of compliance. Do not rely on the directive itself for relief.

Finally, for aircraft that have been out of service for an extended period, recalculate TIS accurately. The 6000 hour TIS clock runs only when the aircraft flies. If the aircraft was stored before accumulating 6000 hours after 31 July 2008, the modification may still be pending. The operator should assess whether the modification is now due when returning the aircraft to service.