AD/CESSNA 208/24 - Alternate Static Air Source Selector Valve Placard

The central concept is the alternate static air source selector valve, a component that allows the pilot to select an alternate source of static air for instruments when the primary source is blocked. On the Cessna 208, this valve has part number 2013142‑18, which superseded earlier versions (‑9, ‑13, and ‑17). The defect is that the part number identification placard, a simple label affixed to the valve body, was placed in a position that covers the valve’s air intake port. This obstruction is not obvious during normal pre‑flight checks and only becomes apparent when the alternate static source is selected in flight, at which point instrument errors may already be dangerous.

Another key concept is instrument flight rules (IFR) operations. IFR flight depends entirely on accurate instrument readings, especially airspeed, altitude, and vertical speed. An obstructed alternate static source could cause these instruments to fail simultaneously, a scenario that is catastrophic in low visibility or cloud. Therefore the AD treats IFR‑equipped aeroplanes differently, imposing tighter initial compliance times (ten days or before further flight). The placard prohibition on IFR operation is a direct operational restriction that prevents the aircraft from being used in instrument meteorological conditions until the valve is inspected and cleared.

Time‑in‑service (TIS) is the measuring stick for compliance deadlines. It means accumulated flight hours, not calendar time except where the alternative “four months” is given. This allows operators who fly infrequently to plan maintenance windows, but it also means a high‑utilisation operator (e.g., a cargo carrier flying many hours per month) must inspect sooner. The use of TIS is typical for ADs, but it imposes a heavier compliance cost on high‑utilisation commercial machines.

Exemptions are provided through prior compliance with AD/CESSNA 208/22. That earlier AD addressed the same defect for a narrower population, presumably for valves shipped earlier. Operators who have already performed the required rework and remain compliant are not covered by AD/CESSNA 208/24. This creates an incentive to ensure continued compliance with 208/22 to avoid additional inspection duties, but also adds a record‑keeping burden to prove that status.

The AD also introduces the concept of a temporary placard as a compliance method. Rather than requiring immediate inspection for IFR aircraft, operators can choose to placard the aircraft as non‑IFR and prohibit use of the alternate static source. This is a pragmatic concession that allows continued visual flight rules (VFR) operations while scheduling the inspection at a more convenient time. However, the placard must later be removed after the inspection, adding a second maintenance action.

Directly affected are the owners and operators of Cessna 208 and 208B aeroplanes that were delivered new from the manufacturer between 1 January 1993 and 31 March 2008, unless they have already complied with AD/CESSNA 208/22 and remain compliant. Also affected are any aeroplanes that had a replacement part number 2013142‑18 alternate static air source selector valve installed after 1 January 1993, regardless of the aircraft’s original delivery date. This second category could capture much older airframes that happened to have the valve replaced with the affected part, increasing the population beyond the initial delivery window. Because CASA admits it cannot determine which aircraft have the problem valve without inspecting them all, the AD casts a wide net.

The Australian register of Cessna 208 series aircraft is modest, but the AD applies to every one that falls within the criteria. Commercial operators - such as freight carriers, charter companies, and aerial survey firms - are most affected because they typically fly IFR and have high utilisation. For them, the ten‑day compliance option for IFR aircraft may force an unscheduled grounding, causing revenue loss or disruption to contracts. The alternative placard option allows continued VFR operation, but if the aircraft is used primarily for IFR charter, that option is commercially useless. The cost of inspection labour, plus any necessary placard removal and logbook entry, must be absorbed.

Less obvious is the impact on parts suppliers and maintenance organisations. Maintenance providers must obtain the relevant Cessna service bulletin, perform the inspection in accordance with its procedures, and document compliance. They may also need to refuse to install a replacement valve that has not been inspected, which could create friction with operators who bring in an unbranded or used valve. Parts distributors holding stock of P/N 2013142‑18 must ensure that any future sale includes only inspected valves, potentially requiring them to inspect or quarantine existing inventory.

Spare‑parts owners are indirectly affected. The AD does not mandate inspection of spares in storage, but when such a valve is eventually installed, it must have been inspected. That means a private owner with a spare valve bought years ago may find it is now non‑compliant unless it is inspected before installation. The AD does not provide a mechanism for inspecting spares in advance, so the cost falls at the time of installation.

The broader class of indirectly affected parties includes insurers, who may condition coverage on AD compliance, and buyers and sellers of affected aircraft, who will need to verify AD status in any pre‑purchase inspection. Non‑compliance with an AD is a material defect in an aircraft sale, likely reducing the sale price.

The primary duty is to inspect the alternate static air source selector valve within the prescribed timeframes. For non‑IFR aeroplanes, this must be done within 100 hours TIS or four months, whichever occurs first. For IFR‑equipped aeroplanes, the operator has a choice between two compliance paths, but each imposes a duty: either inspect within ten days (path 2a) or install a placard before further flight (path 2b). Under path 2b, a second duty arises: within 100 hours TIS or four months, the valve must be inspected and the placards removed before further flight. That removal is itself a duty, not optional.

If at any inspection the placard is found to be obstructing the port, the duty is to remove and discard the placard, and then verify the port is open and unobstructed before further flight. This is a “before further flight” action, meaning the aircraft is grounded until compliance.

Additionally, from ten days after the effective date, anyone installing a replacement alternate static air source selector valve has a duty to use only a P/N 2013142‑18 valve that has been inspected and found free of obstruction. This duty applies to all affected aeroplanes and to any person performing installation - owner, operator, or maintenance organisation.

The duties are strict and time‑limited; there are no extensions or alternatives. The AD does grant the operator the right to choose between inspection or placard for IFR aircraft, but that choice is constrained by the later inspection requirement. The operator also has the right to rely on prior compliance with AD/CESSNA 208/22 to escape the scope of this AD, provided that compliance is ongoing. This is a valuable right, as it avoids the new inspection altogether. However, proving that status may require documentary evidence that the earlier rework was done and that the aircraft has remained in compliance (e.g., no subsequent unapproved modifications to the alternate static system).

There is no right to compensation from CASA or Cessna for the cost of compliance. The AD is a regulatory mandate; the operator bears the cost. The only rights are procedural: to challenge the AD through administrative review or judicial review if there is an error in the directive or if the operator believes it is not applicable to its specific aircraft. Those avenues are not mentioned in the source text but are inherent under Australian administrative law.

The AD itself does not recite penalty provisions, but an airworthiness directive issued under the Civil Aviation Regulations (CARs) carries the force of law. Under the Civil Aviation Act 1988 and CAR 39, failure to comply with an AD is an offence. The typical enforcement tools available to CASA include infringement notices (fines), suspension or cancellation of the aircraft’s airworthiness certificate, and criminal prosecution for conduct that endangers the safety of the aircraft. For a first offence involving a simple inspection oversight, a fine in the range of several thousand dollars is plausible. For deliberate or repeated non‑compliance, prosecution under the Act could yield much larger penalties or imprisonment if the defect leads to an incident.

CASA also has administrative powers. If an affected aircraft is found to be non‑compliant during a routine ramp check or maintenance audit, CASA can issue a direction to ground the aircraft until compliance is achieved. The cost of that grounding - loss of revenue, diversion of aircraft - is an indirect penalty. CASA may also impose conditions on the operator’s certificate of approval or maintenance organisation’s approval.

The AD references the equivalent FAA AD 2008‑26‑10, indicating that CASA has harmonised with the US directive. For Australian aircraft that operate internationally, non‑compliance with this AD could also lead to enforcement by foreign civil aviation authorities. The Australian AD is likely accepted by other states under the Convention on International Civil Aviation, so a foreign state could ground the aircraft for non‑compliance.

Enforcement risk is highest for commercial operators who are routinely scrutinised. Private owners may have lower detection risk, but the consequences of an instrument failure in flight are catastrophic, so the incentive to comply is strong even absent enforcement. The AD does not provide for self‑disclosure or amnesty; the duties are absolute. However, CASA sometimes issues exemption or extension letters in response to hardship, but this AD does not mention that possibility.

The penalty regime for AD non‑compliance is well established in Australian aviation law. What this AD does not do is impose any penalty on the manufacturer Cessna for shipping defective valves. The regulatory burden falls entirely on aircraft owners, who are the victims of the defect. This is a classic example of cost externalisation by a manufacturer, with the regulator and the private owner bearing the cost of correction.

This AD is made under the Civil Aviation Regulations 1988, specifically CARs 37 to 39 which empower CASA to issue airworthiness directives. It adopts the substance of FAA AD 2008‑26‑10, reflecting the bilateral airworthiness agreement between Australia and the United States. That means Australian operators must comply with a directive that mirrors US requirements, and CASA expects the Australian industry to align with FAA findings. There is no conflict; the two directives are consistent.

The AD interacts with prior AD/CESSNA 208/22. Operators who have complied with that earlier directive and remain in compliance are exempt from this one. This creates a conditional interaction: the prior AD is effectively a safe harbour. However, if the prior compliance lapses (e.g., if a later modification re‑introduces the defective valve), the aircraft falls back under the scope of this AD. Operators must maintain records proving ongoing compliance with 208/22.

The AD also interacts with the Cessna service bulletins it references: Cessna Single Engine Service Bulletin SB08‑34‑02 Revision 1, Cessna Caravan Service Bulletin CAB08‑04 Revision 1, Cessna Single Engine Service Bulletin SEB08‑5, and Cessna Multi‑engine Service Bulletin MEB08‑6. These bulletins become mandatory through the AD. If a bulletin is later revised or superseded, the operator must use the revision cited in the AD (dated 6 October or 13 October 2008) unless CASA permits deviation. This fixes the inspection procedure at a point in time, preventing the use of potentially improved future versions without a separate approval.

The AD interacts with the aircraft’s type certificate data sheet (TCDS) and maintenance manual. Any inspection or placard installation must be performed in a manner consistent with the approved data. If the service bulletin procedure conflicts with the TCDS, the operator may need CASA approval before deviating. The AD does not address that, but it is a latent interaction.

For ICAO compliance, an Australian AD is part of the state’s continued airworthiness obligations under Annex 6. An operator of an Australian aircraft flying internationally must demonstrate compliance with all applicable ADs. This AD therefore affects the aircraft’s ability to operate under a foreign state’s validation.

Finally, the AD may interact with commercial law concerning the sale of parts. The requirement that only inspected valves be used from ten days after the effective date affects the chain of supply. A parts seller who sells an uninspected P/N 2013142‑18 after that date may be deemed to be supplying a component that cannot lawfully be installed, exposing the seller to liability under the Competition and Consumer Act (for supplying a product that is not fit for purpose) or under aviation regulations.

The source text presents AD/CESSNA 208/24 as a new directive effective 16 January 2009. It does not list any prior amendments to this specific AD. However, the background section reveals that it was issued in response to reports coming to light after the FAA issued AD 2008‑10‑02 and CASA issued the earlier AD/CESSNA 208/22. That prior AD addressed the same defect for a smaller population (presumably valves shipped between certain dates). The FAA later received reports of 15 additional aeroplanes not previously affected, each with the same port obstruction. That prompted the FAA to issue AD 2008‑26‑10, which CASA has now mirrored in this AD.

Thus, AD/CESSNA 208/24 effectively expands the scope and tightens the compliance timeframes compared to the earlier 208/22. The later AD is not an amendment of 208/22, but a standalone directive covering a wider population. It does not supersede 208/22; aircraft that complied with 208/22 are exempt, but the two ADs coexist.

There is no indication in the source that AD/CESSNA 208/24 has been subsequently amended by CASA. The document appears to be the final version. However, it is common for ADs to be edited for typographical errors or to extend compliance times, but no such information is in the source. An operator would need to check the current Consolidated List of Airworthiness Directives on the CASA website to see whether later amendments exist.

The AD references “Revision 1” of the service bulletins, implying that earlier revisions existed (likely Revision 0, issued in early 2008). The use of Revision 1 indicates that the manufacturer refined the inspection procedure based on experience with the earlier AD. The AD does not describe those changes.

Because the AD itself is not an amendment to a previous regulation, but a new legislative instrument, its amendment history is limited to any post‑2009 CASA actions. The source text is the original issue. Given that the defect relates to a specific part number and a short manufacturing window (1993‑2008), it is likely that this AD is time‑limited; once the population of defective valves is purged from service, the AD may be cancelled or replaced. No such cancellation is in the source.

The source text contains no reference to any litigation concerning AD/CESSNA 208/24 or the underlying defect. No cases are cited. This is consistent with the nature of airworthiness directives: they are administrative safety mandates that typically do not generate litigation unless they are legally challenged as invalid or applied unfairly. There are no facts in the source suggesting a challenge. The AD relies on FAA findings and CASA’s own risk assessment, which courts would likely defer to on technical matters.

Potential litigation could arise in two arenas: (1) an owner or operator suing CASA for damages caused by the AD (e.g., lost revenue during grounding) if the AD were alleged to be unreasonable or based on incorrect facts, and (2) an owner suing Cessna or the parts distributor for selling a defective valve, claiming that the cost of compliance should be borne by the manufacturer. No such cases are recorded in this source.

The AD’s background notes that the FAA had received reports of 15 aeroplanes not previously affected by the earlier AD. That investigation may have involved manufacturer communications, but not litigation. The source also notes that CASA was informed that all P/N 2013142‑18 valves shipped from Cessna Parts Distribution between 1 January 1993 and 31 March 2008 may have the obstruction. That statement was presumably provided by Cessna, perhaps under regulatory compulsion, but again not litigation.

The absence of litigation history does not mean no disputes occurred. It is possible that some owners contested the AD through administrative appeal within CASA, but such proceedings are not public in the source. Given the narrow, technical nature of the defect and the small Australian fleet size, litigation is inherently unlikely. Legal challenge to an AD is expensive and rarely succeeds; the cost‑benefit for an individual owner points to compliance rather than court action.

The only litigation angle worth noting is the potential for a class action against Cessna if multiple owners experienced significant economic harm from grounding. In Australia, such a claim would need to show that Cessna breached a duty of care or the consumer guarantees. The AD itself is not a defendant; it is the trigger for the loss. No such action is documented in the source.

Several features of this AD are easy to overlook and could catch an operator out.

Delivery date versus replacement date. The AD applies to aircraft “initially delivered from the manufacturer between 1 January 1993 and 31 March 2008.” But it also applies to any aircraft that had a P/N 2013142‑18 installed as a replacement part anytime after 1 January 1993, regardless of the aircraft’s original delivery date. That means very old aircraft (e.g., a 1986 Cessna 208) are caught if the valve was changed out after 1993. Operators who assume their older aircraft is exempt because it was delivered before 1993 need to check maintenance records for the valve replacement history.

Spare parts trap. The AD says that when a replacement valve is needed, only a valve that “has been inspected and the port is found free from obstruction” can be installed. It does not explicitly require that the inspection be performed before installation, but the timing of the requirement (as of ten days after the effective date) means any valve installed after that date must already be inspected. If a maintenance shop holds uninspected spares in stock and does not inspect them before installation, they breach the AD at the moment of installation. The AD does not provide a grace period for already‑stocked parts.

The placard removal requirement in path 2b. Operators who choose the placard option for IFR aircraft may think the placard is a one‑off solution. But requirement 3 of the AD states that after the later inspection, the placards must be removed before further flight. If the operator neglects to remove them, the aircraft remains placarded as “IFR PROHIBITED” even though the valve is now clear. This restricts the aircraft’s operational capability unnecessarily and constitutes non‑compliance because the placard is not authorised after the inspection.

IFR equipment definition. The AD distinguishes between “aeroplanes that are not equipped for flight under instrument flight rules” and those that are “equipped.” It does not define “equipped” in detail. An aircraft that has IFR certified instruments but is currently used only for VFR still counts as equipped, and the stricter timelines apply. The operator cannot avoid the ten‑day option simply by deciding never to fly IFR; the equipment itself triggers the requirement.

Interaction with AD/CESSNA 208/22 exemption. To rely on the exemption, the aircraft must have done the modification/rework required in 208/22 and remain in compliance. “Remains in compliance” means that no subsequent work has undone that rework. For example, if the alternate static valve was replaced after complying with 208/22 with a new unmodified valve, the exemption lapses. Operators need to document the chain of compliance.

Service bulletin updates. The AD references specific bulletins and revisions. If the operator uses a later revision not listed, CASA might not accept it as compliance. The AD is frozen at those revisions unless CASA issues an amendment. Using a newer bulletin without approval is risky.

Compliance begins with correctly classifying the aircraft. The operator must first determine whether the aircraft is within the scope of the AD: confirm it is a Cessna 208 or 208B, check the initial delivery date, and examine maintenance records to see if any replacement valve P/N 2013142‑18 was installed after 1 January 1993. If the aircraft has complied with AD/CESSNA 208/22 and the records show the rework is still in effect, no further action is needed. If not, the AD applies fully.

Step 1: Obtain the applicable service bulletin. The AD lists four possible bulletins: Cessna Single Engine Service Bulletin SB08‑34‑02 Revision 1, Cessna Caravan Service Bulletin CAB08‑04 Revision 1, Cessna Single Engine Service Bulletin SEB08‑5, or Cessna Multi‑engine Service Bulletin MEB08‑6. The correct one depends on aircraft model and configuration. The operator or maintenance provider must secure the relevant bulletin and follow the inspection procedure.

Step 2: Determine IFR status. If the aircraft is not equipped for IFR, the requirement is a straightforward inspection of the alternate static air source selector valve to see whether the part number identification placard obstructs the port. This must be done within 100 hours TIS or four months from the effective date (16 January 2009). A logbook entry should record the inspection and results.

Step 3: For IFR‑equipped aircraft, choose a path. Option 2a: inspect the valve within ten days of the effective date, before any further IFR flight (though the AD does not prohibit VFR flight before the inspection). Option 2b: before further flight after the effective date, fabricate and install a placard with the specified wording (“IFR OPERATION IS PROHIBITED” and “USE OF THE ALTERNATE STATIC AIR SOURCE IS PROHIBITED”) in the pilot’s clear view using letters at least 1/8 inch. This placard grounds the aircraft for IFR but allows continued VFR operation. Thereafter, within 100 hours TIS or four months, perform the same valve inspection. Immediately after the inspection, remove the placard before further flight.

Step 4: Act on inspection findings. If during any required inspection the placard is found obstructing the port, remove the placard from the valve body, discard it, and confirm the port is open and unobstructed. This must be done before further flight.

Step 5: Manage replacement valves. From 26 January 2009 (ten days after the effective date), only install replacement valves P/N 2013142‑18 that have been inspected and confirmed to have an unobstructed port. The same inspection procedure applies. If a valve needs to be replaced before that date, the AD does not restrict it, but practical prudence suggests using only known good stock.

Record keeping. Each compliance step must be entered in the aircraft maintenance records: date, TIS at inspection, placard installation/removal (if applicable), and reference to the AD and service bulletin. This documentation is essential for proving compliance during audits and for future sales.

Cost and logistics. The inspection itself is likely a simple visual check requiring access to the valve. Labour cost is modest, but the operational impact for IFR operators choosing the placard route may be significant. Operators should weigh the cost of an unscheduled inspection against the revenue loss from being grounded for IFR for up to four months. In most cases, the ten‑day inspection is cheaper in forgone revenue than prolonged IFR restriction.