AD/PREMIER/4 - Stall Warning System Angle-of-Attack Transmitters

The directive revolves around the stall warning system and the angle‑of‑attack (AOA) transmitters. The stall warning system in the Hawker Beechcraft Model 390 provides audible and tactile cues (including stick pusher activation) to alert the pilot of an approaching stall. The system uses two AOA probes - one on the left hand (LH) side and one on the right hand (RH) side - that sense the angle at which air meets the wing. Those probes are electrically heated to prevent ice accretion, which could render them inoperative. The core problem identified by the FAA and adopted by CASA is the potential for an unannunciated loss of heating in those probes. That means the pilot has no cockpit indication that a probe has lost heating; the system remains electrically live, but the heating element fails silently. In icing conditions, an unheated probe could ice over, leading to inaccurate angle‑of‑attack readings, which in turn could produce an inadequate stall warning and loss of the stick pusher function. The stick pusher is a last‑resort mechanical device that physically pushes the control column forward to lower the nose and prevent a stall; its loss significantly reduces the safety margin during flight in certain conditions. The directive introduces a two‑phase approach. In the short term (immediately after the effective date and before the modification), it requires a physical check for residual heat after each flight. The concept of “residual heat” is key: even if the heating element fails during flight, the probe may retain some heat for a period after engine shutdown, so a post‑flight tactile check can indicate whether the heater had been working at some point during the previous flight. The check is performed by holding a hand near the heated area or moving the hand gradually from ambient temperature toward the heated area until warmth is felt - a deliberately cautious procedure to avoid burns. If no residual heat is detected, that suggests the heater did not operate during the flight, triggering a maintenance manual operational test before the next flight. The long‑term solution (within 250 hours or 12 months) is to modify or replace the AOA transmitters themselves. The modification involves uploading new software to the existing transmitters (part numbers SLZ8060‑3 or SLZ8060‑4) via a field software upload kit. Alternatively, the owner or operator may replace those transmitters with new part‑number SLZ8060‑5 transmitters, which presumably incorporate the updated software at manufacture. The directive also introduces a spare‑parts prohibition: after the effective date, any unmodified SLZ8060‑3 or SLZ8060‑4 transmitter may not be installed as a replacement spare on any Model 390 aeroplane. This prevents the reintroduction of unmodified units into the fleet via the supply chain. The AFM temporary change (Part No. 390‑590001‑0003CTC7) serves as the immediate instruction document for the post‑flight check procedure; it must be incorporated within 15 hours time‑in‑service or 30 days, whichever occurs first, and then removed once the modification or replacement is accomplished.

The directive applies directly to owners and operators of Hawker Beechcraft (Raytheon) Model 390 aeroplanes with serial numbers RB‑4 through RB‑204. That is a defined population of aircraft manufactured within a particular serial number range. If you operate an aircraft outside that serial number range, this directive does not apply to you. The affect extends to maintenance organisations, licensed aircraft maintenance engineers (LAMEs), and pilots who act as owner/operators. For the initial AFM incorporation and the post‑flight check, the directive expressly permits the check to be performed by “the owner/operator who holds at least a private pilot licence”. That is an unusual delegation: typically, post‑flight inspections of this nature would be carried out by a licensed aircraft maintenance engineer under a maintenance release. Here, CASA has authorised a pilot with a private licence to perform the tactile residual‑heat check, provided that after the check, an appropriate entry is made in the aircraft technical records certifying its completion. This lowers the barrier to compliance by removing the need to involve a maintenance organisation after every flight, but it places a record‑keeping obligation on the owner/operator. The owner/operator must also be the one to accomplish the AFM temporary change insertion (if not already done) within the first 15 hours or 30 days, though that task itself may be done by the owner/operator or a maintenance provider - the directive does not specify who must insert the AFM change, only that it must be incorporated. The more technical steps (the maintenance manual operational test of AOA probe heat, replacement of probes, software upload, or replacement of transmitters) require a person qualified under the relevant maintenance regulations to perform them, as they involve accessing the aircraft’s systems and potentially swapping components. The directive also affects spare‑parts suppliers and anyone who installs replacement AOA transmitters: as of the effective date, unmodified SLZ8060‑3 or SLZ8060‑4 transmitters cannot be installed as replacement spares on any aeroplane. That creates a compliance burden for parts inventory management: stock of those part numbers must be either upgraded (for example, through the software upload) or disposed of if they are not to be used again on affected aircraft. The owners of aeroplanes that are leased or operated under charter arrangements also need to coordinate compliance with the operator. Furthermore, the directive indirectly affects insurers and financiers: non‑compliance may void airworthiness and affect insurance coverage or asset value.

The directive imposes mandatory duties on the registered operator (or owner, if different) of each affected aircraft. The primary duties are chronological. Duty 1: Within 15 hours time‑in‑service or 30 days after 3 September 2008 (whichever occurs first), incorporate the AFM temporary change (P/N 390‑590001‑0003CTC7) into the Approved Aircraft Flight Manual. Duty 2: Following every flight, until the transmitter modification or replacement is completed, conduct a post‑flight check for residual heat in both LH and RH stall warning AOA probes, following the procedure in that AFM temporary change. The duty is ongoing and repetitive; failure to perform it after any single flight is a breach. Duty 3: If residual heat is not detected, then before further flight, arrange for a maintenance manual operational test of the heat of the AOA probes, using the procedures in the AFM temporary change and Service Bulletin 27‑3787. Duty 4: If that operational test reveals a failure, replace the failed probe(s) before further flight. Duty 5: Within 250 hours time‑in‑service or 12 months after 3 September 2008 (whichever occurs first), either upload new software (Kit No. 123‑3436) to both AOA transmitters, or replace any SLZ8060‑3 or SLZ8060‑4 transmitters with new SLZ8060‑5 transmitters. Duty 6: After that modification or replacement is accomplished, remove the AFM temporary change (P/N 390‑590001‑0003CTC7) from the AFM. Duty 7: As of 3 September 2008, do not install an AOA transmitter that is part number SLZ8060‑3 or SLZ8060‑4 that does not have the new upgraded software per the software upload option (i.e., that has not been modified) as a replacement spare on any aeroplane. This duty applies even if the aircraft is not the one being operated by the person subject to the other duties - it is a fleet‑wide spare‑parts prohibition. The directive confers a right: the owner/operator who holds at least a private pilot licence is expressly permitted to perform the post‑flight residual‑heat check and must make an appropriate entry in the aircraft technical records. That entry is not a maintenance release but a certification that the check was completed. This right to self‑perform the check reduces the need to involve a maintenance provider after every flight, but it also imposes a record‑keeping obligation. There is also a right to use later revisions of Service Bulletin 27‑3787 that have been approved by the FAA as an Alternate Method of Compliance (AMOC) to FAA AD 2008‑16‑02; such revisions are deemed acceptable for compliance with the equivalent requirements of this Australian directive. However, that right is conditional: the revision must be approved by the FAA as an AMOC, and it is only acceptable for the equivalent requirements - not for any extra requirements that the Australian directive may impose that are beyond the FAA AD.

The source text does not specify penalties. As an Airworthiness Directive issued by CASA under the Civil Aviation Act 1988 (Cth) and the Civil Aviation Regulations 1988 (CAR 1988), failure to comply is an offence under the Act. Under s 98 of the Civil Aviation Act, a person must not operate an aircraft that is not airworthy, and an airworthiness directive is a direct condition of the aircraft’s type certificate and continuing airworthiness. Operating an aircraft without complying with a mandatory directive is likely a breach of CAR 37 (as it then stood) or the current Civil Aviation Safety Regulations (CASR) Part 39, which governs airworthiness directives. The maximum penalties under the Civil Aviation Act for an individual can include fines of up to 1,000 penalty units (each penalty unit is currently A$313, so A$313,000 maximum) and/or imprisonment for up to two years for some offences. For bodies corporate, fines can be five times that amount. CASA also has enforcement powers including suspension or cancellation of the aircraft’s certificate of airworthiness, grounding the aircraft, issuing a direction to comply, or seeking a court injunction to prevent non‑compliant operation. The practical consequence of non‑compliance can be severe: if the aircraft is flown without the AFM change or without performing the post‑flight check, the aircraft may be deemed unairworthy, and the operator could face civil liability if an incident or accident occurs. The directive states a compliance timeline with some flexibility (15 hours or 30 days for the AFM change, 250 hours or 12 months for the modification). However, the “before further flight” deadlines for the operational test and probe replacement leave no room for delay: if residual heat is not detected, the aircraft cannot be flown again until the operational test is done; if the test fails, the probe must be replaced before the next flight. A breach of those immediate requirements could lead to immediate enforcement action. There is also the risk of re‑licence action: if a pilot or owner/operator fails to make the required entry in the technical records, that could be a false or misleading entry, attracting further penalties under the Act. The directive does not provide any grace period or exemption mechanism; it is mandatory on its effective date. The only flexibility is the ability to use later FAA‑approved revisions of the service bulletin, but that is a compliance method, not a waiver.

The directive expressly references the United States Federal Aviation Administration Airworthiness Directive 2008‑16‑02 (Amdt 39‑15620). The Australian AD is issued as a separate instrument but is underpinned by the same safety concern and technical solution. The note in the directive states that later revisions of Service Bulletin 27‑3787 approved by the FAA as an Alternate Method of Compliance to FAA AD 2008‑16‑02 are considered acceptable for compliance with the equivalent requirements of this Australian directive. This creates a mutual recognition mechanism: if the FAA later issues a revision to the service bulletin that it accepts as an alternative method, CASA will also accept that revision as satisfying the Australian requirements, without needing a separate Australian approval. However, the acceptance is limited to “the equivalent requirements” - if the Australian directive goes further than the FAA AD (for example, by imposing a different compliance time or an additional action), the FAA‑approved revision may not cover that extra element. The directive also operates within the broader legal framework of the Civil Aviation Act 1988 and Civil Aviation Regulations 1988 (and later the Civil Aviation Safety Regulations). Under CAR 37 (and CASR Part 39), the holder of an aircraft’s certificate of airworthiness must comply with all applicable airworthiness directives. A failure to comply renders the aircraft unairworthy, which prohibits operation. The directive also interacts with the Aircraft Flight Manual (AFM) approval system. The AFM is an approved document under the type certificate; a temporary change to the AFM is a lawful method of introducing mandatory procedures without amending the entire manual. The directive requires the temporary change to be removed after the modification is done, so the AFM returns to its original configuration (or is updated by a permanent revision). There is no apparent interaction with state or territory laws, but it may affect contractual obligations: an aircraft lease, charter agreement, or sale contract typically includes a warranty that the aircraft complies with all applicable ADs. Non‑compliance could trigger a breach of contract claim. Furthermore, the directive’s spare‑parts prohibition (no installation of unmodified SLZ8060‑3 or SLZ8060‑4 transmitters) interacts with supply chain regulations under the Airworthiness Directives themselves, the Airworthiness Standards (Part 23 and Part 25 of the CASR), and the maintenance regulations governing component lifecycle.

The source text does not record any amendment history. It appears to be the original issuance of AD/PREMIER/4, dated 1 August 2008 and effective 3 September 2008. There is no reference to earlier versions, amendments, or supersedure. However, it is standard practice for CASA to issue airworthiness directives in sequential numbering for each type. This directive is numbered “4” for the Premier series, indicating that there were at least three previous directives for the same aircraft type. But the source does not disclose what those were, whether they are related, or whether this directive supersedes or amends any previous directive. The directive includes a note: “FAA AD 2008‑16‑02 Amdt 39‑15620 refers.” That indicates that the FAA issued its own AD on the same subject before or around the same time. The Australian AD may have been harmonised with the FAA AD. There is no mention of any subsequent CASA amendments to AD/PREMIER/4. Later revisions of Service Bulletin 27‑3787 are stated to be acceptable if approved by the FAA as an AMOC, but those are revisions to the service bulletin, not amendments to the directive itself. In practice, the AD remains in force until it is superseded, amended, or withdrawn by a later CASA notice. The absence of amendment history in the source means that as of the date of the document (1 August 2008), this is the authoritative text. For a current compliance assessment, one would need to check the CASA website for any subsequent amendments or suspensions.

The source text contains no reference to any litigation, court challenges, or judicial review concerning this directive. There is no mention of any objections from owners, operators, or manufacturers. Given that the directive is a mandatory safety instrument issued under delegated authority from CASA, it is susceptible to administrative law challenge (e.g., under the Administrative Decisions (Judicial Review) Act 1977) if an affected person could show that CASA acted beyond power, failed to observe procedural fairness, or made an error of law. However, the source does not record any such challenge. The directive’s background cites “reports” of potential unannunciated loss of heating, suggesting the underlying technical problem is documented but not contested. In Australia, airworthiness directives are rarely litigated directly, because compliance is a precondition to lawful operation and because the courts typically defer to the technical expertise of the regulator unless there is a clear jurisdictional error. The directive references the FAA AD, and if there were litigation in the United States regarding the same issue, it might be persuasive but not binding in Australia. Without any case citations in the source, one cannot infer that litigation has occurred. It is also possible that the directive was complied with without controversy, or that any disputes were resolved informally through CASA’s internal review mechanisms. The absence of litigation history does not mean the directive is immune from future challenge, but as of the source’s date, none is recorded.

Several traps for unwary owners and operators arise from the wording of this directive. First, the post‑flight residual‑heat check must be performed “following every flight” until the modification or replacement is accomplished. This is an ongoing obligation that starts as soon as the AFM temporary change is incorporated (or within 15 hours/30 days) and does not end until either the software upload or transmitter replacement is done. Missing a single flight’s check could be a breach. The compliance time for the check is not specified as a deadline; it is simply “following every flight”. That means the check must be done immediately after each flight, not at the next maintenance opportunity. If the aircraft flies multiple sectors in a day, a check must be done after each sector. Second, the check may be performed by the owner/operator who holds at least a private pilot licence. That is a permissive delegation, but it carries with it the requirement to “make an appropriate entry in the aircraft Technical Records certifying completion of the check”. If that entry is not made, the check is not documented, and the aircraft might be deemed non‑compliant on that leg. The entry must be in the technical records, not just the pilot’s logbook or a company record. Third, the caution in the directive about burns is not a mere suggestion: “TO PREVENT POSSIBLE BURNS, USE EXTREME CAUTION TOUCHING HEATED AREAS.” The probe can become hot enough to cause thermal injury if the heating element is functioning correctly. The prescribed method is to hold the hand near the heated area or move gradually from ambient toward the heated area until warmth is felt. If the probe is very hot, touching it directly could cause burns. That is a workplace health and safety issue for the person performing the check. Fourth, the directive states that later revisions of SB 27‑3787 approved by the FAA as an AMOC are acceptable for compliance with “the equivalent Requirements” of this Directive. That means one cannot simply rely on any later revision of the service bulletin; it must be specifically approved by the FAA as an AMOC to the FAA AD. If a later revision is issued but not yet FAA‑approved as an AMOC, it is not automatically acceptable under the Australian directive. Fifth, the spare‑parts prohibition in Requirement 7 applies “as of 3 September 2008” and is ongoing. That means anyone who stocks unmodified SLZ8060‑3 or SLZ8060‑4 transmitters for future installation must either upgrade them (by software upload) or dispose of them. The prohibition is not limited to the aircraft to which the directive applies; it says “on any aeroplane”. That implies even if the aircraft is not a Model 390, the installation is prohibited? The directive’s applicability is Model 390, but the spare‑parts prohibition could be interpreted as a worldwide restriction under the Australian AD? In practice, it would affect installations on Australian‑registered Model 390 aircraft, but the phrase “on any aeroplane” is ambiguous. Careful reading of the applicability section limits the directive to Model 390 serial numbers RB‑4 through RB‑204, so the spare‑parts prohibition would be read as applying only to those aircraft, but the text says “on any aeroplane”. This could be a drafting oversight; an operator installing that part on a different type might argue the directive does not apply to that type, but the text is unambiguous: “any aeroplane”. A cautious approach would be to treat it as a prohibition on installing those transmitters on any aircraft operating under an Australian certificate of airworthiness. Sixth, the directive does not specify who is responsible for the cost of compliance. That falls on the owner/operator. The software upload kit (Kit No. 123‑3436) and the new transmitters (P/N SLZ8060‑5) have direct costs, plus labour, plus the recurrent cost of performing the post‑flight check and making entries. For a fleet operator with many rotation cycles, the check after every flight can be a significant operational burden. Seventh, the directive does not provide any extension mechanism for parts availability. If the required software upload kit or replacement transmitters are backordered, the operator must still comply within 250 hours or 12 months; if not possible, they may need to ground the aircraft or seek an alternative method of compliance from CASA.

Compliance with AD/PREMIER/4 is a sequence of steps with specific deadlines. Step 1: Immediately identify whether the aircraft is within the applicability (Model 390, serial numbers RB‑4 through RB‑204). If not, the directive does not apply. Step 2: Determine if the AFM temporary change (P/N 390‑590001‑0003CTC7) has already been incorporated. If not, incorporate it within 15 hours time‑in‑service or 30 days after the effective date (3 September 2008), whichever occurs first. Insert the temporary change into the aircraft flight manual and remove any previous version if present. Step 3: After the AFM temporary change is inserted, commence the post‑flight residual heat check on both LH and RH AOA probes following every flight. The check must be performed in accordance with the procedure in the AFM temporary change. If the person performing the check is the owner/operator and holds at least a private pilot licence, they are authorised to do so. Record the completion of each check in the aircraft technical records, with a certification that the check was performed. The entry should include the date, flight details, aircraft registration, result (heat detected or not detected), and signature of the person. Step 4: If the check reveals residual heat, no further action is required before the next flight (other than the next check after the next flight). If residual heat is not detected, step 5 applies. Step 5: Before further flight, arrange for a maintenance manual operational test of the heat of the AOA probes, following the procedures in the AFM temporary change and Service Bulletin 27‑3787 (May 2007 edition, or a later revision that has been FAA‑approved as an AMOC). This test must be performed by a qualified person. Step 6: If the operational test shows the probe heating is functioning, the aircraft may be flown again, but the post‑flight check must continue. If the test reveals a failure, replace the failed probe(s) before further flight. Use the procedures in SB 27‑3787. The replacement must be done by a qualified person. Step 7: Plan for the long‑term compliance step (Requirement 5). Within 250 hours TIS or 12 months after 3 September 2008, accomplish either: (a) upload new software to both AOA transmitters using Kit No. 123‑3436 (Field Software Upload), or (b) replace any SLZ8060‑3 or SLZ8060‑4 transmitters with new SLZ8060‑5 transmitters. Both actions must be in accordance with SB 27‑3787. Ensure that all transmitters on the aircraft are addressed (both LH and RH). Step 8: After the modification or replacement is completed, remove the AFM temporary change (P/N 390‑590001‑0003CTC7) from the AFM. The AFM should then be returned to its original configuration or be updated with a permanent revision. Step 9: Review spare‑parts inventory. As of the effective date, any unmodified SLZ8060‑3 or SLZ8060‑4 transmitters in stock should not be installed on any aeroplane. Either upload the new software to those units (if possible) to make them serviceable, or dispose of them or return them to the manufacturer. Step 10: Maintain records of compliance for each action: the AFM change insertion date and signature, every post‑flight check entry, any operational test results, any probe replacements, and the software upload or transmitter replacement. These records may be required for future airworthiness reviews or by CASA on request.