Center Director
Electronics Center of Excellence and Expertise
U.S. Customs and Border Protection
One World Trade Center, Suite 601
Long Beach, CA 90831

Attn: Pauline Garcia, Senior Import Specialist

Re: Protest and Application for Further Review No. 0411-16-100001; Classification of circuit card assemblies for aircraft electronic control units

Dear Center Director:

The following is our decision as to Protest and Application for Further Review No. 0411-16-100001, timely filed on October 19, 2016 on behalf of Triumph Engine Control Systems LLC (“Triumph” or “Protestant”), concerning classification of certain merchandise under the Harmonized Tariff Schedule of the United States (HTSUS). The merchandise at issue consists of circuit card assemblies (CCAs) which are designed for use in aircraft electronic control units (ECUs). The CCAs were entered with and liquidated by U.S. Customs and Border Protection (CBP) at the Port of Hartford (“the Port”). Protestant asserts that CBP’s classification of the subject merchandise at liquidation is incorrect.


The subject CCAs consist of fiberglass boards equipped with copper traces, connectors, and various electronic components, including resistors, capacitors, microprocessors, and memory devices. They are specifically designed for use in certain ECUs that are in turn designed for implementation in aircraft “full authority digital engine control” (“FADEC”) systems. Product literature included with the protest indicates that each ECU contains numerous inputs and outputs – including, inter alia, multiple solenoid drivers, lamp drivers, and power supplies – assembled within a single housing.

The product literature also includes the following depictions of the ECUs into which the CCAs are incorporated:

    “EMC-50” ECU “EMC-100” ECU “EMC-101” ECU   The combination of these ECUs with various external input sensors, electrical connectors, and auxiliary components makes up a complete FADEC system. As Triumph states in its protest, a FADEC system is a type of aircraft control system in which engine control is fully automated, rather than subject to pilot intervention. See also Fed. Aviation Admin., Aviation Maintenance Technician Handbook-Powerplant (FAA-H-8083-32), Vol. 1 p. 2-34 (2012), available at [hereinafter FAA-H-8083-32]. Within this system, the sensors continuously measure variables such as engine pressure, fuel temperature, and engine speed, and convey this data electronically to the ECUs. See id. at 2-34, 2-37 to 2-41, 4-12 to 4-14. The ECUs in turn process the received data to calculate the volume of fuel required by the engine to provide optimal thrust for a given flight mode (i.e., takeoff, acceleration, cruise, or deceleration). See id. at 2-37 to 2-41. Based on this calculation, the ECU electrically actuates a fuel-metering valve to trigger injection of fuel – at the proper temperature, rate of flow, and interval timing, as determined by the ECU – into the engine. See id. at 2-37 to 2-41, 4-12 to 4-13. In effect, the pilot need only select the proper flight mode, at which point the FADEC autonomously conducts the various processes necessary to give effect to this selection.

In addition to managing fuel delivery, FADEC systems conduct diagnostic checks on their internal electrical components, conveying the results electronically to visual indicators in the cockpit, and store collected data to assist in subsequent engine diagnostics. See id. at 4-13; see also Nikhil Kumar and Shavran Kumar, Full Authority Digital Engine Control (FADEC), Int’l Journal of Emerging Trends in Science and Tech. Vol.2, Issue 10, p. 3299 (2015), available at As Triumph states in its protest, the ECUs themselves have various “ancillary functions” within the FADEC system, including tracking of engine operating data, delivery of data to cockpit displays and signaling devices, engine ignition and shut-off, activation of reverser solenoids, and guidance of vane actuators and switches. This is consistent with the above-mentioned product literature, which indicates that each ECU has separate data ports for aircraft communication and maintenance data.

The specific functions of the CCAs within the ECUs, and the overarching FADEC system, are described by Triumph as follows:

There are three types of CCAs in an ECU; a Power Supply/Interface CCA, a Computer System CCA and an Assembly Driver CCA.

The Power Supply/Interface CCA serves to: 1) receive and convert airframe electrical power to the voltages needed to operate the various electronic circuits on the CCAs; 2) provide protection against high voltage or electromagnetic interference (e.g., from a lightning strike or from radio interference); and 3) receive electronic analog signals from external sensors and convert these to digital values for further processing. These CCAs are also sometimes referred to as “Power Supply” CCAs or “Interface Board” CCAs on supplier invoice descriptions.

The Computer System CCA contains a microprocessor (computer chip), memory devices, data buses, and other logic for the engine control system. It controls the sampling of the digital input sensor data, processes this information, and has an output function that automatically sends commands to the output devices (e.g., fuel valve) needed to control the engine thrust. Software is installed on this CCA in the computer system memory and this software provides the engine control functionality. These CCAs are also sometimes referred to on supplier invoice descriptions as “Computer Dual Channel” CCAs and “CPU Assembly” CCAs.

The Assembly Driver CCA serves to drive the devices that carry out the functions commanded by the Computer System CCA such as rotational measurement transducers, stepper motors and the over-speed circuit.

The Power Supply/Interface CCA, Computer System CCA and the Assembly Driver CCA work together to carry out the required functions of the ECU and are specifically designed to carry out only these functions and would have no other application or commercial use.

The instant protest covers 18 separate entries of the CCAs entered between June 22, 2015 and August 7, 2015 and liquidated between May 6, 2016 and June 17, 2016. The CCAs in all 18 entries were both entered and liquidated in heading 8538, HTSUS, which provides for “Parts suitable for use solely or principally with the apparatus of heading 8535, 8536 or 8537.” Triumph claims that the CCAs are properly classified in heading 9032, HTSUS, which provides for “Automatic regulating or controlling instruments and apparatus; parts and accessories thereof.” ISSUE:

Whether the subject CCAs are properly classified in heading 8504, HTSUS, as electrical transformers, in heading 8538, HTSUS, HTSUS, as parts suitable for use solely with apparatus of heading 8537, HTSUS, or in heading 9032, HTSUS, as parts of automatic regulating or controlling apparatus.


Initially, we note that the matter protested is protestable under 19 U.S.C. §1514(a) (2) as a decision on classification. The protest was timely filed within 180 days of liquidation of the first entry. (Miscellaneous Trade and Technical Corrections Act of 2004, Pub.L. 108-429, § 2103(2) (B) (ii), (iii) (codified as amended at 19 U.S.C. § 1514(c) (3) (2006)). Further Review of Protest No. 0411-16-100001 is properly accorded to Protestant pursuant to 19 C.F.R. § 174.24(c) because Triumph alleges that although Customs has previously ruled upon this matter, Triumph’s protest raises legal arguments which had not been considered in those previous determinations.

Merchandise imported into the United States is classified under the HTSUS. Tariff classification is governed by the principles set forth in the General Rules of Interpretation (GRIs) and, in the absence of special language or context which requires otherwise, by the Additional U.S. Rules of Interpretation. The GRIs and the Additional U.S. Rules of Interpretation are part of the HTSUS and are to be considered statutory provisions of law for all purposes.

Classification under the HTSUS is made in accordance with the General Rules of Interpretation (GRIs). GRI 1 provides that the classification of goods shall be determined according to the terms of the headings of the tariff schedule and any relative section or chapter notes. In the event that the goods cannot be classified solely on the basis of GRI 1, and if the headings and legal notes do not otherwise require, the remaining GRIs 2 through 6 may then be applied in order.

The Harmonized Commodity Description and Coding System Explanatory Notes (“ENs”) constitute the official interpretation of the Harmonized System at the international level. While neither legally binding nor dispositive, the ENs provide a commentary on the scope of each heading of the HTSUS and are generally indicative of the proper interpretation of these headings. See T.D. 89-80, 54 Fed. Reg. 35127, 35128 (August 23, 1989).

The HTSUS provisions under consideration in the instant case are as follows:

8504 Electrical transformers, static converters (for example, rectifiers) and inductors; parts thereof

8538 Parts suitable for use solely or principally with the apparatus of heading 85.35, 85.36 or 85.37

9032 Automatic regulating or controlling instruments and apparatus; parts and accessories thereof

In its protest, Triumph claims that the subject CCAs are classified in heading 9032, HTSUS, as parts of “automatic regulating or controlling apparatus.” Note 3 to Chapter 90 provides that “[t]he provisions of notes 3 and 4 to section XVI apply also to this chapter.” In turn, Note 3 to Section XVI provides as follows:

Unless the context otherwise requires, composite machines consisting of two or more machines fitted together to form a whole and other machines designed for the purpose of performing two or more complementary or alternative functions are to be classified as if consisting only of that component or as being that machine which performs the principal function.

With specific regard to heading 9032, Note 7 to Chapter 90 provides as follows:

Heading 9032 applies only to:

Instruments and apparatus for automatically controlling the flow, level, pressure or other variables of liquids or gases, or for automatically controlling temperature, whether or not their operation depends on an electrical phenomenon which varies according to the factor to be automatically controlled, which are designed to bring this factor to, and maintain it at, a desired value, stabilized against disturbances, by constantly or periodically measuring its actual value; and

Automatic regulators of electrical quantities, and instruments or apparatus for automatically controlling non-electrical quantities the operation of which depends on an electrical phenomenon varying according to the factor to be controlled, which are designed to bring this factor to, and maintain it at, a desired value, stabilized against disturbances, by constantly or periodically measuring its actual value.

(emphasis added).

EN 90.32 further clarifies the definition of “automatic control apparatus,” within the meaning of Note 7(a) to Chapter 90, as follows:


Automatic control apparatus for liquids or gases and apparatus for automatically controlling temperature form part of complete automatic control systems and consist essentially of the following devices:

A device for measuring the variable to be controlled (pressure or level in a tank, temperature in a room, etc.); in some cases, a simple device which is sensitive to changes in the variable (metal or bimetal rod, chamber or bellows containing an expanding liquid, float, etc.) may be used instead of a measuring device.

A control device which compares the measured value with the desired value and actuates the device described in (C) below accordingly.

A starting, stopping or operating device.

Apparatus for automatically controlling liquids or gases or temperature, within the meaning of Note 7 (a) to this Chapter, consists of these three devices forming a single entity or in accordance with Note 3 to this Chapter, a functional unit.

Per EN 90.32, Note 7 to Chapter 90 explicitly restricts heading 9032 to apparatus which are fully equipped to take measurements of a particular variable, compare those measurements to a desired value for the same variable, and actuate the device needed to bring the variable into alignment with the corresponding desired value. See Belimo Automation A.G. v. United States, 2013 Ct. Intl. Trade LEXIS 154, *20, aff’d 774 F.3d 1362 (Fed. Cir. 2014), and Applied Biosystems v. United States, 34 C.I.T. 769, 780, 715 F. Supp. 2d 1327, 1336 (2010) (both strictly applying criteria of EN 90.32(I) in determining applicability of heading 9032 to merchandise at issue). Accordingly apparatus that possess functionality beyond that referred in Note 7 to Chapter 90 fall outside the scope of heading 9032. Under this principle, we have previously found vehicular ECUs which calibrate a variable to an optimal value that is autonomously determined, and continually adjusted, by the apparatus itself to be outside the scope of heading 9032. See, e.g., Headquarters Ruling Letter (HQ) H088421, dated May 10, 2012 (“As the EPS ECU does not return or maintain torque of the torsion bar at a predetermined or desired value, we find that the merchandise fails to satisfy the terms of Note 7(b)…”). We have reached the same conclusion with respect to similar articles which measure and adjust multiple variables for the overarching purpose of optimizing vehicle engine performance. See HQ H222091, dated April 25, 2016 (citing HQ 963805, dated December 14, 2001); see also NY N275130, dated May 10, 2016, and NY N271216, dated December 28, 2015 (both determining that ECUs which measure and adjust multiple variables have “functionality beyond those products intended to be classified in heading 9032”).

Here, because Triumph claims the CCAs to be parts of automatic regulation or controlling apparatus of heading 9032, the initial inquiry is whether a FADEC ECU qualifies as the latter. As Triumph concedes in its protest, and as the accompanying product literature indicates, the ECUs conduct a host of functions extending beyond those described in Note 7 to Chapter 90 and EN 90.32. Aside from calibrating flow of fuel to the engine, they heat the fuel, track and transmit engine operating data, start and stop the engine, and activate and guide various other components. In recognition of this, Triumph argues that pursuant to Note 3 to Section XVI, as applied to heading 9032 by virtue of Note 3 to Chapter 90, a FADEC ECU is nevertheless a product of the heading because its “principal function” is the measurement and calibration of fuel injection.

Even assuming the fuel control function were in fact the “principal” function of a FADEC ECU, notwithstanding the various other functions it performs, this would not bring the ECU within the scope of heading 9032. As stated above, a FADEC ECU receives pressure, temperature, speed, and other variable measurements, processes these measurements to determine the optimal rate of fuel intake for a given flight mode, and actuates the valves to give effect to this determination. In other words, like the ECUs in the above-cited rulings, it does not measure a particular variable for the purpose of bringing that variable to a desired value. Rather, it measures multiple variables (i.e., pressure, temperature, and speed) for the purpose of calibrating a different variable altogether (i.e., fuel flow). Nor does it actually bring this variable to a “desired” value, insofar as the optimal level of fuel intake is autonomously determined, and continually adjusted, by the ECU itself. The pilot’s manual selection of the flight mode cannot be equated to the setting of a “desired” fuel intake rate, given that the pilot exercises no control over the latter. See FAA-H-8083-32, supra p. 1, at 2-34 (“The FADEC-type control gives the electronic controller (computer) complete control.”). We also note that the ECU does not actually contain the sensors which measure the variables driving the fuel intake calculation; these are located elsewhere within the FADEC system. As such, the product differs from that described in EN 90.32, part (I)(A). In view of all this, the ECU cannot be considered an automatic regulating or controlling apparatus of heading 9032. The subject CCAs, by extension, cannot be considered “parts” of the heading.

In opposing this conclusion, Triumph cites HQ 954950, dated December 23, 1993, and New York Ruling Letter (NY) B81443, dated February 3, 1997, in which ECUs were classified as articles of heading 9032, HTSUS. Triumph also cites NY 874584, dated June 18, 1992, in which CBP classified module board assemblies for use in an aircraft engine trust management system as parts of the heading. However, these rulings were issued prior to the advent of current Note 7 to Chapter 90, which was implemented as part of the 2001 HTSUS revisions, and are therefore inapplicable. See HQ H222091, supra (specifically determining that HQ 954950 and NY B91443 are revoked by operation of law). Moreover, our conclusion is consistent with myriad rulings issued since Note 7’s implementation, including those cited above. We therefore remain of the view that the subject merchandise is excluded from heading 9032, HTSUS. We next consider whether the CCAs are classifiable in a heading of Chapter 85. Note 2(a) and (b) to Section XVI, under which Chapter 85 falls, state as follows:

Subject to note 1 to this section, note 1 to chapter 84 and to note 1 to chapter 85, parts of machines (not being parts of the articles of heading 8484, 8544, 8545, 8546 or 8547) are to be classified according to the following rules:

Parts which are goods included in any of the headings of chapter 84 or 85 (other than headings 8409, 8431, 8448, 8466, 8473, 8487, 8503, 8522, 8529, 8538 and 8548) are in all cases to be classified in their respective headings;

Other parts, if suitable for use solely or principally with a particular kind of machine, or with a number of machines of the same heading (including a machine of heading 8479 or 8543) are to be classified with the machines of that kind or in heading 8409, 8431, 8448, 8466, 8473, 8503, 8522, 8529 or 8538 as appropriate. However, parts which are equally suitable for use principally with the goods of headings 8517 and 8525 to 8528 are to be classified in heading 8517

(emphasis added).

In accordance with Note 2(a), we initially consider whether any of the CCAs are classifiable in heading 8504, HTSUS, which provides, inter alia, for electrical transformers. EN 85.04 defines “electrical transformers” for purposes of the heading as follows:

Electrical transformers are apparatus which, without having any moving parts, transform, by means of induction and using a preset or adjustable system, an alternating current into another alternating current of different voltage, impedance, etc.

In its protest, Triumph identifies two of the subject CCAs as “power supply” CCAs, which receive and convert electrical current to current of a different voltage. More precisely, according to supplemental information provided by the importer, the “power” function refers to circuitry designed to take an input power supply from an external source which it processes and transmits the power outputs to various power rails that supply power to functional blocks in the ECU. It was noted, however, that power supply CCAs do not have an individual “power” function, but rather, they also have “interface” functions, i.e., the handling and management of inputs and outputs to and from the ECU respectively.

As per GIR 1, the Notes to Section XVI, to the extent they are applicable, shall be used to classify the goods at issue. Note 3 to Section XVI instructs that composite machines consisting of two or more machines designed for the purpose of performing two or more complementary or alternative functions are to be classified as if consisting only of that component which performs the principal function. As these CCAs provide both “power” and “interface” functions, they are considered composite machines and the principle function should be determined. Based on the information provided to this office, we find that neither of the cited functions can be said to be the principal function. When it is not possible to determine the principal function of the machine as provided for in Note 3 to Section XVI, and when the context does not otherwise require, it is necessary to apply GRI 3(c) and classify the good in the heading which occurs last in numerical order among those which equally merit consideration. In this case, the “interface” function would fall to be classified in heading 8538, as discussed below.

With respect to the remaining Computer System, Assembly Driver, and Interface CCAs, we consider heading 8538, HTSUS, which provides for parts suitable solely or principally with the apparatus of, inter alia, heading 8537, HTSUS. For reference, heading 8537 includes bases that exercise “electric control” and are equipped with two or more apparatus of heading 8536, which in turn includes apparatus for making connections within (1,000-volt maximum) electrical circuits. EN 85.37 states, with respect to the products classifiable in heading 8537, as follows:

The heading…covers: * * * “Programmable controllers” which are digital apparatus using a programmable memory for the storage of instructions for implementing specific functions such as logic, sequencing, timing, counting and arithmetic, to control, through digital or analog input/output modules, various types of machines.

Pursuant to the plain language of heading 8537, and consistent with EN 85.37, CBP has previously determined that ECUs and similar vehicular control units qualify as products of the heading. See HQ H088421, supra, and HQ H242032, dated December 15, 2014. We have specifically found these articles to be “programmable controllers” of the type described in EN 85.37, insofar as their ultimate purpose is to control separate apparatus via the transmission of logic-based electrical commands. See HQ H088421, supra, HQ H242032, supra.

The ECUs into which the subject CCAs are incorporated are no different. Similar to automotive ECUs, they formulate logic and timing-based commands and issue these as electrical transmissions directly to the fuel metering valve, cockpit display screens, and various other apparatus throughout the aircraft. Moreover, as stated and depicted in the above-referenced product literature, the ECUs incorporate numerous (i.e., far more than two) outputs used to form electrical circuits for the transmission of these commands. We accordingly find the ECUs to be bases for “electric control” within the meaning of heading 8537, HTSUS.

In effect, the Computer System, Assembly Driver, and Power Supply/Interface CCAs, all of which are indisputably designed for incorporation into the ECUs, are “parts suitable for use solely or principally with the apparatus of heading 8537.” Pursuant to Note 2(b) to Section XVI, they classified in heading 8538, HTSUS.


By application of GRI 1, the Computer System and Assembly Driver are classified in heading 8538, HTSUS. By application of GIRs 1 (Note 3 to Section XVI) and 3(c), the Power Supply/Interface CCA is also classified in heading 8538, HTSUS. More specifically, all of the CCAs at issue are classified in subheading 8538.90.30, HTSUS, which provides for “Parts suitable for use solely or principally with the apparatus of heading 8535, 8536 or 8537: Other: Printed circuit assemblies: Other.” The 2015 general column one rate of duty for subheading 8538.90.30, HTSUS, is 3.5% ad valorem.

Duty rates are provided for your convenience and are subject to change. The text of the most recent HTSUS and the accompanying duty rates are provided on the internet at

You are instructed to DENY the Protest.

In accordance with Sections IV and VI of the CBP Protest/Petition Processing Handbook (HB 3500-08A, December 2007, pp. 24 and 26), you are to mail this decision, together with the CBP Form 19, to the Protestant no later than 60 days from the date of this letter. Any reliquidation of the entry or entries in accordance with the decision must be accomplished prior to mailing the decision.

Sixty days from the date of the decision, the Office International Trade, Regulations and Rulings, will make the decision available to CBP personnel, and to the public on the CBP website at, by means of the Freedom of Information Act, and other methods of public distribution.


Myles B. Harmon, Director
Commercial and Trade Facilitation Division