nht89-3.35 | NHTSA

TYPE: Interpretation-NHTSA

DATE: November 7, 1989

FROM: S. Kadoya -- Manager, Safety and Technology, Mazda Research & Development of North America, Inc.

TO: Stephen P. Wood -- Acting Chief Counsel, NHTSA; George Parker -- Assoc. Administrator-Enforcement, NHTSA

TITLE: Re Request for Interpretation of 49 CFR Parts 571 and 581 with respect to active suspension systems.

ATTACHMT: Attached to letter dated 10-2-90 from P.J. Rice to S. Kadoya (A36; Std. 108; Std. 111; Std. 209; Std. 208; Std. 212; Std. 219; Std. 301; Part 581

TEXT:

The purpose of this letter is to request NHTSA's interpretation of the requirements and test conditions of the following Federal Motor Vehicle Safety Standards (FMVSS); as they apply to active suspension systems:

S108, "Lamps, reflective devices, and associated equipment" S111, "Rearview mirrors" S204, "Steering control rearward displacement" S208, "Occupant crash protection" S212, "Windshield mounting" S219, "Windshield zone intrusion of S301, "Fuel system integrity"

In addition, Mazda also requests an interpretation of the requirements of Part 581, "Bumper Standard," as they apply to active suspensions. Because this interpretation request covers several safety standards and because each standard may involve a parti cular person that is assigned to it, Mazda's questions regarding these individual standards have been presented in separate appendices to this letter. Each appendix addresses only one safety standard. Mazda hopes that this method will facilitate distri bution of this document to the appropriate NHTSA personnel. Mazda is writing to you both because the questions raised concern not only the interpretation of a given standard but enforcement issues as well.

Mazda is currently developing an active suspension system for possible use in future vehicle programs. The benefits of such a system have been, by now, well documented and, therefore, will not be repeated here. More importantly, Mazda is now working to establish a compliance testing protocol to the requirements of 49 CFR Parts 571 and 581. In attempting to establish this testing protocol numerous questions have arisen regarding the applicability, test conditions, and testing logistics of these Parts as they pertain to active suspension systems. In formulating this request, Mazda has reviewed past NHTSA interpretations for similar types of suspension systems. This request covers those questions that Mazda feels were not answered by previous interpr etations.

In order to obtain a meaningful interpretation of the requirements of the above listed safety standards, Mazda would like to stipulate an assumed active suspension system. For the purposes of this interpretation request the assumed system is actuated by hydraulic fluid or compressed air. An

electronic controller with feedback control regulates vehicle attitude to programmed design positions based on such inputs as:

1. vehicle speed 2. lateral acceleration 3. steering angle, and 4. suspension height

The primary sensed parameter for feedback control is suspension height. This system maintains a level vehicle body attitude, controls body pitch and roll, and effects a more aerodynamic vehicle profile at highway speeds. At vehicle speeds in excess of " Z" mph, where Z is greater than 35 mph, the suspension height is lowered by "x" mm. Control pressure is developed by a hydraulic pump or air compressor driven off the engine. Consequently, the active suspension system is only operational when the vehicl e's engine is operating. If the engine/vehicle should remain unused for a period of, say, days pressure in the control system will fall such that the suspension height may be lowered by as much as "y" mm, where "y" is greater than "x". The suspension h eight is returned to its nominal or design position for vehicle operation after such an extended period of inoperation almost immediately after starting the vehicle's engine. For convenience, let's call this assumed system, the ACS system.

Mazda is concerned about the protocol of compliance testing of vehicles equipped with an active suspension system. These concerns arise because many of the safety standards, primarily those listed above, do not specify a suspension height that is to be used during compliance testing. This has not been necessary with conventional suspension systems, and it may not be necessary with vehicles equipped with active suspension systems, if it is assumed for the purposes of compliance testing that the vehicle 's ignition switch is in the "on" position, i.e., the engine is operational and, thus, so is the system's hydraulic pump/air compressor. If this is indeed the case, the system is able to determine automatically a specified suspension height given a vehi cle speed and vehicle loading condition; just as a conventional shock absorber/spring system would determine mechanically a suspension height for these same given conditions. Unfortunately, the above listed standards do not specify explicitly the status of the vehicle's ignition switch. In most instances it is obvious that the ignition switch must be "on" for the vehicle to be able to fulfill its intended purpose. However, Mazda seeks a definitive interpretation of the status of a vehicle's ignition s witch, as well as the applicability of these standards as a function of the status of the ignition switch.

Furthermore, Mazda is concerned about the logistics of compliance testing. This is because the assumed active suspension system derives its power from the vehicle's engine when it is running, i.e., the system's ability to maintain and regulate suspension height is only possible during engine operation. For reasons of practicality and safety, a vehicle's engine is not actually operational during compliance testing. Therefore, Mazda is seeking from NHTSA guidelines by which Mazda may be able to establis h a means to maintain the intended suspension height for compliance testing purposes in the absence of engine operation. Mazda is reluctant to establish these means without such guidelines from NHTSA because it is

concerned that NHTSA may consider tests conducted in this manner to be in violation of the requirements of 49 CFR Parts 571 and 581 and, thus, invalid.

Mazda sincerely appreciates the opportunity for NHTSA's review of the issues raised in this letter and the attached appendices. Furthermore, Mazda would appreciate any further insight that NHTSA may wish to offer regarding these issues. NHTSA may also wish to consider how NCAP test procedures may be affected by the issues raised. Should NHTSA require further information or clarification of the issues raised in this letter and its attachments, please do not hesitate to contact either myself or Mr. R. Strassburger of my staff.

FMVSS No. 108, "Lamps, reflective devices, and associated equipment"

Prologue: NHTSA has previously issued an interpretation of the requirements of FMVSS No. 108; at the request of a confidential applicant and dated February 12, 1985, with respect to active suspension equipped vehicles. This interpretation stated that th e requirements of FMVSS No. 108 must be meet,"...at any time in which...",lamps, reflective devices, and associated equipment are to be,"...operated for its intended purpose." Consequently, headlamps, tailamps, stoplamps, the license plate lamp, and side marker lamps, must comply with the location requirements of FMVSS No. 108 when ever the vehicle's ignition is in the "on" position. Conversely, reflex reflectors, and turn signal lamps that also function as hazard warning signal flashers must comply wi th the location requirements when the vehicle's ignition is in either the "on" or "off" position. However, it is Mazda's interpretation that hazard warning flashers are not intended to be operational for a period of days, but rather for a period of hour s, at maximum, only.

Question A1: Is Mazda's understanding of the subject NHTSA interpretation accurate?

Question A2: Is Mazda's interpretation of the maximum intended operating duration of hazard warning signal flashers correct?

APPENDIX B: FMVSS No. 111, "Rearview mirrors"

Prologue: Section S5 of this standard describes the requirements for passenger cars. Section S5.1.1 establishes the requirements for,"Field of view." The location of the driver's eye reference points are established pursuant to the guidelines of FMVSS No. 104," Windshield wiping and washing systems." Safety standard no. 104 references SAE recommended practice J941," Motor vehicle driver's eye range,"; which describes a procedure for locating a locus of points representative of the eye locations for 9 0th, 95th, and 99th percentile distributions of a population mix of primarily US licensed drivers. Because the location requirements of J941 are made referenced to points within the vehicles cabin, it is not anticipated that the ACS system will perturb or otherwise interfere with these measurements. However, S5.1.1 requires further that the field of view,"...with an included horizontal angle measured from the projected eye point of at least 20 degrees, and sufficient vertical angle to provide a view o f a level road surface extending to the horizon

beginning at a point not greater than 200 feet to the rear of the vehicle..." As was stated in the cover letter to this appendix, the ACS system suspension height may fall by "y" mm if the vehicle is not used for a period of days. In a previous NHTSA i nterpretation of FMVSS No. 108, at the request of a confidential applicant and dated February 12, 1985, NHTSA stated that,"...the minimum height requirement should be met for any lamp at any time in which it is operated for its intended purpose." Using this "intended purpose" argument Mazda's interpretation of FMVSS No. 111 is that the requirements of this standard are to be met when the vehicle's ignition is in the "on" position as rearview mirrors are not intended to be used when the vehicle's engine is not operating.

Question Bl: Is Mazda's interpretation of the requirements FMVSS No. 111 with respect to the state of the vehicle's ignition switch correct?

Question B2: For the purposes of compliance testing to the requirements of FMVSS No. 111, what means of maintaining the intended suspension height for a given vehicle speed and operating condition would be satisfactory to NHTSA?

Appendix C: FMVSS No. 204, "Steering control rearward displacement"

Prologue: Section S4 of this standard specifies the compliance parameter for this standard. Section S5 specifies the testing conditions to determine compliance with this standard. Section S5.1 specifies that the vehicle be loaded to its unloaded vehicl e weight. Section S5.5 specifies that the vehicles fuel tank be filled with Stoddard solvent to any capacity between 90 and 95 percent of the total capacity of the tank. Mazda's interpretation of the requirements of this standard is that they are to be met when the vehicle's ignition switch is in the "on" position only. Furthermore, Mazda interprets the vehicles suspension height pursuant to S5.1 and S5.5 to be the intended suspension height for the vehicle given the conditions of S4, i.e., 30 mph veh icle speed and steered wheels are positioned straight ahead.

Question C1: Is Mazda's interpretation of the requirements of FMVSS No. 204 correct?

Question C2: For the purposes of compliance testing to the requirements of FMVSS No. 204, what means of maintaining the intended suspension height for a given vehicle speed and operating condition would be satisfactory to NHTSA?

Appendix D: FMVSS No. 208, "Occupant Crash Protection"

Prologue: This standard establishes performance criteria for the protection of vehicle occupants involved in crashes. Section S5 of this standard establishes occupant crash protection requirements for a range of crash scenarios. Section S8 of this stan dard specifies the testing conditions to be used for frontal, lateral, and rollover compliance testing. Section S8.1.1(d), "Vehicle test attitude," specifies the procedure for determining the vehicle test attitude that is to be used for testing. Specif ically, this section requires that the vehicle's pretest attitude,"...shall be equal to either the as delivered or fully loaded

attitude or between the as delivered and fully loaded attitude." The as delivered attitude is defined by S8.1.1(d) as being,"...the distance between a level surface and a standard reference point on the test vehicle's body, directly above each wheel ope ning, when the vehicle is in its "as delivered" condition. The "as delivered" condition is the vehicle as received at the test site..." Because it is highly likely that the test vehicle will not have been operated for a period of days prior to arriving at the test site, the suspension height may have fallen by "y" mm. The fully loaded attitude is defined as the attitude of the vehicle when loaded in accordance with S8.1.1(a) or (b) and a determination of the height of the suspension at the fully load ed condition is made from the same level surface, using the same standard reference points, as were used to determine the "as delivered" condition. The definition of the "as delivered" condition is quite clear. However, Mazda interprets the "fully load ed condition" of the vehicle to be the condition when the vehicle's ignition is "on". In this instance it is likely that the height of the standard reference points on the vehicles body when in the "fully loaded condition" relative to the level surface will be greater than for the "as delivered" condition. Conversely, conventional vehicle suspension systems will like have an "as delivered" height greater than the "fully loaded" height. However, this fact is of no importance as S8.1.1(d) states that t he pretest vehicle attitude may be,"...between the as delivered and the fully loaded attitude." With respect to the injury criteria specified by section S6 of this standard, Mazda's interpretation is that these criteria must be met with the vehicle's ig nition in the "on" position only.

Section S8.2.7 specifies additional test conditions to be used for lateral moving barrier crash testing. Section S8.2.7(a) states that the vehicle,"...is at rest in its normal attitude." Mazda interprets the meaning of "normal attitude" to be that vehi cle attitude which is intend when the vehicle's ignition is in the "on" condition, with the vehicle loaded pursuant to S8.1.1(a) or (b), and while the vehicle is at rest.

Appendix D (con't): FMVSS No. 208, "Occupant crash protection" Question D1: Is Mazda's interpretation of the definition of the "fully loaded condition" correct with respect to the condition of the ignition switch?

Question D2: Is Mazda's interpretation of the irrelevance of the relative relationship between the "as delivered" and "fully loaded" conditions correct?

Question D3: Is Mazda's interpretation of the meaning of "between the as delivered and the fully loaded attitude" correct?

Question D4: For the purposes of compliance testing to the requirements of FMVSS No. 208, what means of maintaining the intend suspension height for a given vehicle speed and operating condition would be satisfactory to NHTSA? Question D5: Is Mazda's interpretation of the meaning of "normal attitude" correct?

Appendix E: FMVSS No. 212, "Windshield mounting"

Prologue: Customarily, compliance testing to the requirements of this standard is conducted concurrently with compliance testing to the frontal crash requirements of FMVSS No. 208. Therefore, many of the test protocol issues that might be raised in thi s instance have already been raised in Appendix D. Moreover, NHTSA has previously issued an interpretation of this standard with respect to adjustable height suspension systems at the request of Mazda. This interpretation was issued on August 10, 1982. The central premise of NHTSA's interpretation was that the subject vehicle could possibly be operated at two distinct suspension heights at any given vehicle speed. In that instance such a situation was possible because the suspension height was manua lly determined, i.e., established by the operator, thereby justify compliance testing with the vehicle's suspension height adjusted to any position possible or at minimum to the worst case position. However, the ACS system described in the cover letter to these appendices states that the vehicle's suspension height is determined by an on-board electronic controller and not by the vehicle operator. Consequently, only one unique set of suspension height parameters is possible for a given vehicle speed an d loading condition as is the case with conventional suspension systems. Therefore, because it is possible to determine exactly what the intended suspension height should be for a given situation, it is Mazda's opinion that the test vehicle should be te sted at the intended suspension height given the statutory speed and loading requirements. Lastly, the final issue is whether the requirements of FMVSS No. 212 must be met with the vehicles ignition in the "on" or "off" condition, or both. Using a "int ended purpose" argument, Mazda concludes that the requirements of FMVSS No. 212 are to met whenever the vehicle's ignition is in the "on" condition only.

Question E1: Is Mazda's interpretation that NHTSA previously issued interpretation of this standard with respect to adjustable height suspension systems not applicable in this instance given the facts presented?

Question E2: Is Mazda's interpretation of the requirements of FMVSS No. 212 with respect to the state of the vehicle ignition switch correct?

Appendix F: FMVSS No. 219, "Windshield zone intrusion"

on-board electronic controller and not by the vehicle operator. Consequently, only one unique set of suspension height parameters is possible for a given vehicle speed and loading condition as is the case with conventional suspension systems. Therefore, because it is possible to determine exactly what the intended suspension height should be for a given situation, it is Mazda's opinion that the test vehicle should be tested at the intended suspension height given the statutory speed and loading require ments. Lastly, the final issue is whether the requirements of FMVSS No. 219 must be met with the vehicles ignition in the "on" or "off" condition, or both. Using a "intended purpose" argument, Mazda concludes that the requirements of FMVSS No. 219 are to met whenever the vehicle's ignition is in the "on" condition only.

Question F1: Is Mazda's interpretation that NHTSA previously issued interpretation of this standard with respect to adjustable height suspension systems not applicable in this instance given the facts presented?

Question F2: Is Mazda's interpretation of the requirements of FMVSS No. 219 with respect to the state of the vehicle ignition switch correct?

Appendix G: FMVSS No. 301, "Fuel system integrity" Prologue: Customarily, compliance testing to the requirements of this standard is conducted concurrently with compliance testing to the frontal crash and lateral requirements of FMVSS No. 208. Therefore, many of the test protocol issues that might be ra ised in this instance have already been raised in Appendix D. Moreover, NHTSA has previously issued an interpretation of this standard with respect to adjustable height suspension systems at the request of Mazda. This interpretation was issued on Augus t 10, 1982. The central premise of NHTSA's interpretation was that the subject vehicle could possibly be operated at two distinct suspension heights at any given vehicle speed. In that instance such a situation was possible because the suspension heigh t was manually determined, i.e., established by the operator, thereby justify compliance testing with the vehicle's suspension height adjusted to any position possible or at minimum to the worst case position. However, the ACS system described in the co ver letter to these appendices states that the vehicle's suspension height is determined by an on-board electronic controller and not by the vehicle operator. Consequently, only one unique set of suspension height parameters is possible for a given vehi cle speed and loading condition as is the case with conventional suspension systems. Therefore, because it is possible to determine exactly what the intended suspension height should be for a given situation, it is Mazda's opinion that the test vehicle s hould be tested at the intended suspension height given the statutory speed and loading requirements. Lastly, the final issue is whether the requirements of FMVSS No. 301 must be met with the vehicles ignition in the "on" or "off" condition, or both. U sing a "intended purpose" argument, Mazda concludes that the requirements of FMVSS No. 301 are to met whenever the vehicle's ignition is in the "on" condition only.

Section S7.3 of this standard specifies that the test conditions that are to be used during rear moving barrier crash testing are those specified by

section S8.2 of FMVSS No. 208. The issues that might be raised regarding S7.3, therefore, have already been raised in Appendix D.

Question G1: Is Mazda's interpretation that NHTSA previously issued interpretation of this standard with respect to adjustable height suspension systems not applicable in this instance given the facts presented?

Question G2: Is Mazda's interpretation of the requirements of FMVSS No. 301 with respect to the state of the vehicle ignition switch correct?

Appendix H: 49 CFR Part 581, "Bumper Standards" Prologue: The stated scope and purpose of this standard is, "...to reduce physical damage to the front and rear ends of passenger motor vehicles from low speed collisions." NHTSA has previously issued an interpretation of this standard with respect to a djustable height suspension systems. One of these interpretations was issued by NHTSA on February 12, 1985 at the request of a confidential applicant. Another interpretation was issued May 16, 1986 at the request of Subaru of America. In the interpreta tion issued on February 12, 1985, NHTSA states,"...the vehicle is required to meet the pendulum test (581.6(b)) of Part 581 in any vehicle use scenario in which the system operates, and the barrier test (581.6(c)) of Part 581 when the engine is idling." In the subsequent interpretation of 581.6, issued on May 16, 1986, NHTSA states, "Given the absence of a specific test condition concerning suspension height, it is our interpretation that a vehicle must be capable of meeting the standard's damage crite ria at any height position to which the suspension can be adjusted." Consequently, with respect to 581.6(c) these interpretations appear to be in conflict when applying the regulations of Part 581 to the ACS system in that the 1985 interpretation states that the damage criteria must be met at IDLE while the 1986 interpretation states that the damage criteria must be met at ANY height position to which the system can be adjusted. Moreover, the 1985 interpretation infers that the damage criteria for 581 .6(c) must be met when the vehicle's ignition switch is in the "on" condition only. Furthermore, the 1985, with respect to 581.6(b), and 1986 interpretations seem to be in conflict with this standards stated purpose to reduce physical damage to motor ve hicles in LOW speed collisions by requiring bumpers to meet the damage criteria of 581.5 at,"...any vehicle use scenario in which the system operates..."

Question H1: Could NHTSA please provide an interpretation of 49 CFR Part 581 with respect to the ACS system?

Interpretation ID: nht89-3.35