P c/ U.S. Depoment of Trunspmtation FwJeml A- Administmtion Advisory Circular Subject: AIRW~EiINESSAPP~VRL OF Date: g/12/88 AC No: 20-129 VER!LTC2& NAVIGATION WNAW SYSTEMS Initiated by: AIR-120 Change:
FOR USE IN THE U.S. NATIONAL AIRSPACE SYSTEM uws) AND ALASKA 1 PtRPOSE. This advisory circular establishes an acceptable ms, but rw>t & only mans, of obtaining airworthiness approval of an airborne vertical navigation system for use under VF'R bisual flight rules) and IFR (instrument flight rules) within the conterminous United States, Alaska, and surrounding U.S. waters. Like all advisory mterial, this advisory circular is not, in itself, mandatory and does not constitute a regulation. It is issued for guidance purposes and to outline one method of carrpliance with aimrthiness requirenrtnts. As such, the terms %hall" and *' rnuSt'* used in this advisory circular pertain to an applicant who chooses to follow the method presented.
2 . RELATEDFAR. Federal Aviation Regulations (FAR) IWts 23, 25, 43, and 91.
3 RExA!mD 0 READINGMATERZALS.
a. Federal Aviation Administration (FAA)/Technical Standard Order (TSO) C115, Area Navigation EQuipmnt Using Multi-Sensor Inputs; TSO CdOb, Area Mvigation JQuijymnt Using Lroran< Inputs; ati TSO C120, Area Navigation Hquipzrmt Using ma/VW Inputs. Copies array be obtained from the Department of Transportation, FAA, Aircraft Certification Service, Aircraft Engineering Division (AIR-120), 800 Independence Amue, SW.I Mshington, DC 20591.
b Radio Technical Ccmnission for Aeronautics WEA), Ibcumnt No.
RX&O-160B, Envirormntal Conditions and Test Procedures for Airborne E;quip- =t, Dxzumznt No. RWID-178A, Software'Considerations in AirborneSystenrs and 4-G-t Certification; RTCA/DO-187, Minirmnn @erational Performme Standards for Airbrne Area Navigation EQuiwt Using Multi-Sensor Inputs;
RTCA/oO-194, Minimum C@rational Perfommc e Standards for Airborne Area Navigation Equi-t Using Iman< Inputs; and RTCA/Do-190, Minimum Operational Performance Standards for Airborne Area Nwigation EQuipnt Using ma/VU?
Inputs. Copies may be purchased from RTCA Secretariat, One McPherson Square, Suite 500, 1425 K Street, NW., Mashington, 1Dc 20005.
a, System Description. Vertical navigation WN?W equipnt provides vertical path guidance mmputed as deviation from a desired ascending or descending path to a specified altitude at a waypoint. Vertical guidance is generally provided as a linear deviation from the desired track defined by a line joining tw waypoints with specified altituti or as a vertical angle from a specified waypoint. Suchsystemmybeenhancedbyinclusionof secondary
AC 20-129 g/12/88 inputs such as optimized cliti or descent profiles, vertical acceleration and true airspeed. Thedesiredvertical pathrmybepilots@kctableormaybe determined by the VNW muter.by amputations based on the altitudes associated with successive waypints.
b. General Operational Limitations. A wrtia1 navigation system my be approved for en route, terminal and approach usewithinthe conterminous United States andAlaska.
5 l DEFINITIONS.
a. Amroach Operations. Approach operations are those flight phases anducted on charted Inst-nt Approach Procedures (IAPW -irq at the initial approach fix (IAF') andconcluding atlandingorthemissed approach holding fix, as appropriate.
b. En mute Operations. En route operations are those flight phases conductedoncharted Very HighF'requency~ Range (WR) routes designatadas high or low altitude routes (Jet or Victor), direct point-to-point operations bet-n waypints definedaspxtofthesechartedroutes, or along great circle routes as described in Advisory Circular 90-82, Ran&m Air Navigation Routes.
c. Fliqht Path Anqle. The angle that the vertical flight path of the aircraft makes with the local horizontal.
d. Slant Range. The actual straight line distance between an aircraft in flight and a ground location. This distance is greater than the geographical surface range because of the aircraft altitude.
e. Slant Range Error, Slantrangeerror is the differencektweenthe distance of an aircraft to a Distance Measuring EQuiFt KME) station on the surface and the distance from the station to a point directly beneath the aircraft on the surface. The error magnitude is a function of aircraft altitude above the station and the distance to the station.
f Terminal AreaOperations. Terminal area operations are those flight @a& amducted on charted Standard Instrummt Departures (SID), on charted Standard Terminal Arrivals (STAR), or other flight operations between the last en route f ix/wapint and an initial approach fix/waypoint.
g Vertical Deviation. The deviation of the aircraft above or beluwthe verti&l profile as displayed on an indicator such that deflection is up when the aircraft is beluw the vertical profile.
h Vertical Profile. A line or curve, or series Of connected lines and/or cur& in the vertical plane, defining an ascending or descending flight path either emanating from or terminating at a specified waypoint and altitude, or connecting tm or mre specified waypoints and altitudes. Inthis sense,a curve may be defined by performnce of the airplane relative to the aimmss.
2 I 2
g/12/86 i , 1\1c 20-129 ' 8 ' t I I 4 L i w r i ,t,I # Vkzticki profile,Angle Ekror, c
i. Thedifference indeqxesthatthe ' '1 current aircraft flight path angle makeswith the verticai profile. i 7 . I Vertical Profile Interce@ Point.
aircrkt flight path angle intercepts the The'point at which the current vertical profile.
6 AIR.~NEssCONsI~IoNs, Vertical mvigation equipnt has been certificate& for VFR and IFR use as a &ical flight path guidance system for en route, terminal and approach navigation in the National Airspace System UHS).
This' paragraph establishes acceptable criteria for VNKV systems. B 1 , I 1 ce :; . a. VNAVWp nt Installations Us& forwations Un&r Visual Fliqht Rules (VFR) Only. @erators wishing ito u&e VN?Wkqui@nt that is not coupled to an autopilot or flight'director (except as mted in 6a(5) below) for operations limited to VFR my obtainppproval of the installation by Type Certificate (TC),SuQple~~tal Type Certificate WK), data field approved by the FAA on an FAAForm 547, Major Repair and Alteration, or by the use of previously approveddata. me approval for return to service should be signed by o&of ' the entities noted in FAR 43;!,i.e., repair station, mnufacturer, holder of an inspection authorization, etc. The.installation verification should ensure, but .
is 1y)t limited to, the following:
' e 4 1
(1) TheVNWEquip nt Installati& does not interfere with the norml operation of other equipllent installed in the aircraft. This is acamplished by a ground test and flight test to check that tk VW.. a-t is not a source of objection& electromagnetic interference @ML), is functioning properly and , safely, and operates in accordance with the mmufacturer~s specifications.
(2) The Structural-Mounting of the VNAV Quiptrent is sufficient to ensuretherestraintof theequipmentwhensubj~edtothe'~gencylanding loads appropriate to the aircraft category. ' .
(3) A Vertical Navigation Sour& Annunciator is Provided on or adjacent to the display if the VNAV equipent installation supplies any information to displays such as a horizontal situation indicator (HSI) or course deviation indicator (CD11 tiich can also display information from other systm normally ' used for aircraft navigation. c r1 'i * I
(4) The VNW IEQuipsrrent @ontrols and Displays are Instkled with a placard(s) which states %J?W Qui-t Not Approved for IFRrtt
(5) The VNW Equipnt May Not Be Coupled to an autopilot or flight director unless the same installation has previously been made using the Sara VNZW equi-nt, autopilot, and/or flight director in the S~IIE aircraft under I either Tc or STC approval. . i 1, i . t E
b. WAS7 Quipnt Installations Used for *rations Under IFR. Acceptable criteria for approval of WAS7 equipment to be used under IFR are contained 'in this advisory circular. The initial certification of a,VNW system requires an engineering evaluation because of the need to verify &fo-ce, failure indications, envirolurrental qualifications, etc. Subsequent installations of the 3' same VNAV quiprrrent systeminother aircraft may require'additionalengineering Par. 5 3
AC 2O-li?9 g/12/88 evaluation, depending upon the degree of integration of the system with other aircraft systems, inparticular autopilot andflightdirector system, VNW systems for use under IFR should provide the following:
(I) Fliqhtcrew Inputs of:
(i) Altitude associated with the active waypoint in term of feet at least to the nearest 100 feet for en route and terminal flight phases and 10 feet for the approach phase. If provided, wygoint horizontal position in incrercrents Iy)t greater than 0.1 nautical miles (rmi) or 0.2 degrees karing from the waypoint.
(ii) Ascent or descent angle in terms of degrees at least to the mares t 0.1 degree, fnr amiimnnnt e&i& crruylli fi nc rrrrrAi ant anrrl ne &WA bybupIbAAb bayshA& &KS&9 YAULUGAAL uuy’LfG3 0
(iii) Station elevation, if necessary for eq&pnt erqloying slant range error correction, in term of feet, at least to the nearest 1,000 feet for en route and terminal flight phases and 100 feet for the awroach phase.
(iv) For terminal and approach operations, the ability to enter the altitude associated with at least eight (for to-frm equi-t) or nine (for to-to qui~nt) successive waypoints.
W A rrreans to confirm correctness of input data prior to utilization of the new data by the system,
(2) The system displays should qive no operationally misleading information and should provide:
(i) A continuous display of vertical path deviation with En Route/Terminal Approach (feet) (feet) Minimum Full-Scale Deflection >500 * >150 Readability 7100 7 30 Minimum Discernable bbvemmt 7 10 75 * NOTE: Smiler values of minirrtum full-scale deflection for approach may be acceptable provided th6“proposed value is found satisfactory by an engineering evaluation.
(ii) Entry of waypoint altitude in tam of feet to at least the nearest 100 feet for en route and terminal flight phases and 10 feet for the approach phase.
(iii) A vertical guidance presentation compatible with the aircraft% flight inst -t&ion such that the pilot is continuously furnished vertical deviation of the aircraft with respect to the preprqrmmzd ascent/ descent or level flight profile.
(iv) An annunciation of iqending vertical waypoint crossing.
4 Par 6
g/12/88 AC 20429
(3) Caution Indicationk) for the System Should Be bxated on or near the indicator specified in paragraph 6b(2) (i) and should provide a readily di~ernible caution indication(s) to the pilot(s) for any of the folluwing:
(i) Inadequate or invalid navigation signals or sources.
(ii) The absence of primary puwer.
(iii) Inadequate or invalid navigation displays or output sources.
(iv) Equipnt failures.
ISKKPEi: These failure/status indications shall occur independently of any operator action. EQww or navigation quipnt failures my be indicated in a com0n manner. In the approach mde, the lack of adequate navigation signals or sources shall be annunciated by mans of a flag displayed on the primry vertical navigation display. In other mdesI an appropriately located annunciator IIlEty be used.
(4) The System Shall Be Capable of Providinq Navigation Guidance to the accuracy specified in paragraph 8 within 20 seconds after input of the desired vertical track information (assuming sensor outputs are available).
(5) The System Shall Gorrect IME Range for Slant Range error unless it is demnstrated that the accuracies specified in paragraph 8 cxn be achieved without slant range error correction.
(6) Navigation Guidance Should Be Available within five seconds of waypoint data input.
(7) The IQuipnt Should Have the Capability to met the criteria outlined in paragraph 6b(l) through 6b(6) throughout the range of environmntal conditions which-will be em&&red in act& service. &posureoftheequiprrrent to the envirommtal test conditions of ED% C60b, C115, or Cl20 may be used to d-n&rate this capability. For VNKV systems certified independent of an area navigation system, the enviromental test conditions contained in KTCA Bxumnt No. D16OB may be used to demonstrate this ability.
(8) The Equivnt Should Provide a Means for the Flightcrew to determine system status prior to flight.
(9) The Equip-rent Should Provide the Navigation Accuracy specified in paragraph 8 for all. groundspeeds up to a maximm value to be set by the manufacturer and for all ascent and descent rates up to a mximum value to be set by themanufacturer.
(10) The l!QuiFt Should Provide Means to Alert tk Flightcrew prior to arrival at a wamint to permit anticipation of necessary vertical maneuvering. This indicator sbuld be located on or m&the indictor specified in paragraph 6b(2)(iL For VNWqui~tthatis notcoupledtoa flight director or autopilot, a procedural mxms based on a amtinmus and properly located distance to waypoint display my be used for vertical mneuver Par. 6 5
AC 20-129 g/12/88 anticipation. Systems which provide steering signals for flight directors or autopilots should provide automtic vertical mmewer anticipation and a waypoint alert which occurs prior to the initiation of the vertical meuver.
System that are coupledto theautoatic guidance/oontrolsystemO shoUldnot cause the aircraft to depart an assigned altitude until the iqending altitu& change is indicated to the crew within the pilot's primary field of view, then acknowl&ged by tirrrrely crew action. If thisacknmledgmntisstored bythe quipmnt, acceptaxe of the acknowledgmmt should mt precede the indication.
The timing of acknowledgmmt of an impending vertical path change is dependent on operational procedures and aircraft/w-t design; howlever, past practice has shown that this aclawrwledqznt should mt ocmr mre than five minutes prior totheirrpendingverticalpathchange.
(11) If a Capability for Parallel Offset Tracks is Provided, waypoint alerting and vertical maneuver anticipation should be provided prior to arriml at the point where the offset track intersects the angle bisector of the parent track. These functions should opeYate as described in paragraph 6bUOO.
(12) The Ii!Zquipt Shmld Be Capable of Providiq correct vertical path guidance when interfaced with lateral navigation equiprwJnt providirq turn anticipation. The WAS7 equipment shotid recqnizetheangle bisectorofthe lateral track change as the "zero distance to waypoint" location.
c. SahmreChaqes. Tk provisions of this paragraph apply to VNW equipment which utilizes a digital coquter to provide navigation information for system monitoring. Tkccmputer progmm (software) operatesthecargder and provides the basic functions of these system. The software for navigation functions of VW7 equiptent described in paragraph 6b (for VNAV equipnt used for IFR operations) should be verified and validated to at least the level 2 rquiremaks as defined by RICA/DO-178A. Any changes to software which affects navigation functions are considered to be mjor changes to the quiFprrent.
Unless software ptitioning has been previously established, any change to Ieve 1 or&& 2 software of WAS7 quipmnt should be verified and validated to the appropriate level and should be demonstrated as not having inadvertently affected the remining navigation functions. manges to softwareusedfor VNW equi-t limited to VFR use or equiwnt having established partitioning frcxn software &ich provides navigatioml functions in IFR systm are considered to be minor and do not rquire prior approval by the FAA, providing the rrmufacturerof the VNW equipmnthas a software configurationmnagntand quality assurance plan approved by the FAA. All software changes must be identified on the outside of the associated line replaceable unit in accorda&e with the criteria of RTCA/Do-178A. SoftwarechangesinTSO approvedequi~nt must be reported to the cognizant Aircraft Certification Office. If the equipnt displays a software identifier to the flightcrew, the airplane or rotorcraft flight mnual (or appropriate placard) should indicate*the approved identifier. Software changes incorporated in equipent already installed in an aircraft rmy require additional evaluation and possible flight mnual revision prior to returning the aircraft tO service, d&ending up&the smpe of the change.
6 par. 6
g/12/88 2c 20429 7 l ~mP@!mIXNSU&LZWION~IS6IDEEWI OKSFORUSEUNDER IF'R.
a. l&cation of the VPSIV System Display. Each display ekmnt, used as a qimary flight instruent in the guidance and control of the aircraft, should be l-ted where it is clearly visible to the pilot with the least practicable deviation fran the pilot's normal position am3 line of vision when looking forward along the flight path.
b. Failure Protection. Anyprobablefailureoftheairborne VN?Wsysten, should mtdegradethenormloperationof other requiredquipnentor createa flight hazard. I!bnml operation of the VN?W equimt installation should not adversely affect theperfominceof otheraircraftquiptlent.
c. Ekwirormzntal Conditions. The aircraft environmnt in which the VNKV systemis installed shouldbe found to becoqatible with the envirommtal categoriestowhichtheequi~twastested.
d. E&ctrmaqnetic Interference. The~Vsystemshouldnotbethesource of objectionable electranagnetic interference f nor beadversely affectedby electromagnetic interference from other quipmnt in the aircraft.
e. Dynamic Responses. The system should indicate aircraft vertical position to the accuracy specified in paragraph 8 within five seconds after any maneuvering or changes in attitude encountered in nomal operations.
f, System Controls. The system controls should be arranged to provide ade- * quate protection against inadvertent system turnoff. The controls for system operation should be readily accessible tm, and useable by, the flightcrew and be visible under all expected lighting conditions, including night and direct sunlight.
g iwolves SystemTests. Tkinitialapproval of a VNM7systemfor IFRuse extensive testing to &rrmstrate operational performance, environmntal qualifications, etc. When no autopilot/flight director interface is provided, subsquent installations of the sam WAS7 systeminother aircraftneedonlybe tested to the extent necessary to demonstrate ‘praper operation of interfacing navigation and display equimt, satisfactory cl~ance of electromqnetic interference U3tI~~ an;d functional check of the VNWequi~t. For thr>se system interfaced with an autopilot/flight director system, each mV/aircraft canbination should be carefully evaluated using the guidelines presented in this advisory circular,
h. Manufacturerls Instructions. VNW equipnentshouldbeinstalledin accordance with instructions and limitations provided by the mufactumr of the equipirrrerrt* 8 l SYSTEMA~.
a. En mute, Terminal and arach IFR Operation in the NAS. The error of the airborne WEW equipnt, excluding altietry, should be less than that shown below on a 99.7 percent pkbability basis:
Par. 7 7 I
AC 20-129 g/12/88 Altitude Region Tpvel Flight segments andCli&/IkscentInterc~t Cli~/DescentAloq Specifi&Nertical of Specified Altitudes Profile bqle) (ft) (ft1 At or below 5,000 ft 50 100 5,000 ft to 10,000 ft 50 150 Above 10,000 ft 50 220 IWIES:
1 I MaxlIlrrum operating altitudes to & predicated on ccarp?liamx with t.&a.l akuracytolerance.
2. VNW guidance may be used in level flight en route as in the case of altitude hold mntrol laws, which are integrated with speed control laws to provide an energy trade. The incremental error coqqnent contributed by the VBW equi-t must be offset by a corresponding reduction in other error conponents, such as flight technical error, toensurethatthe total error budget is not exceeded.
3 . Altimetry Error. Refers to the electrical output and includes all errors attributable to the aircraft altinrretry installation includirq position effects resulting from nor-~& aircraft flight attitudes. In high performance aircraft, it is expected that altixrretry correction will be pro-' vided. Swh correction should be done automtically. In lower perforrclance aircraft, upgrading of the altimetry systm may be necessary.
4. VN?W Quipmnt Error. Includes all error;3 resulting fmmthe vertical guidance quipnt installation. IBes not include errors of the altirrreter system but-do& include any additional errors resulting from the addition of theVNAS7qui~nt. This error corrponent may be zero in level en route flight if the operation is limited to guidance by BS of the altimeter only. It should not be disregarded in terminal and approach operations where the pilot is expected to follow the VNW indications.
b 'Fliqht Technical (Pilotage) Errors.
cal &anceinformation, With satisfactory displays of verticonsensus estirmtes baseduponexperience andscm limited testing indicate that flight technical errors can be expected to be less thanthevalues shownbelow ona three-sigma basis.
Altitude Reqion Ievel Flight Segments Climb/Descent Along andCli&/IkscentIntercept Specified Vertical of Specified Altitudes Profile (angle) et) et) At or below 5,000 ft 150 200 5,000 ft to 10,000 ft 240 300 Above 10,000 ft 240 300 P&r. 8
g/12/88 x 20-129 Sufficient flight tests of the installation should be conducted to verify that thesevalm canbemaintained. Smaller values for flight technic1 errors shouldnotbeexpected,unlesstheVNAVsystemistobeusedonlywhencoupled toanautopilot; hawlevex,atleastthetotalsystemvertical accuracy shown belowshouldbemintained.
If an installation results in larger flight technical errors, the total vertical error of the system (excluding altimetry) shouldbedeterminedbycmmbining equi~ntandflighttechnicalerrors usingtheroot sumsquare (E) mthod.
Theresultshouldbeless thanthevalues listed below.
Imel Flight Sqtmts Climb/DescentAlong andClimb/Descent Intercept SpecifiedVC&cal Altitude Region of Specified Altitudes - Profile (anqle) (ft) et1 At or below 5,000 ft 158 224 5,000 ft to 10,000 ft 245 335 Above 10,000 ft 245 372 9 IFRAIR~REIINESS .APPRDVAL. There are two types of approval which differ gkatlyas totestrequirezilents anddataanalysis.
a. First-Tim Aimrthiness Approval. Thistypeof approval refers tothe very first tim an applicant presents a particular mdel VNW quipmmt for FAA airworthiness installation approval and certification for an IFR Mvigation system. Any new models of VNZW equipment by the sam manufacturer should undergo the sam approval process as the original equipment unless it can be sham by analysis and tests that the new mdel will function as well or better than the approved equipmnt. A first-tixm approval is conducted in three phases:
(1) Lab/Bench Tests and IQuipmnt Data Evaluation. This phase consists of the following:
(i) Analysis of the manufacturer's procedures for verification and validation of software and review of supporting documntation in accordance with the guidelines of EETcA/Do-178A.
(ii) Verification of compliance with appropriate envirommkal qualification standards such as ~DCH6OB.
(iii) Examination of the equipment% display capabilities with eqhasis on warning, caution, and advisory annunciations.
(iv) Analysis of failure-es.
(VI Review of reliability data to establish that all probable failures are detected.
Par. 8 4 9
AC 20-129 (vi> Evaluation of the ease of use of the controls and of the viewing ease of the displays and annunciations from a humn factors pint of view.
(vii) Review of installation and maintenance manuals.
(viii) Evaluation of operator's manual (pilot% guide).
(2) Aircraft Installation Data Evaluation. Normally the mnufacturer of the mV equi-t will provide an aircraft as a test bed for a first-time installation approval. The first-tim installation approval will serve as a basis for subsquent installation approvals on the same type of aircraft inmrporating the sam autopilot/flight director system and for other aircraft installations not incorporating autopilot/flight director interface with the VNW equipment. The following assessments are to be made:
(i) E&view of installation drawings, wiring diagram, and descriptive wiring routing.
(ii)= Emmination of a m&pit layout of the installed equipment with emphasis on quipnent controls, applicable circuit breakers (labels and accessibility), switching arrangerrrent and related indicators, displays, annunciators, etc.
(iii) Analysis of a data flow diagram in order to review Which equipment tranmits aat data to which other equiprent.
(iv) Review of a structural. analysis of the equipnt installation in order to ascertain whether all system mqonents are satisfactorily attached to the basic aircraft structure.
(VI Examination of an electrical load analysis in order to verify that the added eleckrical power rquiremnts of the system installation will mt cause overloading of the aircraft's electrical generating capacity.
(vi) Emluation of the integration with the associated lateral navigation equipment.
(3) Flight Test Evaluations. Flight tests are conducted in txm stages:
(i) Functional Fliqht Tests consist of:
A Evaluation of all operating mdes of the VNKV equipnt.
B Examination of the interface (function) of other equipnt connected to the V&S7 system.
C Review of various failure m&s and associated annunciations such as loss-of electrical power, loss of lateral navigation signals, VNAV equipment failures, etc.
10 Par. 9
g/12/88 AC 20-123 l D Evaluation of steering response while autopilot is coupled to the VNAV quip&& during a variety of lateral and vertical track changes including selection of VN?W modes while operating at the maximm and minimm speeds approved for WAS7 use.
E Gvaluation of displayed VN?N navigation paramters on interfaced flight &ck instrumnts such as HSI, CDI, etc.
F Assessment of all switching and transfer functions pertaining to the VNKV e&xmt including high-pow electrical loads and electrical bus switching.
G Evaluation to determine whether there exists any electro- magnetic or ra&jo Freguency intsfweme *Et= tie VwV eqGpnt insbiiation and other onboard equipxnt, or vice versa, W Evaluation of the accessibility of all controls pertaining to the VNW systeiCinstallation.
I Evaluation of the visibility of the displays and annunciators pertaining to-tie VNKV system installation during day and night lighting conditions, No distracting cockpit glare or reflections my be introduced.
J Analysis of crew wmkload when operating the VNAV -
(ii) Determination of Naviqation Error Flight Test. The initial certification of each VNAV system to be used for IE'R operations should be based on a demonstration of system performance by recording the VN?W equipment vertical guidance and co-ring it to the actual position of the aircraft along a pre-established vertical flight path. This evaluation can be made by use of theodolite observation, cowison against Instrmmt Landing System (or microwave landing system (MLS)) glide path signals, or by equivalent masuring techniques. Data should be gathered usirq a variety of descent/ascent rates, angles, and lateral navigation source inputs available to the W!U7 system. The data should demonstrate that the appropriate accuracy criteria of paragraph 8 are met on a 99.7 percent probability basis. Flights into kmwn poor performance areas, outside system angle and/or rate limits, using large (greater than 100 degrees) lateral track changes, etc. should be evaluated to verify proper operation of caution indications and lateral navigation interface.
Niormal flight maneuvers should not cause loss of system sensor inputs and the system dynamic response should be confim&. Any unusual flight technical errors or errors resulting from use of the autopilot and flight director should beevaluatedandexamined.
b. Followan Airworthiness Installation Approvals. This type of approval refers to installation approvals of the system in the same type of aircraft with the sam autopilot/flight director integration and for other aircraft installations not incorporatiq autopilot/flight director interfqce with the VNAV equipment. Installation of VWW systems in different types of aircraft where autopilot/flight director interface is provided or where a different autopilot/flight director is interfaced with the VNAV equipnt require Par. 9 11
AC 20429 g/12/88 engineering approval, Follmn approvals may use the first time airmrthiness approval, tiich was either a TC or an SIC, as a basis for installation approval.
Folkwen installation approvals my be accomplished by TC or STC, or may be in the form of a field approval on an FAA Form 337. The applicant or installing agency requesting a follow-on VNAV system installation utilizing this method of data approval should:
(1) Contact either the mnufacturer or organization responsible for obtaining the first-tim airworthiness approval in order to:
(i) Obtain a Sample airplane flight rclanual UXFN or rotorcraft flight manual (RFM) supplemnt (or supplemental flight manual, as appropriate).
(ii) Obtain verification of the equipment approval status, including the software program identification and lateral navigation equipmnt that my be interfaced with the system.
(iii) Discuss any problem areas and seek assistance in their solution.
(2) Conduct a similar data evaluation as outlined in paragraph 9a(2).
(3) clonduct flight emluations similar to the flight tests outlined in paragraph 9a(3HiL
(4) Verify that the mximm expected groundspeed of the aircraft is less than khexmximm operating speed for tiich the VNKV quipnt is qualified.
is> Spot check VN?W performance by conducting an evaluation flight incorporating at 1-t three ILS approaches (or MLS corrparing VNAV vertical guidance to that provided by the ILS glideslope) and three nonprecision approaches to a specified minimum descent altitude (not a descent angle).
Accuracy should be verified by comparison to the ILS (MU3 glideslope indication and altimeter reading. The purpose of this test flight is mt to validate VNAV navigation error values, but rather to verify that in the murse of this installation mthing was done to coIrprmise the accuracy of the system as determined by the first-time approval. Significant differences bet-en the vertical path data provided by the ILS MS) glideslope and/or altimeter and VNW equi-t should be evaluated to determine possible causes. If a logical explanation is mt available, additional flight test data points should be collected. If such error(s) persists, approval of the installation should be withheld.
10. OPERATIONAL CONSIDERATION,
a. Operation in the NAS. VNAV equipment my be used to provide supplerrrental vertical path guidance to aid in more efficient and precise operation of the aircraft. The altimeter shall always be the priory altitude reference for all flight operations.
112 Per. 9