Appendix A – TAWS installations testing guidance material

General Testing:

(a)     Most of the testing of a TAWS installation can be achieved by ground testing that verifies system operation, interfaces between affected aeroplane systems, correct warning prioritisation, and freedom from unwanted interaction or interference.

(b)     The use of the TAWS as an integrated part of the aeroplane flight deck should be demonstrated. The TAWS should be shown to be compatible with the operation of the installed navigation systems, the airborne collision and avoidance system (ACAS), the windshear warning system, and the weather radar.

(c)      The tests should evaluate the effects of sensor failure on TAWS operation.

(d)     Flight testing should be carried out to evaluate overall operation, compatibility of TAWS with warning systems, navigation systems, and displays, freedom from unwanted interference, and to assess, during adverse flight conditions, instrument visibility, display intelligibility, sound levels and intelligibility of voice announcements, and the effects of electrical transients.

(e)     Adequate flight testing to evaluate the terrain display can be conducted while verifying all the other required TAWS functions. Emphasis could be placed on showing compliance with CS ACNS.E.TAWS requirements during normal aeroplane manoeuvres for all phases of flight. Pop-up and auto-ranging features could be evaluated if applicable. Sustained turns could be performed, to evaluate for example symbol stability, flicker, jitter, display update rate, readability, the use of colour to depict relative elevation data, caution and warning alerts, and overall suitability of the display.

GPWS Testing:

(a)     Flight testing to verify the proper operation of Basic GPWS functions can be conducted in any area where the terrain elevation is known to the flight crew. The following information provides an example of guidance for conducting flight tests to verify the proper operation of each GPWS function.

(1)     Excessive Rate of Descent. Descents toward near level terrain are recommended if they provide the best results and ease of correlation with designed Mode 1 envelopes. This test verifies the operation of barometric altitude (and the corresponding computation of barometric altitude rate) and radio altitude.

(2)     Excessive Closure Rate To Terrain. It is recommended that one level test run at an altitude between 150 m (500 ft.) and 300 m (1000 ft.) above the terrain elevation be conducted. This test will verify the proper installation of the radio altimeter.

(3)     Negative Climb Rate or Altitude Loss After take-off. If it is adequate this test can be conducted immediately after take-off before climbing above 700 AGL or above runway elevation. This test verifies the proper operation of barometric altitude, barometric altitude rate and radio altitude.

(4)     Flight Into Terrain When Not In Landing Configuration. If it is adequate this test can be conducted while on a visual approach to a suitable runway. This test verifies the proper installation of barometric altitude, barometric altitude rate and radio altitude as well as the gear and flap sensor inputs to TAWS.

(5)     Excessive Downward Deviation from a glide slope or glide path. These tests should be conducted, as applicable, during:

(i)      an ILS approach to verify the proper operation of the ILS glide slope input to TAWS;

(ii)     an RNP approach to LPV minima to verify the proper operation of the glide path input from the GNSS receiver or FMS to the TAWS;

(iii)     a GBAS approach to verify the proper operation of the GBAS glide path input to TAWS.

(6)     Voice Callout ‘Five Hundred ft. This test should be conducted during an approach to a suitable runway in order to verify the proper operation of barometric altitude and/or radio altitude.

(7)     Go-around. This test can be performed to confirm that nuisance alerts do not occur during normal go-around manoeuvres.

FLTA Testing:

(a)     Flight testing to verify the proper operation of the FLTA function can be conducted in an area where the terrain elevation for the test runs is known within approximately 90 m (300 ft.). Two test runs can be performed:

(1)     In level flight at approximately 150 m (500 ft) above the terrain of interest.

(2)     While descending toward the terrain of interest.

(b)     In each test case, the terrain display, the aural and visual alerts, the navigation source input, and the terrain data base can each be evaluated if necessary. Confirmation that the specific terrain cells do generate the required alert can also be evaluated if necessary.

Note: To conduct the test as described, the chosen terrain could be for example at least 28 Km (15 NM) away from the nearest airport. If this is not practical, the fly-over altitude will have to be lowered, for example to 90 m (300 ft.) or less above the terrain in order to generate a TAWS alert.

PDA Testing:

(a)     Flight testing to verify the proper operation of the PDA function can be conducted in any airport area within an adequate distance of the nearest runway for example, 18.5 Km (10 NM). The aeroplane should be configured for landing at an adequate height for example, 450 m (1500 ft.) AGL, along the final approach segment of the runway at an adequate distance from the runway, for example, 18.5 Km (10 NM).

(b)     At a suitable point, a normal flight path angle descent, for example, three degrees can be initiated and maintained until the PDA alert occurs. This test may exercise also, if necessary the 500 ft. voice callout.

The adequacy of the PDA aural alert should be verified during this test. If necessary, this test could verify the adequacy of the airport data base, the navigation source input and the barometric and/or radio altitude inputs to TAWS.

Note: The area in the vicinity of the runway selected for this test should be relatively free from terrain and obstacles to preclude activation of the FLTA function. Approximately level terrain along the final approach segment will exercise the PDA function.

(c)      Flight tests should be conducted to verify that conditions at 300 m (1000 ft) AGL within 18.5 – 28 Km (10 -15 NM) of the nearest airport the TAWS system does not generate alerts.

[Issue: CS-ACNS/2]

[Issue: CS-ACNS/4]