What must a failure detection system indicate to the pilot and to systems utilizing radio altimeter data?

A failure detection system must be incorporated to indicate a failure of the radio altimeter to accomplish its intended function because of: (1) loss of power, and (2) loss of signal or altitude sensing capability when within the manufacturer's stated operating altitude range.

What accuracy requirements apply to altimeters with rate outputs for heights from 3 to 100 feet and rates from 0 to 15 ft/sec?

For heights 3-100 ft and rates 0-15 ft/sec, accuracy must be ± (1.5 ft + 0.01 h + 0.1 |r|) ft/sec for at least 95 percent of all observations.

What accuracy requirements apply to altimeters with rate outputs for heights from 100 to 200 feet and rates from 0 to 20 ft/sec?

For heights 100-200 ft and rates 0-20 ft/sec, accuracy must be ± (2.0 ft + 0.01 h + 0.1 |r|) ft/sec for at least 95 percent of all observations.

Appendix 1 to ETSO-C87a - Modifications and Additions to EUROCAE ED-30 for Minumum Performance Standards for Low-Range Radio Altimeters

Q: What should an applicant do if they desire alternate accuracy requirements not meeting ED-30 paragraph 3.2.1?

The applicant should apply for a deviation in accordance with paragraph 3.g of ETSO-C87a.

Q: What must be included with the application for ETSO if a radio altimeter is designed and tested to tighter accuracy requirements than Category C?

Include the design information, test results, and limitations with the application for ETSO and document the performance in the installation manual.

Q: Which document should be referenced for external loop loss standards instead of TSO-C87 and RTCA/DO-123?

Reference RTCA/DO-155, Minimum Performance Standards Airborne Low-Range Radar Altimeters, Appendix B, for external loop loss standards.

Q: Is a rate data output required for compliance with the minimum performance standard?

No, the equipment need not provide a rate data output as a condition of compliance.

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Appendix 1 to ETSO-C87a –
Modifications and Additions to EUROCAE ED-30 for Minumum Performance Standards for Low-Range Radio Altimeters

ED Decision 2013/012/R

1.0. ED-30 REQUIREMENT MODIFICATIONS

1.1. ED-30 Paragraph 1.3 (Radio Altimeters with Auto-Surveillance). ETSO-C87a does not include a separate category for monitoring. Design the radio altimeter to support the failure condition classification of the intended installation.

1.2. ED-30 Paragraph 2.2 (Transmitter Operating Frequency). Add the following requirement to ED-30, paragraph 2.2: The radio altimeter shall meet the International Telecommunication Union (ITU) regulations, if applicable.

1.3. ED-30 Paragraph 2.5 (Failure Warning). Add the following sentence to the beginning of ED-30, paragraph 2.5, to clarify that a failure detection system is required: ‘A failure detection system must be incorporated in the equipment to indicate to the pilot, and to any systems utilizing the radio altimeter data, of a failure of the radio altimeter to accomplish its intended function because of the following conditions: (1) Loss of power, and (2) Loss of signal or altitude sensing capability when within the manufacturer’s stated operating altitude range.’

1.4. ED-30 Paragraph 3.2.2 (Category A2). ETSO-C87a does not include Category A2. If alternate accuracy requirements not meeting the requirements of paragraph 3.2.1 are desired, the applicant should apply for a deviation in accordance with paragraph 3.g. of this ETSO.

1.5. ED-30 Paragraph 3.2.4 (Category C). ETSO-C87a does not include Category C. If the radio altimeter has been designed and tested to tighter accuracy requirements, include the design information, test results, and limitations with the application for ETSO and document the performance in the installation manual.

1.6. ED-30 (Appendix). The ED-30 appendix references TSO-C87 and RTCA/DO-123 for external loop loss standards. As TSO-C87 and DO-123 are no longer current, reference RTCA/DO-155, Minimum Performance Standards Airborne Low-Range Radar Altimeters, Appendix B, for external loop loss standards instead.

2.0. REQUIREMENT ADDITIONS to ED-30: Rate Data. The equipment need not provide a rate data output as a condition of compliance with this minimum performance standard. Altimeters with rate outputs must meet the following accuracy requirements for at least 95 percent of all observations for heights from the terrain to the antenna:

RATE DATA
Height (ft)	Range (ft/sec)	Accuracy (ft/sec)
3–100	0–15	± (1.5 ft.+ 0.01 h + 0.1 /r/)
100–200	0–20	± (2.0 ft.+ 0.01 h + 0.1 /r/)

Where: h = altitude in feet; and /r/ = absolute value of rate (feet/sec.)

[Amdt ETSO/8]

Details

Source-Title: Appendix 1 to ETSO-C87a - Modifications and Additions to EUROCAE ED-30 for Minumum Performance Standards for Low-Range Radio Altimeters View latest amendments

Erulesid: ERULES-1963177438-9178 Compare versions

Domain: Initial airworthiness

Amendedby: Amendment 8

Applicabilitydate: 15 July, 2013

Entryintoforcedate: 15 July, 2013

Regulatorysource: ED Decision 2013/012/R Navigate

Regulatorysubject: CS-ETSO

Typeofcontent: CS (Certification specification)

Parentir: ETSO-C87a

Origin: EASA

Category: EAR

Appendix 1 to ETSO-C87a – Modifications and Additions to EUROCAE ED-30 for Minumum Performance Standards for Low-Range Radio Altimeters

Details

Appendix 1 to ETSO-C87a –
Modifications and Additions to EUROCAE ED-30 for Minumum Performance Standards for Low-Range Radio Altimeters