BS G 226:1979

Foreword
Specification
1 Scope
2 References
3 General construction requirements
4 Particular requirements
4.1 Construction
4.2 Performance
5 Tests
5.1 General
5.2 Test conditions
6 Type tests
6.1 Ranging accuracy and hysteresis test
6.2 Damping test
6.3 Barometric pressure scale test
6.4 Instrument attitude error test
6.5 Leakage tests
6.6 Drift and after effect test
6.7 Servo chase rate test
6.8 Friction test
6.9 Threshold test
6.10 Pressure overload test
6.11 Test of failure warning device
6.12 Altimeter-encoder tests (type B instruments only)
6.13 Temperature tests
6.14 Vibration test
6.15 Acceleration test
6.16 Tropical exposure test
6.17 Mould growth test
6.18 Salt mist test
6.19 Electrical tests
7 Production routine tests
8 Production quality tests
Appendix
A Serviceability tests
Tables
1 Altitudes, pressures and permissible errors
2 Test points for barometric pressure scale test
3 Friction test: altitudes and tolerances
4 Test points for altimeter-encoder test
Figure
1 Encoder 'turn-on' voltage limits

Gives general design and performance requirements for pressure altimeter systems having a combined counter and single pointer presentation, either with a panel-mounting indicator associated with its own internal or external pressure sensing mechanism or similar, but incorporating an encoder for altitude reporting purposes. Suitable for instrument systems operating over an indicated range of -2000 ft to +80 000 ft (geopotential) or such other range as may be declared. Complete with a barometric pressure setting facility and may have provision for applying corrections for the aircraft static pressure system error. Includes serviceability tests.

This British Standard specifies the general design and performance requirements for pressure altimeter systems having a combined counter and single pointer presentation in two forms as follows.

1. Type A. A panel-mounting indicator associated with its own internal or external pressure sensing mechanism.
2. Type B. As type A but incorporating an encoder for altitude reporting purposes.

Provision is made for instrument systems operating over an indicated range of − 2 000 ft to + 80 000 ft (geopotential) or such other range as may be declared.

The design includes a barometric pressure setting facility and may include provision for applying corrections for the aircraft static pressure system error.