Side-by-Side Comparison
Avionics & Flight Operations
Altimeter Pressure Settings vs. ARINC 429 Data Bus
Comparing 2 standards across 10 specifications. 10 key differences identified.
Comparing:
Altimeter Pressure Settings
ARINC 429 Data Bus
Barometric altimeters compute aircraft height based on atmospheric pressure subscale settings: QNH (altimeter indicates true altitude above Mean Sea Level), QFE (altimeter indicates height above airport runway threshold), and QNE (standard 29.92 inHg / 1013.25 hPa for Flight Levels above transition altitude).
The ARINC 429 standard is the predominant two-wire differential data bus used across commercial and transport avionics, transmitting 32-bit digital words over a single transmitter / multi-receiver shielded twisted pair using Bipolar Return-to-Zero (BPRZ) modulation.
Specification Comparison Table
10 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standard Pressure Setting (QNE)
|
29.92 inHg (inches of mercury) = 1013.25 hPa (hectopascals/millibars) | — |
|
US Transition Altitude
|
18,000 ft MSL (Flight Level 180 / FL180) | — |
|
European Transition Altitude
|
Varies by airport (typically 3,000 ft to 6,000 ft AGL) | — |
|
Lapse Rate
|
1.00 inHg per 1,000 ft (~30 ft per 1 hPa/mb) | — |
|
Specification
|
— | Aeronautical Radio, Inc. (ARINC) 429 Mark 33 Digital Information Transfer System |
|
Physical Topology
|
— | Single transmitter, up to 20 receivers (simplex broadcast, point-to-point) |
|
Wiring Medium
|
— | 78 Ω shielded twisted pair cable |
|
Low-Speed Baud Rate
|
— | 12.5 kbps (bit duration 80 μs) |
|
High-Speed Baud Rate
|
— | 100.0 kbps (bit duration 10 μs) |
|
Modulation Scheme
|
— | Bipolar Return-to-Zero (BPRZ: +10V High, -10V Low, 0V Null) |