DO-160G Section 4: What Altitude Testing Actually Requires for Airborne Equipment

The test plan cited DO-160G. The Section 4 temperature and altitude test was scheduled at a laboratory with a temperature/humidity chamber. The chamber was capable of −55°C to +70°C and 95% RH. It had been used for dozens of DO-160 programmes. The altitude test was conducted at ambient atmospheric pressure.

Section 4 of DO-160G is the temperature and altitude section. The altitude component requires reduced atmospheric pressure. A standard climatic chamber operates at sea-level pressure. It cannot perform the altitude portion of Section 4 regardless of its temperature range. The test had not been conducted to the standard it cited.

This is not an unusual error. DO-160G Section 4 is frequently misread as a temperature test that also specifies altitude conditions in the equipment category definitions. It is both: a temperature test and an altitude test, with the altitude portion requiring dedicated low-pressure equipment.

01What DO-160G Section 4 governs

RTCA DO-160G, Section 4 — Temperature and Altitude — defines the environmental qualification requirements for airborne equipment across a range of temperature and altitude conditions corresponding to different aircraft installation environments. The current revision, DO-160G, was published in 2010 and remains in effect. In Europe, the technically identical equivalent is EUROCAE ED-14G, referenced in EASA certification specifications and ETSOs.

Section 4 covers three distinct test types: temperature and altitude exposure, decompression, and overpressure. Each addresses a different aspect of the pressure and temperature environment that airborne equipment encounters across its operational life.

02Equipment categories — what they mean

DO-160G Section 4 defines equipment categories based on the installation environment — specifically, whether the installation is pressurised or unpressurised, and the maximum altitude of the aircraft. The category determines the temperature range and pressure conditions used in testing.

The category is determined by the aircraft installation — not by the equipment specification. Equipment that will be installed in the pressurised avionics bay of a commercial aircraft is Category A or B. Equipment installed in an unpressurised wing root compartment on a high-altitude aircraft may be Category D or E. The test plan must state the category and the basis for its selection.

03The three test types

Altitude testing. The equipment is operated at its maximum duty cycle while the test chamber pressure is reduced to the altitude equivalent specified for the category. The test begins at ambient temperature, and temperature is stabilised as pressure is reduced. For Category A equipment, the pressure is reduced to 57.2 kPa (15,000 ft equivalent). For Category F, it is reduced to 3.7 kPa (70,000 ft). The equipment must operate within its specified performance limits throughout.

Decompression testing. The equipment is operating, and the chamber pressure is first set to the equivalent of 8,000 ft (75.2 kPa) — simulating a pressurised cabin environment. The pressure is then rapidly reduced to the maximum operational altitude of the aircraft on which the equipment will be installed. This test applies to Categories C, D, E, and F — unpressurised installations where the equipment could experience decompression if an adjacent pressurised section fails.

Overpressure testing. The equipment is not operating (unless otherwise specified). The chamber is pressurised to a level equivalent to −15,000 ft — a pressure above sea level, simulating ground conditions where the aircraft is pressurised above ambient. This test applies to equipment that may experience overpressure during ground operations.

04The chamber requirement

All three test types in DO-160G Section 4 require a low-pressure altitude chamber — equipment capable of reducing internal pressure below atmospheric to simulate altitude conditions. A standard climatic chamber, which operates at atmospheric pressure, cannot perform any of the Section 4 altitude or decompression tests regardless of its temperature range.

For combined temperature and altitude testing — the most common Section 4 requirement — a combined temperature/altitude chamber is required: equipment that controls both temperature and pressure simultaneously. This is more specialised equipment than a stand-alone altitude chamber, and less widely available. Many commercial test laboratories that offer DO-160 testing have one; not all do.

For decompression testing, the chamber must additionally be capable of rapid pressure change — achieved through a fast-acting valve or equivalent mechanism. The decompression rate requirement varies by category and the altitude differential being simulated. Confirm the chamber's decompression capability before scheduling.

05DO-160G vs MIL-STD-810H Method 500

DO-160G Section 4 and MIL-STD-810H Method 500 both govern altitude testing and both require low-pressure chambers. They differ in scope, application, and the detail of their procedural requirements.

The most important practical difference: DO-160G Section 4 specifies temperature and altitude as a combined test — the equipment is exposed to both reduced temperature and reduced pressure simultaneously. MIL-STD-810H Method 500 addresses altitude (pressure) only; the combined temperature and altitude stress is addressed by Method 520. A programme that tests to Method 500 but not Method 520 has not addressed the combined stress scenario that DO-160G Section 4 covers in a single test sequence.

06ED-14G — the European equivalent

EUROCAE ED-14G is the European publication of the same technical standard as RTCA DO-160G. The two documents are identical in technical content. ED-14G is referenced in EASA certification specifications and ETSOs in the same way that DO-160G is referenced in FAA TSOs.

For equipment being certified for both FAA and EASA approval, a single test campaign to DO-160G / ED-14G satisfies both regulatory references. The test report should cite both document references — RTCA DO-160G and EUROCAE ED-14G — to support dual certification submissions without requiring separate test campaigns.

07What a compliant test report must contain

A test report claiming DO-160G Section 4 compliance must contain:

Equipment category. The specific category (A1, B, D, etc.) and the basis for its selection — the aircraft installation environment and pressurisation status.

Test types conducted. Which of the three test types (altitude, decompression, overpressure) were conducted, and for any not conducted, the technical justification for why they were not applicable to the equipment and installation.

Chamber identification. The low-pressure chamber used, its calibration reference, and confirmation that it is capable of achieving and maintaining the specified test pressures within tolerance. A report citing Section 4 that identifies only a climatic chamber has a provable compliance gap.

Pressure data. The actual pressure achieved during testing, in kPa. The altitude equivalent may be stated for reference, but pressure is the compliance parameter.

Functional test results. Performance assessment during altitude exposure and after return to ambient for all test types conducted.

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