AAMedP-1.4 minimum requirements for G protective systems

What it is

What AAMedP-1.4 covers

AAMedP-1.4 is NATO's Allied Aeromedical Publication setting minimum requirements for G protective systems: the anti-G valve, the pressure-breathing-for-G (PBG) regulator, and the aircrew anti-G and chest counter-pressure ensembles that protect a pilot against the effects of sustained acceleration in flight. Edition B, version 1 was promulgated in February 2024 and supersedes the previous edition, which nations were required to destroy on receipt. It sets the criteria to be observed in the development, selection and use of anti-G systems, and it acknowledges up front that member nations use different combinations of equipment depending on the degree of protection an aircraft or role demands, rather than mandating one design.

This is a document for those who develop, select and use anti-G systems, not a general framework for a software or services supplier. It names no certification scheme for an organisation, and it does not itself set a contract clause: like every NATO Allied Publication, it reaches a company through a nation's own procurement specification or a contract that names it.

Anti-G protection methods

The document names the range of methods member nations use, without mandating which one an aircraft must carry: the anti-G straining manoeuvre alone, the only protection some aircraft have, whose effectiveness depends on trained technique that fatigue can erode (training and use of the manoeuvre itself sits in STANAG 3827, not here); anti-G trousers, in partial or full-coverage designs, which can be combined with a chest counter-pressure garment for high-altitude protection; trousers used with the straining manoeuvre, the primary means of protection in many fighter and most attack aircraft; and that same combination with a PBG system added, which reduces the respiratory effort of straining and is common at the higher end of the sustained-acceleration range. Separately, the anti-G system as a whole must maintain adequate operating and breathing-oxygen pressure across the aircraft's full range of cabin altitudes, including after a decompression, and keep functioning across a stated range of hot and cold environmental temperatures, including for a period after exposure to more extreme cold. This page does not reproduce the specific altitude, pressure or temperature figures involved.

The anti-G valve

The valve senses the acceleration applied to the seated aircrew member and delivers a corresponding inflation pressure to the anti-G trousers; several different pressure schedules are in use across member nations, and more have been proposed, rather than one being mandated. The document sets a minimum speed at which the valve must inflate the trousers as acceleration rises, a stricter target where a PBG system is fitted, an optional pilot-selectable pre-inflation feature, and a comparable requirement for venting pressure as acceleration falls. It caps the valve's maximum outlet pressure under both normal and failure conditions, and it requires a press-to-test feature so a crew can verify the system works before flight, with an additional breathing-pressure check where PBG is fitted. None of the speed, pressure or altitude values behind these requirements are reproduced here.

The PBG breathing regulator

These requirements apply in addition to STANAG 3198's own requirements for the regulator, not in place of them. The PBG schedule is deliberately sequenced so pressure breathing cannot begin before the anti-G trousers are already adequately inflated, a safety interlock rather than a numeric limit, and a straight-line or a more complex pressure-to-acceleration relationship is acceptable provided that interlock holds and a single agreed ceiling on mask pressure is respected. Where a pressure-breathing-for-altitude system is also fitted, the regulator delivers whichever of the two schedules calls for more pressure at a given moment, rather than adding them together. It sets a speed requirement for reaching target pressure as acceleration changes, a press-to-test feature comparable to the valve's, and an optional mode selector for use without a chest counter-pressure garment, which is explicitly not mandatory for PBG use since the evidence found no added risk of lung over-distension at the accelerations concerned, though tighter mask-pressure limits then apply, including on the press-to-test feature, below a stated acceleration threshold. A relief valve limits pressure spikes from head movement, hose pumping or the regulator's own overshoot, with a larger allowance for the brief surge that follows a rapid decompression, larger again where a chest counter-pressure garment is worn, and briefly larger still for a very short transient. This page names that these limits exist without printing the pressure or time values themselves.

Aircrew anti-G ensembles

General requirements apply across the trousers and chest garment together: flexible, comfortable material that limits heat stress; a restraint layer that limits inflated growth and holds a defined safety margin above normal operating pressure before bursting; a preference for flame-retardant material; and no hazardous or toxic smoke, fumes or gases from burning or heating the garment. Fit must be adjustable and snug without limiting the range of motion needed for normal operations or emergency egress, since fit is treated as critical to the equipment working at all, and the garment must don and doff quickly without assistance, ideally with zippers for a looser non-flying fit. It must be compatible with the rest of the aircrew equipment ensemble and the cockpit, not obstructing controls or visibility when inflated, and its connectors must disable PBG when the trousers are disconnected, resist inadvertent disconnection, and ideally warn the crew if it happens; participating nations must share information to help adapt ensembles to other aircraft types.

Coverage is specified separately: the trousers cover the abdomen below the rib margin down through the thighs and calves, with full or extended coverage preferred where a PBG system is fitted, and the chest garment covers the entire upper torso above the trousers, including the diaphragm and front of the chest. Both garments' supply hoses must resist kinking and crushing.

Annex A fixes the terms the rest of the document relies on: G and its axes, with Gz, the head-to-seat axis, singled out as the one that matters operationally; the anti-G system as a whole and each of its components; the anti-G straining manoeuvre; G tolerance; and pressure schedule. The annex's own definition of G tolerance touches on physiological symptoms and how tolerance is measured; this page names that the annex defines the term rather than reproducing that clinical detail.

How it binds

AAMedP-1.4 binds through NATO's standardisation process. Its own Letter of Promulgation records that it "has been approved by the nations in the Military Committee Air Standardization Board," and that "the agreement of nations to use this publication is recorded in STANAG 3200," which is the cover that gives it force. Nations recorded specific reservations at promulgation: the Czech Republic noted its aircraft met the requirements only in principle pending new equipment, France declined to implement one clause on pressure-reduction control because it uses a different method to the same end, and the United States recommended ratifying with a reservation limiting its own procurement and training beyond current national requirements. AAMedP-1.4 does not bind a company directly: a nation carries its requirements to a supplier through a procurement specification, an airworthiness requirement, or a contract that names it, typically as part of a wider aircraft or aircrew life-support equipment programme.

How you are evaluated

AAMedP-1.4 names no accredited certification body, notified body or self-declaration scheme, and it describes no process by which an organisation becomes certified against it. What it sets are minimum technical requirements for the anti-G valve, PBG regulator and ensemble; demonstrating that a specific system meets them is left to a nation's own procurement, airworthiness and qualification process, run against whatever contract or specification incorporated AAMedP-1.4 in the first place. The document's own built-in check is the press-to-test feature it requires on both the valve and the PBG regulator, which lets a crew verify a fitted system's function before flight, a crew-level function check, not an audit of the organisation that designed or built the system.

Standards it references

• [STANAG 3200](/standards/stanag-3200) - the NATO agreement recording nations' commitment to use this publication; the document's own Letter of Promulgation names it as where that agreement is recorded, and it is the cover that gives AAMedP-1.4 its force.
• [STANAG 3198](/standards/stanag-3198) - the PBG breathing regulator requirements apply "in addition to the requirements of" this STANAG, building on it rather than replacing it; separately, aircrew anti-G ensembles may be used for high-altitude emergency descent protection "as described in" the same STANAG, a more informational cross-reference.
• [STANAG 3827](/standards/stanag-3827) - named as where the requirements for training and use of the anti-G straining manoeuvre are addressed, rather than in this document.

Standards it references

• STANAG 3198Binds
• STANAG 3827Background