NMX‑SAT‑650 / Rev 01 / Air Cycle · DGAQA GE-279 / Noida · India 2026 · Product Page

NMX-SAT-650 · ENGINEERED TO ORDER — DGAQA GE-279 DESIGN

Aircraft ground air-conditioning cart. Cold air from air. No refrigerant at all.

Name: Aircraft Ground Air-Conditioning Cart — Service Air Trolley SAT-650
Brand: Neometrix

A self-contained, towable ground cart engineered to the Indian Air Force’s DGAQA GE-279 specification for the Service Air Trolley: 650 CFM of dry, oil-free air at 5–15 °C into the instrument, radar and avionics bays of Su-30 family aircraft on the ground — and 50–65 °C hot air to drive off the moisture that condenses on them. The cold comes from an air cycle, not a refrigerant: a screw compressor and a screw expander sharing one bull gear. Nothing to leak, nothing to re-gas, and it cold-starts at −20 °C.

Enquire — ground support equipment Capability sheet (PDF)

Representative render — aircraft ground air-conditioning cart on an airfield apron: olive-grey multi-door canopy with louvred cooling grilles on a twin-axle chassis with all-terrain tyres, A-frame tow bar, roof lifting eyes, corner obstacle lamps, gauge panel behind an open door and a heat-insulated air hose coiled on the side

Fig · 01 The cart — representative render of the GE-279 envelope: 4,675 × 2,150 × 2,000 mm, ~4 tonnes, towable

Cold Air Flow

650CFM · oil free

Cold Air Temp

5–15°C at the outlet

Hot Air Mode

50–65°C · moisture removal

Refrigerant

Noneair cycle

Ambient

−20 to +50°C · cold start −20 °C

ISO 9001 / 14001 Designed to DGAQA GE-279 Air cycle — no refrigerant AN-32 transportable Noida · India

Overview

The aircraft is parked. The avionics are still cooking.

A fighter’s radar and avionics bays are cooled in flight by the aircraft’s own environmental control system, driven by engine bleed air. On the ground, with the engines shut down, that cooling stops — and on a 45 °C apron the boxes keep making heat. Ground testing, arming, avionics checks and turnround all need the bays held at a temperature the equipment was designed for.

Representative render — the heat-insulated ground-cooling hose and its machined aluminium adaptor coupled to a ground-cooling connector on the underside of a grey military jet fuselage, with faint condensation misting at the joint

Fig · 02 The connection — insulated hose and adaptor at the aircraft’s ground-cooling port (representative render)

The Service Air Trolley is the answer the specification writes down: a diesel-powered cart, towed to the aircraft, that pushes 650 CFM of dry, oil-free air at 5–15 °C through a heat-insulated hose into the instrument, radar and avionics bays of Su-30 family aircraft. Then it does the opposite job: switched to heating, the same machine delivers 50–65 °C air to wipe out atmospheric moisture that has condensed and deposited on the avionics — the quiet killer of connectors and boards in a monsoon climate.

What makes it interesting is how it makes cold. There is no refrigerant in the machine. Air is drawn from atmosphere, compressed, cooled, dried, and then expanded through a screw expander that takes shaft work out of it — and air that has given up work comes out cold. Which is why the cart carries no gas bottle, no charge to leak, and no re-gassing schedule.

The working fluid is the air the cart is standing in. It cannot leak what it just breathed.

Designed · DGAQA GE-279

A specification, answered clause by clause

The design responds to DGAQA GE-279 Issue-I line by line — duty, flow, temperatures, air quality, climate, envelope, noise, engine rating and acceptance testing — as a complete engineered system rather than a bought-in box on a trailer.

Recovery · Common Bull Gear

The expander pays for part of the compressor

Compressor and expander sit on one bull gear, so the work recovered from the expanding air goes straight back into compressing the next lot. That is the specification’s “energy recovery system”, and it is why the engine can be smaller than the compressor’s standalone shaft demand.

Delivered · The Wider Line

The flight line is our home ground

The same ground-support engineering line has delivered oxygen and nitrogen charging & distribution vehicles to the Indian Air Force, a mobile aircraft-engine test facility to an Indian gas-turbine research establishment, and hydraulic servicing trolleys to an Indian military-aircraft manufacturing and overhaul organisation.

Architecture

One engine, two machines, one bull gear.

The schematic below is the whole cart — the air path, the drive train, the work that comes back, and the blend line that sets the outlet temperature.

FIG · 03AIR-CYCLE SCHEMATIC · ENERGY RECOVERY · BLEND CONTROL

Fig · 03 Atmosphere in, cold air out — compressor and expander on a common bull gear, with the expander’s recovered work driving back into it

Arc · 01

The Air Cycle

Atmospheric air is filtered and drawn into a screw compressor. The heat of compression is rejected in an air-cooled heat-exchanger cascade, and the air is dried in a rotary drum dryer to below 3 g of water per kg. It then enters a screw expander, which extracts shaft work as the air expands — a near-isentropic expansion, not a throttle. Air that has done work leaves cold, at 5–15 °C and 0.1–0.5 kg/cm², and goes to the aircraft through heat-insulated hoses and adaptors. Outlet temperature is trimmed by blending dry pre-expander air back in, downstream of the dryer, in the right proportion — fast, stable, and with no penalty for holding an intermediate temperature.

Arc · 02

Energy Recovery

The specification asks for “air cycle technology with energy recovery”, and the bull gear is where the recovery happens. Compressor and expander are driven from one common bull gear in a lubricated gearbox, so the expander is not braking against a dump load — its recovered work is fed mechanically back into compression. The diesel only supplies the difference, which is why a machine of this duty does not need an engine sized for the compressor alone.

Arc · 03

The Dryer That Regenerates Itself

Cold air at 5–15 °C is useless if it arrives wet, so the specification caps water at 3 g/kg. The dryer is a sectored desiccant drum, and the elegant part is how it is regenerated: the hot air leaving the screw compressor is passed over the drum’s sectors in sequence, driving moisture back out of the silica gel before that same air goes on to be de-humidified in its turn. The compressor’s own hot discharge does the regeneration, and it happens without wasting any air — nothing is bled off as purge.

Arc · 04

The Cart Around It

A turbo-charged, water-cooled inline six rated at least 127 BHP gross prime continuous at 1500 rpm per BS 5514 / IS 10002, running at 1800 rpm, with a cold-start kit down to −20 °C; 4-inch aluminium piping on flexible joints to survive the vibration; a PLC with the safety interlocks, which stops the machine and sounds an alarm on any unhealthy condition, and watches the filters for clogging. Around it: a multi-door canopy with a detachable top, obstacle lamps for tarmac movement, a search light for night work, D-shackle lifting points, and noise treatment holding 75–80 dB at 3 m.

Holding a ground-cooling, ACU or flight-line support requirement? Send it across — clause-by-clause compliance matrix within two working days · [email protected]

Send tender spec

Specifications

Reference specification, as designed.

The parameters below follow DGAQA GE-279 Issue-I. Flow, temperatures, engine rating and envelope are re-scoped against your specification and your aircraft.

Full specification — expand

Product	Service Air Trolley (SAT-650) — self-contained, towable aircraft ground air-conditioning cart · design, manufacture, qualification and documentation
Duty	Dry, cold air for effective cooling of the instrument, radar and avionics bays of Su-30 family aircraft during ground operations · hot air to wipe out atmospheric moisture condensed and deposited on avionics
Cooling Method	Air cycle with energy recovery — no refrigerant of any kind · screw compressor and screw expander driven from a common bull gear for optimum power utilisation · compressor draws air from atmosphere
Cold Air	Flow 650 CFM · temperature 5–15 °C · delivery pressure 0.1–0.5 kg/cm² · oil free · water content <3 g/kg of cold air
Hot Air	50–65 °C in heating mode, for moisture removal from avionics
Temperature Control	Outlet temperature trimmed by blending post-expander and pre-expander air in the correct proportion
Air Treatment	Air-cooled heat-exchanger cascade · rotary drum dryer, continuous duty · oil-removal filtration · header drains for condensate · filters interlocked to the PLC against clogging · one set of filter elements supplied with the unit
Prime Mover	Turbo-charged, water-cooled, inline 6-cylinder direct-injection diesel · rated output per BS 5514 / IS 10002 gross prime continuous at 1500 rpm, minimum 127 BHP · operating speed 1800 rpm, low idle 1400–1500 rpm · cold-start kit for engine start to −20 °C
Ancillary Cooling	Finned aluminium tube oil cooler for compressor lubricating oil · copper-tube radiator for compressor jacket water · forced cooling by a fan driven from the engine PTO
Piping	4-inch aluminium piping with flexible joints to handle vibration · heat-insulated air hose and adaptors to the aircraft
Control	Battery-powered PLC carrying all safety interlocks — stops the machine and raises an audible alarm on any unhealthy condition · operator panel in a hinged canopy door
Climate	Outdoor operation · −20 °C to +55 °C · humidity to 95% · wind to 100 km/h · sea level to 2000 m · light drizzle to heavy rain
Duty Environment	Ambient −20 °C to +50 °C · cold start to −20 °C · altitude to 2000 m AMSL
Noise	75–80 dB at 3 m · noise-control treatment applied to the trolley
Envelope	Length 4,675 mm max · width 2,150 mm max · height 2,000 mm (2,150 mm with filter-hood top) · ground clearance 150 mm min · weight ~4,000 kg · transportable by AN-32 aircraft
Chassis	Towable trolley on all-terrain tyres with suitable-capacity axles · D-shackle and rope-catcher lifting arrangements · multi-door canopy with detachable top for maintenance access · sliding battery mounting bracket
Flight-Line Fit	Obstacle lamps for movement on the tarmac · search light and panel illumination for night operation · operable without a highly skilled operator · routine maintenance limited to air, diesel and lube-oil filters
Acceptance	Performance test on rate of flow, delivery pressure, air temperature (cold and hot), water content and oil content · user trial with the store positioned by the supplier · acceptance test on each item for bulk production · material testing of critical components
Documentation	User manual and on-trolley operating instructions in Hindi and English
Status	Engineered to order — designed to DGAQA GE-279 Issue-I · configurable to customer specification and aircraft type

PDF · 1 page

Service Air Trolley SAT-650 — Capability Sheet

Tender Response

Send your specification — compliance matrix in two working days

Variants

One cold-air discipline, many flight lines.

Requirements call this a service air trolley, an air-conditioning cart, an aircraft ground-cooling trolley, a cold air unit or a ground ACU (air-conditioning unit). The architecture answers all of them.

Var · 01

The GE-279 Cart

The 650 CFM, 5–15 °C configuration on this page — air cycle, common bull gear, rotary drum dryer, blend control and hot-air mode — as designed to DGAQA GE-279 Issue-I.

Var · 02

Other Flows & Aircraft

Higher and lower cold-air flows, different outlet temperatures and delivery pressures, and adaptors to suit other fighter, transport and helicopter ground-cooling connectors — the cycle scales; the connection is what changes.

Var · 03

Fixed & Shelter Installations

The same cycle in a hangar-fixed or shelter-mounted form for maintenance docks and avionics bays, where the cart’s chassis, tow bar and obstacle lamps are not needed and mains power replaces the diesel.

Var · 04

The Wider Flight Line

Alongside our delivered ground-support line — oxygen and nitrogen charging & distribution vehicles, hydraulic servicing trolleys, nitrogen charging rigs, aircraft access ladders and washing rigs — from one supplier and one documentation discipline.

Applications

Where it serves.

Wherever avionics have to work with the engines shut down.

A · 01Su-30 family flight lines — instrument, radar and avionics bay cooling on the ground

A · 02Fighter & helicopter squadrons — pre-flight checks, arming and turnround in hot climates

A · 03Naval air stations & coastal bases — hot-air mode against salt-laden condensation

A · 04MRO, overhaul and depot bases — extended avionics ground runs without the aircraft ECS

A · 05Deployed & high-altitude operations — cold start to −20 °C, AN-32 transportable

A · 06Export air forces & MRO operators — subject to Government of India authorisation

FAQ

Common questions.

Plain-language answers from the engineering team.

Q · 01 How does a machine make cold air without any refrigerant?

By making the air do work on its way out. Air is compressed, and the heat that compression creates is rejected to atmosphere in the heat exchangers — so the air leaves that stage at roughly ambient, but at pressure. It is then expanded through a screw expander that is mechanically loaded: the air pushes the rotors round and loses energy doing it. Energy out means temperature down, and the air arrives at the aircraft at 5–15 °C. Worth being precise, because it is often described wrongly: this is not Joule-Thomson throttling, which is what you get from squeezing gas through an orifice and which barely cools air at all at these conditions. The cooling here comes from extracting shaft work — a near-isentropic expansion — and that work is not wasted, it goes back into the compressor.

Q · 02 Why is no refrigerant worth caring about?

Because a refrigerant is a consumable with a compliance file attached. It leaks, it needs recovery and re-gassing, it needs certified handling, it has an ozone and global-warming number against its name, and the number keeps being revised — which means a fleet of vapour-cycle carts bought today can face a re-gas or replacement problem a decade in. An air-cycle machine carries no charge at all. Its working fluid is the atmosphere it is standing in, it cannot leak anything it did not just breathe, and it will not be legislated out of use. The aircraft itself uses an air cycle in flight, for its own reasons: bleed air is already there, and the machines are light.

Q · 03 What is the common bull gear for?

Energy recovery, which the specification asks for by name. The expander has to be loaded by something — the air can only cool by pushing against a resistance. You could brake it and throw that work away as heat. Instead, the compressor and the expander are driven from a single bull gear inside a lubricated gearbox, so the expander’s recovered work is fed mechanically straight back into compressing the next lot of air. The diesel then only has to make up the difference rather than supply the compressor’s whole shaft demand, which is what keeps a 650 CFM machine inside a four-tonne, AN-32-transportable cart.

Q · 04 Why does a cooling cart need a hot-air mode?

Because the enemy of parked avionics is not only heat — it is water. An airframe that has been cold at altitude and then sits in humid air condenses moisture onto exactly the surfaces you least want it on: connectors, boards, waveguide runs. The specification therefore asks the same trolley to do both jobs: cool the bays at 5–15 °C, and blow 50–65 °C air through the same hoses to drive that condensed moisture back off before it does damage. One machine, one connection to the aircraft, two duties — which is the whole reason the requirement asks for a hot-air facility inside a cooling cart rather than a second trolley.

Q · 05 How is the outlet temperature actually held at 5–15 °C?

By blending, not by throttling. A proportion of the air is taken off after the dryer but before the expander, and mixed back into the cold air downstream of it; move the split and the outlet temperature moves, quickly and stably, with no penalty for sitting at an intermediate setting. Taking the blend from downstream of the dryer is the point — the air being mixed back in has already been dried, so the dryness spec and the temperature spec are not fighting each other, and trimming the temperature upward never carries moisture back into the delivery.

Q · 06 What is the status — and can you build to our specification?

The cart is engineered to order. The design exists as a complete clause-by-clause response to DGAQA GE-279 — cycle, machine selection, drive train, controls, envelope and acceptance regime — and manufacture, testing and delivery are undertaken against contract. It sits alongside ground-support equipment we have delivered and commissioned for the Indian Air Force, for an Indian gas-turbine research establishment and for an Indian military-aircraft overhaul organisation — itemised further up this page. Send your requirement — aircraft type, flow, temperatures, climate, connector — and a compliance matrix returns within two working days. Export engagements are managed end-to-end, subject to Government of India authorisation.

↗

Ground support equipment from Neometrix.

Engineered and manufactured at our Noida facility for the flight line.

↗ Flight-Line Gas

Get a quotation

Send your ground-cooling
specification.

The Projects desk replies within two working days with a line-by-line compliance matrix and a budgetary quotation. Write to [email protected] or use the form.

Enquire — ground support equipment Capability sheet (PDF) +91 7777 876 876

ISO 9001 / 14001 DESIGNED TO DGAQA GE-279 AIR CYCLE · NO REFRIGERANT MADE IN NOIDA · INDIA

Aircraft ground air-conditioning cart. Cold air from air. No refrigerant at all.

The aircraft is parked. The avionics are still cooking.

A specification, answered clause by clause

The expander pays for part of the compressor

The flight line is our home ground

One engine, two machines, one bull gear.

The Air Cycle

Energy Recovery

The Dryer That Regenerates Itself

The Cart Around It

Reference specification, as designed.

One cold-air discipline, many flight lines.

The GE-279 Cart

Other Flows & Aircraft

Fixed & Shelter Installations

The Wider Flight Line

Where it serves.

Common questions.

Ground support equipment from Neometrix.

Oxygen Charging & Distribution Vehicle

Nitrogen Generation, Charging & Distribution Vehicle

Universal Hydraulic Service Trolley

Send your ground-cooling
specification.

Similar Products

Share This Page

Aircraft ground air-conditioning cart. Cold air from air. No refrigerant at all.

The aircraft is parked. The avionics are still cooking.

A specification, answered clause by clause

The expander pays for part of the compressor

The flight line is our home ground

One engine, two machines, one bull gear.

The Air Cycle

Energy Recovery

The Dryer That Regenerates Itself

The Cart Around It

Reference specification, as designed.

One cold-air discipline, many flight lines.

The GE-279 Cart

Other Flows & Aircraft

Fixed & Shelter Installations

The Wider Flight Line

Where it serves.

Common questions.

Ground support equipment from Neometrix.

Oxygen Charging & Distribution Vehicle

Nitrogen Generation, Charging & Distribution Vehicle

Universal Hydraulic Service Trolley

Send your ground-coolingspecification.

Similar Products

Share This Page

Send your ground-cooling
specification.