NMX‑MGB‑30 / Rev 00 / rotorcraft testing / torque loop · mast loads · run-dry 2026 · Product Page

NMX-MGB-30 · ENGINEERED TO ORDER — HELICOPTER MAIN GEARBOX LOAD TEST RIG

The whole helicopter hangs from it. Prove it on the ground.

Name: Helicopter Main Gearbox Load Test Rig
Brand: Neometrix

A main gearbox takes two turbine inputs at ~20,000 rpm down to a rotor's few hundred — near 80:1 — while the aircraft's entire lift and hub moments pass through its case. Engines are duplicated; the gearbox is one, and even autorotation needs it turning. The rig that proves it is built around three ideas. Circulate the power: article against slave gearbox in a closed torque loop, so megawatts go round and the motor pays only the losses. Load every path at once: lift and moments hung on a dummy mast while the loop runs, because case distortion is what moves tooth contact. And the certification case is losing the oil — drain it on command, keep recording, stay turning on the order of thirty minutes. The rig does deliberately what the aircraft must survive. No delivered helicopter gearbox rig is claimed.

Enquire — gearbox load test rig Capability sheet (PDF)

Illustrative image, not a delivered system — a newly built back-to-back gear test rig in a clean test hall: two freshly painted grey ribbed gear cases with bright machined flange faces on a fabricated grey bedplate, their connecting shafts enclosed in solid safety-yellow coupling guards, a dark finned drive motor at one end, neat black lubrication hoses and bright steel pipes dropping into a clean shallow drip tray, an orderly tool-board workbench along the far wall, light-grey floor with crisp yellow walkway lines, daylight through the hall door, no people and no readable markings

Fig · 01 Back-to-back — two gearboxes locked in a torque loop, megawatts circulating, the motor paying only the losses — illustrative, not a delivered system

Reduction

~80:1turbine in, rotor out

Power

circulatedthe motor pays losses

Loads

all at oncetorque + mast + tail

The case

run-dryoil gone, still turning

Record

decadessubstantiation is the point

ISO 9001 / 14001 Engineered to order Delivered transmission-rig franchise Turnkey commissioning Noida · India

Overview

One gearbox. No second chances.

Rotorcraft carry two engines precisely so one can fail. There is no such arithmetic for the main gearbox: one case, one train of gears, every newton of lift and every horsepower of drive passing through it, with overhaul lives measured in thousands of hours that someone has to substantiate. That someone works on this rig.

Illustrative image, not a delivered system — a polished vertical test mast rising from a compact ribbed grey gear housing on a clean grouted baseplate, loaded by a rigid overhead frame of light-grey box-section columns: new hydraulic cylinders at different working angles pull on a bright machined hub flange through clevis-ended tie rods, their black hoses looping in natural unequal curves to a tidy manifold, a fresh yellow safety railing behind and a clean hydraulic power pack with cooler beyond it, swept floor with faint scuff arcs, no people and no readable markings

Fig · 02 The mast frame — lift, bending and side loads hung on a dummy hub while the torque loop runs underneath — illustrative, not a delivered system

Circulate the power; pay only the losses. Absorbing megawatts in a brake means buying megawatts, then cooling them away all day. The back-to-back answer locks the article against a slave gearbox in a closed loop and winds torque in with a twist unit; the megawatts then circulate around the loop and the drive motor supplies only the few percent that friction takes. The price of the elegance is that the loop is a torsional system in its own right — analyse its dynamics or it resonates at exactly the mesh orders you are trying to measure.

Torque alone is a flattering test. In flight the mast carries the aircraft — tonnes of lift, hub bending, side loads — and that load path distorts the case, which moves tooth contact and bearing alignment. So the rig hangs those loads on a dummy mast and hub through an overhead hydraulic frame while the torque loop runs, and loads the tail take-off and accessory pads besides. Combined loading is not a refinement; it is the difference between testing the gearbox and testing a gearbox-shaped object.

And the famous case is failure. Certification demands the gearbox keep turning, under power, for on the order of thirty minutes after the oil is gone — the crew's time to put it down. A rig must therefore do something rigs are normally built to prevent: create the failure on purpose, drain on command, keep every channel alive while temperatures climb, and contain whatever the ending is.

We engineer the rig — bedplate, torque loop, loading frames, lube and run-dry systems, drives, acquisition, protection, containment — including to your specification and drawings, beside our delivered vehicle-transmission test rigs. The gearbox under test and its design are yours.

Circulated

Megawatts in a loop

Back-to-back architecture — full power on the gears, a fraction at the wall.

Combined

Every path at once

Torque, lift, moments, tail and accessories together — the case shape flight actually sees.

Survivable

Run-dry, on record

The oil drained deliberately, every channel recording, the outcome contained.

Architecture

Spin, wind, hang, run.

The schematic follows the test — the article at speed, torque wound into the loop, the aircraft's loads hung on the mast, the spectrum run to a certificate — and the machine underneath: torque loop and drives, loading frames, lubrication and run-dry, acquisition and protection.

FIG · 03GEARBOX RIG ARCHITECTURE · TORQUE LOOP + DRIVES / MAST + TAIL LOADING / LUBE + RUN-DRY / DAQ, PROTECTION & RECORD

Fig · 03 Do deliberately, safely, what the aircraft must survive

Arc · 01

Torque Loop & Drives

Article, slave gearbox and twist unit on a bedplate stiff enough to stay aligned through thermal growth — with the loop's torsional dynamics analysed first.

Arc · 02

Mast & Tail Loading

Overhead hydraulic frames on a dummy mast and hub — lift, bending and side loads applied while the loop runs, tail and accessory pads loaded too.

Arc · 03

Lubrication & Run-Dry

Supply, conditioning and per-jet instrumentation — and the drain-on-command system for the one test that must not be improvised.

Arc · 04

DAQ, Protection & Record

Sampling fast enough for gear mesh, trips for overspeed, chip and temperature, containment — and records kept for decades.

Establishing a gearbox test facility, or re-instrumenting one? Send the power class, the gearbox envelope and the test programme — a clause-by-clause compliance matrix within two working days · [email protected]

Send tender spec

Specifications

Reference rig, built to the gearbox.

The parameters below describe a reference rig. Power class, loop architecture, loading capacities, lubrication envelope and channel count all follow from three givens: the gearbox's power and speeds, the load spectrum it must be proven against, and whether the programme is development, production acceptance or overhaul substantiation.

Illustrative image, not a delivered system — a newly assembled lubrication oil conditioning skid in a clean plant room: a freshly painted grey reservoir with a bolted lid and clear side sight glass, guarded pump-and-motor sets under yellow mesh guards on top, a plate heat exchanger and twin vertical filter housings with new red changeover levers, small pressure gauges angled away along bright pipework, red and black valve handwheels, new black flexible hoses joining steel pipe runs on a spotless bund tray, clean light walls and a doorway down the aisle, no people and no readable markings

Fig · 04 The lube skid — supply, conditioning, filtration and the instrumentation that turns oil into data — illustrative, not a delivered system

Where gearbox rigs go wrong

Absorbing the power instead of circulating it — megawatts bought, then boiled away, forever. A torque loop with no torsional analysis, resonating at the mesh orders it was built to measure. Torque without mast load, testing tooth contact in a case shape flight never produces. Run-dry improvised on the day, on a machine not designed to survive it. Lubrication treated as a service rather than instrumented as a measurement, so the losses map and the health signals never exist. Alignment set cold and never tracked as megawatt shafting grows with temperature. Acquisition too slow for mesh frequencies, so gear health hides between samples. Containment as an afterthought on a rig whose defining test is a deliberately failing gearbox. And records that stop at handover, when overhaul substantiation — decades of it — is the entire point.

So the discipline runs the other way. The loop is torsionally modelled before it is built, and the bedplate is sized for alignment under heat, not just weight. Mast, tail and accessory loads are applied together with torque, against the spectrum. The run-dry system is engineered as a first-class function — drain on command, protected sensors, containment proven. The lube circuit carries per-jet instrumentation and calorimetry. Acquisition resolves mesh; protection trips are tested; and every run enters a record structured to still make sense to an overhaul engineer twenty years on.

Full specification — expand

System	Helicopter main gearbox load test rig — torque loop, mast & tail loading, lubrication & run-dry, drives, DAQ, protection & containment
Governing Idea	The whole helicopter hangs from it — engines are duplicated, the main gearbox is one, and the rig proves it on the ground
Reduction Context	Turbine inputs ~20,000 rpm to rotor speeds of a few hundred — a reduction near 80:1, in two or three stages, at megawatt powers
Architecture	Back-to-back power circulation — article locked against a slave gearbox in a closed torque loop; the drive supplies only the losses
Torque Application	Hydraulic or phase-shifting twist unit; loop torsional dynamics analysed before build so the rig cannot resonate at mesh orders
Combined Loading	Lift, hub bending & side loads on a dummy mast/hub via overhead hydraulic frames, applied while the loop runs; tail take-off and accessory pads loaded
Run-Dry	The certification case — oil drained on command, gearbox kept turning under power on the order of 30 minutes, every channel recording, outcome contained
Lubrication	A test article, not a service — flow & jet pressure per bearing and mesh, temperature-rise losses map, chip detection, filtration condition
Efficiency	Measured as heat — calorimetry on oil and cooling circuits; a few percent of megawatts is tens of kilowatts
Endurance	Mission-spectrum cycling, overhaul substantiation, vibration baselines correlated to on-aircraft health monitoring
Structure	Bedplate stiff enough that megawatt shafting stays aligned through thermal growth; guarding & containment sized for the deliberate failure
DAQ & Protection	Sampling that resolves gear mesh; trips for overspeed, chip, temperature and pressure; tested aborts; records kept for decades
Siblings	Intermediate & tail gearbox functional rigs · lubrication-pump check facilities · DAQ retrofit & refurbishment of existing rigs
Scope Boundary	Ours: rig architecture, bedplate, torque-loop mechanicals, loading frames, lube & run-dry systems, drives integration, DAQ, protection, containment, installation, commissioning, documentation, training, spares & AMC — including build to your specification and drawings. Bought-in certified: drive motors & VFDs, torquemeters, couplings, slave gearboxes where sourced, chip detectors, DAQ hardware. The customer's: the gearbox under test and its design
The Family	Beside the delivered vehicle-transmission test rigs on this site, and the rotor-test and servo-hydraulic franchises
Status	Engineered to order · quoted across main-gearbox, intermediate and tail-gearbox rig, gearbox test-stand and transmission-rig requirements · no delivered helicopter gearbox rig is claimed on this page

PDF · 1 page

Helicopter Main Gearbox Load Test Rig — Capability Sheet

Tender Response

Send power class, gearbox envelope & programme — compliance matrix in two working days

Variants

One discipline, four rigs.

What changes is the gearbox on the bedplate, and whether the requirement is a new facility or the modernisation of one that exists.

Var · 01

Main Gearbox Load Rigs

Back-to-back torque loop with combined mast, tail and accessory loading — development, acceptance and endurance at full power.

Var · 02

Intermediate & Tail Gearbox Rigs

Functional and load rigs for the right-angle boxes — the same discipline at smaller scale, often on one shared bedplate family.

Var · 03

Lubrication & Pump Check Facilities

Standalone rigs proving lube pumps, jets and circuits — flow, pressure and integrity before the pump ever meets a gearbox.

Var · 04

DAQ Retrofit, Refurbishment & AMC

Modern acquisition, protection and record-keeping on existing rigs — and the refurbishment that keeps a facility believable.

Applications

Wherever gears carry lives and megawatts.

Rotorcraft first — and every heavy transmission after.

A · 01Helicopter programmes — development & production acceptance

A · 02MRO & overhaul re-qualification of gearboxes

A · 03Vehicle & tracked-platform transmission rigs

A · 04Engine & accessory gearbox testing

A · 05Marine & industrial gearing

A · 06Research institutes & certification support

FAQ

Common questions.

Plain-language answers from the engineering team.

Q · 01 Why does a helicopter gearbox deserve its own class of test rig?

Because nothing else on the aircraft combines its duty, its criticality and its loneliness. The duty: two turbine engines delivering their full power at around twenty thousand revolutions per minute, geared down to a rotor turning at a few hundred — a reduction near eighty to one, achieved in two or three stages of gearing that run continuously at combat-aircraft power densities. The criticality: the rotor mast is structurally part of the gearbox, so every newton of lift the aircraft generates, every hub moment and every control load passes through the gearbox case on its way to the airframe. And the loneliness: engines are duplicated precisely so one can fail, but there is one main gearbox, no redundancy, and even an engines-off autorotation depends on it turning freely. Its overhaul life — thousands of hours — has to be substantiated by evidence, and the evidence comes from ground testing: development runs, production acceptance, endurance to a mission spectrum, and re-qualification after overhaul. A rig that can do all of that — full power, full loads, deliberate failure cases, decades of records — is a facility in its own right, which is why programmes procure it as one.

Q · 02 What does “back-to-back” actually mean, and why do it?

It is the trick that makes megawatt testing affordable. The naive rig drives the gearbox with a motor sized for its full power and absorbs that power in a brake or dynamometer — which means buying megawatts of drive, megawatts of absorption, and the cooling to throw it all away, every hour the rig runs. The back-to-back rig instead couples the article to a slave gearbox so their shafts form a closed mechanical loop, then uses a twist unit — hydraulic or phase-shifting — to wind a torsional preload into that loop. Torque now circulates around the loop continuously: the gears carry full load, but the power is recirculating, not being consumed. The drive motor only has to make up the losses — typically a few percent — so a multi-megawatt test runs on a few hundred kilowatts at the wall. Two disciplines come with the elegance. First, the loop is a torsional spring-mass system with its own natural frequencies, and it must be analysed and detuned so none of them sit at gear-mesh orders in the operating range — otherwise the rig manufactures the very vibration it is measuring. Second, the twist unit must hold torque steadily and change it controllably, because the load spectrum is a schedule, not a constant.

Q · 03 Why is mast loading applied at the same time as torque?

Because the gearbox in flight is not merely transmitting torque — it is holding the aircraft up while doing so. Lift arrives as tonnes of upward pull on the mast; manoeuvre arrives as bending moments and side loads at the hub; and all of it reacts through the gearbox case into the airframe mounts. Those loads deflect the case, and case deflection is not cosmetic: it moves bearing outer races, tilts gear axes, and shifts the tooth contact patches that the whole design's life calculation depends on. A rig that applies torque alone tests the gears in a case shape that flight never produces — the results are real numbers about an unreal condition. So a load rig adds an overhead frame with hydraulic cylinders acting on a dummy mast and hub: lift, pitch and roll moments and side loads, applied to the flight spectrum simultaneously with the circulating torque, while the tail take-off shaft and accessory drive pads carry their own loads. The combination is the test. It also drives the rig's structural design, because the loading frame's reactions and the torque loop's reactions all land on the same bedplate, which must stay aligned to shaft-coupling tolerances while carrying them.

Q · 04 What happens in the run-dry test, and what does the rig need for it?

It is the most dramatic requirement in the book: demonstrate that the gearbox, at power, will keep turning for on the order of thirty minutes after its oil is gone — the time a crew needs to get the aircraft on the ground after a lubrication failure. Designers meet it with emergency lubrication schemes, oil-retaining geometry and materials chosen to survive momentary starvation; the rig's job is to prove it, deliberately. That takes engineering most rigs never need. A drain-and-bypass system that removes lubrication on command, cleanly and completely, at a defined test point. Instrumentation that survives the event it is measuring — temperatures climb hundreds of degrees, and the channels must keep reporting through it. Containment and fire provision sized for the honest possibility that the test article does not make the full duration. And a protection philosophy tuned for the occasion: on any other day the rig trips on high temperature; on this day high temperature is the test, so trips are re-armed around different limits with people and hardware protected by design rather than by hope. It is the clearest example of the rig's strange duty: to do, on purpose and safely, the thing the aircraft must survive.

Q · 05 What gets measured, beyond torque and speed?

The interesting measurements are mostly thermal and vibrational, because that is where a gearbox tells the truth about itself. Losses as heat: efficiency at these powers is measured honestly by calorimetry — flow and temperature rise across the oil and cooling circuits — because two to three percent of megawatts is tens of kilowatts, far too large to infer from electrical input alone on a circulating rig. The lubrication map: flow and jet pressure at each bearing and mesh, confirming every point receives what the designers assumed; a starved jet is invisible in overall flow and fatal in service. Chip detection: the primary health signal, watched continuously, with debris captured and analysed because what the metal is says which component is distressed. Vibration: accelerometers resolving gear-mesh frequencies and their sidebands, which is where tooth damage announces itself — and which sets the acquisition rate, because mesh frequencies run to kilohertz and health hides between slow samples. Temperatures across bearings, meshes and scavenge lines; deflections where case behaviour matters. And all of it against the load spectrum, into a record structured for the engineer who opens it twenty years later to substantiate an overhaul-life extension.

Q · 06 What do you build, and what is not yours?

Divided honestly. What Neometrix provides: the rig architecture and bedplate, sized for alignment under thermal growth rather than merely for weight; the torque-loop mechanicals and twist-unit integration, with the loop's torsional analysis; the mast, tail and accessory loading frames and their hydraulic systems; the lubrication supply, conditioning and instrumentation, and the run-dry drain-and-bypass system engineered as a first-class function; drives integration; data acquisition fast enough to resolve gear mesh, with protection trips, tested aborts, guarding and containment; and installation, commissioning, documentation, operator training, spares and AMC — including build to your specification and drawings, which is how such facilities are usually procured. This stands beside our delivered vehicle-transmission test rigs, which carry the same discipline at ground-vehicle scale. What is bought-in certified: drive motors and variable-frequency drives, torquemeters, couplings, slave gearboxes where sourced rather than customer-furnished, chip detectors and acquisition hardware. What is the customer's: the gearbox under test, its design and its qualification requirements. Engineered to order; quoted across main-gearbox, intermediate and tail-gearbox rig, gearbox test-stand and transmission-rig requirements; no delivered helicopter gearbox rig is claimed on this page.

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The rotating-test family from Neometrix.

The delivered transmission rig, the rotor test line, and the actuators beside them — engineered at our Noida facility.

↗ Delivered

Power Shuttle Transmission Test Rig

The delivered vehicle-transmission rig — the franchise this page grows from.

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Rotor Dynamics Test Facility

High-speed rotating machinery, instrumented and proven.

↗ Helicopter Test

Main Rotor Actuator Test Rig

The rotorcraft test family — flight-critical components, proven on the ground.

Browse all Neometrix product lines.

Get a quotation

Send the power class
and the spectrum.

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

Enquire — gearbox load test rig Capability sheet (PDF) +91 7777 876 876

ISO 9001 / 14001 ENGINEERED TO ORDER — HELICOPTER MAIN GEARBOX LOAD TEST RIG POWER CIRCULATED · EVERY PATH LOADED · RUN-DRY ENGINEERED · RECORDS FOR DECADES ENGINEERED IN NOIDA · INDIA

The whole helicopter hangs from it. Prove it on the ground.

One gearbox. No second chances.

Megawatts in a loop

Every path at once

Run-dry, on record

Spin, wind, hang, run.

Torque Loop & Drives

Mast & Tail Loading

Lubrication & Run-Dry

DAQ, Protection & Record

Reference rig, built to the gearbox.

Where gearbox rigs go wrong

One discipline, four rigs.

Main Gearbox Load Rigs

Intermediate & Tail Gearbox Rigs

Lubrication & Pump Check Facilities

DAQ Retrofit, Refurbishment & AMC

Wherever gears carry lives and megawatts.

Common questions.

The rotating-test family from Neometrix.

Power Shuttle Transmission Test Rig

Rotor Dynamics Test Facility

Main Rotor Actuator Test Rig

Send the power class
and the spectrum.

Similar Products

Share This Page

The whole helicopter hangs from it. Prove it on the ground.

One gearbox. No second chances.

Megawatts in a loop

Every path at once

Run-dry, on record

Spin, wind, hang, run.

Torque Loop & Drives

Mast & Tail Loading

Lubrication & Run-Dry

DAQ, Protection & Record

Reference rig, built to the gearbox.

Where gearbox rigs go wrong

One discipline, four rigs.

Main Gearbox Load Rigs

Intermediate & Tail Gearbox Rigs

Lubrication & Pump Check Facilities

DAQ Retrofit, Refurbishment & AMC

Wherever gears carry lives and megawatts.

Common questions.

The rotating-test family from Neometrix.

Power Shuttle Transmission Test Rig

Rotor Dynamics Test Facility

Main Rotor Actuator Test Rig

Send the power classand the spectrum.

Similar Products

Share This Page

Send the power class
and the spectrum.