Common aircraft parts delivered during AOG events
Aircraft are grounded by small components far more often than by dramatic failures. This is what actually moves during an AOG, what each category needs in transit, and the classified items that most often stop a collection at the door.
- The parts that ground aircraft most often are small — what makes them critical is availability, not value
- Avionics and LRUs are the largest category, and their damage is often invisible
- Wheels and brakes are a loading problem: a tail-lift is needed at both ends, not one
- Calibrated tooling arriving out of calibration is worse than tooling not arriving
- Lithium batteries and oxygen generators hide inside larger assemblies — declare at booking
Most AOGs are caused by small things
The mental image of a grounded aircraft usually involves something substantial. In reality the components that ground aircraft most often are the ones that are cheap, small and everywhere.
The reason is simple arithmetic: an aircraft has an enormous number of small parts and comparatively few large ones, and many of the small ones are required for dispatch. A sensor the size of a fist can stop a hundred-tonne aircraft as effectively as an engine problem.
- The parts that ground aircraft most often are small, and frequently not expensive
- What makes them critical is availability, not value
- The transport question is therefore almost never about size — it is about where the nearest serviceable one is
Avionics and line-replaceable units
Probably the single largest category in AOG transport. Modern aircraft are built around units designed to be swapped rather than repaired in place — which is precisely why they travel so often.
| What they are | Flight deck displays, navigation and communication units, control boxes, computers and sensor units |
|---|---|
| Why they move | Designed for replacement rather than in-situ repair, so the fix is nearly always a swap |
| Size and weight | Usually small enough for a car or small van — a box rather than a pallet |
| Handling | Static sensitive. They travel in the anti-static packaging the stores applied, in a specified orientation, and should not be unpacked in transit |
| The catch | Damage is frequently invisible. A unit that looks fine may test unserviceable, which is why packaging integrity matters more than appearance |
Wheels, tyres and brakes
The most physically demanding category, and the one most likely to cause a wasted journey if described loosely at booking.
| What they are | Main and nose gear wheel assemblies, tyres, brake units |
|---|---|
| Why they move | Wear, damage on landing, and the fact that changes are often done on the stand rather than in a hangar |
| Size and weight | Heavy and awkward. This is a loading problem rather than a fragility problem |
| Handling | Secured against rolling; brake surfaces protected from contamination |
| The catch | A tail-lift may be needed — and it is needed at both ends. An assembly that arrives somewhere with no way to unload it has not really arrived |
Specialist and calibrated tooling
The quietest cause of a delayed start, because tooling tends to be assumed rather than tracked.
| What it is | Type-specific tooling, torque equipment, jigs, fixtures and test sets |
|---|---|
| Why it moves | Shared between bases, and often has to travel to wherever the engineer and the aircraft are |
| Handling | Carried in its supplied cases, secured and kept away from heavy items |
| The catch | Calibration can be invalidated by impact. Tooling that arrives out of calibration is worse than tooling that has not arrived, because the problem may not be noticed immediately |
Seals, fasteners, filters and consumables
| What they are | Seals, O-rings, fasteners, filters, fluids, adhesives and workshop supplies |
|---|---|
| Why they move | Individually trivial, but a task cannot be completed without the right one |
| Size and weight | Often tiny. A consignment can be smaller than an envelope |
| Handling | Straightforward, with one significant exception below |
| The catch | A high proportion of this category is classified as dangerous goods — adhesives, paints, aerosols and some fluids. This is where undeclared items most often appear |
The dangerous goods most people forget
This deserves its own section because it is the commonest reason a collection fails at the door, and it is nearly always accidental rather than deliberate.
| Item | Why it is easy to miss |
|---|---|
| Lithium batteries | Frequently built into a larger unit. The paperwork names the assembly, not the battery inside it |
| Oxygen generators | Contained within cabin components, so the consignment looks like an interior part |
| Aerosols and adhesives | Ordinary-looking workshop stock that happens to be classified |
| Compressed gas items | Cylinders and charged components within assemblies |
| Flammable fluids | Sent as part of a kit alongside unclassified items |
Engine components and larger assemblies
| What they are | Engine accessories, modules, and larger structural or system components |
|---|---|
| Why they move | Less frequently than the categories above, but with far more planning required |
| Size and weight | The determining factor. Vehicle choice and lifting arrangements have to be settled first |
| The catch | The question that saves the most time is how the item will be loaded and unloaded. A component requiring a forklift at collection and finding none at delivery is a problem best identified at booking |
The item people forget is an item at all
Technical documentation is not a component, but it is a consignment, and it can ground an aircraft as effectively as any part.
| What it covers | Release certificates, technical records, certification packages |
|---|---|
| Why it matters | A part without valid certification cannot be fitted and the aircraft cannot be released to service |
| The failure mode | Certification separated from the component it certifies — both then arrive, but neither is usable |
| Why dedicated helps | On a dedicated movement there is no sorting process, so documentation physically cannot become separated from the part |
What this means when you book
| Category | Tell the dispatcher |
|---|---|
| Avionics / LRUs | That it is static sensitive and any orientation requirement |
| Wheels, tyres, brakes | The weight, and whether a tail-lift is needed at each end |
| Tooling | That it is calibrated, if it is |
| Consumables and kits | Whether anything in the kit is classified |
| Engine and large components | Dimensions, weight and the lifting equipment available at both ends |
| Documentation | That it must travel with the part, not separately |
How RushXO helps
RushXO carries all of the categories above in dedicated vehicles matched to the consignment, with the sender's packaging left intact and certification travelling alongside the part.
| Vehicle matched to the item | From a car for an avionics box to a tail-lift van for wheel assemblies |
|---|---|
| Packaging undisturbed | We do not unpack or repack components |
| Dangerous goods | Declare at booking and carriage arrangements are confirmed case by case before dispatch |
| Documentation with the part | No sorting process, so certification cannot be separated |
| 24/7, UK-wide | Collection from suppliers, stores, MROs and cargo terminals nationwide |
Handling detail by part type is on our aircraft parts delivery page, and the emergency service on AOG courier.
We do not claim certified ESD handling facilities, temperature-controlled transport or ADR capability. Components are protected by your packaging and by careful loading and securing.
📞 Call 020 8888 9988 · 💬 WhatsApp · Request a quote →
Frequently asked questions
What kind of parts most commonly ground an aircraft?
Small ones. Avionics and line-replaceable units, sensors, valves, tyres and brake components account for a large share of AOG events. What makes a part critical is whether a serviceable replacement is available locally, not what it costs.
Why are avionics units moved so often?
Because modern aircraft are designed around units that are swapped rather than repaired in place. When one fails, the fix is a replacement unit — so the unit has to travel from wherever a serviceable one is held.
What is the main risk with avionics in transit?
Static discharge and shock, and the difficulty that damage is often invisible. A unit that looks undamaged may test unserviceable. That is why components should stay in the anti-static packaging the stores applied and should not be unpacked in transit.
What is the commonest problem with wheel and brake deliveries?
Loading. They are heavy and awkward rather than fragile, and the recurring failure is a tail-lift being available at the collection point but not at the delivery point. Confirm lifting arrangements at both ends when booking.
Why does calibrated tooling need special care?
Because calibration can be invalidated by impact, and the problem may not be discovered until the tool is used. Calibrated equipment travels in its supplied cases, secured and separated from heavy items.
Which dangerous goods are most often overlooked?
Lithium batteries built into larger units, oxygen generators inside cabin components, and aerosols or adhesives sent as part of a kit. In each case the paperwork names the assembly rather than the classified item inside it. Declare anything you are unsure about at booking.
Can technical documentation be sent separately from the part?
It can, but it should not be. A component without valid certification cannot be fitted, so a part and its paperwork arriving separately leaves the aircraft grounded anyway. On a dedicated movement there is no sorting process, so the two cannot become separated.
What should I tell a courier when booking?
Dimensions and weight, whether the item is static sensitive or calibrated, whether anything is classified as dangerous goods, what lifting equipment is available at both ends, and the moment it must be on site.