Ground support equipment (GSE) is the broad category of powered and non-powered tools, vehicles, and systems used to service, move, and maintain aircraft on the ramp and in the hangar. From tow tractors and aircraft jacks to fuel trucks and ground power units (GPUs), GSE is essential to keeping aircraft airworthy and on schedule. For the Aviation Maintenance Technician (AMT), understanding how to operate GSE safely and correctly is not just a practical workplace skill — it is a tested knowledge area on the FAA AMT General written examination and a genuine safety imperative. Misuse of GSE is a leading cause of ramp injuries, ground damage incidents, and costly aircraft repairs.
This article covers the major categories of ground support equipment, the principles that govern their safe operation, the specific hazards each type presents, and the regulatory and procedural framework AMTs follow to keep themselves, their coworkers, and the aircraft safe.
Categories of Ground Support Equipment
GSE falls into several functional groups, each with its own operating principles and hazard profile.
Aircraft Towing Equipment
Tow tractors (also called tugs or pushback tractors) move aircraft that cannot taxi under their own power or that must be repositioned without engine operation. Towbars connect the tug to the nose gear. A towbarless tug cradles the nose gear directly, eliminating the towbar as a potential failure point.
The most critical concept in aircraft towing is the nose gear turning radius limit. Every aircraft type has a published maximum steering angle for the nose gear. Exceeding this angle — even briefly — can shear the nose gear torque links, collapse the gear, or buckle the firewall. Before any tow operation, the AMT must look up the specific aircraft's maintenance manual for the allowable tow angle and ensure the tug and towbar combination is rated for the aircraft's gross weight. Tow pins must be properly seated and safety-wired or pinned per the manual's instructions.
Walkaround inspections of the tug are required before use: check tire pressure, fluid levels, lights, brakes, and hitch security. A wingwalker must be positioned at each wingtip during any tow in a congested area, and a qualified operator must be at the tug's controls at all times. Clear, pre-briefed hand signals between the tug operator and wingwalkers are essential because engine and ambient noise makes verbal communication unreliable.
Aircraft Jacks and Lifting Equipment
Three types of jacks are commonly used in aircraft maintenance: tripod jacks (placed under wing jack points for raising the entire aircraft), axle jacks (used to raise individual landing gear for wheel and brake work), and hydraulic floor jacks (used for heavier components). Lifting an aircraft incorrectly is one of the most consequential mistakes an AMT can make — an improperly positioned jack can punch through aircraft skin, damage spars, or cause the aircraft to topple.
Jack points are clearly identified in the aircraft maintenance manual and are often marked on the aircraft structure itself. The AMT must verify that the jack's rated capacity exceeds the load it will bear, that the jack is placed on a hard, level surface, and that all safety collars or lock rings are engaged before anyone works beneath the aircraft. Aircraft should never be left unattended while jacked. If an aircraft must remain on jacks for extended maintenance, safety stands (also called maintenance stands or jack stands) are placed as a secondary support after jacking is complete.
Ground Power Units
A ground power unit (GPU) supplies electrical power to aircraft systems when the aircraft's own APU or engines are not running. GPUs prevent excessive battery drain during lengthy maintenance, avionics testing, or pre-flight checks. GPUs may be AC or DC units; matching the output voltage, frequency (typically 115V AC at 400 Hz for most transport-category aircraft), and amperage to the aircraft's electrical specifications is mandatory. Connecting an incorrect GPU — for example, a 28V DC unit to an aircraft expecting 115V AC — can destroy avionics and electrical components instantly.
Connection and disconnection sequence matters: always confirm the GPU is off or set to standby before connecting or disconnecting the power plug. Inspect the cable and connector for damage before each use. Keep GPU cables clear of prop and rotor arcs, engine inlets, and moving aircraft components.
Fuel Servicing Equipment
Fuel trucks, hydrant carts, and defueling equipment all present fire, explosion, and contamination hazards. Proper bonding and grounding procedures are mandatory before any fuel transfer. Bonding means electrically connecting the fuel nozzle or truck to the aircraft to equalize static charge between the two — this prevents a spark as the nozzle approaches the fuel port. Grounding connects the aircraft or truck to the earth, dissipating accumulated charge. Grounding and bonding connections are established before the fuel cap is removed, and disconnected only after fueling is complete and the nozzle has been removed; the exact order of grounding the equipment and bonding the aircraft to the truck can vary by procedure, so technicians must follow the specific fueling checklist and local procedures in use.
Fuel type verification is a life-critical step. Jet-A (turbine fuel) and 100LL (aviation gasoline) must never be mixed. The nozzle sizes are intentionally different to reduce misfueling risk, but the AMT must still verify fuel grade against the aircraft placard and fuel order before opening any valve. Fuel contamination — including water, particulates, and wrong fuel type — is a primary cause of in-flight engine failure.
Oxygen Servicing Equipment
High-pressure oxygen servicing carts supply breathing oxygen and inflate pneumatic systems. Oxygen under high pressure is a severe fire and explosion risk. Absolutely no oil, grease, or petroleum-based lubricants may contact any oxygen system fitting, valve, or line — even a thin film of oil can combust violently in the presence of high-pressure oxygen. Technicians must use only approved oxygen-compatible tools and wear clean gloves. Oxygen servicing must be done in a well-ventilated area away from open flames and with appropriate fire extinguishers accessible.
Why GSE Safety Matters
The FAA's maintenance regulations under 14 CFR Part 43 hold the AMT responsible for the airworthiness of work performed. Ground damage caused by improper GSE use — a cracked nose gear, a dented fuselage from an over-extended jack, or a wiring harness shorted by an incorrect GPU — can go undetected, enter service, and lead to in-flight failure. Beyond the aircraft, ramp environments are statistically hazardous workplaces: rotating propellers, jet blast, fuel vapors, and heavy vehicle traffic converge in a small area.
Many ramp injuries are preventable through adherence to established procedures. The FAA, through the Aviation Maintenance Technician Handbook (FAA-H-8083-30), emphasizes that maintenance personnel must be familiar with the equipment they operate and follow manufacturer and airline or FBO procedures at all times.
Key Numbers and Rules
- Nose gear tow angle: Always determined by the specific aircraft maintenance manual — never assumed. Exceeding the limit risks structural damage.
- GPU frequency: Most commercial aircraft require 115V AC at 400 Hz; confirm against the aircraft specs before connecting.
- Bonding before fueling: Bonding and grounding connections must be established before opening the fuel cap — this prevents electrostatic spark ignition of fuel vapors; always follow the specific fueling checklist for exact sequencing.
- Jack capacity: Jack's rated load must exceed the weight it will support; always engage safety collars before working beneath the aircraft.
- Oxygen and oil: Zero tolerance — no petroleum-based products near any oxygen system component, ever.
- Fire extinguisher: Have a suitable extinguisher appropriate for flammable-liquid fires immediately accessible during all fuel servicing operations, per local fueling safety procedures.
- Personnel protection: High-visibility vests, hearing protection, and FOD-prevention footwear are standard ramp PPE at most regulated operations.
Common Test Traps
- Confusing bonding with grounding: Bonding equalizes charge between two objects (truck to aircraft). Grounding dissipates charge to the earth. Both are required for fuel servicing, and both must be established before opening the fuel cap.
- Assuming one GPU fits all aircraft: GPU voltage, frequency, and amperage must match the aircraft's specifications. Connecting the wrong GPU is a common and very damaging mistake.
- Ignoring nose gear limits: The question may describe a tow scenario and ask what the technician should do before turning — the answer is always consult the maintenance manual for the specific aircraft's nose gear turning radius.
- Thinking safety collars are optional: Some students believe jacks can be used without engaging safety locks for quick jobs. This is incorrect and dangerous — safety collars must be engaged before any person works beneath a jacked aircraft.
- Overlooking oxygen system contamination: Test questions may describe using a standard (petroleum-based) lubricant on an oxygen fitting. This is always wrong — only oxygen-compatible, non-petroleum products may be used.
Understanding ground support equipment operation and safety is fundamental to professional aircraft maintenance. The principles of proper sequencing, equipment matching, adherence to maintenance manual limits, and hazard awareness combine to protect both people and aircraft. Every time an AMT takes the time to verify, inspect, and follow procedure before operating GSE, they are practicing the same systematic discipline that airworthiness depends on.