Ground Operations, Safety and Human Factors
9% of the exam 2 min
Ground operations and servicing (9%) with human factors (6%): fire classes, fuels and fueling, towing and tie-down, engine starts, oxygen, taxi signals and FOD, then the Dirty Dozen and the FAA's error models.
Fire and fuel
Class A fires burn ordinary combustibles, Class B flammable liquids such as fuel, oil, solvents and paint, Class C energized electrical equipment, and Class D flammable metals such as a magnesium wheel. Never use water or CO2 on a Class D fire; the cooling can cause explosive expansion. CO2 can also starve the operator of oxygen in a confined space and gets cold enough to cause frostbite. AVGAS is color coded: 80 red, 100 green, 100LL blue, 115 purple; jet fuel is marked black on piping and is itself clear to straw colored.
Fueling, towing and starting
When fueling from a truck, ground the aircraft, then the truck, bond them, then ground the nozzle to the aircraft before opening the tank; never use the propeller as a ground point, and do not fuel within 500 feet of operating ground radar. Before towing, a qualified person sits in the flight deck to work the brakes, wing walkers watch each tip, doors are closed, ladders retracted and gear-down locks installed. Tie aircraft down headed into the wind. During any engine start a fireguard stands by with a CO2 extinguisher of at least 5-pound capacity. A hot start is an EGT overtemperature, usually from a rich mixture; a hung or false start is rpm that stalls at a low value. Shut down in either case.
Oxygen, signals and FOD
Only oxygen marked Aviator's Breathing Oxygen (Federal Specification BB-O-925A Grade A or equivalent) goes into an aircraft breathing system; industrial oxygen may contain impurities and medical oxygen contains water that can freeze at altitude. Oxygen combines with oil or grease into a highly explosive mixture, so fittings and equipment are kept spotless. Tower light signals while taxiing: flashing green cleared to taxi, steady red stop, flashing red taxi clear of the runway in use, flashing white return to the starting point, alternating red and green exercise extreme caution. FOD is controlled with clean ramps, a tool control program and receptacles for used hardware and towels.
Human factors: the Dirty Dozen and the models
The Dirty Dozen, identified by Transport Canada, are lack of communication, complacency, lack of knowledge, distraction, lack of teamwork, fatigue, lack of resources, pressure, lack of assertiveness, stress, lack of awareness and norms. PEAR stands for People, Environment, Actions and Resources. An unintentional error is an accidental deviation, such as transposing 26 into 62; an intentional one is treated as a violation. An active error is the obvious event and a latent error the company condition that set it up. MEDA investigates root causes instead of assigning blame. The primary cause of fatigue is lack of sleep, and a shift turnover must cover work that later installation will hide.
Where people lose points
✗ "CO2 is safe on any fire."
✓ Never on Class D metal fires, and use caution in confined spaces.
✗ "100 octane is blue."
✓ 100 is green; 100LL is blue.
✗ "Medical oxygen is purest, so it is best for aircraft."
✓ It contains water that can freeze. Use Aviator's Breathing Oxygen only.
✗ "Complacency means not knowing the procedure."
✓ That is lack of knowledge. Complacency is false confidence from repetition.
✗ "MEDA finds who made the error."
✓ It finds the contributing factors and root causes, not someone to blame.
Numbers to memorize
| Class B fire | Flammable liquids |
| Class D fire | Flammable metal; no water or CO2 |
| AVGAS 100LL | Blue |
| AVGAS 100 | Green |
| Jet fuel marking | Black on piping |
| No fueling near ground radar | Within 500 feet |
| Engine start fireguard | CO2, at least 5 lb |
| Flashing white (tower) | Return to starting point |
| PEAR | People, Environment, Actions, Resources |
| Primary cause of fatigue | Lack of sleep |
Test yourself
No answers here on purpose — retrieving them is the practice. Drill this domain if any of these stall you.
- Give the four fire classes and one extinguisher to avoid on each risky one.
- List the towing precautions the FAA handbook requires.
- Explain the difference between a hot start and a hung start.
- Recite the Dirty Dozen.
- Describe a good shift turnover for a half-finished job.