The subject with the most ways to be killed

Twenty-nine skill elements — the largest inventory in the certificate, 15% of all Airframe skills. Forty-eight elements in total, twelve of them needing a station.

And six risk elements, three of which describe ways people are killed. Start there.

1. The three that kill

R2 — use of aircraft jacks. An aircraft on jacks is unstable by definition. It comes off jacks because the surface was soft, or not level, or a jack was on the wrong point, or someone worked on it in a way that shifted the load. Nobody is under a jacked aircraft. Ever. Stands or safety collars go under it as soon as it is up, and they stay there.

R1 — wheel and tire practices. A wheel assembly is a pressure vessel. Multi-piece and split-rim wheels separate explosively if the through-bolts are disturbed while the tire is inflated, and the separation is a recognized cause of fatal injury. Deflate completely, and confirm deflation, before touching a through-bolt. Inflate in a cage, and stand clear of the plane of the wheel.

R6 — retractable gear around personnel. The sweep of a retracting gear leg is a place that becomes lethal without warning. Nobody in the sweep, warning before actuation, and the aircraft's weight on jacks and stands before anyone cycles anything.

R3 and R5 are the fourth way: a shock strut is a charged pressure vessel, and S9, S15 and S20 all open one. Documented depressurization first, face protection, and never assume a strut is discharged because it looks compressed.

This unit is where a curriculum stops being about competence and starts being about survival, and it is why the landing gear station specification specifies guards, cages and interlocks rather than relying on care.

2. Only four of twenty-nine skills need the aircraft

S1 inspect and service gear, S5 jack the aircraft, S19 gear alignment, S29 tube gear.

The other twenty-five are bench or rig work, which is the finding that drives procurement: the aircraft is the most expensive, least parallelisable asset in the program and it constrains 14% of this subject.

For a candidate, the useful version of that fact is: most of what you need to learn here can be learned on components, and the aircraft time is for the operations that genuinely need a whole airplane — jacking, alignment, and a gear retraction check.

3. A shock strut is two springs and a damper

K3, S9, S15, S16.

The gas is the spring. The oil is the damper. Compressing the strut compresses the gas, which resists; the oil is forced through an orifice, which dissipates energy so the aircraft does not bounce.

That is why servicing is a two-part operation and why the order matters. Fill with oil first, with the strut fully compressed and the gas removed, then charge the gas with the strut extended. Getting the ratio wrong produces a strut that:

• has too much oil — it will be harsh, may bottom hydraulically, and the extension will be wrong;
• has too little oil — it will not damp, and the aircraft will oscillate on landing;
• has the wrong gas pressure — it will sit at the wrong extension, changing the aircraft's attitude, the gear geometry and the loads.

And all three look like a normal strut when the aircraft is parked. The measurement that matters is the extension dimension with the aircraft at a stated weight, from the manual — not how it feels.

R5 is the safety half: the gas charge is what makes strut disassembly dangerous. The valve core must be removed and the strut confirmed discharged before any nut is slackened.

4. Brakes: air, and heat

S8, S10, S11, S12, S20, S27.

Two failure modes feel similar to a pilot and are different faults (AF-F Concepts §4):

• Air in the system gives a spongy pedal that firms up with repeated pumping. The fix is bleeding.
• A leak gives a pedal that sinks under steady pressure. The fix is finding the leak.

Brake fade is a third thing entirely — heat, not hydraulics. Overheated brakes lose friction and recover when cool, and a brake that has been badly overheated may have damaged the disc, the linings or the seals.

S12, removing and installing a wheel brake assembly, and S8, brake linings, are where wear limits are applied. Linings are measured, not judged, and the limit is from the manufacturer.

5. Shimmy is a resonance, not a looseness

S17, S28, K5.

Candidates diagnose shimmy by looking for the loose part. Sometimes there is one, and often the system is oscillating because several small things combine.

The contributors: shimmy damper condition and fluid level, torque link wear and play, wheel bearing adjustment, tire balance and condition, nose gear trail and geometry, and strut extension. Any one may be within limits while the combination is not.

So S28 is a system diagnosis and not a part swap, and the honest procedure works through the contributors in order rather than replacing the damper and hoping.

6. Anti-skid: three elements, no hardware, decided

K8, S2, S3, S4.

S3 and S4 are Locate — documentation satisfies them. S2 requires anti-skid hardware absent from any realistic training fleet, and it is held out of scope with the reason recorded under the competency standard §3.2.

That is a documented decision, not an omission, and it is stated here so that a candidate reading the curriculum finds the reasoning where they need it rather than in an equipment document.

You are still examined on K8 on the written. Know what anti-skid does and how it does it: it detects a wheel decelerating faster than the aircraft — which means it is about to skid — and releases brake pressure to that wheel.

7. Six troubleshooting elements, and an open question

S6, S11, S16, S21, S23, S28 — every troubleshooting element in the subject — are classified for simulator delivery.

the landing gear station specification doubts that assignment: a simulator tests whether you know where to put the probe, not whether you can put it there, and for a hydro-mechanical system, operating it and observing the result is part of the skill.

It is the largest single apparatus question in the program, and AF-L §2 proposes testing it cheaply before the rigs are built.

For your purposes as a candidate it changes nothing: the diagnostic reasoning is the same whether you practice it on a simulator or a rig.

8. What consumes this unit

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