Part-66 Module 17 Propeller Questions

Part-66 Module 17 is the propeller module, and it is one of the more contained papers in the licence: seven sub-modules, a clear body of theory and a lot of practical maintenance. If you are looking for Part-66 Module 17 questions, the first thing to sort out is which version you sit. Under UK CAA rules there are two modules, 17A for categories A and B1 and 17B for B3. Under EASA rules there has been a single Module 17 since June 2024, with the depth set per category.

This page gives every paper size under both systems, explains the 17A and 17B split, walks through each sub-module with what examiners test and the classic traps, and ends with a study plan. Part-66 Prep is an independent study aid, not EASA, the UK CAA or a Part-147 organisation. For the full module list, see the Part-66 modules guide.

Module 17 paper size: 17A and 17B, EASA and UK CAA

Category	Module (UK name)	EASA questions / time	UK CAA questions / time
A1, A2 (site: category A)	17A	20 / 25 min	20 / 25 min
B1.1, B1.2	17A	32 / 40 min	32 / 40 min
B3	17B	32 / 40 min	28 / 35 min
A3, A4, B1.3, B1.4, B2, B2L	—	not required	not required

All papers are three-option multiple choice, 75 seconds a question, 75% to pass, with no essays. The EASA figures come from Appendix II as replaced by Regulation (EU) 2023/989 and the UK figures from the retained Appendix II on legislation.gov.uk.

Key fact: The only Module 17 paper that differs between the two systems is B3: 32 questions under EASA rules, 28 under UK rules. A and B1 papers are identical in size.

17A, 17B and the single EASA Module 17

The UK text keeps the original structure. Module 17A carries a note that it does not apply to B3, and Module 17B carries a note that its scope reflects the propeller technology of aeroplanes in the B3 category, meaning light piston aeroplanes up to 2,000 kg. The topic list is the same in both; the difference is scope and depth.

The EU syllabus merged them. EASA Module 17 has columns for A1/A2 and for B1.1, B1.2 and B3 together, so a B3 candidate under EASA rules studies to the same knowledge levels as a B1 candidate. Under UK rules, 17B is level 2 throughout, including maintenance, while 17A sets maintenance at level 3 for B1. Certificates of recognition still name the module the way your system does.

Knowledge levels

Sub-module	A (EASA and UK)	B1 (both); B3 (EASA)	B3 (UK 17B)
17.1 Fundamentals	1	2	2
17.2 Construction	1	2	2
17.3 Pitch control	1	2	2
17.4 Synchronising	not required	2	2
17.5 Ice protection	1	2	2
17.6 Maintenance	1	3	2
17.7 Storage and preservation	1	2	2

Where the marks are

The EASA guidance on question spread (AMC1 to Appendix II) suggests this split. Our papers follow it for EASA mode and scale it for the shorter UK B3 paper.

Sub-module	Category A (20 Q)	B1 and B3 (32 Q)
17.1 Fundamentals	5	8
17.2 Construction	4	5
17.3 Pitch control	4	6
17.4 Synchronising	—	2
17.5 Ice protection	2	3
17.6 Maintenance	3	6
17.7 Storage and preservation	2	2

Fundamentals, pitch control and maintenance make up 20 of the 32 B1 questions.

Sub-module 17.1: fundamentals

This is the theory core and the biggest single block.

Angles and blade element theory

Blade element theory treats each section of the blade as a small aerofoil moving along a helix: its velocity combines the rotational speed (which grows with radius) and the aircraft's forward speed (the same for every section). That is why blades are twisted, with a larger blade angle at the root than at the tip.

Get the definitions exact, because distractors swap them:

Term	Definition
Blade angle	between the chord line and the plane of rotation
Helix angle	between the relative airflow and the plane of rotation
Angle of attack	between the chord line and the relative airflow
Fine pitch	small blade angle, high rpm, take-off and climb
Coarse pitch	large blade angle, lower rpm, cruise

Pitch and slip

Geometric pitch is the distance the propeller would advance in one revolution with no slip; effective pitch is the distance the aircraft actually moves. Slip is the difference. A worked example of the method: a light aircraft propeller with a geometric pitch of 60 in turns at 2,500 rpm while the aircraft covers 125,000 in per minute. Effective pitch is 125,000 ÷ 2,500 = 50 in, so slip is 10 in, or about 17% of geometric pitch. The usual trap is to express slip as a percentage of effective pitch instead.

Forces and moments

Know all five: centrifugal force (the largest, pulling the blades out of the hub), thrust bending (tips bend forward), torque bending (blades bend against the direction of rotation), the aerodynamic twisting moment (tends to increase blade angle) and the centrifugal twisting moment (tends to decrease blade angle, and is the stronger of the two). That last pair drives many pitch control questions. Torque reaction, slipstream effect, gyroscopic precession, P-factor, vibration and resonance complete the sub-module.

Exam tip: CTM goes to fine pitch, ATM goes to coarse pitch, and CTM wins. Learn that sentence and half the pitch-change questions become straightforward.

Sub-module 17.2: construction

Blade terminology is examined directly: hub, shank, butt, back (the cambered, forward-facing side), face (the flat side facing the pilot), leading and trailing edges, tip, cuff and blade stations, which are measured outwards from the hub centre. Materials: laminated wood with fabric sheathing, metal tipping and drain holes; forged aluminium alloy; and composite blades over a foam core with a metal erosion shield and lightning protection.

Propeller types run from fixed-pitch (climb or cruise versions) through ground-adjustable and controllable-pitch to constant-speed, feathering and reversing. Installation questions cover flanged, tapered and splined shafts, cones and the contact check on a splined or tapered fit, and spinners.

Sub-module 17.3: pitch control

This is where the practical questions get detailed.

The governor

A hydromechanical governor has a gear pump to boost engine oil pressure, flyweights, a speeder spring set by the propeller lever, a pilot valve and a relief valve. On speed, the flyweights balance the spring and oil is trapped. Overspeed: flyweights move out, the pilot valve moves, blade angle increases and rpm falls back. Underspeed: the reverse.

Which force moves the blades which way

Propeller design	Oil pressure drives blades to	Opposing force	Loss of oil pressure gives
Typical single-engine non-feathering	high pitch	CTM and spring	low pitch, high rpm
Counterweight type	low pitch	counterweights	high pitch
Feathering (piston twins)	low pitch	counterweights, spring, nitrogen charge	feather

The logic matters more than memorising the table: a single-engine aeroplane wants full power available if the governor fails, while a twin wants a failed engine's propeller to feather.

Feathering, reverse and overspeed

Feathering on piston twins is done by pulling the propeller lever to the feather detent, which dumps oil from the hub. Start locks hold the blades at low pitch when the engine is shut down normally on the ground, so it can be restarted, and an unfeathering accumulator or electric pump brings the blades out of feather in flight. Turboprops add beta range, reverse, flight-fine stops, beta lights and auto-feather. Overspeed protection includes the overspeed governor, fuel topping governor, pitch lock and low-pitch stop. Electric and electronic pitch change (slip rings and brushes, dual-channel electronic propeller control with beta feedback) is part of the syllabus too.

The pitch control and synchronising note covers each design, and the Pro pitch control drill focuses your practice on this sub-module.

Sub-modules 17.4 and 17.5: synchronising and ice protection

Synchronising, which category A does not sit, is a two-question topic with one key distinction: synchronising matches rpm to remove the beat; synchrophasing also holds a set phase angle between the blades of different propellers to reduce cabin noise further. Both use pulse pickups and trim the slave governor within a limited range.

Ice protection covers fluid systems (a pump feeds alcohol or glycol to a slinger ring, and centrifugal force spreads it along feed shoes) and electrical de-icing (heater boots fed through slip rings and brushes, cycled by a timer, with an ammeter to confirm each cycle). Electrical de-icing is only run briefly on the ground because the elements overheat without airflow.

Sub-modules 17.6 and 17.7: maintenance, storage and preservation

Maintenance is level 3 for B1, so expect questions that test judgement. Static balancing is done off the aircraft on a knife-edge stand; dynamic balancing is done on the aircraft with an accelerometer and an optical or magnetic phototach, with weights usually added at the spinner bulkhead. Blade tracking checks that every tip follows the same path.

Damage assessment is a favourite: nicks and dents on a metal leading edge can be dressed out within the manufacturer's limits, cracks in metal blades are rejectable, erosion is restored within limits, corrosion is removed and treated, and composite or wooden blades are checked for delamination with a coin-tap test. After a ground strike or sudden stoppage the propeller is removed for inspection and the engine must also be inspected to the engine manufacturer's instructions. Storage questions include keeping wooden propellers horizontal so moisture does not migrate into one blade, and recording nitrogen pressure on charged hubs.

Module 17 alongside Modules 15 and 16

Propellers sit beside the engine modules. For B1.1, Module 17A follows Module 15 gas turbine engines, where turboprop reduction gearboxes and torque indication are covered. For B1.2 and B3, it pairs with Module 16 piston engines: governor oil comes from the engine, and propeller run-up checks are part of engine ground running. The airframe modules, Module 11 in its A, B or C version, cover the cockpit controls and ice protection on the aircraft side. For B3 candidates, the B3 licence guide shows where 17B sits among the 13 papers.

Background reading: the FAA's Aviation Maintenance Technician Handbook – Powerplant has a thorough propeller chapter covering governors, feathering, balancing and damage limits. It uses US rules, so treat it as a textbook only.

Practising Module 17

Part-66 Prep has 343 original Module 17A questions and 247 Module 17B questions. The sample questions on this page come from the 17A bank; B3 candidates should practise on the 17B papers, which are scoped to light aircraft propellers.

• B1.1: Module 17A paper 1
• B1.2: free Module 17A quick practice
• Category A: Module 17A for category A
• B3: Module 17B paper 1
• Printable sheets: Module 17A and Module 17B, 50 questions each with an answer key

These are exam-style papers built to the official paper sizes. Neither EASA nor the CAA publishes past papers, and we never use recalled exam questions.

Your study plan

1. Check whether you sit 17A or 17B and under which rules, so you know whether your paper is 20, 28 or 32 questions.
2. Read the free propeller fundamentals note, or the free 17B fundamentals and construction note if you are B3.
3. Write out the angle definitions and the five forces until you can reproduce them without looking.
4. Take the free quick practice, for example B1.2 Module 17A, then sit the full Module 17A paper 1 or the 17B paper 1.
5. Drill pitch control and maintenance, then sit papers 2 to 10 with Pro.
6. Book when you score 85% or more on three different papers. Unsure where you stand overall? Take the free B1.1 diagnostic.