Part-66 Module 12 questions are the helicopter equivalent of the aeroplane Module 11: rotor aerodynamics, the controls that tilt a spinning disc, the transmission that drives it, the airframe, and every system from fuel to lighting. For B1.3 candidates it is one of the two longest papers they sit, together with Module 15. This page gives the paper sizes, explains how the EASA partial-exam rule applies, walks through every sub-module and shows how to plan your preparation.
Part-66 Prep is an independent study aid, not EASA, the UK CAA or a Part-147 organisation. The Module 12 syllabus is in Appendix I and the paper size in Appendix II of Part-66: see the EASA Easy Access Rules for Continuing Airworthiness and Regulation (EU) 2023/989 for the EU, and UK Part-66 on legislation.gov.uk for the UK. The Part-66 modules guide lists Module 12 with the other aircraft modules.
Part-66 Module 12 exam size and who sits it
| Category | EASA questions / minutes | UK CAA questions / minutes | Correct answers needed (75%) |
|---|---|---|---|
| A3 (turbine helicopters) and A4 (piston helicopters) | 100 / 125 | 100 / 125 | 75 |
| B1.3 (turbine helicopters) and B1.4 (piston helicopters) | 128 / 160 | 128 / 160 | 96 |
Module 12 is one of the papers where EASA and UK sizes match. There are no essays.
A B1.3 licence needs Modules 1 to 10, Module 12 and Module 15 (gas turbine engine). A B1.4 licence needs Module 16 (piston engine) instead of 15. Category A3 sits Module 12 with Module 15, and A4 with Module 16. Part-66 Prep covers B1.3 and category A; we do not run B1.4 practice. The Part-66 B1 licence guide compares the B1 subcategories, and the category A licence guide explains A3 and A4.
Partial exams under EASA rules
Under the EU exam standard, an exam with more than 90 minutes allowed may be split into two partial exams, and one over 180 minutes into three. Both Module 12 papers are over 90 minutes and under 180, so an EASA exam centre may run them as two parts. Each part must cover complementary parts of the module, take a similar time, contain a number of questions that is a multiple of four, be passed at 75% on its own, and be taken at the same organisation. A 128-question paper could, for example, be split 64 and 64. UK Part-66 has no general partial-exam rule (it allows a split only for the B2 Module 13 paper), so a UK candidate should expect one sitting unless the centre says otherwise.
Key fact: 160 minutes is a long time to concentrate. Whether or not your centre splits the paper, practise full-length papers so the last 30 questions get the same attention as the first.
Depth by category
Module 12 has some of the highest knowledge levels in the syllabus. Many B1 topics are at level 3 (detailed knowledge, able to combine and apply it), which means examiners can ask about operation, faults and maintenance tasks, not just definitions.
| Sub-module | A3 / A4 | B1.3 / B1.4 |
|---|---|---|
| 12.1 Theory of flight, rotary wing aerodynamics | 1 | 2 |
| 12.2 Flight control systems | 2 | 3 |
| 12.3 Blade tracking and vibration analysis | 1 | 3 |
| 12.4 Transmission | 1 | 3 |
| 12.5 Airframe structures | 2 (concept) / 1 (construction) | 2 |
| 12.6 Air conditioning | 1 | 2 (air supply) / 3 (air conditioning) |
| 12.7 Instruments and avionic systems | 1 | 2 (instruments) / 1 (avionics) |
| 12.8 Electrical power | 1 | 3 |
| 12.9 Equipment and furnishings | 2 / 1 | 2 / 1 |
| 12.10 Fire protection | 1 | 3 (detection and extinguishing) / 1 (portable) |
| 12.11 Fuel systems | 1 | 3 |
| 12.12 Hydraulic power | 1 | 3 |
| 12.13 Ice and rain protection | 1 | 3 |
| 12.14 Landing gear | 2 | 3 |
| 12.15 Lights | 2 | 3 |
| 12.17 Integrated modular avionics | 1 | 2 |
| 12.18 On-board maintenance systems | 1 | 2 |
| 12.19 Information systems | 1 | 2 |
Sub-module 12.16 is reserved in the EASA syllabus; the UK syllabus still uses 12.16 for pneumatic and vacuum systems.
Practise at your size: B1.3 Module 12 paper 1 or category A Module 12 paper 1.
The helicopter-specific sub-modules
12.1 Rotary wing aerodynamics
Terminology (rotor disc, tip-path plane, coning, feathering, flapping, lead and lag, solidity), gyroscopic precession, torque reaction and directional control, dissymmetry of lift and blade tip stall, translating tendency, the Coriolis effect, vortex ring state, power settling and overpitching, autorotation and ground effect.
What examiners like: how flapping corrects dissymmetry of lift (the advancing blade flaps up and its angle of attack falls), why the retreating blade stalls first at high forward speed, why raising collective needs more anti-torque pedal, the difference between pitch angle and angle of attack, and the regions of the disc in autorotation. Trap: precession acts 90° later in the direction of rotation, so control inputs are applied ahead of where the disc should tilt. The free rotary wing aerodynamics note covers all of it, and the theory of flight drill tests it.
Exam tip: Draw the rotor disc from above with the direction of rotation and the advancing and retreating sides marked before answering any dissymmetry, precession or translating-tendency question. Most wrong answers come from getting the side wrong.
12.2 Flight control systems
Cyclic, collective and anti-torque pedals; the swashplate (rotating and non-rotating stars); mixing units; main rotor heads (fully articulated, semi-rigid, rigid and bearingless); blade dampers; blade construction and attachment; tail rotor, fenestron and NOTAR yaw control; trim, stabilisers and artificial feel; balancing and rigging.
What examiners like: which control changes pitch collectively and which cyclically, what each type of rotor head allows, why lead-lag dampers are needed on an articulated head, and how a fenestron differs from a tail rotor. Trap: the semi-rigid (teetering) two-blade rotor has no lead-lag hinges. Read the flight control systems note.
12.3 Blade tracking and vibration analysis
Rotor alignment, main and tail rotor tracking, static and dynamic balancing, vibration types and how they are reduced, and ground resonance.
What examiners like: classifying vibration by frequency relative to rotor speed (low, medium and high frequency), the difference between track and balance, what tracking equipment measures, and why ground resonance happens on articulated rotors with soft undercarriage. Trap: an out-of-track rotor typically gives a vertical vibration, while a lateral vibration points to balance. This is level 3 for B1, so expect procedure questions. Drill it with the blade tracking and vibration topic.
12.4 Transmissions
Gearboxes (main, intermediate and tail rotor), clutches, freewheel units, rotor brakes, and tail rotor drive shafts with their couplings and hanger bearings.
What examiners like: why a freewheel unit is essential for autorotation, what a rotor brake is for and when it may be used, chip detectors in gearbox oil, and the function of flexible couplings in a tail rotor drive. Level 3 for B1.
12.5 Airframe structures
Airworthiness requirements for structural strength, primary, secondary and tertiary structure, fail-safe, safe-life and damage-tolerant design, zonal and station identification, stresses, drains and ventilation, lightning protection and bonding, construction methods, and the special areas of a helicopter such as the tail boom, engine mounts and transmission deck.
What examiners like: the difference between safe-life and fail-safe, which structure is primary, and how stations and zones are identified. In our bank this is one of the largest Module 12 sub-modules.
The systems sub-modules
From 12.6 onwards, Module 12 runs through the aircraft systems in ATA chapter order. The principles are close to the aeroplane versions in Module 11, with helicopter-specific details:
| Sub-module | Helicopter details examiners like |
|---|---|
| 12.6 Air conditioning (ATA 21) | bleed air and engine-driven supplies, vapour-cycle cooling, distribution and temperature control |
| 12.7 Instruments and avionics (ATA 31, 22, 23, 34) | pitot-static and gyro instruments, vibration indicating and health and usage monitoring (HUMS), avionics layouts at level 1 |
| 12.8 Electrical power (ATA 24) | batteries, DC and AC generation, emergency power, distribution and circuit protection, external power |
| 12.9 Equipment and furnishings (ATA 25) | emergency equipment, seats and harnesses, hoists and cargo hooks (lifting systems), emergency flotation |
| 12.10 Fire protection (ATA 26) | engine fire detection and extinguishing, portable extinguishers |
| 12.11 Fuel systems (ATA 28) | tank layout, crash-resistant systems, indication, refuelling and defuelling |
| 12.12 Hydraulic power (ATA 29) | servo actuators for the flight controls, dual systems, fluids and servicing |
| 12.13 Ice and rain protection (ATA 30) | ice detection, anti-icing versus de-icing, probe heating, rain removal |
| 12.14 Landing gear (ATA 32) | skids and wheels, shock struts, retraction, air-ground sensing |
| 12.15 Lights (ATA 33) | external, internal and emergency lighting, searchlights |
| 12.17 to 12.19 (ATA 42, 45, 46) | integrated modular avionics, central maintenance computers and data loading, information systems |
Several of these are level 3 for B1, so a question can describe a fault and ask for the most likely cause. The study notes from the flight control note onwards cover each group; instruments and avionics, airframe structures and electrical power are the biggest sub-modules in our bank.
How Module 12 links to the rest of the B1.3 licence
- Module 8 basic aerodynamics gives you lift, drag and stability; Module 12.1 applies them to a rotating wing.
- Module 7 maintenance practices covers the inspection and rigging methods that 12.2 and 12.3 assume.
- Module 15 gas turbine engine covers the turboshaft engines that power most B1.3 helicopters, including free turbine designs that feed the transmission in 12.4. See the Module 15 questions page.
- Module 11 is not on the B1.3 list, but its systems sub-modules are close enough that aeroplane study material can help with 12.6 onwards, as long as you check the helicopter differences.
How to prepare for Module 12
Split the module into three blocks
- Rotor block: 12.1 to 12.4 (aerodynamics, controls, tracking and vibration, transmissions). The most helicopter-specific and the hardest for people from an aeroplane background.
- Structure block: 12.5.
- Systems block: 12.6 to 12.19, best learned system by system with a schematic in front of you.
Work through one block at a time, and sit a full paper after each to check what you have retained across the whole module.
Free and Pro practice
- Free Module 12 quick practice for B1.3: 20 questions with explanations, no account.
- B1.3 Module 12 paper 1: the full 128-question timed paper, free; category A candidates can use the 100-question A paper.
- Printable Module 12 sheet: 50 questions with answers to print or save as PDF. These are exam-style questions written for the app; EASA and the CAA do not publish past papers.
- Pro, on the pricing page, adds papers 2 to 10, sub-module drills such as rotor aerodynamics or tracking and vibration, and all eleven Module 12 notes. No pass guarantee comes with it.
Booking and retakes
You can sit Module 12 at a Part-147 organisation or, in the UK, with the CAA; see the CAA engineer licensing pages. After a fail you wait 90 days, or 30 days after tailored Part-147 retraining. EASA allows three attempts in any 12 months; the UK allows three consecutive attempts and then a one-year wait. Under EASA rules, if the paper was split, each partial exam is passed on its own at 75%.
Your study plan
- Take the B1.3 diagnostic (or the category A diagnostic) to see how Module 12 compares with your other modules.
- Read the free rotary wing aerodynamics note and do the free Module 12 quick practice.
- Work through the rotor block, then structures, then systems.
- Sit Module 12 paper 1 at full length and time.
- Drill the sub-modules where you scored lowest, especially level 3 topics.
- Book when you score 85% on three different papers.
20 free Part-66 Module 12 Helicopter aerodynamics, structures and systems practice questions with answers
Try each one, then open the answer. For the timed experience use the free exam-style paper or the printable version.
1. Emergency breathing systems carried on offshore helicopters provide:
- A. a short air supply to help escape under water
- B. oxygen for high-altitude flight
- C. smoke protection for the pilots only
Show answer
A. a short air supply to help escape under water
Compressed-air or rebreather units give occupants extra time to escape a capsized helicopter.
2. A sudden increase in 1/rev vibration after a bird strike on a main rotor blade most likely indicates:
- A. a normal increase due to fuel burn
- B. blade damage affecting track or balance
- C. a tail rotor gearbox chip light fault
Show answer
B. blade damage affecting track or balance
Damage (dent, skin debond, lost tip cap weight) changes a blade's aerodynamic or mass properties, producing out-of-track or out-of-balance 1/rev vibration; the blade must be inspected to limits before further flight.
3. A 24 V, 40 Ah battery can theoretically supply 8 A for:
- A. 5 hours
- B. 320 hours
- C. 3 hours
Show answer
A. 5 hours
Time = capacity / current = 40 Ah / 8 A = 5 h (ignoring the reduction in capacity at high discharge rates and low temperature).
4. Helicopter VNE usually decreases with increasing altitude because:
- A. retreating blade stall occurs at a lower airspeed
- B. tail rotor authority increases with altitude
- C. engine power increases with altitude
Show answer
A. retreating blade stall occurs at a lower airspeed
At higher density altitude the retreating blade must work at higher angle of attack, so stall is reached at a lower forward speed. VNE placards often show this variation.
5. Some Fenestron-type fan-in-tail units have blades spaced unevenly round the hub. The main reason is to:
- A. save weight by using fewer blades
- B. make the fan turn in both directions
- C. reduce noise by spreading the blade-passing tones
Show answer
C. reduce noise by spreading the blade-passing tones
Uneven (modulated) blade spacing spreads the acoustic energy over several frequencies instead of one strong tone, reducing the noise perceived.
6. Fire extinguisher squib cartridges must be replaced when:
- A. the bottle pressure is low
- B. the fire warning test is done
- C. their life or date limit is reached
Show answer
C. their life or date limit is reached
Squibs contain explosive material with a limited life; they are replaced by date or hours.
7. On helicopters fitted with an auxiliary power unit (APU), the APU can supply:
- A. main rotor drive in flight
- B. fuel pressure for engine start only
- C. bleed air and electrical power on the ground
Show answer
C. bleed air and electrical power on the ground
An APU is a small gas turbine providing compressed air for heating/cooling and engine starting and driving a generator, allowing operation on the ground without main engines.
8. Fretting at a bolted or riveted joint is dangerous in helicopter structure because it:
- A. increases the clamping force of fasteners
- B. damages surfaces and starts fatigue cracks
- C. seals the joint against moisture
Show answer
B. damages surfaces and starts fatigue cracks
Small relative movement under vibration causes fretting wear and corrosion, which acts as a crack initiation site.
9. Why is an instrument's vibration isolation (shock mount) important in a helicopter panel?
- A. Vibration improves the accuracy of gyros
- B. Rotor vibration can damage instruments
- C. Shock mounts provide the instrument earth
Show answer
B. Rotor vibration can damage instruments
Panels or individual instruments are shock-mounted to reduce transmitted high-frequency vibration, which would otherwise shorten instrument life and cause pointer flutter and gyro precession errors.
10. Before loading a database, the technician checks:
- A. the database file size only
- B. the loader software version only
- C. the effective date and part number
Show answer
C. the effective date and part number
Ensure the correct, current data is loaded. Databases have effective periods; loading the wrong cycle or part number gives incorrect data.
11. When a fuel quantity gauge reads correctly on the ground but reads low in flight at a nose-down attitude, the probable cause is:
- A. water contamination in the fuel
- B. probe coverage changing with attitude
- C. a blocked fuel tank vent line
Show answer
B. probe coverage changing with attitude
Gauging accuracy depends on probe positions relative to fuel with changing attitude. Multiple probes and calibration compensate; errors are greatest at extreme attitudes.
12. A permanent hydrophobic coating on a windscreen differs from liquid rain repellent in that it:
- A. is applied on the ground and lasts for a long period
- B. is sprayed from the cockpit when it rains
- C. must be removed before every flight
Show answer
A. is applied on the ground and lasts for a long period
Hydrophobic coatings are durable treatments applied during maintenance. Liquid repellent systems spray fluid in flight as required.
13. In a typical helicopter IMA layout, the cockpit displays receive their data:
- A. over the avionics network from hosted applications
- B. directly from each sensor by separate wires
- C. from the HUMS ground station
Show answer
A. over the avionics network from hosted applications
Display applications receive data across the network from IMA modules and data concentrators instead of hard-wired sensor connections.
14. The requirement for a main rotor gearbox to continue safe operation for a period after loss of lubricating oil is known as:
- A. run-dry (loss of lubrication) capability
- B. freewheel overrun capability
- C. rotor overspeed capability
Show answer
A. run-dry (loss of lubrication) capability
CS-29 requires Category A rotorcraft to show that the rotor drive system can continue to operate for a defined period (typically 30 min) after loss of lubrication, to allow a safe landing.
15. Integration of HUMS data with the on-board maintenance system allows:
- A. automatic replacement of worn gears in flight
- B. vibration findings to be viewed with system faults
- C. the rotor rpm limit to be increased
Show answer
B. vibration findings to be viewed with system faults
Combining HUMS and fault data gives maintenance a fuller picture of the helicopter's condition and simplifies record keeping.
16. Phosphate ester hydraulic fluids (e.g. Skydrol) require seals made of:
- A. neoprene (synthetic rubber)
- B. butyl rubber or ethylene-propylene
- C. natural rubber compounds
Show answer
B. butyl rubber or ethylene-propylene
Seal material must match the fluid. Phosphate esters attack neoprene and many paints and plastics; they are also irritant, so protective equipment is used.
17. A gear 'unsafe' indication with the selector down and no green light is first checked in the cockpit by:
- A. retracting the gear again immediately
- B. pressing lamp test to check the bulbs
- C. switching off the hydraulic system
Show answer
B. pressing lamp test to check the bulbs
A failed lamp or sensor can give a false unsafe indication. The crew checks lamps, then uses alternate indications and the emergency extension procedure if necessary.
18. A tail-mounted white position light on a helicopter shows:
- A. forward over 110°
- B. downward only
- C. rearward over 140°
Show answer
C. rearward over 140°
The white tail light covers 70° either side of directly aft (140° total), completing all-round position light coverage.
19. Energy-attenuating helicopter seats are designed to:
- A. lock rigidly so the occupant cannot move
- B. fold forward to clear the exits
- C. stroke downward to absorb vertical crash loads
Show answer
C. stroke downward to absorb vertical crash loads
Crashworthy seats include energy absorbers that let the seat pan stroke down in a severe vertical impact, reducing the spinal load on the occupant.
20. A vertical one-per-revolution vibration is caused mainly by:
- A. one blade producing more lift than the others
- B. a spanwise mass imbalance of the main rotor
- C. a worn hanger bearing on the tail rotor drive
Show answer
A. one blade producing more lift than the others
A 1/rev vertical bounce comes from a lift (track) difference between blades. Spanwise mass imbalance gives a lateral 1/rev; drive shaft problems give high frequency.
Frequently asked questions
+How many questions are in Part-66 Module 12?
B1.3 and B1.4 candidates sit 128 questions in 160 minutes; A3 and A4 candidates sit 100 questions in 125 minutes. The numbers are the same under EASA and UK CAA rules, and there are no essays.
+Who needs Module 12?
Anyone seeking a helicopter licence: B1.3 (turbine helicopters), B1.4 (piston helicopters), A3 and A4. Aeroplane categories sit Module 11 instead, and B2 candidates cover helicopters within Module 13.
+What is in Module 12 helicopter aerodynamics, structures and systems?
Rotary wing aerodynamics, flight control systems, blade tracking and vibration analysis, transmissions and airframe structures, followed by the aircraft systems: air conditioning, instruments and avionics, electrical power, equipment, fire protection, fuel, hydraulics, ice and rain protection, landing gear, lights, integrated modular avionics, on-board maintenance and information systems.
+Is Module 12 harder than Module 11?
They are different rather than harder. The B1.3 Module 12 paper is 128 questions against 140 for B1.1 Module 11A, but Module 12 adds helicopter-specific topics such as rotor dynamics, tracking and vibration, and transmissions, several of them at level 3 for B1.
+What are the main rotor aerodynamics topics?
Dissymmetry of lift, retreating blade stall, translating tendency, gyroscopic precession, the Coriolis effect, vortex ring state and overpitching, autorotation and ground effect. These sit in sub-module 12.1 and come up on every paper.
+Can Module 12 be split into partial exams?
Under EASA rules, yes: an exam with more than 90 minutes allowed may be split into two partial exams, each with a number of questions that is a multiple of four and each passed at 75%, taken at the same organisation. UK Part-66 has no general partial-exam rule, so ask your exam centre how it runs the paper.
+How long should I study for Module 12?
No authority publishes a figure, and Module 12 is one of the longest papers a B1.3 candidate sits. Most people give it more time than any of Modules 1 to 10. Book when you score 85% or more on three different full papers.
Study offline on your phone too
The Part-66 Prep: EASA & UK CAA app has the same questions plus a module board, essay coach, units drill and an attempt tracker for resit dates.
Keep reading
- Part-66 Modules 1 to 17: The Complete GuideAll 17 Part-66 modules explained: what each covers, which categories sit it, EASA and UK CAA question counts and times, and free practice papers.
- The Part-66 B1 Licence: Modules, Exams and ExperienceThe Part-66 B1 licence explained: B1.1, B1.2 and B1.3 privileges, modules and paper sizes under EASA and UK CAA rules, experience, costs and timescales.
- Part-66 Module 15 Gas Turbine Engine QuestionsPart-66 Module 15 gas turbine questions: 92 for B1.1 and B1.3, 60 for A1 and A3, all 22 sub-modules explained, worked thrust example and free paper.
- Part-66 Module 11 Questions: Aeroplane Structures and SystemsPart-66 Module 11 questions for 11A, 11B and 11C: paper sizes per category, partial exams, every ATA sub-module explained and free timed papers.
- Part-66 Category A Licence (A1 to A4) GuideThe Part-66 category A licence explained: what A1 to A4 holders certify, modules and paper sizes under EASA and UK rules, experience and the path to B1.