Part-66 Module 13 questions are the core of the B2 avionics licence: autopilots, radios, navigation aids, instruments, power generation and the way electrical and avionic systems control the rest of the aircraft. It is the longest exam in Part-66, and B2L candidates meet it in a different shape, one paper per system rating. This page gives the exact paper sizes under EASA and UK CAA rules, explains partial exams and the B2L rating papers, walks through all 22 sub-modules and shows how to build up to a 188-question sitting.
Part-66 Prep is an independent study aid. The exam standard is Appendix II to Part-66 in Regulation (EU) No 1321/2014, replaced for EASA exams by Regulation (EU) 2023/989 from 12 June 2024, and the retained UK Part-66 for UK exams. The Part-66 modules guide shows how Module 13 fits the other modules.
Part-66 Module 13 paper size for B2
| EASA | UK CAA | |
|---|---|---|
| Questions | 188 | 180 |
| Time | 235 minutes | 225 minutes |
| Marks needed (75%) | 141 | 135 |
| Splitting | Up to 3 partial exams (over 180 minutes) | "May be split into two examinations" |
| Essays | None | None |
The format matches every other module: three options, one correct, about 75 seconds a question, 75% pass mark, no negative marking.
Partial exams in practice
Under EASA rules (Appendix II point 1.12), an exam over 90 minutes may be split into two partial exams and one over 180 minutes into three. Each part covers complementary sub-modules, takes a similar time, has a number of questions that is a multiple of four, must be passed at 75% on its own, and must be taken at the same organisation and recorded on the same certificate of recognition. For a 188-question paper, a three-way split gives parts of roughly 60 questions each.
The UK rule is narrower: only the B2 Module 13 paper is named as one that may be split, and only into two. Whether your exam is split, and how, is up to the CAA or your Part-147 organisation, so ask before you book.
Key fact: Splitting changes the stamina problem, not the standard. Each part is still marked at 75% on its own, and failing one part means retaking that part under the usual 90-day rule.
Module 13 for B2L: one paper per system rating
B2L is the limited avionics licence for aircraft outside group 1. Instead of one Module 13 paper, candidates sit a basic paper plus the papers for the system ratings they want endorsed.
| B2L paper | Sub-modules | EASA questions / time | UK CAA questions / time |
|---|---|---|---|
| Basic requirements | 13.1, 13.2, 13.5, 13.9 | 32 / 40 min | 28 / 35 min |
| Communication and navigation | 13.4(a) | 24 / 30 min | 24 / 30 min |
| Instruments | 13.8 | 20 / 25 min | 20 / 25 min |
| Autoflight | 13.3, 13.7 | 28 / 35 min | 28 / 35 min |
| Surveillance | 13.4(b) | 20 / 25 min | 8 / 10 min |
| Airframe systems | 13.11 to 13.19 (UK 13.11 to 13.18) | 52 / 65 min | 32 / 40 min |
A B2L candidate also needs Module 14 only for the instruments and airframe systems ratings. The B2L licence guide explains the ratings and their experience requirements.
How our site handles B2L: our B2L Module 13 papers use the full B2 Module 13 size and cover every sub-module, because the app and the site do not yet offer separate rating papers. If you are sitting individual rating papers, use the sub-module drills for your ratings and treat the full paper as extra coverage.
What Module 13 covers, sub-module by sub-module
B2 works at knowledge level 3 (detailed knowledge) on most avionics topics in Module 13, and at levels 1 and 2 on the mechanical systems and structures. The question numbers in brackets are EASA's suggested figures for the 188-question B2 paper from AMC1 to Appendix II; exam setters may vary them.
13.1 and 13.2 Theory of flight and structures (about 12 questions)
Aeroplane aerodynamics and flight controls, a little rotary wing aerodynamics, and structural general concepts: zones and stations, bonding, lightning strike protection and the fundamentals of structural systems. Our free theory of flight and structures note covers this block.
13.3 Autoflight, ATA 22 (about 24 questions)
The biggest single topic. Fundamentals of automatic flight control: control loops, inner and outer loops, autopilot modes (heading, altitude, vertical speed, approach), yaw dampers, Mach trim, flight directors and autopilot engagement and disengagement logic. Then autothrottle and automatic landing systems, including the categories of approach and the redundancy that makes autoland possible (fail-passive and fail-operational). The autoflight note explains each mode, and the autoflight drill (Pro) targets it.
Exam tip: Many autoflight questions ask what the system does when something fails or is disconnected. Learn the warnings and the order in which modes drop out, not just what each mode does when it works.
13.4 Communication, navigation and surveillance, ATA 23 and 34 (about 27 questions)
Radio wave propagation, antennas, transmitters and receivers, VHF and HF communication, SATCOM, data link, SELCAL, emergency locator transmitters, cockpit voice recorders and passenger address. Navigation: VOR, ADF, ILS, marker beacons, DME, area navigation, flight management systems, GNSS and inertial reference. Surveillance (13.4(b)): transponders and secondary radar, TCAS, ADS-B, weather radar and radio altimeters. Our notes split these into communications, navigation and surveillance, and the communication and navigation drill covers 13.4(a).
Know frequency bands and which system uses which, what each nav aid measures (bearing, distance, deviation), and the principle of each surveillance system.
13.5 Electrical power, ATA 24 (about 13 questions)
Batteries, DC and AC generation, emergency generation, voltage and frequency regulation, power distribution, inverters, transformers, rectifiers, circuit protection and external power. Bus logic and load shedding are frequent topics.
13.6 Equipment and furnishings (about 5 questions)
The electronic side of emergency equipment, cabin entertainment and other electrical equipment.
13.7 Flight controls, ATA 27 and 67 (about 12 questions)
Primary and secondary controls, actuation, protection (stall protection, envelope protection), system operation including fly-by-wire, and rotorcraft flight controls. For B2 the focus is on the electrical and computing side: sensors, flight control computers and redundancy.
13.8 Instruments, ATA 31 (about 20 questions)
Air data (pitot-static, air data computers), gyroscopic and inertial instruments, compasses, angle of attack, stall warning, ground proximity warning, flight data recorders, electronic flight instrument systems, instrument warning systems and engine indications in the cockpit. The instruments note has the detail.
13.9 and 13.10 Lights and on-board maintenance systems (about 12 questions)
External, internal and emergency lights, then central maintenance computers, data loading, electronic library, printing and structure monitoring.
13.11 to 13.19 The mechanical systems from an avionics view (about 54 questions in total)
Air conditioning and pressurisation, fire protection, fuel, hydraulics, ice and rain protection, landing gear, oxygen, pneumatics and water and waste. Each is small on its own (two to eleven questions), but together they make up nearly a third of the paper. The emphasis is on sensors, controllers, indications and warnings: fuel quantity probes, pressure controllers, fire detection loops, anti-skid and air-ground sensing.
13.20 to 13.22 IMA, cabin and information systems (about 9 questions)
Integrated modular avionics, cabin systems such as cabin intercommunication and in-flight entertainment, and information systems such as the electronic flight bag and network servers.
The same systems, different depth
Module 13 overlaps with the B1 Module 11A syllabus, but the knowledge levels flip. From the Appendix I columns:
| Topic | B1.1 in Module 11A | B2 in Module 13 |
|---|---|---|
| Autoflight, communications, navigation | Level 1 (fundamentals of layout and operation) | Level 3 |
| Instruments | Level 2 | Level 3 |
| Electrical power | Level 3 | Level 3 |
| Flight control actuation and system operation | Level 3 | Levels 2 and 3 |
| Fuel system layout and fuel handling | Level 3 | Levels 1 and 2 |
| Hydraulic system operation | Level 3 | Level 3 |
So a B2 candidate needs the deepest knowledge in exactly the areas where a B1 needs only an overview, and the reverse on the plumbing of fuel and structures.
Where B2 candidates lose marks in Module 13
Because the paper is so broad, people rarely fail Module 13 on one topic. They lose a few marks everywhere. The patterns to watch:
- Confusing similar systems. VOR and ADF both give bearings, DME and the radio altimeter both measure distance, TCAS and the transponder both work with secondary radar. Learn what each one measures, from where, and on which band.
- Mode logic. Autopilot and autothrottle questions often hinge on which mode is armed and which is engaged, and what happens at capture.
- Units and conventions. Feet versus metres, knots versus Mach, magnetic versus true. A procedural-error distractor usually uses the wrong one.
- Neglecting the mechanical systems. Some B2 candidates skip fuel, hydraulics and landing gear as "B1 topics". Together they are worth more than autoflight, and the questions focus on sensors and indications, which is B2 work.
- Rushing the late questions. Accuracy drops in the last hour of a long paper. Practise full-length papers so your pace holds.
Using hangar experience
If you already work on aircraft, use it. Before you study a sub-module, look at the system description chapter of the maintenance manual for a type you know and note the components, the indications and the warnings. Then compare it with the syllabus. The exam is generic and does not test one aircraft type, but having a real system in your head makes the generic questions much easier to place. Engineers who have spent time on line maintenance often find the communication, navigation and instrument chapters straightforward and need most work on autoland, IMA and information systems, which they rarely touch. Those coming from a classroom route tend to find the opposite.
How Module 13 links to the rest of the B2 licence
Module 13 builds directly on Module 5 digital techniques (data buses, displays, computers) and Module 4 electronics, and it is paired with Module 14 propulsion, which covers engines from the avionics side. Most candidates sit it last or near last. The Part-66 B2 licence guide shows the full module plan, and B1 vs B2 explains how the B2 depth compares with the B1 view of the same systems in Module 11.
Building up to a 188-question paper
Four hours of exam questions is a test of concentration as much as knowledge. A practical approach:
- Study by sub-module. Use the notes and drills to work through the 22 sub-modules, starting with the heavy ones: autoflight, communication and navigation, instruments and electrical power.
- Mix sets of 40 to 60 questions. Once you have covered several sub-modules, practise in blocks the size of a partial exam.
- Sit a full paper once a fortnight. Even if you will take the real exam in parts, sitting a full paper builds the pace you need: 75 seconds a question for nearly four hours.
- Track weak sub-modules. Write down every sub-module where you drop below 75% and revisit it before the next full paper.
Exam tip: In a long paper, mark questions you are unsure about, answer them with your best guess and move on. There is no negative marking, so a blank answer is the only guaranteed lost mark.
Practising Module 13 on Part-66 Prep
Our Module 13 bank holds 1,911 original three-option questions, 284 of them free, the largest bank of any module. Papers are spread over the sub-modules in line with the AMC weighting, and you choose EASA (188) or UK CAA (180) size on the start screen.
Free, without an account: B2 Module 13 paper 1 at full length, B2L Module 13 paper 1, a 20-question quick practice with explanations, and the printable Module 13 sheet of 50 questions with an answer key. Neither EASA nor the CAA publishes past papers; these are exam-style papers written for the app. Papers 2 to 10, all sub-module drills and the remaining 14 Module 13 notes come with Pro.
Your study plan
- Take the free B2 diagnostic to check Modules 1 to 10 before you start.
- Read the free theory of flight and structures note, then work through autoflight, communication and navigation, instruments and electrical power.
- Use the free quick practice after each block.
- Sit paper 1 at full length, then decide with your exam organisation whether to split the real exam.
- Book when you score 85% or more on three different full papers.
20 free Part-66 Module 13 Aircraft aerodynamics, structures and systems (B2) 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. The ADC applies static source error correction to compensate for:
- A. altimeter hysteresis after climbs
- B. the effect of the Earth's rotation
- C. pressure errors due to static port position
Show answer
C. pressure errors due to static port position
The static pressure at the port differs from true ambient depending on speed, Mach and configuration. SSEC corrects this.
2. The propeller de-ice ammeter drops to a lower value during one part of the timer cycle. This indicates:
- A. normal operation of the timer
- B. an open element or brush fault in that section
- C. a short circuit giving high current
Show answer
B. an open element or brush fault in that section
Each step of the timer powers a known set of heater elements, so the ammeter should show a steady current. A lower reading during one step shows lost continuity in that circuit.
3. In a fly-by-wire aircraft with a sidestick, control 'feel' is provided by:
- A. springs and dampers in the sidestick unit
- B. aerodynamic forces fed back from the surfaces
- C. the trim tab on each surface
Show answer
A. springs and dampers in the sidestick unit
There is no mechanical path from surfaces to the stick, so feel is artificial. Passive sidesticks use springs and dampers; active sidesticks use motors to generate forces and link the two pilots' sticks electronically.
4. A hydraulic system overheat warning usually indicates:
- A. a high reservoir fluid level
- B. low nitrogen precharge in the accumulator
- C. excessive fluid temperature at a pump or reservoir
Show answer
C. excessive fluid temperature at a pump or reservoir
Temperature sensors in pump case drain lines or reservoirs trigger an overheat warning, often due to pump wear, low fluid or heat exchanger problems. The affected pump is normally switched off.
5. The GPS L5 signal (1176.45 MHz) is useful for aviation mainly because, together with L1, it:
- A. replaces the need for accurate satellite clocks
- B. lets the receiver measure and remove ionospheric delay
- C. provides a voice channel between aircraft and ATC
Show answer
B. lets the receiver measure and remove ionospheric delay
Ionospheric delay depends on frequency, so comparing ranges on two frequencies lets the receiver calculate and remove it. L5 is in a protected aeronautical band suitable for safety-of-life use.
6. Flight deck 'flood' lighting differs from integral panel lighting because flood lights:
- A. are built into each instrument face
- B. come on only after an emergency landing
- C. light the panels from outside, from above
Show answer
C. light the panels from outside, from above
Integral lighting is built into instruments and panels. Flood lights shine onto the panels from above or the glare shield, giving general illumination.
7. The engine low-pressure fuel shut-off (spar) valve on a transport aircraft is usually operated by:
- A. a hydraulic actuator
- B. a push-pull cable only
- C. an electric motor actuator
Show answer
C. an electric motor actuator
The LP valve is a motor-operated valve driven from the engine master or fuel control switch and from the fire handle. Position switches provide valve indications.
8. A four-axis helicopter AFCS adds control of the:
- A. collective
- B. tail rotor gearbox
- C. engine starter
Show answer
A. collective
Three-axis systems control pitch, roll and yaw. A fourth axis adds collective control for altitude or speed holds.
9. Before towing an aircraft with hydraulic nose wheel steering, the technician normally:
- A. applies the parking brake
- B. pressurises the hydraulic system
- C. inserts the steering bypass pin
Show answer
C. inserts the steering bypass pin
The bypass (towing) pin depressurises the steering actuator so the nose wheel can turn freely with the tow bar, preventing damage. The parking brake must be released during towing.
10. A high-pressure ground air cart is connected to the aircraft's:
- A. pneumatic manifold through a ground connector with a check valve
- B. low-pressure mix manifold of the conditioning system
- C. fuel tank vent system through a check valve
Show answer
A. pneumatic manifold through a ground connector with a check valve
The HP ground connection feeds the pneumatic manifold for engine start and pack operation. A check valve prevents back-flow.
11. An electronic library system on board is used to:
- A. control the in-flight entertainment content
- B. record fault codes from the engines
- C. store and display manuals and documents electronically
Show answer
C. store and display manuals and documents electronically
The electronic library (or electronic flight bag functions) replaces paper manuals, charts and procedures with digital documents, retrievable on flight deck or maintenance terminals.
12. Functions that may be hosted in IMA modules include:
- A. only the in-flight entertainment
- B. bleed, fuel and brake temperature functions
- C. only the standby magnetic compass
Show answer
B. bleed, fuel and brake temperature functions
The AMC lists examples such as bleed and pressure control, ventilation, electrical load management, circuit breaker monitoring, fuel management, braking and steering control, gear extension and tyre, oleo and brake temperature indication.
13. A static inverter used for emergency AC usually delivers:
- A. three-phase 200 V AC, 50 Hz
- B. 28 V DC to the battery bus
- C. single-phase 115 V AC, 400 Hz
Show answer
C. single-phase 115 V AC, 400 Hz
Static inverters supply essential single-phase AC loads, such as instruments, from the battery.
14. A passenger cabin information system may provide passengers with:
- A. control of the cabin pressurisation
- B. access to the flight deck door
- C. flight information such as moving maps
Show answer
C. flight information such as moving maps
Passenger information systems show moving maps, flight progress, destination information and announcements.
15. Chemical oxygen generators are started by:
- A. an electric current from the cabin bus
- B. pulling the mask, which fires a firing pin
- C. cabin pressure loss acting on a diaphragm
Show answer
B. pulling the mask, which fires a firing pin
Once started, the sodium chlorate reaction cannot be stopped and the generator becomes very hot.
16. The position of a bleed air valve shown on the synoptic page is normally sensed by:
- A. a pressure transducer downstream
- B. the pack outlet temperature
- C. position switches on the valve
Show answer
C. position switches on the valve
Valves carry position (limit) switches or position sensors that report open, closed or in transit. Downstream pressure is shown separately, but valve position is taken directly from the valve.
17. Lift dumpers reduce the landing roll mainly by:
- A. increasing lift for a softer touchdown
- B. reversing the airflow through the engines
- C. putting the aircraft's weight onto the wheels for braking
Show answer
C. putting the aircraft's weight onto the wheels for braking
Destroying wing lift transfers weight to the wheels, so the brakes become effective sooner. They also add aerodynamic drag.
18. When a wing bends upward under flight loads, the upper wing skin is mainly in:
- A. compression
- B. tension
- C. torsion only
Show answer
A. compression
Upward bending shortens the upper surface and stretches the lower surface. The upper skin and spar caps are therefore in compression and the lower skin in tension.
19. The vacuum toilet system on the ground uses:
- A. cabin pressure differential only
- B. a vacuum generator (blower)
- C. a venturi on the fuselage
Show answer
B. a vacuum generator (blower)
Below a certain altitude the vacuum blower provides the differential. Below a set altitude, cabin pressure is too low to move the waste, so an electric blower creates the vacuum.
20. A cabin monitoring system (CMS) may include:
- A. sensors measuring engine vibration levels
- B. cameras at the cabin and flight deck door
- C. the radio altimeter transceivers
Show answer
B. cameras at the cabin and flight deck door
Cabin video monitoring allows the flight crew to identify persons requesting flight deck entry and observe cabin areas.
Frequently asked questions
+How many questions are in Part-66 Module 13?
For B2 it is 188 questions in 235 minutes under EASA rules and 180 questions in 225 minutes under UK CAA rules. B2L candidates sit separate papers for the basic requirements and each system rating they want, from 8 to 52 questions each.
+Is Module 13 the longest Part-66 exam?
Yes. The B2 Module 13 paper is the longest in either system, longer than the 140-question B1.1 Module 11A paper. That is why both systems allow it to be split.
+Can Module 13 be split into two exams?
Under EASA rules any exam over 180 minutes may be split into up to three partial exams, so the 235-minute paper can be taken in two or three parts. The retained UK Appendix II says the B2 Module 13 paper may be split into two examinations.
+What is in Module 13 for B2?
Twenty-two sub-modules covering theory of flight, structures, autoflight, communication and navigation, surveillance, electrical power, equipment, flight controls, instruments, lights, maintenance systems, the mechanical systems from an avionics view, integrated modular avionics, cabin systems and information systems.
+How does Module 13 work for B2L system ratings?
B2L candidates sit a basic requirements paper plus one paper for each system rating: communication and navigation, instruments, autoflight, surveillance and airframe systems. Each paper has its own size and is passed at 75% on its own.
+Is Module 13 different under UK CAA rules?
The UK paper is slightly shorter at 180 questions, and the UK B2L rating papers are smaller, for example surveillance is 8 questions under UK rules against 20 under EASA rules. The syllabus subjects are largely the same.
+How long should I study for Module 13?
There is no official figure. It is the biggest single module in the licence, and many candidates spend three months or more on it alongside work. Book when you can pass full-length timed papers with a margin.
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 B2 Avionics Licence ExplainedThe Part-66 B2 avionics licence explained: what a B2 engineer certifies, the 12 modules and paper sizes under EASA and UK rules, experience and routes in.
- The Part-66 B2L Licence and Its System RatingsThe Part-66 B2L licence explained: the five system ratings, which modules each needs, EASA and UK CAA paper sizes, experience and the upgrade to B2.
- Part-66 Module 14 Propulsion Questions (B2 and B2L)Part-66 Module 14 propulsion for B2 and B2L: EASA and UK CAA paper sizes, the EASA and UK syllabus differences, every sub-module explained, free practice.
- Part-66 Module 5 Digital Techniques QuestionsPart-66 Module 5 questions with a free timed paper: EASA and UK paper sizes for every category, all 15 sub-modules, data buses and number systems.
- B1 vs B2: Comparing the Part-66 Mechanical and Avionics LicencesB1 vs B2 licence compared: privileges, the modules and paper sizes that differ, experience, adding the other category and which suits your career.