SHIP'S MAGNETISM, PART -04, NAV AIDS, PHASE -II, CHIEF MATE EXAM (MMD), Coefficient A

Coefficient A — Constant Magnetic Compass Deviation Explained 🧭 | Ship’s Magnetism | Mmd exam This lesson explains **Coefficient A**, the type of magnetic compass deviation that remains constant regardless of the ship’s heading. Coefficient A represents a *fixed error* on the compass and is divided into two key parts — both important for compass correction and exam numericals: 🧲 REAL A — Constant Deviation from Soft Iron Real A occurs due to *unsymmetrical horizontal soft iron* in the ship, such as: • unequal longitudinal structures • unequal athwartship beams • irregular soft-iron distribution Because the iron is not balanced, induced magnetism produces the *same deviation on every heading* (North, East, Northeast, etc.). ➡️ Real A is rare on modern ships because most vessels are built symmetrically. So instead of correcting it physically, it is normally treated as *index error on the deviation card.* 🧭 APPARENT A — Not Magnetic, But Looks Like It Apparent A behaves like Real A, but is caused by: • defective compass card • mis-aligned lubber line • observation or calculation mistakes These produce constant deviation — but *not due to magnetism.* 📐 HOW COEFFICIENT A IS FOUND Coefficient A is calculated by averaging deviations on multiple headings. Adjusters usually use *eight headings* (cardinal + inter-cardinal) so other coefficients cancel out — leaving only A. This method is standard during *compass adjustment & deviation card preparation.* 🎯 Who Should Watch ✔ Chief Mate / Mate (MMD) ✔ OOW & Cadets ✔ Compass adjustment learners ✔ Anyone studying ship magnetism & deviation Understanding Coefficient A builds a strong base for compass numericals and safe bridge navigation. 🌐 Connect with Sailor Rider YouTube:    / @sailor_rider   Facebook:   / 19imzynlrp   Instagram: https://instagram.com/sailor_rider?ig... Threads: https://www.threads.com/@sailor_rider 🏷 TAGS Coefficient a ship magnetism constant compass deviation explained real a compass error apparent a compass deviation horizontal soft iron magnetism index error deviation card magnetic compass correction tutorial merchant navy compass deviation chief mate magnetism lesson oow compass deviation study navigation aids compass correction induced magnetism ships compass adjustment explanation deviation coefficients explained marine navigation magnetic compass #MagneticCompass #Navigation #MerchantNavy #ChiefMateExam #NauticalScience