Q1. A direct reading compass should be swung when:
A compass re-swing is required when there is a large, and permanent, change in magnetic latitude.
Q2. A direct reading compass should be swung when:
A compass re-swing is required when there is a large, and permanent, change in magnetic latitude.
- 1 (Physics): The Earth’s magnetic field strength (H and Z components) changes with latitude.
- 2 (Effect): This changes the induction in soft iron components, altering the deviation coefficients. Therefore, a significant latitude change requires a re-swing.
Q3. A magnetic compass must be swung after?
Long term change in latitude. (
- Reiteration: Matches logic of Question 14. Permanent/Long-term change in Latitude affects Soft Iron magnetism.
)
Q4. Aircraft magnetism caused by hard iron:
is not usually influenced by the earth’s magnetic field (
- Definition: Hard Iron is permanent.
- Stability: Its strength is constant and does not depend on the current external field strength or induction.
)
Q5. Aircraft magnetism caused by vertical soft iron:
varies with magnetic latitude but not with heading (
- Component: Vertical Soft Iron (e.g., landing gear struts).
- Induction: Induced by the Vertical (Z) component of Earth’s field.
- Variable: Z changes with Latitude (Dip). Therefore, the magnetism varies with Latitude.
)
Q6. An aircraft has hard iron magnetism only, and this hard iron magnetism is represented by a red pole in relative bearing 070 from the compass. On what heading will the westerly deviation be maximum?
Correct answer is – Heading 020
- Calculate the Aircraft Heading: The red pole is fixed to the aircraft at a relative bearing of 070° (meaning it is always 70° to the right of the aircraft’s nose).
- To find the required heading, use the relationship:
- Magnetic Bearing of Pole = Aircraft Magnetic Heading Relative Bearing of Pole
- 090° = Heading 070°
- Heading = 090° – 070°
- Heading = 020°
- Conclusion: When the aircraft is on a heading of 020°, the red pole (situated 70° to the right) is positioned due East (090° Magnetic), pushing the North-seeking needle to the West and causing maximum Westerly deviation due to Hard iron magnetism.
Q7. Coefficient B, as used in aircraft magnetism, presents
Correct answer is – A value representing the deviation registered on headings East and West
Q8. Compass deviation is defined as the angle between:
Correct answer is – Magnetic North and Compass North
Q9. Compass swings should be carried out:
only on the compass swinging base or site (
- Requirement: The environment must be free of external magnetic interference (underground cables, rebar, other aircraft).
- Location: Designated Compass Swing Bases are certified free of such interference.
)
Q10. Consider the following statements on coefficient A, as used to describe deviation:
Correct answer is – All 3 answers are correct
Q11. Deviation applied to magnetic heading gives:
Correct answer is – compass heading
Q12. Deviation applied to magnetic heading gives:
compass heading (
- Formula: Compass + Deviation = Magnetic.
- Re-arrangement: Applying deviation to Magnetic yields Compass (calculating backwards from the chart to the cockpit).
)
Q13. Deviation due to coefficient A is mainly caused by:
a misaligned lubber line (
- Coefficient A: Constant error on all headings.
- Mechanical Cause: Often due to the instrument being installed crookedly (Lubber line not aligned with longitudinal axis).
)
Q14. Deviation on MH 180 is -5 and on MH 000 it is +3. Calculate coefficient C:
The correct answer is b) Coefficient C = +4.
- Concept: Coefficient C acts along the lateral axis, producing maximum deviation on North and South headings.
- Given Values: Deviation on North = +3, Deviation on South = -5.
- Formula: Coefficient C = (Deviation on North – Deviation on South) ÷ 2
- Calculation: (+3 – (-5)) ÷ 2 = 8 ÷ 2 = +4
Q15. Hard iron magnetism in aircraft
Correct answer is – Is permanent of nature
Q16. Hard iron magnetism in aircraft may be caused by
Correct answer is – All 3 answers are correct
Q17. If the total force of the earth’s field at a point is T and the horizontal and vertical components H and Z, the value of H is found by the formula:
H=T cos dip (
- Trigonometry: H is the adjacent side to the Dip angle. T is the hypotenuse.
- Formula: H = T times cos(Dip).
)
Q18. In discussing parameters P, Q and R of aircraft hard iron magnetism
The correct answer is a) -Q indicates a blue pole in the left wing.
Here is the breakdown of the aircraft hard-iron magnetism components (P, Q, and R) based on the sources, which explains why only statement (a) is correct:
- Component P (Longitudinal): This represents the hard-iron magnetism acting along the fore-and-aft axis of the aircraft. By convention, a P component indicates that the blue pole is forward (in the nose), not a red pole.
- Component Q (Lateral): This represents the magnetism acting along the wing-tip to wing-tip axis. A Q component means the blue pole is to starboard (the right wing). When the polarity is reversed to -Q, it means the blue pole is to port (the left wing), making statement (a) correct.
- Component R (Vertical): This represents the magnetism acting vertically through the aircraft. A R component indicates that the blue pole is beneath the compass, not a red pole.
Because statements b and c describe the opposite polarities for their respective positive components, they are incorrect.
Q19. In the calculation of deviation, the following headings are recorded: MH CH 358 356 091 087 182 186 273 271 Coefficient A is
Correct answer is – +1. Using the data provided:
- North: MH 358° – CH 356° = +2° (Easterly)
- East: MH 091° – CH 087° = +4° (Easterly)
- South: MH 182° – CH 186° = -4° (Westerly)
- West: MH 273° – CH 271° = +2° (Easterly)
- Step 2: Sum the deviations algebraically. Add the calculated deviations from the four headings together: (+2) + (+4) + (-4) + (+2) = +4
- Step 3: Calculate the average. Divide the total sum by the number of observations (which is 4) to find Coefficient A: +4 ÷ 4 = +1
Therefore, Coefficient A is +1, exactly matching the correct answer from your query.
Q20. In the calculation of deviation, the following headings are recorded: MH CH 358 356 091 087 182 186 273 271 Coefficient B is
Correct answer is – +1
- Step 1: Calculate the deviation for the East and West headings. Deviation is the angular difference between the Magnetic Heading (MH) and the Compass Heading (CH), calculated as Deviation = MH – CH. Positive values indicate Easterly deviation, while negative values indicate Westerly deviation. Using the data provided in your query:
- East: MH 091° – CH 087° = +4° (Easterly)
- West: MH 273° – CH 271° = +2° (Easterly)
- Step 2: Apply the formula for Coefficient B. Coefficient B is calculated by taking half the algebraic difference between the deviations on the East and West compass headings. The formula is: Coefficient B = (Deviation on East – Deviation on West) ÷ 2.
- Step 3: Perform the calculation.
- Coefficient B = (+4 – (+2)) ÷ 2
- Coefficient B = (+4 – 2) ÷ 2
- Coefficient B = 2 ÷ 2
- Coefficient B = +1
Therefore, Coefficient B is +1.
Q21. In the calculation of deviation, the following headings are recorded: MH CH 358 356 091 087 182 186 273 271 Coefficient C is
- Step 1: Calculate the deviation for the North and South headings. Deviation is the difference between the Magnetic Heading (MH) and the Compass Heading (CH), calculated as Deviation = MH – CH. Using the data provided:
- North: MH 358° – CH 356° = +2° (Easterly)
- South: MH 182° – CH 186° = -4° (Westerly)
- Step 2: Apply the formula for Coefficient C. Coefficient C is calculated by taking half the algebraic difference between the deviations on the North and South compass headings. The formula is: Coefficient C = (Deviation on North – Deviation on South) ÷ 2
- Step 3: Perform the calculation.
- Coefficient C = (+2 – (-4)) ÷ 2
- Coefficient C = (+2 + 4) ÷ 2
- Coefficient C = 6 ÷ 2
- Coefficient C = +3
Therefore, the correct answer for Coefficient C is +3.
Q22. Magnetic compass swinging is carried out to reduce as much as possible:
deviation. (
- Object: We cannot change Variation (Earth) or Acceleration errors (Physics).
- Target: We swing the compass to measure and nullify Deviation caused by the aircraft’s metal.
)
Q23. Permanent magnetism in aircraft arises chiefly from:
Correct answer is – hammering, and the effect of the earth’s magnetic field, whilst under construction
Q24. Soft iron is comparatively ……. to magnetize whilst hard iron is ……. to demagnetize.
easy; difficult (
- Properties: Soft Iron (High permeability, low retentivity) magnetizes easily but loses it easily.
- Hard Iron (Low permeability, high retentivity) is hard to magnetize but hard (difficult) to demagnetize.
)
Q25. Soft iron magnetism in aircraft
Correct answer is – Is non-permanent of nature, and cannot be reduced by de-gaussing (de-magnetisation)
Q26. The aim of a compass swing is: (1. find deviation/coeffs, 2. eliminate coeffs, 3. record residual)
answers 1, 2 and 3 are all correct (
- Procedure: First, measure the error (1). Second, adjust magnets to remove it (2). Third, record whatever error remains on the card (3).
)
Q27. The angle between Magnetic North and Compass North is called:
Correct answer is – compass deviation
Q28. The compass heading can be derived from the magnetic heading by reference to a:
deviation correction card / curve (
- Relationship: Compass to Magnetic requires Deviation.
- Source: Deviation is recorded for the specific aircraft on a Deviation Card located near the compass.
)
Q29. The deviation of a compass is described as +4. This means that
Correct answer is – The compass heading will have a lower number in degrees than the magnetic heading
Q30. The deviation will change with a change in aircraft heading
Correct answer is – Because the undesired magnetic pole then is moved relative to the direction of the Earth’s magnetic field
Q31. The magnetic force causing compass deviation will be a force in direction
Correct answer is – Perpendicular to the compass needle
Q32. The main requirements of a direct reading magnetic compass are that it should be:
aperiodic, horizontal, sensitive (
- Specs: Aperiodic (does not oscillate/dead beat), Horizontal (to allow card rotation), Sensitive (reacts to weak Earth field).
)
Q33. The maximum permissible deviations after compensation are:
one degree for a remote indicating compass, and ten degrees for a direct reading magnetic compass (
- Standards: Remote systems (flux valves) are precise (pm 1^{circ}). Standby/Direct compasses are allowed larger tolerances (pm 10^{circ} residual deviation is the limit cited here, though practical limits are often tighter, e.g., 3-5 degrees).
)
Q34. The purpose of a compass swing is to?
Align compass north with magnetic north. (
- Goal: To make the compass reading match the actual magnetic heading as closely as possible.
- Process: This involves adjusting compensator magnets to remove deviation, effectively aligning Compass North with Magnetic North.
)
Q35. The quadrantal deviation of the magnetic compass is due to the action of:
the soft iron pieces influenced by the geomagnetic field. (
- Coefficient D: Quadrantal deviation.
- Cause: Induced magnetism in horizontal Soft Iron (induced by the Earth’s field).
)
Q36. When an aircraft is moved to a place of lower magnetic latitude
Correct answer is – The deviation values will decrease because the horizontal component of the terrestrial field is becoming stronger
Q37. Which of the following is an occasion for carrying out a compass swing on a Direct Reading Compass?
After an aircraft has passed through a severe electrical storm, or has been struck by lightning (
- Event: Lightning strikes involve massive currents.
- Effect: This can instantly magnetize the aircraft’s steel structure (Hard Iron), drastically altering the deviation. Immediate swing is required.
)
Q38. Which of the following will probably NOT result in a deviation change on a DRC
Correct answer is – Turning the ADF on in flight