The Vertical Speed IndicatorNavigation — Instrumentation — DGCA CPL practice questions
Question 1 of 9
The vertical speed indicator indications may be in error for some seconds after starting or finishing a climb or descent. The error is a result of:
All 9 questions — The Vertical Speed Indicator
Navigation — Instrumentation · DGCA CPL. The correct option is marked on each.
Q1. The vertical speed indicator indications may be in error for some seconds after starting or finishing a climb or descent. The error is a result of:
- A.a combination of time lag and manoeuvre induced errors✓
- B.a combination of position error and manoeuvre induced errors
- C.manoeuvre induced errors only
- D.a combination of time lag and instrument error
Why: When starting or finishing a climb/descent both time lag (choke needs seconds to establish new differential) and manoeuvre-induced error (vent fluctuations + counterweight inertia during attitude change) occur simultaneously. See Section 6 . — "Some seconds of error" = time lag + manoeuvre-induced. These two almost always pair together in DGCA questions.
Q2. The advantage of having the VSI dial presentation in logarithmic spacing rather than in linear spacing is that:
- A.at low rates of climb or descent the pointer movement is much larger and so is more easily read✓
- B.readings are instantaneous
- C.a greater range of rates of climb and descent is shown
- D.the internal mechanism is simplified by deletion of the calibration choke
Why: On a logarithmic scale, graduations near zero are widely spaced, so a small rate produces a proportionally larger pointer arc — improving readability at the low rates typical of IFR approaches. See Section 8 . — Logarithmic = better resolution at low rates, NOT greater range or simpler mechanism.
Q3. In the IVSI, lag error:
- A.is overcome by feeding a sample of static pressure to the case and delaying it to the capsule
- B.is overcome by using a special dashpot accelerometer assembly✓
- C.is overcome by the use of logarithmic presentation
- D.is only overcome when initiating a climb or descent
Why: The dashpot (vertical acceleration pump) responds instantly to vertical acceleration, providing an immediate pressure signal before the normal choke differential develops. See Section 7 . — "Dashpot", "accelerometer", and "dynamic vane" are synonymous IVSI terms — know all three.
Q4. Because the VSI measures rates of change of static pressure and not actual values of static pressure, position error:
- A.never affects VSI indications
- B.may cause errors in the VSI during the take-off run✓
- C.may cause errors in VSI indications whenever airspeed is changed
- D.may cause errors in VSI indications whenever airspeed is changed, even if there is no change in position error
Why: Position error manifests most strongly when airspeed is changing rapidly. The take-off run is the most significant case of rapid acceleration. The VSI interprets the transient false static pressure as a rate of change. See Section 6.2 . — The VSI is a rate instrument — position error affects it through the rate of change of position error with changing airspeed, not by its static value alone.
Q5. When entering a steep turn, an IVSI is likely to show:
- A.no change in altitude
- B.a climb✓
- C.a descent
- D.a slight descent at high airspeed only
Why: In a steep turn, centrifugal force pushes the dashpot piston towards the bottom of its cylinder. This lowers the pressure on the capsule side, which the instrument interprets as a climb (capsule contracts as if static pressure is falling). See Section 7.2 . — IVSI steep turn = false CLIMB. Memorise: centrifugal → piston sinks → capsule contracts → reads climb.
Q6. If the static vent becomes blocked during a climb:
- A.the VSI will stop at the rate of climb of the aircraft at the time of blockage
- B.the VSI will indicate a decreasing rate of climb
- C.the VSI will return to zero✓
- D.the VSI will indicate an increasing rate of climb
Why: With static blocked, no pressure change reaches either the capsule or the case. The existing differential across the choke equalises through the choke itself, collapsing to zero — the needle returns to zero. See Section 6 . — VSI blockage → zero. Unlike the altimeter (freezes) or ASI (reads take-off speed), the VSI measures differential — so both sides equalise and the reading drops to zero.
Q7. In conditions of clear air turbulence:
- A.the standard VSI is more sensitive
- B.the IVSI is more sensitive✓
- C.both types will react the same
- D.the vertical acceleration pump will not be affected
Why: The IVSI dashpot responds to every vertical acceleration, including random turbulent bumps. This makes the IVSI pointer flutter considerably in CAT, which is a known limitation. See Section 7.2 . — In severe turbulence, the IVSI pointer may be nearly useless. Use altimeter trend or standard VSI for reliable information.
Q8. Change of temperature as an aircraft climbs or descends:
- A.will affect VSI readings whenever temperature lapse rate differs from standard conditions
- B.is compensated at the metering unit by means of a capillary and orifice✓
- C.has no effect on the VSI as only static pressure is used in this instrument
- D.may be allowed for by use of tables or computer
Why: The capillary-and-orifice combination in the metering unit provides built-in compensation for the varying relationship between pressure change and altitude at different altitudes and temperatures — giving a consistent ft/min output. See Section 4 . — Metering unit = capillary + orifice = altitude (density/temperature) compensation. This is the defining design feature of the VSI.
Q9. Permissible limits of accuracy of the VSI are ....... when ....... within a temperature range of ....... and ....... outside this range.
- A.±250 fpm, on the ground, −20°C to +50°C, ±300 fpm
- B.±200 fpm, at any height, −20°C to +30°C, ±300 fpm
- C.±250 fpm, at any height, −20°C to +50°C, ±300 fpm
- D.±200 fpm, on the ground, −20°C to +50°C, ±300 fpm✓
Why: The serviceability limits are ±200 ft/min on the ground within the temperature range −20°C to +50°C , and ±300 ft/min outside that range. See Section 9 . — Learn this sequence: 200 / ground / −20 to +50 / 300 . Tested verbatim in DGCA. The +50 vs +30 confusion is the most common error.