DGCA Technical General: Oxygen Systems Questions
48 exam-style Oxygen Systems questions for the DGCA Technical Generalpaper (CPL & ATPL). The first 12 are free below with answers and explanations — sign up free to practise all of them with progress tracking.
- Q1
Without added oxygen the time of useful consciousness at 30000 ft is approximately:
- Atwenty seconds
- Beighty seconds
- Cone to two minutes
- Dsix minutes
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Correct answer: C. one to two minutes
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- Q2
The passenger oxygen drop-down mask stowage doors are released
- A By a lanyard operated by a barometric capsule
- BMechanically
- CElectrically for chemical oxygen generators and pneumatically for gaseous system
- D Manually by the cabin crew
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Correct answer: C. Electrically for chemical oxygen generators and pneumatically for gaseous system
In installations using chemical oxygen generators the mask stowage doors are released electrically, latches being tripped by a signal from the cabin altitude sensing circuit, whereas in gaseous systems the doors are released pneumatically by oxygen pressure admitted to the door actuators. Both are triggered automatically at the preset cabin altitude.
- Q3
An unpressurised aircraft is flying above FL 100 and therefore must have sufficient oxygen for:
- A Both pilots immediately and the cabin crew plus all passengers after 30 minutes above FL 100 but below FL 130
- B Both pilots only
- C Both Pilots and all passengers
- D Both pilots immediately and the cabin crew plus some passengers after 30 minutes above FL 100 but below FL 130
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Correct answer: D. Both pilots immediately and the cabin crew plus some passengers after 30 minutes above FL 100 but below FL 130
Above FL100 an unpressurised aircraft must carry oxygen for both pilots immediately, plus the cabin crew and a proportion of the passengers for any period spent above 10,000 ft and up to 13,000 ft in excess of 30 minutes. Not every passenger needs a supply at these lower cabin altitudes, only a specified percentage.
- Q4
Without added oxygen the time of useful consciousness at 40000 ft is approximately:
- Atwenty seconds
- Bthree minutes
- Ceighty seconds
- Dsix minutes
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Correct answer: A. twenty seconds
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- Q5
The demand valve of a diluter demand oxygen regulator in normal mode operates when
- AThe pressure to the regulator is more than 500 psi
- B User breathes in
- CUser requires 100% oxygen
- D Diluter control is in the ‘normal’ position
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Correct answer: B. User breathes in
In the normal (NORMAL) mode a diluter-demand regulator only delivers oxygen when the user inhales, the drop in pressure created by breathing in opening the demand valve. This conserves oxygen because nothing flows between breaths.
- Q6
The maximum altitude without oxygen at which flying efficiency is not seriously impaired is:
- A10,000 feet
- B17,500 feet
- C25,000 feet
- D30,000 feet
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Correct answer: A. 10,000 feet
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- Q7
To reduce control effectiveness
- A Full face and provide a continuous flow of oxygen
- B Mouth and nose and provide a continuous flow of oxygen
- C Full face and provide oxygen on demand
- D Mouth and nose and provide oxygen on demand
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Correct answer: A. Full face and provide a continuous flow of oxygen
Protective breathing equipment for smoke and fumes uses a full-face design to seal and shield the eyes, nose and mouth, and supplies a continuous flow of oxygen to keep contaminated air out of the mask. The continuous flow and full-face coverage give complete protection in a smoke-filled environment.
- Q8
In a pressure demand oxygen system:
- AEach member of the crew has a regulator
- BEach member of the crew has a continuous oxygen supply
- COxygen is supplied with a continuous pressure flow
- DOxygen demand will cause the pressure to rise
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Correct answer: A. Each member of the crew has a regulator
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- Q9
Oxygen supplied to the flight deck is
- A Gaseous, diluted with ambient air if required
- B Chemically generated and diluted with cabin air if required
- C Gaseous, diluted with cabin air if required
- D Chemically generated, diluted with ambient air if required
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Correct answer: C. Gaseous, diluted with cabin air if required
Flight-deck crew oxygen is supplied as gaseous oxygen from storage cylinders through diluter-demand regulators that mix in cabin air as required to conserve oxygen at lower altitudes. Chemical generators are used for passenger supplies, not the flight deck.
- Q10
When smoke appears in the cockpit, after donning the oxygen mask the pilot should select
- ANormal
- B 100%
- C Diluter
- DEmergency
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Correct answer: D. Emergency
With smoke in the cockpit the pilot dons the mask and selects EMERGENCY, which supplies 100% oxygen under positive pressure. The positive pressure keeps smoke and fumes from leaking into the mask, which the plain 100% (normal) setting would not guarantee.
- Q11
In a continuous flow oxygen system, oxygen is supplied:
- Aonly when the mask is plugged into the socket connection
- Bonly on passenger inhalation through the mask
- Conly when the cabin altitude is above 18000 f
- Donly when the supply has been regulated by the pilot
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Correct answer: A. only when the mask is plugged into the socket connection
This Explanation is Coming Soon
- Q12
What happens if a gaseous oxygen cylinder is over pressurised
- A A pressure relief valve vents the excess pressure into the atmosphere
- BA bursting disc vents the complete contents of the cylinder(s) to atmosphere
- CA pressure regulator will prevent the excess pressure damaging the system
- D A pressure relief valve vents the excess pressure into the fuselage
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Correct answer: B. A bursting disc vents the complete contents of the cylinder(s) to atmosphere
Gaseous oxygen cylinders are protected by a bursting disc that ruptures at a preset overpressure and vents the entire contents of the cylinder overboard. A green indicating disc on the fuselage skin blows out to show ground crew that a thermal discharge has taken place.
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