Flight Instruments & Airplane Systems Flashcards
What are the three essential components needed for engine operation?
Fuel, Air, and Ignition
These three components form the basic requirements for internal combustion: Fuel provides the energy source, Air provides oxygen for combustion, and Ignition provides the spark to start the combustion process. All three must be present in the correct proportions and conditions for the engine to operate properly.
What is the primary purpose of magnetos in an aircraft engine?
To generate electricity independently of the electrical system for spark plugs, providing redundancy
Magnetos are self-contained devices that generate electrical current for the spark plugs without requiring the aircraft’s battery or electrical system. They are spun by the engine itself, creating a redundant ignition source. Most aircraft have dual magnetos for safety - even if the entire electrical system fails, the engine will continue running because magnetos generate their own electricity.
What type of pressure does a static port measure?
Static pressure (air not moving relative to the aircraft)
The static port measures the ambient air pressure unaffected by the aircraft’s forward motion. It’s carefully positioned on the fuselage where the air is as undisturbed as possible. This static pressure is crucial for altimeter, vertical speed indicator, and airspeed indicator operation since these instruments compare static pressure with other pressures to function.
What memory aid tells us where our true altitude will be compared to our indicated altitude when flying from high to low pressure areas?
Assuming we don’t change the altimeter setting
High to low, look out below
This memory aid reminds pilots that when flying from an area of high pressure to low pressure without adjusting the altimeter setting, the aircraft will be lower than what the altimeter indicates. This is crucial for terrain clearance - if you don’t update your altimeter setting when flying into an area of lower pressure, you’re actually flying lower than your instruments show.
**What are the two power sources for gyroscopic instruments?
Vacuum system and Electric system
Aircraft use two different power sources for redundancy: The vacuum system (driven by engine vacuum pumps) typically powers the attitude indicator and heading indicator, while the electric system powers the turn coordinator. This dual-power arrangement ensures some gyroscopic instruments remain operational if one system fails.
What is the main difference between Indicated Airspeed (IAS) and True Airspeed (TAS)?
IAS is what the instrument shows, while TAS is actual speed through the air (increases with altitude)
IAS is the raw reading from the airspeed indicator, measuring dynamic pressure from the pitot tube compared to static pressure. TAS is the actual speed through the air mass, which is higher than IAS at altitude due to lower air density. The difference becomes significant at higher altitudes - TAS increases by about 2% per thousand feet of altitude.
What’s the magnetic compass acceleration error when flying on East/West headings?
Acceleration makes the compass show a turn towards North, deceleration makes it show a turn towards South
Use the memory aid ANDS: Accelerate North, Decelerate South
This error occurs due to the compass’s pendulous mounting and the Earth’s magnetic field. When flying East or West, accelerating causes the compass card to tilt, resulting in an erroneous turn indication toward North. Deceleration causes the opposite effect. This is why pilots use the mnemonic “ANDS” (Accelerate North, Decelerate South).
How much does True Airspeed (TAS) increase per 1,000 feet of altitude?
In percent
2%
Due to decreasing air density with altitude, true airspeed increases approximately 2% per thousand feet above sea level while maintaining the same indicated airspeed. This means at 10,000 feet, your true airspeed would be about 20% faster than your indicated airspeed.
[Actual FAA Written Question]
If an aircraft is equipped with a fixed-pitch propeller and a float-type carburetor, what would be the first indication of carburetor ice?
Loss of RPM
In a fixed-pitch propeller system, the RPM is directly related to engine power. When carburetor ice forms, it restricts the fuel/air mixture, reducing engine power. Since the propeller pitch can’t change, this power reduction is immediately reflected as a drop in RPM.
This is different from constant-speed propeller systems, where manifold pressure would typically show the first indication.
What are the instruments powered by the pitot-static system?
Airspeed Indicator, Altimeter, and Vertical Speed Indicator
These three core flight instruments all rely on air pressure measurements. The Airspeed Indicator uses both pitot (ram air) and static pressure, while the Altimeter and Vertical Speed Indicator use only static pressure. Understanding which instruments use the pitot-static system helps pilots troubleshoot system failures and understand instrument limitations.
What is precession in gyroscopic instruments and why does it matter?
Precession is the tendency of gyroscopic instruments to drift over time, requiring periodic realignment
This is particularly noticeable in the heading indicator, which must be realigned with the magnetic compass periodically. Precession occurs due to the Earth’s rotation and friction in the gyro system. Pilots need to realign their heading indicator typically every 15 minutes or when differences from the magnetic compass are noted.
What information does an airspeed indicator need to calculate airspeed?
Ram air (total pressure) from pitot tube and static air pressure from static port
The airspeed indicator works by comparing these two pressures. Ram air pressure increases with aircraft speed, while static pressure is the ambient air pressure. The difference between these pressures represents the dynamic pressure, which translates to an indicated airspeed. This is why blockage of either the pitot tube or static port will cause airspeed indication errors.
How does the Vertical Speed Indicator differ from an altimeter in terms of pressure measurement?
The VSI measures the RATE of static pressure change, while the altimeter measures absolute static pressure
This is why the VSI shows climb/descent rate while the altimeter shows absolute altitude. The VSI uses a calibrated leak to detect pressure changes, which causes its characteristic 6-9 second lag time. The altimeter, meanwhile, provides instantaneous altitude readings based on current static pressure.
What’s an instrument that would work if both the vacuum and electrical systems fail?
The magnetic compass
Unlike gyroscopic instruments, the magnetic compass requires no power source as it uses Earth’s magnetic field. However, it’s subject to several errors (acceleration, turning, magnetic dip) which make it less reliable in turns or when changing speed. This is why it’s considered reliable only in straight, level, unaccelerated flight.
