Commercial - Aircraft Systems Flashcards
Prop Gov, Oxygen, Pressurization, & Icing Systems
For the two given scenarios regarding the operation of the Prop Governor, describe the end result.
1. Oil Pressure increase
2. Oil Pressure Decrease
DA 40 NG Systems slide
- Oil Pressure increase = Pitch increase = Low RPM
- Oil Pressure decrease = Pitch Decrease = High RPM
Briefly describe how a Prop Governor works, include the effect of high and low oil pressure on prop pitch.
DA40 NG
- The EECUs control a mechanism which compresses or decompresses a spring, the spring sits on top of the L shaped flyweights
- The L shaped flyweights rotate with the prop RPM, when they speed up, centrifugal force pushes them out and that allows for the Pilot valve to open and oil pressure enters the hub, increasing oil pressure & pitch, which decreases RPM. The opposite occurs when the flyweights are slowed down.
- This controls a pilot valve which will open or close a pathway allowing for oil pressure to increase and decrease inside the prop hub, changing the pitch angle of the prop.
With a Fixed Pitch Propeller, what are the different flying conditions that change the efficiency of the prop and RPM?
- Aircraft attitude
- Climbing results in the prop taking a bigger bite of air and therefore decreasing RPM
- Descent results in the prop taking a smaller bite of air and therefore increasing RPM - Aircraft Airspeed
- Acceleration creates a decrease in the prop AOA creating a low pitch condition resulting in an increase in RPM - Altitude
- Higher altitudes can result in high RPMs due to the decrease in air density.
Explain what this image from the DA40NG AFM is meant to convey
That the prop RPM is set to be higher (low pitch) at low power settings to aid in the quick & responsive thrust that is needed to accomplish a go-around.
During what different scenarios can oxygen be helpful?
- Hypoxia
- Hyperventilation
- Carbon Monoxide poisoning
- Smoke/Fumes in the cabin
- Rapid Decompression
What are the 3 components of an oxygen system?
- Storage (containers)
- Delivery system (tubes)
- Mask or Nasal Cannula
What are the 4 types of Oxygen storage systems available?
- ABO - Aviators Breathing Oxygen
* Stored as a gas (cheaper)
* Stored in high or low pressure containers
* Very heavy - LOX - Liquid Aviators Oxygen
*Stored in a liquid state
* The expansion that occurs when oxygen goes from a liquid to a solid allows for space/weight to be saved
*Must be stored at extremely cold temperatures (skin exposure can cause frostbite)
*Becomes flammable when in contact with petroleum products - Solid-State Oxygen - Sodium Chlorate Candles
*A chemical that when exposed to high temperatures, will release oxygen
* Saves weight and space
*Once the chemical reaction occurs, it can be hard to stop
*More of a fire hazard than the 1st two due to the high temps necessary. - MSOG - Molecular Sieve Oxygen Generators
*A machine separate the oxygen from other elements in the air
What are the 3 main types of Oxygen Delivery Systems?
- Continuous Flow
- Diluter Demand
- Pressure Demand
Explain the following type of Oxygen Delivery System: Continuous Flow
- A continuous flow of oxygen flows to the user from the storage container
- Economical, cheap
- Very wasteful, flows whether you are breathing or not
- Typically used at FL280 and below
Explain the following type of Oxygen Delivery System: Diluter Demand
- Only provides oxygen when the user is inhaling
- Diluted with Cabin air to provide the proper percentage of Oxygen
- Typcially used at FL400 and below
Explain the following type of Oxygen Delivery System: Pressure Demand
- Oxygen is under positive pressure
- This causes the lungs to inflate, forcing the oxygen into the lung nodules
- Used above FL400, because other systems become inneffective.
What are the different types of oxygen masks?
- Nasal Cannulas
- Oral-Nasal Re-Breather
- Quick-Don
- Drop Down units (Dixie Cups)
Explain how the following Oxygen mask works: Nasal Cannulas
- Continuous flow device
- Use is restricted to 18,000ft (FAR)
* This is due to the fact the blood oxygen levels can be reduced if you breath out of your mouth or talk too much
Explain how the following Oxygen mask works: Oral-Nasal Re-Breather
- Has a plastic bag that is used to collect the exhaled air where it is mixed with oxygen to be inhaled again.
- Common and cheap
- Used up to FL250
Explain how the following Oxygen mask works: Quick-Don
- Must be donned with ONE hand in LESS THAN 5 seconds
- Must also be able to accomdoate glasses
- Usually rated up to FL400
How are cabins pressurized in piston driven aircraft?
Air is taken from the Turbocharger after being compressed (pressurized), it is then sent through a Sonic Venturi (flow limiter), a Cooler, and then to the cabin.
Sonic Venturi: Limits the amount of air taken from turbo by accelerating air to sonic speeds creating a shock wave which acts as a barrier;
How does Pressurized air leave the Cabin?
Via the Outflow Valve, calibrated to keep pressure at safe levels
* There is also a Safety Dump Valve in case the Outflow Valve fails or cannot lower cabin pressure fast enough
PHAK Ch 7
What are stall strips for & how do they work?
Purpose
* To make a stall more controllable by ensuring the wing stalls away from the Ailerons first
Function
* Stall strips work by changing the Stagnation point on that part of the wing (point at which the air separates above and below the wing)
* The stall strip causes the airflow behind it to separate from the wing before the rest of the wing normally stalls.
Source: Boldmethod
https://www.boldmethod.com/learn-to-fly/aircraft-systems/how-stall-strips-work-on-aircraft-explained/
