What does the pitot tube measure?
The total pressure, which is the sum of the dynamic and static pressures
The pressure coming in through the pitot tube inflates a little balloon in the ASI. What role does the static pressure play in this?
The static pressure fills the interior of the ASI, surrounding the balloon and resisting its expansion, which balances the static portion of the total pressure inside the balloon l, which makes the balloon respond only to the dynamic pressure
As the aircraft moves faster thru the air, the more the balloon expands and the higher the needle on the ASI is pushed.
What 3 types of errors can the ASI have that will display a different airspeed on the ASI than what our actual speed through the air is? (IAS vs TAS)
- Position and Instrument error
- Compressability error
- Density error
What does ICE T stand for, in relation to airspeeds?
Indicated (what I read off the ASI)
Calibrated (corrected for positional error, found in the POH)
Equivalent (due to compressability, not an issue in small planes
True Airspeed (Density and temp correction using the E6B)
These are calculated in order.
How does your airpseed indicator behave if the Pitot system becomes fully blocked (both pitot hole and drain hole are blocked) but the static port is still working normally?
It will act like an altimeter
- Airspeed will increase in a climb
- Decrease in a descent
How does our ASI behave if the static port becomes blocked (but the pitot system is still working)?
ASI will behave somewhat normal, so is not realiable in diagnosing a static blockage.
- Airspeed will decrease in a climb
- Airspeed with increase in a descent
This blockage is much more dangerous than a pitot blockage. Because your airspeed will increase in a descent, you will pull back and back and back until you stall because you think you are approaching too fast.
How does the ASI behave with a partial pitot blockage (the front hole is blocked but the drain hole is still open)?
What is the white arc on your ASI?
The flap operating range
Top of the white arc is the highest speed at which you can have flaps extended.
Bottom of the white arc is the slowest speed you can operate with power off and full speed (approach configuration) before you will stall (Vso)
What is the green arc on the ASI?
Normal Operating Range of the AC
- The top of the green arc is your Vno (do not exceed except in smooth air)
- The bottom of the green arc is the slowest you can go in a clean configuration before you will stall (Vs)
What is the Yellow Arc on the ASI?
The Caution Speed Range
- The bottom of this arc is your Vno (Vno is also the top of the green arc)
- The top of the yellow arc/red line is your Vne (never exceed speed)
On multi-engine AC, what is the blue line on the ASI?
The best single-engine rate of climb (Vyse). This is the speed you want to maintain in the event of an engine failure.
In terms of our stalling speed, what should we remember about the IAS?
Our stalling speed will always be the same in terms of Indicated Airspeed and we should not alter our approach speeds from the values stated in the POH
What is Calibrated Airpseed and how do you calculate it? Why is the difference between IAS and CAS so different at low speeds and almost the same as your speed increases?
This is IAS corrected for the instrument and installation error in the pitot-static system.
CAS can be found on the airspeed calibration chart in your POH
At slower airspeeds, your angle of attack is higher, causing air to not go directly into the pitot tube, therefor there is a larger margine of error between CAS and IAS at lower speeds
What is TAS and how do you calculate it?
True Airspeed. The actual speed that the AC is moving through the air. TAS is CAS corrected for the air density.
Found using the E6B
As we climb, what happens in regards to our stall speeds and the TAS?
The TAS at which the AC will stall is always going to be higher than the IAS when at high altitudes or high temperatures.
However the IAS stall speed will always be the same
What is GS?
Ground speed. The actual speed we are moving over the ground. This is our TAS corrected for winds. Can only be estimated during flight planning. Can only get accurate ground speeds when doing GS checks during the flight.
What is a TAA ASI?
Like in the diamond or any other glass cockpit. Tape style ASI with the TAS displayed right on the bottom for you. Which is nice.
Also shows you all your V speeds, which is awesome. Ground Speed is also given in a TAA system.
Why does the TAS stalling speed increase as altitude increases but IAS stall speeds stay the same as what is published in the POH?
The stalling speed at, say, 10000ftASL is greater than the TAS at sea level because the AC must fly faster at higher altitudes to obtain the same IAS and generate the same amount of lift because the air is thinner.
What factors will increase the stall speed (IAS)?
- Stall speed increases as bank angle increases (see picture for formula to calculate stall speed based on bank angle). There is also a chart(s) for this in the POH.
How does the center of gravity affect your indicated stalling speed?
- A forward C of G will have an increased stall speed - Pilot must pull back to hold the nose up. To counter this nose up, there is increase pressure on the horizontal stabilizer, acting as more weight. The AC will have to fly at a higher angle of attack to achieve the same airspeed as compared to a rearward loading or lighter AC.
- An aft C of G will decrease the stall speed. The pilot must push forward on the control column to hold the nose down. This leads to less countering force needed by the horizontal stabilizer and the AC will fly at a lower angle of attack for the same airspeed as compared to a heavier or forward loaded AC
How does turbulence affect stall speeds?
A sudden gust under the wing will shove it up and could drastically increase the angle of attack and stall you then and there even tho you werent close to the stall range.
In a wind shear, you could abruptly lose airspeed in a gust of tail wind or something, causing you to stall even tho you were above the stall speed to begin with.
On a gusty day, what should you do with your approach speed?
Add one half of the gust factor to your approach speed.
EX: Winds are 10G20
Gust factor is 10 so add 5kts to your approach speed
Contamination similar in roucghess to medium or coarse sandpaper on the leading edge of a wing can reduce wing lift by as much as ______ and increase drag by as much as _______.
- Reduce wing lift by 30%
- Increase drag by 40%
How/why does the application of power reduce the the stall speed of the AC?
Reduced angle of attack as well as increases airflow over the wing
