B - The ASI (17/18-05-18) Flashcards
How does an ASI work?
The capsule is fed with pitot/total pressure and the casing is fed with static.
The difference is therefore just dynamic pressure and this is used to show IAS.
What are the errors associated with an ASI?
Instrument error
Maneouvre error
Position error
Compressibility error
Density error
What happens if there is a blockage in the ASI?
PUDSOD
POCSUC
What happens if there is a leak in the pitot tube in an ASI?
Some of the total pressure will escape and therefore the ASI will under read.
What happens if there is a leak in the static line of the ASI in an unpressurised aircraft?
The static pressure will be the same as that in the cabin which is slightly lower than actual static pressure due to suction forces from airflow.
Therefore it will slightly over read.
What happens if there is a leak in the static line of an ASI in a pressurised aircraft?
The static pressure will then become cabin pressure so the ASI reading will be useless.
What is the position error of an alternate static source in comparison to the main one?
Slightly more due to the main static port being in the best place, therefore the alternate must be in a slightly worse place with slightly more position error.
How can static pressure be regained if all static ports are blocked?
The face of the VSI can be smashed to allow static pressure to run through it’s inner workings.
This sacrifices the VSI.
What is VNE and how is it shown on an ASI face?
It is the never exceed speed, going faster will cause structural damage, it is usually a light aircraft speed.
The red line at the end of the dial.
What is VNO and how is it shown on the ASI face?
It is the normal operating speed that should not be exceeded but can be in calm air conditions, usually for light aircraft. Doing so may cause damage so ground crew must be informed.
It is shown by the start of the amber region.
What is VS1 and how is it shown on an ASI face?
It is the clean wing 1g stall speed and is shown on the ASI face at the start off the green region.
What is VFE and how is it shown on an ASI face?
It is the max speed with flaps extended and is shown by the ending of the white region.
What is VS0 and how is it shown on an ASI face?
It is the stall speed in full landing configuration, and is shown by the start of the white region.
What is VYSE and how is it shown on an ASI face?
It is the best rate of climb speed for an engine failure on a twin engine aircraft and is shown by the blue line on the ASI.
What is VMO?
The maximum operating CAS in a large aircraft.
What is MMO and how is it shown on an ASI/Mach meter?
The maximum operating Mach number for a large aircraft.
It is shown by the barbers pole (red and white striped needle)
