Instruments Flashcards
What is Brass?
an alloy of copper and zinc
What is steel?
an alloy of iron and carbon
What is a Wheatstone bridge?
The measuring of electrical resistance to measure temperature, as electrical resistance changes with temperature of a resistor exposed to the outside air.
What is a TAT probe made of?
Nickel-plated beryllium copper with a platinum wire resistance sensor inside
What 3 air temp errors exist?
Instrument error
Environmental error (solar heating (use shading), icing)
Heating error - friction
What total air temp prob does the 737 have?
Aspirated - generates airflow from bleed air to pull in outside air when stationary.
What are the 2 basic types of air temp thermometer?
Direct reading
Remote reading
What is static air temperature?
Temp of undisturbed air
TAT =
and
RAT =
TAT = SAT + RAM RISE
RAT = SAT + MEASURED RAM RISE
What is TAT?
Max temp of air when brought to a stop, inc heating
What is ram rise?
Difference between air temp and temp due to heating
Or put another way: difference between SAT and TAT
What is measured ram rise?
Unable to measure exact due to inefficiencies - less that total ram rise
What does RAT stand for?
Ram Air Temperature - similar to TAT but less due to inefficiencies
What is the recovery factor Kr?
Ratio of measured ram rise to total ram rise.
Measured ram rise formula =
Ram rise x Kr
SAT formula =
RAT/ 1+(0.2 x Kr x M^2)
In Kelvin
TAT read out on 737 is really what?
RAT - because cannot get entirely accurate
What can SAT sometimes be called?
OAT or COAT (Corrected Outside Air Temp)
What is RAT sometimes called?
IOAT (Indicated Outside Air Temp)
RAT can be converted to SAT by which 4 methods?
Navigation computer
Accurate formula
Tables
Air Data Computer
What is the rapid formula to work out ram rise in the air?
(TAS/100)^2
What is absolute zero in deg C?
-273
What is 0 deg C in Fahrenheit?
32 deg F
PITOT PRESSURE =
DYNAMIC + STATIC
What instruments use only static pressure?
Altimeter
VSI
Which instruments use static and pitot pressure?
ASI
Machmeter
What is position error?
Location on aircraft will affect air.
Suction will reduce static pressure. Pitot affected too.
How much depends on location, speed, turb, aoa etc
Position error is greatest when?
High aoa and low speed
What is manoeuvre Induced Error?
Temporary fluctuations of air pressure at the static vents mostly due to change in aoa, flaps/slats activation.
Pressure instruments can lag and may not be instant due to…?
Manoeuvre Induced Error
Higher Alt = the longer the Error will last
What is CAS or RAS corrected for?
Position error and Instrument error
What is VFE?
Max flap operating speed
What is VS0?
Flaps down stall speed also with undercarriage down.
What is VLO?
Max landing gear operation speed
What is VLE?
Max speed with landing gear extended
With a blocked static vent the ASI will:
In a descent…?
In a climb…?
Descent = over-read
Climb = under-read
With a blocked pitot tube, the ASI will:
In descent…?
In climb…?
Descent = under-read
Climb = over-read
If there is a leak in the pitot tube what will happen to the ASI?
Reduce pitot pressure so ASI will under-read
What is ISA at MSL?
Pressure =
Temp =
Density=
Pressure = 1013.25 hPa Temp = 15 deg C Density= 1225 g/m^3
From MSL up to 36,090 (11km) temp reduces by…?
1.98 deg C/1000ft
From what Alt is temp a constant -56.5 deg C?
36,090 ft up to 65,617 ft (20km)
How many feet per hPa at ISA MSL?
27 ft
Density Alt formula =
Density Alt = Pressure Alt + (ISA Deviation x 120)
