Teaching and Learning Flying - Airplane Instrument Rating

Pitot-Static System

DEFINITION

SAFETY FACTORS

• Proper altimeter setting necessary for safe terrain clearance and traffic separation
• Pitot heat in IMC (iced pitot tube and drain hole may cause ASI to act like ALT)
• Flying from high (temperature and/or pressure) to low, "look out below"

TOLERANCES

a. pitot-static
b. altimeter
c. airspeed indicator
d. vertical speed indicator

1. Exhibit adequate knowledge of the elements related to preflighting instruments, avionics and navigation equipment cockpit check by explaining the reasons for the check and how to detect possible defects
2. Perform the preflight on instruments, avionics and navigation equipment cockpit check by following the checklist appropriate to the aircraft flown
3. Determine that the aircraft is in condition for safe instrument flight including
f. altimeter
h. vertical speed indicator
j. clock
l. pitot heat

4. Note any discrepancies and determine whether the aircraft is safe for instrument flight or requires maintenance

OBJECTIVES

PROCEDURES

1) Includes three basic pressure-operated instruments:
a) Sensitive altimeter
b) Airspeed indicator (ASI)
c) Vertical speed indicator (VSI)

2) Static (ambient) pressure


3) Pitot pressure (impact or ram air pressure)
4) Position error

1) Aneroid barometer
2) Principle of operation
a) Evacuated, corrugated bronze aneroid capsules
b) Pilot adjustable barometric scale, visible in the Kollsman window
3) Altimeter errors
a) Preflight check for mechanical error: (75 feet)
b) Nonstandard temperature effects c) Nonstandard pressure effects ("flying from high to low, look out below!")
4) Encoding altimeter
a) Mode C transponder
b) 125 feet
5) Absolute altimeter (radar or radio altimeter)

1) ASI is a differential pressure guage that measures dynamic pressure
2) Indicated airspeed (IAS)
3) Calibrated airspeed (CAS)
4) Equivalent air speed (EAS)
5) True airspeed (TAS) (TAS = CAS, standard atmosphere at sea level)
6) Mach number (TAS:speed of sound)
7) Airspeed color codes:
• White arc: flap-operating range (from flaps-down stall speed to maximum airspeed with flaps down)
• Green arc: Normal operating range (from flaps-up stall speed to maximum airspeed in rough air)
• Blue radial line: Best single-engine rate of climb speed
• Yellow arc: Structural warning area (from maximum rough air speed to never-exceed speed)
• Red radial line: Never-exceed speed

1) Rate-of-pressure-change instrument
2) Static pressure and calibrated orifice
3) VSI lags behind actual pressure change, but more sensitive than alitimeter

Ammeter indication
Pitot tube warms

COMMON ERRORS

• Failure to study POH for details of pitot-static system in a specific aircraft
• Failure to complete preflight pitot-static instument check
• Failure to detect abnormal operation of pitot-static

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