Understanding Your Airspeed

Understanding Your Airspeed

 

General Information

In its purest form, an air speed indicator is simply a differential pressure gauge. This means that it is displaying the difference between two different pressure sources that are being simultaneously applied. In the case of airspeed, the two pressures are Pitot Pressure and Static Pressure.

Pitot Pressure is the pressure that is generated when air is forced into the aircraft Pitot tube because of the forward motion of the aircraft. The Pitot tube is a slender tube that is typically mounted near the front of the aircraft. The opening of the tube is facing forward so that air is forced into it. This tube is connected directly to the input of the air speed indicator.

Static pressure is the standard air pressure at the current altitude. Static pressure will vary due to altitude changes and due to changes in weather.

Standard Static pressure at sea level altitude on a “standard” day is typically 29.92 In Hg (inches of mercury) as measured on a class “A” barometer. Static pressure on an aircraft is measured at the static port. The static port is a small hole usually located on the side of the aircraft. This pressure is applied to all instruments in the aircraft static system, of which the air speed indicator is one.

 

Airspeed Indicators – Product Familiarization

Airspeed Indicators – Product Familiarization

 

General Information

The Air Speed indicator provides the basic function of indicating to the pilot the current speed of his aircraft. The indicator is normally a 31/8” size dial face with a single pointer. Location of this indicator is typically in the top row of instruments on the left side of the panel. In a standard “T”, configuration instrument panel the airspeed indicator would be located just to the left of the attitude gyroscope.

 

Types of Air Speed Indicators

  1. Indicated Air Speed Indicator
  2. True Air Speed Indicator (Manually Operated)
  3. True Air Speed Indicator (Automatically Operated)
  4. Maximum Allowable Air Speed Indicator
  5. Mach Air Speed Indicator
  6. F1 Air Speed Indicator
  7. Helicopter Air Speed Indicator
  8. Dual Scale Indicators

 

Indicated Air Speed Indicators
The Indicated Air Speed (IAS) Indicator provides the pilot with a speed-reading, which is based only on Pitot and Static pressure inputs. This type of indicator does not take into account other variable inputs such as temperature or altitude.

 

True Air Speed Indicator (Manually Operated)
The manually operated True Air Speed Indicator provides the pilot with a method of inputting pressure altitude and outside air temperature via a knob on the instrument face. This knob controls a sub-dial which will provide the pilot with “True Airspeed’ data

 

True Air Speed Indicator (Automatically Operated)
An automatically operated True Air Speed Indicator has both a temperature bulb and altitude aneroid built into the instrument. This type of indicator will always display the true speed of the aircraft without user input.

 

Maximum Allowable Air Speed Indicator
A Maximum Allowable Air Speed Indicator has a second pointer that is set to indicate the maximum permitted speed of the aircraft at the current altitude. This pointer is usually a red barber pole.

 

Mach Air Speed Indicator
A Mach Air Speed Indicator indicates the speed of the aircraft as a percent of the speed of sound. When an object is traveling at the speed of sound it is traveling at Mach 1, twice the speed of sound would be Mach 2, etc…

 

F1 Air Speed Indicator
An F1 Air Speed Indicator is a high-speed indicator, typically 600 Kts. or higher and typically is a drum type indicator.

 

Helicopter Air Speed Indicator
A Helicopter Air Speed Indicator is typically an Indicated Air Speed Indicator that has very low speed-readings.

 

Dual Scale Indicator
One Knot, one Nautical Mile, is equal to 1.15077945 Statute Miles.
One Statute Mile is equal to 0.86897624 Knots. A dual scale air speed indicator will indicate both Knots (KPH or Kts.) and Statute Miles (MPH). Always verify if the customer wants the Kts. or MPH on the outer or inner scale of the dial.