Air Data System Total Air Temperature Probe Use of NCEP Warm Bias Data Presented by David Cole.

Air Data SystemTotal Air Temperature Probe

Use of NCEP Warm Bias Data

Presented by David Cole

BUG

Air Data System

Air Data System

AIR DATA MODULE

TAT PROBE

TAT FUNCTION

TOTAL AIR TEMPERATURE

• Δtw Total air temperature error correction due to resistance of the nominal length of wiring between the probe and the air data computer (degrees).

• TTi Indicated total air temperature - the total air temperature as measured at the input terminals of the air data computer (degrees absolute).

TOTAL AIR TEMPERATURE/STATIC AIR

TEMPERATURE• TT Total air temperature - indicated total air

temperature corrected for wiring resistance and recovery error (degrees absolute); the air data computer output in degrees C.

• Ts Static air temperature - total air temperature corrected for the adiabatic temperature rise due to compressibility (degrees absolute); the air data computer output in degrees C.

FORMULASTOTAL AIR TEMPERATURE

• TT= Indicated Total Air Temp + Total Air Temp Error Corr. Due to Wire Resistance

1- 0.2 * Computer Mach Number Squared

STATIC AIR TEMPERATURE

• TS= Total Air Temp

1+ 0.2 * Computer Mach Number Squared

TAT TEMPERATURE CURVE

TAT/ADIRU FUNCTION

TAT PROBE ANALYSIS

0

1

2

3

4

5

6

7

8

Engine TAT delta

Mean airframe TAT delta

airframe TAT - Left engine TAT

TAT PROBE REVIEW• NCEP DATA ALLOWS CAL TO ISOLATE TAT

PROBES THAT HAVE A HIGHER THAN NORMAL TEMPERATURE READING

• ISOLATION OF THESE PROBES ALLOWS CAL TO REPLACE THEM PRIOR TO A POSSIBLE FAILURE

• CAL AND BOEING ARE IN THE PROCESS OF IDENTIFYING HOW A HIGHER THAN NORMAL TAT PROBE TEMPERATURE CAN ALTER FUEL MILEAGE