FAAM CORE Rosemount/Goodrich type 102 Total Air Temperature probes, deiced and non-deiced models
The temperature probes consist of Goodrich/Rosemount type 102 housings, one with a deicing facility (deiced) and one without (non-deiced). Both probes employ similar inlets to draw flow across a sensor using inlets that have been designed to minimise water and particle ingress, as well as minimising interaction of the air with the inlet walls. The deiced housing contains a heater that is operated by the flight manager only during periods when icing is suspected. A correction is automatically applied to the data during these periods to account for the effect of deicing heat on the ambient measurement. The deiced inlet is slightly larger and has a much higher airflow through the sensor to minimise the impact of deicing heat on the ambient air sample. As a result the scoop area on the front of the inlet is also greater on the deiced inlet.
Three types of sensor are available for use; all three types can be used in either housing and the same type of sensor need not be used in both housings. Before a campaign, PIs should specify which type of sensor they would like to be fitted in the de-iced and non-de-iced housings. The three types are as follows:
- "Loom"-type PRTs. These are the original sensors from Rosemount, and consist of a thin platinum loom wound round a mica support. They have been used at FAAM for many years, but are no longer routinely manufactured and are thus in short supply. They are prone to drift and can break unpredictably. They exhibit a relatively complex time response comprising two components - the fast response of the platinum wire, and the slower response of the mica supports. Overall, 1s is FAAM's estimate for the response time as per the standard processing, but corrections have been developed to extract fast-response (~150 ms) data (not part of core processing, contact FAAM for further details).
- "Plate"-type PRTs. These sensors replace the original platinum loom with a commercially-sourced thin film PRT. They are readily available and inexpensive, and have been shown to hold their calibration over long periods of flying. When two plate-type PRTs are fitted in the de-iced and non-de-iced housings, the average difference between the two reported temperatures is often better than 0.1 K over the course of many flights. They are slower to change temperature than the loom-type PRTs due to their slightly higher thermal mass, giving them a ~1 s response time.
- Thermistors. For this type of sensor, a commercially-sourced glass bead thermistor replaces the original PRT. Very much in the development stage, it is hoped that these thermistors will replace the loom PRTs to provide a fast, reliable measure of temperature on the FAAM aircraft. There are complicating factors such as self-heating which need to be accounted for during calibration, but these sensors show great promise and can be tested on upcoming flights.
The report from the first Temperature working group is available here:
A report written in March 2016 on the existing issues and development of alternatives to platinum loom sensors is available here:
pdf FAAM Air Temperature Measurements on the BAe-146 Current issues and the development of alternatives to existing sensors (3.80 MB)
The Goodrich Total Temperature Sensors Technical Report 5755 (Revision C 1994) details the probe housings fitted to the FAAM aircraft, and is available from UTC Aerospace.
Data from both probes are reported at 32Hz. FAAM processing simply applies standard calibration corrections (including dynamic heating, recovery factors etc.) to the measured resistance of the probe, and reports this as true air temperature.
|Deiced (right and) non-deiced housings||platinum loom-type probe element||probe assembly|