Modified 102E Rosemount thermometer housings used for aerosol sampling.

Inlet Locations

There are three locations on the BAe-146 where Rosemount inlets are employed to sample aerosol, a schematic of their loaction can be seen here. Historically the inlets were designed to house platinum resistence thermometers (PRT), their deisgn has been modified by passing a 3/8" stainless steel tube up the length of the inlet allowing a sample aerosol to be drawn into the cabin.
Rosemount Schematic
Figure 1. Schematic of an unmodified Rosemount 102E housing with the usual PRT embedded on the left and the modified version used for aerosol sampling on the BAe-146.
During the conversion of the BAe-146 in 2001 these inlets, which where routinely used for sampling on the MRF C-130, were designated as aerosol inlets and fitted to the new BAe-146 airframe.
Figure 2. The two Rosemount pairs on the port side of the aircraft (left). (right) The starboard single inlet pair.
If as an instrument user you are considering using one of these inlets to sample from you should keep in mind that these inlets are often some distance from your instrument location on the aircraft. Sample pipe runs of multiple meters are often needed to supply your instrument, as such the transport losses can be appreciable and must be considered.

Documentation

The following documents are available to registered users:
The Rosemount pair aerosol inlet iconTechnical Specification.
A icon Rosemount pair schematic (94.39 kB) of the Rosemount pair hardpoint installation.
FAAM Tech. Note 1, icon Inlet Efficiency (6.62 MB) describing the sampling efficiencies of a modeified Rosemount housings for sampling aerosol

Inlet Behaviour

The Rosemount inlets operate subisokinetically and therefore enhance ambient aerosol, the inlet efficiency is a function of the deceleration of the air in the inlet housing, the density of the particle and the angle of the inlet with respect to the air stream. Examples of efficiency curves for two different aerosol compositions can be seen below. These data are for the Rosemount inlet that the CCNc usually samples from, the rearward port inlet.
Figure 3. Comparison of two different aerosol compositions and the CCN inlet sampling efficiency for each. The black represents the data taken during the Fennec project, the blue represents data taken from one instrument test flight over the North Sea on June 14 2011. Both traces of represent the median and the interquartile ranges of the data collected.
The line pressure behind these inlets can be predicted from ram pressure theory,
Ram Pressure = (Rho·v2)/2
where Rho is air denstity and v the true air speed of the aircraft.
Figure 4.Empirical model to describe the pressure in the sample line behind a Rosemount inlet compared to the static ambient pressure. The relation- ship is based on five flights of data using the pressure transducer in the TSI, 3786 CPC and a validatory set of data recorded using a Digitron manometer from flight B599. No error bars are shown as 1σ is too small to be represented on the plot, ranging from 1.05 to 4.24 hPa across all flights. These data fit well to ram pressure theory.
Assuming an adiabatic process this increased pressure causes a localised heating of a sample. These estiamtes are theoretical maximums as there is no accounting for local heat removal by air the flow in the calculations.
Table 1. Dynamic heating of sample in the Rosemount inlet calculated assuming an adiabatic process.
For a full description of the experiments used to assess the operation of the Rosemount inlets sampling performance with respect to aerosol please see FAAM Tech Note 1, icon Inlet Efficiency or read the chapter on in situ measurements in Jamie's PhD thesis, Airborne CCN Measurements.

Instruments

The Rosemount pairs have no measurements associated with their opperation per se. However, they are the first part of a number of aerosol sampling systems. Namely the aerosol mass spectometer (AMS), the cloud condensation nuclei counter (CCNc), the condensation particle counter (CPC), Nephelometer, the particle soot absorption photometer (PSAP), the volatile aerosol concentration and composition (VACC), the scanning mobility particle spectrometer (SMPS) and the single particle soot photomoter (SP2).

Publications and Presentations

  • Foltescu, V, Selin, E, Below, M, 1995: Corrections for particle losses and sizing errors during aircraft aerosol sampling using a Rosemount inlet and the pms las-x, Atmospheric environment, 29 (3): 449-453
  • Petzold, A, 2009: Interim Report to Subtask 4.1: Characterisation of a Rosemount inlet for airborne aerosol measurement, April 2009
  • Trembath, J, 2012: Aircraft inlets. How good are they? Presentation given at OBR Conference 2012, icon Inlet Presentation 2012 (10.88 MB)

Further Details

This information is made available to all users of the FAAM website. Please note that this work is currently in draft for publication. If you plan to use any information on this page please contact Jamie at FAAM to ensure it is used in the correct manner.

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