file:  Blower.txt
version:  29Jun99
contents:  Notes from Dave's log book on air sampling and operation of 
           the air sample blower on the community air sample inlet 

"Blower" refers to the centrifugal fan on the community air sample duct. 
Its volume flow rate was measured by the C-130 data system variables
INFLOW and INFLOWC.

a. The air sample duct blower was mounted in the rack with CSU ice 
   nuclei equipment.  During the May 1998 field project, Dave Rogers was 
   responsible for turning the blower on/off and checking on the flow. 
   In general, the blower was off before take-off, to avoid creating low 
   pressure in the sample duct from the blower suction.  After it was 
   switched on, a valve was adjusted to get INFLOW or INFLOWC values of 
   about 1000 LPM.  That value was based on advice from Al Schanot, in 
   order to obtain approximately isokinetic flow at the inlet, outside 
   the airplane.  There was usually sufficient flow even with the blower 
   OFF.  The flow showed some sensitivity to air speed and angle of 
   attack.  Once adjusted, the flow was fairly steady, so it did not get 
   adjusted very often. 

b. In supercooled clouds with >~0.2g/m3 liquid water, the air sample 
   inlet sometimes rimed shut, as evidenced by INFLOW decreasing and 
   lack of response to valve adjustments.  The rime always melted off 
   after a minute or two, and INFLOW recovered.  Sometimes the rime 
   would form again.  There was no way to confirm that the anti-ice 
   heater was working, such as measuring its temperature.  Examples
   of this occurred on the May 18 flight, 22:00-23:40, and a plot
   can be seen at:
   http://lamar.colostate.edu/~dcrogers/Arctic/inflow/518_flow.htm
   
c. At the beginning of the May field project, we noticed that the NCAR 
   CN counter was not correctly piped into its sample tube.  So it was 
   measuring some mixture of outside air and cabin air.  The problem was 
   found and fixed May 9.  Tests with a HEPA particle filter showed the 
   piping fix was ok.  There are a few comments in Dave's flight notes, 
   comparing NCAR, CSU and Hudson CN values.  The CN counter seemed to 
   work fine after the piping was fixed.  
   
d. When the cabin was cold-soaked overnight, it took more than an hour 
   for the CN counters to warm up to operating temperature. 

e. Problems with the "interstitial" air sample inlets were recognized 
   fairly early in the May 1998 project, and showed contamination from 
   the aircraft pressurization system exhaust.  Jim Hudson organized 
   several tests of this problem and had the flight engineer cycle the 
   cabin pressure up and down.  The CSU equipment was almost always 
   connected to the community duct inlet, which did not show any 
   evidence of a contamination problem in May.

f. The CSU equipment was disconnected from the air sample piping and 
   removed from the rack.  Other equipment was mounted in the rack for 
   the July field program.

Following are specific notes about operation of the blower and some 
comparative CN values during the May campaign.

980424
    1257 blower OFF
    1311 blower ON; displayed values INFLOW are not calibrated (volts?) 

980502 
    1813 blower OFF 

980504 
    1510 cabin is cold ~2C; ground power ON
    1733 CN status light red (too cold), both NCAR and CSU
    1813 CN status light green (ok)
    2201 NCAR CN 1700/cc; CSU 170; Hudson 170 
    0054 blower ON, adjust valve to ~1/2
    0351 blower OFF

980507 
    1724 blower OFF 
    1843 blower OFF during taxi
    1916 duct flow 830 LPM; turn blower ON - flow 950 LPM
    2123 NCAR CN 2000/cc; CSU 800; Hudson 360
    2341 NCAR CN 2000/cc; CSU 200; Hudson 200
    ~0012-0030 cabin pressure up/dn - Hudson tests
    0320 blower OFF

980511
    1708 NCAR CN 6000/cc; CSU same
    1810 blower ON
    1812 NCAR CN ~400/cc = CSU = Hudson 
    1830 adjust blower 2000 LPM -> 950
    2253 CSU shows CN spikes = probably exhaust from ship or C-130
    2353 NCAR CN 350/cc; CSU 400; Hudson 430

980515
    1651 blower OFF
    1702 INFLOW 600; INFLOWC 4000? (should be about the same ..?)
    1825 blower ON
    1919 air is clean, NCAR CN 130/cc; CSU 400; Hudson 300
    2114 NCAR CN 270/cc; CSu 350; Hudson 270
    2125 CN up/dn, peaks about 800/cc; maybe crossing C-130 exhaust
    2317 NCAR CN 80/cc; CSU 100; Hudson 100
    2329 CN amazingly clean: NCAR and CSU ~20/cc
    0002 INFLOW zero, then recovered to ~1000.  Suspect inlet rimed shut 
         in cloud. 

980518
    1644 blower OFF
    1831 blower ON, INFLOW 900
    2237 INFLOW zero then recovered.  Suspect inlet rimed shut in cloud. 
    2301 ditto
    2309 see about 1/2" rime ice on nose of fuel tank 

980520
    1654 blower OFF, adjust INFLOW to 600 LPM
         during ferry to FAI, NCAR CN ~25000/cc = CSU
    1829 blower ON, adjust INFLOW 1000
    213044 over ship in down-looking video
    222025 ditto
    2217 - 2226 CN spikes NCAR, CSU and Hudson = crossing exhaust plume

980524
    1653 blower OFF
    1809 blower ON

980527
    1652 blower OFF
    1822 blower ON, adjust INFLOW 900
    1853 adjust blower valve
    1921 low CN, NCAR 10; CSU 80; Hudson 300
    2200 adjust blower valve INFLOW 400 increased to 900
    2345, 2354 low CN, ~50/cc at 100m altitude
    0140 adjust blower valve
    0228 adjust blower valve

  --end--