STORMFEST92: PROP Messages: 18 Entries..

PROP FIX: 
 
	Propvane #4 did not register wind 
speed information. The wind speed photochopper 
and the digital interface board were ok. It is 
assumed the problem is in the cabling or the 
wind direction transducer is having some effect. 
The decision was made to move the wind speed 
photochopper unit to sensor #3. The photochopper 
unit for sensor #3 has a high threshold. 
 

PROP CALS & ANGLES: 
 
Below are the calibration factors for 
the wind sensors. 
 
prop #		sensor		pitch 
 
1		001		288 
7		002		290 
10		003		295 
3		004		290 
9		005		293 
6		006		292 
 
NOTE: prop #10 was moved with sensor #004 speed 
head (refer to earlier logbook enter under "PROP FIX"). 
 
ANGLES: 
 
height		sensor		angle (measured) 
 
1m		1		92.40 
2m		2		92.54 
4m		3		91.37 
7m		5		91.37 
10m		6		91.12 
 

LOSS OF 10M WIND SPEED. 
	 
	THE 10M ANEMOMETER LOST ITS WIND SPEED   
AROUND 1230 GMT. 
 

10m WIND SPEED: 
 
	The 10m wind speed came back to life 
at 18:45 GMT. 
 

10m WIND SPEED: 
 
	The 10m wind speed went bad again 
at 8:50 GMT. At the time, the temperature was 
dropping and the humidity was up above 95%. 
 

1m PROP WIND DIRECTION 
 
The plot of wind direction differences suggests that the 1m wind 
direction is off by ~2 degreees from the other prop-vanes.  This  
could be some flow distortion near the surface.  Steve will  
re-shoot the 1m boom azimuth. 
 
 

10m WIND SENSOR: 
 
	The 10m meter wind sensor was removed 
and fixed today. A broken wire in the wind 
speed photochopper unit was to blame. The 
sensor was restalled at 19:40 GMT. 
The angle alignment was checked. The new 
angle is 91.87 degrees. 
 

1M wind sensor. 
 
	The angle of the 1M wind sensor  
was reshot today. the reshot angle is 
93.2 degrees. 
 

Removed 10m prop for repairs. 
 

Replaced speed sensor on 10m prop, 
which is now working. 
 

1M PROP: 
 
	While working on the 1m prop 
it fixed itself. The digital board was 
changed with the improvements. If it goes 
down again, the commutator will be checked. 
While re-assembling the sensor, a pin on the 
connector to the digital encoder broke. I 
recommend we change this connector or strain 
relief the cable. 
 

NEW ANGLES FOR PROPS: 
 
	Since the difference between the 
new prop angles and the old are less than 
1 degree they will not be changed except for 
the 10m unit which is out by more than 1 degree. 
 
NOTE: while changing the 10m prop angle the 
wrong command was sent to the sensor. The 
boom needs to be reset. This happened at 
~22.25Z. 
 

1M PROP REMOVED: 
 
	The 1m prop was removed at 14:45Z 
for repairs. 
 

1M PROP INSTALLED: 
 
	The commutator was cleaned with 
alcohol and installed at 15:35Z. 
 

1M PROP WORK: 
 
	The fix to the 1m prop was not 
successful. The speed photo-detector unit 
was replaced. This happened at about 16:00Z. 
Since then it has looked good. 
 

10M PROP LOOSE: 
 
	The 10m propeller was loose. 
 

Logbook summary for prop-vane anemometers 
 
Feb 1: 
No wind speed output from prop vane #4.  Moved photochopper unit  
from unit #4 to unit #3, since #3 photochopper had high threshold. 
 
Placed at following heights: 
 
height          sensor          angle (measured) 
 
1m              1               92.40 
2m              2               92.54 
4m              3               91.37 
7m              5               91.37 
10m             6               91.12 
 
Feb 4: 
10m speed quit around 1230 GMT; recovered at 1845 GMT. 
 
Feb 5: 
10m speed quit again at 0850 GMT. 
 
1m wind direction appears off by ~2 deg from other prop-vanes. 
Reshot ange at 93.2 deg. 
 
10m prop repaired by fixing a broken wire in the photochopper. 
Reinstalled at 1940 GMT; angle measured at 91.87 deg. 
 
(Note both angles are ~0.8 deg greater than first measurement.) 
 
Feb 18: 
Removed 10m prop for repairs.  Replaced speed sensor and is now working. 
 
Mar 8: 
Worked on 1m prop. 
Exchanged 10m and 1m props. 
 
Remeasured aligment angles: 
 
props:  height          angle (degrees) 
        10m             90.63 
         7m             91.60 
         4m             91.60 
         2m             91.60 
         1m             92.62 
 
Changed alignment angle for 10m prop, but sent wrong command to sensor 
at 2225 GMT and now the boom needs to be reset. 
 
Mar 9: 
1m prop removed at 1445 for repairs.  Cleaned commutator and reinstalled 
at 1535.  Replaced photo-detector at 1600. 
 
Mar 15: 
Found 10 prop loose. 
 
 

Calculated aerodynamic roughness length: 
 
Found near-neutral periods and fit logarithmic profile 
to prop wind speeds: 
 
Jday	Wind Dir	zo (cm)		u* (cm/s)	rms error (cm/s) 
 
45	SE		0.5		35		1.0 
46	NW		0.5		41		1.7 
48	SE		0.3		51		3.8 
49	NW		0.5		41		1.6 
52	NE		0.5		35		1.8 
69	N		0.4/0.5		92		2.9/3.2 
70a	N		0.4		56		2 
70b	N		0.4		41		0.7 
 
Thus the roughness length appears to be 0.5 cm for winds from SE, NE or 
NW and 0.4 cm for winds from N.