Cargo air taxi flight lands below minimums due in-flight WX.

Attributes
ACN	233479
Time
Date	199302
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dsm
State Reference	IA
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : dsm
Operator	common carrier : air taxi
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 90 flight time total : 3200 flight time type : 800
ASRS Report	233479
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
Events
Anomaly	inflight encounter : weather inflight encounter other non adherence : published procedure non adherence : far other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation

Narrative:

Encountered lower unforecasted visibility in a large region and stronger winds aloft than forecasted. Due to the required freight load, flight planning on fuel was limited to destination of dsm and an alternate of msp with 45 mins reserve. Combination of hard winds and ice increased fuel consumption to the point that msp was no longer attainable. All other alternates within the region were way below minimums with the exception of oma which was marginal at the time with a dew point spread of 1 degree. If I had diverted to oma I would have had to complete an approach regardless of conditions, due to remaining usable fuel at that time. I elected to try the ILS 13L at dsm even though the RVR was at 2600 ft instead of 4000 ft as required to initiate the approach under part 135 regulations. At decision ht of the approach, I had the field and made a normal landing.

Original NASA ASRS Text

Title: CARGO AIR TAXI FLT LANDS BELOW MINIMUMS DUE INFLT WX.

Narrative: ENCOUNTERED LOWER UNFORECASTED VISIBILITY IN A LARGE REGION AND STRONGER WINDS ALOFT THAN FORECASTED. DUE TO THE REQUIRED FREIGHT LOAD, FLT PLANNING ON FUEL WAS LIMITED TO DEST OF DSM AND AN ALTERNATE OF MSP WITH 45 MINS RESERVE. COMBINATION OF HARD WINDS AND ICE INCREASED FUEL CONSUMPTION TO THE POINT THAT MSP WAS NO LONGER ATTAINABLE. ALL OTHER ALTERNATES WITHIN THE REGION WERE WAY BELOW MINIMUMS WITH THE EXCEPTION OF OMA WHICH WAS MARGINAL AT THE TIME WITH A DEW POINT SPREAD OF 1 DEG. IF I HAD DIVERTED TO OMA I WOULD HAVE HAD TO COMPLETE AN APCH REGARDLESS OF CONDITIONS, DUE TO REMAINING USABLE FUEL AT THAT TIME. I ELECTED TO TRY THE ILS 13L AT DSM EVEN THOUGH THE RVR WAS AT 2600 FT INSTEAD OF 4000 FT AS REQUIRED TO INITIATE THE APCH UNDER PART 135 REGS. AT DECISION HT OF THE APCH, I HAD THE FIELD AND MADE A NORMAL LNDG.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.