B737 captain feels air carrier flight plans fail to reflect real world fuel requirements.

Attributes
ACN	757453
Time
Date	200710
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 6500
Environment
Flight Conditions	IMC
Weather Elements	Rain Ice Snow
Aircraft 1
Controlling Facilities	tracon : zzz.tracon
Operator	common carrier : air carrier
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	descent : approach ground : maintenance
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	757453
Events
Anomaly	inflight encounter : weather other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other
Supplementary
Problem Areas	Flight Crew Human Performance Weather Company FAA
Primary Problem	Company

Narrative:

Flight plans are issued; according to written guidance; without regard for the reality of the day. Fuel planning allows for minimum change. Flight plans are never flown according to the written plan as to altitude; route; speed which all change in actual flight. Other carriers convince commercial radio to demand and force changes in flight which the flight plan does not take into account. A combination of minimum fuel flight planning with unrealistic flight plans combine to create hazardous fuel situations. On the flight to ZZZ the alternate is listed as 'nil' and when dispatch is queried states that the plan is based on the taf and this is all that is required. I requested and received an extra 1000 pounds of fuel and upon arrival into the ZZZ area we were required to conduct an IFR letdown to an ILS to runway 34 in icing conditions and when we broke out at 6500 ft found ourselves in a snow shower situation.

Original NASA ASRS Text

Title: B737 CAPTAIN FEELS ACR FLT PLANS FAIL TO REFLECT REAL WORLD FUEL REQUIREMENTS.

Narrative: FLT PLANS ARE ISSUED; ACCORDING TO WRITTEN GUIDANCE; WITHOUT REGARD FOR THE REALITY OF THE DAY. FUEL PLANNING ALLOWS FOR MINIMUM CHANGE. FLT PLANS ARE NEVER FLOWN ACCORDING TO THE WRITTEN PLAN AS TO ALT; RTE; SPD WHICH ALL CHANGE IN ACTUAL FLT. OTHER CARRIERS CONVINCE COMMERCIAL RADIO TO DEMAND AND FORCE CHANGES IN FLT WHICH THE FLT PLAN DOES NOT TAKE INTO ACCOUNT. A COMBINATION OF MINIMUM FUEL FLT PLANNING WITH UNREALISTIC FLT PLANS COMBINE TO CREATE HAZARDOUS FUEL SITUATIONS. ON THE FLT TO ZZZ THE ALTERNATE IS LISTED AS 'NIL' AND WHEN DISPATCH IS QUERIED STATES THAT THE PLAN IS BASED ON THE TAF AND THIS IS ALL THAT IS REQUIRED. I REQUESTED AND RECEIVED AN EXTRA 1000 LBS OF FUEL AND UPON ARR INTO THE ZZZ AREA WE WERE REQUIRED TO CONDUCT AN IFR LETDOWN TO AN ILS TO RWY 34 IN ICING CONDITIONS AND WHEN WE BROKE OUT AT 6500 FT FOUND OURSELVES IN A SNOW SHOWER SITUATION.

Data retrieved from NASA's ASRS site as of January 2009 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.