title: Why IFR (instrument flight rules)?
abstract: BACKGROUND
  Air medical services can use aircraft equipped to fly under visual flight rules (VFR) or instrument flight rules (IFR). IFR allows the pilot to fly safely into lower weather minimums, potentially increasing the number of EMS flights that can be completed. We examined the advantages and disadvantages of both methods of helicopter flight, the potential service gain with IFR capability, and the financial feasibility of using IFR in an urban air medical program.
  
  
  METHODS
  Retrospective data were collected on the number of missed flights for Vanderbilt LifeFlight during a 6-year period. Focusing on 2 recent years, we examined the number of flights missed because of weather. Data were prospectively obtained on missed flights that could have been completed with IFR from April 1997 to March 1998. Financial estimates were calculated to determine the revenue potential of an IFR program.
  
  
  RESULTS
  An average of 24% of flights were missed from 1991 to 1997. In 1996-97, primary reasons for missed flights included poor visibility and low clouds, conditions in which IFR capable helicopters could fly. Prospective data from 1997-98 indicated an average of 6.7 missed flights per month potentially could have been completed with IFR. Analysis of expenses and revenue suggest that converting a ship from VFR to IFR, which involves both equipment purchases and pilot training, is economically feasible given the potential revenue gained by the number of flights completed during marginal weather conditions.
  
  
  CONCLUSIONS
  Implementing an IFR program increases the safety margin and allows better EMS service to the community.
authors.affiliation: Vanderbilt LifeFlight, Nashville, Tenn., USA.
authors.forename: C
authors.initials: C
authors.lastname: Shuford
authors.forename: R N
authors.initials: RN
authors.lastname: Anderson
mesh_terms: D017732:Air Ambulances / Q000592:standards*; D001359:Aviation / Q000592:standards*; D003362:Cost-Benefit Analysis; D006801:Humans; D012189:Retrospective Studies; D017751:Safety Management / Q000191:economics; D014481:United States; D014887:Weather