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HELICOPTER AIR SERVICE PROGRAM 405

Table III-II
AVERAGE BLOCK SPEED
[[ 3 columned table]]
|---|---|---|
|Aircraft Type| Year in Service| Average Block Speed (miles per hour)|
|Sikorsky S-51| 1947| 60.5|
|Bell 47| 1949| 58|
|Sikorsky S-55| 1952| 70|
|Sikorsky S-58| 1956| 88.1|
|Vertol 44*| 1958| 59|
|Vertol 107| 1962| 108.7|
|Sikorsky S-61| 1962| 106.5
[[/end table]]

Block speeds are substantially lower than cruise speeds as they reflect the entire period from take-off to let-down rather than cruise time alone. Length of aircraft hop is a prime determinant in block speed so that differences in route and operating characteristics of the carriers will account for variations in achieved speed with identical or similar equipment. Increased speed, combined with the increased seating capacity, produces a compounded effect on seat mile productivity. In the table below is shown the substantial increase in aircraft productivity which is represented by the recent, rapid increases in vehicle design.

Table III-12
SEAT MILE PRODUCTIVITY
[[3 columned table]]
|---|---|---|
|Aircraft Type| Seats| Seat Mile Productivity Per Block Hour|
|Sikorsky S-51| 3| 182|
|Bell 47| 3| 174|
|Sikorsky S-55| 7| 490|
|Sikorsky S-58| 12| 1,057|
|Vertol 44*| 15| 885|
|Vertol 107| 25| 2,718|
|Sikorsky S-61| 28| 2,982|

[[underlined]] Trend of Unit Operating Costs [[/underlined]]

The influence on unit operating costs of the increased seat mile productivity of the new turbine aircraft can be seen in the average expenses per available seat mile for the industry. The effect of the economies of new equipment on average industry costs cans be seen even though only two of the three carriers have new equipment available. The adverse effect of CHA's present holding operation with older equipment is evident in the cost data shown in Table III-13. Whereas the unit costs of LAA and NYA have dropped substantially with the operation of turbine equipment, the seat mile costs of CHA have increased from the level achieved when Midway-O'Hare flight frequency was at a peak. 

III-14