very few modifications would make the cut if the only considerations were economic. If the payback period is long, measures providing only modest cost savings—say, through fuel savings—can become economically attractive. Unfortunately, the length of time a particular MDS will remain in the inventory from today is not predictable with much confidence.

The Air Force has a planned retirement schedule for all MDSs based on a number of important factors, only one of which is the estimated airframe life in hours. Other factors include such things as the vintage of the component technology, which affects reliability, the availability of spares, the viability of the vendor base, and other factors that in turn affect not only the estimates of future support costs but also, in some cases, the operational suitability of the aircraft for modern conflict. Aircraft of the class examined by this study typically have long airframe lives, about 30,000-50,000 hours. Considering that a typical utilization rate for these aircraft might be ~500 hours per year, they could be around for 60 to 100 years, if and only if estimated airframe life were the only consideration, which it is not. The other considerations typically lead to the much earlier planned retirement of a particular MDS. These plans become very volatile, however, as budgetary pressures preclude replacement of the MDS with more modern airframes.

Table 2-1 shows the inventory of various MDSs and illustrates the above points by estimating the remaining life assuming 30,000 hours airframe life for those aircraft with very stressful missions and

TABLE 2-1 Inventory and Estimated Retirement Dates Based on Assumed Airframe Lives and Flight Hours Shown

Aircraft Type

Total Active Inventory

Annual Flight Time for an Aircraft (hr)

Assumed Service Life (hr)

Remaining Life (hr)

Estimated Year of Retirementa

Minimum

Maximum

Start

Complete

B-1B

65

273

30,000

23,072

27,007

2089

2103

B-2A

21

275

30,000

25,088

28,378

2095

2107

B-52H

76

316

30,000

8,964

17,080

2032

2058

C-130E

151

502

30,000

−5,727

14,604

1993

2033

C-130E other variants

16

483

30,000

−4,737

11,757

1994

2028

C-130H

272

433

30,000

9,219

27,221

2025

2067

C-130H other variants

130

428

30,000

8,016

26,574

2023

2066

C-130J

37

352

30,000

27,475

29,970

2082

2089

C-130J other variants

16

246

30,000

27,659

29,916

2116

2125

C-135 other variants

32

414

40,000

−7,608

26,007

1986

2067

C-17A

154

1108

40,000

28,247

39,947

2030

2040

C-5A/B/C

111

367

40,000

16,194

26,819

2048

2077

E-3B/C

32

537

40,000

16,886

22,575

2035

2046

E-4B

4

309

40,000

26,219

28,077

2089

2095

E-8C

19

512

40,000

Refurbishedb

Refurbishedb

2035

2045

KC-10A

59

783

40,000

18,607

25,701

2028

2037

KC-135D/Ec

115/65

306

40,000

13,338

23,907

2048

2082

KC-135R/T

420

366

40,000

9,460

26,963

2030

2078

Other

151

538

40,000

23,850

39,922

2048

2078

aIllustrative start retirement date is [2004 + (assumed service life − minimum time remaining (hr))/annual flight time per aircraft], where 2004 is the year the data in the table were collected. The illustrative end retirement date is similar but substitutes maximum time remaining.

bWhile the Boeing 707 was near the end of its commercial life when purchased by the Air Force, the refurbishment was so extensive it might be reclassified as a remanufactured aircraft when put into Air Force service.

cThe Air Force is currently withdrawing the KC-135D/E from the active inventory. Of the 115 total aircraft, 65 KC-135D/E are carried in the active inventory in 2006.

SOURCE: United States Air Force, Program Data System database.



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