There are currently 67 B-1B bombers in the Air Force fleet plus 29 aircraft in mothballs. They fly approximately 275 hours per aircraft per year. The Air Force would like to improve fuel efficiency, mission flexibility, and altitude capability, which could increase the B1-B utilization rate. The increase in altitude capability is needed to minimize their vulnerability to surface-to-air missiles and to 57 mm and anti-aircraft artilleries; also, they need to be refueled at 20,000 feet or less, which could put both the B-1B and the refueling aircraft in harm?s way. There is, in addition, a chronic low-pressure turbine failure problem associated with high-temperature operation, and this leads to high maintenance costs.

In 2002, Maj Gen Dan Leaf asked Boeing to find the best way to increase B-1B mission flexibility, specifically by increasing altitude capability (see Summary 9 in Appendix C). Boeing studied many aircraft modifications and subsystem upgrades and concluded that re-engining of the F119 was the best solution. It found that the original B-1A altitude and Mach 2.2 speed (which the B-1B structurally inherited) could be restored by increasing the specific thrust of the production F119 engines.

The committee identified one candidate for engine modification:

1. Modify the current F101 through a SLEP. This program would include a thrust increase, maximizing thrust at both midpower and augmentation, along with durability improvement incorporated in the low-pressure turbine. This would improve altitude capability by an additional 5,000 to 10,000 feet. There would be no specific fuel consumption benefits.

Figure 3-4 describes the existing F110 (engine used on F-16) SLEP. The F101 engine used by the B-1B uses the same core as the F110. The F101 SLEP would be similar to the F110 SLEP described in the figure.

The committee identified three re-engining candidates for the B-1B:

1. Proposed SFC upgrade of the F101 (see Figure 3-5), which would incorporate a new two-stage fan, a SLEP F101 core, a modified low-pressure turbine (LPT) new radial augmenter, and a new elliptical nozzle known as an augmented load-balanced exhaust nozzle (ALBEN) (see Figure 3-6), which has a 10 percent better SFC. The recurring cost is $500,000 per engine. An additional 3,000 foot altitude improvement is expected over the F101 engine modification SLEP. A 40 percent reduction in engine maintenance cost is projected with a time on the wing of 1,000 hours. The first aircraft delivery would occur 48 months after go-ahead. A fuel saving cost of $2.9 million per aircraft per year is anticipated.

FIGURE 3-4 F110 SLEP. SOURCE: General Electric.

FIGURE 3-5 Engine comparison of current versus proposed F101 upgrade. SOURCE: General Electric.

2. First, re-engine the B-1B with a production F119 engine (see Figure 3-7). The F119 engine provides survivability to eliminate the need for radar cross section vanes in the aircraft inlet. Then, optimize the robust F119 fan for improved spillage drag. Finally, integrate a new elliptical low-observable exhaust system (see Figure 3-8), which eliminates significant boat tail drag. Lift/drag improvements could allow the F119-powered B-1B to supercruise for sustained rapid respons

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   FIGURE 3-6 F101 Upgrade-ALBEN. SOURCE: General Electric.

   

   FIGURE 3-7 F119 cross section. SOURCE: Pratt & Whitney.

   

   FIGURE 3-8 Elliptical nozzle. SOURCE: Pratt &Whitney.

   ability. This system solution could provide the Air Force with Global Strike/Global Persistence attack and fighter/attack capability equivalent of seven F-18s in a Global Response Bomber size at a 50 percent improvement in propulsion system total cost of ownership. The F119 upgrade could be achieved for a nonrecurring engineering (NRE) cost (propulsion only) of $100 million.

   3. Re-engining the B-1B with a derivative F119/F135 fan option could trade performance margin for improved fuel economy and enhance the total system impact to the B-1B range/persistence capability. This derivative configuration could be achieved for an NRE of $450 million.

      Fuel Consumption

      To fulfill the statement of task, which is to reduce fuel consumption for the B-1B, there are two alternatives:

      1. EMDP for the F101, which includes a new fan and new nozzle to maximize fuel efficiency for the aircraft. This should decrease fuel consumption by 10 percent at NRE costs of $100 million.

      2. An EMDP of the F119 engine, which would include a new fan and a low-observable elliptical nozzle to maximize fuel efficiency for the aircraft. This is estimated at an NRE cost (propulsion system only) of $450 million to $500 million each.