B-737 MMA

The 737 Gets Bomb Racks (11/29/04 entry)

Strategy Page has an update on the Navy’s new Multimission Maritime, the replacement for the P-3 Orion. Back in February I noted that Lockheed thought their prop-driven P-3 replacement was superior to Boeing’s 737-based idea, but this summer the Navy decided to go with Boeing and is going to get seven 737s modified to the MMA standard for testing and training before production begins by the end of the decade.

Although the B-737 MMA is a two engine jet, compared to the four engine turboprop P-3, it is a more capable plane. The MMA has 23 percent more floor space than the P-3, and is larger (118 foot wingspan, versus 100 foot) and heavier (83 tons versus 61). Most other characteristics are the same. Both can stay in the air about ten hours per sortie. Speed is different. Cruise speed for the MMA is 910 kilometers an hour, versus 590 for the P-3. This makes it possible for the MMA to get to a patrol area faster, which is a major advantage when chasing down subs spotted by sonar arrays or satellites. However, the P-3 can carry more weapons (9 tons, versus 5.6.) This is less of a factor as the weapons (torpedoes, missiles, mines, sonobouys) are, pound for pound, more effective today and continuing that trend. Both carry the same size crew, of 10-11 pilots and equipment operators. Both aircraft carry search radar and various other sensors. The 737 has, like the P-3. been equipped with bomb hard points on the wings for torpedoes or missiles.

Also, from Aviation Today:

The reason for the P-3 replacement? “The major need comes from the P-3s’ having reached their service life–the metal in the aircraft is reaching its fatigue life,” explains Tim Norgart, director of business development for Boeing’s MMA program. “So if they were retained, they would basically have to be rebuilt.”

“Right now [the P-3s] are being retired at a pretty significant rate,” he adds. “Their processing systems and sensors also are in dire need of upgrades.” Norgart, a former P-3C wing commander, says the Navy found it would be difficult to upgrade older aircraft with newer systems because of their older architecture. He believes the Navy has “a quantifiable need for [the B737] platform for its `assured access’ mission.” A long-range patrol aircraft capable of doing anti-submarine warfare (ASW) is a major requirement in the Navy’s Seapower 21 war fighting doctrine, which outlines how the Navy will fight for the next 20 years.

“If you can’t get into a body of water to operate an aircraft carrier, then you can’t get a whole lot of Hornets [F/A-18s] across the beach,” says Norgart. “So the MMA will be out there in front of the fleet, clearing the way and making sure the water is safe for them to go through.”


Skeptics may question the U.S. Navy’s selection of a commercial jetliner for missions that include low-level, over-the-water surveillance. Not to worry, says Boeing’s Tim Norgart. “We’ve taken the aircraft [the Boeing Business Jet, based on the B737] out twice now and let the Navy fly it. We put weight on board to duplicate an MMA’s mid-mission weight, above 150,000 pounds [68,040 kg], and let the Navy pilots fly it [at] 200 feet off the water at loiter speeds of 208 knots.” (MMA’s maximum takeoff weight is 184,200 pounds [83,555 kg].)

The high-bypass turbofan engines are fuel-efficient, says Norgart, adding that the fuel burn curve at 500 feet (about 4,000 pounds per hour) vs. 30,000 feet is only about 700 pounds different per hour. He adds that the turbofan is more reliable than the turboprop because it has fewer parts.

The Navy’s range and endurance requirements call for 1,200 nm out, four hours on station searching for submarines, and 1,200 nm back home. Boeing says its aircraft exceeds that requirement. Norgart points out that while a P-3 will take four hours to get to the target, MMA will be there in less than three hours. “That equates to a higher probability of target detection, since it can’t travel away as far from the tracking aircraft,” he says.

Another advantage of the Boeing jet over a turboprop aircraft is the ability to self-deploy faster, according to Norgart. A fully loaded MMA is billed as having a 4,800- to 4,900-nm self-deployment range, cruising at 445 knots. Aerial refueling presumably would need to be infrequent. The Navy has bases that allow deployment worldwide, Boeing maintains.

Although I can’t tell when that Aviation Today article was originally published, it’s got a lot of good info, including more-detailed rundowns of the avionics and weapons systems.

Also, b737.org has a little page on the MMA that notes the conversion to an MMA from a standard production aircraft will happen at Wichita, which is where the coversion of 767s into USAF tankers was going to happen.