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"Engine Upgrades, Digitization to Keep B-52s Flying " Topic


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15 Sep 2018 6:23 a.m. PST
by Editor in Chief Bill

  • Removed from Modern Aviation Discussion (1946-2007) board
  • Crossposted to Ultramodern Warfare (2008-present) board


232 hits since 9 Sep 2018
©1994-2018 Bill Armintrout
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Tango01 Supporting Member of TMP10 Sep 2018 2:41 p.m. PST

…Into 2050s.

"The Air Force has begun a series of major upgrades to its oldest aircraft the B-52H Stratofortress to keep the fleet viable until about 2050.

The iconic B-52 airframes first came off the production line more than six decades ago.

The service currently possesses 76 of the long-range subsonic strategic bombers, split between Barksdale Air Force Base, Louisiana, and Minot Air Force Base, North Dakota, and operated by the service's Global Strike Command as well as Air Force Reserve Command.

The B-52H has a robust airframe and flexible mission capabilities for both conventional and nuclear warfare, which has allowed it to keep flying as much younger aircraft are retired, said Maj. Jacob Davis, chief B-52 requirements officer at Global Strike Command…."
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TGerritsen10 Sep 2018 2:57 p.m. PST

Currently they plan on sticking to 8 engines, which seems silly to me in the modern age. They get no real advantage but increase fuel expenditure and have to do a lot of maintenance as a result. Wouldn't make more sense to go with 4 engines and the improvements in maintenance, flying costs per hour and reliability?

Lion in the Stars10 Sep 2018 6:19 p.m. PST

There's much less re-engineering to stick with 8 engines.

Also, note that the B52 was originally delivered with J57 (JT3Cs to a civilian) engines, and later refitted with TF33s (JT3Ds, which added a small fan section to the basic JT3C). Same engines as on the 707. Just twice as many, because the BUFF was a lot heavier at full load.

I'd recommend going with 8x CFM56s (as used on current 737s, including P8 Poseidons). They're current production, if a technology-generation old, and there are literally tens of thousands of them in service. CFM56s are ~60-61" across the fan, while the TF33s are 53" across the fan.

Stepping up to something massive like the engines used on a 777 runs into ground clearance problems. At full fuel load, the B52's wings droop enough to put the outboard engine intakes 5-6 feet off the ground!

Using CFM-56-3 or -7s (both used on 737s, the -7 is used on the P8 Poseidon so is already in military service) means an engine already designed around a ground clearance issue. And the -7s used on the Poseidon push 27,000lbs thrust, 10klbs more than the existing engines.

Pretty sure no pilot will ever tell you that their airplane has too much power. evil grin

I will admit that having 8x engines instead of 4x means you have double the engine maintenance hours. But CFM56s are rather spectacularly low-maintenance (up to 50,000 hours before the first shop visit!), and sufficiently reliable that the FAA gives 737s using those engines a 180-minutes over water flight approval (1 inflight shutdown in every 333,000 hours of operation).

Thresher01 Supporting Member of TMP10 Sep 2018 7:18 p.m. PST

100 years of operational service out of an aircraft.

Not bad!!!

Rumors are for some F-35 variants, we may get less than 8,000 hours of service, which boils down to just over 330 days of life, assuming they fly 24 hours/day, which of course they don't. Still, the difference in longevity is astounding.

Lion in the Stars10 Sep 2018 8:33 p.m. PST

The first generation F16s only lasted about 5000 flight hours, required reinforcement to last 8000 hours.

8000 hours is 4 years flying 40 hours a week, about what you'd expect in wartime. NATO pilot standards are only 200 hours a year for minimum competence, so that's 40 years at minimal flight hours.

Thresher01 Supporting Member of TMP10 Sep 2018 9:39 p.m. PST

Might be able to squeeze even more out of them then, at least in Europe, since I've read some pilots there are only getting 80 – 100 hours, or so a year.

TGerritsen11 Sep 2018 12:43 a.m. PST

Lion, thanks for the detailed answer. I wonder if after re-engining they will get a range boost.

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