Old dog, new engines

a reply to: thebozeian

They actually designed a cruise missile truck based on the 747. It had a rail system on the ceiling to move the missiles to the launch position, and would launch them under the tail.

a reply to: Zaphod58

Yes the CMCA concept in the late 70's. It could carry something like 72 AGM-86's. I still think it could work today for a number of tasks. It would be akin to the USN Ohio class boomers that were modified as SSGN's.

originally posted by: Zaphod58
a reply to: Flipper35

Or how large it would have to be to have full rudder authority if they went to a four engine setup, and lost an outboard.

I suppose a full flying ruddervator would allow it to be small enough to fit in a hangar.

Surely by now they have a system or software program which can control flight through asymmetric thrust control if and when required..? I know there where trials and tests years ago but did anything come of them..?a reply to: Zaphod58

a reply to: Silentvulcan

It would require a pretty significant computer upgrade to do, and it was designed with smaller aircraft in mind.

Rolls Royce is offering the F130 engine used by the E-11A and C-37. They'll undergo final assembly and integration at their Indianapolis plant. The Air Force anticipates a digital flyoff to decide on the new engines.

www.airforcemag.com...

Does it share the same footprint as the P&W,s? If not some new fairing work will need to be done.Wonder if the new algorithm for drag reduction will be added as well?

a reply to: Blackfinger
Zaph and I were discussing this on the previous page a couple of years back. The work on the pylon/nacelle will be part of the contract but limited to only what is absolutely needed to keep it simple and costs down.

a reply to: Silentvulcan

The problem here, assuming a move to 4 engines, if you lose an outboard engine you just lost 25% of your thrust instead of 12.5%. If you throttle the outboard back on the other side to have close to symmetric thrust you are losing 50ish% of your total thrust. Not good during take off or climbing out. If you stay at 8, assuming one doesn't grenade and take its twin in the nacelle with it, your computer can increase thrust in the remaining engine in the nacelle and slightly reduce the opposite side. 15% reduction in thrust. Ish.

a reply to: Flipper35

Even losing two in the current configuration wouldn't hurt nearly as bad as a 4 engine configuration. And that's before even getting into the rudder issues involved with 4.

Interesting comments from the Air Force chief of acquisition about both ABMS and the B-52 engine program. They're expecting a virtual prototype in October, then plan to move on to physical prototypes.

In the case of B-52 re-engine, we are using that time to do digital engineering for the engine and pod integration, so we have all three industry bidders on one contract. We have Boeing on contract. They are working together as part of the source selection. They will deliver their virtual prototype to us by October. We would normally not even be on contract, and already we have a deliverable that will help us understand the challenges of integration. Are they able to keep the center of gravity and the fluid flow around the power pod? Are they able to keep that the same? We will have that earlier.

Source

The draft RFP for 608 commercial derivative engines dropped today. The Air Force plans to award the contract in May 2021. Four engines are expected to be offered.

GE- CF34-10, and Passport.
Pratt&Whitney- PW800
Rolls Royce- F130

www.flightglobal.com...

The formal bidding process opened with the formal RFP. Under phase one, GE, Pratt&Whitney, and Rolls Royce will submit virtual prototypes of their submissions (CF34 or Passport, or both for GE, PW800 for Pratt, and BR.725 for Rolls). Phase two will use data from the virtual prototype, and an integration risk analysis. The selected company will ultimately provide 608 engines and support equipment.

aviationweek.com...

a reply to: Zaphod58

Somehow I missed this one. Good article on why you just cannot bolt on 4 CMF's are have at it.

a reply to: FredT

I had a guy that was claiming to be an instructor insist that I was wrong and the B-52 would have plenty of rudder authority with 4 engines, because it has enough authority now.

a reply to: Zaphod58

LOL to be fair I would have never thought about the rudder

a reply to: FredT

Most people don't. But if you get a chance to see it up close, it's freaking tiny. If they were doing the certification program today, they'd probably have to redesign it.

Talked about this somewhere, but I forgot where. Rolls has since confirmed their proposal includes both manufacturing and assembly at the Indianapolis plant.

Its a wonder they dont go for a full fin rudder these days..

The RFP closed today. As expected, the F130, CF34-10, and PW800 were offered.

www.airforcemag.com...