KC-135R T/R's
 

I could have sworn that I read somewhere that the R's do not have thrust reversers and use only speed brakes to slow down. Is this true or not?

I know the E's did. If the R's do not, why is that??

Thanks for the info!

E's and R's
 

The E's all got their engines from 707s that were being scrapped. The Air Force bought them up, stripped them of engines, landing gear, and as I understand, Horizontal Stabs. They were airliner engines, so they came with T/Rs.

The R doesn't have them. I believe (don't know for sure) that the Air Force didn't get T/Rs on the R because:

1. It cost more.

2. It makes the airplane weigh more (limits your payload; increases landing distance).

3. Causes more maintenance costs.

4. Doesn't legally shorten your landing distance (that's true in the civilian world, so I assume it's true in the mil-world).

They shouldn't be worried about a tanker's landing distance seeing that they almost always come back to the nest empty.

TRs are most helpful (and used for calculations) in aborts and abnormal landing configurations.

I would bet that the performance gained by those big engines negated the stopping performance of the TRs. In other words, the engines are so powerful, they lowered the runway required so much that they made the TRs optional.

The story goes that the Air Force actually paid extra to have the Thrust Reversers removed for the KC-135R.

In addition to the bigger motors, the airplane also got a beefed up wing (higher max landing weight), better brakes, and better anti-skid.


If I'm not mistaken, the RC-135s are getting (some have already gotten) the CFM-56 (the engine that makes the KC-135A into a KC-135R) with Thrust Reversers. Since it has no APU, further engine modifications were required to provide bare-base capabilities.

So much for commonality. :)






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Not sure how true this is since I've never worked the E-6, but while I worked on the 135R/T, we were told that some of the differences between the KC-135 and the Navy E-6 were the engines and the brakes. The 135 has the CFM-56-2B and the Navy has the CFM-56-2A engines. The E-6's brakes aren't beefed up like the 135, maybe because the weight of the 135 vs the E-6, and the E-6 has the trust reversers where the 135's don't, again maybe because of the brake differences. The 135's engines were cake to work on. Thrust reversers would've made them a PITA. The 10 years I worked them we dropped only 4 because of FOD.

The 135R/T has two APU's. They're called a QSAS, Quick Start Auxillary System. They sit side by side in the aft part of the cargo deck in an enclosure cabinet just infront of the boom pod. The inlet and exhaust are both on the left side of the fuselage. The 135 is completely self sufficient and requires no ground equipment to start engines. The QSAS has one generator mounted on either of the APU's, usually the number 1 APU which is the one furthest aft, to provide the aircraft electrical power. It also provides air to the main engines for starting.

Lemme make sure I've got my terminology correct.

KC-135A + Re-engine (etc.) = KC-135R

KC-135E + Re-engine (etc.) = KC-135T


Both referred to as KC-135R/T

True?


My comments about APU were about the RC-135s (S,U,V,W, and X models). They don't have APUs.


Well, at least they didn't use to. :)


(As best I can tell, the re-engined RC-135s are designated RC-135R. Since the suffixes previously denoted specifc mission-oriented configurations, I wonder how they keep 'em straight now. )






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KC-135A had the old steam engines, water injected J-57's, which I worked on at my first base Plattsburg. The A model had one type of fuel onboard, JP-4 or later JP-8. The KC-135E had the TF-33 engines, an upgraded larger fan version of the J-57 minus the water injection, but still had just the one type fuel system like the A model. The Q model had the J-57's and had two types of fuel onboard, JP-4 or JP-8 for the tanker itself and also JP-10 for refueling the SR-71. So let me see if I can explain it easier...


KC-135A had the water injected J-57's with only one fuel type on board
KC-135Q had the water injected J-57's with two fuel types on board
KC-135E had the slightly more powerful TF-33 engines and one fuel type
KC-135R is an upgraded A or E model with the CFM-56 or the military designation of F-108
KC-135T is an upgraded Q model with the CFM-56/F-108 engines.

When they upgraded to the R/T the landing gear was replaced with taller gear to clear the bigger engine cowls. The horizontal stabs were also replaced with larger stabs and they also added stiffeners to the rear of the fuselage to allow for additional fuel to be stored in the tail, called the upper deck tank which holds either 1400 or 14000 more lbs of fuel giving the R model a total take off fuel load of some 209,000 lbs of fuel.

Just for gee whiz, when you see video of A model tankers or B-52A thru G models taking off and there is all that smoke belching out the tailpipes, that's the J-57 engines with water injection. We called it banging water.

Gotcha... As and Es became Rs, Qs became Ts. (Qs and Ts configured to refuel the Sled)

I flew As in CCTS (initial qual and upgrade) and CFIC (Instructor school) before differences training in RCs -- very familiar with water injection.


The TF-33s on the Es had reversers. So did the TF-33s on the RC-135W. I think (it's been a few years, now) the RC-135X, RC-135S, TC-135W, and TC-135S also had reversers. The RC-135Us and Vs had the TF-33 without reversers.







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The J-57 birds had "cartridge start" capabilities. Explosive cartridge produced
gas that spun a two stage turbine that produced enough pressure to get one engine lit. A mechanical marvel!