US Herk hypothesized: "I don't think there are too many KC-135E models flying anymore. I schedule 3-7 AAR sorties every week as part of the OCU here and we use all units - active, guard, & reserve. I haven't seen a KC-135E in well over a year...I'm not about to say they're all gone, as I don't have that bit of info, but I would at least put them on the endangered species list..."
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Aren't the KC-135E models the first to be replaced by the New and Shiny?
To all: if you don't like what Wiki says, you are invited to correct it. They do provide references for the doubters and deeper delvers.
Re-engining
"All KC-135s were originally equipped with Pratt & Whitney J-57 turbojet engines which produced approximately 13,000 pounds of thrust and, in some conditions, utilized water-injection to boost takeoff power output. In the 1980s the first modification program re-engined 157 Air Force Reserve (AFRES) and Air National Guard (ANG) tankers with the
Pratt & Whitney TF-33-PW-102 engines from retired 707 airliners. The re-engined tanker, designated the KC-135E, is 14% more fuel efficient than the KC-135A and can offload 20% more fuel. Only the KC-135E aircraft were equipped with thrust-reversers for takeoff aborts and shorter landing rollouts."
"The second modification program re-engined more than 410 with new
CFM56 engines produced by CFM-International. The re-engined tanker, designated either the KC-135R or KC-135T, can offload 50% more fuel, is 25% more fuel efficient, costs 25% less to operate and is 96% quieter than the KC-135A..."
"Upgrading the remaining KC-135E into KC-135R would cost about three billion dollars, about 24 million dollars per aircraft.
[4]. According to Air Force data, the KC-135 fleet had a total operation and support cost in fiscal year 2001 of about $2.2 billion. The older E model aircraft averaged total costs of about $4.6 million per aircraft, while the R models averaged about $3.7 million per aircraft. Those costs include personnel, fuel, maintenance, modifications, and spare parts
[5]."
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OK, so each KC-135R did not get a double engine upgrade, but there have been two upgrades.
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Replacing the KC-135
"As of 2006, the KC-135E fleet is flying an annual average of 350 hours per aircraft and the KC-135R fleet is flying an annual average of 710 hours per aircraft. The KC-135 fleet is currently flying double its planned yearly flying hour program to meet airborne refueling requirements, and has resulted in higher than forecasted usage and sustainment costs.
[9]"
"The Air Force projects that E and R models have lifetime flying hour limits of 36,000 and 39,000 hours, respectively. According to the Air Force, only a few KC-135s would reach these limits before 2040, but at that time some of the aircraft would be about 80 years old."
"The Air Force estimates that their current fleet of KC-135s have between 12,000 to 14,000 flying hours on them-only 33 percent of the lifetime flying hour limit.
[10]"
"Nevertheless these aircraft are over 40 years old and maintenance costs are increasing, with airframe corrosion being the worst problem."
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Please describe a typical AAR mission, US Herk, in terms of number of hookups and total fuel transfered. Do you often need the additional tonnage of the KC-10A?
GB