707 Re-engining

Thu Jun 08, 2000 10:07 pm

Have any airlines gone to re-engine their 707s? I know the USAF has re-engined its KC-135s (717s) with CFM56 turbofans, and I believe a JT8D-200 re-engining would make sense for smaller cargo lines. Has anyone taken the re-engine option, or is hushkitting JT3Ds the popular choice?
Triple Seven
Posts: 518
Joined: Fri Apr 07, 2000 10:04 pm

Omega's 707

Thu Jun 08, 2000 10:40 pm

Omega Air operates a 1991 (yes!!!) built 707-300 with CFM56 engines. The only commercial 707 operator to do so. This 707 was built as a brand new E-6 Mercury aircraft for the USN. Instead of buying new airframes the USN bought up 18 older commercial airframes for the E-6 program instead and sold this only one off to Omega.

- Triple Seven

E-8 & Seven Q Seven

Fri Jun 09, 2000 4:54 am

Omega Air doesn't own that B707 anymore - they sold it shortly after acquiring it from the USAF in exchange for several B707-320Cs (sorry, I can't remember how many, but I think it was about 7). It is now owned by Raytheon and is currently in storage. I don't know how suitable this aircraft proved in commercial service, but I have read in an article on the RAF's E-3D AWACS aircraft (which have the same engines & u/c) that the ground clearance of the CFM56s is very low, and these aircraft cannot be landed in a crosswind.

This aircraft was built as the production prototype for the E-8 Joint-STARS program (not the E-6 program) and went into service with the USAF with the designation YE-8B. By the time the USAF got the green light to go ahead with the JSTARS program Boeing had already closed the B707 production line, so the decision was made to use ex-commercial airliner B707s instead of new-build airframes. Omega supplied the first batch of old B707s in exchange for the YE-8B, which they registered as N707UM. The "production" JSTARS aircraft, designation E-8C, are now entering service at the rate of 2-3 a year. The majority of the aircraft in service so far (7) are ex-Qantas, along with one ex-Pan Am and one ex-World Airways example. The next batch to enter service are likely to be the ex-Canadian Air Force CC-137 examples.

These aircraft are given a thorough overhaul at Northrop Grumman's Lake Charles, Louisiana, plant to zero-time the airframes and upgrade the electrics, amongst other things. I've noticed from photos that the cargo doors are also removed - which makes me wonder whether some of those retired B707-320Bs at Davis-Monthan with huge chunks missing from their forward fuselages have become the donor aircraft for the required sheet metal?

There was an article in a recent copy of Flight Int'l in which it was announced that USAF was seeking tenders for the re-engining of these aircraft. Engines to be considered included the CFM56 and the JT8D-200. The latter is being proposed by Seven-Q-Seven of Dallas, Texas, a joint venture that includes Omega Air and Pratt & Whitney as partners. Flight tests are currently being done on an ex-Challenge Air Cargo/ex-Lufthansa B707-330C (rego N707HE) at the moment, and certification is expected around the middle of this year. 7Q7 are hoping to get orders from both commercial and governmental/air force operators for their JT8D-200 re-engining program.

Some websites of interest:
Northrop Grumman's ISA division - JSTARS:
A press release from Pratt & Whitney re. re-engining of B707s:
Posts: 256
Joined: Sat Jan 29, 2000 7:58 am

RE: 707 Re-engining

Fri Jun 09, 2000 5:29 am

Sorry, but I have to give my "there is no such thing as zero-timing an airframe" speech. You will never get the metal back to brand-new production state. Even if you reamed every single fastener hole to get out the tiny little fatigue cracks, you would still be behind because now the holes are larger than they used to be, and will not have the original fatigue life. There are also little bits of hidden corrosion all over, mostly around the fasteners.

What you can do is overhaul the known problem areas and catch up on all Airworthiness Directives and Aging Aircraft Inspections. This is what JSTARS has done so they will get 20 more years out of the aircraft.

By the way, the main deck cargo door is still there; it just doesn't show up very well with that color.

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