Up close and personal with DC-7 tankers: specifcations

This is the first of two articles on specifications of Butler's DC-7's. Tomorrow I will post an article focusing on the power plant (engines) specifications.

Weights of aircraft

Gross weights: The weights of Butler's DC-7's are 113,000 pounds gross with 100/130 avgas. The actual design gross weight was 122,000 pounds gross with 115/145 avgas (no longer easily available). According to Larry Kraus: "the difference is due to reduced horsepower available with the lower power settings allowed with 100/130 avgas. Our take-off power with the higher octane115/145 avgas was 3,250 power per engine. It is 2,880 with the reduced power settings".

Landing weights: Landing weights for Butler's late models DC-7's (T-62, T-66) is 100,000. Larry says that T-66 (a DC-7B) "had some structural reinforcement around the landing gear and also for the flaps. The landing weight for Tanker 60 is 102,000. That airplane has the same power reduction as the straight seven's, so the maximum take-off weigh for Tanker 60 is also 113,000.

Normal take-off weight loaded with retardant: 108,000 pounds.

Turning diameter (on the ground)

I have seen references to the turning radius in specifications of various tankers, so I asked Larry about this. It turns out that the spec that I had from one of the USFS documents (72 feet 8 inches or a diameter of 145 feet 4 inches) was close. I was interested in his comparison of the turning diameter of the DC-7B with the turning diameter of the C-118A (the military equivalent of the DC-6B). He sent me a copy of the turning radius page from the only DC-manual that he has available along with a manual page showing the equivalent information for the C-118A because it shows that the outer wing tip clearance is 74 feet. I want to point out here that the simulator that Larry and his co-pilot use is a C-118A simulator. This is what Larry had to say about turning radii:

This is close to what the USFS info gave for the DC-7. As you can see, it all depends on what you use as a basis for the turning radius.The reason for the slightly larger radius for the DC-6 vs the DC-7,even though the DC-7 is slightly longer with the same wingspan,has to do with the nosewheel steering limits.The DC-7 nosewheel turns 71 degrees either way and I think that the DC-6 only goes 67 degrees.

 

As you can see, the turning diameter of the DC-7B is 142 feet 5 inches and the turning diameter of the C-118A is 148 feet 2 inches

And in an earlier e-mail he spoke about the tight turning radius of a DC-7:

It's tight enough that the airplane doesn't pivot around a locked wheel on the inside of the turn.The inside wheel actually turns backwards.It still amazes me sometimes how tight of a parking spot you can get the DC-7 out of using maximum nose wheel steering.

Fuel Capacity

I'll let Larry explain the fuel capacity of Butler's DC-7's:

The DC-7 and DC-7B with the larger capacity fuel system (top in the above page from the Douglas manual) can carry 5512 gallons of fuel.That's the capacity on Butler's 7's.Our normal tanker fuel load is between 500-600 gallons per engine in the main tanks and 50-75 gallons per engine in the alternates.That allows between 3.5 and 4.5 hour flying.Our oil tanks also hold 46 gallons of 60 weight oil each.Avgas weighs 6 pounds per gallon and oil is 7.5 pounds per gallon.

Retardant Capacity

Butler's DC-7's can carry up to 3,000 gallons of retardant.


Dimensions

I think that this Douglas manual page that Larry sent me showing the dimensions of the DC-7 is self explanatory so I attach it below without comment.

Note: Double click on the manual pages to enlarge the view for easy reading