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C-53B / C-47 / DC-3 mileage & petroleum consumption

Fri Jan 12, 2018 12:18 am

For a novel for which I'm researching, to keep the scenarios grounded I need to estimate realistic fuel and oil consumption of the plane's two Pratt & Whitney R1830-92 1200bhp engines. A 1957 manual from Quebecair states that a fully fueled DC-3 (670 Imp.gal = 804 USgal) at 25,200 lb., 6000 feet, and expending 550bhp will achieve ~1500mi/1300nm range.

Est. Fuel consumption: @550bhp estimated at ~73 Imp.gal/hr (87.6 USgal/hr) or 2.23 mi./Imp.gal (1.85 mi./USgal).

To a first approximation, this suggests a max 09:11 flight time and avg. groundspeed of 163.4mph/142kt.

Est. Oil consumption over such a journey:
calc A: 8g/hp·engine·hour, so 8*550*2*9.17 = 80.8kg = 178 lb oil (~27 USgal)
calc B: 7 liters/hour*9.17 = 64 liters (17 gallons) = 51kg = 112 lb oil

Okay. So much for theory. In the present (semi-)post-apocalypse scenario, our heroes (my protagonist having survived her 737 BBJ plane crash) have conveniently managed to secure the use and piloting of a restored C-53B, the "winterized" special build of which only 8 were ever made, supposed to possess cold-temperature features & extra fuel capacity. And of course in the artificial ice age caused by the Bad Guys, they'll have to attach skis on the landing gear.

So, my questions for experienced pilots/owners/mechanics of the C-53 / C-47 / DC-3 family:

1a) To fly nonstop the e.g. 1313nm from KTMK to PAMR through unknown head-/tail-/cross-wind/refueling conditions, would it be prudent simply to fill all fuel tanks (up to takeoff wt.<29000) and hope for the best? What was the "extra" fuel capacity of the C-53B?

1b) Are such fuel & oil consumption figures seen in practice? The oil rate seems huge by lay standards; when our heroes prep for the journey into the unknown, should they take along a 50 USgal drum (or fight off bandits to scavenge oil)?

2) What would be the turnaround time to (re)fuel 800 USgal (from a typical self-service 100LL-dispensing fueling station) & top up the oil?

4) If they had to make do, could our heroes use a) high-octane unleaded auto gasoline? Do the P&Ws require leaded fuel? What do today's owners feed their engines? and b) automotive-grade engine oil? Which SAE oil weight would be compatible with the P&Ws?

5) For extreme-cold starts, the C-47 Pilot's Flight Operating Instructions recommends restarting the semi-cooled engines (e.g. after 15 min, Toil≤35C) and diluting the warm (Toil≤40C) oil with fuel (hold Dilution switch for 4 min.) to reduce cold-oil viscosity. The fuel in the oil is then volatilized away during subsequent start and warm-up.

What happens to the fuel being driven from the oil? Is it burned in the cylinders, or passed unburned in the exhaust gases? Would such a temporarily "rich" exhaust stream be explosive or inflammable? I could create far-fetched but vivid drama in which torch-bearing bad guys running after the taxiing plane get enveloped in a fireball of their own kindling... hopefully without blowing up the engines too. Great cinema even as DC-3 owners roll their eyes...

6) I read somewhere that for long-range flight, to ride the top of the efficiency curve, PROPS would be set at 1750 rpm, POWER set to 25 in. MP, and MIXTURES set to AUTO LEAN. How would these settings necessarily be altered at the start (heavy), middle, & end (near fumes) of said 1300nm flight?

7) Given that GPS and all other SATNAV gadgets are offline (plot necessity), and that most of the flight is over the waters of the N. American coast, which venerable inertial nav system (surplus/scavenged from a small bizjet?) could our resourceful pilot could hang off the C-53B's front panel?

8) Everyone's seen the cinematic cliched bullet-hole in the wing tank peril: "Gee, Captain, we're unexpectedly running low on fuel." Is there a less-overused, more-compelling scenario that would bring about a both-engine failure at the worst possible time, e.g. on final approach, necessitating a dead-stick landing? Maybe gradual loss of oil pressure (a bullet nicked an oil line), necessitating a heroic in-flight patch job, followed in the end by props feathering + engines shutdown (if that's even possible with failing oil pressure!)

But I've read dire warnings that a DC-3 must always be landed 2-point and controllable, i.e. with thrust present. Then again it's also said that, with ski landing gear on a slick surface, a 3-point landing is appropriate to mitigate the greater risk of a nose-down event. Any tips for dead-stick landing a DC-3 on skis? (Just to be extra thrilling, I'll probably snatch disaster from the jaws of an otherwise safe landing by 1) adding obscuring heavy snowfall; and 2) placing a polar bear or 450-lb bearded seal on the runway, as happened at PABR a while back).

Thanks for any insight & hints!

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