Correct Siguarda al fine, For those of you who are not familiar with the DC-3, look at this photograph as proof (the hydraulic pressure gauges are on the sidewall of the cockpit) :-http://www.airliners.net/photo/AVIAC-(Aerovias-Centroamericanas/Douglas-C-47...-Skytrain/1591070/L/&sid=440565ad08e8867a7f95bde1d7e3534d
It is not possible for the landing gear to automatically extend after it has been retracted and a hydraulic failure occurs, as it is held by a "hydraulic lock", for which reason the selector is kept in the neutral position after retraction. Landing gear hydraulic pressure on both up and down lines is ZERO when the gear is up and the lever positioned in neutral as it should be. Normal cruise position for the selector lever is NEUTRAL, not up.
Further the airplane is equipped with three hydraulic pumps (2 engine driven and one hand pump), in the event of an engine failure/fire, only two aircraft related things can prevent you from raising the landing gear - a) A hydraulic failure following the engine failure (almost completely unlikely, unless the crew fail to follow the engine failure/fire drill (not actuating the engine fuel/oil/hyd oil shut off valve) and hydraulic fluid is lost through lines that are burnt through (they should be covered with fire sleeving, thats an SB)), b) The landing gear pins still being in position. Other than that, only the crew themselves through circumstances in the cockpit, could omit to raise the gear. The Captains briefing before take off, the words should be to the effect of, "if an engine should fail after ...., we will continue the take-off, my first command will be 'gear up'...."
I must ask though, 411a, what relevance has this to the crash of RP-C550?

Yes, it is true that the DC-3 is not considered a transport category airplane by the FAA and hasn't been at least the late 1940's, as it cannot comply with CAR 4b in all performance respects, but again, what bearing does that have on the crash of RP-C550? Nobody in this discussion implied or said anything to have any relevance to the certification basis of the DC-3?

Are you trying to score points off this because you THINK you know something about DC-3's? Your "two things" do not appear to relate to the topic at all.