I didn't include the DC-3,just the 4 engine types which would mean more engines,more maint,etc to be taken into consideration.There are still quite a few 4's flying,less 6's and hardly any 7's.Still looking for thoughts from board members as I have my own being that I was a mech on the 3,4 and 6. ;D
Post by Chris Trott on May 22, 2012 11:40:11 GMT -5
Unfortunately, I have to say none of the above. The reason being that the numbers still flying don't match a "durable" aircraft. They are very hard to maintain and the few still flying fill a very niche market. However, there are other platforms capable of the same payload that outnumber them and aren't much younger like the Convair 580 which can carry 25,000 pounds of cargo further and faster than the DC-4 and the cubic capacity isn't much smaller than the DC-6. Having less than 5% of your total built strength still active isn't a viable number of aircraft. There are actually more P-51's flying than DC-6's. While the number is a small percentage of the total built, there are enough flying that makes it possible for them to get new parts made for a reasonable cost. This is something not necessarily possible with the DC-4/6/7 and even with the number available still in storage for parts, some things can't be stored indefinitely like brake pucks, seals, rubber parts, and glazing. This means that as those parts dwindle, the aircraft become unmaintainable. The DC-6 has the advantage of using the R2800, which is also in the CV-340/440 and used by several warbirds like the F6F, F4U, A-26, and P-47. As such, there are still shops that make parts and can overhaul the engines for a reasonable cost which makes it possible to reasonably operate them. The R3350 of the DC-7 is a rare breed of engine with only really 2 shops doing work on them. The R2000 of the DC-4 is similarly a rare commodity because you've got only the CL-215 that still flies with that engine and there aren't many of them and most of them are owned by government agencies who inflate the prices because they'll basically pay whatever is asked until they convert the aircraft to CL-415's because the cost gets too high.
The numbers aren't good for any of them -
DC-4 - 25 airworthy out of 1242 built (2% of original strength) - Includes now defunct Brooks Air Fuel fleet which may not be really airworthy and may not be bought by other concerns.
DC-6 - 29 airworthy out of 704 built (4% of original strength) - I honestly think the number is 20, but I'm not questioning the sources I use as they usually have better info than I do.
DC-7 - 5 airworthy out of 338 built (1% of original strength)
I did not include museum aircraft that are flying as they are flown infrequently and do not make revenue. There are types out there that are extinct outside of museum examples, so they shouldn't be included in this kind of discussion.
Now, for comparison -
CV-340/440 - 15 airworthy of 308 built and not converted to turboprop (5% of original strength) CV-580/5800/640 - 61 airworthy of 202 built (30% of original strength)
Of course, comparing a turboprop to a piston plane is a little like apples and oranges. The 580 is more comparable to the L-188 Electra, etc. But I agree the airframe is still older than that. I guess Convair built them strong...
Post by Chris Trott on May 23, 2012 0:49:30 GMT -5
Yes, but look at the missions the DC-4 and DC-6s are being used for. They're shorter flights (under 3 hours). The only time the DC-4 and DC-6 had an advantage during their heyday was range. Because jets are the "primary" airframes now, even the CV-580 isn't used much beyond its non-stop 3-hour range. The issue is that the DC-4 and DC-6 have 4 engines to transport the same payload as the CV-340/440/580 can with 2. Additionally, the DC-4 and DC-6 airframe lifespans are not as long as the Convairs. Most Convairs have a structural life of about 80,000 hours. The DC's are only around 60,000 hours and many fewer cycles due to their original long-range design. This is the problem you run into when you try to turn a long range aircraft into a short range "trash hauler" and why neither the DC-4 nor DC-6 have survived in large numbers and instead the Convairs, Fokkers, DHC-8's, and ATR's fill that need.