Radial piston engine oil leaks, DC-4 thru DC-7 and Constellations
 

Any offers on why these engines leaked so much? I'm talking about the copious oil you would always see over the wings of all the Douglas airplanes from DC-4 to DC-7 and the Constellations.

I think this was the reason Delta got fed up and painted dark blue a large swathe of wing behind each of the 4 engines cowlings to hide the oil.

In actual fact, the amount of oil actually leaked was quite small, as just a small bit looks to the casual observer, quite a lot more.
The airflow spreads a small amount out quite a lot so it looks much greater.

By far, the greatest, was oil consumption.
The CurtisWright turbocompound engine, for example, used on the DC-7 consumed (burned) at least one half US gallon, per hour, per engine.
The limit (generally) was two US gallons/hour/engine.

And yes, gallons is correct...not pints, quarts or liters.

Just the nature of the beast. Had to have all that oil for lubrication and cooling and they (R-2800s & R-3350s, etc.) were not tight-fitting engines. That's why the oil tanks were so huge. 56 gallons as I remember. The 'G' Connie I flew could not carry a full load of fuel because the oil capacity was not large enough. A limitation (fuel/oil ratio) that may no longer exist; I don't know. It only burned about 5 gallons a hour!

Since you have such large pieces of metal heating up at different rates the clearances are fairly large which lets lots of oil loose.

DC-ATE - The ratios are still in part 25 if anyone wants to design a new large piston engine. Thirty to one without a tranfer system, 40 to 1 if you can transfer oil. Flew some converted T-29s that had to have an aux oil tank installed because the Air Force had larger fuel tanks than the regular 240.

Many long range aircraft had aux oil tanks for transfer to the engines. The L-1049 Super Connie had a 67-gallon bag tank in the port wing root - The WV-2/EC-121 radar Connies, because of additional fuel, had a second aux oil tank in the starboard wing root. These tanks and lines had electric heat so the stuff would flow when cold. The Douglas types with aux oil thinned it with gasoline so it would flow.

Some engines types were notorious oil leakers - the R-3350 BA series on the L-049/L149 Connies was one such, probably the worst engine ever on an airliner. Had old type hose and clamp seals on the pushrod housings (36 of them) which leaked all the time. Lots of connections for rocker box drains that leaked. In fact if you saw a really clean area on a BA engine, you immediately suspected an fuel injection line leak. Later models (BD, CA, DA, EA) were much better so far as leakage goes.

MarkerInbound -
I sure don't see that happening any time soon, but it'd be nice.:8

I wish people wouldn't refer to the Wright R3350 as a Curtis Wright machination!!

JO

Used to get a regular PAA DC7C daytime layover at my first aviation base. First order of business after chocks in was to put drip trays under all the engines and small collector trays that clipped on to some of the engine drains to keep the airport authority happy as they did not like the black gold all over their precious ramp. During the layover cleaners would wash down the upper wing surfaces behind the engines to remove the oil. There was even an oil slick on the tailplane from the inboard engines.
On start up later in the day the engines usually spat a good dollop of oil out the exhaust on to the wing straight away kinda ruining the cleaners efforts.
I once asked the PAA guys about the size of the oil tank on the R3350 turbo compounds and oil consumption and was told it held 56 gallons and that they didn't worry until consumption reached 4 gallons an hour. If it reached 6 gallons an hour with no obvious leak the engine was removed.

Why do the engines leak so much? The problem starts when the engine stops leaking. If a radial engine stops leaking, then it's out of oil, and that's bad.

When pushrod tube seals are clamped in place using band clamps over rubber hoses, when rocker box through-bolts are sealed with o-rings held against bolts with loose enough tension to only require castelated nuts, when there's no end of parts with the clearance to pass oil, when oil congregates in the lower part of the engine by virtue of gravity and design and gets blown out exhausts on start up...you're going to find oil dripping from the engine.

I've spent a reasonable amount of time piloting radial engine airplanes, and a lot more working on them. Whomever thought up the idea of white shirts for pilots around airplanes was an idiot. Especially in times of radial engines.

In motors like the R2600, typical consumption runs about three gallons an hour. Sometimes more, sometimes less. Some powerplants leak or burn less than others, and the type of operation has a lot to do with it, too.

Suffice it to say that when taking on fuel, nearly always one endevors to fill it up with oil, too. We often operated for three or four hours before fueling, and would end up putting in 40 to 60 gallons of oil while refueling.

Yup.....fill her up with oil and check the fuel!:8

So they used more oil than a 2 stroke .... multigrade 20-60 ?

wonder what the ratio leak:burn was !

Is the aviation gasoline available today still the same formula as used in the 50/60s? Sweet smell I recall much more aromatic than car gasoline - my mother used to tell me not to breath it when I wondered around underneath a DC-3 looking and touching everything until one day I burnt my fingers on very hot break disks.

Oh ...and fabric elevators and rudder always puzzled me why fabric was used?

Worst oil leak I ever saw was on a RAAF Convair 440 Metropolitan when during the take off, the main oil line to the oil cooler split asunder and we lost the full contents of 35 gallons very quickly which resulted in a runaway propeller at 800 feet. Fortunately the oil tank had a stand-pipe with just enough to feather the prop. The oil leak soaked the wheel well, the brake units and all over the elevator area.

If I remember well, DC4 had a capacity of 20 USG per engine and a 50 USG tank for in flight transfer, while the DC6-B had respectively 40 USG per engine and a 26 USG oil tank ..... and great to fly ... these were the days!!!

MP

B377

We'd do straight 50 weight oil in the winter and 60 weight in the summer.

There used to be at least 5 grades of av gas -

80-87 was red
91-96 was blue
100-130 was green
108-135 was brown
115-145 was purple

And I seem to recall there was yellow down in the 70-78 range.

Now about all you find is 100LL and 80 UL, totally different stuff.

You touched a disk brake on a Three? All I ever had were drums and expander tubes.

Fabric is lighter.

Yup, still using about a gallon an hour! These days with turnarounds measured in days or weeks we get plenty of time to chase oil leaks. Done properly, this results in no more oil than you can clean away with a rag after flight.

We've recently used W100 and Phillips 66. In any given conditions the latter works best on 2800s for some reason whereas W100 always suited the C47/R1830. No idea.

BTW, new DC-6 forum over at www.thedc6.com/forum by the Air Atlantique people. Not much to see unless you register, but it's new so probably waiting for input from us lot.

Recall the tongue in cheek advice if you could jump over the puddle of oil on a preflight it wasn't a leak.

Leaky Radials
 

Don't think I ever encountered an engine which came even close to leaking as much oil as a Bristol Hercules Sleeve Valve. On manufacture joints were metal to metal, which was fine until some boofhead split components by driving a screwdriver between the surfaces. Even buckets full of Hermatite sealer could not keep the oil inside the engine. First action by the groundies when the aircraft stopped on the ramp was drain bucket under the nacelle drain tube and then the chocks in place. With sleeve valves to be lubricated plenty of oil also made its way out the exhaust ports. We jokingly called them "High powered Oil Pumps"

Radial Engine Oil Leaks
 

Oil leaks were bad on small radials as well. Flew a 600HP P and W around
PNG for a couple of years, It had a 9 gallon oil tank, used about .5 of a
gallon per hour. Had a close one with oil loss [DHC3]. Had a short flight of
15 min, 10 min into flight oil poured up windscreen, oil pressure a little low
but steady, landed ok. jumped out to find a couple of gallons on the ground.
Dipped the tank , only under .5 of gallon in tank. Couple of minutes more
flight and I would have been not here today. The problem was the HP
pitch control pump had been overhauled some 50 hours before hand and
the pressure adjustment bolt locknut came undone. Had a couple that
night.

99

MARKERINBOUND
They sure looked like disks to me. Mind you it these were two COLPET DC-3s ( in Colombia) sporting uncommon wheel spats that recieved plenty of TLC from company mechanics .. so had ungraded brakes perhaps? else I am wrong.

Still remember the clicking of the hot engine and exhaust metal after shutting down.

That is an amazing list of gasoline grades had no idea! How would you choose when filling up?

One of the things about having a plane operate for 50-60-70 years is a lot of work can be done on them. The Super DC-3s had disks from Douglas, I guess it wouldn't be too hard to get an STC.

The AFM or Pilot Handbook would tell you what grade to use. You could always go up, just didn't want to use a lower grade than what was approved.