Question: Who invented oli dilution as a cold start aid for aircraft engines and when/where was it taken into use? It definitely seems that 1930s bush pilots (at least some of them) in Canada were familiar with the idea, but was there any testing or use prior to that?
Oil dilution for cold starting
- Thread starter Trilisser
- Start date
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I think you will have an interesting time with that topic. I have seen comments about trials at the RAE in UK and Rechlin in Germany. Of course, many engines were trialed for suitability and dilution advice. However, who can claim the earliest experiments, I do not know, but I bet it was somewhere with severe cold winters.
Eng
Eng
MiTasol
1st Lieutenant
It certainly worked well in Canada in the 60's and 70's and made for reliable engines.
- Thread starter
- #4
In some German pilot memoirs it is claimed that Luftwaffe supposedly learned it from Soviet PoWs implying that Soviets invented it. I doubt that.
Post-WW2 at least one Finnish AF Bf 109 was lost as a result of gasoline vapour from crankcase breather pipes catching fire on take-off, thanks to poor position of the pipe outlets. The accident investigation committee recommended relocating the outlets.
Post-WW2 at least one Finnish AF Bf 109 was lost as a result of gasoline vapour from crankcase breather pipes catching fire on take-off, thanks to poor position of the pipe outlets. The accident investigation committee recommended relocating the outlets.
MiTasol
1st Lieutenant
The proper procedure is to wait until the oil reaches a certain temperature. The oil will remain close to ambient while there is fuel in the oil but will rise rapidly as soon as the fuel has all vaporised. Only then should you increase above idle rpm because until then the oil is too thin to lubricate properly. Going to take off rpm would massively increase the vaporisation rate thus producing the fire risk as well are hastening bearing failure.
kmccutcheon
Airman
- 51
- Jan 1, 2013
U.S. Army Air Corps Materiel Command Engineering Division Power Plant Laboratory issued Memorandum Report E-57-731-1, Oil Dilutoin Tests, on 24 May 1935. This report describes initial tests that had been performed on a Wright R-1820 followed by the subject tests on a Wright V-1570 ,pimted on a torque stand.
swampyankee
Chief Master Sergeant
- 4,020
- Jun 25, 2013
I would not be surprised if it was simultaneously invented in many places.
Hi, I guess this is a response to Trilissers comment about a Finnish Bf 109 fire? There is more info about the use of oil dilution and the Bf 109. So, the DB 601 DB 605 engine handbooks list the procedures to be used. For readiness states of "Quick take-off operation" the oil temperature did not have to be considered, just the oil pressure if the correct dilution had been used for that readiness state. This relaxation of the normal cold start dilution warm-up reflects an operational requirement to minimise time to get airborne, such as in a scramble.
Eng
Simon Thomas
Senior Airman
From:
DILUTION …: AS AN AID TO LOW TEMPERATURE STARTING OF AIRCRAFT ENGINES, KENNETH C. HUNT
Industrial Lubrication and Tribology, Vol. 5 No. 5, pp. 14-17, 1 May 1953 DILUTION …: AS AN AID TO LOW TEMPERATURE STARTING OF AIRCRAFT ENGINES | Emerald Insight
Mr. Weldon Worth of the then U.S. Army Air Corps working at Wright field evolved and patented the basic oil dilution system. Canadian Airways was the first commercial operator in Canada to take up this system, and had two installations in very successful operation during the winter of 1938/39.
There may have been use before this, but evidently the author was not aware of them. Research is vastly easier now than in 1953.
Chart from the paper. No help at all wrt the question, but I thought it was interesting.
DILUTION …: AS AN AID TO LOW TEMPERATURE STARTING OF AIRCRAFT ENGINES, KENNETH C. HUNT
Industrial Lubrication and Tribology, Vol. 5 No. 5, pp. 14-17, 1 May 1953 DILUTION …: AS AN AID TO LOW TEMPERATURE STARTING OF AIRCRAFT ENGINES | Emerald Insight
Mr. Weldon Worth of the then U.S. Army Air Corps working at Wright field evolved and patented the basic oil dilution system. Canadian Airways was the first commercial operator in Canada to take up this system, and had two installations in very successful operation during the winter of 1938/39.
There may have been use before this, but evidently the author was not aware of them. Research is vastly easier now than in 1953.
Chart from the paper. No help at all wrt the question, but I thought it was interesting.
Thanks for the info Simon, the other pages would be interesting if you can easily post?
As regards the Bf 109 with DB 601 or DB 605, the maximum dilution was 25% for expected start-up temperatures of -20C and below.
The Bf 109 oil system did not have a "Hot-pot" or thermostat controlled warming circulation, the oil thermostat only controlled the oil cooler air outlet door, so the whole 60-odd litres of oil in the tank/engine/cooler/pipes circulated and slowly warmed-up.
Eng
As regards the Bf 109 with DB 601 or DB 605, the maximum dilution was 25% for expected start-up temperatures of -20C and below.
The Bf 109 oil system did not have a "Hot-pot" or thermostat controlled warming circulation, the oil thermostat only controlled the oil cooler air outlet door, so the whole 60-odd litres of oil in the tank/engine/cooler/pipes circulated and slowly warmed-up.
Eng
MiTasol
1st Lieutenant
Thanks Eng
I was quoting civil procedures in the 60s/70s and naturally they do not allow for military quick take offs so I should have qualified my post as civil post war.
Thank you for the correcting my post and adding to the knowledge pool on the subject.
Thanks.
The German procedures are quite complicated, partly because they include the additional "Quick take-off operation" as well as normal "Cold temp operation".
For instance, the Quick take-off operation goes up to +25C OAT requiring 10% dilution.
In addition, the various procedures also include; Low temperature pre-start engine and starter exercise, low temperature volatile priming fuel, low temperature warming of engine systems with warm air and very-low temperature starting with Acetylene gas.
Eng
RichardSuhkoi
Airman 1st Class
- 158
- Apr 27, 2021
No direct answers but I remember talking to an old bush pilot Northern Quebec and he said his procedure was to do fewer pump strokes than typical, then do as n my any hand prop pulls as he could so as to mix the gasoline and oil prior start attempt. He said he could feel the prop moving more easily as he pulled by hand. Then, after start, to hold at idle at least 10 minutes to ensure boil off and adequate oil pressure. Once at destination, replace the oil as it did not recover normal viscosity.
MiTasol
1st Lieutenant
My experience was that you followed the airframe manufacturers requirements which was to dilute PRIOR to engine shut down. Each aircraft type had its own chart similar to the one in Simons post #9. On the Otters and Beavers the dilution time at -40C-40F was about five minutes from memory and on the DC-3 it was well over ten minutes.
Diluting prior to start is a total waste of time as the engine oil pump is not capable of sucking the congealed oil into the engine and circulating it and that is the reason that oil dilution was developed.
Manufacturers recommended the oil was changed at the normal intervals but the company I worked for did them twice as often as oil dilution cleans a lot of the crap out of the inside of the engine.
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MiTasol
1st Lieutenant
For those who do not know how the physical layout of an oil dilutions system the following applies to all US, Canadian and British aircraft fitted with that system.
A pipe line runs from the outlet side of the engine driven fuel pump, NOT an airframe hand pump, to the dilution valve. When the valve is electrically activated the fuel flows through the valve to the inlet (suction) side of the engine oil pump where it is injected/sucked into the engine oil and then further mixed as it goes through the oil pump. The reason that dilution takes so long is on the DC-3 you are adding typically at -40 around seven gallons of oil to a nominally 29 gallon tank. I say nominally because that is the full tank level but the engines use a lot of oil in service so during winter ops after a long flight with full oil tank the level is down significantly and during cold weather ops it is never filled to the 29 gallon mark. In winter operators use a lower "full" level so as to allow for the dilution. This is safe unless you are operating maximum range flights which few, if any, do these days.
A pipe line runs from the outlet side of the engine driven fuel pump, NOT an airframe hand pump, to the dilution valve. When the valve is electrically activated the fuel flows through the valve to the inlet (suction) side of the engine oil pump where it is injected/sucked into the engine oil and then further mixed as it goes through the oil pump. The reason that dilution takes so long is on the DC-3 you are adding typically at -40 around seven gallons of oil to a nominally 29 gallon tank. I say nominally because that is the full tank level but the engines use a lot of oil in service so during winter ops after a long flight with full oil tank the level is down significantly and during cold weather ops it is never filled to the 29 gallon mark. In winter operators use a lower "full" level so as to allow for the dilution. This is safe unless you are operating maximum range flights which few, if any, do these days.
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Simon Thomas
Senior Airman
Full paper
MiTasol
1st Lieutenant
An excellent paper. Fuel had obviously improved considerably in the 14 years between the article being written and my experience as we used stock fuel for starting, not a special brew.
One item barely covered was engines with electric starters need the lead acid batteries kept warm as the voltage drops rapidly with temperature below a certain point and if you get too cold the battery will freeze which cracks the case. The two main options are to fit a battery heater of some sort or to keep a battery charger attached and charging as that keeps the battery warm. In my experience many operators in northern Canada also had small electric heaters in the accessory compartment to keep the magnetos dry internally and the carburettor warm. Obviously ice inside either of those components was going to cause major problems. The battery charger and heaters were always powered from an apu that was left running 24/7 on the ground and no battery boost was needed but many operators used an external battery start just to ensure that the ships batteries were not overloaded.
One item barely covered was engines with electric starters need the lead acid batteries kept warm as the voltage drops rapidly with temperature below a certain point and if you get too cold the battery will freeze which cracks the case. The two main options are to fit a battery heater of some sort or to keep a battery charger attached and charging as that keeps the battery warm. In my experience many operators in northern Canada also had small electric heaters in the accessory compartment to keep the magnetos dry internally and the carburettor warm. Obviously ice inside either of those components was going to cause major problems. The battery charger and heaters were always powered from an apu that was left running 24/7 on the ground and no battery boost was needed but many operators used an external battery start just to ensure that the ships batteries were not overloaded.
I am often surprised how long the oil change intervals are. Operating the Bf 109 G with DB 605 A, I changed the oil on every pre-winter lay-up and engine inhibit, so that the engine sat with new oil all winter, so that was an oil change at every 20 hours, a far shorter period than the original servicing requirement, but even so, the combustion soot load in the oil was considerable.
Dispersant oils are a factor, with some engines still needing non-dispersant oils.
The German procedure was very much the same as described, dilution fuel cock turned on for a defined time according to planned temperature on a warmed engine before shut-down.
Eng
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Thanks for posting!
The info here are is quite generally applicable. However, all different engines have specific strict procedures and limitations that must be used.
An interesting difference of emphasis that I have also seen is that starting-up with thick cool or cold oil is the very high oil pressure that can occur, indicating poor oil circulation in the engine and stressing oil system components with high drive loads and pressure at the same time as bearings are not getting good oil flow.
Eng
MiTasol
1st Lieutenant
A good point. As a general rule too thick or too thin oil is always a potential problem which is why following the makers recommendations and changing oil for cold weather ops and warm weather ops between 80 and 100 grade is required on many aero engines. Cold and warm operating ranges are specified by the maker.
