Preheating

[Dave Clark]

I have a temp probe on the oil sump that reads out digitally on my EI UBG gauge. Using multi weight oil I've often wondered what minimum temperature I could see on that gauge before requireing preheat. Most of the time here in the AZ mountains 40 degrees F would be the temperature on colder mornings in the hangar. Unless of course we get a real cold front where the hangar gets cold soaked. Any suggestions on minimum temp without preheat?

[N1478D]

My temp minimum at the hangar is 50 degrees, it's just so easy to do for such huge benefits. The heater setup is similar to the one George describes, but faster!

Cold starting an engine probably is the single most unnecessary wear intensive operation a person can do to an aircraft engine. The blanket goes on and the warm air baths the entire engine compartment, and if it is below 40 degrees, also open up the cabin heat vent and let the instruments have some too.

No matter what kind of oil is used, with the different types of metals contracting/expanding at different rates - having them all start off closer to operating temps is money in the bank and power over the mountain ridges and treetops. Course, down in Awstin area there's a B that's dragged sideways up a hill with a 9N before it's chocked for some reason! Can't climb so it has to be dragged, but sideways Draggin something that slow around has enough friction to warm up lots of stuff.

[N3067A]

"minimum temp without preheat?" It depends---mostly on how easy (or difficult) it is to preheat. I'll plug in my Tanis heater in the evening if I'm flying the next morning and I expect the outside temp to go below 40 degrees in the night. If I'm away from home and a preheat would require hiring the FBO to heat it, I'll prob'ly start without preheat down to 20 degrees or so. Below twenty above if preheat is available at all, I'll use it. You can get a cold soaked engine started down to about zero if you have to, but it's not good for the engine. If I lived someplace where it seldom dropped below 40 degrees and almost never dropped below freezing I wouldn't bother installing an engine preheat system.
John C. Saubak
Peerless
Montana

[blueldr]

I've been camping at Johnson Creek, ID, in May and even in June, when the temperature drops below freezing at night. In the morning, in order to fly out for breakfast, we crank up and taxi across the runway to the west side so the sun will earlier thaw the frost and ice off of the airframe. The runway is oriented 17/35 and is down in a canyon, so the sun coming up reaches the west side well before the east side where the campground is located. I use Shell 100 oil and it is pretty thick on those cold mornings, but I've never noticed any adverse effect from those cold starts. I do, however ,have my primer system modified to prime all six cylinders at the intake ports, which makes for a much smoother start and a more positive one. Over the years I've never had any problems nor have I noticed any excessive wear. However, I only do this perhaps eight or ten times a year up in Idaho. It never really gets very cold around my home in California, or at least I don't try to go flying when it does. Of course, I never run the power up until the oil is warmed up and the engine accellerates smoothly. I figure that if the engine starter willcrank it over at a reasonable rate, the oil will flow enough to provide the necessary cushion and lubrication.

[GAHorn]

I personally am not too concerned about different metals in the construction of the engine. I am concerned about proper lubrication during the warm-up period. If I can pull the dipstick rapidly and oil drops off it quckly then I figure it'll pump quickly throughout the engine also. But, when it acts like the head on a pint o' Guinness....where you can write your initials in it and still read it several minutes later... ...then it needs to be warmed up first.
If I lived where I had to fly on really cold mornings all the time without pre-heat.....I'd strongly consider multi-grade oils. But down here in central Texas where I only see freezing temps about 20 days a year....I use AeroShell 80W (SAE 40) Dec thru Feb and preheat below freezing when at home and below 20 when elsewhere. I use AeroShell 100W (SAE 50) the rest of the year.

[N1478D]

I personally am not too concerned about different metals in the construction of the engine. I am concerned about proper lubrication during the warm-up period. If I can pull the dipstick rapidly and oil drops off it quckly then I figure it'll pump quickly throughout the engine also. But, when it acts like the head on a pint o' Guinness....where you can write your initials in it and still read it several minutes later... ...then it needs to be warmed up first.
If I lived where I had to fly on really cold mornings all the time without pre-heat.....I'd strongly consider multi-grade oils. But down here in central Texas where I only see freezing temps about 20 days a year....I use AeroShell 80W (SAE 40) Dec thru Feb and preheat below freezing when at home and below 20 when elsewhere. I use AeroShell 100W (SAE 50) the rest of the year.

Well George, not being testy or dissagreeable - just discussing. You have stated that you ARE concerned about the different metals on letdown and shock cooling have you not? What is the difference between warming up and cooling down in this regard. Proper lubrication is one of the issues in both situations and an engine with warm parts has a much better chance of having proper lubrication than one with some parts colder than other cold parts. Preheat is so easy, and so good for the engine that I am somewhat cold shocked that you are not promoting it.

[GAHorn]

An engine in flight is running EGT's and CHT's of 1400+ and 350+ and can be cooled down so much faster/greater with greater damage potential (all the while those parts are running at 1500 rpm or more and cooling air blowing thru the cowl at 120 mph or so) than one can being started from frozen to idle (which is a relatively gradual warmup only to/in the mid 100's of degrees. If lubrication is good and rpm kept around 800 for the first minute or so...there's little likelihood of any damage from different materials. Just an opinion.

[170C]

Joe, are you going to let that last statement of George's go without a comment? The one about the airplane letting down "at 120 mph or so". Do you think that B model will go that fast, even going downhill? GRIN!

[GAHorn]

Joe, are you going to let that last statement of George's go without a comment? The one about the airplane letting down "at 120 mph or so". Do you think that B model will go that fast, even going downhill? GRIN!

Thanks, Frank! I WAS talking about a slow glide, of course! Joe only descends at 160 or greater. (That's why he has a super-cooling problem.)

[N1478D]

Joe, are you going to let that last statement of George's go without a comment? The one about the airplane letting down "at 120 mph or so". Do you think that B model will go that fast, even going downhill? GRIN!

Thanks, Frank! I WAS talking about a slow glide, of course! Joe only descends at 160 or greater. (That's why he has a super-cooling problem.)

Hey, I resemble that!

Frank, someone was telling me that at Reklaw, they saw an adjust knob in the middle of George's airspeed indicator. Apparently, he can set it to any speed he needs to. That away, he can discuss his cruise speeds, etc here on the forum without stretching the truth, sort of. Understand also that he really had that bird polished out to a deep shine there too.

[mvivion]

I run multi grade oil all year. My normal pre-heat threshold is 0 Celcius, or right at freezing. If its' colder than freezing, its time for pre-heat.

The manufacturer's guidance suggests pre-heat is only "required" at much colder temps, so 32 F is still pretty conservative.

Mike V

[ak2711c]

After having rebuilt seveal engines that had been regularly cold started with out preheat I am a believer in preheat. I'm not talking 20-30 degrees but colder where you have to prime it to death to get it started and keep it running. Each of those engines main bearings had streaking on them and one actually spun the bearing and ruined the case. I try to peheat below around 35 and won't even attempt to start with out preheat below 25. Just my two cents.
Shawn

[dkalwishky]

Thanks Guys, I appriciate all the comments on this question.

No, If I purchas a tanis preheater or a Reiff cna I install it myself or will I need an A&P to sign the logs?

Dave

[mvivion]

Either of those systems, or anything else you install on the airplane, will require a basis for approval, such as an stc or field approval and a form 337 signed by a mechanic and submitted to the FAA. Both the Rieff and Tanis systems come with stc paperwork.

If you order the Tanis, be aware that they sell two temperature ranges of probes. I recommend getting the high heat range probes, cause I live in Fairbanks. Nonetheless, you never know when you might need to heat things up quickly, and the high heat probes will do that. If you are going to leave it plugged in over night at +25, the high heat probes might be overkill, but just leave the engine cover off in that case.

Mike V

[Shodan]

I live in southern British Columbia. Lately it has been down to 0 and - 10 overnight. I preheat my 170 in as little as twenty minutes to a very warm temperature and hot in an hour with two car warmers and and a Honda generator and some shipping blankets. By the time I've done my walk around the motor is fairly warm. Very little hassel.