Really cold weather operation

[Shadrach]

Why not?

I base my ops in this department on something that Walter Atkinson of APS told me years ago. He said that they've run engines with temp sensors positioned around the cyl and other areas that you would never be able to read with a standard engine monitor. Their findings were that running on the ground with cowl flaps closed often led to hot spots in the engine compartment that were significantly hotter than optimal. Running to too hot is bad, running too cold is bad, running both too hot and too cold is the worst... IIRC, Walt explained that their instrumentation showed that the temp on a single cylinder barrel had deltas of 100df or more during ground ops with CFs closed, which seems like an efficient way to encourage cylinders to deform (out of round).

Incidentally, this analysis also showed that the engine got more air with the wind blowing against the face of the prop (wind at the tail) rather than into the wind. This is why APS will recommend (or did) downwind run ups as opposed to the conventional "into the wind" run up... I don't really do much of a run up, so I don't really care.

All of this being said, I preheat the whole engine compartment so I don't worry about things being frozen as my cowl and everything inside of it is usually around 65df when I hit the starter.

The stock F cowl is far from efficient, but it certainly does not run hot. If anything it has an over abundance of airflow. I recall Byron had some thoughts on the cooling differences between the stock F and the J cowl.

[FlyDave]

We usually get the 110+ days in late June and Early July. The dew points are quite low that time of year down in the 30 and 40. It truly is a dry heat HEAVE.

 

I would take a dry 115 over 98 deg and 98%RH any day. I did a marathon skate race in Tahiti once (2002). It was 90+ and almost 100% RH. That was the hottest I have ever been. My skin suit was stiflingly hot. One of the top finishers (Eddie Metzger) was wearing a speedo and a straw hat.

 

I hope everybody is enjoying all the talk about extreme heat!

 

I lived in Phoenix for 27 years, moved to Los Angeles in 2003 and didn't want to move back to Phoenix after a year.

We moved to Northern California (~20 miles north of the Golden Gate Bridge) in December of 2012 and now I don't want to go back to Los Angeles. I think we have the best balance of weather up here.

[aviatoreb]

We usually get the 110+ days in late June and Early July. The dew points are quite low that time of year down in the 30 and 40. It truly is a dry heat.

 

I would take a dry 115 over 98 deg and 98%RH any day. I did a marathon skate race in Tahiti once (2002). It was 90+ and almost 100% RH. That was the hottest I have ever been. My skin suit was stiflingly hot. One of the top finishers (Eddie Metzger) was wearing a speedo and a straw hat.

 

I hope everybody is enjoying all the talk about extreme heat!

 

Wow - blast from the past.  I used to do 5-wheel inline races in the early 1990s when I was a bike racer in Boulder.  I used to know Eddie Metzger!  Not really well but well enough that when I was in Europe (for work) I stopped in Holland for a week to sample the ice skating ovals, and I sat down on a bus....right across from Eddie - and we immediately recognized each other and hung out for two days.  He was an awesome racer.  I was a mediocre racer.  :-O  Good thing I had a plan B for a career.  I was a better bike racer - especially on the track, but still - good thing I had a plan B for a career.  I'm still a decent bike racer ... for an aging dude.  I do 10 mi time trials mostly now.  I did 60 minutes on the computrainer this morning, and 20 minutes on the concept II xc skiing poling machine - our XC skiing has melted and refrozen to ice..doh!

 

I was in Pheonix at the end of May 2013....I brought my bike.  It was 105F.  I rode the hills near Pheonix.  It was HOT for this poor Northerner.  Dang, if I had to choose 115F or -20F, that would be a hard choice.  If I had to choose 10F or 100F, I would choose 10F.  

[SkyPilot]

I'm dubious. If there is not a positive pressure on the top of the engine how does any air flow though the cooler? (I have 201 style cowl. Baffles direct inlet air to the top of the engine.)

Nice pics Bob, I'm looking at relocating my oil cooler like yours. Back home it is -15 C right now.

[Super Dave]

Why not?

I can't seem to find it now, but I think one of John Deakin's articles says basically what Shadrach said. With cowl flaps closed on the ground, there is potential for hot spots that could damage cylinders, or accessories.

[aviatoreb]

I understand now. Thanks for informing me!

[BigTex]

FWIW, Lycoming SI 1505 specifically states that when using high volume hot air to Pre-heat, cowl flaps are to remain open to avoid heat build-up that can damage wiring, hoses, etc.

[jlunseth]

Yeah, John Deakin and Walter Atkinson are good guys, I went to their seminar.  They live about 600 miles south of here.  I don't remember them saying a thing in that seminar about extreme cold weather ops.  That's when the "hot spots" in your engine are around 250 dF and the rest of it is running under 200.  You want all the "hot spots" you can get.  I would agree with keeping the cowl flaps open if you have a propane burner toasting your engine, the heat from those at close proximity can be impressive.  Not trying to pick a fight, just trying to get across that you need to produce and retain all the heat you can get in extreme cold temps. 

 

On another cold weather topic, it is important to keep a close eye on all your systems until the cockpit warms up a little.  I was out yesterday, it was "warm" here, in the high 30's and about 4 C at 3,000 feet.  I was flying some approaches VFR for practice, I did the first couple with the AP, and the AP was not holding altitude in the turns.  It would lose two or three hundred feet, which is not what you want during an approach.  Once the aircraft warmed up a little inside, it worked fine.  Sometimes the old Bendix-King screens don't want to light up until they get a little warmer.  Ideal would be to run a heater in the cockpit for awhile before you get to the airport, but that is not often practical.   

[Super Dave]

Yeah, John Deakin and Walter Atkinson are good guys, I went to their seminar. They live about 600 miles south of here. I don't remember them saying a thing in that seminar about extreme cold weather ops. That's when the "hot spots" in your engine are around 250 dF and the rest of it is running under 200. You want all the "hot spots" you can get. I would agree with keeping the cowl flaps open if you have a propane burner toasting your engine, the heat from those at close proximity can be impressive. Not trying to pick a fight, just trying to get across that you need to produce and retain all the heat you can get in extreme cold temps.

I finally found the Deakin reference:

http://www.avweb.com/news/pelican/186619-1.html

"Cowl flaps should always be fully open on the ground, even in arctic conditions."

I agree that proper pre heat is critical, and oil cooler restriction may be appropriate in lower temps. I'm even on board with closing cowl flaps as early as the takeoff run; but not before.

Once the airplane is moving through the air, the engine compartment is cooled by ram air, even if cowl flaps are closed. On the ground, the prop blade roots do not provide any significant ram air to the cowl openings, but opening the cowl flaps into the prop blast from the outer portion of the blades creates a low pressure area that pulls air through the engine compartment. Closing cowl flaps on the ground doesn't just reduce airflow through the cowl a little bit, it nearly stops it all together.

This is pure guess on my part, but I think you might be underestimating the hot spots at 250 dF. I have no data, but the boys from Ada do. I'll take their advice.

[jkhirsch]

This is my first winter with the Mooney, but it is also my first winter with a Tanis pre-heater. My procedure has been shoddy at best, so far, but I plug the pre-heater in and let it roll for hours in advance of flying--I'm also not in a hangar. Up to this point I have paid no attention to whether the cowl flaps were open or closed while preheating, I also do not have a cowl blanket yet, nor do I have any of the orifices plugged. I have done this several times and the engine has started on the second or third blade, and quickly warms up to the green arc. I have been leaving the cowl flaps closed for the 5 minutes or so until I line up for take-off to promote extra hot air staying in the engine compartment. Up to this point I have noticed no issue with the instrumentation or avionics. As far as in-flight operating temperatures, if I remember correctly my oil seems to stay hot (180+) and my cylinders seem to stay proportionately cold to the OAT. I want to say that I have seen the temps go below 300 on the brutal flight back from Florida on Jan 6th.

[aaronk25]

Someone was looking for a picture of my beautiful homemade oil cooler block off devise made out of duct insulation. Really doesn't need gorilla tape on the sides as it will stay put with nothing. Aluminum foil tape might be a better choice but either way it's tested and true.

[aviatoreb]

ImageUploadedByTapatalk1390607697.964791.jpg

Someone was looking for a picture of my beautiful homemade oil cooler block off devise made out of duct insulation. Really doesn't need gorilla tape on the sides as it will stay put with nothing. Aluminum foil tape might be a better choice but either way it's tested and true.

 

Ooh - cool.  Hate to be picky - DO you have another picture zoomed out just a little bit for perspective?

[aaronk25]

Sorry I don't only took one.....pretty simple just block the airflow with something that won't melt or damage the cooler.

[aviatoreb]

Sorry I don't only took one.....pretty simple just block the airflow with something that won't melt or damage the cooler.

 

I'm not sure I understand what I am looking at in the picture. Is that the opening in the front of the cowl?

[aaronk25]

It is a 77j and a picture of the oil cooler on the pilots side aft of the engine. Other coolers on other models are in different configurations. Just get some aluminum heat tape and cover off about 1/2 to 1/3 of it depending on how cold it is.

[PLN_FXR]

In the cold weather, you can cover the entire oil cooler with a piece of aluminum or aluminum tape, leaving a hole in the center about the size of a silver dollar (+/-1.5" to 2" diameter).  This will have to be removed when ambient temperatures exceed 50 degrees F or when your oil temps start getting high.  Please ensure you adequately preheat the engine prior to start - this doesn't mean a quick 15 minutes preheat; adequate preheating will take an hour or more.  Be sure you do fly after preheating, or moisture will re-condense as the engine cools.

 

Please do not do your ground runs with cowl flaps closed.  Although this will warm the oil more quickly, it will not allow adequate cooling for the cylinders - they need all the airflow they can get during ground operations.

 

I flew an M20J for hundreds of hours out of TVF in northwestern Minnesota, where -50 was unusual but not unheard of, and -20's were "just another day".  Keep 'em flying!