question about overboosting NA engines in extreme cold

[bd32322]

I am going flying tonight - nice weather except for the 10 F temperature. Engine is preheated and all but wondering if I will be developing way too much power compared to the engines design.

 

Of course as soon as I start climbing that power reduces - so thats good.

 

 

[Hank]

I've departed at 8F with no problem. WOT & 2700 to altitude. Really great climb!

[1964-M20E]

I guess you could however on the flip side the much cooler air temps will keep the EGTs and CHTs form going too high.

 

I know in the R22 helicopter we bounce OAT against max MP that can be pulled during flight.

[jetdriven]

Cylinder pressure can exceed design limits at very cold temps and at low altitudes. That guy who posted the AOPA video where he returned to the field in his M20C? Blew a cylinder head off. Density altitude?  Minus 2000 feet.

[bd32322]

Cylinder pressure can exceed design limits at very cold temps and at low altitudes. That guy who posted the AOPA video where he returned to the field in his M20C? Blew a cylinder head off. Density altitude?  Minus 2000 feet.

 

Thats what I was wondering - so fly partial throttle on take off?

The POH says 0.4 MP for every 10C deviation from standard - but thats for cruise

[jetdriven]

calculate density altitude and if its lower than -1000' or so, limit MP to 29".  I've only had to do it a couple times.

[bonal]

Very interresting, I should think If you went 2700 like always and set throttle to give MP for a standard day you would be good for a normal climb performance. I will see what others think cause its winter and I do sometimes go whale watching close to the ocean and need to climb out to clear our costal mountains to get home.

[bd32322]

calculate density altitude and if its lower than -1000' or so, limit MP to 29".  I've only had to do it a couple times.

 

thanks - its going to be way lower than 1000 feet today

[aviatoreb]

We can get density altitude of -3000 or -4000 around here in the winter at our 474ftMSL field.  I limit boost in my turbo charged airplane very simply by keeping my finger between the end of the MP black knob and the firewall by the way I press it in.  That keeps indicated pressure at 34 or 35'' (redline is 38'') - and still in those conditions I max out my VSI.  Enough is enough eh?

[Houman]

Erik, is that why they call it a Rocket ? lol, it just climbs and climbs... Thanks for your post, I might fly this Sunday if weather is nice, I will use your advise as to not over stress the engine...

[aviatoreb]

Erik, is that why they call it a Rocket ? lol, it just climbs and climbs... Thanks for your post, I might fly this Sunday if weather is nice, I will use your advise as to not over stress the engine...

 

Yup - but that is just arctic cold weather advise - since in warm conditions full fuel allows a special dose of cooling fuel to the engine plus short take off to minimize time at the ackward pre-safe altitude.  In a rocket hopefully you can minimize the time between no safe landing a head or high enough to turn back (I call out turn back altitude at 1000ft) depending on your runway length.  But yeah - >2000fpm is enough.  But in arctic conditions - cooling is not an issue on take off - not at all - in fact I start take off roll with cowl flaps closed when it is arctic cold out since ending temps will barely peak in the low 300s even that way if its -20C or so at ground.

 

I learned not to "overboost' in my IO360 in my DA40 in the same arctic days.

 

if you fly Sun I hope good weather - I dropped my plane at BTV on Tuesday for avionics upgrade - so I won't have it back til mid next week.  As I look out the window - at a blizzard - its a fine time to have the airplane in the shop getting upgraded.

[jetdriven]

We can get density altitude of -3000 or -4000 around here in the winter at our 474ftMSL field.  I limit boost in my turbo charged airplane very simply by keeping my finger between the end of the MP black knob and the firewall by the way I press it in.  That keeps indicated pressure at 34 or 35'' (redline is 38'') - and still in those conditions I max out my VSI.  Enough is enough eh?

Even 35" may not be low enough.  Standard day, 4000' of altitude is 4". 

[aviatoreb]

Even 35" may not be low enough.  Standard day, 4000' of altitude is 4". 

 

Actually, now that you say that - I realize you are right.  Luckily - I am still ok.  We DO GET density altitudes as low as and even lower than -4000 on occasion.  But you won't find me at the airport on those days.  Too cold - for reasons I have said at other times on other threads.  Long story short- my nose gets cold even preflighting the airplane if it is -5f and lower and I start thinking about what would happen in worst case scenario of how survivable would an off field landing be - even a nice smooth one - if it is so cold you freeze to death.

 

I have many times flown in -3000 density altitude (and a tad lower) even twice this past week.  As I said if I stick my finger joint between the black knob and the firewall as I push it in not all the way it get's 34-35 - I will keep in mind your note if I want to limit at tad more even. Thanks,

[Mooneymite]

Ahhhhhh!

 

The problems we southern boys avoid.....   

[Danb]

Erik..you have an extra scarf for teddy..what u having done at the avionics shop?. Still Xmas shopping for the a Rocket?

I just can't wait until end of month to dash down Fla..winter all ready old..

[bd32322]

Ahhhhhh!

The problems we southern boys avoid.....

I have personally modified the saying "when things go south " to "when things go north ". Going south seems very nice and pleasant

[aviatoreb]

Erik..you have an extra scarf for teddy..what u having done at the avionics shop?. Still Xmas shopping for the a Rocket?

I just can't wait until end of month to dash down Fla..winter all ready old..

 

co-pilot bear isn't as tough as me.  I think he is a Southern Bear.  You can tell by his accent.

 

933 is getting her EDM700 replaced with an EDM830.  :-)  No more constantly pressing the button to see what temps each individual cylinder is doing - and lots more functions.

[Hank]

I have personally modified the saying "when things go south " to "when things go north ". Going south seems very nice and pleasant

I like that! Note that I also moved back South eleven months ago. No complaints, other than this morning--it was 9°F, windchill -2°F. Not any more fun here than it was further north. Of course, the last time temps here sank to 10°F was in February 1996,

[Mooneymite]

I like that! Note that I also moved back South eleven months ago. No complaints, other than this morning--it was 9°F, windchill -2°F. Not any more fun here than it was further north. Of course, the last time temps here sank to 10°F was in February 1996,

Well, Hank....maybe you were the varmit what brought the cold down here! :-)

[Houman]

co-pilot bear isn't as tough as me.  I think he is a Southern Bear.  You can tell by his accent.

 

933 is getting her EDM700 replaced with an EDM830.  :-)  No more constantly pressing the button to see what temps each individual cylinder is doing - and lots more functions.

Erik, let me know how it goes, and what it ends costing you, I'm looking to go from an EDM 700 to a 900 as primary or 930.

Thanks !!!

[aviatoreb]

Erik, let me know how it goes, and what it ends costing you, I'm looking to go from an EDM 700 to a 900 as primary or 930.

Thanks !!!

 

Sure thing!  Send me a pm - do you have my email?  Can you get avionics done at KBTV with your C-numbered tail number? - I really like them there and they are close to you too.

[Houman]

Not sure about doing avionics in the states, it has to be a shop or installer that is Transport Canada certified I think, not sure... and also with the exchange rate right now, it might not be so much cheaper...

[aaronk25]

I think we spend to much time worrying about it. Sure it make a bit more power maybe 20-30hp, but there's lots of cooling available so that helps keep temps down and steel strength up. I've taken off at -3800 DA a couple times and -2500da routinely. Enjoy the extra power.

If the engine comes apart at cold temps, it was gonna come apart a couple hours later anyway.

I don't here about Alaskan pilots blowing up engines every day and it's -5000da up there!

[Marauder]

I think we spend to much time worrying about it. Sure it make a bit more power maybe 20-30hp, but there's lots of cooling available so that helps keep temps down and steel strength up. I've taken off at -3800 DA a couple times and -2500da routinely. Enjoy the extra power.

If the engine comes apart at cold temps, it was gonna come apart a couple hours later anyway.

I don't here about Alaskan pilots blowing up engines every day and it's -5000da up there!

Amen brother! On my last flight I saw 1600FPM for a bit. Made me feel like that extra 10 pounds I put on over the holidays weren't there!

[BorealOne]

Don't worry about it and enjoy the extra performance. I take off routinely in my 310 hp O in -5000 DA. Manage the engine as you would under any other circumstance.