masonaries
Posts: 91
Joined: Thu Jun 08, 2000 11:10 pm

Cold Weather Engine Performance.

Wed Feb 02, 2005 12:07 pm

I take several early morning flights a year out of Lansing Capital City (LAN) and I've often had this question. They simply push back, start the engines, make a very short taxi out to the runway and just go. Is there any concern of a turbine engine needing to warm up after sitting all night on the ramp in sub zero temperatures? Just wondering.

Bondo
 
EMBQA
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RE: Cold Weather Engine Performance.

Wed Feb 02, 2005 12:13 pm

No...and by the way, jet engines LOVE cold weather. Cold, crisp air will give you fantastic performance..!!
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greasespot
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RE: Cold Weather Engine Performance.

Wed Feb 02, 2005 12:18 pm

Our PW120's have Tanis heaters on the RGB and Compressor section to keep them warm in the Arctic. The jet fleet just starts and go every morning no matter how cold.

As long as you have N1 and N2 they will start. Besides at 500F + they do not stay cold long.

When it is -40C they smoke really really bad on start up...
GS
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masonaries
Posts: 91
Joined: Thu Jun 08, 2000 11:10 pm

RE: Cold Weather Engine Performance.

Wed Feb 02, 2005 12:23 pm

Thanks for the quick responses.

Bondo
 
SlamClick
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RE: Cold Weather Engine Performance.

Wed Feb 02, 2005 12:43 pm

The only problem I can recall off the top of my head related to extreme cold. I was told that some airliner departing MDW in the dead of winter in a manner like you describe, had both generators trip off line right after liftoff.

I think they reset okay, but it had to have been fun for a moment.
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speedracer1407
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RE: Cold Weather Engine Performance.

Wed Feb 02, 2005 7:21 pm

OK, seems like cold weather is good for engine performance, atleast as far as power is concerned; i assume it's a due to the density of cold air, much like a car loves cold air in its combustion chambers to make the most efficient air-fuel burn. However, my imagination suggests to me (perhaps incorrectly) that a jet engine on a heavy airliner needs to run on with warm lubricants to prevent obvoius problems with cold oil, as well as warm critical parts to ensure proper operating tolerances. Greasespot mention earlier that "PW120's have Tanis heaters on the RGB and Compressor section to keep them warm in the Arctic," but I'm wondering if there are any warmup concerns for airliners starting up cold in normally chilly conditions, like a 20 degree F spring morning in the midwest, since this happens hunreds of times per day all over the country. If there is, is it the usual "idle for a while" doctrine that governs most heavy machinery, or are jet engines unique in this respect. Thanks for your replies..

O
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FredT
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RE: Cold Weather Engine Performance.

Wed Feb 02, 2005 7:36 pm

Some aircraft do have restrictions on the time from startup to take off in cold conditions, talking -20 deg centigrade here. This was for the exact reason that you wanted the engine oil temp to come up a bit. We're talking a few minutes here though, so not really a concern for airliners.

Cheers,
Fred
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HAWK21M
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RE: Cold Weather Engine Performance.

Wed Feb 02, 2005 8:03 pm

If your Engine is running 400degF + its probably warmed up Already.
And with All Parameters in range,thats all whats required.
regds
MEL
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air2gxs
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RE: Cold Weather Engine Performance.

Wed Feb 02, 2005 10:43 pm

Oil temperature is your limiting parameter. Jet oil has a relatively low viscosity compared to car engine oil. Even so, in cold weather, it can be fairly sluggish. The rule of thumb we've always used is to wait until oil temp is in the green band. It was not uncommon on the JT8 equipped B727's to have the oil pressure light on until the oil warmed up on cold days. The JT9 oil pressure had a tendency to bounce around +/-1 or 2 psi until the oil temp stabilized.

I know the AMM on the B767 & B757 have lower limit where no starts are allowed. I'm not sure of the number, but it's somewhere well below -15c.
 
XXXX10
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RE: Cold Weather Engine Performance.

Mon Feb 07, 2005 12:26 am

I was on a BA757 departing LHR years ago, before take off we were told by the captain that we would have to wait a few a minutes while the oil temp warms (he said that the plane had been in the mx base all night).

We parked up while the engines were revved and the whole plane shook for a minute or two.

The he lined us up and off we went.
 
Alias1024
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RE: Cold Weather Engine Performance.

Mon Feb 07, 2005 7:21 am

The CRJ-200 has a couple of limitations, but it is only if the aircraft is cold-soaked at an ambient temperature of -30 C or -22 F for more than 8 hours.

First, the engines have to be motored for 60 seconds and fan rotation must be verified before starting the engines.

Second, before the first flight the thrust reversers must be actuated until the deploy and stow cycle is less than five seconds.
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L-188
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RE: Cold Weather Engine Performance.

Mon Feb 07, 2005 10:29 am

As mentioned cold can increase engine efficency and performance. Which is one of the big reasons oil production at the north slcope goes up in winter.

However if an engine isn't properly pre-heated it can be a complete pain to get going.

I used to spend a good hour with a couple of torpedo heaters trying to get aircraft engines warm in -10-15 degree weather because the company was too cheap to buy the proper equipment for the job.
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troubleshooter
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RE: Cold Weather Engine Performance.

Mon Feb 07, 2005 8:35 pm

The AE3007A on the ERJ´s must have a minimum oil temperature of 40° C before setting N2 above 83%.
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speedracer1407
Posts: 330
Joined: Fri Dec 24, 2004 4:19 pm

RE: Cold Weather Engine Performance.

Mon Feb 07, 2005 9:40 pm

Do cold starts result in increased wear on a jet engine, and if so, do airlines arrange flight schedules to avoid cold starts?

O
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air2gxs
Posts: 1443
Joined: Mon Jun 18, 2001 1:29 pm

RE: Cold Weather Engine Performance.

Tue Feb 08, 2005 6:36 am

"Cold Starts" affect jets the same way they affect recips. Bearings go dry and need to be lubed up. The main difference is that the bearings on jet engines perform better than those on recips. So, a cold start really doesn't cause as much wear, relatively.

The main issue, again, is oil temperature. The oil needs to be warm in order to perform its intended functions efficiently.

Here's a little tidbit of information. The APUs on B757/B767 (and I'm sure most modern APUs) have a de-oiling system. This system purges the oil from the bearing cavities of the APU when shutdown. This prevents any super-cooled oil (from sitting at altitude for several hours) from gumming up the bearings during start. The APU begins its rotation with relatively dry bearings. Of course, that only lasts as long as it takes the APU oil pump to move oil back to the bearings.

And no, airlines do not schedule aircraft around because of temperature. The limiting temperatures in the AMM are well below the average in most major airports.
 
L-188
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RE: Cold Weather Engine Performance.

Tue Feb 08, 2005 9:50 am

Speedracer....Differently engine designs will have different effects.

For example, I used to work with a lot of aircraft with TPE-331 engines. On those engines the gearbox and propeller are driven directly off the shaft in the engine. So when you get very cold oil in the gearbox, it can prevent the engine from turning fast enough to prevent a "Hot Start" or what some have dubbed up here a "Garrett pre-heat"

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tepidhalibut
Posts: 183
Joined: Fri Dec 10, 2004 8:19 pm

RE: Cold Weather Engine Performance.

Wed Feb 09, 2005 5:30 pm

Yes, starting in very cold conditions doesn't do the engines much good. As mentioned, the oil is so thick that it's not great at lubricating the bearings. However, at low speeds, that's not too much of a problem.

Looking at some B757/RB211 paperwork :
Minimum Oil Temp for starting : -40°C
Minimum for opening up : 0°C (ie accelerating above idle.)

Once the engine is warmed up, and it does take time for the big turbine discs etc warm up all the way through, cold air is great for engine performance - Nice dense air, producing tons of thrust. Nice cold air keeping turbine temperature down.

Actually, on the B757, Boeing did do a little test to confirm the cold starting ability. After spending 12 hours at -54ºC in Yakutsk, the test engine started perfectly. Bet it was fun hanging around waiting for the engines to cool...
 
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BALandorLivery
Posts: 313
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RE: Cold Weather Engine Performance.

Thu Feb 10, 2005 1:31 am

The Fokker 100 needs to have its engines warmed up before take off power is applied.

I saw this in a flight deck video. The captain explained that it was because the oil needed to get up to temperature, if I remember correctly.

Regds.

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