concentriq
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Temperature And Reliability Of Equipment

Mon Oct 30, 2006 2:09 pm

There was a discussion in Civ, regarding how outside temperature affects reliability of the planes in general. I wanted to know more: is there any merit to the statement that when temperature outside (just temperature, not snow or high winds) gets colder, the reliability goes down significantly enough to cause sustained delays. Especially on MD80

My thinking is that at 30-40 thousand feet, the temperature will be colder than almost anything on the ground, and somehow that doesnt affect the reliability. Some people provided data (or talked about the data. Thanks Sideflare75) that showed the dependence of delays to season, but my thinking is it is due to general fact of worse weather. However same data talked about no change in reliability with other types of equipment. Some also pointed to airlines themselves talking about unreliable performance of some of the planes (Thanks TVNWZ). Could anyone answer this question?

Here is the original topic. The discussion starts near the end... Midwest Airlines Reports 3Q Profit! (by N917ME Oct 26 2006 in Civil Aviation)
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futurecaptain
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RE: Temperature And Reliability Of Equipment

Mon Oct 30, 2006 2:48 pm

I have never heard of just a temp change causing a/c delays. Now, I'm just a Cessna pilot, but lower temps usually mean better t/o and landing performance, better initial rate of climb, lower density altitudes, lower overall fuel burn, better engine temps, ect, ect.

I would much like to hear from people flying bigger birds about this topic too. I cant understand how ONLY lower temps would affect an airliner completely different from my Cessna.
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fr8mech
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RE: Temperature And Reliability Of Equipment

Mon Oct 30, 2006 10:24 pm

My evidence is anecdotal, but temperature certainly affects reliability. It just seems that more hydraulic seals begin to leak, especially dynamic ones. Then, of course, you get the standard PAC write-ups about not being able to maintain temperature on the ground.

Why the difference? Who knows, but we definelty see more leaks in the winter.
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Vref5
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RE: Temperature And Reliability Of Equipment

Tue Oct 31, 2006 12:48 am

Are these things (e.g. hydraulic seals) more sensitive in a narrow temperature range like what is experienced in the winter on the ground only?

The reason why I ask is because at the FL's (flight levels), it's pretty darned cold up there. Big grin And jets goes up there every flight segment... but yet, you don't get as much of these squawks in the summer? That's why I'm curious about the temperature range thing affecting dispatch reliability.
 
777wt
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RE: Temperature And Reliability Of Equipment

Tue Oct 31, 2006 1:08 am

On the ERJ-145, the cold temps are related to the gust lock not releasing due to ice buildup on top of the T-tail or the 'APU FAIL' occurs when deicing fluid is sprayed into the intake of the APU and the APU overspeeds then shutdown.

Maint. is called out to defer the APU which can take 10-15 mins from pulling the C/B's for the APU and doing the paperwork and phone call wth mtx control.

As for anything else...once in a while an captain of a ERJ-170 calls us because it's freezing inside the cabin...well duh the aircraft has been sitting overnight at this airport and you didn't even fire up the APU...


Don't forget it's also due to deicing delays at a busy airport and they may have to return for another deicing if the holdover time expires and the ATC is unable to get them in the air in time.

[Edited 2006-10-30 17:20:13]
 
EMBQA
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RE: Temperature And Reliability Of Equipment

Tue Oct 31, 2006 1:12 am

Quoting Futurecaptain (Reply 1):
but lower temps usually mean better t/o and landing performance, better initial rate of climb, lower density altitudes, lower overall fuel burn, better engine temps, ect, ect.

Yup... jet engines LOVE cold crisp air. I did a test flight one night back in BGR in a Saab 340. I think it was -10c or so....we took off like a rocket and passed the mid field mark holding around a 30deg angle till about 15,000ft. The engines were nice and cool and putting out all kinds of power. I got a good chuckle when the F/O asked that Capt if he wanted to start leveling off.. "Nope"

[Edited 2006-10-30 17:14:44]
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N231YE
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RE: Temperature And Reliability Of Equipment

Tue Oct 31, 2006 3:45 am

Quoting Futurecaptain (Reply 1):
I have never heard of just a temp change causing a/c delays.

I know off the top of my head, that it has happened once. Back in the '80s, at PHX, it was so hot that the aircraft performance charts did not go up that high, so of course, there were delays.

Nowadays, aircraft performance charts are calibrated to higher outside temperatures, so that does not happen again.
 
Vref5
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RE: Temperature And Reliability Of Equipment

Tue Oct 31, 2006 4:12 am

777WT: Makes sense; thanks!

[Edited 2006-10-30 20:28:02]
 
futurecaptain
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RE: Temperature And Reliability Of Equipment

Tue Oct 31, 2006 5:35 pm

Quoting N231YE (Reply 6):

I do remember that. I lived in the PHX area for many years. It was always a good story to tell.

But cold temps? Ever heard of that being harmful?
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N231YE
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RE: Temperature And Reliability Of Equipment

Tue Oct 31, 2006 10:39 pm

Quoting Futurecaptain (Reply 8):
But cold temps? Ever heard of that being harmful?

Not with cold temps. That is also why Boeing and Airbus "cold soak" their prototype airplanes (like the A380 in Canada), to make sure that everything can withstand the lower temperatures.


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[Edited 2006-10-31 14:43:47]
 
Vref5
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RE: Temperature And Reliability Of Equipment

Wed Nov 01, 2006 12:41 am

I remember when Embraer sent their new pre-EIS 170 to FAI for some cold weather tests during end of the last week of January 2003 or so. Caught my attention when I saw an Embraer I didn't immediately recognize on the apron.
Later confirmed it was the 170 from a story in the Fairbanks News-Miner daily newspaper.

I seem to vaguely recall they had to do some FAI-BRW flying instead of ANC-FAI due to a sudden and major heat wave that had hit Alaska at that time. The jet stream had significantly moved so northern U.S. (lower 48 states) were much colder than Alaska! I was sweating in Fairbanks, which normally has arctic weather in the winter!

In a more average January, it would have had been anywhere between -20 to -60 degrees F at FAI as the low temperature for the day.

Ah, found a photo:

http://www.alaskaaerofuel.com/cwt.html
 
greasespot
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RE: Temperature And Reliability Of Equipment

Wed Nov 01, 2006 11:08 am

3 winters ago we made a lot of money off the CRJ operators who retracted their flaps during the winter. Then the cable would freeze and they could not extend them.

I think that the solution at that time was to leave the flaps in T/O settings at shut down.

I found a report that R.R perpared on our Arctic operations in the early 90's with regards to our Darts. They called our environment much harsher than anything they fly in Africa.. Once we learned a few little quirks we got pretty good dispatch on the HS748's and ATR's.

GS
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Tristarsteve
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RE: Temperature And Reliability Of Equipment

Wed Nov 01, 2006 5:40 pm

Once the aircraft is flying, it is not the temperature that is a problem, but the winter weather. Items that can be despatched iaw the MEL in the summer, like wing antice, pitot heaters windscreen heat, are no go in the winter. But this is due to the clouds, not the temps.
On the ground it's the same story. Most winter troubles are due to water systems freezing when the aircraft gets too cold. We drain the water at night, and put a heater on the aircraft, but still the water system causes problems.
What we need is an additive that you can put in drinking water so it doesn't freeze, and you can still drink it!!!
 
Curmudgeon
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RE: Temperature And Reliability Of Equipment

Wed Nov 01, 2006 7:36 pm

The difference between cruise level temperatures (-56) and ground temps is that the systems are cold soaked on the ground after a prolonged shut down.

Hydraulic systems, prop seals, cable actuated controls, water tanks, galleys all have problems at very cold temps. Once the temps got into the -40 range we used to call it 'cold enough to freeze the nuts off a jeep'. Airplanes too.
Things like fuel pumps not running, fuel being close to the freeze point even before take off, pilots frozen to the seats (DON'T lick the controls!) were common. Frost on wings. Engines no start due ignition exciters/igniters failing.

On the piston engine transports its common to have oil heaters and bring the batteries indoors.

Another delay reason is the F/O being late because his POS car didn't start.
Don't ask me how I know this.
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Starlionblue
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RE: Temperature And Reliability Of Equipment

Wed Nov 01, 2006 9:07 pm

Quoting TristarSteve (Reply 12):
What we need is an additive that you can put in drinking water so it doesn't freeze, and you can still drink it!!!

Alcohol would work. Big grin
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