redtailsforever
Topic Author
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Heat Temps And Takeoff Performance

Mon Jul 02, 2012 6:02 pm

This is for all the airline people in the know. With the U.S. heat wave going on, has there been a big issue in say some nothern markets not used to long heat spells, of having to reduce avail seating, so the planes can get off the ground? Have pilots had to use less derated takeoffs, so they can get airborne. Is it only when it say gets above 100 deg does it matter? Thanks for the info.
 
tdscanuck
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RE: Heat Temps And Takeoff Performance

Mon Jul 02, 2012 7:10 pm

Quoting redtailsforever (Thread starter):
Is it only when it say gets above 100 deg does it matter?

All engines have a full thrust temperature (i.e. they can generate full rated thrust up to some outside temp). As long as you're below that temp you're good; above it you have to take a thrust cutback and may have problems. I don't think any civilian turbofan goes all the way too 100F without a thrust cutback but it's typically about 80F.

Tom.
 
Woodreau
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RE: Heat Temps And Takeoff Performance

Mon Jul 02, 2012 7:31 pm

It really depends on a lot of factors, the aircraft, airport altitude, outside air temperature, QNH, headwind/tailwind on the runway, runway length, terrain obstructions. Each airport and each runway at the airport is different.

Normally the climb and runway length performance exceeds by a large margin the maximum structural takeoff weight for the aircraft, so even when it get hot or really hot, it may or may not affect the payload of the aircraft as much as you think.
Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
imiakhtar
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RE: Heat Temps And Takeoff Performance

Mon Jul 02, 2012 7:55 pm

This pdf contains the flat ratings for CFM56 engines on the A32X and B737. Some of the engine variants have flat ratings of 113F!   

http://www.cfm56.com/pdf/cfm-technical-data.pdf
Whatever happened to Leon Trotsky?
 
tdscanuck
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RE: Heat Temps And Takeoff Performance

Tue Jul 03, 2012 1:58 am

Quoting imiakhtar (Reply 3):
This pdf contains the flat ratings for CFM56 engines on the A32X and B737. Some of the engine variants have flat ratings of 113F!

In the case of the CFM56 that's not surprising. Those engines span a huge thrust range and run basically the same core; as a result, the lower thrust versions aren't working the core very hard even at full thrust so they've got a lot of room.

Tom.
 
prebennorholm
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RE: Heat Temps And Takeoff Performance

Tue Jul 03, 2012 2:17 am

Quoting imiakhtar (Reply 3):
Some of the engine variants have flat ratings of 113F!

Yup! Those engines with high flat rating temps are those which are FADEC software limited to rather low power, but otherwise identical to their more powerful siblings. Typically used on A318/A319, or maybe short range A320 - planes which are registered at reduced MTOW to lower landing fees because they are never used at their full range potential.

The more powerful siblings will manage at least the same high temperature when derated to the max power of their lower rated siblings.
Always keep your number of landings equal to your number of take-offs
 
redtailsforever
Topic Author
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RE: Heat Temps And Takeoff Performance

Tue Jul 03, 2012 2:36 am

Thanks so much for the info. That PDF was quite interesting. On a side note I did some spotting at MSP an hour ago, and all the E-175' s were really using up the property on takeoff. How is their hot weather performance?
 
aklrno
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RE: Heat Temps And Takeoff Performance

Tue Jul 03, 2012 6:14 am

Does anyone here know the temp at which PHX closes? I think it is 118F or 120F. Nothing operates after that.
 
Woodreau
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RE: Heat Temps And Takeoff Performance

Tue Jul 03, 2012 12:36 pm

Quoting redtailsforever (Reply 6):
On a side note I did some spotting at MSP an hour ago, and all the E-175' s were really using up the property on takeoff. How is their hot weather performance?

You can't use how much runway an aircraft uses as an indication of its takeoff performance. If you derate a takeoff on a cool day, you'll be using up as much runway as a full power takeoff on a hot day, up to the takeoff limit for the aircraft. However it may not be taking as much payload on that hot day as compared to a cool day. It would vary from airport to airport, every runway for that airport, terrain considerations, etc.

Basing an E-175 performance off the performance of a CRJ-700/900, (since the two aircraft use the same engine) the temperature would need to get above 42C before a runway limit would begin reducing the allowable payload. Runway choices would begin to be restricted above 38C, but no payload reductions would occur until 42C.

Quoting aklrno (Reply 7):
Does anyone here know the temp at which PHX closes? I think it is 118F or 120F. Nothing operates after that.

That's because (at least on the aircraft I fly) we've only got performance numbers for PHX up to 48 C. After it gets above 48C, we can't go anywhere as we have no performance numbers to work with. so 48C = 118.4F. I imagine other aircraft are similar. It's not that the airport is closed, airlines don't have the takeoff performance data to fly their airplanes.

When it get's that high, I'm looking for using either 25R or 26 as that gives me the most payload out of that airport when the temperature is that high, even with up to a 5kt tailwind. Once the winds go above a 5kt tailwind, takeoff performance would be better off using Rwy 8.



[Edited 2012-07-03 05:44:15]
Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
pilotpip
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RE: Heat Temps And Takeoff Performance

Tue Jul 03, 2012 5:09 pm

Quoting redtailsforever (Reply 6):
Thanks so much for the info. That PDF was quite interesting. On a side note I did some spotting at MSP an hour ago, and all the E-175' s were really using up the property on takeoff. How is their hot weather performance?

Just fine. I've yet to do a max power takeoff this summer due to performance limitations.
DMI
 
rcair1
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RE: Heat Temps And Takeoff Performance

Tue Jul 03, 2012 5:43 pm

Week ago yesterday I flew DEN to AUS on a CRJ-700;. At DEN we were told the aircraft was weight limited and they were requesting volunteers for delay. Heard similar announcements on other gates (all RJ's). One was asking for 10 people.
Temp ~104F, airport 5000 ft.

Anyway - we got a few volunteers ($200 credit and flight next day). When we taxied out we:
* Went to a holding place where we burned off fuel for 10 minutes - according to the captain, we needed to reduce weight a little.
* Went to 17R and performed max performance (apparent) takeoff
* Full stop at end of runway.
* Effort to turn on to runway with max length.
* Pacs and bleed air off
* Full spool up while holding in position, brakes on.
* Extended TO roll and very slow climb out.

Tried to watch the distance signs to get a sense of takeoff roll - over 5000ft.

Pac's came back on about 1minute after lift off.
rcair1
 
phxpilot
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RE: Heat Temps And Takeoff Performance

Wed Jul 04, 2012 3:06 am

Quoting aklrno (Reply 7):
Does anyone here know the temp at which PHX closes? I think it is 118F or 120F. Nothing operates after that.

PHX itself doesn't close, although that is a common misconception.

The reason you don't see most aircraft operating in those conditions is that performance data generally max out at a certain temperature. Operating outside the published performance envelope is not recommended as a smart career move!

When I was flying for YV out of PHX in the summer, I seem to recall our performance data would max out at 48 degrees C, which is 118.4F. IIRC, some airlines have paid the manufacturer to generate performance data so they can operate at temperatures and/or altitudes outside those normally published.
 
Alias1024
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RE: Heat Temps And Takeoff Performance

Wed Jul 04, 2012 3:44 am

Quoting rcair1 (Reply 10):

Week ago yesterday I flew DEN to AUS on a CRJ-700;. At DEN we were told the aircraft was weight limited and they were requesting volunteers for delay. Heard similar announcements on other gates (all RJ's). One was asking for 10 people.
Temp ~104F, airport 5000 ft.

Anyway - we got a few volunteers ($200 credit and flight next day). When we taxied out we:
* Went to a holding place where we burned off fuel for 10 minutes - according to the captain, we needed to reduce weight a little.
* Went to 17R and performed max performance (apparent) takeoff
* Full stop at end of runway.
* Effort to turn on to runway with max length.
* Pacs and bleed air off
* Full spool up while holding in position, brakes on.
* Extended TO roll and very slow climb out.

Tried to watch the distance signs to get a sense of takeoff roll - over 5000ft.

Pac's came back on about 1minute after lift off.

Did you do an air start at the gate? It seems very strange to turn the packs off, unless the APU was inpoerative. Typically the APU would be kept on in a maximum performance situation to provide pressurization without having to steal bleed air off the engines.
It is a mistake to think you can solve any major problems with just potatoes.
 
Woodreau
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RE: Heat Temps And Takeoff Performance

Wed Jul 04, 2012 4:32 am

Quoting Alias1024 (Reply 12):
Did you do an air start at the gate? It seems very strange to turn the packs off, unless the APU was inpoerative. Typically the APU would be kept on in a maximum performance situation to provide pressurization without having to steal bleed air off the engines.

That sounds right for a CRJ-700. Using bleed air for any purpose (APU or engine) causes a degradation in takeoff performance. A max performance takeoff for a CRJ-700 is packs off. The APU runs just fine for engine start and everything else, it just can't be use to supply bleed air for the packs for a max power takeoff. It was a recent change within the past year, and It doesn't make any sense to me though.

For DEN, a temperature above 21C/70F causes a weight restriction, it doesn't matter which runway you use, by the time it's 39C/102F your 65/66 seat CRJ-700 is a 44-50seat CRJ-200/EMB-144 and you're not going anywhere above 39C.

One flight out of DEN when it was that hot, they boarded 56. When the final numbers came in, we needed 6 more volunteers, but since the pax were already on the plane, no one volunteered, and no one got taken off. Instead all 1300 lbs of checked bags got taken off, and the only cargo loaded were the gate checked bags. Lots of irritated pax at the destination.
Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
pilotpip
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RE: Heat Temps And Takeoff Performance

Wed Jul 04, 2012 6:46 pm

That type of takeoff isn't at all unusual when performance dictates. The bleed air required to power the packs take a considerable amount of power. In hot/high density alt situations (100+ degrees in DEN for sure) we often use flaps 1 and ecs (packs) off in addition to no flex. MThe big difference is that we usually keep the apu running to power the packs. The apu in the 170 blows the CRJ apu away.
DMI
 
rcair1
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RE: Heat Temps And Takeoff Performance

Wed Jul 04, 2012 8:04 pm

Quoting Alias1024 (Reply 12):
Did you do an air start at the gate? It seems very strange to turn the packs off, unless the APU was inpoerative. Typically the APU would be kept on in a maximum performance situation to provide pressurization without having to steal bleed air off the engines.

We did an APU start at the gate, but packs off at takeoff. Sounds like that is normal.
rcair1
 
LH707330
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RE: Heat Temps And Takeoff Performance

Wed Jul 04, 2012 8:42 pm

Quoting woodreau (Reply 13):

For DEN, a temperature above 21C/70F causes a weight restriction, it doesn't matter which runway you use, by the time it's 39C/102F your 65/66 seat CRJ-700 is a 44-50seat CRJ-200/EMB-144 and you're not going anywhere above 39C.

Is this because of tire speed limits?
 
Woodreau
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RE: Heat Temps And Takeoff Performance

Thu Jul 05, 2012 2:46 am

Same reason why you're not going anywhere in PHX above 48C. For DEN there is no performance data available above 39C so we'd be stuck waiting for temps to get below 39C
Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
ThePinnacleKid
Posts: 497
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RE: Heat Temps And Takeoff Performance

Thu Jul 05, 2012 3:26 am

Quoting LH707330 (Reply 16):
Is this because of tire speed limits?

Can't speak for the "Climb Restricted Jet".. but the "Taco Rocket" is limited simply by rated/measured performance values... she is rated as a max of ISA+35.... period. Above that... she becomes a paper weight.... unfortunately in the record heat... it simply is that... very pretty to look at but, she ain't goin' anywhere... in DEN.. the issue at play here is it's SO high and that high of temps... it's much easier to exceed the certificated ops specs for the aircraft than say Phoenix which is almost 4000' lower MSL............ As to performance data.. remember it is ALWAYS predicated on worst case scenario... in T/O, that is the ability at FULLY MAXED weights being able to climb Single Engine at very predisposed climb tables (angles by segment of a 4 segmented climb profile) per FAA guidelines....
"Sonny, did we land? or were we shot down?"
 
MD-90
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RE: Heat Temps And Takeoff Performance

Thu Jul 05, 2012 5:23 am

When ATL hit 105 last week I'm betting there were many flights affected. I just thank God it wasn't as humid as normal--the highest temperature we saw in Alabama was 107 and even in the relatively low (for AL) humidity it was a scorcher.

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