Curious
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Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 3:35 am

Just wandering if in general there some aircraft, engine type that are not suited to these conditions and those that are. e.g I have been told MD83 is not suitable?

Thanks
 
COERJ145
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 4:29 am

I think the CRJ has had some problems/weight restrictions with high altitudes(ex. DL out of ASE)
 
BCAInfoSys
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 4:34 am

Quoting COERJ145 (Reply 1):
I think the CRJ has had some problems/weight restrictions with high altitudes(ex. DL out of ASE)

If that's the case, then why does Skywest run a huge fleet of them out of SLC? Doesn't quite add up, sorry.
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gigneil
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:10 am

The CRJ-100 and -200 does, in fact, feature poor takeoff performance at hot or high fields. It has no moveable leading edges. That doesn't help you get off the road.

The CRJ-700 and -900 have resolved that issue.

N
 
Goldenshield
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:19 am

Quoting Gigneil (Reply 3):
The CRJ-100 and -200 does, in fact, feature poor takeoff performance at hot or high fields. It has no moveable leading edges. That doesn't help you get off the road.

The CRJ-700 and -900 have resolved that issue.

Depending on the airfield in question, the answer could be either/or. Yes, there are some airfields where the -200 will be able to operate with a higher payload percentage than the -700. However, since Aspen has been mentioned in this thread, it must be noted that the CRJ-200 would not be authorized to operate into that airport since the airport is closed to CAT D aircraft. The CRJ-700 has its fair share of issues in this market—as did the AVRO, but to a lesser degree.
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Amazonphil
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:19 am

Quoting BCAInfoSys (Reply 2):
Quoting COERJ145 (Reply 1):
I think the CRJ has had some problems/weight restrictions with high altitudes(ex. DL out of ASE)

If that's the case, then why does Skywest run a huge fleet of them out of SLC? Doesn't quite add up, sorry.

SLC is not really that high(4607ft) nor that hot(average of 80-85F summer time....ASE is high 7800ft. but can reach 75-80F average in the summer.
The almost 3000ft difference between these two examples makes much difference when loaded. I learned to fly in Colorado(been to ASE and LXV(Leadville at 10000ft.) many times and believe me, density altitude problems multiply quickly with every thousand feet when you start to get above 4-5000ft.
On the other hand I do agree with you to some extent. The CRJs do eat up alot of runway I've noticed, even down here in PHX at 1200ft average.

Cheers,
amazonphil

[Edited 2006-07-29 22:23:55]
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737-990
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:24 am

Quoting Curious (Thread starter):
Just wandering if in general there some aircraft, engine type that are not suited to these conditions and those that are. e.g I have been told MD83 is not suitable?

Thanks

I have heard the opposite, the MD-80s are good for hot and high. AeroMexico uses them in and out of MEX at over 7,700 feet in elevation.

The 737-400 is definitely not a good hot & high aircraft, one of the reasons United didn't order it to replace the 727s and instead went with with A320s for it's Denver hub.
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Amazonphil
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:26 am

Quoting 737-990 (Reply 6):
Quoting Curious (Thread starter):
Just wandering if in general there some aircraft, engine type that are not suited to these conditions and those that are. e.g I have been told MD83 is not suitable?

Thanks

I have heard the opposite, the MD-80s are good for hot and high. AeroMexico uses them in and out of MEX at over 7,700 feet in elevation.

The 737-400 is definitely not a good hot & high aircraft, one of the reasons United didn't order it to replace the 727s and instead went with with A320s for it's Denver hub.

I agree, AV and P5(AeroRepublica) use them extensively out of BOG(8600ft) so I believe the MD-80 is a good higher altitude aircraft.
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SLCUT2777
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:30 am

Quoting Amazonphil (Reply 5):
SLC is not really that high(5000ft) nor that hot(average of 80-85F summer time....ASE is high 7800ft. but can reach 75-80F average in the summer.
The almost 3000ft difference between these two examples makes much difference when loaded. I learned to fly in Colorado(been to ASE and LXV(Leadville at 10000ft.) many times and believe me, density altitude problems multiply quickly with every thousand feet when you start to get above 4-5000ft.
On the other hand I do agree with you to some extent. The CRJs do eat up alot of runway I've noticed, even down here in PHX at 1200ft average.

The CRJ can handle SLC and it's 4,300' elevation quite well, and the runways at SLC being 12,000' can easily accommodate one that is fully laden with passengers, cargo and fuel. The a/c in Delta's fleet that has the problems here in SLC is the MD-88 which is only a very rare visitor here during the summer months. Hot, Humid and High are the three inhibitors for planes taking off. While SLC and DEN don't have problems with high relative humidity being at altitudes of 4,300' and 5,300' respectively make these the highest altitude high use airports in North America. If you want to try out an airport that is HOT, Humid and High, try MEX.
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Goldenshield
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:35 am

Quoting SLCUT2777 (Reply 8):
The CRJ can handle SLC and it's 4,300' elevation quite well, and the runways at SLC being 12,000' can easily accommodate one that is fully laden with passengers, cargo and fuel.

Not in all cases when the tempurature is above 90.
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Amazonphil
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:37 am

Quoting SLCUT2777 (Reply 8):
Quoting Amazonphil (Reply 5):
SLC is not really that high(5000ft) nor that hot(average of 80-85F summer time....ASE is high 7800ft. but can reach 75-80F average in the summer.
The almost 3000ft difference between these two examples makes much difference when loaded. I learned to fly in Colorado(been to ASE and LXV(Leadville at 10000ft.) many times and believe me, density altitude problems multiply quickly with every thousand feet when you start to get above 4-5000ft.
On the other hand I do agree with you to some extent. The CRJs do eat up alot of runway I've noticed, even down here in PHX at 1200ft average.

The CRJ can handle SLC and it's 4,300' elevation quite well, and the runways at SLC being 12,000' can easily accommodate one that is fully laden with passengers, cargo and fuel. The a/c in Delta's fleet that has the problems here in SLC is the MD-88 which is only a very rare visitor here during the summer months. Hot, Humid and High are the three inhibitors for planes taking off. While SLC and DEN don't have problems with high relative humidity being at altitudes of 4,300' and 5,300' respectively make these the highest altitude high use airports in North America. If you want to try out an airport that is HOT, Humid and High, try MEX.

This is kind of my point, SLC and DEN(with a 16000ft runway) wouldn't and don't seem to present to much trouble even for a CRJ.
I hadn't known that about the MD-88 out of SLC though. Seems strange for an MD-88 as it's a newer bretheren of the MD-80 series. As I stated in my last post, the MD-80 performs well out of BOG and MEX. Must be a lower engine thrust rating or something else that degrades the MD-88.

amazonphil
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DesertFlyer
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:43 am

Quoting 737-990 (Reply 6):
The 737-400 is definitely not a good hot & high aircraft, one of the reasons United didn't order it to replace the 727s and instead went with with A320s for it's Denver hub.

Although we are not high, we are hot here at PSP and we get 3 737-400s a day. Maybe it's the high more than the hot that doesn't go well with the 734s?
 
Amazonphil
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:47 am

Quoting DesertFlyer (Reply 11):
Quoting 737-990 (Reply 6):
The 737-400 is definitely not a good hot & high aircraft, one of the reasons United didn't order it to replace the 727s and instead went with with A320s for it's Denver hub.

Although we are not high, we are hot here at PSP and we get 3 737-400s a day. Maybe it's the high more than the hot that doesn't go well with the 734s?

At PSP's 470 some odd ft., as you said, the height isn't really hampering the 734 at all. It takes height AND heat to really affect certain types of aircraft.

Cheers,
amazonphil
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flydreamliner
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:48 am

The 757-300 has to be on the list. NW's PW powered 753's take forever to lift off on hot days. It's about 97 here in MSP today, and the 753s are taking up as much runway as the DC-10s do to get off the ground (and we're only about 1100-1200ft elevation).

My understanding is the the Airbus A340-300 has a pretty long takeoff roll in hot/high conditions as well.
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1337Delta764
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:52 am

Quoting Amazonphil (Reply 10):
Seems strange for an MD-88 as it's a newer bretheren of the MD-80 series

The MD-88 is the same as the MD-82, but with an updated cockpit.

In September, Delta is pulling the MD-88s on ATL/CVG-ABQ flights. The ATL-ABQ flights will be served by two 757-200s and one 737-800, and the CVG-ABQ flight is being served by one 737-800. I am not sure if the hot and high conditions at ABQ are the reason why the MD-88s are being pulled, but it does seem rather likely.
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Amazonphil
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:57 am

Quoting 1337Delta764 (Reply 14):
The MD-88 is the same as the MD-82, but with an updated cockpit.

In September, Delta is pulling the MD-88s on ATL/CVG-ABQ flights. The ATL-ABQ flights will be served by two 757-200s and one 737-800, and the CVG-ABQ flight is being served by one 737-800. I am not sure if the hot and high conditions at ABQ are the reason why the MD-88s are being pulled, but it does seem rather likely.

The pull out of DL out of ABQ of the MD-88s might be also because of the bankerupcy and as they restructer the fleet and routes, their desire to update it all, etc,etc. not just because of hot and high density altitude problems. Don't know, just a thought.
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ROA757
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:58 am

Quoting Amazonphil (Reply 10):
DEN(with a 16000ft runway)

Wow...when did KDEN get a 3 miler? I totally missed that one....
 ashamed 
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DLKAPA
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 6:06 am

Quoting ROA757 (Reply 16):
Wow...when did KDEN get a 3 miler? I totally missed that one....

Hah... 3 years ago.
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Amazonphil
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 6:06 am

Quoting ROA757 (Reply 16):
Quoting Amazonphil (Reply 10):
DEN(with a 16000ft runway)

Wow...when did KDEN get a 3 miler? I totally missed that one....

Yes, 16R/34L X 200ft wide...Been there for about 7years?? Not sure exactly, wasn't there when we opened the airport in 2/1995 or for the first 3-4 years anyways. I have photos of the place from the air when the whole place was a praire land. Then photos of the first bulldozer, etc. etc.
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1337Delta764
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 6:07 am

Quoting Amazonphil (Reply 15):
The pull out of DL out of ABQ of the MD-88s might be also because of the bankerupcy and as they restructer the fleet and routes, their desire to update it all, etc,etc. not just because of hot and high density altitude problems. Don't know, just a thought.

Before last December, ABQ did not get any of Delta's MD-88s at all. The ATL/CVG-ABQ runs were operated by a mixture of 737-800s and 757-200s. The SLC-ABQ runs were operated by CRJ-200s and one 737-300. Last December, all flights from ATL and CVG were changed to MD-88s, and mainline service from SLC was discontinued. This upcoming September, Delta is switching back to the 737-800 and the 757-200 for flights from ATL and CVG, and is adding in CRJ-700 flights from SLC.
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Amazonphil
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 6:10 am

Ok, 3 years!  Big grin Haven't been to DIA in a while as I fly into APA most of the time myself, so I hadn't kept track of the the progress toward the 3 miler.
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Amazonphil
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 6:12 am

Quoting 1337Delta764 (Reply 19):
Quoting Amazonphil (Reply 15):
The pull out of DL out of ABQ of the MD-88s might be also because of the bankerupcy and as they restructer the fleet and routes, their desire to update it all, etc,etc. not just because of hot and high density altitude problems. Don't know, just a thought.

Before last December, ABQ did not get any of Delta's MD-88s at all. The ATL/CVG-ABQ runs were operated by a mixture of 737-800s and 757-200s. The SLC-ABQ runs were operated by CRJ-200s and one 737-300. Last December, all flights from ATL and CVG were changed to MD-88s, and mainline service from SLC was discontinued. This upcoming September, Delta is switching back to the 737-800 and the 757-200 for flights from ATL and CVG, and is adding in CRJ-700 flights from SLC.

You would know better than anyone, I was only taking a guess at a possible reason...757s and 738s are nicer anyways... Big grin
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COERJ145
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 8:22 am

Quoting FlyDreamliner (Reply 13):
NW's PW powered 753's take forever to lift off on hot days. It's about 97 here in MSP today, and the 753s are taking up as much runway as the DC-10s do to get off the ground (and we're only about 1100-1200ft elevation).

I noticed that too. I was in MSP on tues, for NW170 to BOS on a 753. We used a good 6-7000ft of runway to lift off and we didn't have a large load.
 
DLKAPA
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 8:31 am

Quoting Amazonphil (Reply 20):
Ok, 3 years! Big grin Haven't been to DIA in a while as I fly into APA most of the time myself, so I hadn't kept track of the the progress toward the 3 miler.

Actually they started construction on the runway when they started construction on the rest of the airport, unfortunately there were geological issues in the area of the runway that at the time weren't overcomeable at a reasonable price, so they basically buried the partially completed runway under dirt then waited until they could afford to fix it.

1997:


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Amazonphil
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 10:24 am

Quoting DLKAPA (Reply 23):
Actually they started construction on the runway when they started construction on the rest of the airport, unfortunately there were geological issues in the area of the runway that at the time weren't overcomeable at a reasonable price, so they basically buried the partially completed runway under dirt then waited until they could afford to fix it.

Now that you mention it, I do remember when I lived in Denver at the time talks about the 16K ft. runway and then it was sidelined. But I never learned why, but didn't care at all then as I was very angry with the whole airport thing as it caused me to loose my "cush" Stapleton maint. job there and my living in Denver eventually. Good ol' Stape was a great airport and was just fine...for that time then in the early 90's. But now....it would be too small. Guess the airport gods were correct then about thinking to the future. While DIA is beautiful in alot respects, I still don't care for it that much. Too far away from all I do in Denver and my beloved mountains. That's why I fly my own Cessna T210 into Centinnenial and go from there.

Thanks for the "buried" info that you brought to the surface!! Also thanks for the pics from 1997 and 1999. I should send you some from 1989 when the plowing/bull dozing started!! Unless you have them also.  Big grin

Cheers,
amazonphil

[Edited 2006-07-30 03:29:22]
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EddieDude
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 10:27 am

Quoting SLCUT2777 (Reply 8):
If you want to try out an airport that is HOT, Humid and High, try MEX.

I would not say it is humid. The warm weather in Mexico City is dry... if you get under the shade, it feels much better (not like in the U.S. southeast). In addition, the reason why summer nights in Mexico are temperate is that the absence of humidity allows the heat to disperse.
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usair320
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 1:30 pm

ABQ is very hot and somewhat high at 5200 ft. I was aboard a CO 735 last july and we used up every inch of that 12000 foot runway.
 
eastbay
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 1:39 pm

SLCUT2777,

humidity is a consideration? when I run the numbers on my aircraft (I've flown many including the Be-1900, B-737-200, DC-10-30 and A-320) humidty is not one of the factors considered.

Runway length, temperature, field elevation, and even more so, second stage climb are limiting factors on takeoff performance. Humidity doesn't enter the picture.
 
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SLCUT2777
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 2:21 pm

Eastbay: In your professional opinion (since you're a pilot I value it), are the runways at SLC too short to be able to adequately handle the day to day hub operations DL does here? My assessment is that 12,000' is too short to handle longer trans-cons and especially Hawaii flights without any weight restrictions, and as you're aware DL does a lot of these from SLC. I would like to see at least on any future master plan an extension of runway 34L-16R to at least 15,500,' to better deal with this issue. I watched a 764 depart earlier today in temperatures of 104 degrees F (roughly 40 C), and it took every bit of length of 34R to get off the ground (I'm sure it was weight restricted as well--hopefully no fuel stop at SFO).
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SLCUT2777
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:02 pm

Quoting Goldenshield (Reply 9):
Not in all cases when the temperature is above 90.

Typically when it gets that hot, the 763s and 764s begin to encounter weight restrictions, and in some cases the 752s (when the temp hits 100 F or 39 C). I'm certain that if DL starts to more regularly be sending 772s into SLC, you will see a push to get at least one of the two runways (most likely 34L-16R) extended by at least 3,000.'
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samair
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 5:06 pm

concorde used to have to have a third less passengers when taking off from hot and high areas
the captain has now dimmed the lights for take off this is a routine procedure for flights during the hours of darkness!
 
VEEREF
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 6:07 pm

SAAB340 for sure.
Doesn't exactly paste you to the back of your seat when fully loaded and hot.
8,000 ft altitude restriction for takeoff.
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Lucky42
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 6:38 pm

NW'S DC-9-50 will eat up all the runway on a hot day for sure.
 
LHR777
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 7:50 pm

As an aside to the OP's question - what are the effects of hot and humid (but NOT high) on aircraft at take-off? e.g. - a fully laden B747-400 at LHR in 34c heat with 76% humidity? (As we had a few days like this in the last 2-3 weeks).

Does it require more thrust? Higher V1/VR/V2? Weight restriction? Any clues please? Cheers!
 
deltagator
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 10:30 pm

Quoting SLCUT2777 (Reply 8):
The a/c in Delta's fleet that has the problems here in SLC is the MD-88 which is only a very rare visitor here during the summer months.

A few weeks back in DEN on an MD-88 Delta had to boot 15 passengers because of weight restrictions due to the heat and altitude. It was about 98F that day though the humidity wasn't incredibly high.
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jbguller
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 10:32 pm

Quoting LHR777 (Reply 33):
Does it require more thrust? Higher V1/VR/V2? Weight restriction? Any clues please? Cheers!

...I think it requires more runway!!! Big grin
 
NZ8800
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 10:48 pm

Was reading through this thread and thinking landings at hot and high airports can cause problems as well as takeoffs can. Antananarivo's Aeroport Ivato (Madagascar) is at 4196ft (1279m), runway length 10171ft (3100m). Pretty much the entire time a 747 is on the ground at Ivato is spent spraying the brakes with water, so that they will be cool enough for the aeroplane to be able to take off again.
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Rbgso
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 11:10 pm

Pretty much the entire time a 747 is on the ground at Ivato is spent spraying the brakes with water, so that they will be cool enough for the aeroplane to be able to take off again.

Help me out here, what do cool brakes have to do with take-off performance?
 
NZ8800
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 11:21 pm

Quoting Rbgso (Reply 37):
Help me out here, what do cool brakes have to do with take-off performance?

So that they do not cause a fire in the wheel wells.

Albeit a smaller aircraft - that is exactly what happened recently here when a New Zealand Post Metroliner took off with the brakes too hot (in this case, one parking brake left on by mistake) - and a fire was started in the wheel bays - then the fire spread to the fuel tanks, and the aeroplane exploded completely.
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litz
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RE: Aircraft Not Suited To Hot & High

Sun Jul 30, 2006 11:56 pm

Quoting Rbgso (Reply 37):
Help me out here, what do cool brakes have to do with take-off performance?

Not only the fire threat mentioned above, but remember - if you have to abort your takeoff, you need those brakes in prime condition ... and hot brakes will not perform as well as cool ones.

Add in the heat you build up braking during taxi, and you want to get those brakes as far down, temp-wise, as you can before you start rolling.

- litz
 
EMB195
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RE: Aircraft Not Suited To Hot & High

Mon Jul 31, 2006 1:05 am

Another aircraft that has had a little bit of problems here in SLC is the ERJ-170. I have a friend who works in baggage handling for DL. He told me that once they had to remove about 60 bags off a 170 because of weight restrictions during a hot day. Has anyone heard anything about that also?
 
Spoke2Spoke
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RE: Aircraft Not Suited To Hot & High

Mon Jul 31, 2006 1:16 am

The A321 from what I've heard is not the best hot and high aircraft. Does anyone know what sort of weight restrictions this aircraft can experience in these conditions?
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warreng24
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RE: Aircraft Not Suited To Hot & High

Mon Jul 31, 2006 1:32 am

Have you guys ever watched the Champion Air 727's on take off from LAS during the summer? Amazing.
 
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AA777223
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RE: Aircraft Not Suited To Hot & High

Mon Jul 31, 2006 1:36 am

I'm surprised that the 753 is a poor performer in higher altitudes and temperatures. I realize that it is longer and weighs more than its smaller brother, but the 752 is the hot rod fof the airliners scene with "fighter-like" performance. I would think this would mean a moderately stretched version would therefore be at least an adequate performer even in hot and high conditions.
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onetogo
Posts: 286
Joined: Thu Feb 02, 2006 1:40 pm

RE: Aircraft Not Suited To Hot & High

Mon Jul 31, 2006 1:37 am

Quoting Eastbay (Reply 27):
Humidity doesn't enter the picture.

You are 100% correct. Funny how everyone sort of ignored that. What is causing the confusion is that for people, additional humidity makes it *feel* hotter (i.e. "heat index") however jet engines dont care.
 
j.mo
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Joined: Fri Feb 15, 2002 12:29 am

RE: Aircraft Not Suited To Hot & High

Mon Jul 31, 2006 1:45 am

Quoting SLCUT2777 (Reply 28):
I would like to see at least on any future master plan an extension of runway 34L-16R to at least 15,500,' to better deal with this issue.

http://www.slcairport.com/pdf/planning/ap1_alp.pdf

It looks like 14,300ft is in the cards for 34R.

Jeremy
 
N353SK
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RE: Aircraft Not Suited To Hot & High

Mon Jul 31, 2006 1:49 am

Quoting EMB195 (Reply 40):
Another aircraft that has had a little bit of problems here in SLC is the ERJ-170. I have a friend who works in baggage handling for DL. He told me that once they had to remove about 60 bags off a 170 because of weight restrictions during a hot day. Has anyone heard anything about that also?

One isolated incident doesn't really prove anything. The plane could have had to take on extra fuel for weather, or it could have accidentally been over-fueled. Maybe the heat had something to do with it, maybe not.
 
kcrwflyer
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Joined: Tue May 18, 2004 11:57 am

RE: Aircraft Not Suited To Hot & High

Mon Jul 31, 2006 2:42 am

Quoting BCAInfoSys (Reply 2):
I think the CRJ has had some problems/weight restrictions with high altitudes(ex. DL out of ASE)

If that's the case, then why does Skywest run a huge fleet of them out of SLC? Doesn't quite add up, sorry.

Slc has plenty of runway for a CRJ.


Also, arent there certain conditions where an aircraft will be weight restricted regardless of runway length

Quoting Goldenshield (Reply 4):
it must be noted that the CRJ-200 would not be authorized to operate into that airport since the airport is closed to CAT D aircraft.

I thought the CRJ was CAT C. They operate here and we're CAT C.
 
Goldenshield
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RE: Aircraft Not Suited To Hot & High

Mon Jul 31, 2006 2:48 am

Quoting KcrwFlyer (Reply 47):
I thought the CRJ was CAT C. They operate here and we're CAT C.

The CRJ-200 is approach category D. The CRJ-700 is category C. What you are referring to is the airspace around the airport itself, which is CLASS C airspace, and has nothing to do with aircraft performance.
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727forever
Posts: 304
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RE: Aircraft Not Suited To Hot & High

Mon Jul 31, 2006 2:49 am

Humidity does not play a factor in jet performance, as was stated by a few here, but several factors do. Altitude, Temp, weight, and flap setting do affect performance.

These things are all taken into account when running your takeoff, and landing, performance data. The more flaps you use the lower your takeoff speed will be. This is because the addititional flap gives you more drag, which also gives you more lift at a lower speed (yes, I know very basic aerodynamic explination for the 13 year experts) thereby reducing V1 and Vr speeds to get off the ground quicker. However, once you get off the ground the additional drag created by the flap will result in a lower 2nd and 3rd segment climb until you get to acceleration altitude, retract the flaps, and climb clean. If I have a really short runway at low altitude, with no obstacles, I will use the highest flap setting that I have.

If I use a lower flap setting for takeoff the opposite is true. My take off roll will be much longer because I do not have the lift at lower speed that is generated by the flaps. I will need much more runway to get to the higher V1 and VR. However, my climb rate once rotating will be much better to acceleration altitude because I have less drag.

Now lets throw in the effects of altitude into the equation. At higher altitudes several things are happening. First, the air is thinner and non-turbocharged piston, turbo-prop, and turbojet engines do not make as much thrust/power as they would at lower altitude. Second, with the air being thinner your indicated airspeed (the speed that the wing thinks it is going) is lower as well. To get to the speed that the wing needs to fly, your actual speed (TAS) will be much higher. This will result in more distance to accelerate to that speed (VR). Third, at higher altitudes the airplane will not climb as well for all of the reasons listed above. If you were to loose an engine at takeoff decision speed (V1) you would need max performance to climb above all obstacles. All of the effects of altitude are compounded when you loose an engine so you are going to want the flap configuration that gives you the best engine out climb profile to clear all obstacles.

So, to put this all together. When flying from an airport on a hot/high altitude, I will use the lowest flap setting possible. In the CRJ it is flaps 8 vs. 20, 727 it is flaps 5 vs. 15 or 25, 737 it is flaps 1 vs. 5 or 15, Airbus 320 it is flaps 1 vs. 2 or 3, and I'm not sure about others. I will accept the longer takeoff role, in many cases all of the runway, so that I can maximize the engine out climb performance. These aircraft all do fine at high altitude airports so long as you remember to look at all possible configurations for takeoff.

Also, the brake cooling prior to takeoff is so that you have max braking energy available in the event of a rejected takeoff prior to V1. The hotter your brakes get, the less stopping power they have for a rejected takeoff. We do carry a chart that analyses this called a V1/V1mbe chart that will help you decide how much time is needed to cool the brakes after an RTO or landing. Yes a brake fire in the wheel wells is possible, but unless you have a stuck caliper on takeoff, the max brake temp to takeoff should be well lower than that to start a wheel well fire from hot brakes.

I digress.

727forever
727forever

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