Bryan Becker
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Time To Get To 35000ft

Mon Mar 19, 2001 10:50 am

I was just woundering how long it would take a jetliner to get to 35000ft if they were to do a constant climb all the way up? Smile




bryan+becker=bryanbecker Smile
 
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RE: Time To Get To 35000ft

Mon Mar 19, 2001 10:54 am

It depends on so many things weight being the main the one, it take a full 747 much longer to climb to 35,000 then an empty lear! I know when I was upfront in a A340, it was quite long into the flight till we got up around 35,000!
Iain
 
Guest

RE: Time To Get To 35000ft

Mon Mar 19, 2001 11:24 am

I agree with Lain, it definetly depends on weight. Also, some aircraft have better climbing performance than others. For example, I know the 757 climbs the best of all twin engine jets (or so I've been told by one very "cocky" captain). But most of your "heavy" jetliners have initial crusing altitudes at which they remain at until burning off sufficient fuel. Then they may climb a few more thousand feet and fly there until enogh fuel has been burned to climb higher. They climb in segments until they get to the most efficient altitude to remain at until descent. It's not to say they couldn't climb that high, but it certainly wouldn't be economical.

Chris
 
Bryan Becker
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RE: Time To Get To 35000ft

Mon Mar 19, 2001 11:26 am

I just want a estimate,lets say a A320 with 140 passengers or less and full fuel on it's way from Sky Harbor to SFO,just a approx.............................. Smile


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AAR90
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RE: Time To Get To 35000ft

Mon Mar 19, 2001 12:48 pm

135,000 lbs MD90 will do it in about 15 minutes. Best climb I've done is Brake Release to FL410 in 16.5 minutes in a B757 (and we left it at derate-2 all the way). Would have been real interesting at full power.  Big grin
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
chdmcmanus
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RE: Time To Get To 35000ft

Wed Mar 21, 2001 3:48 am

As stated before by the experts it depends on a lot of physical factors, but it also depends on what type of climb profile, ie, max rate, max angle, max speed, or econ. I have found through experince for most acft that loaded, using a SID and vectors to initial cruise the average time was around .5-.6 hrs (30-40 min) from T/O power set to cruise check, assuming you can reach FL350 immediately.
"Never trust a clean Crew Chief"
 
DE727UPS
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RE: Time To Get To 35000ft

Wed Mar 21, 2001 4:31 am

I'm gonna say 30 minutes in the RR Tay powered 727-100QF at normal takeoff weights. It's doggy about 250 you have much weight at all.
 
Guest

RE: Time To Get To 35000ft

Wed Mar 21, 2001 8:05 am

About 15 years ago I was flying for a major airline. One day when I was jumpseating to LAX I asked the captain of the B727-200 I was on how long he had been flying 3-holers. His answer: "12 years, that's 6 years in climb, 3 years in cruise, and 3 years in descent." As they say, "they don't climb so good." Our Astra SPX will get to FL350 in approxiamately 11 minutes. We can do FL410 at mid weights in about 17 to 18 minutes.
 
Guest

RE: Time To Get To 35000ft

Wed Mar 21, 2001 9:23 am

AAR90,
Just curious. Does the B757 go from Climb 1 or 2 to Climb at 10,000ft and apply power to reach that setting by 12,500ft so giving max climb thrust from that point on up anyway?
Thanks.
 
Guest

RE: Time To Get To 35000ft

Sat Mar 24, 2001 12:02 am

Does the B757 go from Climb 1 or 2

Feret, that terminology just slipped me. Just give me an idea of what you mean?
Thanks, Tom
 
Joona
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RE: Time To Get To 35000ft

Sat Mar 24, 2001 9:04 am

In 757/767 there are three different kind of climb modes; CLB, CLB1 and CLB2. (Climb, Climb 1 and Climb 2 respectively)

CLB: This mode sets the N1 bug at upper EICAS (Engine Indicator and Crew Alerting System) page on the N1 indicator to the maximum N1 setting for the climb. This is the highest N1 setting that can be used for climb and and if EECs (Electric Engine Control) are turned on (they need to be in order to use the TRP (Thrust Rating Panel (this is where you set those TO, CLB, 1, 2, CON, CRZ modes))) they will automatically limit the power to this setting even if you pushed the thrust levers all the way to forward.

CLB1: This mode is exactly the same as CLB mode but the N1 setting is smaller, thus calling it 'de-rated climb' 1. With this mode you have less power in use and can save fuel.

CLB2: This is the third mode. Exactly the same as modes CLB and CLB1, but the N1 setting is smaller than in CLB1. This mode saves a lot of fuel during climb.

The way these modes are used:

For example, your climb will be done by LNAV driven by the FMC. The FMC has calculated your ECON CLB SPD as 308kts. This means, you get the most out of the climb ans save the most fuel by maintaining 308kts during climb. Now, you choose CLB mode after departure. By doing that, you limit the available power to the one specified by the CLB N1 setting in the EICAS. Now, you engage the LNAV mode in MCP (Mode Control Panel (the place where you can control AFDS (like autopilot))) and then engage the AFDS. Now, the FMC will maintain this CLB power setting and a vertical speed high enough to maintain 308kts.

Of course if you use CLB1 or CLB2 mode you have less power to use for climb and thus the FMC need to maintain a smaller vertical speed to maintain 308kts, thus calling it a 'de-rated takeoff'.

Hope this cleared something...it's 2am here, and getting pretty tired so I take all responsibility for all mistakes Big grin

Joona
1740 days idle. Beat that.
 
AAR90
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RE: Time To Get To 35000ft

Sat Mar 24, 2001 12:43 pm

>Does the B757 go from Climb 1 or 2 to Climb at 10,000ft and
>apply power to reach that setting by 12,500ft so giving
>max climb thrust from that point on up anyway?

Nope. Power setting remains whatever is set until changed manually or by mode of flight (i.e. cruise vs climb). Suspect you're thinking of the B767 which automatically shifts to full climb power at approx. 12,500'.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
Bryan Becker
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RE: Time To Get To 35000ft

Sat Mar 24, 2001 12:53 pm

THANKS for all you posts!!!!!!!!!!! Smile



-Bryanbecker Big thumbs up
 
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RE: Time To Get To 35000ft

Sat Mar 24, 2001 1:31 pm

AAR90,

So if you start your climb in CLB2, it will remain there regardless of the rate of climb? Is there no value in FPM where the FMC will select CLB1?
 
Joona
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RE: Time To Get To 35000ft

Sat Mar 24, 2001 9:35 pm

Ambasaid, read my post above the modes a couple of posts above.

However, I'm not 100% sure of it..anyway, I've understood you need to change the Climb mode manually.

And a tiny correction to my previous post:

It's VNAV, not LNAV.
VNAV = VERTICAL Navigation
LNAV = Lateral Navigation

Told ya there may be mistakes...that's what happends when you post messages like that at 2am... Big grin

Joona
1740 days idle. Beat that.
 
Buff
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RE: Time To Get To 35000ft

Sun Mar 25, 2001 12:38 am

CLB1: This mode is exactly the same as CLB mode but the N1 setting is smaller, thus calling it 'de-rated climb' 1. With this mode you have less power in use and can save fuel.

CLB2: This is the third mode. Exactly the same as modes CLB and CLB1, but the N1 setting is smaller than in CLB1. This mode saves a lot of fuel during climb.


Actually Joona, you've got it reversed. While just about everything else in your post is close to the mark, the B757 burns less fuel in its climb to altitude with full CLB. CLB 1 is 94% of full climb; CLB 2 is 88% - on the RB211-535-E4 engines.

...thus calling it a 'de-rated takeoff'. This is not correct, as it is comparing apples to oranges!

Note: In answer to the actual question, our typical time to climb to FL350 would be about 20-25 minutes at 110,000 kg, the maximum weight allowable at FL350. Under those weight conditions, we would in all likelihood level off at FL310 or FL330 max. As you exceed your optimum altitude, fuel burns increase.

Climb derates conserve engine life. That is there principle reason for being. Our company uses the greatest derate possible switching manually to the higher setting only when rate of climb becomes an issue.

Best Regards,

Buff
 
Guest

RE: Time To Get To 35000ft

Sun Mar 25, 2001 1:43 am

Buff,

I'm still surprised that you dont use Derate for takeoff...

Do you actually select the higher climb at a specific VSI or is it automatic. On the FMC's that I'm used to, they automatically change over when the VSI reaches 500 fpm.

 
Buff
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RE: Time To Get To 35000ft

Sun Mar 25, 2001 8:02 am

I didn't say that! Yes, we use derate for takeoff most of the time. One has to separate the two distinctly different parts of the flight: the takeoff segment and the climb segment. Different numbers/terminologies apply to each of these parts of the flight.

It may be that full thrust is used for takeoff because of contaminated runway, windshear, having deiced or any number of other reasons, and then CLB 2 for the climb segments.

Remember, the takeoff part of the flight commences from the time of application of takeoff power until the aircraft has achieve 35 feet of height at the departure end.

From that point, the climb segments begin. The first segment climb commences immediately after the aircraft reaches 35'. This is the segment where the a/c accelerates to V2 or V2+(increment - usually 10-20 Kts.). The second segment commences upon gear retraction and ends at 400'AGL or when the gear is fully retracted, whichever is later. The third segment is an acceleration segment where climb power is selected, and flaps are retracted; the fourth segment is a clean climb up to 1500'.

All these altitudes are minimum altitudes that apply to a Seneca II or a B747. They are defined by regulation. In practice, we maintain a fourth segment climb speed up to 3000' above aerodrome elevation because the defined altitudes get passed very quickly.

Unless of course you've had an engine failure...

Different thread.

Best Regards,

Buff
 
Joona
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RE: Buff

Sun Mar 25, 2001 9:31 am

Thanks for correcting me here and pointing out my mistakes.....ya always learn something new here  Smile

Joona

1740 days idle. Beat that.
 
Guest

RE: Time To Get To 35000ft

Sun Mar 25, 2001 1:55 pm

Sorry Buff,

I thought that in the Derate Engine topic last week, you said that you didnt use fixed derates for takeoff?

 
AAR90
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RE: Time To Get To 35000ft

Sun Mar 25, 2001 3:03 pm

>So if you start your climb in CLB2, it will remain there regardless
>of the rate of climb? Is there no value in FPM where the
>FMC will select CLB1?

For AA's B757s, there is only one method of obtaining an "automatic" change in Thrust Rating Computer (TRC) power settings and that is the SNA quiet climb mode. A brief description of AA B757 SNA departure procedure follows.

Preselect CLB2 on the Thrust Rating Panel (TRP) prior to takeoff. Also program in a climb speed (V2+20) & altitude (3,000 feet) restriction on the FMC Climb page. Perform a max power takeoff and maintain V2+20 speed until reaching 3,000 feet. Throttles will go into HOLD mode during takeoff roll and remain there until new autothrottle mode is selected. At 800 feet select VNAV mode. Autothrottles will reactivate and command a thrust setting for the SNA quiet climb mode (significantly less than CLB2 setting). They will maintain that thrust setting until the airplane passes 3,000 feet (the climb restriction set in the FMC). Above 3,000 feet the autothrottles will slowly and smoothly advance to the normal CLB2 setting. At this point everything returns to normal procedures and the only way to change climb power setting is to manually change TRP setting or to change out of a climb mode.

The above only works for AA B757 FMC/TRC (special programming required). Other airlines' B757s have been known to refuse 19R departures at SNA at significantly less weights due to noise concerns while AA's B757s continued to utilize 19R at max gross weights. So I don't know what or how their programs are set up.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
Buff
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RE: Time To Get To 35000ft

Mon Mar 26, 2001 12:18 am

I thought that in the Derate Engine topic last week, you said that you didnt use fixed derates for takeoff?

We don't use FIXED derates for takeoff. That is correct. We use VARIABLE derates for takeoff using the assumed temperature method. There are strict guidelines for use of any reduced thrust for takeoff. They include some of the restrictions I posted above.

We do use FIXED derates in climb. We do not have VARIABLE climb derates.

Hope that's clear!

Buff
 
Guest

RE: Time To Get To 35000ft

Mon Mar 26, 2001 3:33 am

Thanks Buff, that clears up my confusion.

Thanks AAR90, interesting departure procedure.
 
Buff
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RE: Time To Get To 35000ft

Mon Mar 26, 2001 5:27 am

Funny how discussions wind up going down different paths as the thread gets longer!

Buff
 
Guest

RE: Time To Get To 35000ft

Mon Mar 26, 2001 1:07 pm

I guess thats because some people already know how long it takes to get to 35,000 feet and are therefore looking to make the discussion more interesting.

 
XXXX10
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Derates

Tue Mar 27, 2001 8:09 pm

Am I correct in assuming that t/o derates are acheived by programming the n1 speed into the fmc and clb derates are prograammed into the thrust rating pane using assumed temp.
 
Guest

RE: Time To Get To 35000ft

Tue Mar 27, 2001 8:52 pm

Xxxx10,

There are two types of Takeoff Derates, Fixed Derate and Assumed Temperature Derate.

The fixed derate is selected by the manufacturer/airline and is programmed into the FMS as a thrust rating, the crew then select the rating which suits them on the day. I believe that you can have up to a 25% thrust reduction, although we only use 20%.

An assumed temperature derate is a procedure where an "assumed" temperature is entered into the FMS, this leads the engine to believe that the OAT is hotter than actual, the engine therefore delivers less power. Assumed Temperature Derates are limited to a 25% thrust reduction.

You can use the assumed temperature method of thrust reduction on a fixed derated engine to give you a total reduction of around 40%.

Climb Derates, I'm not sure if i would call them Derates or settings, but either way they are similar to the Fixed Derate Takeoff rating. They do not work with assumed temperature.

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