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convair880mfan
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Maximum gross weight step climb question

Wed Jul 28, 2021 7:16 pm

Which jetliners are [were] capable of taking off at maximum gross weight and reaching final cruising altitude without the need for a weight-related step climb?

I think the Boeing 707 required a weight related step climb under certain conditions. Not sure about other jetliner types. Perhaps pilots and former pilots could answer this. Thanks to one and all for your responses.

I framed the question to exclude ATC required step climbs. I'm primarily interested in aircraft performance at MGW.
 
hitower3
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Re: Maximum gross weight step climb question

Wed Jul 28, 2021 7:22 pm

While I can't answer based on hard facts, my bet would be on shorter range aircraft, as these will lose less weight in-flight.
I would not be surprised if an ATR 42 could reach FL250 after taking off at MTOW.

Also, the shortest aircraft of a family sharing the same wing, e. g. A318, B736... might be good candidates.
 
GalaxyFlyer
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Re: Maximum gross weight step climb question

Wed Jul 28, 2021 7:29 pm

I doubt any of them can, none of the six bizjets, B727 or the C-5 could.
 
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Starlionblue
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Re: Maximum gross weight step climb question

Thu Jul 29, 2021 2:43 am

A lot depends on environmental conditions on the day. If the air is colder, you can climb higher at the same weight.

That being said, I'm with GalaxyFlyer. I doubt any jetliner can climb to the operational ceiling after a MTOW takeoff.
 
Max Q
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Re: Maximum gross weight step climb question

Thu Jul 29, 2021 4:01 am

By ‘final cruising altitude’ I think you mean maximum certificated ceiling, the former is your maximum for the particular flight and rarely the same as the latter


And I don’t know of any transport category aircraft that can climb to its maximum ceiling after a maximum take off weight departure
 
convair880mfan
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Re: Maximum gross weight step climb question

Thu Jul 29, 2021 4:30 am

So no jetliner is capable of climbing to its final cruise altitude in an uninterrupted climb if it takes off at its maximum gross weight?

Maybe I am asking my question incorrectly. I think I am using terms incorrectly. Lets say aircraft x has 25,000 feet as its best cruise altitude for the conditions and it takes off very heavy. Does it need to climb in steps?

In the Boeing 707, a former TWA Captain told me that the aircraft would often need to level off and burn off some fuel weight before it could continue its climb. I was wondering if other aircraft required that or if more modern jetliners were capable of an uninterrupted climb to cruise altitude without leveling off for awhile to burn off fuel weight.

I realize that ATC can call for a level off during a climb for various reasons. What I am asking about is aircraft performance. Maybe maximum gross weight is the problem with my question. Maybe aircraft seldom take off at maximum gross weight?

Although I may be totally misinformed [I am out of my element] it is hard for me to imagine that, say, a Boeing 757, would need to make several level offs to burn off fuel before reaching its cruise altitude for that flight.

Sorry if I am not framing this question correctly! The TWA Captain told me that the Flight Engineer had to do lots of calculations and would say things like: "we're still too heavy to climb to flight level x. We should be able to resume our climb after x number of minutes."
 
Max Q
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Re: Maximum gross weight step climb question

Thu Jul 29, 2021 4:59 am

convair880mfan wrote:
So no jetliner is capable of climbing to its final cruise altitude in an uninterrupted climb if it takes off at its maximum gross weight?

Maybe I am asking my question incorrectly. I think I am using terms incorrectly. Lets say aircraft x has 25,000 feet as its best cruise altitude for the conditions and it takes off very heavy. Does it need to climb in steps?

In the Boeing 707, a former TWA Captain told me that the aircraft would often need to level off and burn off some fuel weight before it could continue its climb. I was wondering if other aircraft required that or if more modern jetliners were capable of an uninterrupted climb to cruise altitude without leveling off for awhile to burn off fuel weight.

I realize that ATC can call for a level off during a climb for various reasons. What I am asking about is aircraft performance. Maybe maximum gross weight is the problem with my question. Maybe aircraft seldom take off at maximum gross weight?

Although I may be totally misinformed [I am out of my element] it is hard for me to imagine that, say, a Boeing 757, would need to make several level offs to burn off fuel before reaching its cruise altitude for that flight.

Sorry if I am not framing this question correctly! The TWA Captain told me that the Flight Engineer had to do lots of calculations and would say things like: "we're still too heavy to climb to flight level x. We should be able to resume our climb after x number of minutes."



Need to clarify some things, the maximum certificated ceiling of the aircraft is just that, it is the maximum altitude permitted by the certification authority


It’s rare for a transport category aircraft to reach this altitude unless it’s very light, has burned off a lot of fuel and / or has a light load


You aim to fly at the most efficient altitude you can get approved by ATC, if 25000 feet is your most efficient altitude then that’s the altitude you would request but it most likely wouldn’t be your maximum, it would be your ‘optimum’ although this is also affected by wind, you might choose to fly lower to avoid a headwind and higher to take advantage of a tailwind but there’s a lot of factors involved


As you burn off fuel you would normally request a higher altitude, it’s more ‘optimal’ to fly higher as you get lighter so yes it’s very common to go higher in a series of steps as your weight reduces and if ATC allows of course


The FMC will actually show three cruise altitudes ‘optimum’ which is just that for your weight,
‘Recommended’ which also considers the effect of wind and ‘maximum’ which is the maximum for your current weight and probably not the maximum certificated ceiling which can only be reached at very light weights,


Your final cruising altitude is whatever you plan for and / or works best for the particular flight, there are many other factors to consider though, at the beginning of an oceanic crossing you may attempt get a higher than recommended cruising altitude approved as it can be difficult to get this clearance later or you may want to go higher to remain clear of weather although you have to be careful with that



The 757 like all jet transports cannot go to its maximum certificated altitude (42000 feet) immediately after a maximum weight take off, like all other types it would require a series of steps to burn off fuel first and on most flights it wouldn’t get light enough
 
T54A
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Re: Maximum gross weight step climb question

Thu Jul 29, 2021 6:07 am

Any airliner will be able to climb directly to its INITIAL cruise altitude. No steps required. This initial cruise altitude will be lower than max certified altitude at high weights.

As an example. A A340-600 taking off at 368 000kg will have an initial optimum cruise altitude (actually Flight Level) of 28 000-30 000ft. It will climb directly to this level after take off. After 16hrs of flying it will end up at between 39 000ft and 41 000ft due to weight lost by fuel burn.
 
VMCA787
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Re: Maximum gross weight step climb question

Thu Jul 29, 2021 10:02 am

convair880mfan wrote:

Maybe I am asking my question incorrectly. I think I am using terms incorrectly. Lets say aircraft x has 25,000 feet as its best cruise altitude for the conditions and it takes off very heavy. Does it need to climb in steps?

You have really answered your own question.

A 744 or 777ER if they take off at MTOW, their initial "best altitude for the conditions" will be around FL300 +/- about 1000 feet. There are a couple of things you have to understand. At MTOW, the aircraft will have several altitudes it can choose from. On Boeings, the FMC from my experience defaults to ECON Cruise which is 99% max range cruise. Generally, that is the altitude you would use, assuming correct for the direction of flight, and then as the aircraft gets lighter you can climb. MRC, at heavyweights, will get you a higher altitude and slightly higher speed. Then you have LRC which will result in slightly lower speed and altitude. All of those altitudes and speeds vary as the weight changes. Finally, you will have MAX ALT for your weight and cruise selection. That is the altitude for your current weight and environmental conditions. And of course, you also have your max certified FL. So, in your statement, you have already stated the best cruise alt is 250 based on the conditions. As the aircraft burns off fuel, that will increase. Unless you are flying very short sectors, there is no one best altitude for your entire route of flight.

Hope I helped out.
 
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zeke
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Re: Maximum gross weight step climb question

Thu Jul 29, 2021 10:36 am

T54A wrote:
As an example. A A340-600 taking off at 368 000kg will have an initial optimum cruise altitude (actually Flight Level) of 28 000-30 000ft. It will climb directly to this level after take off. After 16hrs of flying it will end up at between 39 000ft and 41 000ft due to weight lost by fuel burn.


Strange, the A346 I flew was able to climb to FL330 after a MTOW departure.
 
Woodreau
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Re: Maximum gross weight step climb question

Thu Jul 29, 2021 3:04 pm

The only aircraft that I have flown that I have flown that could reach max certificated altitude at MAx structural takeoff weight were the BE-1900 and EMB-145.

Flights on the 1900 would routinely be taking off at max structural takeoff and we could go all the way up to FL250. But the legs are so short, the flight would be over before we got to FL250.

We would also routinely takeoff at MTOW on the EMB-145 (not as much as the 1900) and there was no performance limitation that would prevent us from going up to FL370.

We would be at MTOW on the CRJ700 fairly often departing Aspen and having to do maneuvers for terrain clearance and traffic avoidance immediately after takeoff.. But aircraft performance was not an issue departing ASE at MTOW. Even had a windshear warning departing ASE once that caused us to follow a different departure procedure leaving ASE instead of the normal procedure, basing the departure turn to 270 on distance from runway vs reaching a specific altitude.

Since flying the 320 family of aircraft these last 8 years, i don’t think I’ve ever taken off at max structural takeoff weights in a 319/320/321 ever. If I had a flight that I took off at max structural takeoff weight, it would be an unusual event that I would remember. Maybe a few times, I’d be runway or obstacle climb limited for takeoff. Taking off a mtow is not a routine event on a narrowbody like it was for RJs, in my limited experience.
 
T54A
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Re: Maximum gross weight step climb question

Fri Jul 30, 2021 7:30 am

zeke wrote:
T54A wrote:
As an example. A A340-600 taking off at 368 000kg will have an initial optimum cruise altitude (actually Flight Level) of 28 000-30 000ft. It will climb directly to this level after take off. After 16hrs of flying it will end up at between 39 000ft and 41 000ft due to weight lost by fuel burn.


Strange, the A346 I flew was able to climb to FL330 after a MTOW departure.


Perhaps the ISA deviation out of JNB, or perhaps the westerlies kept our OPT down, but we seldom went straight to FL330 on the JFK flights where we were often at 368t.
 
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zeke
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Re: Maximum gross weight step climb question

Fri Jul 30, 2021 7:40 am

T54A wrote:

Perhaps the ISA deviation out of JNB, or perhaps the westerlies kept our OPT down, but we seldom went straight to FL330 on the JFK flights where we were often at 368t.


I would have been going eastbound. The CG location also played a part, like it does for takeoff.

The 77W would only get 290 and we would always out-climb them.
 
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ElroyJetson
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Re: Maximum gross weight step climb question

Sat Jul 31, 2021 3:29 pm

The 77W at MTOW or near MTOW seems to generally top off at FL 29 or 30 initially. If you look at Flightaware an EK 77W from LAX-DXB as an example, it will step climb up to FL 30 and stay there for a long time. You start to see a gradual increase in elevation somewhere past Greenland up to FL 38 or so after a lot of fuel is burned off.

I am not sure if the same pronounced effect exists with newer generation 787's or A 350's.
 
LH707330
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Re: Maximum gross weight step climb question

Mon Aug 02, 2021 5:10 pm

ElroyJetson wrote:
I am not sure if the same pronounced effect exists with newer generation 787's or A 350's.

Both of those designs have a lower wing loading than the 777-300ER, so they tend to have higher initial cruise altitudes, unless it makes sense to start lower for some reason (stronger tailwinds, ATC, turbulence high, etc.).
 
gloom
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Re: Maximum gross weight step climb question

Wed Aug 04, 2021 6:11 am

ElroyJetson wrote:
I am not sure if the same pronounced effect exists with newer generation 787's or A 350's.

It does in terms of general step climb procedure. However, both 787 and A350 will start higher (approx 36,37 at MTOW) and will climb higher a bit quicker. In many cases up to F430, depending on ZFW.

Cheers,
Adam
 
GalaxyFlyer
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Re: Maximum gross weight step climb question

Wed Aug 04, 2021 1:33 pm

Extreme example but none of the F510 certified bizjets, after a MTOGW departure, go near F510. More like F400-F430, depending on Mach. In my experience, the CL350 (max F450) is the closest and it typically starts at 430 or 450 unless temps are warm and absolute grossed out at take-off. Most trips, with unrestricted climb F430 is about 20 minutes to level.
 
thepinkmachine
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Re: Maximum gross weight step climb question

Wed Aug 04, 2021 3:12 pm

gloom wrote:
It does in terms of general step climb procedure. However, both 787 and A350 will start higher (approx 36,37 at MTOW) and will climb higher a bit quicker. In many cases up to F430, depending on ZFW.

Cheers,
Adam


A heavy 787 will start at approximately FL330, not sure about the A350.

430 will only be reached by a fairly light 788
 
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ElroyJetson
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Re: Maximum gross weight step climb question

Wed Aug 04, 2021 3:19 pm

gloom wrote:
ElroyJetson wrote:
I am not sure if the same pronounced effect exists with newer generation 787's or A 350's.

It does in terms of general step climb procedure. However, both 787 and A350 will start higher (approx 36,37 at MTOW) and will climb higher a bit quicker. In many cases up to F430, depending on ZFW.

Cheers,
Adam


The 787-10 is only certified for FL 410. The 789 and 788 are certified for FL 430. But I take your point. The 77W is generally limited to FL 290 or FL 300 at or near MTOW until enough fuel is burned off. The 787 can generally make it to FL 330 per pink machine who is a 787 pilot. I would assume the A350 is similar but I do not know for certain.
 
gloom
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Re: Maximum gross weight step climb question

Wed Aug 04, 2021 7:07 pm

thepinkmachine wrote:
A heavy 787 will start at approximately FL330, not sure about the A350.

430 will only be reached by a fairly light 788


Right, my airline started with 788 and usually 380 as initial. Forgot it's not the case for 789/78J.

359 at MTOW goes straight to 370, IIRC. 430 is quite reachable - on HKG-HEL leg, we travelled almost 3 hrs on 430. OH-LWF going HEL-JFK climbs now to 430, just above Greenland shores, with 2845km straight line on FR24.

35J is not able to reach 430, max cruise is 410, and general rule Zeke once claimed was +4000ft on 773, I guess 34, 35 for departure and up to 41 when ZFW allows.

Cheers, Adam
 
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ElroyJetson
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Re: Maximum gross weight step climb question

Wed Aug 04, 2021 10:18 pm

Frisco Heavy said he was on a QR flight from DOH to JNB on a 788 and said the last 3-4 hours of the flight made it up to FL 410. But as pinkmachine has said the 788 and 789 have to be pretty light to approach FL 430.

The A35J listed ceiling is FL 410. I do not know at MTOW how high it can initially go. If the A359 can initially go right up to FL 370 at MTOW that is impressive.

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