Step Climb

[scandinavian13 5,192]

Kyle, that's a very good point and I will remember it. I think even over the big pond there will be somebody being keen to know where you are.

 

However, I would like to know whether you could principally request a flightplan telling ATC that you want to be cleared in about 1200 NM (or probably 300 NM, south of Greenland?) to climb from FL360 to FL380. At the moment I don't believe that this could work.

 

Axel, glad it helped.

 

You will find some flight plans with the proposed step points in them (with F390M85 as Flight Level 390, Mach 0.85...or similar). I forget the legalese behind them, in terms of how, if a controller clears the flight "as filed," if the altitude changes are included in that clearance or not. Maybe Ryan (ryanbatcund) can answer that more clearly.

 

As far as oceanic control goes, they need to know even more as they don't have you on radar at all. It's all about position and speed reports, and math. They tend to be resistant to altitude changes in busier times because the separation minimums are a lot higher when not under radar control. Some say the general rule of thumb during the waves is to request the MAX ALT as declared by the FMC while still talking to a radar controller (before going non-radar). That way, you're at your optimum altitude about half way across, and not under it the whole way across in case you can't get a climb approved.

[FlyingAxx 2]

Thanks again Kyle! I used the 738WL NGX just for one long flight (from Shannon to New York) and I tried to find out the limits of the bird. I cannot remember anymore the correct figures but I took about 23,800kg fuel on board the "normal" reserve of 5t and I've set the Cost Index to 25. This setup allowed about 150 PAX (not really sure). However, most time I was riding on FL360 and I was able to STEP to FL380 a bit SW of Greenland - more than the half way. The gained efficiency was about 7.8% only and finally even a bit less due to the horrible head winds of >100 kn. Okay, I was keen to STEP as I wanted to try it out and the saved fuel might be a merit in RL but I'm not sure whether a real flight would be planned like this as I used a bit of my reserves finally. I think this would not be the right distance for having passengers on board - probably something for a private plane. It would have been better to go directly from your European starting point (for me EDDT) to Gander for re-fueling. The the distance to STEP would be more predictable I suppose.

[Mean Aerodynamic Chord 269]

Can anyone explain to me how exactly step climbing saves an airline fuel? I've never done a flight with step climbing, I'm not sure how it works.

[Tabs 2,790]

Can anyone explain to me how exactly step climbing saves an airline fuel? I've never done a flight with step climbing, I'm not sure how it works.

 

When you're heavy, you can't climb as high initially because of the weight. Airplanes lose a lot of weight over the course of a flight as they burn off fuel, so at a certain point it becomes more fuel efficient to climb to a higher altitude. If you didn't you'd incur unnecessary drag penalties from flying lower in the thicker air and that that would reduce your max range. This is really more of an issue with long haul flying though - you'll have to step climb on long flights with the 777 and 744v2.

[victorlima01 4]

In the real 777 I know all you gotta do is go to the LEGS page and put in say FL390S for step and it will do it automatically when you get to the waypoint. I guess the 737ng doesn't have that feature I guess. But yeah I guess it's made that way for the reason you mentioned.

 

Martin, inputing a flightlevel with the letter "S" next to a fix in the legs page will not make the 777´s Vnav automatically climb to the new FL once the fix is reached. It merely changes the way the fix is displayed in the ND and updates the information avaiable in the cruise page of the CDU. Like someone else mentioned earlier, The AP (almost) never violates what is dialed in the MCP window. Once you reach your intented s/c fix you still have to call it in and dial it in the MCp if you get the clearance.

[MartinBeauchemin 0]

 

 

Martin, inputing a flightlevel with the letter "S" next to a fix in the legs page will not make the 777´s Vnav automatically climb to the new FL once the fix is reached. It merely changes the way the fix is displayed in the ND and updates the information avaiable in the cruise page of the CDU. Like someone else mentioned earlier, The AP (almost) never violates what is dialed in the MCP window. Once you reach your intented s/c fix you still have to call it in and dial it in the MCp if you get the clearance.

 

True but it helps with the VNAV and fuel predictions. And in flight plans they usually have for example SEFIX/M083F340 or something like that in the ICAO flightplan. So doesn't that clear you to climb unless otherwise stated by ATC? Correct me if I'm wrong. I'm beggining to see why it's so much easier to enter it in at the time of clearence though.

[davidz 26]

You will find some flight plans with the proposed step points in them (with F390M85 as Flight Level 390, Mach 0.85...or similar). I forget the legalese behind them, in terms of how, if a controller clears the flight "as filed," if the altitude changes are included in that clearance or not. Maybe Ryan (ryanbatcund) can answer that more clearly.

 

Even though "as filed" is used, a separate "maintain FLxxx" is issued so flight planned levels do not constitute a clearance to climb to those levels.

[scandinavian13 5,192]

Even though "as filed" is used, a separate "maintain FLxxx" is issued so flight planned levels do not constitute a clearance to climb to those levels.

 

Thanks for that!

[Mean Aerodynamic Chord 269]

 

 

When you're heavy, you can't climb as high initially because of the weight. Airplanes lose a lot of weight over the course of a flight as they burn off fuel, so at a certain point it becomes more fuel efficient to climb to a higher altitude. If you didn't you'd incur unnecessary drag penalties from flying lower in the thicker air and that that would reduce your max range. This is really more of an issue with long haul flying though - you'll have to step climb on long flights with the 777 and 744v2.

 

Thanks for that explanation, Ryan! It really helped.

 

So how high do you go? Say you're flying from KLAX to KLAS. I always use FL240/FL220 on that route, via Dagget. Should you go up to FL300? Wouldn't that be too high for such a short route, thus making you say at FL300 for 2 minutes then decending?

[Fabo 213]

Diego: the TRIP ALT shown in PERF window will show you the ideal FL, regarding weight, distance, performance - CI... for the ideal fuel/time usage. You should try and fly as close the level as possible, even if it means just a minute or two on the cruise level (that is actually the most efficient way indeed)

[scandinavian13 5,192]

So how high do you go? Say you're flying from KLAX to KLAS. I always use FL240/FL220 on that route, via Dagget. Should you go up to FL300? Wouldn't that be too high for such a short route, thus making you say at FL300 for 2 minutes then decending?

 

You go to the efficient altitude for your weight. The FMC will tell you this: OPT ALT. If it's a shorter flight, I think the INIT Page shows you another altitude (TRIP ALT?) that takes into account the most optimum altitude for that route segment, but I could be wrong there.