Maximum climb and descent rate during normal operations

[WebMaximus 372]

As the topic suggests, what would be considered max climb and descent rate in FPM during normal operations of the 737 or the 737-800 with winglets to be more specific?I have a program called XPax from HiFi and looking at the options these values are by default set to max 8000 ft/min for climb and max 4000 ft/min for descent and just want to know if these values are realistic for a 738WL a/c?TIA,

[steve inwood 67]

As the topic suggests, what would be considered max climb and descent rate in FPM during normal operations of the 737 or the 737-800 with winglets to be more specific?I have a program called XPax from HiFi and looking at the options these values are by default set to max 8000 ft/min for climb and max 4000 ft/min for descent and just want to know if these values are realistic for a 738WL a/c?TIA,

B738 TOGW can be anywhere between 120,000 lbs and 174,000 lbs so initial climb rates can be anywhere between 10 feet/minute and 6,000+ feet/minute. If one were to assume approximately 150,000 lbs aircraft one could also assume 4-6,000 feet/minute initial climb rate reduced to 2-4,000 feet/minute at approximately 1,000 feet AGL. These are very generalized figures. Edited January 26, 2012 by Steve Inwood

[ccarter06 3]

The MCP range is -7900 ft/min to +6000 ft/min. Those would be your max's. Typical descent rate is whatever rate gives you a 3 degree descent. That rate is dependant upon your groundspeed. If you're in final landing configuration, it could be 600 ft/min (GS of 120 kts). If you're at altitude descending with 150 kt tailwind, it could be 3000 ft/min (GS of 600 kts). It is possible to descend with the nose up in the sky (both within the normal flight envelope, or stalled), so the rate of descent may or may not cause discomfort to the passengers. Also, the pressurization may or may not increase its rate. If you're getting close to landing, the pressurization may have already settled close to the landing elevation, so it may not cause discomfort either. It's all dependant on the situation. Me personally, I started getting irritated with the pressurization when it hits 400-500 ft/min, and I'm pretty sure someone is freaking out in the back when I'm descending at a pitch angle greater than about 10 degrees.

[WebMaximus 372]

Thanks for your input guys!

[flygarn1 0]

Climb=when at CLB trust you will be steady on the speed specified in the MCP or VNAV you have max climbe rate, decrease climbe rate you will speed up and increase climb and you will slow down (all this will the TOGA and FMC do for you). Yor biggest problem with descent rate on the 800WL is to slow down for landing so I wouldent see more than 1000-1500ft/min to have a chance to slow down (use the alt arc on ND to plan your descent).

[WebMaximus 372]

Yeah, the 800WL sure can be tricky to slow down unless you don't plan for your descent well like you say.

[WebMaximus 372]

A follow-up question...is it possible in the FMC to limit the climb and descent rate flying in VNAV mode?

[ccarter06 3]

A follow-up question...is it possible in the FMC to limit the climb and descent rate flying in VNAV mode?

I've had a similar question for a while. I can change the degree of the descent in the MCDU for the plane I fly (so I can fly 4 degrees, or 3 degrees, or 2.1 degrees, etc). Is this possible with the NGX?

[Buzz313th 0]

A follow-up question...is it possible in the FMC to limit the climb and descent rate flying in VNAV mode?

Strictly in Vnav Climb mode, the only way I'm aware of, would be by a derate or another Thrust climb mode.In regards to your descent in Vnav... You can slow the rate of descent by managing throttle in "Throttle Hold, or Arm Mode" . Once above the Desc path, your pitch annucation will change to "Vnav Speed" and will indicate that the pitch channel is no longer holding "path" and now holding pitch for power and airspeed. To increase rate of desc in Vnav Desc mode, you can enter a higher desc speed in the FMC prior to TOD. This will force the FMC to calculate a steeper descent path due to increased parasitic drag from an airspeed higher than optimal glide speed.But don't be afraid to take it outa Vnav and use the other pitch modes. Or even better yet, handfly it.JB Edited January 26, 2012 by Buzz313th

[adamant365 28]

A follow-up question...is it possible in the FMC to limit the climb and descent rate flying in VNAV mode?

Yes, by changing the Cost Index. I forget which way it works. I probably have this backwards, but I think a lower CI will cause a higher climb angle and possibly higher rate of climb. My thinking being to be more fuel efficient, you have to get to cruise alt faster, but your time to destination is longer. Conversely, a higher CI causes a slower rate of climb because more energy will be spent traveling forward as opposed to upwards. You'll get to your destination faster but burn more fuel as you will spend more time at sub-optimal altitude. And I would think it would work the same for descent.EDIT: Someone else may have to weigh in on how CI affects climb rate. From what I've been reading, CI only affects IAS. I don't know how that would affect climb rate, if at all. Edited January 26, 2012 by adamant365

[WebMaximus 372]

Ok, was thinking maybe there was a similar way to limit your climb/descent rate as you can put in other limitations/restrictions in the FMC.Reason I asked is that sometimes VNAV commanded a descent rate my XPax virtual passengers didn't like :wink:Speaking about descent another thing I noticed is that 9 out of 10 times VNAV calculates the descent in a way where I'm forced to use the speed brakes in order to meet the various speed restrictions and keep to the planned descent path.

[Buzz313th 0]

Ok, was thinking maybe there was a similar way to limit your climb/descent rate as you can put in other limitations/restrictions in the FMC.Reason I asked is that sometimes VNAV commanded a descent rate my XPax virtual passengers didn't like

Real Tubeliner drivers will often transition from different phases of flight through the use of Handflying, Vertical Speed Mode, or disengaging autothrottle, to smooth things out and make the flight more comfortable for the passengers. The higher the rate of sustained climb/descent, the more "Ear Popping" the passengers experience durring pressurisation/de-pressurisation. It can be minimized by manually controlling the rate of pressurisation if the auto mode isn't doing it's job as well as it should, but I doubt FXPax is taking this into consideration.

Speaking about descent another thing I noticed is that 9 out of 10 times VNAV calculates the descent in a way where I'm forced to use the speed brakes in order to meet the various speed restrictions and keep to the planned descent path.

Check winds aloft before TOD and enter them in the legs page. It will help calculate a better descent path to accomidate winds. Also, Disengage AT at TOD and you will be able to better manage the VNAV descent and anticipate further ahead than the autothrottle. Again, the real 73 drivers will often disengage AT just before TOD. It's not uncommon to hear the Flight Crew say, "Ok, what the hell is it doing now"? "I have control".JB Edited January 26, 2012 by Buzz313th

[japascoe 98]

EDIT: Someone else may have to weigh in on how CI affects climb rate. From what I've been reading, CI only affects IAS. I don't know how that would affect climb rate, if at all.

In VNAV when climbing the engine is set to climb power and IAS is controlled by means of pitch, which relates to rate of climb. Lower speed = higher rate of climb and vice versa.

[Buzz313th 0]

In VNAV when climbing the engine is set to climb power and IAS is controlled by means of pitch, which relates to rate of climb. Lower speed = higher rate of climb and vice versa.

Excellent point, but only if your not on the backside of the power/drag curve and hopefully your not except durring short final. :)JB Edited January 26, 2012 by Buzz313th

[WebMaximus 372]

Real Tubeliner drivers will often transition from different phases of flight through the use of Handflying, Vertical Speed Mode, or disengaging autothrottle, to smooth things out and make the flight more comfortable for the passengers. The higher the rate of sustained climb/descent, the more "Ear Popping" the passengers experience durring pressurisation/de-pressurisation. It can be minimized by manually controlling the rate of pressurisation if the auto mode isn't doing it's job as well as it should, but I doubt FXPax is taking this into consideration.Check winds aloft before TOD and enter them in the legs page. It will help calculate a better descent path to accomidate winds. Also, Disengage AT at TOD and you will be able to better manage the VNAV descent and anticipate further ahead than the autothrottle. Again, the real 73 drivers will often disengage AT just before TOD. It's not uncommon to hear the Flight Crew say, "Ok, what the hell is it doing now"? "I have control".JB

No you're right, XPax only looks at the rate of climb/descent and the default values are the ones in my original post.Thanks for your tips using using different vertical modes and inputting wind conditions, I actaully know about this but it's easy to be a bit "lazy" being a virtual FS pilot but I'll give it a try and see how much difference it makes.