Vertical speed advice

[pschlute 37]

 I was at FL340 .86 around 293kts so are you suggesting hit flch at TD at my crz speed until the aircraft reaches the fmc econ descent speed, and that I don't need to physically idle my throttles

 

If you are using FLCH:

 

As you approach TD you will normally have both A/P and A/T on. So hit FLCH and let the A/T take care of the throttles, you dont need to touch them. You will descend at 0.86 so if you want to wind back the speed to the FMC calculated descent MACH speed then do that if you wish. This will of course reduce your vertical speed.  At the MACH/IAS crossover point change the speed window from MACH to IAS and continue your descent at the FMC calculated IAS descent speed.

 

Just to add, FLCH unlike VNAV is not taking any guidance from the FMC. It works in the descent by placing the throttles at idle (idle setting varies according to altitude) and using pitch to maintain the speed you select on the MCP.

[skelsey 765]

"RW pilots abhor using speed brakes. Considered a screwed up descent if speed brakes are needed."

 

I've flown around the real world four times and seen speed brakes in use on every type that has them fitted. They wouldn't be there if they weren't needed. And they are needed because in the real world ATC often needs to make last-minute changes to maintain safe separation on approaches.

 

If the descent is properly planned, then you should not need the speedbrake. They are noisy, inefficient, waste fuel and uncomfortable for the passengers. One of the RW captains on our team refers to them as the "lever of shame".

 

Of course, the speedbrake is a flight control to be used if you need it, and occasionally ATC may require a particular profile that is unachievable without additional drag. But generally speaking it is possible to anticipate and plan ahead sufficiently in order to manage the energy level of the aircraft appropriately.

 

Thanks for all the follow up.

Why isn't the Simfest 747 simulator plummetting upon initial FLCH descent?

 

Probably because it doesn't use the iFly flight model ;-).

[Wink207 78]

"RW pilots abhor using speed brakes. Considered a screwed up descent if speed brakes are needed."

 

I've flown around the real world four times and seen speed brakes in use on every type that has them fitted. They wouldn't be there if they weren't needed. And they are needed because in the real world ATC often needs to make last-minute changes to maintain safe separation on approaches.

 

Different ships, different square knots

[ghiom 2]

If the descent is properly planned, then you should not need the speedbrake. They are noisy, inefficient, waste fuel and uncomfortable for the passengers. One of the RW captains on our team refers to them as the "lever of shame".

 

Of course, the speedbrake is a flight control to be used if you need it, and occasionally ATC may require a particular profile that is unachievable without additional drag. But generally speaking it is possible to anticipate and plan ahead sufficiently in order to manage the energy level of the aircraft appropriately.

 

 

Probably because it doesn't use the iFly flight model ;-).

Thanks

Do you know which one it is? Could not find it online...

So I need to assume their model isn't correct?

[skelsey 765]

Thanks

Do you know which one it is? Could not find it online...

So I need to assume their model isn't correct?

The flight model/instruments/systems are all Aerowinx PSX, the outside view is P3D.

 

The PSX flight model is a whole lot more accurate than either iFly or the PMDG 747! I don't have the iFly, but from what I've read I'm not impressed from an FDE point of view -- one reported that it was taking just 14 minutes and less than 100NM to get to FL340 at MTOW, which is frankly ridiculous and more like 757 performance than a 747!

 

The PMDG flight model is better but is probably slightly underpowered in the initial climb and it burns too much fuel (closer to 12 tonnes/hour vs a more typical 10).

[ghiom 2]

The flight model/instruments/systems are all Aerowinx PSX, the outside view is P3D.

 

The PSX flight model is a whole lot more accurate than either iFly or the PMDG 747! I don't have the iFly, but from what I've read I'm not impressed from an FDE point of view -- one reported that it was taking just 14 minutes and less than 100NM to get to FL340 at MTOW, which is frankly ridiculous and more like 757 performance than a 747!

 

The PMDG flight model is better but is probably slightly underpowered in the initial climb and it burns too much fuel (closer to 12 tonnes/hour vs a more typical 10).

Mmmm...

[G550flyer 1,007]

If the descent is properly planned, then you should not need the speedbrake. They are noisy, inefficient, waste fuel and uncomfortable for the passengers. One of the RW captains on our team refers to them as the "lever of shame".

 

Of course, the speedbrake is a flight control to be used if you need it, and occasionally ATC may require a particular profile that is unachievable without additional drag. But generally speaking it is possible to anticipate and plan ahead sufficiently in order to manage the energy level of the aircraft appropriately.

 

 

Probably because it doesn't use the iFly flight model ;-).

The thing is, no matter what properly planning you do for descent, ATC often see other wise.I'm based in the DC region and they all ways give what I call the slam dunk. In heavy traffic areas along with departure and arrival corridors, ATC tend to keep you up longer than you want. Even when you prompt for lower, they may step you down 2 to 4 thousand at a time due to airspace and traffic beneath that they are not controlling. Modern jets will either slow down or go down, not both. Some guys may start slowing getting close to their planned descent point but technically you are changing your contracted airspeed with ATC. Many times in these congested areas, ATC will make you keep your speed up or request a speed reduction while descending. Both of these will lead to speed brake use at some point. The thing about speed brakes is knowing when and how to use them. If you realize you are going to need the brakes, you ease them out early on. When you need them right away, you again ease them out slowly and retract them slowly. It's like getting out of and in bed while your spouse is sleeping without waking them. When using them early on and easing them out, passengers initially notice the rumble and forget about it. When easing them out slowly, many don't pay attention and will not notice the increase of the rumble. Smooth movement also prevents abrupt pitching. I only use the speed brakes when needed and will trade them for flaps at some point. I've also had to drop gear earlier than normal when i'm really hosed.Really knowing your aircraft's performance capability will immediately cue you in if you will need them or not. Once you figure the descent required and all ready know the rates you get with different configurations to include gear, you know immediately. Even when I commercial out, those guys will ride the brakes through approach. When i return to KDCA commercially, when riding a 737, 320 or 757, those guys ride the brakes through out the river approach. When on MD80s, the plane create so much drag that they trade the brakes for flaps. I will say that speed brakes have never caused a paycheck change or bad review. A missed approach, go around or runway over run associated with poor energy management will.

 

Rich

[ghiom 2]

Mmmm...

Is there a video somewhere of a real 747 descending in idle mode where I can see on the PFD the pitch and the v/s?

Thanks

Ghiom

[vadriver 247]

team

 

you've all added some worthy notes since my post #3 less than a week ago .... !

 

we have all been writing about the econ type descent @ around the 3 deg vpath.

 

we should remember (for those flying FAA skies) that many of the "recent" RNAV stars are predominately through altitude "gates" (below / above) where the vpath is about 2.5deg between most fixes.  this is where v/s seems the mode of choice. (if atc doesn't take you off it).

 

with this, 250' per nm / 4nm per 1000' / 400 fpm per 100k G/S. 

[Constantine 16]

Hi thank you for the advice Commencing descent in FLCH at crz speed gives a much more realistic initial descent than when I used to roll back the speed to the FMC econ descent speed prior to descent, and the aircraft would fall like a brick.

 

However one problem I encounter is switching from FLCH to -VS on the descent I have tried prior to my cleared level e.g 2000ft or perhaps 5000ft when I open the VS window and attempt to enter a VS speed the VS window blanks each time I begin to enter a desired VS speed so I end up completing the flight returning to VNAV I don't understand why this happens, is it possible to change from FLCH to VS in continued descent or do I need to level off at my desired altitude prior to using VS ? 

 

Any advice most appreciated !

    Thank you

Richard

Appologies I entered my reply in your comment area, sorry, it was mean't to be obviously in response to mine which began this particular topic.

[pschlute 37]

You should just change directly from FLCH to V/S. Try pressing the V/S button and the current V/S should appear in the V/S window.

[ViperPilot 81]

Thanks to everyone that provided their Tips and Suggestions... for those of us who don't fly the Heavy Iron very much, these are invaluable to help get these big airplanes down from on high, and for learning what the proper procedure is for setting up Descent to a NAVAID or Waypoint.

 

A question for you all... is there a way to essentially 'narrate' a typical Tubeliner flight, from start to finish, using a format similar to what's been posted above? For instance, we have the typical Procedure to set up a Descent from a given Speed and Altitude, but what happens...

 

-- For example, right after Rotation, what would be the typical Procedure for Climbing to Cruising Altitude? One long, gradual lift to Cruise Alt., or a series of shorter runs at a higher V/S until reaching the Mark?

 

-- And... would the same Procedures be similar for smaller Bizjets or VLJ's, like a CRJ-135 or HondaJet?

 

Thanks!

 

Alan  :smile:

[Constantine 16]

THanks Peter, obviously I do that but when i try to adjust the vs figures in the window the window blanks each time.

anyway thanks once again

Richard

[G550flyer 1,007]

Thanks to everyone that provided their Tips and Suggestions... for those of us who don't fly the Heavy Iron very much, these are invaluable to help get these big airplanes down from on high, and for learning what the proper procedure is for setting up Descent to a NAVAID or Waypoint.

 

A question for you all... is there a way to essentially 'narrate' a typical Tubeliner flight, from start to finish, using a format similar to what's been posted above? For instance, we have the typical Procedure to set up a Descent from a given Speed and Altitude, but what happens...

 

-- For example, right after Rotation, what would be the typical Procedure for Climbing to Cruising Altitude? One long, gradual lift to Cruise Alt., or a series of shorter runs at a higher V/S until reaching the Mark?

 

-- And... would the same Procedures be similar for smaller Bizjets or VLJ's, like a CRJ-135 or HondaJet?

 

Thanks!

 

Alan  :smile:

Ok, ill give you a quick and dirty run down on how a flight would go.

 

Departure: Usually on departure you will follow a departure procedure or a vectored departure. Some procedures might be RNAV in nature and others may be a basic procedure that has turns/altitudes. These types may be flown in LNAV/VNAV or LNAV depending on its length and altitude restrictions. Departures with various speeds and hard altitudes are the ones I prefer to fly in LNAV/VNAV or when i have to be strictly precise in noise sensitive or terrain areas. Some of them are short and give you a turn then leads to a vector. Short types are not even worth flying in VNAV because it leads to a discontinuity requiring a different lateral or vertical mode(HDG/VS). You also have to know if its a heading or a track. This is important especially on a windy day. Departures that lead to a heading after a turn can get you in trouble in LNAV. The system will be in takeoff mode and limit the bank during the turn requiring an adjustment after it sequences from takeoff. This will lead to a different heading as the system corrects back to departure course. This may lead to ATC requesting confirmation of departure heading.

 

Takeoff: Initial climb is usually V2+10 until accel height on a departure or initial heading. At accel height, you most likely select a low V/S to allow the aircraft to accel for clean up. From what I see normally, you usually end up on a vectored heading being taken off of the DP. This is most likely when you will use V/S or FLCH for climb. Keep in mind that a light aircraft will climb like crazy making level off suspect. No need to climb at 5000ft per minute when only changing a few thousand feet. This is a perfect time to use V/S to keep things from strong pitching and making things manageable.  Being off the FMS flight plan prevents use of VNAV. Speed at this point is 250 or minimum maneuver which ever is higher. Yes, if your AFM minimum maneuver is higher than 250, you will fly the MINMAN. No, there is no way to verify climb performance with flaps and slats hanging because climb performance charts are based on getting clean asap all engines or engines out. No, Ive never had to request speed permission and I flew KC10s and D10s all over the world. No, ATC is not going to box me into a climb configuration that i can't verify performance for restrictions for the sake of 250kts. This is why you have type designation on the flight plan and your call sign is suffixed with heavy.  It just doesn't happen. Unless you are in low traffic areas, you will be vectored for climb or given small altitudes on your way up.

 

10000ft: This is when you will transition to your enroute climb speed. By 10,000, you are usually given a intercept or cleared direct to a point on your filed plan. Once this is executed in your FMS, it's a good time to use V/S, FLCH or VNAV. VNAV depends on the climb given. Small altitude climbs are not worth VNAV because of the constant adjustment and steps to re use it. VNAV is best when given a large climb and on FMS plan. I prefer FLCH at this point. It's just one button push without having to adjust the FMS for VNAV. Keep in mind that my technique is to smoothly vert speed up to a VVI that the engines reach climb power. Once there, I hit FLCH. This results in a smooth transition.

 

Mach change over: Changer happens at 28 to 31 thousand depending on aircraft type and climb speed. This is where you will see the most pitching with FLCH. It gets annoying and can get you slow/off speed quickly. Some guys revert to V/S at this point and just keep an eye on speed. I like to use FLCH, but i keep an eye on the mach. As soon as there is a bump in mach caused by temp inversion or wind change, i hit V/S to lock in the vert speed and adjust it to climb mach. The thing is that there is more variance between mach numbers than between knots. This is why the autopilot easily gets off of climb mach resulting in picth up or down to capture the mach. It overshoots easily in mach leading to sea sawing. This is why vert speed is easier to manage. You should be watching the aircraft anyway, not the time to discuss golf or pull out the magazine. Get slow this high up, it takes for ever and a lot of gas to get back on schedule.

 

Cruise: Most climb schedules will lead to reaching cruise altitude at cruise speed. This is a good point to compare flight plan fuel against the FMS fuel against actual fuel. If there is an issue, it will show itself right here. Prior to descent, its a good time to come up with a descend no later than point. Guys will use 3 x the altitude to lose or 4 x the altitude to lose depending on aircraft. I like 4 x because it gives me room for slowing prior to 10,000ft. So in my example. We are at 40,000ft and the approach altitude takes place at 3000ft. 40000 - 3000 = 37000ft to loose. Drop the three zeros and you have 4 x 37 = 148 miles. This can be adjusted if you are having to over fly the airport to shoot from the opposite direction. So, approaching 148 miles from the IAF, have the non flying pilot request lower if you have not received a descent. The request for lower usually cues the controller that you are asking because you are reaching a limit. The FMS will give you a descent point, but remember that it wants to keep you up as long as possible in order to conserve fuel. 

 

Descent: Usually you are at your cruise mach at the start of descent. I personally like to start with 2500 to 3000ft per minute while holding mach. Once the mach intercept indicated descent speed, I may get ahead and swap to indicated. Some aircraft will handle this very well and makes the switch automatically. Keep in mind that it takes more true airspeed to maintain mach at lower altitudes. So FLCH in mach can lead to some serious descent rates at lower altitudes and can lead to over speeding. I see this from time to time when guys hard select mach speed and it can't change over automatically. It is most common to receive restriction such as "descend and maintain 8 thousand, cross 30 miles south of dixie at 15,000". Typically in busy airspace, you will be held up and stepped down. You may get vectored off flight plan often. You may get an arrival but usually are given altitudes. Descend VIA(VNAV) doesn't happen that often. Once in airspeed mode, FLCH works well. Approaching 10,000, i use the 12 at 12 technique. I set 1200 feet per minute at 12,000ft. This is why i like 4 x the altitude. Usually the aircraft will reach 250kts at 10,000 with little adjusting when using 12 at 12 in every type jet Ive flown. You may get alot of restrictions so you have to be able to do public math on the fly. Guys will use the mach technique when seeing if a restriction can be made. If you are at mach .78, guys will assume 8 miles a minute. They also consider descent rate and altitude to lose. This technique helps with deciding if you will make an altitude by a certain distance or point. You can do it by adding it into the FMS, but calculating on the fly will let you know immediately if you need to inform the controller or use the brakes.

 

10,000ft: Most aircraft can only descend at 1500ft per minute clean and maintain 250kts. Anything more and the aircraft will accelerate requiring brakes, slats, slats and brakes or slats, brakes and flaps aircraft depending. When below 10,000ft, i strictly use FLCH. At this point your are on a heading and using V/S or FLCH

 

Approach: Key for approach is proper configuring. In my current aircraft, I use the 2,4, 6,8 technique. 8 miles-flaps 10, 6 miles-flaps 20, 4 miles-gear/glide path or slope and 2 miles-flaps 39. The DC10 was easy, slats at 10,000. flaps 22 during final vectors. Gear down approaching glide path/slope and flaps 35 at path/gs intercept. These are just basic configuring techniques to help you remember configuring. Different situations may dictate otherwise. Its a good idea to come up with something to create a habit pattern. The type of approach is going to dictate your automation use. GPS/non precisions can be flown in LNAV/V/S, LNAV/VNAV or HDG/VS. Localizer done in LNAV/LOC with V/S or VNAV depending the type aircraft. ILS in ILS.  

 

These are just typical and generic from my experience and aircraft. There are many different ways to do things in the real world, just depends on pilot preference. You can fly a non precision raw data, but most will fly in FMS for accuracy. Only having the pointer displayed on a VOR APP while flying LNAV/VNAV is legal FAA wise. It's all preference and SOPs.   

[ViperPilot 81]

Rick,

 

Thank you so much! This is exactly what I was looking for; a general Guide. It's a type of flying that has mystified me in the past, but with your Guide, I'm excited to give it a go one more time.

 

One thing... most of the big birds I have don't have a functional FMS, however I do have a couple that have Garrett Smith's FMC. Is this sufficient to input STARS/SIDS, or do I meed a 3rd party add on? Also, for the ones that don't... I could enter Waypoints into the FS9 Flight Planner and effectively 'create' a Flight Plan, right?

 

(of course, I guess I could load Garrett's FMS into all of them, or go online and get a .pln from a website...)   :wink:

 

Alan  :smile: