737-800 descent angle in different configurations

[GMS]

I will soon be converting onto the 737-800, having flown the 757/767 for many years. As in my airline we carry out many visual approaches, I am seeking information on the descent angle of the 737-800 for different configurations. As an example, the 757 with gear down and F20 comes down at 6 degrees. What would be the figure for the 737-800 at gear down F15, and gear down F25, both without speedbrake?

Thank you for your help.

[737 Elpiloto]

You can take, approx, these figures:

Speed 250kts, F0 : BA 4° and thrust at 65%
Speed 210kts, F0 : BA 6° and thrust at 60%
Speed 180kts, F5 : BA 6° and thrust at 60%
Speed Vref + 5kts, F15 : BA 5° and thrust at 52%
Speed 140 kts, F25 : BA 4° and thrust at 52%
Speed Vref + 5kts, F30 : BA 2,5° and thrust at 57%
Speed Vref + 5kts, F40 : BA 1° and thrust at 62%

Off course this can be taken as a guidance and will change with weight, wind, etc....
But, I always used these figures to get used to the 737 during training.

With speedbrake I do not know, than it's an whole different ball game...

[GMS]

737 Elpiloto,

Thank you for taking the time to post all that information. It will be very usefull no doubt.

What I am really after is the aircraft flight path angle, at idle thrust, for those two configurations, to better judge a visual approach, not the aircraft body attitude. For example, 6 degrees equates to 600 Ft. per NM.

[de facto]

What would be the figure for the 737-800 at gear down F15, and gear down F25, both without speedbrake?

We dont use speedbrake when Flaps 15 or more on the 737,at least not on purpose:E

As you seem to have plenty of 757 experience ,it wont take you long to pick those pitch settings up.
I personally never paid attention to IDLE thrust pitch attitude as one would simply have to pitch for airspeed,no?
Now if you are planning for an idle thrust continuous descent rather than a proper 'visual',then gear down flaps 15 will be about pitch -2/-1deg and 1300ft/min, flaps 30 about 15-1600ft for speeds of 140-150 kts.

For 'stabilised' approach pitch and thrust settings the post from 'elpiloto' seems quite correct except the 4 deg for 250 kts,the NG will always at speeds 250 or more what ever the altitude(5000 or FlL 410) will be level at 2.5 deg.

The 737 has 5 basic pitch one must know.(15/7.5/11/6/2.5),with a few sims youll know which ones are which.

Enjoy:ok:

[ImbracableCrunk]

I think the OP is talking about FPA, not pitch.

I can try to find some numbers, but I think you can do about -6 to -6.5 degrees at F30 and Vref+15. I think the most I've gotten was about -9 and that was gear down and speed brakes at 250-270kias.

[de facto]

I think the most I've gotten was about -9 and that was gear down and speed brakes at 250-270kias.


Were you getting shot at?:E

I guess yes he was asking about FPA ,no idea,never even switch on the FPV,ill keep this for the day i get into an inverted stall.:eek:

[RAT 5]

It's a curious question because in B757/767 & 737 I tend to think of loss of height versus distance. For normal descents at 280kts and 250/100 then 170 as you intercept G/S the usual 3 x HT plus a few to slow down works.

Once at circuit speeds and assuming idle thrust:
210kts is roughly UP speed at common ELW. On a 3 degree ILS the speed will slowly accelerate: speed brake will just about hold it.
F1/190 will stabilise on G/S. F5/170 will do likewise, but selecting F5 will not slow you down from F1 speed. F10 will come down slightly steeper. Gear & F15 is about 2 x height in distance. F40 at Vref will just about do 1nm/1000'. Thus F25/30 will be in between 2x & 1x height.

A quick way to get down is F5 220kts & speed brake. This will also be about 2 x Ht. perhaps more. You then need to slow down 50kts which is best done in level flight and hit G/S o speed. I appreciate these are not FPA's, but they are useful in assessing distance required to lose height, which surely is what it is all about if you want to hit the correct crash point. As your grandma would have told you, "suck it and see." Use the same as B757/767 and adjust your datums. Always a good way to start. There's less inertia in B738 and like all slippery a/c it won't go down and slow down.

[ImbracableCrunk]

Were you getting shot at?http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/evil.gif

"The ATIS said 20R? Well, you're cleared for 2L."

[PPRuNeUser0190]

Hello,

roughly:

F UP - 1 - 5: 3°
adding of gear: add 1.5°
Gear down + F15: around 5.5 - 6°
Gear down + F30: around 7°
Gear down + F40: around 9°

[GMS]

Thank you all for your contributions.

Rvblyky7; precisely what I was after, thank you.

[RAT 5]

GMS. I'm curious; why are you interested in the FPV for the descents. Flying your previous types and the NG I'm interested in how much height can I lose in how many nm's. I also fly gliders, as a jet is with thrust at idle, almost. Please enlighten us as to your techniques. Thanks.

[GMS]

RAT 5,

I asked for angle of descent information; I could have asked for feet per NM, same thing. This is nothing to do with FPV.

Give or take a few feet, an aircraft descends about 100 ft/NM/degree. So on a 6 degree descent that would be about 600 ft/NM.

If at a given configuration the aircraft descends at 600 ft/NM, my calculation for deciding when to turn onto final from a 1.5/2 NM abeam downwind is as follows; distance from threshold in NM x 600 + Elevation. If my altitude is at or below this figure I turn onto final.

As an example, take a position 8 NM downwind for a sea level airport. 8 x 600 = 4800. If you are at 4800 ft or lower at this point, turn onto final. By the time you roll out you will be at 8 NM and 3600 ft. At 7 NM 3000 ft, 6 NM 2400 ft, 5NM 1800 ft, 4 NM 1200 ft, select landing flap and you will be stable between 500/1000 ft.

If the aircraft descends at 500 ft/NM, use 500 x NM + elevation, and so forth for different descent rates.

Any headwind on final will add to your descent angle, and if you feel it's a bit tight you could always select landing flap earlier.

What I like about calculating a descent this way is that you could be in a clean configuration as you pass abeam the threshold, and when cleared visual, establish the configuration and start calculating your NM/Alt. You don't need to time from abeam the threshold, and it's very satisfying to switch off all the automatics and fly the aircraft.

It also works for a straight in approach, you just have to reduce your altitude calculation by 1000/1500 ft to meet stabilised criteria.

I hope this helps to clear things up.

[RAT 5]

Many ways to skin the same cat. Enjoy yours, but I'm too long in the tooth and have too many doggie spots developed over the years. I enjoyed all 3 a/c very much, having flown long & short haul in them, and into some tiny looking airfields, even with the big bird. I said I'd never go back to a small cockpit after B757/767. Short-haul was fine in B738, at first, but then they turned it into long-haul by flying 4 sector 10-11hr days. No room to stand up and do a few knee bends. It is a fine a/c to pole around the islands with Mk.1. eyeball arrivals. I hope they let you do so.

[GMS]

Thankfully they do RAT5, all within the bounds of common sense. I find it the most satisfying aspect of this job.

Thanks for your input.

[JRT]

Hi GMS,

Just out of curiosity I m not sure if I understood your example. When you say a 8 NM downwind do you mean that you are about 8NM, abeam to the rwy th threshold?

I usually used height abeam x 3 to get approximate time to turn in seconds.

If at 1500 / 100 x 3 = 45 seconds when I would turn final.

But are interested in how you where calculating ?

If you able to upload a picture or drawing :-D

[nitpicker330]

So you've not even sat in the seat and already you'd like to know max performance approach figures!!! Settle down and learn the standard normal stuff first would be my suggestion. As part of your line training the Trainer will cover what he thinks you need to know. :ok:

And read the FCTM, that's what Boeing says you need to know to fly their Aircraft safely through all normal, non normal and Emergency situations.

Leave the Top Gun maneuvers to Tom Cruise!!

[737Jock]

That comment is not really warrented nitpicker. As he explained he is calculating height vs distance on the downwind leg. He still has to turn base and final.
Base leg will reduce height considerably and turns increase the descent rate even more. So by the time he is on final he is nowhere near max performance.

[nitpicker330]

Huh?????

There is enough info in the FCTM on how to conduct a visual circuit, with regards to timings and config.

His Sim instructor will give him Pitch attitudes and N1 settings he needs during conversion.

Then his Training Captain will "train" him on the line with all the stuff he needs to safely fly the Jet day to day. This will include what to do if you capture GS from above etc......

:ok:

[GMS]

Thank you for your continued interest. I have now completed the simulator faze, had a good look at the information displayed in the FMC Descent page, namely FPA information, and had spare time to practice several different approach scenarios in the simulator.

Nitpicker330; Is a visual approach a Top Gun manoeuvre in your book? Sad state of affairs if so.

JRT; 8 NMs away from the threshold and about 1.5/2 NMs abeam the runway centreline.

GMS

[737Jock]

Nitpicker I guess you must be a trainer. Some people however like to think for themselves, and standard FCTM scenarios won't get you out of the **** every single time. Nor will glideslope intercept from above procedures, for instance with visuals that don't have a glideslope. And even that procedure needs to be modified if ATC leaves you really high on an ILS.
Sim-time is very limited so any information that can be processed and taught outside the sim is very valuable. To purely rely in trainers to get you up to speed is foly imho. And what he described certainly doesn't constitute top gun maneuvers, it doesn't even come near.

There are many ways to skin a cat, the FCTM nor the trainer will teach you all. It's always a good idea to know what the aircraft is capable of. If only to builtnin safety margins.

For allyou know this guy is a captain with 10.000 hours, yet you are treating him like some fresh out of school cadet!:ok:

[nitpicker330]

He quoted "F20 idle thrust in a 757 gives 6 deg descent path" and wanted to know how the 738 compared......

So if you're on a visual approach hand flying the beast around the circuit you may not want to be banking 30 deg while "dive bombing" down F20 idle thrust to recover a stuffed up approach..... Call me an old fart but that is a recipe for disaster!!

I guess if you were conducting a straight in Vis approach and ATC ( or terrain ) left you high then this info would be useful to recover back to profile. For a new Pilot on a type I'd suggest this isn't an ideal situation to be in until you do get to know the Aircraft.

I can see what he's after but I'd suggest he get used to the 738 in normal ops first.

Anyway....

[ImbracableCrunk]

I guess if you were conducting a straight in Vis approach and ATC ( or terrain ) left you high then this info would be useful to recover back to profile. For a new Pilot on a type I'd suggest this isn't an ideal situation to be in until you do get to know the Aircraft.

I can see what he's after but I'd suggest he get used to the 738 in normal ops first. It sounds like he understands jets, and just needs a piece of unpublished info. "I can do X in plane A, can I do X in plane B?" Yes. Problem solved.

[flyzhz]

I do not understand the following,is it for level flight or descend?
Speed Vref + 5kts, F15 : BA 5° and thrust at 52%
Speed 140 kts, F25 : BA 4° and thrust at 52%