Vertical Speed Question.

[chris1060]

I was wondering is it typical for the vertical speed in the 737-400 to be at 2000 fpm from takeoff to cruise altitude of 35000ft. Or do pilots lower the vertical speed as they gain altitude.

[flaminghotsauce]

I would imagine as you get up into the flight levels, you'd need to lower the fpm to keep from getting too slow, but I don't know the 737 numbers (i keep it low and prop-slow). I have attempted an auto-pilot ascent to the mid thirty-thousands before and stalled as the AP ran out of trim.

Just off the top of my head, I'd say that by the mid twenties, I'd be lowering it to 1500 fpm, then above 30K I'd put it to 1000'.

[Opa]

I was wondering is it typical for the vertical speed in the 737-400 to be at 2000 fpm from takeoff to cruise altitude of 35000ft. Or do pilots lower the vertical speed as they gain altitude.

I cannot answer your question but this site has a great deal of info regarding all Boeing aircraft:

http://www.boeing.com/commercial/737fam ... round.html

[Nav]

chris1060, the default rate of climb on the FS9 airliners is usually 1,800 fpm, which is fine at first. But, as flamingohotsauce says, it's best to 'step that down' as you get up into the thinner air - otherwise you're risking a stall.

In addition, your speed setting counts - the engines can only deliver a finite amount of power, and obviously if all that is being used to maintain a high airspeed there may be nothing to spare for the climb.

As far as airspeed is concerned, in most parts of the world you can't exceed 250 knots below 10,000 feet. Once above 10,000, I'd suggest increasing it to 275. Above 20,000 feet, best to switch to Mach speed - I usually set it at 0.65 in the climb.

Then keep an eye on the instruments. To avoid using too much fuel in the climb I find that it's best to keep N1 in the range 70%-80%; and you should also keep an eye on the airspeed. If the power creeps up above the desired range, or the actual airspeed begins to drop below the set figure, it's a sure sign that the engines are running out of puff, and you should reduce the rate of climb until 'normal service is resumed.'

It's important to bear in mind that too steep a rate of climb at high altitude doesn't just drink fuel - it also slows your progress over the ground, so you're losing out both ways. I generally reckon on 1,500 above say 25,000, 1000 above 30,000 - but I'm sure you'll develop your own techniques and preferences.

[727 driver]

SHORT ANSWER yes the higher you climb the less vertical speed you will have

I was wondering is it typical for the vertical speed in the 737-400 to be at 2000 fpm from takeoff to cruise altitude of 35000ft. Or do pilots lower the vertical speed as they gain altitude.

[Dickert]

You will want to use the speed mode in the climb since that is the safer mode.  A mode that maintains a particular pitch above the horizon will allow speed to drop off as the air thins during climb, resulting in less power from the engines, thus a drop in speed, and risking stall if the pilots forget to monitor performance.
Using Vertical Speed mode will give basically the same problem, while using Speed mode during climb may actually result in an over-speed of Mach number as altitude is gained.  If your asleep at the yoke and do get the over-speed warning, you owe the other guy a beer, but no harm is done (if you only touch the bar that is).  This will usually happen if you forget to transition to Mach during the climb.  So if you do hit the warning, switch the mode from IAS

[beaky]

That's a great explanation, Harold... file under "the AP is only as smart as you are".

[JBaymore]

Harold, that is a great description of real world procedures.  Thanks.

best,

...............john

[flaminghotsauce]

Hey Harold! That little rocket of yours.....



Thanks, great fun!