HI!

Im having trouble in my manual descents.

for example when I begin my descent (727) in a clean configuration, (autopilot disengaged) and I want to maintain for example 1500 fpm rate of descent; its very hard (if not impossible) to maintain that specific rate. I have to keep trimming up or down the whole way down
because the needle keeps moving up or down.

I dont think im doing anything wrong,(or am I?) I also use the throttle to try to control the VS.  but still cant accomplish a constant VS.

Im no pilot, but I dont think its like that, can you please tell me the correct procedure. ???

thanks

Juanca

Ozzy he's talking about the initial descent and in this case, 1500ft is not a steep descent at all.

Infact around 2000ft is considered normal, and that's not even an idle throttle descent, if you did that the V/S would drop to nearly 4000ft per minute (Now that's more like it eh Ozman )  

And it's normal to use the trim to get a perfect balance between power, attitude and speed, we're not talking about elevator trim, but horizontal stabilizer trim.

When descending say at 300kts the pitch should be no more than -1 degree, that's enough!
In the 737 pulling the thrust levers back will bring the nose down, but depending on your desired decent speed AND vertical speed you should properly trim the aircraft. the real 737 autopilot does this aswell when you to descend with the autoflight system.
Remember: the rate of descent will decrease slightly in the lower atmosphere because TAS is slowing but the CAS remains constant. 

However, what Ozzy said that is so true, is that you have to get the feeling for it. Flying is a skill and has to be learned in the air  

Edit: Oops, overlooked that you flew a 727 Juanca...
Due to the placement of the engines the 727 acts a little bit different, but use the info above as a general rule of thumb...hope it helped anyway!

You know me Nexus, if it doesn't have a shiny spinny thing, then its foreign to me
Barring certain HEAVY stunt planes

thanks for your replies, although  my question is ..how to maintain a constant rate of decent? (manually)

because the needle on the VS dont seem to stay put! even if I use throttle to try to "balance" rate of decent.

Oh yes i'm a 737

maybe i'm not explainig myself properly...

for example: I'm 27000 ft and 90 miles to KMIA
                  270/3 =90

Start me descent  at a rate of 1350  270*5=1350

If I dont maintain these rate of descend I will end to high or to low (ok? of course I know I have to keep calculating the rate of descend as I slow down and so on)

My problem is with the needle in the VS; I cant seem to keep it in that specific rate (I want to fly manally), because it keeps increasing or decresing...  I try to maintain that rate of descent for that specific part of the descent  with trim, and trying to balance with the throttle,  but the darn needle has a mind of its own, and I have to keep  tapping the trim all the way down, wich causes fatige, and I was wondering if this is so on real aircrafts???

thanks for your tips

Juanca

I use FD!

I just cant get the needle in the VS to stay at a specific and constant rate of descent for long.........

Lets say you are descending  at 2000 fpm......,  you can only maintain that rate with the autopilot, but if you try it manually you have to keep trimming and trimming and trimming to maintain that specific rate of descent.


I want to know the technic applied to avoid this

   HI
Well I Have Read  All Pro Con, So thought I tell you how I do it.
Don`t know about those Axial Flow Blow Torch   So will Used My A26.
When you power down from cruse setting, Some thing change The
Elevator does more then just set pitch, It Also control SPEED (I know
you thought the throttles did that) An now used Power To control
Rate of decent or VSI.  In my A26 I know that 30 inch MP And 28
click of up trim Will net me 150 mph An 2000 Fpm decent on VSI
Every Time.  You Will Haft to Play with Number to get what you want.
   [ Elevator TRIM TO CONTROL SPEED  POWER TO CONTROL Rate of decent ]
HO that Also works on all real airplane I have Flown to 8)
     Rich

How are you adjusting your pitch trim Juanca?

Contrary to popular public simviation opinion, constant RATE descents are not only possible, they are taught at the most  basic levels of instrument instruction. AND they are practiced everyday during NORMAL jet operations. Although most pilots in jets DO use the A/P and set V/S mode, it is NOT that hard to maintain a constant rate of descent. As with anything else, it just requires practice.
If you want to MANUALLY fly a descent at a constant RATE, you will need to continuously adjust your pitch trim. What your airplane wants to do(depending on it's Dynamic lateral stability)is called a parabola. When the speed increases the rate will decrease and when the speed decreases the rate increases. That is, unless you make constant pitch trim corrections.  Even in swept wing aircraft(which are a LITTLE more pitch sensitive than your Invader oldhorse    )  you will eventually find a "sweet spot" in the trim setting but in swept wing aircraft this harmony is usually shortlived and you will need a "click" or two of trim again.