IFR Turbo Decent and turbulance

Ted DuPuis said:
Even in the turbine world we've done 500 FPM descents when it makes sense.
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I and many folks Do them all them time for a short duration , but from the flight levels to All the way to the ground in a turbine ...that's just not the way that usually works.
 
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taters said:
I and many folks Do them all them time for a short duration , but from the flight levels to All the way to the ground in a turbine ...that's just not the way that usually works.
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1) The OP isn't flying a CRJ-700 or anything close. It's a piston single.
2) Sure it can make sense in a turbine. Good example in the Commander: we're at FL270, approaching DC, given a descent to 15,000. We're still more than an hour out from our destination, but that stupid DC/PHL/NYC corridor gets you down low early. Descend at 500 FPM keeps us up high longer, burning less fuel. My boss dialed in 2,000 FPM, I said "Why? 500 is all we have to do, and we aren't in any hurry." "Oh, you're right." Probably saved 50 lbs.

No, not all the way to the ground most of the time in a turbine. Turbo piston ops aren't turbine ops.
 
Great perspective and responses so far...

chartbundle said:
With the fully automatic wastegate on the 182 G1000 I flew a couple weeks back it was basically: 2000 rpm, 25" MP , Mixture to keep TIT up(seemed to stay at 1400-1500) and a 600FPM descent at the top of the green. But this was only from 10,000 or so, haven't had a chance to try it from higher.
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2000 rpm and 25" is still about 65% power. That is what my level cruising power was. To get 600 fpm descent at that power level, the airspeed will increase significantly. I was trying to descend as well as keeping the airspeed lower to Va for turbulence and maintain a minimum power level.
 
Remember that Va isn't required for any turbulence, so saying you need to descend at or below Va isn't by itself true. I'm usually descending closer to Vno, and if I'm worried about turbulence, I pull back on the yoke just a hair to ease the descent and reduce speed. I also find most planes need to be pointed pretty heavily towards the earth to get into the yellow arc - drag just gets in the way.

Where Va becomes a concern structurally is severe turbulence. Light to moderate you're fine being above Va and below Vno. The yellow arc is where you need to make sure you're in smooth air. Only once have I needed to reduce to Va for turbulence.

The only plane I've flown with a restriction for moderate turbulence was the Commander 690A. Those large wings had snapped off in a few cases, and there was a restriction of 180 KIAS or less in moderate turbulence. I forget Va, I think it was around 140. One Cessna 402 had its wings fall off, but that was around a 30k hour airframe IIRC, and a freight dog.

Overall, you only hear of wings snapping off when people are doing something extraordinarily stupid, like aerobatic maneuvers at high speed in an airplane not so equipped.
 
Years ago, I flew unpressurized commuter planes. We were to never exceed 500 fpm and the operative term we used was unable when dealing with ATC.


taters said:
I and many folks Do them all them time for a short duration , but from the flight levels to All the way to the ground in a turbine ...that's just not the way that usually works.
Click to expand...
 
Ted DuPuis said:
Remember that Va isn't required for any turbulence, so saying you need to descend at or below Va isn't by itself true. I'm usually descending closer to Vno, and if I'm worried about turbulence, I pull back on the yoke just a hair to ease the descent and reduce speed. I also find most planes need to be pointed pretty heavily towards the earth to get into the yellow arc - drag just gets in the way.

Where Va becomes a concern structurally is severe turbulence. Light to moderate you're fine being above Va and below Vno. The yellow arc is where you need to make sure you're in smooth air. Only once have I needed to reduce to Va for turbulence.

The only plane I've flown with a restriction for moderate turbulence was the Commander 690A. Those large wings had snapped off in a few cases, and there was a restriction of 180 KIAS or less in moderate turbulence. I forget Va, I think it was around 140. One Cessna 402 had its wings fall off, but that was around a 30k hour airframe IIRC, and a freight dog.

Overall, you only hear of wings snapping off when people are doing something extraordinarily stupid, like aerobatic maneuvers at high speed in an airplane not so equipped.
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This is interesting. From my POH it says:

MAXIMUM RECOMMENDED TURBULENT AIR
PENETRATION SPEED
3100 POUNDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 KIAS
2600 POUNDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101 KIAS
2100 POUNDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91 KIAS

These speeds are the same as Va.

There is no indication as to how turbulent this is for. How would one know this would not apply to light or moderate turbulence as well?

Assuming, as you say, this would only apply to severe turbulence, would one ever expect to see severe turbulence through or under common puffy clouds in an area far away from thunderstorm or Airmet Tango's?
 
I think anything under 5,000 fpm is for wimps. My Comanche does that all day long. Screw the passengers ears, they can buy new ones.
 
You'd be best off talking to people with mountain flying experience. I don't fly out that way often. I hear those rocks can make good bumps. But in general, I have an idea when I'm going to get bumps and adjust speeds accordingly.

For light or moderate, don't worry about going a bit faster. At least, I wouldn't.
 
skidoo said:
Assuming, as you say, this would only apply to severe turbulence, would one ever expect to see severe turbulence through or under common puffy clouds in an area far away from thunderstorm or Airmet Tango's?
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As an OWNER I always try to be really easy on my airframe. I don't want to be pounding it any more than I have to.

You are in Montana. Rocks create a lot of clear air turbulence, I'm sure you already know this. When 2000 FPM down becomes 2000 FPM up in a couple of seconds.... I want to be at Va.

In Winter the jet stream can get down into the lower flight levels in your area. You can really find some turbulence there as well.
 
most of the time i do cruise power descents. I maintain my engine warm and cozy while descending at anywhere between 1000 and 1500 fpm. On the terminal area/approach the engine has time to cool down appropiately until I shutdown at the ramp.
 
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